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91.
The electrochemical behavior and application of a new sensor, a silver solid amalgam paste electrode (AgSA-PE), based on the mixture of a fine silver solid amalgam powder (60:40 (w(Hg)/w(Ag))) and a suitable organic pasting liquid (Paraffin oil) in a ratio of 20:1 (w/w), was investigated in an aqueous-methanolic media (1:1). This alternative working electrode provides simple preparation and handling, adequate mechanical stability, easily renewable electrode surface, sufficiently wide cathodic potential window (up to -1200 mV within a pH range of 2.7-12.3), and sufficient sensitivity without any necessary pretreatment. The practical usability of the AgSA-PE was verified by the development of voltammetric methods for the determination of selected environmentally important pollutants (1,3-, 1,5-, and 1,8-dinitronaphthalenes) in an aqueous-methanolic media (1:1). The differential pulse voltammetric methods at AgSA-PE give linear concentration dependences in the range of 1-100 μmol l(-1) with limits of detection of about 1 μmol l(-1) in a mixture of Britton-Robinson buffer of appropriate pH and methanol (1:1). 相似文献
92.
Ales Styskalik David Skoda Jiri Pinkas Sanjay Mathur 《Journal of Sol-Gel Science and Technology》2012,63(3):463-472
Novel non-hydrolytic syntheses of titanosilicate xerogels by polycondensation of silicon acetate, Si(OAc)4, with titanium (IV) dimethylamide or diethylamide, Ti(NR2)4 (R?=?Me, Et), are presented. The reactions are based on acetamide elimination and yield gels with a high content of Si?CO?Ti bonds in comparison with the ester elimination route. Although a ligand exchange was observed, it was interestingly not followed by homo-condensation and during the synthesis the phase separation to SiO2 and TiO2 was avoided. The degree of condensation reached up to 68?%. The xerogels prepared for a comparison by ester elimination from Si(OAc)4 and titanium (IV) isopropoxide featured a significantly lower content of the Si?CO?CTi bonds. The initial tests in the epoxidation of cyclohexene by cumyl hydroperoxide (CHP) indicated a high selectivity and moderate activity of the xerogels. The catalytic properties were significantly improved by combining non-hydrolytic and hydrolytic methods yielding mesoporous and homogeneous Si/Ti mixed oxides. The catalysts prepared by these methods provided a complete epoxidation of cyclohexene in 2?h at?65?°C. 相似文献
93.
Lenka Sochorova Mojmir Baron Katerina Dadakova Tomas Kasparovsky Jiri Sochor 《Molecules (Basel, Switzerland)》2021,26(7)
Cadmium (Cd) is a heavy metal that occurs in all areas of the environment, including the food chain. In the body, it causes oxidative stress by producing free radicals that are harmful to the cells. Grape seed extract (GSE) contains a wide range of biologically active components that help to neutralize the adverse effects of free radicals. In this study, the effects of GSE prepared form semi-resistant grapevine cultivar Cerason, which is rich in phenolics, on biochemical markers of brown rats exposed to the effects of cadmium were monitored. GSE increased the plasma antioxidant activity and, in the kidneys and the liver, Cd content was significantly lowered by GSE co-administration. Accordingly, the increase in creatinine content and alanine aminotransferase activity and the decrease of catalase and superoxide dismutase activities caused by cadmium were slowed down by GSE co-administration. The results of this work reveal that grape seed extract offers a protective effect against the intake of heavy metals into the organism. 相似文献
94.
Path integral expressions are given for the wave function and for the density matrix in a theory which describes state vector reduction. The magnitude of the contribution of each classical path to the propagator is not unity, as in ordinary quantum theory, but depends upon the path. 相似文献
95.
96.
The aim of this study was to obtain quantitative characteristics of the ultraviolet absorption spectra as the molecular absorptivity at the wavelength of maximum absorbance. Organic as well as inorganic compounds were explored. A gas chromatography—ultraviolet absorption instrument has been used in the quantitative study of molecular ultraviolet absorption spectra in the vapour phase. The wavelength range studied was between 168 and 330?nm. The absorbance of 170 compounds was determined relative to perchloroethylene and their molecular absorptivities were calculated. For various groups of compounds, these relative absorptivities varied within two to three orders of magnitude. Standard curves were linear within four orders of magnitude from limit of quantification up to an absorption value of 1.5 absorbance units. The noise level was 3?×?10?5 absorbance units peak to peak at a bandwidth of 1.7?nm and a wavelength range from 180 to 330?nm was preferred. The detection limit for mesitylene was calculated to be 2 pg/s and for naphthalene 1 pg/s with 4?s store cycle time. 相似文献
97.
Atomic-Scale Studies of Fe3O4(001) and TiO2(110) Surfaces Following Immersion in CO2-Acidified Water
Dr. Francesca Mirabella Dr. Jan Balajka Dr. Jiri Pavelec Markus Göbel Florian Kraushofer Prof. Dr. Michael Schmid Prof. Dr. Gareth S. Parkinson Prof. Dr. Ulrike Diebold 《Chemphyschem》2020,21(16):1788-1796
Difficulties associated with the integration of liquids into a UHV environment make surface-science style studies of mineral dissolution particularly challenging. Recently, we developed a novel experimental setup for the UHV-compatible dosing of ultrapure liquid water and studied its interaction with TiO2 and Fe3O4 surfaces. Herein, we describe a simple approach to vary the pH through the partial pressure of CO2 ( ) in the surrounding vacuum chamber and use this to study how these surfaces react to an acidic solution. The TiO2(110) surface is unaffected by the acidic solution, except for a small amount of carbonaceous contamination. The Fe3O4(001)-( × )R45° surface begins to dissolve at a pH 4.0–3.9 ( =0.8–1 bar) and, although it is significantly roughened, the atomic-scale structure of the Fe3O4(001) surface layer remains visible in scanning tunneling microscopy (STM) images. X-ray photoelectron spectroscopy (XPS) reveals that the surface is chemically reduced and contains a significant accumulation of bicarbonate (HCO3−) species. These observations are consistent with Fe(II) being extracted by bicarbonate ions, leading to dissolved iron bicarbonate complexes (Fe(HCO3)2), which precipitate onto the surface when the water evaporates. 相似文献
98.
Jiri Müller 《International journal of quantum chemistry》1981,19(5):885-889
The barrier to predissociation of the first excited states of NH3 (3s1,3 A) is computed from a truncated first-order wave function using the iterative natural orbital method. The results show that the barrier is lower than when calculated with RHF and the CI wave functions, where single and double replacements to a truncated virtual space are carried out. These findings are used to interpret experimental data. 相似文献
99.
Aromatic 1,4-diazabuta-1,3-dienes in glacial acetic acid with thiocyanates produce via criss-cross cycloaddition reactions
the corresponding perhydroimidazo[4,5-d]imidazole-2,5-dithiones. When a mixture of thiocyanate and cyanate in a proper ratio was reacted together, nonsymmetrical
5-thioxo-perhydroimidazo[4,5-d]imidazole-2-ones were isolated. With cyanates substituted aromatic 1,4-diazabuta-1,3-dienes afforded product of acetic acid
addition to primary formed 1,3-dipole intermediate 5-(4-substituted phenylamino)-3-(4-substituted phenyl)-2-oxoimidazolidin-4-yl
acetate. 相似文献
100.
Karel Cizek Jiri Barek Jan Fischer Karolina Peckova Jiri Zima 《Electroanalysis》2007,19(12):1295-1299
The voltammetric behavior of 3‐nitrofluoranthene and 3‐aminofluoranthene was investigated in mixed methanol‐water solutions by differential pulse voltammetry (DPV) at boron doped diamond thin‐film electrode (BDDE). Optimum conditions have been found for determination of 3‐nitrofluoranthene in the concentration range of 2×10?8–1×10?6 mol L?1, and for determination 3‐aminofluorathnene in the concentration range of 2×10?7–1×10?5 mol L?1, respectively. Limits of determination were 3×10?8 mol L?1 (3‐nitrofluoranthene) and 2×10?7 mol L?1 (3‐aminofluoranthene). 相似文献