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  • 1
    Digitale Medien
    Digitale Medien
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 65 (1989), S. 4603-4607 
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: A laser-induced fluorescence technique for the detection and measurement of ionized barium atoms near the vicinity of an oxide-coated electrode in a low-pressure discharge lamp is presented. Ionized Ba atoms are produced by the ionization of neutral Ba atoms in the electrode fall region of the discharge. Radiation at 455.4 nm obtained from a pulsed dye laser was used to excite Ba ii from the ground state, 62S1/2, to the resonance level, 62P3/2, and the fluorescence radiation at 614.2 nm for the 62P3/2→52D5/2 transition was measured. The number density of Ba ii atoms as determined from the measured intensity of the fluorescence signal (614.2 nm) is dependent on the discharge current, and the polarity of the neighboring electrode. It is found to be larger when it is acting as an anode than when it is a cathode.
    Materialart: Digitale Medien
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  • 2
    Digitale Medien
    Digitale Medien
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 65 (1989), S. 4595-4602 
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: A laser-induced fluorescence method for measuring the loss rate of barium from Ba-Sr-Ca oxide coated electrodes of low-pressure discharge lamps is presented. The oxide coating from the electrode surface is depleted during lamp operation. Using this technique, the Ba loss rate from an electrode, when it is acting both as a cathode and an anode during ac operation, was measured. A significantly larger amount of neutral barium is detected in the vicinity of the electrode when it acts as an anode over when it acts as a cathode. The consumption rate of Ba and hence the life of an oxide coating depends upon the phase of the lamp current, the shape, and the magnitude of the current supplied by the lamp ballast. The consumption rate for the coating increases linearly with the discharge current. A simplified theoretical analysis of the technique for a three-level atomic system irradiated by a pulse laser beam is discussed.
    Materialart: Digitale Medien
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  • 3
    Digitale Medien
    Digitale Medien
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 68 (1990), S. 2687-2693 
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: Spatially resolved arc temperatures and sodium density measurements are presented for two high-pressure sodium arcs. Absolute intensities of the optically thick 818/819-nm lines were used to determine the arc temperature while the radial profile of the optically thin 514-nm line was Abel inverted to determine the Na atomic density. Agreement with an independent measurement of the Na density obtained by controlling pressure of sodium in the lamp with a tin bath consistently required a value for the Na 514-nm transition probability 2–3 times smaller than the literature value (A=0.011×108 s−1 ) of Wiese, Smith, and Miles [Atomic Transition Probabilities, NSRDS-NBS 4 (NBS, Washington, DC, 1971), Vol. II], obtained from quantum mechanical calculations. The results of three separate experiments indicate that the value should be modified to A=0.0040×108 s−1 with a standard deviation of ±21%. A more detailed error analysis including systematic error would indicate an accuracy to within ±33%.
    Materialart: Digitale Medien
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  • 4
    Digitale Medien
    Digitale Medien
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 84 (1986), S. 1598-1605 
    ISSN: 1089-7690
    Quelle: AIP Digital Archive
    Thema: Physik , Chemie und Pharmazie
    Notizen: A fast and accurate method for the calculation of molecular overlap integrals involving exponential-type orbitals is discussed on the basis of the Fourier transform convolution theorem. The overlap integrals are related to a one-dimensional integral for which an exact analytical expression is given in a computationally convenient form. The numerical stability of the analytical expression is examined over a wide range of values of relevant parameters. Alternative procedures for evaluating the one-dimensional integral in regions of the parameter space where the analytical expression becomes unreliable are examined. The speed, accuracy, and the range of applicability of the method for the evaluation of overlap integrals are discussed in the light of recent work by other authors.
    Materialart: Digitale Medien
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  • 5
    Digitale Medien
    Digitale Medien
    s.l. : American Chemical Society
    The @journal of physical chemistry 〈Washington, DC〉 35 (1931), S. 653-655 
    Quelle: ACS Legacy Archives
    Thema: Chemie und Pharmazie , Physik
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 6
    ISSN: 1432-1866
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Geologie und Paläontologie
    Notizen: Abstract Intimate association of ∼ 2 billion years old stromatolite with pyritic lead-zinc ores in the Precambrian polymetallic deposit at Rajpura-Dariba in Rajasthan, which hitherto remained unreported, provides an additional documentation of the syn(-dia)-genetic mineralization. The growth form and petrography of the stromatolite structure have been described and an explanation sought regarding the concentration of sulfides along the siliceous and carbonaceous laminations, as well as in the intercolumnar regions. Consideration of the geologic features noted in the mineralized zone and surrounding region suggests that the stratiform ores were deposited in a near-shore shallow marine environment, developed on basement highs and associated with euxinic conditions. Later, the ores were metamorphosed under conditions reaching upto amphibolite facies during a three-stage deformational history of their enclosing rocks. Some salient features of the secondary structures in the ores have been discussed in relation to this deformation history.
    Materialart: Digitale Medien
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  • 7
    Digitale Medien
    Digitale Medien
    Springer
    Mineralium deposita 15 (1980), S. 401-405 
    ISSN: 1432-1866
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Geologie und Paläontologie
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 8
    Digitale Medien
    Digitale Medien
    [s.l.] : Nature Publishing Group
    Nature 131 (1933), S. 840-841 
    ISSN: 1476-4687
    Quelle: Nature Archives 1869 - 2009
    Thema: Biologie , Chemie und Pharmazie , Medizin , Allgemeine Naturwissenschaft , Physik
    Notizen: [Auszug] SINCE 1916, when one of us1 reported that this reaction is very sensitive to light and that the dark reaction has a high temperature coefficient, a large amount of work has been carried out on this chemical change by several chemists2. The majority of workers ...
    Materialart: Digitale Medien
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  • 9
    Digitale Medien
    Digitale Medien
    Springer
    Entomologia experimentalis et applicata 15 (1972), S. 238-247 
    ISSN: 1570-7458
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Beschreibung / Inhaltsverzeichnis: Zusammenfassung Tribolium confusum-Larven wurden vom Schlüpfen bis zur Larven-Puppen-Häutung an geschrotetem Weizen, fein gemahlenem Weizen, fein gemahlenem Weizen + 5% Bierhefe oder Weizenkeimlingen aufgezogen. Der Kot wurde quantitativ gesammelt und mittels Dünnschichtchromatographie, der enzymatisch-spektrophotometrischen Methode und colorimetrischen Methoden auf Stickstoff-Endprodukte analysiert. Mit geschrotetem Weizen oder Weizenkeimlingen gefütterte Larven hatten einen größeren Gesamtgehalt an Stickstoff-Metaboliten als die anderen. Die relativen Mengen von Hypoxanthin, Xanthin, Harnsäure und Allantoin, welche diesen Gesamtgehalt ergaben, wechselten mit der Diät. Auf den Gesamtgehalt bezogen blieb Allantoin prozentual relativ konstant, aber die Anteile der übrigen End-produkte variierten beträchtlich. Kot nach Ernährung mit geschrotetem oder fein gemahlenem Weizen enthielt etwa 30% Harnsäure, während Kot von mit Weizenkeimlingen oder mit gemahlenem Weizen + Bierhefe ernährten Tieren etwa 68 bzw. 50% Harnsäure und entsprechend geringere Mengen Hypoxanthin und Xanthin enthielt. Harnstoff und Ammoniak waren ebenfalls vorhanden jedoch vermutlich durch die Mikroorganismen des Kots gebildet worden.
    Notizen: Abstract Tribolium confusum duVal larvae were reared from hatching to the larval-pupal ecdysis on cracked wheat, finely ground wheat, finely ground wheat plus 5% brewer's yeast, or wheat germ. Feces were collected quantitatively and analyzed for nitrogenous end products by thin layer chromatography, the enzymatic-spectrophotometric method, and colorimetric methods. Larvae fed cracked wheat or wheat germ excreted a larger total of nitrogenous metabolites than did the others. The relative quantities of hypoxanthine, xanthine, uric acid, and allantoin which made up the total varied with diet. Calculated on the basis of the total, the percent allantoin remained relatively constant, but the proportions of the other end products varied considerably. Feces derived from cracked wheat or finely ground wheat contained about 25% uric acid, while feces derived from wheat germ or ground wheat with brewer's yeast contained about 61% and 45% uric acid respectively and correspondingly reduced quantities of hypoxanthine and xanthine. Urea and ammonia were also present. Correction for the estimated urine content of the feces results in an increase in the calculated approximate digestibility and a decrease in the calculated efficiency of conversion of digested food. The changes are small, but significant. The size of the change varies with the diet.
    Materialart: Digitale Medien
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  • 10
    ISSN: 1435-1536
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Maschinenbau
    Beschreibung / Inhaltsverzeichnis: Zusammenfassung Die Wanderungsgeschwindigkeit an der Grenze von As2S3 and FeOH3-Solen wurde gemessen, und zwar bei konstantem Strom. Eine neue Methode zur Messung der Wanderung bei konstantem Strom wird vorgeschlagen. Die Veränderungen der Bewegung der Grenze mit der Zeit werden diskutiert, und es wird vermutet, daß Messungen der kataphoretischen Geschwindigkeit von Kolloidpartikeln bei konstantem Strom theoretisch mehr Aussagen geben als Messungen bei konstanter Spannung, weil Widerstandsänderungen in den einzelnen Teilabschnitten des Kataphoreserohres bei konstantem Strom ein korrekteres Bild gibt. Ein Potentialröhrenvoltmeter wurde für die Messung des Spannungsabfalls angewendet, so daß zeitliche Änderungen verzögerungsfrei aufgezeichnet werden konnten.
    Notizen: Summary The migration velocities of the boundary of As2S3 and Fe(OH)3 sols have been measured under constant current. A new set up for measuring the movement of the boundary under constant current has been devised. The changes in the boundary movement with time have been observed under constant current condition and it has been discussed and suggested that measurements of cataphoretic velocity of colloidal particles under constant current is theoretically more cogent than the measurements taken under constant voltage, because the changes in the resistance shown by the changes in the potential developed across the different elements in the U-tube at constant current give a more correct picture of what happens in the cataphoretic tube when cataphorisis takes place. A potentio-valve-voltmeter has been employed to measure the instantaneous changes of voltage across the mainU-tube without any time lag. This is a new device which has not been tried before.
    Materialart: Digitale Medien
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