Neutron Scattering Facility for the Measurement of Light Quenching Factors of Dark Matter Detectors at Low Temperatures

The light yield of scintillating crystals which is quantified by light Quenching Factors (QFs) strongly depends on the kind of interaction in the crystal. For Dark Matter experiments like CRESST the precise knowledge of QFs is crucial for the discrimination of background events from possible WIMP signals. At the tandem accelerator of the Maier-Leibnitz-Laboratorium (MLL) in Garching a low-temperature scattering facility was set up, which in its current phase aims at the determination of the QFs of O, Ca, and W in CaWO₄ crystals as used in the CRESST experiment. A CRESST detector module consists of a 300?g CaWO₄ target crystal operated as a phonon detector and a separate silicon-on-sapphire (SOS) light detector to detect the corresponding scintillation light simultaneously. In order to disentangle the light yield corresponding to O, Ca and W recoils, monoenergetic neutrons (11 MeV) produced by the accelerator are scattered off an especially developed CRESST-like detector module, which is operated at mK temperatures in a dilution refrigerator. Arrays of liquid-scintillator detectors placed at fixed scattering angles allow one to identify the recoiling nuclei by a neutron time-of-flight measurement. The unique facility is suited for the characterization of different detector materials and will be a powerful tool also for the future multi-material experiment EURECA. We report on the experimental approach, the low-temperature setup and present first results.     

Modeling and measurements of heat transfer phenomena in two-phase PbSn alloy solidification in an external magnetic field

The main aim of this work is to study numerically the influence of an external magnetic field on the solidification processes of two-component materials. Based on the continuum model of two-phase flow a mathematical model for the directional solidification of a binary alloy in a magnetic field is presented. The model includes mass, momentum, energy and species mass conservation equations written in compressible form and additional relationships describing the temperature-solute coupling. The geometry under study is a cylindrical mold with adiabatic walls and cooled bottom. The macroscale transport in the solidification of alloys is governed by the progress of the two-phase mushy zone, which is treated by means of a porous medium approach. The volume fraction of liquid and solid phases, respectively, is calculated from a 2D approximation of the phase diagram. The results of calculation are compared with experimental data.     

Expression of apoptosis-regulating proteins and outcome of esophageal cancer patients treated by combined therapy modalities

The present study retrospectively examines the correlation between the outcome of patients with locally advanced esophageal squamous cell carcinoma (LAEC) after multimodal treatment (radiochemotherapy +/- surgery) and the expression of apoptosis-regulating proteins in pretherapeutic biopsies. Thirty-eight patients with LAEC who took part in a prospective multicentric trial received radiochemotherapy, optionally followed by surgery. Pretreatment tumor biopsies were immunohistochemically investigated for expression of p53, Bcl-2, Bax (bcl-2-associated X protein), and Bcl-X(L) (bcl-2-related X protein). The overall expression of p53, Bcl-2, Bax, and Bcl-X(L) was 52.6, 57.9, 100, and 97.4% respectively. Tumors without p53 expression and tumors with weak Bcl-X(L) expression showed response to chemotherapy more frequently (55.6 and 52.6%, respectively) than tumors positive for p53 expression and tumors with strong Bcl-X(L) expression (30.0 and 31.6%, respectively); however, these differences did not attain statistical significance. No correlations were found between the expression of Bcl-2 and Bax and the response to chemotherapy. In patients treated by radiochemotherapy and surgery, p53-negative tumors showed a significantly better outcome than p53-positive tumors (mean survival, 31.1 months versus 11.3 months; P = 0.0378). Additionally, a more favorable outcome was observed in tumors positive for Bcl-2 (not significant), whereas no differences in survival were observed in relation to the expression of Bax or Bcl-X(L). No differences in survival were observed in patients treated by radiochemotherapy without subsequent resection therapy in relation to the expression of apoptosis-regulating proteins. Immunohistochemical examination of pretherapeutic tumor biopsies for expression of apoptosis-regulating proteins may help to identify patients with LAEC who may benefit from multimodal treatment and those who may not.     

The effect of pulsed electrical currents on the formation of macrosegregation in solidifying Al–Si hypoeutectic phases

Within this study, we conducted experimental investigations focusing on the formation of macrosegregation in Al-7wt-%Si alloys exposed to electric current pulses (ECP) during solidification. The distribution of eutectic phase was measured on various sections of the solidified samples. The results do not show the formation of reproducible segregation pattern. This finding can be attributed to the specific pattern and the turbulent character of the flow generated by the ECP treatment, the equiaxed growth of free-moving crystals and a non-symmetric distribution of the electromagnetic force due to an uneven wetting of the electrodes. An increasing input of energy by ECP intensifies the melt flow and increases the variations of phase distribution over a longitudinal section.     

Bücherchau

Ohne Zusammenfassung VDI     

Sexual maturation in East German girls

According to the internationally accepted classification (Tanner, 1962; van Wieringen, 1971), sexual maturation was investigated in 8703 healthy East German girls by means of the status quo method and probit regression analysis. The third, 50th and 97th centiles were calculated for the development of breasts, axillary and pubic hair, and the shape of the hips. The findings were compared with those of recent studies from different European countries. Special attention was paid to the stages at the beginning and at the end of sexual maturation, e.g. B2/B5, AH2/AH3, etc.     

Basaloid squamous cell carcinoma of the esophagus: diagnosis and prognosis

BACKGROUND: Basaloid squamous cell carcinoma (BSCC) is a recently recognized, poorly differentiated variant of squamous cell carcinoma (SCC), which is located predominantly in the upper aerodigestive tract. METHODS: In this study, clinical and pathologic parameters of 17 BSCCs and 133 typical SCCs of the esophagus that underwent potentially curative resection (no distant metastases, no residual tumor) were compared. In addition, light microscopic, electron microscopic, and immunohistochemical features of BSCC were investigated, to determine whether this type of carcinoma could be differentiated from other poorly differentiated carcinomas of the esophagus. RESULTS: Light microscopic study showed that BSCC was composed of relatively small tumor cells, arranged in solid lobules with abundant comedo-type necrosis. BSCC was almost invariably accompanied by areas of concomitant typical SCC, foci of squamous cell differentiation, and/or severe squamous cell dysplasia or carcinoma in situ of the adjacent mucosa. Ultrastructurally, BSCC inconsistently showed features of squamous cell differentiation. Immunohistochemically, BSCC displayed poor reactivity for antibodies against wide-range cytokeratins and cytokeratin subtypes that are typical of squamous cell epithelia (cytokeratin 13 and cytokeratin 14). Infrequently, expression of Leu7, smooth muscle actin, and S-100 protein was found. In comparison with typical SCC, the characteristic features of BSCC were older patient age, higher proliferative activity (MIB-1 labelling index), and higher apoptotic indices. No differences were found with regard to pT classification, pN classification, tumor size, blood vessel invasion, lymphatic vessel invasion, neural invasion, or patient gender. Moreover, no differences in overall survival rates were found. CONCLUSIONS: BSCC is a distinct histopathologic variant of SCC, characterized by a poor degree of differentiation and high proliferative activity. However, after potentially curative resection, the prognosis of patients with BSCC of the esophagus does not differ from that of patients with typical SCC.