Biomedical subjects
Publications and source records attributed to J Steinhauer.
A dressed basis is used to calculate the dynamics of three-wave mixing between Bogoliubov quasiparticles in a Bose condensate. Because of the observed oscillations between different momentum modes, an energy splitting, analogous to the optical Mollow triplet, appears in the Beliaev damping spectrum of the excitations from the oscillating modes.
We measure the response of an elongated Bose-Einstein condensate to a two-photon Bragg pulse. If the duration of the pulse is long, the total momentum transferred to the condensate exhibits a nontrivial behavior which reflects the structure of the underlying Bogoliubov spectrum. It is thus possible to perform a spectroscopic analysis in which axial phonons with a different number of radial nodes are resolved. The local density approximation is shown to fail in this regime, while the observed data agree well with the results of simulations based on the numerical solution of the Gross-Pitaevskii equation.
We report a measurement of the suppression of collisions of quasiparticles with ground state atoms within a Bose-Einstein condensate at low momentum. These collisions correspond to Beliaev damping of the excitations, in the previously unexplored regime of the continuous quasiparticle energy spectrum. We use a hydrodynamic simulation of the expansion dynamics, with the Beliaev damping cross section, in order to confirm the assumptions of our analysis.
We report a measurement of the excitation spectrum omega(k) and the static structure factor S(k) of a Bose-Einstein condensate. The excitation spectrum displays a linear phonon regime, as well as a parabolic single-particle regime. The linear regime provides an upper limit for the superfluid critical velocity, by the Landau criterion. The excitation spectrum agrees well with the Bogoliubov spectrum in the local density approximation, even close to the long-wavelength limit of the region of applicability. Feynman's relation between omega(k) and S(k) is verified, within an overall constant.
BACKGROUND: In-utero surgical repair of fetal myelomeningocele has been performed as a means to improve the postnatal condition of affected infants. CASE: A nulliparous woman underwent in-utero surgical repair of a fetal lumbosacral myelomeningocele at 24 weeks' gestation. Her postoperative convalescence was complicated by pulmonary edema, abdominal pain, chronic oligohydramnios, and preterm labor. The infant was delivered by cesarean at 33 weeks' gestation, but expired from respiratory distress caused by pulmonary hypoplasia at 9 hours of age. CONCLUSION: Until the benefits of in-utero repair of fetal myelomeningoceles are determined by well-controlled clinical trials, this technique remains investigational. Physicians and their patients who are considering this procedure must be fully aware of the potential risks that can occur.
BACKGROUND: Laser canalicular plastic surgery using the erbium-YAG laser is a new method for treating canaliculus stenosis. We compared results of this method with those of conventional surgical operations on canaliculi. PATIENTS AND METHODS: Between 1996 and 1998 a total of 44 cases of symptomatic canaliculus stenosis were treated by laser. An erbium-YAG laser with a maximum power of 100 mJ was used in conjunction with a sapphire fiber 3 cm long and 325 microns in diameter. Endoscopic diagnosis of the other parts of the lacrimal passage was carried out before and after laser treatment and after tubular intubation. After an average of 12 months the results were assessed via questionnaires and follow-up examinations. RESULTS: The success rate for reducing epiphora was 67%. Overall 86% of patients reported an improvement in canaliculus communis stenosis. CONCLUSIONS: Laser canalicular plasty as minimally invasive surgical treatment is an excellent surgical method for treating point-focal, noninflammatory canalicular stenosis.
BACKGROUND: After performing endoscopy of the lacrimal passage, the endoscopic system can be connected to an erbium-YAG laser if the indications are appropriate. MATERIALS AND METHODS: In a bi-center study we performed laser dacryoplasty in 53 cases out of 261 endoscopy procedures (18 stenoses of the canaliculi, 19 stenoses of the sac, 9 stenoses of the nasolacrimal duct, 9 restenoses following DCR). In 35 cases an examination was done and in all 53 cases the results were obtained by means of a questionnaire. RESULTS: Epiphora and irrigation were improved in more than 75%. CONCLUSION: Suitable indications are small stenoses in the sac or duct membranes following DCR. Laser dacryoplasty is a promising method, but more studies still need to be conducted to obtain long-term results. The technical system must also still be improved to make it easier to handle.
Shigella flexneri is an intracellular pathogen that is able to move within the cytoplasm of infected cells by the continual assembly of actin onto one pole of the bacterium. IcsA, an outer membrane protein, is localized to the old pole of the bacterium and is both necessary and sufficient for actin assembly. IcsA is slowly cleaved from the bacterial surface by the protease IcsP (SopA). Absence of IcsP leads to an alteration in the distribution of surface IcsA, such that the polar cap is maintained and some IcsA is distributed along the lateral walls of the bacillus. The mechanism of unipolar localization of IcsA and the role of IcsP in its unipolar localization are incompletely understood. Here, we demonstrate that cleavage of IcsA occurs exclusively in the outer membrane and that IcsP is localized to the outer membrane. In addition, we show that IcsA at the old pole is susceptible to cleavage by IcsP and that native IcsP is active at the pole. Taken together, these data indicate that IcsP cleaves IcsA over the entire bacterial surface. Finally, we show that, immediately after induction from a tightly regulated promoter, IcsA is expressed exclusively at the old pole in both the icsP- icsA- and the icsA- background. These data demonstrate that unipolar localization of IcsA results from its direct targeting to the pole, followed by its diffusion laterally in the outer membrane.
UNLABELLED: In the years from 1995 to 1997 in the eyeclinic of Darmstadt and the eyeclinic of the St. Josef Hospital Hagen 261 dacryoendoscopies were done in a bicentrical study. PATIENTS AND METHODS: A dacryoendoscopy was done in 261 patients with an average age of 46.6 years (143 women, 93 men and 25 children). In dependance of the assessment of the mucosa conditions intraoperatively in all 261 cases the planed operative strategy was checked and if needed changed. As following surgical interventions of the lacrimal system were seen 70 cases of dacryocystorhinostomia externa, 138 cases of intubation of the lacrimal drainage system and 53 cases of laserdacryoplastic. RESULTS: The dacryoendoscopy had succeeded as method for the assessment of the mucosa conditions [5, 6]. In a study of 261 dacryoendoscopies an examination of the mucosa was possible in every case. No complications were seen while dacryoendoscopy. With help of the dacryoendoscopy the planed operative strategy was determined. Therefore we had the possibility to choose a minimal invasive operation-procedure in 53 cases. CONCLUSIONS: The dacryoendoscopy is a new important diagnostic development in diagnosis of diseases of the lacrimal drainage system. With help of better developed endoscopy-systems a much better quality of the picture is attainable. The results of the dacryoendoscopy offer the possibility to check the preoperative indication and to optimate the surgical treatment. At last only with help of the dacryoendoscopy these findings could be ascertained in which case a laserdacryoplastic is senseful.
BACKGROUND: In a bicentrical study in the eye clinic of Darmstadt and the eye clinic of the St. Josef Hospital Hagen 261 dacryoendoscopies were performed until February 1997. MATERIALS AND METHODS: In 261 dacryoendoscopies (143 women, 93 men and 25 children, the average age was 46.6 years). In dependence of the assessment of the mucosa conditions intraoperatively in all 261 cases the planed operative strategy was checked and if needed changed. After surgical interventions of the lacrimal system 70 cases of dacryocystorhinostomia externa were seen 138 cases of intubation of the lacrimal drainage system and 53 cases of laserdacryoplastic. Intubation of the lacrimal system was always performed after laserdacryoplastic and after a patency was produced (average age 58.3 years). RESULTS: Suitable indications for a laserdacryoplastic are: circumscribed stenosis of the distal saccus, point-sized stenosis of the canaliculus, membranous restenosis after dacryocystorhinostomia externa. The method shows no important rate of intraoperative complications, only in one case there was intraoperatively a protrusion bulbi and a haematoma of the eyelid, which postoperatively eased fastly away. The postoperative convalescence is in comparence to conventional surgical interventions of the lacrimal drainage system enormously shortened. The follow-up after 3 months showed a subjective improvement of epiphora in more than 75% of the patients, the success of this intervention therefore could be compared with conventional surgical methods of the lacrimal drainage system. CONCLUSION: The dacryoendoscopy is a new important diagnostic development, which shows with help of better developed endoscopy-systems compared to previous systems a much better quality of the image and is therefore a valuable diagnostic help. Due to the check of the preoperative indication it is intraoperatively possible to confirm or, if needed, to change the indication after dacryoendoscopy. The laserdacryoplastic is an important new therapeutical development of the dacryoendoscopy and shows in suitable indications a comparable success-rate of conventional surgical interventions of the lacrimal drainage system. Therefore the possibility exists to carry out minimal invasive interventions of the lacrimal drainage.
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