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  • Electronic Resource  (7)
  • 1990-1994  (7)
  • 1985-1989
  • 1950-1954
  • 1991  (7)
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  • Electronic Resource  (7)
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  • 1990-1994  (7)
  • 1985-1989
  • 1950-1954
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  • 1
    Electronic Resource
    Electronic Resource
    Growth and characterization of reactively sputtered thin-film platinum oxides (1991)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 69 (1991), S. 1596-1604 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Thin-film oxides of platinum have been prepared by reactive sputtering and characterized primarily by x-ray diffraction (XRD) and Raman scattering. Different phases of the Pt-O system were obtained by adjusting sputtering parameters such as gas composition, deposition rate, and substrate temperature. Optimum conditions for producing crystalline α-PtO2 and PtO were identified. Raman spectra of α-PtO2 films show two sharp lines at 514 and 560 cm−1, in agreement with those from commercially available powders. XRD and high-resolution scanning electron microscopy (HRSEM) analyses indicate that these samples have a poorly crystallized structure with lack of order along the c axis. The Raman spectra from PtO show two broad peaks at 438 and 657 cm−1, close to the lines seen in PdO, which has the same structure as PtO. Estimates from XRD line broadening and HRSEM photographs indicate mean crystallite sizes on the order of 300 A(ring). Infrared reflectivity spectra yield two of the three ir-active phonons, and along with scanning tunneling microscopy measurements suggest that PtO is a semiconductor. Thermoelectric measurements show that the predominant carriers are p-type, and ir reflectivity data indicate a carrier concentration of ∼4×1018 cm−3.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.347255
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Preparation of oriented silicon carbide films by laser ablation of ceramic silicon carbide targets (1991)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 59 (1991), S. 2266-2268 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Stoichiometric films of SiC, 60–150 nm thick, were deposited on [001] and [111] Si wafers by laser ablation of ceramic stoichiometric SiC targets. Films grown at substrate temperatures above 1050 °C show orientation epitaxial to the Si substrate along the film normal. Depending on the deposition conditions, the oriented crystallite dimension along this direction ranges from 20 nm up to the film thickness. The crystallite dimensions in the film plane range from 20 to 70 nm. Raman spectra indicate that the films often contain material other than crystalline SiC. Some of that is in the form of small (3–5 nm) graphitic inclusions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.106065
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Efficiency of Early Selection for Yield Performance in Wheat (1991)
    Oxford, UK : Blackwell Publishing Ltd
    Plant breeding 107 (1991), S. 0 
    Details
    ISSN: 1439-0523
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Selection for yield in early generations is difficult, mainly due to a shortage of seed. In the breeding company Fr. Strube the breeder uses three-way crosses and first selects for yield between F2′-derived lines in the F4′. The generations are called F1, F2′, etc., because the first generation is already segregating. The efficiency of this selection was checked in the F5′ and F6′. For this purpose F3′-derived progenies, corresponding to poor and good yielding bulks in F4′, were selected. In later generations the average yield of the group of strains with good yield in the F4′ was 4 % (F5′) and 3 % (F6′) higher, respectively, than the mean of the strains with low yield in the F4′. Strains with very low yielding potential can easily be discarded in the F4′. The risk of discarding lines with a very high yield is minimal. Selection for yield in the F4′ was as effective as in the F5′. The importance of testing F2′-derived bulks in the F4′ is not only based on the assessment of yield but also on the possibility of reliable intensive selection through recording visual characters (height, resistance against diseases) in a second environment in parallel to the single plant progenies.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1439-0523.1991.tb00536.x
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  • 4
    Electronic Resource
    Electronic Resource
    Tierexperimentelle Untersuchungen zum gestielten Dünndarm-transplantat als partieller extrahepatischer Gallengangsersatz (1991)
    Springer
    Langenbeck's archives of surgery 376 (1991), S. 77-84 
    Details
    ISSN: 1435-2451
    Keywords: Bile duct stricture ; Pedicle graft
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Zusammenfassung Mit einem gestielten Dünndarmpatch konnte in Einzelfällen eine Gallengangsstriktur dauerhaft erweitert werden. Man beobachtet jedoch eine Dilatation des Patches, deren Ursache ebenso wie deren Folgen auf die Leberfunktion bislang ungeklärt sind. Mit einem gestielten Dünndarmpatch ist tierexperimentell ein partieller extrahepatischer Gallengangsersatz möglich. Eine Erweiterung des Patches wird regelmäßig beobachlet. Ursache hierfür ist weder eine Denervation des Patches noch der intraduktale Gallengangsdruck, sondern möglicherweise ein Zug am Gefäßstiel. Morphologische Veränderungen treten am Patch nach bis zu 15 Monaten nicht auf. Leberfunktionsstörungen können weder laborchemisch noch histologisch nachgewiesen werden. Der gestielte Darmpatch stellt daher eine gute Möglichkeit zum partiellen Gallengangsersatz tar. Im Gegensatz zu einer Choledochuszyste scheint die regelmäßig zu beobachtende Dilatation des Patches aufgrund der erhaltenen Kontraktionsfähigkeit nicht zu einer Stase der Galle mit Entwicklung von Cholangitiden oder Konkrementen zu führen. Voraussetzung für these Operationstechnik ist allerdings ein freier Abluß über die Papille.
    Notes: Summary A pedicle graft of the jejunum can in some cases enlarge a bile duct stricture. The enlargement of the patch and its consequences on the liver function are possible problems. In an animal experiment the following questions were sought. 1) Is a partial replacement of the bile duct with a pedicle graft of small bowel possible? 2) Is there an enlargement of the patch in every case and what are the consequences on the biliary tract and on liver function. The experiments were performed on 14 minipigs over a long-term observation period of 450 days. The red and white blood cell count, the GPT, GOT, GPT, bilirubin and alkaline phosphatase and copper were checked monthly. After 2, 6 and 12 months the intra- and extrahepatic biliary tract were visualized via a PTC. After 8 months an angiography of the pedicle graft was performed. 15 months later the animals were killed and the bile duct, the graft and the liver were histologically examined. 1) With a pedicle graft of small bowel a partial replacement of the extrahepatic bile duct is possible. 2) An enlargement of the patch is seen in every case. The enlargement is a consequence of tension at the pedicle. After 15 months no morphological changes were observed at the patch nor were there any irregularities in liver function.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01263464
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  • 5
    Electronic Resource
    Electronic Resource
    Ein gestieltes Dünndarmsegment zum zirkulären Ersatz des extrahepatischen Gallengangs bei erhaltener papillärer Passage (1991)
    Springer
    Langenbeck's archives of surgery 376 (1991), S. 351-358 
    Details
    ISSN: 1435-2451
    Keywords: Small bowel segment ; Extrahepatic bile duct
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Zusammenfassung Der extrahepatische Gallengang wurde bei 12 Göttinger Miniaturschweinen unter Erhalt einer papillären Passage durch ein gestieltes Dünndarmsegment ersetzt. In monatlichen Abständen wurden das Blutbild, die Cholestaseparameter und der Serumkupferspiegel überprüft. Nach 2, 6 und 12 Monaten erfolgte eine PTC und nach 8 Monaten wurde der Gefäßstiel des Dünndarmtransplantats angiographisch dargestellt. Nach 420 Tagen wurden die Tiere getötet, der Gefäβstiel, das Dünndarmtransplantat und die Leber histologisch untersucht. Die Laborparameter waren bei allen Tieren im Beobachtungszeitraum von 420 Tagen im Normbereich. In der PTC fanden sich keine Anastomosenstenosen. Bei Obduktion waren die Transplantate reizlos eingeheilt. Histologisch war der Aufbau des Transplantats erhalten geblieben. Es fanden sich intakte Nervenfasern im Dünndarmtransplantat und im Gefäßstiel. Die Leberbiopsien waren nach bis zu 420 Tagen unauffällig. Das gestielte Dünndarmtransplantat stellt daher eine vielversprechende Möglichkeit zum vollständigen Ersatz der extrahepatischen Gallenwege dar. Voraussetzung ist allerdings ein freier Abfluβ über die Papille. Die klinische Anwendung muβ zeigen, ob die Langzeitergebnisse denen der biliodigestiven Anastomosen überlegen sind.
    Notes: Summary The effect of a small bowel segment as a extrahepatic bile duct replacement was examined in 12 pigs followed-up for a period of 420 days. No complications, either during the operation or postoperatively, were observed in any of the animals. The laboratory parameters were within normal range over the entire observation period of 420 days. After 2, 6, and 12 months there was no anastomotic stenosis in the PTC. The intrahepatic biliary tract was not dilated. There was obvious peristalsis of the small bowel transplant towards the papilla of Vater. The autopsy showed that the grafts had healed without any sign of irritation. Histologically the structure of the graft remained undisturbed. There was a clear distinction between the mucosa of the bile duct and that of the small bowel, with no sign of a chronic infection. In the graft as well as in the vascular pedicle the nerve fibres were intact. Liver biopsy showed no pathological changes. In the light of these experiments, a small bowel segment presents a very promising alternative replacement of the extrahepatic biliary tract.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00186428
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  • 6
    Electronic Resource
    Electronic Resource
    Study of a Hamiltonian describing orbital excitations (1991)
    Springer
    The European physical journal 84 (1991), S. 221-228 
    Details
    ISSN: 1434-6036
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The physics of Mott-Hubbard insulators with almost degenerate orbitals is described by the Kugel-Khomskii Hamiltonian, representing the coupling of spin and orbital degrees of freedom. In this paper we study by analytical methods, and by exact diagonalization techniques, the phase diagram and ground state correlations functions for a one and two dimensional version of the Hamiltonian. In particular, we study two limits; in the one, the orbital degrees of freedom are predominant while in the other, there is an interplay between spin and orbital energies leading to effects analogous to a Peierls instability.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01313540
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  • 7
    Electronic Resource
    Electronic Resource
    Raman investigation of simple and complex oxides of platinum (1991)
    Chichester [u.a.] : Wiley-Blackwell
    Journal of Raman Spectroscopy 22 (1991), S. 1-9 
    Details
    ISSN: 0377-0486
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Raman spectra were obtained from PtO, Pt5O6, Pt3O4, α-PtO2, β-PtO2, MxNayPt3O4 (M = Co, Ni), PtCoO2 and MPt3O6 (M = Mn, Co, Cd). An enumeration of the allowed Raman modes is made for all of these oxides except Pt5O6, for which the structure is unknown. Polarization measurements allow symmetry species assignments to be made for the lines from α-PtO2 and PtCoO2, and a likely assignment of the lines from β-PtO2 is made by analogy with rutile-structured materials with the rutile structure.
    Additional Material: 15 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jrs.1250220102
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