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  • 1
    Digitale Medien
    Digitale Medien
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 52 (1988), S. 742-744 
    ISSN: 1077-3118
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: The structure of In1−xGaxAsyP1−y/InP superlattices (x=0.27 and y=0.60) is investigated by small-angle x-ray diffraction method. The interference peaks due to the superlattice structure were clearly observed up to the 6th order. The period of the superlattice was determined from the angular positions of the peaks using the modified Bragg's law. By analyzing the diffraction patterns of the first and the secondary peaks according to the optical multilayer theory, the thickness of each component (In1−xGaxAsyP1−y and InP) was uniquely determined within an error of ±1 A(ring). This method can be used to determine any type of superlattice structure.
    Materialart: Digitale Medien
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  • 2
    Digitale Medien
    Digitale Medien
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 54 (1989), S. 1353-1355 
    ISSN: 1077-3118
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: We grew In1−xGaxAsyP1−y/InP quantum wells (QWs) by low-pressure metalorganic vapor phase epitaxy. The In1−xGaxAsyP1−y layer was closely lattice matched to InP with a composition of y=0.9 (x=0.47y). We investigated structural imperfections such as composition fluctuations, interface roughness, and nonperiodicity analyzing the low-temperature photoluminescence linewidth. We found that the InGaAsP layer composition fluctuated, causing about 5 meV inhomogeneity in the exciton energy level in QWs wider than about 3 nm. Since we obtained very smooth interfaces with less than one monolayer of fluctuation and excellent periodicity by lowering growth temperature to 570 °C, the inhomogeneity of the exciton energy level could be held at 6 meV for 20-period 10-nm multiple QWs. As a result, despite composition fluctuations, a clear room-temperature exciton optical absorption peak was observed at 1.5 μm for the first time to our knowledge.
    Materialart: Digitale Medien
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  • 3
    Digitale Medien
    Digitale Medien
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 53 (1988), S. 2290-2292 
    ISSN: 1077-3118
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: We evaluated the magnitude of broadening factors of ground-state exciton absorption peaks in In1−xGaxAsyP1−y/InP (x=0.47y) multiple quantum wells (MQW's) with about 10 nm wells. The absorption peaks broadened with a decrease of y. Analyzing the absorption peak broadening with increasing temperature, the thermal broadening factor at 300 K was found to be about 9 meV and composition independent. Analyzing the photoluminescence linewidth at 4.2 K, it was found that composition fluctuations in the well caused an inhomogeneity of the exciton energy level of 4.4 meV for the y=1.0 MQW and 7.5 meV for the y=0.6 MQW, being the greatest contributors to inhomogeneous broadening. We conclude that the exciton absorption peak broadening with a decrease of y is primarily due to the increase of composition fluctuations.
    Materialart: Digitale Medien
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  • 4
    Digitale Medien
    Digitale Medien
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 62 (1993), S. 2384-2386 
    ISSN: 1077-3118
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: The evolution of photocurrent in time under ultraviolet (UV) irradiation of free-standing diamond thin films, prepared by chemical vapor deposition method, have been observed. A significant enhancement of the photosensitivity in visible-near-infrared region of UV illuminated samples have been obtained. The linear dependence of relative change of photocurrent on UV radiant intensity have been found. The photoconductivity spectra have been investigated in the energy range 1–6.2 eV. The results of investigation have shown that diamond thin films possess similar properties as radiation damaged crystalline diamond.
    Materialart: Digitale Medien
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  • 5
    Digitale Medien
    Digitale Medien
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 65 (1994), S. 593-594 
    ISSN: 1077-3118
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: Temperature dependences of the hole concentration and Hall mobility in Mg-doped GaN and Al0.08Ga0.92N grown by metalorganic vapor phase epitaxy were measured by the van der Pauw method over a wide temperature range from 100 to 500 K. Assuming that the effective mass of holes in Al0.08Ga0.92N is equal to that of GaN, the activation energy of the Mg shallow acceptor in Al0.08Ga0.92N is estimated to be about 35 meV deeper than that in GaN.
    Materialart: Digitale Medien
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  • 6
    Digitale Medien
    Digitale Medien
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 61 (1992), S. 772-773 
    ISSN: 1077-3118
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: We have deposited diamond films from CF4-H2 mixed gas by microwave plasma chemical vapor deposition method. The diamond films were characterized by scanning electron microscopy, x-ray diffraction, Raman spectrometry, and secondary ion mass spectrometry. (111) peak line of diamond crystal observed by x-ray diffraction and the peaks at 1333 cm−1 in the Raman spectroscopies of the deposited films showed that the films consisted of diamond. We observed that the quality of diamond films got better as the concentration (from 2.5% to 40%) of CF4 (tetrafluoromethane) got lower. It was observed from the optical emission spectra that CF, CF2, CF3, CH, and C2 fragments existed in the microwave plasma of CF4-H2 mixed gas. But it was observed from secondary ion mass spectroscopies that impurities (Si, F, and H) were present in the diamond films.
    Materialart: Digitale Medien
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  • 7
    Digitale Medien
    Digitale Medien
    Oxford, UK : Blackwell Science Ltd
    British journal of dermatology 143 (2000), S. 0 
    ISSN: 1365-2133
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Medizin
    Materialart: Digitale Medien
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  • 8
    Digitale Medien
    Digitale Medien
    Oxford, UK : Blackwell Science Ltd
    British journal of dermatology 147 (2002), S. 0 
    ISSN: 1365-2133
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Medizin
    Notizen: Summary Background The molecular basis of senescence and immortalization is not still understood, but one hypothesis for which there has recently been much evidence involves the shortening of telomeres. It can be hypothesized that abnormalities of telomerase contribute to the emergence of abnormal fibroblast clones in systemic sclerosis (SSc). Objectives To study possible telomere abnormalities with respect to polymorphism of the telomerase RNA component gene. Methods Fifty-three patients with SSc and 98 normal controls were studied. Polymerase chain reaction was used to amplify 598 bp of the telomerase RNA component gene. Amplified fragments were digested with restriction enzyme BsrDI. Results The frequency of the A allele in SSc (41·5%) showed no significant difference from that in the normal controls (32·1%). The frequency of the A/A alleles in SSc (18·9%) was significantly higher than in normal controls (5·1%), compared with G/G (35·8% and 40·8%, respectively; P 〈 0·02), G/A (45·3% and 54·1%, respectively; P 〈 0·01) and G/G plus G/A (81·1% and 94·9%, respectively; P 〈 0·01). Conclusions These results showed the possible involvement of a telomerase abnormality in the emergence of abnormal fibroblast clones in SSc skin-derived fibroblasts.
    Materialart: Digitale Medien
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  • 9
    Digitale Medien
    Digitale Medien
    Oxford, UK : Blackwell Science Ltd
    British journal of dermatology 147 (2002), S. 0 
    ISSN: 1365-2133
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Medizin
    Notizen: Background Transforming growth factor (TGF)-β has been shown to be a potent stimulator of collagen production by fibroblasts, and could play a role in the pathogenesis of systemic sclerosis (SSc). Objectives To study the possible involvement of TGF-β1 gene polymorphism in Japanese patients with SSc. Methods Fifty-nine patients with SSc and 110 normal subjects were studied. Genomic DNA was extracted from skin tissues, and was amplified in a thermal cycler, generating a TGF-β1 gene fragment with a size of 294 bp. The T to C transition at T869C (Leu10Pro) and the G to C transition at G915C (Arg25Pro) were identified by digestion with MspA1I and BglI, respectively. Results At T869C (Leu10Pro), the frequency of the C allele in SSc (65·3%) was significantly higher than in normal controls (50·5%) (P 〈 0·01). SSc showed C/C allele 42·4%, C/T 45·8% and T/T 11·2%. Normal controls showed C/C allele 26·4%, C/T 48·2% and T/T 25·5%. The frequency of the C/C allele in SSc was significantly higher than in normal controls, in comparison with the T/T allele (P 〈 0·02), but no significant difference was found between the frequency of the C/C allele vs. the C/T allele. The frequency of the C/C allele showed no significant difference between diffuse and limited SSc. At G915C (Arg25Pro), all the normal controls and SSc patients showed only the G/G allele. These results are different from a previous study in which the frequency of the T/T allele was high in SSc at T869C (Leu10Pro). Conclusions This discrepancy may indicate that Japanese patients with SSc show a different genetic predisposition to TGF-β1.
    Materialart: Digitale Medien
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  • 10
    Digitale Medien
    Digitale Medien
    Oxford, UK : Blackwell Science Ltd
    British journal of dermatology 145 (2001), S. 0 
    ISSN: 1365-2133
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Medizin
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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