576 research outputs found
Finite elements modelling of scattering problems for flexural waves in thin plates: Application to elliptic invisibility cloaks, rotators and the mirage effect
We propose a finite elements algorithm to solve a fourth order partial
differential equation governing the propagation of time-harmonic bending waves
in thin elastic plates. Specially designed perfectly matched layers are
implemented to deal with the infinite extent of the plates. These are deduced
from a geometric transform in the biharmonic equation. To numerically
illustrate the power of elastodynamic transformations, we analyse the elastic
response of an elliptic invisibility cloak surrounding a clamped obstacle in
the presence of a cylindrical excitation i.e. a concentrated point force.
Elliptic cloaking for flexural waves involves a density and an orthotropic
Young's modulus which depend on the radial and azimuthal positions, as deduced
from a coordinates transformation for circular cloaks in the spirit of Pendry
et al. [Science {\bf 312}, 1780 (2006)], but with a further stretch of a
coordinate axis. We find that a wave radiated by a concentrated point force
located a couple of wavelengths away from the cloak is almost unperturbed in
magnitude and in phase. However, when the point force lies within the coating,
it seems to radiate from a shifted location. Finally, we emphasize the
versatility of transformation elastodynamics with the design of an elliptic
cloak which rotates the polarization of a flexural wave within its core.Comment: 14 pages, 5 figure
Qualitative aspects of the entanglement in the three-level model with photonic crystals
This communication is an enquiry into the circumstances under which
concurrence and phase entropy methods can give an answer to the question of
quantum entanglement in the composite state when the photonic band gap is
exhibited by the presence of photonic crystals in a three-level system. An
analytic approach is proposed for any three-level system in the presence of
photonic band gap. Using this analytic solution, we conclusively calculate the
concurrence and phase entropy, focusing particularly on the entanglement
phenomena. Specifically, we use concurrence as a measure of entanglement for
dipole emitters situated in the thin slab region between two semi-infinite
one-dimensionally periodic photonic crystals, a situation reminiscent of planar
cavity laser structures. One feature of the regime considered here is that
closed-form evaluation of the time evolution may be carried out in the presence
of the detuning and the photonic band gap, which provides insight into the
difference in the nature of the concurrence function for atom-field coupling,
mode frequency and different cavity parameters. We demonstrate how fluctuations
in the phase and number entropies effected by the presence of the
photonic-band-gap. The outcomes are illustrated with numerical simulations
applied to GaAs. Finally, we relate the obtained results to instances of any
three-level system for which the entanglement cost can be calculated. Potential
experimental observations in solid-state systems are discussed and found to be
promising.Comment: 28 pages, 10 figures: Accepted in Applied Physics B: Laser and Optic
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Anti-V3 Monoclonal Antibodies Display Broad Neutralizing Activities against Multiple HIV-1 Subtypes
Background: The V3 loop of the HIV-1 envelope (Env) glycoprotein gp120 was identified as the βprincipal neutralizing domainβ of HIV-1, but has been considered too variable to serve as a neutralizing antibody (Ab) target. Structural and immunochemical data suggest, however, that V3 contains conserved elements which explain its role in binding to virus co-receptors despite its sequence variability. Despite this evidence of V3 conservation, the ability of anti-V3 Abs to neutralize a significant proportion of HIV-1 isolates from different subtypes (clades) has remained controversial. Methods: HIV-1 neutralization experiments were conducted in two independent laboratories to test human anti-V3 monoclonal Abs (mAbs) against pseudoviruses (psVs) expressing Envs of diverse HIV-1 subtypes from subjects with acute and chronic infections. Neutralization was defined by 50% inhibitory concentrations (IC50), and was statistically assessed based on the area under the neutralization titration curves (AUC). Results: Using AUC analyses, statistically significant neutralization was observed by β₯1 anti-V3 mAbs against 56/98 (57%) psVs expressing Envs of diverse subtypes, including subtypes A, AG, B, C and D. Even when the 10 Tier 1 psVs tested were excluded from the analysis, significant neutralization was detected by β₯1 anti-V3 mAbs against 46/88 (52%) psVs from diverse HIV-1 subtypes. Furthermore, 9/24 (37.5%) Tier 2 viruses from the clade B and C standard reference panels were neutralized by β₯1 anti-V3 mAbs. Each anti-V3 mAb tested was able to neutralize 28β42% of the psVs tested. By IC50 criteria, 40/98 (41%) psVs were neutralized by β₯1 anti-V3 mAbs. Conclusions: Using standard and new statistical methods of data analysis, 6/7 anti-V3 human mAbs displayed cross-clade neutralizing activity and revealed that a significant proportion of viruses can be neutralized by anti-V3 Abs. The new statistical method for analysis of neutralization data provides many advantages to previously used analyses
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