No abstract available

[en] Two-dimensional simulations of beam-driven turbulence in the auroral ionosphere have shown the formation and instability of phase-space tubes. These tubes are a generalization of electron phase-space holes in a one-dimensional plasma. In a strongly magnetized plasma, such tubes vibrate at frequencies below the bounce frequency of the trapping potential. A theory for these vibrations yields quantitative agreement with kinetic simulations. Furthermore, the theory predicts that the vibrations can become unstable when resonantly coupled to electrostatic whistlers -- also in agreement with simulations

[en] This paper reports on an vitro study performed to examine the ability of current-day radiography for detecting metaphyseal bone loss. A block was cut from the anterior aspect of a cadaveric distal femur, sequential sections (approximately 4% of the BMC of the block) were cut from the block, and a fat-equivalent material was substituted in to the void. Following removal of each bone section, the femur was placed in a water bath, a lateral radiography was taken, and the ash content of the section was determined. Five readers each evaluated over 100 combinations of two radiographs side by side, noting whether there was no difference or whether one femur's region of interest was denser. The readings were compared with bone mineral differences as determined by ashing. All readers identified losses of 25% or more, and 5%-10% losses were seen by four of five readers half of the time

[en] Radionuclide bone imaging can be of value in assessing the osseous changes around porous-coated femoral prostheses. Scintimetry appears to be a promising method for determining if radiodensities seen in radiographs of long-term prostheses are indicative of accelerated bone turnover or represent stable osseous structures. In dogs, the periosteal reaction which often occurs within two months of joint surgery masks endosteal-intramedullary osseous changes, including bone ingrowth into the porous coating

[en] The nuclear medicine and biophysics laboratory of the Necker-Enfants malades University Hospital Centre has built a microprocessor controlled Cardiac flowmetre. The principle of the cardiac output measurement from a radiocardiogram is well established. After injection of a radioactive indicator upstream from the heart cavities the dilution curve is obtained by the use of a gamma-ray precordial detector. This curve normally displays two peaks due to passage of the indicator into the right and left sides of the heart respectively. The output is then obtained from the stewart Hamilton principle once recirculation is eliminated. The graphic method used for the calculation however is long and tedious. The decreasing fraction of the dilution curve is projected in logarithmic space in order to eliminate recirculation by determining the mean straight line from which the decreasing exponential is obtained. The principle of the use of microprocessors is explained (electronics, logics)

[en] Training specialists in medical radiation protection is ensured by the Continuous Training Center of University Rene Descartes since 1990. The necessity of updating knowledge has urged us to develop an Internet site (http://www.citi2.fr/RADIO). Besides the mandatory functions of the educational management (secretariat, information on the stages, registrations, etc.) this site provides: 1. Practical information (addresses of administrative and technical organisms, presentation of radiation protection programs); 2. Scientific information (bibliographic bulletin of the EDF service of radiation protection, updated every two months, description of recent radiation protection works); 3. Institutional documentation (analysis of recent basic texts, ICRP publications, European directives). The interrogation of general interest asked via e-mail and forum allowing communication between experts, graduated students and the education faculty will be available on the site. The communication will be augmented by tele-formation modules for continuous distant training

[en] Since two years ago nuclear medicine service of Laennec Hospital has implemented transmission and distribution networks of scintigraphic images. A new stage was reached at present by developing an Intranet and Extranet system for nursing units and other services of nuclear medicine. The Intranet link to the services of Laennec Hospital and AP HP is based on a image server connected to the service gamma camera and, after a possible post-processing, the images are transmitted in PCX format by e-mail, attached to the medical record. For communication between nuclear medicine services, a heavier procedure making use of a program for image processing under inter-file standards has been implemented. To achieve the Extranet link with services and physicians of town, exterior to AP HP, a procedure was installed which allows reaching any nursing unit or town physicians having at their disposal e-mail on a secured network. This procedure will be generalized when the Health secured network, linking the medical bodies to Health insurance institutions, will be operational. The interactive tele-medicine will be achieved by means of a procedure based on Internet cooperative tools (wild cards, video- and vision-conferences) which will permits in all situations an interactive work on all the transmitted patient files

[en] Clinical evaluations of canal-filling, uncemented, femoral stems continue to reveal a loss of density and thickness of the cortex of the proximal femur, consistent with a stress-shielding process. This finding has stimulated interest in the implementation of more flexible carbon fiber-reinforced polymer (CFRP) composite devices. In this study, unilateral total hip arthroplasty was performed on 34 canines using CFRP or geometrically identical titanium alloy femoral endoprostheses for periods of 6, 12, or 24 months. The CFRP composite stems had approximately one-half the bending stiffness of the metallic controls. The collarless, straight stems had a canal-filling design developed expressly for dogs. The prostheses were uncoated, with a relatively smooth surface, and were implanted with a press-fit. Computed tomography (CT) was used to quantify the remodeling of bone around the implants

[en] Spinal cord injury (SCI) presents a complex regenerative problem due to the multiple facets of growth inhibition that occur following trauma to the cord parenchyma and stroma. Clinically, SCI is further complicated by the heterogeneity in the size, shape and extent of human injuries. Many of these injuries do not breach the dura mater and have continuous viable axons through the injury site that can later lead to some degree of functional recovery. In these cases, surgical manipulation of the spinal cord by implanting a preformed scaffold or drug delivery device may lead to further damage. Given these circumstances, in situ-forming scaffolds are an attractive approach for SCI regeneration. These synthetic and natural polymers undergo a rapid transformation from liquid to gel upon injection into the cord tissue, conforming to the individual lesion site and directly integrating with the host tissue. Injectable materials can be formulated to have mechanical properties that closely match the native spinal cord extracellular matrix, and this may enhance axonal ingrowth. Such materials can also be loaded with cellular and molecular therapeutics to modulate the wound environment and enhance regeneration. This review will focus on the current status of in situ-forming materials for spinal cord repair. The advantages of, and requirements for, such polymers will be presented, and examples of the behavior of such systems in vitro and in vivo will be presented. There are helpful lessons to be learned from the investigations of injectable hydrogels for the treatment of SCI that apply to the use of these biomaterials for the treatment of lesions in other central nervous system tissues and in organs comprising other tissue types. (topical review)

No abstract available