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101.
The first observation of the ESR spectra of Mn2+, entering substitutionally for Fe2+ in the Van Vleck paramagnet FeS2 (polycrystals), is reported. The data from 5 to 295 K fits the spin-Hamiltonian + , with g = 2.000 ± 0.001, A/β = ?95.0 ± 0.5 Oe and D/β varying from 50 Oe (5K) to 59 Oe (295 K). The temperature dependence of D can be described in terms of a single phonon-mode with frequency ? 145 cm?1. 相似文献
102.
The kinetics of reaction between benzyl chloride and phenol (or substituted phenols) in the presence of sodium hydroxide have
been investigated. A differential application of the effect of substituents on the reaction rate to distinguish between a
rate-limiting oxygen or carbon attack has been attempted. Considerable scatter in the Hammett plot for the latter attack points
to an essentially O-alkylation. The rate constants correlate well with pKa values of the different phenols. The influence of salt and solvent on the reaction rate suggests this reaction to be an ion-dipole
one. 相似文献
103.
Carbon-13 NMR spectra of a variety of mono- and bicyclic β-lactams have been measured and the chemical shifts of the ring carbon atoms have been assigned unambiguously. Effects of substituents on the chemical shifts of these carbons are also discussed. 相似文献
104.
In a Talbot interferometer the self image of a periodic pattern, such as a Ronchi ruling of period d, illuminated by a monochromatic plane wavefront of wavelength λ, is formed at distances which are integral multiples of 2d2/λ. A refracting object placed in front of the Ronchi ruling distorts the self image. A computer generated pattern can be designed, such that, when placed in a self imaging plane, a uniform intensity or a distinct moire pattern characterising a standard object is obtained. A method of computing the required patterns and experimental results for some aspherical objects are described. 相似文献
105.
Neutron diffraction data available in the literature have been analyzed statistically to arrive at the ideal geometry for the commonly occurring groups, NH
4
+
, NH
3
+
, CH3, CH2, and CH; this has yielded optimum experimental values for the bond length and bond angle parameters. They are: N-H distance of 1.030 Å in both NH
4
+
and NH
3
+
groups, H-N-H angle of 109.47° and 108.1° respectively in NH
4
+
and NH
3
+
and 110.8° for the corresponding X-N-H angle in –NH
3
+
. For CH3, CH2, and CH groups the bond length C-H is 1.090 Å, while the H-C-H and X-C-H angles are respectively 108.2° and 110.5° in CH3 and 107.2° and 109.3° in CH2. The importance of using precise values of both bond lengths and bond angles for the ideal geometry when estimating theoretical second moments is emphasized.Contribution No. 564 from the Department of Crystallography and Biophysics, University of Madras, Guindy Campus, Madras-600025, India. 相似文献
106.
Srinivasan Kesavan 《Comptes Rendus Mathematique》2005,340(1):27-30
Let Ω be a bounded, connected and simply connected open subset of with a Lipschitz continuous boundary. It is shown that an irrotational vector field whose components are in is the gradient of a function in . It is also shown that this generalization of a classical lemma of Poincaré is equivalent to a well-known lemma of J.L. Lions. To cite this article: S. Kesavan, C. R. Acad. Sci. Paris, Ser. I 340 (2005). 相似文献
107.
A.?NarayananEmail author R.?Srinivasan U.?K.?Khan A.?Vudayagiri H.?Ramachandran 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2004,31(1):107-112
The unusually narrow features in the fluorescence from 85Rb driven by two laser fields L1 and L2, reported in [1], are explained on the basis of a four-level density matrix calculation. The L2 laser enables atom transfer to the fluorescing levels connected by the strong L1 laser. In turn the L1 laser causes the Autler-Townes splitting of the upper levels connected by L2 laser. These two effects are shown to maximise fluorescence within a narrow spectral range of the scanned L2 laser due to velocity selection of atoms from co-propagating and counter propagating L1 and L2 lasers. The analysis reveals the existence of narrow spectral features from a collection of atoms at room temperature even in the absence of induced coherences between the levels.Received: 2 July 2004, Published online: 21 September 2004PACS:
42.50.Hz Strong-field excitation of optical transitions in quantum systems; multiphoton processes; dynamic Stark shift - 32.80.Bx Level crossing and optical pumping 相似文献
108.
A comparative study of myo-inositol quantification using LCmodel at 1.5 T and 3.0 T with 3 D 1H proton spectroscopic imaging of the human brain 总被引:2,自引:0,他引:2
Myo-inositol is a strongly coupled system and resonates at four chemical shift positions. At 1.5 T, only the singlet component at 3.57 ppm is detected. However, at 3 T this resonance is resolved into its components at 3.55 ppm and 3.61 ppm. Due to the increased spectral resolution and signal-to-noise ratio, it is anticipated that the quantification of myo-inositol should improve at 3 T. Using data from normal controls and the LCmodel quantification procedure, we found that the quantification precision, reproducibility and detection sensitivity of myo-inositol is significantly better at 3 T relative to 1.5 T. 相似文献
109.
Anuradha?MishraEmail author Rajani?Srinivasan Malvika?Bajpai Rashmi?Dubey 《Colloid and polymer science》2004,282(7):722-727
The chemical modification of Plantago psyllium mucilage (Psy), an anionic polysaccharide, was done by grafting polyacrylamide (PAM) chains to prepare a graft-copolymer (Psy-g-PAM). It was synthesized in the presence of nitrogen using ceric ammonium nitrate–nitric acid redox initiator and characterized by IR spectroscopy, scanning electron microscopy and viscosity measurements. This grafted copolymer was tested for its flocculation efficiency in textile wastewater by the standard Jar test method. The effects of polymer concentration, pH and contact time on the percentage removal of solid wastes [total dissolved solids (TDS) and suspended solids (SS)] and color from textile effluent are reported. The optimum dose was found to be 1.6 mg l–1, at which maximum solid removal (SS and TDS) was seen. The most suitable pH for TDS and color removal was neutral (7.0) and for SS removal alkaline pH (9.2) was found to be most suitable. The optimum treatment duration for solid waste removal was 5 h. The X-ray diffraction analysis of Psy-g-PAM and solid waste before and after treatment suggests the interaction of the solid waste and Psy-g-PAM copolymer. 相似文献
110.
V.C. Selvaraju S. Asokan V. Srinivasan 《Applied Physics A: Materials Science & Processing》2003,77(1):149-153
The I–V characteristics of bulk As40Te60-xSex and As35Te65-xSex glasses have been studied with a current sweep of 0–18 mA-0, over a wide range of compositions (4≤x≤22). All the glasses
studied showed a threshold electrical switching behaviour. The number of switching cycles withstood by the samples has been
found to depend on the ON-state current. It is seen that the switching voltages increase with increase in selenium content.
Further, the switching voltages are found to be almost independent of the thickness of the sample (d), in the range 0.18–0.3 mm.
Also, the switching voltages and the number of switching cycles withstood by the samples are found to decrease with temperature.
Received: 6 November 2002 / Accepted: 8 November 2002 / Published online: 29 January 2003
RID="*"
ID="*"Corresponding author. Fax: +91-80/360-0135, E-mail: sasokan@isu.iisc.ernet.in 相似文献