There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality.

Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

I and i

抗原变异可使得多种致病微生物易于逃避宿主免疫应答。表达在感染红细胞表面的恶性疟原虫红细胞表面蛋白1（PfPMP1）与感染红细胞、内皮细胞、树突状细胞以及胎盘的单个或多个受体作用，在黏附及免疫逃避中起关键的作用。每个单倍体基因组var基因家族编码约60种成员，通过启动转录不同的var基因变异体为抗原变异提供了分子基础。

疟原虫var基因转换速率变化导致抗原变异[英]／Paul H, Robert P, Christodoulou Z, et al//Proc Natl Acad Sci U S A

Surface composites by friction stir processing: A review

Corrosion behavior of an equiatomic CoCrFeMnNi high-entropy alloy compared with 304 stainless steel in sulfuric acid solution

Friction stir welding/processing of metals and alloys: A comprehensive review on microstructural evolution

High Oxidation Resistance of AlCoCrFeNi High Entropy Alloy through Severe Shear Deformation Processing

Friction stir processing (FSP) of Mg based AE42 alloy was performed under single pass as well as double pass conditions. The evolution of microstructure was investigated using electron back scatter diffraction (EBSD) analysis. EBSD revealed that the grain size and texture varies within the nugget zone of friction stir processed region. The variation of mechanical properties across the nugget region was evaluated using nanoindentation. Hardness and Young's modulus was found to increase along the depth of the friction stir processed specimen. This was attributed to a finer grain structure with increasing depth. The friction stir processed specimen showed higher tendency toward strain hardening compared to as-cast alloy. Understanding microstructure–property relationship paves the way for optimization of FSP conditions and development of advanced functional Mg alloys.

Microstructure-Property Relationship for Friction Stir Processed Magnesium Alloy†

Erosion is a serious concern for machinery dealing with particle-laden fluids. For protection against erosion, coatings are usually recommended. Laboratory experiments are conducted to evaluate the erosion rates of these coatings. Alternatively, one could consider the use of modeling and simulation to predict the erosion rates. Although several models are available in literature for bulk materials, there is limited work reported in this direction for coatings. In present work, several models from literature were evaluated for their ability to predict the slurry erosion of coatings. A model based upon contact-fracture theory (CFT), proposed in present work, was also evaluated. Another variant of this model considered the effect of splat size. It was observed that none of the existing models evaluated in the present work could predict the erosion rates of the coatings. The proposed CFT model was able to predict the erosion rates with reasonable accuracy, whereas another variant of this model based upon splat size was observed to be inappropriate for predicting erosion rates of coatings. Possible reasons for the observed disparity are discussed.

A Phenomenological Model for Slurry Erosion Prediction of Thermal Spray Coatings

Thermal spray coatings (TSCs) are widely utilized for limiting degradation of structural components. However, the performance of TSCs is significantly impaired by its inherent non-homogeneous micro...

https://pubs.acs.org/doi/pdf/10.1021/acsomega.0c03053

Facile and Green Engineering Approach for Enhanced Corrosion Resistance of Ni-Cr-Al2O3 Thermal Spray Coatings.

This work investigates the effect of ultrafine-grain microstructure on the oxidation behavior of AlCoCrFeNi high entropy alloy (HEA). The ultrafine-grain microstructure is obtained using stationary friction processing performed at two different rotational speeds, 400 and 1800 rpm, for 5 min duration. Processed samples demonstrate high depth of refinement (DOR) and ultrafine grain size (0.43–1 μm) at high rotational speeds along with significant phase transformations from BCC/B2 to FCC microstructure. Further, surface free energy of the ultrafine-grain microstructure is enhanced up to 35%. Oxidation kinetics of the ultrafine-grained sample is decelerated up to 12–48% in a temperature range of 850–1050 °C for a duration of 100 h. Chromia and alumina were the predominant oxides formed in almost all the samples oxidized at elevated temperature. In addition, spinel Co(Cr,Fe)2O4/Fe(Co,Cr)2O4 formation is also detected in the unprocessed oxidized samples. Processed samples rich in grain boundaries (GBs) promote internal oxidation to form Al-rich inner oxides. The enhanced oxidation resistance of the processed samples is attributed to the microstructural refinement and homogenization resulting in the formation of protective chromia followed by Al-rich inner oxides.

Harpreet Singh Grewal

Papers

High Oxidation Resistance of AlCoCrFeNi High Entropy Alloy through Severe Shear Deformation Processing

Microstructure-Property Relationship for Friction Stir Processed Magnesium Alloy†

A Phenomenological Model for Slurry Erosion Prediction of Thermal Spray Coatings

Facile and Green Engineering Approach for Enhanced Corrosion Resistance of Ni-Cr-Al2O3 Thermal Spray Coatings.

Enhanced Oxidation Resistance of Ultrafine-Grain Microstructure AlCoCrFeNi High Entropy Alloy