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1.
CV Tomy D Pal SS Banerjee S Ramakrishnan AK Grover S Bhattacharya MJ Higgins G Balakrishnan McK Paul 《Pramana》2002,58(5-6):925-935
The weakly pinned single crystals of the hexagonal 2H-NbSe2 compound have emerged as prototypes for determining and characterizing the phase boundaries of the possible order-disorder
transformations in the vortex matter. We present here a status report based on the ac and dc magnetization measurements of
the peak effect phenomenon in three crystals of 2H-NbSe2, in which the critical current densities vary over two orders of magnitude. We sketch the generic vortex phase diagram of
a weakly pinned superconductor, which also utilizes theoretical proposals. We also establish the connection between the metastability
effects and pinning. 相似文献
2.
A novel podophyllotoxin lignan from Justicia heterocarpa 总被引:2,自引:0,他引:2
Chromatographic separation of the extract of Justicia heterocarpa T. ANDERS. afforded, in addition to known fatty acids, terpenoids and steroids, a new podophyllotoxin lignan. Structures were elucidated by spectroscopic methods, and the structure of the new lignan was confirmed by single crystal X-ray diffraction studies, which have shown that there is a H-bonding stabilized dimer. 相似文献
3.
In subnormal glow discharge under d.c. excitation at different pressure in a varying transverse magnetic field (0 to 30 G)
some measurements have been carried out for various initial average tube currents. The voltage across the discharge increases
and average tube current and residual current decreases in the magnetic field. With the help of Beckman’s expression [4] for
the axial field and the electron density distribution in a transverse magnetic field the observed variation of current and
voltage can be satisfactorily explained. The variation of axial electric field with transverse magnetic field can be represented
to a fair degree of accuracy by the derived equation. The behaviour of residual current with magnetic field has been observed
in these oscillations. 相似文献
4.
An integral equation formulation for buoyancy-driven convection problems is developed and illustrated. Buoyancy-driven convection in a bounded cylindrical geometry with a free surface is studied for a range of aspect ratios and Nusselt numbers. The critical Rayleigh number, the nature of the cellular motion, and the heat transfer enhancement are computed using linear theory. Green's functions are used to convert the linear problem into linear Fredholm integral equations. Theorems are proved which establish the properties of the eigenvalues and eigenfunctions of the linear integral operator which appears in these equations. 相似文献
5.
WANG Er-Kang ZHOU Wei-HongLaboratory of Electroanalytical Chemistry Changchun Institute of Applied Chemistry Chinese Academy of Sciences Changchun Jilin SS China 《中国化学》1996,14(2):131-137
Capillary electrpphoresis (CE)/electrochemical detection (EC) for the simultane-ous determination of hydrazine and isoniazid has been developed.The electrochemical method uses a novel modified electrode dispersed with ultrafine platinum particles on the surface of a 30μm carbon fiber microelectrode.The unique characteristic of the Pt-particles modified carbon fiber microelectrode is its excellent stability.The current measurement for hydrazine is more sensitive than that of isoniazid.Selective determination of trace amount of free hydrazine in isoniazid and its formulation can be achieved at applied potential of 0.5V. 相似文献
6.
Salih S. Al-Juaid Colin Eaborn Paul D. Lickiss J. David Smith Kayumars Tavakkoli Alexander D. Webb 《Journal of organometallic chemistry》1996,510(1-2):143-151
Mercury compounds of the types HgR1R (R1 = C(SiMe3)3; R = Me, iPr, Bu, tBu or Ph) and HgR2R(R2 = C(SiMe2Ph)3; R = Me, Bu, CH2Ph or Ph) have been prepared. Those containing R1 were made by reactions of the bromides HgR1Br with the Grignard reagents MgRX, and those containing R2 by reaction of HgR2Cl with LiR or, for R = CH2Ph, with Mg(CH2Ph)Cl. Replacement of one R group in HgR2 by the bulky R1 or R2 group leads to a large increase in thermal stability, a marked shift in the 199Hg resonance to lower frequency and an increase in the coupling constant 1J(13C---199Hg) for the Hg---R bond. The compound HgR2Cl does not react further with LiR2 in tetrahydrofuran, but with LiR1 gives HgR1R2; the arrangement of the SiMe2Ph groups in the latter in solution in CH2C12 at low temperature appears to be different from that in the solid. 相似文献
7.
Ala'a K. Abdul-Sada Salih Al-Juaid Anthony M. Greenway Peter B. Hitchcock Matthew J. Howells Kenneth R. Seddon Thomas Welton 《Structural chemistry》1990,1(4):391-394
The crystal and molecular structures of [Me2Etim]Cl, [Me2Etim]2[CoCl4], and [Me2Etim]2[NiCl4] ([Me2Etim]+ = 1,2-dimethyl-3-ethylimidazolium cation) all contain evidence that the H4 and H5 protons of the imidazolium cation enter into hydrogen bonds; the implications of this observation for the interactions in room-temperature chloroaluminate(III) ionic liquids are considered. 相似文献
8.
A. Y Obaid A. O. Alyoubi A. A. Samarkandy S. A. Al-Thabaiti S. S. Al-Juaid A. A. El-Bellihi El-H. M. Deifallah 《Journal of Thermal Analysis and Calorimetry》2000,61(3):985-994
The thermal decomposition of copper(II) acetate monohydrate was studied in air and nitrogen atmospheres by means of DTA-TG
and SEM measurements. The kinetics of the thermal decomposition steps in air was studied by using isothermal and non-isothermal
thermogravimetric techniques. The results are discussed in terms of various reaction interface models and different techniques
of computational analysis of non-isothermal data. The activation parameters, calculated by using a composite method of integral
analysis of non-isothermal data, revealed not only their independence from the heating rate and fractional reaction, but also
a better correlation and agreement with the results obtained under isothermal conditions.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
9.
A Soibel SS Banerjee Y Myasoedov ML Rapparort E Zeldov S Ooi T Tamegai 《Pramana》2002,58(5-6):893-898
Using a novel differential magneto-optical imaging technique we investigate the phenomenon of vortex lattice melting in crystals
of Bi2Sr2CaCu2O8 (BSCCO). The images of melting reveal complex patterns in the formation and evolution of the vortex solid-liquid interface
with varying field (H)/temperature (T). We believe that the complex melting patterns are due to a random distribution of material disorder/inhomogeneities across
the sample, which create fluctuations in the local melting temperature or field value. To study the fluctuations in the local
melting temperature/field, we have constructed maps of the melting landscape T
m(H, r), viz., the melting temperature (T
m) at a given location (r) in the sample at a given field (H). A study of these melting landscapes reveals an unexpected feature: the melting landscape is not fixed, but changes rather
dramatically with varying field and temperature along the melting line. It is concluded that the changes in both the scale
and shape of the landscape result from the competing contributions of different types of quenched disorder which have opposite
effects on the local melting transition. 相似文献