Estimación de esfuerzos inducidos durante el llenado y vaciado de silos metálicos para almacenamiento de cemento

The present article show the structural analysis realized to metallic silo for storage cement through of the parametric model development in the finite element software ASNYS APDL, the fill and discharge pressures applied on the silo wall is determined with the Eurocode normative EN 1991-4.The model is development with type shell elements allowing that the structure silo fits to the cylindrical and conical geometric of the silo. It explains each of the phases having the development of the model and is made a detailed analysis of the results delivered by the software; different models are evaluated changing the sheet thickness for select the most appropriate. Also the results are analyzed when be changing the tilting the hopper and is reviewed the behavior of the silo when is analyzed with its structure. © The author; licensee Universidad Nacional de Colombia

Molecular diversity of arbuscular mycorrhizal fungi in onion roots from organic and conventional farming systems in the Netherlands

Diversity and colonization levels of naturally occurring arbuscular mycorrhizal fungi (AMF) in onion roots were studied to compare organic and conventional farming systems in the Netherlands. In 2004, 20 onion fields were sampled in a balanced survey between farming systems and between two regions, namely, Zeeland and Flevoland. In 2005, nine conventional and ten organic fields were additionally surveyed in Flevoland. AMF phylotypes were identified by rDNA sequencing. All plants were colonized, with 60% for arbuscular colonization and 84% for hyphal colonization as grand means. In Zeeland, onion roots from organic fields had higher fractional colonization levels than those from conventional fields. Onion yields in conventional farming were positively correlated with colonization level. Overall, 14 AMF phylotypes were identified. The number of phylotypes per field ranged from one to six. Two phylotypes associated with the Glomus mosseae-coronatum and the G. caledonium-geosporum species complexes were the most abundant, whereas other phylotypes were infrequently found. Organic and conventional farming systems had similar number of phylotypes per field and Shannon diversity indices. A few organic and conventional fields had larger number of phylotypes, including phylotypes associated with the genera Glomus-B, Archaeospora, and Paraglomus. This suggests that farming systems as such did not influence AMF diversity, but rather specific environmental conditions or agricultural practice

Lignin particles for multifunctional membranes, antioxidative microfiltration, patterning and 3D structuring

This document is the Accepted Manuscript version of a Published Work that appeared in final form in ACS Applied Materials & Interfaces, copyright © American Chemical Society after peer review and technical editing by the publisher. To access the final edited and published work see https://doi.org/10.1021/acsami.9b16931We introduce a new type of particle-based membrane based on the combination of lignin particles (LPs) and cellulose nanofibrils (CNF), the latter of which are introduced in small volume fractions to act as networking and adhesive agents. The synergies that are inherent to lignin and cellulose in plants are re-engineered to render materials with low surface energy (contact angle measurements) and can be rendered water-resistant with the aid of wet-strength agents (WSAs). Importantly, they are most suitable for antioxidative separation (ABTS•+ radical inhibition): membranes with uniform porous structures (air permeability and capillary flow porosimetry) allow effluent oxidation at 95 mL/cm2, demonstrating, for the first time, the use of unmodified lignin particles in flexible membranes for active microfiltration. Moreover, the membranes are found to be nonfouling (protein adhesion and activity rate). The inherent properties of lignin, including UV radiation blocking capacity (UV transmittance analysis) and reduced surface energy, are further exploited in the development of tailorable and self-standing architectures that are almost entirely comprised of nonbonding LP (solids content as high as 92 w/w%). Despite such composition, the materials develop high toughness (oscillatory dynamic mechanical analysis), owing to the addition of minor amounts of CNF. Multifunctional materials based on thin films (casting), 3D structures (molding), and patterned geometries (extrusion deposition) are developed as a demonstration of the potential use of lignin particles as precursors of new material generation. Remarkably, our observations hold for spherical LPs since a much poorer performance was observed after using amorphous powder, indicating the role of size and shape in related applicationsPostprint (author's final draft

Aproximación ontosemiótica de prácticas de aula sobre la medida en educación primaria

En este trabajo se presenta un estudio exploratorio sobre prácticas de aula, relacionadas con las magnitudes longitud, tiempo y masa, llevadas a cabo en Educación Primaria en Portugal. El estudio fijó como objetivos determinar qué objetos y procesos matemáticos están implicados en esas prácticas y qué funciones ejecutan profesor y alumnos durante la realización de las mismas. Los resultados han evidenciado el predominio del conocimiento procedimental y algorítmico y el uso de situaciones extramatemáticas o de la vida cotidiana. El profesor es el gestor sistemático del trabajo de los alumnos así como de los tiempos, espacios y materiales disponibles en el aula

Cartografía Corológica Ibérica.

Sin resume

Alternative chemo-enzymatic treatment for homogeneous and heterogeneous acetylation of wood fibers

A new chemo-enzymatic treatment is proposed to produce cellulosic fibers suitable for heterogeneous- or homogeneous-phase acetylation. The procedure included enzymatic (laccase–violuric acid) lignin removal from the precursor fibers (unbleached sulfite pulp) followed by hydrogen peroxide treatment. An optional intermediate stage included partial hydrolysis (endoglucanase) to increase fiber reactivity. The obtained ‘‘biobleached’’ fibers were acetylated in the heterogeneous phase with acetic anhydride in nonpolar solvents, yielding various acetyl group contents, depending on the severity of the reaction. The degree of acetylation was highly sensitive to the treatment conditions, mainly the acetic anhydride activity in the system. The results were compared to those obtained after acetylation of commercial, dissolving-grade fibers, used as reference. The effect of the inherent nature of the fibers tested were elucidated as far as hemicellulose content, fiber length, fine content and crystallinity. Acetyl group content of up to 24% were determined after heterogeneous reaction with the chemoenzymatic fibers. The substitution of hydroxyl groups by acetyl moieties resulted in a lower hydrophilicity, as assessed by measurement of the water contact angle. Homogeneous acetylation of the chemo-enzymatic and reference fibers resulted in relatively similar acetyl group content (up to 36 and 33%, respectively). These samples were soluble in acetone and produced transparent films (via solvent casting), with enhanced dry strength and lower hydrophilicity. Overall, it is concluded that the proposed chemo-enzymatic treatment is a feasible alternative for the production of fibers that are suitable for efficient acetylationPostprint (author's final draft

Laryngeal Involvement of Multiple Myeloma

The objectives of this paper are to discuss a rare cause of laryngeal multiple myeloma, to review unique pathologic findings associated with plasma cell neoplasms, to discuss epidemiology, differential diagnosis, and treatment options for plasma cell neoplasms of the larynx. Laryngeal multiple myeloma, also noted in the literature as “metastatic” multiple myeloma, presenting as a de novo laryngeal mass is extremely rare with few reported cases. Laryngeal involvement of extramedullary tumors is reported to be between 6% and 18% with the epiglottis, glottis, false vocal folds, aryepiglottic folds, and subglottis involved in decreasing the order of frequency. We present the case of a 58-year-old male with a history of IgA smoldering myeloma who presented to a tertiary care laryngological practice with a two-month history of dysphonia, which was found to be laryngeal involvement of multiple myeloma. We review the classification of and differentiation between different plasma cell neoplasms, disease workups, pathologic findings, and treatment options

Cellulose acetate films from chemo-enzymatic dissolving pulps

The purpose of this work is to obtain dissolving cellulose fibers that are suitable for the manufacturing of cellulose derivatives. Therefore, the combination of enzymatic and chemical treatments during the bleaching stage (lignin removal) and purification stage (hemicellulose removal) is proposed. The obtained dissolving cellulose was submitted to acetylation reactions, and then acetate films were prepared as an example of end product. Assessing the quality of acetate films, it was concluded that dissolving cellulose fibers had good properties and fulfilled the quality requirements. These satisfactory results were compared with acetate films obtained under same acetylation conditions, but the dissolving cellulose fibers used as a raw material came from a conventional and industrial process.This publication is part of the PID2020-114070RB-I00 (CELLECOPROD) project, funded by MCIN/AEI/10.13039/501100011033. O.J.R. acknowledges funding support by the Academy of Finland through its Center of Excellence Program (2014–2019) “Molecular Engineering of Biosynthetic Hybrid Materials Research”.Peer ReviewedPostprint (published version

Studying the effects of laccase treatment in a softwood dissolving pulp: cellulose reactivity and crystallinity

An enzymatic biobleaching sequence (LVAQPO) using a laccase from Trametes villosa in combination with violuric acid (VA) and then followed by a pressurized hydrogen peroxide treatment (PO) was developed and found to give high bleaching properties and meet dissolving pulp requirements: high brightness, low content of hemicellulose, satisfactory pulp reactivity, no significant cellulose degradation manifested by a-cellulose and HPLC, and brightness stability against moist heat ageing. The incorporation of a laccase–mediator system (LMS) to bleach sulphite pulps can be a good alternative to traditional bleaching processes since thermogravimetric analysis (TGA) showed that the laccase treatment prevented the adverse effect of hydrogen peroxide on fibre surface as observed during a conventional hydrogen peroxide bleaching treatment (PO). Although VA exhibited the best results in terms of bleaching properties, the performance of natural mediators, such as p-coumaric acid and syringaldehyde, was discussed in relation to changes in cellulose surface detected by TGAPostprint (author’s final draft

Trabeculectomy, still today’s surgical choice : observational descriptive study in San Ignacio’s University Hospital in Bogota

Introducción: el glaucoma es una enfermedad del nervio óptico de carácter crónico y progresivo que constituye un problema epidemiológico serio, ya que es responsable de la segunda causa de ceguera irreversible en el mundo. Existen diferentes modalidades de tratamiento, entre ellos medicamentos, láseres y cirugías. La trabeculectomía es el procedimiento quirúrgico de elección en el paciente adulto cuando la terapia médica y los procedimientos con láser fracasan en detener esta neuropatía óptica.Objetivo: analizar una serie de pacientes sometidos a trabeculectomía en el Hospital San Ignacio entre el 2005 y el 2011.Conclusión: los resultados, a pesar de ser una serie pequeña de pacientes, nos permiten afirmar que dicha cirugía continúa siendo una buena alternativa en el control de la presión intraocular y, por consiguiente, en la progresión del daño glaucomatoso sobre el nervio óptico.278-285Introduction: Glaucoma is a progressive and chronic optic neuropathy being the second cause of irreversible blindness worldwide. Several approaches are used to try to avoid this course, being the Trabeculectomy the surgical choice in the adult patient. Objetive: To analyze a cohort of patients that had trabeculectomy between 2005 and 2011 in San Ignacio’s University Hospital. Conclusion: Although is a small cohort of patients it enables us to confirm that this surgery is a good choice in the control of the intraocular pressure in order to avoid further damage to the optic nerve