Parameterized maximum likelihood method (PML): application to space-time radar localization

We present a maximum likelihood method for the localization of sources with known waveforms . It's a joint space time radar localization which is a generalisation of recent methods to coherent signal . The obtained results are usefull in wireless communications for the identification of propagation channel with a pilot signal . An exact maximum likelihood method is presented . Variances of estimation and related Cramer Rao Bound are established . Simulations results illustrate the behaviour of the algorithm.Nous présentons une technique du maximum de vraisemblance qui localise des sources dont les formes d'ondes sont identiques et connues. Il s'agit d'une localisation radar conjointe direction-retard qui est une extension aux cas de signaux cohérents des méthodes actuellement utilisées et exploitant la connaissance des signaux émis. Les résultats obtenus s'appliquent de la même manière aux cas des communications mobiles pour lesquelles on veut identifier le canal de propagation à l'aide d'un signal connu. Un estimateur exact du maximum de vraisemblance est présenté. Les variances d'estimation ainsi que les bornes de Cramer-Rao sont établies. Des résultats de simulations viennent illustrer le comportement des algorithmes pour lesquels les performances sont comparées à la borne de Cramer-Rao

Synthesis of Novel Polyhydroxylated Tetrahydropyranopyrroles

The stereoselective access to original polyhydroxylated tetrahydropyranopyrroles is described. The key steps involve an ­inverse-demand Diels-Alder reaction and a ring contraction of a ­pyridazine heterocycle

Learning to reach by reinforcement learning using a receptive field based function approximation approach with continuous actions

Reinforcement learning methods can be used in robotics applications especially for specific target-oriented problems, for example the reward-based recalibration of goal directed actions. To this end still relatively large and continuous state-action spaces need to be efficiently handled. The goal of this paper is, thus, to develop a novel, rather simple method which uses reinforcement learning with function approximation in conjunction with different reward-strategies for solving such problems. For the testing of our method, we use a four degree-of-freedom reaching problem in 3D-space simulated by a two-joint robot arm system with two DOF each. Function approximation is based on 4D, overlapping kernels (receptive fields) and the state-action space contains about 10,000 of these. Different types of reward structures are being compared, for example, reward-on- touching-only against reward-on-approach. Furthermore, forbidden joint configurations are punished. A continuous action space is used. In spite of a rather large number of states and the continuous action space these reward/punishment strategies allow the system to find a good solution usually within about 20 trials. The efficiency of our method demonstrated in this test scenario suggests that it might be possible to use it on a real robot for problems where mixed rewards can be defined in situations where other types of learning might be difficult

Dichlorodioxomolybdenum(VI) complexes bearing oxygen-donor ligands as olefin epoxidation catalysts

Treatment of the solvent adduct [MoO2Cl2(THF)2] with either 2 equivalents of N,N-dimethylbenzamide (DMB) or 1 equivalent of N,N'-diethyloxamide (DEO) gave the dioxomolybdenum(vi) complexes [MoO2Cl2(DMB)2] () and [MoO2Cl2(DEO)] (). The molecular structures of and were determined by single-crystal X-ray diffraction. Both complexes present a distorted octahedral geometry and adopt the cis-oxo, trans-Cl, cis-L configuration typical of complexes of the type [MoO2X2(L)n], with either the monodentate DMB or bidentate DEO oxygen-donor ligands occupying the equatorial positions trans to the oxo groups. The complexes were applied as homogeneous catalysts for the epoxidation of olefins, namely cis-cyclooctene (Cy), 1-octene, trans-2-octene, α-pinene and (R)-(+)-limonene, using tert-butylhydroperoxide (TBHP) as oxidant. In the epoxidation of Cy at 55 °C, the desired epoxide was the only product and turnover frequencies in the range of ca. 3150-3200 mol molMo(-1) h(-1) could be reached. The catalytic production of cyclooctene oxide was investigated in detail, varying either the reaction temperature or the cosolvent. Complexes and were also applied in liquid-liquid biphasic catalytic epoxidation reactions by using an ionic liquid of the type [C4mim][X] (C4mim = 1-n-butyl-3-methylimidazolium; X = NTf2, BF4 or PF6] as a solvent to immobilise the metal catalysts. Recycling for multiple catalytic runs was achieved without loss of activity

Gastrointestinal Dysfunction in a Parkinson’s Disease Rat Model and the Changes of Dopaminergic, Nitric Oxidergic, and Cholinergic Neurotransmitters in Myenteric Plexus

This study aims to explore the gastrointestinal dysfunction and the changes of dopaminergic, nitric oxidergic, and cholinergic neurons in the myenteric plexus of a Parkinson’s disease (PD) rat model. A PD rat model was induced through unilateral substantia nigra administration of 6-hydroxydopamine. Four weeks later, the feces in 1 h and residual solid food in stomach at 2 h after feeding were measured. Changes in tyrosine hydroxylase (TH) in substantial nigra, TH, choline acetyltransferase (ChAT), and neuronal nitric oxide synthase (nNOS) in gastric antrum and colon tissue were examined by immunohistochemistry. Reverse transcription (RT) polymerase chain reaction (PCR) and Western blot were used to evaluate and compare the levels of messenger RNA (mRNA) and protein expression of TH, ChAT, and nNOS in the GI tract between normal and 6-hydroxydopamine-lesioned rats. Compared with control samples, the number of TH+ cells in the damaged side of substantia nigra of 6-hydroxydopamine-lesioned rats decreased significantly (P < 0.01). The weight and water content of the fecal matter decreased (P < 0.01), and the percentage of residual solid food increased (P < 0.01). The average integrated optical densities of TH-positive areas in the gastric antrum and colon tissue increased significantly (P < 0.01), nNOS decreased significantly (P < 0.01), and there were no significant changes in ChAT (P > 0.05). TH and nNOS mRNA levels in the gastric antrum and proximal colon decreased (P < 0.01), there were no significant changes in ChAT mRNA levels (P > 0.05). The protein levels of TH in the GI tract were significantly increased (P < 0.01), nNOS significantly decreased (P < 0.01), and ChAT had no significant changes (P > 0.05). 6-Hydroxydopamine-lesioned rats had delayed gastric emptying and constipation that might be related to the gastrointestinal TH increase and nNOS decrease. These symptoms were not related to changes in cholinergic transmitters

RemoveDebris Mission, In Orbit Operations

International audienceThe RemoveDebris mission has been the first Active Debris Removal (ADR) mission to give in orbit demonstrations of cost effective technologies that can be used to obser ve, capture and dispose of space debris. The craft was launched to the ISS on the 2nd of April 2018, on board a Dragon capsule. From here the satellite was deployed via the NanoRacks Kaber system into an orbit at 405km altitude and has performed key technology demonstrations including the use of a net, a harpoon, vision-based navigation (VBN) and a dragsail in a realistic space operational environment. Two CubeSats have been released by the main platform and used as targets for the net demonstration and for the VBN, whereas the harpoon demonstration has used a target mounted at the end of a boom deployed from the platform. These have been the first ever in-orbit successful demonstrations of technologies for large space debris capture. The dragsail demonstration presented some anomalies, however the lessons learned have already been implemented in new successful dragsails already deployed in space missions. This paper briefly outlines the development of the mission, discussing some of its challenges, and focusses on the various in orbit experiments, describing the operations and overall outcomes

White matter changes in microstructure associated with a maladaptive response to stress in rats

In today's society, every individual is subjected to stressful stimuli with different intensities and duration. This exposure can be a key trigger in several mental illnesses greatly affecting one's quality of life. Yet not all subjects respond equally to the same stimulus and some are able to better adapt to them delaying the onset of its negative consequences. The neural specificities of this adaptation can be essential to understand the true dynamics of stress as well as to design new approaches to reduce its consequences. In the current work, we employed ex vivo high field diffusion magnetic resonance imaging (MRI) to uncover the differences in white matter properties in the entire brain between Fisher 344 (F344) and Sprague-Dawley (SD) rats, known to present different responses to stress, and to examine the effects of a 2-week repeated inescapable stress paradigm. We applied a tract-based spatial statistics (TBSS) analysis approach to a total of 25 animals. After exposure to stress, SD rats were found to have lower values of corticosterone when compared with F344 rats. Overall, stress was found to lead to an overall increase in fractional anisotropy (FA), on top of a reduction in mean and radial diffusivity (MD and RD) in several white matter bundles of the brain. No effect of strain on the white matter diffusion properties was observed. The strain-by-stress interaction revealed an effect on SD rats in MD, RD and axial diffusivity (AD), with lower diffusion metric levels on stressed animals. These effects were localized on the left side of the brain on the external capsule, corpus callosum, deep cerebral white matter, anterior commissure, endopiriform nucleus, dorsal hippocampus and amygdala fibers. The results possibly reveal an adaptation of the SD strain to the stressful stimuli through synaptic and structural plasticity processes, possibly reflecting learning processes.We thank Neurospin (high field MRI center CEA Saclay) for providing its support for MRI acquisition. JB was supported by grants from Fondation pour la Recherche Médicale (FRM) and Groupe Pasteur Mutualité (GPM). This work was supported by a grant from ANR (SIGMA). This work was performed on a platform of France Life Imaging (FLI) network partly funded by the grant ANR-11-INBS-0006. This work and RM were supported by a fellowship of the project FCT-ANR/NEU-OSD/0258/2012 founded by FCT/MEC (www.fct.pt) and by Fundo Europeu de Desenvolvimento Regional (FEDER). AC was supported by a grant from the Fondation NRJ.info:eu-repo/semantics/publishedVersio

Colonic Biopsies to Assess the Neuropathology of Parkinson's Disease and Its Relationship with Symptoms

The presence of Lewy bodies and Lewy neurites (LN) has been demonstrated in the enteric nervous system (ENS) of Parkinson's disease (PD) patients. The aims of the present research were to use routine colonoscopy biopsies (1) to analyze, in depth, enteric pathology throughout the colonic submucosal plexus (SMP), and (2) to correlate the pathological burden with neurological and gastrointestinal (GI) symptoms.A total of 10 control and 29 PD patients divided into 3 groups according to disease duration were included. PD and GI symptoms were assessed using the Unified Parkinson's Disease Rating Scale part III and the Rome III questionnaire, respectively. Four biopsies were taken from the ascending and descending colon during the course of a total colonoscopy. Immunohistochemical analysis was performed using antibodies against phosphorylated alpha-synuclein, neurofilaments NF 220 kDa (NF) and tyrosine hydroxylase (TH). The density of LN, labeled by anti-phosphorylated alpha-synuclein antibodies, was evaluated using a quantitative rating score. Lewy pathology was apparent in the colonic biopsies from 21 patients and in none of the controls. A decreased number of NF-immunoreactive neurons per ganglion was observed in the SMP of PD patients compared to controls. The amount of LN in the ENS was inversely correlated with neuronal count and positively correlated with levodopa-unresponsive features and constipation.Analysis of the ENS by routine colonoscopy biopsies is a useful tool for pre-mortem neuropathological diagnosis of PD, and also provides insight into the progression of motor and non-motor symptoms