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排序方式: 共有352条查询结果,搜索用时 31 毫秒
41.
Mahendra Yadav 《Journal of organometallic chemistry》2010,695(6):841-763
The meso-pyridyl substituted dipyrromethane ligands 5-(4-pyridyl)dipyrromethane (4-dpmane) and 5-(3-pyridyl)dipyrromethane (3-dpmane) have been employed in the synthesis of a series of complexes with the general formulations [(η6-arene)RuCl2(L)] (η6-arene = C6H6, C10H14) and [(η5-C5Me5)MCl2(L)] (M = Rh, Ir). The reaction products have been characterized by microanalyses and spectral studies and molecular structures of the complexes [(η6-C10H14)RuCl2(4-dpmane)] and [(η5-C5Me5)IrCl2(3-dpmane)] have been determined crystallographically. For comparative studies, geometrical optimization have been performed on the complex [(η5-C5Me5)IrCl2(4-dpmane)] using exchange correlation functional B3LYP. Optimized bond length and angles are in good agreement with the structural data of the complex [(η5-C5Me5)IrCl2(3-dpmane)]. The complexes [(η6-C10H14)RuCl2(3-dpmane)], [(η5-C5Me5)RhCl2(3-dpmane)] and [(η5-C5Me5)IrCl2(3-dpmane)] have been employed as a transfer hydrogenation catalyst in the reduction of aldehydes. It was observed that the rhodium and iridium complexes mentioned above are more effective in this regard in comparison to the ruthenium complex. 相似文献
42.
A simple, rapid, and solvent-free method for quantitative determination of benzene, toluene, and Xylene in exposed Drosophila larvae was developed using headspace solid-phase microextraction (HS-SPME) coupled to GC/MS. Larvae fed on standard Drosophila food mixed with benzene, toluene, and Xylene for 48 h were homogenized in Milli-Q water. Extraction of benzene, toluene, and Xylene was performed at 65 degrees C for 30 min on the SPME fiber (silica-fused). Subsequently, the fiber was desorbed in the GC injection port, followed by GC/MS analysis in the selected-ion monitoring mode. An external calibration curve was used for the quantification of benzene, toluene, and Xylene in the exposed organism. Recoveries were in the range of 78-82% (intraday) and 76-81% (interday) in larvae, and 91-96% (intraday) and 87-92% (interday) in the diet. LOD with an S/N of 3:1 and LOQ with an S/N of 10:1 were in the range of 0.01-0.023 and 0.034-0.077 microg/L, respectively. Percent RSD values for benzene, toluene, and Xylene were in the range of 0.50-0.81 (intraday) and 0.89-1.23 (interday) for retention time, and 2.16--3.85 (intraday) and 2.99-4.95 (interday) for peak concentration, showing good repeatability. This method was sensitive enough to quantitate benzene, toluene, and Xylene in small exposed organisms like Drosophila larvae. The SPME/GC/MS method developed may have wider applications in various in vivo toxicological studies. 相似文献
43.
Structurally diverse spiroheterocycles incorporating medicinally privileged heterosystems have been synthesized by a simple
and convenient synthesis involving triethylamine catalyzed multicomponent domino reaction of 2-aminobenzothiazoles with isatin
and cyclic 1,3-diketones. 相似文献
44.
Dattatray J. Late Mahendra A. More Sucharita Sinha K. Dasgupta Pankaj Misra B. N. Singh Lalit M. Kukreja Sudha V. Bhoraskar Dilip S. Joag 《Applied Physics A: Materials Science & Processing》2011,104(2):677-685
The paper deals with the comparative study of nanocrystalline Lanthanum hexaboride (LaB6) thin films grown on various substrates by Pulsed laser deposition and Arc plasma method. Field emission studies were carried
out on LaB6 films deposited on various substrates show metallic behavior of the emitters. The high value of field enhancement factors,
indicating that the electron emission from LaB6 nanoscale protrusions deposited on emitter surface. The post field emission surface morphology of the emitters showed no
significant erosion of the films during continuous operation. The observed behavior indicates that it is linked with the growth
of LaB6 films on substrate crystal structure. The LaB6 nanocrystallites/nanowires films were synthesized using arc plasma method shows good emission current stability. The LaB6 micro/nanocrystallites were also obtained by picosecond laser irradiation which gives high enhancement β factor, and good emission current stability along with high current density. The results reveal that nanocrystalline LaB6 films, exhibit high resistance to ion bombardment and excellent structural stability and are more promising emitters for
practical applications in field emission based new generation devices. 相似文献
45.
This note reports the dependence of shape factor corresponding to the portion of wall behind a berm and above the ground on the angle of berm; the results have been obtained by thermal simulation of heat transfer between the ground and the wall through the berming. 相似文献
46.
Mahendra K. Verma 《Pramana》2003,61(3):577-594
Energy cascade rates and Kolmogorov’s constant for non-helical steady magnetohydrodynamic turbulence have been calculated
by solving the flux equations to the first order in perturbation. For zero cross helicity and space dimensiond = 3, magnetic energy cascades from large length-scales to small length-scales (forward cascade). In addition, there are energy
fluxes from large-scale magnetic field to small-scale velocity field, large-scale velocity field to small-scale magnetic field,
and large-scale velocity field to large-scale magnetic field. Kolmogorov’s constant for magnetohydrodynamics is approximately
equal to that for fluid turbulence (≈ 1.6) for Alfvén ratio 05 ≤r
A ≤ ∞. For higher space-dimensions, the energy fluxes are qualitatively similar, and Kolmogorov’s constant varies asd
1/3. For the normalized cross helicity σc →1, the cascade rates are proportional to (1 − σc)/(1 + σc , and the Kolmogorov’s constants vary significantly with σcc. 相似文献
47.
Surjeet Verma Shiv Kumar Santosh Kumar Srivastava Mahendra P. Darokar 《中国化学会会志》2014,61(10):1121-1126
A new clionasterol glucoside, clionasterol‐[(1'→3α)‐O‐β‐D]‐glucopyranoside ( 1 ), a new acylated clionasterol glucoside, clionasterol‐[6'‐O‐acyl‐(1'→3β)‐O‐b‐D]‐glucopyranoside ( 2 ) and clionasterol ( 3 ) were isolated from the aerial parts of Oplismenus burmannii. The nature and length of fatty acid acyl chains in 2 was identified by alkaline methanolysis of compound 2 . The aglycone fraction on GC‐MS analysis showed three peaks in GC at tR 49.86 (82.1%), 51.13 (13.3%) and 56.53 (4.6%) min, which were characterized as arachidic acid methyl ester ( a ) oleic acid methyl ester ( b ) and 12‐methyltetradecanoic acid methyl ester ( c ) respectively. Thus 2 was characterized as a mixture of three new compounds, clionasterol‐[6'‐O‐eicosanoyl‐(1'→3β)‐O‐β‐D]‐glucopyranoside ( 2a ), clionasterol‐[6'‐O‐(8Z)‐octa‐deca‐9‐enoyl‐(1'→3β)‐O‐β‐D]‐glucopyranoside ( 2b ) and clionasterol‐[6'‐O‐(12‐methyltetradecanoyl)‐(1'→3β)‐O‐β‐D]‐glucopyranoside ( 2c ). 相似文献
48.
B. Lakshmi Prakash Gouda Avaji K.N. Shivananda Praveen Nagella S.H. Manohar K.N. Mahendra 《Polyhedron》2011,30(9):1357-1515
A series of binuclear Co(II), Ni(II) and Cu(II) complexes were synthesized by the template condensation of glyoxal, biacetyl or benzil bis-hydrazide, 2,6-diformyl-4-methylphenol and Co(II), Ni(II) or Cu(II) chloride in a 2:2:2 M ratio in ethanol. These 22-membered macrocyclic complexes were characterized by elemental analyses, magnetic, molar conductance, spectral, thermal and fluorescence studies. Elemental analyses suggest the complexes have a 2:1 stoichiometry of the type [M2LX2]·nH2O and [Ni2LX22H2O]·nH2O (where M = Co(II) and Cu(II); L = H2L1, H2L2 and H2L3; X = Cl; n = 2). From the spectroscopic and magnetic studies, it has been concluded that the Co(II) and Cu(II) complexes display a five coordinated square pyramidal geometry and the Ni(II) complexes have a six coordinated octahedral geometry. The Schiff bases and their metal complexes have also been screened for their antibacterial and antifungal activities by the MIC method. 相似文献
49.
Kumar A Lal Tamta M Negi N Chandrasekhar K Singh Negi D 《Natural product research》2011,25(18):1680-1686
The essential oil of Premna latifolia Roxb. was obtained by hydrodistillation of fresh leaves of the plant having an oil yield of 0.05%, both non-polar and essential oil were analysed by GC and GC-MS. Hexane fraction of the leaves of P. latifolia was transesterified and analysed by GC and GC-MS, 40 non-polar components were identified comprising 89.3%. The most abundant fatty acid constituents were hexadecanoic acid (25.04%), 8,11,14-docosatrienoic acid (13.62%), octadecanoic acid (6.82%), 9,12-octadecadienoic acid (4.19%) and 29 components were investigated in the essential oil which comprises 78.1%. The most abundant oil constituents were 1-octen-3-ol (35.69%), terpendiol II (7.19%), δ-guaiene (7.49%) 2-undecanone (4.80%) and α-pinene (3.27%). Different extracts were also tested against polyphagous crop pest Spodoptera litura for antifeedant activity. Essential oil showed maximum growth reduction of 56.83% followed by chloroform extract of 43.93%. 相似文献
50.
Mahendra Dhanu Singh Kusnadi Liem Vladimirs Leontjievs Andr��s Kecskem��thy 《Meccanica》2011,46(1):171-182
Described in this paper is a six-legged Stewart-Gough parallel platform driven by a relatively new type of fluidic muscles. The advantage of the platform is that it is virtually free of stick-slip effects. Thus, the device is well-suited for fine-tuned force control and for physical simulation of virtual force-displacement laws. The legs of the platform are of type RRPS and are equipped with a coaxial coil spring and a fluidic muscle providing push and pull forces. Each leg is equipped with a force sensor, a pressure sensor, and a magnetostrictive position encoder. The control for the platform consists of six control loops for the six operated actuators with model-based force control comprising individual gas models as well as the rubber nonlinearities for each leg. The control law also includes the gas flow in the proportional directional control valve in 3/3-way function. The present paper describes the basic architecture of the platform, the dynamic models, as well as testbed results for the existing fluidic-muscle parallel platform DynaHex. It is shown that the presented control scheme leads to a stable force control of the platform for quasi-static motion. As an application, the device will be employed in fields of biomechanics, as well as in general environments requiring physical simulation. 相似文献