A two‐step synthesis of a novel mesostructured silicate, KIL‐2, and its manganese‐containing analogue, Mn/KIL‐2, has been developed. KIL‐2 possesses interparticle mesopores with pore dimensions between 5 and 60 nm and a surface area of 448 m2. The mesopores are formed by the aggregation of silica nanoparticles, which creates a network with interparticle voids. The particle size and the pore diameters depend on the temperature of the ageing step (first step) and on the solvothermal treatment in ethanol (second step), respectively. Mn/KIL‐2 contains octahedrally coordinated Mn3+ (80 %) and tetrahedrally coordinated Mn2+ (20 %) ions. Mn3+ ions are present in the extra‐framework MnOx nanoparticles with typical dimensions of 2 nm, which are homogeneously distributed throughout the material. Mn2+ ions occur as isolated manganese framework sites. The material is also able to retain its structure characteristics after the hydrothermal treatment in boiling water. Because of its non‐toxic nature and cost‐effective synthesis, Mn/KIL‐2 thus exhibits properties that are needed for an environment‐friendly catalyst. 相似文献
Phenylketonuria is a common metabolic disorder disease. Those affected appear normal at birth, but without treatment they develop severe psychomotor retardation. Throughout life, they must control their blood levels of phenylalanine (Phe) and consume a diet containing adequate amounts of Phe and tyrosine (Tyr). We have developed a liquid chromatographic/mass spectrometric (LC/MS) method for the quantitative evaluation of Phe and Tyr in food samples. This method takes advantage of the good separation of LC and the selective and reliable quantification provided by MS in the electrospray ionization mode. The LC/MS method is very suitable for the determination of selected amino acids in various matrixes. It is sensitive to levels as low as about 0.30 ppm for Tyr and 0.70 ppm for Phe and robust. Nearly 100 nondietary food samples were analyzed by the developed method. 相似文献
JPC – Journal of Planar Chromatography – Modern TLC - The Eurachem/Citac Guide on measurement uncertainty establishes general rules for evaluating and expressing measure¬ment... 相似文献
The crystal structures of the first stable α‐diol from the α‐halogenopyruvamide series, 3‐chloro‐2,2‐dihydroxy‐3‐phenylpropanamide, C9H10ClNO3, and three products [3‐(4‐chlorophenyl)‐2‐cyano‐2,3‐epoxypropanamide, C10H7ClN2O2, 3‐bromo‐2‐cyano‐2‐hydroxy‐3‐p‐tolylpropanamide, C11H11BrN2O2, 3‐bromo‐2‐oxo‐3‐p‐tolylpropanamide, C10H10BrNO2] obtained during the systematic synthesis of α‐halogenopyruvamides are reported. The crystal structures are dominated by hydrogen bonds involving an amide group. The stability of the geminal diol could be ascribed to hydrogen bonds which involve both hydroxyl groups. 相似文献
Optical emission spectroscopy and mass spectrometry was used to characterize gaseous plasma in an industrial reactor of volume 5 m3 during deposition of protective coatings. Plasma was created in mixtures of hexamethyldisiloxane (HMDSO) and oxygen at the powers between 1 and 8 kW. The plasma density was somehow below 1014 m?3. The flows of both gases were varied up to 200 sccm while the effective pumping speed was adjusted by changing the roots pump rotation speed between 250 and 4000 rpm. At such conditions the HMDSO was only partially dissociated to fragments. The behaviour of optical emission lines and mass ion currents was well correlated indicating that even one single technique was sufficient to monitor the behaviour of plasma at various discharge conditions. The optical emission spectroscopy as a simple and economic method is therefore suitable for controlling key processing parameters in such a plasma reactor.
Light scattering observation of nematic director fluctuations in confined geometries can be used to obtain interaction parameters of liquid crystals with surfaces. We present the basics of the method and some examples of the results in planar and cylindrical geometries. These results were obtained after neglecting the coupling of the director motion to flow. We give analytical and numerical results of flow effects on director fluctuations in a slab. The backflow contribution to the effective viscosity is strongly suppressed so that the results for the anchoring energy remain valid. Modal dispersion relations show an interesting behaviour of avoiding crossings. 相似文献
Recently, we reported that appropriately substituted 2-fluorobenzonitriles undergo cyclization with guanidine carbonate to afford 2,4-diaminoquinazolines usually in good to excellent yield. This paper describes the preparation of a variety of new 2,4-diaminoquinazolines substituted at positions five or seven. In addition, the reactions of selected 2-fluorobenzonitriles with formamidine acetate or acetamidine acetate were examined. The results obtained demonstrate that the analogous 4-amino- and 2-methyl-4-aminoquinazolines can be prepared by this approach but that the yields are considerably lower than when guanidine carbonate is employed as the cyclization reagent. 相似文献
Syntheses of some hydroxylaminoazines, their quaternized derivatives or N-oxides and N-amino compounds are described. Several transformations of these compounds and cyclization reactions are presented. 相似文献
Electroporation is a phenomenon during which exposure of a cell to high voltage electric pulses results in a significant increase in its membrane permeability. Aside from the fact that after the electroporation the cell membrane becomes more permeable, the cells' geometrical and electrical properties change considerably. These changes enable use of the force on dielectric particles exposed to non-uniform electric field (dielectrophoresis) for separation of non-electroporated and electroporated cells. This paper reports the results of an attempt to separate non-electroporated and electroporated cells by means of dielectrophoresis. In several experiments we managed to separate the non-electroporated and electroporated cells suspended in a medium with conductivity 0.174 S/m by exposing them to a non-uniform electric field at a frequency of 2 MHz. The behaviour of electroporated cells exposed to dielectrophoresis raises the presumption that in addition to conductivity, considerable changes in membrane permittivity occur after the electroporation. 相似文献