Reversible 2D Phase Transition Driven By an Electric Field: Visualization and Control on the Atomic Scale.

We report on a reversible structural phase transition of a two-dimensional system that can be locally induced by an external electric field. Two different structural configurations may coexist within a CO monolayer on Cu(111). The balance between the two phases can be shifted by an external electric field, causing the domain boundaries to move, increasing the area of the favored phase controllable both in location and size. If the field is further enhanced new domains nucleate. The arrangement of the CO molecules on the Cu surface is observed in real time and real space with atomic resolution while the electric field driving the phase transition is easily varied over a broad range. Together with the well-known molecular manipulation of CO adlayers, our findings open exciting prospects for combining spontaneous long-range order with man-made CO structures such as "molecule cascades" or "molecular graphene". Our new manipulation mode permits us to bridge the gap between fundamental concepts and the fabrication of arbitrary atomic patterns in large scale, by providing unprecedented insight into the physics of structural phase transitions on the atomic scale.

Dosimetric feasibility study for an extracorporeal BNCT application on liver metastases at the TRIGA Mainz.

This study investigates the dosimetric feasibility of Boron Neutron Capture Therapy (BNCT) of explanted livers in the thermal column of the research reactor in Mainz. The Monte Carlo code MCNP5 is used to calculate the biologically weighted dose for different ratios of the (10)B-concentration in tumour to normal liver tissue. The simulation results show that dosimetric goals are only partially met. To guarantee effective BNCT treatment the organ has to be better shielded from all gamma radiation.

Irradiation facility at the TRIGA Mainz for treatment of liver metastases.

The TRIGA Mark II reactor at the University of Mainz provides ideal conditions for duplicating BNCT treatment as performed in Pavia, Italy, in 2001 and 2003 [Pinelli, T., Zonta, A., Altieri, S., Barni, S., Braghieri, A., Pedroni, P., Bruschi, P., Chiari, P., Ferrari, C., Fossati, F., Nano, R., Ngnitejeu Tata, S., Prati, U., Ricevuti, G., Roveda, L., Zonta, C., 2002. TAOrMINA: from the first idea to the application to the human liver. In: Sauerwein et al. (Eds.), Research and Development in Neutron Capture Therapy. Proceedings of the 10th International Congress on Neutron Capture Therapy, Monduzzi editore, Bologna, pp. 1065-1072]. In order to determine the optimal parameters for the planned therapy and therefore for the design of the thermal column, calculations were conducted using the MCNP-code and the transport code ATTILA. The results of the parameter study as well as a possible configuration for the irradiation of the liver are presented.

Determination of the irradiation field at the research reactor TRIGA Mainz for BNCT.

For the application of the BNCT for the excorporal treatment of organs at the TRIGA Mainz, the basic characteristics of the radiation field in the thermal column as beam geometry, neutron and gamma ray energies, angular distributions, neutron flux, as well as absorbed gamma and neutron doses must be determined in a reproducible way. To determine the mixed irradiation field thermoluminescence detectors (TLD) made of CaF(2):Tm with a newly developed energy-compensation filter system and LiF:Mg,Ti materials with different (6)Li concentrations and different thicknesses as well as thin gold foils were used.

The lecithin/spingomyelin quotient as determined using a modified method and human placental lactogen in the amniotic fluid. / Der Lezithin/Sphingomyelin-Quotient, bestmmt nach einer modifizierten Methode, und HPL im Fruchtwasser

Thirty amniotic fluid samples in late gestational age were analysed for HPL-values and the L/S-ratio. The pregnant women used in this study were healthy except three patients who developed a rh-incompatibility. The amniotic fluid was only obtained by abdominal amniocentesis. We found a decreasing tendency of the HPL-values in late pregnancy. The L/S-ratio increased. A significant correlation of both values could not be observed. In all three cases of rh-incompatibility the decrease of HPL and the increase of the L/S-ratio occurred obviously earlier and steeper. Further studies will prove the significance of these results.