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  • 1
    Electronic Resource
    Electronic Resource
    Hydrodynamic stability of flow between rotating porous cylinders with radial and axial flow (1997)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Fluids 9 (1997), S. 3687-3696 
    Details
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A linear stability analysis was carried out for axial flow between a rotating porous inner cylinder and a concentric, stationary, porous outer cylinder when radial flow is present for several radius ratios. The radial Reynolds number, based on the radial velocity at the inner cylinder and the inner radius, was varied from −15 to 15, and the axial Reynolds number based on the mean axial velocity and the annular gap was varied from 0 to 10. Linear stability analysis for axisymmetric perturbations results in an eigenvalue problem that was solved using a numerical technique based on the Runge–Kutta method combined with a shooting procedure. At a given radius ratio, the critical Taylor number at which Taylor vortices first appear for radial outflow decreases slightly for small positive radial Reynolds numbers and then increases as the radial Reynolds number becomes more positive. For radial inflow, the critical Taylor number increases as the radial Reynolds number becomes more negative. For a given radial Reynolds number, increasing the axial Reynolds number increases the critical Taylor number for transition very slightly. The critical wave velocity decreases slightly for small positive radial Reynolds numbers, but increases for larger positive and all negative radial Reynolds numbers. The perturbed velocities are very similar to those for no axial flow. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.869506
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  • 2
    Electronic Resource
    Electronic Resource
    CLOSTRIDIAL TOXINS AS THERAPEUTIC AGENTS: Benefits of Nature's Most Toxic Proteins (1999)
    Palo Alto, Calif. : Annual Reviews
    Annual Review of Microbiology 53 (1999), S. 551-575 
    Details
    ISSN: 0066-4227
    Source: Annual Reviews Electronic Back Volume Collection 1932-2001ff
    Topics: Biology
    Notes: Abstract Toxins are increasingly being used as valuable tools for analysis of cellular physiology, and some are used medicinally for treatment of human diseases. In particular, botulinum toxin, the most poisonous biological substance known, is used for treatment of a myriad of human neuromuscular disorders characterized by involuntary muscle contractions. Since approval of type-A botulinum toxin by the US Food and Drug Administration in December 1989 for three disorders (strabismus, blepharospasm, and hemifacial spasm), the number of indications being treated has increased greatly to include numerous focal dystonias, spasticity, tremors, cosmetic applications, migraine and tension headaches, and other maladies. Many of these diseases were previously refractory to pharmacological and surgical treatments. The remarkable therapeutic utility of botulinum toxin lies in its ability to specifically and potently inhibit involuntary muscle activity for an extended duration. The clostridia produce more protein toxins than any other bacterial genus and are a rich reservoir of toxins for research and medicinal uses. Research is underway to use clostridial toxins or toxin domains for drug delivery, prevention of food poisoning, and the treatment of cancer and other diseases. The remarkable success of botulinum toxin as a therapeutic agent has created a new field of investigation in microbiology.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1146/annurev.micro.53.1.551
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  • 3
    Electronic Resource
    Electronic Resource
    Definitive ab initio structure for the X˜ 2A′H2PO radical and resolution of the P–O stretching mode assignment (1998)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 109 (1998), S. 2694-2699 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Previous ab initio studies of the X˜ 2A′H2PO radical have reported dramatically differing P–O bond distances when using spin-restricted wave functions predicting two artifactual isomers of H2PO: a singly bonded oxygen-centered radical and a doubly bonded phosphorus-centered radical. We show that large basis sets coupled with high levels of dynamical electron correlation are required to correctly describe the P–O bond in H2PO as well as the unpaired electron density as evidenced by the Fermi contact terms and anisotropic components of the 31P, 1H, and 17O hyperfine splitting (hfs) constants. The optimized geometry, harmonic vibrational frequencies, and hfs constants of H2PO were determined at several coupled-cluster levels of theory using both spin-restricted (ROHF) and spin-unrestricted (UHF) Hartree–Fock reference wave functions. The geometrical parameters at the coupled-cluster level with single, double, and perturbatively applied triple substitutions [CCSD(T)] using Dunning's correlation consistent polarized valence quadruple-ζ basis set (cc-pVQZ) are r(P–O)=1.492 Å; r(P–H)=1.410 Å; (angle)(HPH)=102.63°; (angle)(HPO)=114.92°. These are in excellent agreement with those derived from recent gas phase microwave data, with the surprising exception of the P–H distance which deviates 0.02 Å from experiment. The value of the P–O harmonic stretching frequency at the CCSD(T) level within the cc-pVQZ basis set is 1190 cm−1, in good agreement with the experimental fundamental frequency of 1147 cm−1 obtained by Withnall and Andrews and in constrast to previous speculation that this experimental band may have been misassigned. Hyperfine splitting constants determined at the TZ2P(f,d)/UHF-CCSD(T) level are in very good agreement with experimental values with an average deviation of 23 MHz. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.476869
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