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101.
Suraj Chandra Sharma Rekha Goswami Shrestha Lok Kumar Shrestha Kenji Aramaki 《Colloid and polymer science》2008,286(14-15):1613-1619
Rheological behavior of viscoelastic wormlike micelles in an aqueous system of mixed sodium dodecyl trioxyethylene sulfate (SDES)–monolaurin (ML) is presented. Dilute aqueous solution of SDES has a high fluidity and follows Newtonian liquid-like behavior due to formation of small globular type of micellar structure. Addition of lipophilic nonionic cosurfactant ML to dilute or semidilute solution of SDES decreases the interfacial curvature of the aggregates favoring one dimensional micellar growth, and hence, viscosity increases. After a certain concentration of ML, the elongated micelles get entangled with each other leading to the formation of viscoelastic wormlike micelles. The viscoelastic solution follows Maxwell model of a single stress relaxation mode at low-frequency region. Further addition of ML decreases the viscosity of the solution due to formation of micellar joints in the network structure. The viscosity of the viscoelastic wormlike micelles decreases upon heating, and the system with poor viscoelastic character is observed at higher temperatures. 相似文献
102.
Spin, charge, and orbital orderings are influenced by electron/hole doping, cation radii, oxygen stoichiometry, temperature, magnetic field, and so on. In order to understand the role of electron/hole doping, we have studied variations in spin, charge, and orbital ordering in terms of d-band filling for YBaT 2O 5 (T = Mn, Fe, Co). The calculations were performed using density functional theory as implemented in the full-potential linearized augmented-plane-wave method. We have carried out calculations for nonmagnetic, ferromagnetic, and antiferromagnetic configurations. A ferrimagnetic ground state was established for YBaMn 2O 5, whereas YBaFe 2O 5 and YBaCo 2O 5 have antiferromagnetic ground states; all of these results are in agreement with experimental findings. The effects of spin-orbit coupling, the Hubbard U parameter, and orbital polarization on the magnetic properties were also analyzed. The electronic band characteristics were analyzed using total as well as site- and orbital-projected densities of states. Inclusion of spin-orbit coupling and Coulomb correlation effects in the calculations was found to be important in order to reproduce the experimentally established semiconducting behaviors of YBaFe 2O 5 and YBaCo 2O 5. In order to quantify the charges at each atomic site, we made use of the Bader "atom-in-molecule" concept and Born effective-charge (BEC) analyses. The structural optimizations and BEC tensor calculations were performed using the VASP-PAW method. The different types of charge and orbital orderings in these compounds were visualized using the energy-projected density matrices of the d electrons. Substantial differences in ordering patterns with respect to d-band filling emerged. Ordering of the d z (2) orbital of Mn in YBaMn 2O 5 gave rise to G-type ferrimagnetic spin ordering along the c direction and checkerboard-type charge ordering, whereas ordering of the d x (2) - y (2) orbital of Fe in YBaFe 2O 5 caused Wollan-Koehler G-type antiferromagnetic spin ordering along the b direction and stripe-type charge ordering. Similarly, a complex pattern of orbital ordering in YBaCo 2O 5 activated spin and charge orderings similar to those in YBaFe 2O 5. 相似文献
103.
The aim of the paper is to investigate the propagation of a pulse in a micropolar fluid contained in a visco-elastic membrane. It was undertaken with a view to study how closely we can approximate the flow of blood in arteries by the above model. We find that for large Reynolds number, the effect of micropolarity is hardly perceptible, whereas for small Reynolds numbers it is of considerable importance. 相似文献
104.
Suraj P. Narula Sukhjeevan Kaur Surinder K. Sharma David C. Povey 《Journal of chemical crystallography》1992,22(2):139-143
Reaction of 1,4-dimethylpyridinium chlorosulphite with anhydrous copper(II) chloride in an atmosphere of dry nitrogen yields an ionic complex containing discrete [CuCl4]2– anions and 1,4-dimethylpyridinium cations. Electronic (solid and in solution), far infrared and1H NMR spectral data predict a distortedT
d
structure which has been confirmed by X-ray crystallography. The crystal structure was solved by the heavy-atom method and refined by full-matrix least squares toR=0.059 for 1685 observed reflections. The [CuCl4]2– anions exhibit twofold symmetry and there are no unusual interactions with the cations. Bond lengths and angles place it in the select class of complexes with the least flattenedT
d
structure. 相似文献
105.
106.
Vibha Gautam Veera Babu KagitaSudhir Nambiar Gutala PhaneendraSulur G. Manjunatha Sridharan RamasubramanianM. Suresh Babu Jaikumar KeshwanSagar Bhagat Ravindran PrakashRamachandra Puranik 《Tetrahedron letters》2014
A simple synthetic approach has been developed towards one pot synthesis of 2-imidazolines under mild acidic conditions from N-acetyl glucosamine via reductive amination followed by dehydrative cyclization. Synthetic studies were explored in detail with different amines and sugar derivatives. While the conversion was good, the corresponding substituted imidazolines were obtained in moderate yields. 相似文献
107.
G. Madhurambal B. Ravindran M. Mariappan S. C. Mojumdar 《Journal of Thermal Analysis and Calorimetry》2012,108(3):911-914
Single crystal of bisthiourea iron(II) sulphate was grown by slow evaporation technique at 303?K. The structural properties of the grown crystals were characterized by FTIR spectroscopy, UV spectroscopy and powder X-ray diffraction. FTIR and UV spectra provide information about the presence of functional groups. Thermal analysis confirms the crystal is thermally stable up to 167.02?°C. 相似文献
108.
Saprativ P. Das Rajeev Ravindran Shadab Ahmed Debasish Das Dinesh Goyal Carlos M. G. A. Fontes Arun Goyal 《Applied biochemistry and biotechnology》2012,167(6):1475-1488
The enhancement of the biomass productivity of Escherichia coli cells harbouring the truncated 903?bp gene designated as glycoside hydrolase family 43 (GH43) from Clostridium thermocellum showing hemicellulase activity along with its further use in simultaneous saccharification and fermentation (SSF) process is described. (Phosphoric acid) H3PO4?Cacetone treatment and ammonia fibre expansion (AFEX) were the pretreatment strategies employed on the leafy biomass of mango, poplar, neem and asoka among various substrates owing to their high hemicellulose content. GH43 showed optimal activity at a temperature of 50?°C, pH?5.4 with stability over a pH range of 5.0?C6.2. A 4-fold escalation in growth of the recombinant E. coli cells was observed when grown using repeated batch strategy in LB medium supplemented with glucose as co-substrate. Candida shehatae utilizing pentose sugars was employed for bioethanol production. AFEX pretreatment proved to be better over acid?Cacetone technique. The maximum ethanol concentration (1.44?g/L) was achieved for AFEX pretreated mango (1%, w/v) followed by poplar with an ethanol titre (1.32?g/L) in shake flask experiments. A 1.5-fold increase in ethanol titre (2.11?g/L) was achieved with mango (1%, w/v) in a SSF process using a table top 2-L bioreactor with 1?L working volume. 相似文献
109.
Rekha?Goswami?ShresthaEmail author Suraj?Chandra?Sharma Kenichi?Sakai Hideki?Sakai Masahiko?Abe 《Colloid and polymer science》2012,290(4):339-348
Formation of wormlike micelles (WLMs) in an aqueous mixture of polyoxyethylene cholesteryl ether (ChEOn; where n = 20 and 30) and polyoxyethylene dodecyl ether (C12EOm; where m = 3 and 4) has been reported; rheological and small angle X-ray scattering (SAXS) measurements have been performed in the
micellar solutions of ChEOn as a function of C12EOm for the structural elucidation. When lipophilic cosurfactant, C12EOm is added to the micellar solutions of ChEOn, it favors the sphere-to-cylinder transition due to the penetration of C12EOm in the palisade layer of ChEOn micelle accompanying an increase in viscosity. When the concentration of C12EOm is increased, entangled network of WLMs is formed. A strong shear thinning has been observed in highly viscous samples indicating
the presence of transient networks. Such samples exhibited viscoelastic behavior and could be described by the Maxwell model
with a single stress relaxation mode. A maximum is observed in zero-shear viscosity-C12EOm plot. With further addition of C12EOm, viscosity declines and ultimately a phase separation occurs with the formation of turbid solution of vesicular dispersion.
This decline has been interpreted in terms of micellar branching induced by an increase in endcap energy, E
c (which is compensated by the formation of branch points, having a mean curvature opposite to that of endcaps). The C12EOm induced one-dimensional micellar growth has been confirmed by SAXS. 相似文献
110.
M. Premila S. Abhaya R. Rajaraman T.R. Ravindran G. Amarendra C.S. Sundar 《Journal of Non》2012,358(6-7):1014-1018
Iron phosphate glasses have been investigated using positron lifetime and micro Raman spectroscopy to study the crystallization kinetics and defect evolution across the glass and crystallization transitions. Positron lifetime parameters show distinct changes at temperatures corresponding to both the transitions. These changes have been understood as the signature of the evolution of open volume defects and their clustering across the amorphous to crystalline interfaces. Micro Raman measurements on annealed samples have identified the crystalline phases as Fe3(P2O7)2 and FePO4. Ab-initio positron lifetime computations reveal that the positron probes the Fe/P sites in defect free crystals. The nature of open volume defects produced upon annealing is identified by computing positron lifetimes for various possible defect clusters. A combination of both experimental and theoretical techniques has provided insights in understanding the evolution of defects across the phase transition in these glasses. 相似文献