Radon and air ion balance

In connection with the study of equilibrium among radon and its conversion products attention has been paid to air ionisation or, more precisely, to light atmospheric ions. Air ionisation variability and relationship between positive and negative ions concentration in the presence of ionizing radiation, local and microclimatic conditions have been observed. A very good correlation between light atmospheric ions concentration and radon volume activity or equilibrium equivalent of radon decay products has been found. Concrete measurements were conducted in karst caves and mine galleries without any meteorological influences. It was discovered that in most cases negative ions concentration predominated over positive ions concentration. This non-equilibrium was caused by a number of factors. In this work we have concentrated our attention to microclimatic and regime conditions of the individual locations.     

Coulomb potentials and the energy-angular momentum balance in heavy ion transfer reactions

Coulomb terms in optical model parameters and in the effective interaction are discussed for DWBA in charged particle transfer in heavy ion reactions. It is shown that certain discrepancies in shapes of calculated angular distributions are due to incorrect treatment of Coulomb terms.     

A computer model of particle balance in ECR ion sources

The investigation of the widespread model of particle balance and energy transport [1–5] for calculating the ion charge state distribution (CSD) in an electron cyclotron resonance (ECR) ion source [6] is given. The modification of this model that makes it possible to describe the confinement and accumulation processes of highly charged ions in ECR plasma for the case of gas mixing is more precisely discussed. The discussion of the new technique for calculating the time confinement of ions and electrons, which is based on the Pastukhov theory [7, 8], is given: calculation of confinement times during two step minimization of special type functionals. The preliminary results obtained with this approach have been compared with available experimental data. The text was submitted by the authors in English.     

Radon daughters' concentration in air and exposure of joggers at the university campus of Bangalore, India

The concentration of radon daughters in outdoor air was measured continuously from January 2006 to December 2006 near the Department of Physics, Bangalore University campus, Bangalore. The concentration was measured by collecting air samples at a height of 1 m above the ground level on a glass micro fibre filter paper with a known air flow rate. The results show that the radon progeny concentration exhibits distinct seasonal and diurnal variations that are predominantly caused by changes in the temperature gradient at the soil-atmosphere interface. The concentration was found to be high from 20.00 to 8.00 hrs, when the turbulence mixing was minimum and low during the rest of the time. In terms of the monthly concentration, January was found to be the highest with September/August being the lowest. The diurnal variations in the concentrations of radon progeny were found to exhibit positive correlation with the relative humidity and anti-correlation with the atmospheric temperature. From the measured concentration, an attempt was made to establish the annual effective dose to the general public of the region and was found to be 0.085 mSv/a. In addition, an attempt was also made for the first time to study the variation of inhalation dose with respect to the physical activity levels. Results show that in the light of both the effect of chemical pollutants and radiation dose due to inhalation of radon daughters, evening jogging is advisable.     

Specific ion adsorption and short-range interactions at the air aqueous solution interface

We have investigated the surface composition of alkali-halide aqueous solutions using grazing incidence x-ray fluorescence. Using mixtures of salts as a means to enhance the short-range effects, small differences in concentration over a few angstrom could be resolved, with, for example I- or Br- > Cl-. In order to explain our data, we need to include an effective potential accounting for the short-range (A) solvent mediated couplings, responsible for specific effects together with dispersion forces. This attractive potential (few k{B}T for halides) leads to concentration profiles which are in good agreement with recent numerical simulations.     

Numerical solution of momentum balance equations for plasmas with two ion species

In plasmas bounded by material surfaces the Bohm criterion has to be satisfied at the entrance of the Debye sheath near the surface. With a single ion species this constraint prescribes a boundary condition for the momentum balance equation governing the ion mass velocity. If, however, several ion species are present a generalization of the Bohm criterion does not provide enough number of boundary conditions. Additional “intermediate” conditions follow from the requirement that spatial derivatives of the ion velocities are finite everywhere within the plasma volume. The amount of such independent conditions is sufficient to determine, in an iterative way, also the position in the plasma where they have to be imposed. A numerical approach to find unique regular solutions of fluid motion equations, satisfying the generalized Bohm criterion at the plasma boundary, is elaborated and realized for the case of two ion species.     

脉冲电场介导的植物空气负离子发射的倍增效应及其意义

介绍了空气负离子(NAI)的物理概念及其在空气净化中的作用,讨论了正常生态条件下空气中NAI的来源.通过实验结果说明了脉冲电场可以使植物产生NAI发射的倍增效应,分析了其产生的机理.     

Radon emanation from soil samples

The soil or bedrock beneath a building is one of the sources of radon gas in the indoor air. The ²³⁸U content of samples of the soil or the bedrock can be measured by gamma ray spectrometry and is of interest because the uranium content in the soil is a precursor of the presence of the radon gas in the soil. The emanation of radon gas from different types of material can be estimated to some extent if the content of ²³⁸U of a sample is known and the ²²⁶Ra content is only minorly affected. The true emanation is, however, affected by various parameters. One of these parameters is the possibility or not for the gas to come out from the grains into the air in the space between the grains of the sample.

In this study we report the results from measurements of radon gas emanating from samples of soil frequent in the Lund region in Sweden and in the Barcelona region in Spain. As soils have different grain size it is important to know the type of soil. The ²³⁸U content of the soil is measured with gamma ray spectrometry. The radon measurements are made by Kodak plastic film in closed cans, filled with the soil according to a technique, developed for radon measurements in water samples.

The result shows, that the combination of grain size and uranium content is important for the emanation of the radon gas from the grains of the soil.     

Inverse Radon Transform at Work

Physics of Particles and Nuclei Letters - The inverse Radon transform allows to obtain partonic double distributions from (extended) generalized parton distributions. We express the extension of...     

Radon inversion of plasma emission

An analytical inversion of plasma spectral emission using the Radon transform is discussed for a plasma with a constant coefficient of absorption and a model displaced gaussian as the spatial distribution of its coefficients of emission.     

Rotation-invariant texture analysis using Radon and Fourier transforms

Texture analysis is a basic issue in image processing and computer vision, and how to attain the rotationinvariant texture characterization is a key problem. This paper proposes a rotation-invariant texture analysis technique using Radon and Fourier transforms. This method uses Radon transform to convert rotation to translation, then utilizes Fourier transform and takes the moduli of the Fourier transform of these functions to make the translation invariant. A k-nearest-neighbor rule is employed to classify texture images. The proposed method is robust to additive white noise as a result of summing pixel values to generate projections in the Radon transform step. Experiment results show the feasibility of the proposed method and its robustness to additive white noise.     

Crossing and Radon tomography for generalized parton distributions

The crossing properties of the matrix elements of non-local operators, parameterized by generalized parton distribution, are considered. They are especially simple in terms of the double distributions which are common for the various kinematical regions. As a result, double distributions may be in principle extracted from the combined data in these regions by making use of the inverse Radon transform, known as a standard method in tomography. The ambiguities analogous to the ones for the vector potential in the two-dimensional magneto-statics are outlined. The possible generalizations are discussed.     

Ar ion laser assisted chemical etching of via holes in tungsten sheets in air

Ar ion laser assisted chemical etching of 150 m thick annealed tungsten sheets in air is reported. The material removal mechanism involves local heating by the laser to temperatures in the range of 1000–1500 °C that causes rapid oxidation of the W to WO₃ which volatilizes readily. Holes with straight walls and slightly enlarged entrances near the surface were drilled with etch rates as high as 11.5 m/s at 13.8 W, and a minimum hole diameter of 21 m at 8.1 W. The diameters of the holes and the etch rates were measured and found to increase as a function of the laser power. It was found that by increasing the laser power above 11–12 W, no change was observed in the hole diameters which remained constant at about 31 m, whereas the etch rates continued to increase even faster than at low powers. Distinct adjacent holes of 25 m diameter could be drilled with their centers separated by as little as 60 m. This is therefore also the etching resolution in the present study.     

Radon transform and kinetic equations in the tomographic representation

Statistical properties of classical random processes are considered in the tomographic representation. The Radon integral transform is used to construct the tomographic form of the kinetic equations. The relationship between the probability density on the phase space for classical systems and the tomographic probability distribution is elucidated. Examples of simple kinetic equations like the Liouville equations for one and many particles are studied in detail.