873 research outputs found
Some remarks on the spectral functions of the Abelian Higgs Model
We consider the unitary Abelian Higgs model and investigate its spectral
functions at one-loop order. This analysis allows to disentangle what is
physical and what is not at the level of the elementary particle propagators,
in conjunction with the Nielsen identities. We highlight the role of the
tadpole graphs and the gauge choices to get sensible results. We also introduce
an Abelian Curci-Ferrari action coupled to a scalar field to model a massive
photon which, like the non-Abelian Curci-Ferarri model, is left invariant by a
modified non-nilpotent BRST symmetry. We clearly illustrate its non-unitary
nature directly from the spectral function viewpoint. This provides a
functional analogue of the Ojima observation in the canonical formalism: there
are ghost states with nonzero norm in the BRST-invariant states of the
Curci-Ferrari model.Comment: 32 pages, 12 figure
Dirac-Surface-State-Dominated Spin to Charge Current Conversion in the Topological Insulator Films at Room Temperature
We report the spin to charge current conversation in an intrinsic topological
insulator (TI) film at room temperature. The spin
currents are generated in a thin layer of permalloy (Py) by two different
processes, spin pumping (SPE) and spin Seebeck effects (SSE). In the first we
use microwave-driven ferromagnetic resonance of the Py film to generate a SPE
spin current that is injected into the TI layer in
direct contact with Py. In the second we use the SSE in the longitudinal
configuration in Py without contamination by the Nernst effect made possible
with a thin NiO layer between the Py and layers.
The spin-to-charge current conversion is attributed to the inverse Edelstein
effect (IEE) made possible by the spin-momentum locking in the electron Fermi
contours due to the Rashba field. The measurements by the two techniques yield
very similar values for the IEE parameter, which are larger than the reported
values in the previous studies on topological insulators.Comment: 18 pages and 7 figure
Purificação e caracterização parcial de uma toxina protéica presente na alga Vidalia obtusiloba (Mertens ex C. Agardh) J. Agardh.
Coleta e armazenagem de algas ; Preparação do extrato total e da fração 0/60 (F0/60); Determinação de proteÃnas; Atividade hemaglutinante; Atividade inibidora de tripsina; Atividade tóxica; Termoestabilidade das atividades hemaglutinantes e tóxicas; Cromatografia de troca iônica em coluna de DEAE-Sephacel; Cromatografia de interação hidrofóbica em coluna de Phenyl-Sepharose CL-4B; Cromatografia de exclusão molecular em coluna de superose -1 2 HR acoplada ao sistema de FPLC; Eletroforese em gel de poliacrilamida.bitstream/item/36601/1/Doc72.pd
Eu2+ spin dynamics in the filled skutterudites EuM4Sb12 (M = Fe, Ru, Os)
We report evidence for a close relation between the thermal activation of the
rattling motion of the filler guest atoms, and inhomogeneous spin dynamics of
the Eu2+ spins. The spin dynamics is probed directly by means of Eu2+ electron
spin resonance (ESR), performed in both X-band (9.4 GHz) and Q-band (34 GHz)
frequencies in the temperature interval 4.2 < T < 300 K. A comparative study
with ESR measurements on the Beta-Eu8Ga16Ge30 clathrate compound is presented.
Our results point to a correlation between the rattling motion and the spin
dynamics which may be relevant for the general understanding of the dynamics of
cage systems.Comment: 6 pages, 4 figures, accepted for publication in Phys. Rev.
Valorization of fine wood dust waste to produce lightweight dense/porous bi-layered ceramic tile
Abstract The Brazilian wood furniture industry generates a significant amount of fine wood dust waste. In this work, a new lightweight dense/porous bi-layered ceramic tile was developed using fine wood dust waste as a substitute for ceramic tile paste by up to 10 wt% in the porous bottom layer. The bi-layered ceramic tile pieces were prepared by double uniaxial pressing and fired at 1235 ºC. The technical properties and sintered microstructure were investigated. The results showed that the fine wood dust waste acted as an effective pore-forming agent. The new bi-layered ceramic tiles showed good technical properties (water absorption=6.16-9.66% and flexural strength=18.10-28.74 MPa). The results also suggested that up to 10 wt% of fine wood dust waste can be valorized in the production of lightweight bi-layered ceramic tiles, which brings together the precepts for sustainable environmental management applications
KamLAND, terrestrial heat sources and neutrino oscillations
We comment on the first indication of geo-neutrino events from KamLAND and on
the prospects for understanding Earth energetics. Practically all models of
terrestrial heat production are consistent with data within the presently
limited statistics, the fully radiogenic model being closer to the observed
value ( geo-events). In a few years KamLAND should collect
sufficient data for a clear evidence of geo-neutrinos, however discrimination
among models requires a detector with the class and size of KamLAND far away
from nuclear reactors. We also remark that the event ratio from Thorium and
Uranium decay chains is well fixed , a constraint that
can be useful for determining neutrino oscillation parameters. We show that a
full spectral analysis, including this constraint, further reduces the
oscillation parameter space compared to an analysis with an energy threshold
.Comment: 12 pages, RevTeX file, 3 ps figures included in the correct order,
corrected some typos and added references. Accepted for publication on Phys.
Lett.
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