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  • Springer  (166)
  • International Union of Crystallography (IUCr)
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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    The journal of membrane biology 167 (1999), S. 43-52 
    ISSN: 1432-1424
    Keywords: Key words: HeLa cells — Inward rectifier — Cloning — Kir2.1 —Xenopus oocyte — Channel
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract. Previous patch-clamp studies have shown that the potassium permeability of the plasma membrane in HeLa cells, a cell line derived from an epidermoid carcinoma of the cervix, is controlled by various K+-selective pores including an IRK1 type inwardly rectifying K+ channel. We used the sequence previously reported for the human heart Kir2.1 channel to design a RT-PCR strategy for cloning the IRK1 channel in HeLa cells. A full-length clone of 1.3 kb was obtained that was identical to the human cardiac Kir2.1 inward rectifier. The nature of the cloned channel was also confirmed in a Northern blot analysis where a signal of 5.3 kb corresponding to the molecular weight expected for a Kir2.1 channel transcript was identified not only in HeLa cells, but also in WI-38, ECV304 and bovine aortic endothelial cells. The HeLa IRK1 channel cDNA was subcloned in an expression vector (pMT21) and injected into Xenopus oocytes. Cell-attached and inside-out single channel recordings obtained from injected oocytes provided evidence for a voltage-independent K+-selective channel with current/voltage characteristics typical of a strong inward rectifier. The single channel conductance for inward currents measured in 200 mm K2SO4 conditions was estimated at 40 ± 1 pS (n= 3), for applied voltages ranging from −100 to −160 mV, in agreement with the unitary conductance for the IRK1 channel identified in HeLa cells. In addition, the single channel conductance for inward currents, Γ, was found to vary as a function of αK, the external K+ ion activity, according to Γ=Γ0 [αK]δ with Γ0= 3.3 pS and δ= 0.5. Single channel recordings from injected oocytes also provided evidence of a voltage-dependent block by external Cs+ and Ba2+. The presence of 500 μm Cs+ caused a voltage-dependent flickering, typical of a fast channel blocking process which resulted in a reduction of the channel open probability at increasingly negative membrane potential values. The fractional electrical distance computed for the Cs+ blocking site was greater than 1 indicating a multiple ion channel occupation. In contrast, external Ba2+ at concentrations ranging from 25 to 100 μm caused a slow channel block, consistent with the binding of a single Ba2+ ion at a site located at half the membrane span. It is concluded on the basis of these observations that HeLa cells expressed a Kir2.1 type inwardly rectifying channel likely to be involved in maintaining and regulating the cell resting potential.
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Archives of microbiology 152 (1989), S. 215-217 
    ISSN: 1432-072X
    Keywords: Cyanobacterium ; Oscillatoria limnetica ; Anacrobic unsaturated fatty acid synthesis ; Positional isomers
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The mechanism for synthesis of monounsaturated fatty acids under aerobic and anaerobic conditions was studied in the facultative anaerobic cyanobacterium, Oscillatoria limnetica. The hexadecenoic acid (C16∶1) of aerobically grown O. limnetica was shown to contain both the Δ7 (79%) and Δ9 (21%) isomers, while the octadecenoic (C18∶1) acid was entirely the Δ9 acid. Incorporation of [2-14C] acetate into the fatty acids under aerobic conditions resulted in synthesis of the Δ7 and Δ9 C16∶1 and the Δ9 C18∶1. Synthesis of unsaturated fatty acids in the presence of DCMU required sulfide. Anaerobic incubations in the presence of DCMU and sulfide (less than 0.003% atmospheric oxygen) resulted in a two-fold increase in monounsaturated fatty acids of both Δ7 and Δ9 C16∶1 and Δ9 and Δ11 C18∶1. The synthesis of these isomers is characteristic of a bacterialtype, anaerobic pathway.
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Applied physics 50 (1990), S. 13-17 
    ISSN: 1432-0649
    Keywords: 32.80P
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract 172Yb+ ions in an rf trap have been laser cooled for the first time by driving the 2 S 1/2–2 P 1/2 transition at 369.5 nm. It was necessary to irradiate the ions with 2.438 μm infra-red radiation to depopulate the metastable 2 D 3/2 state. An upper limit on ion energies was determined by observing the size of the trapped cloud and corresponds to a temperature below 2 K. Cooled ion lineshapes were compared with simulations and coherence nulls were observed in the infra-red frequency scans.
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  • 4
    Electronic Resource
    Electronic Resource
    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 33 (2000), S. 1162-1174 
    ISSN: 1600-5767
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Geosciences , Physics
    Notes: The instrumental transparency functions of five commercially available texture goniometers were measured experimentally with six monocrystalline samples cut in different orientations from a large highly perfect silicon crystal with a rocking curve of less than 0.01°. Transparency functions were measured in steps of 0.02 to 0.2° in the pole-figure angles α, β. The window size Δα depends on the Bragg angle θ in the form 1/sinθ; the window size Δω is constant for each goniometer. The dominant instrumental parameter determining the long axis Δα of the pole-figure window is the axial width of the detector entrance slit. This parameter is smallest for area detectors (smaller by more than an order of magnitude compared with conventional scintillation detectors as well as one-dimensional position-sensitive detectors). The main features of the pole-figure window and their dependence on the instrumental parameters can be deduced fairly well from a simple geometrical model. The particular shapes of the transparency functions of the studied goniometers are markedly different. Particularly, they are not very well represented by Gauss functions. The two-dimensional transparency function can be fairly well characterized by its α and β profiles. The normalized profiles are virtually independent of the goniometer angles 2θ and α. The increasing size of the pole-figure window with decreasing θ puts a lower limit on the Bragg angle below which pole-figure measurement ceases to be meaningful.
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  • 5
    Electronic Resource
    Electronic Resource
    Oxford [u.a.] : International Union of Crystallography (IUCr)
    Acta crystallographica 45 (1989), S. 1697-1699 
    ISSN: 1600-5759
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Colloid & polymer science 255 (1977), S. 927-927 
    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
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    Journal of comparative physiology 11 (1930), S. 345-385 
    ISSN: 1432-1351
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Springer
    Heat and mass transfer 17 (1983), S. 115-119 
    ISSN: 1432-1181
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Description / Table of Contents: Zusammenfassung Bewegungen von Gasblasen in einem vertikalen Temperaturgradienten werden experimentell untersucht. Die neben der Erdschwere als Bewegungsursache auftretende Grenzflächenkonvektion (Marangonikonvektion) an der Grenzfläche Blase/Medium wird im Lichte der Theorie von Young et al. diskutiert. Die Größe der Marangonizahl im Blaseninnern (N i Ma) bzw. im äußeren Medium (N e Ma) wird als Kriterium für die Anwendbarkeit der Theorie eingeführt. Die Experimente demonstrieren die Anwendbarkeit der Young-Theorie bis zur MarangonizahlN i Ma=10−2 bzw.N e Ma=2.
    Notes: Abstract This is an experimental study on gas bubble motion in a vertical temperature gradient. Surface tension convection (Marangoni convection) superimposing gravity is discussed with respect to the theory of Young et al. as another cause for bubble motion. The Marangoni numbers for the convection inside the bubble (N i Ma) and outside the bubble in the medium (N e Ma) are introduced as criterion for the applicability of the theory. It is shown by the experiments that the Young theory holds up to Marangoni numbersN i Ma=10−2 and Ne Ma=2, respectively.
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  • 9
    Electronic Resource
    Electronic Resource
    Springer
    Journal of pest science 6 (1930), S. 97-101 
    ISSN: 1612-4766
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Zusammenfassung Die GetreidemotteSitotroga cerealella Oliv. entwickelt in der palästinensischen Küstenzone jährlich 5–6 Generationen. Der Entwicklungsnullpunkt liegt bei 10,3° C, die Thermalkonstante beträgt 474°. Die Eizahl schwankt zwischen 80 und 180 pro ♀, die Verteilung der Geschlechter ist wie 1∶1. Während das Entwicklungspotential einesSitotroga-Pärchens bei 6 Generationen in einem Jahr über 30 Milliarden Motten betragen müßte, beträgt die tatsächliche Nachkommenziffer eines Pärchens im Laufe eines Jahres unter den klimatischen Bedingungen der palästinensischen Küstenebene nur 400–450 Motten. Durch die extremen Temperaturen im Winter und Sommer wird die Zahl der Tiere derart reduziert, daß ihre Zahl im neuen Jahr von der des Vorjahres nicht sehr variiert.
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  • 10
    Electronic Resource
    Electronic Resource
    Springer
    Cellular and molecular life sciences 27 (1971), S. 399-399 
    ISSN: 1420-9071
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary InSylvia borin andS. atricapilla, circannual rhythmicity was found in moult, migratory restlessness and in changes of body weight and gonad size under constant photoperiodic conditions.
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