Baumann V.,University WurzburgWurzburg |
Rodel R.,University WurzburgWurzburg |
Rodel R.,Max Planck Institute for Solid State Research |
Heidemann M.,University WurzburgWurzburg |
And 4 more authors.
Physica Status Solidi (A) Applications and Materials Science | Year: 2014
We report on the structural and optical properties of self-assembled (Al,Ga)InP quantum dots (QDs) with varying material composition embedded in a (Al0.30Ga0.70)0.51In0.49P matrix. The samples were grown by gas-source molecular beam epitaxy. Atomic force microscopy was used to study the structural properties of the quantum dots, revealing a strong dependence of the morphology on the material composition. Low-temperature ensemble photoluminescence was observed between 590 nm and 720 nm. Temperature and excitation power dependent, as well as time resolved measurements were performed, indicating a significantly reduced electron confinement and a reduced overlap of the electron/hole wavefunctions for Al- and/or Ga-rich compositions. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
Kampf T.,University WurzburgWurzburg |
Helluy X.,University WurzburgWurzburg |
Gutjahr F.T.,University WurzburgWurzburg |
Winter P.,University WurzburgWurzburg |
And 4 more authors.
Magnetic Resonance in Medicine | Year: 2014
Purpose The quantification of myocardial perfusion using a Look-Locker flow-sensitive alternating inversion recovery- arterial spin labeling experiment is considered. Due to the anatomy of the heart, a substantial but unintended partial inversion of the inflowing blood occurs during the slice-selective inversion. Both, the partial inversion as well as the Look-Locker pulse train, influence the myocardial perfusion quantification and are addressed in this work. Methods The mean relaxation time approximation is used to calculate the monoexponential relaxation time of the signal in perfused tissue under Look-Locker readout. The left ventricular blood serves as an approximation of the inflowing blood in the description of FAIR-ASL measurements with global and slice-selective inversion to correctly quantify the myocardial perfusion. Results The analysis shows that the myocardial perfusion can be overestimated if the T1-based quantification method is not adapted respecting the Look-Locker pulse train explicitly. Additionally, it turns out that without correction for the partial inversion of the blood pool during the slice-selective inversion the myocardial perfusion is underestimated. Conclusion It is shown that the Look-Locker readout as well as the nonideal slice-selective inversion experiment have a considerable influence and have to be included properly to correctly quantify myocardial perfusion. © 2013 Wiley Periodicals, Inc.