Background: The prevalence of Helicobacter pylori is higher in developing countries. The aim of this study was to investigate the prevalence and risk factors of H. pylori infection in areas with high prevalence of gastric cancer in Jiangsu

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Nickel borides are promising multifunctional materials for high hardness and excellent properties in catalysis and magnetism. However, it is still a blank of intrinsic properties in Ni−B compounds, because crystallization of the single phases of Ni−B compounds with micro-size is a challenge. In this work, single phases of Ni 2 B (I4/mcm), α-Ni 4 B 3 (Pnma), β-Ni 4 B 3 (C2/c), and NiB (Cmcm) are synthesized by high pressure and high temperature (HPHT). The results indicate that synthesizing α-Ni 4 B 3 and β-Ni 4 B 3 requires more energy than Ni 2 B and NiB. The growth process of Ni−B compounds is that Ni covers B to form Ni−B compounds under HPHT, which also makes the slight excess of B necessary. So, generating homogeneous distribution of starting materials and increasing the interdiffusion between Ni and B are two keys to synthesize well crystallized and purer samples by HPHT. This work uncovers the growth process of Ni−B compounds, which is significant to guide the synthesis of highly crystalline transition metal borides (TMBs) in the future.

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The hardness of materials is a complicated physical quantity, and the hardness models that are widely used do not function well for transition metal light element (TMLE) compounds. The overestimation of actual hardness is a common phenomenon in hardness models. In this work, high-quality Mn3N2 bulk samples were synthesized under high temperature and high pressure (HTHP) to investigate this issue. The hardness of Mn3N2 was found to be 9.9 GPa, which was higher than the hardness predicted using Guo’s model of 7.01 GPa. Through the combination of the first-principle simulations and experimental analysis, it was found that the metal bonds, which are generally considered helpless to the hardness of crystals, are of importance when evaluating the hardness of TMLE compounds. Metal bonds were found to improve the hardness in TMLEs without strong covalent bonds. This work provides new considerations for the design and synthesis of high-hardness TMLE materials, which can be used to form wear-resistant coatings over the surfaces of typical alloy materials such as stainless steels. Moreover, our findings provide a basis for establishing a more comprehensive theoretical model of hardness in TMLEs, which will provide further insight to improve the hardness values of various alloys.