Thermal diagnostics of friction in sliding bearings with account for propagation of heat and movement of shaft

A method for the thermal diagnostics of friction in a sliding bearing is considered for the case when a three-dimensional mathematical model of the thermal process taking into account the motion of the shaft is used. Basic relations for restoring the specific power of the frictional heat generation in the friction zone of the bearing using temperature data and results of computational experiments are presented, which show the stability of a solution of the corresponding inverse boundary problem to errors of the temperature data.     

Liquid Chromatography Orbitrap Mass Spectrometry Method for Analysis of Homocysteine and Related Aminothiols in Cereal Products

Liquid chromatography Orbitrap mass spectrometry method for quantification of biological aminothiols (cysteine, homocysteine, and glutathione) in cereal products has been developed. The assay is based on preliminary derivatization with N-(2-acridonyl)maleimide and high resolution accurate mass spectrometry with utilization of dl-Homocystine-3,3,3′,3′,4,4,4′,4′-d₈ (homocystine-d₈) as internal standard. The limits of quantification for homocysteine, cysteine, and glutathione are 19.44, 40.78, and 338.93 pg, respectively, per 10 μl injection. Intra- and inter-day precision expressed as relative standard deviations are in the range of 1.76 to 2.94 % and 1.06 to 4.13 %, respectively. The average recoveries were 98 % for Hcy, 87 % for Cys, and 92 % for GSH. Wheat, maize, and bakery products with different origin were analyzed. The content of Hcy in the investigated samples was found to be in range of 9–436 μg/100 g, Cys in range of 29–6,895 μg/100 g and GSH in range of 259–14,795 μg/100 g.     

Selective Chemical Activation of Piezo1 in Leukemia Cell Membrane: Single Channel Analysis

Piezo1/2 are mechanosensitive calcium-permeable channels that can be activated by various modes of membrane deformation. The identification of the small molecule Yoda1, a synthetic Piezo1 agonist, revealed the possibility of chemical activation of the channel. Stimulating effects of Yoda1 on Piezo1 have been mainly documented using over-expressing cellular systems or channel proteins incorporated in artificial lipid bilayers. However, the activating effect of Yoda1 on native Piezo1 channels in the plasma membrane of living cells remains generally undefined, despite the increasing number of studies in which the agonist is utilized as a functional tool to reveal the contribution of Piezo1 to cellular reactions. In the current study, we used the human myeloid leukemia K562 cell line as a suitable model to examine chemically induced Piezo1 activity with the use of the patch-clamp technique in various specific modes. The functional expression of Piezo1 in leukemia cells was evidenced using a combinative approach, including single channel patch-clamp measurements. Utilizing our established single-current whole-cell assay on K562 cells, we have shown, for the first time, the selective real-time chemical activation of endogenously expressed Piezo1. Extracellular application of 0.5–1 µM Yoda1 effectively stimulated single Piezo1 currents in the cell membrane.     

On the long-term strength of specimens made of phenol-formaldehyde press powders

The study of the long-term strength (LTS) of polyethylene, poly(vinyl chloride), and polyoximethylene shows that the In τ–σ relation for specimens, undergoing tension, is S-shaped. Structure changes during the process of deformation may occur in these polymers. However, the structure of spatial-grid polymers (solidifying phenol–formaldehyde resins, for instance) does not prove to be stress-sensitive and experiments show that the In τ–σ relation can be described with sufficient accuracy by employing an equation of the form τ = τ₀ exp[(U ? γσ)/(RT + ασⁿ)].     

Dynamic Uplift Scenarios for Floating Ice

Three uplift scenarios in the forced dynamics of floating ice are studied. Linear, quadratic, and square-root uplift forcing functions are considered and the associated uplift displacement functions are computed numerically. In each case, the uplift forcing is known and the displacement at the point of forcing is unknown. This is the so-called “direct” problem. In essence, this study is aimed at learning more about the “indirect” or inverse problem, where the uplift displacement function is known and the forcing is unknown. A model problem, that is able to be solved in closed form for each of the three forcing functions considered, is used to verify the numerical calculations. By curve fitting the relative error between the model problem and the actual uplift problem, a general modus operandi is arrived at for deriving approximate expressions for the otherwise intractable uplift displacement. These approximate expressions satisfy the required initial conditions and are shown to be accurate.     

Predicting the Yield of Coking Products

The properties of coal concentrates are determined: the technical analysis, clinkering properties, petrographic and elementary analysis, and the product yields in coking. Structural characteristics of the coal’s organic mass are also calculated. The results obtained for Kuznetsk Basin coal are subjected to mathematical analysis. The experimental dependences obtained may be used to formulate optimal coking batch in actual production conditions.     

Microfluidic chips for the study of cell migration under the effect of chemicals

Numerical simulation of the formation of a chemoattractant gradient in reaction chambers of a chip having different geometries enabled the determination of a structure suitable for the study of cell migration, in accordance with which hybrid polymer–glass microfluidic devices were manufactured. Verification of the procedures of alignment of cells in the reaction chamber of the chip by centrifugal force and subsequent culturing of the cells showed that microfluidic chips can be used to study cell migration under the effect of the chemoattractant gradient in vitro.     

Modified polypropylene wood flour composites. II. Fracture,deformation, and mechanical properties

The effect of grafting level of maleic anhydride (MA) in the maleated polypropylene (PPMA) on the fracture, deformation mechanisms, and mechanical properties of polypropylene (PP) wood flour composites was studied. Tensile strength, elongation at break, and impact strength are noticeably improved with addition of interfacial modifiers as maximum values of the examined mechanical properties were detected when concentration of MA in the compatibilizer was 1 wt %. To explore the microstructure and deformation mechanisms, scanning electron microscopy was employed. It was found that low concentrations of MA up to 1 wt % led to the creation of a thin and irregular polymer layer assisted formation of fibrillated plastic deformation zone around the wood particles, while the bulk PP matrix experienced voiding and brittle fracture. Higher concentrations of MA fetch to stronger interaction between PP and wood flour, the reason for brittle fracture and reduced ductility of the matrix. The impact fracture behavior of the composites during Instrumented impact tests is also discussed with respect to the interfacial bond strength. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 1286–1292, 2004