Cosmological Applications of Gravitational Lensing

The last decade has seen an enormous increase of activity in the field of gravitational lensing, mainly driven by improvements of observational capabilities. I will review the basics of gravitational lens theory, just enough to understand the rest of this contribution, and will then concentrate on several of the main applications in cosmology. Cluster lensing, and weak lensing, will constitute the main part of this review.Comment: 26 pages, including 2 figures (a third figure can be obtained from the author by request) gziped and uuencoded postscript file; to be published in Proceedings of the Laredo Advanced Summer School, Sept. 9

Investigation of osteoconductive bone substitute by particles analysis, numerical simulation and optical coherence tomography

The amount of available alveolar ridge is an important factor in planning to replace a tooth with an implant. Inadequate bone height and width may compromise the implant placement. Therefore, augmenting ridge defects is essential in the proper installation of the implant. In case an implant is placed in a defective ridge, additional augmentation will be required in order to improve the aesthetic appearance. An osteoconductive bone substitute promotes bone growth in periodontal and maxillofacial osseous defects. It provides the body with a matrix for bone cell migration and is integrated into the natural physiologic remodelling process. In order to investigate the osteoconductive bone substitute, particle analysis was used. Numerical simulation and optical coherence tomography were employed in order to analyze the results of the remodelling process. A particle analyzer can offer two complementary measurement techniques. Its concept integrates laser and video measurements to provide complete sample information on both particle size distribution and particle shape distribution. The analyzer used can measure particle sizes in a range of 100 Nanometer up to 3600 Micron. Numerical simulation provides information concerning the biomechanical behaviour of the augmentation materials in the whole bone volume. For the Optical Coherence Tomography Investigation, a combined OCT/confocal system operating at 1300 nm/970 nm was used. This has a high numerical aperture (NA) interface optics which gives a small field of view of 1 mm by 1 mm with a transverse resolution of better than 4 mu m. Results of bone remodelling process are presented using different osteoconductive bone substitutes which have been proven through years of clinical experience