Real-time estimation of dominant motion in underwater video images for dynamic positionning

International audienceIn this paper, we propose a 2D visual motion estimation method which can be exploited to achieve a dynamic positioning (eg. by gaze control) with respect to a sea-bottom area of interest of a video camera mounted on a subsea vehicle. It mainly involves a dominant 2D motion robust estimation step from underwater video sequences. Optimizations carried out on the motion estimation code have made possible the use of our algorithm in ``application-related real-time'' for scientific exploration or inspection tasks. We have developed a friendly and efficient interface to perform this algorithm in an operational context. Experiments dealing with complex real underwater scenes are reported and validate the approach

Twenty two cases of canine neural angiostronglyosis in eastern Australia (2002-2005) and a review of the literature

Cases of canine neural angiostrongylosis (NA) with cerebrospinal fluid (CSF) evaluations in the peer-reviewed literature were tabulated. All cases were from Australia. A retrospective cohort of 59 dogs was contrasted with a series of 22 new cases where NA was diagnosed by the presence of both eosinophilic pleocytosis and anti-Angiostrongylus cantonensis immunloglobulins (IgG) in CSF, determined by ELISA or Western blot. Both cohorts were drawn from south east Queensland and Sydney. The retrospective cohort comprised mostly pups presented for hind limb weakness with hyperaesthesia, a mixture of upper motor neurone (UMN) and lower motor neurone (LMN) signs in the hind limbs and urinary incontinence. Signs were attributed to larval migration through peripheral nerves, nerve roots, spinal cord and brain associated with an ascending eosinophilic meningo-encephomyelitis. The contemporary cohort consisted of a mixture of pups, young adult and mature dogs, with a wider range of signs including (i) paraparesis/proprioceptive ataxia (ii) lumbar and tail base hyperaesthesia, (iii) multi-focal central nervous system dysfunction, or (iv) focal disease with neck pain, cranial neuropathy and altered mentation. Cases were seen throughout the year, most between April and July (inclusive). There was a preponderance of large breeds. Often littermates, or multiple animals from the same kennel, were affected simultaneously or sequentially. A presumptive diagnosis was based on consistent signs, proximity to rats, ingestion/chewing of slugs or snails and eosinophilic pleocytosis. NA was diagnosed by demonstrating anti-A. cantonensis IgG in CSF. Detecting anti-A. cantonensis IgG in serum was unhelpful because many normal dogs (20/21 lb dogs; 8/22 of a hospital population) had such antibodies, often at substantial titres. Most NA cases in the contemporary series (19/22) and many pups (16/38) in the retrospective cohort were managed successfully using high doses of prednisolone and opioids. Treatment often included antibiotics administered in case protozoan encephalomyelitis or translocated bacterial meningitis was present. Supportive measures included bladder care and physiotherapy. Several dogs were left with permanent neural deficits. Dogs are an important sentinel species for NA. Human cases and numerous cases in tawny frogmouths were reported from the same regions as affected dogs over the study period

Visual Servoing using Image Motion Information

Visual servoing is a framework for achieving the tight coupling of camera movements and information from images. We consider a typical visual servoing approach that uses geometric information about image features for controlling the position and attitude of a camera. We claim that image motion information can be used as well. We substantiate this claim by presenting two different approaches to visual tasks that use motion information. The first one uses the focus of expansion. The second one incorporates the parameters of the 2D affine motion model in the control equations. We illustrate both these approaches by means of a task to align the optical axis of the camera with the unknown direction of the translational motion of the system on which it is mounted, and present results of experiments done with a six DOF robot. The contribution of this work is in showing that a tight coupling between the camera behavior and image motion is possible

Localisation de sources ponctuelles à large bande

On présente une nouvelle méthode de goniométrie par vecteurs propres dans le cas de sources à large bande. Le problème du défilement du vecteur source avec la fréquence est résolu par une technique d'interpolation du signal utile sur des capteurs synthétiques le long de l'axe de l'antenne. La corrélation du bruit produite par l'interpolation est réduite par un traitement utilisant un banc de filtres sphéroïdaux. La méthode est ensuite étendue au cas d'une analyse par secteurs

Structure antigénique du Nématode

Angiostrongylus cantonensis, parasite du rat et agent de la méningite à éosinophiles de l’homme, présente une mosaïque antigénique complexe. Parmi les 25 composants antigéniques mis en évidence par l’analyse immuno-électrophorétique de l’extrait de vers adultes, deux semblent jouer un rôle prépondérant. L’étude de l’extrait antigénique larvaire n’a permis de révéler que quinze composants. Il existe des parentés antigéniques restreintes avec les Cestodes et les Trématodes (2) et plus nombreuses avec les Nématodes (6). Des parentés ont été observées entre le parasite, l’hôte intermédiaire et l’hôte définitif et peuvent expliquer un des aspects des modalités de l’adaptation parasitaire. La connaissance théorique de l’antigène Angiostrongylus cantonensis a été complétée par l’étude des anticorps précitants élaborés au cours de l’angiostrongylose expérimentale du rat en fonction de la chronologie et de l’intensité de l’infestation. Chez l’homme où Angiostrongylus cantonensis est en impasse parasitaire et ne dépasse pas le stade larvaire, les anticorps précipitants sont mis en évidence aussi bien par l’antigène extrait d’adultes que de larves