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121.
Daniela Marques Ana I. Esteves Marise Almeida Joana Xavier Madalena Humanes 《Marine Biology》2008,153(5):807-813
The aim of this work is to investigate the activity of the antioxidant enzyme superoxide dismutase in the cosmopolitan sponge
Cliona celata (Grant, 1826), since this enzyme has been described as a useful biomarker for marine pollution in other marine invertebrates.
The quantification of the catalytic activity for superoxide dismutase is quite complex because its substrate is an unstable
free radical. Several methods have been developed for this enzymatic activity determination; most of them are based on inhibition
of a redox reaction involving the superoxide radical. In this work, two methods are compared, for crude sponge extracts, as
far as repeatability, reproducibility and sensibility are concerned. The adrenaline oxidation method seems to be the most
adequate for these determinations. Statistical treatment of the data indicates that the reference value for the specific superoxide
dismutase activity in C. celata should be in the interval [0–535.5] U/mg of total protein in wet tissues, for normal populations. 相似文献
122.
In the present work we investigate whether the distribution of energy flows in ecosystems responds to criteria of trophic organization. We analyzed weighted and unweighted food webs estimating, for each node, trophic position (TP), Shannon's index of inflow diversity (H) and individual contribution to the whole average mutual information (AMI). Finally, we performed the same analysis on simulated webs that were constructed using the following criteria: (a) preserving topology and varying link strength; (b) modifying position of links and their intensities. 相似文献
123.
R. Webster West Daniela K. Nitcheva Walter W. Piegorsch 《Environmental and Ecological Statistics》2009,16(1):63-73
A primary objective in quantitative risk assessment is the characterization of risk which is defined to be the likelihood
of an adverse effect caused by an environmental toxin or chemcial agent. In modern risk-benchmark analysis, attention centers
on the “benchmark dose” at which a fixed benchmark level of risk is achieved, with a lower confidence limits on this dose
being of primary interest. In practice, a range of benchmark risks may be under study, so that the individual lower confidence
limits on benchmark dose must be corrected for simultaneity in order to maintain a specified overall level of confidence.
For the case of quantal data, simultaneous methods have been constructed that appeal to the large sample normality of parameter
estimates. The suitability of these methods for use with small sample sizes will be considered. A new bootstrap technique
is proposed as an alternative to the large sample methodology. This technique is evaluated via a simulation study and examples
from environmental toxicology.
相似文献
R. Webster WestEmail: |
124.
José Fortes Lopes Ana Cristina Cardoso Maria Teresa Moita Alfredo C. Rocha Juan A. Ferreira 《Ecological modelling》2009
The main objective of this paper is to implement a coupled three-dimensional physical and ecological model for the Aveiro coast, and to apply it to study the temperature and the phytoplankton biomass spatial distributions along the coastal ecosystem. The Aveiro coast is located at Portugal within the upwelling system of the Atlantic Iberian coast, characterized by nutrients availability and phytoplankton biomass accumulation, from April to October. In order to implement the ecological model, its validation was assessed by comparing simulations to data relative to the horizontal and vertical distributions of the temperature, nutrients and phytoplankton biomass, obtained during the CICLOS I survey off the Portuguese coast [Moita, M.T., 2001. Estrutura, Variabilidade e Dinâmica do Fitoplâncton na Costa de Portugal Continental. PhD Thesis. Faculdade de Ciências da Universidade de Lisboa, 272 pp.]. A sensitivity analysis of the model has been performed in order to assess the influence of the main ecological model variables. The simulation results show that the model is capable of predicting realistic the temperature, the nutrients and the chlorophyll-a distributions for the study area. The scenarios evidence the setup of a thermal stratification pattern resulting from the upwelling of deep and rich in nutrients water to the surface layer and a chlorophyll-a maxima extending offshore, along the picnocline and the nutricline. The results confirm the crucial role played by the physical processes in the phytoplankton bloom along the Aveiro coast. They also evidence the close link between the surface phytoplankton distribution and the surface temperature distribution. 相似文献
125.
Marcela González Cristina Dapeña Bibiana Cerne Odon Sánchez-Ccoyllo Saulo Freitas Pedro L. Silva Dias Héctor Panarello 《Environmental Fluid Mechanics》2009,9(4):409-425
The SALLJEX experiment was held during the summer 2002–2003. It consisted of three-dimensional observation of the atmosphere
to study the structure of the low level jet along the eastern slopes of the Andes. Daily precipitation water samples were
collected at two stations (Resistencia and Salta) in northern Argentina and isotope content was analyzed. The isotope data
were used in conjunction with air parcel trajectories obtained from a 3-D kinematic model (3D-MTC) developed by the University
of Sao Paulo, Brazil. Values of deuterium excess were related with air masses of continental origin, whilst low values were
associated with air masses with longer oceanic trajectories. Furthermore, although data are scarce, results show that oxygen-18
and deuterium excess in rainwater are related with the occurrence of the low level jet. 相似文献
126.
Cristina B. Gibson 《组织行为杂志》2001,22(7):789-808
Efficacy‐effectiveness relationships were examined for individual nurses and nursing teams who were either trained or untrained in goal‐setting. At the individual level, positive direct relationships were demonstrated between self‐efficacy and effectiveness, between training and subsequent self‐efficacy, and between training and effectiveness. Initial self‐efficacy also moderated the training‐effectiveness relationship. Nurses low in initial self‐efficacy realized greater effectiveness gains from the training than did nurses high in initial self‐efficacy. At the team level, group efficacy was related to effectiveness, and training was related to subsequent group efficacy, but training was not related to effectiveness, and there were no moderation effects for initial group efficacy. Collective cognition and behavioral plasticity are potential explanations for different effects at the individual and team level and avenues for theory development and future research. Copyright © 2001 John Wiley & Sons, Ltd. 相似文献
127.
Acquaroni Mercedes Peluso Julieta Svartz Gabriela Aronzon Carolina Pérez Coll Cristina 《Environmental science and pollution research international》2021,28(31):41772-41779
Environmental Science and Pollution Research - There is a great concern worldwide about the global decline of amphibians, particularly by agrochemical pollution. The aim of this study was to assess... 相似文献
128.
Organic matter lability can be determined with different approaches, based on the quantitative and qualitative estimate of its nutritional value. the C/N ratio and the particulate organic matter (as the sum of protein, carbohydrate and lipid bulks) vs total suspended matter (POM/TSM) deal with a quantitative assessment of the organic matter bulk, while other indices such as proteins/carbohydrates ratio (PRT/CHO) may give also qualitative information. Gordon (1970) proposed a functional approach, based on organic carbon decrease after enzymatic digestion. Coupling Gordon's approach with the evaluation of the main biochemical components (proteins, carbohydrates and lipids) contained in the particulate organic matter, a simple method to assess lability and nutritional value of organic substrates is proposed.
Water samples were collected at the surface and close to the bottom in a shallow coastal station (10 m depth) in the Marconi Gulf (Ligurian Sea, NW Mediterranean). the difference between “total labile” and “hydrolyzed labile” organic matter (respectively before and after enzymatic digestion) suggests a relevant presence of resuspended refractory materials vs about 60% of labile hydrolyzed organic matter, thus confirming the importance of a more qualitative approach to organic matter studies. 相似文献
Water samples were collected at the surface and close to the bottom in a shallow coastal station (10 m depth) in the Marconi Gulf (Ligurian Sea, NW Mediterranean). the difference between “total labile” and “hydrolyzed labile” organic matter (respectively before and after enzymatic digestion) suggests a relevant presence of resuspended refractory materials vs about 60% of labile hydrolyzed organic matter, thus confirming the importance of a more qualitative approach to organic matter studies. 相似文献
129.
Antonio Cao Angela M. Falchi Teresa Tuveri Maria T. Scalas Giovanni Monni Cristina Rosatelli 《黑龙江环境通报》1986,6(3):159-167
In this report we have summarized our experience with the prenatal diagnosis of β-thalassemia in 1000 pregnancies followed at least until 12 months after birth. In the majority of these cases, the thalassemia lesion was the nonsense mutation at the codon corresponding to amino acid 39, which produces the hematological phenotype of β-thalassemia. Fetal blood sampling was carried out by placental aspiration, by which a sufficient amount of fetal blood for analysis was obtained in the majority of cases (99 per cent). The fetal mortality associated with fetal blood sampling was 6·3 per cent. Those placental samples contaminated by maternal cells were successfully purified by Ørskov lysis. Fetal blood was analysed by globin chain synthesis on CM–52 columns, which gave reliable results. Two misdiagnoses (0·2 per cent) have been made of which one was due to a non-globin protein co-migrating with the β-chains while the other resulted from a misclassification of the type of thalassemia segregating in the family. 相似文献
130.