130 research outputs found
Mapping of mutation-sensitive sites in protein-like chains
In this work we have studied, with the help of a simple on-lattice model, the
distribution pattern of sites sensitive to point mutations ('hot' sites) in
protein-like chains. It has been found that this pattern depends on the
regularity of the matrix that rules the interaction between different kinds of
residues. If the interaction matrix is dominated by the hydrophobic effect
(Miyazawa Jernigan like matrix), this distribution is very simple - all the
'hot' sites can be found at the positions with maximum number of closest
nearest neighbors (bulk).
If random or nonlinear corrections are added to such an interaction matrix
the distribution pattern changes. The rising of collective effects allows the
'hot' sites to be found in places with smaller number of nearest neighbors
(surface) while the general trend of the 'hot' sites to fall into a bulk part
of a conformation still holds.Comment: 15 pages, 6 figure
Resonant THz sensor for paper quality monitoring using THz fiber Bragg gratings
We report fabrication of THz fiber Bragg gratings (TFBG) using CO2 laser
inscription on subwavelength step-index polymer fibers. A fiber Bragg grating
with 48 periods features a ~4 GHz-wide stop band and ~15 dB transmission loss
in the middle of a stop band. The potential of such gratings in design of
resonant sensor for monitoring of paper quality is demonstrated. Experimental
spectral sensitivity of the TFBG-based paper thickness sensor was found to be ~
-0.67 GHz / 10 um. A 3D electromagnetic model of a Bragg grating was used to
explain experimental findings
Low-Loss THz Waveguide Bragg Grating using a Two-Wire Waveguide and a Paper Grating
We propose a novel kind of the low-loss THz Waveguide Bragg Grating (TWBG)
fabricated using plasmonic two-wire waveguide and a micromachined paper grating
for potential applications in THz communications. Two TWBGs were fabricated
with different periods and lengths. Transmission spectra of these TWBGs show 17
dB loss and 14 dB loss in the middle of their respective stop bands at 0.637
THz and 0.369 THz. Insertion loss of 1-4 dB in the whole 0.1-0.7 THz region was
also measured. Finally, TWBG modal dispersion relation, modal loss and field
distributions were studied numerically, and low-loss, high coupling efficiency
operation of TWBGs was confirmed
Interferometric fiber-optic bending / nano-displacement sensor using plastic dual-core fiber
We demonstrate an interferometric fiber-optic bending/micro-displacement
sensor based on a plastic dual-core fiber with one end coated with a silver
mirror. The two fiber cores are first excited with the same laser beam, the
light in each core is then back-reflected at the mirror-coated fiber-end, and,
finally, the light from the two cores is made to interfere at the coupling end.
Bending of the fiber leads to shifting interference fringes that can be
interrogated with a slit and a single photodetector. We find experimentally
that the resolution of our bending sensor is ~3x10-4 m-1 for sensing of bending
curvature, as well as ~70 nm for sensing of displacement of the fiber tip. We
demonstrate operation of our sensor using two examples. One is weighting of the
individual micro-crystals of salt, while the other one is monitoring dynamics
of isopropanol evaporation
Adaptive design of nano-scale dielectric structures for photonics
Using adaptive algorithms, the design of nano-scale dielectric structures for
photonic applications is explored. Widths of dielectric layers in a linear
array are adjusted to match target responses of optical transmission as a
function of energy. Two complementary approaches are discussed. The first
approach uses adaptive local random updates and progressively adjusts
individual dielectric layer widths. The second approach is based on global
updating functions in which large subgroups of layers are adjusted
simultaneously. Both schemes are applied to obtain specific target responses of
the transmission function within selected energy windows, such as discontinuous
cut-off or power-law decay filters close to a photonic band edge. These
adaptive algorithms are found to be effective tools in the custom design of
nano-scale photonic dielectric structures.Comment: 4 pages Revtex, 4 embedded EPS figure
Vortex families near a spectral edge in the Gross-Pitaevskii equation with a two-dimensional periodic potential
We examine numerically vortex families near band edges of the Bloch wave
spectrum in the Gross--Pitaevskii equation with a two-dimensional periodic
potential and in the discrete nonlinear Schroedinger equation. We show that
besides vortex families that terminate at a small distance from the band edges
via fold bifurcations there exist vortex families that are continued all way to
the band edges.Comment: 12 pages, 8 figure
- …