Radial fretting is defined as the damage caused by the relative motion of a ball under a variable normal load. The conducted experimental tests proved the existence of this damage even in contacting ...bodies with similar materials and elastic properties; however, the reviewed analytical methods do not predict damage under these conditions, and the numerical methods are time-consuming, especially when the investigation requires the analysis of several loading cases or during large number of cycles. The main objective of this work was to develop a fast analytical method to analyse radial fretting wear. For this purpose, a novel formulation for contact displacements under a normal variable load was built and merged to different contact mechanic formulas. For validation purposes, false brinelling in thrust bearings was used as a representative industrial example. The results were compared with a FEM model showing a relative difference under 9% and a massive reduction of the calculation time of more than 30 000 times, moreover experimental tests were carried out, showing a good agreement between the density of friction energy and the obtained fretting damage what endorse the use of this formulation for the analysis of a large number of cycles and loading cases.
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•An analytical new formulation for radial fretting wear simulation.•An experimental and numerical validation of the proposed methodology.•An industrial application to false brinelling in stationary thrust bearings under variable loading conditions.•An alternative fretting method to FEM simulations with a massive time reduction of 30 000 times.
Rotational fretting is defined as the localised wear produced in a reciprocating rolling motion of low amplitude. The current techniques used for the analysis of this damage are reduced to ...experimental tests, which involve high costs in specimens and equipment, and to simulation through finite element (FE) models, which involves high mesh density in contact zones and thus drastically increases the computational cost. The main objective of this work is to develop an analytical model for the analysis of rotational fretting. To achieve this aim, the sliding motion of the rolling ball is analysed, and a novel iterative method based on rolling energy minimization is proposed for the calculation of the kinematics and the transient effects are solved. The proposed methodology is applied to the case of study of a thrust bearing and validated in two different stages: first, a numerical validation of tangential stresses is conducted using an FE model where a maximum difference of 10% with respect to the numerical results as well as a massive time reduction of more than 5000 times are achieved; and second, an experimental tests rig is designed and tests are performed showing a mean relative error of 13% in the measured damaged areas.
•A new formulation for rotational fretting wear simulation.•An experimental and numerical validation of the proposed methodology.•An industrial application to false brinelling in a thrust bearing under reciprocal oscillations.•An alternative fretting method to FEM simulations with a massive time reduction of 5000 times.
Small reciprocal movements in bearings can cause wear damage at the contact between the rolling elements and the raceway due to fretting phenomena. This damage is also called false brinelling or ...fretting corrosion, attending to lubrication conditions and causes vibrations and noisy operation, finally resulting in the need for the replacement of the component. Previous works from the literature have focused on experimental analyses of the damage and methodologies to simulate the occurrence of this phenomenon. These previous methodologies are centred on the effects of isolated fretting modes, such as radial fretting, rotational fretting and tangential fretting. However, the effects of external loads in angular bearings lead to high complex scenarios in which multiple fretting modes act simultaneously. In response to this demand, a novel methodology has been developed to analyse fretting damage as a consequence of the variable load and rolling motion. In addition, an analysis of the effects of each fretting mode is accomplished to determine the need to simulate both. The validation of the method is accomplished in two stages. First, a numerical validation through the finite element method (FEM) shows good agreement in the calculation of the contact reaction, the contact angle and tangential stresses, with relative differences under 5% and a considerable time reduction. Second, an experimental validation, which show a 16.1% mean relative difference between the damage areas and a 76% mean overlap of the damage areas.
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•A complete methodology for the analysis of fretting damage at angular contact bearing raceways.•An experimental and numerical validation of the proposed methodology.•An analysis on the contribution of the present fretting modes: radial and rotational fretting to the final damage.
The microbiota is increasingly recognized as a significant factor in the pathophysiology of many diseases, including cardiometabolic diseases, with lifestyles probably exerting the greatest influence ...on the composition of the human microbiome. The main objectives of the study are to analyze the association of lifestyles (diet, physical activity, tobacco, and alcohol) with the gut and oral microbiota, arterial aging, and cognitive function in subjects without cardiovascular disease in the Iberian Peninsula. In addition, the study will examine the mediating role of the microbiome in mediating the association between lifestyles and arterial aging as well as cognitive function.
MIVAS III is a multicenter cross-sectional study that will take place in the Iberian Peninsula. One thousand subjects aged between 45 and 74 years without cardiovascular disease will be selected. The main variables are demographic information, anthropometric measurements, and habits (tobacco and alcohol). Dietary patterns will be assessed using a frequency consumption questionnaire (FFQ) and the Mediterranean diet adherence questionnaire. Physical activity levels will be evaluated using the International Physical Activity Questionnaire (IPAQ), Marshall Questionnaire, and an Accelerometer (Actigraph). Body composition will be measured using the Inbody 230 impedance meter. Arterial aging will be assessed through various means, including measuring medium intimate carotid thickness using the Sonosite Micromax, conducting analysis with pulse wave velocity (PWA), and measuring pulse wave velocity (cf-PWV) using the Sphygmocor System. Additional cardiovascular indicators such as Cardio Ankle Vascular Index (CAVI), ba-PWV, and ankle-brachial index (Vasera VS-2000
) will also be examined. The study will analyze the intestinal microbiota using the OMNIgene GUT kit (OMR-200) and profile the microbiome through massive sequencing of the 16S rRNA gene. Linear discriminant analysis (LDA), effect size (LEfSe), and compositional analysis, such as ANCOM-BC, will be used to identify differentially abundant taxa between groups. After rarefying the samples, further analyses will be conducted using MicrobiomeAnalyst and R v.4.2.1 software. These analyses will include various aspects, such as assessing α and β diversity, conducting abundance profiling, and performing clustering analysis.
Lifestyle acts as a modifier of microbiota composition. However, there are no conclusive results demonstrating the mediating effect of the microbiota in the relationship between lifestyles and cardiovascular diseases. Understanding this relationship may facilitate the implementation of strategies for improving population health by modifying the gut and oral microbiota.
clinicaltrials.gov/ct2/show/NCT04924907, ClinicalTrials.gov, identifier: NCT04924907. Registered on 21 April 2021.
We have investigated mechanisms that contribute to reinforce the relationship between inflammation and cancer. Secreted phospholipase A2 group IIA (sPLA2-IIA) is a molecule relevant in inflammatory ...events and has been proposed as a marker for some of these. Previously, we reported the mitogenic properties of this sPLA2 in the human astrocytoma cell line 1321N1. Here, we go deeper into the mechanisms that link this inflammatory protein with proliferation in one of the most aggressive types of tumors. We found that phosphorylation of the extracellular regulated kinase (ERK) was preceded by the activation of the small GTPase Ras, and both failed to be activated by inhibiting protein kinase C (PKC). Fractionation and immunofluorescence studies revealed translocation of PKC alpha, delta, and epsilon to the membrane fraction upon stimulation with sPLA2-IIA. Immunoprecipitation analysis showed that sPLA2-IIA induces phosphorylation of the epidermal growth factor receptor (EGFR) through a PKC-dependent pathway. We found that phosphorylation of this receptor contributed to Ras and ERK activation and that inhibition of ERK, PKC, and EGFR blocked the mitogenic response induced by sPLA2-IIA. This study showed that sPLA2-IIA is able to bring into play EGFR to trigger its signaling and that PKC leads the distribution of resources. Interestingly, we found that this is not a cell-specific response, because sPLA2-IIA was also able to transactivate EGFR in MCF7 human breast cancer cells. Therefore, this mechanism could contribute to worsen the prognosis of a tumor in an inflammatory microenvironment. We also present more links of the tumor chain possibly susceptible to targeting.
Background:
The aim of this study was to translate and cross-culturally adapt the Olerud-Molander Ankle Score (OMAS) into Spanish and to assess its reliability and validity.
Methods:
The translation ...and adaptation to develop the Spanish version of the OMAS (OMAS-Sp) was performed according to current international guidelines. The OMAS-Sp was administered to 98 patients with a surgically treated ankle fracture, and it was repeated 7-14 days later to assess construct reliability of each question’s score and the total score. Test-retest reliability and the internal consistency were calculated, and concurrent validity was assessed by comparing the OMAS-Sp with the Foot and Ankle Outcome Score (FAOS). The presence of floor and ceiling effects was also analyzed.
Results:
Adequate internal consistency was found with a Cronbach α of 0.821. Excellent test-retest reliability was demonstrated with an interclass correlation coefficient for the total score of 0.970 (95% CI 0.956-0.980; P < .001). Spearman correlation coefficients (r’s) between the OMAS-Sp total score and the 5 FAOS subscales ranged from 0.944 to 0.951 (P < .001). No floor or ceiling effects were found.
Conclusion:
The OMAS-Sp demonstrated adequate psychometric properties and is a valid and reliable tool for assessing outcomes in Spanish-speaking patients with surgically treated ankle fractures.
Level of Evidence:
Level II, prospective cohort study.
El empleo de muestras salivales para la deteccion de estros fue descrito por primera vez en mujeres en 1946, en pruebas de Papanicolau, en las cuales se observo que, al colocar muestras de moco ...cervicovaginal, al ser esparcidas en un portaobjetos y dejandose secar a temperatura ambiente, estas tendian a sedimentar y formar cristalizaciones que al ser observadas al microscopio recordaban hojas de una planta de helecho. estas arborizaciones varian en cantidad y grosor segun el periodo del ciclo en que se encuentre la mujer o las hembras domesticas y se ha comprobado que la mayor arborizacion se presenta en la etapa folicular del ciclo estral. La formacion de cristales en forma de helechos estan influenciadas por los niveles estrogenicos, y que se forman cuando el moco tiene mucoproteinas, cloratos de calcio y sodio o cuando hay un incremento de agua. En especies domesticas se han realizado trabajos en caninos y equinos donde se observo, una arborizacion salival, la cual cambia segun la etapa del ciclo estral en la que se encuentran las perras y las yeguas. No existen trabajos que evaluen si en pequenos rumiantes el patron de arborizacion salival es afectado por la etapa reproductiva en que se encuentre el animal. En este trabajo se evaluo el fenomeno de arborizacion en saliva como alternativa para la deteccion de estros. Se tomaron muestras de saliva diariamente hasta que se registraran 2 ciclos estrales en cada cabra y oveja, dichas muestras se observaron en microscopio optico para su clasificacion. Se encontraron 4 patrones: rosetas, enramada, arbustos, helechos y combinaciones entre estos. Alternativamente se tomaron muestras de sangre (2 veces por semana) para conocer los niveles de progesterona en plasma y asi determinar la fase del ciclo estral en la que se encontraban. Relacionando los distintos dias del ciclo estral con las frecuencia de cada tipo de arborizacion, se observo que no existio diferencia significativa (p.05) entre cualquiera de los tipos; tampoco al comparar las frecuencias con respecto a las etapas del ciclo estral hubo diferencia significativa, que hiciera afirmar que algun patron de arborizacion fuera caracteristico de el ciclo estral en ovinos y caprinos, por lo que se concluye que el fenomeno de arborizacion en saliva de pequenos rumiantes no es un metodo alternativo para la deteccion del estro.
The geomechanical integrity of shale overburden is a highly significant geological risk factor for a range of engineering and energy-related applications including CO
2
storage and unconventional ...hydrocarbon production. This paper aims to provide a comprehensive set of high-quality nano- and micro-mechanical data on shale samples to better constrain the macroscopic mechanical properties that result from the microstructural constituents of shale. We present the first study of the mechanical responses of a calcareous shale over length scales of 10 nm to 100
μ
m, combining approaches involving atomic force microscopy (AFM), and both low-load and high-load nanoindentation. PeakForce quantitative nanomechanical mapping AFM (PF-QNM) and quantitative imaging (QI-AFM) give similar results for Young’s modulus up to 25 GPa, with both techniques generating values for organic matter of 5–10 GPa. Of the two AFM techniques, only PF-QNM generates robust results at higher moduli, giving similar results to low-load nanoindentation up to 60 GPa. Measured moduli for clay, calcite, and quartz-feldspar are
22
±
2
GPa
,
42
±
8
GPa
, and
55
±
10
GPa
respectively. For calcite and quartz-feldspar, these values are significantly lower than measurements made on highly crystalline phases. High-load nanoindentation generates an unimodal mechanical response in the range of 40–50 GPa for both samples studied here, consistent with calcite being the dominant mineral phase. Voigt and Reuss bounds calculated from low-load nanoindentation results for individual phases generate the expected composite value measured by high-load nanoindentation at length scales of 100–600
μ
m. In contrast, moduli measured on more highly crystalline mineral phases using data from literature do not match the composite value. More emphasis should, therefore, be placed on the use of nano- and micro-scale data as the inputs to effective medium models and homogenisation schemes to predict the bulk shale mechanical response.
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