125,791 research outputs found
Virtual Compton Scattering from the Proton and the Properties of Nucleon Excited States
We calculate the contributions to the generalized polarizabilities of
the proton in virtual Compton scattering. The following nucleon excitations are
included: , , , , ,
and . The relationship between nucleon
structure parameters, properties and the generalized polarizabilities of
the proton is illustrated.Comment: 13 pages of text (Latex) plus 4 figures (as uuencoded Z-compressed
.tar file created by csh script uufiles
Low-noise top-gate graphene transistors
We report results of experimental investigation of the low-frequency noise in
the top-gate graphene transistors. The back-gate graphene devices were modified
via addition of the top gate separated by 20 nm of HfO2 from the single-layer
graphene channels. The measurements revealed low flicker noise levels with the
normalized noise spectral density close to 1/f (f is the frequency) and Hooge
parameter below 2 x 10^-3. The analysis of the noise spectral density
dependence on the top and bottom gate biases helped us to elucidate the noise
sources in these devices and develop a strategy for the electronic noise
reduction. The obtained results are important for all proposed graphene
applications in electronics and sensors.Comment: 9 pages, 4 figure
Multi-subband effect in spin dephasing in semiconductor quantum wells
Multi-subband effect on spin precession and spin dephasing in -type GaAs
quantum wells is studied with electron-electron and electron-phonon scattering
explicitly included. The effects of temperature, well width and applied
electric field (in hot-electron regime) on the spin kinetics are thoroughly
investigated. It is shown that due to the strong inter-subband scattering, the
spin procession and the spin dephasing rate of electrons in different subbands
are almost identical despite the large difference in the D'yakonov-Perel' (DP)
terms of different subbands. It is also shown that for quantum wells with small
well width at temperatures where only the lowest subband is occupied, the spin
dephasing time increases with the temperature as well as the applied in-plane
electric field until the contribution from the second subband is no longer
negligible. For wide quantum wells the spin dephasing time tends to decrease
with the temperature and the electric field.Comment: 6 pages, 4 figures in eps forma
K^+ production in baryon-baryon and heavy-ion collisions
Kaon production cross sections in nucleon-nucleon, nucleon-delta and
delta-delta interactions are studied in a boson exchange model. For the latter
two interactions, the exchanged pion can be on-mass shell, only contributions
due to a virtual pion are included via the Peierls method by taking into
account the finite delta width. With these cross sections and also those for
pion-baryon interactions, subthreshold kaon production from heavy ion
collisions is studied in the relativistic transport model.Comment: to appear in Phys. Rev.
Hot-electron effect in spin dephasing in -type GaAs quantum wells
We perform a study of the effect of the high in-plane electric field on the
spin precession and spin dephasing due to the D'yakonov-Perel' mechanism in
-type GaAs (100) quantum wells by constructing and numerically solving the
kinetic Bloch equations. We self-consistently include all of the scattering
such as electron-phonon, electron-non-magnetic impurity as well as the
electron-electron Coulomb scattering in our theory and systematically
investigate how the spin precession and spin dephasing are affected by the high
electric field under various conditions. The hot-electron distribution
functions and the spin correlations are calculated rigorously in our theory. It
is found that the D'yakonov-Perel' term in the electric field provides a
non-vanishing effective magnetic field that alters the spin precession period.
Moreover, spin dephasing is markedly affected by the electric field. The
important contribution of the electron-electron scattering to the spin
dephasing is also discussed.Comment: 11 pages, 11 figures, accepted for publication in Phys. Rev.
Some Properties of Domain Wall Solution in the Randall-Sundrum Model
Properties of the domain wall (kink) solution in the 5 dimensional
Randall-Sundrum model are examined both {\it analytically} and {\it
numerically}. The configuration is derived by the bulk Higgs mechanism. We
focus on 1) the convergence property of the solution, 2) the stableness of the
solution, 3) the non-singular property of the Riemann curvature, 4) the
behaviours of the warp factor and the Higgs field. It is found that the bulk
curvature changes the sign around the surface of the wall. We also present some
{\it exact} solutions for two simple cases: a) the no potential case, b) the
cosmological term dominated case. Both solutions have the (naked) curvature
singularity. We can regard the domain wall solution as a singularity resolution
of the exact solutions.Comment: Typographical error correction for publication. 16 pages, 4 figure
The Measure for the Multiverse and the Probability for Inflation
We investigate the measure problem in the framework of inflationary
cosmology. The measure of the history space is constructed and applied to
inflation models. Using this measure, it is shown that the probability for the
generalized single field slow roll inflation to last for e-folds is
suppressed by a factor , and the probability for the generalized
-field slow roll inflation is suppressed by a much larger factor
. Some non-inflationary models such as the cyclic model do not
suffer from this difficulty.Comment: 16 page
Manejo da micofauna associada a sementes BRS Manicoré submetidas a diferentes métodos de controle.
Objetivou-se avaliar diferentes mĂ©todos de controle quanto ao seu efeito sobre a micofauna associada a sementes hĂbridas BRS ManicorĂ©.Anais do SEMINĂRIO DE AGROECOLOGIA DA AMĂRICA DO SUL, 1; SEMINĂRIO DE AGROECOLOGIA DE MATO GROSSO DO SUL, 5.; ENCONTRO DE PRODUTORES AGROECOLOGICOS DE MATO GROSSO DO SUL, 4.; SEMINĂRIO DE SISTEMAS AGROFLORESTAIS EM BASES AGROECOLOGICA DE MATO GROSSO DO SUL, 1., 2014, Dourados
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Evolutionary bi-stability in pathogen transmission mode
Many pathogens transmit to new hosts by both infection (horizontal transmission) and transfer to the
infected host's offspring (vertical transmission). These two transmission modes require speciÂźc adap-
tations of the pathogen that can be mutually exclusive, resulting in a trade-off between horizontal and
vertical transmission. We show that in mathematical models such trade-offs can lead to the simultaneous
existence of two evolutionary stable states (evolutionary bi-stability) of allocation of resources to the two
modes of transmission. We also show that jumping between evolutionary stable states can be induced by
gradual environmental changes. Using quantitative PCR-based estimates of abundance in seed and vege-
tative parts, we show that the pathogen of wheat, Phaeosphaeria nodorum, has jumped between two
distinct states of transmission mode twice in the past 160 years, which, based on published evidence,
we interpret as adaptation to environmental change. The Âźnding of evolutionary bi-stability has impli-
cations for human, animal and other plant diseases. An ill-judged change in a disease control
programme could cause the pathogen to evolve a new, and possibly more damaging, combination of
transmission modes. Similarly, environmental changes can shift the balance between transmission
modes, with adverse effects on human, animal and plant health
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