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991.
Ibetombi Soibam Sumitra Phanjoubam H. B. Sharma H. N. K. Sarma Chandra Prakash 《Indian Journal of Physics》2009,83(3):285-290
A series of Co substituted lithium zinc ferrite powders with different content of Co (0.00 to 0.1 in steps of 0.02) were prepared
by a novel sol-gel auto combustion process using citric acid. Their spinel structure was confirmed by XRD. The variation in
lattice parameter and density with cobalt concentration was studied which showed an increasing trend. A decreasing pattern
was observed in variation of porosity with increasing Co. Room temperature dielectric constant and resistivity were studied
as a function of composition at 10 KHz. The room temperature dielectric constant decreases with successive addition of Co2+ in the series. The observed variation in dielectric constant has been explained on the basis of space charge polarization
and Koops two layer model. Resistivity is observed to increase with increasing concentration and the observed variation in
resistivity has been explained by Verwey hopping mechanism. 相似文献
992.
Eppakayala Sreedhar R. Sateesh Chandra Kumar G. Venkateswar Reddy A. Robinson K. Suresh Babu J. Madhusudana Rao P.V. Srinivas 《Tetrahedron: Asymmetry》2009,20(4):440-448
A concise total synthesis of neohelmanticins A–D has been accomplished in 15 steps starting from commercially available gallic acid. Swern oxidation conditions, a Grignard reaction, Sharpless kinetic resolution, and regioselective ring opening of an epoxide with lithium aluminum hydride (LAH) are the key features to install the basic core, dihydroxy phenyl propane 2. One hydroxyl group of this core was esterified with tiglic acid followed by the oxidation and esterification with corresponding acids to yield neohelmanticins A–D. 相似文献
993.
Suresh Chandra 《Pramana》2004,62(5):1181-1185
Kaur and Mahajan [1] have claimed to derive a universal relation InG = 1.91578(±0.09727) + 0.97111(±0.03809) In Δ between the Sutherland parameter Δ(=ω
er
e
2
/2De) and the dimensionless parameterG(= 8ω
exe/Be) for the ground as well as excited electronic states of diatomic molecules. Validity of this relation is checked and we find
that the relation is not correct. Next, we checked the validity of the relation Δ = 2.2re for the alkali group diatomic molecules. This relation is also found not to be correct. 相似文献
994.
Rahul Sharma Ramesh Chandra AgarwalaVijaya Agarwala 《Journal of magnetism and magnetic materials》2007
The novel low temperature combustion synthesis (LCS) method for the preparation of nanocrystalline W-type BaW hexaferrite i.e. BaNi2Fe16O27 has been carried out by citrate precursor using the sol-to-gel (S–G) followed by gel-to-nanocrystalline (G–N) conversion. Decomposition behaviors and the phases associated therein are investigated by means of thermal analysis (DTA/DTG/TG) and XRD, respectively. Atomic absorption spectroscopy (AAS) has been used to determine the elemental analysis in different conditions. Surface morphology of the nonporous ultra fine particles have been examined by SEM. The TEM micrographs show that the particles of the size of 10 nm were seemed to be agglomerated in the ‘as synthesized’ condition. Room temperature Fe-57 Mossbauer spectrum, MS has showed doublet of ‘as synthesized’ nanocrystalline powder that indicates the superparamagnetic behavior of the material. This effect is further confirmed by vibrating sample magnetometer (VSM) wherein it was noticed that the magnetic field (10 KG max) did not have any effect on the material. The material was annealed at 400, 700 and 1000 °C in the furnace for 4 h. The grain size is found to increase from 10 to 70 nm after annealing at 1000 °C for 4 h. MS after annealing at 700–1000 °C for 4 h, showed that the doublets of ‘as synthesized’ is further resolved into broad sextets due to the presence of both superparamagnetic and ferrimagnetic particles, in the wide size range from 10 to 70 nm. Only slight increase in particle size (from 10 to 15 nm) is noticed after the heat-treatment for 1–3 and 5 min in microwave oven (2.45 GHz with 760 W) but with predominant phase changes. TEM after the heat treatment revealed the presence of microcrystalline nature of grains of the size ∼70 nm. The transformation of the magnetic properties i.e. from superparamagnetic to ferrimagnetic behaviour after heating in microwave oven has been revealed by hysteresis loops under VSM study. The saturation magnetisation, Ms after heat treatment has been seen to increase from 26.7 to 44.5 emu/gm. Remanence and coercivity have also increased four and seven times, respectively. Ms of the as synthesised hexaferrite nano powder and heat-treated powder in microwave oven for 5 min show doublets, confirming the presence of superparamagnetic relaxation in the nano particles as only slight increase in the particle size is associated with the heat treatment. 相似文献
995.
Prediction and Measurement of Electron Density and Collision Frequency in a Weakly Ionised Pine Fire
Kgakgamatso Mphale Mohan Jacob Mal. Heron 《International Journal of Infrared and Millimeter Waves》2007,28(3):251-262
Pine litter flame is a weakly ionised medium. Electron-neutral collisions are a dominant form of particle interaction in the
flame. Assuming flame electrons to be in thermal equilibrium with neutrals and average electron-neutral collision frequency
to be much higher than the plasma frequency, the propagation of microwaves through the flame is predicted to suffer signal
intensity loss. A controlled fire burner was constructed where various natural vegetation species could be used as fuel. The
burner was equipped with thermocouples and used as a cavity for microwaves with a laboratory quality network analyzer to measure
wave attenuation. Electron density and collision frequency were then calculated from the measured attenuation. The parameters
are important for numerical prediction of electromagnetic wave propagation in wildfire environments. A controlled pine litter
fire with a maximum flame temperature of 1080 K was set in the burner and microwaves (8–10.5 GHz) were caused to propagate
through the flame. A microwave signal loss of 1.6–5.8 dB was measured within the frequency range. Based on the measured attenuation,
electron density and electron-neutral collision frequency in pine fire were calculated to range from 0.51–1.35 × 1016 m−3 and 3.43–5.97 × 1010 s−1 respectively. 相似文献
996.
S. Singh R. Chandra P. K. Rath P. K. Raina J. G. Hirsch 《The European Physical Journal A - Hadrons and Nuclei》2007,33(4):375-388
The two-neutrino double-beta decay of 124, 126Xe , 128, 130Te , 130, 132Ba and 150Nd isotopes is studied in the Projected Hartree-Fock-Bogoliubov (PHFB) model. Theoretical 2ν β-β- half-lives of 128, 130Te , and 150Nd isotopes, and 2ν β+β+ , 2ν β+
EC and 2ν ECEC for 124, 126Xe and 130, 132Ba nuclei are presented. Calculated quadrupolar transition probabilities B(E2 : 0+ → 2+) , static quadrupole moments and g -factors in the parent and daughter nuclei reproduce the experimental information, validating the reliability of the model
wave functions. The anticorrelation between nuclear deformation and the nuclear transition matrix element M
2ν is confirmed. 相似文献
997.
David Eric Cox James G. O’Brien Ronald L. Mallett Chandra Roychoudhuri 《Foundations of Physics》2007,37(4-5):723-733
Using the linearized Einstein gravitational field equations and the Maxwell field equations it is shown that the plane of
polarization of an electromagnetic wave is rotated by the gravitational field created by the electromagnetic radiation of
a ring laser. It is further shown that this gravitational Faraday effect shares many of the properties of the standard electromagnetic
Faraday effect. An experimental arrangement is then suggested for the observation of this gravitational Faraday effect induced
by the ring laser. 相似文献
998.
The design of o-nitrobenzyl containing photocleavable lipid-amino acid conjugates, and their application in liposomal uncorking are described. 相似文献
999.
Gonnade RG Bhadbhade MM Shashidhar MS Sanki AK 《Chemical communications (Cambridge, England)》2005,(47):5870-5872
Crystallization of tri-O-[p-halobenzoyl]-myo-inositol 1,3,5-orthoformates from ethyl acetate-petroleum ether solution produced concomitant dimorphs that have different halogen bonding contacts; the kinetic form with C-Br...O-C contacts upon heating to 185 degrees C, converts completely to the thermodynamic form with C-Br...O=C contacts via crystal-to-crystal first order phase transition. 相似文献
1000.
Chandra S Gupta N Gupta R Bawa SS 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2005,62(1-3):552-556
Aza-macrocyclic complexes have gained importance because of their pharmacological properties. Hexa-aza-macrocycles containing glutarimide efficiently coordinate as hexa-dentate ligand, to give complexes of Cu(II) possessing tetragonal structure and Mn(II), Co(II) and Ni(II) metal ions that are essentially octahedral. Spectroscopic, and chemical characterizations of these systems are presented in this article. For Ni(II) complexes results on electron transfer processes measured by cyclic voltammetry and colourimetry have been studied. 相似文献