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  • 1
    ISSN: 1520-4804
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Physics of Fluids 30 (1987), S. 3448-3454 
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Two types of small-aspect-ratio slot jets were investigated. An orifice slot jet with a 3:1 aspect ratio was shown to have features similar to an elliptic jet with a well-designed contraction. A larger spreading rate and enhanced turbulent mixing, relative to a circular jet, can be obtained using this orifice nozzle, which is advantageous for many practical applications. By adding a conical contraction to the slot jet (tapered slot jet) the characteristics were totally altered. The axes switching, typical to an elliptic jet, did not occur and the spreading rate at the major axis plane was larger than at the minor axis plane. The turbulence amplification in the initial core region was higher than both in the circular and elliptic jets. The transition from the conical contraction of the nozzle to the slot shape of the outlet section produced three-dimensional vortical structures. These structures interacted with the asymmetric vortices shed from this noncircular configuration to enhance the small scale turbulence in the core region as well as in the jet circumference. The large spreading rate of the two configurations of slot jets is beneficial to increase the bulk mixing with the surrounding fluid through entrainment. The augmented turbulence level of the tapered slot jet is important for reacting flows where small scale mixing is required.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Physics of Fluids 31 (1988), S. 1410-1419 
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The generalized shooting method, previously developed for the analysis of spatial instability modes of arbitrary shape jets, is applied to incompressible jets with triangular core regions of constant flow. The instability modes of these jets are classified, and calculations are carried out for spatial growth rates, phase velocities, and velocity fluctuation eigenfunctions of three fundamental and two overtone modes. All of the calculated eigenfunctions show negligible velocity fluctuations at the triangle vertices, in good correlation with experimental findings.
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  • 4
    Electronic Resource
    Electronic Resource
    Oxford [u.a.] : International Union of Crystallography (IUCr)
    Acta crystallographica 47 (1991), S. 2365-2367 
    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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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Landscape ecology 15 (2000), S. 219-227 
    ISSN: 1572-9761
    Keywords: heterogeneity ; landscape ; scale ; species diversity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract In this paper, we quantify the effects of habitat variability and habitat heterogeneity based on the partitioning of landscape species diversity into additive components and link them to patch-specific diversity. The approach is illustrated with a case study from central Switzerland, where we recorded the presence of vascular plant species in a stratified random sample of 1'280 quadrats of 1 m2 within a total area of 0.23 km2. We derived components of within- and between-community diversity at four scale levels (quadrat, patch, habitat type, and landscape) for three diversity measures (species richness, Shannon index, and Simpson diversity). The model implies that what we measure as within-community diversity at a higher scale level is the combined effect of heterogeneity at various lower levels. The results suggest that the proportions of the individual diversity components depend on the habitat type and on the chosen diversity aspect. One habitat type may be more diverse than another at patch level, but less diverse at the level of habitat type. Landscape composition apparently is a key factor for explaining landscape species richness, but affects evenness only little. Before we can test the effect of landscape structure on landscape species richness, several problems will have to be solved. These include the incorporation of neighbourhood effects, the unbiased estimation of species richness components, and the quantification of the contribution of a landscape element to landscape species richness.
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  • 6
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Two new cyclic analogues of physalaemin were designed on the basis of the conformation found in DMSO solution. Glp-Ala-cyclo(-Asp-Pro-Asn-Lys-)-Phe-Tyr-Gly-Leu-Met-NH2(1) was synthesized by cyclization of physalaemin. In 2 the Asp residue was replaced by Glu. The linear analogue of 2 was synthesized by the solid phase method and subsequently cyclized. Two-dimensional nmr methods were employed to assign the proton and carbon resonances. Proton-proton distances were extracted from rotating frame nuclear Overhauser effect spectra and used as restraints in the molecular dynamics calculations. Analogue 1 was found to have a similar conformation as physalaemin, whereas 2 did not form intramolecular hydrogen bonds. The pharmacological evaluation revealed that both peptides have similar potencies as physalaemin in the dog carotid artery (NK-1 receptor). Therefore, the charged side chains of physalaemin appear not essential for NK-1 activation. However, the other tachykinin receptors show good sensitivity to the cyclic peptides. It is concluded that the replacement of a salt bridge by an amide bond connecting the side chains of natural residues might provide useful information about the biological significance of some charged side chains of neurokinins.
    Additional Material: 3 Ill.
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  • 7
    ISSN: 0044-2313
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Zur Reaktion von 3-Dimethylamino-(1,1-dimethyl)propylmagnesiumchlorid mit Zinn(IV)- und Zinn(II)-chloriden. Stabilisierung eines SnCl+-Kations im neuartigen Zinn-Cluster [Me2NCH2CH2C(Me2)SnCl]3 · SnCl2Die Reaktionen des funktionellen Grignardreagenzes Me2 NCH2CH2C(Me2)MgCl (4) mit Zinntetrachlorid, Dimethyldichlorstannan und Zinn(II)-chlorid werden beschrieben. Aus diesen Umsetzungen resultieren die Verbindungen Bis(3-dimethylamino-1,1-dimethylpropyl)zinndichlorid, [Me2NCH2CH2C(Me2)]2SnCl2 5, dimethyl(3-dimethylamino-1,1-dimethylpropyl) chlorostannan, Me2ClSnC(Me2)CH2CH2NMe2 6, 1,1,2,2-Tetramethyl-1,2-bis(3-dimethylamino-1,1-dimethylpropyl) distannan, [Me2SnC(Me2)CH2CH2NMe2]2 7, 3-dimethylamino-(1,1-dimethyl)propylzinn(II)-chlorid, Me2NCH2CH2C(Me2)SnCl 8, Hexakis(3-dimethylamino-1,1-dimethylpropyl)cyclotristannan, {[Me2NCH2CH2C(Me2)]2Sn}39a und der Zinn-Cluster [Me2NCH2CH2C(Me2)SnCl]3 · SnCl2 10. Die Verbindungen wurden durch Multikern-NMR- uud Mößbauerspektroskopie sowie durch Röntgenbeugung charakterisiert. 10 kristallisiert in der trigonalen Raumgruppe P31 mit den Zellparametern a = 11,938, c = 21,873 Å, V = 2699,6 Å3 Z = 3. Die Struktur wurde bis zu einem R-Wert von 0,064 verfeinert. 10 stellt einen vierkernigen Cluster dar, dessen Gerüst aus vier Zinnatomen und einem verbrückenden Cl aufgebaut ist. Formal stellt das zentrale Zinnatom ein SnCl+-Kation dar, welches durch drei Stannyleneinheiten in einer Ψ-trigonal-bipyramidalen Umgebung stabilisiert ist. Die Sn-Sn-Bindungslängen betragen 288,2, 287,3 und 315,6 pm. Die intramolekularen Sn-N-Wechselwirkungen betragen 242,8, 247,4 und 221,0 pm.
    Notes: The reactions of the functional Grignard reagent Me2 NCH2CH2C(Me2)MgCl (4) with tin tetrachloride, dimethyltin dichloride, and tin (II) chloride are described. From the reactions the compounds bis(3-dimethylamino-1,1-dimethylpropyl) tin dichloride, [Me2NCH2CH2C(Me2)]2SnCl2 (5), dimethyl(3-dimethylamino-1,1-dimethylpropyl) chlorostannane, Me2ClSnC(Me2)CH2CH2NMe2 (6), 1,1,2,2-tetramethyl-1,2-bis(3-dimethylamino-1,1-dimethylpropyl) distannane,[Me2SnC(Me2)CH2CH2NMe2]2 (7), 3-dimethylamino-(1,1-dimethyl)propyl tin (II) chloride, Me2NCH2CH2C(Me2)SnCl (8), hexakis(3-dimethylamino-1,1-dimethylpropyl) cyclotristannane, {[Me2NCH2CH2C(Me2)]2Sn}3(9a), and the tin cluster [Me2NCH2CH2C(Me2)SnCl]3 · SnCl2 (10) have been isolated and characterized by means of multinuclear NMR and Mössbauer spectroscopy, and X-ray diffraction. 10 crystallizes in the trigonal space group P31 with the unit cell dimensions a 11.938, c 21.873 Å, V 2699.6 Å3 Z = 3. The structure was refined to a final R value of 0.064. 10 represents a tetranuclear cluster the skeleton of which is composed out of 4 Sn and a bridging Cl. Formally, the central tin atom is a SnCl+ cation stabilized by three stannylene units in a Ψ-trigonal bipyramidal environment. The tin-tin bond lengths are 288.2, 287.3 and 315.6 pm. The intramolecular Sn—N interactions amount to 242.8, 247.4 and 221.0 pm.
    Additional Material: 4 Ill.
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  • 8
    Publication Date: 2018-01-16
    Description: Bioluminescence imaging of single cells is often complicated by the requirement of exogenous luciferins that can be poorly cell-permeable or produce high background signal. Bacterial bioluminescence is unique in that it uses reduced flavin mononucleotide as a luciferin, which is abundant in all cells, making this system purely genetically encodable by the lux operon. Unfortunately, the use of bacterial bioluminescence has been limited by its low brightness compared with other luciferases. Here, we report the generation of an improved lux operon named ilux with an approximately sevenfold increased brightness when expressed in Escherichia coli; ilux can be used to image single E. coli cells with enhanced spatiotemporal resolution over several days. In addition, since only metabolically active cells produce bioluminescent signal, we show that ilux can be used to observe the effect of different antibiotics on cell viability on the single-cell level.
    Print ISSN: 0027-8424
    Electronic ISSN: 1091-6490
    Topics: Biology , Medicine , Natural Sciences in General
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  • 9
    Publication Date: 2018-05-29
    Description: Compared with localization schemes solely based on evaluating patterns of molecular emission, the recently introduced single-molecule localization concept called MINFLUX and the fluorescence nanoscopies derived from it require up to orders of magnitude fewer emissions to attain single-digit nanometer resolution. Here, we demonstrate that the lower number of required fluorescence photons enables MINFLUX to detect molecular movements of a few nanometers at a temporal sampling of well below 1 millisecond. Using fluorophores attached to thermally fluctuating DNA strands as model systems, we demonstrate that measurement times as short as 400 microseconds suffice to localize fluorescent molecules with ∼2-nm precision. Such performance is out of reach for popular camera-based localization by centroid calculation of emission diffraction patterns. Since theoretical limits have not been reached, our results show that emerging MINFLUX nanoscopy bears great potential for dissecting the motions of individual (macro)molecules at hitherto-unattained combinations of spatial and temporal resolution.
    Print ISSN: 0027-8424
    Electronic ISSN: 1091-6490
    Topics: Biology , Medicine , Natural Sciences in General
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  • 10
    Publication Date: 2019-12-02
    Description: Bioluminescence-based imaging of living cells has become an important tool in biological and medical research. However, many bioluminescence imaging applications are limited by the requirement of an externally provided luciferin substrate and the low bioluminescence signal which restricts the sensitivity and spatiotemporal resolution. The bacterial bioluminescence system is fully genetically encodable and hence produces autonomous bioluminescence without an external luciferin, but its brightness in cell types other than bacteria has, so far, not been sufficient for imaging single cells. We coexpressed codon-optimized forms of the bacterialluxCDABEandfrpgenes from multiple plasmids in different mammalian cell lines. Our approach produces high luminescence levels that are comparable to firefly luciferase, thus enabling autonomous bioluminescence microscopy of mammalian cells.
    Print ISSN: 0027-8424
    Electronic ISSN: 1091-6490
    Topics: Biology , Medicine , Natural Sciences in General
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