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  • 2000-2004  (4)
  • 1975-1979  (1)
  • 1920-1924
  • 2000  (4)
  • 1977  (1)
  • 1
    Electronic Resource
    Electronic Resource
    Time-resolved dissociative intense-laser field ionization for probing dynamics: Femtosecond photochemical ring opening of 1,3-cyclohexadiene (2000)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 112 (2000), S. 8347-8362 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The concerted photochemical ring opening of 1,3-cyclohexadiene was investigated in the gas phase by low-intensity pumping at 267 nm and subsequent probing by high-intensity photoionization at 800 nm and mass-selective detection of the ion yields. We found five different time constants which can be assigned to traveling times along consecutive parts of the potential energy surfaces. The molecule is first accelerated in the spectroscopic state 1B along Franck–Condon active coordinates, then alters direction before changing over to the dark state 2A. All constants including that for leaving the 2A surface are below 100 fs. These times are shorter than appropriate vibrational periods. Such a maximum speed is evidence that the pathway is continuous leading from surface to surface via real crossings (conical intersections) and that the molecule is accelerated right into the outlet of the 2A/1A funnel. On the ground state it arrives as a compact wave packet, indicating a certain degree of coherence. The experimental method promises a high potential for investigating dynamics, since many consecutive phases of the process can be detected. This is because the fragmentation pattern depends on the location on the potential energy surface, so that monitoring several different ions permits to conclude on the population flow through these locations. Ionization at the intensities used is normally considered to be an effect of the electric field of the radiation. But in our case it is enhanced by resonances in the neutral molecule and in particular in the singly positive ion, and it is not sensitive for the length of the molecule (different conformers of the product hexatriene). The ionic resonances explain why hexatriene has a much richer fragmentation pattern than cyclohexadiene. Coulomb explosion is observed from an excited state of a doubly positive ion. Its mechanism is discussed. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.481478
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    On the Approximation of Certain Mass Distributions Appearing in Distance Geometry (2000)
    Springer
    Acta mathematica hungarica 87 (2000), S. 295-316 
    Details
    ISSN: 1588-2632
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics
    Notes: Abstract Let X be a compact subset of the n-dimensional Euclidean space R n . A theorem of G. Björck implies the existence of a unique probability measure μ0 which maximizes the value ∫ X ∫ X d 2(x, y) dμ(x) dμ(y), where μ ranges over all probability measures on X and d 2 denotes the Euclidean distance on R n . In this paper we introduce and investigate an algorithm which is easy to describe and which inductively constructs a sequence ω = x 1, x 2,... in X such that ω is uniformly distributed with respect to μ0. Geometrical and topological interpretations and applications, and concrete numerical examples are given.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1006773702255
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Die muskuläre Dämpfung niederfrequenter Schwingungen im Tierversuch (1977)
    Springer
    Archives of orthopaedic and trauma surgery 87 (1977), S. 317-323 
    Details
    ISSN: 1434-3916
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Zusammenfassung Zur Klärung vibrationsbedingter Wirbelsäulenbeschwerden bei Hubschrauberpiloten wurde tierexperimentell die muskuläre Dämpfung untersucht. Am Pirbright-Meerschweinchen wurden auf einem Schwingtisch Beschleunigungswerte einmal unter Abwehrspannung, im zweiten Versuch unter maximaler Relaxation der Muskulatur gemessen. Das verspannte Tier dämpfte die bei 5 Hz auftretenden Resonanzen nahezu vollständig. Beim relaxierten Tier ließ sich im gleichen Frequenzbereich eine eindeutige Resonanzkurve entwickeln. Hingegen wurden höherfrequente Vibrationen bis 15 Hz beim relaxierten Tier in zunehmendem Maße stärker gedämpft als unter muskulärer Abwehrspannung. Die Schutzfunktion einer nicht ermüdeten Stammesmuskulatur zur Abwehr besonders schlecht tolerierter Resonanzvibrationen wird diskutiert.
    Notes: Summary For the further clarification of helicopter pilot's spinal troubles caused by vibration the muscular absorption was examined with the help of animal experiments. On a swinging-table acceleration values were measured in Pirbright cavies; at first this was done under a defence reaction of the muscles, and in second experiment under maximum muscular relaxation. In the tense animal the resonance occurring at 5 Hz was almost completely absorbed, whereas in the relaxed animal a clear resonance—curve could be developed at 5 Hz. On the other hand vibration at a higher frequency up to 15 Hz were to an increasing extent better absorbed in the relaxed animal than in animal with a muscular defence reaction. For this reason the protective function of a not fatigued musculature for the defence of especially badly tolerated resonance vibrations is being discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00416007
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  • 4
    Electronic Resource
    Electronic Resource
    Induction of an Acute Attack of Calcium Pyrophosphate Dihydrate Arthritis by Intra-articular Injection of Hylan G-F 20 (Synvisc) (2000)
    Springer
    Clinical rheumatology 19 (2000), S. 147-149 
    Details
    ISSN: 1434-9949
    Keywords: Key words:Calcium pyrophosphate dihydrate arthritis – Hylan G-F 20 – Side-effects – Viscosupplementation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract: Little is known about the induction of acute calcium pyrophosphate dihydrate arthritis after the intra-articular injection of hylan G-F 20 (Synvisc). Two reports have documented this adverse effect after the intra-articular injection of hyaluronan. Our patient, a 60-year-old man with osteoarthritis in both knees, presented with a history of an arthroscopy with meniscus shaving 7 years previously. He was given an injection of hylan G-F 20 in the right knee joint. Two days after the second injection, pain and swelling of the knee occurred. There was a severe loss of physical function. Systemic inflammatory reactions such as fever were not observed. A microscopic investigation of the synovial fluid showed evidence of calcium pyrophosphate dihydrate crystals. Bacterial contamination was not detected. There was no indication for calcium pyrophosphate dihydrate in the history of the patient. Some days after receiving non-steroidal anti-inflammatory drugs and an intra-articular injection of steroids, the symptoms disappeared.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s100670050034
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    Paper (German National Licenses)
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  • 5
    Electronic Resource
    Electronic Resource
    Simple device to monitor aerobic biotransformations by in situ 1H-NMR (2000)
    Springer
    Biotechnology letters 22 (2000), S. 1135-1141 
    Details
    ISSN: 1573-6776
    Keywords: aerobic biotransformations ; in situ 1H-NMR ; 1H-NMR in 1H2O
    Source: Springer Online Journal Archives 1860-2000
    Topics: Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract A simple device for taking in situ proton NMR measurements in 1H2O is described. This allows aeration of reactions in a 10 mm diameter NMR tube without modifying the magnet or the probe head. With this device, aerobic biotransformations can be monitored in the NMR-tube placed in the spectrometer. It allows in situ analyses of the transformations, separating the aeration period temporally from the measurement time, not unlike traditional Warburg respiratory experiments. Two reactions determining kinetic and stoichieometric parameters: (i) a biotransformation by a growing Pseudomonas putida culture and (ii) l-phenylalanine oxidation catalysed by l-amino acid oxidase [E.C. 1.4.3.2]; both incubations were contained in the magnet.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1005664400918
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