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W Wegscheider

Publications and source records attributed to W Wegscheider.

33 records · Page 2Linked to original sources
PubMed2000

Ultrafast optical spectroscopy of large-momentum excitons in GaAs.

Highly energetic excitons with wave vectors much larger than that of an absorbed photon are excited in thin GaAs films. We observe propagation beats between three polariton modes up to 300 meV above the absorption edge employing femtosecond transmission spectroscopy. The dispersion relations of the coherent excitations are measured. Ultrafast exciton damping via scattering with nonequilibrium carriers and with phonons is investigated. The dynamics is found to deviate strongly from the relaxation of free carriers. Theoretical simulations are in quantitative agreement with the data.

Journal Article↗
PubMed2000

Retrospective analysis of Frialit-2 implants in the augmented sinus.

The aim of the present study was to investigate clinical and radiographic data of patients treated with implants in the posterior maxilla in combination with sinus augmentation. Study parameters included Periotest values, radiographic analysis, and survival/success rates up to 5 years. Clinical and radiographic criteria resulted in a success rate of 92.7% for sinus implants. Radiographically, the sinus implants showed a mean coronal bone loss of 0.5 mm at 6 months and 1.2 mm at 48 months. The results showed stable periimplant parameters for sinus implants during the observation period of 5 years. The success rates showed no significant differences regarding different implant-supported treatment options for the posterior maxillary region.

Adult↗
PubMed1999

A Semiconductor-Based Photonic Memory Cell.

Photonic signals were efficiently stored in a semiconductor-based memory cell. The incident photons were converted to electron-hole pairs that were locally stored in a quantum well that was laterally modulated by a field-effect tunable electrostatic superlattice. At large superlattice potential amplitudes, these pairs were stored for a time that was at least five orders of magnitude longer than their natural lifetime. At an arbitrarily chosen time, they were released in a short and intense flash of incoherent light, which was triggered by flattening the superlattice amplitude.

Journal Article↗
PubMed1999

Guided bone regeneration with barrier membranes--a clinical and radiographic follow-up study after 24 months.

The present follow-up study evaluated clinical and radiographic parameters of dental implants placed with simultaneous guided bone regeneration with expanded polytetrafluoroethylene (e-PTFE) membranes. All implants were functioning well 24 months after insertion. In all, 63 patients with a total of 91 e-PTFE-augmented implants were integrated in a regular maintenance protocol. Modified periodontal data of 85 implants in 59 patients were recorded at 24 months and indicated no difference to implants placed in sufficient pristine bone. The mean plaque score (mplI) was 0.29, 74% of the sites showed no plaque. The sulcular probing depth ranged from 1 to 7 mm with a mean of 2.6 mm (SD +/- 0.8). Of the sites 96.5% were < or = 4 mm deep, in 49% of them probing resulted in bleeding. Periotest values 6 and 24 months (mean: -3.4 and -3.4) after placement revealed stable peri-implant conditions and sustained osseointegration. The radiographic evaluation performed 6, 12 and 24 months post insertion yielded a mean bone loss of 0.93, 1.36 and 1.51 mm ranging from 0 to 4 mm. The short-term results of our clinical study demonstrated stable peri-implant conditions 2 years after membrane-protected osseous regeneration. The newly formed bone seemed to be able to withstand functional loading in a predictable manner after 18 months.

Adult↗
PubMed1997

Coupled quantum dots fabricated by cleaved edge overgrowth: from artificial atoms to molecules

Atomically precise quantum dots of mesoscopic size have been fabricated in the gallium arsenide-aluminum gallium arsenide material system by cleaved edge overgrowth, with a high degree of control over shape, composition, and position. The formation of bonding and antibonding states between two such "artificial atoms" was studied as a function of quantum dot separation by microscopic photoluminescence (PL) spectroscopy. The coupling strength within these "artificial molecules" is characterized by a systematic dependence of the separation of the bonding and antibonding levels, and of the PL linewidth, on the "interatomic" distance. This model system opens new insights into the physics of coupled quantum objects.

Journal Article↗
PubMed1989

The system of prosthetic treatment for CLAP patients.

The prosthetic treatment of CLAP patients is usually done in three phases: an interceptive treatment during two stages of orthodontics, the definitive prosthetic treatment and usually the secondary treatment. In the interceptive phase we use clasp-retained partials; the definitive treatment is achieved mostly by telescope-retained partials. There is seldom an indication for Maryland-bridges or for dental implants.

Cleft Lip↗
PubMed1985

[A modern information system for toxicologic analysis based on the (IV+V) system].

After a short description of the background and fundamentals, a program system for a microcomputer is described that permits the implementation of a laboratory-specific database and information system. Due to standardized program and data structures and compatibility with different hardware, as well as portability, similar laboratories have the potential of carrying out cooperative studies on a national and international basis.

Computers↗