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31.
Pham Mai An Nguyen Hoai Thuong A. I. Burkhanov S. V. Mednikov 《Bulletin of the Russian Academy of Sciences: Physics》2013,77(8):1056-1058
The dielectric response of lithium niobate single crystal in ac fields with amplitudes E of 3.74 to 13.1 kV cm?1 is investigated at frequencies of 1 and 10 Hz in the temperature range of 70 to 200°C. The increase in effective dielectric permittivity ?eff′ and the effective dielectric losses ?eff″ is found to be associated with the formation of short-radius Nb Li 4+ polarons at temperatures T > 130°C and their contribution to polarization relaxation in a LiNbO3 crystal. 相似文献
32.
Hoai Thuong Nguyen S. V. Baryshnikov A. Yu Milinskiy I. V. Egorova E.V. Charnaya 《Phase Transitions》2013,86(10):899-906
ABSTRACTThe present work aims at investigating linear and nonlinear dielectric properties of nanocomposites based on diisopropylammonium bromide (C6H16NBr, DIPAB) embedded into Al2O3 films having honeycomb structure with pores of 100?nm in diameter, and into opal matrices with three-dimensional structure containing pores of 100 and 60?nm. The obtained results indicated the shift of Curie point toward lower temperatures for DIPAB in porous aluminum oxide and the appearance of two phase transitions, detected upon heating and cooling for DIPAB in opal matrices. In addition, a ferroelectric phase was found to form between these two phase transitions without significant change of Curie temperature. 相似文献
33.
In this paper, the existence and stability results for ground state solutions of
an m-coupled nonlinear Schrödinger system $$i\frac{∂}{∂ t}u_j+\frac{∂²}{∂x²}u_j+\sum\limits^m_{i=1}b_{ij}|u_i|^p|u_j|^{p-2}u_j=0,$$ are established, where $2 ≤ m, 2≤p<3$ and $u_j$ are complex-valued functions of $(x,t) ∈ \mathbb{R}^2,
j=1,...,m$ and $b_{ij}$ are positive constants satisfying $b_{ij}=b_{ji}$. In contrast with other methods
used before to establish existence and stability of solitary wave solutions where the
constraints of the variational minimization problem are related to one another, our approach
here characterizes ground state solutions as minimizers of an energy functional
subject to independent constraints. The set of minimizers is shown to be orbitally stable
and further information about the structure of the set is given in certain cases. 相似文献
34.
35.
Matsumura Y Moodycliffe AM Nghiem DX Ullrich SE Ananthaswamy HN 《Photochemistry and photobiology》2005,81(1):46-51
We previously demonstrated that CD1d knockout mice were resistant to ultraviolet (UV)-induced immunosuppression. Because immune suppression is a critical factor in the development of UV-induced skin cancers, we investigated the response of wild type (WT) and CD1d-/- mice to UV carcinogenesis. We found that although 100% of WT mice developed skin tumors after 45 weeks of UV irradiation, only 60% of CD1d-/- mice developed skin tumors. To investigate the mechanisms involved in the resistance of CD1d-/- mice to UV-induced carcinogenesis, we determined the time course and kinetics of keratinocyte cell death after UV irradiation. After acute UV exposure, the terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick end-labeling (TUNEL)-positive keratinocytes were eliminated from the skin of WT mice by 72 h post-UV, but they still persisted until 96 h in CD1d-/- mice. The kinetics of p53 protein expression closely followed the kinetics of apoptotic cell death. Chronic UV irradiation resulted in induction of a significantly higher number of apoptotic keratinocytes in CD1d-/- than WT mice. In addition, epidermis and dermis from chronically UV-irradiated CD1d-/- mice harbored significantly fewer p53 mutations than WT mice. These results indicate that the resistance of CD1d-/- mice to UV carcinogenesis may be due to increased cell death and elimination of keratinocytes and fibroblasts containing DNA damage and p53 mutations. 相似文献
36.
Jang J Na M Thuong PT Njamen D Mbafor JT Fomum ZT Woo ER Oh WK 《Chemical & pharmaceutical bulletin》2008,56(1):85-88
Phytochemical study on an EtOAc-soluble extract of the root bark of Erythrina mildbraedii resulted in the isolation of six prenylated flavonoids 1-6. Based on physicochemical and spectroscopic analyses, their structures were determined to be new natural products licoflavanone-4'-O-methyl ether (1), 2',7-dihydroxy-4'-methoxy-5'-(3-methylbut-2-enyl)isoflavone (2), and (3R)-2',7-dihydroxy-3'-(3-methylbut-2-enyl)-2',2'-dimethylpyrano[5',6' :4',5']isoflavan (3), along with three known compounds erythrinin B (4), abyssinin II (5), and parvisoflavone B (6). All the isolates, except for compound 4, inhibited PTP1B activity in vitro with IC(50) values ranging from 5.3 to 42.6 microM. This result further suggests that the prenyl group on the B ring of flavonoids plays an important role in suppressing the enzyme PTP1B. 相似文献
37.
Quy Thuong Lê 《Comptes Rendus Mathematique》2017,355(10):1041-1045
In this note, using Cluckers–Loeser's theory of motivic integration, we prove the integral identity conjecture with framework a localized Grothendieck ring of varieties over an arbitrary base field of characteristic zero. 相似文献
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40.
The chemo-selective hydration of a wide range of non-activated terminal alkynes catalysed by AgSbF(6) under mild conditions is reported. 相似文献