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排序方式: 共有139条查询结果,搜索用时 62 毫秒
21.
Tatiane Lima da Silva Rísia Brígida Gonçalves Cabral Lucas de Assis Silva Andrade Noemia Falcão Nogueira Mariana de Souza Oliveira Ildemar Ferreira 《Journal of Natural History》2018,52(3-4):225-235
Fluvicola nengeta is an insectivorous bird that belongs to the Tyrannidae family, which lives close to bodies of water and can occur in urban areas as well. It makes use of natural and man-made substrates to build its nests. This study aims at describing the reproductive biology of F. nengeta by comparing nests built on vegetation and man-made structures as to their shapes, nest dimensions, building materials, distance from bodies of water and reproductive success. Forty-four nests were found, where 30 were located in vegetation and 14 on man-made structures. Nests did not exhibit any single pattern and were divided into three distinct shapes: closed/globular/base; closed/ovoid/base (45.5%; n = 5 for both) and low cup/base (9%; n = 1). Nests built on man-made structures exhibited a larger amount of anthropic material, such as plastic and paper, instead of plant-derived materials. Nests on man-made structures were found to be higher up from the ground (459.8 ± 46.9 m) and farther from water (232.9 ± 54.8 m) in comparison to those on vegetation (92.2 ± 28.6 m and 7.3 ± 4.7 m, respectively), aside from exhibiting a higher Mayfield reproductive success (37%) when compared to nests built on vegetation (34%). The estimated values of the daily survival rate (DSR) for vegetation nests were 0.997 for the incubation period and 0.928 for the nestling period. In man-made structure nests, DSRs were 0.968 and 0.964, respectively, during the incubation and nestling periods. The period survival rate (PSR) of nests in vegetation was significantly higher than the PSRs of nests in man-made structures during the incubation period. DSRs did not differ between incubation and nestling periods for either nesting sites. 相似文献
22.
<正> This paper shows how the so called von Karman model can be obtained as a singular limitof a modified Mindlin-Timoshenko system when the modulus of elasticity in shear k tends to infinity,provided a regularizing term through a fourth order dispersive operator is added.Introducing dampingmechanisms,the authors also show that the energy of solutions for this modified Mindlin-Timoshenkosystem decays exponentially,uniformly with respect to the parameter k.As k→∞,the authors obtainthe damped von Karman model with associated energy exponentially decaying to zero as well. 相似文献
23.
Parker CV Aynajian P da Silva Neto EH Pushp A Ono S Wen J Xu Z Gu G Yazdani A 《Nature》2010,468(7324):677-680
Doped Mott insulators have a strong propensity to form patterns of holes and spins often referred to as stripes. In copper oxides, doping also gives rise to the pseudogap state, which can be transformed into a high-temperature superconducting state with sufficient doping or by reducing the temperature. A long-standing issue has been the interplay between the pseudogap, which is generic to all hole-doped copper oxide superconductors, and stripes, whose static form occurs in only one family of copper oxides over a narrow range of the phase diagram. Here we report observations of the spatial reorganization of electronic states with the onset of the pseudogap state in the high-temperature superconductor Bi(2)Sr(2)CaCu(2)O(8+x), using spectroscopic mapping with a scanning tunnelling microscope. We find that the onset of the pseudogap phase coincides with the appearance of electronic patterns that have the predicted characteristics of fluctuating stripes. As expected, the stripe patterns are strongest when the hole concentration in the CuO(2) planes is close to 1/8 (per copper atom). Although they demonstrate that the fluctuating stripes emerge with the onset of the pseudogap state and occur over a large part of the phase diagram, our experiments indicate that the stripes are a consequence of pseudogap behaviour rather than its cause. 相似文献
24.
Comparative stability analyses of traditional and selective room-and-pillar mining techniques for sub-horizontal tungsten veins 下载免费PDF全文
Vidal Félix Navarro Torres Carlos Dinis da Gama Matilde Costa e Silva Paula Falc?o Neves Qiang Xie 《矿物冶金与材料学报》2011,18(1):1-8
The stability and productivity concerning a modification on the traditional room and pillar for a new selective technique at the Portuguese Panasqueira Mine have been described. The traditional room-and-pillar stoping uses 5.0-m wide rooms with 3.0 m×3.0 m pillars, while the selective room-and-pillar mining technique consists in stoping with rooms of 4.0 m wide and pillars of 4 m×4 m with a subsequent selective cutting of the quartz veins at the mid pillar of approximately 0.5 m high, to obtain a pillar section with an area of 3.0 m×3.0 m. The stability and productivity analyses indicate that the selective technique obtains smaller average pillar safety factor, more rock mass displacement, more extraction and selectivity ratios, and ore grade improvement, compared with the traditional technique. These results show that the selective technique is also more convenient. This proposed selective room-and-pillar mining technique is applicable to any sub-horizontal narrow quartz veins with wolfram, gold, etc. such as the famous La Rinconada gold mine in the Peruvian Andes. 相似文献
25.
José Afonso de Oliveira Amarildo Jorge da Silva 《Systemic Practice and Action Research》2011,24(6):565-574
The context of this analysis is the golden years of the decade of the 1960s that served as a backdrop for consolidating capitalism
and the globalized world. The aim is to analyze, understand and establish possible connections between the arts in general
and the world in which modern society operates. This is a theoretical essay anchored in theoretical assumptions of sociology,
arts and the culture of the globalized world and built on the practical experience of these researchers. We use the interpretative
approach and technique of hermeneutic phenomenology to give meaning to historical events and the cultural and artistic implications
of these events in the rise of science and technology. A systemic examination supports the relationship between art, culture,
science and technology. The evidence shows that artistic and cultural issues are essential to make sense of life in society
and in the absence of such basis, the world would be meaningless and humans would lose a sense of direction. It can be concluded
that the arts are becoming increasingly relevant as the virtual world becomes large-scale and truly global, and that the development
of science and technology benefits from the rise of the cultural and artistic world of today. Finally, the correspondence
between the artistic and cultural world and the current scientific and technological development confirms the emergence of
a globalized, digitalised (virtual) knowledge society. 相似文献
26.
27.
Modeling European industrial production with multivariate singular spectrum analysis: A cross‐industry analysis 下载免费PDF全文
In this paper, an optimized multivariate singular spectrum analysis (MSSA) approach is proposed to find leading indicators of cross‐industry relations between 24 monthly, seasonally unadjusted industrial production (IP) series for German, French, and UK economies. Both recurrent and vector forecasting algorithms of horizontal MSSA (HMSSA) are considered. The results from the proposed multivariate approach are compared with those obtained via the optimized univariate singular spectrum analysis (SSA) forecasting algorithm to determine the statistical significance of each outcome. The data are rigorously tested for normality, seasonal unit root hypothesis, and structural breaks. The results are presented such that users can not only identify the most appropriate model based on the aim of the analysis, but also easily identify the leading indicators for each IP variable in each country. Our findings show that, for all three countries, forecasts from the proposed MSSA algorithm outperform the optimized SSA algorithm in over 70% of cases. Accordingly, this new approach succeeds in identifying leading indicators and is a viable option for selecting the SSA choices L and r, which minimizes a loss function. 相似文献
28.
Mutations in the gene encoding the 3'-5' DNA exonuclease TREX1 are associated with systemic lupus erythematosus 总被引:1,自引:0,他引:1
Lee-Kirsch MA Gong M Chowdhury D Senenko L Engel K Lee YA de Silva U Bailey SL Witte T Vyse TJ Kere J Pfeiffer C Harvey S Wong A Koskenmies S Hummel O Rohde K Schmidt RE Dominiczak AF Gahr M Hollis T Perrino FW Lieberman J Hübner N 《Nature genetics》2007,39(9):1065-1067
TREX1 acts in concert with the SET complex in granzyme A-mediated apoptosis, and mutations in TREX1 cause Aicardi-Goutières syndrome and familial chilblain lupus. Here, we report monoallelic frameshift or missense mutations and one 3' UTR variant of TREX1 present in 9/417 individuals with systemic lupus erythematosus but absent in 1,712 controls (P = 4.1 x 10(-7)). We demonstrate that two mutant TREX1 alleles alter subcellular targeting. Our findings implicate TREX1 in the pathogenesis of SLE. 相似文献
29.
Yuri Fanchini Messas Herbert Silva Souza Marcelo O. Gonzaga Joao Vasconcellos-Neto 《Journal of Natural History》2017,51(45-46):2661-2679
Population dynamics of spiders may vary according to biotic and abiotic factors. We studied the phenology of the bark-dwelling spider Eustala perfida over a two-year period and investigated how temperature, precipitation, and prey availability were associated with the population of this species. The population of E. perfida presented a well-defined fluctuation, with one reproductive cycle per year. The recruitment of spiders occurred in summer, followed by successive phenological peaks at all stages of development. The species is protogynic, and the population of adult males peaks in the cold/dry season, indicating a winter mature phenological pattern. The diet of E. perfida is composed mainly of medium-sized homopterans, complemented by small dipterans and hymenopterans. We found that the higher abundance of spiders occurred two months after the highest values of precipitation and temperature, and three months after the higher abundance of potential prey items. These results indicate that spiders require time to respond to changes in environmental conditions. The species’ natural history and the structure of the trunks in which it lives may also affect the number of individuals in a particular area and over time. 相似文献
30.
Roberto Malta da Silva Amarildo Jorge da Silva 《Systemic Practice and Action Research》2011,24(6):545-554
Given the scarcity of oil reserves, renewable sources of energy have become important. The Brazilian government has established
standards and policies to foment the use of bio-energy. Bio-fuels have widespread use and have been inserted into the national
energy matrix to help sustainable development. It is necessary to establish the effectiveness of these government initiatives
in preserving ecology; otherwise environmental harm such as the loss of biodiversity will increase. The objective of this
paper is to identify and analyse, from a systems point of view, the potential benefits and risks to the environment which
may arise from the use of bio-energy; whether its production is in agreement with the Brazilian constitution and whether its
environmental impact is beneficial when it is exploited economically. It also examines the legal aspects of the National Energy
Policy and the introduction of bio-diesel. We conclude that the place of bio-fuel in the Brazilian and the world’s energy
matrix is irreversible and furthermore, that its role will increase sharply in the future. 相似文献