RESUMEN
Friction is the natural response of all tribosystems. In a total knee replacement (TKR) prosthetic device, its measurement is hindered by the complex geometry of its integrating parts and that of the testing simulation rig operating under the ISO 14243-3:2014 standard. To develop prediction models of the coefficient of friction (COF) between AISI 316L steel and ultra-high molecular weight polyethylene (UHMWPE) lubricated with fetal bovine serum dilutions, the arthrokinematics and loading conditions prescribed by the ISO 142433: 2014 standard were translated to a simpler geometrical setup, via Hertz contact theory. Tribological testing proceeded by loading a stainless steel AISI 316L ball against the surface of a UHMWPE disk, with the test fluid at 37⯰C. The method has been applied to study the behavior of the COF during a whole walking cycle. On the other hand, the role of protein aggregation phenomena as a lubrication mechanism has been extensively studied in hip joint replacements but little explored for the operating conditions of a TKR. Lubricant testing fluids were prepared with fetal bovine serum (FBS) dilutions having protein mass concentrations of 5, 10, 20 and 36â¯g/L. The results were contrasted against deionized, sterilized water. The results indicate that even at protein concentration as low as 5â¯g/L, protein aggregation phenomena play an important role in the lubrication of the metal-on-polymer tribopair. The regression models of the COF developed herein are available for numerical simulations of the tribological behavior of the aforementioned tribosystem. In this case, surface stress rather than film thickness should be considered.
Asunto(s)
Fricción , Ensayo de Materiales/normas , Polietilenos , Acero , Lubrificación , Estándares de Referencia , Análisis de RegresiónRESUMEN
The incorporation of aluminum acetylacetonate as alumina source during the gelation of titanium alkoxide reduces the nucleation sites for the formation of large rutile crystals on temperatures ranging from 400 to 800°C. As a result, the aggregation of anatase crystals is prevented at high temperature. A relationship among the specific surface area, pore size, energy band gap, crystalline structure and crystallite size as the most relevant parameters are evaluated and discussed. According to the results for the photocatalytic degradation of 2,4-dichlorophenoxyacetic acid, the specific surface area, pore size, Eg band gap are not determinant in the photocatalytic properties. It was found that the anatase crystallite size is the mores important parameter affecting the degradation efficiency.
Asunto(s)
Ácido 2,4-Diclorofenoxiacético/química , Óxido de Aluminio/efectos de la radiación , Herbicidas/química , Nanopartículas/efectos de la radiación , Titanio/efectos de la radiación , Óxido de Aluminio/química , Calor , Nanopartículas/química , Fotólisis , Semiconductores , Titanio/química , Rayos UltravioletaRESUMEN
Rheumatoid arthritis (RA) is the prototype of the rheumatic diseases worldwide. Methotrexate (MTX) is the drug of first choice in the treatment of this disease due to its immunosuppressant effect. However, side events are present in 30% of the patients. The C677T and A1298C polymorphisms of the methylenetetrahydrofolate reductase (MTHFR) gene are involved in the metabolism of MTX. Earlier studies reported an association between these polymorphisms and elevation of hepatic enzymes. We analyzed the frequencies of both polymorphisms and the presence of transaminasemia in 70 Mexican patients with rheumatic arthritis treated with MTX. The 19% (13/70) of patients had an increase in the serum level of transaminases. The A1298C polymorphism was associated with elevation of transaminases (P=0.024). The identification of MTHFR genotypes for C677T and A1298C polymorphisms could lead clinicians to identify patients in risk of elevation of transaminases, and give them an individualized treatment, as is a goal of pharmacogenetics.
Asunto(s)
Antirreumáticos/efectos adversos , Artritis Reumatoide/tratamiento farmacológico , Artritis Reumatoide/genética , Metotrexato/efectos adversos , Metilenotetrahidrofolato Reductasa (NADPH2)/genética , Polimorfismo Genético , Transaminasas/sangre , Antirreumáticos/farmacocinética , Artritis Reumatoide/enzimología , Artritis Reumatoide/etnología , Estudios de Casos y Controles , Distribución de Chi-Cuadrado , Frecuencia de los Genes , Genotipo , Humanos , Metotrexato/farmacocinética , Metilenotetrahidrofolato Reductasa (NADPH2)/metabolismo , México/epidemiología , Oportunidad Relativa , Farmacogenética , Fenotipo , Medicina de Precisión , Medición de Riesgo , Factores de Riesgo , Resultado del Tratamiento , Regulación hacia ArribaRESUMEN
A serologic survey in domestic animals (birds and mammals) was conducted in four communities located in the Lacandón Forest region of northeastern Chiapas, Mexico, during June 29 to July 1, 2001, with the objective to identify zoonotic arboviruses circulating in this area. We collected 202 serum samples from healthy domestic chickens, geese, ducks, turkeys, horses and cattle. The samples were tested by plaque-reduction neutralization test for antibodies to selected mosquito-borne flaviviruses (family Flaviviridae), including St. Louis encephalitis (SLE), Rocio (ROC), Ilheus (ILH), Bussuquara (BSQ), and West Nile (WN) viruses, and selected alphaviruses (family Togaviridae), including Western equine encephalitis (WEE), Eastern equine encephalomyelitis (EEE), and Venezuelan equine encephalitis (VEE) viruses. Neutralizing antibodies to SLE virus were detected in two (8%) of 26 turkeys, 15 (23%) of 66 cattle, and three (60%) of five horses. Antibodies to VEE virus were detected in 29 (45%) of 65 cattle. Because some of these animals were as young as 2 months old, we demonstrated recent activity of these two viruses. Sub-typing of the VEE antibody responses indicated that the etiologic agents of these infections belonged to the IE variety of VEE, which has been reported from other regions of Chiapas. WN virus-neutralizing antibodies were detected in a single cattle specimen (PRNT(90) = 1:80) that also circulated SLE virus-neutralizing antibodies (PRNT(90) = 1:20), suggesting that WN virus may have been introduced into the region. We also detected weak neutralizing activity to BSQ virus in four cattle and a chicken specimen, suggesting the presence of this or a closely related virus in Mexico. There was no evidence for transmission of the other viruses (ROC, ILH, EEE, WEE) in the study area.
Asunto(s)
Animales Domésticos/virología , Infecciones por Arbovirus/epidemiología , Infecciones por Arbovirus/veterinaria , Arbovirus/aislamiento & purificación , Zoonosis/epidemiología , Animales , Infecciones por Arbovirus/sangre , Bovinos , Culicidae/virología , Recolección de Datos , Caballos/virología , Insectos Vectores/virología , México/epidemiología , Pruebas de Neutralización , Aves de Corral/virología , Zoonosis/virologíaRESUMEN
OBJECTIVE: To analyze the bacteriological quality of drinking water (BQDW) and its association with diarrhoea and intestinal parasites in children 1 to 14 years old, in areas of high levels of poverty in Chiapas, Mexico. MATERIAL AND METHODS: From March to September 1998, drinking water was collected from a random sample of 99 households in the Border Region of Chiapas, Mexico; data on diarrhoeal disease (in the past 15 days) were collected and stool testing for intestinal parasites was performed in children 1 to 14 years old (n = 322). The BQDW was determined by the filtration membrane technique. Intestinal parasitic infections were determined by the Faust Method. The chi 2 statistic was used to analyse factors associated with BQDW. RESULTS: Only 31% of the water samples were adequate for human consumption. The BQDW and the presence of diarrhoea (informed by the mothers of the children) showed no association. Children living in households with inadequate BQDW had a higher prevalence of Entamoeba histolytica and a greater tendency to have intestinal parasites. CONCLUSIONS: It is necessary to develop programs that improve BQDW and to develop education efforts aimed at increasing the use of boiled water and the adequate management and care of community water storage sites.