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151.
The mobility and speciation of Pt was investigated in dust deposited in highway tunnels and in gully sediments. For this, a sequential extraction technique was used in combination with a microwave digestion procedure, followed by detection of Pt with high resolution ICP-MS. A digestion procedure using HNO3/HCl/H2O2
was developed and its efficiency tested for environmental materials. Total Pt contents ranged from approximately 100 to 300 g/kg. The high share of chemically mobile Pt in the tunnel dust (up to about 40%) indicates that Pt is predominantly emitted in a mobile form from the converter. The absence of a mobile fraction in the gully sediment is explained by the elution of Pt by run-off. Except for the mobile and easily mobilised fractions none of the other fractions of the sequential extraction contains Pt, neither in the dust samples nor in the gully sediment. 相似文献
152.
A real-valued function f defined on an open, convex set D ofa real normed space is called (, )-midconvex if it satisfies
The main result of the paper states that if f is locally boundedfrom above at a point of D and is (, )-midconvex, then it satisfiesthe convexity-type inequality
where : [0, 1] R is a continuous function satisfying
The particular case = 0 of this result is due to Ng and Nikodem(Proc. Amer. Math. Soc. 118 (1993) 103108), while thespecialization = = 0 yields the theorem of Bernstein and Doetsch(Math. Ann. 76 (1915) 514526). 2000 Mathematics SubjectClassification 26A51, 26B25. 相似文献
153.
Paul G. Mezey Peter Warburton E. Jako Zsolt Szekeres 《Journal of mathematical chemistry》2001,30(4):375-387
The dimensions of databases can be defined based on a variety of concepts, ranging from the standard tools of principal component analysis to context-biased approaches. The effective dimensions of databases, in particular the effective dimensions involving continua such as electron density data, provide a set of important tools for database comparisons and for the evaluation of some aspects of database quality. The problems associated with database comparisons and database mergers, such as those occurring in the process of database unification in the actual merger of two pharmaceutical companies, provide challenging tasks and opportunities for data science. Some of the tools for effective dimension reduction and dimension expansion are reviewed in the context of database quality control and conditions for database compatibility are presented. A common misconception affecting data sampling techniques for data quality evaluation is discussed and methods for circumventing the associated sampling errors are described. 相似文献
154.
Influence of Metal,Ligand and Solvent on Supramolecular Polymerizations with Transition‐Metal Compounds: A Theoretical Study
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Naidel A. M. S. Caturello Dr. Zsolt Csók Prof. Dr. Gustavo Fernández Dr. Rodrigo Q. Albuquerque 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(49):17681-17689
The nature of intermolecular interactions governing supramolecular polymerizations is very important for controlling their cooperativity. In order to address this problem, supramolecular columns made of PtII and PdII complexes of oligo(phenylene ethynylene)‐based pyridine (OPE) and tetrazolylpyridine ligands (TEP) were investigated through the dispersion‐corrected PM6 method. Aromatic, CH–π, M–Cl and metallophilic interactions helped stabilize the supramolecules studied, and their geometries and associated cooperativities were in excellent agreement with experimental data. The OPE ligand and/or the presence of PtII led to stronger metallophilic interactions and also to cooperative supramolecular polymerizations, which clearly suggests that metallophilic interactions are a key factor for controlling cooperativity. The results indicate that sequential monomer addition is in general less spontaneous than the combination of two larger preformed stacks. The present theoretical investigations contribute to the further understanding of the relation between the thermodynamics of supramolecular polymerizations and the nature of different synthons. 相似文献
155.
156.
157.
A library of 1,3-difunctionalized pinane derivatives was synthesized and applied as chiral catalysts in the addition of diethylzinc to benzaldehyde. The key intermediate β-lactam 2 was prepared regio- and stereoselectively from (?)-apopinene 1. The treatment of 2 with di-tert-butyl dicarbonate afforded N-Boc β-lactam 3, while acid-catalyzed ring opening of 2 resulted in amino acid 4. Nucleophilic ring opening of 3 with dimethylamine, followed by deprotection and benzylation, furnished β-amino amides 5, 8, and 11, which were transformed in two steps into the corresponding N-tosyldiamines 7, 10, and 13, respectively. Since the use of other amines, such as diethylamine, to study the influence of dialkyl substitution was unsuccessful, an alternative synthetic route was applied. Amidation of tosylated β-amino acid 14 furnished amides 15–25. Reduction of 15, 16, 19, 20, and 24 resulted in N-tosyl diamines 26–30. The β-amino amides and N-tosylated diamines were used as chiral ligands in the enantioselective alkylation of benzaldehyde with diethylzinc, resulting in (R)- and (S)-1-phenyl-1-propanol. The (R)-enantiomer was predominant except when 17, 22, 23, and 25 were used as ligands, in which case the opposite stereochemistry was observed. The best ee values (up to 83%) were obtained when 17, 20, 23, and 25 were used as catalysts. 相似文献
158.
Lindstrom Richard M. Révay Zsolt 《Journal of Radioanalytical and Nuclear Chemistry》2017,314(2):843-858
Journal of Radioanalytical and Nuclear Chemistry - Prompt gamma neutron activation analysis has become an important part of the analytical toolkit, practiced at several research reactors worldwide.... 相似文献
159.
In this paper various notions of convexity of real functions with respect to Chebyshev systems defined over arbitrary subsets of the real line are introduced. As an auxiliary notion, a concept of a relevant divided difference and also a related lower Dinghas type derivative are also defined. The main results of the paper offer various characterizations of the convexity notions in terms of the nonnegativity of a generalized divided difference and the corresponding lower Dinghas type derivative. 相似文献
160.