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- Author or Editor: A. Garg x
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Abstract
151Sn Mössbauer spectroscopy was performed with tin triflate Sn(OTf)2 in order to determine its Mösbauer parameters for analytical purposes. The typical Mössbauer parameters at 80 K for crystalline Sn(OTf)2 are IS=4.01±0.02 mm/s and QS=1.20±0.04 mm/s and show that the stannous ion is at a site with less than cubic symmetry under perturbation of the crystal field effect.
Summary
Fourteen samples of fresh curry leaves (Murraya Koenigii) were collected from 13 states of India and analyzed for 6 minor (Ca, Cl, K, Mg, Na and P) and 14 trace (Br, Ce, Co, Cr, Cs, Fe, Hg, Mn, Rb, Sb, Sc, Se Th and Zn) elements by 2-minute irradiation in a reactor followed by high resolution g-ray spectrometry. Peach Leaves (SRM-1547) and Mixed Polish Herbs (MPH-2) were used as comparator standards. Phosphorus was determined by counting the b-activity from 32P using an end-window GM counter. Most elements were found to vary in a wide range depending on their origin of location, e.g., Na (104-455 mg/g), K (10.3-30.3 mg/g), Ca (9.44-28.3 mg/g), Mg (1.14-7.19 mg/g), P (0.43-1.69 mg/g), Mn (24.8-63.0 mg/g), Fe (72.5-195 mg/g), Se (40.1-131 ng/g) and Zn (7.90-70.5 mg/g). Variation in the elemental concentrations of the same species of different origin may be attributed to ecological and geographical variations. Further, column and thin layer chromatography were used for separating three organic constituents from the ethanolic extract; 3-methylthiopropanenitrile; 1,2-benzenedicarboxylic acid, mono (2-ethylhexyl ester) and 1-penten-3-ol and characterized by IR and GC-MS. Inorganic elements may be present as complexes with the organic compounds.
Abstract
The application of Mössbauer spectroscopy, X-ray diffractometry, thermogravimetric analysis and PIXE in the characterization of the particulate matter in atmospheric aerosols in Metropolitan Region of Vitória (MRV), Brazil have been investigated. The main sources of particulate matter, natural, industrial and antropogenic from human activities, have been studied to identify its contribution in the atmospheric particles. During the years 1995 to 1999 samples of total suspended particles (TSP, Ø 
100 
m) were collected from four points within MRV. The inhalable particles (PM10 Ø 10 m) and sedimented particles (SP) were also collected from the same region. A receptor modeling was used for the identification of the source of particulate matter in the collected urban aerosol.
Chromium(III) complexes of the type Cr(A)(A′)2, Cr(A)2(A′) and Cr(A)3 have been prepared (whereA is either piperidyldithiocarbamate or morpholyldithiocarbamate andA′ is glycine or oxine or acetylacetone moiety). The mixed ligand complexes have been charac terized by elemental analyses, magnetic susceptibility measurements and thermal studies. The complexes show magnetic moment in the range of 3.5–4.3 B.M. which corresponds to three unpaired electrons. TG studies have also been carried out, in order to study the mode of decomposition of the complexes and to evaluate various kinetic parameters.
Abstract
57Fe and 151Eu Mössbauer spectroscopy as well as RF susceptibility measurements were applied to study the effects of Pr substitution either into the rare earth or into the Ba site in Eu1–x
Pr
x
Ba2Cu3O7–
and EuBa2–x
Pr
x
Cu3O7–
, respectively. Site mixing of Pr between the rare earth and Ba sites could be excluded by the utilization of 57Fe Mössbauer spectroscopy. It was found that there exists a correlation between the 151Eu isomer shift and the onset temperature of the superconducting transition independent of the location of Pr. RF susceptibility measurements provide an evidence for a difference in the magnetic moment of Pr substituted for the Eu or Ba sites. The obtained results can be explained by hole filling as the dominant effect of Pr substitution.
Abstract
Sediments from the Admiralty Bay, King George Island, Antarctica, were investigated by 57Fe Mössbauer spectroscopy, X-ray diffractometry, and radiometry. Quartz, feldspar, chlorite, calcite, dolomite, mica, kaolinite, hematite and magnetite were identified as constituent minerals in the sediment samples. The phase composition and the iron distribution among the crystallographic sites of iron-bearing minerals (silicates, magnetite and hematite) of samples from different location have been derived from the complex Mössbauer spectra. At different locations sediments had significant characteristic differences in the mineral composition, in the iron distribution among the crystallographic site of silicates, and in the specific radioactivity of Cs radionuclides. These results indicate differences in the rock formation and alteration by the sediments in this maritime part of Antarctica. There is a much higher amount of iron oxides in the sediments from south part of the geological fault across the Admiralty Bay than in the north part. This can be associated with much more alteration in the rocks in the south part compared to the northern one. This finding can contribute to the question of the history of the formation and alteration of volcanic rocks in the border of Antarctica.
We report on the synthesis of 2-(dimethylamino)ethyl methacrylate by atom transfer radical polymerization (ATRP) in tubular microreactors. Different process parameters, temperature, pressure, and shear rate, were considered to accelerate the reaction. Increase in temperature induced a faster reaction, but controlled nature of ATRP decreased past a threshold value that can be increased up to 95 °C by reducing the residence time. Positive effect of pressure was observed since significant increases in monomer conversion (+12.5 %) and molecular weight (+5,000 g/mol) were obtained. Moreover, polydispersity index was found to decrease from 1.52 at normal pressure to 1.44 at 100 bars. Benefit of pressure was more visible in smaller reaction space (smaller tube diameter). Finally, shear rate has quite an influence on the early stage of the polymerization and is expressed by an increase in the reaction rate. However, the effect was dimed for long residence times.
