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81.
Dhayal V Chaudhary A Choudhary BL Nagar M Bohra R Mobin SM Mathur P 《Dalton transactions (Cambridge, England : 2003)》2012,41(31):9439-9450
[Zr(OPr(i))(4)·Pr(i)OH] reacts with [HOSi(O(t)Bu)(3)] in anhydrous benzene in 1:1 and 1:2 molar ratios to afford alkoxy zirconosiloxane precursors of the types [Zr(OPr(i))(3){OSi(O(t)Bu)(3)}] (A) and [Zr(OPr(i))(2){OSi(O(t)Bu)(3)}(2)] (B), respectively. Further reactions of A or B with glycols in 1:1 molar ratio afforded six chemically modified precursors of the types [Zr(OPr(i))(OGO){OSi(O(t)Bu)(3)}] (1A-3A) and [Zr(OGO){OSi(O(t)Bu)(3)}(2)] (1B-3B), respectively [where G = (-CH(2)-)(2) (1A, 1B); (-CH(2)-)(3) (2A, 2B) and (-CH(2)CH(2)CH(CH(3)-)} (3A, 3B)]. The precursors A and B are viscous liquids, which solidify on ageing whereas the other products are all solids, soluble in common organic solvents. These were characterized by elemental analyses, molecular weight measurements, FAB mass, FTIR, (1)H, (13)C and (29)Si-NMR studies. Cryoscopic molecular weight measurements of all the products, as well as the FAB mass studies of 3A and 3B, indicate their monomeric nature. However, FAB mass spectrum of the solidified B suggests that it exists in dimeric form. Single crystal structure analysis of [Zr{OSi(O(t)Bu)(3)}(4)(H(2)O)(2)]·2H(2)O (3b) (R(fac) = 11.9%) as well as that of corresponding better quality crystals of [Ti(O(t)Bu){OSi(O(t)Bu)(3)}(3)] (4) (R(fac) = 5.97%) indicate the presence of a M-O-Si bond. TG analyses of 3A, B, and 3B indicate the formation of zirconia-silica materials of the type ZrO(2)·SiO(2) from 3A and ZrO(2)·2SiO(2) from B or 3B at low decomposition temperatures (≤200 °C). The desired homogenous nano-sized zirconia-silica materials [ZrO(2)·nSiO(2)] have been obtained easily from the precursors A and B as well as from the glycol modified precursors 3A and 3B by hydrolytic sol-gel process in organic media without using any acid or base catalyst, and these were characterized by powder XRD patterns, SEM images, EDX analyses and IR spectroscopy. 相似文献
82.
The paper reports the pulsed laser-based time-resolved time-dependent Photo-acoustic (PA) spectroscopy of NO2 gas in a specially designed multi mode-Resonant PA Cell which is made of Stainless Steel and has a “Q” value of the order of 79. Furthermore the designed cell allows us to excite some of the longitudinal, radial and azimuthal
resonance modes of the photo-acoustic signals simultaneously in a very efficient manner. The presence of many newly excited
modes occur at 7050 Hz, 10350 Hz and 14650 Hz frequencies is observed for the first time in NO2 at room temperature. These results are obtained by employing second harmonics i.e. λ=532 nm pulses from Q-switched Nd:YAG laser having 7 ns pulse duration. Some of the new acoustic spectrum lines at higher frequencies are recorded
between 0.5–10 ms data acquisition time, which also extends the frequency monitoring range of our system. The study also highlights
some of the important aspects such as the decaying behavior of some of these resonant acoustic spectrum lines occur on the
expense of others as well as the saturation behavior of some other modes in the NO2 gas sample. The estimated low level detection limit of NO2 buffered in air is of the order of 17.9 ppbV. 相似文献
83.
R.H. Chilkulwar S.D. Sharma N. Chaudhary S. Acharya Y.S. Mayya K.C. Mittal L.M. Gantayet 《Radiation measurements》2012,47(8):628-633
The high dose rate electron beams are increasingly being used for radiation processing of various products worldwide. A comprehensive dosimetric evaluation of an in-house developed 10 MeV industrial electron beam irradiator was carried out in static as well as in dynamic mode of irradiations. Radiochromic B3 film and graphite calorimeter were used for dosimetric measurements. The dose rate from the electron beam was also calculated using the empirical relation prescribed in the ASTM report E2232-02. The measured electron beam profile indicates the dose rate variation within 8% in the irradiated product boxes. The most probable energy determined from the depth dose distribution in PMMA, Al and water was found in agreement with the intended energy of the electron beam. Measured dose rate using radiochromic film and graphite calorimeter were found in good agreement with each other and also found comparable with the theoretically estimated dose rates. Experimentally measured dose rates were considered for the trial irradiation of medical and industrial products. Dosimetric data obtained through this study confirms the suitability of the irradiator for routine radiation processing of various products. 相似文献
84.
Electrochemical synthesis of multi-armed CuO nanoparticles and their remarkable bactericidal potential against waterborne bacteria 总被引:1,自引:0,他引:1
Pratibha Pandey S. Merwyn G. S. Agarwal B. K. Tripathi S. C. Pant 《Journal of nanoparticle research》2012,14(1):709-13
Copper (II) oxide multi-armed nanoparticles composed of 500–1000 nm long radiating nanospicules with 100–200 nm width near
the base and 50–100 nm width at the tapered ends and ~25 nm thickness were synthesized by electrochemical deposition in the
presence of an oxidant followed by calcination at 150 °C. The nanoparticles were characterized using SEM/EDX for morphology
and composition, Raman spectroscopy for compound identification, and broth culture method for antibacterial efficacy. The
CuO nanoparticles have shown remarkable bactericidal efficacy against Gram-positive and -negative waterborne disease causing
bacteria like Escherichia coli, Salmonella typhi, staphylococcus aureus and Bacillus subtilis. E. coli has been chosen as representative species for waterborne disease causing bacteria. In antibacterial tests 500 μg/mL nano
CuO killed 3 × 108 CFU/mL E. coli bacteria within 4 h of exposure. Moreover, 8.3 × 106 CFU/mL E. coli were killed by 100 and 10 μg/mL nano CuO within 15 min and 4 h of exposure, respectively. Antibacterial activity of nano
CuO has been found many-fold compared with commercial bulk CuO. The fate of nanoparticles after antibacterial test has also
been studied. The synthesized CuO nanoparticles are expected to have potential antibacterial applications in water purification
and in paints and coatings used on frequently touched surfaces and fabrics in hospital settings. 相似文献
85.
86.
BM Kobilka AV Dubrovskiy MD Ewan AL Tomlinson RC Larock S Chaudhary M Jeffries-El 《Chemical communications (Cambridge, England)》2012,48(71):8919-8921
3,7-Diiodo-2,6-di(thiophen-2-yl)benzo[1,2-b:4,5-b']difurans are efficiently prepared by an iodine-promoted double cyclization. This new heterocyclic core is readily modified by the attachment of alkyl chains for improved solubility. The use of these compounds for the synthesis of new conjugated polymers is also reported. 相似文献
87.
Ruby Chauhan Ashavani Kumar Ram Pal Chaudhary 《Research on Chemical Intermediates》2012,38(7):1443-1453
Undoped and silver-doped TiO2 nanoparticles (Ti1?x Ag x O2, where x?=?0.00?C0.10) were synthesized by a sol?Cgel method. The synthesized products were characterized by X-ray diffraction (XRD), particle size analyzer (PSA), scanning electron microscope (SEM), and UV?CVisible spectrophotometer. XRD pattern confirmed the tetragonal structure of synthesized samples. Average crystallite size of synthesized nanoparticles was determined from X-ray line broadening using the Debye?CScherrer formula. The crystallite size was varied from 8 to 33?nm as the calcination temperature was increased from 300 to 800?°C. The incorporation of 3 to 5% Ag+ in place of Ti4+ provoked a decrease in the size of nanocrystals as compared to undoped TiO2. The SEM micrographs revealed the agglomerated spherical-like morphology of particles. SEM, PSA, and XRD measurements show that the particles size of the powder is in nanoscale. Optical absorption measurements indicated a red shift in the absorption band edge upon silver doping. Direct allowed band gap of undoped and Ag-doped TiO2 nanoparticles measured by UV?CVis spectrometer were 3.00 and 2.80?eV, respectively, at 500?°C. 相似文献
88.
Jitender M. Khurana Ankita Chaudhary Bhaskara Nand Anshika Lumb 《Tetrahedron letters》2012,53(24):3018-3022
The utilization of water as solvent and indium trichloride as promoter for the three-component combinatorial synthesis of a variety of bioactive pyrimidine and pyrazole derivatives (2–10) from aldehydes, 1,3-dicarbonyl compounds, and electron-rich amino heterocycles like 6-amino-1,3-dimethyl uracil and 3-methyl-1-phenyl-1H-pyrazol-5-amine catalyzed by indium trichloride under reflux has been studied. A new class of pyrimidine derivatives (2) has also been synthesized and the structure was confirmed by single crystal X-ray analysis. The reactions are environmentally benign, reaction product could be isolated easily and the catalyst could be recycled, which makes it an appealing synthetic protocol. 相似文献
89.
In this article we obtain a new class of well behaved charged solutions by using particular forms of the metric potential
g
44 and electric intensity, which involves a parameter K. The metric describing the superdense stars joins smoothly with the Reissner-Nordstrom metric at the pressure free boundary.
This class of solutions describes well behaved charged fluid balls. The class of solutions gives range of parameter K (0.13≤K≤1.9999) for which the solution is well behaved hence, suitable for modeling of super dense star. The interior of the stars
possess there energy density, pressure, pressure-density ratio and velocity of sound to be monotonically decreasing towards
the pressure free interface. In view of the surface density 2×1014 gm/cm3, the maximum mass of the charged fluid balls and corresponding radius are 0.4711M
Θ and 7.0122 km. The red shift at the centre and boundary are found to be 0.1640 and 0.1100 respectively. 相似文献
90.
J. P. Singh Pratibha Singh Raj Bali 《International Journal of Theoretical Physics》2012,51(12):3828-3838
We present an isotropic and homogeneous flat cosmological model for bulk viscous fluid distribution. We consider the vacuum density proportional to Hubble expansion parameter and time dependent bulk viscosity related to the velocity and acceleration of universe. The behaviour of resulting solutions are in accordance with recent astronomical observations. The model obtained evolves with a decelerating expansion followed by late time acceleration. Cosmological term Λ being very large at initial epoch relaxes to a genuine cosmological constant asymptotically. Presence of bulk viscosity prevents the matter density to vanish asymptotically and the matter density continues to be of the order of vacuum density after a finite time. Thus, we obtain a universe having the possibility of cosmic coincidence. 相似文献