Université de Rennes
Institut De Physique De Rennes
The mines of the Laurion plateau were in full operation from 480 to 431 BC. These silver-bearing lead mines, the exploitation of which remains mysterious, will contribute to the prestige of Athens and Pericles. Very many mine shafts will... more
The mines of the Laurion plateau were in full operation from 480 to 431 BC. These silver-bearing lead mines, the exploitation of which remains mysterious, will contribute to the prestige of Athens and Pericles. Very many mine shafts will be dug in marble by slaves. These mine shafts sometimes go down to a hundred meters. "However, from twenty to thirty meters, the measurements showed that oxygen began to be scarce. Impossible to descend and even less to dig without respiratory assistance ..." To extract the rubble it was necessary to prevent all oscillatory movements with the bucket. It was suspended from a 100 m rope and moved through one of the conduits of the compartmentalized well. The bucket was fringed with flexible plants, self-centering in the extraction duct. The access conduit was a free column with baffles. Each time the bucket was raised, an atmospheric depression was produced in this column, thus creating a movement of around one hundred cubic meters of fresh air. For ten thousand winches we arrive at a fairly substantial volume of one million cubic meters of fresh air. It is quite likely that the venting of the Laurion mines was fortuitous.
- by Alain Faisant
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Experimental observations of confined granular materials in the presence of an electric field that induces cohesive forces are reported. The angle of repose is found to increase with the cohesive force. A theoretical model for the... more
Experimental observations of confined granular materials in the presence of an electric field that induces cohesive forces are reported. The angle of repose is found to increase with the cohesive force. A theoretical model for the stability of a granular heap, including both the effect of the sidewalls and cohesion is proposed. A good agreement between this model and the experimental results is found. The steady-state flow angle is practically unaffected by the electric field except for high field strengths and low flow rates.
On one hand the graph isomorphism problem (GI) has received considerable attention due to its unresolved complexity status and its many practical applications. On the other hand a notion of compatible topologies on graphs has emerged from... more
On one hand the graph isomorphism problem (GI) has received considerable attention due to its unresolved complexity status and its many practical applications. On the other hand a notion of compatible topologies on graphs has emerged from digital topology (see [5, 7, 17, 9, 14, 16]). In this article we study GI from the topological point of view. Firstly we explore the poset of compatible topologies on graphs and in particular on bipartite graphs. Then, from a graph we construct a particular compatible Alexandroff topological space said homeomorphic-equivalent to the graph. Conversely from any Alexandroff topology we construct an isomorphic-equivalent graph on which the topology is compatible. Finally using these constructions, we show that GI is polynomial-time equivalent to the topological homeomorphism problem (T opHomeo). Hence GI and T opHomeo are in the same class of complexity. Key words: Graph isomorphism problem, compatible topology on graph, homeomorphism
Experimental observations of confined granular materials in the presence of an electric field that induces cohesive forces are reported. The angle of repose is found to increase with the cohesive force. A theoretical model for the... more
Experimental observations of confined granular materials in the presence of an electric field that induces cohesive forces are reported. The angle of repose is found to increase with the cohesive force. A theoretical model for the stability of a granular heap, including both the effect of the sidewalls and cohesion is proposed. A good agreement between this model and the experimental results is found. The steady-state flow angle is practically unaffected by the electric field except for high field strengths and low flow rates.
Context Changes in environmental conditions may influence bird populations, including pest bird species, and their distribution. In Argentina, particularly in the Pampas region, agricultural expansion has resulted in important changes in... more
Context Changes in environmental conditions may influence bird populations, including pest bird species, and their distribution. In Argentina, particularly in the Pampas region, agricultural expansion has resulted in important changes in agroecosystems, with impacts on bird species. Aims This study analysed the relationship between pest bird densities and the environmental variables associated with land use and/or cover, vegetation productivity and climate. The study focused on the most important pest bird species to grain crops in Argentina and Uruguay: the eared dove (Zenaida auriculata) and the monk parakeet (Myiopsitta monachus). Methods An area in Central Argentina was divided into three agro-productive regions, one predominantly agricultural and two with mixed production activities: agricultural rangeland and agricultural forested rangeland. Bird populations were sampled on a yearly basis between 2003 and 2011 in point-transects located along secondary roads (47 routes in tota...
We have studied single curved films stabilized by globular proteins, using small angle scattering. By combining both the use of in-house X-ray and synchrotron radiation, we have measured the structural properties of films (thickness,... more
We have studied single curved films stabilized by globular proteins, using small angle scattering. By combining both the use of in-house X-ray and synchrotron radiation, we have measured the structural properties of films (thickness, electronic density) by controlling the physicochemical properties of protein (ovalbumin, pH 7, bulk concentration 10 g L À1). For each experiment, solutions of highly purified protein were freshly prepared to eliminate any problem of aging. The observation of Kiessig fringes shows that the films are thin with an average thickness of 60 nm. Benefiting from the fine angular resolution and the short acquisition time of a synchrotron source, we have highlighted a stratification formation inside the films. This phenomenon suggests protein structural reorganization under confinement, possibly driven by high osmotic pressure.
lished human temporal bone measurements. We showed that the cochlea influences the transfer function only at high frequency and could be omitted from a surgical simulator. In addition, surgeons were able to manipulate the validated middle... more
lished human temporal bone measurements. We showed that the cochlea influences the transfer function only at high frequency and could be omitted from a surgical simulator. In addition, surgeons were able to manipulate the validated middle ear model with a real-time haptic feedback. The computational efficiency of our approach allowed real-time interactions, making it suitable for use in a training simulator.
Cochlear implant array insertion forces are potentially related to cochlear trauma. We compared these forces between a standard (Digisonic SP; Neurelec, Vallauris, France) and an array prototype (Neurelec) with a smaller diameter. The... more
Cochlear implant array insertion forces are potentially related to cochlear trauma. We compared these forces between a standard (Digisonic SP; Neurelec, Vallauris, France) and an array prototype (Neurelec) with a smaller diameter. The arrays were inserted by a mechatronic tool in 23 dissected human cochlea specimens exposing the basilar membrane. The array progression under the basilar membrane was filmed together with dynamic force measurements. Insertion force profiles and depth of insertion were compared. The recordings showed lower insertion forces beyond 270° of insertion and deeper insertions with the thin prototype array. This will potentially allow larger cochlear coverage with less trauma.
- by Yann Nguyen and +1
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- Robotics, Robotic Surgery, Tissue Banks, Cochlear Implant
Computer-assisted navigation systems can now potentially guide the surgeon to the cochlea with a trajectory avoiding the facial nerve through a keyhole approach. Five temporal bone specimens, with 4 titanium screws placed in the mastoid... more
Computer-assisted navigation systems can now potentially guide the surgeon to the cochlea with a trajectory avoiding the facial nerve through a keyhole approach. Five temporal bone specimens, with 4 titanium screws placed in the mastoid cortex, were studied. Preoperative computed tomographic scan images were loaded on an electromagnetic computer-assisted surgery (CAS) system (Digipointeur, Collin, Bagneux, France). A drill was connected to the CAS to monitor its progression continuously. A conical approach passing through the facial recess and ending in the scala tympani was performed. A 0.5-mm wire was inserted into the cochlea. The keyhole approach was technically feasible in all cases. No facial nerve injury was observed on imaging and dissection control. The wire was positioned in the scala tympani and the position accuracy of the CAS was <0.76 mm on the target in all cases. The CAS system with fiducial markers yielded sufficient precision to allow a minimally invasive approach to the cochlea.
Otological microsurgery is delicate and requires high dexterity in bad ergonomic conditions. To assist surgeons in these indications, a teleoperated system, called RobOtol, is developed. This robot enhances gesture accuracy and handiness... more
Otological microsurgery is delicate and requires high dexterity in bad ergonomic conditions. To assist surgeons in these indications, a teleoperated system, called RobOtol, is developed. This robot enhances gesture accuracy and handiness and allows exploration of new procedures for middle ear surgery. To plan new procedures that exploit the capacities given by the robot, a surgical simulator is developed. The simulation reproduces with high fidelity the behavior of the anatomical structures and can also be used as a training tool for an easier control of the robot for surgeons. In the paper, we introduce the middle ear surgical simulation and then we perform virtually two challenging procedures with the robot. We show how interactive simulation can assist in analyzing the benefits of robotics in the case of complex manipulations or ergonomics studies and allow the development of innovative surgical procedures. New robot-based microsurgical procedures are investigated. The improvement offered by RobOtol is also evaluated and discussed.
- by Yann Nguyen and +1
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- Robotics, Algorithms, Technology, Microsurgery
Introduction. In order to achieve a minimal trauma to the inner ear structures during array insertion, it would be suitable to control insertion forces. The aim of this work was to compare the insertion forces of an array insertion into... more
Introduction. In order to achieve a minimal trauma to the inner ear structures during array insertion, it would be suitable to control insertion forces. The aim of this work was to compare the insertion forces of an array insertion into anatomical specimens with three different insertion techniques: with forceps, with a commercial tool, and with a motorized tool. Materials and Methods. Temporal bones have been mounted on a 6-axis force sensor to record insertion forces. Each temporal bone has been inserted, with a lateral wall electrode array, in random order, with each of the 3 techniques. Results. Forceps manual and commercial tool insertions generated multiple jerks during whole length insertion related to fits and starts. On the contrary, insertion force with the motorized tool only rose at the end of the insertion. Overall force momentum was 1.16 ± 0.505 N (mean ± SD, = 10), 1.337 ± 0.408 N ( = 8), and 1.573 ± 0.764 N ( = 8) for manual insertion with forceps and commercial and motorized tools, respectively. Conclusion. Considering force momentum, no difference between the three techniques was observed. Nevertheless, a more predictable force profile could be observed with the motorized tool with a smoother rise of insertion forces.
Hypothesis: Loading otoprotective drug into cochlear implant might change its mechanical properties, thus compromising atraumatic insertion. This study evaluated the effect of incorporation of dexamethasone (DXM) in the silicone of... more
Hypothesis: Loading otoprotective drug into cochlear implant might change its mechanical properties, thus compromising atraumatic insertion. This study evaluated the effect of incorporation of dexamethasone (DXM) in the silicone of cochlear implant arrays on insertion forces. Background: Local administration of DXM with embedded array can potentially reduce inflammation and fibrosis after cochlear implantation procedure to improve hearing preservation and reduce long-term impedances. Methods: Four models of arrays have been tested: 0.5-mm distal diameter array (n = 5) used as a control, drug-free 0.4-mm distal diameter array (n = 5), 0.4-mm distal diameter array with 1% eluded DXM silicone (n = 5), and 0.4-mm distal diameter array with 10% eluded DXM silicone (n = 5). Via a motorized insertion bench, each array has been inserted into an artificial scala tympani model. The forces were recorded by a 6-axis force sensor. Each array was tested seven times for a total number of 140 insertions. Results: During the first 10-mm insertion, no difference between the four models was observed. From 10-to 24-mm insertion, the 0.5-mm distal diameter array presented higher insertion forces than the drug-free 0.4-mm distal diameter arrays, with or without DXM. Friction forces for drug-free 0.4-mm distal diameter array and 0.4-mm distal diameter DXM eluded arrays were similar on all insertion lengths. Conclusion: Incorporation of DXM in silicone for cochlear implant design does not change electrode array insertion forces. It does not raise the risk of trauma during array insertion, making it suitable for long-term in situ administration to the cochlea.
This paper is centered on the development of a new training and rehearsal simulation system for middle ear surgery. First, we have developed and validated a mechanical atlas based on finite element method of the human middle ear. The... more
This paper is centered on the development of a new training and rehearsal simulation system for middle ear surgery. First, we have developed and validated a mechanical atlas based on finite element method of the human middle ear. The atlas is based on a microMRI. Its mechanical behavior computed in real-time has been successfully validated. In addition, we propose a method for the registration of the mechanical atlas on patient imagery. The simulation can be used for a rehearsal surgery with the geometrical anatomy of a given patient and with mechanical data that are validated. Moreover, this process does not necessitate a complete re-built of the model.
Middle ear surgery involves the smallest and the most fragile bones of the human body. Since microsurgical gestures and a submillimetric precision are required in these procedures, the outcome can be potentially improved by robotic... more
Middle ear surgery involves the smallest and the most fragile bones of the human body. Since microsurgical gestures and a submillimetric precision are required in these procedures, the outcome can be potentially improved by robotic assistance. Today, there is no commercially available device in this field. Here, we describe a method to design a teleoperated assistance robotic system dedicated to the middle ear surgery. Determination of design specifications, the kinematic structure, and its optimization are detailed. The robot-surgeon interface and the command modes are provided. Finally, the system is evaluated by realistic tasks in experimental dedicated settings and in human temporal bone specimens.
- by Yann Nguyen and +1
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- Robotics, Computational Biology, Microsurgery, Software
Hypothesis: The aim of the study was to evaluate force profiles during array insertion in human cochlea specimens and to evaluate a mechatronic inserter using a 1-axis force sensor. Background: Today, the surgical challenge in cochlear... more
Hypothesis: The aim of the study was to evaluate force profiles during array insertion in human cochlea specimens and to evaluate a mechatronic inserter using a 1-axis force sensor. Background: Today, the surgical challenge in cochlear implantation is the preservation of the anatomical structures and the residual hearing. In routine practice, the electrode array is inserted manually with a limited sensitive feedback. Material and methods: Hifocus 1J electrode arrays (Advanced Bionics Inc., Valencia, CA) were studied. The bench test comprised a mechatronic inserter combined to a 1axis force sensor between the inserter and the base of the array and a 6-axis force sensor beneath the cochlea model. Influence of insertion tube material, speed (0.15, 0.5 and 1.5 mm/s) and lubricant on frictions forces were studied (no-load). Different models were subsequently evaluated: epoxy scala tympani model and temporal bones. Results: Frictions forces were lower with in the plastic tube compared to the metal tube 0.09±0.028 vs 0.14±0.034 at 0.5 mm/s, p<0.001) and with the use of hyaluronic acid gel. Speed did not influence frictions forces in our study. Insertion force profiles provided by the 1-and 6-axis force sensors were similar when friction forces inside the insertion tool (no-load measurements) were subtracted from the 1-axis sensor data in the epoxy and temporal bone models (mean error: 0.01±0.001 N). Conclusion: Using a sensor included in the inserter, we were able to measure array insertion forces. This tool can be potentially used to provide real-time information to the Powered by Editorial Manager® and Preprint Manager® from Aries Systems Corporation surgeon during the procedure.
- by Yann Nguyen and +1
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- Zoology, Cochlear Implants, Friction, Clinical Sciences
RobOtol is a micro-surgical tele operated system designed to assist middle ear surgery. A new prototype, with an improved controller system and mechanical enhancement is presented. Surgeons and engineers evaluated the robot by tasks... more
RobOtol is a micro-surgical tele operated system designed to assist middle ear surgery. A new prototype, with an improved controller system and mechanical enhancement is presented. Surgeons and engineers evaluated the robot by tasks specific to middle ear surgery with two command modes (position-velocity and position-position) and by questionnaires. There was no prevailing command mode. A human robot interface was developed to offer easy and fast intra operative adaptation of the command mode to surgeons' preferences and specific situations.
- by Yann Nguyen and +1
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- OPERATING SYSTEM
Middle ear surgery requires micro-surgical techniques and may benefit from robotic assistance. A prototype of tele-operated system is presented. Methods to determine design specifications, kinematic structure and optimization of the... more
Middle ear surgery requires micro-surgical techniques and may benefit from robotic assistance. A prototype of tele-operated system is presented. Methods to determine design specifications, kinematic structure and optimization of the micro-manipulator are described. First evaluation of the robot by a stapedial removal through the external auditory meatus in human temporal bone specimens, simulating the surgery of otosclerosis, is presented. In this procedure, the robot yielded accessibility to the target area with a reduced visual impairment and, an enhanced tool stability compared to the surgeon's hand.
- by Yann Nguyen and +1
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- Surgery, OPERATING SYSTEM, Visual Impairment, Telerobotics
In order to design a drug delivery system to the human cochlea, a magnetic pump driving Fe3O4 super paramagnetic nanoparticles (MNP) attachable to a drug was evaluated. Such a device could be inserted into the cochlea by a minimally... more
In order to design a drug delivery system to the human cochlea, a magnetic pump driving Fe3O4 super paramagnetic nanoparticles (MNP) attachable to a drug was evaluated. Such a device could be inserted into the cochlea by a minimally invasive technique. In this study, the effect of a magnetic field generated by solenoids coiled around a 1 mm diameter catheter filled with 200 nm MNP was studied. Results showed that, particles can be concentrated at different locations of the catheter for a precise delivery at different cochlear locations. The particles could also be driven between 2 solenoids 50 mm apart with 150 mA which is compatible with current sources in available cochlear implants.
- by Yann Nguyen and +1
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