169 research outputs found
A Multi-Robot Cooperation Framework for Sewing Personalized Stent Grafts
This paper presents a multi-robot system for manufacturing personalized
medical stent grafts. The proposed system adopts a modular design, which
includes: a (personalized) mandrel module, a bimanual sewing module, and a
vision module. The mandrel module incorporates the personalized geometry of
patients, while the bimanual sewing module adopts a learning-by-demonstration
approach to transfer human hand-sewing skills to the robots. The human
demonstrations were firstly observed by the vision module and then encoded
using a statistical model to generate the reference motion trajectories. During
autonomous robot sewing, the vision module plays the role of coordinating
multi-robot collaboration. Experiment results show that the robots can adapt to
generalized stent designs. The proposed system can also be used for other
manipulation tasks, especially for flexible production of customized products
and where bimanual or multi-robot cooperation is required.Comment: 10 pages, 12 figures, accepted by IEEE Transactions on Industrial
Informatics, Key words: modularity, medical device customization, multi-robot
system, robot learning, visual servoing, robot sewin
Focusing of in-plane hyperbolic polaritons in van der Waals crystals with tailored infrared nanoantennas
Phonon polaritons (PhPs),light coupled to lattice vibrations,with in-plane
hyperbolic dispersion exhibit ray-like propagation with large wavevectors and
enhanced density of optical states along certain directions on a surface. As
such, they have raised a surge of interest as they promise unprecedented
possibilities for the manipulation of infrared light with planar circuitry and
at the nanoscale. Here, we demonstrate, for the first time, the focusing of
in-plane hyperbolic PhPs propagating along thin slabs of MoO3. To that end, we
developed metallic nanoantennas of convex geometries for both the efficient
launching and focusing of the polaritons. Remarkably, the foci obtained exhibit
enhanced near-field confinement and absorption compared to foci produced by
in-plane isotropic PhPs. More intriguingly, foci sizes as small as lamdap/5
=lamda0/50 were achieved (lamdap is the polariton wavelength and lamda0 the
photon wavelength). Focusing of in-plane hyperbolic polaritons introduces a
first and most basic building block developing planar polariton optics
utilizing in-plane anisotropic van der Waals materials and metasurfaces
Differential association of the Na+/H+ exchanger regulatory factor (NHERF) family of adaptor proteins with the raft- and the non-raft brush border membrane fractions of NHE3
Background/Aims: Trafficking, brush border membrane (BBM) retention, and signal-specific regulation of the Na+/H+ exchanger NHE3 is regulated by the Na+/H+ Exchanger Regulatory Factor (NHERF) family of PDZ-adaptor proteins, which enable the formation of multiprotein complexes. It is unclear, however, what determines signal specificity of these NHERFs. Thus, we studied the association of NHE3, NHERF1 (EBP50), NHERF2 (E3KARP), and NHERF3 (PDZK1) with lipid rafts in murine small intestinal BBM. Methods: Detergent resistant membranes ('lipid rafts') were isolated by floatation of Triton X-incubated small intestinal BBM from a variety of knockout mouse strains in an Optiprep step gradient. Acid-activated NHE3 activity was measured fluorometrically in BCECF-loaded microdissected villi, or by assessment of CO2/HCO3 - mediated increase in fluid absorption in perfused jejunal loops of anethetized mice. Results: NHE3 was found to partially associate with lipid rafts in the native BBM, and NHE3 raft association had an impact on NHE3 transport activity and regulation in vivo. NHERF1, 2 and 3 were differentially distributed to rafts and non-rafts, with NHERF2 being most raft-associated and NHERF3 entirely non-raft associated. NHERF2 expression enhanced the localization of NHE3 to membrane rafts. The use of acid sphingomyelinase-deficient mice, which have altered membrane lipid as well as lipid raft composition, allowed us to test the validity of the lipid raft concept in vivo. Conclusions: The differential association of the NHERFs with the raft-associated and the non-raft fraction of NHE3 in the brush border membrane is one component of the differential and signal-specific NHE3 regulation by the different NHERFs
Infrared permittivity of the biaxial van der Waals semiconductor -MoO from near- and far-field correlative studies
The biaxial van der Waals semiconductor -phase molybdenum trioxide
(-MoO) has recently received significant attention due to its
ability to support highly anisotropic phonon polaritons (PhPs) -infrared (IR)
light coupled to lattice vibrations in polar materials-, offering an
unprecedented platform for controlling the flow of energy at the nanoscale.
However, to fully exploit the extraordinary IR response of this material, an
accurate dielectric function is required. Here, we report the accurate IR
dielectric function of -MoO by modelling far-field, polarized IR
reflectance spectra acquired on a single thick flake of this material. Unique
to our work, the far-field model is refined by contrasting the experimental
dispersion and damping of PhPs, revealed by polariton interferometry using
scattering-type scanning near-field optical microscopy (s-SNOM) on thin flakes
of -MoO, with analytical and transfer-matrix calculations, as well
as full-wave simulations. Through these correlative efforts, exceptional
quantitative agreement is attained to both far- and near-field properties for
multiple flakes, thus providing strong verification of the accuracy of our
model, while offering a novel approach to extracting dielectric functions of
nanomaterials, usually too small or inhomogeneous for establishing accurate
models only from standard far-field methods. In addition, by employing density
functional theory (DFT), we provide insights into the various vibrational
states dictating our dielectric function model and the intriguing optical
properties of -MoO
Cómo manipular nanoluz en varias frecuencias
En este estudio también han participado científicos de otros centros nacionales (DIPC, CIC nanoGUNE y la Universidad del País Vasco) e internacionales (Academia de Ciencias de China, Universidad Case Western Reserve de EE UU, Instituto Tecnológico de Austria, Centro de Materiales de París y Universidad de Tokio).Científicos de la Universidad de Oviedo y el Centro de Investigación en Nanomateriales y Nanotecnología han descubierto un método para controlar la frecuencia de la luz en la nanoescala intercalando átomos de sodio en los llamados materiales de van der Waals. El avance se podría aplicar en tecnologías de la información y sensores biológicos de alta sensibilidad.Peer reviewe
25th annual computational neuroscience meeting: CNS-2016
The same neuron may play different functional roles in the neural circuits to which it belongs. For example, neurons in the Tritonia pedal ganglia may participate in variable phases of the swim motor rhythms [1]. While such neuronal functional variability is likely to play a major role the delivery of the functionality of neural systems, it is difficult to study it in most nervous systems. We work on the pyloric rhythm network of the crustacean stomatogastric ganglion (STG) [2]. Typically network models of the STG treat neurons of the same functional type as a single model neuron (e.g. PD neurons), assuming the same conductance parameters for these neurons and implying their synchronous firing [3, 4]. However, simultaneous recording of PD neurons shows differences between the timings of spikes of these neurons. This may indicate functional variability of these neurons. Here we modelled separately the two PD neurons of the STG in a multi-neuron model of the pyloric network. Our neuron models comply with known correlations between conductance parameters of ionic currents. Our results reproduce the experimental finding of increasing spike time distance between spikes originating from the two model PD neurons during their synchronised burst phase. The PD neuron with the larger calcium conductance generates its spikes before the other PD neuron. Larger potassium conductance values in the follower neuron imply longer delays between spikes, see Fig. 17.Neuromodulators change the conductance parameters of neurons and maintain the ratios of these parameters [5]. Our results show that such changes may shift the individual contribution of two PD neurons to the PD-phase of the pyloric rhythm altering their functionality within this rhythm. Our work paves the way towards an accessible experimental and computational framework for the analysis of the mechanisms and impact of functional variability of neurons within the neural circuits to which they belong
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