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931.
The present work refers to the challenging issue of fluoride anion recognition/binding in water by taking advantage of the unique possibilities offered by the porous molecular nanocontainers of the {Mo132} Keplerate type allowing the study of a variety of new phenomena. Reaction of the highly reactive carbonate‐type capsule with aqueous HF results in the release of carbon dioxide and integration of an unprecedentedly large number of fluoride anions—partly as coordinated ligands at both the pentagonal units and the linkers, partly as a disordered water/fluoride assembly inside the cavity. The internal assembly and some of the fluoride ligands are easily released, which provides interesting options for future studies regarding coordination chemistry and catalysis under confined conditions.  相似文献   
932.
It is known that 1H NMR spectroscopy represents a good tool for predicting the grape variety, the geographical origin, and the year of vintage of wine. In the present study we have shown that classification models can be improved when 1H NMR profiles are fused with stable isotope (SNIF-NMR, 18O, 13C) data. Variable selection based on clustering of latent variables was performed on 1H NMR data. Afterwards, the combined data of 718 wine samples from Germany were analyzed using linear discriminant analysis (LDA), partial least squares-discriminant analysis (PLS-DA), factorial discriminant analysis (FDA) and independent components analysis (ICA). Moreover, several specialized multiblock methods (common components and specific weights analysis (ComDim), consensus PCA and consensus PLS-DA) were applied to the data.  相似文献   
933.
Adhesion measurements were performed by AFM (Atomic Force Microscopy). It was shown that many parameters need to be controlled in order to provide reproducible and quantitative results. Adhesion forces were shown to depend on combination of materials characteristics and testing geometry as well as experimental protocol (contact time, contact force and contact area). This contact area was modified by means of FIB (Focused Ion Beam) milling and deliberate abrasion. As a result, a drastic change in adhesion could be observed. Still, those are problems connected to adjustment of interacting surfaces.  相似文献   
934.
Isocyanates are important in industrial hygiene and workplace monitoring. Owing to their severe acute toxicity and sensitizing properties, analytical methods with high sampling efficiency and sensitivity in the low ppb to ppt range are required. The reactivity of isocyanates necessitates initial derivatization with nucleophilic agents—usually amines—for stabilization and enrichment; this is often followed by chromatographic separation with spectroscopic, electrochemical, or mass spectrometric detection. Sampling strategies for airborne isocyanates comprise active, i.e. pumped, or passive, i.e. diffusive, methods; the method selected depends on the application. Whereas active methods rely mainly on impingers, reagent-coated filters, or sampling tubes, passive samplers make use of reagent-coated filters, the surface of which is connected to the air sample by diffusion channels. Because airborne isocyanates are prone to occur in different forms, i.e. as vapors, as aerosols, or adsorbed on particulate matter, denuder sampling has been introduced, thus enabling simultaneous collection of gaseous and aerosol isocyanates. The first part of this review summarizes chemical methods and reagents which have been introduced for derivatization of airborne isocyanates. The advantages and drawbacks of the individual derivatization procedures and their combination with different detection principles are evaluated. In the second part, the most recent developments in air sampling for isocyanates, with special focus on diffusive sampling, are reviewed and critically discussed.  相似文献   
935.

Background  

Insect cells can serve as host systems for the recombinant expression of eukaryotic proteins. Using this platform, the controlled expression of 15N/13C labelled proteins requires the analysis of incorporation paths and rates of isotope-labelled precursors present in the medium into amino acids. For this purpose, Spodoptera frugiperda cells were grown in a complex medium containing [U-13C6]glucose. In a second experiment, cultures of S. frugiperda were grown in the presence of 15N-phenylalanine.  相似文献   
936.
Halogeno Metallates of Transition Elements with Cations of Nitrogen‐containing Heterocyclic Bases. VII Two Oxidation States and Four Different Iron Coordinations in one Compound. Synthesis, Crystal Structure, and Spectroscopic Characterization of 1,4‐Dimethylpiperazinium Chloroferrate(II, III), (dmpipzH2)6[FeIICl4]2[FeIIICl4]2[FeIICl5] [FeIIICl6] The title compound being stable on air crystallizes from aqueous hydrochloric acid solutions in the trigonal space group R3 with a = 13,197(1), c = 38,405(6) Å. Besides the cations in chair form, the structure contains six discrete, mononuclear chloroferrate anions arranged on a threefold axis. Tetrahedral, octahedral, and, for the first time with iron(II), trigonal bipyramidal metal coordinations occur. Four sub‐spectra contributing to the 57Fe Mössbauer spectrum can be distinguished and have been attributed to all four types of chloroferrate anions in the structure. The Raman spectroscopic investigation of orientated single crystals allows to recognize polarized and non‐polarized vibrations as well as to attribute all observed frequencies.  相似文献   
937.
The syntheses and structures of the two mixedvalence crystalline molybdenum blue compounds Na26[Mo142O432(H2O)58H14] · ca. 300 H2O ( 1 ) (containing the maximal number of well defined defects which influence the overall structure and the reactivity of the anionic cluster) and Na16[(MoO3)176(H2O)63(CH3OH)17H16] · ca. 600 H2O · ca. 6 CH3OH ( 2 ) (obtained in an optimized high-yield synthesis) are reported with reference to the critical conditions required for the isolation of corresponding crystalline materials.  相似文献   
938.
939.
1. INTRODUCTION Since the first report of efficient polymer light emitting diode (PLED) in 1990, conjugated polymers have intrigued great interests because of substantial promise for electro-optical applications [1,2]. It is essential to develop novel str…  相似文献   
940.
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