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251.
Raju Suresh Kumar Stephen Michael Rajesh Subbu Perumal Perumal Yogeeswari Dharmarajan Sriram 《Tetrahedron: Asymmetry》2010,21(11-12):1315-1327
Enantiomerically pure (R)-(1-phenylethyl)-3,5-bis[(E)-arylmethylidene]tetrahydro-4(1H)-pyridinones were synthesized for the first time, and their 1,3-dipolar cycloaddition with nitrile oxides affording di- and trispiroheterocycles regio- and stereoselectively in moderate yields was investigated. These compounds were evaluated against Mycobacterium tuberculosis H37Rv (MTB) and multi-drug-resistant M. tuberculosis (MDR-TB). Among the compounds screened, the dispiroheterocycle, namely, (5R,6R,10S)-3,9-bis(4-chlorophenyl)-10-(2,4-dichlorophenyl)-14-[(E)-(2,4-dichlorophenyl)methylidene]-12-[(R)-1-phenylethyl]-1,4,7-trioxa-2,8,12-tri-azadispiro[4.0.4.4]tetradeca-2,8-diene 5m was found to possess the maximum activity with MIC of 0.49 μM against MTB, being 9.6 and 15.6 times more potent than ciprofloxacin and ethambutol, respectively. Against MDR-TB, 5m displayed maximum activity with an MIC of 0.49 μM, with it thus being more active than rifampicin, isoniazid, ciprofloxacin and ethambutol by 7.8, 23, 77 and 124 times, respectively. 相似文献
252.
253.
A. P. Karande A. K. Fulzele Amrit Prakash Md. Afzal J. P. Panakkal H. S. Kamath 《Journal of Radioanalytical and Nuclear Chemistry》2010,284(2):451-455
Neutron Well Coincidence Counting has been explored as a non destructive assay technique for determining the percentage of
PuO2 in blended mixture of UO2 and PuO2 powders. The method has been applied to MOX blends having PuO2 content varying from 0.4 to 44% for both thermal and fast reactors. The use of Neutron Well Coincidence Counting technique
is validated as a process control step for determining PuO2 content in the fabrication of MOX fuel by comparing it with chemical analysis of sintered pellets. It has been used at Advanced
Fuel fabrication Facility, Bhabha Atomic Research Centre, Tarapur during the manufacture of MOX fuel of various types for
thermal and fast reactors. 相似文献
254.
G.K. Surya Prakash Juan C. Colmenares Patrice T. Batamack Thomas Mathew George A. Olah 《Journal of molecular catalysis. A, Chemical》2009,310(1-2):180-183
The hydrolysis of methyl bromide with neutral water is performed in the presence and absence of various amines in a batch reactor at different temperatures (50–125 °C). Screening of poly(4-vinylpyridine) as a potential reusable solid amine catalyst showed maximum efficiency. This significant enhancement in efficiency is due to the capture of HBr by solid PVP and remains phase-separated driving the reaction forward. The major advantage of this process is that the polymer can be easily regenerated and reused without loss of activity making it a very effective catalyst for the conversion of methyl halides to methanol and dimethyl ether. 相似文献
255.
Mostafa Shazly Vikas Prakash Bradley A. Lerch 《International Journal of Solids and Structures》2009,46(6):1499-1515
In the present study, a modified split Hopkinson pressure bar (SHPB) is employed to investigate the dynamic response of ice under uniaxial compression in the range of strain rates from 60 to 1400 s?1 and at initial test temperatures of ?10 and ?30 °C. The compressive strength of ice shows positive strain-rate sensitivity over the range of strain rates employed; a slight influence of ice microstructure is observed, but it is much less than that reported previously for ice deformation under quasi-static loading conditions [Schulson, E.M., IIiescu, D., Frott, A., 2005. Characterization of ice for return-to-flight of the space shuttle. Part 1 – Hard ice. NASA CR-2005-213643-Part 1]. Specimen thickness, within the range studied, was found to have little or no effect on the peak (failure) strength of ice, while lowering the test temperature from ?10 to ?30 °C had a considerable effect, with ice behaving stronger at the lower test temperature. Moreover, unlike in the case of uniaxial quasi-static compression of ice, the effect of specimen end-constraint during the high rate compression was found to be negligible. One important result of these experiments, which may have important implications in modeling ice impacts, involves the post “peak-stress” behavior of the ice in that the ice samples do not catastrophically lose their load carrying capacity even after the attainment of peak stress during dynamic compression. This residual (tail) strength of the damaged/fragmented ice is sizable, and in some cases is larger than the quasi-static compression strength reported for ice. Moreover, this residual strength is observed to be dependent on sample thickness and the strain rate, being higher for thinner samples and at higher strain-rates during dynamic compression. 相似文献
256.
C. Yohannan Panicker Hema Tresa Varghese K. Madhusoodanan Pillai Y. Sheena Mary K. Raju T.K. Manojkumar Anna Bielenica Christian Van Alsenoy 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2010,75(5):1559-1565
Fourier-transform-Raman and infrared spectrum of 4-azatricyclo [5.2.2.02,6] undecane-3,5,8-trione were recorded and analyzed. The vibrational wavenumbers were examined theoretically using the Gaussian03 set of quantum chemistry codes, and the normal modes were assigned by potential energy distribution (PED) calculations. The first hyperpolarizability, predicted infrared intensities and Raman activities are reported. The calculated first hyperpolarizability is comparable with reported values of similar structures which makes this compound an attractive object for future studies of nonlinear optics. Optimized geometrical parameters of the compound are in agreement with similar reported structures. The red shift of the NH stretching wavenumber in the infrared spectrum from the computational wavenumber indicates the weakening of NH bond. 相似文献
257.
G A Olah T Mathew E R Marinez P M Esteves M Etzkorn G Rasul G K Prakash 《Journal of the American Chemical Society》2001,123(47):11556-11561
Quantitative rearrangement of pivalaldehyde to methyl isopropyl ketone is observed in acids such as trifluoromethanesulfonic acid, anhydrous HF, and trifluoroethyl alcohol-BF3 but not in trifluoroacetic acid. Studies in a mixture of trifluoroacetic acid and trifluoromethanesulfonic acid show that acids with H(o) < or = -11 are able to carry out complete isomerization. These results and density functional theory calculations at the B3LYP/6-31G level suggest that protonated pivalaldehyde undergoes further protosolvation at higher acidities to a reactive superelectrophilic species resulting in rearrangement. A mechanism for the pivalaldehyde rearrangement to methyl isopropyl ketone in strong protic acids involving a reactive protosolvated superelectrophilic intermediate is suggested. Aspects of the related mechanism of the reaction with isobutane with CO in HF/BF3 medium leading to methyl isopropyl ketone are also discussed. 相似文献
258.
The electric field gradient (EFG) and the asymmetry parameter (η) due to transition metal impurities in the host metals Al,
Cu and V are investigated. The valence EFG is formulated using dielectric screening theory in conjunction with pseudopotential
theory. The size EFG is evaluated in the elastic continuum limit for a screened point charge model of the host metal. The
detailed calculations are carried out forAl (Sc, Fe, Cr),Cu (Ni, Pd, Pt) andV (Ti, Cr, Fe, Nb, Ta, W) alloys. 相似文献
259.
R Srinivasan V Sankaranarayanan N P Raju S Natarajan U V Varadaraju G V Subba Rao 《Pramana》1987,29(2):L225-L230
The absolute thermopower of single phase YBa2Cu3O7 and Y0.8Er0.2Ba2Cu3O7 has been measured in the range 250 K to the superconducting transition temperature. It is found that these compounds show
a large enhancement of thermopower in the range 150 K down toT
c. This enhancement shows a steep exponential drop as the temperature increases from the transition temperature. The temperature
variation of the enhancement is too steep to be accounted for by electron-phonon or electron-local structural excitation mechanisms. 相似文献
260.
Spin echo measurements were made on Y(Fe0.99V0.01)2, (Y0.97Ho0.03) (Fe0.99V0.01)2 and Ho(Fe0.96 V0.04)2 compounds. The addition of Ho to YFe2 causes a spin reorientation from <111> to <100> but this is not reflected in the89Y or51V hyperfine fields. A well resolved51V NMR line was observed at 51.5 MHz and 60.0 MHz respectively for Y and Ho Laves compounds but with no evidence of quadrupole satellites. Small quadrupole splittings ¦2Pt¦ = 171 ±5 kHz and 178 ±5 kHz respectively for Y and Ho compounds were deduced from the oscillatory decay of the51V spin echo after a two pulse sequence.On leave from Department of Physics, University College, The University of New South Wales, Australian Defence Force Academy, Campbell, ACT, Australia. 相似文献