680 research outputs found

    Formality and Star Products

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    These notes, based on the mini-course given at the PQR2003 Euroschool held in Brussels in 2003, aim to review Kontsevich's formality theorem together with his formula for the star product on a given Poisson manifold. A brief introduction to the employed mathematical tools and physical motivations is also given.Comment: 49 pages, 9 figures; proceedings of the PQR2003 Euroschool. Version 2 has minor correction

    QED and relativistic corrections in superheavy elements

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    In this paper we review the different relativistic and QED contributions to energies, ionic radii, transition probabilities and Land\'e gg-factors in super-heavy elements, with the help of the MultiConfiguration Dirac-Fock method (MCDF). The effects of taking into account the Breit interaction to all orders by including it in the self-consistent field process are demonstrated. State of the art radiative corrections are included in the calculation and discussed. We also study the non-relativistic limit of MCDF calculation and find that the non-relativistic offset can be unexpectedly large.Comment: V3, May 31st, 200

    Coordinate-space approach to the bound-electron self-energy: Self-Energy screening calculation

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    The self-energy screening correction is evaluated in a model in which the effect of the screening electron is represented as a first-order perturbation of the self energy by an effective potential. The effective potential is the Coulomb potential of the spherically averaged charge density of the screening electron. We evaluate the energy shift due to a 1s1/21s_{1/2}, 2s1/22s_{1/2}, 2p1/22p_{1/2}, or 2p3/22p_{3/2} electron screening a 1s1/21s_{1/2}, 2s1/22s_{1/2}, 2p1/22p_{1/2}, or 2p3/22p_{3/2} electron, for nuclear charge Z in the range 5≤Z≤925 \le Z\le 92. A detailed comparison with other calculations is made.Comment: 54 pages, 10 figures, 4 table

    Determination of selected phthalates by gas chromatography\u2013mass spectrometry in mural paintings from Palermo (Italy)

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    Phthalate esters for decades, and probably even now, were used as softeners in water-based paintings. In general, these compounds are dangerous owing to their carcinogenicity and reproductive effects. Phthalates are not chemically but only physically bound to the matrices, hence, they may be leached into the environment and are ubiquitously found in environmental matrices. Considering that, construction is one of most important\ufb01elds in Europe, and probably worldwide, with respect to its economic, technological and environmental impact. In the present work the phthalate esters content of several mural paintings was evaluated by gas chromatography\u2013 mass spectrometry (GC-MS). Because, this issue is especially important to ensure proper security measurements during processes that could involve particulate inhalation, the total concentrations of 15 compounds in the analyzed mural paintings, ranged from 0.8 to 236 mg/Kg d.w. with anaverage of 39.4 mg/Kg d.w. The highest concentration was found in a mural painting sampled in an apartment built about 50 years ago, though, building age was not signi\ufb01cantly correlated with the levels of total and single PAEs. Among the monitored phthalates, only four (bis(2-ethylhexyl) phthalate, diisobutyl phthalate, Di-n-butyl phthalate and diethyl phthalate) were detected in appreciable quantities. Benzyl butyl phthalate was relevant only for one sample and, at trace levels, only for two samples. In all tested mural paintings, except two samples, predominates the bis(2-ethylhexyl) phthalate (DEHP) (from 30 to 100% of total). In general, occasionally, dinonyl phthalate (DNP) was used as an alternative to DEHP, however, in our case, its occurrence was not found. Diisobutyl phthalate (DiBP) was detected in seven samples and ranged from 0.17 to 13.2 mg/Kg d.w

    Relativistic Calculation of two-Electron one-Photon and Hypersatellite Transition Energies for 12≤Z≤3012\leq Z\leq30 Elements

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    Energies of two-electron one-photon transitions from initial double K-hole states were computed using the Dirac-Fock model. The transition energies of competing processes, the Kα\alpha hypersatellites, were also computed. The results are compared to experiment and to other theoretical calculations.Comment: accepted versio

    Non-perturbative calculation of the two-loop Lamb shift in Li-like ions

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    A calculation valid to all orders in the nuclear-strength parameter is presented for the two-loop Lamb shift, notably for the two-loop self-energy correction, to the 2p-2s transition energies in heavy Li-like ions. The calculation removes the largest theoretical uncertainty for these transitions and yields the first experimental identification of two-loop QED effects in the region of the strong binding field

    Recent Approaches for Chemical Speciation and Analysis by Electrospray Ionization (ESI) Mass Spectrometry

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    In recent years, the chemical speciation of several species has been increasingly monitored and investigated, employing electrospray ionization mass spectrometry (ESI-MS). This soft ionization technique gently desolvates weak metal\u2013ligand complexes, taking them in the high vacuum sectors of mass spectrometric instrumentation. It is, thus, possible to collect information on their structure, energetics, and fragmentation pathways. For this reason, this technique is frequently chosen in a synergistic approach to investigate competitive ligand exchange-adsorption otherwise analyzed by cathodic stripping voltammetry (CLE-ACSV). ESI-MS analyses require a careful experimental design as measurement may face instrumental artifacts such as ESI adduct formation, fragmentation, and sometimes reduction reactions. Furthermore, ESI source differences of ionization efficiencies among the detected species can be misleading. In this mini-review are collected and critically reported the most recent approaches adopted to mitigate or eliminate these limitations and to show the potential of this analytical technique

    QED self-energy contribution to highly-excited atomic states

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    We present numerical values for the self-energy shifts predicted by QED (Quantum Electrodynamics) for hydrogenlike ions (nuclear charge 60≤Z≤11060 \le Z \le 110) with an electron in an n=3n=3, 4 or 5 level with high angular momentum (5/2≤j≤9/25/2\le j \le 9/2). Applications include predictions of precision transition energies and studies of the outer-shell structure of atoms and ions.Comment: 20 pages, 5 figure
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