Parametric oscillation in vertical triple microcavities.

Optical parametric oscillation is a nonlinear process that enables coherent generation of 'signal' and 'idler' waves, shifted in frequency from the pump wave. Efficient parametric conversion is the paradigm for the generation of twin or entangled photons for quantum optics applications such as quantum cryptography, or for the generation of new frequencies in spectral domains not accessible by existing devices. Rapid development in the field of quantum information requires monolithic, alignment-free sources that enable efficient coupling into optical fibres and possibly electrical injection. During the past decade, much effort has been devoted to the development of integrated devices for quantum information and to the realization of all-semiconductor parametric oscillators. Nevertheless, at present optical parametric oscillators typically rely on nonlinear crystals placed into complex external cavities, and pumped by powerful external lasers. Long interaction lengths are typically required and the phase mismatch between the parametric waves propagating at different velocities results in poor parametric conversion efficiencies. Here we report the demonstration of parametric oscillation in a monolithic semiconductor triple microcavity with signal, pump and idler waves propagating along the vertical direction of the nanostructure. Alternatively, signal and idler beams can also be collected at finite angles, allowing the generation of entangled photon pairs. The pump threshold intensity is low enough to envisage the realization of an all-semiconductor electrically pumped micro-parametric oscillator.

Wave-vector-dependent exciton exchange interaction.

The exchange interaction for the yellow 1S orthoexciton in Cu2O is derived up to the order K2. The resulting exchange splittings are verified experimentally using high resolution spectroscopy. In agreement with theory the fine structure shows a characteristic dependence on the direction of the wave vector.

[Choristoma of the diaphragm. Case report of a rare tumor and approach through lateral thoracotomy]. / Choristom des Zwerchfells - Kasuistik eines seltenen Tumors und Versorgung desselben durch laterale Thorakotomie -

Tumors of the diaphragm are rare and caused by there special localisation difficult to diagnose. We describe the case of a 31 year old man with a choristoma of the left diaphragmal crux where the localisation and genesis could only be cleared through lateral thoracotomy. Nor the CT guided puncture or the laparoscopy-although sufficient samples for the pathology could be gained-allowed the right diagnose. The importance of good diagnostic approach to select the right operative procedure-in this case the anterolateral thoracotomy-is described.

Relationship between position of the coronary sinus catheter and distribution of cardioplegia.

BACKGROUND AND AIMS OF THE STUDY: The use of retrograde cardioplegia is controversial, mainly due to differences in theoretic and methodologic aspects. The aim of this study was to identify an optimal position for the cardioplegia catheter within the coronary sinus. METHODS: Thirteen cadaver hearts was used, and three different catheter positions in the coronary sinus were compared, using a radio-opaque dye which had a viscosity similar to that of blood. The distribution of dye at different segments of the heart was examined. RESULTS: Dye distribution, indicative of cardiac perfusion, was found to be related to the position of the catheter in the coronary sinus and the quantity of dye injected. CONCLUSIONS: This study demonstrated the efficiency of retrograde cardioplegia, and also that optimal positioning of the catheter and the use of high-volume cardioplegia are required concomitantly for successful perfusion.

[Intravascular ultrasound findings in calcifying arteriosclerosis: in vitro validation using "soft" roentgen images]. / Intravasale Ultraschallbefunde bei kalzifizierender Arteriosklerose: In-vitro-Validierung mittels "weicher" Röntgenstrahlaufnahmen.

AIM: The aim of this study was to validate the detection of calcified arteriosclerotic plaques with intravascular ultrasound (IVUS). METHOD: 181 arteries were examined by 20/30 MHz IVUS. The ultrasound cross-sections were compared to the corresponding radiologic (30 kV) and histologic cross-sections. RESULTS: Calcified lesions were imaged as bright echos with shadowing. In 13 cases of 161 calcified lesions were too small to detect by IVUS. In 5 ultrasonic sections the diagnosis "calcified lesion" could not be verified neither by radiology nor by histology. The sensitivity was 91.6%, the specificity was 94.7% and the accuracy was 93.0%. CONCLUSIONS: Because of the acoustic properties of calcium, calcified lesions can be detected accurately by IVUS. IVUS can generate new insights into the effect of plaque composition on the response to catheter therapies.

[Evaluating the measuring accuracy of intravascular ultrasound]. / Untersuchungen zur Uberprüfung der Messgenauigkeit des intravasalen Ultraschalls (IVUS).

AIM: Intravascular ultrasound investigations are new tomographic imaging methods for evaluation of artery dimensions and wall morphology. The present study was performed to test accuracy and observer variability. METHOD: 3 plastic phantoms and 1 iliacan artery were assessed. The quantitative measurements were made by computerised 3D reconstruction. RESULTS: The plastic phantoms showed ultrasonically three layers of echogenic structures. An intimal fibrous thickening was seen in the iliac artery. The cross sectional diameters were ultrasonically overestimated by 12.6 +/- 5.6%. Due to the lower velocity of sound in water than in blood there were no significant differences to the true diameters. The intra- and interobserved variabilities were determined to 1.4 +/- 0.8% and 2.6 +/- 1.2%. CONCLUSIONS: Intravascular ultrasound provides a reproducible method for measuring vessel lumen diameters with excellent intraobserver and interobserver variabilities. For in vitro examinations the different velocities of sound in different media have to be taken into account.

The pathology of vascular grafts.

In order to analyse the incorporation pattern of synthetic prosthesis made of Teflon and Dacron in the arterial system, 21 prostheses removed surgically and seven prostheses obtained from autopsies were examined; the duration of the implantation periods ranged from 30 min up to 10 years. Essentially the early phase of prosthetic incorporation (phase I) includes exudative inflammatory reactions as part of acute inflammatory processes. The degree of order within the tissue architecture and the mutual influence of matrix and cells in the reaction appeared to be slight. The cellular infiltrate found on the outer prosthetic surface is of local origin whereas the inner prosthetic lining contains cells of haematogenous origin. The organisation phase (phase II), which is comparable to the reparative-proliferative phase of an inflammatory reaction, showed activation of the reticulo-endothelial system together with the start of phagocytosis and a thinning of the prosthetic structures. Collagen type I and type III and fibronectin served both as a guidance and a growth tract for the cells during the cellular permeation of the prosthesis. Fibronectin and collagen type III have a special "catalytic" function. Collagen type I causes the firm anchoring of the vascular prosthesis in the periprosthetic tissue. The loss of stability of the prosthesis due to phagocytosis of fibres is balanced by the newly formed connective tissue within the wall of the vessel. The fibroblasts involved in the organisation must be derived from the flowing blood and from local mesenchymal cells. A chronic inflammatory reaction persisted during the late phase. In some cases increased proliferation of the inner mesenchymal lining of the prosthesis was observed together with regressive changes. The lack of a continuous surrounding stromal architecture on the luminal side of the vessel can be regarded as the main reason for this proliferation. Transformation of haematogenous cells into angioblasts or endothelial cells was not seen. Small endothelialised areas were only seen in the vicinity of anastomoses and following transprosthetic permeation by capillaries.

[Mediastinal lymph node metastases in bronchial cancer--CT analog horizontal section of an autopsy patient sample]. / Mediastinale Lymphknotenmetastasen beim Bronchialkarzinom--CT-analoge Horizontalschnitte am Obduktionsgut.

On the basis of horizontal sections through the entire heart-lung preparation, the size relationships and topographical features of mediastinal lymph node metastases of lung carcinomas are presented. This sectioning technique is more suitable for the determination of the lymphatic metastasization pattern than the conventional postmortem technique. The detection of multiple areas with focal consolidated lymphatic tissue in the mediastinal fatty tissuereveals additional possibilities for lymphopatic tumour spread in the mediastinum.