Three of a kind : Vicinal tricarbonyl compounds undergo C? C cleavage mediated by ferric ions (see scheme). The observed cleavage of ninhydrin and dehydroascorbic acid has relevance for amino acid detection and the metabolism of vitamin C.
In this paper, a numerical method consists of combining Haar wavelet method and Tikhonov regularization method to determine unknown boundary condition and unknown nonlinear source term for the generalized time-delayed Burgers-Fisher equation using noisy data is presented. A stable numerical solution is determined for the problem. We also show that the rate of convergence of the method is as exponential $\Bigl(O\left(\frac{1}{2^{J+1}}\right)\Bigr)$, where $J$ is maximal level of resolution of wavelet. Some numerical results are reported to show the efficiency and robustness of the proposed approach for solving the inverse problems. 相似文献
Interaction of nicotine with tetracyanoethylene and iodine was investigated spectrophotometrically and found to form strong
CT complexes (n−π and n-σ*, respectively). The donor site involved in CT interaction is the pyrrolidine nitrogen. The nicotine-I2 complex exists as the ionic structure (nicotine) I+-I
3−
. Formation constants of the CT complexes in various solvents were determined from 10 to 25°C and are discussed in terms of
the nature of the electron acceptor and solvent polarity. Solid CT complexes were synthesized and were characterized by microchemical
analysis and infrared spectra techniques. 相似文献
Arylidene-anthranilic acidSchiff base complexes with Th(IV), UO2(II), La(III), Ce(III), and Zr(IV) have been isolated and studied by several techniques, e.g. elemental analysis, electronic and IR spectra and conductance measurements. It is concluded that the salicylideneanthranilic acidL3 is coordinated to the metal ion as bivalent tridentate ONO ligand (L–2) while the other ligands behave as monovalent bidentate ON ligands. Furthermore, the molecular structure effect of these compounds on their tendency towards complex formation was investigated and discussed. The possibility that the Cu(II) complex ofL3 can act as bidentate ligand, coordinating through itscis-oxygen atoms to form binuclear metal complexes was studied.
Ein- und zweikernige Metall-Komplexe von Aryliden-Anthranilsäure-Schiff-Basen
Zusammenfassung Es wurden Aryliden-Anthranilsäure-Schiff-Basen mit Th(IV), UO2(II), La(III), Ce(III) und Zr(IV) isoliert und mittels Elementaranalysen, Elektronen-und IR-Spektroskopie und Leitfähigkeitsmessungen untersucht. Es wird aus den Untersuchungen geschlossen, daß Salicylidenanthranilsäure (L3) als bivalenter dreizähniger ONO-Ligand (L–2) an das Metallion koordiniert, währenddessen die anderen Liganden als monovalente zweizähnige Liganden agieren. Außerdem wurden Struktureffekte dieser Verbindungen in bezug auf ihre Komplexbildungstendenz untersucht. Die Möglichkeit, daß der Cu(II)-Komplex vonL3 über die Koordination mit dencis-Sauerstoff-Atomen und unter Bildung eines zweikernigen Metallkomplexes als zweizähniger Ligand agieren kann, wurde untersucht.
A simple, accurate, precise, rapid and sensitive stability-indicating capillary electrophoresis (CE) method was optimized and validated for the simultaneous determination of norfloxacin and its inactive decarboxylated degradant in pharmaceuticals. The univariant method was used to optimize electrophoretic factors including injection time, separation voltage and column temperature. Electrolyte concentration and pH were optimized using the factorial design and response surface methods. The optimum conditions obtained were: 10 mmol l− 1 phosphate at pH 2.5, hydrodynamic injection time of 8 s at pressure 0.5 p.s.i., separation voltage 25 kV and column temperature 25 °C. The separation was carried out into a fused-silica capillary column (31.2 cm length × 50 μm i.d.) with detection at 301 and 285 nm for the intact drug and the degradant, respectively using a diode array detector. For both analytes, the method enjoys wide dynamic range (1-50 μg ml− 1) with good detectability (limits of detection 0.11 μg ml− 1). In addition, acceptable accuracy (recovery > 95%); and good repeatability and intermediate precision (RSD < 3.5%) were obtained. 相似文献
A specific heat study of (Li1–xKx)2SO4 — LKS — mixed crystals has been made in a wide concentration rangex covering the temperature range 300–800 K. The phase diagram was determined. It is shown that a variation of the Li+:K+ concentration changes the critical behaviour of the specific heat. The results are discussed in terms of scattering mechanisms of energy carriers.
Zusammenfassung Bei Temperaturen zwischen 300 und 800 K wurde für einen breiten Konzentrationsbereich für x die spezifische Wärme von (Li1–xKx)2SO4-Mischkristallen untersucht und das entsprechende Phasendiagramm erstellt. Es wurde gezeigt, daß eine Änderung des Verhältnisses Li+:K+ auch das kritische Verhalten der spezifischen Wärme verändert. Die Ergebnisse werden hinsichtlich von Sreuungsmechanismen der Energieträger diskutiert.
Acta Mechanica Sinica - A pore network model (PNM) is developed for gas diffusion layer (GDL) in the cathode side of polymer electrolyte membrane fuel cells (PEMFCs). The model is coupled to... 相似文献
The aim of the study was to analyze the process of roasting coffee beans in a convection–conduction roaster (CC) without a heat exchanger and a convection–conduction–radiation roaster (CCR) with a heat exchanger for determination of the aroma profile. The aroma profile was analyzed using the SPME/GC-MS technique, and an Agrinose electronic nose was used to determine the aroma profile intensity. Arabica coffee beans from five regions of the world, namely, Peru, Costa Rica, Ethiopia, Guatemala, and Brazil, were the research material. The chemometric analyses revealed the dominance of azines, alcohols, aldehydes, hydrazides, and acids in the coffee aroma profile. Their share distinguished the aroma profiles depending on the country of origin of the coffee beans. The high content of pyridine from the azine group was characteristic for the coffee roasting process in the convection–conduction roaster without a heat exchanger, which was shown by the PCA analysis. The increased content of pyridine resulted from the appearance of coal tar, especially in the CC roaster. Pyridine has an unpleasant and bitter plant-like odor, and its excess is detrimental to the human organism. The dominant and elevated content of pyridine is a defect of the coffee roasting process in the CC roaster compared to the process carried out in the CCR machine. The results obtained with the Agrinose showed that the CC roasting method had a significant effect on the sensor responses. The effect of coal tar on the coffee beans resulted in an undesirable aroma profile characterized by increased amounts of aromatic volatile compounds and higher responses of Agrinose sensors. 相似文献