A method for the quantitative estimation of bacteria from mangrove sediments     

A.H. Dye 《Estuarine, Coastal and Shelf Science》1983,17(2):207-212

A simple and rapid method for the quantitative extraction of bacteria from high silt/clay-content muds associated with mangrove swamps is described. Mud samples are homogenized in filtered sea water and the supernatant is diluted and stained with Acridine Organge. The stained material is trapped on a 0·45 μm membrane filter and bacteria are counted under a fluorescence microscope. Samples may be pre-fixed in 5% formalin if they cannot be examined immediately.  相似文献   

The impact of the herbicide atrazine on growth and photosynthesis of seagrass, Zostera marina (L.), seedlings     

Gao Y  Fang J  Zhang J  Ren L  Mao Y  Li B  Zhang M  Liu D  Du M 《Marine pollution bulletin》2011,62(8):1628-1631

The impact of the widely used herbicide atrazine on seedling growth and photosynthesis of eelgrass was determined. The long-term impact of the herbicide atrazine (1, 10 and 100 μg/L) on growth of eelgrass Zostera marina (L.) seedlings, maintained in outdoor aquaria, was monitored over 4 weeks. Exposure to 10 μg/L atrazine resulted in significantly lower plant fresh weight and total chlorophyll concentration and up to 86.67% mortality at the 100 μg/L concentration. Short-term photosynthetic stress on eelgrass seedlings was determined and compared with adult eelgrass using chlorophyll fluorescence. The effective quantum yield in eelgrass seedlings was significantly depressed at all atrazine concentrations (2, 4, 8, 16, 32 and 64 μg/L) even within 2 h and remained at a lower level than for adult plants for each concentration. These results indicate that atrazine presents a potential threat to seagrass seedling functioning and that the impact is much higher than for adult plants.  相似文献   

荧光光谱学在象牙与猛犸象牙鉴定上的应用     

吴晓  张钧  鲁先虎 《地质科学译丛》2013,(3):50-55

利用红外光谱仪及荧光分光光度计对象牙和猛犸象牙样品进行测试,通过对测试结果的比对、分析,总结二者的谱图特点,旨在探索更准确的象牙与猛犸象牙的检测方法.猛犸象牙内部由于受石化作用小,其红外光谱与象牙的没有本质区别,因此红外光谱仪在象牙饰品与猛犸象牙饰品的检测上难以提供准确信息.荧光光谱的测试结果显示,在280 nm波长光的激发下,由于象牙和猛犸象牙中的氨基酸在微环境及其质量分数不同,象牙的发射光谱峰值在307 nm处,猛犸象牙的发射光谱峰值在315 nm处,且象牙的荧光强度高于猛犸象牙.同步荧光光谱测试中△λ分别取15,60 nm,分别测试样品中的酪氨酸、色氨酸,测试结果显示两类牙质测试图谱谱形一致但强度差异明显,即荧光分光光度计在象牙和猛犸象牙的检测上可提供有效的信息.  相似文献   

CVD合成钻石的层状生长结构和紫外荧光特征     

吕晓敏  张玉冰  兰延  丁汀  宋中华  张健  陆太进  沈美冬  柯捷 《地质科学译丛》2013,(3):30-35

最近NGTC实验室检测出多批次CVD合成钻石,这些CVD合成钻石均具有明显的鉴定特征,使用钻石观测仪（DiamondViewTM）观察可见蓝色、橙红色荧光和蓝色磷光以及细密层状生长纹理,光致发光光谱中可见737 nm处的特征发光线.这些特征均与其生长结构及生长过程中进入钻石晶体中的杂质有关.笔者以最近检测过程中发现的一颗CVD合成钻石为例,使用高倍率显微技术对其层状结构的微细特征及其在钻石观测仪下的荧光特征的关系进行了详细观察和对比.结果显示,此样品与之前检测到的CVD合成钻石略有差异.此次检测到的样品在钻石观测仪（DiamondViewTM）下观察具有较宽的层状生长分区,层与层之间的分界线十分明显且在高倍显微镜下也可见到细微的生长特征.通过对样品特征的分析,了解了晶体生长过程中多阶段生长条件的变化,更直观的展现了CVD合成钻石的生长过程.  相似文献   

Varved sediments of Lake Yoa (Ounianga Kebir,Chad) reveal progressive drying of the Sahara during the last 6100 years   总被引：1，自引：0，他引：1  

Pierre Francus  Hans von Suchodoletz  Michael Dietze  Reik V. Donner  Frédéric Bouchard  Ann‐Julie Roy  Maureen Fagot  Stefan Kröpelin 《Sedimentology》2013,60(4):911-934

The sedimentological and geochemical properties of a 7·47 m long laminated sequence from hypersaline Lake Yoa in northern Chad have been investigated, representing a unique, continuous 6100 year long continental record of climate and environmental change in the eastern Central Sahara. These data were used to reconstruct the Mid to Late Holocene history of this currently hyper‐arid region, in order to address the question of whether the Mid Holocene environmental transition from a humid to a dry Sahara was progressive or abrupt. This study involved a suite of analyses, including petrographic and scanning electron microscope examination of thin sections, X‐ray diffraction, X‐radiography, granulometry, loss on ignition and magnetic susceptibility. The potential of micro‐X‐ray fluorescence core scanning was tested at very high resolution. Detailed microscopic investigation revealed the sedimentary processes responsible for the formation of the fine laminations, identified the season during which they were formed, and confirmed their annually rhythmic nature. High‐resolution X‐ray fluorescence core scanning allowed the distinction of each individual lamination over the entire record, opening new perspectives for the study of finely laminated sediment sequences. Geochemical and mineralogical data reveal that, due to decreasing monsoon rainfall combined with continuous and strong evaporation, the hydrologically open and fresh Mid Holocene Lake Yoa slowly evolved into the present‐day hypersaline brine depleted in calcium, which has existed for about the past 1050 years. During the oldest part of the investigated period, Lake Yoa probably contained a permanently stratified lower water column that was nevertheless disrupted relatively frequently by mixing events. Deep‐water anoxia became more stable because of increased salinity‐driven density stratification. In parallel, the sediment grain‐size proxies record a progressive increase of aeolian input in the course of the last 6100 years. Altogether, all geochemical and sedimentological indicators point to a progressive drying of the eastern Central Sahara, strengthening previous conclusions based on palaeoecological indicators.  相似文献   

利用窄线宽激光测量锶原子束速率分布     

赵亚楠  吴慧  常宏  张首刚 《时间频率学报》2009,32(1):1-5

利用多普勒频移效应,通过线宽2MHz窄线宽激光与锶原子束在大角度作用下的荧光信号分析,测量了锶原子束速率分布。比较和分析表明,理论结果与实验结果符合较好。  相似文献   

Evidence for a warmer period during the 12th and 13th centuries AD from chironomid assemblages in Southampton Island, Nunavut, Canada     

Nicolas Rolland  Isabelle Larocque  Pierre Francus  Reinhard Pienitz 《Quaternary Research》2009,72(1):27-37

This study presents the Late-Holocene evolution of a northern Southampton Island (Nunavut, Canada) lake, using fossil chironomids supported by sedimentological evidences (XRF, grain size and CNS). All proxies revealed a relatively stable environment during the last millennium with short-lived events driving changes in the entire lake ecosystem. The chironomid-based paleotemperatures revealed variations of significant amplitude coincident with changes in the sediment density and chemical composition of the core. Higher temperature intervals were generally correlated to lower sediment density with higher chironomid concentration and diversity. Higher temperatures were recorded from cal yr AD 1160 to AD 1360, which may correspond to the Medieval Warm Period. Between cal yr AD 1360 and AD 1700, lower temperatures were probably related to a Little Ice Age event. This study presents new information on the timing of known climatic events which will refine our knowledge of the paleoclimate and climatic models of the Foxe Basin region. It also provides a new framework for the evolution of such freshwater ecosystems under the “Anthropocene” and underlines the importance of including sedimentological proxies when interpreting chironomid remains as this combined approach provides an extended overview of the past hydrological and geochemical changes and their impacts on lake biota.  相似文献   

GGB-1型X射线荧光光谱分析高频感应熔样机的性能与应用     

邓赛文  梁国立  刘以建  马天芳 《岩矿测试》2009,28(2):169-172

介绍自行研制的GGB-1型X射线荧光光谱分析高频感应熔样机的特点及性能。采用高频感应加热技术和全自动微机控制技术,设计了温度锁相环控制系统,通过控制高频功率发生器输出振荡电流的大小来控制加热速度和温度,使熔样过程智能化、自动化。研究设计的混匀装置,可同时摇摆与自旋,熔融体形成涡流,使熔融体更均匀。根据X射线荧光光谱分析制样的特点,设计了预氧化过程,更适合于矿石类样品的熔融制样。产品的性能测试结果表明,该熔样机的最高温度为1300℃,温控精度为±2℃,各元素制样精密度优于0.3%(RSD,n=11)。  相似文献   

原子荧光光谱法测定铁矿石中的镉     

付冉冉  刘水清  荣德福  康继韬 《岩矿测试》2009,28(6):595-597

样品经盐酸-硝酸-氢氟酸-高氯酸混合酸溶解,用原子荧光光谱法测定铁矿石中的镉。实验确定了最佳酸度、增感剂镍量、抗坏血酸量和硫脲量,并确定了仪器测定最佳条件,对干扰元素的允许量进行了研究。方法检出限为0.20μg/L,精密度为4.5%,线性范围为0~160μg/L,加标回收率为95.9%~103.7%。方法可应用于铁矿石的快速检测。  相似文献   

波长色散X射线荧光光谱法测定铜精矿中铜铅锌硫镁砷   总被引：7，自引：6，他引：1  

田琼  黄健  钟志光  陈广文  曲强  洪武兴 《岩矿测试》2009,28(4):382-384

采用偏硼酸锂和四硼酸锂混合熔剂熔融法制样,波长色散X射线荧光光谱法测定铜精矿中铜、铅、锌、硫、镁、砷,考察了熔剂、玻璃化试剂和预氧化条件对制样的影响。采用理论α系数和经验系数相结合的方法校正元素间的效应。测定铜精矿试样各组分的相对标准偏差(RSD,n=12)均小于3%,结果与化学分析法吻合。  相似文献