78 research outputs found
Optical Coherence Spectro-Tomography by all-Optical Depth-Wavelength analysis
Current spectroscopic optical coherence tomography (OCT) methods rely on a
posteriori numerical calculation. We present an alternative for accessing
optically the spectroscopic information in OCT, i.e. without any
post-processing, by using a grating based correlation and a wavelength
demultiplexing system. Conventional A-scan and spectrally resolved A-scan are
directly recorded on the image sensor. Furthermore, due to the grating based
system, no correlation scan is necessary. In the frame of this paper we present
the principle of the system as well as first experimental results
Characterization and Compensation of XY Micropositioning Robots using Vision and Pseudo-Periodic Encoded Patterns.
International audienceAccuracy is an important issue for microrobotic applications. High accuracy is usually a necessary condition for reliable system performance. However there are many sources of inaccuracy acting on the microrobotic systems. Characterization and compensation enable reduction of the systematic errors of the micropositioning stages and improve the positioning accuracy. In this paper, we propose a novel method based on vision and pseudo-periodic encoded patterns to characterize the position-dependent errors along XY stages. This method is particularly suitable for microscale motion characterization thanks to its high range-to-resolution ratio and avoidance of camera calibration. Based on look-up tables and interpolation techniques, we perform compensation and get improved accuracy. The experimental results show an accuracy improved by 84% for square tracking and by 68% for random points reaching (respectively from 22 ÎŒm to 3.5 ÎŒm and from 22 ÎŒm to 7 ÎŒm)
Dimerization of the voltage-sensing phosphatase controls its voltage-sensing and catalytic activity.
Multimerization is a key characteristic of most voltage-sensing proteins. The main exception was thought to be the Ciona intestinalis voltage-sensing phosphatase (Ci-VSP). In this study, we show that multimerization is also critical for Ci-VSP function. Using coimmunoprecipitation and single-molecule pull-down, we find that Ci-VSP stoichiometry is flexible. It exists as both monomers and dimers, with dimers favored at higher concentrations. We show strong dimerization via the voltage-sensing domain (VSD) and weak dimerization via the phosphatase domain. Using voltage-clamp fluorometry, we also find that VSDs cooperate to lower the voltage dependence of activation, thus favoring the activation of Ci-VSP. Finally, using activity assays, we find that dimerization alters Ci-VSP substrate specificity such that only dimeric Ci-VSP is able to dephosphorylate the 3-phosphate from PI(3,4,5)P3 or PI(3,4)P2 Our results indicate that dimerization plays a significant role in Ci-VSP function
Fast Autofocusing using Tiny Transformer Networks for Digital Holographic Microscopy
The numerical wavefront backpropagation principle of digital holography
confers unique extended focus capabilities, without mechanical displacements
along z-axis. However, the determination of the correct focusing distance is a
non-trivial and time consuming issue. A deep learning (DL) solution is proposed
to cast the autofocusing as a regression problem and tested over both
experimental and simulated holograms. Single wavelength digital holograms were
recorded by a Digital Holographic Microscope (DHM) with a 10
microscope objective from a patterned target moving in 3D over an axial range
of 92 m. Tiny DL models are proposed and compared such as a tiny Vision
Transformer (TViT), tiny VGG16 (TVGG) and a tiny Swin-Transfomer (TSwinT). The
experiments show that the predicted focusing distance is
accurately inferred with an accuracy of 1.2 m in average in comparison
with the DHM depth of field of 15 m. Numerical simulations show that all
tiny models give the with an error below 0.3 m. Such
a prospect would significantly improve the current capabilities of computer
vision position sensing in applications such as 3D microscopy for life sciences
or micro-robotics. Moreover, all models reach state of the art inference time
on CPU, less than 25 ms per inference
Migraine-Associated TRESK Mutations Increase Neuronal Excitability through Alternative Translation Initiation and Inhibition of TREK
Mutations in ion channels contribute to neurological disorders, but determining the basis of their role in pathophysiology is often unclear. In humans, 2 mutations have been found to produce a dominant negative for TRESK, a two-pore-domain K+ channel implicated in migraine: TRESK-MT, a 2 bp frameshift mutation (F139WfsX24) and TRESK-C110R, a missense mutation. Despite the fact that both mutants strongly inhibit TRESK, only TRESK-MT leads to an increase in sensory neuron excitability and is associated with a migraine phenotype. Here, we identify a new mechanism, termed frameshift mutation induced Alternative Translation Initiation (fsATI) that may explain why TRESK-MT but not TRESK-C110R is associated with migraine disorder. fsATI leads, from the same TRESK-MT mRNA, to two proteins: TRESK-MT1 and TRESK-MT2. We show that by co-assembling with and inhibiting TREK1 and TREK2, another subfamily of K2P channels, overexpression of TRESK-MT2 increases trigeminal sensory neuron excitability, a key component of migraine induction, leading to a migraine-like phenotype. This finding identifies TREK as a potential molecular target in migraine pathophysiology and resolves the contradictory lack of effect of TRESK-C110R which targets only TRESK and not TREK. Finally, taking into account the potential for fsATI allowed us to identify a new migraine-related TRESK mutant, Y121LfsX44, which also leads to the production of two TRESK fragments, indicating that this mechanism may be widespread. Together, our results suggest that genetic analysis of disease-related mutations should consider fsATI as a distinct class of mutations
Spadin, a Sortilin-Derived Peptide, Targeting Rodent TREK-1 Channels: A New Concept in the Antidepressant Drug Design
We found that spadin, a natural peptide derived from sortilin, blocks the mouse TREK-1 channel and might be an efficient and fast-acting antidepressant
Les halles et la riviÚre. Un parc métropolitain dans la vallée de la Venoge
Le site de Cossonay-Penthalaz est riche dâune longue histoire industrielle, allant des moulins mĂ©diĂ©vaux, encore actifs aujourdâhui, Ă lâimposante fabrique de cĂąbles. Il sâinscrit au sein de la vallĂ©e de la Venoge, qui a toujours Ă©tĂ© un lieu de passage commercial stratĂ©gique Ă travers le continent et qui revĂȘt, actuellement, un rĂŽle dâartĂšre servante pour la mĂ©tropole lĂ©manique. Chacun Ă leur Ă©poque, lâutopique canal dâEntreroches, le chemin de fer puis lâautoroute permirent le dĂ©veloppement Ă©conomique de la rĂ©gion. Mais ce statut est Ă bien des Ă©gards problĂ©matique, notamment par la confrontation entre les infrastructures dâĂ©chelle nationale et les Ă©lĂ©ments naturels et urbains du territoire Ă lâĂ©chelle locale. Est-il possible de rĂ©concilier nature et production Ă cet endroit? Et ce, non seulement sans faire table rase des vestiges industriels et du canal, mais en revalorisant lâespace de la riviĂšre, en offrant des lieux de qualitĂ© au public et en y maintenant une activitĂ© Ă©conomique stratĂ©gique? Le projet propose un parc mĂ©tropolitain qui accompagne le couloir topographique et industriel de la vallĂ©e jusquâĂ lâagglomĂ©ration lausannoise. Dans le segment traitĂ©, les activitĂ©s de production et logistique cĂŽtoient les programmes publics qui rĂ©pondent aux besoins, tant Ă lâĂ©chelle locale quâĂ celle de la mĂ©tropole. Les habitants des deux localitĂ©s et les visiteurs peuvent ainsi se rĂ©approprier le plateau comme un espace collectif et central, articulĂ© par une promenade continue en relation avec la riviĂšre
Canaux ioniques et mĂ©canismes de transmission de maladies hĂ©rĂ©ditaires Ă lâorigine de la migraine
International audienc
Optogenetic techniques for the study of native potassium channels.
International audienceOptogenetic tools were originally designed to target specific neurons for remote control of their activity by light and have largely been built around opsin-based channels and pumps. These naturally photosensitive opsins are microbial in origin and are unable to mimic the properties of native neuronal receptors and channels. Over the last 8 years, photoswitchable tethered ligands (PTLs) have enabled fast and reversible control of mammalian ion channels, allowing optical control of neuronal activity. One such PTL, maleimide-azobenzene-quaternary ammonium (MAQ), contains a maleimide (M) to tether the molecule to a genetically engineered cysteine, a photoisomerizable azobenzene (A) linker and a pore-blocking quaternary ammonium group (Q). MAQ was originally used to photocontrol SPARK, an engineered light-gated potassium channel derived from Shaker. Potassium channel photoblock by MAQ has recently been extended to a diverse set of mammalian potassium channels including channels in the voltage-gated and K2P families. Photoswitchable potassium channels, which maintain native properties, pave the way for the optical control of specific aspects of neuronal function and for high precision probing of a specific channel's physiological functions. To extend optical control to natively expressed channels, without overexpression, one possibility is to develop a knock-in mouse in which the wild-type channel gene is replaced by its light-gated version. Alternatively, the recently developed photoswitchable conditional subunit technique provides photocontrol of the channel of interest by molecular replacement of wild-type complexes. Finally, photochromic ligands also allow photocontrol of potassium channels without genetic manipulation using soluble compounds. In this review we discuss different techniques for optical control of native potassium channels and their associated advantages and disadvantages
RĂ©gulation des canaux calcium neuronaux sensibles au potentiel
AIX-MARSEILLE2-BU MĂ©d/Odontol. (130552103) / SudocPARIS-BIUP (751062107) / SudocSudocFranceF
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