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  • 1
    Digitale Medien
    Digitale Medien
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 109 (1998), S. 2474-2479 
    ISSN: 1089-7690
    Quelle: AIP Digital Archive
    Thema: Physik , Chemie und Pharmazie
    Notizen: The photochemistry of carbonyl sulfide (OCS) adsorbed to small silver clusters is shown to exhibit a striking odd–even dependence on the number of Ag atoms in the cluster. OCS is found to desorb nondissociatively from even numbered silver clusters. In contrast, on odd silver clusters, a new product channel corresponding to AgnS is observed. Parallels are found with the photochemistry of adsorbates on extended surfaces. Cross-section measurements for OCS desorption from Ag10 and wavelength-dependent measurements of OCS dissociation on Ag9 both indicate that electronic excitation of the cluster initiates chemistry, analogous to substrate mediated surface photochemistry. The size dependence is reasonably explained in terms of a charge-transfer mechanism involving an ion-pair state of the AgnOCS complex. © 1998 American Institute of Physics.
    Materialart: Digitale Medien
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  • 2
    Digitale Medien
    Digitale Medien
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 80 (1996), S. 3228-3237 
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: Defect structures were investigated by transmission electron microscopy for GaN/Al2O3 (0001) epilayers grown by metal-organic chemical vapor deposition using a two-step process. The defect structures, including threading dislocations, partial dislocation bounding stacking faults, and inversion domains, were analyzed by diffraction contrast, high-resolution imaging, and convergent beam diffraction. GaN film growth was initiated at 600 °C with a nominal 20 nm nucleation layer. This was followed by high-temperature growth at 1080 °C. The near-interfacial region of the films consists of a mixture of cubic and hexagonal GaN, which is characterized by a high density of stacking faults bounded by Shockley and Frank partial dislocations. The near-interfacial region shows a high density of inversion domains. Above ∼0.5 μm thickness, the film consists of isolated threading dislocations of either pure edge, mixed, or pure screw character with a total density of ∼7×108 cm−2. The threading dislocation reduction in these films is associated with cubic to hexagonal transformation of the nucleation layer region during high temperature growth. © 1996 American Institute of Physics.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 3
    Digitale Medien
    Digitale Medien
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 77 (1995), S. 5910-5915 
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: The surface layer of crystalline silicon implanted with 1.5 MeV Si ions with doses ranging from 1×1011 to 1×1015 Si+/cm2 has been studied by Raman scattering. Raman line intensities, shapes and shifts have been used to investigate the defects in the near-surface layer. Above doses of 1×1013 Si+/cm2, Raman provides evidence for the presence of amorphous silicon islands within the crystalline structure. The phonon-confinement model (PCM) which is based on the breakdown in wavevector selection rules due to scattering from finite domain sizes has been used to estimate the effective average distance between defects. The PCM has also been modified by introducing a term attributable to residual stress in the near-surface layer. By fitting experimental Raman spectra with the modified PCM, the Raman line shifts due to stress effects are decoupled from those due to phonon confinement. The mechanisms for the stress creation are also discussed. © 1995 American Institute of Physics.
    Materialart: Digitale Medien
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  • 4
    ISSN: 1520-510X
    Quelle: ACS Legacy Archives
    Thema: Chemie und Pharmazie
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 5
    Digitale Medien
    Digitale Medien
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 73 (1998), S. 2468-2470 
    ISSN: 1077-3118
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: We present a study of the transport properties of two-dimensional electron gases formed in GaAs/AlGaAs heterostructures in which InAs self-assembled quantum dots have been inserted in the center of a GaAs quantum well. We observed that, while maintaining a constant carrier density, the mobility increased as the InAs dot density was reduced. The ratio of the transport to the quantum lifetime was measured to be approximately five with the dominant scattering mechanism attributed to short-range scattering from the inserted InAs dots. © 1998 American Institute of Physics.
    Materialart: Digitale Medien
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  • 6
    Digitale Medien
    Digitale Medien
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 73 (1998), S. 49-51 
    ISSN: 1077-3118
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: InAs quantum dots inserted at the middle of a GaAs quantum well structure have been investigated by transmission electron microscopy and scanning transmission electron microscopy. We find that the growth condition of the overlayer on the InAs dots can lead to drastic changes in the structure of the dots. We attribute the changes to a combination of factors such as preferential growth of the overlayer above the wetting layers because of the strained surfaces and to the thermal instability of the InAs dots at elevated temperature. The result suggests that controlled sublimation, through suitable manipulation of the overlayer growth conditions, can be an effective tool to improve the structure of the self-organized quantum dots and can help tailor their physical properties to any specific requirements of the device applications. © 1998 American Institute of Physics.
    Materialart: Digitale Medien
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  • 7
    ISSN: 1460-9592
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Medizin
    Notizen: Upper airway patency can be compromised when children (or adults) receive sedative medication. The study examines the effect of two different positioning techniques (use of the ‘sniff position pillow’ (SPP) and shoulder elevation (SE) on maintenance of upper airway patency using MRI in 21 children sedated with intravenous pentobarbital (5–8 mg·kg-1). Children positioned on the SPP had a significantly greater degree of atlanto-occipital extension (P 〈 0.05), and a significantly greater nasopharyngeal diameter (P 〈 0.05) than those with shoulder elevation. The degree of atlanto-occipital extension was not significantly correlated with pharyngeal diameter (R = -0.68). No clinical signs of upper airway obstruction were noted and oxygen desaturation did not occur. Both positioning techniques were consistently associated with upper airway patency under the study conditions described. In obligate nose breathers to whom sedative agents are administered, the SPP is more likely to maintain nasopharyngeal patency than shoulder elevation.
    Materialart: Digitale Medien
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  • 8
    Digitale Medien
    Digitale Medien
    Oxford, UK : Blackwell Publishing Ltd
    Journal of food science 14 (1949), S. 0 
    ISSN: 1750-3841
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 9
    Digitale Medien
    Digitale Medien
    s.l. : American Chemical Society
    Journal of the American Chemical Society 71 (1949), S. 1512-1512 
    ISSN: 1520-5126
    Quelle: ACS Legacy Archives
    Thema: Chemie und Pharmazie
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 10
    Digitale Medien
    Digitale Medien
    Oxford, UK : Blackwell Publishing Ltd
    Journal of clinical periodontology 22 (1995), S. 0 
    ISSN: 1600-051X
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Medizin
    Notizen: Abstract. Short-term success of the use of self-assessment for motivating adults to improve their oral health status has been reported. The purpose of this trial was to evaluate the long-term effectiveness of two self-assessment strategies, one focused on gingival bleeding (group I) and another focused on plaque (group II). At baseline, 493 14- and 15-year-olds were assigned randomly to a group. Each subject was given a manual describing one of the self-assessment, processes. Dental hygienists provided standardized classroom based instruction and two weeks later, individualized counselling. Examinations were conducted at baseline 6, 12, 18 and 24 months for gingival bleeding on probing, plaque, calculus, and probing depth; and at baseline and 24 months for recession and decayed, missing and filled surfaces (DMFS). Following the 12-momh examination, subjects received an oral prophylaxis and individual counselling. The results revealed no statistically significant differences between groups for any clinical parameter at the final examination. However, the mean number of sites with gingival bleeding decreased steadily from baseline to 24 months with a 59% decrease and 55% decrease for groups I and II, respectively. This study suggests that self-assessment approaches can be effective in improving the long-term periodontal health status of teenagers.
    Materialart: Digitale Medien
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