Effectiveness of upper arm and breathing exercises to improve inflammatory markers in severe COVID-19 patients.

Studies have suggested associations between inflammatory markers with the severity of coronavirus disease 2019 (COVID-19). Therefore, exercises that could reduce the level of inflammatory markers might be beneficial. The aim of this study was to determine the effect of upper arm and breathing exercises on inflammatory markers such as ferritin, lactate dehydrogenase (LDH), and C-reactive protein (CRP) in severe COVID-19 patients. A quasi-experimental with pre-test and post-test control group design was conducted among severe COVID-19 aged 18-70 years old, with or without comorbidities. Baseline data of inflammatory markers (ferritin, LDH, and CRP) were measured before the exercises and repeated post-exercise. The upper arm and breathing exercises were performed for ten days, twice a day (morning and evening) for ten minutes. A paired Student t-test was used to assess the changes in the inflammatory markers' levels. Our data indicated that levels of ferritin and CRP were not significantly different between pre- and post-exercise. However, the level of LDH decreased significantly from 481.35 U/L to 331.80 U/L (p=0.001). This study highlights that pulmonary rehabilitation exercises might be beneficial to enhance the recovery process in severe COVID-19 patients.

Effect of the Polar Head Type on the Surface Adsorption and Tribofilm Formation of Organic Friction Modifiers in Water-Based Lubricants.

Carboxylic acids make up a well-known group of organic friction modifiers (OFMs). OFMs can present different types of polar heads that can eventually lead to different surface adsorption properties and tribological responses. Therefore, the goal of this work is to study the effects of the polar head type on the frictional and wear performances of carboxylic acids in a water-based lubricant. Lauric acid (C12) was chosen as the reference OFM, and methyl laurate and monolaurin were chosen for the comparison. Sliding friction tests were performed on stainless steel against alumina balls under boundary lubricating conditions. The effect of the adsorbed layers and the tribofilm formation was studied by varying the initial maximum hertzian contact pressure, i.e., tests were performed at 1.97 and 0.66 GPa. At the lowest contact pressure, not enough load is applied to obtain enough plastic deformation on the asperity contacts. In this case, a combination of asperity contacts and a thick fluid film formation results in a lack of tribofilm formation, whereas at the highest contact pressure, tribofilms are formed in the asperity contact through tribochemical reactions. Methyl laurate showed no adsorption on the surface, and it was not tested further. C12 and monolaurin showed good adsorption, but the adsorbed layers had different viscoelastic properties. Micro and macrotribological tests showed good frictional behavior for C12 at 0.5 wt % concentration due to the good viscoelastic properties of its adsorbed layer. The adsorbed layer of monolaurin did not show good friction-reducing ability during the micro tribological tests due to its poorer viscoelastic properties. However, the macro tribological tests revealed that monolaurin forms a robust tribofilm protecting the surface from wear and efficiently reducing friction at a concentration of 0.5 wt % resulting in the lowest wear and friction values as observed in this study.

Triboelectrochemical friction control of W- and Ag-doped DLC coatings in water-glycol with ionic liquids as lubricant additives.

In the last years, diamond like carbon (DLC) coatings doped with both carbide forming and non-carbide forming metallic elements have attracted great interest as novel self-lubricating coatings. Due to the inherent properties of DLC, the doping process can provide adsorption sites for lubricant additives depending on the chemical and electrochemical state of the surface. Ionic liquids (ILs) are potential lubricant additives with good thermal stability, non-flammability, high polarity, and negligible volatility. These characteristics make them also ideal for polar fluids, like water-based lubricants. In this work, three different DLC coatings (DLC, W- and Ag-doped DLC) were deposited on stainless steel substrates and their friction in dry and lubricated conditions in water-based lubricants was studied. Three ILs, tributylmethylphosphonium dimethylphosphate (PP), 1,3-dimethylimidazolium dimethylphosphate (IM) and 1-butyl-1-methylpyrrolidinium tris(pentafluoroethyl)trifluorophosphate (BMP) were used as additives and compared with a well-known organic friction modifier (dodecanoic acid). The results showed better mechanical integrity, toughness and adhesion of the doped coatings compared to the undoped DLC. The Ag-doped DLC coating had the best mechanical properties of all the coatings. W formed tungsten carbide precipitates in the DLC coating. Two different additive-adsorption mechanisms controlled friction: a triboelectrochemical activation mechanism for Ag-DLC, and an electron-transfer mechanism for W-DLC resulting in the largest reduction in friction.

Effect of Steel Hardness and Composition on the Boundary Lubricating Behavior of Low-Viscosity PAO Formulated with Dodecanoic Acid and Ionic Liquid Additives.

Two ionic liquids, tributylmethylphosphonium dimethylphosphate (PP) and 1-butyl-1-methylpyrrolidinium tris(pentafluoroethyl)trifluorophosphate (BMP), as lubricant additives in polyalphaolefin (PAO8) were studied under boundary lubricating conditions on two types of steel (AISI 52100 bearing steel and AISI 316L stainless steel). The tribological behavior of these ILs was compared with dodecanoic acid, a well-known organic friction modifier. This study employs a ball-on-disk tribometer with an alumina ball as a counterpart. A range of advanced analytical tools are used to analyze the tribofilms, including scanning electron microscopy equipped with a focused ion beam, scanning transmission electron microscopy equipped with X-ray energy-dispersive spectroscopy, and X-ray photoelectron spectroscopy. A quartz crystal microbalance with dissipation was used to study the surface adsorption of the additives on iron- and stainless steel-coated sensors to reveal the adsorption kinetics, adsorbed layer mass, and bonding strength of the adsorbed layer on the metallic surfaces. The most important factors controlling friction and wear are the thickness and viscoelastic properties of the adsorbed layer, the thickness and chemical composition of the tribofilm, and the hardness and chemical composition of steel. Among all additives studied, BMP on stainless steel gives a strongly adsorbed layer and a durable tribofilm, resulting in low friction and excellent antiwear properties.