951 resultados para Vertical take-off
Resumo:
Ascidians (Ascidiacea: Tunicata) are sessile suspension feeders that represent dominant epifaunal components of the Southern Ocean shelf benthos and play a significant role in the pelagic-benthic coupling. Here, we report the results of a first study on the relationship between the distribution patterns of eight common and/or abundant (putative) ascidian species, and environmental drivers in the waters off the northern Antarctic Peninsula. During RV Polarstern cruise XXIX/3 (PS81) in January-March 2013, we used seabed imaging surveys along 28 photographic transects of 2 km length each at water depths from 70 to 770 m in three regions (northwestern Weddell Sea, southern Bransfield Strait and southern Drake Passage), differing in their general environmental setting, primarily oceanographic characteristics and sea-ice dynamics, to comparatively analyze the spatial patterns in the abundance of the selected ascidians, reliably to be identified in the photographs, at three nested spatial scales. At a regional (100-km) scale, the ascidian assemblages of the Weddell Sea differed significantly from those of the other two regions, whereas at an intermediate 10-km scale no such differences were detected among habitat types (bank, upper slope, slope, deep/canyon) on the shelf and at the shelf break within each region. These spatial patterns were superimposed by a marked small-scale (10-m) patchiness of ascidian distribution within the 2-km-long transects. Among the environmental variables considered in our study, a combination of water-mass characteristics, sea-ice dynamics (approximated by 5-year averages in sea-ice cover in the region of or surrounding the photographic stations), as well as the seabed ruggedness, was identified as explaining best the distribution patterns of the ascidians.
Resumo:
Vertical distributions of benthic denitrification and anammox rates within the sediment were estimated from slurry incubation experiments. Rates were used to calculate the contribution of anammox and denitrification to the total N-loss. Briefly, MUC sediment cores were sliced in 2 cm intervals and the sediment was diluted and incubated with degassed bottom water in a gas tight bag. After pre-incubating the bags for 2 h, 15N-labeled substrates were injected into the bags and the slurries were thoroughly mixed. Incubations were performed in the dark at in situ temperatures. The N2 isotope ratio (28N2, 29N2, and 30N2) was determined by gas chromatography-isotopic ratio mass spectrometry (VG Optima, Micromass) and calculated according to Kuypers et al. (2005) and Holtappels et al. (2011), respectively.Furthermore, total organic carbon and nitrogen concentrations were measured of core sediment layers corresponding to those used for rate measurements. Concentrations of organic carbon and nitrogen were determined by combustion/gas chromatography (Carlo Erba NA-1500 CNS analyzer) of dried sediment samples after acidification. The same sediment layer were also used to extract nucleic acids. The concentrations of the DNA in the samples were measured spectrophotometrically with a NanoDrop instrument (Thermo Fisher Scientific Inc.). The biomarker functional gene nirS, encoding the cd1-containing nitrite reductase, for both denitrifiers and marine anammox bacteria were quantified with real-time PCR, using the primers cd3aF/R3cd (5'-GTSAACGTSAAGGARACSGG-3' (Michotey et al., 2000)/5'-GASTTCGGRTGSGTCTTGA-3'; Throback et al., 2004) and Scnir372F/Scnir845R (5'-TGTAGCCAGCATTGTAGCGT-3'/5'-TCAAGCCAGACCCATTTGCT-3'; Lam et al., 2009).
Resumo:
Vertical carbon fluxes between the surface and 2500 m depth were estimated from in situ profiles of particle size distributions and abundances me/asured off Cape Blanc (Mauritania) related to deep ocean sediment traps. Vertical mass fluxes off Cape Blanc were significantly higher than recent global estimates in the open ocean. The aggregates off Cape Blanc contained high amounts of ballast material due to the presence of coccoliths and fine-grained dust from the Sahara desert, leading to a dominance of small and fast-settling aggregates. The largest changes in vertical fluxes were observed in the surface waters (<250 m), and, thus, showing this site to be the most important zone for aggregate formation and degradation. The degradation length scale (L), i.e. the fractional degradation of aggregates per meter settled, was estimated from vertical fluxes derived from the particle size distribution through the water column. This was compared with fractional remineralization rate of aggregates per meter settled derived from direct ship-board measurements of sinking velocity and small-scale O2 fluxes to aggregates measured by micro-sensors. Microbial respiration by attached bacteria alone could not explain the degradation of organic matter in the upper ocean. Instead, flux feeding from zooplankton organisms was indicated as the dominant degradation process of aggregated carbon in the surface ocean. Below the surface ocean, microbes became more important for the degradation as zooplankton was rare at these depths.
Resumo:
The 60 km wide shelf off Mauritania is cut by several submarine canyons. Its water-circulation is controlled by the cool Canary current and upwelling. Its Recent sediments show faunal associations remarkably related to the grain size distribution which in water depths between 40 and 80 m is strongly influenced by reworking of older coarse sand or sandstone. In this depth range a mixed biofacies originating from Pleistocene and Recent material is encountered. The present lateral faunistic and sedimentological facies change, including horizons of mixed provenance, can be recognized in vertical sequences taken by vibro-coring. This correlation combined with 14C-datations on molluscs enable the reconstruction of the history of the last glacial regression and transgression. Due to the arid climate, the emerging calcareous shelf sediments are indurated and, therefore, protected from subaerial and submarine erosion. During low sea level eolian sand migrates over the shelf, but only about 1/10 of this material remains there and is later incorporated into the sandy shelf sediments. The calculated average rate of total sedimentation during Holocene is 15 cm, and the production rate of carbonate is 5 cm/1000 years.
Resumo:
On cover: Capacity building program.
Resumo:
Mode of access: Internet.
Resumo:
At head of title: Department of scientific and industrial research. Fuel research board ...
Resumo:
Mode of access: Internet.
Resumo:
Mode of access: Internet.
Resumo:
Bibliographical footnotes.
Resumo:
In the last few years, transaction cost economics has become a popular theory within the construction research community. This approach has been singularly applied as a means to explain and predict phenomena concerning the construction firm, including its vertical boundaries. However, this is at a time when the chief proponents of transaction costs are urging researchers to take a pluralistic stance in relation to the theory of the firm. The aim of this paper is to develop a pluralistic approach to the vertical boundaries of the construction firm. In order to achieve this, an integrative framework is described, based on the development of the efficient boundaries problem and the capabilities approach to vertical integration. Specifically, this framework draws on the complementary strengths of transaction cost economics and the resource-based view. It is concluded that the potential relative merits of theoretical pluralism, in terms of the vertical boundaries of the construction firm, are sufficient grounds to motivate empirical testing of the predictions associated with the integrative framework of vertical integration presented
Resumo:
Automatic signature verification is a well-established and an active area of research with numerous applications such as bank check verification, ATM access, etc. This paper proposes a novel approach to the problem of automatic off-line signature verification and forgery detection. The proposed approach is based on fuzzy modeling that employs the Takagi-Sugeno (TS) model. Signature verification and forgery detection are carried out using angle features extracted from box approach. Each feature corresponds to a fuzzy set. The features are fuzzified by an exponential membership function involved in the TS model, which is modified to include structural parameters. The structural parameters are devised to take account of possible variations due to handwriting styles and to reflect moods. The membership functions constitute weights in the TS model. The optimization of the output of the TS model with respect to the structural parameters yields the solution for the parameters. We have also derived two TS models by considering a rule for each input feature in the first formulation (Multiple rules) and by considering a single rule for all input features in the second formulation. In this work, we have found that TS model with multiple rules is better than TS model with single rule for detecting three types of forgeries; random, skilled and unskilled from a large database of sample signatures in addition to verifying genuine signatures. We have also devised three approaches, viz., an innovative approach and two intuitive approaches using the TS model with multiple rules for improved performance. (C) 2004 Pattern Recognition Society. Published by Elsevier Ltd. All rights reserved.
Resumo:
Differencing from previous studies on foreign direct investment (FDI) spillovers to domestic enterprises which mainly focus on productivity, in this paper we take a different perspective by analysing the impacts of FDI to technical efficiency of domestic firms. The paper goes beyond the current literature to shed some light on the spillover effects of FDI to technical efficiency of small and medium enterprises in a developing country. By exploiting a firm-level panel dataset and using SFA models following Battese and Coelli (1995), the paper is able to analyse horizontal spillovers through imitation and competition and labour mobility as well as vertical spillovers through backward and forward linkages on technical efficiency. The paper contributes to the understanding of potential effects on foreign invested enterprises on domestic economy in general and local enterprises performance in particular. Thus it importantly assists policy making by the government of developing countries, where FDI is believed to create technical spillovers on domestic enterprises.