Density and Correlation functions of vortex and saddle points in open billiard systems

We present microwave measurements for the density and spatial correlation of current critical points in an open billiard system, and compare them with the predictions of the Random Wave Model (RWM). In particular, due to a novel improvement of the experimental set-up, we determine experimentally the spatial correlation of saddle points of the current field. An asymptotic expression for the vortex-saddle and saddle-saddle correlation functions based on the RWM is derived, with experiment and theory agreeing well. We also derive an expression for the density of saddle points in the presence of a straight boundary with general mixed boundary conditions in the RWM, and compare with experimental measurements of the vortex and saddle density in the vicinity of a straight wall satisfying Dirichlet conditions.Comment: submitted to Physical Review

Classical wave experiments on chaotic scattering

We review recent research on the transport properties of classical waves through chaotic systems with special emphasis on microwaves and sound waves. Inasmuch as these experiments use antennas or transducers to couple waves into or out of the systems, scattering theory has to be applied for a quantitative interpretation of the measurements. Most experiments concentrate on tests of predictions from random matrix theory and the random plane wave approximation. In all studied examples a quantitative agreement between experiment and theory is achieved. To this end it is necessary, however, to take absorption and imperfect coupling into account, concepts that were ignored in most previous theoretical investigations. Classical phase space signatures of scattering are being examined in a small number of experiments.Comment: 33 pages, 13 figures; invited review for the Special Issue of J. Phys. A: Math. Gen. on "Trends in Quantum Chaotic Scattering

Free flow micropuncture studies of glucose transport in the rat nephron

Tubular free flow micropuncture studies were done in normoglycemic rats to evaluated-glucose handling along the nephron. 1. A rapid removal of filtered glucose occured over the first three millimeters of the proximal tubule. 2. The intratubular glucose concentration remained constant at 0.25±0.20 mmol/l (SD) over the second half of the accessible proximal tubule. This value is similar to one predicted on the basis of kinetic data obtained previously under conditions of zero volume flux. 3. More than 98 per cent of the filtered glucose was reabsorbed by the proximal tubule. 4. No further net flux was detectable between the proximal segment and the end of the distal tubule accessible to micropuncture. 5. The collecting duct reduced glucose excretion to less than 0.1 per cent of the filtered load. The final rate of glucose excretion was independent of the rate of urine flow

Fluorometrisch-enzymatische Mikro- und Ultramikrobestimmung von Inulin und Glucose / Fluorometric-Enzymatic determination of inulin and glucose in the micro and ultramicro range

Enzymatic methods of inulin and glucose determination are adapted to sample sizes in the micro-and ultramicro range and modified for fluorometric measurements. Using a highly sensitive ultramicro method inulin and/or glucose could be measured exactly in concentrations of 5 mgm per cent in samples of 1 nl (1×10−9 l) corresponding to absolute amounts of 1×10−12 gm

Proximal tubular lactate transport in rat kidney: a micropuncture study

Proximal tubular lactate transport in rat kidney: A micropuncture study. Micropuncture studies of renal lactate behavior in the rat showed free filtration across the glomerular membrane. Under free-flow conditions, 95% of the filtered load was reabsorbed by the proximal tubule, thus generating a transtubular concentration gradient. In the absence of volume changes, an intratubular steady-state concentration of lactate was established irrespective of the presence or absence of lactate in the initial test solution, indicating a passive “leak” along the transtubular concentration gradient which increased with higher serum lactate levels. Although proximal tubular hydrogen ion secretion could explain this lactate gradient on the basis of nonionic diffusion, studies in chronic alkalotic rats showed that lactate was reabsorbed even in the absence of a hydrogen ion gradient. Inhibition of intracellular gluconeogenesis from lactate, by alkalosis and through administration of an inhibitor (MICA), abolished development of the transtubular concentration gradient in the proximal tubule. It is concluded that lactate reabsorption in the proximal tubule is caused by simple diffusion across the luminal membrane in response to a concentration gradient created by intracellular utilization of lactate for gluconeogenesis

ICP dry etching for InP based photonic bandgap devices

Periodic nanostructures in InP based epitaxial layers for photonic bandgap materials have to be drilled deep into the substrate for high performance devices. We investigated dry etching using an inductively coupled plasma reactive ion etcher (ICP-RIE) and chemically assisted ion beam etching (CAIBE) for holes in the 300 nm range. Optical measurements on defect waveguides are compared

Assessment of the intrasinusidal volume before and after maxillary sinus augmentation using mri – a pilot study of eight patients

Abstract Purpose The purpose of this study was to evaluate the suitability, accuracy, and reliability of a non-invasive 3-Tesla magnetic resonance imaging technique (3 T-MRI) for the visualization of maxillary sinus grafts in comparison to conventional, X-ray-based, established standard imaging techniques. Methods A total of eight patients with alveolar bone atrophy who required surgical sinus floor augmentation in the course of dental implantation were included in this pilot study. Alongside pre-operative cone-beam computed tomography (CBCT), 3 T-MRI was performed before and 6 months after sinus floor augmentation. Two investigators measured the maxillary sinus volume preoperatively and after bone augmentation. Results In all cases, MRI demonstrated accurately the volumes of the maxillary sinus grafts. Following surgery, the bony structures suitable for an implant placement increased at an average of 4.89 cm3, corresponding with the decrease of the intrasinusidal volumes. In general, interexaminer discrepancies were low and without statistical significance. Conclusion In this preliminary study, we could demonstrate the feasibility of MRI bone volume measurement as a radiation-free alternative with comparable accuracy to CT/CBCT before procedures like sinus floor augmentation. Nevertheless, costs and artifacts, also present in MRI, have to be taken into account. Larger studies will be necessary to justify the practicability of MRI bone volume evaluation