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排序方式: 共有244条查询结果,搜索用时 15 毫秒
221.
Leandro Fontanetti Nascimento Juliana Fonseca Lim Paulo Cesar de Sousa Filho Osvaldo Antonio Serra 《环境科学学报(英文版)》2018,30(11):58-68
We report the application of a solid lanthanum–ceria–zinc catalyst in the catalytic regeneration of diesel particulate filters(DPF) in diesel engines.We synthesized a CeO_2–ZnO–La_2O_3(Ce–Zn–La) mixed oxide by a lactic acid-mediated sol–gel method,which efficiently coated cordierite substrates for soot capture and combustion.We studied the effects of La loading on the physicochemical and catalytic properties of Ce–Zn mixed oxide during lowtemperature soot combustion processes.We characterized the synthesized catalysts by X-ray diffraction(XRD),Fourier-transform infrared spectroscopy(FTIR),N2 adsorption,Raman spectroscopy,oxygen storage capacity(OSC),and scanning and transmission electron microscopy(SEM and TEM).Thermogravimetric and differential thermal analysis(TGA/DTA)confirmed that the catalysts effectively reduced the soot oxidation temperature.The ternary Ce–Zn–La mixed oxide catalyst with Ce/Zn/La atomic ratio of 2:1:0.5 had the highest catalytic activity and promoted soot oxidation at temperatures below 390°C.This indicated that the large number of oxygen vacancies in the catalyst structure generated oxygen species at low temperatures.Raman spectroscopy measurements revealed the presence of oxygen vacancies and lattice defects in Ce–Zn–La samples,which were key parameters concerning the stability and redox properties of the prepared catalysts. 相似文献
222.
Gill-Chin Lim 《Environmental Impact Assessment Review》1985,5(2):133-153
This article offers a conceptual framework for analyzing institutional processes and performance outcome of EIA implementation for developing countries. Eight classes of participants in the EIA process are identified: (1) responsible agency; (2) action proponent; (3) preparer; (4) review agency; (5) rule-setting agency; (6) concerned agencies; (7) general public; and (8) licensing agency. Five types of performance outcome are suggested that may follow the introduction of EIA into a national planning system. These include EIA as (1) a fully internalized element of the planning process, (2) a support for a position of advocacy for the environment, (3) a process of adjustment among conflicting goals, (4) a process to remedy prior environmental damage, and (5) a perfunctory endorsement of public or private actions. Using these categories, the EIA system of the Philippines, Korea, and Brazil are analyzed. Three aspects of EIA implementation are compared: national development planning and environmental goals; institutional structure; and performance evaluation. Based on this analysis, the author concludes that while EIA in developing countries is being hampered in its early stages by institutional factors, there are some specific policies that, if adopted by national governments and international aid agencies, would enhance the integration of EIA into the planning and decision-making process and make EIA a more effective tool for environmental protection in the developing world. 相似文献
223.
Acute (10 day) semi-static toxicity tests in which the midge, Chironomus tepperi, were exposed to atrazine and molinate were conducted in laboratory water and in river water, in the absence and presence of sediment. The bioavailability measured as median lethal concentrations (LC50) and 95% fiducial limits (FLs) of atrazine to C. tepperi in laboratory water in the absence and presence of sediment were 16.6 (14.3-19.4) and 21.0 (18.2-24.1) mg l(-1), respectively while the corresponding values in river water were 16.7 (14.7-19.0) and 22.7 (20.3-25.4) mg l(-1), respectively. For molinate, the LC50 and FL values in laboratory water in the absence and presence of sediment were 8.8 (6.8-11.4) and 14.3 (12.4-16.4) mg l(-1), respectively and the corresponding values in river water were 9.3 (7.6-11.3) and 14.5 (12.4-16.9) mg l(-1), respectively. Atrazine has low toxicity (LC50 > 10 mg l(-1)) while molinate has moderate toxicity (1 mg l(-1) < LC50 < 10 mg l(-1)) to C. tepperi. River water did not significantly (P > 0.05) reduce the bioavailability of either chemical to C. tepperi. However, the presence of sediment did significantly (P < 0.05) reduce the bioavailability of both atrazine and molinate to C. tepperi. 相似文献
224.
R. Williamson M. E. D. Allison T. J. Bentley S. M. C. Lim E. Watson J. Chapple S. Adam M. Boulton 《黑龙江环境通报》1989,9(10):727-734
Inexpensive and accurate carrier testing for cystic fibrosis (CF) will be possible in the near future. There are no existing studies on the attitudes of English persons in the community to carrier testing for CF or any other recessive disorder. We have conducted a trial study of 166 persons at two schools, two doctors' surgeries, and a family planning clinic. Only a minority had clear pre-existing knowledge of cystic fibrosis and its genetic nature. However, over 80 per cent of those questioned expressed interest in knowing their carrier status. Although it is well known that uptake can only be assessed when a service is in place, and while further studies are required to confirm that testing will be of interest to couples of reproductive age with no previous knowledge of CF, the data strongly suggest that there will be interest in communitywide testing for CF carrier status when such a test becomes available in the United Kingdom. 相似文献
225.
Deep-sea hydrothermal vent ecosystems host both symbiotic and non-symbiotic invertebrates. The non-symbiotic vent fauna is
generally assumed to rely on free-living chemoautotrophic bacteria as their main food source but other sources such as detritus
have recently been suggested to be a part of the invertebrate diets. Little is known about how food availability influences
the distribution of vent organisms on a small scale. In addition, the feeding ecology and role of small, often numerically
dominant invertebrates, the meiofauna is poorly understood at vents. In this study, we used stable carbon and nitrogen isotopic
analysis to investigate the role of particulate detritus in the diets of macro- and meiobenthic invertebrates within three
vent assemblages at Axial Volcano, Juan de Fuca Ridge, and Northeast Pacific. Particulate organic matter of a detrital origin
became more important in the diet of invertebrates in assemblages typically associated with low-hydrothermal flow intensities.
Meiobenthic species occupied several different feeding guilds and trophic levels in the assemblages investigated. We conclude
that small-scale spatial variability in food sources is an important feature of vent food webs and that spatial patterns observed
here and elsewhere are shaped by variations in hydrothermal discharge. 相似文献
226.
The three meiobenthic ostracod species Candona neglecta, Paracyprideis fennica and Heterocyprideis sorbyana are commonly encountered in the deep (20-40 m) soft bottoms of the Baltic proper, and may contribute more to the total meiobenthic biomass than any other group. Experimental data indicate substantial differences in their utilisation of settling phytodetritus, with C. neglecta able to exploit newly settled organic material to a larger extent than P. fennica and H. sorbyana. Ostracod species composition, as well as ostracod and sediment carbon isotope contents, were studied in the field from an area with local differences in potential food resources. The study was performed during the late period of summer blooms of the cyanobacteria Aphanizomenon sp. Results showed that when all samples were taken together, adult C. neglecta (-22.4) was significantly more depleted in '13C than adult P. fennica (-21.0) and H. sorbyana (-20.3), indicating differences in food selection among the species. The flocculent sediment layer had, in all instances, lighter carbon ratios than did the lower layers. This trend was mirrored in most cases in the slight enrichment in C. neglecta compared to generally greater enrichment in the other two species. Carbon signatures of C. neglecta also varied significantly between stations, indicating that this species fed on different resources depending on location. Juvenile C. neglecta were far more depleted in '13C than adults and reflected the carbon signature of the cyanobacteria Aphanizomenon sp. The latter is known to be the most '13C-depleted phytoplankton member in the area. 相似文献
227.
Tamara Krügel Michelle Lim Klaus Gase Rayko Halitschke Ian T. Baldwin 《Chemoecology》2002,12(4):177-183
Summary. Research into the genetic basis of the ecological sophistication of plants is hampered by the availability of transformable
systems with a wealth of well-described ecological interactions. We present an Agrobacterium-mediated transformation system for the model ecological expression system, Nicotiana attenuata, a native tobacco that occupies the post-fire niche in the Great Basin Desert of North America. We describe a transformation
vector and a transformation procedure that differs from the standard cultivated tobacco transformation protocols in its use
of selectable markers, explants, media and cultivation conditions. We illustrate its utility in the transformations with genes
coding for key enzymes in the oxylipin cascade (lipoxygenase, allene oxide synthase, hydroperoxide lyase) in antisense orientations
and present high-throughput screens useful for the detection of altered phenotypes for the oxylipin cascade (green leaf volatiles
and jasmonic acid after wounding).
Received 14 March 2002; accepted 10 May 2002 相似文献
228.
Y. K. Ip S. F. Chew C. Y. Lee W. P. Wong A. L. L. Lim D. H. Murphy 《Marine Biology》1993,116(1):103-107
Onchidium tumidium, an intertidal pulmonate, has evolved to depend mainly on the formation of succinate, rather than lactate and opines, to survive in anoxia. For our study O. tumidum were collected from the mud flats of the mangrove swamp at Mandai, Singapore between 1988 and 1991. After 24 h of anoxic exposure, the lactate and succinate contents of the anoxic individuals were approximately 10 and 150 times, respectively, the corresponding values of the normoxic individuals. Alanine and acetate accumulations also occurred during anoxia, though to a much lesser extent. No propionate or octopine was detected. The depletion in aspartate content in O. tumidium could not account for the amount of succinate accumulated during anoxia. The succinate formed might have originated from glycogen involving the flow of carbon through the phosphoenolpyruvate (PEP) branch point of glycolysis. In support of such a hypothesis, results indicate that there was a decrease in the affinity of pyruvate kinase from O. tumidium exposed to 24h of anoxia to PEP to facilitate succinate formation through phosphoenolpyruvate carboxykinase (PEPCK). In comparison, the affinity of PEPCK from O. tumidium exposed to anoxia to PEP was apparently unaltered. 相似文献
229.
Juntaek Lim Seung Gu Shin Seungyong Lee Seokhwan Hwang 《Frontiers of Environmental Science & Engineering in China》2011,5(1):28-39
Real-time quantitative polymerase chain reaction (qPCR) has gained popularity as a technique to detect and quantify a specific
group of target microorganisms from various environmental samples including soil, water, sediments, and sludge. Although qPCR
is a very useful technique for nucleic acid quantification, accurately quantifying the target microbial group strongly depends
on the quality of the primer and probe used. Many aspects of conducting qPCR assays have become increasingly routine and automated;
however, one of the most important aspects, designing and selecting primer and probe sets, is often a somewhat arcane process.
In many cases, failed or non-specific amplification can be attributed to improperly designed primer-probe sets. This paper
is intended to provide guidelines and general principles for designing group-specific primers and probes for qPCR assays.
We demonstrate the effectiveness of these guidelines by reviewing the use of qPCR to study anaerobic processes and biologic
nutrient removal processes. qPCR assays using group-specific primers and probes designed with this method, have been used
to successfully quantify 16S ribosomal Ribonucleic Acid (16S rRNA) gene copy numbers from target methanogenic and ammonia-oxidizing
bacteria in various laboratory- and full-scale biologic processes. Researchers with a good command of primer and probe design
can use qPCR as a valuable tool to study biodiversity and to develop more efficient control strategies for biologic processes. 相似文献
230.