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  • 1
    Digitale Medien
    Digitale Medien
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 68 (1990), S. 4420-4425 
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: We have successfully attained low-noise and high-power operation in GaAlAs lasers by applying high reflectivity facet coating approach to nonabsorbing mirror lasers. High reflectivity coating is used to reduce feedback induced noise coming from hopping between the diode cavity modes and between the external cavity modes. A nonabsorbing mirror structure is used to obtain high-power operation by suppressing mirror degradation and catastrophic optical damage effectively even with the use of high reflectivity coating. Nonabsorbing mirror lasers with the front facet reflectivity 50% showed the relative intensity noise level less than −130 dB/Hz at 3 mW under 0%–10% optical feedback and showed the cw output power as high as 50 mW in fundamental spatial mode operation. Under 30-mW cw operation at 50 °C, on the other hand, obvious degradation has not been observed over 4000 h in the nonabsorbing mirror lasers with 50% front facet reflectivity. Thus the present laser is useful as a low-noise source at a low-power level and also as a high-power source with high reliability.
    Materialart: Digitale Medien
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  • 2
    Digitale Medien
    Digitale Medien
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 95 (1991), S. 2036-2040 
    ISSN: 1089-7690
    Quelle: AIP Digital Archive
    Thema: Physik , Chemie und Pharmazie
    Notizen: The Raman spectra of hydrogen-bonded molecular solid H2S have been measured up to 23 GPa at 300 K in a gasketed diamond-anvil cell. In the orientationally disordered phase I between 0.47 and 11 GPa, the symmetric stretching mode ν1 shows a red-shift in frequency (dν1/dP=−10.1 cm−1/GPa ) and a dramatic broadening with pressure. At about 11 GPa, the antisymmetric stretching band ν3 appears at the higher-frequency side of ν1. Near this same pressure five low-frequency vibrational modes also appear and show pressure-sensitive features. These results indicate a pressure-induced phase transition near 11 GPa. This new solid phase, which persists to at least 23 GPa at 300 K, seems to be the same phase as previously found above 3.3 GPa at 25 K.
    Materialart: Digitale Medien
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  • 3
    Digitale Medien
    Digitale Medien
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 97 (1992), S. 7137-7139 
    ISSN: 1089-7690
    Quelle: AIP Digital Archive
    Thema: Physik , Chemie und Pharmazie
    Notizen: High-pressure Raman studies up to 17 GPa have been made on solid D2S at room temperature. Features of vibron and phonon modes indicate a pressure-induced phase transition near 10 GPa. In the orientationally disordered phase I between 0.5 and 10 GPa, the symmetric stretching mode ν1 shows a red-shift in frequency (dν1/dP=−6.0 cm−1/GPa). By comparing with recent studies of solid H2S, the deuterium isotope effects are investigated for vibrational properties and phase transitions of D2S under ultrahigh pressures.
    Materialart: Digitale Medien
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  • 4
    Digitale Medien
    Digitale Medien
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 89 (1988), S. 2743-2747 
    ISSN: 1089-7690
    Quelle: AIP Digital Archive
    Thema: Physik , Chemie und Pharmazie
    Notizen: The Raman spectra of hydrogen-bonded crystalline HCONH2 and HCOND2 have been measured up to 10 GPa at 300 K in a gasketed diamond anvil cell. The frequencies of the in-plane intermolecular stretching mode which characterizes the hydrogen bond along the zig–zag chain increase with increasing pressure with a slope (dν/dP) of 11.1 cm−1/GPa, and its slope becomes steeper, to 19.2 cm−1/GPa, at about 5.0 GPa (=Pc). The frequencies of the intramolecular ND2 stretching mode decrease with increasing pressure at all pressure range except around Pc where they show an increase of 20 cm−1. It turns out from these results that (1) the hydrogen (deuteron) bonds along the chain direction become stronger in response to the pressure, and their increasing strength are more developed above Pc, and (2) the other type of hydrogen (deuteron) bonds which bridge the chains to make their planar hydrogen-bonded network are weakened around Pc. The pressure-induced phase transition at Pc is discussed by focusing on the behavior of two types of hydrogen bondings and the effect of the interplanar interaction.
    Materialart: Digitale Medien
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  • 5
    Digitale Medien
    Digitale Medien
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 89 (2001), S. 6745-6747 
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: We have observed very large tunneling magnetoresistance (TMR) in Ga1−xMnxAs/AlAs/Ga1−xMnxAs ferromagnetic semiconductor tunnel junctions. A TMR ratio as high as 75% was obtained in a junction with a thin (1.5 nm) AlAs tunnel barrier when the magnetic field was applied along the [100] axis in the film plane. The TMR ratio decreased when the applied magnetic field direction was along the [11¯0] and [110]. This anisotropic TMR was found to be explained by the single-domain theory assuming cubic magnetic anisotropy with the easy axis of 〈100〉, which is induced by the zincblende-type Ga1−xMnxAs crystal structure. © 2001 American Institute of Physics.
    Materialart: Digitale Medien
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  • 6
    Digitale Medien
    Digitale Medien
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 89 (2001), S. 7281-7283 
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: We have fabricated semiconductor-based magnetic superlattices (SLs) containing GaAs:MnAs granular material in which MnAs nanoclusters are embedded in GaAs, and have characterized their structural, optical, and magneto-optical properties. SLs consisting of GaAs:MnAs and AlAs are shown to have good crystalline quality and excellent compatibility with nonmagnetic GaAs/AlAs heterostructures. The optical transmission properties were improved in the SLs, while keeping the strong magneto-optical properties of GaAs:MnAs. We used these magnetic SLs in a semiconductor-based magnetic microcavity as the central magnetic layer, and its optical transmission was found to have improved compared with our previous multilayer structures. © 2001 American Institute of Physics.
    Materialart: Digitale Medien
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  • 7
    Digitale Medien
    Digitale Medien
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 87 (2000), S. 6791-6793 
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: We have studied magnetic circular dichroism (MCD) spectra of ferromagnetic MnAs epitaxial thin films of (1¯101), (1¯100), and (0001) crystallographic growth orientations. The films were grown on Si(001), Si(111), GaAs(001), and GaAs(111)B substrates by molecular-beam epitaxy. We have found strong crystal orientation dependence of MCD spectra of MnAs films in terms of characteristic features and absolute intensity of MCD signals. We have also measured temperature dependence of MCD spectra on a (0001) MnAs film. Features at low temperatures are found to be different from those at room temperature. Our experimental results are compared with the ionic model for the electronic structure of NiAs-type MnAs and with magneto-optical Kerr ellipticity spectra recently calculated using an all electron full potential linear muffin-tin orbital method. © 2000 American Institute of Physics.
    Materialart: Digitale Medien
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  • 8
    Digitale Medien
    Digitale Medien
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 70 (1999), S. 1970-1977 
    ISSN: 1089-7623
    Quelle: AIP Digital Archive
    Thema: Physik , Elektrotechnik, Elektronik, Nachrichtentechnik
    Notizen: A toroidal electrostatic analyzer with a two-dimensional position-sensitive electron detector has been developed for the measurement of differential excitation cross sections in electron-ion collisions. The electron position is resolved simultaneously in the energy and angular dispersive directions of the analyzer. The present electron analyzer is specially designed with a narrow curved entrance slit and a wide exit slit coupled with an exit lens system after the toroidal deflector, which can give a wide energy dispersed range of 20% of the mean pass energy and a large angular range extending from 30° to 120°. The performance of the spectrometer has been studied by measuring the scattered electrons from Ar atoms and from a highly oriented pyrolytic graphite surface, indicating the usefulness of the present analyzer in electron spectroscopy. A brief description of the method for a spectrum transformation from Cartesian coordinates to polar coordinates is also presented. © 1999 American Institute of Physics.
    Materialart: Digitale Medien
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  • 9
    Digitale Medien
    Digitale Medien
    Oxford, UK; Malden, USA : Blackwell Science Inc
    Wound repair and regeneration 12 (2004), S. 0 
    ISSN: 1524-475X
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Medizin
    Notizen: Aim: Keloid lesions develope as a result of abnormal growth of dermal fibroblasts after the injury. On the other hand, cell division cycle (Cdc) 25 is a family of phosphatases that activate the cell cycle regulating cyclin-dependent kinases. The three members of this family, Cdc25A, Cdc25B, and Cdc25C act in different phases of the cell cycle. In this study, we examined the dgree of expression of these phosphatases in keloid fibroblasts. Methods: Primary cultures of keloid and adjacent normal dermal fibroblasts (n = 4) as well as frozen and paraffin-embedded keloid and normal dermal tissues (n = 12 and n = 17 respectively) were examined by Western blot and immunohistochemical analyses for the expressions of Cdc25A, Cdc25B, Cdc25C and phosphorylated Cdk2. Results: Cdc25A protein levels were frequently increased in keloid fibroblasts as compared to the adjacent normal-appearing fibroblasts or different normal dermal fibroblasts. In contrast, Cdc25B and Cdc25C were none or rarely expressed. The incrased levels of Cdc25A were associated with lower levels of its substrate, Cdk2, in a phosphorylated or inactive form. Conclusions: Taken together, our data show that Cdc25A protein levels increase in keloid fibroblasts and this increase may be sufficient to activate its substrate, Cdk2, and accelerate the cell cycling. These results may have implication for the development of strategies to silence Cdc25A activity after the wound healing as a therapeutic modality for the keloid lesions.
    Materialart: Digitale Medien
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  • 10
    Digitale Medien
    Digitale Medien
    Oxford, UK; Malden, USA : Blackwell Science Inc
    Wound repair and regeneration 12 (2004), S. 0 
    ISSN: 1524-475X
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Medizin
    Notizen: Aim: When surgery with postoperative superficial electron irradiation is applied, the recurrence rate of keloid lesion has been found to be 〈30%. In this study, we assessed the molecular changes underlying the effect of electron irradiation by differential global gene expression analyses of both cultured keloid and normal skin fibroblasts. Materials and Methods: Primary cultured fibroblasts from 4 active keloids and their adjacent normal dermal tissues were irradiated at a calibrated dosage of 15 Gy with 6 MeV electron beam generated by a linear accelerator. Corresponding paired non-irradiated cells were used as control. RNA isolated from the collected cells was labeled with 33P, hybridized to the cDNA microarray gene filters and analyzed. Results: After irradiation, the gene expression profiles of keloid and normal skin fibroblasts were closely similar. Electron irradiated keloid fibroblasts showed suppressed levels of collagen typeI (alpha2), collagen typeVI (alpha1), matrix metalloproteinase 2, fibronectin 1, insulin-like growth factor binding protein 3, alpha-1-antichymotorypsin and heparan glucosaminyl 1 as compared with their non–irradiated counterparts. Conclusions: Downregulation of matrix synthesis and upregulation of protease inhibitors and apoptosis promoting genes by electron irradiation may inhibit keloid development. This mode of therapy appears to exert a positive effect toward lowering the recurrence rate of keloid formation.
    Materialart: Digitale Medien
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