27,571 research outputs found
Impact of delay on HIV-1 dynamics of fighting a virus with another virus
In this paper, we propose a mathematical model for HIV-1 infection with
intracellular delay. The model examines a viral-therapy for controlling
infections through recombining HIV-1 virus with a genetically modified virus.
For this model, the basic reproduction number are identified
and its threshold properties are discussed. When , the
infection-free equilibrium is globally asymptotically stable. When
, becomes unstable and there occurs the
single-infection equilibrium , and and exchange their
stability at the transcritical point . If , where is a positive constant explicitly depending on the model
parameters, is globally asymptotically stable, while when , loses its stability to the double-infection equilibrium .
There exist a constant such that is asymptotically stable if
, and and exchange their stability at the
transcritical point . We use one numerical example to
determine the largest range of for the local stability of
and existence of Hopf bifurcation. Some simulations are performed to support
the theoretical results. These results show that the delay plays an important
role in determining the dynamic behaviour of the system. In the normal range of
values, the delay may change the dynamic behaviour quantitatively, such as
greatly reducing the amplitudes of oscillations, or even qualitatively changes
the dynamical behaviour such as revoking oscillating solutions to equilibrium
solutions. This suggests that the delay is a very important fact which should
not be missed in HIV-1 modelling
Polarization screening and induced carrier density at the interface of LaAlO overlayer on SrTiO (001)
We investigate the role of lattice polarization in determination of induced
carrier density at the -type interface of LaAlO overlayer on SrTiO
(001) by carrying out density-functional-theory calculations. When no oxygen
vacancy or defect is present, the magnitude of polarization screening in the
LaAlO layers is found to be correlated with the carrier charge induced at
the interface. For the interfaces with a few LaAlO layers, the induced
charge carrier is compensated by the electrostatic screening and consequently
its density remains far less than 0.5 electrons per unit cell.Comment: 4 pages, 4 figure
Parity violation in pre-inflationary bounce
The power suppression at largest scale in the CMB TT powerspectrum might
imply the occurrence of a pre-inflationary bounce. We calculate the circularly
polarized gravitational wave, leaded by the gravitational Chern-Simons term
which universally appears in particle physics and string theory, in an
inflationary background with the pre-inflationary bounce. The circularly
polarized gravitational wave will induce TB and EB correlations at CMB last
scatting surface. We find that although the BB powerspectrum at largest scale
is also suppressed, the TB and EB powerspectra at corresponding scales may be
enhanced.Comment: 15 pages, 4 figures,the final versio
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