共查询到19条相似文献，搜索用时 218 毫秒
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水汽分子对地面发射辐射能量具有强力的吸收作用,吸收使辐射能量衰减,造成传感器接收到的地面辐射亮度值下降,但水汽分子时刻运动并引起浓度发生变化,浓度的改变使地面发射辐射能穿过大气层时随之发生变化。因此该文利用物理原理,探讨了大气中水分子的运动与其浓度的关系,以及大气中水分子浓度变化引起水汽分子吸收能量和传感器获取亮度值的变化规律。 相似文献
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有丝分裂原活化蛋白激酶(MAPK)级联至少是由三种蛋白激酶组成的独特信号转导系统。MAPK级联介导细胞增殖和分化、细胞生长阻遏和凋亡。这些细胞信号酶把细胞外信号从细胞表面传递到细胞核，导致基因表达发生变化。信号转导级联的组分对肿瘤形成、免疫强化、炎症、伤口愈合和再生提供了新的治疗途径。 相似文献
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粘着斑激酶(FAK)是一种单亚基、非受体型酪氨酸激酶(NTPTKS)。FAK作为一种信号分子参与了多种途径的信号传递,与细胞的黏附、迁移、侵袭、转移、凋亡等相关。本文从介绍FAK的结构功能入手,着重阐述了近年来FAK所介导的信号传递研究进展。 相似文献
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主要介绍了核电站外围γ辐射连续监测系统探测器的选择,讨论了高压电离室数据捕获能力的保障,利用避雷、防潮。报警等质量保证措施,分析了自然环境变化引起环境γ辐射剂量率升高的原因。实践表明,高压电离室能够稳定地实时监测核电站外围环境情况。 相似文献
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陈文 《学生之友(初中版)》2003,(9)
同学们,你们知道1998年度的诺贝尔生理学、医学奖的获得者吗?他们就是美国药理学家Robert F.Furchgott,Louis J.lgnarrt和Ferid urad.这是因为他们发现了“一氧化氮是心血管系统中传播信号的分子”。这一发现使人们第一次认识到气体分子可以在生物体内发挥传递信号的作用,开辟了医学研究的一个全新领域——一氧化氮生化化学,并为深入研究探讨 相似文献
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借助基于二阶高斯-马尔可夫异常位模型的重力异常协方差函数,得到了海洋重力测量中重力异常信号的状态方程．结合实际重力仪的系统状态方程和系统量测方程,提出了级联卡尔曼滤波方法,并将其应用于重力异常畸变信号的校正处理中．在信号处理过程中,首先采用卡尔曼逆滤波恢复含高频干扰的重力异常,然后采用自适应卡尔曼滤波,以重力异常状态方程为系统方程估计实际重力异常值,并与单一卡尔曼逆滤波器的处理结果进行了对比分析．仿真和试验表明,级联卡尔曼滤波方法和单一卡尔曼逆滤波都能在一定程度上减小重力异常信号的畸变,但在相同背景条件下,级联卡尔曼滤波方法的性能优于单一逆卡尔曼滤波． 相似文献
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儿童发展研究中的群体社会化之争 总被引：10，自引：0，他引：10
群体社会化理论认为，社会化具有情境特异性；家庭外的社会化不发生在两两成对的关系中，而发生在儿童、青少年的同伴群体关系中；化的传递和由环境而引起的人格变化都是群体作用的结果。本对群体社会化理论引起的争论进行了综述，并简要评论了该理论。 相似文献
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提出一种基于自适应级联滤波的多分量非平稳网络入侵的高效检测算法。进行网络入侵的多分量非平稳信号模型构建,在此基础上设计自适应级联滤波算法,实现对网络入侵干扰滤波和信号的检测。给定网络入侵信号处于低信噪比的网络数据交互环境下,利用自适应滤波器方法来确定信号频率,用一个四阶累积量表示自适应滤波器的传递函数,利用过去输入样本的有限线性组合来进行自适应滤波,实现算法改进。仿真结果表明,该算法能在低信噪比下高效地检测出网络入侵信号,网络入侵的两个分量特征的频谱特征聚焦性能较好,实现了对入侵特征的准确检测。在相同条件下,检测准确率提高了25.67%,有效保证了网络安全。 相似文献
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植物多样性的分子生物学研究方法 总被引：4，自引：0，他引：4
植物多样性是生物多样性的基础，它的保护和可持续利用是维持全球经济健康发展、全球气候稳定的重要因素之一，也是保持我们赖以生存环境的重要内容。对植物多样性的分子生物学研究方法进行了综述，并着重介绍了分子标记的最新进展及其在植物多样性研究中的广泛应用。 相似文献
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Leaf senescence is often caused by water deficit and the chimeric gene PSA612-1PT is an auto-regulated gene delaying leaf senescence. Using in vitro leaf discs culture system, the changes of contents of chlorophylls, carotenoids, soluble protein and thiobarbituric acid reactive substance （TBARS） and antioxidant enzymes activities were investigated during leaf senescence of PSA612-1PT modified gerbera induced by osmotic stress compared with the control plant （wild type）. Leaf discs were incubated in 20%, 40% （w/v） polyethylene glycol （PEG） 6 000 nutrient solution for 20 h under continuous light [ 130 μmol/（m^2·s）]. The results showed that the contents of chlorophylls, carotenoids and soluble protein were decreased by osmotic stress with the decrease being more pronounced at 40% PEG, but that, at the same PEG concentration the decrease in the transgenic plants was significantly lower than that in the control plant. The activities of superoxide dismutase （SOD）, catalases （CAT）, ascorbate peroxidase （APX）, guaiacol peroxidase （GPX） and dehydroascorbate reductase （DHAR） were stimulated by PEG treatment. However, the increases were higher in PSA612-IPT transgenic plants than in the control plants, particularly at 40% PEG treatment. Lipid peroxidation （TBARS content） was increased by PEG treatment with the increase being much lower in transgenic plant than in the control plant. It could be concluded that the increases in the activities ofantioxidant enzymes including SOD, CAT, APX, GPX and DHAR were responsible for the delay of leaf senescence induced by osmotic stress. 相似文献
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Zheng Tianrun Zhan Junyi Yang Ming Wang Maojia Sun Wenjun Shan Zhi Chen Hui 《Journal of Zhejiang University. Science. B》2021,22(8):682-694
Hemin can improve the stress resistance of plants through the heme oxygenase system. Additionally, substances contained in plants, such as secondary metabolites, can improve stress resistance. However, few studies have explored the effects of hemin on secondary metabolite content. Therefore, the effects of hemin on saponin synthesis and the mechanism of plant injury relief by hemin in Conyza blinii were investigated in this study. Hemin treatment promoted plant growth and increased the antioxidant enzyme activity and saponin content of C. blinii under osmotic stress and cold stress. Further study showed that hemin could provide sufficient precursors for saponin synthesis by improving the photosynthetic capacity of C. blinii and increasing the gene expression of key enzymes in the saponin synthesis pathway, thus increasing the saponin content. Moreover, the promotion effect of hemin on saponin synthesis is dependent on heme oxygenase-1 and can be reversed by the inhibitor Zn-protoporphyrin-IX(ZnPPIX). This study revealed that hemin can increase the saponin content of C. blinii and alleviate the damage caused by abiotic stress, and it also broadened the understanding of the relationship between hemin and secondary metabolites in plant abiotic stress relief. 相似文献
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针对硝基苯废酸提浓尾气处理装置存在的问题,结合废酸提浓尾气处理装置改造实例,分别采用水、未提浓混酸和氢氧化钠溶液、水和双氧水串级做吸收剂。结果表明：采用压缩法脱除有机物气体和加压法水吸收、双氧水两级串联吸收氮氧化物气体的方法,对于尾气中浓度为130000～190000mg／m^3的苯、17～38mg／m^3的硝基苯和30～90×10^4mg／m^3的氮氧化物的平均脱除率可达99％以上。 相似文献
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Essa Ali Nazim Hussain Imran Haider Shamsi Zahra Jabeen Muzammil Hussain Siddiqui Li-xi Jiang 《Journal of Zhejiang University. Science. B》2018,19(2):130-146
The well-known detrimental effects of cadmium (Cd) on plants are chloroplast destruction, photosynthetic pigment inhibition, imbalance of essential plant nutrients, and membrane damage. Jasmonic acid (JA) is an alleviator against different stresses such as salinity and drought. However, the functional attributes of JA in plants such as the interactive effects of JA application and Cd on rapeseed in response to heavy metal stress remain unclear. JA at 50 μmol/L was observed in literature to have senescence effects in plants. In the present study, 25 μmol/L JA is observed to be a “stress ameliorating molecule” by improving the tolerance of rapeseed plants to Cd toxicity. JA reduces the Cd uptake in the leaves, thereby reducing membrane damage and malondialdehyde content and increasing the essential nutrient uptake. Furthermore, JA shields the chloroplast against the damaging effects of Cd, thereby increasing gas exchange and photosynthetic pigments. Moreover, JA modulates the antioxidant enzyme activity to strengthen the internal defense system. Our results demonstrate the function of JA in alleviating Cd toxicity and its underlying mechanism. Moreover, JA attenuates the damage of Cd to plants. This study enriches our knowledge regarding the use of and protection provided by JA in Cd stress. 相似文献
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田学军 《蒙自师范高等专科学校学报》2007,5(5):7-9
热胁迫将对植物造成损伤并诱导植物产生热激反应。通过适当高温热驯和其他胁迫处理,植物的耐热性将得到提高。热激蛋白、植物激素、抗氧化系统、膜脂等包含在植物耐热性中。其中,热激蛋白是植物耐热性的重要因子,而膜脂中饱和脂类的增加将提高植物的耐热性和细胞膜的稳定性。此外,脱落酸和水杨酸预处理、激活植物抗氧化系统也能提高植物的耐热性。 相似文献
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本文从十九世纪德国大学学者对科学发展的贡献、十九世纪德国大学理念对世界大学办学模式的改变出发,通过少数事例的追踪,探讨德国大学对世界科学发展的影响。 相似文献