The adhesive contact between a rigid cylinder and an elastic layer bonded on a rigid half-space is investigated. In the past, several analytical models were proposed in the frame of the JKR model. In ...this research, boundary element method is employed. The traction is derived on the basis of the Lennard-Jones potential and the Derjaguin approximation. The whole solutions are obtained. The effects of Tabor parameter and layer thickness are investigated. The results are compared with the analytical models. The limitations of the analytical models are obtained. The empirical formulas for pull-off forces, jump-in distance, and pull-off distance are proposed.
There exist many well-known analytical models for adhesive contact for spherical asperities. However, in many situations, the asperities are not spherical and may be better described by a power-law ...function. Thus, these well-known analytical models were extended to power-law-shaped axisymmetric asperities in the past decades. In this paper, numerical simulation is employed for the adhesive contact between a rigid power-law axisymmetric asperity and an elastic half-space. The realistic Lennard-Jones potential and the Derjaguin approximation are used for the surface traction. Numerical simulations are performed with different shape indexes and different Tabor parameters. The whole solution is obtained. Semi-empirical formulas for the pull-off forces, the contact radius at zero loads, the jump-in distance, and the pull-off distance are proposed. All these equations are both simple and as accurate as of the numerical simulations.
Helicobacter pylori pathogenesis and disease outcomes are mediated by a complex interplay between bacterial virulence factors, host, and environmental factors. After H. pylori enters the host ...stomach, four steps are critical for bacteria to establish successful colonization, persistent infection, and disease pathogenesis: (1) Survival in the acidic stomach; (2) movement toward epithelium cells by flagella-mediated motility; (3) attachment to host cells by adhesins/receptors interaction; (4) causing tissue damage by toxin release. Over the past 20 years, the understanding of H. pylori pathogenesis has been improved by studies focusing on the host and bacterial factors through epidemiology researches and molecular mechanism investigations. These include studies identifying the roles of novel virulence factors and their association with different disease outcomes, especially the bacterial adhesins, cag pathogenicity island, and vacuolating cytotoxin. Recently, the development of large-scale screening methods, including proteomic, and transcriptomic tools, has been used to determine the complex gene regulatory networks in H. pylori. In addition, a more available complete genomic database of H. pylori strains isolated from patients with different gastrointestinal diseases worldwide is helpful to characterize this bacterium. This review highlights the key findings of H. pylori virulence factors reported over the past 20 years.
The adhesive contact between a rigid sphere and a thin elastic layer bonded on a rigid foundation is investigated using boundary element method (BEM). Surface profile is approximated parabolic. The ...Lennard-Jones potential and the Derjaguin approximation are used for the surface traction. In the past, the adhesive contact between a sphere and a thin layer was analyzed only in the frame of the JKR theory. In this article, the adhesive contact is investigated with different Tabor parameters and different layer thickness. The whole solutions are obtained. The results are compared with the current analytical models and the simulation for the adhesive contact between spheres. The restrictions of the analytical models are obtained. The empirical formulas for jump-in and pull-off distance are proposed.
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Dostopno za:
BFBNIB, DOBA, GIS, IJS, IZUM, KILJ, KISLJ, NUK, PILJ, PNG, SAZU, UILJ, UKNU, UL, UM, UPUK
•A novel “systematic evolution of ligands by exponential enrichment” (SELEX) protocol was developed to screen bacterial aptamers.•A new dual-aptamer, paper-based microfluidic chip was developed for ...fast diagnosis of three common nosocomial bacteria.•The system possesses many advantages such as faster detection times, smaller size and capability to detect multiple pathogens simultaneously.
A bacterial “systematic evolution of ligands by exponential enrichment” protocol was developed herein to identify nucleic acid aptamers capable of binding molecules from three common nosocomial and antibiotic-resistant bacteria: Acinetobacter baumannii, Escherichia coli, and multidrug-resistant Staphylococcus aureus. This high-affinity and high-specificity process featured three selection stages for screening of bacteria-specific aptamers, and the aptamers identified were integrated into a microfluidic system. The biotin-labeled aptamers were first bound to nitrocellulose membranes housed within the chip and then incubated with bacteria; a tetramethyl benzidine (TMB)-streptavidin (blue) color reaction was next exploited upon binding of secondary aptamers to primary ones, thereby permitting bacterial detection. This new dual-aptamer microfluidic chip possesses many advantages over its traditional-scale counterparts, such as faster detection times (35 min), smaller size (7.0 cm × 5.0 cm × 1.2 cm), higher specificity, and the capability to detect multiple pathogens simultaneously; it may therefore be promising for point-of-care bacterial diagnostics.
Boundary element method is used to analyze the adhesive contact between an elastic cylinder and a rigid half-space. Lennard-Jones potential is used for the surface traction. In the past, the ...simulation for the adhesive contact between cylinders usually used parabolic approximation for cylinder surface, and used line loading acting on a half-space. Since line loading may cause infinite deformation, only contact half-width/load relation and pull-off force can be obtained. In this paper, the adhesive contact between an exact elastic cylinder and a rigid half-space is investigated. The S-shaped load-approach curve and the whole solution are obtained. Using the load-approach curves, the pull-off force, pull-off distance and jump-in distance are obtained. The effects of Tabor parameter and radius are investigated. The result is compared with the numerical simulation for the adhesive contact between an elastic parabolically approximated cylinder and a rigid half-space and the two-dimensional JKR model. For large Tabor parameters, two-dimensional JKR model can approximate the adhesive contact. For small Tabor parameters, two-dimensional Bradley model can approximate the adhesive contact. The radii do affect the load-approach relation for large Tabor parameters, and have very small effects for small Tabor parameters. A semi-rigid cylinder model is proposed. This model can predict the load-approach curves for small Tabor parameters and can predict the jump-in distance for large Tabor parameters. In addition, a modified load-approach relation for two-dimensional JKR model is proposed. This relation can approximate the load-approach relation and predict the pull-off distance for large Tabor parameters. It is also found that the radius does not affect the pull-off force.
SUMMARYGroup A
(GAS), also known as
, is a clinically well-adapted human pathogen that harbors rich virulence determinants contributing to a broad spectrum of diseases. GAS is capable of invading ...epithelial, endothelial, and professional phagocytic cells while evading host innate immune responses, including phagocytosis, selective autophagy, light chain 3-associated phagocytosis, and inflammation. However, without a more complete understanding of the different ways invasive GAS infections develop, it is difficult to appreciate how GAS survives and multiplies in host cells that have interactive immune networks. This review article attempts to provide an overview of the behaviors and mechanisms that allow pathogenic GAS to invade cells, along with the strategies that host cells practice to constrain GAS infection. We highlight the counteractions taken by GAS to apply virulence factors such as streptolysin O, nicotinamide-adenine dinucleotidase, and streptococcal pyrogenic exotoxin B as a hindrance to host innate immune responses.
A numerical model with bi-conjugate gradient stabilized method (Bi-CGSTAB) is proposed to simulate the adhesive contact between rough surfaces. This model provides a self-consistent solution of ...surface separation and contact pressure throughout rough surface with the adhesive interactions governed by the Lennard-Jones potential. This model uses the inexact Newton method and the preconditioned Bi-CGSTAB method for each Newton iteration. Both left and right preconditioners are employed. This model is proved to be accurate and feasible and is suitable for the moderate adhesive contact between rough surfaces.
This study reports a new diagnostic assay for the rapid detection of methicillin-resistant Staphylococcus aureus (MRSA) by combing nucleic acid extraction and isothermal amplification of target ...nucleic acids in a magnetic bead-based microfluidic system. By using specific probe-conjugated magnetic beads, the target deoxyribonucleic acid (DNA) of the MRSA can be specifically recognized and hybridized onto the surface of the magnetic beads which are then mixed with clinical sample lysates. This is followed by purifying and concentrating the target DNA from the clinical sample lysates by applying a magnetic field. Nucleic acid amplification of the target genes can then be performed by the use of a loop-mediated isothermal amplification (LAMP) process via the incorporation of a built-in micro temperature control module, followed by analyzing the optical density (OD) of the LAMP amplicons using a spectrophotometer. Significantly, experimental results show that the limit of detection (LOD) for MRSA in the clinical samples is approximately 10 fg μL(-1) by performing this diagnostic assay in the magnetic bead-based microfluidic system. In addition, the entire diagnostic protocol, from bio-sample pre-treatment to optical detection, can be automatically completed within 60 min. Consequently, this miniature diagnostic assay may become a powerful tool for the rapid purification and detection of MRSA and a potential point-of-care platform for detection of other types of infections.
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