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  • 1
    Digitale Medien
    Digitale Medien
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 84 (1998), S. 6871-6876 
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: We report on a novel experimental setup using a miniature integrating sphere fitted into a cryostat to measure spectrally resolved the absolute external photoluminescence quantum efficiency ηlum in the temperature range from 6 K to beyond room temperature. Direct access to ηlum is achieved by an uncomplicated method to calibrate the spatially integrated emission spectra absolutely. The fraction of light coupled out of the sphere into the detection system is in good approximation independent of the emitted wavelength and the emission characteristics of the investigated samples, due to their smallness compared with the total sphere area. This fact is proved by theoretical calculations for the sphere throughput and the irradiance within the sphere. To demonstrate the capabilities of this setup, we investigate in high quality ZnSe/ZnMgSSe 10× multiple quantum wells, the temperature dependence of the quantum efficiency, simultaneously for the quantum well and the barrier luminescence. Within a thermal activation model, three processes are found to contribute to the thermal quenching of ηlum of the quantum well luminescence. © 1998 American Institute of Physics.
    Materialart: Digitale Medien
    Standort Signatur Einschränkungen Verfügbarkeit
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  • 2
    Digitale Medien
    Digitale Medien
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 114 (2001), S. 4669-4684 
    ISSN: 1089-7690
    Quelle: AIP Digital Archive
    Thema: Physik , Chemie und Pharmazie
    Notizen: Combining molecular beam techniques and time-resolved infrared reflection absorption spectroscopy (TR-IRAS) we have studied the kinetics of the CO oxidation reaction on an alumina-supported Pd model catalyst. The Pd particles are deposited by metal evaporation under ultrahigh vacuum (UHV) conditions onto a well-ordered alumina film, prepared on a NiAl(110) single crystal. Particle size, density and structure of the Pd deposits have been characterized in previous studies. In the low temperature region, transient and steady-state experiments have been performed over a wide range of CO and oxygen fluxes by crossing two effusive molecular beams on the sample surface. We determine the steady-state CO2 production rate as a function of the CO fraction in the impinging gas flux. Simultaneously, the occupation of CO adsorption sites under steady-state conditions is monitored by in situ IR spectroscopy. The origin of different types of CO2 transients is discussed. In particular we focus on the transient CO2 production after switching off the CO beam. For the model catalyst investigated, detailed reaction rate measurements in combination with time-resolved IRAS show that the origin of the particular transient behavior of the supported model system is not due to the presence of specific adsorption sites on small particles, as has been proposed previously. Instead, we show that the transient behavior can be semiquantitatively simulated on the basis of a simple kinetic model considering a homogeneous surface, and accounting for the inhibition of the dissociative adsorption of O2 at high CO coverage. Moreover, it is discussed how the inherent heterogeneity of the supported particle system can additionally enhance the observed effect. © 2001 American Institute of Physics.
    Materialart: Digitale Medien
    Standort Signatur Einschränkungen Verfügbarkeit
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  • 3
    Publikationsdatum: 2015-01-01
    Beschreibung: Rationale: There is mounting evidence of a higher incidence of coronary heart disease in cytomegalovirus-seropositive individuals. Objective: The aim of this study was to investigate whether acute myocardial infarction triggers an inflammatory T-cell response that might lead to accelerated immunosenescence in cytomegalovirus-seropositive patients. Methods and Results: Thirty-four patients with acute myocardial infarction undergoing primary percutaneous coronary intervention were longitudinally studied within 3 months after reperfusion (Cohort A). In addition, 54 patients with acute myocardial infarction and chronic myocardial infarction were analyzed in a cross-sectional study (Cohort B). Cytomegalovirus-seropositive patients demonstrated a greater fall in the concentration of terminally differentiated CD8 effector memory T cells (T EMRA ) in peripheral blood during the first 30 minutes of reperfusion compared with cytomegalovirus-seronegative patients (–192 versus –63 cells/μL; P =0.008), correlating with the expression of programmed cell death-1 before primary percutaneous coronary intervention ( r =0.8; P =0.0002). A significant proportion of T EMRA cells remained depleted for ≥3 months in cytomegalovirus-seropositive patients. Using high-throughput 13-parameter flow cytometry and human leukocyte antigen class I cytomegalovirus-specific dextramers, we confirmed an acute and persistent depletion of terminally differentiated T EMRA and cytomegalovirus-specific CD8 + cells in cytomegalovirus-seropositive patients. Long-term reconstitution of the T EMRA pool in chronic cytomegalovirus-seropositive postmyocardial infarction patients was associated with signs of terminal differentiation including an increase in killer cell lectin-like receptor subfamily G member 1 and shorter telomere length in CD8 + T cells (2225 versus 3397 bp; P 〈0.001). Conclusions: Myocardial ischemia and reperfusion in cytomegalovirus-seropositive patients undergoing primary percutaneous coronary intervention leads to acute loss of antigen-specific, terminally differentiated CD8 T cells, possibly through programmed cell death-1–dependent programmed cell death. Our results suggest that acute myocardial infarction and reperfusion accelerate immunosenescence in cytomegalovirus-seropositive patients.
    Schlagwort(e): Pathophysiology, Acute myocardial infarction, Other Research
    Print ISSN: 0009-7330
    Digitale ISSN: 1524-4571
    Thema: Medizin
    Standort Signatur Einschränkungen Verfügbarkeit
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  • 4
    Publikationsdatum: 2015-02-27
    Beschreibung: Rationale: Inflammation in the setting of acute myocardial infarction (MI) has been linked to risk stratification; however, the release kinetics of inflammatory biomarkers in patients with acute MI has been difficult to establish. Objective: The aim of this study was to determine the kinetics of changes in the levels of several biomarkers specifically linked to inflammation after transcoronary ablation of septal hypertrophy, a procedure that mimics acute MI. Methods and Results: We analyzed release kinetics of C-reactive protein, high-sensitivity C-reactive protein, interleukin-6, soluble CD40 ligand, and peripheral blood leukocyte subsets in patients (n=21) undergoing transcoronary ablation of septal hypertrophy. Blood samples were collected before transcoronary ablation of septal hypertrophy and at various times after transcoronary ablation of septal hypertrophy. Serum levels of C-reactive protein were increased at 24 hours (1.0 mg/dL [interquartile range [IQR], 0.7–1.75] versus 0.2 mg/dL [IQR, 0.1–1.05] at baseline [BL]; P 〈0.001), whereas high-sensitivity C-reactive protein increased as early as 8 hours (2.68 mg/L [IQR, 1.23–11.80] versus 2.17 mg/L [IQR, 1.15–5.06] at BL; P =0.002). Interleukin-6 was significantly increased at 45 minutes (2.59 pg/mL [IQR, 1.69–5.0] versus 1.5 pg/mL [IQR, 1.5–2.21] at BL; P =0.002), and soluble CD40 ligand was significantly decreased at 60 minutes (801.6 pg/mL [IQR, 675.0–1653.5] versus 1750.0 pg/mL [IQR, 1151.0–2783.0] at BL; P =0.016). Elevated counts of polymorphonuclear neutrophils were detectable at 15 minutes, with a significant increase at 2 hours (6415 cells/μL [IQR, 5288–7827] versus 4697 cells/μL [IQR, 2892–5620] at BL; P =0.004). Significant monocytosis was observed at 24 hours (729 cells/μL [IQR, 584–1344] versus 523 cells/μL [IQR, 369–701] at BL; P =0.015). Conclusions: Interleukin-6 and neutrophil granulocytes showed a continuous rise at all prespecified time points after induction of MI. Our results provide valuable additional evidence of the diagnostic value of inflammatory biomarkers in the setting of early acute MI.
    Schlagwort(e): Growth factors/cytokines, Ischemic biology - basic studies, Acute myocardial infarction
    Print ISSN: 0009-7330
    Digitale ISSN: 1524-4571
    Thema: Medizin
    Standort Signatur Einschränkungen Verfügbarkeit
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  • 5
    Publikationsdatum: 2015-02-13
    Schlagwort(e): Acute myocardial infarction
    Print ISSN: 0009-7330
    Digitale ISSN: 1524-4571
    Thema: Medizin
    Standort Signatur Einschränkungen Verfügbarkeit
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