Microfluidic bolus induced gradient generator for live cell signalling

Major events in cell biology are initiated by the binding of ligands to cell surface receptors and/or their transport into cells. We present a study of a simple microchannel system that integrates a bolus generator and surface-adhered cell culture domains. Our system allows the delivery of small packets or boluses of biomolecules to a cell population. Owing to pressure driven microfluidic flow of the bolus, a gradient of cell surface bound ligands is established along the length of the microchannel. Experimental data for the epidermal growth factor (EGF) binding to its receptor on A431 cells are presented. We highlight the effect of changing Peclet number (or flowrate), bolus shape, bolus volume and ligand concentration on the gradient formed longitudinally in the microchannel. A mathematical model describing the transient convection, diffusion, dispersion and binding of ligands to cell surface receptors is developed. The model provides essential design guidelines for our system with good qualitative agreement with experimental data. The results suggest ways to modulate the amount of bound ligand and the gradient independently. This simple microsystem is suitable for generating longer range gradients involving larger cell populations as compared to existing microfluidic systems.     

Modeling of white layer formation under thermally dominant conditions in orthogonal machining of hardened AISI 52100 steel

This paper presents a finite element model for white layer formation in orthogonal machining of hardened AISI 52100 steel under thermally dominant cutting conditions that promote martensitic phase transformations. The model explicitly accounts for the effects of stress and strain, transformation plasticity and the effect of volume expansion accompanying phase transformation on the transformation temperature. Model predictions of white layer depth are found to be in agreement with experimental values. The paper also analyzes the effect of white layer formation on residual stress evolution in orthogonal cutting of AISI 52100 hardened steel. Model simulations show that white layer formation does have a significant impact on the magnitude of surface residual stress and on the location of the peak compressive residual stress.     

Effect of Silane-Treated Rice Husk Derived Biosilica on Visco-Elastic,Thermal Conductivity and Hydrophobicity Behavior of Epoxy Biocomposite Coating for Air-Duct Application

Silicon - High performance epoxy biocomposite coating material was prepared using agricultural waste (rice husk) derived biosilica and characterized for visco-elastic, thermal conductivity and...     

Fiber bundle push-out test and image-based finite element simulation for 3D carbon/carbon composites

The interfacial properties such as debond strength, fracture energy release rate in Mode-II and coefficient of friction play important roles in determining the mechanical properties and strength of carbon/carbon (C/C) composites. Push-out tests were conducted on 3D C/C composites and the experimental results were fitted to the shear lag model to determine these interfacial properties. X-ray tomography was used to explore the internal material structure of the composite. The fiber bundle and matrix interfaces were observed as being partially damaged in the tomographic images and the crack network was explored in detail. The tomographic images were also used to reconstruct a finite element (FE) mesh for simulating push-out tests. The interface of the fiber bundle and matrix in the FE mesh was represented by cohesive surfaces with frictional contact. The cohesive surface properties were obtained by matching FE results with the experimental results. The simulations had a good agreement with experiments and values of 0.75 for coefficient of friction, 2–5 N/mm² for debond stress, 1–4 N/mm² for clamping stress and 3–6 N/m for fracture energy release rate were obtained as interfacial parameters for the composite.     

Microstructural Characterisations and High Temperature Oxidation Studies of Nanostructured Co–Al Coatings Deposited on Superalloy

The microstructural characterizations and high temperature oxidation of magnetron sputtered Co?CAl coatings on the superalloy substrate have been studied in the present work. FE-SEM/EDS and XRD were used to characterize the morphology and formation of different phases in the coatings, respectively. Thermo gravimetric technique was used to investigate the oxidation of the coatings, in air at 900°C. The growth kinetics of the oxide layers was predicted using weight change of the coated sample measured during oxidation. It was found that the oxidation rate of Co?CAl coated superalloy was lower than that uncoated superalloy due to the formation of continuous dense, adherent and protective oxide scale such as CoO, Al₂O₃, Cr₂O₃, CoCr₂O₄, and CoAl₂O₄ over the surface of the coatings exposed to air at high temperature oxidation, 900°C. The microstructural features and phases of the oxidised coatings were used to elucidate the mechanism of high temperature oxidation.     

Advances in Nucleoside and Nucleotide Analogues in Tackling Human Immunodeficiency Virus and Hepatitis Virus Infections

Nucleoside and nucleotide analogues are structurally similar antimetabolites and are promising small-molecule chemotherapeutic agents against various infectious DNA and RNA viruses. To date, these analogues have not been documented in-depth as anti-human immunodeficiency virus (HIV) and anti-hepatitis virus agents, these are at various stages of testing ranging from pre-clinical, to those withdrawn from trials, or those that are approved as drugs. Hence, in this review, the importance of these analogues in tackling HIV and hepatitis virus infections is discussed with a focus on the viral genome and the mechanism of action of these analogues, both in a mutually exclusive manner and their role in HIV/hepatitis coinfection. This review encompasses nucleoside and nucleotide analogues from 1987 onwards, starting with the first nucleoside analogue, zidovudine, and going on to those in current clinical trials and even the drugs that have been withdrawn. This review also sheds light on the prospects of these nucleoside analogues in clinical trials as a treatment option for the COVID-19 pandemic.