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排序方式: 共有552条查询结果,搜索用时 62 毫秒
441.
Stefano Goffredo Erik Caroselli Elettra Pignotti Guido Mattioli Francesco Zaccanti 《Marine Biology》2007,152(2):351-361
The correlation between two environmental factors (solar radiation and sea surface temperature), biometry, and population
density was assessed along a latitudinal gradient in the zooxanthellate coral Balanophyllia europaea and in the azooxanthellate coral Leptopsammia pruvoti. With increasing polyp size, the oral disc of B. europaea assumed an oval shape, while that of L. pruvoti retained a circular shape. In both species, biometric parameters varied more with temperature than with solar radiation.
In the zooxanthellate species, temperature explained a higher percentage of biometric parameter variance than in the azooxanthellate
species. While environmental factors did not co-vary with demographic characteristics in L. pruvoti, temperature was negatively related to the population density of B. europaea. It is hypothesized that the negative effect of temperature on biometry and population density of B. europaea depends on photosynthesis inhibition of symbiotic zooxanthellae at high temperatures, which would lower the calcification
rate and availability of energetic resources. 相似文献
442.
Fredrik??strandEmail author Olle?Anderbrant Ann-Britt?Wassgren Gunnar?Bergstr?m Erik?Hedenstr?m Hans-Erik?H?gberg Ba-Vu?Nguyen Michael?Larsson 《Chemoecology》2003,13(3):155-162
Summary. The basic chemical structure of the sex
pheromone of the pine sawfly Microdiprion pallipes
(Fallén) has earlier been identified as the propionate
ester of (2S,3S,7R/S,11R/S)/(2R,3R,7R/S,11R/S)-3,7,11-
trimethyl-2-tridecanol. We now report the results from
further investigations on the male response to individual
stereoisomers and to blends of stereoisomers, both in electroantennographic
(EAG) recordings and in field trapping
experiments. We also present our attempts to determine the
stereochemistry of the compounds present in females of
M. pallipes. By comparing gas chromatograms and mass
spectra obtained from natural extracts with those from synthetic
compounds it was found that the females contain one
or more of the four (2S,3S,7R/S,11R/S)-3,7,11-trimethyl-2-
tridecanol isomers (SS++-1). The active pheromone component
is the corresponding propionate ester 2. In EAG
experiments, males responded most strongly to five propionate
ester samples, namely two four-isomer blends: SS++-2
and SR++-2, and three individual stereoisomers: SSSR-,
SRRR- and SRSR-2. In a series of field trapping experiments
it was found that males were attracted to the SR++-2
four-isomer blend and to the individual isomer SSSR-2.
Based on the EAG-recordings and field responses of males
and the stereoisomers found in the females, we suggest that
the propionate ester of (2S,3S,7S,11R)-3,7,11-trimethyl-2-
tridecanol (SSSR-2) is used as a main component of the sex
pheromone in M. pallipes. Apparently the males react to
other stereoisomers in addition to that or those produced by
the females. 相似文献
443.
Sven Erik Jørgensen 《Ecological modelling》1976,2(4):303-313
A fish model based upon mass balances is set up. Several of the parameters have been determined by experiments. The remaining parameters are based upon literature values and it was not necessray to find any parameter by calibration. The model was validated with a completely acceptable result.The model includes equations giving the fish growth, the production of ammonia and organic matter, the oxygen consumption, and the influence to the temperature.The model can be used for management of fish farms and as a submodel for a total aquatic system. 相似文献
444.
Sven Erik Jørgensen 《Ecological modelling》1976,2(4):322-323
445.
Erik Porse 《Local Environment》2018,23(5):505-517
Urban stormwater systems traditionally used “grey” infrastructure to manage runoff. Contemporary designs now incorporate “green” infrastructure, which offers additional potential benefits such as urban amenities and health. Understanding how green and grey infrastructure investments are distributed across urban areas is important for new goals of promoting environmental justice in planning. In California, for instance, public investments increasingly require a percentage of funds to be spent in disadvantaged communities. Recent advancements in the availability of high-detail geographic data in cities can support prioritising investments to fulfil these multiple benefits. This paper analyses the distribution of stormwater infrastructure in Los Angeles (LA) County in relation to design criteria, urban structure and sociodemographic information. It demonstrates an approach for identifying projects that simultaneously address engineering needs and promote equity. Statistical analysis of high-detail sewer locations reveals geographic correlations with key local design parameters, urban characteristics and sociodemographic indicators. Watershed areas in LA County were identified that support multi-benefit projects, meeting dual criteria for infrastructure improvements and disadvantaged community status. As stormwater systems are increasingly designed for multi-benefit outcomes, new design frameworks can emphasise both performance and social equity. 相似文献
446.
447.
Although there is increasing evidence that bird feathers can be used as a non-destructive biomonitoring tool for organic pollutants [such as polychlorinated biphenyls (PCBs), polybrominated diphenyl ethers (PBDEs) and p,p'-dichlorodiphenyl-trichloroethane and metabolites (DDTs)], the importance of external contamination of these organic pollutants onto the feathers has not been considered. Here we examine to which extent external contamination of organic pollutants occurs onto the feathers of a predatory bird. We have analysed primary wing feathers of 16 common buzzards (Buteo buteo) collected in Belgium. In order to study differences in external contamination within and among wing feathers, the vane and the shaft of each feather were separated and were analysed in parallel, pooled for the three inner and the three outer primary wing feathers. Most organic pollutants could be measured in these pooled samples of both the vane and the shaft. Concentrations of hexachlorobenzene (HCB), DDTs, PCBs and PBDEs were significantly higher in the vane compared to the shaft. The profiles of PCBs and PBDEs in the shaft closely resembled the profiles in liver and muscle tissue, in contrast with the profile of the vane. The PBDE congeners 47, 99 and 153 had a similar contribution in shafts of primary feathers of common buzzards. Although these results suggest that external contamination could be important on the vane, no differences in the profile of PBDEs or PCBs were found between the inner and outer (more exposed) primary feathers. Furthermore, correlation coefficients with internal tissues were not univocally distinct between the shaft and the vane. Therefore our results indicate that the higher concentrations found in the vane in comparison to the shaft do not originate from external contamination via the air, but that other factors such as structure and chemical properties of the feathers may be of importance. The lack of significant external contamination onto the feather surface is an additional asset for the use of feathers as a non-destructive biomonitor for organic pollutants. 相似文献
448.
Maria A. van Noordwijk Erik P. Willems Sri Suci Utami Atmoko Christopher W. Kuzawa Carel P. van Schaik 《Behavioral ecology and sociobiology》2013,67(5):805-814
In most mammals, females pay for reproduction by dramatically increasing net energy intake from conception to mid- or late lactation. To do this, they time their reproductive events in relation to environmental cycles so that periods of peak food availability coincide with peak demand or are used to build energy stores. This timing is not possible in species with slow development in which lactation is prolonged over a multi-year period with fluctuating food availability. Here, mothers are expected to sustain a stable but generally lower level of nutrient transfer. In a sample of over 1,050 complete follow days of eight mother–infant pairs collected over 7 years, we document maternal effort for wild Bornean orangutans (Pongo pygmaeus wurmbii) over their average 6.5-year lactation period. As predicted, maternal feeding time was independent of the age of her growing offspring, indicating a stable sustained “plateau” effort of ≤ 25 % above baseline level, instead of a short peak lactation as seen in seasonal breeders. Infant orangutans started to regularly supplement milk with self-harvested food when they were 1–1.5 years old, indicating milk intake was insufficient from this age onwards, even though maternal effort did not decrease. We expect the same regulation of sustained maternal effort in other large and large-brained mammals with slow infant development. We also predict that mother–infant conflict over suckling may show another peak at the onset of the milk?+?solid food phase, in addition to the well-known conflict around the endpoint of lactation (weaning), which is reached after a long and gradual increase in solid food intake by the infant. 相似文献
449.
An improved method, a palladium-catalyzed cross-coupling reaction the so-called Suzuki-coupling, was used to synthesize 19 monofluorinated analogues (F-PCBs) of polychlorinated biphenyls (PCBs), including analogues of PCBs 28, 52 and 81. The coupling of chlorinated and/or fluorinated isomers of aryl boronic acids with bromo- and/or iodobenzenes gave the desired F-PCB congeners in good to excellent yields. The self-coupling product of the aryl boronic acids was the major impurity, but this limitation could be minimized. The influence of ortho-substitution by chlorine on the reaction time was studied in detail. The F-PCBs were characterized by means of 1H and 19F NMR and mass spectrometry (MS). F-PCBs show remarkably similar characteristics in many aspects to those of the corresponding non-fluorinated parent PCBs. Since fluorine is generally resistant to degradation, once incorporated into a substrate it functions as an indelible label that can be used to monitor structures and dynamics. F-PCBs may prove their usefulness as markers and tracers in mechanistic and toxicological studies. The aim of further research will be to test the suitability of fluorine as a sensitive probe in a broad range of applications, including synthesis, analytical, mechanistic and toxicological studies. 相似文献
450.
Mats Gustafsson Göran Blomqvist Anders Gudmundsson Andreas Dahl Per Jonsson Erik Swietlicki 《Atmospheric environment (Oxford, England : 1994)》2009,43(31):4699-4702
Accelerated pavement wear is one of the major environmental disadvantages of studded tyres in northern regions and results in increased levels of PM10. Measurements of PM10 in a road simulator hall have been used to study the influence of pavement properties, tyre type and vehicle speed on pavement wear. The test set-up included three different pavements (one granite and two quartzite with different aggregate sizes), three different tyre types (studded, non-studded, and summer tyres) and different speeds (30–70 km h?1). The results show that the granite pavement was more prone to PM10 production compared to the quartzite pavements. Studded winter tyres yield tens of times higher PM10 concentrations compared to non-studded winter tyres. Wear from summer tyres was negligible in comparison. It was also shown that wear is strongly dependent on speed; every 10 km h?1 increase yielded an increase of the PM10 concentration of 680 μg m?3 in one of the simulator experiments. 相似文献