Comportamiento del polietileno en un simulador de cadera

Se presentan los resultados del comportamiento friccional de cinco diferentes combinaciones de cabezas protésicas femorales y polietileno acetabular, investigadas en un simulador de cadera. Las cabezas femorales de aleaciones de Cr-Co-Mo, Cr-Co-Mo con implantación iónica y de cerámica de zirconia, se articularon con cotilos de polietileno de ultra-alto-peso molecular y se sometieron a tres millones de ciclos de marcha cada uno, utilizando un simulador de cadera de cinco estaciones. El desgaste de los cotilos protésicos, evaluado por mediciones gravimétricas demostró que cuando el espesor de polietileno era de 10,9 mm el desgaste producido por cabezas de Cr-Co-Mo de 28 mm era de 0,14 mm/año y de 0,09 mm/año si la cabeza utilizada era de 28 mm de aleación de Cr-Co- Mo con implantación iónica. Cuando el espesor del acetábulo era de 7 mm el desgaste ocasionado por cabezas de cerámica de zirconia de 28 mm fue de 0,04 mm/año; sin embargo si tenía espesor 10,9 mm y las cabezas de cerámica de zirconia eran de 28 y 32 mm, no aparecía desgaste alguno. Estos resultados indican que el diámetro de la cabeza de cerámica de 28 y 32 mm, parece no tener importancia alguna, pero sí la tiene el que el espesor del acetábulo protésico sea menor de 10 mm.Ultra high molecular weight polyethylene (UHMWPE) metal backed acetabular cups were articulated against Cr-Co-Mo alloy, ion implanted Cr-Co-Mo and zirconia ceramic femoral heads in a five station hip joint simulator, running three tests of three millions walking cycles with each one of the five different head-cup combinations. The wear rate of the acetabular cups was measured gravimetrically. When the thickness of the cup was 10.9 mm, the mean wear rate against 28 mm diameter Cr-Co-Mo femoral heads was 0.14 mm/year, and 0.09 mm/year 'when the cup was articulated against 28 mm ion implanted Cr-Co-Mo femoral heads. When the thickness of the cup was 7 mm the mean wear rate was 0.04 mm/year against 28 mm zirconia heads. The results indicate that significant reduction in the wear of the UHMWPE cup can be achieved when zirconia femoral head is used and that the diameter of the zirconia femoral head, 28 vs 32 mm, seems unimportant as wear factor. A cup thickness below 10 mm may result disadvantageous

Estallido de la cabeza de cerámica en 1 prótesis total de cadera cementada

Se describen las características clínicas y quirúrgicas de 1 caso de estallido de la cabeza de cerámica en 1 artroplastia total de cadera cementada tipo Weller. A los 6 años y 2 meses de su implante requirió nueva intervención quirúrgica para sustituir el componente dañado. Describimos las posibles causas de esta complicación en base a la literatura revisada. El interés del caso estriba en la rareza de su presentación y en la conservación de la prótesis sustituyendo solamente el núcleo cefálico dañado.The clinical and surgical characteristics of one case of breakage of the ceramic head in a Weller cemented hip arthroplasty is described. The patient needed revision surgery six years and two months after the primary arthroplasty in order to replace the demaged component of the implant. The possible reasons of this complication, according to a literature review, are discussed. The interest of this clinical case is the rare of its presentation, its cause and the surgical solution that allow preservation of the prosthesis, doing exclusively the replacement of the damaged part of the implant

Control and synchronization algorithms for a grid-connected photovoltaic system under harmonic distortions, frequency variations and unbalances

In this paper, an implementation of the control and the synchronization algorithms for a Voltage Source Inverter used as the power conditioner for Photovoltaic renewable energy in a grid-connected structure is carried out. Its main purpose is to show, in a simple manner, the design and combined operation of the control and synchronization algorithms for attaining the proper behaviour of the Grid Inverter when the 3-phase utility grid is disturbed by voltage unbalances, frequency variations and harmonic distortions, according to power quality standards. In order to obtain a high efficiency of the system during perturbations, a Proportional Resonant controller with a Harmonic Compensator structure is designed for the control algorithm, whereas a Dual Second Order Generalized Integrator Frequency-Locked Loop (DSOGI-FLL) is used as the synchronization algorithm. In order to validate both the control and the synchronization algorithms, some simulations using MATLAB/SIMULINK from The MathWorks, Inc. are shown firstly, and secondly, some real-time digital simulations are carried out.This work has been supported by a grant from La Fundación Séneca, Agencia de Ciencia y Tecnología de la Región de Murcia, Spain, as a part of the Project Ref.11948/PI/09, entitled “Design and construction of a hardware/software prototype for the synchronization and monitoring of renewable agents in a Distributed Generation System” (Alexis. B. Rey-Boué), and a scholarship towards the PhD degree from the Universidad Politécnica de Cartagena, Spain, with the Santander Bank support (N. F. Guerrero-Rodríguez)

Calculation of the number of modules and the switching frequency of a modular multilevel converter using near level control

This paper is focused on the modular multilevel converter (MMC) topology that uses the near level control (NLC) method. Specifically, it addresses the relationship between the number of levels or switching modules, the switching frequency and the harmonics superimposed on the generated voltages and currents, making a comparison with the high and medium voltage AC codes. Furthermore, it also assesses the possibility of connecting the MMC to the electrical grid without using any coupling inductor, either using a transformer or simply directly. Finally, it shows how to automate the simulations necessary to select the number of levels and the switching frequency.This work has been partially supported by a grant from the Spanish Government as a part of Project Ref. TEC2016-80136-P, entitled “Nuevas topologías para convertidores en MT para grandes Instalaciones Fotovoltaicas” (A. B. Rey-Boué)

Enhanced controller for grid-connected modular multilevel converters in distorted utility grids

This paper is about the control of Modular multilevel converters, an innovative technology in the design of converters, which is beginning to be included in real installations. Papers about this topic include simulation models, circulating current reduction, voltage modulators, capacitor voltage balancing and control issues. The scheme for current source regulation used in this article includes all control loops, which are, from the outermost to innermost, DC bus voltage regulator, current regulator, voltage modulator, capacitor voltage balancing, and a PLL for the synchronization to the grid. Disposition-sinusoidal pulse width modulation is used as the voltage modulator, and an enhanced control strategy in the stationary reference frame for 3-phase MMCs is used for the inner current control loops. Very detailed simulations of the complete control system have been performed for both the enhanced control strategy in the stationary reference frame, and the well-known control in the synchronous reference frame, as well as some experiments using the hardware-in-the-loop simulation technique. The validation of these control strategies is made by a comparison of the capability of each one to compensate the harmonic distortions of the utility grid according to the grid code. The correct operation has been tested in the case of a strong/weak grid, unbalances and grid failures.This work has been partially supported by a grant from the Spanish Government as a part of 673 Project Ref. TEC2016-80136-P, entitled “Nuevas topologías para convertidores en MT para grandes 674 Instalaciones Fotovoltaicas” (A. B. Rey-Boué

Efficacy and safety comparison of two amoxicillin administration schedules after third molar removal. A randomized, double-blind and controlled clinical trial

Objective: The aim of this comparative double-blind, prospective, randomized, clinical trial was to evaluate two amoxicillin administration patterns. The first was a short prophylactic therapy and the second a long postoperative regimen. Study Design: The study population consisted of 160 patients who underwent mandibular third molar extraction. Patients were randomized into two equal groups. In group 1, 2 grams of amoxicillin were administered 1 hour before the procedure and 1 gram 6 hours after surgery. In group 2, patients received 1 gram of amoxicillin 6 hours after surgery followed by 1 gram every 8 hour for 4 days. All patients received the same number of tablets thanks to the use of placebo pills. A total of 25 variables were evaluated, such as alveolitis, surgical infection, number of analgesic needed, subjective pain scale, post-surgical inflammation, consistency of the diet, axillary temperature and millimetres of mouth opening loss after the surgery. Results: No statistically significant post-operative differences were found within the recorded parameters between the groups. Conclusions: Postoperative 4-days amoxicillin therapy is not justified

La prótesis de cadera con recubrimiento de vidrio Primeros resultados con 2 años de evolución

El presente trabajo analiza los primeros resultados clínicos y radiográficos de un estudio con la prótesis de cadera no cementada con recubrimiento «de vidrio» a nivel metafísario (prótesis CRM). La casuística comprende 80 artroplastias totales implantadas desde 1991 a 1994 con un seguimiento mínimo de 2 años. La evolución clínica, valorada según el sistema de Harris modificado, ha sido satisfactoria en el 90% de los enfermos. La observación radiográfica ha mostrado buena fijación y orientación de los componentes femorales en 72 casos. La conclusión de este análisis preliminar permite apreciar que el recubrimiento protésico con cerámica de vidrio supone un mecanismo de seguridad en la fijación primaria y secundaria de la prótesis de cadera.This work analizes the first clinical and radiological results of a cementless hip prosthesis with glass coating at metaphyseal level (CRM prosthesis). A total of 80 arthroplasties implanted since may 1991 to 1994 were studied with a two year follow-up. The clinical assesment was done by the modified Harris score, being satisfactory in 90% of the patients. The radiological study demonstrated good fixation and orientation of the prosthetic compounds in 72 cases. The prosthetic model studied provides a security mechanism both for primary and secondary fixation of the femoral stem and acetabular cup

Inmunodiagnóstico de la infección chagásica por ELlSA

Demonstration of the infectious agent is the gold standard in parasitic infections but this is not always feasible.Thus diagnosis is confirmed through Trypanosoma cruziantibody detection (in the case of Chagas'disease) by using serological assays. In this study the enzyme immunoassay (ELISA) for the diagnosis of Trypanosoma cruz; infection was standardised and assessed. 595 serum samples taken from people coming from the endemic area of Guateque, Boyaca, were tested against T. cruziepimastigotes from the IRHOlCOl69lGuateque Colombian strain, using both the immunofluorescent antibody test (IFAT) and the ELlSA test. Analysis of the ELlSA test's validity was done through estimation of the area under the receptor-operator curve (ROC). The optimum conditions for the ELlSA test were an antigen concentration of 0.75 ygrlml and sample dilution of 1:1000. The assay's sensitivity for cut-off points of 0.2, 0.3, 0.4 and 0.5 was 0.99, 0.99, 0.98 and 0.93 and its specificity for the same cut-off points was 0.94, 0.96, 0.98 and 0.98.The ELlSA test is a valid and useful test, not only because of its sensitivity and specificity but also because the estimation of the area under the receptor-operator curve (ROC) was 0.9952, this being very close to the ideal. The ELlSA test is better than the IFAT test for detection of Trypanosoma cruzi infection antibodies and could be used in seroepidemiological sur'veys in areas of moderate to high prevalence.La demostración del agente infeccioso es la regla de oro en las parasitosis, pero, esto no siempre es factible. Por ello, en la infección chagásica ce recurre a la detección de anticuerpos contra Trypanosoma cruzi siendo las pruebas serodiagnósticas de gran utilidad. El presente estudio estandarizó y evaluó la prueba inmunoenzimática Elisa para el inmunodiagnóstico de la infección chagásica. Se confrontaron 595 muestras de suero de pacientes provenientes de Guateque, Boyacá, zona endémica de la enfermedad de Chagas, con epimastigotes de Tcruzide la cepa colombiana IRHOICO/69/Guateque utilizando las pruebas inmunodiagnósticas de inmunofluorescencia indirecta (IFI), prueba de referencia, y el ensayo inmunoenzimático ELISA. El análisis de la validez de ésta se realizó mediante el cálculo del área bajo la curva del operador receptor (ROC) como medida de la exactitud (validez). Las condiciones óptimas de la prueba ELlSA fueron: antígeno 0,75 pglml y dilución de la muestra 1:1.000. El ensayo del estudio según los puntos de corte 0,2, 0,3, 0,4 y 0,5 ofrece una sensibilidad de 0,99, 039, 0,98 y 0,93 y una especificidad de 0,94, 0,96, 0,98 y 0,98, respectivamente. El ELlSA del estudio se muestra como una prueba válida no sólo por la sensibilidad y especificidad sino porque el análisis del área bajo la curva ROC fue de 0,9952 que es muy cercano al ideal. La prueba de ELlSA es superior a la de IFI para la detección de anticuerpos contra 1 cruzi y podría ser utilizada en estudios seroepidemiológicos en zonas de alta y moderada prevalencia

Evaluating the thermal performance of Wet Swales housing Ground Source Heat Pump elements through laboratory modelling

The authors wish to acknowledge the CAWR, Coventry University, for the administrative support; and the GITECO Research Group, University of Cantabria, for housing the laboratory experiments.Land-use change due to rapid urbanization poses a threat to urban environments, which are in need of multifunctional green solutions to face complex future socio-ecological and climate scenarios. Urban regeneration strategies, bringing green infrastructure, are currently using sustainable urban drainage systems to exploit the provision of ecosystem services and their wider benefits. The link between food, energy and water depicts a technological knowledge gap, represented by previous attempts to investigate the combination between ground source heat pump and permeable pavement systems. This research aims to transfer these concepts into greener sustainable urban drainage systems like wet swales. A 1:2 scaled laboratory models were built and analysed under a range of ground source heat pump temperatures (20–50 ºC). Behavioral models of vertical and inlet/outlet temperature difference within the system were developed, achieving high R2, representing the first attempt to describe the thermal performance of wet swales in literature when designed alongside ground source heat pump elements. Statistical analyses showed the impact of ambient temperature and the heating source at different scales in all layers, as well as, the resilience to heating processes, recovering their initial thermal state within 16 h after the heating stage