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  • 1
    Electronic Resource
    Electronic Resource
    Medullary respiratory-related neurons with axonal connections to rostral pons and their function in termination of inspiration (1985)
    Springer
    Pflügers Archiv 403 (1985), S. 58-65 
    Details
    ISSN: 1432-2013
    Keywords: Axonal connections ; Medullary respiratory neurons ; Pneumotaxic centre ; Termination of inspiration
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract In urethane-anaesthetized, paralyzed and artificially ventilated rabbits, medullary respiration-related neurons (RRU) were classified according to the phase relation of their burst discharge to phrenic nerve activity. Phase-bound inspiratory (I) or expiratory (E) neurons were discriminated from phase-spanning expiratory-inspiratory (EI) or inspiratory-expiratory (IE) units. Mechanisms of termination of inspiration by electrical stimulation of rostral pontine nuclei (Nc. parabrachialis medialis; Lc. coeruleus) were examined firstly to demonstrate whether RRU receive descending excitatory and inhibitory afferents as well as ascending efferents and secondly to analyse the time course of the neuronal pathways involved. Of 120 RRU, 38 neurons were demonstrated to receive pontine afferents. About 33% of all E neurons became orthodromically excited during rostral pons stimulation whereas 18.2% of all I cells became orthodromically inhibited. Some RRU were shown to project up to the rostral pons. 50% of these were of the phase-spanning IE type. The onset of inspiratory inhibition induced by rostral pons stimulation occurred 3.4 ms after the onset of single electrical pulse stimulation. Based on these results a neuronal model for a pontine mechanism terminating inspiration is proposed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00583283
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  • 2
    Electronic Resource
    Electronic Resource
    Influence of rubrospinal tract and the adjacent mesencephalic reticular formation on the activity of medullary respiratory neurons and the phrenic nerve discharge in the rabbit (1988)
    Springer
    Pflügers Archiv 413 (1988), S. 23-31 
    Details
    ISSN: 1432-2013
    Keywords: Axonal connections ; Control of breathing ; Medullary respiratory neurons ; Midbrain ; Reticular formation ; Rubrospinal tract
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Suprapontine brain sites acting on the central respiratory system have been demonstrated to give rise to inspiratory as well as expiratory facilitatory effects. In the present study the inspiratory inhibitory effect which has been reported in the cat to be elicited consistently by electrical stimulation of the rubrospinal tract and the adjacent mesencephalic reticular formation was examined in the urethane-anaesthetized rabbit. Stimulation of these sites with single electrical shocks of moderate intensity induced a short latency (onset after 3.0 ms) transient (duration: 29 ms) inhibition of the phrenic nerve activity (PHR). Short volleys of stimuli applied in mid- to late-inspiration led to a premature off-switch of inspiration. The extracellularly recorded discharge activity of the different types of medullary respiration-related units (RRU) reflected these alterations, accordingly. Axonal connections of RRU with mesencephalic structures were evaluated. Examination of orthodromic responses of medullary RRU to stimulation of this pathway revealed that most bulbospinal inspiratory neurons (10 out of 13) were paucisynaptically inhibited after short latency (at least 1.2 ms). The conduction time from bulbospinal inspiratory neurons to the recording site of PHR was 1.6 ms. Thus, a disynaptic pathway — including bulbospinal inspiratory neurons — is suggested inducing inspiratory inhibition 3.0 ms after single shock midbrain stimulation. This inhibition results in disfacilitation of phrenic motoneurons. The fact that extensive electrolytic lesions of the pneumotaxic center in rostral pons did not abolish the observed inspiratory inhibitions excludes these structures from being involved. A direct pathway from the red nucleus and the adjacent reticular formation to phrenic nuclei of the spinal cord, however, can not be excluded from being involved in the demonstrated inspiratory inhibition. The described effects may play a role in behavioral or voluntary control of respiration.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00581224
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  • 3
    Electronic Resource
    Electronic Resource
    Multi-reference configuration interaction calculations on the systems Xe 2 + and Xe 3 + (1990)
    Springer
    The European physical journal 15 (1990), S. 161-169 
    Details
    ISSN: 1434-6079
    Keywords: 36.40 ; 31.20
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Potential curves for the ground (2Σ u + ) and the three lowest excited states of the Xe 2 + dimer ion (2Π g ,2Π u ,2Σ g + ) have been calculated using pseudopotentials in MRD-CI (multi-reference single anddouble excitationconfigurationinteraction) calculations. Spin-orbit interaction — leading to the six states 1.(1/2) u , 1.(3/2) g , 1.(3/2) u , 1.(1/2) g , 2.(1/2) u , 2.(1/2) g — has been taken into account using a semiempirical technique [1]. Subsequently, starting with a relaxed Xe 2 + ion in its ground state, the potential energy surface for the system Xe-Xe 2 + was studied. We found that the collinear approach of the Xe atom leads to the most stable geometry. This is a linear symmetric molecule with bond lengths of 6.38 bohr. In the bestT-shaped structure, the Xe atom is 7.83 bohr away from the midpoint of the Xe 2 + (r=6.1 bohr) dimer. The calculated binding energy of 0.25 eV for the equilibrium structure of the Xe 3 + molecule (i.e. the linear symmetric geometry), is in very good agreement with experimental results of 0.27 ± 0.02 eV [2].
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01437010
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  • 4
    Electronic Resource
    Electronic Resource
    Stability and structure of singly-charged argon clusters Ar n + ,n=3–27. A Monte-Carlo simulation (1989)
    Springer
    The European physical journal 11 (1989), S. 239-248 
    Details
    ISSN: 1434-6079
    Keywords: 31.20.T ; 36.40
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Monte-Carlo calculations have been performed for positively charged argon clusters in the temperature range between 10 K and 40 K using two different models (one with a dimer ion core, the other one with a trimer ion). The argon-argon interaction potential stems from empirical data, the ion-neutral atoms potential is determined by ab initio MRD-CI calculations. Special stability is found for clusters sizesn=13, 19, 23 and 25/26 atoms using the ‘trimeric core model’ and for those withn=14,n=17,n=20 using the ‘dimeric core model’. The geometrical structure of the clusters is given and the construction principles are discussed in light of the interactions among neutral argon atoms and the ion-neutral atoms interaction.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01438010
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  • 5
    Electronic Resource
    Electronic Resource
    MRD-CI calculations for the ground state potential energy surface of Ar 3 + (1986)
    Springer
    The European physical journal 4 (1986), S. 195-205 
    Details
    ISSN: 1434-6079
    Keywords: 36.40 ; 31.20
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Configuration interaction calculations are carried out to study the potential energy surface for the system Ar-Ar 2 + . An all-electron as well as a pseudopotential treatment is employed. It is found that in the perpendicular Ar approach the Ar 2 + partner remains essentially unchanged and the potential can be characterized by an electrostatic ion-induced dipole interaction. In the collinear mode of Ar approach the Ar 2 + bond separation increases considerably, the charge is redistributed and the interaction can be characterized as chemical bonding. The minimum on the surface is found to be the linear symmetric molecule with bond lengths of 2.62 Å. The optimum structure in the perpendicular approach lies 0.13 eV above the minimum and is the T-shaped molecule in which the Ar is 3.65 Å away from the midpoint of the Ar 2 + (r=2.46 Å) system; the best equilateral triangle structure has a bond length of 2.99 Å but is found to lie 0.64 eV above the Ar 3 + minimum. The dissociation energy into Ar 2 + + Ar is calculated to be 0.16 eV in reasonable agreement with experimental values of 0.21 eV. The potential curves for the four lowest states of Ar 2 + are also treated.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01437358
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  • 6
    Electronic Resource
    Electronic Resource
    Stability and structure of singly-charged xenon-argon clusters [Xe1Arn−1]+,n=3–27 (1988)
    Springer
    The European physical journal 8 (1988), S. 91-101 
    Details
    ISSN: 1434-6079
    Keywords: 31.20.T ; 36.40
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Monte-Carlo calculations have been performed for positively charged xenon-argon clusters in the temperature range between 10K and 40K for cluster sizes up ton=27. The argon-argon interaction potential stems from empirical data, the Xe+-Ar potential is determined by ab initio MRD-CI calculations and a semi-empirical treatment of spin-orbit effects. Special stability is found for cluster sizesn=10, 13, 19 and less pronounced forn=23 and 25 fairly independent of the temperature. The geometrical structure of the clusters are given and the construction principle is discussed in light of the interactions among neutral argon atoms and the xenon ion — argon interaction. Comparison with measured mass spectra for mixed rare-gas clusters and [Xen]+ clusters is made and shows a consistent picture for the building principle.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01384528
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