59. Verification of the 3-D dose calculation algorithm during total skin electron irradiation with the rotary-dual field technique

Total skin electron irradiation is the commonly used procedure in the treatment of mycosis fungoides. The aim of this paper was to verify the elaborated algorithm for dose calculation during total skin electron irradiation with rotary-dual fields technique (TSEI-RD).Material and method: Authors modified the 2-D algorithm published by Podgorsak taking account of dose distribution along the body midline and doses in the body on a larger depth than in the skin. Depth-dose function, beam profile were measured in TSEI-RD conditions (spoiler, source-skin distance SSD=350cm, field size: 36×36cm at 100cm). Cylindrical vax phantom was used to calculate and then to measure the doses in a depth of 0.4cm during exposure to the electron beam of 6 MeV (at the output of Clinac-2300CD accelerator). Phantom was rotating with the pre-calculated speed during constant exposure to two fields executed one by one in each fraction. Thermoluminescent detectors (TLD) were used for in-phantom dose measurements and Marcus ionization chamber was used for calibration of TLD. Dose homogeneity on the phantom surface was checked for three phantoms with different diameters of 20, 30 and 40cm. Phantoms were irradiated at different rotating speeds.Initial results: Doses measured by TLD were on average by 4% lower than doses pre-calculated using the modified algorithm. Mean doses normalized to those pre-calculated and their standard deviations (both in per cents) were respectively: 96.1% and 0.4% for phantom with diameter of 20; 96.5% and 0.7% for diameter of 30cm and 96.0% and 0.8% for diameter of 40cm.Conclusions: Measured doses proved correctness of elaborated algorithm. Very low standard deviations are resulting from regular cylindrical shape of the phantoms

Correlation Exponent and Anomalously Localized States at the Critical Point of the Anderson Transition

We study the box-measure correlation function of quantum states at the Anderson transition point with taking care of anomalously localized states (ALS). By eliminating ALS from the ensemble of critical wavefunctions, we confirm, for the first time, the scaling relation z(q)=d+2tau(q)-tau(2q) for a wide range of q, where q is the order of box-measure moments and z(q) and tau(q) are the correlation and the mass exponents, respectively. The influence of ALS to the calculation of z(q) is also discussed.Comment: 6 pages, 3 figure

Point-Contact Conductances at the Quantum Hall Transition

On the basis of the Chalker-Coddington network model, a numerical and analytical study is made of the statistics of point-contact conductances for systems in the integer quantum Hall regime. In the Hall plateau region the point-contact conductances reflect strong localization of the electrons, while near the plateau transition they exhibit strong mesoscopic fluctuations. By mapping the network model on a supersymmetric vertex model with GL(2|2) symmetry, and postulating a two-point correlator in keeping with the rules of conformal field theory, we derive an explicit expression for the distribution of conductances at criticality. There is only one free parameter, the power law exponent of the typical conductance. Its value is computed numerically to be X_t = 0.640 +/- 0.009. The predicted conductance distribution agrees well with the numerical data. For large distances between the two contacts, the distribution can be described by a multifractal spectrum solely determined by X_t. Our results demonstrate that multifractality can show up in appropriate transport experiments.Comment: 18 pages, 15 figures included, revised versio

The IOERT IntraLine Accelerator for Intraoperative Radiotherapy

Artykuł przedstawia opracowany w Narodowym Centrum Badań Jądrowych we współpracy z Wielkopolskim Centrum Onkologii mobilny akcelerator IntraLine-IOERT, który jest przeznaczony do napromieniania podczas wykonywanych w salach operacyjnych zabiegów chirurgicznych. Akcelerator generuje terapeutyczną wiązkę elektronów o energii od 4 do 12 MeV, którą można wykonywać napromienianie pól o średnicy od 3 do 10 cm poprzez zastosowanie odpowiednich aplikatorów. Konstrukcja akceleratora zapewnia pełną mobilność całego akceleratora, a w szczególności jego głowicy, co pozwala na wyprowadzenie wiązki elektronów pod różnymi kątami zależnie od położenia komórek nowotworowych w ciele pacjenta.In the article the mobile electron accelerator IntraLine-IOERT developed by National Centre of Nuclear Research in cooperation with The Greater Poland Cancer Centre is presented. The unit is designed for use during surgical procedures in an operating room (Intraoperative Electron Radiation Therapy). The device generates therapeutic electron beam with the energy from 4 MeV to 12 MeV and it allows to irradiate fields of the diameter from 3 to 10 cm using a suitable applicator. IntraLine-IOERT accelerator is a fully mobile device; especially its mobile head allows for easy application of the electron beam under different angels as required by the tumor location in a patient’s body

Participation ratio and fidelity analyses as tools to study BCS-BEC crossover

Solving Bogoliubov-de Gennes (BdG) equations for a two dimensional Hubbard model with random on-site disorder, we compute the participation ratio and fidelity to establish conviction for a BCS-BEC crossover scenario at intermediate values of disorder proposed earlier [P. Dey, S. Basu, J. Phys.: Condens. Matter 20, 485205 (2008)]. The participation ratio analysis suggests the onset of a phase with shrunk pairs extending over moderate number of lattice sites, which however preserves the superfluid character. The fidelity or the ground state overlap for two different (but closely lying) values of the disorder strength shows an abrupt drop at the immediate neighbourhood of the disorder strength where an onset of a paired (bose-like) phase occurs