Library

feed icon rss

Your email was sent successfully. Check your inbox.

An error occurred while sending the email. Please try again.

Proceed reservation?

Export
Filter
  • 2000-2004  (3)
  • 1970-1974  (2)
Material
Years
Year
  • 1
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 116 (2002), S. 984-992 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Electron impact ionization cross sections measured close to threshold are reported for both the monomers and dimers of ozone and OClO using a new high resolution electron impact apparatus. The present appearance energies AE(O3+/O3)=12.70±0.02 eV, AE (OClO+/OClO)=10.55±0.02 and AE(ClO+/OClO=13.37±0.03 eV derived from the measured ionization cross sections are in excellent agreement with the vertical threshold values determined for these ions by high resolution PES and PIMS photoionization studies. The corresponding appearance energies determined for the dimer ions, 10.10±0.3 eV for (O3)2+ and 9.87±0.2 eV for (OClO)2+, are both red shifted with respect to the monomer case. The bond energy (0.70–0.3+0.5) eV of (OClO)2+ estimated from these data is similar to that of other dimer ions, whereas the bond energy of (O3–O3+) with (2.55−0.4+0.6) eV is rather large suggesting an unusual structure for the cationic ozone dimer ion. Based on quantum chemical calculations on various levels we are led to the conclusion that the ion produced by ionization of the ozone dimer is no longer a conventional dimer ion where the two monomer units are still present (as is the case for the OClO system), but rather an ion of form O2(centered ellipsis)O4+ or a twisted ring structure of (O6)+. © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 2
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Using a high resolution two sector field mass spectrometer of reversed geometry we have measured metastable fractions and mass-analyzed ion kinetic energy peaks for metastable decay reactions involving monomer evaporation via (O2)n+*→(O2)n−1++O2. Both, average kinetic energy release 〈KER〉 data derived from the peak shapes and the time dependence of the metastable fractions show a characteristic dependence on cluster size indicating a change in the metastable fragmentation mechanism when going from the dimer to the dekamer ion. Moreover, the 〈KER〉 data contain information about the transition state temperature and thus one can use finite heat bath theory to calculate the binding energies of the decaying cluster ions. The results obtained are in fair agreement with (i) previous results based on gas phase ion equilibria measurements and with (ii) the corresponding bulk value. © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 3
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 113 (2000), S. 616-620 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We have measured the kinetic energy release (KER) distributions for electron-induced dissociation of mass-selected molecular parent and fragment ions of propane. They are compared with distributions determined for spontaneous (metastable) dissociation. The average KER for induced dissociation of C3H8+ into C3H7+ is 13.2±1.2 meV, about 42% larger than for the spontaneous reaction. This large difference is attributed to the dramatically reduced time at which the induced reaction can be sampled. In contrast, the KER for dissociation of C3H7+ into C3H5+, which is characterized by a large reverse activation energy, is hardly affected by the experimental time scale. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Journal of neurology 198 (1970), S. 256-279 
    ISSN: 1432-1459
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Zusammenfassung Unter den bisher erschienenen Mitteilungen über cerebrale Anfälle als besonderes Symptom der Multiplen Sklerose (MS) werden 70 Kasuistiken ausgewertet, bei denen der Zusammenhang gesichert erschien. 19 eigene Beobachtungen aus einer Zahl von insgesamt mehr als 4000 Patienten mit MS werden dieser Gruppe gegenübergestellt. Es ergibt sich, daß nach dem klinischen Anfallstyp in 40% primär generalisierte, gewöhnlich tonisch-klonisch ablaufende Iktus vorkommen. Unter den übrigen Anfallstypen (60%), die durch Herderscheinungen eingeleitet werden oder herdförmig bleiben, überwiegen die mit rein motorischen Erscheinungen. In diesen Fällen kann ein Herd in oder nahe der Präzentralregion vermutet werden. Sie machen einen Anteil von 25% am Gesamtmaterial aus. Die Zuordnung der epileptogenen Herde zu den verschiedenen Hirnabschnitten an Hand des vorliegenden MS-Materials spiegelt in der Häufigkeitsverteilung weitgehend die bekannte Disposition der Rindenareale zur Ausbildung epileptogener Foci wider. Die Gesamthäufigkeit cerebraler Anfälle bei der MS liegt nach den Mitteilungen der Literatur zwischen 1 und 6%. Berechnungen am eigenen Krankengut der Würzburger wie der Göttinger Neurologischen Universitätskliniken nach kritischer Sichtung und Ausscheidung aller nicht gesicherten oder wahrscheinlich zu machenden Fälle ergaben jedoch nur 0,5–0,6%. Beide Umstände zeigen, daß sich die MS wohl nicht im Sinne einer spezifischen epileptogenen Noxe auswirkt. Die Frage nach der Lage der epileptogenen Läsionen in Beziehung zu corticalen Strukturen wird diskutiert. Abschließend wird kurz auf die EEG-Befunde eingegangen.
    Notes: Summary From the communications hitherto reported on cerebral attacks as a particular feature of multiple sclerosis (MS) 70 case histories with an apparently proven relationship were evaluated. The observations in 19 own cases from a total number of 4000 patients with MS are compared to this group. It was found that according to the clinical type of seizure primarily generalized usually tonic-clonic attacks occurred in 40%. Among the other types of seizures (60%) which begin with focal symptoms or remain localized, those with strictly motor symptoms prevail. A focus within or near the precentral region may be presumed to exist in these cases. They comprise 25% of the entire group. The association of the epileptogenic foci with the various brain areas as illustrated by the present cases of MS and the frequency distribution reflect to a large measure the well known predisposition of cortical areas to form epileptogenic foci. The total incidence of cerebral attacks in MS varies between 1 and 6% according to the literature. Computations based on the patients of our own seen at the neurological departments of the universities of Würzburg and Göttingen yielded 0.5 to 0.6% only after all cases were critically reviewed and rejected if not or only partially fufilling our criteria. Both of these observations demonstrate that MS might not act in terms of a specific epileptogenic noxa. The localization of epileptogenic lesions in relation to cortical structures is discussed. In conclusion, EEG findings are briefly mentioned.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Journal of thermal analysis and calorimetry 4 (1972), S. 479-482 
    ISSN: 1572-8943
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract A simple method is described for use with the differential scanning calorimeter for baseline interpolation in continual processes over a wide temperature interval. For the process of water desorption from the synthetic zeolite LiA with the coveragegq=1.5, the measured heat of desorption wasQ=11.2±0.5 kcal/mole.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
Close ⊗
This website uses cookies and the analysis tool Matomo. More information can be found here...