Active rejection-enhancement of spectrally adaptive liquid crystal geometric phase vortex coronagraphs

Geometric phase optical elements made of space-variant anisotropic media customarily find their optimal operating conditions when the half-wave retardance condition is fulfilled, which allows imparting polarization-dependent changes to an incident wavefront. In practice, intrinsic limitations of man-made manufacturing process or the finite spectrum of the light source lead to a deviation from the ideal behavior. This implies the implementation of strategies to compensate for the associated efficiency losses. Here we report on how the intrinsic tunable features of self-engineered liquid crystal topological defects can be used to enhance the rejection capabilities of spectrally adaptive vector vortex coronagraphs. We also discuss the extent of which current models enable to design efficient devices

All-optical switching and multistability in photonic structures with liquid crystal defects

We demonstrate that one-dimensional photonic crystals with pure nematic liquid-crystal defects can operate as all-optical switching devices based on optical orientational nonlinearities of liquid crystals. We show that such a periodic structure is responsible for a modulated threshold of the optical Fr\'eedericksz transition in the spectral domain, and this leads to all-optical switching and light-induced multistability. This effect has no quasi-statics electric field analogue, and it results from nonlinear coupling between light and a defect mode.Comment: 4 pages, 3 figure

Dynamics of history-dependent perceptual judgment

Identical physical inputs do not always evoke identical percepts. To investigate the role of stimulus history in tactile perception, we designed a task in which rats had to judge each vibrissal vibration, in a long series, as strong or weak depending on its mean speed. After a low-speed stimulus (trial n − 1), rats were more likely to report the next stimulus (trial n) as strong, and after a high-speed stimulus, they were more likely to report the next stimulus as weak, a repulsive effect that did not depend on choice or reward on trial n − 1. This effect could be tracked over several preceding trials (i.e., n − 2 and earlier) and was characterized by an exponential decay function, reflecting a trial-by-trial incorporation of sensory history. Surprisingly, the influence of trial n − 1 strengthened as the time interval between n − 1 and n grew. Human subjects receiving fingertip vibrations showed these same key findings. We are able to account for the repulsive stimulus history effect, and its detailed time scale, through a single-parameter model, wherein each new stimulus gradually updates the subject’s decision criterion. This model points to mechanisms underlying how the past affects the ongoing subjective experience

Verdier specialization via weak factorization

Let X in V be a closed embedding, with V - X nonsingular. We define a constructible function on X, agreeing with Verdier's specialization of the constant function 1 when X is the zero-locus of a function on V. Our definition is given in terms of an embedded resolution of X; the independence on the choice of resolution is obtained as a consequence of the weak factorization theorem of Abramovich et al. The main property of the specialization function is a compatibility with the specialization of the Chern class of the complement V-X. With the definition adopted here, this is an easy consequence of standard intersection theory. It recovers Verdier's result when X is the zero-locus of a function on V. Our definition has a straightforward counterpart in a motivic group. The specialization function and the corresponding Chern class and motivic aspect all have natural `monodromy' decompositions, for for any X in V as above. The definition also yields an expression for Kai Behrend's constructible function when applied to (the singularity subscheme of) the zero-locus of a function on V.Comment: Minor revision. To appear in Arkiv f\"or Matemati

Depletion of WFS1 compromises mitochondrial function in hiPSC-derived neuronal models of Wolfram syndrome

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Transfemoral versus transcarotid access for transcatheter aortic valve replacement

Objectives: To compare the outcomes after transcatheter aortic valve replacement (TAVR) through a transfemoral (TF) and transcarotid (TC) access at our institution. Methods: From January 2014 to January 2020, 62 TC-TAVR and 449 TF-TAVR were performed using 2 prosthesis devices (Edwards SAPIEN 3, n = 369; Medtronic Evolut R, n = 142). Propensity score matching was used to adjust for imbalance in the baseline characteristics of the study groups. Results: Propensity score matching provided 62 matched pairs with comparable operative risk (mean European System for Cardiac Operative Risk Evaluation II, TC-TAVR 7.6% vs TF-TAVR 6.6%, P = .17). Thirty-day mortality (4.8% vs 3.2%, P = 1.00) and 2-year mortality (11.3% vs 12.9%, P = .64) after TC-TAVR were comparable with TF-TAVR. Strokes were numerically more frequent after TC-TAVR compared with TF-TAVR (3.2% vs 0%, P = .23), but the difference did not reach statistical significance. TF-TAVR was associated with a significantly greater risk of permanent pacemaker implantation (29.0% vs 12.9%, P = .04) compared with TC-TAVR. Other complications were not frequent and were similarly distributed between the matched groups. Conclusions: TC access for TAVR was associated with satisfactory results compared to the femoral access. TC-TAVR could be considered a valid and safe alternative to TF-TAVR when femoral access is contraindicated. © 2022</p

Roadmap on structured waves

Structured waves are ubiquitous for all areas of wave physics, both classical and quantum, where the wavefields are inhomogeneous and cannot be approximated by a single plane wave. Even the interference of two plane waves, or a single inhomogeneous (evanescent) wave, provides a number of nontrivial phenomena and additional functionalities as compared to a single plane wave. Complex wavefields with inhomogeneities in the amplitude, phase, and polarization, including topological structures and singularities, underpin modern nanooptics and photonics, yet they are equally important, e.g., for quantum matter waves, acoustics, water waves, etc. Structured waves are crucial in optical and electron microscopy, wave propagation and scattering, imaging, communications, quantum optics, topological and non-Hermitian wave systems, quantum condensed-matter systems, optomechanics, plasmonics and metamaterials, optical and acoustic manipulation, and so forth. This Roadmap is written collectively by prominent researchers and aims to survey the role of structured waves in various areas of wave physics. Providing background, current research, and anticipating future developments, it will be of interest to a wide cross-disciplinary audience.Comment: 110 pages, many figure

Thioflavine-T and Congo Red reveal the polymorphism of insulin amyloid fibrils when probed by polarization-resolved fluorescence microscopy.

International audienceAmyloid fibrils are protein misfolding structures that involve a β-sheet structure and are associated with the pathologies of various neurodegenerative diseases. Here we show that Thioflavine-T and Congo Red, two major dyes used to image fibrils by fluorescence assays, can provide deep structural information when probed by means of polarization-resolved fluorescence microscopy. Unlike fluorescence anisotropy or fluorescence detected linear dichroism imaging, this technique allows to retrieve simultaneously both mean orientation and orientation dispersion of the dye, used here as a reporter of the fibril structure. We have observed that insulin amyloid fibrils exhibit a homogeneous behavior over the fibrils' length, confirming their structural uniformity. In addition, these results reveal the existence of various structures among the observed fibrils' population, in spite of a similar aspect when imaged with conventional fluorescence microscopy. This optical nondestructive technique opens perspectives for in vivo structural analyses or high throughput screening