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991.
几种抗菌药物对壳顶幼虫的毒性试验结果表明:(1)以96h平均日生长率作为药物对幼虫毒性的观察指标,求出日生长率仅为对照组一半时的药物浓度(96TLM)及安全浓度(SD)如下:氯霉素69×10-6、6.9×10-6;呋喃西林72×10-6、7.2×10-6;百炎净77×10-6、7.7×10-6;红霉素97×10-6、9.7×10-6;硫酸链霉素48×10-6、4.8×10-6;青霉素钠大于100×10-6、10×10-6。(2)13×10-6的呋喃西林、13×10-6的红霉素、13×10-6的青霉素钠对幼虫生长均有促进作用。(3)各试验组随药物浓度递增,幼虫活动逐渐被抑制;摄食率及眼点率逐渐下降。高浓度红霉素对摄食的抑制作用最强。 相似文献
992.
Rate coefficients have been measured for the reactions of hydroxyl radicals with five aliphatic ethers over the temperature range 242–328 K. Competitive studies were carried out in an atmospheric flow reactor in which the hydroxyl radicals were generated by the photolysis of methyl nitrite in the presence of air containing nitric oxide. The reaction of OH with 2,3-dimethyl-butane was used as the reference reaction and the following Arrhenius parameters have been obtained for the reactions: OH+RORproducts:
相似文献
ROR | E/kJ mol–1 | 1012 A/cm3 molecule–1 s–1 |
---|---|---|
dethyl ether | –2.8±0.4 | 3.5±0.6 |
di-n-propyl ether | –1.2±0.6 | 11.5±2.7 |
methylt-butyl ether | 0.85±0.59 | 4.0±1.3 |
ethyln-butyl ether | –1.3±0.5 | 8.7±1.7 |
ethylt-butyl ether | –1.2±0.6 | 3.0±0.8 |
993.
利用山东22个基本(准)气象站小时气象观测资料,采用A值法计算了山东1961—2017年逐日大气自净能力指数(the atmospheric self-purification capacity index,ASPC),分析了其气候空间分布特征和时间演变规律,利用MK检验(Mann-Kendall检验)和MT检验(Moving-t,滑动t检验)方法对历年ASPC进行了突变检验。结果表明:平均ASPC气候倾向率减小趋势极显著(P<0.01),除章丘和威海外,其他各地ASPC减小趋势均极显著(P<0.01);春季各月ASPC较大,历年各月ASPC随时间明显减小;年和四季ASPC空间分布基本一致,半岛地区较大,鲁南等内陆地区相对较小;年和春、夏、秋、冬季ASPC突变年份分别出现在2003年和2006年、2003年、2003年、2005年。济南、青岛地区ASPC分别从1999年、1993年开始显著减小,低ASPC日数历年变化大致与ASPC变化相反;济南和青岛历年各月ASPC变化差异明显。 相似文献
994.
GRAPES区域集合预报模式的初值扰动增长特征 总被引:4,自引:1,他引:3
基于GRAPES-REPS(Global and Regional Assimilation and Prediction Enhanced System-Regional Ensemble Prediction System)区域集合预报模式和集合变换卡尔曼滤波(Ensemble Transform Kalman Filter,ETKF)初值扰动方法,对2015年6月1~15日10 km与15 km水平分辨率分别进行集合预报试验,通过分析ETKF初值扰动分量、初值扰动方差准确率、动能谱、扰动能量演变、日变化及集合离散度、均方根误差等特征,揭示GRAPES-REPS区域集合预报ETKF初值扰动结构及增长特征。结果表明:(1)ETKF初值扰动方案产生的扰动能够保持所有正交、不相关方向的误差方差,且ETKF分量α参数值及放大因子具有较好的稳定性。(2)ETKF初值扰动方法生成的扰动场以大尺度扰动为主,扰动结构及能量具有随流型依赖特征,低层以内能扰动为主,高层以动能扰动为主,且集合扰动可以有效捕捉预报误差的结构。(3)GRAPES区域集合预报初值扰动总能量和集合离散度随预报时效的延长均呈发展趋势,但离散度增长率小于均方根误差增长率,即集合预报总体存在集合离散度不足的问题。(4)水平分辨率提高可以增加中高层大尺度扰动波谱能量,明显改进等压面及近地面风场及温度场的集合预报效果。值得指出的是,GRAPES-REPS区域集合预报低层内能扰动能量存在明显的日变化特征,特别是青藏高原地区更加显著,需要进一步研究青藏高原初值扰动结构的合理性。 相似文献
995.
从仪器原理、传递函数和观测数据等方面分析目前在网进行1 Hz采样的VP型垂直摆倾斜仪在2~60 s周期内的频率特性,认为该仪器可以观测到频带内的信号变化,但因处于过渡带,观测幅度较真实幅度削弱约20~40 dB。对VP型垂直摆倾斜仪观测频带进行拓展,使2~60 s周期内的观测信号由之前的过渡带进入到仪器的通频带,结果与相同采样率的其他定点形变仪器的观测效果相同,将地倾斜观测量转换为加速度表达后,其幅频特性符合全球地震背景噪声模型。改进后的VP型垂直摆倾斜仪对于远距离震级不大的同震体波震相记录效果略优于改进前,但受地脉动影响,在识别非地脉动信号时需要采用更精细的方法和手段来提高识别效果。 相似文献
996.
Bago River is an important river in Myanmar. Although shorter than other rivers, it has its own river system, and people along
the river rely heavily on it for their daily lives. The upper part of the watershed has changed rapidly from closed forest
to open forest land in the 1990s. Since the recent degradation of the forest environment, annual flooding has become worse
during the rainy season in Bago City. This paper aims at determining soil conservation prioritization of watershed based on
soil loss due to erosion and morphometric analysis in the Bago Watershed by integrating remote sensing and geographic information
system (GIS) techniques. In this study, soil erosion of the Bago watershed was determined using the Universal Soil Loss Equation.
Such factormaps as rainfall, soil erodibility, slope length gradient, and crop management were compiled as input parameters
for the modeling; and the soil loss from 26 sub-watersheds were estimated. Then, the soil erosion maps of the Bago watershed
for 2005 were developed. The resulting Soil Loss Tolerance Map could be utilized in developing watershed management planning,
forestry management planning, etc. 相似文献
997.
珊瑚骨骼生长有年、月、日周期,能够当作古生物钟来记录地质历史。块状珊瑚骨骼密度条带年周期的发现对后来的珊瑚古气候研究产生了深远的影响,随后又发现世界各热带海域的珊瑚存在多种多样的骨骼密度变化模式,起先常从珊瑚的生长环境中寻找骨骼密度变化的控制因素,但是没有成功,从80年代后期,部分学者试图从珊瑚骨骼构架本身出发、综合考虑环境因素和骨骼密度条带之间的关系来探求骨骼密度变化的机理,并提出了一个可以解释大多数块状珊瑚骨骼密度条带变化模式的骨骼生长模型。块状珊瑚软体层厚度是一个十分重要但至今仍没引起足够重视的珊瑚生长参数,它相对于骨骼线性生长率的变化影响着骨骼密度变化模式。骨骼钙化作用和虫黄藻光合作用的相互关系还存有争议,珊瑚骨骼钙化机理仍在探索中。 相似文献
998.
We estimated spatio-temporal evolution of Coulomb stress within the subducted Pacific slab in Hokkaido from the analysis of seismicity rate change. For this purpose we used earthquake catalog from the Institute of Seismology and Volcanology (ISV), Hokkaido University for the period 1993/4/1–2006/12/31 after relocating to compensate location errors due to the heterogeneous P- and S-wave structure beneath Hokkaido. We found that spatial pattern of Coulomb stress change inverted from the seismicity rate change is comparable with static change in Coulomb stress estimated from dislocation models. Our results and analyses reveal important insights on spatio-temporal pattern of deformation of the subducted Pacific slab in terms of Coulomb stress change. We found that the 2003 Tokachi Oki earthquake (Mw = 8.0) pervasively perturbed Coulomb stress in a regional scale with a significant impact to trigger the 2004 Kushiro Oki earthquake. The 2004 Kushiro Oki earthquake (Mw = 7.0) is another significant stressing event that changed the pattern of Coulomb stress in the area. We found that stressing events with magnitude smaller than 7.0 has minimal impact on Coulomb stress change in the Pacific slab. Similarly, comparatively deep focused large earthquakes could not change Coulomb stress significantly. Further the pattern of Coulomb stress change after the 2003 Tokachi Oki earthquake correlates the pattern of afterslip distribution in Hokkaido. 相似文献
999.
Rainfall simulations have been conducted to study the soil erosion process of purple soil in two cultivation practices---contour cultivation and downslope cultivation. Results showed that under the two cultivation practices, the surface runoff can be described by the logarithmic function formula. In the initial period of rainfall, the amount of runoff increased with the rainfall duration and 20 minutes later it became relatively constant. The changing process of soil erosion rate may be described by the logarithmic function formula. The erosion rate increased with the rainfall duration and 20 minutes later it also became constant. Under downslope cultivation condition, the soil erosion rate increased more significantly than that under contour cultivation condition in the case of gentle rainfall intensity, and there is no obvious difference in erosion rate for downslope cultivation and contour cultivation practices. However, with increasing rainfall intensity the soil erosion rate under the downslope cultivation condition could be more than 30 times that under the contour cultivation condition. But this kind of difference would be reduced to some extent in the case of heavy rain. 相似文献
1000.