Statistical significance testing for the association of magnetometer records at high-, mid- and low latitudes during substorm days     

I. Maslova  P. Kokoszka  L. Zhu 《Planetary and Space Science》2010,58(3):437-445

In recent years, the interaction of the auroral substorms with the equatorial and mid-latitude currents has been the subject of extensive research. We introduce a new statistical technique that allows us to test at a specified significance level whether such a dependence exists, and how long it persists. This quantitative statistical technique, relying on the concepts and tools of functional data analysis, uses directly magnetometer records in one minute resolution, and it can be applied to similar geophysical data which can be represented as daily curves. It is conceptually similar to testing the nullity of the slope in the straight line regression, but both the regressors and the responses are curves rather than points. When the regressors are daily high latitude H-component curves during substorm days and the responses are daily mid- or low latitude H-component curves, our test shows significant dependence (the nullity hypothesis is rejected) which exists not only on the same UT day but also extends into the next day for strong substorms.  相似文献   

液核自由运动的变分方法   总被引：2，自引：0，他引：2       下载免费PDF全文

徐建桥  孙和平  傅容珊 《地球物理学报》2004,47(1):61-74

从流体静力平衡地球的弹性-引力运动动量方程出发,以角动 量方程控制弹性地幔、液态外核和弹性内核之间的相对转动,在球对称近似下考虑了地幔和 内核对液核边界扰动的形变响应,并以此作为液核边界运动的约束条件．根据地球简正模对 称性的一般特征,建立了自转、非黏性、椭球分层流体外核自由振荡运动的变分原理并给出 了相应的泛函．  相似文献   

氟利昂C₂Cl₂F₄分子的光谱及解离动力学研究     

何仲福  李凌昊  刘玉柱  罗礼海  王亚丽  秦朝朝 《南京气象学院学报》2016,8(2):181-185

采用密度泛函B3LYP理论对氟利昂C₂Cl₂F₄ (F-114)在6-31G++(d,p)基组水平上进行分子结构优化、红外光谱计算,理论计算所得结果与实验结果基本吻合.此外又通过从头算CIS方法计算了C₂Cl₂F₄及其离子的低激发态,将所得分子低激发态的键长、键角及二面角等参数进行了对比分析,并得到了C₂Cl₂F₄分子的UV-Vis光谱和分子前线轨道,最后对C₂Cl₂F₄⁺离子的低激发态光解离动力学进行了分析.  相似文献   

大菱鲆早期发育过程中免疫器官的发生     

佟雪红  徐世宏  刘清华  李军  肖志忠  马道远 《海洋科学》2011,35(6):62-67

应用组织切片研究了大菱鲆（Scophthalmus maximus）初孵仔鱼至60日龄幼鱼免疫器官的发育过程。结果表明,免疫器官原基出现的先后顺序是头肾、脾脏和胸腺。1日龄仔鱼可以观察到头肾原基,包含未分化的造血干细胞。5日龄时,脾脏原基出现,其淋巴化开始于27日龄且发育速度较慢。13日龄时,大菱鲆仔鱼胸腺原基出现,且...  相似文献   

Seasonal patterns of tidepool macroalgal assemblages in the North of Portugal. Consistence between species and functional group approaches     

M. Rubal  P. Veiga  R. Vieira  I. Sousa-Pinto 《Journal of Sea Research》2011,66(3):187-194

Macroalgae are useful organisms to monitor the environmental quality and to detect impacts due to anthropogenic activities. However, it is very important to identify the scales of variation in natural assemblages, particularly for the detection of environmental impacts. Otherwise, changes due to anthropogenic impacts may be confused with differences due to natural temporal variability. Another important task is to determine the appropriate level of taxonomical effort needed to detect changes in the assemblage structure. Many taxonomical surrogates, at higher taxonomic levels than that of species, have been proposed but, the consistence in space and time of the results produced by surrogates with those obtained at specific level should be tested. The objectives of this study are to identify the seasonal patterns of tidepool macroalgal communities using objective procedures and to test the consistence between the patterns obtained considering data at the species level and functional groups. Results showed that the seasonal pattern obtained using functional groups and species was consistent. Tidepool macroalgal assemblages showed a seasonal pattern with significant differences between spring–summer and autumn–winter. This pattern can be explained by changes in environmental variables and the seasonal development of the dominating species. Ulva spp. and the non-indigenous species Grateloupia turuturu were the species responsible for this pattern due to their high seasonality in terms of biomass. Finally, the abundance and species diversity within the corticated functional group was proposed as indicator of environmental impacts due to its relatively constant abundance and its sensitivity to environmental impacts.  相似文献   

大菱鲆早期发育过程中免疫器官的发生     

佟雪红  徐世宏  刘清华  李军  肖志忠  马道远 《海洋科学集刊》2011,50(6):62-67

应用组织切片研究了大菱鲆(Scophthalmus maximus)初孵仔鱼至60 日龄幼鱼免疫器官的发育过程。结果表明, 免疫器官原基出现的先后顺序是头肾、脾脏和胸腺。1 日龄仔鱼可以观察到头肾原基, 包含未分化的造血干细胞。5 日龄时, 脾脏原基出现, 其淋巴化开始于27 日龄且发育速度较慢。13 日龄时, 大菱鲆仔鱼胸腺原基出现, 且发育速度较快, 分为外区和内区。在大菱鲆早期发育过程中, 胸腺和头肾之间出现细胞迁移现象。免疫器官淋巴化的顺序是胸腺、头肾和脾脏。在免疫器官发育后期, 脾脏和头肾中均发现了黑色素-巨噬细胞中心(MMCs), 脾脏中较丰富, 但在胸腺中尚未发现。在大菱鲆仔鱼早期发育阶段, 免疫器官尚未发育完善, 非特异性防御机制起着重要的免疫作用。  相似文献   

Changes in vegetation structure induced by domestic grazing in Patagonia (Southern Argentina)     

A. Cesa  J.M. Paruelo 《Journal of Arid Environments》2011,75(11):1129-1135

We analyzed the structural differences associated with grazing exclusion on vegetation by studying 24 grazed-ungrazed paired sites in Patagonia (Argentina). Our objectives were to evaluate the effect of grazing on plant species composition, plant diversity, the relative abundance of plant functional types, and the vertical and horizontal structure of the plant community. This study across the shrub-grass steppes of Patagonia highlights some important characteristics of the vegetation response to a major disturbance factor we show that shrub encroachment is not a generalized response of the steppe to grazing. Grazed areas presented lower richness and diversity than exclosures. Physiognomic changes (as describe by relative abundance of plant functional types) were less important than those observed at the species level. These results shown that the status of the shrub-grass steppes of the Occidental district of Patagonia can not be characterized in terms of contrasting physiognomic states as in the case of the grass steppes of the Subandean district. Forbs and a few mesophytic and xerophytic grasses are the key elements to identify the condition of the steppe. Monitoring programs should focus on the relative abundance of these components.  相似文献   

Forms and sources of place attachment: Evidence from two protected areas     

《Geoforum》2014

Sense of place is a widely researched concept that has been used to describe and analyze people–place relationships. However, there is no consensus regarding the forms of place attachment, the relative importance of the sources for such attachments, or the spatial extent of place formation. The purpose of the paper is to contribute case examples of sense of place for significant natural areas, thereby adding to the body of evidence that explicates the diverse sources and forms of place attachment. Using content analysis of qualitative stakeholder interviews, we identify these dimensions of place attachment for two nationally significant Australian natural areas. Our data support a tripartite structure for sense of place comprising affective, functional and cognitive forms of attachment. We also examine the extent to which these place attachments are localized on the study sites and/or spatially generalized across sites possessing the same sources of place formation. Our case studies provide evidence for both localized and generalized senses of place. Localized place attachments had affective and functional components, respectively founded on social and biophysical sources. Generalized senses of place comprised functional and cognitive components, with appreciation of historical values of these places key to the formation of the latter. Our results indicate the spatial diversity of place attachments for protected areas and their social, cultural and biophysical sources.  相似文献   

Feeding behaviour of adult Centropages hamatus (Copepoda, Calanoida): Functional response and selective feeding experiments     

Andrea Saage  Olav Vadstein  Ulrich Sommer 《Journal of Sea Research》2009,62(1):16-21

The feeding behaviour of adults of the marine calanoid copepod Centropages hamatus was studied in laboratory experiments with ciliates and phytoplankton as food sources. The ingestion rate of algal (flagellates, diatoms) and ciliate prey (oligotrichs) as a function of prey concentration could be described by a Holling type III functional response, with close to zero ingestion rates at concentrations below 5 µg C l^− 1. In general, ingestion of ciliates was higher than ingestion of algae, and maximum feeding rates by adult males reached were half the feeding rates of adult females at prey concentrations exceeding 50 µg C l^− 1. When diatoms and ciliates were offered together C. hamatus (both sexes) fed exclusively on ciliates as long as they contributed with more than 5% to the mixture. This indicates the capability of active prey selection and switching between suspension feeding and ambush predation. Therefore, the feeding behaviour of adult C. hamatus can be characterised as omnivorous with a preference for larger motile prey. This implies a trophic level above two, if there is a sufficient abundance of protozoan food available.  相似文献   

The colonisation of leaf litter by Chironomidae (Diptera): The influence of chemical quality and exposure duration in a subtropical stream     

Cristiane Biasi  Alan M. Tonin  Rozane M. Restello  Luiz U. Hepp 《Limnologica》2013,43(6):427-433

This study tested the hypothesis that the community composition of Chironomidae will change according to the duration of the exposure of plant leaves in a subtropical stream. In addition, we expected the chemical quality of the detritus to affect the association of Chironomidae with decaying plant materials. The chironomid colonisation of leaf litter from Campomanesia xanthocarpa and Sebastiania brasiliensis was assessed in a subtropical Atlantic forest stream. Litter bags containing leaves from these two species were incubated in the stream for 22 days. We identified 7245 invertebrates associated with the leaf detritus of both plant species (5110 were Chironomidae, 70.7% of the total). Thirteen genera of Chironomidae were identified, with Rheotanytarsus, Thienemanniella and Corynoneura the most abundant (94% of all Chironomidae collected). Chironomidae assemblages changed with the duration of incubation in the stream. The dissimilarity and the functional composition of the Chironomidae communities were related to the chemical composition of the detritus. The chemical components that best explained the composition of the fauna were tannins, the C:N ratio, calcium, and magnesium. However, the functional feeding groups were explained by the chemical variables organic matter and C:N. This study found that the exposure time of the detritus and therefore its level of degradation and chemical composition are important factors determining the characteristics of the Chironomidae assemblage in subtropical streams.  相似文献