[en] ICRP recommendations, concerning patients protection during treatment with ionizing radiations, are reviewed

[en] The new organization of Israel's radiation protection administration are presented

[en] We introduce a new method for mapping and analyzing (with atomic resolution) molecules adsorbed on surfaces. This method relies on the detection of fluorescence from molecules, electronically excited by inelastic tunneling in STM. It may combines the excellent spatial resolution of STM together with the specificity of fluorescence as an analytical tool. We propose to overcome this problem by choosing 'transparent conductors' (such as Indium Tin Oxides-lTO) as the STM substrate. ITO, characterized by a large optical gap, will not quench electronically excited molecules. We have tested our idea to enhance the quantum efficiency of molecular emission on surfaces by using transparent conductors in the tunneling junction. We have constructed large area tunnel-junctions by using the squeezable tunnel-Junction technique. The principle of this technique is to squeeze together smooth flat surfaces separated by a thin spacer. By applying a controlled force, junctions with surface area of thousands of square angstroms are made. We have recorded light emission from bare tunneling surfaces and from surfaces coated with molecules (DCA, DCM and COUMARINE), as a function of the bias voltage in the range of 0-5 volts. Typical tunneling currents are 50 nano ampere. Our main findings are: The bare ITO surface emits light at biasing voltages larger than 4.0 eV which corresponds to electron-hole excitation over the optical gap of ITO. ITO surfaces coated with chromophore molecules have shown enhanced light emission at a voltage bias which corresponds to the allowed excitations energies in the chromophore. A voltage bias of 2-5 V yielded light emission of 5 * 10³ photon/μC. The corresponding metallic surfaces, bare or coated with a chromophore did not show any emission. In order to test the possibility of using this effect for imaging purposes we have replaced one electrode of junction with an ITO coated glass tip of 180 μm radius. such a tip yield an upper limit of tunneling area of 0.3 μm diameter. (author) 35 refs

No abstract available

[en] The branch of biocorrosion is the youngest of the corrosion sciences, in spite the fact, that the first work was published in the 30's of this century. During these year the microbiology science underwent a great change and development which yielded new discoveries important to the biocorrosion discipline. Along the unexplained corrosion effect to underground communication equipment, appeared in the 70's many publications on biocorrosion. These research works showed that the cause to the unexpected corrosion was bacteria activity. accelerated the microbial activity as a result of industrial products and the environmental pollution of the soil, water and air. This type of corrosion is discovered now in various industries

[en] Multilevel Monte Carlo procedures for calculating statistical properties of configurations in the framework of two spin models are developed. A cluster (two-level) algorithm is constructed for the 3-state antiferromagnetic Potts model on the triangular lattice. Despite of the improved performance compared with classical Monte Carlo, the overall gain appears to be small due to the model structure, which also severely complicates the design of an efficient multilevel generalization of the procedure. In case of two-dimensional XY model, a multigrid algorithm demonstrating the feasibility of calculating thermodynamic limits to a certain accuracy within the optimal number of random number generations is developed. A technique for achieving the optimal performance in terms of the overall computational time is presented. (author)

No abstract available

[en] A high-temperature metallography setup is presented. In this setup the observation of processes such as that of copper recrystallization was made possible, and the structure of metals such as uranium could be revealed. A brief historical review of part of the research works that have been done with the help of high temperature metallographical observation technique since the beginning of this century is included. Detailed description of metallographical specimen preparation technique and theoretical criteria based on the rate of evaporation of materials present on the polished surface of the specimens are given

[en] A process for the encapsulation of radioactive point sources (²⁴¹Am, ²³⁸Pu, ²³⁹Pu) and of an annular (²⁴¹Am) source was developed. The sources were sealed in a stainless steel 304L envelope using automatic tungsten-inert-gas (TIG) welding machine. The welding was carried out in a glovebox specially designeed for such weldings. The decontamination process, the welding parameters, and the special jigs and fixtures needed for the welding are described

[en] Weak radiative decays of baryons are investigated in order to clarify the corresponding basic mechanics. Firstly the Σ⁺pγ vertex which consists of two terms: the magnetic moment transition term and the charge radius term. Both terms contribute to decays in which the photon is virtual, wherease only the magnetic moment term contributes to decays in which the photon is real. Among the several mechanisms that contribute to the above terms, are the single and the two quark transitions. In this work, the ratio of these two terms is studied by investigating the decays of spin 1/2 baryons to Delitz pairs, namely, the decays of the Σ→pl⁺l^-type, where l = e or μ. Secondly, the sdγ vertex is investigated and the QCD corrections to the amplitude of this transition are examined. It is proved that information on sdγ vertex can be obtained by studying decays of the Ω^-→Ξ^-γ type and the Ω^-→Ξl⁺l^- type, since the s→dγ mechanism is the dominant one in these dec???