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  • 1
    Electronic Resource
    Electronic Resource
    Efficient pulsed microwave excitation of a high-pressure excimer discharge (1992)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 71 (1992), S. 5712-5714 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report on a microstrip line structure able to sustain plasmas up to five bars of a He/Xe/HCl mixture, with good stability and reproducibility and without preionization of the mixture. The microwave power coupling has been characterized and the incoherent ultraviolet-308 nm emission has been studied by means of time-resolved spectroscopy.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.350507
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  • 2
    Electronic Resource
    Electronic Resource
    Self-consistent modeling of surface wave produced discharges at low pressures (1991)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 70 (1991), S. 4147-4158 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A self-consistent theory of a low-pressure gas discharge sustained by a surface wave (SW) is presented which provides a complete description of the plasma density (ne) and SW-field distribution both in the radial (r) and the axial (z) directions. The theory is based on a complete set of equations including Maxwell's equations and the boundary conditions for the SW-field, the electron Boltzmann equation which yields local collisional and transport data versus the SW-electric field E, and the continuity and momentum transfer equations for the electrons and the ions. For given operating frequency, gas density, setup dimensions and total incident power Pi(0), the theory enables the determination of: (i) the SW-dispersion relation; (ii) ne(r,z) and E(r,z); (iii) Pi(z); and (iv) θ(z), the radially averaged mean absorbed power per electron. It is shown that E¯(z), the radially averaged field in the plasma, and θ(z) are practically constant along z, in spite of the fact that Pi(z) steadily decreases. Comparison with experiment is made for SW discharges in Ar operated at the frequencies of 433 MHz and 2.45 GHz.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.349137
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  • 3
    Electronic Resource
    Electronic Resource
    Experimental study of energy coupling and plasma breakdown in a pulsed high frequency resonant cavity (2001)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 89 (2001), S. 3108-3114 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: An experimental study of the electromagnetic behavior of a pulsed high frequency resonant cavity, operating in its fundamental TE111 mode, is presented. Typical pulse characteristics are a pulse width of 10 μs, microwave frequency of 1 GHz, and microwave power of a few kW. The various parameters (characteristic time τ, coupling factor β, incident power Pi) that determine the temporal variation of the electrical characteristics (power entering in the cavity, electric field) during the pulse are defined. In particular, the influence of the coupling factor on the transition stage to a steady state is discussed for the cavity without plasma. The temporal behavior of the cavity in the presence of a gas (argon and hydrogen) is also studied. For pressures ranging from 0.5 to 100 Torr, the discharge breakdown parameters (time τb, electric field Eb) in hydrogen are deduced from the experiments (tb∼0.1–1 μs, Eb∼300–3000 V/cm). The conditions to reach a quasisteady state plasma are derived from the qualitative analysis of the cavity behavior. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1351540
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  • 4
    Electronic Resource
    Electronic Resource
    Modulation of Proteolytic Activity During Neuritogenesis in the PC12 Nerve Cell: Differential Control of Plasminogen Activator and Plasminogen Activator Inhibitor Activities by Nerve Growth Factor and Dibutyryl-Cyclic AMP (1991)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 57 (1991), S. 0 
    Details
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Extracellular proteolysis is considered to be required during neuritic outgrowth to control the adhesiveness between the growing neurite membrane and extracellular matrix proteins. In this work, PC12 nerve cells were used to study the modulation of proteolytic activity during neuronal differentiation. PC12 cells were found to contain and release a 70–75-kDa tissue-type plasminogen activator (tPA) and a much less abundant 48-kDa urokinase-type plasminogen activator. A plasminogen activator inhibitor (PAI) activity with molecular sizes of 54 and 58 kDa was also detected in PC12 cell conditioned medium and formed high-molecular-mass complexes with released tPA. Release of PAI activity was dependent on treatment with nerve growth factor (NGF), whereas tPA synthesis and release were under control of a cyclic AMP- dependent mechanism and increased on treatment with dibutyryl-cyclic AMP [(But)2cAMP] or cholera toxin. Simultaneous treatment with NGF and (But)2cAMP resulted in increases of both tPA and PAI release and enhancement of tPA-PAI complex formation. The resulting plasminogen activator activity in conditioned medium was high in (But)2cAMP-treated cultures with short neuritic outgrowth but remained low in NGF- or NGF plus (But)2 cAMP-treated cultures, where neurite extension was, respectively, large and very large. These results suggest that excess proteolytic activity may be detrimental to neuritic outgrowth and that not only PAI release but also tPA-PAI complex formation is associated with production of large and stable neuritic outgrowth. This can be understood as an involvement of PAI in the protection against neurite-destabilizing proteolytic activity.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1471-4159.1991.tb03798.x
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  • 5
    Electronic Resource
    Electronic Resource
    On the influence of the gas velocity on dissociation degree and gas temperature in a flowing microwave hydrogen discharge (1998)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 84 (1998), S. 161-167 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report on the influence of the gas velocity on the discharge equilibrium in a low-pressure (1 Torr) microwave driven hydrogen plasma. We show that the gas velocity has a great influence on the dissociation degree, the key parameter being the residence time of the molecules in the plasma with respect to their effective dissociation time. The power balance (plasma length, electric field...) is substantially modified by the variations of the dissociation degree induced by the change in gas velocity. On the contrary, the gas temperature, determined by Doppler broadening of H atom Balmer lines, is not directly dependent on the gas velocity. Simple calculations confirm that the gas temperature is determined by local parameters and that heat is not axially transported. Surprisingly, dissociation of the H2 molecules does not seem to play any significant role for the heating of the gas. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.368013
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  • 6
    Electronic Resource
    Electronic Resource
    Action of a static magnetic field on an argon discharge produced by a traveling wave (1989)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 65 (1989), S. 1465-1478 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: This paper deals with a low-pressure argon microwave discharge (5–100 mTorr), created and sustained by a traveling wave (390 MHz), in the presence of an axial static magnetic field (up to 550 G). First, the propagation characteristics of the wave (wave number, wave collisional damping, radial distribution of the electromagnetic energy) have been computed from the numerical resolution of the dispersion equation. It has been emphasized that the plasma is sustained either by a surface wave, or by a volume wave, according to the electron density and magnetic field values. Second, the electron density, the effective electron-neutral collision frequency ν for momentum transfer, the mean power θ required to maintain an electron in the discharge, and the effective electric field Eeff for the discharge maintaining have been experimentally determined, versus the pressure and the magnetic field. At a fixed pressure, the power required to maintain the discharge decreases as the magnetic field increases. It has been shown that this experimental result is consistent with simple theoretical modeling, describing the decrease of the electron loss by diffusion and recombination on the discharge tube walls.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.342960
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  • 7
    Electronic Resource
    Electronic Resource
    Influence of the excitation frequency on surface wave argon discharges: Study of the light emission (1987)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 61 (1987), S. 1740-1746 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We compare discharges produced by surface waves at 210 MHz and 2.45 GHz in argon at low pressure (0.1–10 Torr). For plasma lengths up to 1 m, the plasma and wave characteristics are determined (electron density, electric field, effective collision frequency, etc.) and the influence of the excitation frequency is shown. Studying the emission of the discharge, we have established relations between the intensities of Ar i and Ar ii lines and these characteristics, taking into account the wave frequency. That leads to practical criteria for the choice of the excitation frequency.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.338071
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  • 8
    Electronic Resource
    Electronic Resource
    Laser induced stimulated emission for hydrogen atom density measurements in a hydrogen pulsed microwave discharge (1996)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 69 (1996), S. 1553-1555 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The laser induced stimulated emission (LISE) of the Balmer α line is used to measure the ground state hydrogen atom density in an efficient source of hydrogen atoms generated by a low-pressure (1 Torr), pulsed microwave discharge at 2.45 GHz. The H atom kinetics in pure hydrogen discharges and in hydrogen–air mixture discharges are compared. It is shown that, for high atomic density and long plasma length crossing, the LISE Balmer α line is partially absorbed by the plasma. This provides an estimation of the H(n=2) atom density. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.117059
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  • 9
    Electronic Resource
    Electronic Resource
    Validity of actinometry to monitor oxygen atom concentration in microwave discharges created by surface wave in O2-N2 mixtures (1994)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 75 (1994), S. 104-114 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The validity of actinometry to monitor oxygen atom concentration in O2-N2 microwave discharges created by surface wave is investigated. The plasma is created with a gas flow in a quartz tube of inner diameter 16 mm at pressures in the Torr range. First, it is shown that the reliability of actinometry can be deduced from the longitudinal profile of the actinometry signal. Second, absolute concentrations of oxygen atoms are estimated from the experimental actinometry signal and agree satisfactorily with concentrations simultaneously measured by vacuum ultraviolet (VUV) absorption downstream from the plasma. Moreover, upon varying the nitrogen percentage (0%–100%), it is evidenced that the actinometry signal is proportional to the concentration measured by VUV absorption. Furthermore, it is evidenced that the oxygen dissociation rate is only 2% in pure oxygen plasmas, while it reaches 15% (433 MHz) or 30% (2450 MHz) for mixtures containing more than 20% of nitrogen. This drastic increase in [O] upon the addition of N2 is extensively discussed and, finally, attributed to a decrease in the recombination frequency of oxygen atoms on the quartz wall, in the presence of nitrogen.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.355897
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  • 10
    Electronic Resource
    Electronic Resource
    Attempted endogenous tissue repair following experimental spinal cord injury in the rat: involvement of cell adhesion molecules L1 and NCAM? (2000)
    Oxford, UK : Blackwell Science Ltd
    European journal of neuroscience 12 (2000), S. 0 
    Details
    ISSN: 1460-9568
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: It is widely accepted that the devastating consequences of spinal cord injury are due to the failure of lesioned CNS axons to regenerate. The current study of the spontaneous tissue repair processes following dorsal hemisection of the adult rat spinal cord demonstrates a phase of rapid and substantial nerve fibre in-growth into the lesion that was derived largely from both rostral and caudal spinal tissues. The response was characterized by increasing numbers of axons traversing the clearly defined interface between the lesion and the adjacent intact spinal cord, beginning by 5 days post operation (p.o.). Having penetrated the lesion, axons became associated with a framework of NGFr-positive non-neuronal cells (Schwann cells and leptomeningeal cells). Surprisingly few of these axons were derived from CGRP- or SP-immunoreactive dorsal root ganglion neurons. At the longest survival time (56 days p.o.), there was a marked shift in the overall orientation of fibres from a largely rostro-caudal to a dorso-ventral axis. Attempts to identify which recognition molecules may be important for these re-organizational processes during attempted tissue repair demonstrated the widespread and intense expression of the cell adhesion molecules (CAM) L1 and N-CAM. Double immunofluorescence suggested that both Schwann cells and leptomeningeal cells contributed to the pattern of CAM expression associated with the cellular framework within the lesion.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1460-9568.2000.00228.x
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