513 research outputs found
Reconfiguration of quantum states in -symmetric quasi-one dimensional lattices
We demonstrate mesoscopic transport through quantum states in quasi-1D
lattices maintaining the combination of parity and time-reversal symmetries by
controlling energy gain and loss. We investigate the phase diagram of the
non-Hermitian system where transitions take place between unbroken and broken
-symmetric phases via exceptional points. Quantum transport in
the lattice is measured only in the unbroken phases in the energy band-but not
in the broken phases. The broken phase allows for spontaneous symmetry-broken
states where the cross-stitch lattice is separated into two identical single
lattices corresponding to conditionally degenerate eigenstates. These
degeneracies show a lift-up in the complex energy plane, caused by the
non-Hermiticity with -symmetry.Comment: 12 pages, 7 figure
Antiresonance induced by symmetry-broken contacts in quasi-one-dimensional lattices
We report the effect of symmetry-broken contacts on quantum transport in
quasi-one-dimensional lattices. In contrast to 1D chains, transport in
quasi-one-dimensional lattices, which are made up of a finite number of 1D
chain layers, is strongly influenced by contacts. Contact symmetry depends on
whether the contacts maintain or break the parity symmetry between the layers.
With balanced on-site potential, a flat band can be detected by asymmetric
contacts, but not by symmetric contacts. In the case of asymmetric contacts
with imbalanced on-site potential, transmission is suppressed at certain
energies. We elucidate these energies of transmission suppression related to
antiresonance using reduced lattice models and Feynman paths. These results
provide a nondestructive measurement of flat band energy which it is difficult
to detect.Comment: 8 pages, 5 figure
Flat-band localization and self-collimation of light in photonic crystals
We investigate the optical properties of a photonic crystal composed of a
quasi-one-dimensional flat-band lattice array through finite-difference
time-domain simulations. The photonic bands contain flat bands (FBs) at
specific frequencies, which correspond to compact localized states as a
consequence of destructive interference. The FBs are shown to be nondispersive
along the line, but dispersive along the
line. The FB localization of light in a single direction
only results in a self-collimation of light propagation throughout the photonic
crystal at the FB frequency.Comment: 18 single-column pages, 7 figures including graphical to
Emergent localized states at the interface of a twofold -symmetric lattice
We consider the role of non-triviality resulting from a non-Hermitian
Hamiltonian that conserves twofold PT-symmetry assembled by interconnections
between a PT-symmetric lattice and its time reversal partner. Twofold
PT-symmetry in the lattice produces additional surface exceptional points that
play the role of new critical points, along with the bulk exceptional point. We
show that there are two distinct regimes possessing symmetry-protected
localized states, of which localization lengths are robust against external
gain and loss. The states are demonstrated by numerical calculation of a
quasi-1D ladder lattice and a 2D bilayered square lattice.Comment: 10 pages, 7 figure
Non-orientability induced PT phase transition in Moebius ladder lattices
We study parity-time (PT) phase transitions in the energy spectra of ladder
lattices caused by the interplay between non-orientability and non-Hermitian PT
symmetry. The energy spectra show level crossings in circular ladder lattices
with increasing on-site energy gain-loss because of the orientability of a
normal strip. However, the energy levels show PT phase transitions in
PT-symmetric Moebius ladder lattices due to the non-orientability of a Moebius
strip. In order to understand the level crossings of PT symmetric phases, we
generalize the rotational transformation using a complex rotation angle. We
also study the modification of resonant tunneling induced by a sharply twisted
interface in PT-symmetric ladder lattices. Finally, we find that the perfect
transmissions at the zero energy are recovered at the exceptional points of the
PT-symmetric system due to the self-orthogonal states.Comment: 9 pages, 6 figure
Removal of Pb and Cu ions from aqueous solution by Mn3O4-coated activated carbon
Mn3O4-coated activated carbon (Mn3O4/AC) was prepared by supercritical technique and applied for the removal of Pb and Cu ions from aqueous solution. Kinetic and isotherm data of the adsorption by Mn3O4/AC were compared with those of activated carbon (AC) and pure Mn3O4. Adsorption of metals was adequately described by pseudo-second-order kinetics and Langmuir isotherm models. Maximum adsorption capacities of Pb and Cu ions determined by Langmuir model were enhanced 2.2 and 6.1 times for Pb and Cu ions by Mn3O4 coating onto AC, which might be attributed to reduced resistance of intraparticle diffusion and enhanced surface electrostatic interaction and complexation by Mn3O4
Should HLA-B*5701 Screening Be Performed in Every Ethnic Group before Starting Abacavir?
Human leukocyte antigen allele (HLA)-B*5701 is associated with abacavir hypersensitivity. However, the carriage rate of HLA-B*5701 has rarely been studied in Asians. In 534 Korean patients with human immunodeficiency virus infection, HLA-B*5701 status was determined by polymerase chain reaction with HLA-B*5701-specific primers. No patients had the HLA-B*5701 allele (95% confidence interval, 0%-0.7%). This explains the paucity of immunologically confirmed cases of abacavir hypersensitivity in Koreans.Saag M, 2008, CLIN INFECT DIS, V46, P1111, DOI 10.1086/529382Mallal S, 2008, NEW ENGL J MED, V358, P568*PAN ANT GUID AD A, 2008, GUID US ANT AG HIV 1Waters LJ, 2007, AIDS, V21, P2533Sun HY, 2007, J ANTIMICROB CHEMOTH, V60, P599, DOI 10.1093/jac/dkm243Rauch A, 2006, CLIN INFECT DIS, V43, P99Phillips EJ, 2006, CLIN INFECT DIS, V43, P103Martin AM, 2005, TISSUE ANTIGENS, V65, P571, DOI 10.1111/j.1399-0039.2005.00401.xLee KW, 2005, TISSUE ANTIGENS, V65, P437, DOI 10.1111/j.1399-0039.2005.00386.xMiddleton D, 2004, TISSUE ANTIGENS, V63, P555Phillips EJ, 2002, AIDS, V16, P2223Saito S, 2000, TISSUE ANTIGENS, V56, P522Park MH, 1999, TISSUE ANTIGENS, V53, P3861
Fabrication of pyramidal probes with various periodic patterns and a single nanopore
The nanometer-scale patterned pyramidal probe with an electron beam-induced nanopore on the pyramid apex is an excellent candidate for an optical biosensor. The nanoapertures surrounded with various periodic groove patterns on the pyramid sides were fabricated using a focused ion beam technique, where the optical characteristics of the fabricated apertures with rectangular, circular, and elliptical groove patterns were investigated. The elliptical groove patterns on the pyramid were designed to maintain an identical distance between the grooves and the apex for the surface waves and, among the three patterns, the authors observed the highest optical transmission from the elliptically patterned pyramidal probe. A 103-fold increase of the transmitted optical intensity was observed after patterning with elliptical grooves, even without an aperture on the pyramid apex. The nanopore on the apex of the pyramid was fabricated using electron beam irradiation and was optically characterized
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