Showing papers by "National University of La Plata published in 1968"

Thorium lamps and interferometrically measured thorium wavelengths.

Abstract: Wavelengths emitted from an electrodeless thorium iodide lamp are compared with those emitted by water-cooled and liquid-nitrogen-cooled hollow-cathode lamps. Three hundred forty six thorium lines have been interferometrically measured, using a hollow-cathode lamp as a source, in the range from 4574 to 6676 A. The accuracy of the measurements has been tested using the combination principle, and was found to be one part in 6 to 9.5 × 107.

Germination of achira seed (Canna sp.) approximately 550 years old.

Abstract: DURING the excavation of a tomb at the archaeological site of Santa Rosa de Tastil, Argentina (24° 25′ S., 65° 50′ W.), we found a necklace made out of nuts of Juglans australis. Inside each nut was a seed of Canna sp., making a rattle. Samples from bones of cameloids in the upper strata of garbage from the site were taken for carbon-14 analysis by Groningen Laboratories (Holland), and they were dated at about 530 yr (AD 1420). The bones probably belong to the last period of occupation of the city by the Indians. No Incaic elements were found, and the carbon-14 dating implies that the city was developed before AD 1420.

Improved Values for Energy Levels, Ritz Standards, and Interferometrically Measured Wavelengths in Th i†

Abstract: Improved values for 18 even energy levels and 102 odd energy levels of Th i have been calculated from interferometrically measured wavelengths. The wavelengths of 756 lines in the range from 3062 to 11 060 A have been calculated as Ritz standards from the values obtained for the energy levels. The accuracy of the wavelengths has been tested using the combination principle and was found to be one part in 1.3×108 to 3.6×107.

Die IR-Spektren einiger hydratisierter Permanganate

Abstract: Es werden die IR-Spektren von Mg(MnO4)2·6H2O, Ni(MnO4)2·6H2O, Zn(MnO4)2·6H2O und Cu(MnO4)2·2H2O im Bereich 4000–600 cm−1 untersucht und kurz besprochen. Auch fruher angegebene IR-Daten fur einige wasserfreie Permanganate wurden bestatigt.

Some reactions of photochemically generated perfluoromethoxyl and related oxygenated derivatives of the perfluoromethyl radical

Abstract: — Results of some reactions of photochemically produced perfluoromethoxyl and related radicals are presented, including a kinetic study of the photochemical reaction between fluoroxyperfluoromethane (CF3OF) and carbon monoxide leading quantitatively to perfluoromethyl fluoroformate (CF3OC(O)F). Bis (perfluoromethyl) oxalate (CF3OC(O)C(O)OCF3), the supposed chain-ending product of the named reaction is described for the first time. Also, some evidences are presented in favor of the existence of bis(perfluoromethyl)peroxydicarbonate (CF3OC(O)OOC(O)OCF3) and of the mixed mono(perfluoromethyl)ester-monofluoride of peroxydicarbonic acid (CF3OC(O)OOC(O)F), which are believed to be respectively the chain-ending products of the oxidation of carbon monoxide, photochemically sensitized by bis (perfluoromethyl)peroxide and fluoroxyperfluoromethane. Finally, a description is given of a novel synthetic method which gives high yields of bis (perfluoromethyl)trioxide, depending on the oxidation of perfluoromethyl radicals produced photochemically from a mixture of fluorine and perfluoroacetone. RESUMEN Se presentan los resultados de algunas reacciones que llevan a la produccion fotoquimica de perfluorometoxilo y otros radicales analogos, incluyendo un estudio cinetico de la reaccion fotoquimica entre el fluoroxiperfluorometano (CF3OF) y el monoxido de carbono, con formacion cuantitativa de fluoroformiato de perfluorometilo (CF3OC(O)F). Se describe por primera vez el oxalato de perfluorometilo (CF3OC(O)C(O)OCF3) que es justamente el producto final de la cadena de la mencionada reaccion. Tambien se presentan evidencias en favor de la existencia del peroxidicarbonato de perfluorometilo (CF3OC(O)OOC(O)OCF3) y del ester perfluorometilico del monofluoruro del acido peroxidicarbonico (CF3OC(O)OOC(O)F), los cuales se cree son respectivamente los productos finales de la cadena de la oxidacion del monoxido de carbono sensibilizada fotoquimicamente por el peroxido de perfluorometilo y el fluoroxiperfluorometano. Finalmente se da una descripcion de un nuevo metodo sintetico el cual da altos rendimientos de trioxido de perfluorometilo, dependiendo de la oxidacion de radicales perfluorometilo producidos fotoquimicamente a partir de una mezcla de fluor y perfluoroacetona.

Über Cadmiumpermanganat-Hexahydrat

Abstract: Das Pulverdiagramm, mit welchen die Gitterkonstanten und die Raumgruppe festgestellt wurden, sowie das IR-Spektrum und eineDTA-Untersuchung von Cd(MnO4)2·6 H2O werden angegeben und kurz besprochen.

False spectra from a plane grating produced by laser illumination.

Abstract: False spectra produced by intense coherent illumination are studied. This paper presents the well-known geometrical scheme to explain the formation and location of false spectral lines or Rowland ghosts, and from that scheme it was found that the number of ghosts produced by a spectral line is limited. This number is the same for the blazed region of the grating as for the unblazed one, and it includes the Rowland ghosts produced by the line at different spectral orders of the grating. Rowland’s formula, derived on the basis of the geometrical scheme, may be used to calculate ghost wavelengths far away from the parent line. The formula was experimentally checked. Experiments were performed by using a pulsed ruby laser as a light source, and the extreme ghosts were recorded at 1336.9 A and 10761.5 A.

An alternative method in distinguishing cattle transferrin phenotypes.

Abstract: A modification of the method described by Kristjansson (1963) allows easier distinction of the components and position of every major cattle transferrin phenotype. The modification is based on increasing the percentage of starch (15%) and reducing the pH of the gel buffer to 6.8. In all the experiments, when a voltage of 350 was applied, a tray of ice was placed over the starch gel for the remainder of the electrophoresis. Different cattle transferrin phenotypes from our modified electrophoresis method are composed as follows: Type A, 4 bands; D1, 4 bands; D1D2, 4 bands; D2, 4 bands; E, 4 bands; AD1, 6 bands; AD2, 6 bands; AE, 8 bands and sometimes 9 bands; D1E, 6 bands and sometimes 7 bands; and D2E, 6 bands. The position of the fourth D band is distinctly different in D1 vs. D2 types.

The beta-receptors in the rat pancreas.

Abstract: Se estudio el efecto del isoproterenol (ISO) sobre la secrecion de insulina in vitro Los resultados indican que el ISO es capaz de estimular la secrecion de insulina en forma similar a la glucosa en altas concentraciones

The kinetics and the mechanisms of some photochemical reactions of fluorine atoms and fluorine‐containing radicals

Abstract: — The mechanisms of these reactions were established and the kinetic parameters of their partial reactions determined: RESUMEN Se establecieron los mecanismos de las reacciones presentadas a continuacion, ademas de determinarse los parametros cineticos de sus reacciones parciales.

E2 transition probabilities in the davydov model

Abstract: Ratios ofE2-transition probabilities for the de-excitation of levels belonging to the ground-state, beta and gamma rotational bands in the deformed region 150

The theory of separated electronic groups: II. Its possibilities in actual calculations

Abstract: Usually, many-electron wave-functions for molecules are constructed from antisymmetrized products of one-electron orbitals. Configuration interaction and energy level calculations are based on variational principles, and matrix elements are obtained using Slater's rules. In this paper this method is generalized, the orbitals being replaced by group functions, each one describing any number of electrons. It is assumed that wave-functions satisfy separability conditions between groups similar to those already given by Lykos and Parr, and Parks and Parr. This work should be considered as an extension of theirs. Corrections to orbital energies and operators for the interaction between electrons belonging to different groups are given, the expressions are simplified using Mulliken's approximations. The method here developed is compared with McWeeny's density matrix formalism, and similarities and differences pointed out. Possibilities of application in actual molecules are compared with those of other methods.

On the electrojet in south america.

Abstract: The diurnal variation in the horizontal component (H) of south american stations under and close to the electrojet were plotted during the I.G.Y. Thus a dilatation towards the south of the electrojet in the western part of South America was inferred.

Analysis of some nuclear properties according to the donner and greiner model

Abstract: Static and dynamical properties of even-mass heavy deformed nuclei are calculated within the framework of the Donner and Greiner model. Theoretical predictions are in fair agreement with experiment as well as with results obtained using a microscopic description.

The theory of separated electronic groups I. Configuration interaction for some special configurations

Abstract: The previously developed theory of separated electronic groups is applied. The configuration interaction of closed and mixed open and closed shells is considered. Explicit expressions for interaction operators between electrons belonging to different groups and the corresponding matrix elements are given in both cases. The approach developed here is compared with the approximate solution to the interaction problem given by McWeeny.