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W Caliebe

Publications and source records attributed to W Caliebe.

At least 19 recordsLinked to original sources
PubMed2006

Smectic-Calpha*-smectic-C* phase transition and critical point in binary mixtures.

We have investigated the smectic-Calpha*-smectic-C* (SmCalpha*-SmC*) transition in a series of binary mixtures with resonant x-ray diffraction, differential optical reflectivity, and heat capacity measurements. Results show that the phases are separated by a first-order transition that ends at a critical point. We report the observation of such a critical point. We have proposed the appropriate order parameter and obtained values of two critical exponents associated with this transition. The values of the critical exponents suggest that long-range interactions are present in the SmCalpha*-SmC* critical region.

Journal Article↗
PubMed2006

Optical and resonant X-ray diffraction studies confirm a SmC*FI2-SmC* liquid crystal phase sequence reversal.

Employing both null transmission ellipsometry and resonant x-ray diffraction, we confirmed the SmC*FI2-SmC* phase sequence reversal in one liquid crystal compound and specially prepared binary mixtures. This phase sequence reversal was predicted by two recent theoretical advances. Moreover, the temperature range for the SmC*FI2 phase increases significantly in the mixture suggesting that such a phase sequence may exist in other compounds.

Journal Article↗
PubMed2004

Experimental investigations of one liquid-crystal compound exhibiting the no-layer-shrinkage effect near the Sm-A-Sm- C(*) transition.

Three experimental probes have been employed to investigate the nature of the smectic- A -smectic- C ( Sm-A-Sm- C(*) ) phase transition of one liquid-crystal compound showing almost no layer-shrinkage effect through the transition. Results from both x-ray diffraction and optical studies indicate that the compound exhibits a crossover behavior of different molecular packing arrangements within the bulk Sm-A phase window. The calorimetry results show a significant critical anomaly near the Sm-A-Sm- C(*) transition, although it was found to be weakly first order.

Journal Article↗
PubMed2002

Interlayer structures of the chiral smectic liquid crystal phases revealed by resonant X-ray scattering.

The structures of the liquid crystalline chiral subphases exhibited by several materials containing either a selenium or sulphur atom have been investigated using a resonant x-ray scattering technique. This technique provides a unique structural probe for the ferroelectric, ferrielectric, antiferroelectric, and SmC(*)(alpha) phases. An analysis of the scattering features allows the structural models of the different subphases to be distinguished, in addition to providing a measurement of the helical pitch. This paper reports resonant scattering features in the antiferroelectric hexatic phase, the three- and four-layer intermediate phases, the antiferroelectric and ferroelectric phases and the SmC(*)(alpha) phase. The helicoidal pitch has been measured from the scattering peaks in the four-layer intermediate phase as well as in the antiferroelectric and ferroelectric phases. In the SmC(*)(alpha) phase, an investigation into the helical structure has revealed a pitch ranging from 5 to 54 layers in different materials. Further, a strong resonant scattering signal has been observed in mixtures of a selenium containing material with as much as 90% nonresonant material.

Journal Article↗
PubMed2001

Orientational ordering in the chiral smectic-C*FI2 liquid crystal phase determined by resonant polarized x-ray diffraction.

High-resolution resonant polarized x-ray diffraction experiments near the sulfur K edge have been performed on free-standing liquid crystal films exhibiting the chiral smectic-C*FI2 phase. It is widely accepted that this phase has a four-layer repeat unit, but the internal structure of the repeat unit remains controversial. We report different resolved features of the resonant x-ray diffraction peaks associated with the smectic-C*FI2 phase that unambiguously demonstrate that the four-layer repeat unit is locally biaxial about the layer normal and that the measured angle, describing the biaxiality, is in good agreement with optical measurements.

Journal Article↗
PubMed1983

[2d interim evaluation of a chemotherapy study on patients with squamous cell carcinomas of the head-neck area. A comparison of 2 therapy regimens: cis-diamminedichloroplatinum (II) and bleomycin versus methotrexate and vindesine].

52 patients with epidermoid cancer of the head and neck region were either treated with cis-DDP and bleomycin (arm A) or with methotrexate and vindesine (arm B). In case of resistance patients were further treated with the alternative regimen (A leads to B or B leads to A). Treatment results are superior in arm A. Complete and partial remission were in A: 54%, in B: 31%, after crossover 46% and 0%, respectively. Status of pretreatment (operation and/or radiotherapy) is of minor importance for arm A than for the "soft" treatment of arm B. Preliminary analysis of survival and remission duration shows no significant difference in regard to A or B and status of pretreatment. However, those patients resistant to B and further treated with A have an increase of median survival from 3 to 9 months (p = 0.02). With primary chemotherapy inoperable tumors can be made operable with curative intention.

Adult↗
PubMed1982

[Treatment results of Schmincke tumors].

This is a report on the results of a continuous series of 78 previously untreated patients with a lymphoepithelioma (Schmincke-Regaud), who got their diagnosis and therapy in the Medical Center of the University of Kiel between 1951 and 1980. 90% of the patients were treated by radiotherapy alone, which included the primary in the oropharynx (n = 29) or the nasopharynx (n = 48) as well as the regional lymph nodes regardless of whether they were affected (71%) or not; residual lymph nodes of 8 cases were removed afterwards. Thereby a clinically full regression of the tumor disease was achieved in 85%. This group revealed a constant actuarial survival of 39% 7 years later. All therapy failures however, died within two years. The probability to remain free of disease after a primarily successful treatment amount to 86% for the oropharynx tumors (n = 24) and to only 29% for the nasopharynx lesions (n = 31). The analysis of the relapses especially with regard to the nasopharynx tumors showed that in most cases the disease was already very extended at the beginning of the treatment (stage IV according to the UICC-classification). The actuarial survival of this numerous group fell down to a constant rate of 16%, whereas stages I to III finally survive in 59%. The corresponding survival values of the oropharynx tumors were 25% in stage IV and 41% in stages I to III including a lot of age-related deaths. Drawing conclusions out of our retrospective study we recommended to add an appropriate chemotherapy for lymphoepitheliomas of the nasopharynx in stage IV.

Adolescent↗
PubMed1981

[Results of radiation therapy in malignant hypopharyngeal tumors--a retrospective evaluation of 50 cases (author's transl)].

Fifty cases with malignant tumors of the hypopharynx having been irradiated with cobalt-60 at the Radiological Clinic of the Kiel University between 1965 and 1979 are reported. The cumulative 10-year survival rate amounted to 16%. Age and sex, the histology and mode of growth as well as the stage (mostly III or IV) and the primary site of the tumor had no prognostic significance, whereas the tumor response to treatment proved decisive to the prognosis: of the cases clinically revealing complete regression of the tumor, 32% could finally be regarded as cured. Using sole radiation therapy it was possible to obtain total regression of the tumor in 72% with doses between 1500 and 1650 ret, and in 84% with doses between 1651 and 1800 ret. All the patients with clinically incomplete tumor regression deceased within a year.

Adult↗
PubMed1979

[Five-year-cure rate of laryngeal cancer in the Kiel clinic. Report of 216 cases from 1960 to 1967 (then director: Prof. Dr. E. Müller) with special reference to indications for surgical or orthovolt x-ray therapy].

Report about the five-years-cure of all cases of carcinoma of the larynx, the Kiel-University-ORL-Department had to engage in with diagnostical and therapeutical treatment within a period of 7 years. Out of the total of 216 patients the absolute survival rate was 144 (= 66,7%) after five years. Cure rate was the best with carcinoma of the true vocal cord (72,8%), less satisfactory with carcinoma of the supraglottic region (61,1%), only 5/14 with carcinoma of the marginal region, and only 2/8 with advanced and widespread tumours of undefinable origin. After comparing the distribution of the total of our patients with those of other authors, our system of diagnosis, staging, and classification is described in detail being the basis for a skilful choice of primary surgical therapy on the one hand or primary irradiation on the other hand (in our cases orthovolt-X-ray). Both the primary treatment and treatment of recurrence-cases are described in detail, differing from descriptions and claims of other authors for "modern" therapy in many items. Nevertheless we have comparatively very good results, they demand a critical standpoint towards new therapeutical methods. In our opinion close collaboration between laryngologists and radiotherapists concerning classification of tumours, staging and choice of therapy, treatment and post-clinical observation is the fundamental condition for obtaining good and better results in treatment of laryngeal carcinoma.

Female↗