39,269 research outputs found
Pinned modes in lossy lattices with local gain and nonlinearity
We introduce a discrete linear lossy system with an embedded "hot spot" (HS),
i.e., a site carrying linear gain and complex cubic nonlinearity. The system
can be used to model an array of optical or plasmonic waveguides, where
selective excitation of particular cores is possible. Localized modes pinned to
the HS are constructed in an implicit analytical form, and their stability is
investigated numerically. Stability regions for the modes are obtained in the
parameter space of the linear gain and cubic gain/loss. An essential result is
that the interaction of the unsaturated cubic gain and self-defocusing
nonlinearity can produce stable modes, although they may be destabilized by
finite amplitude perturbations. On the other hand, the interplay of the cubic
loss and self-defocusing gives rise to a bistability.Comment: Phys. Rev. E (in press
On the Implementation of Efficient Channel Filters for Wideband Receivers by Optimizing Common Subexpression Elimination Methods
No abstract availabl
Growth of graphene on 6H-SiC by molecular dynamics simulation
Classical molecular-dynamics simulations were carried out to study epitaxial
growth of graphene on 6H-SiC(0001) substrate. It was found that there exists a
threshold annealing temperature above which we observe formation of graphitic
structure on the substrate. To check the sensitivity of the simulation results,
we tested two empirical potentials and evaluated their reliability by the
calculated characteristics of graphene, its carbon-carbon bond-length, pair
correlation function, and binding energy.Comment: 7 pages, 5 figure
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Coronavirus mRNA synthesis: identification of novel transcription initiation signals which are differentially regulated by different leader sequences.
The mRNA synthesis of mouse hepatitis virus (MHV) has been proposed to be the result of interaction between the leader RNA and the intergenic sites. Previously, we have identified a transcription initiation site (for mRNA 2-1), which is more efficiently transcribed by viruses containing two copies of UCUAA sequence in the leader RNA than by those with three copies. In this study, we have identified several sites which are regulated in the opposite way, namely, they are efficiently transcribed by the leader RNA with three UCUAA copies but not by those with two copies. These sites were characterized by primer extension and amplification by polymerase chain reaction. One of these sites is in the gene 3 region of a recombinant virus between A59 and JHM strains of MHV. Another is in the gene 2 region of MHV-1 strain. Both of these sites have a sequence similar to but different from the consensus transcription initiation signal (UCUAAUCUAUC and UUUAAUCUU, as opposed to UCUAAAC). These two novel intergenic sequences are not present in the genome of the JHM strain, consistent with the absence of these mRNAs in the JHM-infected cells. The discovery of this type of transcription initiation site provides additional evidence for the importance of the leader RNA in the transcription initiation of MHV mRNAs
Interference and the lossless lossy beam splitter
By directing the input light into a particular mode it is possible to obtain
as output all of the input light for a beam splitter that is 50% absorbing.
This effect is also responsible for nonlinear quantum interference when two
photons are incident on the beam splitter.Comment: 10 pages, 2 figures, to appear in J. Mod. Op
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