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We prove a Bruckner–Garg type theorem for the fiber structure of a generic map from a continuum X into the unit interval I. We also study the specific case of X=S2. We show that each nondegenerate component of each fiber of a generic map in C(S2,I) is figure-eight-like. This together with a result by Krasinkiewicz and Levin gives that each nondegenerate component of each fiber of a generic map in C(S2,I) is hereditarily indecomposable and figure-eight-like. We also show that pseudoarcs, pseudocircles and Lakes of Wada appear in abundance in fibers of a generic map in C(S2,I). We also exhibit a general method for proving when a P-like hereditarily indecomposable continuum is Q-like when Q is a certain graph containing P. 相似文献
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Xiaoyan Xia Bernard S. Crimmins Philip K. Hopke James J. Pagano Michael S. Milligan Thomas M. Holsen 《Analytical and bioanalytical chemistry》2009,395(2):457-463
Toxaphene is considered to be a problematic organochlorine pollutant because of its bioaccumulation potential and persistence
in aquatic environments. In this study, whole lake trout and walleye composites were used to evaluate two analytical techniques
for total toxaphene and selected congener analysis. The efficacy of using gas chromatography electron ionization tandem mass
spectrometry (GC-EI/MS/MS) and electron capture negative ionization mass spectrometry (GC-ECNI-MS) were compared. Although
the sensitivity using GC-ECNI-MS was approximately five times greater than GC-EI/MS/MS, the latter provided more consistent
inter-Parlar relative response factors (RRF). When using technical calibration mixtures, these results suggest a more accurate
total toxaphene measurement was obtained using the GC-EI/MS/MS method. Total toxaphene concentrations in lake trout composites
from both methods were highly correlated (R
2 = 0.985) with the MS/MS concentrations approximately half of those determined by ECNI, suggesting systematic high bias in
toxaphene concentrations when measured using GC-ECNI. 相似文献
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盐湖盐类水溶液298.15K时稀释热和表观摩尔焓的研究 总被引:4,自引:1,他引:4
有关溶稀释热方面的研究报导很多,例如等溶液的稀释热均已有文献值.但全是采用分批式量热法研究部分间断浓度范围内的稀释热,数据设有连续性,很不全面.在稀释热理论估算方面,Pitier的半经验溶液理论能比较满意的解决一般浓溶液的稀释热估算问题,但文献只给出了某些多数,没有计算出具体的稀释热数据[6-9],也没有将实验测定值与理论估算值相比较.基于Debye-Hckel理论推导出的烙极限公式[10-12]在溶液表观摩尔烂的研究中已得到广泛应用.但迄今没有一篇论文比较全面地将实验测定与Pitier理论和Debye-Hhdel极限公式相结合来研究溶… 相似文献
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Jadranka Barešić Zvjezdana Roller–lutz 《Isotopes in environmental and health studies》2013,49(3):316-329
Plitvice Lakes waters were collected at 14 sampling points, including springs, tributaries and lakes, for the period 2002–2007. The results of the physical and chemical conditions of calcite precipitation as well as the δ13C values of dissolved inorganic carbon (DIC) were used to study the processes influencing calcite precipitation. Significant differences between spring, lake and stream waters as well as changes in the downstream direction were observed. The correlation between δ13CDIC values and physico-chemical conditions for calcite precipitation showed that calcite precipitates in lake waters which are oversaturated with respect to CaCO3 (I sat values 4–10) and with δ13CDIC values between?11.5 and?8.5 ‰. In spring waters, the δ13CDIC values were more negative, from?14 to?12 ‰, and I sat values of 1–2 indicated that equilibrium conditions for calcite precipitation were not attained. The downstream increase in δ13CDIC correlated with the increase in the δ13C values of calcite in the lake sediments, suggesting that the freshwater calcite was mainly of autochthonous origin and precipitated within the water column in isotopic equilibrium with DIC. 相似文献
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M. H. K. Abdel-kader G. R. B. Webster 《International journal of environmental analytical chemistry》2013,93(2):153-165
Abstract A simple and rapid method for the analysis of fenitrothion and its metabolites, fenitrooxon, S-methyl fenitrothion, demethyl fenitrothion, demethyl S-methyl fenitrothion, 3-methyl-4-nitrophenol, and dimethyl phosphorothioic acid in stored wheat has been developed. Simultaneous analysis of the extract was conducted using FPD-GLC after derivatization with diazoethane except for 3-methyl-4-nitrophenol which was analyzed directly by EC-GLC. Recoveries of all compounds from wheat fortified at the levels from 0.1 to 5.0 ppm were greater than 90%. The developed method was used to quantitatively determine major metabolites found in grain treated with fenitrothion and stored at 20°C for 12 months. Demethyl fenitrothion, 3-methyl-4-nitrophenol, and dimethyl phosphorothioic acid were the major breakdown products of fenitrothion found in stored wheat. Confirmation of these metabolites was carried out by chemical derivatization plus FPD-GLC and by TLC. 相似文献
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There is a lack of reliable and easy-to-use methods for the quantitative determination of carbohydrates in natural waters. Among the existing methods, the 3-methyl-2-benzothiazolinone hydrochloride (MBTH) method has been widely used to determine total dissolved carbohydrates in seawater. Its application to freshwaters has, so far, been less frequent. The objective of this study is to critically examine the application of the MBTH method to the analysis of carbohydrates in freshwater samples in order to understand what the method really measures. Following a comprehensive revision of the literature, the method has first been applied to representative model compounds and then to a variety of freshwaters of contrasting trophic characteristics. By simultaneously determining the total dissolved organic carbon and humic-type compounds in the same samples, it has been possible to show that sometimes a significant part of the organic carbon remains undetected. This seems to indicate that a substantial amount of carbohydrate present in some natural waters is probably not ‘seen’ by the MBTH method. 相似文献
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MANAGEMENT STRATEGY EVALUATION OF PHEROMONE‐BAITED TRAPPING TECHNIQUES TO IMPROVE MANAGEMENT OF INVASIVE SEA LAMPREY 下载免费PDF全文
HEATHER A. DAWSON MICHAEL L. JONES BRIAN J. IRWIN NICHOLAS S. JOHNSON MICHAEL C. WAGNER MELISSA D. SZYMANSKI 《Natural Resource Modeling》2016,29(3):448-469
We applied a management strategy evaluation (MSE) model to examine the potential cost‐effectiveness of using pheromone‐baited trapping along with conventional lampricide treatment to manage invasive sea lamprey. Four pheromone‐baited trapping strategies were modeled: (1) stream activation wherein pheromone was applied to existing traps to achieve 10?12 mol/L in‐stream concentration, (2) stream activation plus two additional traps downstream with pheromone applied at 2.5 mg/hr (reverse‐intercept approach), (3) trap activation wherein pheromone was applied at 10 mg/hr to existing traps, and (4) trap activation and reverse‐intercept approach. Each new strategy was applied, with remaining funds applied to conventional lampricide control. Simulating deployment of these hybrid strategies on fourteen Lake Michigan streams resulted in increases of 17 and 11% (strategies 1 and 2) and decreases of 4 and 7% (strategies 3 and 4) of the lakewide mean abundance of adult sea lamprey relative to status quo. MSE revealed performance targets for trap efficacy to guide additional research because results indicate that combining lampricides and high efficacy trapping technologies can reduce sea lamprey abundance on average without increasing control costs. 相似文献