On the theory of cavities with point-like perturbations. Part I: General theory

The theoretical interpretation of measurements of "wavefunctions" and spectra in electromagnetic cavities excited by antennas is considered. Assuming that the characteristic wavelength of the field inside the cavity is much larger than the radius of the antenna, we describe antennas as "point-like perturbations". This approach strongly simplifies the problem reducing the whole information on the antenna to four effective constants. In the framework of this approach we overcame the divergency of series of the phenomenological scattering theory and justify assumptions lying at the heart of "wavefunction measurements". This selfconsistent approach allowed us to go beyond the one-pole approximation, in particular, to treat the experiments with degenerated states. The central idea of the approach is to introduce ``renormalized'' Green function, which contains the information on boundary reflections and has no singularity inside the cavity.Comment: 23 pages, 6 figure

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

Enzymaktivitäten im isolierten proximalen Tubulus der Kaninchenniere / Enzyme activities in the isolated proximal tubule of rabbit kidney

Activities of glutamate dehydrogenase (EC 1.4.1.2), succinate dehydrogenase (EC 1.3.99.1) and fumarase (EC 4.2.1.2) were determined in isolated segments of proximal tubules of the rabbit kidney. Activities per tubular length were the same at the beginning and the end of the pars convoluta. They decreased gradually along the pars recta towards the beginning of the thin loop of Henle. Thus, the capacity to produce energy via the Krebs cycle will be much lower in the pars recta than in the pars convoluta, a finding which parallels the different rates of sodium reabsorption along the isolated proximal tubule reported by Burg and Orloff

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

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

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

Das Verhalten der Pyridinnucleotide und einiger Metaboliten in der Nierenrinde der Ratte bei Normoxie und Anoxie

In der Nierenrinde von Rattenwurde der Gehalt an Pyridinnucleotiden bestimmt. Nach Entnahme des Gewebes durch Gefrierstop ohne Lageveränderung des Organs wurden oxidierte und reduzierte Pyridinnucleotide gleichzeitig extrahiert und durch enzymatisches Cycling gemessen. Der Quotient NADPH/NADP® lag bei 3,1, der Quotient NADH/NAD® bei 0,06. Das NAD-System befindet sich also in einem stärker oxidierten Zustand als man bisher angenommen hat. Der Quotient NADH/NAD® wird durch eine Anoxie von 30 sec Dauer auf 0,21, der Quotient NADPH/NADP® auf 6,6 erhöht. Das Verhältnis der Metaboliten Lactat/Pyruvat und 3-Hydroxy-butyrat/Acetoacetat bleibt innerhalb dieses Zeitraumes konstant. In den folgenden 30 sec ver-ändern sich die Redoxquotienten der Pyridinnucleotid-Systeme nicht signifikant, der Quotient Lactat/Pyruvat steigt dagegen auf das Doppelte des Ausgangswertes an. Die Ergebnisse zeigen, daß in den ersten 30 sec Anoxie das NAD-System in den Mitochondrien reduziert wird und erst in den folgenden 30 sec eine Reduktion im Cytoplasma auftritt. Diese zeitliche Diskrepanz macht auch für die Niere eine Redoxkompartimentierung der Pyridinnucleotid-Systeme wahrscheinlich

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

Triggering extreme events at the nanoscale in photonic seas

This work is supported by Kaust (Award No. CRG-1-2012-FRA-005), by NanoNextNL of the Dutch ministry EL&I and 130 partners and by the EU FET project ‘SPANGL4Q’.Hurricanes, tsunamis, rogue waves and tornadoes are rare natural phenomena that embed an exceptionally large amount of energy, which appears and quickly disappears in a probabilistic fashion. This makes them difficult to predict and hard to generate on demand. Here we demonstrate that we can trigger the onset of rare events akin to rogue waves controllably, and systematically use their generation to break the diffraction limit of light propagation. We illustrate this phenomenon in the case of a random field, where energy oscillates among incoherent degrees of freedom. Despite the low energy carried by each wave, we illustrate how to control a mechanism of spontaneous synchronization, which constructively builds up the spectral energy available in the whole bandwidth of the field into giant structures, whose statistics is predictable. The larger the frequency bandwidth of the random field, the larger the amplitude of rare events that are built up by this mechanism. Our system is composed of an integrated optical resonator, realized on a photonic crystal chip. Through near-field imaging experiments, we record confined rogue waves characterized by a spatial localization of 206 nm and with an ultrashort duration of 163 fs at a wavelength of 1.55 μm. Such localized energy patterns are formed in a deterministic dielectric structure that does not require nonlinear properties.PostprintPeer reviewe