q-Families of CVD(MPFA) Schemes on General Elements: Numerical Convergence and the Maximum Principle

In this paper, families of flux-continuous, locally conservative, finite-volume schemes are presented for solving the general geometry-permeability tensor pressure equation on structured and unstructured grids in two and three dimensions. The schemes are applicable to the general tensor pressure equation with discontinuous coefficients and remove the O(1) errors introduced by standard reservoir simulation (two-point flux) schemes when applied to full anisotropic permeability tensor flow approximation (Edwards and Rogers in Multigrids Methods, vol. 1, pp. 190–200, 1993; Edwards and Rogers in Proceedings: 4th European Conference on the Mathematics of Oil Recovery, 1994; Edwards and Rogers in Comput. Geom. 2:259–290, 1998). Full tensors arise when the local orientation of the grid is non-aligned with the principal axes of the tensor field. Full tensors may also arise when fine scale permeability distributions are upscaled to obtain gridblock-scale permeability distributions. In general full tensors arise when using any structured or unstructured grid type that departs from K-orthogonality.     

Elastically and Plastically Foldable Electrothermal Micro‐Origami for Controllable and Rapid Shape Morphing

Integrating origami principles within traditional microfabrication methods can produce shape morphing microscale metamaterials and 3D systems with complex geometries and programmable mechanical properties. However, available micro‐origami systems usually have slow folding speeds, provide few active degrees of freedom, rely on environmental stimuli for actuation, and allow for either elastic or plastic folding but not both. This work introduces an integrated fabrication–design–actuation methodology of an electrothermal micro‐origami system that addresses the above‐mentioned challenges. Controllable and localized Joule heating from electrothermal actuator arrays enables rapid, large‐angle, and reversible elastic folding, while overheating can achieve plastic folding to reprogram the static 3D geometry. Because the proposed micro‐origami do not rely on an environmental stimulus for actuation, they can function in different atmospheric environments and perform controllable multi‐degrees‐of‐freedom shape morphing, allowing them to achieve complex motions and advanced functions. Combining the elastic and plastic folding enables these micro‐origami to first fold plastically into a desired geometry and then fold elastically to perform a function or for enhanced shape morphing. The proposed origami systems are suitable for creating medical devices, metamaterials, and microrobots, where rapid folding and enhanced control are desired.     

Novel route for rapid biosynthesis of lead nanoparticles using aqueous extract of Jatropha curcas L. latex

We are reporting a novel, low-cost and eco-friendly route for rapid synthesis of lead nanoparticles by using 0.5% aqueous extract of Jatropha curcas L. latex. Lead nanoparticles were characterized initially by UV–vis spectroscopy and shown distinct peak at 218 nm. This peak was highly specific for lead nanoparticles. Formation of Pb (0) was confirmed by X-ray diffraction technique (XRD).Transmission electron microscopy (TEM) was performed for estimating the size and shape of nanoparticles. The average size of lead nanoparticles was found to be in the range of 10 to 12.5 nm. Energy dispersive analysis of X-rays (EDAX) showed distinct peaks of lead. Fourier Transform Infrared Spectroscopy (FTIR) were performed to find the role of cyclic peptides namely curcacycline A (an octapeptide) and curcacycline B (a nonapeptide) as a possible reducing and capping agents present in the latex of Jatropha curcas L. Lead nanoparticles formed by the above method were monodisperse.     

In vitro toxicity study of plant latex capped silver nanoparticles in human lung carcinoma cells

Organically modified silver nanoparticles were prepared by biosynthetic route induced by stem latex of a medicinally important plant, Euphorbia nivulia. The reduction and stabilization is assisted by certain peptides and terpenoids present within the latex. The aqueous formulation of latex capped silver nanoparticles (LAgNPs) being completely free of toxic chemicals can be directly used for administration/in vivo delivery of nanoparticles. The in vitro cytotoxicity evaluation of the latex capped nanoparticles was carried out using human lung carcinoma cells (A549) by MTT cell viability assay. Further, possible cytotoxic mechanisms were evaluated using various biomarkers for cytotoxicity and oxidative stress viz. extracellular lactate dehydrogenase (LDH) release, reactive oxygen species (ROS) generation, intracellular reduced glutathione (GSH), malondialdehyde (MDA), superoxide generation and acridine orange/ethedium bromide staining. It can be concluded from the present study that LAgNP formulation is toxic to A549 cells in a dose dependent manner. Thus plant latex solubilizes the AgNPs in water and acts as a biocompatible vehicle for transport of AgNPs to tumor/cancer cells.     

A case study: Te in ZnSe and Mn-doped ZnSe quantum dots

Photoluminescence (PL) behavior of ZnSe(1-y)Te(y) quantum dots is investigated by varying Te concentration as well as size. The striking effect of quantum confinement is the observation of isoelectronic center-related emission at room temperature in lieu of near-band-edge emission that dominates the optical scenario. ZnSe(0.99)Te(0.01) quantum dots were also doped by Mn(2+) ions. The Mn(2+) ion-related d-d transition is drastically suppressed by Te isoelectronic centers. Incorporation of Mn(2+) at substitutional sites in ZnSe(0.99)Te(0.01) quantum dots is also confirmed by the electron paramagnetic resonance measurements. Effect of Te isoelectronic impurity on the emission behavior is more pronounced than that of Mn(2+) ions. A subtle blueshift in the orange d-d transition is a sign of a decrease in crystal field strength. PL and photoluminescence excitation measurements on Zn(1-x)Se(0.99)Te(0.01)Mn(x) quantum dots indicate that the transition probability from the lowest unoccupied molecular orbital to Te levels is substantially larger than that to Mn(2+) d-d levels.     

Tuning physical properties of polyurethane hard segments through extender chain length variation and doping of pentaerythritol and their effect on in vitro protein adsorption

This study explores the synthesis and characterization of polyurethanes (PUs) derived from hexamethylene diisocyanate (HDI) and 1,n-alkane diols with varying chain lengths (n = 4, 6, and 10). Additionally, pentaerythritol (PE) is introduced as a dopant in PU6 at different weight percentages (25%, 50%, 75%, and 1:1%w/w). The research encompasses a comprehensive analysis of PU properties, including morphology, crystallinity, surface area, porosity, thermal behavior, rheological properties, and electrical conductivity. Of particular interest is the evaluation of protein adsorption capabilities employing bovine serum albumin (BSA) and fibrinogen proteins in in vitro tests. The study emphasizes the crucial role played by the chain length between isocyanate and diol groups and the nature and strength of hydrogen bonds among chains in shaping the polymer's properties, especially crystallinity and biocompatibility. Among the synthesized PUs, PU6 emerges as the top performer in terms of crystallinity and biocompatibility. Furthermore, the addition of PE is found to act as a plasticizer, reducing the glass transition temperature (T_g) from 75°C to 31°C. Electrochemical Impedance Spectroscopy shows that doping influences charge transfer processes, rendering the material semi-conducting, as evidenced by decreased conductance when adding silver nanoparticles to PU6. Notably, protein adsorption studies reveal that undoped PU6 displays superior protein resistance compared to its doped counterpart, with fibrinogen exhibiting a higher adsorption affinity than BSA. The study discusses a plausible mechanism underlying protein adsorption.     

Immobilization of metal nanoparticles on polyurethane membranes: synthesis and electrical properties

Ag and Cu nanoparticles were immobilized into crosslinked polyurethane (PU) membranes by taking advantage of the swelling characteristics of the membranes. The formation, shape and size of the nanoparticles inside the post‐swollen PU membranes were observed by transmission electron microscopy and atomic force microscopy. X‐ray diffraction indicated the presence of the pure Ag and Cu embedded in the amorphous PU matrix. Because of their compatibility, the nanoparticles improved the thermal stability and increased the glass transition temperature of PU. The membranes exhibited interesting conducting behavior with increasing temperature. The metal immobilization increased the ionic conductivity which further increased with temperature, with an activation energy of 0.15 eV indicating a thermally activated conduction mechanism. The optical and electrical properties of these starch‐based membranes can be utilized in the development of novel sensors for biomedical applications. Copyright © 2012 Society of Chemical Industry     

Synthesis and anti-bacterial activity of Cu, Ag and Cu-Ag alloy nanoparticles: A green approach

Metallic and bimetallic nanoparticles of copper and silver in various proportions were prepared by microwave assisted chemical reduction in aqueous medium using the biopolymer, starch as a stabilizing agent. Ascorbic acid was used as the reducing agent. The silver and copper nanoparticles exhibited surface plasmon absorption resonance maxima (SPR) at 416 and 584 nm, respectively; while SPR for the Cu-Ag alloys appeared in between depending on the alloy composition. The SPR maxima for bimetallic nanoparticles changes linearly with increasing copper content in the alloy. Transmission electron micrograph (TEM) showed monodispersed particles in the range of 20 ± 5 nm size. Both silver and copper nanoparticles exhibited emission band at 485 and 645 nm, respectively. The starch-stabilized nanoparticles exhibited interesting antibacterial activity with both gram positive and gram negative bacteria at micromolar concentrations.