FLUKA Simulations of Kß/Kα Intensity Ratios of Copper in Ag-Cu Alloys.

The numerical simulations of Cu Kα and Cu Kß fluorescence lines induced by Rh X-ray tube and by monoenergetic radiation have been presented. The copper Kß/Kα intensity ratios for pure elements as well as for Ag-Cu alloys have been modeled. The results obtained by use of the FLUKA code, based on the Monte-Carlo approach, have been compared to available experimental and theoretical values. A visible relationship was found between the simulated Kß/Kα intensity ratios and the copper content of the Ag-Cu alloy: as the Cu content increases, the Kß/Kα coefficient decreases. The results can play role in elemental material analysis, especially in archaeometry.

Monte Carlo dosimetry using Fluka code and experimental dosimetry with Gafchromic EBT2 and XR-RV3 of self-built experimental setup for radiobiological studies with low-energy X-rays.

Purpose: The aim of this research was to simulate self-built experimental setup for radiobiological research using X-ray diffraction C-tech tube and PW 3830 generator (PANalytical, Netherlands) and to calculate absorbed dose and to compare it with experimental dose measurements. The maximum X-ray energy was 60 keV.Materials and methods: Petri dish was specially adapted to hold biological cells during the irradiation process. Rotation of Petri dish ensured radiation homogeneity and effectiveness of rotation process was confirmed using EBT2 Gafchromic film. Monte Carlo simulation using Fluka 2011 2c.4 was used to model the setup and to calculate dose absorbed by live cells. The EBT2 and XR-RV3 Gafchromic films were used to estimate relative experimental absorbed dose.Results: The radiation homogeneity provided values with maximum deviation equal to ±3.5% from the average value and the absorbed dose rate was 0.9 Gy/min using simulation process and 1 Gy/min or 0.8 Gy/min using experimental methods (XR-RV3 and EBT2 Gafchromic film, respectively). All dose rate values show metrological compatibility.Conclusions: Influence of specially constructed Petri dish on absorbed dose was determined using simulations that showed that low-energy photons, emitted as characteristic line from borosilicate glass forming component of Petri dish, were source of increase in dose absorbed by cells. This experimental setup will be used to conduct radiobiological research.HighlightsA low-energy X-ray system constructed for radiobiological studies was used.Dosimetry was based on a Monte Carlo simulation using Fluka 2011 code version 2c.4.A specially designed rotating Petri dish ensured the uniformity of the radiation distribution.Gafchromic EBT2 and XR-RV3 films were used to experimental dosimetry.Monte Carlo and experimental dosimetry showed metrological compatibility.

CALIBRATION OF LOW ENERGY X-RAY EXPERIMENTAL SETUP WITH STRONGLY FILTERED BEAM USING DATA FROM A SEMICONDUCTOR AND A THERMOLUMINESCENT DETECTORS.

The calibration of low energy X-ray experimental setup with strongly filtered beam dedicated to radiobiological research was performed using the absorbed dose calculated from the data collected by two types detectors. For this purpose a semiconductor (Amptek, USA) and a thermoluminescent (Institute of Nuclear Physics, Krakow, Poland) detectors were applied. The absorbed dose in water values estimated by both detectors are in good agreement.

Mechanism and Thermodynamics of Reductive Cleavage of Carbon-Halogen Bonds in the Polybrominated Aliphatic Electrophiles.

Quantum-mechanical computations revealed that, despite the presence of electron-withdrawing and/or π-acceptor substituents, the lowest unoccupied molecular orbitals (LUMO) of the polybromosubstituted aliphatic molecules R-Br (R-Br = C3Br2F6, CBr3NO2, CBr3CN, CBr3CONH2, CBr3CO2H, CHBr3, CFBr3, CBr4, CBr3COCBr3) are delocalized mostly over their bromine-containing fragments. The singly occupied molecular orbitals in the corresponding vertically excited anion radicals (R-Br(•-))* are characterized by essentially the same shapes and show nodes in the middle of the C-Br bonds. An injection of an electron into the antibonding LUMO results in the barrierless dissociation of the anion-radical species and the concerted reductive cleavages of C-Br bonds leading to the formation of the loosely bonded {R(•)···Br(-)} associates. The interaction energies between the fragments of these ion-radical pairs vary from ∼10 to 20 kcal mol(-1) in the gas phase and from 1 to 3 kcal mol(-1) in acetonitrile. In accord with the concerted mechanism of reductive cleavage, all R-Br molecules showed completely irreversible reduction waves in the voltammograms in the whole range of the scan rates employed (from 0.05 to 5 V s(-1)). Also, the transfer coefficients α, established from the width of these waves and dependence of reduction peak potentials Ep on the scan rates, were significantly lower than 0.5. The standard reduction potentials of the R-Br electrophiles, E(o)R-Br/R·+X(-), and the corresponding R(•) radicals, E(o)R(•)/R(-), were calculated in acetonitrile using the appropriate thermodynamic cycles. In agreement with these calculations, which indicated that the R(•) radicals resulting from the reductive cleavage of the R-Br molecules are stronger oxidants than their parents, the reduction peaks' currents in cyclic voltammograms were consistent with the two-electron transfer processes.

Land conversion for suburban housing: A study of urbanization around Warsaw and Olsztyn, Poland.

In Poland of the 1990s, urban demand for housing land around city agglomerations increased rapidly. The decreasing profitability of agricultural production also caused farmers to become interested in the sale of agricultural land for nonagricultural purposes, and new land legislation granted them the right to sell their land. Polish counties simultaneously received self-governing status, which allowed them to define the priorities for local development. Counties received additional responsibility for land management and quickly demonstrated strong support for land conversion, which was perceived as a factor of local development. This paper argues that decentralization and the extension of private control over land have led to a loss of rural landscapes in Poland because farmers, county governments, and rural society in general gained from the conversion of agricultural to housing land. Rapid urbanization has significantly reduced the availability of open space around cities and threatened valuable landscapes, for it has occurred in the absence of environmental safeguards. This paper reports findings from research in two counties, located in regions with diverse economic growth rates. Decentralization is particularly problematic if tax regulations and intergovernmental fiscal relations reward local authorities for urbanization but not environmental protection.