High temperature formability of graphene nanoplatelets-AZ31 composites fabricated by stir-casting method

Outstanding mechanical properties of graphene nanoplatelets (GNPs) make them ideal reinforcement for mass production of composites. In this research, the composites were fabricated by stir-casting method. GNPs were added in 1.5 and 3.0 wt.% into Mg–3wt.% Al–1wt.% Zn (AZ31) magnesium alloy. As cast ingots were preheated for one hour and extruded at 350 °C with extrusion ratio of 5.2:1. As extruded AZ31-GNPs composites were micro-structurally characterized with X-ray diffraction, optical microscopy and scanning electron microscopy. Vickers micro-hardness of synthesized materials was investigated both in parallel and perpendicular to extrusion directions. Room temperature mechanical testing revealed that with increasing GNP's content, tensile fracture strain was remarkably increased without significant compromise in tensile strength. Furthermore, as extruded AZ31-3GNPs composites were subjected to tensile testing at temperatures ranging from 75 °C to 300 °C with initial strain rate of 2 × 10−3 s−1 to evaluate high temperature formability of composite. It was found that like CNTs, GNPs also have the potential to sustain tensile strength at high temperatures

Cucumber Metallothionein-Like 2 (CsMTL2) Exhibits Metal-Binding Properties

We identified a novel member of the metallothionein (MT) family, Cucumis sativus metallothionein-like 2 (CsMTL2), by screening a young cucumber fruit complementary DNA (cDNA) library. The CsMTL2 encodes a putative 77-amino acid Class II MT protein that contains two cysteine (Cys)-rich domains separated by a Cys-free spacer region. We found that CsMTL2 expression was regulated by metal stress and was specifically induced by Cd2+ treatment. We investigated the metal-binding characteristics of CsMTL2 and its possible role in the homeostasis and/or detoxification of metals by heterologous overexpression in Escherichia coli cells. Furthermore, we produced a deletion mutant form of the protein, CsMTL2m, that contained the two Cys-rich clusters but lacked the spacer region, in E. coli. We compared the metal-binding properties of CsMTL2 with those of CsMTL2m, the β domain of human metallothionein-like protein 1 (HsMTXb), and phytochelatin-like (PCL) heterologously expressed in E. coli using metal-binding assays. We found that E. coli cells expressing CsMTL2 accumulated the highest levels of Zn2+ and Cd2+ of the four transformed cell types, with levels being significantly higher than those of control cells containing empty vector. E. coli cells expressing CsMTL2 had a higher tolerance for cadmium than for zinc ions. These findings show that CsMTL2 improves metal tolerance when heterologously expressed in E. coli. Future studies should examine whether CsMTL2 improves metal tolerance in planta

SlbZIP38, a Tomato bZIP Family Gene Downregulated by Abscisic Acid, Is a Negative Regulator of Drought and Salt Stress Tolerance

The basic leucine zipper (bZIP) transcription factors have crucial roles in plant stress responses. In this study, the bZIP family gene SlbZIP38 (GenBank accession No: XM004239373) was isolated from a tomato (Solanum lycopersicum cv. Ailsa Craig) mature leaf cDNA library. The DNA sequence of SlbZIP38 encodes a protein of 484 amino acids, including a highly conserved bZIP DNA-binding domain in the C-terminal region. We found that SlbZIP38 was differentially expressed in various organs of the tomato plant and was downregulated by drought, salt stress, and abscisic acid (ABA). However, overexpression of SlbZIP38 significantly decreased drought and salt stress tolerance in tomatoes (Ailsa Craig). The findings that SlbZIP38 overexpression reduced the chlorophyll and free proline content in leaves but increased the malondialdehyde content may explain the reduced drought and salt tolerance observed in these lines. These results suggest that SlbZIP38 is a negative regulator of drought and salt resistance that acts by modulating ABA signaling

Effect of boron on the grain refinement and mechanical properties of as-Cast Mg alloy AM50

The effect of B addition on the microstructure and mechanical properties of AM50 was investigated, and the mechanism of grain refinement was clarified. Optical microscopy, X-ray diffraction, scanning electron microscopy, and electron probe microanalysis were used to characterize the microstructure evolution. The grain size of as-cast AM50 decreased from 550 m to 100 m with the B content increasing from 0 to 0.15 wt.%. AlB2 particles in the Al-3B master alloy transformed to Mg-B, and acted as the grain refiner. The addition of B to as cast AM50 alloy results in improved mechanical properties of AM50 + xB alloys. For instance, the YTS (yield tensile strength), UTS (ultimate tensile strength), and elongation of as cast AM50 + 0.15 wt.% B alloy was 94 MPa, 215 MPa, and 12.3%