967 resultados para Heavy quark


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A realistic self-consistent charge correlation diagram calculation of the Kr{^2+} - Kr{^2+} system has been performed. We get excellent agreement for the 4(3/2)_u level with an experimentally observed MO level at large distances. Possible reasons for discrepancies between experiment and theory at small distances are discussed.

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Due to the tremendous spin-orbit splitting of quasi-molecular levels in superheavy collision systems (Z = Z_1 + Z_2 {\ge\approx} 137) bombarding energy 0.5-6 MeV N{^-1}, unusual couplings may occur around Z \simeq 165. Experimental evidence for such a theoretically predicted coupling is discussed.

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The quasimolecular M radiation emitted in collisions between Xe ions of up to 6 MeV energy and solid targets of Ta, Au, Pb and Bi, as well as a gaseous target of Pb(CH_3)_4, has been studied. Using a realistic theoretical correlation diagram, a semiquantitative explanation of the observed peak structure is given.

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Within the quasimolecular (MO) kinematic dipole model we predict a strong dependence of the anisotropy of the MO radiation on the orientation of the heavy ion scattering plane relative to the direction of the photon detection plane.

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Diatomic correlation diagrams are the main basis for the description of heavy-ion collisions. We have constructed the first realistic relativistic many-electron correlation diagrams based on nonrelativistic self-consistent-field, Hartree-Fock calculations of diatomic molecules plus relativistic corrections. We discuss the relativistic influences as well as the many-electron screening effects in the I-Au system with a combined charge of Z = 132 as an example.

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The time dependent Dirac equation which describes a heavy ion-atom collision system is solved via a set of coupled channel equations with energy eigenvalues and matrix elements which are given by a selfconsistent field many electron calculation. After a brief discussion of the theoretical approximations and the connection of the many particle with the one particle interpretation we discuss first results for the systems F{^8+} - Ne and F{^6+} - Ne. The resulting P(b) curves for the creation of a Ne K-hole are in good agreement with the experimental results.

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Quasi-molecular X-rays observed in heavy ion collisions are interpreted within a relativistic calculation of correlation diagrams using the Dirac-Slater model. A semiquantitative description of noncharacteristic M X rays is given for the system Au-I.

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Little is known about the heavy metal and microbial contamination of vegetables produced in Central Asian cities. We therefore measured the concentration of cadmium (Cd), copper (Cu), lead (Pb), and zinc (Zn) and of faecal pathogens (Coliform bacteria, Salmonella sp., Shigella sp., Ascaris lubricoides, Entamoeba sp. and pinworms [Oxyuris vermicularis syn. Enterobius vermicularis]) in soil, irrigation water, and marketed vegetables of Kabul City, Afghanistan. Leaf Pb and Zn concentrations of leafy vegetables were with 1–5 and 33–160 mg kg^{-1} dry weight (DW) several-fold above respective international thresholds of 0.3 mg Pb kg^{-1} and 50 mg Zn kg^{-1}. The tissue concentration of Cu was below threshold limits in all samples except for spinach in one farm. Above-threshold loads of microbes and parasites on vegetables were found in five out of six gardens with coliforms ranging from 0.5–2 × 10^7 cells 100g^{-1} fresh weight (FW), but no Salmonella and Shigella were found. Contamination with 0.2 × 10^7 eggs 100g^{-1} FW of Ascaris was detected on produce of three farms and critical concentrations of Entamoeba in a single case, while Oxyuris vermicularis, and Enterobius vermicularis were found on produce of three and four farms, respectively. Irrigation water had Ascaris, Coliforms, Salmonella, Shigella, Entamoeba, and Oxyuris vermicularis syn. Enterobius vermicularis ranging from 0.35 × 10^7 to 2 × 10^7 cells l^{-1}. The heavy metal and microbial loads on fresh UPA vegetables are likely the result of contamination from rising traffic, residues of the past decades of war and lacking treatment of sewage which needs urgent attention.

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Suplemento Música y más música, n. 5

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Los objetivos específicos de este proyecto de formación en centro son: 1. Actualización científica sobre nuevos sistemas experimentales en el laboratorio 2. Experimentación y aprendizaje en el terreno de la industria electrónica 3. Incremento de la rentabilidad en el uso del material de laboratorio 4. Desarrollo de nuevas aplicaciones didácticas en el laboratorio, con incidencia en el proceso de aprendizaje de los alumnos 5. Desarrollo de criterios comunes e interdisciplinares en la formulación química y en el simbolismo matemático. Tienden a que se generalice el trabajo práctico de laboratorio sobre la instrumentación más moderna de la que los centros están dotados abarcando: 1. Instrumentación electrónica. 2. Fuentes de luz láser. 3. Utilización didáctica de fuentes radioactivas de baja intensidad. 4. Banco de aire y fotografía estroboscópica en la enseñanza de la cinemática y dinámica. 5. Aplicaciones didácticas de los espectroscopios; utilización de fuentes de alta tensión 6. Utilización en química y biología de ph-metros y balanzas electrónicas con posible toma de datos por ordenador. 7. Aplicaciones de los procesos redox en los campos de la química y bioquímica 8. Utilización didáctica del telescopio y teodolito en física y matemáticas, aplicándolo a problemas astronómicos y topográficos sencillos. 9. Unificación y conocimientos del lenguaje y simbolismo empleado en los temas comunes a distintos seminarios. Se adjunta memoria final en la que se señala el logro de un alto porcentaje de los objetivos propuestos, la evaluación continua del proyecto, el alto porcentaje de actividades experimentales realizadas y la eficaz colaboración de los profesores docentes. En conclusión, 1. Se ha iniciado a la mayor parte de los profesores del área de ciencias del centro en el uso de los recursos más modernos disponibles, 2. Se intenta rentabilizar mediante un uso extensivo, la adquisición de modernos equipos de laboratorio, 3. Se ha intentado unificar criterios didácticos entre los diversos seminarios del área de ciencias, 4. Se han desarrollado condiciones para facilitar entre los profesores el trabajo en equipo.

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Pollution by toxic compounds is one of the most relevant environmental damages to ecosystems produced by human activity and, therefore, it must be considered in environmental protection and restoration of contaminated sites. According to this purposes, the main goal of this doctoral thesis has been to analyse the impact of several chlorophenols and heavy metals on the microbial communities of two typical Mediterranean soils. The ecological risk concentrations of each pollutant, which have been determined according to respirometric activity and changes in the microbial community composition, and the factors that influence on their effective toxic concentrations (bioavailable pollutants) have been analysed in order to predict their potential impact on different soil ecosystems and provide scientific data for the regulation of the soil protection policies. Moreover, resistant microorganisms with pollutant removal capacities have been isolated from artificially contaminated soil microcosms and tested in axenic cultures, to infer their potential usefulness for bioremediation.

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