Microstructures and mechanical properties of mullite-(yttria, magnesia- and ceria-stabilized) zirconia composites

The microstructures and some mechanical properties of composites containing mullite and each of three different zirconias stabilized with low concentrations of yttria, magnesia, and ceria, have been studied. A sol-gel derived, high-purity, mullite was used as a matrix phase. In the present study, composites were prepared by conventional sintering of mullite and zirconia milled powder mixture. In all the composite materials, large fractions of the tetragonal zirconia (ZrO2) transformed into monoclinic form during cooling from the fabrication temperature. In the use of ceria-stabilized ZrO2, large internal macroscopic voids appeared in the sintered body. The thermal expansion hysteresis associated with the tetragonal/monoclinic transformation was evident only in the mullite/yttria-stabilized ZrO2 composite from which the Ms temperature could be determined. This revised version was published online in November 2006 with corrections to the Cover Date.     

Microstructural analysis of martensitic hard surfacing on low chromium alloy steel

This study focuses on the metallurgical characterization of single and multi-layer martensitic hard surfacing onto non-standardized low-chromium alloy steel with a single buttering layer using an automatic submerged arc welding process as a standard reference. The metallurgical properties of hard surfaced samples are examined using an optical microscope, energy dispersive x-ray spectroscopy, and x-ray diffractometer. Micro-Vickers hardness testing is also conducted to analyze and confirm the metallographic results of hard surfacing. The current study finds that the microstructure of each region is influenced by three key factors: chemical composition, heat input, and dilution. The structural type is determined by the chemical composition of materials, heat input influences the structural characteristics in the heat-affected zone (needle-shape martensite and tempered martensite), and dilution affects the structural characteristics of the hard surfacing layers (martensite with retained austenite). Comparing multi-layer hard surfacing to single-hard surfacing, the hardness values of the heat-affected zone of the multi-layer hard surfacing are greatly reduced, while the hardness values of the hard surfacing layers are raised.     

Development of a Rapid Fluorescent Diagnostic System for Early Detection of the Highly Pathogenic Avian Influenza H5 Clade 2.3.4.4 Viruses in Chicken Stool

Rapid diagnosis is essential for the control and prevention of H5 highly pathogenic avian influenza viruses (HPAIVs). However, highly sensitive and rapid diagnostic systems have shown limited performance due to specific antibody scarcity. In this study, two novel specific monoclonal antibodies (mAbs) for clade 2.3.4.4 H5Nx viruses were developed by using an immunogen from a reversed genetic influenza virus (RGV). These mAbs were combined with fluorescence europium nanoparticles and an optimized lysis buffer, which were further used for developing a fluorescent immunochromatographic rapid strip test (FICT) for early detection of H5Nx influenza viruses on chicken stool samples. The result indicates that the limit of detection (LoD) of the developed FICT was 40 HAU/mL for detection of HPAIV H5 clade 2.3.4.4b in spiked chicken stool samples, which corresponded to 4.78 × 10⁴ RNA copies as obtained from real-time polymerase chain reaction (RT-PCR). An experimental challenge of chicken with H5N6 HPAIV is lethal for chicken three days post-infection (DPI). Interestingly, our FICT could detect H5N6 in stool samples at 2 DPI earlier, with 100% relative sensitivity in comparison with RT-PCR, and it showed 50% higher sensitivity than the traditional colloidal gold-based rapid diagnostic test using the same mAbs pair. In conclusion, our rapid diagnostic method can be utilized for the early detection of H5Nx 2.3.4.4 HPAIVs in avian fecal samples from poultry farms or for influenza surveillance in wild migratory birds.     

High-Efficiency Perovskite Quantum Dot Photovoltaic with Homogeneous Structure and Energy Landscape

The energy disorder originating from quantum dot (QD) size and relevant solid film inhomogeneity is detrimental to the charge transport and efficiency of QD based solar cells. The emergence of halide perovskite QDs (PQDs) have attracted great attention as promising absorbers in QD photovoltaics. However, it is currently difficult in preparing structural uniform PQD film with homogenous energetic landscape, which is essential for highly reproducible and efficient solar cells. Herein, assisted by a bidentate ligand 2,5-thiophenedicarboxylic acid, a facile solution phase anchoring (SPA) strategy is first reported for design and preparation of all-inorganic CsPbI₃ PQD film with reduced structure and energy disorder. The SPA can enhance PQD dispersion as well as dot-to-dot interaction, which is beneficial for fabricating high-quality PQD arrays and photovoltaic devices. The engineered CsPbI₃ PQD solar cell exhibits enhanced reproducibility, and higher open–circuit voltage together with a champion efficiency of 16.14%, which is among the highest report to date. These results are believed to provide design principle of uniform PQDs for high-performance optoelectronic application.     

Structures and Mechanisms of a Novel Bacterial Transport System for Fatty Acids

Bacterial acquisition of metabolites is largely facilitated by transporters with unique substrate scopes. The tripartite ATP-independent periplasmic (TRAP) transporters comprise a large family of bacterial proteins that facilitate the uptake of a variety of small molecules. It has been reported that some TRAP systems encode a fourth protein, the T component. The T-component, or TatT, is predicted to be a periplasmic-facing lipoprotein that enables the uptake of metabolites from the outer membrane. However, no substrates were revealed for any TatT and their functional role(s) remained enigmatic. We recently identified a homolog in Methylococcus capsulatus that binds to sterols, and herein, we report two additional homologs that demonstrate a preference for long-chain fatty acids. Our bioinformatics, quantitative analyses of protein-ligand interactions, and high-resolution crystal structures suggest that TatTs might facilitate the trafficking of hydrophobic or lipophilic substrates and represent a new class of bacterial lipid and fatty acid transporters.