Thin-Film Composite Matrimid-Based Hollow Fiber Membranes for Oxygen/Nitrogen Separation by Gas Permeation.

In recent years, the need to reduce energy consumption worldwide to move towards sustainable development has led many of the conventional technologies used in the industry to evolve or to be replaced by new alternatives. Oxygen is a compound with diverse industrial and medical applications. For this reason, obtaining it from air is one of the most interesting separations, traditionally performed by cryogenic distillation and pressure swing adsorption, two techniques which are very energetically expensive. In this sense, the implementation of membranes in a hollow fiber configuration is presented as a much more efficient alternative to carry out this separation. The aim of this work is to develop cost-effective multilayer hollow fiber composite membranes made of Matrimid and polydimethylsiloxane (PDMS) for the separation of oxygen and nitrogen from air. PDMS is used as a cover layer but can also enhance the performance of the membrane. In order to compare these two materials, three different configurations are studied. First, integral asymmetric Matrimid hollow fiber membranes were produced using the spinning method. Secondly, by using dip-coating method, a PDMS dense selective layer was deposited on a self-made polyvinylidene fluoride (PVDF) hollow fiber support. Finally, the performance of a dual-layer hollow fiber membrane of Matrimid and PDMS was studied. Membrane morphology was characterized by SEM and separation performance of the membranes was evaluated by mixed-gas permeation experiments. The novelty presented in this work is the manufacture of hollow fiber membranes and the way Matrimid is treated. This makes it possible to develop much thinner dense layers than in the case of flat-sheet membranes, which leads to higher permeance values. This is a key factor when implementing this technology on an industrial scale. Membranes prepared in this work were compared to the current state of the art, reporting quite good performance for the dual-layer membrane, reaching O2 permeance of 30.8 GPU and O2/N2 selectivity of 4.7, with a thickness of about 5-10 µm (counting both selective layers). In addition, the effect of operating temperature on the membrane permeances has been studied experimentally; we analyze its influence on the selectivity of the separation process.

Hydrogen Recovery from Coke Oven Gas. Comparative Analysis of Technical Alternatives.

The recovery of energy and valuable compounds from exhaust gases in the iron and steel industry deserves special attention due to the large power consumption and CO2 emissions of the sector. In this sense, the hydrogen content of coke oven gas (COG) has positioned it as a promising source toward a hydrogen-based economy which could lead to economic and environmental benefits in the iron and steel industry. COG is presently used for heating purposes in coke batteries or furnaces, while in high production rate periods, surplus COG is burnt in flares and discharged into the atmosphere. Thus, the recovery of the valuable compounds of surplus COG, with a special focus on hydrogen, will increase the efficiency in the iron and steel industry compared to the conventional thermal use of COG. Different routes have been explored for the recovery of hydrogen from COG so far: i) separation/purification processes with pressure swing adsorption or membrane technology, ii) conversion routes that provide additional hydrogen from the chemical transformation of the methane contained in COG, and iii) direct use of COG as fuel for internal combustion engines or gas turbines with the aim of power generation. In this study, the strengths and bottlenecks of the main hydrogen recovery routes from COG are reviewed and discussed.

Kinetic Assessment of Mechanical Properties of a Cellulose Board Aged in Mineral Oil and Synthetic Ester.

In oil-immersed power transformers, the insulation system is constituted of a dielectric oil-solid combination. The insulation oil generally used is mineral oil; however, this fluid has started to be substituted by natural and synthetic esters due to their higher biodegradability and flash point. The introduction of a new fluid in the insulation system of power transformers requires kinetic models that can estimate the degradation rate of insulation solids. The aim of this work was to go further in quantifying through different kinetic models the deterioration suffered by a commercial cellulose board (PSP 3055), which is one of the solid materials used in the insulation system of oil-filled transformers. The aging study was extended to cellulose board specimens immersed in two different oils (mineral and synthetic ester). It was obtained that there is a lower degradation when synthetic ester is used in the insulation system. Additionally, it can be concluded that the use of mechanical properties to quantify the degradation of the cellulose board through kinetic models provides information about the different behavior shown by PSP 3055 when different fiber direction angles are considered.

Experimental dataset on the tensile and compressive mechanical properties of plain Kraft and crepe papers used as insulation in power transformers after ageing in mineral oil.

The solid insulation in the windings of power transformers, which generally consists of oil-impregnated thin paper, is one of the key elements for the performance and durability of these electrical machines. Insulation paper is subjected to static and dynamic forces of electromagnetic origin, in combination with high temperatures and chemical reactions, during the operating life of a power transformer. The mechanical properties of the cellulosic insulation are relevant parameters because its breakage could result in the electric failure of the transformer. Indeed, paper manufacturers usually provide values of the tensile strength and elongation at breakage of the insulating paper in its two principal material directions, the MD (machine direction) and CD (cross-direction). However, paper is a highly anisotropic material and its material properties evolve as the paper insulation ages. The paper insulation in an operating transformer is subjected to a multiaxial stress state field including compressive and shear stresses. This article reports experimental data on the tensile and compressive mechanical properties of two types of paper, plain Kraft and crepe paper, typically used as insulation in power transformers, under different ageing states (which were induced through accelerated thermal ageing and quantified by means of the degree of polymerisation). These data could be reused for several purposes. They can improve the current understanding of the mechanical response and degradation processes of the cellulosic insulation in power transformers, and give some reference values that can be compared with others obtained in the factory by manufacturers. In the field of engineering failure analysis, those values could be reused for the assessment of mechanical failure of paper materials used in power transformers, see [1].

Plataforma para el registro de nefrolitotomía percutánea interinstitucional / Platform for the registration of inter-institutional percutaneous nephrolithotomy

Desde la primera introducción de la nefrolitotomía percutánea (NLP) por Fernstrom y su popularización en EE. UU. por Smith, la NLP se ha convertido en el estándar de oro para pacientes con cálculos renales de gran tamaño.1 Las opciones actuales para el tratamiento de cálculos renales son: la litotripcia extracorpórea, la ureterorrenoscopia flexible y la NLP, escogiendo cada una según el tamaño del cálculo, la anatomía del sistema colector, las características del paciente y las preferencias del especialista.2 Para cálculos piélicos o de cáliz superior mayores de 2 cm o para cáliz inferior mayores de 1,5 cm, se prefiere la NLP.2

Since the first introduction of percutaneous nephrolithotomy (PNL) by Fernstrom and its popularization in the US by Smith, PNL has become the gold standard for patients with large kidney stones.1 Current options for the treatment of kidney stones include extracorporeal lithotripsy, flexible ureterorenoscopy, and PNL, each chosen according to the size of the stone, the anatomy of the collecting system, the patient's characteristics, and the specialist's preferences.2 For upper calyx or skin stones larger than 2 cm or for lower calyx larger than 1.5 cm, PNL is preferred.2

Hand hygiene technique quality evaluation in nursing and medicine students of two academic courses / Avaliação da qualidade da técnica de higiene das mãos em alunos de enfermagem e medicina em dois cursos de graduação / Evaluación de la calidad de la técnica de higiene de manos en alumnos de enfermería y medicina en dos cursos académicos

AbstractObjective: because they are health professionals, nursing and medical students' hands during internships can function as a transmission vehicle for hospital-acquired infections.Method: a descriptive study with nursing and medical degree students on the quality of the hand hygiene technique, which was assessed via a visual test using a hydroalcoholic solution marked with fluorescence and an ultraviolet lamp.Results: 546 students were assessed, 73.8% from medicine and 26.2% from nursing. The area of the hand with a proper antiseptic distribution was the palm (92.9%); areas not properly scrubbed were the thumbs (55.1%). 24.7% was very good in both hands, 29.8% was good, 25.1% was fair, and 20.3% was poor. The worst assessed were the male, nursing and first year students. There were no significant differences in the age groups.Conclusions: hand hygiene technique is not applied efficiently. Education plays a key role in setting a good practice base in hand hygiene, theoretical knowledge, and in skill development, as well as good practice reinforcement.

ResumoObjetivo:assim como as mãos dos professionais de saúde, as mãos dos estudantes de Enfermagem e Medicina durante os estágios clínicos podem funcionar como veículo de transmissão das infecções hospitalares.Método:estudo descritivo com estudantes de Graduação em Enfermagem e Medicina. Avaliou-se a qualidade da técnica de higiene das mãos por meio de prova visual a partir de solução hidro-alcoólica marcada com fluoresceína e lâmpada de luz ultravioleta.Resultados:avaliaram-se 546 alunos, 73,8% da Graduação em Medicina e 26,2% da Enfermagem. As áreas das mãos com correta distribuição de sabão foram as palmas (92,9%); as áreas não esfregadas corretamente foram os polegares (55,1%). Em ambas as mãos, a higienização foi muito boa em 24,7%, boa em 29,8%, regular em 25,1% e má em 20,3%. Os piores foram: os homens, os estudantes de Enfermagem e os estudantes do primeiro ano de escola. Não houve diferenças significativas por idade.Conclusões:a técnica de higiene de mãos não foi realizada de modo eficaz. O papel educativo é fundamental para sedimentar as bases de boas práticas na higienização das mãos, em conhecimentos teóricos e no desenvolvimento de habilidades e reforço de boas práticas.

ResumenObjetivo:al igual que los profesionales sanitarios, las manos de los estudiantes de enfermería y medicina durante las estancias clínicas pueden funcionar como vehículo de trasmisión de las infecciones nosocomiales.Método:estudio descriptivo con estudiantes de Grado de Enfermería y de Medicina. Se evaluó la calidad de la técnica de la higiene de manos por prueba visual con solución hidroalcohólica marcada con fluoresceína y lámpara de luz ultravioleta.Resultados:se evaluó a 546 alumnos, Grado de Medicina 73,8% y 26,2% de Enfermería. Las zonas de las manos con una correcta distribución de desinfectante fueron las palmas (92,9%); las no frotadas correctamente fueron los pulgares (55,1%). En ambas manos fue muy buena en el 24,7%, buena en el 29,8%, regular en 25,1% y mala en 20,3%. Los peores han sido: los hombres, los estudiantes de enfermería y los de primer año de estudio. No hubo diferencias significativas por edad.Conclusiones:no se realizó la técnica de higiene de manos de una manera eficaz. El papel de la educación es fundamental para sentar las bases de buenas prácticas en higiene de manos, en conocimientos teóricos y en el desarrollo de habilidades y el refuerzo de buenas prácticas.

Necrobiosis lipoídica: reporte de un caso / Necrobiosis lipoidica: a case report

Presentamos un paciente femenino con necrobiosis lipoídica no relacionada a diabetes mellitus. Los mecanismos etiopatogénicos son aún poco entendidos y la respuesta a las diversas modalidades de tratamiento es inconstante

Enfermedad de Behcet / Behcet disease

Presentamos un paciente masculino con enfermedad de Behçet mucocutánea. Hacemos hincapié en la dificultad diagnóstica y revisamos brevemente las alternativas terapéuticas