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  • Articles: DFG German National Licenses  (39)
  • Electronic Resource  (39)
  • 1
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 78 (2001), S. 1062-1064 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Temperature-dependent time-resolved photoluminescence measurements were performed on GaN film/AlN buffer/6H–SiC substrate heterostructures grown by metalorganic chemical vapor deposition. The overlying GaN layers were under tension, as estimated from the free A exciton (FEA) position. The recombination lifetimes were determined for the FEA and for the neutral-donor-bound exciton (D0X). We observed that the recombination lifetime for the FEA has the same value of 40–50 ps in all the layers, whereas the recombination time for the D0X varies for different samples. We observed that the recombination lifetimes for D0X have a clear dependence on the position of FEA, i.e., the recombination lifetime increases with decreasing strain in the layers. We discuss the results in term of the hole states involved in the donor-bound exciton recombination. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 70 (1997), S. 2001-2003 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Low-temperature reflectance data on epitaxial GaN thin-film samples covering the widest range of tensile and compressive stress (−3.8–3.5 kbar) thus far explicitly show the nonlinear behavior of the B–A and C–A splittings versus the energy of the A exciton. Lineshape ambiguities that hindered previous interpretations have been resolved with reciprocal-space analysis, allowing us to obtain band parameters such as ΔSO=17.0±1meV with increased confidence. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 69 (1996), S. 2065-2067 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Spectroscopic ellipsometry was used to assess the preparation of smooth and abrupt GaN, AlN, and AlGaN surfaces by wet chemical treatments in real time. About 20–50 A(ring) of overlayer typically can be removed from air-exposed samples. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 73 (1998), S. 2808-2810 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We discuss trends in residual stress as a function of film thickness, growth temperature, and substrate orientation for GaN/AlN/6H–SiC heterostructures. Films are mostly compressive for samples less than about 0.7 μm thick, are tensile up to about 2 μm, then abruptly become less tensile with stress values near 1 kbar thereafter. We interpret this as a successive relief of lattice mismatch and thermal stresses culminating in a catastrophic relief by unknown mechanisms at moderate thicknesses. These data indicate that relaxation processes in these heterostructures are not as well understood as previously supposed. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 63 (1993), S. 3367-3369 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A new form of light emitting devices called BICE (bias induced color-tunable emitter) is reported. It is a voltage controlled multiwavelength semiconductor light emitter based on the bias dependent injection and collection of electrons and holes in quantum wells. In this letter, two-terminal dual wavelength BICE operation is demonstrated. It exhibits coaxial optical output, a large separation between emission wavelengths ((approximately-greater-than)500 A(ring)) and an emission contrast ratio ranging from 4:1 to 1:33 at 77 K.
    Type of Medium: Electronic Resource
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  • 6
    ISSN: 1365-2036
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Background : We have previously reported, in an uncontrolled trial, an improvement in fatigue scores in patients with primary biliary cirrhosis given oral antioxidant supplementation. We now present data from a controlled trial.Patients and methods : Sixty-one patients with primary biliary cirrhosis-associated fatigue were randomized into a double-blind, placebo-controlled, cross-over trial. Participants received 12 weeks each of placebo and antioxidant supplementation (vitamins A, C and E, selenium, methionine and ubiquinone) in random order, separated by a 4-week washout period. The primary trial outcome (fatigue) was assessed using the Fisk scale. Other symptoms of primary biliary cirrhosis were measured using Likert and visual analogue scales.Results : Forty-four patients completed both arms of the trial. No significant changes in fatigue were recorded in the active phase of treatment (median improvement in Fisk score, 1; P = 0.61). Small improvements in Fisk scores were recorded during placebo therapy (median improvement, 4; P = 0.03). Neither medication was associated with improvement in any other symptoms related to primary biliary cirrhosis. Adverse effects were more common during active therapy and were mild and self-limiting. One patient died from unrelated causes during active treatment.Conclusions : Although oral antioxidant supplementation appears to be safe, we could not find any evidence for a beneficial effect on fatigue or other liver-related symptoms.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Anaesthesia 50 (1995), S. 0 
    ISSN: 1365-2044
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: The utilisation of the pre-operative ECG in patients undergoing routine surgery was investigated in 354 adult patients over a 2-week period. Sixty-four percent of patients had an ECG pre-operatively. An ECG was not performed in 17% of patients who, current hospital policy suggests, should have had one. In contrast, an ECG was performed in 33% of patients who, hospital policy suggests, have no need of one (all of which were normal), which represented 18% of the total number of pre-operative ECGs performed. In 62% of patients with known cardiac disease, and 44% of patients with strong risk factors for ischaemic heart disease (in the absence of known disease) the ECG was abnormal. This compares with only 7% of patients aged over 50 with no risk factors in whom the ECG was abnormal. These findings suggest that there is room for improvement in the utilisation of the pre-operative ECG, which may have cost implications.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Anaesthesia 49 (1994), S. 0 
    ISSN: 1365-2044
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: A previously fit 20-year-old man presented with a large haemothorax following a stab wound to the left chest. Pre-operative airway assessment indicated that tracheal intubation would be routine. On induction of anaesthesia, visualisation of the larynx proved impossible because of soft tissue swelling. Successful intubation was eventually achieved with the aid of a gum elastic bougie. At operation, the patient's common carotid artery was found to have been perforated close to its origin on the aorta. The patient made an uneventful recovery.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Anaesthesia 49 (1994), S. 0 
    ISSN: 1365-2044
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: We performed a randomised controlled study in patients undergoing day case laparoscopic sterilisation to assess whether coating Filshie clips with 2% lignocaine gel prior to application to the Fallopian tubes would reduce postoperative pain. Sixty-two patients were studied, in 33 of whom the Filshie clips were coated in sterile 2% lignocaine gel. Pain scores in the lignocaine gel group were significantly lower than in the control group at 1 h after return to the ward, but no differences were found immediately on return to the ward, or at discharge or at 24 h. There were no significant differences between the two groups in postoperative analgesic requirements or in side effects.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Anaesthesia 47 (1992), S. 0 
    ISSN: 1365-2044
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: A double-blind randomised study was performed to assess the value of the addition of pethidine 50 mg to the initial dose of bupivacaine given for epidural analgesia in labour. Forty-nine patients received either I ml of saline (n = 24), or 50 mg of pethidine (n = 25), added to 9 ml of 0.25% bupivacaine as an initial injection for intrapartum epidural analgesia. There was a significant increase in the mean duration of analgesia in the pethidine group. However, pethidine did not increase the speed of onset of analgesia, or improve the quality of analgesia.
    Type of Medium: Electronic Resource
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