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341.
342.
By treatment with LAH in boiling THF, androstane-4,6-diene, 3β-ol 2 is slowly reduced to a mixture of androstenols 3a and 4. The reduction mechanism, as shown by deuteriation, involves an intramolecular hydride transfer, leading to an “allyl-lithium” intermediate. 相似文献
343.
X-ray diffraction studies on both powdered and single crystal samples of (NF4)2NiF6 have shown that the compound crystallises in a tetragonal form derived from the K2 PtCl6 structure. The space group is I 4/m and the unit cell dimensions are : a = 6.828 (5) Å, c = 9.270 (9) Å, c/a = 1.358, and Z = 2. 相似文献
344.
Ha Huy Khoai 《Proceedings of the American Mathematical Society》1997,125(12):3527-3532
We show a class of perturbations of the Fermat hypersurface such that any holomorphic curve from into is degenerate. Applying this result, we give explicit examples of hyperbolic surfaces in of arbitrary degree , and of curves of arbitrary degree in with hyperbolic complements.
345.
Ha Huy Khoai 《中国科学A辑(英文版)》2005,48(Z1)
In this paper we relate the study of unique range sets for meromorphic functions (URSM) with the hyperbolic hypersurfaces and give some remarks on the genericity of unique range sets for meromorphic functions. 相似文献
346.
In this paper we relate the study of unique range sets for meromorphic functions (URSM) with the hyperbolic hypersurfaces and give some remarks on the genericity of unique range sets for meromorphic functions.
相似文献347.
Ho Thanh Huy Nguyen Van Hieu Toyonari Sugimoto Takekazu Ishida 《Journal of magnetism and magnetic materials》2009,321(16):2425-2428
Electrical and magnetic properties of TmCoIn5 and YbCoIn5 single crystals were investigated by means of electrical resistivity and magnetization measurements in the temperature range from 300 to 0.5 K under the magnetic field up to 5 T. TmCoIn5 is an antiferromagnetic metal with a Néel temperature TN=2.6 K. YbCoIn5 shows non-magnetic behavior, reflecting of divalent Yb ion. 相似文献
348.
Luc Huy Hoang Nguyen Thi Minh Hien Nguyen Hoang Hai Pham Van Hai Nguyen The Khoi In‐Sang Yang 《Journal of Raman spectroscopy : JRS》2009,40(11):1535-1538
The room‐temperature ferromagnetism and the Raman spectroscopy of the Cu‐doped Zn1−xCoxO powders prepared by the sol–gel method are reported. The x‐ray diffraction (XRD) data confirmed that the wurtzite structure of ZnO is maintained for ZnO doped with Co below 10 at%. The magnetization–field curves measured at room temperature demonstrated that all Co‐doped ZnO powders were paramagnetic. Ferromagnetic ordering is observed for the samples doped with Cu in Zn0.98Co0.02O and strongly depends on the concentration of Cu. The relative strength of the second‐order LO peak to the first‐order one in the Raman spectra, which is related to the carrier concentration, of the Cu‐doped Zn0.98Co0.02O powder is strongly correlated with the saturation magnetic moment of the system. This seems to be in favor of the Ruderman‐Kittel‐Kasuya‐Yosida (RKKY) or double exchange mechanism of the ferromagnetism in this system. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
349.
We present a comparative study of the control of-group velocity in three-level atomic systems including $\Lambda{}$-, Ladder-, and-V-types via spontaneously generated coherence (SGC) and relative phase of laser-fields. In the steady regime, expressions of group index are derived as an-analytical function of controllable parameters related to SGC and relative phase.-It is shown that the group velocity can be further slowed down or speeded up-under SGC in which modifications of group velocity due to the SGC in $\Lambda{}$--and V-systems are stronger than that in Ladder-system. In particular, when-interference strength of SGC p increases from 0.7 to 1.0, the light-propagation is switched from superluminal to subluminal modes (for $\Lambda{}$--and Ladder-systems) or from subluminal to superluminal modes (for V-system). In-the presence of relative phase, the group velocity changes between subluminal and-superluminal modes with a period of 2$\pi{}$. In resonant region, the largest-positive value of group index reaches at the relative phase $\varphi{}$ = $\pi{}$-while the largest negative value of group index reaches at $\varphi{}$ = 0 and-2$\pi{}$ for the $\Lambda{}$- and Ladder-systems, otherwise, for the V-system the-largest positive group index occurs at $\varphi{}$ = 0 and 2$\pi{}$, and the largest-negative group index occurs at $\varphi{}$ = $\pi{}$. 相似文献
350.
Huy Truong Nguyen Kim Long Vu-Huynh Hien Minh Nguyen Huong Thuy Le Thi Hong Van Le Jeong Hill Park Minh Duc Nguyen 《Molecules (Basel, Switzerland)》2021,26(17)
Panax vietnamensis, or Vietnamese ginseng (VG), an endemic Panax species in Vietnam, possesses a unique saponin profile and interesting biological activities. This plant is presently in danger of extinction due to over-exploitation, resulting in many preservation efforts towards the geographical acclimatization of VG. Yet, no information on the saponin content of the acclimatized VG, an important quality indicator, is available. Here, we analyzed the saponin content in the underground parts of two- to five-year-old VG plants acclimatized to Lam Dong province. Nine characteristic saponins, including notoginsenoside-R1, ginsenoside-Rg1, -Rb1, -Rd, majonoside-R1, -R2 vina-ginsenoside-R2, -R11, and pseudoginsenoside-RT4, were simultaneously determined by HPLC coupled with UV and with a charged aerosol detector (CAD). Analyzing the results illustrated that the detection of characteristic ocotillol-type saponins in VG by CAD presented a superior capacity compared with that of UV, thus implying a preferential choice of CAD for the analysis of VG. The quantitative results indicating the saponin content in the underground parts of VG showed an increasing tendency from two to five years old, with the root and the rhizome exhibiting different saponin accumulation patterns. This is the first study that reveals the preliminary success of VG acclimatization and thereby encourages the continuing efforts to develop this valuable saponin-rich plant. 相似文献