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51.
Kamlakar Avasthi Sangeeta Aswal Prakas R. Maulik 《Acta Crystallographica. Section C, Structural Chemistry》2001,57(11):1324-1325
In the crystal structure of 1,1′-(1,3-propanediyl)bis(5-ethyl-6-methylthio-4,5-dihydro-1H-pyrazolo[3,4-d]pyrimidin-4-one), C19H24N8O2S2, the pairs of pyrazolo[3,4-d]pyrimidine rings of the molecule stack between the heterocyclic rings, due to intramolecular π–π interactions. The substituted ethyl and methyl groups are comparable as far as intramolecular stacking is concerned. 相似文献
52.
53.
Ajay Singh D.K. Aswal N. Padma Y. Babu C.S. Viswanadham S.K. Gupta 《Solid State Communications》2006,138(9):430-435
We have investigated magnetoresistance (MR) and electroresistance (ER) of well characterized La0.6Pb0.4MnO3 (LPMO) films having two different crystallinity (i) (00l) oriented single-crystalline, SC, i.e. without any grain boundaries, and (ii) nanocrystalline, NC, with an average grain size of 17 nm. Both MR and ER were remarkably different for the two films, that is, (i) NC films exhibited a highest MR of ∼100% near the metal-insulator transition temperature; while for SC films the MR was in the range of 40-60%, (ii) NC films exhibited a finite ER, which increased monotonically with decreasing temperature; while in SC films ER was completely absent. Using current-voltage characteristic and ferromagnetic resonance studies we demonstrate that both enhanced MR and ER in NC films are extrinsic in nature and originate due to the presence of spin glassy grain boundaries. 相似文献
54.
We demonstrate that chaos can be controlled using multiplicative exponential feedback control. Unstable fixed points, unstable
limit cycles and unstable chaotic trajectories can all be stabilized using such control which is effective both for maps and
flows. The control is of particular significance for systems with several degrees of freedom, as knowledge of only one variable
on the desired unstable orbit is sufficient to settle the system onto that orbit. We find in all cases that the transient
time is a decreasing function of the stiffness of control. But increasing the stiffness beyond an optimum value can increase
the transient time. We have also used such a mechanism to control spatiotemporal chaos is a well-known coupled map lattice
model. 相似文献
55.
We review the subject of control of chaotic systems paying special attention to exponential control. We also discuss the application
of synchronization of chaotic systems to security in communications. 相似文献
56.
PEO—PPO—PEO triblock copolymer P85 [(EO)26(PO)39(EO)26] dissolves as unimers and detergent sodium dodecyl sulfate (SDS) forms micelles in aqueous solution at 20°C. The mixing of
detergent with triblock copolymer induces the micellization of triblock copolymers. Contrast variation small-angle neutron
scattering measurements show that triblock copolymer forms mixed micelles with detergent and the mixing of two components
in the mixed micelles is uniform. 相似文献
57.
Sangeeta Sahoo 《Journal of Physics and Chemistry of Solids》2003,64(2):361-366
Ge clusters are grown on Si substrate at room temperature (Ge-RT) and also at liquid nitrogen temperature (Ge-LNT) by cluster evaporation technique. These clusters show blue luminescence. Raman measurement demonstrates the increase in strain with annealing in diffused disordered Si at the interface between Ge-LNT clusters and Si substrate. This manifests in strain-relaxation in the clusters as observed by Photoluminescence (PL) measurements. The decrease in PL intensity for Ge-RT with annealing has been attributed to reduction in surface oxide species, which is supported by Raman spectroscopic measurements. The objective of the paper is to understand the effect of thermal annealing on both interfacial strain and interdiffusion of elemental Si at the interface, together with luminescence characteristics of the clusters. 相似文献
58.
A series of bifunctional chelates containing a tridentate donor set for complexation of the M(CO)3+ core and a maleimide group for site-specific coupling to peptides and proteins containing free thiol groups has been prepared and their Re(CO)3+ complexes and glutathione conjugates structurally characterized. The flexibility of design allows preparation of ligands suitable for both fluorescence imaging, radioimaging and radiotherapeutic studies of proteins and peptides as well as other biopolymers using site specific conjugation. 相似文献
59.
Biswaranjan Mohanty V. K. Aswal J. Kohlbrecher H. B. Bohidar 《Journal of Polymer Science.Polymer Physics》2006,44(12):1653-1667
Length scale hierarchy in gelatin sol, gel, and coacervate (induced by ethanol) phases, having same concentration of gelatin in aqueous medium (13% w/v), has been investigated through small angle neutron scattering and rheology measurements. The static structure factor profile, I(q) versus wave vector q, was found to be remarkably similar for all these samples. This data could be split into three distinct q‐regimes: the low‐q regime, Iex(q) = Iex(0)/(1+q2ζ2)2 valid for q < 3Rg?1; the intermediate q‐regime, I(q) = I(0)/(1+q2ξ2) for 3Rg?1 < q < ξ?1; and the asymptotic regime, I(q) = (c/q) exp(?Rc2q2/2) for q > ξ?1. Consequently, three distinct length scales could be deduced from structure factor data: (a) inhomogeneity of size, ζ = 20 ± 1 nm for all the three phases; (b) average mesh size, ξ0 = 2.6 ± 0.2 nm for sol and gel, and smaller mesh size, ξos = 1.2 ± 0.2 nm for coacervate; and (c) cross section of gelatin chains, Rc = 0.35 ± 0.04 nm. In addition, the structure factor data obtained from coacervating solution analyzed in the Guinier region, I(q) = exp(?q2Rg2/3), yielded value of typical radius of gyration of clusters, Rg ≈ 69 nm that indicated existence of triple‐helices of length, L ≈ 239 nm; (d) Frequency and temperature sweep measurements conducted on coacervate samples revealed two other length scales: (e) viscoelastic length, ξve = 14 ± 2 nm and (f) correlation length at melting, ξT = 500 ± 70 nm. Thus, existence of six distinct length scales, (a–f), ranging from 1.2 to 500 nm has been established in the coacervate phase of gelatin–ethanol–water system. Results are discussed within the framework of Landau‐Ginzburg treatment of dynamically asymmetric systems (Prog Theor Phys 1977, 57, 826; Phys Rev A 1991, 44, R817; J Phys II (France) 1992, 2, 1631). © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 1653–1667, 2006 相似文献
60.
Sangeeta Dhingra A.K. Srivastava Vinod Dhingra 《Journal of Saudi Chemical Society》2010,14(2):213-215
Synthesis and antiAIDS, anticancer, antitubercular, fungicidal and antibacterial activities of 2-methyl-4-N-2′-cyanoethyl-N-methane/benzenesulphonylaminobenzaldehyde and their hydrazones are reported. 相似文献