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101.
喹啉及其衍生物的多相不对称氢转移是制备杂环手性化合物的理想策略.多相手性催化体系具有催化剂可循环利用及产物分离提纯容易等优势.然而,喹啉及其衍生物的多相手性高效催化体系鲜有报道.这主要是由于多相手性氢转移为水-油-固三相反应,在反应的过程中,传质问题极大影响固体催化剂的催化性能.因此,发展具有相转移功能的手性催化材料,... 相似文献
102.
Muthuvel A. Jothibas M. Manoharan C. Jayakumar S. Johnson 《Research on Chemical Intermediates》2020,46(5):2705-2729
Research on Chemical Intermediates - In the present study, biosynthesized CeO2-NPs using Solanum nigrum leaf extract were compared with chemically synthesized one. The synthesized CeO2-NPs were... 相似文献
103.
B.B. Lahiri S. Bagavathiappan P.R. Reshmi John Philip T. Jayakumar B. Raj 《Infrared Physics & Technology》2012,55(2-3):191-199
Active (lock-in and pulsed) thermography technique is used to quantify defect features in specimens of glass fiber reinforced polymer, high density rubber, low density rubber and aluminum bonded low density rubber with artificially produced defects. The relationship between phase contrast and thermal contrast with defect features are examined. Using lock-in approach, the optimal frequencies for different specimens are determined experimentally. It is observed that with increasing defect depth, the phase contrast increases while the thermal contrast decreases. Defects with radius to depth ratio greater than 1.0 are found to be discernible. The phase difference between sound and defective region as a function of square root of excitation frequency for glass fiber reinforced polymer specimen is found to be in good agreement with the predictions of Bennet and Patty model [1]. Further, using pulsed thermography, the defects depth could be measured accurately for glass fiber reinforced polymer specimen from the thermal contrast using the analytical approach of Balageas et al. [2]. 相似文献
104.
Lead metal ions are of great concern and the monitoring of their concentration in the environment has become extremely important. In the present study, a new inorganic-organic hybrid assay of Ag nanorods (AgNR)-Rhodamine 6G (R6G) was developed for the sensitive and selective determination of Pb(2+) ions in aqueous solutions. To the best of our knowledge there is almost no literature on the use of silver nanorod sensors for determination of lead ions in aqueous solutions. The sensor is developed by the coating of R6G on the surface of AgNRs. The sensing is based on the photoluminescence of R6G. The sensor was rapid as the measurements were carried out within 3 min of addition of the test solution to the AgNR-R6G hybrid. Moreover, the system showed excellent stability at tested concentration levels of Pb(2+) ions. The naked eye detection of the colour was possible with 1 mg L(-1) of Pb(2+) ions. The present method has a detection limit of 50 μg L(-1) of Pb(2+) (for a signal/noise (S/N) ratio > 3). The selectivity toward Pb(2+) ions against other metal ions was improved using chelating agents. The proposed method was validated by analysis using different techniques. 相似文献
105.
Jayakumar Beena Divya Kontham Kulangara Varsha Kesavan Madhavan Nampoothiri 《Applied biochemistry and biotechnology》2012,167(5):1314-1324
Five newly isolated lactic acid bacteria were identified as Weissella cibaria, Enterococcus faecium, and three different strains of Lactobacillus plantarum by 16S rRNA sequencing. Essential probiotic requirements of these isolates such as tolerance to phenol, low pH, high sodium chloride, and bile salt concentration were checked. Efficiency in adherence to mucin and hydrophobicity of the bacterial cell were also evaluated by in vitro studies. Antimicrobial activities against some pathogens were tried, and the sensitivity of these strains against 25 different antibiotics was also checked. Further studies revealed Weissella and Enterococcus as substantial producers of folic acid. Folate is involved as a cofactor in many metabolic reactions, and it has to be an essential component in the human diet. The folate level in the fermented samples was determined by microbiological assay using Lactobacillus casei NCIM 2364 as indicator strain. The three strains of L. plantarum showed significant inhibitory activity against various fungi that commonly contaminate food stuffs indicating their potential as a biopreservative of food material. 相似文献
106.
M. Jayakumar K. A. Venkatesan T. G. Srinivasan P. R. Vasudeva Rao 《Journal of Radioanalytical and Nuclear Chemistry》2010,284(1):79-85
The electrochemical behavior of ruthenium(III) and rhodium(III) in nitric acid medium has been studied at platinum and stainless
steel electrodes by cyclic voltammetry. The cyclic voltammograms consisted of surge in cathodic current occurring at potentials
of −0.13 V (Vs. Pd) and −0.15 V (Vs. Pd), which culminates into peaks at −0.47 V and −0.5 V due to the reductions of Ru(III)
and Rh(III) to their metallic forms, respectively. Electrodeposition was carried out at stainless steel electrode and unlike
palladium, the recovery of ruthenium and rhodium was limited to ~4% and ~14%, respectively. However, a different scenario
was observed in case of electrodeposition from a ternary solution containing all these platinum metals. Ruthenium and rhodium
deposited underpotentially in the presence of palladium and the recovery of ~20% and ~5% was observed for ruthenium and rhodium,
respectively. Evolution of RuO4 at the anode and deposition of RuO2 in the anodic side was observed in all cases during electrolysis of ruthenium(III) containing solutions. 相似文献
107.
Hamed Ashraf M. Shabana Ahmed A. Jayakumar Paramsothy Letherwood Michael D. 《Nonlinear dynamics》2011,66(4):809-824
Existing multibody system (MBS) algorithms treat articulated system components that are not rigidly connected as separate
bodies connected by joints that are governed by nonlinear algebraic equations. As a consequence, these MBS algorithms lead
to a highly nonlinear system of coupled differential and algebraic equations. Existing finite element (FE) algorithms, on
the other hand, do not lead to a constant mesh inertia matrix in the case of arbitrarily large relative rigid body rotations.
In this paper, new FE/MBS meshes that employ linear connectivity conditions and allow for arbitrarily large rigid body displacements
between the finite elements are introduced. The large displacement FE absolute nodal coordinate formulation (ANCF) is used to obtain linear element connectivity conditions in the case of large relative rotations between the finite
elements of a mesh. It is shown in this paper that a linear formulation of pin (revolute) joints that allow for finite relative
rotations between two elements connected by the joint can be systematically obtained using ANCF finite elements. The algebraic
joint constraint equations, which can be introduced at a preprocessing stage to efficiently eliminate redundant position coordinates,
allow for deformation modes at the pin joint definition point, and therefore, this new joint formulation can be considered
as a generalization of the pin joint formulation used in rigid MBS analysis. The new pin joint deformation modes that are
the result of C
0 continuity conditions, allow for the calculations of the pin joint strains which can be discontinuous as the result of the
finite relative rotation between the elements. This type of discontinuity is referred to in this paper as nonstructural discontinuity in order to distinguish it from the case of structural discontinuity in which the elements are rigidly connected. Because ANCF finite elements lead to a constant mass matrix, an identity generalized
mass matrix can be obtained for the FE mesh despite the fact that the finite elements of the mesh are not rigidly connected.
The relationship between the nonrational ANCF finite elements and the B-spline representation is used to shed light on the
potential of using ANCF as the basis for the integration of computer aided design and analysis (I-CAD-A). When cubic interpolation
is used in the FE/ANCF representation, C
0 continuity is equivalent to a knot multiplicity of three when computational geometry methods such as B-splines are used.
C
2 ANCF models which ensure the continuity of the curvature and correspond to B-spline knot multiplicity of one can also be
obtained. Nonetheless, B-spline and NURBS representations cannot be used to effectively model T-junctions that can be systematically
modeled using ANCF finite elements which employ gradient coordinates that can be conveniently used to define element orientations
in the reference configuration. Numerical results are presented in order to demonstrate the use of the new formulation in
developing new chain models. 相似文献
108.
A. AnnaduraiM. Manivel Raja K. PrabaharAtul Kumar M.D. KannanS. Jayakumar 《Journal of magnetism and magnetic materials》2011,323(22):2797-2801
The residual stress instituted in Ni-Mn-Ga thin films during deposition is a key parameter influencing their shape memory applications by affecting its structural and magnetic properties. A series of Ni-Mn-Ga thin films were prepared by dc magnetron sputtering on Si(1 0 0) and glass substrates at four different sputtering powers of 25, 45, 75 and 100 W for systematic investigation of the residual stress and its effect on structure and magnetic properties. The residual stresses in thin films were characterized by a laser scanning technique. The as-deposited films were annealed at 600 °C for 1 h in vacuum for structural and magnetic ordering. The compressive stresses observed in as-deposited films transformed into tensile stresses upon annealing. The annealed films were found to be crystalline and possess mixed phases of both austenite and martensite, exhibiting good soft magnetic properties. It was found that the increase of sputtering power induced coarsening in thin films. Typical saturation magnetization and coercivity values were found to be 330 emu/cm3 and 215 Oe, respectively. The films deposited at 75 and 100 W display both structural and magnetic transitions above room temperature. 相似文献
109.
Sayed FN Mandal BP Jayakumar OD Arya A Kadam RM Dixit A Naik R Tyagi AK 《Inorganic chemistry》2011,50(22):11765-11772
A series of Mn-substituted BaMgF(4) samples have been synthesized by a hydrothermal route. X-ray diffraction study reveals that the products are monophasic in nature. Scanning electron microscopy (SEM) and energy-dispersive spectrometry (EDS) studies were carried out to investigate the morphology and stoichiometry for these compounds. X-ray photoelectron spectroscoy (XPS) and electron spin resonance (ESR) studies were done to confirm the oxidation state of dopant ion. Room temperature ferromagnetism was observed on Mn substitution at the Mg site in BaMgF(4) samples. The saturation magnetization increases initially, shows a peaking effect, and then decreases with further increase in Mn concentration in BaMg(1-x)Mn(x)F(4) (0.0 ≤ x ≤ 0.15). However, ferroelectricity was found to decrease with an increase in Mn concentration in the series of investigated BaMg(1-x)Mn(x)F(4) (0.0 ≤ x ≤ 0.15) samples. First-principle calculations, using the projector augmented wave potentials on Mn-substituted BaMgF(4), confirmed the decrease in magnetic moment with an increase in Mn content beyond certain concentration. These samples exhibit very weak magnetocapacitive coupling, which can be attributed to the very small magnetic signal observed in these samples. 相似文献
110.
Andrews Maneesha E. Murali Jayaraman Muralidharan Chellappa Madhulata Wuppalamarthy Jayakumar Rajadas 《Colloid and polymer science》2003,281(8):766-770
The molecular mechanism of the stabilization of collagen with hydrolyzable tannin, corilagin, has been investigated using techniques like centrifugation, shrinkage temperature, infrared spectroscopy, and differential scanning calorimetry. Thermodynamic measurements were also carried out for the collagen–corilagin interaction. Results of this study indicate the enthalpic nature of non-specific binding of collagen with corilagin. The shrinkage temperature increases linearly with corilagin, indicating that the helix–to–coil transition is hindered by corilagin interaction with collagen triple helix. This study suggests that ingested polyphenols (corilagin) alter the stability of the proline-rich protein in the gut. Thereby, the stability of collagen present in the serosa layer may be hindered. 相似文献