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51.
Arvind Saxena Prashant Kumar Swaroop Banerjee K. P. Subramanian Bhas Bapat 《光谱学快报》2014,47(2):114-118
A hollow cathode sputter source is developed to trace the production of carbon clusters and study the influence of discharge current and argon gas pressure on cluster production using an optical emission spectroscopic technique. Optical emission spectra from the hollow cathode source reveal the production of the C2 Swan band. The sputter source is optimized for the maximum carbon cluster yield. The vibrational temperature analysis of the C2 cluster is carried out using the Boltzmann plot method. The dependence of vibrational temperature on argon gas pressure is discussed and the dominant method for C-C association in the glow discharge is suggested. 相似文献
52.
Subramanian S Devasahayam N McMillan A Matsumoto S Munasinghe JP Saito K Mitchell JB Chandramouli GV Krishna MC 《Journal of magnetic resonance (San Diego, Calif. : 1997)》2012,214(1):244-251
Oxygen maps derived from electron paramagnetic resonance spectral-spatial imaging (EPRI) are based upon the relaxivity of molecular oxygen with paramagnetic spin probes. This technique can be combined with MRI to facilitate mapping of pO(2) values in specific anatomic locations with high precision. The co-registration procedure, which matches the physical and digital dimensions of EPR and MR images, may present the pO(2) map at the higher MRI resolution, exaggerating the spatial resolution of oxygen, making it difficult to precisely distinguish hypoxic regions from normoxic regions. The latter distinction is critical in monitoring the treatment of cancer by radiation and chemotherapy, since it is well-established that hypoxic regions are three or four times more resistant to treatment compared to normoxic regions. The aim of this article is to describe pO(2) maps based on the intrinsic resolution of EPRI. A spectral parameter that affects the intrinsic spatial resolution of EPRI is the full width at half maximum (FWHM) height of the gradient-free EPR absorption line in frequency-encoded imaging. In single point imaging too, the transverse relaxation times (T(2)(?)) limit the resolution since the signal decays by exp(-t(p)/T(2)(?)) where the delay time after excitation pulse, t(p), is related to the resolution. Although the spin densities of two point objects may be resolved at this separation, it is inadequate to evaluate quantitative changes of pO(2) levels since the linewidths are proportionately affected by pO(2). A spatial separation of at least twice this resolution is necessary to correctly identify a change in pO(2) level. In addition, the pO(2) values are blurred by uncertainties arising from spectral dimensions. Blurring due to noise and low resolution modulates the pO(2) levels at the boundaries of hypoxic and normoxic regions resulting in higher apparent pO(2) levels in hypoxic regions. Therefore, specification of intrinsic resolution and pO(2) uncertainties are necessary to interpret digitally processed pO(2) illustrations. 相似文献
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54.
Archana Sivasubramaniyan Ranganathan Raja Dinesh Murugan Arul Ponnusamy Ponnuswamy Alagusundaram Kalaiselvi Patchaiah Chellammal Subbiah Subramanian Gopalan 《Research on Chemical Intermediates》2017,43(4):2471-2490
Research on Chemical Intermediates - A library of pyrazolinyltriazole hybrids (3a–l, 4a–l) was synthesized via azide–alkyne dipolar (Huisgen) cycloaddition of azidoacetyl... 相似文献
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56.
Role of aspartic acid in collagen structure and stability: A molecular dynamics investigation 总被引:3,自引:0,他引:3
Raman SS Parthasarathi R Subramanian V Ramasami T 《The journal of physical chemistry. B》2006,110(41):20678-20685
A molecular dynamics (MD) simulation study has been carried out to understand the stability of the triple helical collagen models. The calculations show that the presence of the aspartic acid residue in different positions leads to the local variation in the structure. Analyses of root-mean-square deviation (RMSD), radial distribution function (RDF), puckering effect, dihedral angle variation, hydrogen bond (H-bond), and conformational changes during molecular dynamics simulation reveal that the local perturbation in the sequences, increase in chain flexibility due to removal of five membered rings in the collagen by aspartic acid, change of intermolecular H-bonding pattern, and differences in the association of water are mainly influencing the nature of stabilization of collagen by aspartic acid. 相似文献
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58.
The thermodynamics of the complexing between hexavalent U and 1-phenyl-3-methyl-4-benzoylpyrazolone-5 (PMBP) have been studied in 70 vol% aqueous—dioxane medium at 25 and 35±0.1°C following the Bjerrum—Calvin pH titration technique, as applied by Van Uitert and Haas. The ligand is mono-protonic. The refinement of results of formation constants has been accomplished by the method of least squares treatment after an algebraic transformation. The formation of 1:1, 1:2 and 1:3 complexes has been observed, the order of stability being log K1 > log K2 > log K3. The stability invariably increases with an increase in temperature both in aqueous as well as aqueous dioxane media. The changes in ΔG0, ΔH0 and ΔS0 at 25 and 35°C for the overall equilibrium constants have also been evaluated. Uranyl complexes of PMBP are entropy stabilized, the values of enthalpy changes being positive. Other factors which affect chelate stability are briefly discussed. 相似文献
59.
60.
Monolayers of alkanethiols with varied chain lengths, CH3(CH2)nSH where n = 3, 5, and 7, on gold substrates have been prepared by adsorption from (1) neat thiol, (2) millimolar thiol solution
in alcohol (conventional method), and (3) potential-controlled adsorption. Reflection absorption infrared spectroscopy (RAIRS)
and electrochemical quartz crystal microbalance (EQCM) have been used to characterize the integrity of the monolayers. Methylene
and methyl stretching modes along with C–S stretching modes have been used as benchmarks to follow the order–disorder transitions
in the monolayer structure, in the temperature range from 25 to 175 °C. Monolayers adsorbed from neat thiol show superior
quality in terms of stability and structural arrangement. Short chain thiols with n = 3, 5, and 7 do show substantial stability.
The possibility of multilayer formation is ruled out by EQCM studies comparing the frequency and mass change associated with
the monolayer desorption. Self-assembled monolayers (SAMs) adsorbed under potential control behave very similarly to the monolayers
adsorbed from neat thiol as far as stability and structural orientation are concerned, irrespective of the chain length. The
adsorption from neat thiol gets rid of the solvent-induced defects and arrests the propagation of defects under temperature
constraints. 相似文献