4,151 research outputs found
Proposal of a phase-shift fiber Bragg grating as an optical differentiator and an optical integrator simultaneously
We show analytically and numerically that a practically realizable phase-shift fiber Bragg grating (PS-FBG) can function as a temporal first-order optical differentiator and a temporal first-order optical integrator at the same time. The PS-FBG working in reflection implements the differentiation and working in transmission implements the integration. We provide both the generalized conditions for a PS-FBG functioning as a first-order optical differentiator and a first-order optical integrator. The proposed PS-FBG can perform the time differential and integral of the complex envelope of an arbitrary input optical signal with high accuracy, respectively
Quantification of the influence of drugs on zebrafish larvae swimming kinematics and energetics
The use of zebrafish larvae has aroused wide interest in the medical field for its potential role in the development of new therapies. The larvae grow extremely quickly and the embryos are nearly transparent which allows easy examination of its internal structures using fluorescent imaging techniques. Medical treatment of zebrafish larvae can directly influence its swimming behaviours. These behaviour changes are related to functional changes of central nervous system and transformations of the zebrafish body such as muscle mechanical power and force variation, which cannot be measured directly by pure experiment observation. To quantify the influence of drugs on zebrafish larvae swimming behaviours and energetics, we have developed a novel methodology to exploit intravital changes based on observed zebrafish locomotion. Specifically, by using an in-house MATLAB code to process the recorded live zebrafish swimming video, the kinematic locomotion equation of a 3D zebrafish larvae was obtained, and a customised Computational Fluid Dynamics tool was used to solve the fluid flow around the fish model which was geometrically the same as experimentally tested zebrafish. The developed methodology was firstly verified against experiment, and further applied to quantify the fish internal body force, torque and power consumption associated with a group of normal zebrafish larvae vs. those immersed in acetic acid and two neuroactive drugs. As indicated by our results, zebrafish larvae immersed in 0.01% acetic acid display approximately 30% higher hydrodynamic power and 10% higher cost of transport than control group. In addition, 500 μM diphenylhydantoin significantly decreases the locomotion activity for approximately 50% lower hydrodynamic power, whereas 100 mg/L yohimbine has not caused any significant influences on 5 dpf zebrafish larvae locomotion. The approach has potential to evaluate the influence of drugs on the aquatic animal’s behaviour changes and thus support the development of new analgesic and neuroactive drugs
Nucleosome Structure Incorporated Histone Acetylation Site Prediction in \u3ci\u3eArabidopsis thaliana\u3c/i\u3e
BackgroundAcetylation is a crucial post-translational modification for histones, and plays a key role in gene expression regulation. Due to limited data and lack of a clear acetylation consensus sequence, a few researches have focused on prediction of lysine acetylation sites. Several systematic prediction studies have been conducted for human and yeast, but less for Arabidopsis thaliana. ResultsConcerning the insufficient observation on acetylation site, we analyzed contributions of the peptide-alignment-based distance definition and 3D structure factors in acetylation prediction. We found that traditional structure contributes little to acetylation site prediction. Identified acetylation sites of histones in Arabidopsis thaliana are conserved and cross predictable with that of human by peptide based methods. However, the predicted specificity is overestimated, because of the existence of non-observed acetylable site. Here, by performing a complete exploration on the factors that affect the acetylability of lysines in histones, we focused on the relative position of lysine at nucleosome level, and defined a new structure feature to promote the performance in predicting the acetylability of all the histone lysines in A. thaliana. ConclusionWe found a new spacial correlated acetylation factor, and defined a ε-N spacial location based feature, which contains five core spacial ellipsoid wired areas. By incorporating the new feature, the performance of predicting the acetylability of all the histone lysines in A. Thaliana was promoted, in which the previous mispredicted acetylable lysines were corrected by comparing to the peptide-based prediction
Gapless topological Fulde-Ferrell superfluidity in spin-orbit coupled Fermi gases
Topological superfluids usually refer to a superfluid state which is gapped
in the bulk but metallic at the boundary. Here we report that a gapless,
topologically non-trivial superfluid with inhomogeneous Fulde-Ferrell pairing
order parameter can emerge in a two-dimensional spin-orbit coupled Fermi gas,
in the presence of both in-plane and out-of-plane Zeeman fields. The
Fulde-Ferrell pairing - induced by the spin-orbit coupling and in-plane Zeeman
field - is responsible for this gapless feature. This exotic superfluid has a
significant Berezinskii-Kosterlitz-Thouless (BKT) transition temperature and
has robust Majorana edge modes against disorder owing to its topological
nature.Comment: 5 pages, 5 figures; add the results on the critical BKT temperature
and superfluid density, as well as the discussion on the robustness of the
chiral edge states against disorde
Anomalous second-order skin modes in Floquet non-Hermitian systems
The non-Hermitian skin effect under open boundary conditions is widely
believed to originate from the intrinsic spectral topology under periodic
boundary conditions. If the eigenspectra under periodic boundary conditions
have no spectral windings (e.g., piecewise arcs) or a finite area on the
complex plane, there will be no non-Hermitian skin effect with open boundaries.
In this article, we demonstrate another scenario beyond this perception by
introducing a two-dimensional periodically driven model. The effective Floquet
Hamiltonian lacks intrinsic spectral topology and is proportional to the
identity matrix (representing a single point on the complex plane) under
periodic boundary conditions. Yet, the Floquet Hamiltonian exhibits a
second-order skin effect that is robust against perturbations and disorder
under open boundary conditions. We further reveal the dynamical origin of these
second-order skin modes and illustrate that they are characterized by a
dynamical topological invariant of the full time-evolution operator.Comment: 10 pages, 4 figure
- …