The effect of ferric and manganese oxides dopants on thermal and physicochemical properties of Mn-oxide/Al2O3 and Fe2O3/Al2O3 systems has been studied separately. The pure and doped mixed solids were thermally treated at 400–1000°C. Pyrolysis of pure
and doped mixed solids was investigated via thermal analysis (TG-DTG) techniques. The thermal products were characterized
using XRD-analysis. The results revealed that pure ferric nitrate decomposes into Fe2O3 at 350°C and shows thermal stability up to1000°C. Crystalline Fe3O4 and Mn3O4phases were detected for some doped solids precalcined at 1000°C. Crystalline γ-Al2O3 phase was detected for all solids preheated up to 800°C. Ferric and manganese oxides enhanced the formation of α-Al2O3 phase at1000°C. Crystalline MnAl2O4 and MnFe2O4 phases were formed at 1000°C as a result of solid–solid interaction processes. The catalytic behavior of the thermal products
was tested using the decomposition of H2O2 reaction.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
Fermentation of (+)-androsta-1,4-diene-3,17-dione ([structure: see text]) with Cephalosporium aphidicola for 8 days yielded oxidative and reductive metabolites, androst-4-ene-3,17-dione ([structure: see text]), 17beta-hydroxyandrosta-1,4-diene-3-one ([structure: see text]), 11alpha-hydroxyandrosta-1,4-diene-3,17-dione ([structure: see text]), 11alpha-hydroxyandrost-4-ene-3,17-dione ([structure: see text]), 11alpha,17beta-dihydroxyandrost-4-ene-3-one ([structure: see text]) and 11alpha,17beta-dihydroxyandrosta-1,4-diene-3-one ([structure: see text]). The fermentation of [structure: see text] with Fusarium lini also yielded metabolites [structure: see text]. The structures of these metabolites were elucidated on the basis of spectroscopic techniques. 相似文献
Three new pentacyclic triterpenoids, camarin ( 1 ), lantacin ( 2 ), and camarinin ( 3 ) were isolated from the aerial parts of Lantana camara Linn ., together with seven known compounds. The structures of the new constituents were elucidated by chemical transformation, HR‐EI mass spectrometry, and NMR spectroscopy, including 1D (1H‐ and 13C‐NMR) and 2D (1H,1H‐COSY, NOESY, 1H,1H‐TOCSY, J‐resolved, HMQC, and HMBC) experiments. 相似文献
The present paper describes the results of various attempts to synthesize 5‐bromo‐6‐ketone ( 11 ). When standard procedures for the α‐bromination were tried, a mixture of 5‐bromo‐6‐ketone ( 11 ) and 7‐bromo‐6‐ketone ( 12 ) was obtained. However, when bromination was carried out under buffered conditions, the desired 5‐bromo‐6‐ketone ( 11 ) could be obtained in a good yield. 相似文献
In this work chitin was extracted chemically from shrimp shells. Seventeen Bacillus isolates were screened for chitinolytic activity. The chitinolytic strains of Bt. were screened at different temperatures and pHs for their hydrolytic potentials. By using a pair of specific primers, endochitinase gene was amplified from SBS Bt-5 strain through PCR, and then cloned into pTZ57 TA cloning vector and transferred in Escherichia coli DH5α strain. The sequenced gene (GenBank Accession No: HE995800) consists of 2031 nucleotides capable of encoding 676 residues. The protein consisted of three functional domains with a calculated molecular mass of 74.53 kDa and a pI value of 5.83. The amino acid sequence of chi gene showed 99% similarity to the genes of Bt MR11 endochitinase, Bt serovar kurstaki chitinase (kchi), Bt strain MR21 endochitinase and Bacillus cereus B4264. 相似文献
The effects of calcination temperature and doping with K2O on solid–solid interactions and physicochemical properties of NiO/Fe2O3 system were investigated using TG, DTA and XRD techniques. The amounts of potassium, expressed as mol% K2O were 0.62, 1.23, 2.44 and 4.26. The pure and variously doped mixed solids were thermally treated at 300, 500, 750, 900 and 1000 °C. The catalytic activity was determined for each solid in H2O2 decomposition reaction at 30–50 °C. The results obtained showed that the doping process much affected the degree of crystallinity of both NiO and Fe2O3 phases detected for all solids calcined at 300 and 500 °C. Fe2O3 interacted readily with NiO at temperature starting from 700 °C producing crystalline NiFe2O4 phase. The degree of reaction propagation increased with increasing calcination temperature. The completion of this reaction required a prolonged heating at temperature >900 °C. K2O-doping stimulates the ferrite formation to an extent proportional to its amount added. The stimulation effect of potassium was evidenced by following up the change in the peak height of certain diffraction lines characteristic NiO, Fe2O3, NiFe2O4 phases located at “d” spacing 2.08, 2.69 and 2.95 Å, respectively. The change of peak height of the diffraction lines at 2.95 Å as a function of firing temperature of pure and doped mixed solids enabled the calculation of the activation energy (ΔE) of the ferrite formation. The computed ΔE values were 120, 80, 49, 36 and 25 kJ mol−1 for pure and variously doped solids, respectively. The decrease in ΔE value of NiFe2O4 formation as a function of dopant added was not only attributed to an effective increase in the mobility of reacting cations but also to the formation of potassium ferrite. The calcination temperature and doping with K2O much affected the catalytic activity of the system under investigation. 相似文献
Coumarins are the phytochemicals, which belong to the family of benzopyrone, that display interesting pharmacological properties. Several natural, synthetic and semisynthetic coumarin derivatives have been discovered in decades for their applicability as lead structures as drugs. Coumarin based conjugates have been described as potential AChE, BuChE, MAO and β-amyloid inhibitors. Therefore, the objective of this review is to focus on the construction of these pharmacologically important coumarin analogues with anti-Alzheimer’s activities, highlight their docking studies and structure–activity relationships based on their substitution pattern with respect to the selected positions on the chromen ring by emphasising on the research reports conducted in between year 1968 to 2017.
The optogalvanic (OG) spectrum — over the tuning range of R 6G dye (568 nm to 605 nm) — of a Pr/Ne discharge tube is studied. The positive OG signals are approximately two orders of magnitude larger than the negative OG signals. The magnitude of the signals depend mainly on the operating regime of the discharge. Specifically, operation of the discharge in the abnormal glow regime leads to an enhancement in the negative OG signals. The operating point on theV-I characteristic of the discharge should be stipulated. To study the variation of the OG signal with the intensity of the laser beam two OG signals, of different polarities, were examined. We observed that with respect to positive OG signals, there is a trend towards pumping saturation. A minimum threshold of 0.3 kW laser power is required to generate negative OG signals. For the same attenuation in the laser beam there is a ten times more efficient reduction in the negative OG signals than in the case of positive OG signals. This confirms the important role of metastable atoms in the conduction in gas discharges.The hypothesis that negative OG signals can be obtained only abnormal glow regime needs more experimental data. The required study of the temporal variation in the OG signal with increase in the discharge current is being carried out and the results are to be published. 相似文献