Dr. Waldo J. E. Beek Profile

Dr. Waldo J. E. Beek

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Publications (3)

Proceedings Article | 4 October 2005 Paper

Hybrid ZnO:polymer bulk heterojunction solar cells from a ZnO precursor

Waldo J. Beek, Lenneke Slooff, Martijn Wienk, Jan Kroon, René A. Janssen

Proceedings Volume 5938, 59380L (2005) https://doi.org/10.1117/12.614891

KEYWORDS: Zinc oxide, Solar cells, Polymers, Humidity, Annealing, Photovoltaics, Crystals, Luminescence, Absorption, Coating

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Proceedings Article | 4 October 2005 Paper

Hybrid bulk heterojunction solar cells: blends of ZnO semiconducting nanoparticles and conjugated polymers

Waldo J. Beek, Martijn Wienk, René A. Janssen

Proceedings Volume 5938, 59380Z (2005) https://doi.org/10.1117/12.614911

KEYWORDS: Zinc oxide, Solar cells, Nanoparticles, Photovoltaics, Polymers, Electrodes, Heterojunctions, Laser induced fluorescence, Quantum efficiency, Aluminum

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Proceedings Article | 4 February 1999 Paper

Ablation velocity and thermal damage of myocardial tissue using a CO2 laser for transmyocardial laser revascularization

Anna Sachinopoulou, Johan Beek, Ton van Leeuwen, W. Beek

Proceedings Volume 3564, (1999) https://doi.org/10.1117/12.339164

KEYWORDS: Laser ablation, Carbon dioxide lasers, Tissues, Laser tissue interaction, Excimer lasers, Heart, In vitro testing, Patents, Velocity measurements, Laser induced damage

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Transmyocardial Laser Revascularization (TMLR) is a new experimental method for relief of angina pectoris in patients with severe coronary artery disease. TMLR aims at revascularizing chronic hibernating myocardium by creating transmural channels. One of the working mechanism hypotheses is that the endocardial side of the channels remains open, enabling perfusion of the hibernating myocardium directly from the left ventricle. Although the working mechanism of TMLR is still unknown (perfusion through patent channels, induction of angiogenesis, relief of angina through destruction of sympatic innervation, others?), first clinical studies are successful. Currently, the Heart Laser^TM and other CO₂ lasers, XeCl Excimer laser and Ho:YAG laser are under investigation for TMLR. The initial attempts of TMR with needles were soon replaced by laser induced channels. Efforts were focused on developing a CO₂ laser that could penetrate a beating heart during its relaxation phase. Later, the position of the beam could be fixed in the myocardial wall using lasers with fiber delivery systems and perforation was achieved within multiple cycles. Various researchers reported on both patent and non-patent channels after TMLR. Our belief is that the extent of laser induced thermal damage is one of the factors that determine the clinical outcome and the extent of angiogenesis (and, possibly, the patency of the channel). The purpose of this study is to present a simple theoretical model to predict the extent of thermal damage around a transmyocardial channel. In vitro experiments were performed on myocardial bovine tissue and damage was assessed. The results were used to determine the final parameters of the approximating theoretical equation. To evaluate our results, we compared our results to in vitro data using the Heart Laser^TM from the literature. Ablation velocities were also measured and the results were compared to ablation velocity calculations using a model described by Ostegar et al.

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