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971.
972.
以一种新型的醌类光敏剂—菌生素 (HMB)为模型化合物 ,利用量子化学从头算HF/ 6 31G和含时密度泛函TD B3LYP/ 6 31G方法计算研究了卤代作用对醌类光敏剂分子性质和光敏活性的影响 .结果发现 ,卤代作用降低了HMB母体的HOMO和LUMO能级 (EHOMO和ELUMO)及其差值△E ,随卤族元素从上到下 ,EHOMO和ELUMO呈增大趋势 ,而△E呈减小趋势 ,使得分子激发光谱有不同程度的红移 ,在增加PQP三重态量子产率的同时降低了分子最低三重激发态的能量 ,两种作用相互抵消 ,使得卤代物的 1O2 量子产率与母体相似 ;增加了分子的绝热电子亲合势 ,使分子产生O2 -的能力下降 ;卤原子的引入 ,降低了HMB母体分子内氢键的强度 ,同时使顺式构型的分子内质子传递势垒增大 ,而使反式构型势垒减小 . 相似文献
973.
Shaping command input or preshaping is used for reducing system oscillation in motion control. Desired systems inputs are altered so that the system finishes the requested move without residual oscillation. This technique, developed by N.C. Singer and W.P. Seering, is used for example in the aerospace field, in particular in flexible structure control. This paper presents the study of ZV shaper for explicit fractional derivative systems (generalized derivative systems). A robustness study of ZV shaper is then presented and applied to improve second generation CRONE control response time. Results from simulation and from a DC motor bench are also given. 相似文献
974.
The thermally stimulated properties of PbWO4 in the temperature range 90–400 K have been investigated on undoped and terbium-doped crystals after X-ray irradiation at 90 K. Doping with terbium changes the concentration of shallow traps, which are responsible for retrapping free electrons and holes. Light illumination can change the distribution of the traps. The optically stimulated luminescence is observed. The influence of light illumination on the TSL curves and emission properties is studied. The possible mechanism of TSL phototransformation is discussed. 相似文献
975.
976.
977.
An experimental Dalitz plot distribution for the decay η → π
+
π
−
π
0 is fitted by the theoretical one obtained in chiral perturbation theory with unitarity corrections taken into account. The
fit shows that the difference of light-quark masses is larger than is expected from electromagnetic mass differences of neutral
and charged kaons.
From Yadernaya Fizika, Vol. 67, No. 2, 2004, pp. 443–445.
Original English Text Copyright ? 2004 by Martemyanov, Sopov.
This article was submitted by the authors in English. 相似文献
978.
G. E. Abrosimova A. S. Aronin Yu. P. Kabanov D. V. Matveev V. V. Molokanov 《Physics of the Solid State》2004,46(5):885-890
The structure forming under controlled crystallization of a bulk Fe72Al5P10Ga2C6B4Si1 amorphous alloy has been studied using differential scanning calorimetry, transmission electron microscopy, and x-ray diffraction.
Crystallization of the alloy was established to result in the formation of a nanocrystalline structure consisting of three
phases. The domain structure and magnetic properties of amorphous and nanocrystalline samples were investigated using the
magnetooptic indicating film technique (MOIF) and a vibrating-sample magnetometer. The coercive force and the saturation magnetization
of the amorphous samples were found to be 1 Oe and 130 emu/g, respectively. It was shown that the formation of the nanocrystalline
structure entails a dramatic decrease in domain size (down to 1–4 μm) as compared to an amorphous sample (∼1 mm). Simultaneously,
a decrease in the saturation magnetization and a strong increase in the coercive force of the samples were observed.
__________
Translated from Fizika Tverdogo Tela, Vol. 46, No. 5, 2004, pp. 858–863.
Original Russian Text Copyright ? 2004 by Abrosimova, Aronin, Kabanov, Matveev, Molokanov. 相似文献
979.
Crystal and magnetic structure of the Sm0.55Sr0.45MnO3 and (Nd0.545Tb0.455)0.55Sr0.45MnO3 manganites
A. I. Kurbakov V. A. Trounov A. M. Balagurov V. Yu. Pomyakushin D. V. Sheptyakov O. Yu. Gorbenko A. R. Kaul 《Physics of the Solid State》2004,46(9):1704-1710
Neutron diffraction data are presented for the 152Sm0.55Sr0.45MnO3 (SSM) and (Nd0.545Tb0.455)0.55Sr0.45MnO3 (NTSM) manganites. The Nd and Tb contents in the latter composition are such that the average radius of the A cation 〈r
A
〉 in these two compounds is the same. The difference in local tolerance factor fluctuations was about 10%. It was found that
replacement of a rare-earth cation with leaving 〈r
A
〉 unchanged has practically no effect on the structural and transport properties; indeed, both compounds are metals at low
temperatures, have the same crystal structure from liquid-helium to room temperature, and exhibit the same pattern of structural
distortions at the onset of magnetic ordering. Magnetic moments of Mn ions in both compositions are ferromagnetically ordered
at low temperatures, with T
C
=122 and 90 K for the SSM and NTSM, respectively. Below 80 K, the rare-earth cation moments in NTSM undergo additional ordering.
In contrast to compositions that are close in Sr concentration (x
Sr=0.4, 0.5), which feature a phase-separated state with a mixture of the ferromagnetic metallic and antiferromagnetic insulator
phases, the ground state of both studied compositions with x
Sr=0.45 is uniformly ferromagnetic and metallic.
__________
Translated from Fizika Tverdogo Tela, Vol. 46, No. 9, 2004, pp. 1650–1656.
Original Russian Text Copyright ? 2004 by Kurbakov, Trounov, Balagurov, Pomyakushin, Sheptyakov, Gorbenko, Kaul. 相似文献
980.
R. M. Vlasova N. V. Drichko B. V. Petrov V. N. Semkin E. I. Zhilyaeva R. N. Lyubovskaya I. Olejniczak A. Kobayashi H. Kobayashi 《Physics of the Solid State》2004,46(11):1985-1993
Polarized reflectance and optical conductivity spectra of single crystals of two new isostructural organic conductors based
on the BEDT-TSeF molecule, namely, the κ-(BETS)4Hg2.84Br8 superconductor (T
c
=2 K) and the κ-(BETS)4Hg3Cl8 metal, which undergoes a smooth transition to the dielectric state near 35 K, have been obtained in the spectral region 700–6500
cm−1 at temperatures of 300–15 K. At 300 K, the spectra of both compounds are nearly identical and differ from the Drude spectrum
characteristic of metals. The nature of the observed difference is discussed, and the spectra are described in terms of a
cluster approach with inclusion of electron-electron correlations in the Hubbard approximation combined with the Drude model.
The parameters of the theory were determined, including the electron transfer integrals between molecules in a cluster. The
spectra in the conducting plane of the crystals were found to be essentially anisotropic, which should be assigned to specific
features of in-plane interaction between molecules. The spectra of the superconductor and the metal become increasingly different
as the temperature is lowered. The spectra of the metal obtained for T<150 K exhibit splitting of the broad electronic maximum in the mid-IR region into two bands, which is accompanied by a splitting
of a vibronic feature deriving from electron interaction with intramolecular BETS vibrations of ν3(A
g
) symmetry. No such splitting is observed in the superconductor spectra with decreasing temperature.
__________
Translated from Fizika Tverdogo Tela, Vol. 46, No. 11, 2004, pp. 1921–1929.
Original Russian Text Copyright ? 2004 by Vlasova, Drichko, Petrov, Semkin, Zhilyaeva, Lyubovskaya, Olejniczak, A. Kobayashi,
H. Kobayashi. 相似文献