Thickness uniformity measurements and damage threshold tests of large-area GaAs/AlGaAs crystalline coatings for precision interferometry.

Precision interferometry is the leading method for extremely sensitive measurements in gravitational wave astronomy. Thermal noise of dielectric coatings poses a limitation to the sensitivity of these interferometers. To decrease coating thermal noise, new crystalline GaAs/AlGaAs multilayer mirrors have been developed. To date, the surface figure and thickness uniformity of these alternative low-loss coatings has not been investigated. Surface figure errors, for example, cause small angle scattering and thereby limit the sensitivity of an interferometer. Here we measure the surface figure of highly reflective, substrate-transferred, crystalline GaAs/AlGaAs coatings with a custom scanning reflectance system. We exploit the fact that the reflectivity varies with the thickness of the coating. To increase penetration into the coating, we used a 1550 nm laser on a highly reflective coating designed for a center wavelength of 1064 nm. The RMS thickness variation of a two inch optic was measured to be 0.41 ± 0.05 nm. This result is within 10% of the thickness uniformity, of 0.37 nm RMS, achieved with ion-beam sputtered coatings for the aLIGO detector. We additionally measured a lower limit of the laser induced damage threshold of 64 MW/cm 2 for GaAs/AlGaAs coatings at a wavelength of 1064 nm.

Huddle test measurement of a near Johnson noise limited geophone.

In this paper, the sensor noise of two geophone configurations (L-22D and L-4C geophones from Sercel with custom built amplifiers) was measured by performing two huddle tests. It is shown that the accuracy of the results can be significantly improved by performing the huddle test in a seismically quiet environment and by using a large number of reference sensors to remove the seismic foreground signal from the data. Using these two techniques, the measured sensor noise of the two geophone configurations matched the calculated predictions remarkably well in the bandwidth of interest (0.01 Hz-100 Hz). Low noise operational amplifiers OPA188 were utilized to amplify the L-4C geophone to give a sensor that was characterized to be near Johnson noise limited in the bandwidth of interest with a noise value of 10-11 m/Hz at 1 Hz.

[Oral and pharyngeal dysphagia]. / Oropharyngeale Dysphagien.

A severe impairment of nutrition frequently occurs with morphological alterations in the oral cavity and the pharynx as well as with neurogenic disorders of the swallowing articulation. Complications like frequent aspirations are life-threatening. If the natural protection reflex for the respiratory tract, the cough reflex, does not work because of a reduced tracheal sensitivity, swallowing disorders often remain unrecognized. The ability of swallowing must be examined particularly with stroke-patients and weakened old patients. With radiological and endoscopic evaluations, oropharyngeal dysphagias can be assessed in detail. A wide spectrum of surgical measures and exercise treatment can clearly improve the life quality of the patients even if the aim, to make a complete and safe oral nutrition possible again, is not reached in every case.

[When there is pharyngeal obstruction]. / Wenn's die Kehle zuschnürt.

Any narrowing of the throat not only impairs the patient's voice, but also his swallowing abilities and even more dramatically his airways. Changes of the patient's voice due to tumors, trauma or functional disturbances do not immediately endanger the patient's live but render his vocal communication abilities more difficult or even impossible. Swallowing disturbances--often not diagnosed at an early stage--may lead to a life threatening pneumonia due to repeated aspirations. Laryngeal airway obstruction can be caused by functional disorders of the laryngopharyngeal musculature, by benign or malignant tumors, or may present as a consequence of surgery and/or irradiation. A variety of treatment options are available to restore the patient's voice, rehabilitate his swallowing and maintain the airway patency. Often times minor surgical interventions (e.g. phonosurgery) help to improve the patient's quality of life, even in a palliative situation.

[Deglutition disorders--simple to diagnose and difficult to treat?]. / Schluckstörungen--einfach zu diagnostizieren und schwierig zu behandeln?

The swallowing sequence can be disturbed by different structural and neurological disorders especially in its oral and pharyngeal phases. Beside the suffering from the loss of a basic physical function dysphagia causes life-threatening complications as malnutrition, pneumonia or the blockage of the airways. In general radiographic and endoscopic evaluations provide sufficient information about the specific pathology of a case of dysphagia so that an individual treatment plan with surgery, behavioral therapy and prosthetic aids can be formulated. The aim of treatment is to regain a save and as complete as possible an oral nutrition. Dysphagia is often not detected when patients have impaired cognitive abilities or communication disorders.

[Influence of a high fat diet on serum uric acid levels in rats]. / Zum Einfluss einer Hochfettdiät auf den Serumharnsäurespiegel bei Ratten.

In present paper the behaviour of uric acid is investigated in serum from rats fed with a 50% fat containing diet in comparison with 3% fat diet as control group. After feeding high-fat diet 5 resp. 52 weeks the level of uric acid is significantly elevated. In the same diet group heavier animals showed higher uric acid levels than lighter animals. In these experiments the age of animals is without influence of the uric acid level in serum.

Audiologic manifestations in fetal alcohol syndrome assessed by brainstem auditory-evoked potentials.

In 29 of 36 children with fetal alcohol syndrome brainstem auditory-evoked potentials were performed and the auditory threshold was determined. The hearing of patients with a pathologic finding was then subject to a thorough ear-nose-throat examination. Additionally the IQ was determined and an audiolinguistic examination was carried out. Seventy-five % of the children showed a peripheral hearing disorder on the basis of conductive hearing loss. In two children (7%) sensorineural hearing loss was located to the inner ear. A dysfunction of the auditory pathway was found in 6 patients (21%). The results of an isolated ear-nose-throat examination in 7 further children supported these findings. The mean performances in the linguistic tests were far below average and displayed a strong relation to the IQ. This study shows that a peripheral hearing disorder, especially an obstruction of the auditory tube as well as dysfunctions of the inner ear and the central hearing pathway, are different manifestations of the fetal alcohol syndrome. An etiologic connection between craniofacial abnormalities in these children and an increased susceptibility to peripheral hearing disorders could not be demonstrated. To avoid a retardation of the linguistic development in addition to the intellectual deficits a strong emphasis must be put on an early and comprehensive auditory examination of children with FAS.

Experimental and clinical evaluation of laryngeal chondrosynthesis.

The aim of this study was to investigate and develop techniques for stabilization and reconstruction of laryngeal defects with a method similar to osteosynthesis. In an anatomical study, 400 extrusion forces of sutures and various screws (Howmedica) were measured in the thyroid cartilage of fresh cadavers. A new screw was then especially designed for cartilage and a new technique was developed for stabilizing cartilage, using a screw-nut made out of bone. To date, 30 patients have undergone chondrosynthetic reconstruction of the larynx. Measurements of extrusion forces were found to depend on the degree of calcification present in the area of the laryngeal skeleton examined and the type of fixation device used. Good clinical results were achieved in all 30 patients studied and depended on stabilization of the two sides of the thyroid cartilage after thyrotomies, bridging of laryngeal defects and splinting of laryngeal fractures. Besides the increased extrusion forces the advantages of chondrosynthesis lay within the possibilities of axial stabilization and exact bridging of defects with or without implants.