NeuroMap: A Spline-Based Interactive Open-Source Software for Spatiotemporal Mapping of 2D and 3D MEA Data

A major characteristic of neural networks is the complexity of their organization at various spatial scales, from microscopic local circuits to macroscopic brain-scale areas. Understanding how neural information is processed thus entails the ability to study them at multiple scales simultaneously. This is made possible using microelectrodes array (MEA) technology. Indeed, high-density MEAs provide large-scale coverage (several square millimeters) of whole neural structures combined with microscopic resolution (about 50 μm) of unit activity. Yet, current options for spatiotemporal representation of MEA-collected data remain limited. Here we present NeuroMap, a new interactive Matlab-based software for spatiotemporal mapping of MEA data. NeuroMap uses thin plate spline interpolation, which provides several assets with respect to conventional mapping methods used currently. First, any MEA design can be considered, including 2D or 3D, regular or irregular, arrangements of electrodes. Second, spline interpolation allows the estimation of activity across the tissue with local extrema not necessarily at recording sites. Finally, this interpolation approach provides a straightforward analytical estimation of the spatial Laplacian for better current sources localization. In this software, coregistration of 2D MEA data on the anatomy of the neural tissue is made possible by fine matching of anatomical data with electrode positions using rigid-deformation-based correction of anatomical pictures. Overall, NeuroMap provides substantial material for detailed spatiotemporal analysis of MEA data. The package is distributed under GNU General Public License and available at http://sites.google.com/site/neuromapsoftware

Real-time biomimetic Central Pattern Generators in an FPGA for hybrid experiments

This investigation of the leech heartbeat neural network system led to the development of a low resources, real-time, biomimetic digital hardware for use in hybrid experiments. The leech heartbeat neural network is one of the simplest central pattern generators (CPG). In biology, CPG provide the rhythmic bursts of spikes that form the basis for all muscle contraction orders (heartbeat) and locomotion (walking, running, etc.). The leech neural network system was previously investigated and this CPG formalized in the Hodgkin–Huxley neural model (HH), the most complex devised to date. However, the resources required for a neural model are proportional to its complexity. In response to this issue, this article describes a biomimetic implementation of a network of 240 CPGs in an FPGA (Field Programmable Gate Array), using a simple model (Izhikevich) and proposes a new synapse model: activity-dependent depression synapse. The network implementation architecture operates on a single computation core. This digital system works in real-time, requires few resources, and has the same bursting activity behavior as the complex model. The implementation of this CPG was initially validated by comparing it with a simulation of the complex model. Its activity was then matched with pharmacological data from the rat spinal cord activity. This digital system opens the way for future hybrid experiments and represents an important step toward hybridization of biological tissue and artificial neural networks. This CPG network is also likely to be useful for mimicking the locomotion activity of various animals and developing hybrid experiments for neuroprosthesis development

A Guide to RBF-Generated Finite Differences for Nonlinear Transport: Shallow Water Simulations on a Sphere

The current paper establishes the computational efficiency and accuracy of the RBF-FD method for large-scale geoscience modeling with comparisons to state-of-the-art methods as high-order discontinuous Galerkin and spherical harmonics, the latter using expansions with close to 300,000 bases. The test cases are demanding fluid flow problems on the sphere that exhibit numerical challenges, such as Gibbs phenomena, sharp gradients, and complex vortical dynamics with rapid energy transfer from large to small scales over short time periods. The computations were possible as well as very competitive due to the implementation of hyperviscosity on large RBF stencil sizes (corresponding roughly to 6th to 9th order methods) with up to O(105) nodes on the sphere. The RBF-FD method scaled as O(N) per time step, where N is the total number of nodes on the sphere. In Appendix A, guidelines are given on how to chose parameters when using RBF-FD to solve hyperbolic PDEs

Mini-bâteau récupérateur de micro-énergie de vaguelette

This paper introduces an original research work on experimental demonstration of micro-energy harvesting from water wave. To implement this demonstrator, commercial piezo-electric elements are used as an electromechanical aquatic energy transducer. The proof-of-concept is constituted by electrical micro-energy sensor circuit implemented on a mini-boat external surface. The water wave is generated by the valve oscillating motion placed in a water tank. Because of the wave interaction with the piezo, it was shown that the electrical circuit placed on the micro-boat surface generates instantaneous electrical power with microwatt amplitude under some Volts amplitude instantaneous voltage. The influence of the boat orientation in function of the water wave propagation direction is investigated

Kinematic Characterisation of Hexapods for Industry

International audiencePurpose-The aim of this paper is to propose two simple tools for the kinematic characterization of hexapods. The paper also aims to share the authors' experience with converting a popular commercial motion base (Stewart-Gough platform, hex-apod) to an industrial robot for use in heavy duty aerospace manufacturing processes. Design/methodology/approach-The complete workspace of a hexapod is a six-dimensional entity that is impossible to visualize. Thus, nearly all hexapod manufacturers simply state the extrema of each of the six dimensions, which is very misleading. As a compromise, we propose a special three-dimensional subset of the complete workspace, an approximation of which can be readily obtained using a CAD/CAM software suite, such as CATIA. While calibration techniques for serial robots are readily available, there is still no generally-agreed procedure for calibrating hexapods. We propose a simple calibration method that relies on the use of a laser tracker and requires no programming at all. Instead, the design parameters of the hexapod are directly and individually measured and the few computations involved are performed in a CAD/CAM software such as CATIA. Findings-The conventional octahedral hexapod design has a very limited workspace, though free of singularities. There are important deviations between the actual and the specified kinematic model in a commercial motion base. Practical implications-A commercial motion base can be used as a precision positioning device with its controller retrofit-ted with state-of-the-art motion control technology with accurate workspace and geometric characteristics. Originality/value-A novel geometric approach for obtaining meaningful measures of the workspace is proposed. A novel, systematic procedure for the calibration of a hexapod is outlined. Finally, experimental results are presented and discussed

Logistik: Hur påverkar Just-In-Time på lönsamheten av ett företag?

Ett företag har som grunduppgift att hållas verksamt genom att ekonomiskt prestera bättre för varje år. Logistik är det verksamhetsområde som står för majoriteten av ett företags kostnader. Kostnader i sig är en dålig sak för företag, men det är även en möjlighet för logistiken att sänka dessa kostnader, vilket i sin tur är bra för företagets lön-samhet. Just-In-Time (JIT) är en produktions- och styrfilosofi inom logistiken, där det huvudsakliga målet är att minska lagernivåerna och att eliminera allt onödigt. Syftet med denna studie är att finna ett samband mellan JIT och lönsamhet ur ett logistiskt perspektiv. Vid studien används DuPont-modellen som definition av lönsamhet samt som ett jämförelseverktyg där sex olika finansiella faktorer mäts. Metoden för studien är kvalitativ i form av en litteraturstudie. Materialet som analyseras hämtas endast från Arcadas databaser och analysen av materialet sker i form av innehållsanalys. Resultaten av materialet som analyserades är väldigt blandat. Många studier påpekar att det råder brist på forskning inom detta ämnesområdet, vilket även kan vara orsaken till dessa blandade resultat. Det går dock att urskilja tre finansiella mått från DuPont-modellen som påver-kas positivt av JIT. Dessa är: intäkter, kostnader och lager. Ingen studie visade att JIT skulle ha negativ inverkan på ett företags lönsamhet. Andra intressanta faktorer som JIT hade en positiv inverkan på är operativa prestanda, t.ex. minskade ledtider

Prospective Study of a Serogroup X Neisseria meningitidis Outbreak in Northern Ghana

After an epidemic of serogroup A meningococcal meningitis in northern Ghana, a gradual disappearance of the epidemic strain was observed in a series of five 6-month carriage surveys of 37 randomly selected households. As serogroup A Neisseria meningitidis carriage decreased, an epidemic of serogroup X meningococcal carriage occurred, which reached 18% (53/298) of the people sampled during the dry season of 2000, coinciding with an outbreak of serogroup X disease. These carriage patterns were unrelated to that of Neisseria lactamica. Multilocus sequence typing and pulsed-field gel electrophoresis of the serogroup X bacteria revealed strong similarity with other strains isolated in Africa during recent decades. Three closely related clusters with distinct patterns of spread were identified among the Ghanian isolates, and further microevolution occurred after they arrived in the district. The occurrence of serogroup X outbreaks argues for the inclusion of this serogroup into a multivalent conjugate vaccine against N. meningitidi