Abstract Plasma nitriding is a plasma-activated thermochemical method widely used to increase the fatigue strength, hardness and wear resistance of low-alloy steels. In this work, a new structure consisting of a hollow cathode metal plate can produce a hollow cathode discharge and heat the workpiece by radiation. This principle is used to perform hollow cathode source plasma nitriding (HCSPN). Herein, 42CrMo steels were treated by conventional plasma nitriding (CPN) and HCSPN treatments. The 42CrMo steels were nitrided at 525 °C for 6 h in NH3 atmosphere. The mechanical and dry wear properties were measured by nano-indentation, Vickers micro-indentation and ball-on-disk tribometer, respectively. The H3/E⁎2 ratio was 0.0274 GPa (H=11.51 GPa and E⁎=235.84 GPa) for the CPN sample and 0.0276 GPa (H=10.87 GPa and E⁎=215.54 GPa) for the HCSPN sample. Compared with the untreated 42CrMn steel, all the nitrided samples possess increased fracture toughness. Because the workpiece was not used as a discharge cathode, this HCSPN treatment overcame the disadvantages of the conventional CPN treatment. Additionally, results showed that the surface of the HCSPN sample was smoother than that of the CPN sample, and its tribological performance was better.

Allogeneic mesenchymal stem cells (allo-MSCs) have recently garnered increasing interest for their broad clinical therapy applications. Despite this, many studies have shown that allo-MSCs are associated with a high rate of graft rejection unless immunosuppressive therapy is administered to control allo-immune responses. Cytotoxic T-lymphocyte-associated protein 4 (CTLA4) is a co-inhibitory molecule expressed on T cells that mediates the inhibition of T-cell function. Here, we investigated the osteogenic differentiation potency of allo-MSCs in an activated immune system that mimics the in vivo allo-MSC grafting microenvironment and explored the immunomodulatory role of the helper T cell receptor CTLA4 in this process. We found that MSC osteogenic differentiation was inhibited in the presence of the activated immune response and that overexpression of CTLA4 in allo-MSCs suppressed the immune response and promoted osteogenic differentiation. Our results support the application of CTLA4-overexpressing allo-MSCs in bone tissue engineering.

Conyza canadensis é uma espécie de planta daninha comum que forma populações densas na maioria das regiões da China. Foram realizados bioensaios em placas de Petri com extratos aquosos das partes visíveis e das raízes de C. canadensis em três concentrações (0,05, 0,1 e 0,2 g mL-1), a fim de investigar os efeitos autotóxicos dessa espécie, bem como os possíveis efeitos em três espécies nativas dominantes: Plantago asiatica, Digitaria sanguinalis e Youngia japonica. Os resultados mostraram que a germinação de sementes e o crescimento de rebentos das três espécies nativas eram inibidos significativamente pelos extratos aquosos de C. canadensis em quase todas as concentrações, que aumentaram geralmente com uma concentração cada vez maior de extratos. Contudo, a germinação de sementes e o crescimento de rebentos da própria C. canadensis não foram alterados significativamente pelos mesmos extratos em todas as concentrações. Esses resultados sugerem que os potenciais compostos alelopáticos produzidos pelo tecido de C. canadensis podem contribuir para o seu sucesso invasivo no sul da China.

Conyza canadensis is a widespread weed species forming dense populations in most regions of China. Petri dish bioassays with aqueous extracts of the aboveground parts and roots of C. canadensis at three concentrations (0.05, 0.1, and 0.2 g mL-1) were undertaken to investigate the autotoxic effects of C. canadensis, and the possible effects on three dominant native weed species, Plantago asiatica, Digitaria sanguinalis and Youngia japonica. The results showed that seed germination and the shoot length of three native species were significantly inhibited by aqueous extracts of C. canadensis at almost all concentrations that generally increased with increasing extract concentration. However, the seed germination and shoot length of C. canadensis itself was not significantly affected by the same extracts at all concentrations. These results suggested that the potential allelopathic compounds produced by the tissue of C. canadensis may contribute to its invasive success in invading southern China.