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111.
Fritz G. Will Krystyna Cedzynska Denton C. Linton 《Journal of Electroanalytical Chemistry》1993,360(1-2)
Reproducible tritium generation well above background has been observed in tightly closed D2SO4-containing cells in four out of four Pd wire cathodes of one type. Tritium analysis was performed before and after each experiment on the Pd, the electrolyte and the gas in the head space. No tritium generation was observed in four identical Pd cathodes in H2SO4 cells operated at the same time under the same conditions. A cyclic loading-unloading regime with low current densities, rather than the usual continuous constant current regime, was employed to attain D/Pd and H/Pd loadings of 1±0.05 reproducibly. D/Pd loadings greater than 0.8±0.05 appear to be necessary to generate tritium. The largest amount of tritium, generated in 7 days of continuous electrolysis, was 2.1 × 1011 tritium atoms, compared with a background of 4 × 109 tritium atoms. The concentration of tritium and its axial distribution in the Pd were determined and concentrations of up to 9 × 1010 atoms/g Pd were found compared with a maximum background of 5 × 108 atoms g−1. The T/D ratio in the Pd is about 100 times larger than in the electrolyte or gas and indicates that tritium generation occurs in the Pd interior rather than at its surface. No tritium generation was observed in two other types of Pd electrodes in D2SO4, despite the attainment of D/Pd ratios near 1:1. Thus high D/Pd ratios appear to be a necessary but not sufficient condition for tritium generation in D2SO4 electrolysis. 相似文献
112.
The possibility of selective preconcentration of platinum group metal ions by Donnan dialysis was investigated. The effect of sample matrix (glycine) on self diffusion of the following platinum group metal ions Pt(IV), Pd(II), Rh(III), Ir(III) and Ir(IV) was determined. To separate a sample from the receiver electrolyte (0.5M NH4Cl), anion or cation-exchange membrane were used. Excellent selective preconcentration of Pd(II) in the sample and Ir(III) in the receiver solution was achieved. Experiments performed enable to draw some conclusion on the charge sign of glycinepalladium complexes. 相似文献
113.
The sorption of metal ions (e.g. Cd2+, Cu2+, Ni2+ and Pb2+) from aqueous solution on the anion exchange resin Amberlite IRA-904 modified with tetrakis(4-carboxyphenyl)porphyrin (TCPP) was studied in batch equilibrium experiments. The influence of operating variables such
as initial pH and contact time between solution and the resin on the equilibrium parameters was measured. The selectivity
order of investigated metal ions was evaluated as follows: Pb2+ > Ni2+ > Cu2+ > Cd2+. The matrix cations, such as Mg2+ and Ca2+, exhibit very low affinity for TCPP-modified resin. The rate uptake of the sorption procedure is predominantly controlled
by film diffusion. The best retention kinetic was observed for lead where half the saturation of the TCPP-modified sorbent
was achieved in less than 5 min.
Author for correspondence. E-mail: kryspyrz@chem.uw.edu.pl
Received November 20, 2002; accepted January 26, 2003
Published online May 5, 2003 相似文献
114.
Krystyna Bugajska 《International Journal of Theoretical Physics》1987,26(7):623-636
We investigate the Finkelstein-Misner geons for a non-simply-connected space-time manifold (M, g
0). We use relations between different Lorentzian structures unequivalent tog
0 and topological properties ofM given by the Morse theory. It implies that to some pieces of geons we have to associate Wheeler's worm-holes. Geons that correspond to time-orientable Lorentz structures are related tog
0 by Morse functions that describe the attaching of a handle of index one. In the case of geons associated to time-nonorientable Lorentzian structures, appropriate handles are related to loops along which the notion of time reverses. If we assume electromagnetic properties of geons, then only four species, v, e, p, m, of different geons can exist and geon m has to decay according to mv+p+e. 相似文献
115.
Summary Vibrational spectra of lanthanide oxines have been measured in the far-infrared region. In addition, the similar yttrium complex was investigated for further experimental evidence for the proposed band assignments. The most important metal-oxygen and metal-nitrogen bond vibrations have been attributed to absorptions between 390–350 cm–1 and 210–170 cm–1, respectively.
Ferne IR-Spektren von Lanthanidenkomplexen mit 8-Hydroxychinolin
Zusammenfassung Es wurden die Vibrationsspektren von Lanthanid-Oxinen im fernen IR-Bereich gemessen. Zusätzlich wurde der analoge Yttrium-Komplex untersucht, um die Bandenzuordnungen experimentell zu stützen. Die wichtigsten Metall-Sauerstoff- und Metall-Stickstoff-Bindungsschwingungen wurden den Absorptionen zwischen 390–350 cm–1 und 210–170 cm–1 zugeordnet.相似文献
116.
Krystyna Stępień Anna Dzierżęga-Lęcznar Slawomir Kurkiewicz Irena Tam 《Journal of the American Society for Mass Spectrometry》2009,20(3):464-468
Pigmentation of human skin is determined by the presence of melanin, the polymeric pigment that is produced in melanocytes
and transferred to adjacent keratinocytes. Epidermal melanocytes produce two distinct types of melanin pigments: eumelanin,
composed mainly of indole-type monomers, and pheomelanin that contains benzothiazine-type backbone. Eumelanin protects skin
against UV-induced damages, whereas pheomelanin is believed to act as a potent UV photosensitizer and promote carcinogenesis.
In this study, pyrolysis in combination with gas chromatography and mass spectrometry (Py-GC/MS) was applied for structural
studies of the epidermal pigment isolated from the cultured human melanocytes. The analysis was preceded by investigations
of DOPA-originated synthetic eumelanin and pheomelanin standards. This allowed determination of pyrolytic markers for both
types of melanin pigments. To obtain additional information on the natural pigment structure, the samples were thermally degraded
in the presence of tetramethylammonium hydroxide as the derivatizing agent. It was shown that the analyzed pigment from normal
human epidermal melanocytes derived from moderately pigmented skin is of eumelanin type with little incorporation of a pheomelanin
component. The results indicate that Py-GC/MS is a rapid and efficient technique for the differentiation of epidermal melanin
types and may be an alternative to commonly used methods based on chemical degradation. 相似文献
117.
Honey is rich in phenolic acids and flavonoids, which exhibit a wide range of biological effects and act as natural antioxidants. The analysis of polyphenols has been regarded as a very promising way of studying floral and geographical origins of honeys. This review surveys recent literature on determination of these active compounds in honey. The analytical procedure to determine individual phenolic compounds involves their extraction from the sample matrix, analytical separation and quantification. We pay particular attention to sample pre-treatment and separation techniques (e.g., high-performance liquid chromatography and electrophoresis). 相似文献
118.
Krystyna Srogi 《Mikrochimica acta》2006,154(3-4):191-212
This article reviews the analysis of drugs and drug metabolites in hair by chromatographic procedures, including the pretreatment
steps, and the extraction methods. The general tendency in the last years, to highly sophisticated techniques (GC–MS–NCI,
HPLC–MS, GC–MS–MS) illustrates the constant fight for sensitivity. 相似文献
119.
Datta B Schuster GB McCook A Harvey SC Zakrzewska K 《Journal of the American Chemical Society》2006,128(45):14428-14429
A series of polyaniline (PANI) oligomers was constructed from monomer units covalently linked to duplex DNA through N-(2-aminoethyl) groups bonded through cytosines. DNA oligomers containing the aniline monomers were treated with horseradish peroxidase (HRP) and H2O2 under conditions known to cause polymerization of aniline. No change in the absorption spectrum of the DNA was observed for samples containing fewer than four contiguous aniline groups. However, for oligomers containing four, five, or six aniline units, treatment with HRP and H2O2 led to the appearance of absorption features characteristic of the conducting "proton doped" emeraldine oxidation state of PANI. Molecular modeling shows that the DNA is distorted in the region of the PANI, but flanking regions of the DNA maintain their B-form structure. These findings provide a method to exploit the self-recognition, self-assembly, and sequence programmability of DNA for the formation of conducting polymers. 相似文献
120.
Edyta Piskorska Krystyna Lawniczak-Jablonska Iraida N. Demchenko Ewa Benko Markku Heinonen 《Mikrochimica acta》2004,145(1-4):159-163
X-ray photoelectron spectroscopy (XPS) is used to estimate phase and element contents of the composites based on cubic boron nitride. A composite is a mixture of several compounds and the use of traditional X-ray diffraction for phase analysis in many cases can be difficult. By using XPS, we were able to evaluate the atomic concentration of elements and the content of different compounds of each element. SEM and XPS showed that samples are heterogeneous. The TiB2 phase, expecting from thermodynamic calculations, was formed in both investigated samples of cBN/Ti3SiC2/TiC but in different amount. The Ti3SiC2 additive was found more chemically active then TiC. 相似文献