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111.
In the present work, single-walled carbon nanotubes (SWCNTs) were dispersed in a room temperature nematic liquid crystal 4-pentyl-4′-cyanobiphenyl at the concentration of 0.02 and 0.05 wt%. Differential scanning calorimetry and temperature-dependent dielectric studies suggest decrease in clearing temperature of the composite materials as compared to the pure material. Ionic conductivity increases by two orders of magnitude due to the dispersion of such a low concentration (0.05 wt%) of SWCNTs. Dielectric studies also show that the presence of the SWCNTs decreases the effective longitudinal as well as transverse components of the dielectric permittivity. For homeotropic aligned samples, a relaxation mechanism has been detected in the lower MHz region both for the pure as well as dispersed samples. Presence of SWCNTs increases the relaxation frequency corresponding to flip-flop motion of molecules around their short axes. From frequency-dependent dielectric studies, important dielectric parameters such as relaxation frequency, dielectric strength and distribution parameters have been determined. Electro-optical experiments show that the threshold voltage decreases and the steepness of the transmission voltage curve improves due to the dispersion of SWCNTs. 相似文献
112.
R.L. Verma 《International Journal of Non》1981,16(1):65-69
In this paper, a theoretical investigation of the effect of slip velocity in externally pressurized porous thrust bearing has been made by using the boundary condition given by Beavers and Joseph. The expressions of bearing characteristics have been obtained in closed form. It has been noticed that the load-capacity and time of approach is greatly influenced by a new dimensionless parameter, called the “Bearing Number”, which gives the effect of the slip parameter. 相似文献
113.
Preparation of electrodeless discharge lamps for emission studies of uranium isotopes at trace level
G.K. Bhowmick R. Verma M.K. Verma V.A. Raman A.R. Joshi M.N. Deo L.M. Gantayet A.K. Tiwari K.L. Ramakumar Navin Kumar 《Spectrochimica Acta Part B: Atomic Spectroscopy》2010,65(12):1047-1051
A simplified method for preparation of electrodeless discharge lamp for uranium isotopes with specific concerns for 232U is described. Micro-gram quantities of solid uranium oxides and aqueous solution of uranium nitrate have been used as a starting material for in situ synthesis of uranium tetraiodide. High temperature iodination reaction is carried out in the presence of inert gas neon. By careful design, the preparation time and surface area of quartz reaction tubes have been reduced considerably. The latter decreases the level of contamination which has a direct bearing on the operational lifetime of the lamps. Incorporation of steps to purify the product from an unwanted material improved the stability of the lamps. The procedure provides a safe and convenient way of handling 232U in particular but can be extended in general to any actinides having radioactivity similar to that of freshly separated 232U. Characteristic emission of uranium isotopes have been recorded by Fourier Transform Spectrometer to show the satisfactory operation of the lamps as well as their usage for studying emission spectra of the specific isotope. 相似文献
114.
Fusion toxins are an emerging class of targeted therapeutics for the treatment of cancer. Diphtheria toxin-stem cell factor
(DT-SCF) is one such novel fusion toxin designed to target malignancies expressing c-kit. Since, c-kit overexpression has
been reported on many types of cancers, it appeared to be a reasonably good molecule to target. In the present study, we report
construction, expression, purification, and characterization of DT-SCF. DT-SCF gene coding for 1–387 amino acids of diphtheria
toxin, His-Ala linker, 2–141 amino acids of SCF was cloned into expression vector with C terminal His tag. The induced DT-SCF
protein was exclusively expressed in insoluble fraction. Purification of DT-SCF was achieved by inclusion body isolation and
metal affinity chromatography under denaturing and reducing conditions. Purified DT-SCF was renatured partially on-column
by gradually reducing denaturant concentration followed by complete refolding through rapid dilution technique. Cell viability
assay provided the evidence that DT-SCF is a potent cytotoxic agent selective to cells expressing c-kit. The novelty of this
study lies in employing SCF as a ligand in construction of fusion toxin to target wide range of malignancies expressing c-kit.
Efficacy of DT-SCF fusion toxin was demonstrated over a range of malignancies such as chronic myeloid leukemia (K562), acute
lymphoblastic leukemia (MOLT4), pancreatic carcinoma (PANC-1), and cervical carcinoma (HeLa 229). This is the first study
reporting specificity and efficacy of DT-SCF against tumor cells expressing c-kit. There was significant correlation (P = 0.007) between c-kit expression on cells and their sensitivity to DT-SCF fusion toxin. 相似文献
115.
Bruno Fabre Soraya Ababou-Girard Prabhpreet Singh Jitendra Kumar Sandeep Verma Alberto Bianco 《Electrochemistry communications》2010,12(6):831-834
Redox-active ferrocene was assembled on gold surfaces through the hydrogen bonding interactions between adenine-substituted ferrocene and a uracil-terminated organothiol monolayer. The surface coverage of ferrocene Γ could be varied from ca. 4 × 10? 11 to 2.0 × 10? 10 mol cm? 2 by diluting the thiol-modified uracil derivative with inert 1-octanethiol. A decrease in the apparent electron transfer rate constant for ferrocene, kapp, from ca. 50 to 10 s? 1 was observed upon increasing Γ. 相似文献
116.
117.
A new, selective and sensitive method has been developed for the determination of tricyclic antidepressant drugs, amoxapine and nortriptyline, in human blood plasma and serum, involving their reaction with allyl isothiocyanate and extraction of thiourea derivatives with water-miscible organic solvent acetonitrile. The phase separation was effected by addition of ammonium sulphate, a process called salt-assisted liquid-liquid microextraction. The extract was analyzed by HPLC with UV detection at 254?nm. The method has been optimized for derivatization reaction time and temperature, solvent for extraction, and salt for solvent phase separation. Under the optimal conditions, a linear calibration graph was obtained between the amount of drug and the peak area of thiourea derivatives in the range of 0.002-20?mg/L drugs. The correlation coefficient and limit of detection values for amoxapine and nortriptyline in serum/plasma samples were in the range of 0.9953-0.9999 and 0.46-0.58?μg/L, respectively. The recovery in spiking experiments ranged, respectively, 75-88% (RSD 3.4-7.2%) and 79-97% (RSD 3.7-7.9%) for the two drugs. 相似文献
118.
Terbium ion doped MO–Al2O3 (M = Mg, Ca, Sr and Ba) series phosphors have been synthesized through combustion technique and their luminescence properties have been studied and compared. Terbium ion in different phosphors has shown different fluorescence properties due to the presence of different ratios of Tb3+ and Tb4+ states in different samples. The UV/Visible absorption and XPS techniques have been used to probe the existence of Tb3+ and Tb4+ states. The host sensitive 4f–5d and the charge transfer transitions enabled the use of terbium ion as an indicator of the structure. 相似文献
119.
Poonam Singh U.P. Verma Per Jensen 《Journal of Physics and Chemistry of Solids》2011,72(12):1414-1418
The structural, electronic and optical properties of HgAl2Se4 are investigated using the full potential linear augmented plane wave method based on density functional theory. The calculated structural parameters using LDA are in excellent agreement with the available experimental result. The obtained energy band gap (2.24 eV) using EV-GGA approximation is in excellent agreement with experimental data (2.20 eV). Variation in the energy band gap as a function of the unit cell lattice parameter has been studied. The optical properties show a considerable anisotropy, which makes this compound very useful for various linear–nonlinear optical devices. 相似文献
120.
K. Kholiya S. Verma 《The European Physical Journal B - Condensed Matter and Complex Systems》2011,83(1):23-28
The structural and elastic properties of cerium chalcogenides (CeZ, Z = S, Se, Te) under high pressure have been investigated
by using the potential model considered up to third nearest neighbor interaction. The computed values of B1-B2 phase transition
pressure, equation of state (compression curve), bulk modulus, its first order pressure derivative and elastic constants in
the case of cerium chalcogenides agree well with the experimental results. The present study shows the anomalous behavior
of cerium chalcogenides in comparison to the alkaline earth chalcogenides, due to the presence of Kondo effect and reentrant
valence behavior of Ce in cerium chalcogenides. 相似文献