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  • 1
    ISSN: 1573-0662
    Keywords: tropospheric hydroxyl radicals ; laser absorption spectroscopy ; OH-radical chemistry ; field experiment
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract Absolutely calibrated in-situ measurements of tropospheric hydroxyl radicals, formaldehyde, sulfur dioxide, and naphthalene (C10H8) were performed by long-path laser absorption spectroscopy during the field campaign POPCORN. The absorption light path was folded into an open optical multiple reflection cell with a mirror separation of 38.5 m. Using a light path length of 1848 m and an integration time of 200 s, the average 1σ-detection limits of OH, HCHO, SO2 and C10H8 during POPCORN were 8.7 · 105 cm−3, 8.3 · 109 cm−3, 2.4 · 109 cm−3, 1.5 · 108 cm−3, respectively. In total, 392 identifications of OH in air spectra were made in a rural environment between August 5 and August 23, 1994. We present and discuss OH absorption spectra and diurnal OH concentration profiles of three days which are representative for measurements under different pollution conditions during POPCORN. The observed maximum and median OH radical concentrations are 1.3 · 107 OH/cm3 and 4.0 · 106 OH/cm3, respectively. The measured diurnal variation of the OH concentration shows a good correlation with the primary formation reaction of OH radicals which is the photolysis of ambient ozone. Deviations from this correlation in the morning and evening hours, when the OH concentration is higher than expected from the ozone photolysis, demonstrate the importance of other photochemical HOx production pathways during POPCORN.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1573-0662
    Keywords: OH intercomparison ; laser absorption spectroscopy ; DOAS ; laser induced fluorescence ; LIF ; troposphere
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract In-situ OH measurements by laser-induced fluorescence (LIF) spectroscopy and folded long-path differential optical absorption spectroscopy (DOAS) were carried out in a rural environment in North-East Germany as part of the field experiment POPCORN in August 1994. The large set of OH data obtained allowed an intercomparison of both techniques based on relative diurnal profiles and simultaneously measured absolute concentrations. Most of the time the two OH instruments encountered the same air and agreed well in the measured relative diurnal variations. Only on a few occasions the measurements significantly disagreed due to a perturbation of the DOAS measurements by a local OH source in the north-western wind sector. Excluding data from this wind direction, the statistical analysis of 137 data pairs yields a correlation coefficient of r = 0.90 and a weighted linear fit with a slope of 1.09 ± 0.12. The correlations are carefully analyzed. The comparison of both instruments is discussed in the light of newly published effective absorption cross-sections for H2O and O2 that affect the calibration of LIF.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1435-1536
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Zusammenfassung Zu Beginn der Arbeit wurden die im praktischen Teil zur Verwendung gelangten Untersuchungsmethoden wiedergegeben. Hierbei wurde festgestellt, daß: 1. Die von Föppl und Bach für Metallstäbe (speziell Eisenträger) von schmalem, rechteckigen Querschnitt aufgestellten Formeln des Torsionsmoduls auch für plastische Materialien (Filme von Gelatine- und Nitrozellulose-Gelen) gültig sind. 2. Es wurde mit dem speziell in der Textilindustrie als Materialcharakteristik auftretenden Begriff der Schmiegsamkeit als physikalisch meßbare Größe der Torsionsmodul in Verbindung gebracht. Der Hauptteil der Arbeit, welcher sich mit dem Einfluß chemischer Zusatzmittel auf die mechanischen Eigenschaften einiger Gele befaßte, gab folgende Ergebnisse: 1. Die Festigkeit nimmt im allgemeinen unter dem Einfluß des Zusatzes ab. Die Feuchtigkeitsadsorption des Zusatzes setzt die Festigkeit noch weiter herab. 2. Die elastischen Eigenschaften (Elastizitätsmodul) stehen im gleichen Abhängigkeitsverhältnis von den Zusätzen wie die Festigkeitseigenschaften. 3. Der Torsionsmodul steht ebenfalls im gleichen Verhältnis zu den Mengen der Zusätze wie die Festigkeit. Auch der Feuchtigkeitseinfluß macht sich in ähnlicher Weise geltend.
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  • 4
    ISSN: 1572-9338
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics , Economics
    Notes: Abstract This overview focuses on lexicographic choice under conditions of uncertainty. First, lexicographic versions of traditional (von Neumann-Morgenstern) expected utility theory are described where the usual Archimedean axiom is weakened. The role of these lexicographic variants in explaining some well-known “paradoxes” of choice theory is reviewed. Next, the significance of lexicographic choice for game theory is discussed. Finally, some lexicographic extensions of the classical maximin decision rule are described.
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Plant systematics and evolution 108 (1961), S. 351-353 
    ISSN: 1615-6110
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Plant systematics and evolution 109 (1962), S. 182-182 
    ISSN: 1615-6110
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
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  • 7
    ISSN: 1617-4623
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The inactivation of λ repressor was followed by the specific DNA binding assay during the course of lysogenic induction provoked by incubation at 42°C of an E. coli tif-1 lysogenic strain. The presence of up to 400 μg/ml chloramphenicol during the inducing treatment did not impair the loss of repressor binding activity, whilst concentrations of 200 μg/ml neomycin and 100 μg/ml rifampicin effectively inhibited the inactivation of λ repressor. Residual protein synthesis in the presence of chloramphenicol, neomycin and rifampicin was 5%, 5% and 27% respectively of that observed in the drug-free control. This residual synthesis did not appear to involve amplification of the X-protein. These results suggest that tif-mediated inactivation of the λ repressor requires the activation of some specific gene(s), the translation of which appears to be resistant to chloramphenicol.
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  • 8
    ISSN: 1615-6110
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Zusammenfassung 1. Durch Versuche mit 2-14C-markiertem Na-Acetat konnte gezeigt werden, daßEndomycopsis vernalis, ebenso wieTorulopsis utilis, Acetat aufnimmt und zur Lipidsynthese verwendet. 2. In der Lipidfraktion vonEndomycopsis vernalis waren Ergosterin, freie Fettsäuren, Sterin- und Fettsäureester und vermutlich Squalen nachweisbar. 3. Die Hemmwirkungen von Acetat, Propionat, Valerianat und Caprylat sind vom pH abhängig. Für die Hemmwirkung sind die undissoziierten Säuren verantwortlich. 4. Endomycopsis vernalis ist gegen alle genannten Säuren empfindlicher alsTorulopsis utilis. 5. Die Absterberate ruhender Zellen vonEndomycopsis vernalis wird durch undissoziierte Essigsäure beschleunigt. 6. Versuche mit14C-Acetat ergaben keine Anhaltspunkte für eine bevorzugte Aufnahme undissoziierter Essigsäure in die Zellen vonEndomycopsis vernalis.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Springer
    Zoomorphology 92 (1979), S. 191-200 
    ISSN: 1432-234X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Dark- and light-adapted ocelli of three seastars (Patina miniata, Leptasterias pusilla, Henricia leviuscula) were studied by transmission and scanning electron microscopy. In the dark-adapted state the process of each receptor cell is relatively devoid of clear vesicles. Numerous long microvilli arise from the tips and sides of the processes. Cilia from the sensory processes project into the lumen of an ocellus; they are unconnected to the microvilli. In light-adapted ocelli each process is filled with clear pinocytotic vesicles of varying size. The microvilli are now irregular. Many lie free in the lumen of an ocellus or within phagocytic vacuoles in the supportive and corneal cells. These findings are evidence of a microvillar (rhabdomeric) type of photoreceptor in seastars and of cyclic turnover of receptoral membrane.
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  • 10
    ISSN: 1432-234X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The ocelli of trochophore and segmented larvae of the archiannelid Polygordius cf. appendiculatus were studied by electron microscopy. An eye consists of two pigmented supportive cells forming an eyecup that encloses one sensory cell bearing one (trochophore) or two (segmented larva) ranks of microvilli and one adventitious cilium. Remarkably abundant tubules (submicrovillar endoplasmic reticulum) radiate from the perinuclear region of the sensory cell, which lies outside the ocellus, toward its receptoral end. Possible functions of the tubules are proposed: carriers of ions, metabolites and photopigments; pinocytic uptake of products resulting from photoreception; storage of membrane; and light guides. Finally, the eyes of Polygordius larvae are believed to have evolutionary significance and provide further support for Eakin's theory of diphyletic origin of photoreceptors.
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