Existence of a tribo-modified surface layer of BR/S-SBR elastomers reinforced with silica or carbon black

The existence of a modified surface layer on top of a rubber disk, in contact with a rigid counter-surface, is still a point of discussion. In this study, we show that a modified surface layer with different mechanical properties exists. Modification of the reinforced elastomers is discussed and the subsequent effect of existence of such a layer on the friction is emphasized. The elasticity modulus both inside and outside the wear track is determined by atomic force microscope nano-indentations and compared with the macroscale mechanical properties measured using dynamical mechanical analysis. The elastic modulus inside the wear track is lower than the bulk. Intensifying the tribological conditions by means of increasing normal pressure and sliding velocity will result in a greater loss of mechanical propertie

Modelling of a thin soft layer on a self-lubricating ceramic composite

Friction and wear of a self-lubricating ceramic composite under unlubricated sliding contact conditions is dependent on the formation and regeneration of a thin soft surface layer. Experimental observations have shown that a thin soft layer (third body) may be formed depending on the tribological tests conditions. This thin soft layer is a pre-requirement for the occurrence of low friction in the mild wear regime. This paper proposes a physically based model for the process of the formation and removal of the soft layer. The model is developed on the basis of mechanical stresses in the soft second phase and the elastic–plastic contact between a rough surface and a flat surface. Based on the model, the thickness of the soft surface layer on a ceramic substrate is predicted. The results show that the thickness of the soft layer is mainly determined by the mechanical properties of soft phase as well as the applied load

Detección de parvovirus canino por PCR y su asociación con algunos de los factores de riesgo

Objetivo. El parvovirus canino es una de las enfermedades más importantes en perros en todo el mundo la cual amenaza su salud. El objetivo de este estudio fue determinar la prevalencia del parvovirus canino en perros remitidos a la Clínica de Pequeños Animales de la Universidad de Teherán en la provincia de Teherán por el método de detección del genoma. Materiales y Métodos. Se obtuvieron muestras de heces diarreicas de 60 perros durante los años 2014-2016 y se investigó la presencia de CPV por el método de PCR. Resultados. La prevalencia de infección por parvovirus canino en los perros estudiados fue del 8,33% (5 0f 60). No se encontraron diferencias significativas entre los diferentes grupos de edad y razas. Sin embargo, la infección fue significativamente mayor en perros con diarrea hemorrágica (3 de 25), pero no fue estadísticamente significativa usando la prueba de chi-cuadrada (P>0,05). Conclusiones. Este estudio demostró que la diarrea hemorrágica y la falta de vacunación pueden considerarse como síntomas y factores de riesgo importantes de la infección por parvovirus canino en perros, y que los propietarios de perros en Irán deben ser conscientes del hecho de que la vacunación contra la infección CPV debe hacerse con cuidado y a tiempo para controlar y prevenir el virus.

Simultaneous removal of phenol and linear alkylbenzene sulfonate from automotive service station wastewater: Optimization of coupled electrochemical and physical processes

This work investigates the feasibility of the coupled electrochemical (electrocoagulation/flotation) and physical processes (sedimentation, sand filtration, and activated carbon) for the treatment of automotive service wastewater (ASWW). The impacts of critical parameters, viz. pH solution, reaction time and current intensity on linear alkylbenzene sulfonate (LAS), and phenol removal efficiencies as well as energy consumption and operating cost are studied. Central composite design results reveal that at the optimum conditions, LAS and phenol removal efficiencies, energy consumption and operating cost are obtained 96.7%, 87.65%, 15.99 Wh, 0.001 US$, respectively. This process reveals a feasible technology for phenol and LAS removal from ASW

Existence of a Tribo-Modified Surface Layer on SBR Elastomers: Balance Between Formation and Wear of the Modified Layer

In most of the tribological contacts, the composition and tribological properties of the original interface will change during use. The tribo-films, with modified properties compared to the bulk, are dynamic structures that play a significant role in friction. The existence of a tribo-modified surface layer and its importance on the overall friction of elastomers has been shown both theoretically and experimentally before. The characteristics of the modified surface layer deserve specific attention since the tribological properties of elastomers in contact with a rough counter-surface are determined by these modified surfaces together with the properties of bulk of the material. Both the formation of the modified layer and the break down (wear) of it are of importance in determining the existence and thickness of the tribo-modified layer. In this study, the importance of the wear is emphasized by comparing two styrene butadiene rubber-based elastomers in contact with a granite sphere. A current status of perception of the removal and the stability of the modified surface layers on rubbers is introduced as well as experimental work related to this matter and discussion within literature. Pin-on-disk friction tests are performed on two SBR-based samples in contact with a granite sphere under controlled environmental conditions to form the modified surface layer. Although the hysteresis part of the friction force which has a minor contribution in the overall friction is not markedly different, the total measured friction coefficient differs significantly. Mechanical changes both inside and outside the wear track are determined by atomic force microscope nano-indentations at different timescales to examine the modified surface layer on the test samples. The specific wear rates of the two tribo-systems are compared, and the existence of the modified surface layer, the different measured friction coefficient and the running-in distances toward steady-state friction are explained considering different wear rates. A conceptual model is presented, correlating the energy input into the tribo-system and the existence of a modified surface layer

Global, regional, and national burden of colorectal cancer and its risk factors, 1990–2019: a systematic analysis for the Global Burden of Disease Study 2019

Funding: F Carvalho and E Fernandes acknowledge support from Fundação para a Ciência e a Tecnologia, I.P. (FCT), in the scope of the project UIDP/04378/2020 and UIDB/04378/2020 of the Research Unit on Applied Molecular Biosciences UCIBIO and the project LA/P/0140/2020 of the Associate Laboratory Institute for Health and Bioeconomy i4HB; FCT/MCTES through the project UIDB/50006/2020. J Conde acknowledges the European Research Council Starting Grant (ERC-StG-2019-848325). V M Costa acknowledges the grant SFRH/BHD/110001/2015, received by Portuguese national funds through Fundação para a Ciência e Tecnologia (FCT), IP, under the Norma Transitória DL57/2016/CP1334/CT0006.proofepub_ahead_of_prin