4,128 research outputs found
Characterization of self-injected electron beams from LWFA experiments at SPARC_LAB
The plasma-based acceleration is an encouraging technique to overcome the
limits of the accelerating gradient in the conventional RF acceleration. A
plasma accelerator is able to provide accelerating fields up to hundreds of
, paving the way to accelerate particles to several MeV over a short
distance (below the millimetre range). Here the characteristics of preliminary
electron beams obtained with the self-injection mechanism produced with the
FLAME high-power laser at the SPARC_LAB test facility are shown. In detail,
with an energy laser on focus of and a pulse temporal length (FWHM) of
, we obtained an electron plasma density due to laser ionization of
about , electron energy up to and beam
charge in the range .Comment: 6 pages, 11 figures, conference EAAC201
Sc substitution for Mg in MgB2: effects on Tc and Kohn anomaly
Here we report synthesis and characterization of Mg_{1-x}Sc_{x}B_{2}
(0.12T_{c}>6 K.
We find that the Sc doping moves the chemical potential through the 2D/3D
electronic topological transition (ETT) in the sigma band where the ``shape
resonance" of interband pairing occurs. In the 3D regime beyond the ETT we
observe a hardening of the E_{2g} Raman mode with a significant line-width
narrowing due to suppression of the Kohn anomaly over the range 0<q<2k_{F}.Comment: 8 pages, 4 EPS figures, to be published in Phys. Rev.
Validation of FEM models based on Carrera Unified Formulation for the parametric characterization of composite metamaterials
Identification of RAPD marker linked to blast resistance gene in a somaclone of rice cultivar Araguaia.
O gene Pi-ar confere resistência para a raça IB-45 de Pyricularia grisea no somaclone derivado de panÃculas imaturas da cultivar de arroz (Oryza sativa) Araguaia. A técnica RAPD foi usada para identificar marcadores ligados a este gene utilizando a análise de misturas segregantes. Inicialmente o DNA do pai doador resistente SC09 e da cultivar Araguaia foram analisados usando primers arbitrários. Dos 240 primers, 203 produziram produtos amplificados. O DNA dos pais e dos bulks resistente e suscetÃvel da população F2 foram testados usando 48 primers que diferenciaram os pais resistente e suscetÃvel. Enquanto oito primers diferenciaram o bulk resistente do suscetÃvel bem como o somaclone SC09 e Araguaia, somente o primer OPC02 ('GTGAGGCGTC') estava fortemente ligado (1,7cM) ao gene de resistência do somaclone SC09
Exchange and correlation near the nucleus in density functional theory
The near nucleus behavior of the exchange-correlation potential in Hohenberg-Kohn-Sham density functional theory is investigated. It is
shown that near the nucleus the linear term of of the spherically
averaged exchange-correlation potential is nonzero, and that
it arises purely from the difference between the kinetic energy density at the
nucleus of the interacting system and the noninteracting Kohn-Sham system. An
analytical expression for the linear term is derived. Similar results for the
exchange and correlation potentials are also
obtained separately. It is further pointed out that the linear term in
arising mainly from is rather small, and
therefore has a nearly quadratic structure near the nucleus.
Implications of the results for the construction of the Kohn-Sham system are
discussed with examples.Comment: 10 page
Exact exchange-correlation potential for a time-dependent two electron system
We obtain an exact solution of the time-dependent Schroedinger equation for a
two-electron system confined to a plane by an isotropic parabolic potential
whose curvature is periodically modulated in time. From this solution we
compute the exact time-dependent exchange correlation potential v_xc which
enters the Kohn-Sham equation of time-dependent density functional theory. Our
exact result provides a benchmark against which various approximate forms for
v_xc can be compared. Finally v_xc is separated in an adiabatic and a pure
dynamical part and it is shown that, for the particular system studied, the
dynamical part is negligible.Comment: 23 pages, 6 figure
Oesophagitis dissecans superficialis as the presenting sign oisolated oesophageal mucous membrane pemphigoid
Functional MR Imaging Correlates of Neuropsychological Impairment in Primary-Progressive Multiple Sclerosis
BACKGROUND AND PURPOSE: Cognitive deficits affect ≤30% of patients with PPMS. We investigated the functional correlates of cognitive network dysfunction in patients with PPMS and their correlation with the extent of structural MR imaging damage. MATERIALS AND METHODS: From 16 right-handed patients with PPMS and 17 matched controls, structural and fMRIs (during the performance of the 2-back task) were acquired. Neuropsychological tests exploring memory, attention, and frontal lobe cognitive domains were administered. T2 LL, NBV, and CC areas were measured. RESULTS: Six patients with PPMS were CI. Structural MR imaging measures did not differ between patients who were CI and those who were CP. Compared with patients who were CI, patients who were CP had increased activations of the left caudate nucleus, PFC, and inferior parietal lobule. Compared with controls and patients who were CP, patients who were CI had increased activations of the SII, cerebellum, and insula. Compared with controls, they also had increased activations of the right precentral gyrus and a reduced recruitment of the left PFC. In patients with PPMS, a decreased composite cognitive score correlated with increased activity of the cerebellum, insula, and SII, as well as decreased PFC activity. T2 LL correlated with decreased PFC recruitment and increased SII recruitment. CONCLUSIONS: In PPMS, an increased recruitment of cognitive-related networks might represent a functional reserve with the potential to limit the severity of cognitive impairment. The accumulation of T2 lesions and the consequent exhaustion of frontal lobe plasticity might contribute to cognitive impairment in PPMS
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