Bibliothek

feed icon rss

Ihre E-Mail wurde erfolgreich gesendet. Bitte prüfen Sie Ihren Maileingang.

Leider ist ein Fehler beim E-Mail-Versand aufgetreten. Bitte versuchen Sie es erneut.

Vorgang fortführen?

Exportieren
  • 1
    Digitale Medien
    Digitale Medien
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 81 (1997), S. 5763-5765 
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: Polycrystalline samples of the mixed-valence perovskite-type manganites (Sm0.7A0.3)MnO3 (A=Ca2+,Sr2+,Ba2+,Pb2+) have been synthesized and their transport properties studied. The electrical conductivity of the series involves a variable-range hopping mechanism in the paramagnetic state, which extends well below TC for three of the samples. Only (Sm0.7Sr0.3)MnO3 shows a metal-insulator transition. There is a peak in the resistivity at a temperature Tp, just below the Curie point, TC=70 K with a transition from thermally activated type to metallic conductivity at low temperature with a large residual resistivity, ρ0=6×10−4 Ω m. By comparison with the (Ln0.7A0.3)MnO3 compounds, Ln=La, Pr, Nd the samarium compounds are more localized. The decrease of both Tp and TC with decreasing lanthanide radius and increasing mass depends on the nature of the substituted divalent cation, but the data cannot be scaled on a universal curve with respect to average ionic radius or tolerance factor. © 1997 American Institute of Physics.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 2
    Digitale Medien
    Digitale Medien
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 85 (1999), S. 5384-5386 
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: Magnetization curves up to 25 T at 4.2 K are reported for mixed-valence manganites (R0.7A0.3)MnO3. All the R=La compounds show an extrapolated ferromagnetic moment of ∼3.4 μB/f.u. The A=Sr and Ca compounds show essentially no high-field slope, dM/dB〈0.001 μB/T whereas the Pb and Ba compounds show slopes of 0.0047 and 0.0025 μB/T, suggesting that electrons of both spins are present at the Fermi level. All Pr compounds show much greater slopes, dM/dB(approximate)0.02 μB/T associated with a singlet ground state for Pr3+. All except the Ca compound have extrapolated moments of 3.6±0.3 μB/f.u. but (Pr0.7Ca0.3)MnO3 exhibits two first-order magnetization processes, at 5 and 6 T, due respectively to melting of charge order as the compound becomes ferromagnetic and a level-crossing transition for the Pr3+ ion. All the Nd compounds, except for the charge ordered, Ca containing compound, have a magnetization which is ∼1 μB greater than their La counterparts, due to ferromagnetic alignment of Nd and Mn moments. © 1999 American Institute of Physics.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 3
    ISSN: 1432-1017
    Schlagwort(e): Key wordsα-helical coiled coil ; Sedimentation equilibrium ; Circular dichroism ; Peptide and protein self-association
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Physik
    Notizen: Abstract Alpha-helical coiled coils are proving to be almost ideal systems for the modelling of peptide and protein self-association processes. Stable oligomeric systems, in which the stoichiometry is well defined, can be produced by the careful selection of the appropriate amino acid sequence, although the principles behind this are still not fully understood. Here we report on a 35 residue peptide, FZ, synthesized by the solid phase method, which was originally designed to form a dimer, but which, in fact, associates to the trimeric state. A detailed characterization of the associative properties of the peptide has been performed by circular dichroism spectroscopy and, in particular, by sedimentation equilibrium in the analytical ultracentrifuge. The presence of the trimeric state, which is stable even at low peptide concentrations, has been confirmed by various, independent methods of analysis for molar mass. The effects of both temperature and of guanidinium chloride on the peptide have been investigated and both found to be peptide-concentration dependent. The unfolding induced by the denaturant cannot be adequately described by a simple, two state monomer-trimer equilibrium.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 4
    Digitale Medien
    Digitale Medien
    Springer
    Digestive diseases and sciences 42 (1997), S. 592-596 
    ISSN: 1573-2568
    Schlagwort(e): NITRIC OXIDE ; SUPEROXIDE ; SUPEROXIDE DISMUTASE ; ESOPHAGUS ; ESOPHAGEAL MOTILITY ; SMOOTH MUSCLE ; ENTERIC NERVOUS SYSTEM
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Abstract Nitric oxide mediates esophageal peristalsis andlower esophageal sphincter (LES) relaxation. Superoxideproduced with inflammation inactivates nitric oxide.Superoxide is cleared in biological systems by superoxide dismutase. We tested thehypothesis that superoxide and the superoxide scavengingsystem modulate LES function. Transverse strips ofmuscle from the opossum LES relaxed when stimulated by an electrical field. Diethyldithiocarbamite wasused to inhibit copper/zinc superoxide dismutase.Xanthine and xanthine oxidase were used to generatesuperoxide. Xanthine with xanthine oxidase ordiethyldithiocarbamite alone had no effect on the LES. However,xanthine/xanthine oxidase and diethyldithiocarbamitereduced LES relaxation 34.1% and increased its restingtone 71.2%. Superoxide dismutase did not affect LESfunction, but protected the tissue from the effects ofdiethyldithiocarbamite and xanthine/xanthine oxidase.These studies are consistent with the hypothesis thatsuperoxide acts by inactivating nitric oxide and suggest that these antioxidant enzyme systemsmay play a role in the maintenance of LESfunction.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
Schließen ⊗
Diese Webseite nutzt Cookies und das Analyse-Tool Matomo. Weitere Informationen finden Sie hier...