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排序方式: 共有96条查询结果,搜索用时 31 毫秒
11.
Masihhur R. Laskar Tapas Ganguli A. A. Rahman A. P. Shah M. R. Gokhale Arnab Bhattacharya 《固体物理学:研究快报》2010,4(7):163-165
We report the metal organic vapor phase epitaxy (MOVPE) growth and characterization of non‐polar (11 0) a ‐plane Alx Ga1–xN on (1 02) r ‐plane sapphire substrates over the entire composition range. Alx Ga1–xN samples with ~0.8 μm thick layers and with x = 0, 0.18, 0.38, 0.46, 0.66, and 1.0 have been grown on r ‐plane sapphire substrates. The layer quality can be improved by using a 3‐stage AlN nucleation layer and appropriate V/III ratio switching following nucleation. All a ‐plane AlGaN epilayers show an anisotropic in‐plane mosaicity, strongly influenced by Al incorporation and growth conditions. Careful lattice parameter measurements show anisotropic in‐plane strain that results in an orthorhombic distortion of the hexagonal unit cell, making Al composition determination from X‐ray diffraction difficult. In general lower Al incorporation is seen in a ‐plane epilayers compared to c ‐plane samples grown under the same conditions. (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
12.
Bhattacharya S Chattopadhyay S Laskar S Banerjee M 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2006,63(2):313-319
Electron donor-acceptor (EDA) complexes of tri-n-octylamine (TOA) with [60]- and [70]fullerenes and some other electron acceptors have been studied in chloroform medium by absorption spectrophotometric technique. Charge transfer (CT) absorption bands are observed in the visible region. Vertical ionization potential of TOA was determined utilizing CT transition energy. Oscillator strengths, transition dipole strengths and resonance energies for all the complexes have been calculated. [60]Fullerene/TOA and [70]fullerene/TOA complexes are found to decay slowly with time. Kinetics of these reactions have been studied and activation energies for such processes have been estimated. Ab initio calculations suggest that complexation of [70]fullerene with TOA is enthalpy favoured. 相似文献
13.
Cellulose catalyzed oxidative hydroxylation of aryl and hetero-arylboronic acids to the corresponding phenols under metal and base free strategy has been demonstrated. The sustainable ipso-hydroxylation takes place using hydrogen peroxide as an oxidant in water under mild condition in shorter period of time. Interestingly, easy recovery and reusability of heterogeneous catalyst without significant loss in catalytic yield makes the protocol environmentally benign. 相似文献
14.
Renu Laskar 《Discrete Applied Mathematics》2009,157(2):330-338
The question of whether a graph can be partitioned into k independent dominating sets, which is the same as having a fallk-colouring, is considered. For k=3, it is shown that a graph G can be partitioned into three independent dominating sets if and only if the cartesian product G□K2 can be partitioned into three independent dominating sets. The graph K2 can be replaced by any graph H such that there is a mapping f:Qn→H, where f is a type-II graph homomorphism.The cartesian product of two trees is considered, as well as the complexity of partitioning a bipartite graph into three independent dominating sets, which is shown to be NP-complete. For other values of k, iterated cartesian products are considered, leading to a result that shows for what values of k the hypercubes can be partitioned into k independent dominating sets. 相似文献
15.
P Alam M Karanam AR Choudhury IR Laskar 《Dalton transactions (Cambridge, England : 2003)》2012,41(31):9276-9279
Strong solid-state greenish-blue emitting, mono-cyclometalated iridium complexes, [Ir(ppy)(PPh(3))(2)(H)(Cl)], 2a and [Ir(F(2)ppy)(PPh(3))(2)(H)(Cl)], 2b [ppyH = 2-phenylpyridine; F(2)ppyH = 2-(2',4'-difluoro)phenylpyridine], have been synthesized by a convenient route. The 'aggregation induced enhanced phosphorescence (AIEP)' activity exhibited by these complexes has been rationalized. 相似文献
16.
Narayanan J Deotare VW Bandyopadhyay R Sood AK 《Journal of colloid and interface science》2002,245(2):267-273
We report the dynamic light scattering study of the gelation of aqueous solutions of the biopolymer, pectin, induced by the addition of calcium chloride. The time correlation function data are analyzed under the framework of the coupling model. As the solution enters the semidilute regime where gelation sets in, the relaxation process shows a stretched exponential behavior. The stretching exponent decreases and the characteristic time of the stretched exponential diverges as the system evolves to a gel. Aqueous pectin solutions in the presence of 0.1 M NaCl show similar behavior. Thus, the molecular relaxation modes of pectin solutions can be well described by the coupling model. 相似文献
17.
18.
Ranjini Raghunandan Fabio J. Mazzotti John P. Maier 《Journal of the American Society for Mass Spectrometry》2010,21(5):694-697
Measurement of the 3Π-3Π transition of C6H+ in the gas phase near 19486 cm−1 is reported. The experiment was carried out with a supersonic slit-jet expansion discharge using cavity ringdown absorption
spectroscopy. Partly resolved P lines and observation of band heads permitted a rotational contour fit. Spectroscopic constants
in the ground and excited-state were determined. The density of ions being sampled is merely 2×108 cm−3. Broadening of the spectral lines indicates the excited-state lifetime to be ≈100 ps. The electronic transition of HC6H2+ at 26402 cm−1 assumed to be 1A1-X1A1 in C2v symmetry could not be rotationally resolved. 相似文献
19.
Several surfactant molecules self-assemble in solution to form long, cylindrical, flexible wormlike micelles. These micelles
can be entangled with each other leading to viscoelastic phases. The rheological properties of such phases are very interesting
and have been the subject of a large number of experimental and theoretical studies in recent years. We shall report our recent
work on the macrorheology, microrheology and nonlinear flow behaviour of dilute aqueous solutions of a surfactant CTAT (Cetyltrimethylammonium
Tosilate). This system forms elongated micelles and exhibits strong viscoelasticity at low concentrations (∼0.9 wt%) without
the addition of electrolytes. Microrheology measurements of G(θ) have been done using diffusing wave spectroscopy which will be compared with the conventional frequency sweep measurements
done using a cone and plate rheometer. The second part of the paper deals with the nonlinear rheology where the measured shear
stress σ is a nonmonotonic function of the shear rate
. In stress-controlled experiments, the shear stress shows a plateau for
larger than some critical strain rate, similar to the earlier reports on CPyCl/NaSal system. Cates et al have proposed that the plateau is a signature of mechanical instability in the form of shear bands. We have carried out extensive
experiments under controlled strain rate conditions, to study the time-dependence of shear stress. The measured time series
of shear stress has been analysed in terms of correlation integral and Lyapunov exponent to show unambiguously that the behaviour
is typical of low dimensional dynamical systems. 相似文献
20.
B. Basak U. K. Bhattacharyya A. Sinhababu S. Laskar 《Applied biochemistry and biotechnology》1994,49(3):281-290
Studies have been carried out on the protein solubility profile of Kulthi (Macrotylona uniflorus, Lam.) seed in aqueous solution over various pHs and at different concentrations of NaCl, Na2SO3, CaCl2, and MgCl2 at pH 8.0. Amino acid analysis of isolated protein identified 17 amino acids, 9 of which are essential. Gel-permeation chromatography on Sephadex G-200 revealed the presence of seven components in the protein fraction. Their molecular weights were determined by two comparable standard methods. Extractable Kulthi seed proteins in salt solutions were separated electrophoretically into eight fractions whose molecular weights were found to be 186,200, 131,800, 108,400, 91,200, 53,700, 44,700, 38,000, and 27,500. 相似文献