Open System Tribology and Influence of Weather Condition

Abstract

The tribology of an open system at temperatures ranging between 3 °C and −35 °C, with and without snow, was investigated using a pin-on-disc tribometer mounted in a temperature-controlled environmental chamber. The relationship between the microstructure and ductility of the materials and the tribology at the contacting surfaces was investigated. The study shows that during continuous sliding, pressure causes snow particles to melt into a liquid-like layer, encouraging the generation of oxide flakes on the contact path. The friction coefficient and wear rate are dramatically reduced through an oxidative friction and wear mechanism. In the absence of snow, the tribological process is controlled by the low temperature brittleness of steel in the temperature range from 3 °C to −15 °C. At these temperatures, cracks are prone to form and extend on the worn surfaces, resulting in the spalling of bulk scraps, which are crushed into debris that increases the friction coefficient and wear rate due to strong abrasion. When the temperature falls to −25 °C, an ice layer condenses on the metal surfaces and relaxes the tribological process in the same way as the added snow particles, which significantly decreases the friction and wear.

Current state of a dual behaviour of antimicrobial peptides—Therapeutic agents and promising delivery vectors

“…In some cases, above a certain threshold, the increasing positive charge does not improve antimicrobial activity, which is explained by the fact that an increase in the charge is closely related to the reduced hydrophobicity of peptides (and also the modification of the hydrophobic moment). [16][17][18] AMPs have substantial portions of hydrophobic residues (over 30%), while the ratio of hydrophobic and uncharged residues (e.g. leucine, phenylalanine or tryptophan) to charged amino acids can vary from 1:1 to 2:1.…”

“…[3,22] However, to maintain surface activity, at least seven or eight amino acids are needed, [15] while 15-20 amino acids are required to span the membrane in the case of helical peptides. [18] Recent research has revealed that the decreasing chain length of peptides in a certain range retains its high antimicrobial activity by reducing its toxicity. The molecular weights of AMPs are less than 10 kDa and typically in the range of 1-5 kDa.…”

Antibacterial activities and molecular mechanism of amino‐terminal fragments from pig nematode antimicrobial peptide CP‐1

“…There are some determinant factors that affect the antimicrobial activity of peptides, such as net charge, [49][50][51] hydrophobicity, [52] α-helix propensity, [32] and the length of the peptide. [14] In this study, WL2 and WL3 have stronger antimicrobial activity than WL1, which is mainly due to the α-helical propensity in the membrane environment. The peptides transformed from random conformations in the aqueous environment to amphipathic α-helices, which increase the partition into the membrane and increase the antimicrobial activity.…”

“…The microbial sample was initially prepared as described for early SEM analysis. [14] The overnight cultures of logarithmic phase E. coli ATCC 25922 and S. aureus ATCC 29213 cells were harvested by centrifuging at 1,000 × g for 10 min, washed twice with PBS, and diluted to an OD 600 of 0.1-0.2. The 1 × MIC peptides were challenged with bacteria at 37°C for 1 hr, and the bacterial growth in PBS was used as control.…”

“…[12] So, truncating and redesigning the natural antimicrobial peptides to generate more efficient antimicrobial agents for clinical application have been considered. [13,14] As seen in previous studies, truncating the N-terminus or C-terminus of natural peptides can keep their excellent characteristics increase the biocompatibility of the parental peptide and save production costs. [15] Tandem repeat units can increase the net charge and hydrophobicity of antimicrobial peptides, rapidly increasing the antimicrobial activity.…”