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  • 1
    ISSN: 1432-1238
    Keywords: Sepsis ; Peritonitis ; Monocyte deactivation ; IL-10 ; TNF-alpha ; IFN-gamma ; GM-CSF ; Plasmapheresis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Inflammatory cells, in particular monocytes/macrophages, release pro-inflammatory mediators in response to several infectious and non-infectious stimuli. The excessive release of these mediators, resulting in the development of whole body inflammation, may play an important role in the pathogenesis of sepsis and septic shock. TNF-alpha, acting synergistically with cytokines such as IL-1, GM-CSF and IFN-gamma, is the key mediator in the induction process of septic shock, as shown in several experimental models. Based on this concept and on the encouraging results obtained in several experimental models, a number of clinical sepsis trials targeting the production or action of TNF-alpha or IL-1 have been performed in recent years. Unfortunately, these trials have failed to demonstrate a therapeutic benefit. One reason for this may be the lack of exact immunologic analyses during the course of septic disease. Recently, we demonstrated that there is a biphasic immunologic response in sepsis: an initial hyperinflammatory phase is followed by a hypo-inflammmatory one. The latter is associated with immunodeficiency which is characterized by monocytic deactivation, which we have called “immunoparalysis”. While anti-inflammatory therapy (e.g. anti-TNF antibodies, IL-1 receptor antagonist, IL-10) makes sense during the initial hyperinflammatory phase, immune stimulation by removing inhibitory factors (plasmapheresis) or the administration of monocyte activating cytokines (IFN-gamma, GM-CSF) may be more useful during “immunoparalysis”.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 76 (1994), S. 5754-5759 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: In the present work we study the growth of diamond in a dual-mode microwave/radio frequency plasma. We investigate the effect of the thickness of predeposited hydrogenated amorphous carbon (a-C:H) films and of ion bombardment on the nucleation process and on the crystal quality. The deposits are characterized by x-ray photoelectron spectroscopy (XPS) and by scanning electron microscopy. The XPS spectra of the C(1s) carbon peak and of the plasmon features confirm the presence of an amorphous, carbonaceous phase and of silicon carbide on the surface. Radio frequency biasing during the initial stage of diamond growth leads to a lower crystal quality, but to a higher nucleation density (ND). Without biasing, good quality, predominantly (100) oriented diamond crystals are obtained on a Si(100) surface. The ND values are found to increase with the thickness of the predeposited a-C:H layer. Evolution of the nucleus size distributions indicates that the a-C:H film contributes to the carbon supply, enhancing the nucleation efficiency and shortening the incubation time of seed crystals. Before a continuous layer is formed, the growth of crystals is determined by the interaction with the gas phase as well as by the amount of carbon available on the surface.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 74 (1993), S. 1354-1361 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Noncrystalline hydrocarbon films were deposited from methane plasmas in an electron-cyclotron-resonance plasma reactor. The films were characterized by infrared spectroscopy and high-energy ion-beam analysis. Film properties were investigated as a function of the energy of ions impinging on the surface of the growing film. The ion energy was varied by applying a dc bias to the sample in the range from 30 to 200 eV. The ion energy was measured with a retarding field analyzer under identical experimental conditions. An abrupt change was found in the sp3/sp2 ratio in the energy interval from 80 to 120 eV. Other film properties such as the refractive index, density, and hydrogen-to-carbon ratio exhibit a more or less monotonic dependence on the ion energy. The results are compared with published data on hydrocarbon films. An analytical model was developed to describe the energy dependence of the hydrogen fraction in the films. It is based on the assumption that displacement of hydrogen atoms is the dominating mechanism that controls the hydrogen fraction in hydrocarbon films. The results are also discussed on the basis of the fully constrained network model.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 78 (1995), S. 4855-4858 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Ion energy distribution functions (IEDF) were measured at the surface of a grounded or a rf-powered electrode exposed to a microwave (MW, 2.45 GHz) or a rf (13.56 MHz) discharge in argon. The IEDFs measured on the grounded electrode in both the rf and the MW modes show a higher contribution of low-energy ions when the pressure is raised. The maximum ion energy Em decreased from 12.0 to 8.5 eV in the MW plasma, but remained at 26±0.5 eV in the rf plasma. The mean ion energy E¯ decreased from 6.1 to 3.8 eV (MW) and from 16.0 to 12.0 eV (rf) when the pressure was raised from 30 to 210 mTorr. The IEDFs in the rf mode exhibit a single peak, while a bimodal structure is observed in the MW mode. When the electrode is rf powered to achieve a negative dc bias voltage VB, the Em values reach ∼1.2eVB (rf) and ∼1.1eVB (MW), respectively. The IEDFs in the rf mode display a multiple peaked structure which is associated with a rf-modulated sheath. In the dual-frequency MW/rf mode the IEDF is single peaked, narrow, and centered around eVB. A nearly tenfold increase in the ion flux is observed when increasing the MW input power, while the ion energy remains unchanged for a constant VB value. This allows an independent control of ion energy and ion flux, suitable for the control of material properties in plasma processing. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 88 (2000), S. 5597-5604 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: In the present study nanocrystalline c-BN films deposited with a mass selected ion beam were subjected to a hydrogen plasma or atomic hydrogen produced by the hot filament method. Film composition and electronic properties of the surface were subsequently analyzed in situ by photoelectron spectroscopy in the x-ray and ultraviolet regime, and by electron energy loss spectroscopy. The sp2-bonded surface layer, which is native to ion beam deposited c-BN films, is rapidly removed by hydrogen plasma etching and the almost phase pure c-BN layer uncovered. Continuation of hydrogen plasma exposure leads to a removal of the c-BN layer at an etch rate of about 0.65 nm/min until finally the sp2-BN nucleation layer is detected. No preferential etching of either B or N is observed and an equal concentration of the constituents is maintained throughout the experiment. The large atomic hydrogen flux from the plasma is held responsible for the efficient etching, which could not be achieved with the hot filament method. The valence band spectra of nanocrystalline c-BN can be understood in the framework of published density of states calculations and allows to identify characteristic spectral features for both phases. The nanocrystalline c-BN surface exhibits a negative electron affinity, which might be connected to a hydrogen termination of the surface. The hydrogen plasma etching offers a comparatively easy route for future investigations of surface reactivity and the exploitation of the NEA property of the material. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 84 (1998), S. 2876-2881 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Reactions at Ti/Cu interfaces were investigated by ultraviolet and x-ray photoelectron spectroscopy (UPS, XPS). For Ti deposition onto copper substrates at ambient temperature, our measurements strongly suggest that at the interface an amorphous alloy is formed. This idea is supported by the comparison of our UPS data to the ones of bulk glassy CuxTi1−x. The thickness of this amorphous interlayer which is built up onto the polycrystalline Cu substrate corresponds to a nominal Ti coverage of about 10 monolayers. At a substrate temperature of 300 °C, however, the interface reaction is still present at nominal Ti coverages over a hundred monolayers. Presumably the crystalline phase Cu3Ti2 is formed. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 84 (1998), S. 2612-2617 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: In this study we present an investigation of the bias-enhanced nucleation and early stages of diamond growth on molybdenum. The progression of the different stages of the nucleation and growth was observed using photoelectron spectroscopy with excitation energies in the ultraviolet and x-ray regime. Subsequent to the film deposition the samples were transferred to the analysis chamber without breaking the vacuum. To achieve high nuclei densities methane concentrations in excess of about 20% diluted in hydrogen and a dc bias of −400 V are required. During the bias-enhanced nucleation period a molybdenum carbide interface is formed and the codeposition of a graphitic carbon layer and diamond is observed. The graphitic carbon layer is subsequently removed during the diamond growth step, where deposition conditions conducive of diamond growth are maintained and a continuous diamond film is formed after 40 min. The results are compared with those obtained for the bias-enhanced nucleation on silicon. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 81 (1997), S. 2396-2399 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We used the characteristic changes in the electronic structure of the valence band of amorphous carbon films upon the formation of graphitic clusters to monitor the temperature induced graphitization of a variety of hydrogen-containing (a-C:H) as well as hydrogen-free (a-C) films. The valence band spectra of the films, which were prepared in situ by ion-beam deposition and electron beam evaporation, were determined using photoelectron spectroscopy with excitation energies in the ultraviolet regime (ultraviolet photoemission spectroscopy, HeI, hν=21.22 eV and HeII, hν=40.82 eV). By choosing a variety of deposition parameters we are able to illustrate that the extent of temperature induced structural changes is on one hand determined by the bulk and surface diffusion coefficients of carbon atoms, and on the other hand by the ion irradiation which inhibits the graphitization process. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 68 (1996), S. 22-24 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Polycrystalline diamond films were deposited in a MW-PECVD reactor employing bias-enhanced nucleation as pretreatment to promote the subsequent diamond nucleation. The substrate temperature during the bias-enhanced nucleation was varied between 600° and 760 °C by external heating, while the other deposition parameters namely the microwave input power were kept constant. Likewise, the deposition parameters were not changed in the subsequent diamond growth period throughout the experiment. The films formed during the bias-enhanced nucleation were analyzed employing electron energy loss spectroscopy (EELS) and scanning electron microscopy (SEM). The nuclei density (ND) obtained for good quality diamond crystals after the nucleation step and an additional growth period increases considerably from 1×106 cm−2 or less to 1×1010 cm−2 in a narrow temperature range between 670 and 700 °C. For temperatures exceeding 700 °C continuous films are formed. The structure of the pretreatment deposit also undergoes considerable changes: the intensity of the diamond plasmon increases with the substrate temperature, which is indicative of an increase in the concentration of diamond crystallites embedded in an otherwise amorphous carbon matrix. Our experiments suggest that diamond crystallites formed during the pretreatment serve as nucleation centers for the subsequent diamond growth. We can also conclude that the variation in the substrate temperature rather than the changes in the microwave input power or, respectively, plasma chemistry, drive the observed structural changes and increase in ND. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    Amsterdam : Elsevier
    Surface Science Letters 293 (1993), S. A640 
    ISSN: 0167-2584
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Physics
    Type of Medium: Electronic Resource
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