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排序方式: 共有206条查询结果,搜索用时 171 毫秒
191.
Camacho Jos A. da Silva Almeida Lucas Rodrguez Mercedes Molina Jess 《Environment, Development and Sustainability》2022,24(4):4602-4622
Environment, Development and Sustainability - In order to adequately assess energy policies and set clear objectives, a key preliminary step is to know the energy use patterns of the different... 相似文献
192.
193.
Fernando G. Brun Fabio Cummaudo Irene Olivé Juan José Vergara José Lucas Pérez-Lloréns 《Marine Biology》2007,151(5):1917-1927
Disaggregating seagrass meadows and studying its components separately (clones, ramets, shoots) can provide us insights on
meadow dynamics and growth patterns. The clonal growth, dependent upon clonal rules may regulate and impose constraints to
plant architecture and, therefore, determine how individual clones evolve into the environment. In order to investigate the
relationship between clonal growth rules and clone architecture, the belowground network architecture of single-clones of
the seagrass Zostera noltii was studied. Networks were traced in situ after washing out the overlying sediment, and network characteristics were measured
using digital analysis: area covered by clone, total rhizome length, type of rhizomatic axes (main, secondary, tertiary, quaternary),
number and length of the internodes, branching angles and branching frequencies. This approach revealed that Z. noltii is able to develop into large clones integrating up to 300 internodes, 676 cm of rhizome, 208 shoots and 4,300 cm2 of plant area. Internodal length depended on both, the distance to the apical shoot (time effect) and the axes type (apical
dominance effect). However, average branching angle was independent of axis type (average 58.3 ± 0.75), but varied significantly
depending on the distance from the apical shoot. This average branching angle allows Z. noltii maximize the rate of centrifugal expansion, maintaining a high density in colonized areas to produce close stands but also
minimizing the investment in belowground biomass and ramets overlapping. The clonal architecture of Z. noltii seems to be regulated by the interaction of both, apical dominance strength and clonal integration distance. Moreover, clonal
growth rules and growth pattern seem to constrain clonality through (clonal) plant architecture regulations (i.e. branching
is restricted in secondary axes, similar average branching angles regardless the axes, the higher the distance to the apex
the higher the number of internodes in secondary axes, shorter internodes in secondary and tertiary axes). Future research
efforts should focus on how these complex relationships between apical dominance and clonal integration interact to elucidate
the temporal (seasonal) and spatial scales of both processes and the outcome at the plant architectural level. 相似文献
194.
Fabio de Oliveira Lucas Igor Jos Chaves de Oliveira Fernando Brenha Ribeiro 《Journal of environmental radioactivity》2009,100(10):875-883
The assembling of a system for field sampling and activity concentration measurement of radon dissolved in groundwater is described. Special attention is given in presenting the calibration procedure to obtain the radon activity concentration in groundwater from the raw counting rate registered in a portable scintillation detector and in establishing the precision of the activity concentration measurements. A field procedure was established and the system tested during one year of monthly observations of 222Rn activity concentration in groundwater drawn from two wells drilled on metamorphic rocks exposed at Eastern São Paulo State, Brazil. The observed mean 222Rn activity concentrations are 374 Bq/dm3 in one well and about 1275 Bq/dm3 in the other one. In both wells the 222Rn activity concentrations showed a seasonal variation similar to variations previously reported in the literature for the same region. 相似文献
195.
The lack of fundamental data on the abfrontal surface of bivalve gills has prompted a comparative study of cilia and mucocytes
on this surface, using scanning electron microscopy and histology on eight species of bivalves, representing seven families
and the four major gill types: Mytilus edulis, Modiolus modiolus, Arca zebra, Placopecten magellanicus, Crassostrea virginica, Spisula solidissima, Mercenaria mercenaria, and Mya arenaria. Abfrontal cilia and mucocytes were found in all species studied, with types and densities differing within and between gill
types. The three species of homorhabdic filibranchs presented different densities of abfrontal cilia and mucocytes, from very
dense in M. edulis to sparse in A. zebra. The heterorhabdic gills had intermediate cilia and mucocyte densities, with highest concentrations of both abfrontal cilia
and mucocytes on the principal filaments. The eulamellibranchs showed low ciliary densities together with high mucocyte densities,
especially in S. solidissima, where the abfrontal mucocytes were glandular. These results indicate that: (1) the abfrontal surface is a vestigial mucociliary
surface; (2) the abfrontal surface cannot participate in water pumping in most species, due to low ciliary densities; and
(3) species with high densities of abfrontal mucocytes could utilize abfrontal mucus to reduce drag, especially in the highly
fused gills, such as those of the eulamellibranchs. The differing distributions of abfrontal cilia and mucocytes may reflect
different selective pressures acting on the gills within the various taxa.
Received: 12 February 2000 / Accepted: 10 September 2000 相似文献
196.
Marcos Pérez-López Francisco Soler Rodríguez David Hernández-Moreno Lucas Rigueira Luis Eusebio Fidalgo Ana López Beceiro 《毒物与环境化学》2016,98(1):109-117
Cd, Pb, and Zn were quantified in liver and kidney of red foxes (Vulpes vulpes) which were hunted during the 2003–2011 hunting seasons in Galicia (NW Spain). The effects of age and gender were evaluated to determine whether these variables should be included in future biomonitoring studies. The concentrations of hepatic and renal Cd (average 0.6 and 1.3 µg/g) and Pb (0.8 and 0.06 µg/g, respectively) were similar to background levels, with no known toxicological relevance. Similarly, the average levels of Zn in liver and kidney (77 and 17 µg/g) were in the range of physiological levels for canids. Although no significant gender-dependent variations were observed, the effect of aging was evident: the levels of hepatic Pb and both hepatic and renal Cd were higher in adults than in juveniles. Age should be included as a parameter during future biomonitoring programs focusing on trace metal bioaccumulation in red foxes. 相似文献
197.
The sorption and desorption behavior of hexavalent chromium and chlorinated ethenes in a sandy ground water aquifer with a low reduction capacity was evaluated by performing a variety of analyses and experiments at the laboratory (batch and column studies) and field (in situ injection-withdrawal experiment) scales. The partitioning coefficients determined from the field and laboratory experiments are generally similar. Both sets of experiments yielded relatively low partition coefficients for chromium and chlorinated ethenes. The column studies and injection-withdrawal experiment indicate that chromium has the potential to leach from aquifer sediments and act as a secondary source of contamination. However, the magnitude of the secondary source effect is not significant due to low concentrations of leachable contamination. The chromium sorption isotherm data were also simulated using the triple layer surface complexation model (TLM). The isotherm data were modeled using the TLM, illustrating the applicability of geochemical modeling for sorption of chromium to these sediments under variable pE-pH conditions. 相似文献
198.
Cameron R Bass Robert S Salzar Scott R Lucas Martin Davis Lucy Donnellan Benny Folk Ellory Sanderson Stanley Waclawik 《International journal of occupational safety and ergonomics》2006,12(4):429-442
First responders and military personnel are particularly susceptible to behind armor blunt thoracic trauma in occupational scenarios. The objective of this study was to develop an armored thorax injury risk criterion for short duration ballistic impacts. 9 cadavers and 2 anthropomorphic test dummies (AUSMAN and NIJ 0101.04 surrogate) were tested over a range of velocities encompassing low severity impacts, medium severity impacts, and high severity impacts based upon risk of sternal fracture. Thoracic injuries ranged from minor skin abrasions (abbreviated injury scale [AIS] 1) to severe sternal fractures (AIS 3+) and were well correlated with impact velocity and bone mineral density. 8 male cadavers were used in the injury risk criterion development. A 50% risk of AIS 3+ injury corresponded to a peak impact force of 24,900 +/- 1,400 N. The AUSMAN impact force correlated strongly with impact velocity. Recommendations to improve the biofidelity of the AUSMAN include implementing more realistic viscera and decreasing the skin thickness. 相似文献
199.
Ivonne Bedei Tascha Gehrke Karl-Philipp Gloning Matthias Meyer-Wittkopf Daria Willner Martin Krapp Alexander Scharf Jan Degenhardt Kai-Sven Heling Peter Kozlowski Kathrin Trautmann Kai M. Jahns Annegret Geipel Jan-Erik Baumüller Lucas Wilhelm Ingo Gottschalk Andreas Schröer Alexander Graf Aline Wolter Johanna Schenk Axel Weber Ignatia B. Van den Veyver Roland Axt-Fliedner 《黑龙江环境通报》2023,43(2):192-206
Objective
We aimed to investigate how the presence of fetal anomalies and different X chromosome variants influences Cell-free DNA (cfDNA) screening results for monosomy X.Methods
From a multicenter retrospective survey on 673 pregnancies with prenatally suspected or confirmed Turner syndrome, we analyzed the subgroup for which prenatal cfDNA screening and karyotype results were available. A cfDNA screening result was defined as true positive (TP) when confirmatory testing showed 45,X or an X-chromosome variant.Results
We had cfDNA results, karyotype, and phenotype data for 55 pregnancies. cfDNA results were high risk for monosomy X in 48/55, of which 23 were TP and 25 were false positive (FP). 32/48 high-risk cfDNA cases did not show fetal anomalies. Of these, 7 were TP. All were X-chromosome variants. All 16 fetuses with high-risk cfDNA result and ultrasound anomalies were TP. Of fetuses with abnormalities, those with 45,X more often had fetal hydrops/cystic hygroma, whereas those with “variant” karyotypes had different anomalies.Conclusion
Both, 45,X or X-chromosome variants can be detected after a high-risk cfDNA result for monosomy X. When there are fetal anomalies, the result is more likely a TP. In the absence of fetal anomalies, it is most often an FP or X-chromosome variant. 相似文献200.
Fast climate changes in the western Antarctic Peninsula are reducing krill density, which along with increased fishing activities in recent decades, may have had synergistic effects on penguin populations. We tested that assumption by crossing data on fishing activities and Southern Annular Mode (an indicator of climate change in Antarctica) with penguin population data. Increases in fishing catch during the non-breeding period were likely to result in impacts on both chinstrap (Pygoscelis antarcticus) and gentoo (P. papua) populations. Catches and climate change together elevated the probability of negative population growth rates: very high fishing catch on years with warm winters and low sea ice (associated with negative Southern Annular Mode values) implied a decrease in population size in the following year. The current management of krill fishery in the Southern Ocean takes into account an arbitrary and fixed catch limit that does not reflect the variability of the krill population under effects of climate change, therefore affecting penguin populations when the environmental conditions were not favorable.Electronic supplementary materialThe online version of this article (10.1007/s13280-020-01386-w) contains supplementary material, which is available to authorized users. 相似文献