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71.
Novel chromogenic thiourea based sensors 4,4′-bis-[3-(4-nitrophenyl) thiourea] diphenyl ether 1 and 4,4′-bis-[3-(4-nitrophenyl) thiourea] diphenyl methane 2 having nitrophenyl group as signaling unit have been synthesized and characterized by spectroscopic techniques and X-ray crystallography. The both sensors show visual detection, UV-vis and NMR spectral changes in presence of fluoride and cyanide anions in organic solvent as well as in aqueous medium. The absorption spectra indicated the formation of complex between host and guest is in 1:2 stoichiometric ratios. 相似文献
72.
Bipin Singh Koranga Vinod Kumar A. Jha 《International Journal of Theoretical Physics》2011,50(8):2609-2613
We give a phenomenological model of CPT violating neutrino oscillation above the GUT scale. In this paper, we consider the
effect of Planck scale operators on neutrino mixing. We assume that the main part of neutrino masses and mixing arise through
GUT scale operators The dispersion relation for the CPT violating neutrino and anti-neutrino oscillation are discussed. 相似文献
73.
The optical absorption coefficients and changes in the refractive index in GaAs/AlGaAs, disk shaped quantum dots (DSQD) with simultaneously applied laser and magnetic field are studied in detail. The use of the density matrix formalism is made to study the variations in linear and non-linear polarizability with the frequency of the electric field. It is found that the absorption coefficient and the refractive index changes depend not only on the optical wave but also on the strength of the static magnetic field. 相似文献
74.
P. Saravanan G. Venkata RamanaK. Srinivasa Rao B. SreedharV.T.P. Vinod V. Chandrasekaran 《Journal of magnetism and magnetic materials》2011,323(15):2083-2089
Self-assembled Sm-Co nanoparticles in the form of spherical aggregates (referred as nanospheres) with diameter ranging from 50 to 180 nm were achieved by means of polyol technique. The size distribution of the Sm-Co nanospheres can be regulated close to ∼100 nm by controlling the molar ratio of Sm:Co precursor. The spherical aggregates exhibited Sm2Co7 phase as a major constituent; while the aggregates obtained at higher Co concentration showed co-existence of Co-phase with Sm2Co7 phase. Upon annealing, the biphasic nature of nanospheres (Sm2Co7/Co) transformed into Sm2Co17 structure. By varying the Sm:Co precursor ratio from 1:5 to 1:9, the coercivity (Hc) and magnetization (Ms) values of the as-synthesized nanospheres can be tuned from 336 to 140 Oe and from 63.7 to 108 emu/g, respectively, and these values significantly improved after annealing. Maximum values of Hc (1050 Oe) at the Sm:Co molar ratio of 1:5 and Ms of 184.6 emu/g at the Sm:Co molar ratio of 1:9 were achieved in the annealed samples. 相似文献
75.
JPC – Journal of Planar Chromatography – Modern TLC - A densitometric HPTLC method has been established for simultaneous quantification of sennosides A and B and gallic acid in a... 相似文献
76.
77.
A one-pot three-component coupling of aldehydes and amines in presence of terminal alkynes has been efficiently catalyzed by copper (I) complex of i-Pr-pybox-diPh 2b or s-Bu-pybox-diPh 2c. The process is simple and allows the synthesis of various propargylamines in good to excellent enantioselectivities (up to 99% ee) and in higher yields. The nature of the substituents attached to imines plays a vital role on the enantioselectivities obtained. The presence of gem-diphenyl group at C-5 position and secondary alkyl substituents at the C-4 chiral center of the oxazoline rings of the chiral ligands was found to be crucial for higher enantioselectivities. A transition state model involving π–π stacking is also proposed for the stereochemical outcome. 相似文献
78.
Adsorption of Sb at a very low flux rate results in an epitaxial layer-by-layer growth on Si(111) surface held at room-temperature. Band-bending is not observed for submonolayer Sb coverages while sharp changes in the photoemission features are observed for 1.0 monolayer (ML) Sb adsorption. Changes in the core level binding energy and width in X-ray photoelectron spectroscopy, surface related feature in Electron energy loss spectroscopy and spot intensity ratios in Low energy electron diffraction studies suggest a surface phase transition upon adsorption of 1.0 monolayer of Sb. A plausible model is proposed to explain the abrupt metal-semiconductor transformation at this critical coverage of 1.0 ML. 相似文献
79.
The characteristics of harmonic radiation due to electron oscillation driven by an intense femtosecond laser pulse are analyzed considering a single electron model. An interesting modulated structure of the spectrum is observed and analyzed for different polarization. Higher order harmonic radiations are possible for a sufficiently intense driving laser pulse. We have shown that for a realistic pulsed photon beam, the spectrum of the radiation is red shifted as well as broadened because of changes in the longitudinal velocity of the electrons during the laser pulse. These effects are more pronounced at higher laser intensities giving rise to higher order harmonics that eventually leads to a continuous spectrum. Numerical simulations have further shown that by increasing the laser pulse width broadening of the high harmonic radiations can be limited. 相似文献
80.
Motivated by ABR class of service in ATM networks, we study a continuous time queueing system with a feedback control of the
arrival rate of some of the sources. The feedback about the queue length or the total workload is provided at regular intervals
(variations on it, especially the traffic management specification TM 4.0, are also considered). The propagation delays can
be nonnegligible. For a general class of feedback algorithms, we obtain the stability of the system in the presence of one
or more bottleneck nodes in the virtual circuit. Our system is general enough that it can be useful to study feedback control
in other network protocols. We also obtain rates of convergence to the stationary distributions and finiteness of moments.
For the single botterneck case, we provide algorithms to compute the stationary distributions and the moments of the sojourn
times in different sets of states. We also show analytically (by showing continuity of stationary distributions and moments)
that for small propagation delays, we can provide feedback algorithms which have higher mean throughput, lower probability
of overflow and lower delay jitter than any open loop policy. Finally these results are supplemented by some computational
results.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献