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排序方式: 共有409条查询结果,搜索用时 31 毫秒
91.
92.
The LSD (Logic for Structure Determination) program gener-ates organic molecular structures from 1D and 2D NMR data without resorting to chemical shift databases. Its use in the res-olution of natural product structure determination problems has been already reported in the literature. This paper describes how data and structures are internally represented and pro-cessed by LSD to build solution structures. 相似文献
93.
Mustafa Imamoglu Asuman Ozturk Şeyma Aydın Aynur Manzak Ali Gündoğdu Celal Duran 《Journal of Dispersion Science and Technology》2018,39(8):1144-1148
Hazelnut husk (HH), an agricultural waste, was converted to carbonaceous material by chemical activation using potassium acetate. The produced activated carbon (KAHHAC) was characterized by FTIR, SEM, N2 adsorption–desorption experiments, CHN elemental analysis, and determination of moisture, ash, and point of zero charge. KAHHAC was used for the batch adsorption of Cu(II) ions from aqueous solutions. Optimum pH and contact time were found to be 5.0 and 240 minutes, respectively. The adsorption equilibrium data were described well by the Langmuir equation providing 105.3?mg?g?1 Cu(II) adsorption capacity. The pseudo-second-order model successfully described the kinetic of Cu(II) adsorption by KAHHAC. The adsorbed Cu(II) onto KAHHAC was completely desorbed by 0.5?M nitric acid. In conclusion, HH activated carbon (AC) produced by the potassium acetate activation method is a very useful and efficient sorbent material for the removal of Cu(II) from aqueous solution. 相似文献
94.
A. Adam F. Schmidt B. Tollens Marchand Grote F. Soxhlet Szombathy A. Wynter Blyth Boorhoeve Ph. du Roi F. Clausnizer Adolf Mayer N. Gerber und P. Radenhausen 《Fresenius' Journal of Analytical Chemistry》1880,19(1):362-368
Ohne Zusammenfassung 相似文献
95.
G. Erdoğ;du 《Journal of Analytical Chemistry》2006,61(7):673-676
An electroanalytical method has been developed for the determination of methidathion by squarewave voltammetry on a Nafion®-coated glassy carbon electrode in aqueous solutions with 0.05 M acetate buffer as a supporting electrolyte. The best voltammetric conditions were found to be pH 4.0, a preconcentration potential of 0.45 V, and a preconcentration time of 60 s. The experimental parameters, such as pH, film thickness, preconcentration potential, preconcentration time, and square-wave voltammetric parameters, were optimized. Using this method, the calibration curve is linear in the range 5 × 10?8?7 × 10?7 M with a detection limit (S/N = 3) of 30 nM. 相似文献
96.
Wolf-Walther du Mont Hans-Joachim Breunig Herbert Schumann Horst Götz Helga Juds Freimut Marschner 《Journal of organometallic chemistry》1975,96(1):49-56
The PE spectra of [(CH3)3Sn]3N, [(CH3)3E]3P (E = C, Si, Sn), [(CH3)3Si]3As and [(CH3)3E]3Sb (E = C, S, Ge, Sn) are analyzed. The constant level of the ionization potentials of the n-hybrid orbitals of N, P, As, and Sb, together with changes in the hybridization and interactions with ligand MO's is discussed by qualitative MO investigations. 相似文献
97.
Douglas du Boulay Reiko Yamashita Nobuo Ishizawa 《Acta Crystallographica. Section C, Structural Chemistry》2002,58(3):i40-i44
The structure of a new orthorhombic trirubidium pentatantalum oxide (Rb3Ta5O14) phase with Pnma symmetry was identified from a half sphere of synchrotron X‐ray data measured at a wavelength of 0.85 Å. This notionally linked TaO6 octahedral structure broadly consists of three different modifications of the pyrochlore ring motif with layer stacking normal to (205) planes. Successive pyrochlore layers do not simply stack normal to these planes but are offset along the [100] axis. An unusual aspect of this structure is the occurrence of TaO5 trigonal bipyramids in structurally complex regions where the modified pyrochlore rings connect. 相似文献
98.
99.
The phase transitions proceeding during melting of selected Sn–Ag–Cu alloys were determined by means of the DSC technique. Twelve compositions were studied along two cross-sections with silver to copper molar ratios X(Ag)/X(Cu) = 1 and 7/3 and tin concentration from 0.4 to 0.9 mol fraction. The transition temperatures were calculated using Pandat software package and thermodynamic parameters from the SOLDERS database. The experimental results were compared with both available literature data and calculation results, and a good agreement was observed. Deconvolution of DSC complex curves was performed using PeakFit v.4.12 software package. Eutectic mixture mass fractions involved in the eutectic transformation were determined. The obtained results were compared with the data calculated using thermodynamic parameters and good agreement was achieved in the case of alloys of higher content of Sn. The discrepancy was found in the case of alloys with lower Sn content where initial structure of the samples subjected to DCS analysis was partly a result of the occurrence of peritectic transformation. 相似文献