[en] Within the frame of our programme on realistic Monte Carlo calculations for dosimetry and treatment planning, the detailed simulation of the treatment head of radiotherapy accelerators has been focused on a MM50 Racetrack microtron. The project includes the improvement of bremsstrahlung target design and the effect of neutron production on the irradiation of patients with high-energy scanned beams. Most applications by other authors have so far used the EGS4 Monte Carlo system.; their implementation has been usually based on the coding of the specific geometry of each machine. Our project concentrates in using 'public' and standardized software tools for both geometry description and simulation to minimize manpower and economical requirements. Accelerator head structures are described using the Combinatorial Geometry (CG) package where 3D 'bodies' are combined using Boolean algebra; this enables an almost universal characterization that can be easily adapted to any accelerator treatment head. Graphical visualization is accomplished with the code SABRINA, which processes both CG (and specific inputs for the MCNP Monte Carlo system); SABRINA runs in almost every UNIX workstation. Simulations are performed with the ACCEPT code of the ITS 3.0 MC system, fully based on CG inputs and containing 'state-of-the-art' bremsstrahlung cross-sections; it also allows a direct implementation of the purging magnet in the MM50 head. Our interest in neutron production will consider the utilization of MCNP when a planned version containing the electron transport of ITS 3.0 becomes a reality. All the software is available in Europe through the NEA data bank. This presentation will describe the selected tools and actual status of the project. Support from K Van Riper (LANL) and R Kensek and J Halbleib (Sandia Labs) is greatly acknowledged

[en] Using Noether's theorem, the conservation laws for the general Lagrangian in Einstein-Cartan theory are derived. The general covariant energy-momentum conservation law for the general Lagrangian including torsion is obtained from the general displacement transformation x/sup '//sup μ/ = x/sup μ/+e/sup μ//sub a/b/sup a/. It is shown that in such a case, the superpotential V/sup μ//sup ν//sub a/ must exist. This result is a natural extension of the theory in Refs. 1 and 2

[en] Graphical abstract: Mutual diffusion coefficients of isopropanol + n-heptane as a function of mass fraction of isopropanol. - Highlights: • D_1_2 of isopropanol + n-heptane and isobutanol + n-heptane were measured. • Effect of T, w and M of the solute on D_1_2 were analyzed. • A new correlation is proposed for the experimental data. - Abstract: The mutual diffusion coefficients of isopropanol + n-heptane and isobutanol + n-heptane were measured at different concentrations and in the temperature range from (283.15 to 323.15) K. The measurements were carried out using a digital holographic interferometry system. For all the mixtures investigated, the mutual diffusion coefficient increases as the temperature increases. At the same concentration and temperature, the mutual diffusion coefficients of isobutanol + n-heptane were lower than those of isopropanol + n-heptane due to the fact that the molecular weight of isobutanol is larger than that of isopropanol. A new correlation is proposed for the mutual diffusion coefficients of isopropanol + n-heptane and isobutanol + n-heptane. The absolute average relative deviation between the correlation and experiment is less than 1.90%.

[en] Thermal history simulation of Apatite Fission Track shows the thermal structure history in Cenozoic and the relationship between Songliao Basin and Daxinganling Mountain. Uplift of Daxinganling reveals its act character; its velocity shows 5 decreasing phases and 4 increasing ones. Although basin evolvement is quite complex, it behaved as three uplifts and two sedimentations. It is considered here that the relationship between Songliao Basin and Daxinganling includes three styles and 4 phases, that is, basin uplifted with mountain during 65.5-50 Ma; basin subsided while mountain uplifted slowly and basin uplifted rapidly while mountain uplifted rapidly during 50-36 Ma; basin subsided slowly while mountain uplifted slowly and basin subsided rapidly while mountain uplifted rapidly during 36-5.83 Ma; the latest phase was the same with the first one. (authors)

[en] In order to obtain higher separation power of the gas centrifuge, the code was developed to solve the flow-field of the counter-current to acquire the separation power, which was integrated with the iSight software, so a numerical optimization model for separation power was presented, in which the driver conditions and the geometry parameters of the waste baffle were optimized to get the maximum separation power using the sequential quadratic programming arithmetic, and the 12% higher results was acquired, which shows the feasibility of this method. The results also note that the separation power of gas centrifuge is sensitive to the driver conditions and the structure parameters of the waste baffle, so it is necessary to perform the optimization calculation for the certain gas centrifuge model. (authors)

[en] A high resolution phoswich detector has been developed to reduce event mispositioning and improve the spatial resolution of the detector. Crystal identification electronics and algorithm is designed for identifying LYSO and YSO crystals in phoswich detector coupled to PMT. After shaping and filtering, events are sampled at 105 MSPS by an analog to digital converter (ADC) and acquired by FPGA. A crystal identification algorithm based on Auto-Regressive Moving-Average with noise (ARMAX) model is proposed. Excellent discrimination are (>98%) has been achieved without considering crosstalk between crystals. For LYSO/YSO array, the system achieves a discrimination rate of (93.6%). Then the 2D map of each kind of crystal has also been generated individually which has little overlap. (authors)

[en] Two accurate algorithms for calculating the required incident energy fluence distributions from the optimal irradiation density distribution in inverse radiation therapy planning have been developed. The algorithms are characterized by a high speed and accuracy and an ability to handle both divergent and parallel beams even for extremely heterogeneous target volumes. The fastest algorithm is based on a longitudinal distance weighting method, whereas the slower but more accurate algorithm uses an area weighting method which has the advantage that it also works very well at low spatial resolutions. Both algorithms have been inverted for forward calculation of the delivered absorbed dose distribution from known fluence profiles. (author)

[en] A new design of look-up-table (LUT) electronics for a small animal positron emission tomography (PET) system is Proposed. Position and energy signals for a coincidence event are generated in a coincidence circuit board and sent to the LUT board,in which the centroid of this event is calculated by the LUT approach. The centroid is used as an index of the crystal element. Corresponding coordinates and energy threshold of this crystal are obtained from the other tables, and the scattered events are rejected. Interfaces for receiving respiratory and electro cardiac gate signals are designed for future use. All the look-up-tables are stored in NOR flash memory which is controlled by a Complex Programmable Logic Device. The LUT board communicates with PC through Ethernet board. The advantage of this specific hardware design is that the LUT operation can be performed in a more efficient way, with a < 100 ns time delay. The paper also describes the operation of the flash-memory with a CPLD, and the data flow between this LUT and other modules in our PET system. (authors)

[en] Objective: To study the application of the assistant digital subtraction angiography (DSA) with selective intra-arterial embolization in comprehensive treatment of juvenile nasopharyngeal angiofibroma. Methods: Among 17 patients with juvenile nasopharyngeal angiofibroma confirmed by surgery and biopsy from February 2000 to June 2005, 13 cases underwent DSA examination and selective intra-arterial embolization on 1-4 days before surgical operation, and 4 cases with uncontrollable epistaxis through conventional therapy were carried out urgent DSA and embolization as well as surgical operation on a scheduled day. Angiographic manifestations and hemostatic effects and impacts in surgical operation were observed. Results: The extent and blood supply of lesions and the features of feeding artery were clearly demonstrated by DSA. Supplying vessel was mainly maxillary artery originating from external caroted artery in 16 cases, and double supplying vessels from ramus of internal and external carotid arteries in 1 case. In general, the higher the nasopharyngeal angiofibroma grade was the more supplying branches would exist. As for epistaxis patients, the number of the presence of irregular distal vessels and the punctiform extravasation of contrast media were displayed in positive proportion. No severe complications occurred and active bleeding was stopped after embolization and furthermore with less blood loss during surgical operation statistically about 280-1600 ml (460±255.5). Conclusions: DSA examination and selective arterial embolization can not only present more accurate important clinical imaging features but also in favour of stop bleeding and enhance surgical outcomes for patients with nasopharyngeal angiogibroma. (authors)

[en] Light-induced degradation is an important problem concerning hydrogenated amorphous silicon (a-Si:H) solar cells. A-Si:H films of lower Si-H₂ bond density exhibit less light-induced degradation. In this study, Raman spectroscopy measurements of a-Si:H films with P-layer/I-layer structure reveal that high-density Si-H₂ bonds exist in the I-layer within 60 nm of the P/I interface. These Si-H₂ bonds originate from surface reactions of SiH₃ radicals, as the alternative origin (i.e., cluster incorporation) is considerably suppressed by a multi-hollow discharge plasma chemical vapor deposition method. For an I-layer thickness of 20 nm, the density ratio of Si-H₂ and Si-H bonds in the I-layer decreases from 0.133 to 0.053 as the substrate temperature increases from 170degC to 250degC. Fine tuning of the substrate temperature during the initial stage of I-layer deposition is thus effective in suppressing Si-H₂ bond formation at the P/I interface. (author)