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C Biedermann

Publications and source records attributed to C Biedermann.

At least 19 recordsLinked to original sources
PubMed2000

Measurement of the radiative cooling rates for high-ionization species of krypton using an electron beam ion trap

We describe a measurement of the radiative cooling rate for krypton made at the Berlin electron beam ion trap (EBIT). The EBIT was tuned to a charge-state distribution approaching the ionization balance of a plasma at a temperature of about 5 keV. To determine the cooling rate, we made use of EBIT's capabilities to sample a wide range of electron-beam energies and distinguish between different radiation channels. We have measured the x-ray emission from bremsstrahlung, radiative recombination, dielectronic recombination, and line radiation following electron-impact excitation. The dominant contribution to the cooling rate is made by the n=3-2, n=4-2, ellipsis x rays of the L-shell spectra of krypton, which produce more than 75% of the total radiation loss. A difference with theoretical calculations is noted for the measured total cooling rate. The predicted values are lower by a factor of 1.5-2, depending on the theoretical model. For our measurement of the cooling rate, we estimate an uncertainty interval of 22-30 %.

Journal Article↗
PubMed1995

Adjuvant treatment with a vitamin A analogue (etretinate) after transurethral resection of superficial bladder tumors. Final analysis of a prospective, randomized multicenter trial in Switzerland.

Vitamin A and its derivatives, the retinoids, have antiproliferative effects and may induce cellular differentiation. Etretinate, a synthetic retinoid, has a more favorable therapeutic index experimentally than all-trans-retinoic acid or 13-cis-retinoic acid. Ninety patients with superficial papillary bladder tumors stages Ta and T1 entered a prospective randomized double-blind multicenter trial in Switzerland. Seventy-nine of the patients were eligible and received either 25 mg of etretinate or a placebo orally each day. The early withdrawal of a significantly greater number of patients in the placebo group for treatment failure during the first year of the study resulted in a secondary positive selection in this group. High-risk patients were removed and low-risk patients remained. In those patients who had tumor recurrences after randomization, the time to first recurrence was similar in both groups with 13.5 and 13.6 months in the placebo and etretinate groups, respectively. However, the mean interval to subsequent tumor recurrence was significantly longer in the etretinate group. The mean interval between recurrences in these subgroups was 12.7 months in the placebo arm and 20.3 months in the etretinate arm (p = 0.006). Consequently, the number of transurethral resections per patient-year was also reduced significantly in the etretinate group (p < 0.001). In patients with more than one transurethral resection of papillary tumors before randomization, the annual transurethral resection rate in the two treatment groups dropped from 1.7 to 1.3 in the 30 patients in the placebo group (NS, p = 0.1) and from 2.1 to 0.95 in the 25 patients in the etretinate group (p < 0.001). The side effects of etretinate (cheilitis, dryness of mucous membranes and skin) were acceptable to most patients. The relationship of the 3 myocardial infarcts observed in the etretinate group to the retinoid is not clear. Despite their significant effect on the recurrence rate of superficial papillary bladder tumors, retinoids should only be used in well-controlled prospective trials until more is known about their dosage-toxicity profiles.

Adult↗
PubMed1994

Adjuvant cisplatin chemotherapy following cystectomy for bladder cancer: results of a prospective randomized trial.

Between April 1984 and May 1989, 77 eligible patients with invasive, nonmetastatic (stage M0) transitional cell carcinoma of the bladder were stratified after radical cystectomy and pelvic lymph node dissection on the basis of nodal status (stage pN0 versus pN1-2) and were randomly assigned to either observation or postoperative cisplatin chemotherapy (3 courses of 90 mg./m.2 cisplatin given for 3 consecutive days at monthly intervals). Patient eligibility included a creatinine clearance of greater than 60 ml. per minute. There were 40 eligible patients in the control group (median age 61 years) and 37 in the cisplatin group (median age 64 years). In regard to postoperative tumor stage and nodal status, there was no statistical difference between the 2 patient groups. In the cisplatin group 21 patients received the full dose, 9 required dose reduction and 7 refused treatment. Median followup was 5 years 9 months (range 3 to 8 years). Survival analysis showed no significant difference (log rank p = 0.65) between the 40 patients in the control group and the 37 in the cisplatin group. The survival rate at 5 years was 54% (95% confidence interval 39 to 69%) in the control group and 57% (95% confidence interval 40 to 74%) in the treatment group. Patients with cancer confined to the bladder wall (stage pT3a or less) had a 5-year overall survival rate of 70% and those with tumor growth in the perivesical fat or into the prostate (stages pT3b plus pT4a) had a 5-year overall survival rate of 40%. This difference in survival between the low stage subgroup (stages pT3a or less) and the high stage subgroup (pT3b plus pT4a) is highly significant (p = 0.0043). However, no difference between the controls and the cisplatin group was found within either the low or high stage subgroups. The reasons for failing to show a survival benefit from adjuvant high dose cisplatin monotherapy after radical cystectomy are discussed.

Carcinoma, Transitional Cell↗