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T Klinger

Publications and source records attributed to T Klinger.

10 recordsLinked to original sources
PubMed2005

Laser-induced fluorescence measurement of the ion-energy-distribution function in a collisionless reconnection experiment.

Observations in space and laboratory plasmas suggest magnetic reconnection as a mechanism for ion heating and formation of non-Maxwellian ion velocity distribution functions (IVDF). Laser-induced fluorescence measurements of the IVDF parallel to the X line of a periodically driven reconnection experiment are presented. A time-resolved analysis yields the evolution of the IVDF within a reconnection cycle. It is shown that reconnection causes a strong increase of the ion temperature, where the strongest increase is found at the maximum reconnection rate. Monte Carlo simulations demonstrate that ion heating is a consequence of the in-plane electric field that forms around the X line in response to reconnection.

Journal Article↗
PubMed2004

Repopulation of moderately well-differentiated and keratinizing GL human squamous cell carcinomas growing in nude mice.

PURPOSE: It has been suggested that, reminiscent of the regulated proliferative response of normal squamous epithelium, squamous cell carcinomas that have preserved characteristics of differentiation have a greater repopulation capacity during fractionated irradiation than undifferentiated tumors. The aim of the present study was to investigate repopulation in moderately well-differentiated and keratinizing GL human squamous cell carcinomas in nude mice. METHODS AND MATERIALS: GL human squamous cell carcinomas were transplanted s.c. into the right hind leg of NMRI nu/nu mice. Irradiation was performed with 5.4 Gy fractions under clamp hypoxia or with 2 Gy fractions under ambient conditions. Six, 12, or 18 fractions were given daily, every second day, or every third day. Graded top-up doses were applied under clamp hypoxia to determine the tumor control dose 50% (TCD(50)). A total of 20 TCD(50) assays were performed and analyzed using maximum-likelihood techniques. RESULTS: With an increasing number of daily 5.4 Gy fractions under clamp hypoxia, the top-up TCD(50) values decreased significantly from 50.9 Gy (95% CI: 47, 54) after single doses to 0 Gy after 18 fractions. For the same number of fractions, the top-up TCD(50) increased with increasing overall treatment time. The results are consistent with a constant repopulation rate with a clonogenic doubling time (T(clon)) of 12.7 days (8.6, 16.8). Under ambient blood flow, the top-up TCD(50)s for daily 2 Gy fractions decreased significantly, but were less pronounced than for 5.4 Gy fractions under clamp hypoxia. For a given number of fractions under ambient conditions, the top-up TCD(50)s did not increase significantly with overall treatment time, except for irradiation with 12 fractions in 36 days compared to 12 and 24 days. The T(clon) value from these data was 24.0 days (11.6, 36.4). CONCLUSION: Our data demonstrate a slow but significant rate of repopulation of clonogenic tumor cells during fractionated irradiation of GL human squamous cell carcinomas under clamp hypoxia without indication of a change of the repopulation rate during treatment. Less pronounced repopulation was observed for irradiation under ambient conditions, which might be explained by preferential survival of hypoxic and therefore nonproliferating cells. Taken together with our previous studies on poorly differentiated FaDu tumors (Petersen et al., IJROBP 2001;51:483-493), the results support important heterogeneity of kinetics and mechanisms of repopulation, in particular of the influence of the oxygenation status of surviving clonogenic cells on the repopulation rate during fractionated irradiation, in different experimental squamous cell carcinoma.

Algorithms↗
PubMed2002

Treatment with donepezil in Alzheimer patients with and without cerebrovascular disease.

Donepezil, a selective acetylcholinesterase inhibitor, is approved for the symptomatic treatment of mild to moderate Alzheimer's disease (AD). In a post-marketing surveillance (PMS) study in Germany, patients under routine treatment conditions were observed while treatment was switched from other antidementia drugs (i.e., nootropics) to donepezil. A total of 913 patients were enrolled (60.1% female, mean+/-S.D. age 73.4+/-8.6 years, mean Mini-Mental Status Examination [MMSE] 18.0+/-5.3), and were treated with donepezil (5 or 10 mg/day according to recommended dosing). 709/913 (77.1%) of patients had been pretreated with other antidementive drugs (piracetam, memantine, ginkgo, and others). In 29.6% of patients, investigators documented concomitant cerebrovascular disease (CVD+) according to their clinical judgment. Observation period was 3 months for the individual patient. Efficacy parameters were changes in MMSE, global clinical (investigators) judgment of efficacy, and a clinical judgment about the patients' quality of life (QoL). Adverse events were also analyzed. The objective of the present investigation was to compare-in a "real-life" setting-the differential efficacy and tolerability of donepezil in AD patients with and without concomitant cerebrovascular disease. After 3 months, patients had improved by a mean MMSE change from baseline of 2.2 points (CVD+: 2.4 pts, CVD-: 2.1 pts). QoL was judged "improved" in 70.0% of patients (CVD+: 72.5%, CVD-: 69.6%). Adverse events were reported in 85/913 (9.3%) of patients (CVD+: 11.2%, CVD-: 7.9%). Reported adverse events were substantially less than reported previously in controlled clinical trials. This suggests that donepezil therapy is effective and well tolerated in AD patients, both with and without concomitant cerebrovascular disease.

Adult↗
PubMed2002

New advanced operational regime on the W7-AS stellarator.

A promising new plasma operational regime on the Wendelstein stellarator W7-AS has been discovered. It is extant above a threshold density and characterized by flat density profiles, high energy and low impurity confinement times, and edge-localized radiation. Impurity accumulation is avoided. Quasistationary discharges with line-averaged densities n(e) to 4 x 10(20) m(-3), radiation levels to 90%, and partial plasma detachment at the divertor target plates can be simultaneously realized. Energy confinement is up to twice that of a standard scaling. At B(t) = 0.9 T, an average beta value of 3.1% is achieved. The high n(e) values allow demonstration of electron Bernstein wave heating using linear mode conversion.

Journal Article↗
PubMed2001

Mode selective control of drift wave turbulence.

Experiments on spatiotemporal open-loop synchronization of drift wave turbulence in a magnetized cylindrical plasma are reported. The synchronization effect is modeled by a rotating current profile with prescribed mode structure. Numerical simulations of an extended Hasegawa-Wakatani model show good agreement with experimental results.

Journal Article↗
PubMed2001

Synchronization of drift waves.

Based on a thorough experimental study of the equilibrium plasma state and the description of coherent drift modes in the framework of a linear, nonlocal model, the response of drift modes to different external driver signal is reported. Purely temporal perturbations as well as corotating and counter-rotating electric fields of various mode numbers are applied to the system. Drift mode synchronization and periodic pulling, typical for driven nonlinear oscillator systems, are investigated in detail. The full spatio-temporal behavior of periodic pulling is observed with multiprobe arrays.

Journal Article↗