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1.
The effect of heat stress on the components of grain weight was analysed in wheat ( Triticum aestivum L.) varieties differing in grain weight stability. The wheat varieties PBW154, Sonalika and Hindi62 were raised in the field (New Delhi, India; 77°12' E, 28°40' N, 228.6 m a.s.l.) at three dates of sowing: 19 November 1992 (DOS I), 14 December 1992 (DOS II) and 18 January 1993 (DOS III). The late-sown crop (DOS III) experienced 6–8 °C warmer temperatures during grain development than the crop sown at the normal time (DOS I). The heat susceptibility index (S) revealed that grain weight was less susceptible to heat in Sonalika and PBW154 than in Hindi62. Heat stress reduced both the grain growth duration (GGD) and the grain growth rate (GGR). The grain weight reduction in PBW154 and Sonalika was mainly due to a reduction in GGR, while that of Hindi62 was due to a reduction in GGD. In vivo studies on starch and protein synthesis in excised endosperm at 15, 25 and 35 °C revealed that both processes were more thermotolerant in Hindi62 than in PBW154. The grain starch content was stable in Hindi62 while that in PBW154 was significantly reduced under heat stress. The grain nitrogen content at maturity increased in both varieties under heat stress. It was concluded that the heat susceptibility of grain weight in Hindi62 was mainly due to a reduction in GGD, although GGR, starch and protein synthesis were more thermotolerant in developing grains of Hindi62 than in those of PBW154. 相似文献
2.
以对氯苯甲酸、甲醇、水合肼、对硝基苯甲醛、对甲氧基苯甲醛、苯乙酮为原料,合成了对硝基苯甲醛对氯苯甲酰腙、对甲氧基苯甲醛对氯苯甲酰腙及苯乙酮对氯苯甲酰腙。目标化合物的结构通过核磁共振氢谱、元素分析和红外光谱进行了表征,并试验了目标化合物对菜粉蝶幼虫的杀虫活性。活性筛选试验结果表明,对硝基苯甲醛对氯苯甲酰腙的触杀活性和胃毒活性最强。系列浓度试验表明,处理24h后,对硝基苯甲醛对氯苯甲酰腙对菜粉蝶幼虫的触杀活性和胃毒活性的EC50分别为497.85mg/L、287.01mg/L;处理48h后,二者分别为272.21mg/L、145.75mg/L。 相似文献
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该工程为利用某化肥项目生产过程中产生的余热进行发电。通过对化肥项目生产流程产生的废气与余热蒸汽总量分析,提出余热利用发电的装机方案,对该规模项目余热利用的方式与规模进行探讨。 相似文献
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[目的]研究一种以壳聚糖作为还原剂及稳定剂、通过一步水热合成法制备纳米银颗粒的新方法.[方法]用水热法合成以壳聚糖为稳定剂的银纳米颗粒,利用水热法产生的较高温度和较高压力的条件来制备稳定的银纳米颗粒,并考察颗粒的稳定性.[结果]制备的纳米银溶胶具有较好的稳定性,可在室温下长期保存.通过改变反应初始pH值,可调控其大小和形貌.在酸性条件下,测得纳米银颗粒带正电,这非常有利于将其应用在抗菌研究中.[结论]该方法具有环保、简便、产量高等特点,有望应用到以壳聚糖分子为稳定剂的其他金属纳米材料的合成研究中. 相似文献
7.
黄飞 《黑龙江八一农垦大学学报》2014,26(4):71-75
研究了苯甲醛与乙酸酐的物质的量比、反应时间、催化剂种类以及混合催化剂物质的量比对合成肉桂酸的影响。实验结果表明,苯甲醛与乙酸酐的物质的量比为1∶3,反应时间为60 min,反应温度为170℃,催化剂为氟化钠/碳酸钾(其物质的量比为1∶2)时,肉桂酸的产率达76.6%。该工艺降低了反应温度,缩短了反应时间,提高了产率,并且该方法简单,环境污染小,产品纯度高。 相似文献
8.
利用局部综合法对非零正传动弧齿锥齿轮副进行大重合度加工参数设计,克服了非零正传动由于啮合角增大而使得重合度降低的不足。通过实例与常规设计的结果进行仿真与应力分析对比,结果表明,在同样的载荷条件下,新设计比常规设计的小轮最大齿根拉伸应力减小27.6%,最大齿根压缩应力减小23.5%,最大齿面接触应力减小6.5%,同时大轮的齿根应力也有所降低,使得齿轮副具有更高的寿命和可靠性。 相似文献
9.
Alkaloids are a large and structurally diverse group of marine-derived natural products. Most marine-derived alkaloids are biologically active and show promising applications in modern (agro)chemical, pharmaceutical, and fine chemical industries. Different approaches have been established to access these marine-derived alkaloids. Among these employed methods, biotechnological approaches, namely, (chemo)enzymatic synthesis, have significant potential for playing a central role in alkaloid production on an industrial scale. In this review, we discuss research progress on marine-derived alkaloid synthesis via enzymatic reactions and note the advantages and disadvantages of their applications for industrial production, as well as green chemistry for marine natural product research. 相似文献
10.
Oceans are a rich source of structurally unique bioactive compounds from the perspective of potential therapeutic agents. Marine peptides are a particularly interesting group of secondary metabolites because of their chemistry and wide range of biological activities. Among them, cyclic peptides exhibit a broad spectrum of antimicrobial activities, including against bacteria, protozoa, fungi, and viruses. Moreover, there are several examples of marine cyclic peptides revealing interesting antimicrobial activities against numerous drug-resistant bacteria and fungi, making these compounds a very promising resource in the search for novel antimicrobial agents to revert multidrug-resistance. This review summarizes 174 marine cyclic peptides with antibacterial, antifungal, antiparasitic, or antiviral properties. These natural products were categorized according to their sources—sponges, mollusks, crustaceans, crabs, marine bacteria, and fungi—and chemical structure—cyclic peptides and depsipeptides. The antimicrobial activities, including against drug-resistant microorganisms, unusual structural characteristics, and hits more advanced in (pre)clinical studies, are highlighted. Nocathiacins I–III (91–93), unnarmicins A (114) and C (115), sclerotides A (160) and B (161), and plitidepsin (174) can be highlighted considering not only their high antimicrobial potency in vitro, but also for their promising in vivo results. Marine cyclic peptides are also interesting models for molecular modifications and/or total synthesis to obtain more potent compounds, with improved properties and in higher quantity. Solid-phase Fmoc- and Boc-protection chemistry is the major synthetic strategy to obtain marine cyclic peptides with antimicrobial properties, and key examples are presented guiding microbiologist and medicinal chemists to the discovery of new antimicrobial drug candidates from marine sources. 相似文献