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121.
122.
A three-component accelerometer balance system is used to study the drag reduction effect of an aerodisc on large angle blunt cones flying at hypersonic Mach numbers. Measurements in a hypersonic shock tunnel at a freestream Mach number of 5.75 indicate more than 50% reduction in the drag coefficient for a 120° apex angle blunt cone with a forward facing aerospike having a flat faced aerodisc at moderate angles of attack. Enhancement of drag has been observed for higher angles of attack due to the impingement of the flow separation shock on the windward side of the cone. The flowfields around the large angle blunt cone with aerospike assembly flying at hypersonic Mach numbers are also simulated numerically using a commercial CFD code. The pressure and density levels on the model surface, which is under the aerodynamic shadow of the flat disc tipped spike, are found very low and a drag reduction of 64.34% has been deduced numerically. 相似文献
123.
The nature of nonlinear molecular deformations in a homeotropically aligned nematic liquid crystal (NLC) is presented. We start from the basic dynamical equation for the director axis of a NLC with elastic deformations and adopt space curve mapping procedure to analyze the dynamics. The NLC is governed by an integro-differential perturbed nonlocal nonlinear Schrödinger equation and we solve the same using Jacobi elliptic function method aided with symbolic computation and construct an exact solitary wave solution. In order to better understand the effect of nonlocality on the director reorientations of nematic liquid crystal, we have constructed the component forms of director axis using Darboux vector transformation. This intriguing property as a result of the relation between the coherence of the breather-like solitary deformation and the nonlocality reveals a strong need for a deeper understanding in the theory of self-localization in NLC systems. 相似文献
124.
Tarafder Md. Tofazzal H. Saravanan N. Crouse Karen A. Ali Abdul Manaf b. 《Transition Metal Chemistry》2001,26(6):613-618
A bidentate and a quadridentate Schiff base having NS and NNSS donor sequences were prepared by condensing S-benzyldithiocarbazate (NH2NHCSSCH2Ph) with 2,3-butanedione (1:1 and 1:2 mole ratio). NiII and CuII complexes of these ligands were studied and characterised by elemental analyses and various physico-chemical techniques. The nickel complexes, [Ni(NS)2] and [Ni(SNNS)], were diamagnetic with square-planar and five-coordinate structures, respectively. The copper complex was, however, pentacoordinated. The ligands and the complexes were screened for anticancer activity against T-lymphoblastic leukemic cells (CEM-SS) and colon cancer cells (HT-29). The NS Schiff base was strongly active against leukemic cells with a CD50 value of 2.05 g cm–3. The nickel and copper complexes were found to be stronger antioxidants than Vitamin E. 相似文献
125.
Two-dimensional laminar convection in low Prandtl number liquids driven by the buoyancy force is studied. The liquid is contained in a closed square cavity with isothermal vertical walls kept at different temperatures. The top and bottom walls are assumed to be insulated. The thermal conductivity of the liquid is assumed to depend on temperature. ADI and SOR schemes are employed. The heat transfer is found to decrease appreciably across the cavity with a decrease in thermal conductivity. 相似文献
126.
Hydrazinium 2,n-pyridinedicarboxylates of general compositions N2H5HA, (N2H5)2A·H2O and N2H5HA·H2A, where H
2
A=2,n-pyridinedicarboxylic acid (n=3, quinolinic acid;n=4, lutidinic acid; n=5, isocinchomeronic acid and n=6, dipicolinic acid) have been prepared by the neutralisation of aqueous solution of hydrazine hydrate with the respective
acids, in stoichiometric ratios. Formation of these hydrazinium derivatives has been confirmed by analytical, IR spectral
and thermal studies. Among these, the monohydrazinium salts are anhydrous whereas the dihydrazinium salts are monohydrated.
While lutidinic and dipicolinic acids form all the three types of salts, the quinolinic and isocinchomeronic acids do not
form N2H5HA·H2A and N2H5HA, respectively, except the other two types. Infrared spectra of these salts reveal N-N stretching frequencies of the hydrazinium
ion in the region 970-950 cm-1. The simultaneous TG and DTA of these salts show that all of them decompose without clear melting and lose hydrazine endothermically
between 200 and 280°C, except dihydrazinium isocinchomeronate monohydrate in which half of the hydrazine molecule is lost
exothermically, to give pyridinemono- or dicarboxylic acid intermediate which further decomposes exothermically to gaseous
products.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
127.
G. Saravanan M. Ravikumar M. J. Jadhav M. V. Suryanarayana N. Someswararao P. V. R. Acharyulu 《Chromatographia》2007,66(3-4):291-294
This study deals with a stability indicating HPLC reverse phase method for quantitative determination of temozolomide. A chromatographic
separation was achieved on an Inertsil ODS 3V, 250 × 4.6 mm ID, 5 μm column using mobile phase A (buffer 5 mL glacial acetic
acid in 1,000 mL of Milli Q water ) and mobile phase B (methanol). Forced degradation studies were performed on bulk sample
of temozolomide using acid (0.5 N hydrochloric acid), base (0.5 N sodium hydroxide), oxidation (10% v/v hydrogen peroxide), heat (60 °C) and UV light (254 nm). Degradation of the drug substance was observed in base hydrolysis
and oxidation. Degradation product formed under these conditions was found to be Imp-A. When the stress samples were assayed,
the mass balance was close to 99.5%. The sample solution was stable up to 48 h at 5 °C and mobile phase was found to be stable
up to 48 h at 25 °C. The developed method was validated with respect to linearity, accuracy, precision, robustness and forced
degradation studies prove the stability indicating power of the method. 相似文献
128.
M. Saravanan B. Arul Prakasam K. Ramalingam G. Bocelli A. Cantoni 《无机化学与普通化学杂志》2005,631(9):1688-1692
Three new transition metal complexes [Zn(bipyrtds)I2]( 1 ), [Cd(bipyrtds)I2] ( 2 ) and [Hg(pipdtc)I]( 3 ) (where bipyrtds = bipyrrolidine thiuamdisulfide and pipdtc = piperidinecarbodithioate) were prepared by the reaction of the corresponding biscarbodithioates with iodine and were characterized by elemental analysis, IR and NMR spectra. The structures of all the three complexes were determined by single crystal X‐ray crystallography. Compounds 1 and 2 contain four coordinated metal atoms and both ZnII and CdII complexes are isostrucutral. Interestingly, complex 3 was found to contain effectively four coordinated mercury atom as a dimer with a relatively long Hg‐S (3.084Å) bond. The IR studies are in keeping with the observed thioureide distances. 1H NMR spectra of 1 and 2 show clear differences in environments of α‐ and β‐CH2 protons. However, in 1 a broad signal was observed at 4.02 ppm for α‐protons and a multiplet at 2.10 for β‐protons. For 2 , two triplets appeared at 4.26 and 4.03 ppm for α‐protons and two quintets appeared in the range of 2.18 and 2.28 ppm for β‐protons. Complex 3 gave three sets of signals. Variation of stereochemical environment with respect to α and β protons of the rings is very clearly observed in the NMR spectra. 相似文献
129.
Saravanan Raju Ray J. Butcher Harkesh B. Singh 《Acta Crystallographica. Section C, Structural Chemistry》2019,75(3):336-341
The structures of the 18‐membered diselenide‐linked macrocycle 10,27‐di‐tert‐butyl 11,28‐dioxo‐2,3,19,20‐tetraselena‐10,12,27,29‐tetraazapentacyclo[28.4.0.04,9.013,18.021,26]tetratriaconta‐1(30),4(9),5,7,13,15,17,21,23,25,31,33‐dodecaene‐10,27‐dicarboxylate, C36H34N4O6Se4, and its precursor di‐tert‐butyl 2,2′‐[diselane‐1,2‐diylbis(2,1‐phenylene)]dicarbamate, C22H28N2O4Se2, are reported. The precusor to the macrocycle contains two tert‐butyl phenylcarbamate arms connected to a diselenide group, with Se—C and Se—Se bond lengths of 1.914 (4) and 2.3408 (6) Å, respectively. The macrocycle resides on a crystallographic center of inversion in space group P with one molecule in the unit cell (Z′ = ). It contains an 18‐membered macrocyclic ring with two diselenide linkages. In this macrocycle, there are two free and two protected amino groups. 相似文献
130.
The object of this study was to develop hydroxypropyl methylcellulose (HPMC) based cephalexin extended release tablet, which can release the drug for six hours in predetermined rate. Twenty-one batches of cephalexin tablets were prepared by changing various physical and chemical parameters, in order to get required theoretical release profile. The influences of HPMC, microcrystalline cellulose powder (MCCP), granulation technique, wetting agent and tablet hardness on cephalexin release from HPMC based extended release tablets were studied. The formulated tablets were also characterized by physical and chemical parameters. The dissolution results showed that a higher amount of HPMC in tablet composition resulted in reduced drug release. Addition of MCCP resulted in faster drug release. Tablets prepared by dry granulation was released the drug slowly than the same prepared with a wet granulation technique. Addition of wetting agent in the tablets prepared with dry granulation technique showed slower release. An increase in tablet hardness resulted in faster drug release. Tablets prepared with a wet granulation technique and having a composition of 9.3% w/w HPMC with a hardness of 10-12 kg/cm(2) gave predicted release for 6 h. The in vitro release data was well fit in to Higuchi and Korsmeyer-Peppas model. Physical and chemical parameters of all formulated tablets were within acceptable limits. One batch among formulated twenty-one batches was successful and showed required theoretical release. The effect of storage on in vitro release and physicochemical parameters of successful batch was studied and was found to be in acceptable limits. 相似文献