Jožef Stefan Institute

About: Jožef Stefan Institute is a facility organization based out in Ljubljana, Slovenia. It is known for research contribution in the topics: Liquid crystal & Dielectric. The organization has 3828 authors who have published 12614 publications receiving 291025 citations.

Bottom-up induction of functional dependencies from relations

Abstract: Data dependencies express the presence of structure in database relations, that can be utilised in the database design process. The discovery of data dependencies can be viewed as an induction process. Like in induction, we can distinguish between top-down approaches and bottom-up approaches. In top-down approach, dependencies are generated and then tested against the given relation. Since each test requires O(n2) comparisons, where n is the number of tuples in relation, this can be computationally costly. We propose an alternative approach which differs from the top-down approach in that it starts with an analysis of the tuples in the relation: a bottom-up approach.

Search for photons with energies above 10$^{18}$ eV using the hybrid detector of the Pierre Auger Observatory

Abstract: A search for ultra-high energy photons with energies above 1 EeV is performed using nine years of data collected by the Pierre Auger Observatory in hybrid operation mode. An unprecedented separation power between photon and hadron primaries is achieved by combining measurements of the longitudinal air-shower development with the particle content at ground measured by the fluorescence and surface detectors, respectively. Only three photon candidates at energies 1 - 2 EeV are found, which is compatible with the expected hadroninduced background. Upper limits on the integral flux of ultra-high energy photons of 0.027, 0.009, 0.008, 0.008 and 0.007 km -2 sr -1 yr -1 are derived at 95% C.L. for energy thresholds of 1, 2, 3, 5 and 10 EeV. These limits bound the fractions of photons in the all-particle integral flux below 0.1%, 0.15%, 0.33%, 0.85% and 2.7%. For the first time the photon fraction at EeV energies is constrained at the sub-percent level. The improved limits are below the flux of diffuse photons predicted by some astrophysical scenarios for cosmogenic photon production. The new results rule-out the early top-down models - in which ultra-high energy cosmic rays are produced by, e.g., the decay of super-massive particles - and challenge the most recent super-heavy dark matter models.

Effects of UV light irradiation on colour stability of thermally modified, copper ethanolamine treated and non-modified wood: EPR and DRIFT spectroscopic studies

Abstract: A series of experiments were carried out to investigate the colour stability of chemically treated and thermally modified wood compared to non-modified wood during long term artificial UV light irradiation. One set of wood samples was vacuum-pressure impregnated with alkaline (pH 9.8) copper (II) ethanolamine aqueous solution, while another set of samples from the same wood block was thermally modified at 210°C and −0.90 bar for 2 h. The treated and modified wood samples along with the non-modified ones were exposed to artificial UV light with the wave length in the region of UVA (315–400 nm) and UVB (280–315 nm) intermittently for 500 h. Colour measurements were carried out throughout the irradiation period at an interval of 100 h according to CIEL*a*b* system, where the results are presented in terms of ΔE, ΔL*, Δa* and Δb* values. Better photo-stability in terms of colour changes was recorded for both treated and modified woods compared to the non-modified one. By means of EPR and DRIFT spectroscopic study it was shown that some degree of colour stability of treated and modified woods, achieved during artificial UV light irradiation, resulted from lignin modifications and monomers of phenolic compounds.

Applications of mass spectrometry to identifying pharmaceutical transformation products in water treatment

Abstract: Measuring the elimination of an organic pollutant is not sufficient to assess the efficiency of water-treatment techniques, as transformation products, more persistent and/or more hazardous than the parent compounds, may be generated. The identity, the fate and the effects of these compounds are the subjects of an increasing number of studies, in which the development of mass spectrometry (MS)-based methods has resulted in increased sensitivity and selectivity and has been widely applied in the investigation of breakdown products and pathways. This review covers recent applications of MS to identifying pharmaceutical-degradation products formed via the oxidation and chlorination reactions utilized in water treatment. We give an overview of the current status and future prospects of advanced hyphenated MS techniques. We discuss the capabilities, the potential and the limitations of different mass analyzers for some of the most commonly studied pharmaceuticals.