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  • 1
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 104 (1996), S. 942-949 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We investigated dimethyl-s-tetrazine (-h6 and -d6) in a n-heptane (-h16 and -d16) lattice with hole burning techniques. Stark experiments definitely show that the two methyl groups in dimethyl-s-tetrazine (DMST) are inequivalent. Hence, the respective rotational tunneling dynamics can be different. This is clearly seen in the behavior of DMST-d6 in both lattices n-heptane-h16 and -d16: Hole burning produces three pairs of sideholes symmetrically shifted from the laser frequency. The tunneling dynamics of the central hole as well as of the sideholes is governed by two relaxation times which differ by about one order of magnitude. Due to the narrow temperature range accessible, an unambiguous assignment of the microscopic tunneling relaxation process is not possible. On the other hand, DMST-h6 relaxes via a Raman process above 3 K and via a direct process below. In the Raman-active regime the tunneling rates for both host lattices fall on top of each other in agreement with theory. There are, however, features in the tunneling dynamics which are not yet understood. For instance, in the temperature regime where the direct process prevails, host deuteration speeds up the tunneling relaxation by an order of magnitude. In addition, the sidehole pattern of DMST-h6 is quite different from DMST-d6: Only one pair is observed. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 99 (1993), S. 1-6 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Spectral hole burning is used to measure spin-conversion relaxation of methyl groups attached to a dye probe. The dye is dimethyl-s-tetrazine, the host is n-octane, which is, at low temperatures, a Shpol'skii-matrix. The temperature dependence of the spin-conversion relaxation follows the same pattern for the protonated and the perdeuterated methyl-rotor. However, the relaxation rates of the perdeuterated rotor are higher by almost two orders of magnitude. Partial deuteration destroys the rotor symmetry and leads to a breakdown of the correlation between nuclear spin and rotational wave function.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 105 (1996), S. 9762-9770 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Rotational tunneling of monodeuterated methyl groups of dimethyl-s-tetrazine guest molecules in n-octane and tetramethylbenzene crystalline matrices is characterized by optical spectroscopy including hole burning methods. An analysis of the level structure shows that the asymmetric substitution leads to a partial localization of one of the methyl groups in n-octane, while in the tetramethylbenzene host both groups are equivalent and are strongly localized. The relaxation, by incoherent tunneling, between different orientations proceeds on a time scale of 〉107 s−1 in n-octane at temperatures below 2 K. The coupling of the orientation of the methyl group with the environment is estimated from information on inhomogeneous broadening attributed to random strain fields in the crystal. The strength of this coupling is related to the observed relaxation behavior. The origin of the asymmetry of the rotational potential is discussed in terms of static and dynamic contributions which are due to changes of bond length upon isotopic substitution and the dependence of vibrational frequencies on orientation. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    s.l. : American Chemical Society
    The @journal of physical chemistry 〈Washington, DC〉 99 (1995), S. 14561-14565 
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 0022-2313
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
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  • 6
    ISSN: 0022-4731
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Biology , Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Amsterdam : Elsevier
    Biochimica et Biophysica Acta (BBA)/Protein Structure and Molecular 1037 (1990), S. 178-185 
    ISSN: 0167-4838
    Keywords: Macropain ; Proteasome ; Proteinase
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Type of Medium: Electronic Resource
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  • 8
    ISSN: 0167-4838
    Keywords: Macropain ; Multicatalytic proteinase ; Proteasome ; Ubiquitin
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Springer
    Der Chirurg 68 (1997), S. 898-901 
    ISSN: 1433-0385
    Keywords: Key words: Acute posttraumatic and postoperative cholecystitis ; Ultrasonographic findings. ; Schlüsselwörter: Cholecystitis ; akute postoperative und posttraumatische ; Ultraschallkriterien.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Zusammenfassung. Eine oft unbemerkte, jedoch potentiell fatale Komplikation im posttraumatischen Verlauf intensivpflichtiger Patienten ist die reaktive akute Cholecystitis. Aufgrund der hohen Spezifität der Ultraschalldiagnostik im biliären System war es unser Ziel, die Ultraschallkriterien zur frühzeitigen Objektivierung der posttraumatischen Cholecystitis zu überprüfen. Prospektiv wurde über 12 Monate bei 40 beatmungspflichtigen Patienten an jeweils 7 Tagen eine Ultraschalluntersuchung des Oberbauchs durchgeführt. Die Ergebnisse zeigen, daß Beatmung, parenterale Ernährung und die Auswirkungen einer zuvor stattgehabten Traumatisierung des Patienten zu einer verzögerten Verdickung (28/40) bzw. Dreischichtung (9/40) der Gallenblasenwand führen kann. Sonographisch waren in 22,5 % (9/40) die Zeichen einer akuten Cholecystitis nachweisbar. In Korrelation mit den klinischen Parametern ergab sich jedoch nur in 2 Fällen die Indikation zur Cholecystektomie. Unsere Studie zeigt, daß das morphologische Korrelat einer verdickten dreischichtigen Gallenblasenwand auch ohne zugrundeliegende Cholecystitis im Rahmen systemischer Veränderungen auftreten kann. Eine sichere Diagnose einer akuten reaktiven Cholecystitis mit der Indikation zur Cholecystektomie konnte bei pathologischem Sonographiebefund nur in enger Korrelation mit klinischen Parametern gestellt werden.
    Notes: Summary. An often unrecognized but potentially fatal complication, mostly seen in posttraumatic patients under intensive care, is reactive acute cholecystitis. On account of the high specificity of ultrasound diagnosis in the biliary system we decided to examine the ultrasound criteria for early detection of posttraumatic cholecystitis. Ultrasound of the abdomen was performed prospectively, seven times on different days, in each of 40 artificially respirated patients under intensive care conditions over a period of 12 months. The results show that artificial respiration, parenteral feeding and previous trauma can lead to tardive (28/40) wallthickening or to a three-layered wall of the gallbladder (9/40). In 22.5 % of patients (9/40) we found the sonographic signs of acute cholecystitis. In correlation with the clinical signs, cholecystectomy was indicated in only two patients. The preoperative ultrasonographic findings and clinical signs of 23 patients with the diagnosis of acute reactive cholecystitis were analysed retrospectively. We found good correlation between sonographic and clinical signs of acute cholecystitis in 21 of these 23 patients. Our study shows that the morphological correlate of a thickened three-layered gallbladder wall can occur in the context of systemic alterations, even if there is no underlying cholecystitis. The diagnosis of acute reactive cholecystitis and the indication for cholecystectomy should be based on the synopsis of pathologic and clinical findings.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    Springer
    Journal of cancer research and clinical oncology 120 (1994), S. 657-661 
    ISSN: 1432-1335
    Keywords: Photodynamic therapy ; Fluorescence ; 5-ALA ; Experimental colonic tumour
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract 5-Aminolevulinic acid (5-ALA) is a precursor in the biosynthesis of haem. External application of 5-ALA leads to the formation of protoporphyrin IX, the last intermediate product before haem, which is an effective sensitiser. The 5-ALA-induced endogenous photosensitisation of tumour cells has been exploited for photodynamic therapy (PDT). Experimental human G-3 colonic tumours were transplanted into nude mice, and ten mice were treated by PDT. Ten animals served as controls. We measured a fluorescence intensity of the tumour that was about eight times higher than in the surrounding tissue; a good correlation between the fluorescence intensity and the photodynamic effect was found. Tumour growth was inhibited significantly after PDT, two tumours being destroyed completely after the second PDT treatment. In addition, on-line fluorescence detection during PDT showed a change in the intensity and the fluorescence spectrum of protoporphyrin IX caused by photobleaching and the formation of photoproducts.
    Type of Medium: Electronic Resource
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