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本文证明君子兰花粉在RNA和蛋白质合成完全被抑制的条件下仍可达到95%右左的萌发率,并长出有限长度的花粉管。RNA酶和蛋白酶均可影响直至完全阻止花粉的萌发和/或花粉管的伸长。统计表明:成熟花粉内已有的蛋白质可维持花粉管约70μm的伸长,预存mRNA转译的蛋白质可维持花粉管约530μm的伸长。散粉后合成的RNA和蛋白质对花粉管后继伸长的速度和晚期生长(>2400μm)都是必需的。环己亚胺3h或放线菌素D,10h以上的处理会引起花粉管畸形,畸变率与抑制剂浓度及处理时间相关。适量的抑制剂在培养的头5h内可阻碍生殖细胞通过分裂中期,10h以后加抑制剂,不再影响精细胞的形成。 相似文献
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卡尔曼 波—分光光度法用于复方雷锁辛涂剂中苯酚与间苯二酚的测定 总被引:19,自引:1,他引:19
本文研究了卡尔曼滤波-分光光度法及其在多组分混合物同时光度测定中的应用。测定复方雷琐辛涂剂中苯酚与间苯二酚,平均回收率分别为100.86%与98.76%。 相似文献
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Exploring fundamental laws of classical mechanics via predicting the orbits of planets based on neural networks 下载免费PDF全文
Jian Zhang 《中国物理 B》2022,31(9):94502-094502
Neural networks have provided powerful approaches to solve various scientific problems. Many of them are even difficult for human experts who are good at accessing the physical laws from experimental data. We investigate whether neural networks can assist us in exploring the fundamental laws of classical mechanics from data of planetary motion. Firstly, we predict the orbits of planets in the geocentric system using the gate recurrent unit, one of the common neural networks. We find that the precision of the prediction is obviously improved when the information of the Sun is included in the training set. This result implies that the Sun is particularly important in the geocentric system without any prior knowledge, which inspires us to gain Copernicus' heliocentric theory. Secondly, we turn to the heliocentric system and make successfully mutual predictions between the position and velocity of planets. We hold that the successful prediction is due to the existence of enough conserved quantities (such as conservations of mechanical energy and angular momentum) in the system. Our research provides a new way to explore the existence of conserved quantities in mechanics system based on neural networks. 相似文献
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基于非局部近场动力学(PD)理论,在常规微弹脆性(PMB)本构模型基础上,引入能够反映物质点间作用强度随物质点间距变化规律的核函数修正项,以提高PD方法的定量计算精度;并通过附加物质点转动自由度建立以双参数描述的PD微极模型,突破了常规单参数PMB本构模型的泊松比限制等缺陷。通过引入动态松弛算法和粒子系统失衡力准则等系列数值算法,构建了能够自然模拟准脆性裂纹扩展全过程的PD算法体系。经典悬臂梁挠度曲线计算结果表明,本文模型和算法的定量计算误差小于3.5%,对含切口三点弯梁的裂纹扩展过程模拟结果与试验结果吻合。通过改变加载位置和初始裂纹位置,对三点弯梁的破坏模式和承载能力进行了分析。结果表明,裂纹始终由初始裂纹位置向加载位置扩展,且初始裂纹位置和加载位置越靠近三点弯梁中部时,结构的承载能力越低。 相似文献
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Under the condition of completely inhibited RNA and protein synthesis, the rate of pollen grain germination of Clivia nobilis still reaches about 95% and the pollen tubes grow up to a certain length.RNase or pronase E added to the medium affected the germination and the elongation of the pollen tubes till they were completely blocked. Statistical results show that the original proteins may maintain the elongation of pollen tubes at about 70 μm, the proteins translated from pre-existing mRNA maintain them at about 530 μm.The RNA and protein synthesized after dehiscence of the anther are necessary for the normal rate of subsequent elongation and the growth of pollen tubes in the later stage (>2400 μm). Treatment of long duration such as CHM 3h and AmD 10h gives rise to aberration of pollen tubes, the rate of aberration being related to the concentration of inhibitors and the duration of treatment.In the first 5h of culture a suitable amount of inhibitors may block the progress of meta- phase of the gen 相似文献
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重金属污染已经成为全球性问题,由于其毒性、持久性和在食物链中的生物富集特点,对水生环境构成严重威胁。本研究选取乌梁素海为研究区域,采用电感耦合等离子体质谱法(ICP-MS)测定、分析了该湖泊中上覆水、沉积物、龙须眼子菜、芦苇和四种鱼类样品中重金属的含量,以探究其空间分布、富集特征、风险评估和可能的来源。结果表明:(1) Cr,Ni,Cu,Mn,Pb和Zn的平均含量大小顺序为:沉积物>龙须眼子菜(沉水植物)>芦苇(挺水植物)>鱼类>上覆水;但是上覆水中As的浓度高于芦苇和鱼类。芦苇中Cd的含量几乎是普通植物的50倍,且鱼类中Cd的含量是中国允许标准阈值的3.3倍。因此,推测Cd可能通过食物链生物累积对鱼类和人类的健康造成潜在危害。(2) 在沉积物中,As和Cd属于中度严重的富集程度。龙须眼子菜具有较高的生物富集因子(BCF)和较低的生物-沉积物积累因子(BASF),表明该物种更有可能从上覆水中积累重金属,并可以作为超积累植物去除乌梁素海的重金属。(3) 沉积物中的Eri和RI值表明,Cd具有相当高的生态风险,可能对周围环境产生高风险。由于湖泊的入口、出口处及西北部重金属污染程度较高,因此应被当作金属污染监测和管理的优先区域。(4) 重金属源解析结果表明,Zn和Cd是来自采矿和工业废水,而As与农业的面源污染有关。本研究结果可为改善水环境质量、减少重金属污染对乌梁素海和黄河水质管理带来的风险提供重要信息。 相似文献