Nonlinear Optical Response in Single Alkaline Niobate Nanowires

We have synthesized and characterized three types of perovskite alkaline niobate nanowires: NaNbO3, KNbO3, and LiNbO3 (XNbO3). All three types of nanowires exhibit strong nonlinear response. Confocal imaging has been employed to quantitatively compare the efficiency of synthesized nanowires to generate second harmonic signal and to show that LiNbO3 nanowires exhibit the strongest nonlinear response. We also investigated the polarization response of the second harmonic generation (SHG) signal in all three types of alkaline nanowires for the two geometries tractable by our optical trapping setup. The SHG signal is highly influenced by the nanowire crystallinity and experimental geometry. We also demonstrate for the first time wave-guiding of SHG signal in all three types of alkaline niobate nanowires. By carefully examining nonlinear properties of (XNbO3) nanowires we suggest which type of wires are best suited for the given application

Detecting the translocation of DNA through a nanopore using graphene nanoribbons

Solid-state nanopores can act as single-molecule sensors and could potentially be used to rapidly sequence DNA molecules. However, nanopores are typically fabricated in insulating membranes that are as thick as 15 bases, which makes it difficult for the devices to read individual bases. Graphene is only 0.335 nm thick (equivalent to the spacing between two bases in a DNA chain) and could therefore provide a suitable membrane for sequencing applications. Here, we show that a solid-state nanopore can be integrated with a graphene nanoribbon transistor to create a sensor for DNA translocation. As DNA molecules move through the pore, the device can simultaneously measure drops in ionic current and changes in local voltage in the transistor, which can both be used to detect the molecules. We examine the correlation between these two signals and use the ionic current measurements as a real-time control of the graphene-based sensing device

Label-Free Optical Detection of Biomolecular Translocation through Nanopore Arrays

In recent years, nanopores have emerged as exceptionally promising single-molecule sensors due to their ability to detect biomolecules at subfemtomole levels in a label-free manner. Development of a high-throughput nanopore-based biosensor requires multiplexing of nanopore measurements. Electrical detection, however, poses a challenge, as each nanopore circuit must be electrically independent, which requires complex nanofluidics and embedded electrodes. Here, we present an optical method for simultaneous measurements of the ionic current across an array of solid-state nanopores, requiring no additional fabrication steps. Proof-of-principle experiments are conducted that show simultaneous optical detection and characterization of ssDNA and dsDNA using an array of pores. Through a comparison with electrical measurements, we show that optical measurements are capable of accessing equivalent transmembrane current information

Erreur d'estimation intervenant dans l'analyse de fluctuations accessibles sous de faibles rapports signal sur bruit

On compare l'erreur d'estimation due au temps de mesure fini pour différentes méthodes d'analyse spectrale : estimation de la corrélation directe ou croisée, ou estimation de la densité spectrale de puissance par filtrage dans une fenêtre étroite, ou transformation de Fourier, le plus souvent F.F.T., directement sur le signal ou sur la corrélation. Dans toutes les méthodes, on peut approximer dans le cas gaussien la variance de l'estimateur par une expression déjà connue. En introduisant la notion de bande équivalente du second ordre on peut généraliser les résultats. Dans le cas pratique où l'on cherche à estimer le signal constitué par la partie corrélée de deux voies de mesure bruitées, on donne l'influence du bruit sur cette variance par l'intermédiaire d'un rapport signal sur bruit, de définition différente selon la méthode. Ceci permet de préciser l'avantage en rapidité de convergence de l'intercorrélation sur l'auto-corrélation corrigée du bruit, ou même de l'interspectre sur l'autospectre corrigé, qui apparaît dans le cas d'un rapport signal sur bruit faible. La validité de ce calcul est vérifiée par la mesure de l'erreur d'estimation dans le cas d'une analyse spectrale directe et croisée du bruit thermique de résistances, effectuée par F.F.T. dans un domaine de rapport signal sur bruit allant de 0,01 à 20

Correction to Nonlinear Optical Response in Single Alkaline Niobate Nanowires

Correction to Nonlinear Optical Response in Single Alkaline Niobate Nanowire

Short-term effect of neck muscle vibration on postural disturbances in stroke patients

International audienceBalance disorders after stroke have a particularly detrimental influence on recovery of autonomy and walking. The present study is aimed at assessing the effect of proprioceptive stimulation by neck muscle vibration (NMV) on the balance of patients with right hemispheric lesion (RHL) and left hemispheric lesion (LHL). Thirty-one (31) patients (15 RHL and 16 LHL), mean age 61.5 years (±10.6), mean delay 3.1 (±1.6) months after one hemispheric stroke were included in this prospective study. The mean position in mediolateral and anteroposterior plane of the CoP (center of pressure) and the surface were evaluated using a force platform at rest and immediately after 10 min of vibration on the contralesional dorsal neck muscle. NMV decreases the lateral deviation balance induced by the stroke. Twenty patients (64.5 %) experienced a visual illusion of light spot moving toward the side opposite stimulus. These patients showed more improvement by vibration than those without visual illusion. There was an interaction between sensitivity and side of stroke on the effect of NMV. Proprioceptive stimulation by NMV reduces postural asymmetry after stroke. This short-term effect of the vibration is more effective in patients susceptible to visual illusion. This result was consistent with a central effect of NMV on the structures involved in the elaboration of perception of body in space. © 2016, Springer-Verlag Berlin Heidelberg

DETERMINISTIC LATERAL DISPLACEMENT FOR THE SORTING OF EXTRACELLULAR VESICLES FROM COMPLEX BIOLOGICAL SAMPLES

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Nanopore Detection of Single Molecule RNAP–DNA Transcription Complex

In the past decade, a number of single-molecule methods have been developed with the aim of investigating single protein and nucleic acid interactions. For the first time we use solid-state nanopore sensing to detect a single <i>E. coli</i> RNAP–DNA transcription complex and single <i>E. coli</i> RNAP enzyme. On the basis of their specific conductance translocation signature, we can discriminate and identify between those two types of molecular translocations and translocations of bare DNA. This opens up a new perspectives for investigating transcription processes at the single-molecule level