排序方式: 共有20条查询结果,搜索用时 31 毫秒
1.
2.
R. Rentzsch B. Sandow A. N. Ionov N. V. Agrinskaya M. J. Lea P. Fozooni 《Czechoslovak Journal of Physics》1996,46(5):2447-2448
In this work, we report the results of magnetoresistance studies of variable range hopping down to 30 mK in isotopically engineered Ge with low compensation, and in n-CdTe crystals. Experimentally we find a decrease and disappearance of the negative magnetoresistance with decreasing temperature down to 200 mK, in weak magnetic fields. Such behaviour is in disagreement with the quantum interference theory of Nguen, Spivak and Shklovskii. 相似文献
3.
N. V. Agrinskaya V. I. Kozub R. Rentzsch M. J. Lea P. Fozooni 《Journal of Experimental and Theoretical Physics》1997,84(4):814-822
An observation of the suppression of negative magnetoresistance in samples of doped CdTe that are far from the metal-insulator
transition as the temperature is lowered in the temperature range 3–0.4 K was previously reported [N. V. Agrinskaya, V. I.
Kozub, and D. V. Shamshur, JETP 80, 1142 (1995)]. The results of an investigation of samples that are closer to the transition in the low-temperature region
below 36 mK are presented. It is discovered that the samples investigated (which do not exhibit the suppression of negative
magnetoresistance at comparatively high temperatures) display this effect at low temperatures and that, as previously, the
suppression of the negative magnetoresistance correlates with the transition to conduction via Coulomb-gap states. A plateau-like
magnetoresistance feature is displayed at low temperatures for the sample that is closest to the metal-insulator transition.
The results obtained are analyzed within existing theoretical models that take into account the role of both the orbital and
spin degrees of freedom. In particular, the low-temperature feature indicated is interpreted as a manifestation of positive
magnetoresistance caused by spin effects. Nevertheless, it is shown within a detailed analysis supplemented by numerical calculations
that the observed suppression of the negative magnetoresistance cannot be attributed only to the appearance of spin positive
magnetoresistance. Moreover, the possibility of observing spin positive magnetoresistance is determined to a certain extent
specifically by the suppression of the negative magnetoresistance competing with it.
Zh. éksp. Teor. Fiz. 111, 1477–1493 (April 1997) 相似文献
4.
P. Stefanyi C. C. Zammit P. Fozooni M. J. Lea G. Ensell 《Czechoslovak Journal of Physics》1996,46(5):2433-2434
A critical point in the non-linear conductivity has been observed in epitaxial silicon in the variable range hopping regime, due to a negative differential resistance with a dc bias currentI dc. This gives thermal breakdown via the electron-phonon coupling and circuit-limited oscillations with a frequencyf∝I dc, below a critical temperatureT c. This critical behaviour is intrinsic, and forR(T)=R 0 exp(T 0 /T)1/2 we show thatT c=0.00512T 0. 相似文献
5.
6.
A. M. Tikdari S. Fozooni H. Vazee H. Hamidian 《Russian Journal of Organic Chemistry》2005,41(7):1046-1049
Reactions of 4,5-dihydrooxazol-5-one derivatives with 4-methylbenzene-1,2-dithiol in the presence of triethylamine includes nucleophilic attack by the thiol group on the carbonyl carbon atom in the oxazole ring, followed by opening of the latter and recyclization to 1,4-benzodithiine derivatives.__________From Zhurnal Organicheskoi Khimii, Vol. 41, No. 7, 2005, pp. 1067–1070.Original English Text Copyright © 2005 by Tikdari, Fozooni, Vazee, Hamidian.The original article was submitted in English. 相似文献
7.
The transverse acoustic impedance of a 4He film has been measured at 3.11 K and 20.5 MHz and shows the occurence of standing shear waves in the film. This is in good agreement with calculations using transmission line theory and gives a new method of measuring the thickness of liquid films. 相似文献
8.
The transverse acoustic impedance Z of a fluid can be determined from measurements of the complex reflection coefficient of a transverse ultrasonic wave incident on a plane solid/fluid interface. Inhomogeneities in the fluid close to the solid surface may have a significant effect on the measured values of Z. We have derived the Riccati equation which determines Z in an inhomogeneous viscous fluid, using transmission line theory. This equation was integrated numerically to obtain the impedance of viscous films and for inhomogeneities due to healing lengths and van der Waals forces near the solid/fluid interface. The results show that the measurement of both the real and imaginary parts of Z can be a powerful technique for investigating any inhomogeneities which occur on a length scale comparable with the viscous penetration depth in the fluid. 相似文献
9.
10.
Hamidian H Fozooni S Hassankhani A Mohammadi SZ 《Molecules (Basel, Switzerland)》2011,16(11):9041-9048
A novel synthesis of triazolo[1,2-a]indazole-1,3,8-trione derivatives by reaction of urazole, dimedone and aromatic aldehydes under conventional heating and microwave irradiation and solvent-free conditions using silica nanoparticles prepared from rice husk ash as catalyst is described. The new method features high yields, multicomponent reactions and environmental friendliness. 相似文献