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91.
S Rayaprol Krushna Mavani CM Thaker DS Rana Keka Chakravorty SK Paranjape M Ramanadham Nilesh A Kulkarni DG Kuberkar 《Pramana》2002,58(5-6):877-880
A new series of mixed oxide superconductors with the stoichiometric composition La2−x
Dy
x
Ca
y
Ba2Cu4+y
O
z
(x=0.0 − 0.5, y=2x) has been studied for structural and superconductiong properties. Our earlier studies on La2−x
(Y/Er)
x
Ca
y
Ba2Cu4+y
O
z
series, show a strong dependence of T
c on hole concentration (p
sh). In the present work, the results of the analysis of the neutron diffraction measurements at room temprerature on x=0.3 and 0.5 samples are reported. It is interesting to know that Ca substitutes for both La and Ba site with concomitant
displacement of La onto Ba site. Superconductivity studies show that maximum T
c is obtained for x=0.5, y=1.0 sample (T
c ∼ 75 K), for La1.5Dy0.5Ca1Ba2Cu5O
z
(La-2125). 相似文献
92.
Sujith Sukumaran 《Combustion Theory and Modelling》2016,20(5):913-940
A multicomponent vaporization model is integrated with detailed fuel chemistry and soot models for simulating biodiesel–diesel spray combustion. Biodiesel, a fuel mixture comprised of fatty-acid methyl esters, is an attractive alternative to diesel fuel for use in compression-ignition engines. Accurately modelling of the spray, vaporization, and combustion of the fuel mixture is critical to predicting engine performance using biodiesel. In this study, a discrete-component vaporization model was developed to simulate the vaporization of biodiesel drops. The model can predict differences in the vaporization rates of different fuel components. The model was validated by use of experimental data of the measured biodiesel drop size history and spray penetration data obtained from a constant-volume chamber. Gas phase chemical reactions were simulated using a detailed reaction mechanism that also includes PAH reactions leading to the production of soot precursors. A phenomenological multi-step soot model was utilized to predict soot emissions from biodiesel–diesel combustion. The soot model considered various steps of soot formation and destruction, such as soot inception, surface growth, coagulation, and PAH condensation, as well as oxidation by oxygen and hydroxyl-containing molecules. The overall numerical model was validated with experimental data on flame structure and soot distributions obtained from a constant-volume chamber. The model was also applied to predict combustion, soot and NOx emissions from a diesel engine using different biodiesel–diesel blends. The engine simulation results were further analysed to determine the soot emissions characteristics by use of biodiesel–diesel fuels. 相似文献
93.
Studies on the feasibility of using crystalline silicotitanates for the separation of cesium-137 from fast reactor high-level liquid waste 总被引:1,自引:0,他引:1
K. A. Venkatesan V. Sukumaran M. P. Antony T. G. Srinivasan 《Journal of Radioanalytical and Nuclear Chemistry》2009,280(1):129-136
The commercially available crystalline silicotitanate inorganic ion exchanger, IONSIV IE-911, and its parent precursor, TAM-5,
have been evaluated for the removal of 137Cs from nitric acid medium and simulated high-level liquid waste. The distribution coefficient (K
d
) of cesium decreased with increasing nitric acid concentration and at 3.0 M nitric acid, a distribution coefficient of 1150
mL/g and 2600 mL/g were obtained for IONSIV IE-911 and TAM-5, respectively. Rapid uptake of cesium followed by the establishment
of equilibrium occurring within three hours. Loading of cesium in ion exchangers increased with the increase in the concentration
of cesium in aqueous phase and from Langmuir adsorption model the apparent capacity of cesium was 69 mg/g and 82 mg/g for
IONSIV IE-911 and TAM-5, respectively. The performance of the sorbent under dynamic conditions was assessed by following a
breakthrough (BT) curve up to C/C
o
= 1, where C and C
o
are the concentrations of cesium in the effluent and feed, respectively. 相似文献
94.
95.
96.
Retro-ene type [2π + 2π + 2σ] and [3,3]-sigmatropic shift reactions involving the substituent groups R in heteroatom-substituted cyanates and thiocyanates RX-YCN and the isomeric isocyanates and isothiocyanates of the type RX-NCY (X = CR(2), NR', O, or S; Y = O or S) have been investigated computationally at the B3LYP/6-311++G(d,p) level. Retro-ene reactions of alkyl derivatives of the title compounds afford alkenes, imines, carbonyl and thiocarbonyl compounds together with HNCO (HNCS) or HOCN (HSCN). [3,3]-Sigmatropic shifts (hetero-Cope rearrangements) of the corresponding allyl, propargyl, benzyl, and aryl derivatives causes allylic rearrangements, propargyl-allenyl rearrangement, conversion of benzyl cyanates to o-isocyanatotoluenes, and conversion of N-cyanatoarylamines to o-isocyanatoanilines, etc. The corresponding rearrangements of allyl thiocyanates, arylamino thiocyanates and isothiocyanates, and arylsulfenyl thiocyanates and isothiocyanates are also described. 相似文献
97.
Aravind Madhavan Raveendran Sindhu Binod Parameswaran Rajeev K. Sukumaran Ashok Pandey 《Applied biochemistry and biotechnology》2017,183(2):636-651
Microorganisms are found throughout every corner of nature, and vast number of microorganisms is difficult to cultivate by classical microbiological techniques. The advent of metagenomics has revolutionized the field of microbial biotechnology. Metagenomics allow the recovery of genetic material directly from environmental niches without any cultivation techniques. Currently, metagenomic tools are widely employed as powerful tools to isolate and identify enzymes with novel biocatalytic activities from the uncultivable component of microbial communities. The employment of next-generation sequencing techniques for metagenomics resulted in the generation of large sequence data sets derived from various environments, such as soil, the human body and ocean water. This review article describes the state-of-the-art techniques and tools in metagenomics and discusses the potential of metagenomic approaches for the bioprospecting of industrial enzymes from various environmental samples. We also describe the unusual novel enzymes discovered via metagenomic approaches and discuss the future prospects for metagenome technologies. 相似文献
98.
Neutron scattering from equilibrium-swollen networks 总被引:1,自引:0,他引:1
Sukumaran SK Beaucage G Mark JE Viers B 《The European physical journal. E, Soft matter》2005,18(1):29-36
Small-angle neutron scattering measurements were performed on end-linked poly (dimethylsiloxane) (PDMS) networks swollen to
equilibrium with d-benzene. Comparison was made with equivalent concentration PDMS solutions. Equilibrium-swollen networks
consistently displayed a linear scattering regime at low q followed by a good-solvent-like scaling regime at high q in agreement with the predictions of the Gel Tensile Blob (GTB) model. Data are fit using the unified function modified for
the GTB model (3-parameter fit). Equilibrium-swollen networks display a base structural size, the gel tensile-blob size, ξ,
that was found to be independent of the molecular weight between crosslinks for the series of molecular weights studied, consistent
with the predictions of the model. The length of the extended tensile structure, L, can be larger than the length of the fully extended network strand. The predicted scaling relationship for L, L ∼ Q1/2Navg, where Navg = (1/fNc2+1/4Ne2
, Q is the equilibrium swelling ratio, Nc is the molecular weight between crosslinks, Ne is the entanglement molecular weight and f is the crosslink functionality is in agreement with experimental results for the networks studied. 相似文献
99.
Shashwati Sen DK Aswal Ajay Singh TV Chandrasekhar Rao KP Muthe JC Vyas LC Gupta SK Gupta VC Sahni 《Pramana》2002,58(5-6):867-870
The MgB2 superconductor, synthesized using solid-state and liquid-phase sintering methods, have been characterized for various properties.
The upper critical field, irreversibility line and critical current density have been determined using magnetization data.
The current-voltage characteristics recorded under an applied magnetic field revealed the existence of vortex glass transition.
The surface analysis using X-ray photoelectron spectroscopy shows that MgB2 is sensitive to atmospheric degradation. 相似文献
100.
K. A. Venkatesan V. Sukumaran M. P. Antony P. R. Vasudeva Rao 《Journal of Radioanalytical and Nuclear Chemistry》2004,260(3):443-450
Organic complexing moieties such as amine, 2°-amide and benzamide functional groups were covalently linked to silica gel by
performing organomodification on commercially available silica gel. The extraction of uranium as a function of pH, time, concentration
of uranium and the effect of ions such as Fe2+, Co2+, Ni2+ and CO3
2- on the distribution coefficient of uranium by sorbent was studied. The data was fitted into Langmuir adsorption isotherm.
The selectivity of the sorbents towards uranium were found to decrease in the order gel-amine >> gel-benzamide ≅ gel-2°-amide
at all pHs. The presence of metal ions such as Fe2+, Co2+, Ni2+ and CO3
2- were found to decrease the distribution coefficients (K
d, ml/g) of uranium and the decrease was very high when Fe2+ was present. The performance of the sorbent, gel-amine, under a given column condition was tested by following the breakthrough
curve of uranium up to C/C
0 = 0.025. The sorbent was found to be good for the quantitative pre-concentration of uranium from a large amount of sodium.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献