2,921 research outputs found
Quasinormal-mode modeling and design in nonlinear nano-optics
Based on quasinormal-mode theory, we propose a novel approach enabling a deep
analytical insight into the multi-parameter design and optimization of
nonlinear photonic structures at subwavelength scale. A key distinction of our
method from previous formulations relying on multipolar Mie-scattering
expansions is that it directly exploits the natural resonant modes of the
nanostructures, which provide the field enhancement to achieve significant
nonlinear efficiency. Thanks to closed-form expression for the nonlinear
overlap integral between the interacting modes, we illustrate the potential of
our method with a two-order-of-magnitude boost of second harmonic generation in
a semiconductor nanostructure, by engineering both the sign of at
subwavelength scale and the structure of the pump beam
Memory effects in a Markov chain dephasing channel
We study a dephasing channel with memory, modelled by a Markov chain. We show
that even weak memory effects have a detrimental impact on the performance of
quantum error correcting schemes designed for uncorrelated errors. We also
discuss an alternative scheme that takes advantage of memory effects to protect
quantum information.Comment: 5 pages, 1 figure, NIC@QS proceeding
Impaired ATP synthase assembly associated with a mutation in the human ATP synthase subunit 6 gene
Mutations in human mitochondrial DNA are a well recognized cause of disease. A mutation at nucleotide position 8993 of human mitochondrial DNA, located within the gene for ATP synthase subunit 6, is associated with the neurological muscle weakness, ataxia, and retinitis pigmentosa (NARP) syndrome. To enable analysis of this mutation in control nuclear backgrounds, two different cell lines were transformed with mitochondria carrying NARP mutant mitochondrial DNA. Transformant cell lines had decreased ATP synthesis capacity, and many also had abnormally high levels of two ATP synthase sub-complexes, one of which was F1-ATPase. A combination of metabolic labeling and immunoblotting experiments indicated that assembly of ATP synthase was slowed and that the assembled holoenzyme was unstable in cells carrying NARP mutant mitochondrial DNA compared with control cells. These findings indicate that altered assembly and stability of ATP synthase are underlying molecular defects associated with the NARP mutation in subunit 6 of ATP synthase, yet intrinsic enzyme activity is also compromised
Fungal solid state fermentation on agro-industrial wastes for acid wastewater decolourization in a continuous flow packed-bed bioreactor
This study was aimed at developing a process of solid state fermentation (SSF) with the fungi Pleurotus ostreatus and Trametes versicolor on apple processing residues for wastewater decolorization. Both fungi were able to colonize apple residues without any addition of nutrients, material support or water. P. ostreatus produced the highest levels of laccases (up to 9 U g-1 of dry matter) and xylanases (up to 80 U g-1 of dry matter). A repeated batch decolorization experiment was set up with apple residues colonized by P. ostreatus, achieving 50% decolorization and 100% detoxification after 24 h, and, adding fresh wastewater every 24 h, a constant decolorization of 50% was measured for at least 1 month. A continuous decolorization experiment was set up by a packed-bed reactor based on colonized apple residues achieving a performance of 100 mg dye L-1 day-1 at a retention time of 50
Quaternionic eigenvalue problem
We discuss the (right) eigenvalue equation for , and
linear quaternionic operators. The possibility to introduce an
isomorphism between these operators and real/complex matrices allows to
translate the quaternionic problem into an {\em equivalent} real or complex
counterpart. Interesting applications are found in solving differential
equations within quaternionic formulations of quantum mechanics.Comment: 13 pages, AMS-Te
Right eigenvalue equation in quaternionic quantum mechanics
We study the right eigenvalue equation for quaternionic and complex linear
matrix operators defined in n-dimensional quaternionic vector spaces. For
quaternionic linear operators the eigenvalue spectrum consists of n complex
values. For these operators we give a necessary and sufficient condition for
the diagonalization of their quaternionic matrix representations. Our
discussion is also extended to complex linear operators, whose spectrum is
characterized by 2n complex eigenvalues. We show that a consistent analysis of
the eigenvalue problem for complex linear operators requires the choice of a
complex geometry in defining inner products. Finally, we introduce some
examples of the left eigenvalue equations and highlight the main difficulties
in their solution.Comment: 24 pages, AMS-Te
Photoelastic coupling in gallium arsenide optomechanical disk resonators
We analyze the magnitude of the radiation pressure and electrostrictive
stresses exerted by light confined inside GaAs semiconductor WGM optomechanical
disk resonators, through analytical and numerical means, and find the
electrostrictive force to be of prime importance. We investigate the geometric
and photoelastic optomechanical coupling resulting respectively from the
deformation of the disk boundary and from the strain-induced refractive index
changes in the material, for various mechanical modes of the disks.
Photoelastic optomechanical coupling is shown to be a predominant coupling
mechanism for certain disk dimensions and mechanical modes, leading to total
coupling g and g reaching respectively 3 THz/nm and 4 MHz. Finally,
we point towards ways to maximize the photoelastic coupling in GaAs disk
resonators, and we provide some upper bounds for its value in various
geometries
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