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81.
A method for the determination of soluble lead in human teeth by potentiometric stripping analysis with constant inverse current in the analytic step (PSA-iR), is described. The metal ions were concentrated as their amalgams on the glassy carbon surface of a working electrode that was previously coated with a thin mercury film and then stripped by a suitable oxidant. This paper examined effect of various factors on the PSA-iR results including the electrolysis potential, the solution stirring rate, and the constant inverse current. Quantitative analysis was carried out by both standard addition and calibration curve methods; a good linearity was obtained in the concentration range from 5 to 25 μg/dm3. A detection limit of 0.64 μg/dm3 was obtained, with a 5.21% coefficient of variation. Results obtained for teeth were not significantly different from these obtained by flameless atomic absorption spectrophotometry (FAAS). 相似文献
82.
Biljana A CavicMichael Thompson 《Analytica chimica acta》2002,469(1):101-113
Acoustic wave devices have continued to gain attention as biosensor structures because of their relative ease of operation and sensitivity to interfacial biochemical events. In the present paper, we review the use of the thickness-shear mode device for the label-free detection of processes involving nucleic acid moieties that are imposed at the sensor-liquid interface. Following a concise discussion of the theory and technology connected to the operation of the sensor in liquids, we outline a number of protocols that have been adopted for the attachment of oligonucleotides to sensor surfaces, many of which have been employed in ultrasonic biosensing. The various categories of applications are then surveyed in some detail. By far, the largest group is the study of duplex formation at the sensor surface, involving a compendium of experiments involving complementary and mismatched sequences. Considerably less attention has been paid to the detection of interaction of surface-bound nucleic acids with small molecules such as specific-binding peptides and drugs.A comprehensive appraisal of the literature in this field strongly suggests that acoustic coupling phenomena are particularly sensitive to interfacial physical chemistry. Accordingly, acoustic shear wave technology offers unique advantages over other sensor configurations because of its ability to produce multidimensional information through the recording of various parameters obtained from acoustic network analysis. 相似文献
83.
Formation of N-phenyl substituted hydroxamic acids in the reaction of formaldehyde with substituted mtrosobenzene is strongly catalysed by Fe3+ ions, which stabilize the transition state for the rate-controlling proton transfer from the carbon of nitrosocarbinolic cation intermediate leading to the product, hydroxamic acid 相似文献
84.
Geiger CA Alekseev E Lazic B Fisch M Armbruster T Langner R Fechtelkord M Kim N Pettke T Weppner W 《Inorganic chemistry》2011,50(3):1089-1097
Recent research has shown that certain Li-oxide garnets with high mechanical, thermal, chemical, and electrochemical stability are excellent fast Li-ion conductors. However, the detailed crystal chemistry of Li-oxide garnets is not well understood, nor is the relationship between crystal chemistry and conduction behavior. An investigation was undertaken to understand the crystal chemical and structural properties, as well as the stability relations, of Li(7)La(3)Zr(2)O(12) garnet, which is the best conducting Li-oxide garnet discovered to date. Two different sintering methods produced Li-oxide garnet but with slightly different compositions and different grain sizes. The first sintering method, involving ceramic crucibles in initial synthesis steps and later sealed Pt capsules, produced single crystals up to roughly 100 μm in size. Electron microprobe and laser ablation inductively coupled plasma mass spectrometry (ICP-MS) measurements show small amounts of Al in the garnet, probably originating from the crucibles. The crystal structure of this phase was determined using X-ray single-crystal diffraction every 100 K from 100 K up to 500 K. The crystals are cubic with space group Ia3?d at all temperatures. The atomic displacement parameters and Li-site occupancies were measured. Li atoms could be located on at least two structural sites that are partially occupied, while other Li atoms in the structure appear to be delocalized. (27)Al NMR spectra show two main resonances that are interpreted as indicating that minor Al occurs on the two different Li sites. Li NMR spectra show a single narrow resonance at 1.2-1.3 ppm indicating fast Li-ion diffusion at room temperature. The chemical shift value indicates that the Li atoms spend most of their time at the tetrahedrally coordinated C (24d) site. The second synthesis method, using solely Pt crucibles during sintering, produced fine-grained Li(7)La(3)Zr(2)O(12) crystals. This material was studied by X-ray powder diffraction at different temperatures between 25 and 200 °C. This phase is tetragonal at room temperature and undergoes a phase transition to a cubic phase between 100 and 150 °C. Cubic "Li(7)La(3)Zr(2)O(12)" may be stabilized at ambient conditions relative to its slightly less conducting tetragonal modification via small amounts of Al(3+). Several crystal chemical properties appear to promote the high Li-ion conductivity in cubic Al-containing Li(7)La(3)Zr(2)O(12). They are (i) isotropic three-dimensional Li-diffusion pathways, (ii) closely spaced Li sites and Li delocalization that allow for easy and fast Li diffusion, and (iii) low occupancies at the Li sites, which may also be enhanced by the heterovalent substitution Al(3+) ? 3Li. 相似文献
85.
We introduce a generated Choquet integral with respect to absolutely monotone and sign stable set functions. Another type of integrals defined with respect to such a set function is obtained as a limit of an appropriate sequence of generated Choquet integrals. 相似文献
86.
87.
Liquid chromatography/tandem mass spectrometry for simultaneous determination of undeclared corticosteroids in cosmetic creams
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88.
Biljana Dekić Vidoslav Dekić Niko Radulović Rastko Vukićević Radosav Palić 《Chemical Papers》2010,64(3):354-359
A series of new coumarin derivatives has been synthesized by condensation of 4-chloro-3-nitrocoumarin and the appropriate
arylamine and sulfonamide in ethyl acetate in the presence of triethylamine. The synthesized compounds were screened for their
in vitro antimicrobial activity against thirteen strains of bacteria and three fungal/yeast strains using disk diffusion assays.
They were shown to possess a wide range of activities from almost completely inactive compounds to medium active ones. (4-[(5-Chloropyridin-2-yl)amino]-3-nitro-2H-chromen-2-one) showed similar activity against Klebsiella pneumoniae as tetracycline. 相似文献
89.
90.
Mike Lange Kiwon Ok Geoffrey D. Shimberg Biljana Bursac Lajos Mark Ivana Ivanovi‐Burmazovi Sarah L. J. Michel Milos R. Filipovic 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(24):8081-8085
H2S is a gaseous signaling molecule that modifies cysteine residues in proteins to form persulfides (P‐SSH). One family of proteins modified by H2S are zinc finger (ZF) proteins, which contain multiple zinc‐coordinating cysteine residues. Herein, we report the reactivity of H2S with a ZF protein called tristetraprolin (TTP). Rapid persulfidation leading to complete thiol oxidation of TTP mediated by H2S was observed by low‐temperature ESI‐MS and fluorescence spectroscopy. Persulfidation of TTP required O2 , which reacts with H2S to form superoxide, as detected by ESI‐MS, a hydroethidine fluorescence assay, and EPR spin trapping. H2S was observed to inhibit TTP function (binding to TNFα mRNA) by an in vitro fluorescence anisotropy assay and to modulate TNFα in vivo. H2S was unreactive towards TTP when the protein was bound to RNA, thus suggesting a protective effect of RNA. 相似文献