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排序方式: 共有207条查询结果,搜索用时 15 毫秒
71.
James T. Tanner Jeffrey S. Smith Gerald Angyal Phillip W. Defibaugh Melina C. Villalobos Martin P. Bueno G. V. Iyengar Wayne Wolf Rolf Zeisler 《Fresenius' Journal of Analytical Chemistry》1987,326(7):696-698
Summary The search for organic nutrient standards is approached from two sides. On the one hand, useful standards are selected from currently available SRMs; on the other hand, a representative food is developed representing the daily intake of a typical consumer. It is a composite of 201 foods, collected and prepared in a table-ready fashion. 相似文献
72.
Melina Cheah 《Journal of solid state chemistry》2006,179(6):1775-1781
The perovskite Sr2MnSbO6 has been synthesized using conventional ceramic techniques and structurally characterized using high-resolution powder X-ray and neutron diffraction. The structure is tetragonal in space group I4/m. The octahedra were found to feature Jahn-Teller (JT) distortion due to the presence of Mn3+, and this is identified as strongly contributing to the octahedral tilting. Evidence for B-site cation ordering is presented however there is extensive anti-site disorder. The disordering of the Mn3+ and Sb5+ cations is believed to be a result of the similar size of these two cations and the polarizability of the Sb5+ cation. The structure was found to undergo a transition to cubic symmetry at 521 °C with removal of the octahedral tilting leading to the quenching of the JT distortion. This phase transition was found to be continuous and tricritical in nature. 相似文献
73.
U. Reimer T. Zehl M. Wahab P. Schiller H.-J. Mgel 《Colloids and surfaces. A, Physicochemical and engineering aspects》2006,290(1-3):25-32
The production of high-performance ceramics requires the protection of powder particles against chemical reactions. Hydrolysis and oxidation of nanoscaled non-oxidic powders can be impeded by a coating consisting of a dense adsorbed layer of amphiphilic molecules. Using Monte Carlo simulations for a coarse grained model the adsorption equilibrium of differently shaped amphiphiles in apolar and polar solvents is investigated. For estimating the protection capability of the adsorbed surfactant film in aqueous environment we study the diffusion of small hydrophilic particles through the adsorbed surfactant film. The surfactants considered as coating agents differ in the number of hydrocarbon tails. It is found that amphiphiles with a single hydrocarbon tail or at most two branches are more suitable to protect particle surfaces than amphiphiles with three or four branches, although the adsorption energy of amphiphiles with many branches is higher. 相似文献
74.
A new pentacyclic triterpene, named ursethoxy acid (1) was isolated from the aerial parts of Lantana camara Linn. Its structure has been elucidated as 3,25-epoxy-3alpha-ethoxy-urs-12-en-28-oic acid through extensive 1D- and 2D-NMR (COSY-45, NOESY, J-resolved, HMQC and HMBC) studies. 相似文献
75.
M. Farooq Wahab Alain Berthod Daniel W. Armstrong 《Journal of separation science》2019,42(24):3604-3610
Power functions, , are embedded in some modern chromatography detectors and software which not only alter the linear dynamic range of such detectors but also improve the cosmetic aspects of the chromatograms. These aspects include a reduction in baseline noise, improved peak symmetry, and better resolution. However, after raising the electronic output of a detector to a selected power (n > 1), the original peak area information is lost as are very small peaks. Recent advances in the peak processing protocol allow us to recover peak areas from overlapping peak areas, even in noisy environments using power functions. One of the primary protocol requirements of this approach was to have resolution factors ≥0.9. An increasing positive bias in the recovered area was observed as the resolution factors decreased below 0.9. In this work, we extend the capabilities of power function to lower resolution values. This bias is addressed by considering the increasing contributions in peak height coming from adjacent peaks. It is shown that the power function can now be used as long as the peak maxima are visible, making = 0.5, the lower treatable resolution factor for two peaks of similar areas. 相似文献
76.
Sabira Begum SyedaQamar Zehra Aneela Wahab BinaShaheen Siddiqui 《Helvetica chimica acta》2006,89(9):1932-1941
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
77.
Computational modeling of the adsorption and photodegradation of 4-chlorophenol on anatase TiO2 particles 总被引:1,自引:0,他引:1
In the present work, the adsorption and photodegradation of 4-chlorophenol (4-CP) on the (100) surface of TiO2 anatase with semiempirical SCF MO method MSINDO has been investigated. The (100) surface is modeled with free clusters (TiO2)n, where n = 20–80. The surface lattice titanium atoms, which are Lewis acid sites, are considered as adsorption sites. Molecular dynamics (MD) simulations have been used for the investigation of 4-CP adsorption conformations and the surface reaction mechanism studies. The 4-CP molecule has revealed parallel adsorption upon optimization, whereas under excitation conditions the perpendicular configuration is dominant. The aromatic ring cleavage by atomic oxygen has been studied computationally and accordingly, the relevant mechanism was suggested. By comparison with experimental and other theoretical calculations, it is shown that MSINDO can reproduce literature data with acceptable accuracy. 相似文献
78.
Lantanilic acid, camaric acid and oleanolic acid possessing nematicidal activity were isolated from the methanolic extract of the aerial parts of Lantana camara Linn. through bio-assay guided fractionation. These compounds exhibited 98%, 95% and 70% mortality respectively against root-knot nematode Meloidogyne incognita at 0.5% concentration. Conventional nematicide furadan showed 100% mortality at this concentration. 相似文献
79.
M. Z. Barakat M. F. Abdel Wahab Y. M. Megahed 《Monatshefte für Chemie / Chemical Monthly》1964,95(6):1613-1622
Zusammenfassung Der Ascorbinsäuregehalt von fünf Leguminosen, nämlich Vicia faba, Vigna sinensis, Phaseolus vulgaris, Trigonella foenum graecum und Lupinus termis, wird angegeben. Die durchschnittliche Veränderung im Vitamin C-Gehalt der Samen während der Keimung wird aufgezeigt. Die Auswirkung von -Strahlen, die kleine Mengen von radioaktivem H3
32PO4 aussenden, sowie die der -Strahlung von radioaktivem131J,137Cs oder60Co auf die Keimlinge wird beschrieben.
Mit 9 Abbildungen 相似文献
The ascorbic acid content of five sorts of leguminous plants, viz., Vicia Faba, Vigna Sinensis, Phaseolus Vulgaris, Trigonella Foenum Graecum and Lupinus Termis is given. The average variations in the vitamin C content of the seeds during germination are shown. The effects or -irradiation emitted from small doses of radioactive H3 32PO4 as well as -irradiation of131I,137Cs or60Co on the seedlings are demonstrated.
Mit 9 Abbildungen 相似文献
80.
Abdelati Jermi Yadong He Qudrat Ullah Khan Nasrul Wahab 《Polymer Science Series B》2018,60(3):354-362
Effectiveness of the content of maleic anhydride (MAH) and polyamide 6 (PA6) on mechanical, thermal, barrier (moisture and oxygen) properties of HDPE/PA6 blends was investigated. Blends of HDPE with PA6 were prepared by in situ method. Molau test and FTIR spectroscopy results confirmed the reactive compatibilization through grafting of MAH on HDPE and PA6 chains in PA6/HDPE blends. Low concentration of benzoyl peroxide (BPO) and MAH reduced the particle size, improved phase morphology and mechanical properties of PA6/HDPE blends. Decrease in mechanical properties of PA6/HDPE blends was observed at high concentration of BPO and MAH. 相似文献