Showing papers by "Indian Association for the Cultivation of Science published in 1974"

Anomalous magnetic behaviour in ferrous perchlorate hexahydrate crystals at low temperatures

Abstract: An attempt has been made to explain our measurements on magnetic susceptibility and anisotropy of Fe(ClO4)2·6H2O in the range 300 to 80 °K, consistent with anomalous Mossbauer results at low temperatures. The crystal undergoes a phase transition at Tc = (237 ± 1) °K from the pseudohexagonal C2v7 to the monoclinic P21/c structure. The experimental results above Tc can be fitted with theory taking into account a small trigonal elongation of the coordination octahedron along one of the body diagonal and below Tc the data can be fitted with a different set of tetragonally distorted field and overlap parameters. It is further found that the axial field parameter changes sign and magnitude from 180 to −155 cm−1. The magnitude of the axial field splitting is also small compared to other ferrous salts. Es wird der Versuch gemacht, fruhere Messungen der magnetischen Suszeptibilitat und Anisotropie von Fe(ClO4)2·6H2O im Bereich 300 bis 80 °K zu erklaren, die mit anomalen Mosbauereffektergebnissen bei niedrigen Temperaturen ubereinstimmen. Die Kristalle machen einen Phasenubergang bei Te = (237 ± 1) °K von der pseudohexagonalen C2v7-zur monoklinen P21/c-Struktur durch. Die experimentellen Ergebnisse oberhalb Tc konnen an die Theorie angepast werden, wenn eine geringe trigonale Elongation des Koordinationsoktaeders in Richtung einer Raumdiagonale berucksichtigt wird, und unterhalb Tc lassen sich die Werte mit einem davon verschiedenen tetragonal verzerrten Feld und verschiedenen Uberlappungsparametern anpassen. Es wird weiterhin gefunden, das die axialen Feldparameter sowohl das Vorzeichen als auch die Grose von 180 auf −155 cm−1 andern. Die Grose des Axialfeldes ist ebenfalls klein im Vergleich zu anderen Ferrosalzen.

An X-ray Fourier line shape analysis in cold-worked hexagonal zirconium

Abstract: Detailed Fourier analysis of line shapes has been carried out in hexagonal zirconium metal in the cold-worked and partially recovered states. X-ray diffraction profiles from the fault-unaffected 10.0, 00.2, 11.0, 11.2 and 00.4 and fault-affected 10.1, 10.3, 20.1, 10.2 and 20.2 reflections have been recorded using a counter diffractometer for this purpose. The line shape analysis has shown small anisotropy as regards the domain sizes and strains, the average values being of the order of 280 A and 2.08×10−3 respectively in the cold-worked state with a small recovery at a higher temperature. Least-square solution applied to fault-affected reflections has yielded very small concentration of deformation faults with a negligible proportion of growth faults. Results are found to be consistent with earlier X-ray measurements and recent electron microscope investigations on zirconium.

Studies on the mechanism of redox polymerization initiated by N‐haloamines and iron(II)

Abstract: The mechanism of the redox polymerization of methyl methacrylate in aqueous medium in the dark was studied for the redox initiator systems N-halodiethylamine + Fe(II) and triethylamine + halogen + Fe(II), by analysis of the polymer end groups using the dye partition method. In the case of chlorine, both these initiator systems incorporate only the amino group into the polymer to an extent of about one group per polymer molecule. The polymers are found to be free from chlorine. Furthermore, a large portion of the total amino groups introduced into the polymer, using the initiator system triethylamine + halogen + Fe(II) are quaternary in nature. In the case of bromine, both the initiator systems introduce only a bromine atom and no amino group into the polymer. The initiator systems containing chlorine prove to be useful for the preparation of polymers containing amino groups at the one end only. Zur Aufklarung des Mechanismus der Redox-Polymerisation von Methylmethacrylat, die die Redox-Startsysteme N-Halogendiathylamin + Fe2+ und Triathylamin + Halogen + Fe2+ in wasrigem Medium unter Lichtausschlus bewirken, wurden die Endgruppen des Polymeren nach der Farbstoff-Verteilungsmethode untersucht. Im Falle von Chlor als Halogen kommt es mit beiden Startsystemen lediglich zum Einbau von Aminogruppen in das Polymere in einem Ausmas von ca. 1 Endgruppe pro Polymermolekul. Bei Verwendung des Startsystems Triathylamin + Halogen + Fe2+ liegen daruber hinaus die in das Polymer eingebauten Aminogruppen zu einem grosen Teil in quaternarer Form vor. Mit Brom als Halogen findet bei beiden Anregungssystemen lediglich ein Bromeinbau, nicht jedoch ein Einbau von Aminogruppen in das Polymere statt. Die Chlor enthaltenden Startsysteme haben sich fur die Herstellung von solchen Polymeren nutzlich erwiesen, die eine Aminogruppe nur an einem der beiden Kettenenden besitzen sollen.

Absolute sea level muon spectrum near equator in the momentum range 0.32-3 GeV/c

Abstract: A study has been made on the differential spectrum of single muons near the geomagnetic equator (12°N) in the momentum range 0.32–3 GeV/c by using the differential range spectrograph results. The corrected experimental spectrum has been compared with those of other workers determined at low high and high latitudes. The present results agree with the theoretical spectra calculated after Barrett et al. and Olbert for the same location within 10% above muon momentum 1 GeV/c. The corrections for the geomagnetic and atmospheric latitude effects have been applied to our low latitude spectrum by using the theory of Olbert and Jabs to explain the deviation of the Kiel muon spectrum of Allkofer and Knoblich from ours.

Spectrophotometric (U.V.) investigation on Metal Biguanidinium Complexes

Abstract: From the U.V. spectra study of series of metal biguanides, attempt has been made to find out any interaction between the filled ligand orbital with the vacant metal orbital which may give rise to delocalisation of electron system over the whole complex molecule. This type of interaction may develop aromatic character in metal biguanide ring. The benzenoid character of the metal acetylacetonate can be cited as parallel to that of the metal biguanide. The U.V. study of metal biguanides concludes that there is a definite indication of the suggested overlap of the ligand and metal orbitals with consequent shifting of absorption bands with different substitutions. UV-spektroskopische Untersuchung von Metall-Biguanidin-Komplexen Aus der UV-spektroskopischen Untersuchung einer Reihe von Metall-Biguanidinen wurde versucht, eine Wechselwirkung zwischen dem vollem Liganden-Orbital und dem leeren Metall-Orbital zu finden, das zum Ansteigen der Delokalisierung des Elektronensystems der ganzen Molekel fuhren konnte. Diese Art der Wechselwirkung konnte einen aromatischen Charakter im Metall-Biguanidin-Ring hervorrufen. Der benzoide Charakter der Metall-Acetylacetonate stellt eine Parallele zu dem der Metall-Biguanidine dar. Die Untersuchung der Metall-Biguanidine im UV zeigt, das es klare Hinweise fur die Uberlappung der Liganden- und Metall-Orbitale gibt, die mit einer Verschiebung der Absorptionsbanden verbunden ist.

Schottky Defects in Sodium and Potassium Chloride

Abstract: The energy of formation of Schottky defects, the binding energy of the Schottky pair in the ground state and the entropies of formation of isolated vacancies and vacancy pairs for NaCl and KCl have been computed assuming an elastic displacement in the form proposed by Boswarva and Lidiard. In the calculation of the displacement of the ten immediate neighbours of the vacancy pair, the relaxation of the distant neighbour was also considered. The calculations show a reasonable agreement with the recent experimental values. Es werden die Bildungsenergie von Schottkydefekten, die Bindungsenergie von Schottky-Paaren im Grundzustand und die Bildungsentropien von isolierten Leerstellen und Leerstellenpaaren fur NaCl und KCl unter der Annahme einer elastischen Verschiebung, wie sie von Boswarva und Lidiard vorgeschlagen wurde, berechnet. Bei der Berechnung der Verschiebung der zehn nachsten Nachbarn des Leerstellenpaares wurde auch die Relaxation der entfernten Nachbarn berucksichtigt. Die Rechnungen zeigen befriedigende Ubereinstimmung mit kurzlich publizierten experimentellen Werten.

The g-value of the 2E state of K3CR(CN)6 and the lower symmetry field

Abstract: The 4 A 2 → 2 E transition of potassium chromicyanide has been studied under magnetic field. It has been found that the g -value is nearly isotropic, quite unlike the case of ruby. An attempt has been made to explain the zero-field splittings of 2E , 2 T 1 and 2 T 2 states and the g -value of the 2 E state on the assumption that the distant ions are mainly responsible for lowering of symmetry of the crystal field from O h . A reasonable choice of parameters can make the calculated values agree with the observed ones.

Studies on the Thermal Diffusion in the Binary Gas Mixtures Ne-N2O and Kr-N2O

Abstract: The thermal diffusion factors α T of the systems Ne-N 2 O and Kr-N 2 O have been measured as functions of temperature and composition by the two-bulb method. Attempts have been made to interpret the experimental data by changing the intermolecular potential and considering inelastic collision effects on thermal diffusion. Although some significant insights into the problem have been obtained by the analysis, it has not been possible to explain the data satisfactorily. By comparison with the available α T data for Ne-CO 2 and Kr-CO 2 systems it has been concluded that molecular symmetry has significant effect on thermal diffusion factor.

Studies on intramolecular association of salt groups in polymers following their binding with a metachromatic dye

Abstract: Intramolecular association in dilute solution between carboxylate groups present at the ends of a polymer molecule was studied with reference to the effect of solvent and chain length of the polymers. The interaction was followed from the spectral change of a cationic metachromatic dye, pinacyanol (1), bound to the carboxylic groups of α,ω-poly(butadiene dicarboxylic acid)s and α,ω-poly(styrene dicarboxylic acid)s. It was found, as expected, that the extent of association decreases with the increase in polymer chain length and the increase in solvent polarity. Evidence was presented for the fact that in case of short chain polymeric dicarboxylic acids in benzene bis-dye salt formation occurs to a considerable extent, even if less than 50% of the carboxylic groups are converted to the dye salt. Gegenstand der Untersuchungen war die intramolekulare Assoziation zwischen endstandigen, in das Polymere eingebauten Carboxylgruppen als Funktion der Losungsmittelgute und der Kettenlange der Polymeren in verdunnter Losung. Die Wechselwirkung wurde anhand der spektralen Anderung eines an die Carboxylgruppen von α,ω-Polybutadiendicarbonsauren oder α,ω-Polystyroldicarbonsauren gebundenen kationischen metachromatischen Farbstoffs, Pinacyanol (1), verfolgt. Erwartungsgemas zeigte sich, das das Ausmas der Assoziation mit steigender Kettenlange des Polymeren abnimmt und mit steigender Losungsmittelpolaritat zunimmt. Die Ergebnisse sprechen dafur, das bei kurzkettigen Polymerdicarbonsauren in Benzol die Bildung des Di-Farbstoffsalzes sogar dann in betrachtlichem Ausmas erfolgt, wenn weniger als 50% der Carboxylgruppen in eine salzartige Verbindung mit dem Farbstoff ubergefuhrt wurden.

On the trace and the relativistic scalar products involving Dirac matricesγ i and the 4 × 4 unit matrix

Abstract: In this paper we have dealt with the relativistic scalar products likeγ i uγ i,Tr(γ i u) Tr(γ i v) and Tr(γ i γ j v). Here any string likeu andv involve Dirac matrices in the manneru=Π =1 a r where the element $$a_r = a_{r_i } \gamma _i + ia_{r_5 }$$ i.e.,a r in general involves a term $$ia_{r_5 }$$ which is multiplied by a 4 × 4 unit matrix. We have further evaluated Tr (γ b u) Tr (γ b v) where the suffix ‘b’, unlike the dummy suffixesi andj, does not imply any summation and can assume any specific value from 1 to 5. Some reduction formulae for the evaluation of Tr (γ5 u) and Tr(u) have been obtained in this paper.