Marion Bauer

Structural transitions in amorphous H2O and D2O: the effect of temperature

We have recently observed amorphous-amorphous transitions incurred upon decompressing very high density amorphous ice (VHDA) at 140 K from 1.1 to <0.02 GPa in a piston-cylinder setup by monitoring the piston displacement as a function of pressure and by taking powder x-ray diffractograms of quench-recovered samples (Winkel et al 2008 J. Chem. Phys. 128 044510). Here we study the effect of changing the temperature from 77 to 160 K during decompression from 1.1 to <0.02 GPa, and the effect of substituting D 2 O for H 2 O at 140 and 143 K. At 77 K all structural transitions are arrested and six-coordinated VHDA is quench recovered. At 125-136 K the continuous transition to five-coordinated expanded high density amorphous ice (eHDA) takes place. At 139-140 K, both the continuous transition to eHDA and the quasi-discontinuous transition to four-coordinated LDA are observed, i.e. VHDA→ eHDA→ LDA. At 142-144 K, crystallization to mixtures of cubic ice Ic and ice IX is observed prior to the quasi-discontinuous transition, i.e. VHDA → eHDA→ ice Ic/ice IX. At 160 K ice Ic is recovered, which most likely transforms from a high-pressure ice (HPI) such as ice V, i.e. VHDA →HPI → ice Ic. Exchanging D 2 O for H 2 0 at 140 K does not significantly affect the amorphous-amorphous transitions: both the decompression curves and the powder x-ray diffractograms are unaffected within the experimental resolution. However, at 143 K D 2 O-VHDA can be decompressed according to the sequence VHDA → eHDA→ LDA, i.e. crystallization can be suppressed at ∼3 K higher temperatures.

Raman Spectroscopic Study of the Phase Transition of Amorphous to Crystalline β‐Carbonic Acid

Whats the matter? The laboratory Raman spectra for carbonic acid (H(2)CO(3)), both for the beta-polymorph and its amorphous state, are required to detect carbonic acid on the surface of the pole caps of Mars in 2009, when the Mars Microbeam Raman Spectrometer lands on the planet. The picture shows a martian crater with ice of unknown composition, possibly containing carbonic acid (image adapted from DLR, with permission from ESA, DLR, and FU Berlin--G. Neukum).

Cryoflotation: Densities of Amorphous and Crystalline Ices

We present an experimental method aimed at measuring mass densities of solids at ambient pressure. The principle of the method is flotation in a mixture of liquid nitrogen and liquid argon, where the mixing ratio is varied until the solid hovers in the liquid mixture. The temperature of such mixtures is in the range of 77-87 K, and therefore, the main advantage of the method is the possibility of determining densities of solid samples, which are instable above 90 K. The accessible density range (~0.81-1.40 g cm(-3)) is perfectly suitable for the study of crystalline ice polymorphs and amorphous ices. As a benchmark, we here determine densities of crystalline polymorphs (ices I(h), I(c), II, IV, V, VI, IX, and XII) by flotation and compare them with crystallographic densities. The reproducibility of the method is about ±0.005 g cm(-3), and in general, the agreement with crystallographic densities is very good. Furthermore, we show measurements on a range of amorphous ice samples and correlate the density with the d spacing of the first broad halo peak in diffraction experiments. Finally, we discuss the influence of microstructure, in particular voids, on the density for the case of hyperquenched glassy water and cubic ice samples prepared by deposition of micrometer-sized liquid droplets.

Brachytherapy of tumour recurrences in the region of the pharynx and oral cavity by means of a remote-controlled afterloading technique

In the period 1981-86, 22 patients with local inoperable tumour recurrences in the mouth and pharynx area had endocavitary contact therapy using a remote-controlled afterloading system at the Radiotherapy Centre of the University of Heidelberg. All patients had had previous surgery and external-beam radiation; some had also received chemotherapy. The technique is described and preliminary results are discussed.

Hexagonal ice transforms at high pressures and compression rates directly into “doubly metastable” ice phases

We report compression and decompression experiments of hexagonal ice in a piston cylinder setup in the temperature range of 170-220 K up to pressures of 1.6 GPa. The main focus is on establishing the effect that an increase in compression rate up to 4000 MPa/min has on the phase changes incurred at high pressures. While at low compression rates, a phase change to stable ice II takes place (in agreement with earlier comprehensive studies), we find that at higher compression rates, increasing fractions and even pure ice III forms from hexagonal ice. We show that the critical compression rate, above which mainly the metastable ice III polymorph is produced, decreases by a factor of 30 when decreasing the temperature from 220 to 170 K. At the highest rate capable with our equipment, we even find formation of an ice V fraction in the mixture, which is metastable with respect to ice II and also metastable with respect to ice III. This indicates that at increasing compression rates, progressively more metastable phases of ice grow from hexagonal ice. Since ices II, III, and V differ very much in, e.g., strength and rheological properties, we have prepared solids of very different mechanical properties just by variation in compression rate. In addition, these metastable phases have stability regions in the phase diagrams only at much higher pressures and temperatures. Therefore, we anticipate that the method of isothermal compression at low temperatures and high compression rates is a tool for the academic and industrial polymorph search with great potential.

Complication Rates of Radiotherapy with Adjuvant Chemotherapy for Conservative Treatment

Over the last 30 years, it has not been possible to bring about any decisive improvements in the prognosis of carcinoma of the breast with radical treatment methods, since by the time most women with breast cancer undergo primary treatment they are already suffering from systemic tumor disease that can no longer be controlled by locoregional therapy, Fisher et al. [12] and Veronesi et al. [35] have shown that the results of less radical, breast-conserving treatments are no worse than those of the conventional radical treatment as far as DFS and OAS are concerned; Fisher bases this conclusion on a follow-up period of 5 years, while Veronesi had followed his patients for 10 years. In both cases, this proved true even for patients in whom histological examination had revealed positive lymph nodes. Nonetheless, we feel that adjuvant chemotherapy is essential when positive lymph nodes are present, at least for premenopausal women [27]. This raises the question of the tolerance of a combination of radiotherapy and adjuvant chemotherapy, especially as experimental studies conducted by Phillips et al. [28], Redpath [31], and Collins and Steel [10] have indicated that when radiotherapy is combined with chemotherapeutic regimens including cyclophosphamide and adriamycin the toxicity is synergistic.

Indikationen, Technik und Frühergebnisse bei brusterhaltender operativ-radiologischer Therapie des Mammakarzinoms

Die radikalen lokalen Masnahmen bei Mammakarzinomen wurden in den letzten Jahrzehnten durch weniger radikale chirurgische Techniken ersetzt (Brinkley, 1968; McWhiter, 1948; Mouridsen, 1979; Patey, 1948; Stewart, 1977).