Microbial modulation in the biomass and toxin production of a red-tide causing alga   总被引：6，自引：0，他引：6  

Zheng TL  Su JQ  Maskaoui K  Yu ZM  Hu Z  Xu JS  Hong HS 《Marine pollution bulletin》2005,51(8-12):1018-1025

The effect of S₁₀, a strain of marine bacteria isolated from sediment in the Western Xiamen Sea, on the growth and paralytic shellfish poison (PSP) production in the alga Alexandrium tamarense (A. tamarense) was studied under controlled experimental conditions. The results of these experiments have shown that the growth of A. tamarense is obviously inhibited by S₁₀ at high concentrations, however no evident effect on its growth was observed at low concentrations. Its PSP production was also inhibited by S₁₀ at different concentrations, especially at low concentrations. The toxicity of this strain of A. tamarense is about (0.95–12.14) × 10⁻⁶ MU/cell, a peak toxicity value of 12.14 × 10⁻⁶ MU/cell appeared on the 14th day, after which levels decreased gradually. The alga grew well in conditions of pH 6–8 and salinities of 20–34‰. The toxicity of the alga varied markedly at different pH and salinity levels. Toxicity decreased as pH increased, while it increased with salinity and reached a peak value at a salinity of 30‰, after which it declined gradually. S₁₀ at a concentration of 1.02 × 10⁹ cells/ml inhibited growth and the PSP production of A. tamarense at different pH and salinity levels. S₁₀ had the strongest inhibitory function on the growth of A. tamarense under conditions of pH 7 and a salinity of 34‰. The best inhibitory effect on PSP production by A. tamarense was at pH 7, this inhibitory effect on PSP production did not relate to salinity. Interactions between marine bacteria and A. tamarense were also investigated using the flow cytometer technique (FCM) as well as direct microscope counting. S₁₀ was identified as being a member of the genus Bacillus, the difference in 16S rDNA between S₁₀ and Bacillus halmapalus was only 2%. The mechanism involved in the inhibition of growth and PSP production of A. tamarense by this strain of marine bacteria, and the prospect of using it and other marine bacteria in the bio-control of red-tides was discussed.  相似文献   

Low‐frequency modulation and trend of the relationship between ENSO and precipitation along the northern to centre Peruvian Pacific coast          下载免费PDF全文

Luc Bourrel  Pedro Rau  Boris Dewitte  David Labat  Waldo Lavado  Aude Coutaud  Andrea Vera  Abigail Alvarado  Julio Ordoñez 《水文研究》2015,29(6):1252-1266

The relationship between El Niño Southern Oscillation (ENSO) and precipitation along the Peruvian Pacific coast is investigated over 1964–2011 on the basis of a variety of indices accounting for the different types of El Niño events and atmospheric and oceanographic manifestations of the interannual variability in the tropical Pacific. We show the existence of fluctuations in the ENSO/precipitation relationship at decadal timescales that are associated with the ENSO property changes over the recent decades. Several indices are considered in order to discriminate the influence of the two types of El Niño, namely, the eastern Pacific El Niño and the central Pacific El Niño, as well as the influence of large‐scale atmospheric variability associated to the Madden and Julian Oscillation, and of regional oceanic conditions. Three main periods are identified that correspond to the interleave periods between the main climatic transitions over 1964–2011, i.e. the shifts of the 1970s and the 2000s, over which ENSO experiences significant changes in its characteristics. We show that the relationship between ENSO and precipitation along the western coast of Peru has experienced significant decadal change. Whereas El Niño events before 2000 lead to increased precipitation, in the 2000s, ENSO is associated to drier conditions. This is due to the change in the main ENSO pattern after 2000 that is associated to cooler oceanic conditions off Peru during warm events (i.e. central Pacific El Niño). Our analysis also indicates that the two extreme El Niño events of 1982/1983 and 1997/1998 have overshadowed actual trends in the relationship between interannual variability in the tropical Pacific and precipitation along the coast of Peru. Overall, our study stresses on the complexity of the hydrological cycle on the western side of the Andes with regard to its relationship with the interannual to decadal variability in the tropical Pacific. Copyright © 2014 John Wiley & Sons, Ltd.  相似文献   

C波段调频连续波天气雷达探测系统及观测试验     

阮征  金龙  葛润生  李丰  吴俊 《气象学报》2015,73(3):577-592

对降水云更高时、空分辨率观测资料的需求推动了天气雷达技术的发展,调频连续波雷达(FMCW)系统采用收发分置双天线体制,采用数字直接移相(DDS)技术和快速傅里叶变换(FFT)信号处理技术,获取高度分辨率达到15、30 m,探测周期2—3 s的回波功率谱分布和谱参数,具有脉冲多普勒雷达无法比拟的探测优势。C波段FMCW(C-FMCW)雷达最小可测信号功率达到-170 dBm,微弱信号的定量标校是技术难点。采用标准信号源输出单频信号,经过数字直接移相扩展为与雷达系统相同扫频范围信号,得到最小输入功率可达-169.77 dBm的定标曲线,由定量标校后的谱分布计算得到回波强度谱密度分布。该雷达于2013年6月起在安徽定远开始观测,利用8月24日降水过程探测数据,与距离该地48 km的蚌埠和83 km的合肥SA扫描雷达观测数据,分别进行对流云与层状云的观测比对分析。对于均匀分布的层状降水云,C-FMCW雷达与SA雷达探测结果基本接近, C-FMCW雷达与蚌埠SA雷达的平均均方根误差为1.75 dB,与合肥SA雷达的平均均方根误差为2.02 dB,C-FMCW雷达与两部SA雷达探测的回波强度差异小于1 dB。对观测试验谱参数及回波强度谱密度分布进行了初步分析,C-FMCW雷达在研究降水云体的相态分区、晴空大气边界层回波等方面有较好的应用前景,有助于加深对强降水云中垂直运动的强烈变化的探测和认识。  相似文献   

长清M4.1地震前区域小震调制比异常分析     

林眉  郑建常 《大地测量与地球动力学》2021,41(11):1207-1210

研究山东内陆地区2008年以来1级以上小震的月相调制效应,并结合地震b值变化进行分析。结果表明,2020-02-18长清M4.1地震前该区存在低b值、高调制比异常,计算综合节面解P轴方位偏转发现,其与小震b值的低值变化时段非常一致。研究区6次4 级以上地震前,有4次出现异常,调制比≥0.33;而2011年和2016年2次范县地震前未出现异常,可能与范县小震集中区受采油作用影响有关。  相似文献   

太阳射电尖峰爆的非线性调制过程     

王德 《天文学报》1994,35(2):204-208

本文论述了在太阳射电尖峰爆中研究观测量之间统计关系的重要性。并在非线性参量稳定性模型的基础上，给出尖峰爆中尖峰出现重复率Ｒ与爆发流量密度ｓ及尖峰的调制幅度△ｓ与ｓ之间统计关系的理论预期。Ｒ－Ｓ统计关系的理论预期与观测结果符合得很好。  相似文献   

The effect of wave breaking on surface wave imaging by Synthetic Aperture Radar     

孙建  管长龙史剑 《中国海洋湖沼学报》2006,24(1):21-27

The effect of ocean wave breaking as a non-Bragg mechanism on backscattering cross-section and modulation transfer functions （MTF） of radar was investigated based on Bragg resonance theory and parametric method. The result showed that the additional effect of wave breaking on backscattering cross-section is not more than 20% except for the small incident angle of VV polarized electromagnetic （e.m.） wave but is significant for HH polarized e.m. wave. Breaking waves lead to increase in the modulus of tilt modulation MTF and the larger the wind speed, the faster the increase. For large incident angle, the modulus of tilt modulation MTF with wave breaking decreases quickly with incident angle for HH polarization and approach to that without wave breaking for VV polarization. The hydrodynamic MTF increases 30%-60% when considering wave breaking and the increase is larger for HH polarization than for VV polarization.  相似文献   

全球巨震的天文背景     

胡辉  韩延本 《天文研究与技术》2006,3(1):77-84

分析了全球8．5M以上巨震的天文背景，分析结果表明，这些巨震大都发生在处于月亮轨道运动所对应的地震活跃期的地震带区，太阳活动的下降段与地球自转的加速期。这是就天文因素的长周期变化而言。对于天文因素的短周期变化，无论是对于地方时，地方恒星时与月相，都有集中发生在某一段时间的现象；对于地球自转的短周期变化更是比较明显，要么发生在其变化最快时期，要么发生在其变化的最慢时期。这一切都表明，这些地震的发生是受天文因素的影响的。天文因素是外界发震动力之一，长周期变化的天文因素可能是对地震的孕育、发展与发生起着调制作用，而短期变化的天文因素则是当其作用于远离平衡态的发震构造上时，引起系统的巨涨落，从而诱发地震。  相似文献   

一种拓展的半物理时空融合算法及其初步应用     

李大成  唐娉  胡昌苗  郑柯 《遥感学报》2014,18(2):307-319

Landsat 5卫星较低的时间分辨率(16天)使得其很难获得大区域的、时相一致的清晰影像数据集。本文发展了一种基于半物理模型的时空融合算法-即乘性调制融合算法,并借助多时序的MODIS反射率数据来生成多时相的Landsat TM/ETM+反射率合成影像,经镶嵌后得到区域尺度的高时空分辨率地表反射率数据集(Landsat TM/ETM+)。本文利用吉林省2006年—2011年的Landsat 5 TM地表反射率数据以及500 m的MOD09A1反射率产品来生成3个时相的Landsat 5 TM反射率合成数据,从而获得研究区在上述时相下地表反射率数据的镶嵌图。初步分析表明,所生成的Landsat 5 TM反射率数据的光谱分布特征与MOD09A1反射率数据较为一致,且图像在整体上光谱特征的连续性较好。  相似文献   

B码应用深入探讨     

戎强  刘铁强  贾杰峰 《全球定位系统》2014,39(4):55-59

在介绍B码构成与原理的基础上,分析了B码时统典型应用实例,针对B码应用中常见的无法跨年和闰秒、B码中断与恢复时存在时间错误、受扰时间跳变、交流B码幅度与调制比受限等问题,提出了B码版本切换与软件跨年及闰秒、强制守时、解码容错、交流B码数控幅度与调制比等解决方法。工程实践表明：这些方法可有效解决B码应用中遇到的对应问题,有效提高了B码时统的稳定性和可用性,具有很好的实用价值。  相似文献   

象山港内湾潮汐应变对横向流及其余环流垂向空间结构的调控研究     

何国风  包义康  徐鹏 《海洋通报》2022,(6)

横向流 (垂直于海湾主轴方向的流动) 对横向动量以及物质分布具有重要影响。已往研究表明,潮汐应变对横向流的垂向空间结构具有重要的调控作用。但这种认识仅局限于强层化海区,弱层化条件下潮汐应变对于横向流空间结构的影响仍未可知。为此,本文以象山港为例,基于实测数据阐释了弱层化条件下潮汐应变对横向流及其余环流垂向空间结构的调控作用。结果显示,象山港内湾横向流的垂向空间结构随大小潮呈现出明显的变化规律。大潮时,潮汐应变现象明显,涨潮时较强的垂向混合使得横向流在高潮阶段呈现出一层结构;落潮时垂向混合较弱,横向流在低潮时呈现两层结构。小潮时,潮汐应变受到抑制,垂向混合在涨落潮时均较弱,因此横向流在高低潮阶段均呈现出两层结构。经过潮时均进一步得到的横向余环流呈现出上层向南、下层向北的两层结构。由于潮汐应变的大小潮变化,横向余环流的反转深度反转点自大潮到小潮呈现出上升的趋势。  相似文献