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1.
Unexpected high 228Ra concentrations, up to 2 Bq 1(-1), were found in waters of a coastal lagoon close to a monazite sand separation plant. Due to their use as process waters in this plant, the initial supposition was a contamination related to its operation. However, it was concluded that these abnormal radium concentrations had a natural origin, springs at the lagoon head area with high 228Ra and 226Ra concentrations. The strong relationship among radium and light rare-earth elements (LREEs), the observed 228Ra/226Ra activity ratio and the rare-earth element pattern in the spring waters suggested that monazite is the main source of nuclides for water, indicating the disturbance of monazite chemical stability by the combined effects of low pH and high salinity. Both factors combined allow relatively low mobility of thorium, but, on the other hand, a relatively high mobility of radium and LREEs.  相似文献   
2.
Aiming to determine the plutonium amount as well as its isotopic composition, in particular, in swipe samples for safeguards purposes, an analytical method was developed with a plutonium separation step based on extraction chromatography using 2 cm TEVA columns and detection with quadrupole ICP-MS applying an ultra-sonic nebulizer coupled with membrane desolvation system. The method was successfully applied to New Brunswick plutonium certified reference materials as well as to Lawrence Livermore National Laboratory round robin samples, based on the round robin samples provided by the Institute for Reference Materials and Measurements (Belgium), as part of the Regular European Interlaboratory Measurement Evaluation Programme (REIMEP), campaign 16 (isotopic abundances of plutonium in plutonium nitrate samples), with a total plutonium amount between 1 and 0.25 ng per sample. After the introduction of an additional separation step, it was also possible to carry out precise and accurate total plutonium, (240)Pu/(239)Pu, (241)Pu/(239)Pu and (242)Pu/(239)Pu atom ratios determination in sediment sample showing its applicability to environmental samples in general, reaching a detection limit equivalent to 5 mBq(239)Pu kg(-1).  相似文献   
3.
The blood feeding vampire bats emerged from New World leaf-nosed bats that fed on fruit and insects. Plasminogen activator, a serine protease that regulates blood coagulation, is known to be expressed in the saliva of Desmodus rotundus (common vampire bat) and is thought to be a key enzyme for the emergence of blood feeding in vampire bats. To better understand the evolution of this biological function, we studied the plasminogen activator (PA) genes from all vampire bat species in light of their feeding transition to bird and subsequently mammalian blood. We include the rare species Diphylla ecaudata and Diaemus youngi, where plasminogen activator had not previously been studied and demonstrate that PA gene duplication observed in Desmodus is not essential to the vampire phenotype, but relates to the emergence of predominant mammalian blood feeding in this species. Plasminogen activator has evolved through gene duplication, domain loss, and sequence evolution leading to change in fibrin-specificity and susceptibility to plasminogen activator inhibitor-1. Before undertaking this study, only the four plasminogen activator isoforms from Desmodus were known. The evolution of vampire bat plasminogen activators can now be linked phylogenetically to the transition in feeding behavior among vampire bat species from bird to mammalian blood. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.  相似文献   
4.
引言 墨西哥城大都市区(MCMA)位于被称作"墨西哥谷(Valle deMexico)"的天然围合的盆地里,海拔2240m.它下辖联邦区和墨西哥州的34个自治市.墨西哥城是墨西哥的首都,位于联邦区(DistritoFederal,DF),四面环山,海拔高度超过5000m.墨西哥州是墨西哥人口最稠密的地区(据报道有1300万居民),人口仅次于它的是墨西哥城,大约有860万人[1].  相似文献   
5.
本文研究了从麦夸里岛上毛皮海豹(Arctocephalus spp.)粪便中发现的164个塑料颗粒(平均长度为4.1mm).其中41个塑料颗粒的电子显微照片显示,从其形状来看,没有一个可被确定为塑料颗柱原料--通常这样的颗粒是圆柱形和球形的.而海豹粪便中的164个塑料颗粒全都是7种颜色的角形颗粒(原料颗粒通常是透明的或白色的),并可被分为两类①沿晶体线碎裂的和可能是紫外线分解的;②被磨蚀成带有圆角的不规则形状(擦痕明显可见).白色、棕色、绿色、黄色以及蓝色是最常见的颜色.在成分上,它们来自于5种聚合物群聚乙烯93%;聚丙烯4%;多(1-CI-1-聚丁二烯)聚氯丁二烯2%;三聚氰胺-尿素(酚)(甲醛)树脂0.5%以及纤维素(绳纤维)0.5%.较大的群是漂浮的,比重小于海水.这些小塑料是由较大颗粒(碎片)分解而成的.它们看来是被水冲上岸的并在卵石海滩上受到研磨的塑料用品分解而成的.大多数颗粒(70%)肯定是由于经过不断的磨蚀而最后形成今天的形状.据假设,塑料颗粒被冲到海洋中,然后按其大小有选择地被一种中上层鱼--Electrona subaspera--吃掉,而这种鱼后来又被毛皮海豹吃掉.因此,这些塑料颗粒是由这种鱼和海豹在其正常的摄食过程中聚集的.  相似文献   
6.
Bamboo presents physical and mechanical characteristics, which turn it an alternative option for product development, replacing native or reforested wood. The sustainability assessment of a Dendrocalamus Giganteus species plantation in Brazil through the emergy methodology evidences a great weight of renewable (30% sej/sej) and human labour contributions (33% sej/sej). These contributions account for the great interface with environment and to the intensive work, respectively. The transformity value of bamboo production is 2.42E + 04 sej/J. The influence human labour has on the total emergy flow and on indicators is evaluated by taking into account different country locations (Brazil, Australia and China). Thus, a different transformity value for labour is assumed for each country. A ranking based on emergy sustainability index (ESI) values shows that bamboo production in China was the first placed, followed by Brazil and Australia (values of 1.18, 0.50 and 0.09, respectively). The insertion of indirect renewability embedded in labour results in the ranking modification, leading to plantation in Brazil in the first place, followed by the Australian and Chinese ones. The relative position of the bamboo systems is visualized in the ternary diagram expressed in terms of emergy. In an attempt to explore the relationship between sustainability and time, a graphic of ESI vs. global productivity is discussed in terms of a prospective evaluation. Indirect support areas of the bamboo production are calculated as a way to evaluate the sustainability-space relationship.  相似文献   
7.
Weathering rates of base cations are crucial in critical load calculations and assessments of sustainable forestry. The weathering rate on a single site with detailed geological data can be modelled using the PROFILE model. For environmental assessments on a regional scale, the weathering rates for sites are scaled into regional maps. The step from sites to regional level requires focus on the spatial variation of weathering rates. In this paper, a method is presented by which weathering rates are calculated for 25589 Swedish sites with total elemental analysis for the soil. Based on a part of the results, a methodology for creating area covering maps by geostatistical analysis and kriging is described. A normative reconstruction model was used to transform total elemental analysis to mineralogy. Information from the Swedish Forest Inventory database and other databases were used to derive texture and other important information for the sites, e.g. climate, deposition and vegetation data. The calculated weathering rates show a regional pattern that indicates possibilities for interpolation of data in large parts of Sweden. Geostatistical analysis of an area in southern Sweden shows different properties for different base cations. Kriging was performed for potassium to demonstrate the method. It was concluded that different base cations and different regions have to be analysed separately, in order to optimise the kriging method.  相似文献   
8.
Using tracking radars, we investigated the variability of flight directions of long-distance nocturnal passerine migrants across seasons (spring versus autumn migration) and sites at the southern (56° N) and northern (68° N) ends of the Scandinavian Peninsula (Lund versus Abisko). Whilst most migrants at Lund are on passage to and from breeding sites in Fennoscandia, the majority of the migrants at Abisko are close to their breeding sites, and migration at Abisko thus to a large degree reflects initial departure from breeding sites (autumn) or final approach to breeding destinations (spring). The radar data were used to test predictions about differences in orientation and wind drift effects between adult and juvenile birds (a large proportion of autumn migrants consists of juvenile birds on their first journey), between situations far away from or near the goals and between different phases of migration (initial departure, en route passage, final approach to goal). The concentrations (both total and within-night concentrations) of flight directions differed significantly between seasons as well as sites, with the highest concentration at Lund in spring (mean vector length of track directions, r = 0.79) and lowest at Abisko during spring (r = 0.35). Partial wind drift and partial compensation were recorded at Lund, with a similar effect size in spring and autumn, whilst possible wind drift effects at Abisko were obscured by the large directional scatter at this site. The results from Lund support the prediction that the high proportion of juveniles in autumn contributes to increase the directional scatter during this season, whilst there was no support for predictions of differential wind drift effects between seasons and situations with different goal distances. The most striking and surprising result was the exceedingly large scatter of flight directions at Abisko, particularly in spring. We suggest that such an exaggerated scatter may be associated with final approach orientation, where migrants reach their specific goals from all various directions by final navigation within a more wide-ranging goal region. The larger scatter of autumn flight directions at Abisko compared to Lund may be due to exploratory flights in variable directions being more common at initial departure from breeding sites than later during migratory passage. These surprising results highlight the importance of studying and analysing orientation during final approach to (and initial departure from) migratory goals for understanding the orientation systems of migratory birds.  相似文献   
9.
10.
The relation among inbreeding, heterozygosity, and fitness has been studied primarily among outbred populations, and little is known about these phenomena in endangered populations. Most researchers conclude that the relation between coefficient of inbreeding estimated from pedigrees and fitness traits (inbreeding‐fitness correlations) better reflects inbreeding depression than the relation between marker heterozygosity and fitness traits (heterozygosity‐fitness correlations). However, it has been suggested recently that heterozygosity‐fitness correlations should only be expected when inbreeding generates extensive identity disequilibrium (correlations in heterozygosity and homozygosity across loci throughout the genome). We tested this hypothesis in Mohor gazelle (Gazella dama mhorr) and Iberian lynx (Lynx pardinus). For Mohor gazelle, we calculated the inbreeding coefficient and measured heterozygosity at 17 microsatellite loci. For Iberian lynx, we measured heterozygosity at 36 microsatellite loci. In both species we estimated semen quality, a phenotypic trait directly related to fitness that is controlled by many loci and is affected by inbreeding depression. Both species showed evidence of extensive identity disequilibrium, and in both species heterozygosity was associated with semen quality. In the Iberian lynx the low proportion of normal sperm associated with low levels of heterozygosity was so extreme that it is likely to limit the fertility of males. In Mohor gazelle, although heterozygosity was associated with semen quality, inbreeding coefficient was not. This result suggests that when coefficient of inbreeding is calculated on the basis of a genealogy that begins after a long history of inbreeding, the coefficient of inbreeding fails to capture previous demographic information because it is a poor estimator of accumulated individual inbreeding. We conclude that among highly endangered species with extensive identity disequilibrium, examination of heterozygosity‐fitness correlations may be an effective way to detect inbreeding depression, whereas inbreeding‐fitness correlations may be poor indicators of inbreeding depression if the pedigree does not accurately reflect the history of inbreeding. Correlaciones Heterocigosidad‐ Adaptabilidad y Depresión Endogámica en Dos Especies de Mamíferos Críticamente en Peligro  相似文献   
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