Characteristics of Dislocation Half-Loop Arrays in 4H-SiC Homo-Epilayer

Dislocation “half-loop arrays” (HLAs) in 4H-SiC homo-epilayers are studied by molten KOH etching and atomic force microscopy (AFM). It is found that the dislocation half-loops in an array exist at different depths in the epilayer, and they are aligned roughly but not exactly perpendicular to the off-cut direction. These results indicate that the dislocation half-loops in an array are not formed simultaneously, but the array extends by generation of new half-loops during growth. It is also demonstrated that the HLAs can be artificially induced by creating strain in the material, followed by annealing.     

Biomonitoring of the adverse effects induced by the chronic exposure to lead and cadmium on kidney function: usefulness of alpha-glutathione S-transferase

A successful prevention of renal diseases induced by occupational exposure to lead (Pb) and/or cadmium (Cd) largely relies on the capability to detect nephrotoxic effects at a stage when they are still reversible or at least not yet compromising renal function. Hence, the aim of this cross-sectional study was to evaluate the usefulness of a set of early biological markers of oxidative stress or nephrotoxicity for the biomonitoring of workers occupationally exposed to Pb and/or Cd in a non-ferrous metal smelter, and gender, age, socioeconomic status, smoking habits, and drug use-matched control individuals. In exposed subjects, mean levels of Pb in blood and urine were also 387.1+/-99.1 microg Pb/L (1.868+/-0.478 micromol Pb/L) and 217.7+/-117.7 microg Pb/g creatinine (1.051+/-0.568 micromol Pb/g creatinine), and mean levels of Cd in blood and urine were 3.26+/-2.11 microg Cd/L (0.029+/-0.019 micromol Cd/L) and 2.51+/-1.89 microg Cd/g creatinine (0.022+/-0.017 micromol Cd/g creatinine), suggesting thereby relatively low occupational exposure levels. Statistically significant variations in zinc protoporphyrin, malondialdehyde, retinol binding protein, alpha-glutathione S-transferase, and urinary protein levels were reported between the two groups, and were closely correlated with Pb and/or Cd exposure levels. Variations in alphaGST levels were closely associated with Pb exposure. Taken together, these results suggest the use of alpha-glutathione S-transferase excretion in urine as a hallmark of early changes in the proximal tubular integrity.     

Dislocation Cores and Hardness Polarity of 4H-SiC

The hardness of opposite basal faces of 4H-SiC single crystals has been measured in the temperature range 25°–1200°C. A strong hardness anisotropy between the silicon-terminated (0001) and carbon-terminated (0001) faces of this polar crystal has been found. Transmission electron microscopy investigation of the dislocations in the plastic zone of the 1200°C indentations shows that they lie predominantly on the basal planes parallel to the indented face, and the extra-half planes of the nonscrew dislocations originate from the indented face. It is also found that, when the (0001) Si-terminated face is indented, the dislocations are either widely dissociated, with the width of the stacking fault ribbon much larger than the equilibrium value, or else they are single leading partials, with the corresponding trailing partials absent. In this case, all the leading partials are found to have a silicon core. On the other hand, the dislocations in the plastic zone of the carbon-terminated face are in the form of dissociated dislocations, with the width of the associated stacking fault ribbons appreciably less than the equilibrium value. Moreover, the leading partials of these dissociated dislocations have a carbon core. The results indicate that the hardness of the polar basal faces of 4H-SiC at elevated temperatures is partly determined by the nature of the dislocation cores nucleated by the indentation process. It is argued that this is due to the influence of the core on the generation and glide of the leading partial dislocations.     

Assessment of fly ash-aided phytostabilisation of highly contaminated soils after an 8-year field trial Part 2. Influence on plants

Aided phytostabilisation is a cost-efficient technique to manage metal-contaminated areas, particularly in the presence of extensive pollution. Plant establishment and survival in highly metal-contaminated soils are crucial for phytostabilisation success, as metal toxicity for plants is widely reported. A relevant phytostabilisation solution must limit metal transfer through the food chain. Therefore, this study aimed at evaluating the long-term efficiency of aided phytostabilisation on former agricultural soils highly contaminated by cadmium, lead, and zinc. The influence of afforestation and fly ash amendments on reducing metal phytoavailability was investigated as were their effects on plant development. Before being planted with a tree mix, the site was divided into three plots: a reference plot with no amendment, a plot amended with silico-aluminous fly ash and one with sulfo-calcic fly ash. Unlike Salix alba and Quercus robur, Alnus glutinosa, Acer pseudoplatanus and Robinia pseudoacacia grew well on the site and accumulated, overall, quite low concentrations of metals in their leaves and young twigs. This suggests that these three species have an excluder phenotype for Cd, Zn and Pb. After 8 years, metal availability to A. glutinosa, A. pseudoplatanus and R. pseudoacacia, and translocation to their above-ground parts, strongly decreased in fly ash-amended soils. Such decreases fit well together with the depletion of CaCl₂-extractable metals in amended soils. Although both fly ashes were effective to decrease Cd, Pb and Zn concentrations in above-ground parts of trees, the sulfo-calcic ash was more efficient.     

Temperature Dependence of Hardness in Yttria-Stabilized Zirconia Single Crystals

The temperature dependence of hardness and microcracking in single-crystal 9.5-mol%-Y₂O₃-fully-stabilized cubic-ZrO₂ was studied as a function of orientation. Crack lengths increased with increased temperature up to 500°C; above 800°C, no cracks were found, indicating an indentation brittle-to-ductile transition of ∼800°C. The temperature dependence of hardness was reduced around 500°C. Etching studies to delineate the plastic zone around and below indents identified the operative slip systems. The role of dislocations and their interactions within the plastic zone on the hardness and indentation fracture behavior of cubic-ZrO₂ are discussed.     

Plant leaves icephobicity

Ice adhesion and accumulation are well known to cause serious problems for different structures such as wind turbines, power transmission and distribution systems, and aircraft. Development of coatings that can resist icing can solve many challenges in various areas of industry. This work was inspired by nature and ice resistivity and superhydrophobicity of plants leaves. Kale is a winter plant with superhydrophobic behaviors, which is normally known as an advantage for cleaning the leaves; however, this article reveals that kale leaves have special surface microstructures delaying the ice formation initiation making them good candidates for designing ice-repellent coatings. In-depth experimental analyses, IR thermography, contact angle measurements, and scanning electron microscopy of the leaves were performed to discover how different plants can prevent icing and further find an optimal design for an artificial ice-repellent coating.     

Green bio-synthesis of Ni/montmorillonite nanocomposite using extract of Allium jesdianum as the nano-catalyst for electrocatalytic oxidation of methanol

In this work, synthesis of Ni nanoparticles was carried out successfully by water extract of Allium jesdianum as a biochemical reducing agent in the presence of montmorillonite clay (MMT) as a natural solid support for the first time. Then the electrochemical activity of the synthesized nanocomposite was investigated in methanol electrocatalytic oxidation. MMT with high cation exchange capacity and nano layer structure was exposed to ion exchange conditions in nickel solution. Then Ni²⁺ ion exchanged form was used in this process as a source of ions and also capping agent. Water extract of Allium jesdianum used as a reducing agent due to abundant availability of phenolic and flavonoid contents. The synthesized Ni/MMT nanocomposite was characterized using UV–Vis spectroscopy (UV–Vis), Fourier Transform Infrared Spectroscopy (FT-IR), X-ray diffraction (XRD), Scanning Electron Microscopy (SEM), Transmission electron microscopy (TEM) and Energy-dispersive X-ray spectroscopy (EDX). The surface of prepared modified electrode has been characterized using SEM to evaluate the morphology, showing uniform dispersion of Ni nanoparticles with mean diameter of 12 to 20 nm. The modified carbon paste electrode was then used in methanol electrocatalytic oxidation reaction. Methanol oxidation on the proposed modified electrode surface occurs at 0.6 V and 0.3 V in alkaline and acidic medium respectively. Also, the results showed the better performance of modified electrode toward methanol electrocatalytic oxidation in comparison with carbon paste electrode that is modified by ion exchanged MMT. Charge transfer coefficients and apparent charge transfer rate constant for the modified electrode in the absence of methanol in alkaline medium were respectively found as: α_a = 0.53, α_c = 0.37 and k_s = 1.6 × 10⁻¹ s⁻¹. Also, the average value of catalytic rate constant for the electrocatalytic oxidation of methanol by the prepared nano-catalyst was estimated to be about 0.9 L·mol^-1·s^-1 by chronoamperometry technique. The prepared electrode was also effective for electrocatalytic oxidation of ethanol and formaldehyde in alkaline medium.     

Emerging Biofabrication Strategies for Engineering Complex Tissue Constructs

The demand for organ transplantation and repair, coupled with a shortage of available donors, poses an urgent clinical need for the development of innovative treatment strategies for long‐term repair and regeneration of injured or diseased tissues and organs. Bioengineering organs, by growing patient‐derived cells in biomaterial scaffolds in the presence of pertinent physicochemical signals, provides a promising solution to meet this demand. However, recapitulating the structural and cytoarchitectural complexities of native tissues in vitro remains a significant challenge to be addressed. Through tremendous efforts over the past decade, several innovative biofabrication strategies have been developed to overcome these challenges. This review highlights recent work on emerging three‐dimensional bioprinting and textile techniques, compares the advantages and shortcomings of these approaches, outlines the use of common biomaterials and advanced hybrid scaffolds, and describes several design considerations including the structural, physical, biological, and economical parameters that are crucial for the fabrication of functional, complex, engineered tissues. Finally, the applications of these biofabrication strategies in neural, skin, connective, and muscle tissue engineering are explored.     

Cross-sectional TEM and KOH-Etch Studies of Extended Defects in 3C-SiC <Emphasis Type="Italic">p</Emphasis><Superscript>+</Superscript><Emphasis Type="Italic">n</Emphasis> Junction Diodes Grown on 4H-SiC Mesas

This article presents cross-sectional transmission electron microscopy and molten-potassium hydroxide etching studies of (111) 3C-SiC diodes which we previously reported to be free of forward-voltage drift despite abundant electroluminescent linear features presumed to be defects. Our results show that the majority of linear features are stacking faults lying in inclined {111} planes. Additionally, high densities of isolated etch pits (10⁶–10⁸ cm⁻²) are observed in 3C films grown on stepped 4H mesas, while 3C films nucleated on step-free 4H mesas exhibited orders of magnitude fewer etch pits and stacking faults. Defect formation mechanisms whose impetuses are steps on the 4H-SiC pregrowth mesa are discussed.