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排序方式: 共有164条查询结果,搜索用时 15 毫秒
41.
Ahmed MK Geetha R Pandey NK Murugesan S Koganti SB Saha B Sahoo P Sundararajan MK 《Talanta》2000,52(5):885-892
A simple but accurate method has been developed for the determination of carbon in uranium carbide powders/pellets as well as in solutions of uranyl nitrates. The methodology involves quantitative conversion of carbon present in the sample to carbon dioxide that is subsequently absorbed in a dilute solution of barium hydroxide. The conductivity shift of the barium hydroxide solution is monitored on-line continuously using a laboratory-built PC-based conductivity measurement system that has been developed in-house based on the direct conversion of conductance to the digital pulse frequency. A new gas absorption cell has been designed to ensure quantitative absorption during the residence time of the gas in the cell. The method is sensitive, accurate and precise to 1-3% at 600-1000 mug of carbon in samples of uranium carbide. 相似文献
42.
Wei-Sheng Huang Yihan Wang Raji Sundaramoorthi R. Mathew Thomas David Wen Shuangying Liu Scott P. Lentini Sasmita Das Geetha Banda Tomi K. Sawyer William C. Shakespeare 《Tetrahedron letters》2007,48(41):7388-7391
The first example of a Heck reaction with 9-vinylpurines and aryl halides is described. It gives exclusively E-9-(arenethenyl)purines in high yields. Subsequent hydrogenation furnishes 9-(arenethyl)purines quantitatively. 相似文献
43.
Saijyothi AV Angayarkanni N Syama C Utpal T Shweta A Bhaskar S Geetha IK Vinay PS Thennarasu M Sivakumar RM Prema P 《Electrophoresis》2010,31(20):3420-3427
Tear proteomics, by 2-DE, can give a fingerprint of the protein profile, which is well suited in clinical proteomics for biomarker identification and in diagnostics. The mode of tear collection can influence the representation of the proteins in the tear and therefore it is important to use the appropriate method. In this study, capillary and Schirmer mode of tear collection was done in the healthy controls and the Schirmer method was validated in dry eye syndrome conditions. 2-D PAGE of normal and dry eye tear was performed using pH 3-10 linear IPG strips followed by 13% SDS-PAGE. The spot intensity was analyzed by the PD quest software. The two methods were compared using Bland-Altman statistical tool. The 2-D map of capillary and Schirmer tear showed 147 ± 8 spots and 145 ± 7 spots respectively. Both the collection methods were in agreement with each other and were comparable. Dry eye tear protein showed differential expression of proteins as observed in 25-35 kDa region. One of the significantly reduced protein was identified as proline-rich 4 protein. Schirmer method of tear collection is reliable in patients with dry eye, which can display the differential protein expression and help in biomarker identification. 相似文献
44.
Effect of Atomic‐Scale Differences on the Self‐Assembly of Thiophene‐based Polycatenars in Liquid Crystalline and Organogel States
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Balaram Pradhan V. M. Vaisakh Dr. Geetha G. Nair Dr. D. S. Shankar Rao Dr. S. Krishna Prasad Dr. Achalkumar Ammathnadu Sudhakar 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(49):17843-17856
Two series of polycatenars are reported that contain a central thiophene moiety connected to two substituted oxadiazole or thiadiazole units. The number, position, and length of the peripheral chains connected to these molecules were varied. The oxadiazole‐based polycatenars exhibited columnar phases with rectangular and hexagonal or oblique symmetry, whereas the thiadiazole‐based polycatenars exhibited columnar phases with rectangular and/or hexagonal symmetry. All of the compounds exhibited bright emission in the solution and thin‐film states. Two oxadiazole‐based molecules and one thiadiazole‐based molecule exhibited supergelation ability in hydrocarbon solvents, which is mainly supported by attractive π–π interactions. These gels showed aggregation‐induced enhanced emission, which is of high technological importance for applications in solid‐state emissive displays. X‐ray diffraction studies of the xerogel fibers of oxadiazole‐based polycatenars revealed a columnar rectangular organization, whereas a hexagonal columnar arrangement was observed for thiadiazole‐based polycatenars. Rheological measurements carried out on the samples quantitatively confirmed the formation of gels and showed that these gels are mechanically robust. The impact of an atomic‐scale difference (oxygen to sulfur, <2 % of the molecular weight) on the self‐assembly and the macroscopic properties of those self‐assembled structures are clearly visualized. 相似文献
45.
S. Swetha S. M. Santhosh R. Geetha Balakrishna 《Photochemistry and photobiology》2010,86(5):1127-1134
Photocatalyst-mediated inactivations generate reactive oxygen species and OH radicals, which induce oxidative destruction of membrane integrity, causing damage to membrane phospholipids of gram negative bacteria like Pseudomonas aeruginosa. Nanosized TiO2 was synthesized by gel to crystalline conversion and Zr-doped TiO2 was synthesized by pulverization using appropriate precursor. The doped nanocrystals retained the anatase phase with a marginal increase in crystallite size, averaging at 25 nm. SEM–EDX analysis of the doped sample depicts the substantial growth of grain size with 1.33 atomic weight % of zirconium. The created electron states in the doped sample act as charge carrier traps suppressing recombination which later detraps the same to the surface of the catalyst causing enhanced interfacial charge transfer. Zr-doped TiO2 at the molecular scale exhibits better photocatalytic activity with lower bandgap energy that can respond to visible light. The redshift caused by the dopants in absorption spectra of TiO2 facilitated the nonintrinsic sample to exhibit nearly 2-fold enhancement of photoinactivation in sunlight. Extent of photoinactivation of P. aeruginosa was observed to be complete (100%) within 150 min of sunlight exposure in the presence of modified TiO2. 相似文献
46.
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
47.
V. Kabaleeswaran S. S. Rajan Geetha Gopalakrishnan G. Suresh T. R. Govindachari 《Journal of chemical crystallography》1997,27(12):731-733
The crystal structure of nimbin has been determined. The crystals are orthorhombic, space groupP212121 witha=6.790(2),b=14.875(4),c=27.160(8) Å andZ=4. The packing of the molecules in the lattice is due to C?H…O type of hydrogen bonds. 相似文献
48.
S. Krishna Prasad K. L. Sandhya Geetha G. Nair Uma S. Hiremath C. V. Yelamaggad S. Sampath 《Liquid crystals》2006,33(10):1121-1125
The behaviour of the anisotropic electrical conductivity of liquid crystal-gold nanoparticle (LC-GNP) composites consisting of a commercially available room temperature nematic compound doped with alkylthiol-capped GNPs has been investigated. The nematic-isotropic transition of the composite decreases nearly linearly with increasing X, the concentration of GNP (in weight %) at a rate of about 1°C /weight %. The inclusion of GNPs increases the electrical conductivity of the system with the value increasing by more than two orders of magnitude for X = 5%. However, the anisotropy in conductivity, defined as the ratio of the conductivity along (σ∥) and orthogonal (σ⊥) to the director shows a much smaller but definite decrease as X increases. 相似文献
49.
Nikoleta Theodoropoulou Vinith Misra John Philip Patrick LeClair Geetha P. Berera Jagadeesh S. Moodera Biswarup Satpati Tapobrata Som 《Journal of magnetism and magnetic materials》2006,300(2):407-411
Clear evidence of ferromagnetic behavior at temperatures >400 K as well as spin polarization of the charge carriers have been observed in Zn1−xMnxO thin films grown on Al2O3 and MgO substrates. The magnetic properties depended on the exact Mn concentration and the growth parameters. In well-characterized single-phase films, the magnetic moment is 4.8 μB/Mn at 350 K, the highest moment yet reported for any Mn doped magnetic semiconductor. Anomalous Hall effect shows that the charge carriers (electrons) are spin-polarized and participate in the observed ferromagnetic behavior. 相似文献
50.
Graphite-furnace atomic absorption spectrometry is used to analyze sodium metal after conversion to sodium nitrate. Chromium, Ni, Co, Cd and Pb have detection limits in sodium of 0.18, 0.48, 0.11, 0.02 and 0.48 μg g-1; these are similar to the concentrations in nuclear-grade sodium, except for lead, which is below the detection limit. The behaviour of sodium nitrate, chloride and sulphate as matrices is compared. 相似文献