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211.
Monitoring biophysical and biochemical vegetation variables in space and time is key to understand the earth system. Operational approaches using remote sensing imagery rely on the inversion of radiative transfer models, which describe the interactions between light and vegetation canopies. The inversion required to estimate vegetation variables is, however, an ill-posed problem because of variable compensation effects that can cause different combinations of soil and canopy variables to yield extremely similar spectral responses. In this contribution, we present a novel approach to visualise the ill-posed problem using self-organizing maps (SOM), which are a type of unsupervised neural network. The approach is demonstrated with simulations for Sentinel-2 data (13 bands) made with the Soil-Leaf-Canopy (SLC) radiative transfer model. A look-up table of 100,000 entries was built by randomly sampling 14 SLC model input variables between their minimum and maximum allowed values while using both a dark and a bright soil. The Sentinel-2 spectral simulations were used to train a SOM of 200 × 125 neurons. The training projected similar spectral signatures onto either the same, or contiguous, neuron(s). Tracing back the inputs that generated each spectral signature, we created a 200 × 125 map for each of the SLC variables. The lack of spatial patterns and the variability in these maps indicate ill-posed situations, where similar spectral signatures correspond to different canopy variables. For Sentinel-2, our results showed that leaf area index, crown cover and leaf chlorophyll, water and brown pigment content are less confused in the inversion than variables with noisier maps like fraction of brown canopy area, leaf dry matter content and the PROSPECT mesophyll parameter. This study supports both educational and on-going research activities on inversion algorithms and might be useful to evaluate the uncertainties of retrieved canopy biophysical and biochemical state variables. 相似文献
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周年逐月采集环沟格特蛤(Katelysiarimularis),分别测定软体部、性腺、足肌和消化腺的蛋白质、脂肪、糖的含量,并测定性腺甾类激素和以细胞磷推算的DNA和RNA含量。结果表明,其蛋白质和脂肪含量的变化与性腺发育周期一致,糖的变化与蛋白质和脂肪相反,提示该种蛤在性腺生长周期糖类向蛋白质和脂肪转化,并且随着性腺的发育,消化腺和足肌的蛋白质和脂肪转运到性腺。环沟格特蛤的甾类激素、DNA和RNA的含量变化与蛋白质及脂肪的含量变化有一致性,提示甾类激素是促进性腺蛋白质合成的内因之一。 相似文献
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A Santulli A Modica C Messina L Ceffa A Curatolo G Rivas G Fabi V DAmelio 《Marine pollution bulletin》1999,38(12):173-1114
The paper reports the results of an experimental seismic survey in the open sea by an air gun, carried out to evaluate the effects of air gun acoustic waves on marine animals. Air gun blast exposition was found to have a marked influence on confined Dicentrarchus labrax. Our data, in fact, demonstrated a biochemical response to acoustic stress induced by air gun blasts. Variations of cortisol, glucose, lactate, AMP, ADP, ATP and cAMP in different tissues of D. labrax, indicate that fish have a typical primary and secondary stress response after air gun detonations. Radiography indicates that air gun blasts do not induce any macroscopic effect on skeletal apparatus. The variations of biochemical parameters returned within physiological values within 72 h indicating a rapid recovery of homeostasis after acoustic stress and no mortality was observed. 相似文献
215.
影响海水中DMS浓度大小的因素很多。本文综述了目前国仙外有关DMS的生物和化学过程的研究进展。 相似文献
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温度对半滑舌鳎的生长、生化组成和能量收支的影响 总被引:1,自引:0,他引:1
研究了不同温度(16,19,22,25,28和31 ℃)对半滑舌鳎(Cynoglossus semilaevis Günther)幼鱼的生长、体成分组成和能量收支的影响.结果表明,随温度的升高,半滑舌鳎幼鱼生长率总体呈现先升高后降低的趋势.其中,在19~25 ℃温度范围内,半滑舌鳎幼鱼的特定生长率相对较高,在16和28 ℃下则有所降低,而在31 ℃下,半滑舌鳎幼鱼特定生长率则显著降低.本研究表明半滑舌鳎幼鱼特定生长率与温度符合二次曲线模型.半滑舌鳎摄食量随温度升高而逐渐增大,但在31 ℃时显著减小,饵料转化率则随温度的升高而降低.鱼体脂肪与能值均随温度升高而降低,蛋白质含量受温度影响不显著.温度对半滑舌鳎的能量收支影响显著,其中,生长能和代谢能主导半滑舌鳎的能量分配,生长能占摄食能比例则随温度的升高而降低,呼吸能占摄食能比例则随温度的升高而升高.本研究表明,半滑舌鳎幼鱼(13~37 g)适宜生长温度范围为18~25 ℃,而不同温度导致的半滑舌鳎摄食量和能量收支的差异可能是温度影响其生长的主要生理生态学机制. 相似文献
219.
Host factors important in sea lice infections 总被引:1,自引:1,他引:1
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