Biodegradable porous silk microtubes for tissue vascularization

Cardiovascular diseases are the leading cause of mortality around the globe, and microvasculature replacements to help stem these diseases are not available. Additionally, some vascular surgeries needing small-diameter vascular grafts present different performance requirements. In this work, silk fibroin scaffolds based on silk/polyethylene oxide blends were developed as microtubes for vasculature needs and for different tissue regeneration times, mechanical properties and structural designs. Systems with 13, 14 and 15% silk alone or blended with 1 or 2% of polyethylene oxide (PEO) were used to generate porous microtubes by gel spinning. Microtubes with inner diameters (IDs) of 150–300 mm and 100 mm wall thicknesses were fabricated. The systems were assessed for porosity, mechanical properties, enzymatic degradability, and in vitro vascular endothelial cell attachment and metabolic activity. After 14 days, all the tubes supported the proliferation of cells and the cell attachment increased with porosity. The silk tubes with PEO had similar crystallinity but a higher elastic modulus compared with the systems without PEO. The silk (13%)/PEO (1%) system showed the highest porosity (20 um pore diameter on average), the highest cell attachment and the fastest degradation profile. There was a good correlation between these parameters with silk concentration and the presence of PEO. The results demonstrate the ability to generate versatile and tunable tubular biomaterials based on silk–PEO blends with potential for microvascular grafts.Centro de Investigación y Desarrollo en Fermentaciones Industriales (CINDEFI)Facultad de Ciencias Exacta

Chacarita Project: Conformation and analysis of a modern and documented human osteological collection from Buenos Aires City - Theoretical, methodological and ethical aspects

Osteological reference collections play a key role in bioanthropological research; they allow the development and testing of methods for sexing and aging individuals using different bone and dental attributes. This paper presents the first stage results of the ongoing Chacarita Research Project, which aims to generate and study a reference collection of adult skeletons representative of the contemporary population of Buenos Aires city. The Chacarita Collection is being conformed of unclaimed human remains of individuals of known nationality, sex, age, cause and date of death from the Chacarita Public Cemetery. Unlike other similar endeavors, this sample has been completely exhumed using archaeological techniques. So far, a total of 146 adult skeletons have been recovered (60 females - 41.1% - and 86 males - 58.90% -), the majority of which have ages-at-death in the range of 71-90 years. They were born primarily in Argentina (n = 133; 91.1%), although other nationalities are also represented. Dates of death go between 1987 and 2000. In the short term, the osteological study of this collection will allow assessment of the performance of classical methods of sex determination and age-at-death estimation in a local setting. A special priority will be given to the study of osteological changes in individuals over 50 years. As the sample is being retrieved by exhumation, the impact of taphonomic agents on the most diagnostic bones structures is also being assessed. In the long term, this osteological collection will be available to generate new population-specific techniques, and to develop comparative biological studies.Fil: Bosio, L. A.. Universidad de Buenos Aires. Facultad de Medicina. Cátedra de Medicina Legal y Deontología Médica. Servicio de Antropología Forense; ArgentinaFil: García Guraieb, S.. Secretaría de Cultura de la Nación. Dirección Nacional de Cultura y Museos. Instituto Nacional de Antropología y Pensamiento Latinoamericano; ArgentinaFil: Luna, Leandro Hernan. Universidad de Buenos Aires. Facultad de Filosofía y Letras. Museo Etnográfico "Juan B. Ambrosetti"; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Aranda, C.. Universidad de Buenos Aires. Facultad de Filosofía y Letras. Museo Etnográfico "Juan B. Ambrosetti"; Argentin

Surface Induced Order in Liquid Metals and Binary Alloys

Measurements of the surface x-ray scattering from several pure liquid metals (Hg, Ga, and In) and from three alloys (Ga-Bi, Bi-In, and K-Na) with different heteroatomic chemical interactions in the bulk phase are reviewed. Surface-induced layering is found for each elemental liquid metal. The surface structure of the K-Na alloy resembles that of an elemental liquid metal. Bi-In displays pair formation at the surface. Surface segregation and a wetting film are found for Ga-Bi.Comment: 10 pages, 3 fig, published in Journal of Physics: Condensed Matte

Synthesis of easily sinterable ceramic electrolytes based on Bi-doped 8YSZ for IT-SOFC applications

Ceramic electrolytes formed by Bi (4 mol%)-doped 8YSZ, i.e., Y2O3 (8 mol%)-doped ZrO2, were synthesized by a simple co-precipitation route, using ammonia solution as precipitating agent. The amorphous as-synthesized powders convert into zirconia-based single phase with fluorite structure through a mild calcination step at 500 \ub0C. The calcined powders were sintered at very low temperatures (i.e., 900-1100 \ub0C) achieving in both cases very high values of relative densities (i.e., > 95%); the corresponding microstructures were highly homogeneous and characterized by micrometric grains or sub-micrometric grains for sintering at 1100 \ub0C and 900 \ub0C, respectively. Very interesting electrochemical properties were determined by Electrochemical Impedance Spectroscopy (EIS) in the best samples. In particular, their total ionic conductivity, recorded at 650 \ub0C, are 6.06 7 10-2S/cm and 4.44 7 10-2S/cm for Bi (4 mol%)-doped 8YSZ sintered at 1100 \ub0C and 900 \ub0C, respectively. Therefore, Bi was proved to be an excellent sintering aid dopant for YSZ, highly improving its densification at lower temperatures while increasing its total ionic conductivity

waste silica sources as heavy metal stabilizers for municipal solid waste incineration fly ash

Abstract The present work discusses a new method, based on the use of silica fume, for heavy metal stabilization. The inertization procedure is reported and compared with other technologies, involving the employ of amorphous silica as stabilizing agent for municipal solid waste incinerator fly ash treatment (i.e. colloidal silica and rice husk ash). The obtained final materials are characterized in terms of chemical composition and phase analysis. The reported method, realized at room temperature, employs all waste or by-product materials. As a consequence it appears to be economically and environmentally sustainable

Changements de phase du gallium à la pression atmosphérique

After pointing out the importance of the choice of small volume samples in the study of nucleation in liquid gallium, the authors show that homogeneous nucleation conditions are obtained at — 123 °C for droplets resulting from the emulsion of the liquid metal. The solid phase which then appears is the inetastable form Gaβ ; the free interfacial enthalpy between the liquid and a Gaβ nucleus is measured. Thèse liquid samples crystal-lise only exceptionally in the stable form Gaα but it is possible to obtain a second solid metastable form Gaγ of which some physical characteristics are determined. From their thermodynamic parameters, the forms Gaβ and Gaγ are respectively identified with the forms Ga II and Ga III, stable at high pressure. The production of these metastable forms from liquid or vapour states is proved by the Ostwald degree rule.Après avoir signalé l'importance du choix des échantillons de faible volume dans l'étude de la germination dans le gallium liquide, on montre que les conditions de la germination homogène sont réalisées vers — 123 °C pour certaines gouttelettes provenant de J'émulsion du métal liquide ; la phase solide qui apparaît est alors la forme métastable Gaβ et l'on mesure l'enthalpie libre interfaciale entre le liquide et un germe de Gaβ. Ces échantillons liquides ne cristallisent qu'exceptionnellement en la forme stable Gaα, mais on peut aussi obtenir une deuxième phase solide métastable Gaγ dont on détermine quelques propriétés physiques. Par leurs paramètres thermodynamiques, les formes Gaβ et Gaγ sont identifiées respectivement aux formes Ga II et Ga III stables à haute pression. Des considérations sur la règle des degrés d'Ostwald permettent de justifier l'obtention de ces formes métastables à partir des états liquide ou vapeur

Approach to a rational rotation number in a piecewise isometric system

We study a parametric family of piecewise rotations of the torus, in the limit in which the rotation number approaches the rational value 1/4. There is a region of positive measure where the discontinuity set becomes dense in the limit; we prove that in this region the area occupied by stable periodic orbits remains positive. The main device is the construction of an induced map on a domain with vanishing measure; this map is the product of two involutions, and each involution preserves all its atoms. Dynamically, the composition of these involutions represents linking together two sector maps; this dynamical system features an orderly array of stable periodic orbits having a smooth parameter dependence, plus irregular contributions which become negligible in the limit.Comment: LaTeX, 57 pages with 13 figure

Experimental investigation of SO2 poisoning in a Molten Carbonate Fuel Cell operating in CCS configuration

[EN] One of the most interesting innovations in the CCS (Carbon Capture and Storage) field is the use of MCFCs as carbon dioxide concentrators, feeding their cathode side (or air side) with the exhaust gas of a traditional power plant. The feasibility of this kind of application depends on the resistance of the MCFC to air-side contaminants, with particular attention to SO2. The aim of this work is to investigate the effects of poisoning when sulphur dioxide is added to the cathodic stream in various concentrations and in different operating conditions. This study was carried out operating single cells (80 cm(2)) with a cathodic feeding composition simulating typical flue gas conditions, i.e. N-2, H2O, O-2 and CO2 in 73:9:12:6 mol ratio as reference mixture. On the anodic side a base composition was chosen with H-2, CO2 and H2O in 64:16:20 mol ratio. Starting from these reference mixtures, the effect of single species on cell poisoning was experimentally investigated considering, as main parameters chosen for the sensitivity analysis, SO2 (0-24 ppm) and CO2 (4-12%) content in the cathodic feeding mixture, H-2 (40-64%) content in the anodic stream as well as the operating temperature (620-680 degrees C). Results showed that degradation caused by SO2 poisoning is strongly affected by the operating conditions. Data gathered during this experimental campaign will be used in a future work to model the poisoning mechanisms through the definition of MCFC electrochemical kinetics which take into account the SO2 effects. (C) 2016 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.The work was partly supported by H2FC European Infrastructure Project (Integrating European Infrastructure to support science and development of Hydrogen and Fuel Cell Technologies towards European Strategy for Sustain-able Competitive and Secure Energy) Theme [INFRA-2011-1.1.16.], Grant agreement 284522.Della Pietra, M.; Discepoli, G.; Bosio, B.; Mcphail, S.; Barelli, L.; Bidini, G.; Ribes-Greus, A. (2016). Experimental investigation of SO2 poisoning in a Molten Carbonate Fuel Cell operating in CCS configuration. International Journal of Hydrogen Energy. 41(41):18822-18836. https://doi.org/10.1016/j.ijhydene.2016.05.147S1882218836414