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  • Polymer and Materials Science  (12)
  • 42.60B  (3)
  • Analytical Chemistry and Spectroscopy  (3)
  • Unit recording  (3)
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  • 1
    Electronic Resource
    Electronic Resource
    Scaling and performance of CO2 lasers at supra-atmospheric pressure (1985)
    Springer
    Applied physics 37 (1985), S. 171-179 
    Details
    ISSN: 1432-0649
    Keywords: 42.55D ; 42.60B ; 58.80
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The performance of a compact uv photo-preionized TE laser is studied in the pressure range 1–5 bar. As the pressure is increased, the laser pulse shape is little altered, but both the peak power and the total output pulse energy increase significantly with pressure, even for constant input electrical energy. For various gas mixtures and excitation source capacitors the measurements suggest approximate output energy scaling with the product of the source charge per unit electrode area [C.m−2] and the molecular partial pressure [CO2+N2+CO]. This is explained in terms of the pressure-dependent discharge impedance. An input-energy-related discharge instability limits the optimum laser pressure to 1.5–2.5 bar, and we show that, at constant input energy, the instability boundary depends on the molecular partial pressure alone. The pre-ionization photo-electron yield varies negligibly with pressure, but the discharge tolerance to added oxygen decreases asp −3 top −4, dependent on gas mixture. Nevertheless sealed operation for 〉105 shots has been obtained with a 5% CO2∶5% CO∶3% N2∶2% H2∶85% He gas mixture at a total pressure of 5 bar.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00692081
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  • 2
    Electronic Resource
    Electronic Resource
    Effective and simplified hybrid TEA laser design and operation (1984)
    Springer
    Applied physics 33 (1984), S. 99-101 
    Details
    ISSN: 1432-0649
    Keywords: 42.60B ; 42.55D
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract A compact hybrid TEA CO2 laser has been developed which, when operated with the low pressure section well below oscillation threshold, demonstrates that little cw gain is necessary to ensure single longitudinal mode (SLM) output pulses with peak power, energy and pulse shape approaching those of normal multi-mode operation. This has allowed reliable SLM operation to be obtained with a very short, wide bore rf-excited low-pressure section, making feasible simple single-mode, large-aperture TEA lasers with high peak powers and energies.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00688354
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  • 3
    Electronic Resource
    Electronic Resource
    X-ray preionized CO2 laser (1985)
    Springer
    Applied physics 37 (1985), S. 219-221 
    Details
    ISSN: 1432-0649
    Keywords: 42.55D ; 33.80E ; 52.80 ; 42.60B
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract A short pulse (100 ns) high-energy x-ray source has been used to preionize a transversely excited carbon dioxide gas discharge laser of 600 cm3 active volume. The maximum output power of 60 MW in a 50 ns FWHM pulse was achieved from a CO2−N2−He−CO−Xe static gas mixture at 600 Torr pressure. The energy conversion efficiency was 6%.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00692945
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  • 4
    Electronic Resource
    Electronic Resource
    Topography of projections from the motor cortex to rubrospinal units in the cat (1973)
    Springer
    Experimental brain research 17 (1973), S. 315-332 
    Details
    ISSN: 1432-1106
    Keywords: Red nucleus ; Unit recording ; Motor cortex ; Topographical organization ; Cat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary A topographical study of the cortico-rubrospinal pathway was conducted in cats anesthetized with chloralose. Extracellular unit recordings were made from cells in the red nucleus projecting to the spinal cord. They were identified by antidromic invasion following stimulation of their axones at the 2nd cervical and 9th thoracic levels of the spinal cord. I. The pericruciate cortical regions from which spikes could be induced in rubrospinal neurons were limited to the lateral part of the anterior sigmoid gyrus, the lateral sigmoid gyrus and the anterior part of the posterior sigmoid gyrus. No responses were obtained from stimulation of the medial part of the anterior sigmoid gyrus or the gyrus proreus. Compared to the somatotopic organization of the motor cortex for the cat described by Woolsey (1958), our results show that the rubrospinal cells receive projections from the motor cortex controlling proximal and distal muscles but not axial muscles. II. Neurons projecting to the cervico-thoracic cord receive afferents from the lateral part of the anterior sigmoid gyrus and the lateral sigmoid gyrus whereas those projecting to the lumbo-sacral cord receive projections from the entire surface of the sigmoid gyrus except the medial part of the anterior sigmoid gyrus and the gyrus proreus. III. A latero-medial organization of cells within the red nucleus was found according to the origin of their cortical afferents. Rubrospinal neurons with fibers terminating in the cervical or thoracic cord receive projections from the motor cortex controlling the proximal musculature of the forelimb when they are located in the dorso-lateral region of the nucleus and the entire forelimb motor cortex when they are located in the medial part of the nucleus. It is suggested that this organization may indicate a control of proximal forelimb musculature by dorsolateral rubrospinal cells and distal musculature by medial cells. IV. Rubrospinal cells placed medially in the nucleus receive more convergent projections (i.e. from a greater cortical surface) than cells placed more laterally. It was shown that for certain cells the convergence occurs in the direct pathway. These results are discussed in terms of a functional organization allowing coordinated movements of different segments of a single limb or of different limbs.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00234669
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  • 5
    Electronic Resource
    Electronic Resource
    Relation of activity in precentral cortical neurons to force and rate of force change during isometric contractions of finger muscles (1975)
    Springer
    Experimental brain research 23 (1975), S. 315-332 
    Details
    ISSN: 1432-1106
    Keywords: Precentral motor cortex ; Unit recording ; Isometric precision grip ; Force and rate of force change ; Microstimulation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The activity of single neurons within the hand area of the precentral motor cortex of primates was recorded during the performance of a maintained precision grip between the thumb and forefinger. The finger opposition forces were exerted against a strain gauge which allowed force changes to be studied under near isometric conditions. Task performance required the generation of a force ramp (the dynamic phase) and thereafter the maintenance of a stable force for one second (the static phase). Intracortical stimulation through the recording electrode was used to verify that the recordings were made from the appropriate somatotopographic area of the motor cortex. From a total of 221 recorded neurons, 76 were found to be either activated or deactivated during performance of the task. Among the 51 activated neurons, most discharged at higher frequencies during the dynamic phase, than during the static phase. The discharge of some of these neurons could be related to both force (F) and rate of force change (df/dt) whereas certain others could only be correlated with df/dt. The change in discharge frequency for these neurons generally occurred prior to the onset of EMG activity. Eight neurons were more active during maintained force than during the force ramp. The discharge frequency could not be correlated with df/dt and only one showed a significant positive relation to force. The change in discharge frequency for these neurons either coincided or occurred after the onset of EMG activity.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00239743
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  • 6
    Electronic Resource
    Electronic Resource
    Topography of rubrospinal units in the cat (1972)
    Springer
    Experimental brain research 14 (1972), S. 363-371 
    Details
    ISSN: 1432-1106
    Keywords: Rubrospinal cells ; Unit recording ; Topographical organization ; Conduction velocity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Mapping of cells at the origin of the rubrospinal tract was conducted in the cat. 1. Rubrospinal neurons sending efferents to cervico-thoracic segments of the spinal cord are located in the dorso-medial part of the nucleus. These neurons are especially medial in the caudal planes and especially dorsal in the rostral planes. Neurons with efferents terminating at the level of lumbo-sacral segments of the cord occupy the ventro-lateral part of the nucleus. These neurons are especially lateral in the caudal planes and especially ventral in the rostral planes. The limit between these two cell populations is clear in the caudal and middle thirds of the nucleus but considerable overlap is seen in the rostral third. These results agree with the anatomical findings of Pompeiano and Brodal (1957). 2. For the population of lumbar neurons the conduction velocities ranged from 31 m/sec to more than 120 m/sec with a mean of 85 m/sec. 3. Rubrospinal cells are found throughout the nucleus. The most caudal planes are essentially composed of cells with rapidly conducting fibers whereas in the middle and rostral planes a cell population with increasingly slower conducting fibers appears. The results of the present study are discussed in relation to classical data on the magnocellular and parvocellular divisions of the red nucleus. 2.The third author acknowledge the personal support of the Medical Research Council of Canada.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00235033
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  • 7
    Electronic Resource
    Electronic Resource
    Chromium depletion from stainless steels during vacuum annealing (1977)
    Weinheim [u.a.] : Wiley-Blackwell
    Materials and Corrosion/Werkstoffe und Korrosion 28 (1977), S. 405-409 
    Details
    ISSN: 0947-5117
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Description / Table of Contents: Chromverarmung nichtrostender Stähle beim Glühen im VakuumBei der selektiven Oxidation von Chrom in nichtrostenden Stählen wird das Oxidatinos-verhalten stark von den Veränderungen der Chromkonzentration an der Metalloberfläche und im Metall beeinflußt. Nach den bisherigen Annahmen verhält sich das Chrom bei der selektiven Oxidation ebenso wie bei der Verflüchtigung während des Vakuumerhitzens auf hohe Temperaturen. In der vorliegenden Arbeit wird die Verdampfung von Chrom aus Stahl 316 bei Vakuumanlassen bei 1000 °C mittels energiedispersiver Röntgenstrahlen- und Neutronenaktivierungsanalyse untersucht. Es wird festgestellt, daß der Chromverlust aus austenitischen nichtrostenden Stählen durch Interdiffusion in der Legierung kontrolliert wird. Entsprechend der Vorhersage nimmt die Chromkonzentration an der Metalloberfläche mit zunehmender Erhitzungsdauer ab. Das Chromverarmungsprofil im Metall stimmt gut über in mit einem früher obgeleiteten Modell, abgesehen von einer anomalen Zone in Oberflächennähe. Die hohe Auflösung der Neutronenaktivierungstechnik läßt erkennen, daß es sich um eine etwa 2μm dicke Zone handelt, wo die Chromkonzentration steiler absinkt als es den erwartungen entspricht.
    Notes: During selective chromium Oxidation of stainless steels the changes in chromium concentration at the metal surface and in the metal have an important bearing on the overall oxidation performance. It has been proposed that an analogue of chromium behaviour during selective oxidation is obtained from volatilisation of chromium during high temperature vacuum annealing. In the present report the evaporation of chromium from 316 type of steel, vacuum annealed at 1000 °C, has been investigated by menas of energy dispersive X-ray analysis and by neutron activation analysis. It was established that chromium loss from austenitic stainless steels is rate controlled by interdiffusion in the alloy. As predicted the chromium concentration at the metal surface decreased with increasing vacuum annealing time. The chromium depletion profile in the metal was in good agreement with the previously derived model apart from an anomalous region near the surface. Here the higher resolution of the neutron activation technique indicated a zone within ∼2μm of the surface where the chromium concentration decreased more steeply than expected.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/maco.19770280603
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  • 8
    Electronic Resource
    Electronic Resource
    Concentration profiles through a duplex oxide grown on 316 stainless steel (1978)
    Weinheim [u.a.] : Wiley-Blackwell
    Materials and Corrosion/Werkstoffe und Korrosion 29 (1978), S. 246-250 
    Details
    ISSN: 0947-5117
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Description / Table of Contents: Konzentrationsprofile in einem Duplex-Oxidzunder auf Stahl 316Konzentrationsprofile in auf vakuumangelassenem Stahl 316 entstandenem Duplex-Oxidzunder wurden mit Neutronenaktivierungsanalyse und energiedispersiver Analyse untersucht. Gute qualitative Übereinstimmung zwischen den beiden Methoden ergab sich für das Konzentrationsprofil von Chrom in der äußeren Oxidschicht; die Ergebnisse deuten auf eine geringe Geschwindigkeit der Stromdiffusion in die äußere Magnetitschicht. Bei der inneren Oxidschicht ist die Übereinstimmung zwischen den beiden Methoden weniger gut, da die Ergebnisse der Neutronenaktivierung durch die Anwesenheit von Metall in der Querschnittsfläche verfälscht werden. Die Ergebnisse der energiedispersiven Analysen dieser Schicht stimmen mit früheren Befunden überein, wonach normale oder nichtselektive Oxydation auftritt.
    Notes: Concentration profiles through duplex scales formed on vacuum annealed 316 stainless steel have been investigated using neutron activation analysis and energy dispersive analysis. Good qualitative agreement between the two analytical techniques was obtained for chromium concentration profiles in the outer oxide. These indicated a low rate of chromium diffusion into the Fe3O4 layer. There was less agreement between the two methods in the inner oxide as the neutron activation results were complicated by the presence of metal in sections through this oxide layer. The energy dispersive results in this layer were consistent with previous findings which indicated conservative or non selective oxidation occurring.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/maco.19780290403
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  • 9
    Electronic Resource
    Electronic Resource
    The oxidation of an 18/8 type stainless steel in CO2 (1979)
    Weinheim [u.a.] : Wiley-Blackwell
    Materials and Corrosion/Werkstoffe und Korrosion 30 (1979), S. 100-104 
    Details
    ISSN: 0947-5117
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Description / Table of Contents: Oxidation eines 18/8 Stahls in KohlendioxidDas Oxidationsverhalten von 18/8-Stahl wurde im Temperaturbereich 873-1258K (600-985°C) durch kontinuierliche Messung der Gewichtszunahme, metallographische Methoden und Rasterelektronenmikroskopie untersucht. Auf eine anfänglich hohe Oxidationsgeschwindigkeit folgt eine Periode mit wesentlich geringerer Oxidation. Im Anfangsstadium entsteht ein zweischichtiger Zunder. weshalb die Abnahme der Oxidationsgeschwindigkeit wahrscheinlich durch die Bildung eines geordneten, chromreichen Spinells an der Grenzfläche Oxid/Metall bedingt sein dürfte.Wenn unter Verwendung des Modells von Hales die Bildung von „heilenden„ Phasen berücksichtigt wurde, ergab sich eine echte parabolische Zeitkonstante: \documentclass{article}\pagestyle{empty}\begin{document}$$ k_p = {\rm 1}{ .8\,\, exp}\left({\frac{{ - {\rm 230}}}{{RT}}} \right)g^2\,\, cm^{ - 4} \,\,\sec ^{ - 1} $$\end{document}Hierin ist die Aktivierungsenergie in KJ. mol-1 (55 kcal · mol-1) ausgedrückt.
    Notes: The oxidation behaviour of an 18/8 type stainless steel has been studied in the temperature range 873-1258 K (600-985 °C) by continous weight gain measurements, metallography and scanning electron microscopy. An initial high oxidation rate was followed by a much slower rate. Duplex scales formed at an early stage of oxidation and the decrease in oxidation rate is probably due to the formation of an ordered chromium rich spinel at the oxide/metal interface.A ture parabolic rate constant (kp) was obtained taking into account the formation of the “healing” phase using the Hales model. This gave: \documentclass{article}\pagestyle{empty}\begin{document}$$ k_p = {1.8\,\, exp}\left({\frac{{ - {\rm 230}}}{{RT}}} \right)g^2\,\, cm^{ - 4} \,\,\sec ^{ - 1} $$\end{document}. where the activation energy is expressed in KJ · mole-1. (55 Kcals mole-1).
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/maco.19790300203
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  • 10
    Electronic Resource
    Electronic Resource
    Diffusion of transition metals in “in situ” duplex oxide grown on a 316 stainless steel (1978)
    Weinheim [u.a.] : Wiley-Blackwell
    Materials and Corrosion/Werkstoffe und Korrosion 29 (1978), S. 441-444 
    Details
    ISSN: 0947-5117
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Description / Table of Contents: Diffusion von Übergangsmetallen in auf Stahl 316 aufgewachsenem Duplex-OxidMit der Methode der sukzessiven Abtragung wurden nach Diffusionsglühen bei 1273 K Konzentrationsprofile von radioaktiven Isotopen (Chrom, Mangan und Eisen) in einem auf Stahl 316 entstandenen doppelschichtigem Zunder ermittelt. Das Eisenisotop diffundiert danach normalerweise sowohl durch die innere als auch durch die äußere Zunderschicht. Die Konzentration der Isotopen von Chrom und Mangan nimmt in der äußeren Magnetitschicht nach Außen hin zu, zeigt aber in der inneren Spinellschicht ein normales Konzentrationsprofil. Die Diffusionskoeffizienten - ermittelt aufgrund der Konzentrationsprofile - lagen, bezogen auf die Diffusion in der Spinellphase, zwischen 6 × 10-12 und 3 × 10-11 cm2 sec-1.
    Notes: Concentration profiles of chromium, maganese and iron radioactive tracers through a duplex oxide grown on 316 stainless steel have been obtained after a diffusion anneal at 1273 K using the serial sectioning technique. The iron tracer diffused normally in both inner and outer oxides of the duplex scale. The concentration of the chromium and manganese tracers increased with increasing penetration into the outer Fe3O4 layer but showed a normal profile in the inner spinel. The diffusion coefficients obtained from the profiles were in the range 6 × 10-12 - 3 × 10-11 cm2 sec-1 for diffusion in the spinel phases.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/maco.19780290702
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