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  • 1
    ISSN: 1434-601X
    Keywords: PACS: 25.30.Fj Nuclear Reactions: Inelastic electron scattering to continuum – 14.20.Dh Properties of Specific Particles: Protons and neutrons – 13.40.Gp Electromagnetic form factors – 25.10.+s Nuclear reactions involving few–nucleon systems
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract: The electric form factor of the neutron G E,n has been determined at the Mainz Microtron MAMI at the low momentum transfer Q 2= 0.15 (GeV/c)2 in a measurement of the recoil polarisation ratio P x/Pz in the quasifree reaction D(e,e′n)p. At this Q 2 the influence of the nuclear binding is strong. A purely kinematical model is used to get some insight into the effect of the initial Fermi momentum distribution of the neutron. The influence of the final state interaction is determined quantitatively by a model of Arenhövel et al.. After the corresponding corrections a value of G E,n(0.15 (GeV/c)2) = 0.0481±0.0065stat±0.0053syst is obtained.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1432-055X
    Keywords: Schlüsselwörter Geriatrische Patienten ; Anästhesie ; Kognitive Funktionen ; Physiologische Parameter ; Hüft-Totalendoprothese ; Key words Geriatric patients ; Anaesthesia ; Cognitive functions ; Physiological parameters ; Hip arthroplasty
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Abstract Objective: The aim of the present study was to show the influence of the parameters of gas exchange (arterial oxygen pressure paO2, arterial oxygen saturation SatO2) and haemodynamics (arterial systolic and mean blood pressure RRs and MAP) on the restitution of cognitive functions in geriatric patients scheduled for elective hip arthroplasty. Methods: A total of 30 patients (70 years, ASA II) were randomized to be operated either in regional anaesthesia (n=15) or general anaesthesia (n=15). PaO2 (by capillary blood gas analysis), RRs and MAP (by oscillometry) were measured 15 and 90 minutes after arrival in the recovery unit (t1 and t2), 24 and 72 hours postoperatively (t3 and t4), and cognitive functions were tested. Intraoperatively, throughout the day and the first night after surgery we measured satO2 by continous pulse oximetry. We recorded MAP and RRs by oscillometry every 3 minutes during the operation and every15 minutes for the rest of that day and night. Results: The parameters of gas exchange and haemodynamics did not differ among the groups. PaO2 was significantly reduced in both groups compared to baseline 24 hours postoperatively (t3) and remained low until 72 hours postoperatively (t4). Nearly all cognitive functions were significantly reduced in both groups compared to baseline 15 and 90 minutes after arrival in the recovery unit (t1 and t2), but recovered on the first postoperative day (t3). Both groups kept deficits in verbal memory and reading capacity up to the third postoperative day (t4). There was no correlation between the physiological parameters and the restitution of the tested cognitive functions. Conclusion: The restitution of cognitive functions during the first three postoperative days in geriatric patients scheduled for elective hip surgery does not depend on the anaesthetic technique. According to our results regional anaesthesia does not show any advantage for geriatric patients undergoing elective hip arthroplasty.
    Notes: Zusammenfassung Fragestellung: Ziel unserer Untersuchung war es, mögliche kognitive Funktionsdefizite geriatrischer Patienten nach Allgemein- und rückenmarknaher Regionalanästhesie mit Parametern des Gasaustauschs (Sauerstoffpartialdruck paO2, Sauerstoffsättigung SatO2) und der Hämodynamik (arterieller systolischer und mittlerer Blutdruck RRs und MAP) in Beziehung zu setzen. Methodik: 30 Patienten (70 Jahre, ASA II), die sich der elektiven Implantation einer Hüft-Totalendoprothese unterzogen, wurden randomisiert entweder in rückenmarknaher Regionalanästhesie (n=15) oder Allgemeinanästhesie (n=15) operiert. 15 bzw. 90 min nach Ankunft im Aufwachraum (AWR – t1 bzw. t2), 24 bzw. 72 h postoperativ (t3 bzw. t4) wurden der paO2 (kapilläre Blutgasanalyse), RRs und MAP (oszillometrische Messung) dokumentiert sowie die kognitive Leistungsfähigkeit testpsychologisch untersucht. Intraoperativ, während des Operationstags und der ersten Nacht wurden im AWR die SatO2 pulsoxymetrisch kontinuierlich aufgezeichnet, der MAP und RRs oszillometrisch intraoperativ alle 3 min, im AWR alle 15 min gemessen. Ergebnisse: Die Parameter des Gasaustauschs und der Hämodynamik unterschieden sich in beiden Gruppen nicht. Der paO2 war in beiden Gruppen 24 h postoperativ (t3) zum präoperativen Ausgangswert (t0) signifikant erniedrigt und blieb auch 72 h postoperativ (t4) deutlich unter der Baseline. Bei beiden Narkoseverfahren erwiesen sich 15 und 90 min nach Ankunft im AWR (t1 und t2) nahezu alle untersuchten kognitiven Funktionen gegenüber dem Ausgangswert als signifikant verschlechtert. Beide Gruppen blieben bis zum 3. postoperativen Tag (t4) in der mittelfristigen verbalen Merkfähigkeit und in der Lesegeschwindigkeit beeinträchtigt. Zwischen den physiologischen Parametern und der postoperativen kognitiven Leistungsfähigkeit bestand in beiden Gruppen keine Korrelation. Schlußfolgerung: Bei geriatrischen Patienten, die sich elektiven hüftgelenknahen orthopädischen Eingriffen unterziehen, erfolgt die Restitution kognitiver Funktionen in den ersten drei postoperativen Tagen unabhängig vom angewandten Anästhesieverfahren. Anhand unserer Daten bietet eine Regionalanästhesie bei hüftchirurgischen Eingriffen für geriatrische Patienten keine nachweisbaren Vorteile gegenüber der Allgemeinanästhesie.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1434-601X
    Keywords: PACS: 14.20.Dh Properties of specific particles: Protons and neutrons – 24.70.+s Nuclear reactions: Polarization phenomena in reactions – 13.40.Gp Specific reactions and phenomenology: Electromagnetic form factors – 25.10.+s Nuclear reactions involving few–nucleon systems – 25.30.Fj Nuclear reactions: Inelastic electron scattering to continuum
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract: The electric form factor of the neutron GEn has been determined in double polarized exclusive 3 He(e,e'n) scattering in quasi–elastic kinematics by measuring asymmetries A ⊥, A ∥ of the cross section with respect to helicity reversal of the electron, with the nuclear spin being oriented perpendicular to the momentum transfer q in case of A⊥ and parallel in case of A∥. The experiment was performed at the 855 MeV c. w. microtron MAMI at Mainz. The degree of polarization of the electron beam and of the gaseous 3 He target were each about 50%. Scattered electrons and neutrons were detected in coincidence by detector arrays covering large solid angles. Quasi–elastic scattering events were reconstructed from the measured electron scattering angles ϑe, φe and the neutron momentum vector p n ′ in the plane wave impulse approximation. We obtain the result 〈G En〉(0.27 〈 Q2c2/GeV2 〈 0.5)= 0.0334 ± 0.0033stat± 0.0028syst which is averaged over the indicated range of Q 2, the squared momentum transfer. This G En value is significantly smaller than measured from the D(e,e'n) reaction under similar kinematical conditions. To what extent final state interactions in 3He quench the G En result is subject of calculations currently in progress elsewhere.
    Type of Medium: Electronic Resource
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