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This text is the written version of a talk at the Société de Biologie on February 17, 2016. It contains reflections of a non-biologist scientist on general problems of biological evolution, including the kind of causality involved, the ideas emerging from it, in particular the constructive and structuring character of phenomena such as predation, the role of stability and attractors. This leads to a larger reflection on dialectics, the general framework of evolving processes, which overpasses formal logic and instantaneousness.

The history of the Orthopaedics and Traumatology Research Laboratory (LROT) is summarized during the last thirty years. The approach, initially focused on bone biomechanics and strength of materials, underwent a rapid diversification as expressed by the list of research topics: monitoring of bone healing; bone strains measurements for different level of activities including microgravity and prevention of disuse osteoporosis; biological effects of electromagnetic fields; evolution of the viscoelastic properties of the callus during bone healing; improvement of the osteoinductive properties of bone substitutes produced by the Tissues Bank of the University Hospital Erasme; Kashin-Beck disease; SICOT telediagnostic, and biomechanics of threaded implants. Those topics, event the most fundamental ones, have immediate significant clinical applications allowing a decrease of the morbidity and an acceleration of the rehabilitation of the patients. The results show the need of multidisciplinary collaborations coordinated around one autonomous laboratory, able to handle specific protocols requiring a dedicate environment.

Extracranial stereotactic body irradiation (ESRT) provides an alternative treatment mode for patients with no other therapeutic solutions. It's based on previous intracranial stereotactic radiosurgery techniques. ESRT with dedicated systems including secure immobilization avoiding patient movement, accurate repositioning, and stereotactic registration of tumor targets and organs at risk (OAR) allows very high doses in few fractions on extra cranial locations. Standard linacs permit performing SBRT with specific immobilization devices including stereotactic location of the target. Different schemes of ESRT have been published. Comparison of these very diverse schemes is not easy since the prescription mode on target volumes and OAR are not always clearly defined. The Radiotherapy Department of Orléans Hospital chose to set up the ESRT on a conventional accelerator using an immobilization device including a Stereotactic Body Frame and an Active Breathing Control system (Elekta). From 120 patients treated with ESRT since 1999, 90 cases are presented; 28 lung metastases were treated with 40 Gy/5 fr/12 d and 17 liver metastases were treated with 30 Gy/5 fr/12 d prescribed on the 70 to 85 % isodose. The local control was obtained in 50 % of the cases. Twenty-eight patients were treated for T1-T2 N0 lung cancer with 50 Gy/10 fr/12 d on the 80 % isodose. Local control was obtained in 50 % of the cases. Seventeen liver cancers were treated with 30 Gy/10 fr/15 d prescribed on the 70 to 80 % isodose. Local control was obtained in 47 % of the cases. ECRT allows controlling localized tumors (primitives or metastases) and it is now a suitable part of our therapeutic tools as radiofrequency or cryotherapy techniques. Phase II studies are required to confirm its therapeutic potential.

The success of diffusion MRI, which was introduced in the mid 1980s is deeply rooted in the powerful concept that during their random, diffusion-driven movements water molecules probe tissue structure at a microscopic scale well beyond the usual image resolution. The observation of these movements thus provides valuable information on the structure and the geometric organization of tissues. The most successful application of diffusion MRI has been in brain ischemia, following the discovery that water diffusion drops at a very early stage of the ischemic event. Diffusion MRI provides some patients with the opportunity to receive suitable treatment at a very acute stage when brain tissue might still be salvageable. On the other hand, diffusion is modulated by the spatial orientation of large bundles of myelinated axons running in parallel through in brain white matter. This feature can be exploited to map out the orientation in space of the white matter tracks and to visualize the connections between different parts of the brain on an individual basis. Furthermore, recent data suggest that diffusion MRI may also be used to visualize rapid dynamic tissue changes, such as neuronal swelling, associated with cortical activation, offering a new and direct approach to brain functional imaging.

Validation of an experimental ultrasound system on erythrocyte suspensions with variable levels of aggregation and application to the echogenicity quantification of UCA under quasi-physiologic flow conditions. MATERIALS AND METHODS. The system is constituted with a Couette cell with variable applied shear rates, an ultrasound emitter/receiver and a digital scope for radio-frequency signal acquisition. Ultrasound indices (UI) were defined for the two experimental established protocols based on the gold standard laser methodology. Washed red cells with or without variable Dextran 70 kD concentrations were used to simulate a wide particle size range. A preliminary application to UCA was conducted with Levovist for calibration of the system.For each protocol, applied ten times on identical whole blood samples, a student t-test revealed no significant variation for all UI. Results on washed red cells were in good agreement with Rayleigh's theory of ultrasound backscattering. Significant correlations were obtained between laser and UI for washed red cells with different Dextran concentrations. An elevation of 12.13 dB in backscattered intensity was obtained after addition of Levovist.The constituted Couette system allowed reproducible and accurate echogenicity quantification of small scatterers such as UCA in quasi-physiologic blood flow conditions.

Aerobatics is an aerial sport which has many physiological constraints, principally cardiovascular, with a risk if not adapted of sudden mid-air incapacity which could jeopardise aviation safety, and thus justifies the selection and surveillance of pilots. The aeronautical constraints during flight are multiple, related to the environment traversed, how the aircraft functions and its movements. Those which cause accelerations (+G in particular) pose the problem of haemodynamic tolerance because they can induce loss of consciousness due to cerebral hypoxia. Tolerance of acceleration varies among individuals; it can be improved with training, certain protective manoeuvres, and is reduced by hypoxia, certain medications, dehydration and heat. Moreover, in aerobatics certain tricks require manoeuvres which reduce this tolerance to +G accelerations. This is the "push-pull" effect (_G acceleration immediately followed by +G acceleration). This leads to a risk of sudden loss of consciousness with a load factor much lower than that which the pilot knows he is capable of tolerating. Besides the haemodynamic effects, the existence of an actual acceleration cardiomyopathy has been suggested but has not been proven in man. Finally, while changes in cardiac rhythm during accelerations are usual and relate to changes in vaso-sympathetic balance, ventricular and supra-ventricular rhythm disturbances are rare and are related to the intensity and duration of the acceleration.

At present, optimizing control of maximum wheel-rail adhesion, from the anti-skidding systems piloting the sliding and the rolling speeds of locomotives, is done on the basis of the wheel-rail contact models available in the literature. Improved accuracy of power train control has highlighted the limits of this optimization technique since the contact conditions of the models, i.e. the stick/slip zones, do not take into account the physical phenomena involved, although they are hardly known. To attenuate this difficulty, the recent works presented in this paper, allow describing the tribological reality of a wheel-rail contact, i.e. the progression of the stick/slip zones. This reality is achieved thanks to monitoring the changes in the the characteristics of the third body present between wheel and rail. The results of tests under initial condition show that there is a correlation between the progressions of the third body flows and that of the adhesion for the various phases of the adhesion-sliding curve. Therefore activation of the intermal flow of third body is in fact the physical manifestation of the theoretical condition of stick. On the other hand, the activation of the internal source and recirculation flows of the third body are the physical manifestation of the theoretical condition of slip. This tribological reality therefore allows us to update the theoretical stick/slip conditions and by consequence, anti-skidding systems.

We describe an original device developed by the biomedical technicians of the University Hospital of Nancy for checking tightness and measuring the capacity of medical gas pipeline network. A leak can be assessed either as a loss of pressure or as a loss of volume per unit of time (cmH2O.min-1 and mL.min-1 respectively). To assess the latter, the capacity of the explored pipeline must have been measured when it still was gas-tight. With the device, a leak can be assessed within a few minutes whereas the official procedure requires a delay between 1 and 24 hours. The device still has to undergo bench evaluation and validation.

The present study was undertaken to determine whether dynamic postural adjustments in sitting subjects occur during the development of isometric forces and whether the performance, i.e., the maximal isometric force, is related to the surface of contact of the ischio-femoral region with the seat. The subjects were asked to exert maximal horizontal two-handed isometric pushes on a bar. External force (Fx), antero-posterior reaction force (Rx) and antero-posterior displacement of the center of pressure (Xp) were measured continuously during the development of isometric forces, the subsequent hold state lasting 5 s. Two postural conditions were studied that differed by the ischio-femoral contact with the seat (100 or 30%), the foot support being bipodal (BP). It was observed that: a) Fx and Rx increased during the development of isometric forces while Xp moved backwards; b) the instantaneous variations in Fx, in relation to Rx and Xp were linearly related; c) the maximal force reached at the end of the ramp effort and the maximal values of Rx and Xp were significantly increased when the ischio-femoral contact was reduced from 100 to 30 BP. It is concluded that isometric ramp efforts are accompanied by dynamic postural adjustments and that the greater these adjustments, the larger the maximal isometric force. These observations are interpreted as supporting the view that any variation in the external force perturbs the balance of the subject, and that the maximal value of this force depends on the intensity of the dynamic postural counter-perturbation.

In this study, we present an experimental and numerical analysis of thermal plumes issued from electric convectors. The study of the mean velocity and temperature profiles measured within the thermal plume shows that the self-similarity of the profiles is only partly achieved. We developed an integral model that takes into account the settlement flow region by the variations of the entrainment coefficient and the ratio between the temperature and velocity profile widths. A comparison between computed and experimental results proves that the model gives a satisfactory prediction of the physical phenomena. We propose finally a simplified thermal plume model for an integration into a thermal building code.

Pulse oximetry has become the leading technique for monitoring hemoglobin oxygen saturation whenever a risk of hypoxia exists. It is based upon the principle of light absorbance of pulsatile arterial blood. Since it uses 2 wavelengths, it can only measure oxyhemoglobin and reduced hemoglobin. Thus, in case of increased methemoglobin or carboxyhemoglobin, pulse oximetry values are not reliable. Low tissue perfusion can also be responsible for inaccurate values. Nevertheless pulse oximetry is a reliable and easy-to-use technique in most of the clinical situations. This article reviews the physical basis, the reliability, the pediatric aspects, and the limitations of the technique.

Stimulated by epidemic outbreaks in years 80's and 90's detection methods for Listeria, and L. monocytogenes particularly, have undergone many important progresses. New selective media for isolation and enrichment have been formulated with the aim to improve bacteriological methods and decrease time delays. For identification of Listeria at the species level, some biochemical miniaturised tests allow response within 24 h. Within the immuno-chemical methods as ELISA or ELFA, the revelation step has been shortened and automated. The elaboration of L. monocytogenes specific antibodies begins to upset immunological methods. As far as concern simplification of detection tests, a new generation of small immunological plate-shaped tests has been marketed. Whatever the immunological method considered, intrinsic sensibility is about 10(5) at 10(6) CFU/ml. Only one method allows more sensibility: the immuno-magnetic separation. With a sensibility of 1 CFU/ml, immunocapture allows shortening of enrichment time of 24 h or eliminates this step altogether if the aim is to count the Listeria directly in the sample. In the biological molecular methods, some hybridization tests with nuclear probes allow rapid and specific detection of L. monocytogenes. The polymerase chain reaction has been improved to simplify and shorten the DNA preparation and the revelation of amplified fragments. This method will be soon used in food samples analysis. The elaboration of new methods that could allow the specific detection of L. monocytogenes pathogenic strains of is one of future stake.

Magnetic resonance imaging is based upon the phenomenon of nuclear magnetic resonance. The patient is placed in a magnet the provides a strong magnetic field inducing a net magnetization due to hydrogen nuclei inside biological tissues. The image is formed from the localized measurement of this magnetization by means of radio-frequency waves. The contrast is a function of the number of hydrogen nuclei and of the time characteristics T1 and T2 of the return to equilibrium. Many other parameters can be measured by this method and the permanent improvement of the technique will extend further the field of its medical application.

Not being able to equilibrate affirmations and negations, the schizophrenic patient accedes only exceptionally to the majoring equilibrations of the second and third levels. In the logico-mathematic field, he does not approach the constructive synthetizing generalisations of reasoning. Lacking reflective abstraction, he cannot balance his logico-mathematic reasoning and differentiate what is structurally possible from what is materially possible, thus explaining his inaccessibility to perceive logic necessities, contrasting with the certainties of his delirium. In the logico-experimental domain, he reaches only rarely clause reasoning generalisation, and relapses regularly to the level of inappropriate generalisations of the extended inductive type. It is useless to try to find the "primum movens" of his difficulties, either in his imbalance assimilation/accommodation, or in his impossibility to see his contradictions, or even in his incapacity to equilibrate affirmations and negations. The majoring equilibrations, of which he is unable, are the functional expression of structures which do not follow the linear causality of Laplace's determinism but the circular causality characteristic of teleonomic processes. After a month of neuroleptic treatment, the decompensated schizophrenic's balance between assimilation and accommodation is partially restored.

Using the same methods as for the measurement of electrical parameters by means of an oscilloscope with a wave shape calculator to determine at all points the energy and impedance values, as well as high speed cinematography, the analysis of the behavior of these parameters for shocks with energies close to those used in clinical medicine can be carried out. It shows namely an important decrease in the impedance at the current peak due to an important ionization of the fulguration bubble. It underlines the different behavior of the anode and cathode bubbles, in relation with the size of the bubbles obtained thanks to rapid cinematography. Comparative measurements concerning the polarity, the size of the indifferent electrode, the medium used in vitro and in vivo have supplied the elements to enable the precise determination of the adequate electrical parameters for the good use of fulguration.

The electrical phenomena produced during the fulguration impulses are analyzed using a digital oscilloscope which enables the calculation, with precision, of the energies consumed all along the curve or between chosen times. Moreover, it enables the calculation of the corresponding impedance values and shows that the latter varies during all the discharge. The explanation for these impedance variations is obtained thanks to rapid cinematography, showing the formation of the fulguration bubble. Hence, one can observe an impedance variation which is quite distinctive from the one which would correspond to the simple passage of an electrical current in saline solution. Particularly at the end of the impulse, an important increase in the impedance corresponds to the loss of ionization of the bubble. Therefore, by simply reading these electrical parameters, it is possible to know the main stages of the fulguration phenomenon for impulses situated around the deflagration threshold.

Endocavitary discharge produces an electrical spark at the end of the probe. This in turn produces a plume of steam which lasts for about ten milliseconds and which subsequently acts like a cavitation bubble. This phenomenon is well known in the branch of physics dealing with dynamics and fluids, and should be subjected to rapid kinetic recording. It may make it possible to explain various barotraumas which are observed during the discharge. However, the plumes of steam produced by the discharge have some highly specific features which are due to the fact that the discharge is usually produced using a monopole in an electrolyte. In addition, the shape of the electrode also affects the formation of the bubble. This results in a description of the cavitation bubble produced by the discharge as the "discharge bubble".

Previous studies have established that efficiency in shooting is influenced partly by the dynamic characteristics of the stick being used and partly by the morphology of the player. The purpose of the present study was therefore to verify the hypothesis stating that flexible sticks were superior to rigid ones in respect to the proficiency of shooting of pee-wee hockey players. This study has confirmed the superiority of the flexible stick over the rigid one in terms of speed and accuracy of shooting among pee-wee hockey players. Moreover morphological parameters and muscular strength were found to play a determining role in efficiency of shooting. In fact, it was suggested that the smaller and weaker the player the more advantageous is the use of a flexible stick. Through the use of strain gages fixed to the experimental hockey sticks, it was possible to determine that the speed of shooting is directly related to the acceleration imparted to the stick during the forward phase of the movement. It was also possible to demonstrate that for a given speed of the puck the more flexible stick required a smaller force than the rigid one.