Detection of primary and secondary cosmic ray particles aboard the ISS using SSNTD stacks.

To study the radiation environment inside the International Space Station, solid state nuclear track detector stacks were used. Within the BRADOS experiments, Phase 1, seven stacks were exposed at different locations of the Russian segment 'Zvezda' for 248 days in 2001. It was supposed that the radiation field inside the ISS was composed from primary cosmic ray particles penetrating the wall of the ISS and secondaries, mainly neutrons induced by primaries in the wall and other structural materials surrounding the detectors.

On-board TLD measurements on MIR and ISS.

This paper presents results from dosimetric measurements made aboard the Mir space station and the International Space Station (ISS) using the Pille portable thermoluminescent dosemeter (TLD) system. This paper includes the dosimetry mapping and automatic readout (trapped and untrapped components) results from Mir and ISS. The mean dose rate in 2001-2003 was 7 microGy h(-1).

Neutron and photon shielding benchmark calculations by MCNP on the LR-0 experimental facility.

In the framework of the REDOS project, the space-energy distribution of the neutron and photon flux has been calculated over the pressure vessel simulator thickness of the LR-0 experimental reactor, Rez, Czech Republic. The results calculated by the Monte Carlo code MCNP4C are compared with the measurements performed in the Nuclear Research Institute, Rez. The spectra have been measured at the barrel, in front of, inside and behind the pressure vessel in different configurations.

Space dosimetry with the application of a 3D silicon detector telescope: response function and inverse algorithm.

One of the many risks of long-duration space flights is the excessive exposure to cosmic radiation, which has great importance particularly during solar flares and higher sun activity. Monitoring of the cosmic radiation on board space vehicles is carried out on the basis of wide international co-operation. Since space radiation consists mainly of charged heavy particles (protons, alpha and heavier particles), the equivalent dose differs significantly from the absorbed dose.

Transport on randomly evolving trees.

The time process of transport on randomly evolving trees is investigated. By introducing the notions of living and dead nodes, a model of random tree evolution is constructed which describes the spreading in time of objects corresponding to nodes. It is assumed that at t=0 the tree consists of a single living node (root), from which the evolution may begin.

Pressure vessel calculations for VVER-440 reactors.

For the determination of the fast neutron load of the reactor pressure vessel a mixed calculational procedure was developed. The procedure was applied to the Unit II of Paks NPP, Hungary. The neutron source on the outer surfaces of the reactor was determined by a core design code, and the neutron transport calculations outside the core were performed by the Monte Carlo code MCNP.

Simulation of fiber deposition in bronchial airways.

Penetration probabilities of inhaled man-made mineral fibers to reach central human airways were computed by a stochastic lung deposition model for different flow rates and equivalent diameters. Results indicate that even thick and long fibers can penetrate into the central airways at low flow rates. Deposition efficiencies and localized deposition patterns were then computed for man-made fibers with variable lengths in a three-dimensional physiologically realistic bifurcation model of the central human airways by computational fluid dynamics (CFD) techniques for characteristic breathing patterns.

Bias in the direct numerical simulation of isotropic turbulence using the lattice Boltzmann method.

Direct numerical simulation of homogeneous, isotropic turbulence using the lattice Boltzmann method is revised. Two-point pressure and velocity correlations are studied and analytical results are derived taking into account the dynamics of the lattice Boltzmann equation. Using the parameters of a two-dimensional (D2Q9) and a three-dimensional (D3Q19) model, it is demonstrated that correlation functions obtained from lattice Boltzmann simulations may have systematic errors at large separation distances due to the second-order error terms.

Stability limits in binary fluids mixtures.

The stability limits in binary fluid mixtures are investigated on the basis of the global phase diagram approach employing a model for the attracting hard-sphere fluid. In addition to the diffusion spinodals the mechanical spinodals are included. As a result one finds topologically different types of the diffusion spinodals while only one shape exists for the mechanical spinodals which are present in the region of liquid-vapor equilibria only.

Analyzing of segregation in mixtures of 3-methylpyridine and heavy water by dynamic neutron radiography.

The closed-loop phase diagram of 3-methylpyridine-heavy water mixture was studied, to our best knowledge, for the first time with dynamic neutron radiography (DNR) at the 10MW VVR-SM Research Reactor in Budapest (Hungary). Visualized were the (i) lower temperature non-segregated states (below 38 degrees C), (ii) transition (40-43 degrees C), (iii) segregated states (46-128 degrees C), (iv) higher temperature transition (110-128 degrees C) and (v) higher temperature non-segregated states. The non-segregated state belonging to 141 degrees C, was found to be definitely dissimilar from the lower temperature state.

Semi-simultaneous application of neutron and X-ray radiography in revealing the defects in an Al casting.

A semi-simultaneous application of neutron and X-ray radiography (NR, XR) respectively, was applied to an Al casting. The experiments were performed at the 10MW VVR-SM research reactor in Budapest (Hungary). The aim was to reveal, identify and parameterize the hidden defects in the Al casting.

Detailed mathematical description of the geometry of airway bifurcations.

Health effects related to the deposition of inhaled aerosol particles in the respiratory system strongly depend on the local deposition patterns. These patterns are highly sensitive to the shape of the airway geometry. The current study presents an exact mathematical description of a morphologically realistic airway bifurcation by further developing an earlier study of the published literature.

The fractal dimension as a measure of the quality of habitats.

Habitat fragmentation produces isolated patches characterized by increased edge effects from an originally continuous habitat. The shapes of these patches often show a high degree of irregularity: their shapes deviate significantly from regular geometrical shapes such as rectangular and elliptical ones. In fractal theory, the geometry of patches created by a common landscape transformation process should be statistically similar, i.

Simulation of deposition and clearance of inhaled particles in central human airways.

In this study local distributions of deposited inhaled particles such as radon progenies in realistic human airway bifurcation models of bronchial generations one to six are computed for different geometries, inlet flow profiles, flow rates and particle sizes with computational fluid particle dynamics methods. The movement of the mucus layer in the large central human airways is also simulated by computational fluid dynamic techniques. There is experimental evidence that bronchogenic carcinomas mainly originate at the central zone of the large airway bifurcations, where primary hot-spots of deposition have been found.

Personal dosimetry for human missions to Mars based on TLD and LET-spectrometry technique.

Exposure of crew to the space radiation environment poses one of the most significant problems in long term missions in low earth orbits and in interplanetary missions. Accurate personal dose measurement will become increasingly important especially during manned missions to Mars. A series of instruments suitable for on-board dose, flux and LET measurements has been developed by the authors'.

Local particle deposition patterns may play a key role in the development of lung cancer.

The apparent discrepancy between the reported preferential occurrence of bronchial carcinomas in central bronchial airways and current dose estimates for inhaled particles suggests that experimentally observed local accumulations of particles within bronchial airway bifurcations may play a crucial role in lung cancer induction. Here, we computed three-dimensional particle deposition patterns in lobar-segmental airway bifurcations and quantified the resulting inhomogeneous deposition patterns in terms of deposition enhancement factors, which are defined as the ratio of local to average deposition densities. Our results revealed that a small fraction of epithelial cells located at carinal ridges can receive massive doses that may be even a few hundred times higher than the average dose for the whole airway.

Characterization of atmospheric particles by electron probe X-ray microanalysis.

Microchemical glass standards were used to validate a quantitation method based on peak-to-background (P/B) ratios from electron probe x-ray microanalysis spectra. This standardless method was applied to the determination of concentrations of individual particles from Malpha or Lalpha lines, as well as from Kalpha lines. The algorithm was tested on particulate glass samples for diameters ranging from 1 to 20 microm.

In vitro cell irradiation systems based on 210Po alpha source: construction and characterisation.

One way of studying the risk to human health of low-level radiation exposure is to make biological experiments on living cell cultures. Two 210Po alpha-particle emitting devices, with 0.5 and 100 MBq activity, were designed and constructed to perform such experiments irradiating monolayers of cells.

Dose measurements in space by the Hungarian Pille TLD system.

Exposure of crew, equipment, and experiments to the ambient space radiation environment in low Earth orbit poses one of the most significant problems to long-term space habitation. Accurate dose measurement has become increasingly important during the assembly (extravehicular activity (EVA)) and operation of space stations such as on Space Station Mir. Passive integrating detector systems such as thermoluminescent dosemeters (TLDs) are commonly used for dosimetry mapping and personal dosimetry on space vehicles.

Local deposition distributions of inhaled radionuclides in the human tracheobronchial tree.

There is experimental evidence that bronchogenic carcinomas originate mainly at the carinal ridges of the large central airways, where primary hot spots of deposition have been found. However, current lung dosimetry models do not take into consideration the inhomogeneity of deposition within the airways. In this study, computed local distributions of deposited inhaled radionuclides such as radon progenies in morphologically realistic human airway bifurcation models are analysed for different flow rates and particle sizes.

An on-board TLD system for dose monitoring on the International Space Station.

This institute has developed and manufactured a series of thermoluminescence dosemeter (TLD) systems for spacecraft, consisting of a set of bulb dosemeters and a small, compact, TLD reader suitable for on-board evaluation of the dosemeters. By means of such a system highly accurate measurements were carried out on board the Salyut-6, -7 and Mir Space Stations as well as on the Space Shuttle. A new implementation of the system will be placed on several segments of the ISS as the contribution of Hungary to this intemational enterprise.

Doses due to the South Atlantic Anomaly during the Euromir'95 mission measured by an on-board TLD system.

During the Euromir'95 mission, a specially designed microprocessor-controlled thermoluminescent detector (TLD) system, called the 'Pille'95', was used by ESA astronaut Thomas Reiter to measure the cosmic radiation dose inside the Mir space station. One of the experiment's objectives was to determine the dose fraction on Mir due to the South Atlantic Anomaly (SAA) on an orbit inclined at 51.6 degrees and at an altitude of about 400 km.

Extra dose due to extravehicular activity during the NASA4 mission measured by an on-board TLD system.

A microprocessor-controlled on-board TLD system, 'Pille'96', was used during the NASA4 (1997) mission to monitor the cosmic radiation dose inside the Mir Space Station and to measure the extra dose to two astronauts in the course of their extravehicular activity (EVA). For the EVA dose measurements, CaSO4:Dy bulb dosemeters were located in specially designed pockets of the ORLAN spacesuits. During an EVA lasting 6 h, the dose ratio inside and outside Mir was measured.

About the ranking of isolated habitats with different shapes: an interior-to-edge ratio study.

Isolated habitats can be compared and ranked by comparing their interior-to-edge ratio (I/E). We would like to show here that results based on ranking by I/E ratio sometimes contradict Diamond's rule, which ranks the most rounded habitat (i.e.

Stochastic model of hysteresis.

The methods of the probability theory have been used in order to build up a model of hysteresis which is different from the well-known Preisach model. It is assumed that the system consists of large number of abstract particles in which the variation of an external control parameter (e.g.