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11.
Guillaume Loiselle Jean-Luc Martel Annie Poulin Simon Lachance-Cloutier Richard Turcotte Judith Fournier Juliane Mai Richard Arsenault 《水文研究》2021,35(6):e14240
The precision of Lake Champlain's water level estimation is a key component in the flood forecasting process for the Richelieu River. Hydrological models do not typically take into consideration the effects of the wind on the water level (also known as the wind set-up). The objective of this study is to create an empirical wind set-up forecast model for Lake Champlain during high wind events. The proposed model uses wind speed and direction across the Lake, as well as wind gusts as inputs. The model is calibrated to a subset of observations and evaluated on an independent sample, considering four wind speed bins. It is tested and compared to a variant of the Zuider Zee equation on 20 wind set-up events that occurred between 2017 and 2019 using hindcast data from five different numerical weather prediction systems (GDPS, RDPS, HRDPS, NOAA and ECMWF). A quantile mapping-based forecast calibration scheme is implemented for each of the forecast products to correct their biases. Results show that events are successfully predicted by the proposed model at least 72 h in advance. These results are better than the other comparative models found in the literature and tested herein. Overall, significant improvements are obtained by including wind speed and wind gusts from different weather stations. 相似文献
12.
Locomotion is essential for vertebrate survival. Forces required for movement are generated by skeletal muscle. Skeletal muscle shortening and/or force generation occur via parallel sliding of two protein filaments: actin and myosin. This is driven by the cycling of cross-bridges, whose unitary nanometer length change and picoNewton force output are fueled by conversion of chemical energy, stored in the form of adenosine triphosphate, into a change in myosin protein configuration. The range of force and length changes of a muscle is determined by factors such as muscle cross section, fiber angle, tendon attachment, and lever geometry, but also by the metabolic pathways available for adenosine triphosphate synthesis and by enzymes involved in cross-bridge cycling. In addition, muscle mechanical activity is affected by the extent of actin and myosin filament overlap. Force output can be graded by selective recruitment of motor units and/or by variation of force output from individual units. The cost of locomotion is subject to species differences and is affected by the environment and form of movement, with an energy efficiency of up to 0.4. Overall, design principles of vertebrate skeletal muscle may serve as an interesting reference point for novel actuator technologies. 相似文献
13.
Susana E Jorge-Villar Liane G Benning Howell GM Edwards AMASE team 《Geochemical transactions》2007,8(1):8
Background
A profile across 8 layers from a fossil travertine terrace from a low temperature geothermal spring located in Svalbard, Norway has been studied using both Raman spectroscopy and SEM (Scanning Electron Microscopy) techniques to identify minerals and organic life signals. 相似文献14.
The dynamics of cyanobacterial silicification was investigated using synchrotron-based Fourier transform infrared micro-spectroscopy. The changes in exo-polymeric polysaccharide and silica vibrational characteristics of individual Calothrix sp. filaments was determined over time in a series of microcosms in which the microbially sorbed silica or silica and iron load was increased sequentially. The changes in intensity and integrated area of specific infrared spectral features were used to develop an empirical quantitative dynamic model and to derive silica load-dependent parameters for each quasi-equilibrium stage in the biomineralization process.The degree of change in spectral features was derived from the increase in integrated area of the combined silica/polysaccharide region (Si-O/C-O, at 1150-950 cm−1) and the Si-O band at 800 cm−1, the latter representing specific silica bonds corresponding to hydrated amorphous SiO4 tetrahedra. From the degree of change, a two-phase model with concurrent change in process was derived. In the first phase, a biologically controlled increase in thickness of the exo-polymeric polysaccharide sheath around the cell was observed. In phase two, a transition to an inorganically controlled accumulation of silica on the surface of the cyanobacterial cells was derived from the change in integrated area for the mixed Si-O/C-O spectral region. This second process is further corroborated by the synchronous formation of non-microbially associated inorganic SiO4 units indicated by the growth of the singular Si-O band at 800 cm−1. During silicification, silica accumulates (1) independently of the growth of the sheath polysaccharides and (2) via an increase in chain lengths of the silica polymers by expelling water from the siloxane bonds. IR evidence suggest that an inorganic, apparently surface catalyzed process, which leads to the accumulation of silica nanospheres on the cyanobacterial surfaces governs this second stage. In experiments where iron was present, the silicification followed similar pathways, but at low silica loads, the iron bound to the cell surfaces slightly enhanced the reaction dynamics. 相似文献
15.
Synchrotron-based Fourier-transform infrared (SR-FTIR) micro-spectroscopy was used to determine the concentration-dependent response of the organic structure of live cyanobacterial cells to silicification. Mid-infrared (4000-600 cm−1) measurements carried out on single filaments and sheaths of the cyanobacteria Calothrix sp. (strain KC97) were used to monitor the interaction between a polymerizing silica solution and the organic functional groups of the cells during progressive silicification. Spectra of whole-cells and sheaths were analyzed and the spectral features were assigned to specific functional groups related to the cell: lipids (-CH2 and -CH3; at 2870-2960 cm−1), fatty acids (>C=O at 1740 cm−1), proteins (amides I and II at 1650 and 1540 cm−1), nucleic acids (>P=O 1240 cm−1), carboxylic acids (C-O at 1392 cm−1), and polysaccharides (C-O between 1165 and 1030 cm−1). These vibrations and the characteristic vibrations for silica (Si-O between 1190 and 1060 cm−1; to some extent overlapping with the C-O frequencies of polysaccharides and Si-O at 800 cm−1) were used to follow the progress of silicification. Relative to unsilicified samples, the intensity of the combined C-O/Si-O vibration band increased considerably over the course of the silicification (whole-cells by > 90% and sheath by ∼75%). This increase is a consequence of (1) extensive growth of the sheath in response to the silicification, and (2) the formation of thin amorphous silica layers on the sheath. The formation of a silica specific band (∼800 cm−1) indicates, however, that the precipitation of amorphous silica is controlled by the dehydroxylation of abiotically formed silanol groups. 相似文献
16.
Tim McCreanor Liane Penney Victoria Jensen Karen Witten Robin Kearns Helen Moewaka Barnes 《New Zealand geographer》2006,62(3):196-207
Abstract: This paper examines the culturally specific experiences of belonging within Oruāmo/Beachhaven, a suburb in North Shore City. In-depth interviews with 32 caregivers of young children expose the fact that the ethnic groups represented – Māori, Samoan and Pākehā– vary in their uses and understandings of, as well as feelings for, residential neighbourhood. Examination of the themes of natural environment, social relations, continuity of residence, facilities, organisations and place transformation reveal that, while representatives of all groups had views on these matters, there was a variable degree of engagement with and priority afforded to these concerns. 相似文献