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孟加拉湾低氧区历史概述
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作者 HOSSAIN Md Jaker sheikh aftab uddin 张经 《华东师范大学学报(自然科学版)》 CAS CSCD 北大核心 2020年第S01期109-113,共5页
世界沿海地区快速的经济发展和人口的增加,以及农业和渔业生产的增加,给沿海生态系统带来了巨大的环境压力.环境压力的最主要症状是缺氧,这是指低氧或贫氧(≤2 mg/L)的区域,动物可能会窒息而死.本研究旨在通过之前有效相关的文献并利用N... 世界沿海地区快速的经济发展和人口的增加,以及农业和渔业生产的增加,给沿海生态系统带来了巨大的环境压力.环境压力的最主要症状是缺氧,这是指低氧或贫氧(≤2 mg/L)的区域,动物可能会窒息而死.本研究旨在通过之前有效相关的文献并利用NOAA的世界大洋图集数据,认知从20世纪70年代至2018年期间孟加拉湾低氧区历史概观.除2018年,至20世纪70年代以来,孟加拉湾氧气浓度在一定程度上保持稳定,在水深100 m (≤1.6 mg/L)区域低氧区长期存在.由于孟加拉湾在2013—2018年期间发生了一些热带气旋, 2018年地表和地下水中的氧气浓度突然增加.次表层水中溶解氧含量的上升主要是由于剧烈的垂向混合、下沉流和上升流.风暴导致的上升流会导致溶解氧含量的下降.相比起中层水(100~500 m)中耗竭的氧浓度,在水深0~100 m和1 000 m的区域氧浓度是较高的.然而,由于各种临近河流的大量淡水输入以及高降雨量,孟加拉湾水体层化现象显著.结合相关物理过程,这种垂向水体分层控制了表层和次表层水的输运和垂向交换,加剧了低氧区的形成,进而影响此区域内浮游植物和水生生物的生长. 展开更多
关键词 溶解氧 低氧 水体层化 孟加拉湾
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Chemically Modified Uridine Molecules Incorporating Acyl Residues to Enhance Antibacterial and Cytotoxic Activities
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作者 Sarkar M. A. Kawsar Hamida A. Ara +9 位作者 sheikh aftab uddin Mohammed K. Hossain Shagir A. Chowdhury Abul F. M. Sanaullah Mohammad A. Manchur Imtiaj Hasan Yukiko Ogawa Yuki Fujii Yasuhiro Koide Yasuhiro Ozeki 《International Journal of Organic Chemistry》 2015年第4期232-245,共14页
A new N-acetylsulfanilylation series of uridine have been synthesized in good yield using direct acylation method and afforded the 5’-O-N-acetylsulfanilyluridine. In order to obtain newer products, the 5’-O-N-acetyl... A new N-acetylsulfanilylation series of uridine have been synthesized in good yield using direct acylation method and afforded the 5’-O-N-acetylsulfanilyluridine. In order to obtain newer products, the 5’-O-N-acetylsulfanilyluridine derivative was further transformed to a series of 2’,3’-di-O-acyl derivatives containing a wide variety of functionalities in a single molecular framework. The chemical structures of the newly synthesized compounds were confirmed on the basis of their FTIR, 1H-NMR spectroscopy, physicochemical properties and elemental analysis. All the synthesized uridine derivatives were tested for their in vitro antibacterial activity against six human pathogenic bacterial strains and for comparison standard antibiotic Ampicillin was also determined. The study revealed that the selectively acylated deriva-tives 5’-O-N-acetylsulfanilyl-2’,3’-di-O-lauroyluridine and 5’-O-N-acetylsulfanilyl-2’,3’-di-O-pivaloyluridine showed highest inhibition against Staphylococcus aureus and Bacillus cereus, respectively. We also observed that the introduction of hexanoyl, decanoyl, lauroyl, myristoyl and pivaloyl groups, the antibacterial functionality of the compound uridine increases. Another noteworthy observation was that the uridine derivatives were found comparatively more effective against Gram-positive microorganisms than those of Gram-negative microorganisms. In addition, the test chemicals were also tested for cyto-toxicity by brine shrimp lethality bioassay and compounds showed different rate mortality with different concentrations. 展开更多
关键词 URIDINE Synthesis Structure Spectroscopy ANTIBACTERIAL CYTOTOXICITY
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