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排序方式: 共有152条查询结果,搜索用时 15 毫秒
71.
The intramolecular carbosilylation of N-[2-(1,3-butenyl)aryl]carbamoyl chloride has been investigated. The reaction with hexamethyldisilane proceeds smoothly in the presence of a catalytic amount of [Pd(η(3)-allyl)Cl](2) to give oxindoles with an allylsilane functional group in good yield. The subsequent subjection of the products to a Sakurai-type reaction provides more advanced tricyclic spirooxindoles by controlling the stereochemistry of three contiguous stereogenic centers. 相似文献
72.
73.
This study presents the results of hydrogeochemical studies carried out in Zeytun thermal springs in Kahramanmaras,located South Middle Anatolia-Turkey.More than 90thermal water samples were collected on a regular basis from 2006to 2008to measure element concentrations as a monitor of earthquake precursors.Water samples were analyzed using ICP-MS.The observed B,Ba,Br and Ge concentrations for 16months are in ranges of 79~422,103~167,28~93and 0.3~1.2 μ g.L-1,respectively.Chloride concentrations for these periods are in range of 7~21mg.L-1.The data identify some element anomalies before earthquakes.These anomalies are characterized by decreases up to 158%in Ba and Cl concentrations.The occurrence of these anomalies can be attributed to stress / strain induced pressure changes in the subsurface water systems.It can be suggested that the thermal springs in the fault line area are ideal sites for precursors of earthquakes. 相似文献
74.
Xiaoling He Haitao Zhou Weining Zhou Zhanggui Hu Changlong Zhang Hande Huo Jinliang Wang Yanbin Zuo Fuhua Lu 《Journal of Crystal Growth》2012,351(1):182-187
In this paper the solubility and optical activity of Bi12SiO20 (BSO) single crystals grown in aqueous NaOH under hydrothermal conditions were reported. BSO was found to have a positive solubility coefficient from 350 to 400 °C in 0.5–3 M NaOH, as well as a positive dependence on mineralizer concentration. The reason why additional SiO2 should be introduced in the mineralizer to grow high quality BSO was analyzed. High quality and colorless BSO crystals were grown using 4 M NaOH as a mineralizer and additional 3 wt% SiO2 introduced in the mineralizer. Results showed that the optical activity of hydrothermal colorless BSO was superior to that of BSO grown by the Czochralski (Cz) method. 相似文献
75.
76.
Hande Petek Çiğdem Albayrak Mustafa Odabaşoğlu İsmet Şenel Orhan Büyükgüngör 《Journal of chemical crystallography》2008,38(12):901-905
Abstract The single crystal X-ray diffraction analysis of the title compound, C15H15NO3, shows that the structure is adopted to its NH tautomeric form and crystallizes in the orthorhombic space group P bcn with a = 21.2424(15) ?, b = 12.7696(9) ?, c = 9.3605(10) ?, Z = 8, V = 2539.1(4) ?3, D
c
= 1.346 g/cm3. The molecular conformation in the crystal is stabilized by an intramolecular H-bond and the crystal structure is stabilized
by the bifurcated O–H···O type intermolecular H-bonds. In order to understand the effects on conformational flexibility of
the title molecule, molecular energy profile was calculated as a function of the selected torsion angle by means of AM1 semi-empirical
method.
Index Abstract Molecular and crystal structure of [(Z)-2-ethoxy-6-[(2-hydroxyphenylamino)methylene]cyclohexa-2,4-dienone], C15H15NO3, have been determined by single crystal X-ray diffraction study, and conformational analysis of the title molecule with respect
to the selected torsion angle has been achieved by AM1 semi-empirical calculations. 相似文献
77.
Acrylamide concentrations in grilled foodstuffs of Turkish kitchen by high performance liquid chromatography-mass spectrometry 总被引:3,自引:0,他引:3
Olcay Kaplan Gokce Kaya Cemile Ozcan Muharrem Ince Mehmet Yaman 《Microchemical Journal》2009,93(2):173-179
For over ten years, there has been a considerable interest in determination of acrylamide in foodstuffs. It was known that both protein-rich and carbohydrates-rich foods cooked at high-temperatures can cause acrylamide formation. However, carbohydrates-rich foods such as potato chips and biscuit samples have been the common studied foods compared with protein-rich foods such as meat samples.In this study, determination of acrylamide in these two group foods was examined using HPLC-MS. For this purpose, firstly, the parameters that are thought to affect the response in the HPLC-MS analysis were optimized. The optimized conditions were found to be 0.3 ml min− 1 for flow rate of mobile phase, 40 µl for injection volume, 5 °C for column temperature and 70 V for fragmentor potential. The optimized method was applied for the determination of acrylamide levels in Turkish foodstuffs including grilled meat and chicken samples, potato chips, coffee and biscuit. The obtained concentrations for all studied foods were in the range of 20–250 µg kg− 1. The results showed that acrylamide concentrations highly varied depending on the kind of food samples. 相似文献
78.
Photon-pair generation by four-wave mixing in optical fibers 总被引:2,自引:0,他引:2
We present a theory to quantify a fundamental limit on correlated photon pairs generated through four-wave mixing inside optical fibers in the presence of spontaneous Raman scattering (SpRS). Our theory is able to explain current experimental data. We show that if correlated photon pairs are generated with polarization orthogonal to the pump the effect of SpRS is significantly reduced over a broad spectral region extending from 5 to 15 THz. 相似文献
79.
Alexander Lytchak Asli Yaman 《Transactions of the American Mathematical Society》2006,358(7):2917-2926
We discuss smoothness of geodesics in Riemannian and Finsler metrics.
80.
Hande Karabyk Beyhan Yiit Murat Yiit smail
zdemir Hasan Karabyk 《Acta Crystallographica. Section C, Structural Chemistry》2019,75(7):941-950
The molecular structure of the benzimidazol‐2‐ylidene–PdCl2–pyridine‐type PEPPSI (pyridine‐enhanced precatalyst, preparation, stabilization and initiation) complex {1,3‐bis[2‐(diisopropylamino)ethyl]benzimidazol‐2‐ylidene‐κC2}dichlorido(pyridine‐κN)palladium(II), [PdCl2(C5H5N)(C23H40N4)], has been characterized by elemental analysis, IR and NMR spectroscopy, and natural bond orbital (NBO) and charge decomposition analysis (CDA). Cambridge Structural Database (CSD) searches were used to understand the structural characteristics of the PEPPSI complexes in comparison with the usual N‐heterocyclic carbene (NHC) complexes. The presence of weak C—H…Cl‐type hydrogen‐bond and π–π stacking interactions between benzene rings were verified using NCI plots and Hirshfeld surface analysis. The preferred method in the CDA of PEPPSI complexes is to separate their geometries into only two fragments, i.e. the bulky NHC ligand and the remaining fragment. In this study, the geometry of the PEPPSI complex is separated into five fragments, namely benzimidazol‐2‐ylidene (Bimy), two chlorides, pyridine (Py) and the PdII ion. Thus, the individual roles of the Pd atom and the Py ligand in the donation and back‐donation mechanisms have been clearly revealed. The NHC ligand in the PEPPSI complex in this study acts as a strong σ‐donor with a considerable amount of π‐back‐donation from Pd to Ccarbene. The electron‐poor character of PdII is supported by π‐back‐donation from the Pd centre and the weakness of the Pd—N(Py) bond. According to CSD searches, Bimy ligands in PEPPSI complexes have a stronger σ‐donating ability than imidazol‐2‐ylidene ligands in PEPPSI complexes. 相似文献