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91.
Khan A Haque E Rahman MM Mosaddik A Rahman M Sultana N 《Natural product research》2007,21(11):959-966
A new triterpenoid 2alpha,3beta,21beta,23,28-penta hydroxyl 12-oleanene and two known compounds were isolated from the roots of Laportea crenulata Gaud. The structures of all compounds were elucidated on the basis of various spectroscopic data. The two known compounds beta-sitosterol and beta-sitosterol 3-beta-D-glucopyranoside are also the first report of isolation from this plant. The antifungal activity of new triterpenoid was studied against Aspergillus flavus, Aspergillus niger, Candida albicans, and Rhizopus aurizae, and compared with the activity of nystatin (30 microg disc(-1)). This compound has shown moderate activity against tested fungi. 相似文献
92.
Summary A turbidimetric micro and sub-micro method is proposed for the determination of organic nitrogen. The method employs sealed tube digestion of an organic compound with sulphuric acid and sodium tetraphenyl boron for the formation of turbidity which is measured for nitrogen content. The method is rapid and accurate within ± 0.3% absolute.
Zusammenfassung Ein turbidimetrisches Mikro- und Ultramikroverfahren zur Bestimmung organisch gebundenen Stickstoffes wurde vorgeschlagen. Es beruht auf der Zerstörung der Substanz mit Schwefelsäure im verschlossenen Rohr und der Verwendung von Natriumtetraphenylborat zur Herstellung einer Trübung, deren Intensität als Maß für den Stickstoffgehalt dient. Die Methode ist rasch und innerhalb ± 0,3% genau.
Résumé On propose une méthode turbidimétrique micro et submicro pour le dosage de l'azote organique. La méthode met en jeu la réaction en tube scellé d'un composé organique avec l'acide sulfurique et le tétraphénylborure de sodium pour la formation du trouble qui représente une mesure de la teneur en azote. La méthode est rapide et donne une précision de ± 0,3% en valeur absolue.相似文献
93.
The suitability of Syrian Portland cement for disposal of solidified low-level radioactive waste was assessed by measuring the leaching rate of 134Cs. In ordinary cement concrete, a leaching rate of 1.309 × 10?3 g/cm2 per day was measured. Mixing this concrete with microsilica reduced significantly the leaching rate to 3.106 × 10?4 g/cm2 per day for 1% mixing, and to 9.645 × 10?5 g/cm2 per day for 3% mixing. It was also found that the application of a latex paint reduced these leaching rates by about 10%. These results, along with mechanical strength tests (under radiation exposure, high temperature, long water immersion and freeze–thaw cycling) indicate that Syrian Portland cement is suited for the disposal of low-level radioactive waste. 相似文献
94.
95.
Raziyeh Erfanifar Khosro Sayevand Nasim Ghanbari Hamid Esmaeili 《Numerical Methods for Partial Differential Equations》2021,37(1):614-625
This study presents a robust modification of Chebyshev ? ‐weighted Crank–Nicolson method for analyzing the sub‐diffusion equations in the Caputo fractional sense. In order to solve the problem, by discretization of the sub‐fractional diffusion equations using Taylor's expansion a linear system of algebraic equations that can be analyzed by numerical methods is presented. Furthermore, consistency, convergence, and stability analysis of the suggested method are discussed. In this framework, compact structures of sub‐diffusion equations are considered as prototype examples. The main advantage of the proposed method is that, it is more efficient in terms of CPU time, computational cost and accuracy in comparing with the existing ones in open literature. 相似文献
96.
A new series of the isocoumarin derivatives of ibuprofen, fluribiprofen, naproxen, valproic acid and 1-naphthoic acid have been synthesized via condensation of homophthalic acid with their respective acid chlorides. The conversion of the latter two isocoumarins into (dl)-3,4-dihydroisocoumarins has also been achieved. Most of the synthesized compounds showed antifungal and antibacterial activities. 相似文献
97.
Md. Nasim Akhtar M. Guru Prem Prasad M. A. Navascués 《Mediterranean Journal of Mathematics》2016,13(6):3965-3984
The fractal interpolation function (FIF) is a special type of continuous function on a compact subset of \({\mathbb{R}}\) interpolating a given data set. They have been proved to be a very important tool in the study of irregular curves arising from financial series, electrocardiograms and bioelectric recording in general as an alternative to the classical methods. It is well known that Jacobi polynomials form an orthonormal system in \({\mathcal{L}^{2}(-1,1)}\) with respect to the weight function \({\rho^{(r,s)}(x)=(1-x)^{r} (1+x)^{s}}\), \({r > -1}\) and \({s > -1}\). In this paper, a fractal Jacobi system which is fractal analogous of Jacobi polynomials is defined. The Weierstrass type theorem providing an approximation for square integrable function in terms of \({\alpha}\)-fractal Jacobi sum is derived. A fractal basis for the space of weighted square integrable functions \({\mathcal{L}_{\rho}^{2}(-1,1)}\) is found. The Fourier–Jacobi expansion corresponding to an affine FIF (AFIF) interpolating certain data set is considered and its convergence in uniform norm and weighted-mean square norm is established. The closeness of the original function to the Fourier–Jacobi expansion of the AFIF is proved for certain scale vector. Finally, the Fourier–Jacobi expansion corresponding to a non-affine smooth FIF interpolating certain data set is considered and its convergence in uniform norm and weighted-mean square norm is investigated as well. 相似文献
98.
M. Nur‐e‐Alam Muhummed Yousaf Samina Qureshi Irfan Baig Shama Nasim Atta‐ur‐Rahman M.Iqbal Choudhary 《Helvetica chimica acta》2003,86(3):607-614
A novel dimeric lignan, bispicropodophyllin glucoside ( 1 ) and a highly oxygenated new withanolide, coagulin S ( 2 ) were isolated from the ethanolic extract of Withania coagulans. The structures were established on the basis of the spectroscopic data and have been identified as (5S*,5aR*,8aR*,9S*,15S*,15aS*,18aS*,19S*)‐9,19‐di‐β‐D ‐glucopyranosyl‐5,8a,9,15,15a,18,18a,19‐octahydro‐5,15‐bis(3,4,5‐trimethoxyphenyl)bis([1,3]dioxolo[4′,5′:6,7]naphtho)[2,3‐c:2,3‐h][1,6]dioxecin‐6,16(5aH,8H)‐dione ( 1 ) and (20S*,22R*)‐5α,6β,14α,15α,17β,20,27‐heptahydroxy‐1‐oxowith‐24‐enolide ( 2 ), respectively. 相似文献
99.
Nasim Seifi M. Hassan Zahedi-Niaki M. Reza Barzegari Abolghasem Davoodnia Raheleh Zhiani Amir Aghaei Kaju 《Journal of molecular catalysis. A, Chemical》2006,260(1-2):77-81
Reaction of 6-hydrazino-1,5-diphenyl-1H-pyrazolo[3,4-d]pyrimidine-4-imine with aromatic aldehyde in presence of Preyssler catalyst yielded 8-aryl-1H-pyrazolo[4,3-e][1,2,4]triazolo[4,3-a] pyrimidine-4(5H)-imine. The performance of different form of Preyssler's anions including H14[NaP5W30O110], H14-P5, mixed-addenda H14[NaP5W29 MoO110], H14-P5Mo, silica supported H14[NaP5W30O110]/SiO2 and H14-P5/SiO2 have been investigated. The reaction results were compared with that of a conventional acid catalyst (H2SO4). 相似文献
100.
Arctotis arctotoides is a perennial herb used medicinally for the treatment of various ailments in the Eastern Cape, South Africa. Different extracts of the plant were investigated for their antimicrobial constituents. This led to the isolation and identification of a new daucosterol derivative 3-O-[beta-D-(6'-nonadeanoate)glucopyranosyl]-beta-sitosterol and seven known compounds namely: serratagenic acid, stigmasterol, daucosterol, zaluzanin D, dehydrocostuslactone, nepetin, and pedalitin. The structures of the compounds were elucidated on the basis of spectral analysis, including homo and hetero nuclear correlation NMR experiments (COSY, NOESY, HMQC, HMBC) and mass spectra as well as by comparison with available data in the literature. The compounds exhibited antibacterial activity except stigmasterol, daucosterol and dehydrocostuslactone. Nepetin was the most active against Bacillus subtilis and Staphylococcus aureus with the minimum inhibitory concentrations of 4 microg mL( - 1) and 31 microg mL( - 1), respectively, while others exhibited moderate activity. 相似文献