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51.
János Osán Szabina Török Bálint Alföldy Anita Alsecz Gerald Falkenberg Soo Yeun Baik René Van Grieken 《Spectrochimica Acta Part B: Atomic Spectroscopy》2007
The rivers in the Hungarian Upper Tisza Region are frequently polluted mainly due to mining activities in the catchment area. At the beginning of 2000, two major mining accidents occurred in the Romanian part of the catchment area due to the failure of a tailings dam releasing huge amounts of cyanide and heavy metals to the rivers. Surface sediment as well as water samples were collected at six sites in the years 2000–2003, from the northeast-Hungarian section of the Tisza, Szamos and Túr rivers. The sediment pollution of the rivers was compared based on measurements of bulk material and selected single particles, in order to relate the observed compositions and chemical states of metals to the possible sources and weathering of pollution. Non-destructive X-ray analytical methods were applied in order to obtain different kinds of information from the same samples or particles. In order to identify the pollution sources, their magnitude and fate, complementary analyses were carried out. Heterogeneous particulate samples were analyzed from a large geographical territory and a 4-year time period. Individual particles were analyzed only from the “hot” samples that showed elevated concentrations of heavy metals. Particles that were classified as anthropogenic were finally analyzed to identify trace concentrations and chemical states of heavy metals. 相似文献
52.
53.
Sten Andersson Christofer Leygraf Torsten Johnsson 《Journal of solid state chemistry》1975,14(1):78-84
The nature of the defect structure of Ru4Si3 has been studied with electron diffraction and electron microscopy methods. Lattice image pictures, interpreted with histogram analysis, reveal that planar defects of chemical twinning type are common in the crystals. 相似文献
54.
55.
56.
Oriňák Andrej Vering Guido Arlinghaus Heinrich F. Andersson Jan T. Halas Ladislav Oriňáková Renáta Turčániová Ľudmila 《平面色谱法杂志一现代薄层色谱法》2005,18(1):44-50
JPC – Journal of Planar Chromatography – Modern TLC - A new hyphenated technique that enables coupling of thin-layer chromatography (TLC) with time-of-flight secondary-ion mass... 相似文献
57.
Age K. Smilde Piet Hein van der Graaf Durk A. Doornbos Ton Steerneman Anita Sleurink 《Analytica chimica acta》1990
When retention measurements are available for a set of solutes on different stationary phases, with varying mobile phase compositions, the resulting data set can be represented by a three-way array. Models that describe the systematic variation in this training set sufficiently, can be used to calibrate a new stationary phase. Two models are tested for this purpose: three-way partial least squares and parallel factor analysis. 相似文献
58.
The base-mediated rearrangement of epoxides into allylic alcohols is a well-known synthetic transformation. The first enantioselective version of the reaction using a chiral base was reported in 1980. Since then, the reaction has received a lot of attention mostly due to the great usefulness of chiral allylic alcohols in organic synthesis. Major breakthroughs in the area were the first report on using a sub-stoichiometric amount of chiral base, and the development of chiral bases for a true catalytic reaction protocol. The present review covers the time from when the first asymmetric epoxide isomerisation reaction was reported (1980) up to now, focusing on the period 1997-2001. 相似文献
59.
John A. Montgomery Anita T. Shortnacy Sarah D. Clayton 《Journal of heterocyclic chemistry》1977,14(2):195-197
The reaction of the trimethylsilyl derivative of 4,6-dichloroimidazo[4,5-c]pyridine with 2,3,5-tri-O-benzoyl- D -ribofuranosyl bromide gave four nucleosides-the α- and β-anomers of the 1-isomer and the α- and β-anomers of the 3-isomer (3.9:2.7:1.5:1). In contrast, the fusion reaction of 4,6-dichloroimidazo[4,5-c ]pyridine with 1,2,3,5-tetra-O-acetyl-β- D -ribofuranose gave a high yield of the 1-β-isomer, which was converted to the known 3-deazaadenosine (4-amino-l-β- D -ribofuranosylimidazo[4,5-c]pyridine). 相似文献
60.
de Souza BM Marques MR Tomazela DM Eberlin MN Mendes MA Palma MS 《Rapid communications in mass spectrometry : RCM》2004,18(10):1095-1102
The social wasp P. paulista is relatively common in southeast Brazil causing many medically important stinging incidents. The seriousness of these incidents is dependent on the amount of venom inoculated by the wasps into the victims, and the characteristic envenomation symptoms are strongly dependent on the types of peptides present in the venom. In order to identify some of these naturally occurring peptides available in very low amounts, an analytical protocol was developed that uses a combination of reversed-phase and normal-phase high-performance liquid chromatography (HPLC) of wasp venom for peptide purification, with matrix-assisted laser desorption/ionization time-of-flight post-source decay mass spectrometry (MALDI-Tof-PSD-MS) and low-energy collision-induced dissociation (CID) in a quadrupole time-of-flight tandem mass spectrometry (QTof-MS/MS) instrument for peptide sequencing at the sub-picomole level. The distinction between Leu and Ile was achieved both by observing d-type fragment ions obtained under CID conditions and by comparison of retention times of the natural peptides and their synthetic counterparts (with different combinations of I and/or L at N- and C-terminal positions). To distinguish the isobaric residues K and Q, acetylation of peptides was followed by Q-Tof-MS analysis. The primary sequences obtained were INWLKLGKMVIDAL-NH(2) (MW 1611.98 Da) and IDWLKLGKMVMDVL-NH(2) (MW 1658.98 Da). Micro-scale bioassay protocols characterized both peptides as presenting potent hemolytic action, mast cell degranulation, and chemotaxis of polymorphonucleated leukocyte (PMNL) cells. The primary sequences and the bioassay results suggest that these toxins constitute members of a new sub-class of mastoparan toxins, directly involved in the occurrence of inflammatory processes after wasp stinging. 相似文献