777 research outputs found
Ferromagnetism in substituted zinc oxide
Room-temperature ferromagnetism is observed in (110) oriented ZnO films
containing 5 at % of Sc, Ti, V, Fe, Co or Ni, but not Cr, Mn or Cu ions. There
are large moments, 1.9 and 0.5 muB/atom for Co- and Ti-substituted oxides,
respectively. Sc-substituted ZnO shows also a moment of 0.3 muB/Sc.
Magnetization is very anisotropic, with variations of up to a factor three
depending on the orientation of the applied field relative to the R-cut
sapphire substrates. Results are interpreted in terms of a spin-split donor
impurity band model, which can account for ferromagnetism in insulating or
conducting high-k oxides with concentrations of magnetic ions that lie far
below the percolation threshold. The variation of the ferromagnetism with
oxygen pressure used during film growth is evidence of a link between
ferromagnetism and defect concentration.Comment: 15 pages, 4 figure
A linear radiofrequency ion trap for accumulation, bunching, and emittance improvement of radioactive ion beams
An ion beam cooler and buncher has been developed for the manipulation of
radioactive ion beams. The gas-filled linear radiofrequency ion trap system is
installed at the Penning trap mass spectrometer ISOLTRAP at ISOLDE/CERN. Its
purpose is to accumulate the 60-keV continuous ISOLDE ion beam with high
efficiency and to convert it into low-energy low-emittance ion pulses. The
efficiency was found to exceed 10% in agreement with simulations. A more than
10-fold reduction of the ISOLDE beam emittance can be achieved. The system has
been used successfully for first on-line experiments. Its principle, setup and
performance will be discussed
Cytokine profiles in pregnant gilts experimentally infected with porcine reproductive and respiratory syndrome virus and relationships with viral load and fetal outcome.
In spite of extensive research, immunologic control mechanisms against Porcine Reproductive and Respiratory Syndrome virus (PRRSv) remain poorly understood. Cytokine responses have been exhaustively studied in nursery pigs and show contradictory results. Since no detailed reports on cytokine responses to PRRSv in pregnant females exist, the objectives of this study were to compare host cytokine responses between PRRSv-infected and non-infected pregnant gilts, and to investigate relationships between cytokine levels in infected gilts and viral load or fetal mortality rate. Serum samples and supernatants of peripheral blood mononuclear cells (PBMC) either stimulated with PRRSv or phorbol myristate acetate/Ionomycin (PMA/Iono) were analyzed for cytokines/chemokines: interleukins (IL) 1-beta (IL1β), IL4, IL8, IL10, IL12, chemokine ligand 2 (CCL2), interferon alpha (IFNα) and interferon gamma (IFNγ). Three cytokines (IFNα, CCL2, IFNγ) in gilt serum differed significantly in inoculated versus control gilts over time. In supernatants of PRRSv stimulated PBMC from PRRSv-infected gilts, levels of IFNα were significantly decreased, while IL8 secretion was significantly increased. PRRSv infection altered the secretion of all measured cytokines, with the exception of IFNα, from PBMC after mitogen stimulation, indicating a possible immunomodulatory effect of PRRSv. IFNα, CCL2, and IFNγ in serum, and IFNγ in supernatants of PMA/Iono stimulated PBMC were significantly associated with viral load in tissues, serum or both. However, only IFNα in supernatants of PRRSv stimulated PBMC was significantly associated with fetal mortality rate. We conclude that of the eight cytokines tested in this study IFNα was the best indicator of viral load and severity of reproductive PRRSv infection
Revista de Indias y Anuario de Estudios Americanos. Visibilidad y uso de la edición electrónica
Una década americanista en lÃnea, 2010, [En lÃnea], Puesto en lÃnea el 25 mayo 2010[EN] In this article we analyze the online visibility and content usage of two Americanist Journals published by CSIC, Revista de Indias and Anuario de Estudios Americanos. The online edition dates back to 2007; contents are comparable in terms of accessible documents, and both Journals are published in Open Access, with a 6-months embargo. We also discuss some methodological issues in terms of the need of a data normalization allowing the measurement of genuine downloads assimilable to document reading. Both Journals registered close to 500,000 normalized downloads along 2008 and 2009, most coming from Latin America and the United States (70%). Data show a high degree of repeated downloads of the same document from the same user (25% of total downloads) and indexation downloads (25% of normalized downloads), and also the lack of correlation between Journal’s visibility (webpage visits) and content usage (document downloads). Access restriction has a negative effect, as evidenced by the low downloading of embargoed documents[ES] En este artÃculo analizamos los datos de visibilidad y uso de las dos revistas de temática americanista editadas por el CSIC, Revista de Indias y Anuario de Estudios Americanos. La edición electrónica de ambas data de 2007, y su contenido en artÃculos accesibles es comparable; ambas se publican en Acceso Abierto (OA) con un embargo de acceso de 6 meses. También analizamos cuestiones metodológicas relativas al análisis de descargas, en el sentido de la necesidad de una normalización de los datos que permita determinar las descargas reales, asimilables a una lectura del documento. Durante los años 2008 y 2009, ambas revistas han recibido cerca de 500.000 descargas normalizadas, que provienen en su mayorÃa de Latinoamérica y Estados Unidos (70%). Los datos muestran el elevado número de descargas repetidas de documentos en periodos cortos de tiempo por el mismo usuario (25% de las totales registradas) y de descargas de indización (25% de las descargas normalizadas), y también la falta de correlación entre visibilidad de las revistas (visitas a páginas web) y uso de los contenidos (descarga de documentos). La restricción de acceso tiene un efecto perjudicial, evidenciado por el bajo nivel de descarga de los documentos sometidos a embargoPeer reviewe
First direct mass-measurement of the two-neutron halo nucleus 6He and improved mass for the four-neutron halo 8He
The first direct mass-measurement of He has been performed with the
TITAN Penning trap mass spectrometer at the ISAC facility. In addition, the
mass of He was determined with improved precision over our previous
measurement. The obtained masses are (He) = 6.018 885 883(57) u and
(He) = 8.033 934 44(11) u. The He value shows a deviation from
the literature of 4. With these new mass values and the previously
measured atomic isotope shifts we obtain charge radii of 2.060(8) fm and
1.959(16) fm for He and He respectively. We present a detailed
comparison to nuclear theory for He, including new hyperspherical harmonics
results. A correlation plot of the point-proton radius with the two-neutron
separation energy demonstrates clearly the importance of three-nucleon forces.Comment: 4 pages, 2 figure
First Penning-trap mass measurement in the millisecond half-life range: the exotic halo nucleus 11Li
In this letter, we report a new mass for Li using the trapping
experiment TITAN at TRIUMF's ISAC facility. This is by far the shortest-lived
nuclide, , for which a mass measurement has ever been
performed with a Penning trap. Combined with our mass measurements of
Li we derive a new two-neutron separation energy of 369.15(65) keV: a
factor of seven more precise than the best previous value. This new value is a
critical ingredient for the determination of the halo charge radius from
isotope-shift measurements. We also report results from state-of-the-art
atomic-physics calculations using the new mass and extract a new charge radius
for Li. This result is a remarkable confluence of nuclear and atomic
physics.Comment: Formatted for submission to PR
Breakdown of the Isobaric Multiplet Mass Equation (IMME) at A=33, T=3/2
Mass measurements on Ar were performed using the Penning trap mass spectrometer ISOLTRAP and a newly constructed linear Paul trap. This arrangement allowed for the first time to extend Penning trap mass measurements to nuclides with half-lives below one second (Ar: T =174 ms). A mass accuracy of about ( keV) was achieved for all investigated nuclides. The isobaric multiplet mass equation (IMME) was checked for the , quartet and found to be inconsistent with the generally accepted quadratic form
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