Mobile Augeninnendruckmessung: Von der Palpation bis zu ersten klinischen Erfahrungen mit dem handgehaltenen dynamischen Konturtonometer

Zusammenfassung: Die Goldmann-Applanationstonometrie gilt immer noch als der Goldstandard der Augeninnendruckmessung und spielt bei der Früherkennung des Glaukoms eine zentrale Rolle. Die Applanationstonometrie wird normalerweise am sitzenden Patienten an der Spaltlampe durchgeführt. Manchmal ist es jedoch notwendig, den Augeninnendruck (IOD) spaltlampenunabhängig messen zu können. Mit den handgehaltenen Geräten wird die Druckmessung ins Krankenzimmer, in den Operationssaal sowie zu Patienten, die nicht in sitzender Position an der Spaltlampe untersuchen werden können, gebracht. Das dynamische Konturtonometer (DCT) stellt eine neue Methode der direkten intraokularen Druckmessung dar. Es arbeitet nach dem Prinzip der piezoelektronischen Konturanpasstonometrie und soll weniger von den biomechanischen Eigenschaften der Hornhaut abhängig sein. Neben dem IOD kann auch die okulare Pulsamplitude erfasst werden. Bisher fanden die DCT-Messungen spaltlampenadaptiert statt. Wir präsentieren einen portablen Prototyp des Geräts. Im Vergleich mit dem Perkins-Tonometer und dem TONO-PENXL zeigt das handgehaltene DCT eine geringere Intra- und Interuntersuchervariabilität. Außerdem bietet das Gerät die Möglichkeit, die okulare Pulsamplitude (OPA) in liegender Position zu erfasse

Processing of temporal duration information in working memory after frontodorsal tumour excisions

This study aimed to test the hypothesis that impairments of temporal duration processing after frontal lobe lesions reflect deficits in executive monitoring functions rather than a domain-specific deficit in the maintenance of duration information in working memory. Patients with frontodorsal lesions, clinical controls with post-central lesions, and healthy controls performed recognition and classification tasks, which should allow for testing maintenance and monitoring functions, respectively. Results showed mild non-selective impairments of the frontal patients on both temporal and spatial recognition tasks, but a marked selective degradation on temporal classification while performance on spatial classification was unimpaired. This suggests that maintenance of duration information in working memory after frontal lesions is basically preserved but that, depending on executive task characteristics, there is a specific deficit in the strategic organization of this type of information

Hypoglycemia in response to glucose and glucagon in insulinoma patients with a negative prolonged fast: Functional and morphological properties

A negative 72-h fast is usually considered to preclude the diagnosis of insulinoma. The aim of this study was to describe the functional and morphological properties of two exceptional patients with an insulinoma who had exhibited pre-operatively a negative 72-h fast. Despite the ability of tumor cells to turn off insulin secretion in response to low plasma glucose during 72 h of fasting, hyperinsulinemic hypoglycemia occurred in both patients in response to stimulation by classical secretagogues. Pre-operatively, both patients underwent oral and iv glucose challenge tests and iv glucagon stimulation test. Insulin secretion was rapidly stimulated by these secretagogues to an exaggerated extent and thereby caused hypoglycemia due to an insulin mass effect. In contrast to the common functional features during suppression and stimulation tests, the tumors differed widely with regard to insulin and proinsulin response to calcium during ASVS tests and morphological properties. In patient 1, the immunohistochemical proinsulin distribution pattern resembled that of normal γ-cells, i.e. the staining was restricted to the perinuclear area; insulin and proinsulin were not stimulated by calcium during the ASVS test. In patient 2, the proinsulin staining pattern was abnormal, i.e. proinsulin was also found in the periphery of tumor cells; insulin and proinsulin were stimulated by calcium. We conclude that normal or exaggerated rather than defective glucose sensing may explain hypoglycemia in these exceptional insulinoma patients. Different functional characteristics of these tumors can be correlated with distinct morphological propertie

First-principles study of spontaneous polarization in multiferroic BiFeO3_3

The ground-state structural and electronic properties of ferroelectric BiFeO$_3$ are calculated using density functional theory within the local spin-density approximation and the LSDA+U method. The crystal structure is computed to be rhombohedral with space group $R3c$, and the electronic structure is found to be insulating and antiferromagnetic, both in excellent agreement with available experiments. A large ferroelectric polarization of 90-100 $\mu$C/cm$^2$ is predicted, consistent with the large atomic displacements in the ferroelectric phase and with recent experimental reports, but differing by an order of magnitude from early experiments. One possible explanation is that the latter may have suffered from large leakage currents. However both past and contemporary measurements are shown to be consistent with the modern theory of polarization, suggesting that the range of reported polarizations may instead correspond to distinct switching paths in structural space. Modern measurements on well-characterized bulk samples are required to confirm this interpretation.Comment: (9 pages, 5 figures, 5 tables

Self-duality in quantum impurity problems

We establish the existence of an exact non-perturbative self-duality in a variety of quantum impurity problems, including the Luttinger liquid or quantum wire with impurity. The former is realized in the fractional quantum Hall effect, where the duality interchanges electrons with Laughlin quasiparticles. We discuss the mathematical structure underlying this property, which bears an intriguing resemblance with the work of Seiberg and Witten on supersymmetric non-abelian gauge theory.Comment: 4 page

The influence of the Hall force on the vortex dynamics in type II superconductors

The effect of the Hall force on the pinning of vortices in type II superconductors is considered. A field theoretic formulation of the pinning problem allows a non-perturbative treatment of the influence of quenched disorder. A self-consistent theory is constructed using the diagrammatic functional method for the effective action, and an expression for the pinning force for independent vortices as well as vortex lattices is obtained. We find that the pinning force for a single vortex is suppressed by the Hall force at low temperatures while it is increased at high temperatures. The effect of the Hall force is more pronounced on a single vortex than on a vortex lattice. The results of the self-consistent theory are shown to be in good agreement with numerical simulations.Comment: 9 pages, 4 figures, published in Physical Review

Compact Frontend-Electronics and Bidirectional 3.3 Gbps Optical Datalink for Fast Proportional Chamber Readout

The 9600 channels of the multi-wire proportional chamber of the H1 experiment at HERA have to be read out within 96 ns and made available to the trigger system. The tight spatial conditions at the rear end flange require a compact bidirectional readout electronics with minimal power consumption and dead material. A solution using 40 identical optical link modules, each transferring the trigger information with a physical rate of 4 x 832 Mbps via optical fibers, has been developed and commisioned. The analog pulses from the chamber can be monitored and the synchronization to the global HERA clock signal is ensured.Comment: 13 pages, 10 figure

Mid-infrared interferometry with K band fringe-tracking I. The VLTI MIDI+FSU experiment

Context: A turbulent atmosphere causes atmospheric piston variations leading to rapid changes in the optical path difference of an interferometer, which causes correlated flux losses. This leads to decreased sensitivity and accuracy in the correlated flux measurement. Aims: To stabilize the N band interferometric signal in MIDI (MID-infrared Interferometric instrument), we use an external fringe tracker working in K band, the so-called FSU-A (fringe sensor unit) of the PRIMA (Phase-Referenced Imaging and Micro-arcsecond Astrometry) facility at VLTI. We present measurements obtained using the newly commissioned and publicly offered MIDI+FSU-A mode. A first characterization of the fringe-tracking performance and resulting gains in the N band are presented. In addition, we demonstrate the possibility of using the FSU-A to measure visibilities in the K band. Methods: We analyzed FSU-A fringe track data of 43 individual observations covering different baselines and object K band magnitudes with respect to the fringe-tracking performance. The N band group delay and phase delay values could be predicted by computing the relative change in the differential water vapor column density from FSU-A data. Visibility measurements in the K band were carried out using a scanning mode of the FSU-A. Results: Using the FSU-A K band group delay and phase delay measurements, we were able to predict the corresponding N band values with high accuracy with residuals of less than 1 micrometer. This allows the coherent integration of the MIDI fringes of faint or resolved N band targets, respectively. With that method we could decrease the detection limit of correlated fluxes of MIDI down to 0.5 Jy (vs. 5 Jy without FSU-A) and 0.05 Jy (vs. 0.2 Jy without FSU-A) using the ATs and UTs, respectively. The K band visibilities could be measured with a precision down to ~2%.Comment: 11 pages, 13 figures, Accepted for publication in A&

Acute effects of LSD on amygdala activity during processing of fearful stimuli in healthy subjects

Lysergic acid diethylamide (LSD) induces profound changes in various mental domains, including perception, self-awareness and emotions. We used functional magnetic resonance imaging (fMRI) to investigate the acute effects of LSD on the neural substrate of emotional processing in humans. Using a double-blind, randomised, cross-over study design, placebo or 100 μg LSD were orally administered to 20 healthy subjects before the fMRI scan, taking into account the subjective and pharmacological peak effects of LSD. The plasma levels of LSD were determined immediately before and after the scan. The study (including the a priori-defined study end point) was registered at ClinicalTrials.gov before study start (NCT02308969). The administration of LSD reduced reactivity of the left amygdala and the right medial prefrontal cortex relative to placebo during the presentation of fearful faces (P<0.05, family-wise error). Notably, there was a significant negative correlation between LSD-induced amygdala response to fearful stimuli and the LSD-induced subjective drug effects (P<0.05). These data suggest that acute administration of LSD modulates the engagement of brain regions that mediate emotional processing