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91.
The elemental and isotopic composition of Ne, Ar, Kr and Xe were measured in the bulk soil samples obtained from Luna 16 and
20 missions. The average cosmic ray exposure ages for the Luna 16 soils is higher than that of Luna 20 soils. The trapped
solar wind composition is deduced by correcting for the cosmogenic component and is found to be in good agreement with the
values published by others. The correlation between the solar wind gases and cosmic ray tracks in lunar samples is quantitatively
studied and some systematic features regarding lunar regolith dynamics are tentatively established. 相似文献
92.
A new modified electrode is fabricated by dispersing gold nanoparticles onto the matrix of poly(3,4-ethylenedioxythiophene)–poly(styrene sulfonic acid), PEDOT–PSS. The electrocatalytic activity of the PEDOT–PSS-Aunano electrode towards the oxidation of β-nicotinamide adenine dinucleotide (NADH) is investigated. A substantial decrease in the overpotential (>0.7 V) has been observed for the oxidation of NADH at the PEDOT–PSS-Aunano electrode in comparison to the potential at PEDOT–PSS electrode. The Au nanoparticles dispersed in the PEDOT–PSS matrix prevents the fouling of electrode surface by the oxidation products of NADH and augments the oxidation of NADH at a less positive potential (+0.04 V vs. SCE). The electrode shows high sensitivity to the electrocatalytic oxidation of NADH. Further, the presence of ascorbic acid and uric acid does not interfere during the detection of NADH. Important practical advantages such as stability of the electrode (retains 95% of its original activity after 20 days), reproducibility of the measurements (R.S.D.: 2.8%; n = 5), selectivity and wide linear dynamic range (1–80 μM; R2 = 0.996) are achieved at PEDOT–PSS-Aunano electrode. The ability of PEDOT–PSS-Aunano electrode to promote the electron transfer between NADH and the electrode makes us to fabricate a biocompatible dehydrogenase-based biosensor for the measurement of ethanol. The biosensor showed high sensitivity to ethanol with rapid detection, good reproducibility and excellent stability. 相似文献
93.
Surface-anchored poly(2-vinyl-4,4-dimethyl azlactone) brushes as templates for enzyme immobilization
Cullen SP Mandel IC Gopalan P 《Langmuir : the ACS journal of surfaces and colloids》2008,24(23):13701-13709
We explored surface-anchored poly(2-vinyl-4,4-dimethyl azlactone) (PVDMA) brushes as potential templates for protein immobilization. The brushes were grown using atom transfer radical polymerization from surface-anchored initiators and characterized by a combination of ellipsometry, atomic force microscopy, and X-ray photoelectron spectroscopy. RNase A was immobilized as a model enzyme through the nucleophilic attack of azlactone by the amine groups in the lysines located in the protein. The surface density of RNase A increased linearly from 5 to 50 nm. For 50 nm thick poly(2-vinyl-4,4-dimethyl azlactone) brushes, 7.5 microg/cm2 of RNase A was bound. The kinetics and thermodynamics of RNase A immobilization, the activity relative to surface density, and the pH and temperature dependence were examined. A Langmuir-like model for binding kinetics indicates that the kinetics are controlled by the rate of adsorption of RNase A and has an adsorption rate constant, k(ads), of 2.8 x 10(-8) microg(-1) s(-1) cm3. A maximum relative activity of approximately 0.95, which is near the activity of free RNase A, was reached at 1.2 microg/cm2 (approximately 3.0 monolayers) of immobilized RNase A. The immobilized RNase A had a similar temperature and pH dependence as free RNase A, indicating no significant change in conformation. The PVDMA template was extended to other biotechnologically relevant enzymes, such as deoxyribonuclease I, glucose oxidase, glucoamylase, and trypsin, with relative activities higher than or comparable to those of enzymes immobilized by other means. PVDMA brushes offer an efficient route to immobilize proteins via the ring opening of azlactone without the need for activation or pretreatment while retaining high relative activities of the bound enzymes. 相似文献
94.
Rajaraman Vasanthi Dharmalingan Kalpana Nedumaram Gopalan Renganathan 《Journal of Solid State Electrochemistry》2008,12(7-8):961-969
LiCoPO4 nanoparticles were precipitated from polyethylene glycol solution of lithium acetate, cobalt acetate, and ammonium dihydrogen phosphate by refluxing at 250 °C for 35 h. The resultant powder samples were heated at 800 °C for different time periods of 2 and 4 h to study the effect of annealing time on the growth of samples. The X-ray diffraction pattern of the obtained samples exhibited olivine phase. The scanning electron microscopic images of dried powder sample and samples heated at 800 °C for 2 and 4 h showed a homogenous orthorhombic morphology with a particle size of few nanometers range. For the first time, orthorhombic olivine was introduced as positive electrode for a hybrid electrochemical supercapacitor cell with carbon nanofoam as negative electrode in 1 M LiClO4 in ethylene carbonate and propylene carbonate (1:1 in volume) solution. A sloping voltage profile of 2 to 0 V is observed for all the three hybrid cells. From the impedance results, we inferred that LiCoPO4 nanoparticles synthesized by polyol process offers less resistance than lithium titanium oxide. According to the results of electrochemical testing for the first time, maximum power density of 192 W/kg at 11 Wh/kg energy density was obtained for LiCoPO4 nanoparticles annealed at 800 °C for 2 h. The dried sample and the sample heated at 800 °C for 2 and 4 h exhibited high capacitances of 5, 19, and 4 F/g, respectively, with an excellent rate capability over 1,000 cycles. 相似文献
95.
Tarek Aboul‐Fadl Gopalan Rajeev Arthur D. Broom 《Journal of heterocyclic chemistry》2008,45(2):445-451
96.
Dr. Man‐Rong Li Maria Retuerto Prof. Peter W. Stephens Prof. Mark Croft Dr. Denis Sheptyakov Vladimir Pomjakushin Zheng Deng Dr. Hirofumi Akamatsu Venkatraman Gopalan Dr. Javier Sánchez‐Benítez Felix O. Saouma Prof. Joon I. Jang Prof. David Walker Prof. Martha Greenblatt 《Angewandte Chemie (International ed. in English)》2016,55(34)
97.
N-Alkyl-N-benzyloxy carbamates, 2, undergo facile intramolecular cyclization with a variety of carbon nucleophiles to give functionalized five- and six-membered protected cyclic hydroxamic acids, 3, in good to excellent yields. This method can be extended to prepare seven-membered cyclic hydroxamic acids in moderate yields. The sulfone intermediates 3 from this study can be alkylated while the corresponding phosphonates have been shown to undergo HWE reaction. The α,β-unsaturated synthon, 8, prepared by thermal elimination of sulfoxide 3m, undergoes Michael addition with secondary amines. The usefulness of this approach to prepare polydentate chelators has been demonstrated by the synthesis of bis cyclic hydroxamic acids 12, 14, and 15. 相似文献
98.
Sundararajan M Rajaraman G Ghosh SK 《Physical chemistry chemical physics : PCCP》2011,13(40):18038-18046
The speciation of uranyl ions in fulvic acid (FA) and humic acid (HA), based on models of larger sizes, is systematically studied using density functional theory (DFT). Four uranyl binding sites are suggested for FA and based on their energetics, the preferential binding sites are proposed. The computed binding sites include two chelating types, one through the carboxylate group and one via the hydroxo group. A systematic way to attain the possible structure for Stevenson's HA model is carried out using a combined molecular dynamics (MD) and quantum chemical approach. Calculated structures and energetics reveal many interesting features such as conformational flexibility of HA and binding of hydrophobic molecules in agreement with the experimental suggestions. Five potential binding sites are proposed for uranyl binding to HA and the calculated geometries correlate nicely with the experimental observations. Our binding energy calculations reveal that apart from uranyl binding at the carboxylate functional group, binding at other functional groups such as those involving quinone and hydroxo sites are also possible. Finally, based on our cluster calculations the strength of uranyl binding to HAs and FAs is largely influenced by neighbouring groups via hydrogen bonding interactions. 相似文献
99.
Nelly Berg Thayalan Rajeshkumar Stephanie M. Taylor Prof. Euan K. Brechin Dr. Gopalan Rajaraman Dr. Leigh F. Jones 《Chemistry (Weinheim an der Bergstrasse, Germany)》2012,18(19):5906-5918
The synthesis and magnetic characterisation of a series of bis‐μ‐alkoxide bridged MnIII dinuclear complexes of general formula [MnIII2(μ‐OR)2(biphen)2(ROH)x(L)y] (where R=Me, Et; H2biphen=2,2′‐biphenol and L=terminally bonded N‐donor ligand) is described, doubling the literature basis set for this type of complex. Building on these findings we have categorised all known μ‐OR bridged MnIII dinuclear complexes into one of three classifications with respect to their molecular structures. We have then employed DFT and MO calculations to assess all potential magneto‐structural correlations for this class of compound in order to identify the structural requirements for constructing ferromagnetic family members. Our analysis indicates that the most influential parameter which governs the exchange interaction in this class of compounds is the relative orientation of the JT axes of the MnIII atoms. A perpendicular orientation of the JT axes leads to a large ferromagnetic contribution to the exchange. These results also suggest that a large ferromagnetic interaction and a large anisotropy are unlikely to co‐exist in such structural types. 相似文献
100.
Kwang-Pill Lee Se-Hee Lee Komathi Shanmuga Sundaram Gopalan Anantha Iyengar 《Radiation Physics and Chemistry》2012,81(9):1422-1425
New multiwalled carbon nanotube/silica supported cobalt-palladium bimetallic nanocatalysts (MWNT@silica/Co–Pd NPs) were prepared by a simple one step gamma irradiation method. The method involves the in-situ surface modification of MWNT with silica (MWNT@silica) and simultaneous formation of Co–Pd bimetallic NPs using gamma irradiation. The bimetallic NPs were stabilized by silica particles formed over the surface of MWNT. Extensive characterization studies have been performed on structural, morphological, and electrochemical, aspects of MWNT@silica/Co–Pd NPs. MWNT@silica/Co–Pd NPs were characterized by field emission scanning microscopy (FESEM), UV–visible spectroscopy, X-ray diffraction (XRD), thermogravimetric analysis (TGA), and Raman spectroscopy. The influence of irradiation dosage levels on the stabilizing effect of silica particles has been studied. The electrolytic activities of the MWNT@silica/Co–Pd NPs were investigated by cyclic voltammetry. 相似文献