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131.
We present measurements of the linewidth for spin wave resonance in 75-25 Permalloy at 33.8 GHz over the temperature range 4–3000 K. Contrary to earlier data, we find that, for high mode numbers, the linewidths are essentially independent of temperature, mode number and film thickness. 相似文献
132.
Ionic chelates of hafnocene with uracil (HL1) (A) and 5-fluorouracil (HL2) (B) of the type [(5- C5H5)2HfL1]+X– (C) and [(5- C5H5)2HfL2]+X– (D) (X = CuCl3, ZnCl3, CdCl3, HgCl3, PhNHNHCS2) have been prepared and characterised by conductivity measurements and by i.r., electronic, 1H-n.m.r. and 13C-n.m.r. spectra. Fluorescence studies of the complexes containing Hg in the anionic moiety, and relevant photochemical parameters, have been elucidated. Thermodynamic parameters have been calculated using thermogravimetric (t.g.) and differential thermal analytical (d.t.a.) curves, and their variations have been correlated with some structural parameters of the complexes. The ligands, as well as their hafnium(IV) complexes, exhibit appreciable antibacterial and antifungal activity against E. coli, S. typhi, P. aeruginosa and Z. mobilis bacterial strains, and versus
A. awamori and A. niger fungal strains, respectively. 相似文献
133.
Srikant Bhagat Ratnesh Sharma Asit K. Chakraborti 《Journal of molecular catalysis. A, Chemical》2006,260(1-2):235-240
Commercially available lithium hydroxide monohydrate (LiOH·H2O) was found to be a novel ‘dual activation’ catalyst for tandem cross-aldol condensation between cyclic/acyclic ketones and aromatic/heteroaromatic/styryl/alkyl aldehydes leading to an efficient and easy synthesis of α,α′-bis(aryl/alkylmethylidene)ketones at r.t. in short times. The reaction of aryl, heteroaryl, styryl and alkyl aldehydes with acyclic and five/six-membered cyclic ketones afforded excellent yields after 2 min to 1.25 h. The reaction conditions were compatible with various electron withdrawing and electron donating substituents, e.g. Cl, F, NO2, OMe and NMe2. The rate of the cross-aldol condensation was influenced by the nature of the ketone and electronic and steric factors associated with the aldehyde. The reaction took place at a faster rate for acyclic ketone (e.g., acetone) than that for cyclic ketone (e.g., cyclohexanone). In case of cycloalkanones, the rate of the reaction was dependent on the size of the ring of the cycloalkanone. The cross-aldol condensation of cyclopentanone was faster than that of cyclohexanone for a common aldehyde. In case of reactions involving aliphatic aldehyde having α-hydrogen atom no self-aldol condensation of the aldehyde took place. 相似文献
134.
Synthesis of new efficient compounds is becoming urgent due to the resistance of organisms to drugs. Salen derivatives have interesting therapeutic and industrial applications. A coumarin based derivative of salen, 7-hydroxy-8-((E)-((2-((E)-((7-hydroxy-5-methyl-2-oxo-3,8a-dihydro-2Hchromen-8-yl)methylene)amino)-4-methylphenyl)imino)methyl)-5-methyl-2H-chromen-2-one (L), and its copper complex, CuL, have been synthesized and characterized. Antibacterial and antioxidant activity of these compounds have been evaluated and electronic, optical and molecular properties have been calculated using density functional theory (DFT) with B3LYP. The results were correlated with the biological activity and reactivity of the compounds. Experimental and theoretical calculations indicate that the studied copper complex has the potential to function as a drug. 相似文献
135.
The presence of a chalcogen atom at the ortho-position of phenols enhances their radical chain-breaking activity. Here, a copper(I)-catalyzed reaction of 2,6-dibromo- and 2,6-diiodophenols with diorganodiselenides has been studied for the introduction of two organoselenium substituents at both ortho-positions of the phenolic radical chain-breaking antioxidants, which afforded 2,6-diorganoseleno-substituted phenols in 80–92% yields having electron-donating CH3, and electron-withdrawing CN and CHO functionalities. Additionally, 2,6-diiodophenols with electron-withdrawing CHO and CN groups also afforded novel 5,5′-selenobis(4-hydroxy-3-(phenylselanyl)benzaldehyde) and 5,5′-selenobis(4-hydroxy-3-(phenylselanyl)benzonitrile) consisting of three selenium and two phenolic moieties along with 2,6-diorganoseleno-substituted phenols has been synthesized. The electron-withdrawing CHO group has been reduced by sodium borohydride to the electron-donating alcohol CH2OH group, which is desirable for efficient radical quenching activity of phenols. The developed copper-catalyzed reaction conditions enable the installation of two-arylselenium group ortho to phenolic radical chain-breaking antioxidants, which may not be possible by conventional organolithium-bromine exchange methods due to the sluggish reactivity of trianions (dicarba and phenoxide anion), which are generated by the reaction of organolithium with 2,6-dibromophenols, with diorganodiselenides. The antioxidant activities of the synthesized bis and tris selenophenols have been accessed by DPPH, thiol peroxides, and singlet oxygen quenching assay. The radical quenching antioxidant activity has been studied for the synthesized compounds by 2,2-diphenyl-1-picrylhydrazyl (DPPH) assay. The bis-selenophenols show comparable radical deactivating activity, while tris seleno-bisphenols show higher radical deactivating activity than α-tocopherol. Furthermore, the tris seleno-bisphenol shows comparable peroxide decomposing activity with ebselen molecules. 相似文献
136.
Bhagat PR Pandey AK Acharya R Natarajan V Rajurkar NS Reddy AV 《Analytical and bioanalytical chemistry》2008,391(3):1081-1089
A molecular iodine selective membrane has been used for preconcentration of I2 generated in situ by iodometric reaction of with excess I− in acidic medium (pH 1–2). This iodometric reaction amplifies the iodine content six times resulting in enhancement of analytical
response ranging from three times for molecular methods to six times for elemental methods. The chemical conditions of this
iodometric reaction were optimized for quantitative generation and subsequent sorption of I2 in the membrane samples (96 ± 3%). The homogeneous transparent membrane was prepared by immobilizing I2-complexing polyvinylpyrrolidone (PVP) in the plasticized cellulose triacetate matrix. Four different analytical methods were
examined for quantitative determination of in iodized salt samples by preconcentrating it as I2 in the membrane matrix. These methods were: (1) spectrophotometry of the PVP-I2 complex formed in the membrane matrix, (2) a radiotracer method using I− tagged with 131I radiotracer, (3) instrumental neutron activation analysis (INAA), and (4) energy-dispersive X-ray fluorescence (EDXRF) analysis.
The contents thus determined in the iodized salt samples by the membrane-based radiotracer method were compared with the total
iodine determined in salt samples by epithermal instrumental neutron activation analysis (EINAA). The membrane-based method
for iodate determination in salt samples has advantages over conventional analytical methods, for example preconcentration
and chemical amplification, and is free from interference from anions.
Figure A molecular iodine selective membrane was used for the quantitative preconcentration of I2 generated in situ by iodometric reaction of with excess Iaˆ’ in acidic medium, which amplifies iodine content six times 相似文献
137.
138.
R. P. Bhagat 《Colloid and polymer science》2001,279(1):33-38
This article describes the adsorption of sodium dodecyl benzene sulfonate, an anionic surfactant, on a hematite surface and
that when the surface is preadsorbed with polyacrylamide. The adsorption of surfactant on a hematite surface has been studied
through equilibration and during kinetics measurements at three pH levels, viz. 4.0, 7.0, 8.9. The surfactant adsorbs strongly
on the hematite surface. The adsorption density at equilibrium as well as the rate of adsorption are dependent on the suspension
pH. The maximum adsorption density has been observed at pH 4, which reflects strong adsorption of negatively charged sulfonate
ions on the oppositely charged Fe2O3 surface (point of zero charge, 6.4). The adsorption density reaches its equilibrium value sooner in the case of an alkaline
suspension and later in the case of acidic pH. The polymer surfactant interaction has been noticed in the present study and
is also a function of pH. The hematite mineral when preadsorbed with the polymer draws fewer of the surfactant molecules at
lower surface coverage (during the initial period of the kinetics measurement) irrespective of the pH. When the adsorption
of the surfactant reaches a value which is near the equilibrium one, the pH effect is evident. In the case of acidic pH, the
surfactant adsorbs more on the hematite surface when preadsorbed with the polymer compared to the bare surface. In the case
of neutral or alkaline pH, however, the density of surfactant adsorption remains lower throughout the kinetics measurement
when the surface is preadsorbed with the flocculant compared to the bare surface. The particles also remain flocculated till
the end of the experiment, whereas at pH 4 the particles are deflocculated. In addition to pH, the electrostatic nature of
the adsorbent and the presence of anionic surfactant have an influence on the flocculation–deflocculation phenomena. The polymer–surfactant
interaction has been schematically represented. The surfactant is bound with polymeric chains as a combination of its monomeric
form as well as in the form of association in the case of acidic media and in competition with polymer in the case of alkaline
media.
Received: 18 April 2000/Accepted: 2 August 2000 相似文献
139.
We report measurements on the electrical conductivity, optical absorption, electron spin resonance, Raman spectrum and electron diffraction of a set of a-Si films vaccum deposited at room temperature. As revealed by absorption at about 10 μm some of the films grown at deposition rates of about 0.4 Å/sec contain considerable amounts of oxygen. All the properties, except Raman spectra and electron diffraction, are found to vary strongly with the deposition rate and the background pressure during evaporation. Qualitatively, these variations show significant correlations. For instance, if the electrical conductivity is higher so is the spin density, the optical absorption and the low-frequency refractive index. Also, increasing oxygen content leads to lower conductivity. In addition, we have tried to establish a rough quantitative relation between the shift in the optical gap and the change in the spin density by connecting each of these changes to the variation in the low-frequency refractive index. The temperature dependence of the electrical conductivity was also measured and it was found that below about 150 K the data are consistent with recent theoretical predictions, i.e., log σ exhibits a ( dependence. 相似文献
140.
Kamlakar Avasthi Deepa Bhagat Chandralata Bal Ashoke Sharon Umesh Yadav Prakas R. Maulik 《Acta Crystallographica. Section C, Structural Chemistry》2003,59(8):o409-o412
The crystal structure of 4,6‐bis(methylsulfanyl)‐1‐phthalimidopropyl‐1H‐pyrazolo[3,4‐d]pyrimidine, C18H17N5O2S2, (VI), reveals an unusual folded conformation due to an apparent intramolecular C—H⃛π interaction between the 6‐methylsulfanyl and phenyl groups. However, the closely related compound 6‐methylsulfanyl‐1‐phthalimidopropyl‐4‐(pyrrolidin‐1‐yl)‐1H‐pyrazolo[3,4‐d]pyrimidine, C21H22N6O2S, (VII), exhibits a fully extended structure, devoid of any intramolecular C—H⃛π or π–π interactions. The crystal packing of both molecules involves intermolecular stacking interactions due to aromatic π–π interactions. In addition, (VI) exhibits intermolecular C—H⃛O hydrogen bonding and (VII) exhibits dimerization of the molecules through intermolecular C—H⃛N hydrogen bonding. 相似文献