Study of the adsorption of anti-wear additives on the surface of butosyl in oil dispersions

The method for evaluating the adsorption capacity of surfactants for plastic lubricants on inorganic thickener, such as silica gel, bentonite, carbon black, colloidal graphite, and others was proposed. The Gibbs adsorption values were calculated based on surface tension curves of samples in oil media, and the adsorption isotherms for each of the media were plotted based on the calculated data. According to the results of the study of the surface tension and refractive index of DF-11 additive solutions in heptane, it was found that 1% of the mass goes to fill the butosil surface, and the rest of its amount remains in the volume. But for the A-22 additive in the reference medium, the filling of the butosil surface occurs at a concentration of 2 % mass. It is shown that the additive A-22 should be used at higher concentrations than DF-11 to improve tribological parameters of silica gel lubricants. It was found that use of butasil based silica-gel grease the mixture of the industrial oil I-40A and PMS-400 as a dispersion medium, allows to reduce concentration of DF-11 and A-22 additives.

Surface tension of O2-Ar, N2-Ar and O2-N2-Ar mixtures

The surface tension of some binary and ternary mixtures was calculated by means of molecular dynamics simulations in a canonical set. The analyzed mixtures were oxygen-argon, nitrogen-argon and oxygen-nitrogen-argon. The force field for argon was recalculated in order to reproduce the experimental surface tension. The corresponding force fields for O2 and N2 were taken from a previous work [Mol. Simul. 45 (2019) 958-966], where it was shown that such force fields reproduce the experimental surface tension curves, as pure fluids. The nitrogen-argon surface tension was calculated for several mole fractions of argon. The obtained curve was compared with those experimental data and a good agreement was found. The standard Lorentz-Berthelot combining rules were employed. For the oxygen-argon mixture it was necessary to modify the cross term of the combining rules in order to reproduce theoretical and experimental data. The surface tension of the ternary mixture was also estimated varying the mole fraction of argon at a certain concentration of oxygen and nitrogen, previously adjusted. Several temperatures were used in order to show a tendency mostly at relatively low temperatures. After comparing the available experimental data, which are scarce, a good agreement was observed.

A nanometer difference in myofilament lattice spacing of two cockroach leg muscles explains their different functions

Muscle is highly organized across scales. Consequently, small changes in arrangement of myofilaments can influence macroscopic function. Two leg muscles of a cockroach, have identical innervation, mass, twitch responses, length-tension curves, and force-velocity relationships. However, during running, one muscle is dissipative, while the other produces significant positive mechanical work. Using time resolved x-ray diffraction in intact, contracting muscle, we simultaneously measured the myofilament lattice spacing, packing structure, and macroscopic force production of these muscle to test if nanoscale differences could account for this conundrum. While the packing patterns are the same, one muscle has 1 nm smaller lattice spacing at rest. Under isometric activation, the difference in lattice spacing disappeared explaining the two muscles’ identical steady state behavior. During periodic contractions, one muscle undergoes a 1 nm greater change in lattice spacing, which correlates with force. This is the first identified feature that can account for the muscles’ different functions.

Use of Thermography for the Analysis of Strength Properties of Mini-Specimens

This paper presents sample applications of passive infrared thermography for research on temperature changes of mini-specimens resulting from monotonously increasing or cyclically variable mechanical load. The MFS system developed in the Department of Machine Design at the University of Technology and Life Sciences in Bydgoszcz (Poland) and designed for testing mechanical properties of microelements were used for tests. The MFS system ensures nanometric measurement accuracy of many static and fatigue-related material properties, including, i.a., static tension curves, cyclic strain curves, fatigue life curves as a function of force, stress and strain. Measurements of the mini-specimens temperature were performed using thermographic camera equipped with microscope lens. The tests have shown that research on the passive infrared thermography may be successfully applied for determining strength properties of materials in micro scale. The used research instrumentation is characterized by sufficient sensitivity and resolution (camera with the microscope lens), while the MFS system ensures accurate load and position control.

A comparison of two Hill-type skeletal muscle models on the construction of medial gastrocnemius length-tension curves in humans in vivo

Human length-tension curves are traditionally constructed using a model that assumes passive tension does not change during contraction ( model A) even though the animal literature suggests that passive tension can decrease ( model B). The study's aims were threefold: 1) measure differences in human medial gastrocnemius length-tension curves using model A vs. model B, 2) test the reliability of ultrasound constructed length-tension curves, and 3) test the robustness of fascicle length-generated length-tension curves to variations between the angle and fascicle length relationship. An isokinetic dynamometer manipulated and measured ankle angle while ultrasound was used to measure medial gastrocnemius fascicle length. Supramaximal tibial nerve stimulation was used to evoke resting muscle twitches. Length-tension curves were constructed using model A {angle-torque [A-T(A)], length-torque [L-T(A)]} or model B {length-torque [L-T(B)]} in three conditions: baseline, heel-lift (where the muscle was shortened at each angle), and baseline repeated 2 h later (+2 h). Length-tension curves constructed from model B differed from those produced via model A, indicated by a significant increase in maximum torque (≈23%) when using L-T(B) vs. L-T(A). No parameter measured was different between baseline and +2 h for any method, indicating good reliability when using ultrasound. Length-tension curves were unaffected by the heel-lift condition when using L-T(A) or L-T(B) but were affected when using A-T(A). Since the muscle model used significantly alters human length-tension curves, and given animal data indicate model B to be more accurate when passive tension is present, we recommend that model B should be used when constructing medial gastrocnemius length-tension curves in humans in vivo.

Intelligent Detection of Yarn Supply Tension during Flat Knitting Process

Yarn supply tension is a key factor which has influences on the quality of knitted fabrics. This paper introduces a method to detect the yarn tension during knitting action. A 3-rollor tension sensor was adopted and a sensory system was assembled on a flat knitting machine. A single chip microcomputer and a specially designed circuit were used for the signal capturing and transmission. Yarn tension changes during the knitting process was recorded and displayed by a PC. In order to verify the validity, several experiments were arranged. The results indicate that the yarn tension can be detected, recorded and displayed. After analyzing the tension curves, it is founded that the knitting action especially the yarn elastic properties and feed spring performance affects the yarn supply tension. We also find this method is practical.

Reduced thin filament length in nebulin-knockout skeletal muscle alters isometric contractile properties

Nebulin (NEB) is a large, rod-like protein believed to dictate actin thin filament length in skeletal muscle. NEB gene defects are associated with congenital nemaline myopathy. The functional role of NEB was investigated in gastrocnemius muscles from neonatal wild-type (WT) and NEB knockout (NEB-KO) mice, whose thin filaments have uniformly shorter lengths compared with WT mice. Isometric stress production in NEB-KO skeletal muscle was reduced by 27% compared with WT skeletal muscle on postnatal day 1 and by 92% on postnatal day 7, consistent with functionally severe myopathy. NEB-KO muscle was also more susceptible to a decline in stress production during a bout of 10 cyclic isometric tetani. Length-tension properties in NEB-KO muscle were altered in a manner consistent with reduced thin filament length, with length-tension curves from NEB-KO muscle demonstrating a 7.4% narrower functional range and an optimal length reduced by 0.13 muscle lengths. Expression patterns of myosin heavy chain isoforms and total myosin content did not account for the functional differences between WT and NEB-KO muscle. These data indicate that NEB is essential for active stress production, maintenance of functional integrity during cyclic activation, and length-tension properties consistent with a role in specifying normal thin filament length. Continued analysis of NEB's functional properties will strengthen the understanding of force transmission and thin filament length regulation in skeletal muscle and may provide insights into the molecular processes that give rise to nemaline myopathy.