Nitrogen-14 NMR of Solutes in Liquid Crystals: NH4NO3 and (CH3)4N NO3 in the DSCG–Water System

Measurements of the nitrogen-14 and deuterium quadrupolar splittings in NH₄NO₃ and (CH₃)₄ N NO₃ dissolved in the disodiumcromoglycate–water liquid crystalline system are presented. Nitrogen-14 T₁ values in aqueous solutions for these salts are also given. The results are discussed and compared with similar studies on solutes containing ¹⁴N in ordered media.     

Theoretical model for non-intermeshing twin screw extruders

A simple theoretical model for flow in nonintermeshing twin screw extruders has been derived. The assumptions which in single screw extruders result in the “two parallel plates” model, in twin screw extruders result in the “three parallel plates” model. The flow rate equation can be expressed, for Newtonian fluids, in terms of drag and pressure flow terms, as in single screw extrusion theory, but each term is multiplied by a geometrical factor. This factor incorporates the effect of one screw on the drag and pressure flow terms of the other. The theoretical model was experimentally verified on a 1 inch diameter Bausano twin screw extruder.     

Torsion of perforated cores: Planar formulation

A planar finite element approximate solution for the torsional analysis of symmetric perforated cores is given. The solution involves neglecting the out-of-plane stiffness of the walls of the core. Only one-quarter of the core is analyzed, using super elements assembled from high order plane stress finite elements. The results of the analysis are compared with the results from three-dimensional finite element analysis. It is observed that for almost all realistic designs the planar approximation is justified. The solution is very close with significant reduction in computation time and data preparation effort.     

Rapid deposition of transparent super-hydrophobic layers on various surfaces using microwave plasma

We report herein on a very fast and simple process for the fabrication of transparent superhydrophobic surfaces by using microwave (MW) plasma. It was found that the reaction of various organic liquids in MW argon plasma yields hydrophobic polymeric layers on a large assortment of surfaces, including glass, polymeric surfaces, ceramics, metals, and even paper. In most cases, these polymers are deposited as a rough layer composed of 10-15 nm nanoparticles (NPs). This roughness, together with the chemical hydrophobic nature of the coated materials, is responsible for the superhydrophobic nature of the surface. The typical reaction time of the coating procedure was 1-10 s. The stability of these superhydrophobic surfaces was examined outdoors, and was found to last 2-5 days under direct exposure to the environment and to last 2 months when the sample was protected by a quartz cover. A detailed characterization study of the chemical composition of the layers followed using XPS, solid-state NMR, and IR measurements. Modifications were introduced in the products leading to a substantial improvement in the stability of the products outdoors.     

Eradication of Multi‐Drug Resistant Bacteria by a Novel Zn‐doped CuO Nanocomposite

Zinc‐doped copper oxide nanoparticles are synthesized and simultaneously deposited on cotton fabric using ultrasound irradiation. The optimization of the processing conditions, the specific reagent ratio, and the precursor concentration results in the formation of uniform nanoparticles with an average size of ≈30 nm. The antibacterial activity of the Zn‐doped CuO Cu_0.88Zn_0.12O in a colloidal suspension or deposited on the fabric is tested against Escherichia coli (Gram negative) and Staphylococcus aureus (Gram positive) bacteria. A substantial enhancement of 10 000 times in the antimicrobial activity of the Zn–CuO nanocomposite compared to the pure CuO and ZnO nanoparticles (NPs) is observed after 10 min exposure to the bacteria. Similar activities are observed against multidrug‐resistant bacteria (MDR), (i.e., Methicillin‐resistant S. aureus and MDR E. coli) further emphasizing the efficacy of this composite. Finally, the mechanism for this enhanced antibacterial activity is presented.     

Self-Healing and -Repair of Nanomechanical Damages in Lead Halide Perovskites

Recovery from damage in materials helps extend their useful lifetime and of devices that contain them. Given that the photodamages in HaP materials and based devices are shown to recover, the question arises if this also applies to mechanical damages, especially those that can occur at the nanometer scale, relevant also in view of efforts to develop flexible HaP-based devices. Here, this question is addressed by poking HaP single crystal surfaces with an atomic force microscope (AFM) tip under both ultra-high vacuum (UHV) and variably controlled ambient water vapor pressure conditions. Sequential in situ AFM scanning allowed real-time imaging of the morphological changes at the damaged sites. Using methylammonium (MA) and cesium (Cs) variants for A-site cations in lead bromide perovskites, the experiments show that nanomechanical damages on methylammonium lead bromide (MAPbBr₃) crystals heal an order of magnitude faster than Cs-based ones in UHV. However, surprisingly, under ≥40% RH conditions, cesium lead bromide (CsPbBr₃) shows MAPbBr₃-like fast healing kinetics. Direct evidence for ion solvation on CsPbBr₃ is presented, leading to the formation of a surface hydration layer. The results imply that moisture improves the ionic mobility of degradation components and leads to water-assisted improved healing, i.e., repair of nanomechanical damages in the HaPs.