Experimental Study of electron acceleration by plasma beat-waves with Nd lasers

International audienceWe have observed the acceleration of electrons by a beat-wave generated in a deuterium plasma by two Nd-YAG and Nd-YLF laser wavelengths. Electrons injected at an energy of 3.3 MeV are observed to be accelerated up to 4.7 MeV after the plasma. The energy gain is compatible with a peak electric field of the order of 1.2 GV/m. The experiment has been performed with different injection energies, from 2.5 to 3.3 MeV, with different plasma dimensions, and with different laser intensitie

Recent trends in the design of large RF, microwave and ECR ion sources for the production of broad ion beams

Recently there have been considerable interest in the application of large RF, microwave and ECR ion sources for the production of monoenergetic ion beams of very large cross-section dedicated to specific surface treatments and modification of materials. We recall the recent trends and novel concepts in the design of these different classes of ion sources. Studies involving the production of singly charged, high density inert or reactive ion beams are described. Particular attention is given to the beam homogeneity and to the production of low energy ion beams. Different kinds of acceleration-deceleration systems including sets of parallel wires are presented and their respective figures of merit outlined. Optimization of the microwave power coupling to the plasma is presented in the case of circular or rectangular waveguides ionization chambers and circular vacuum tight windows which are the most vulnerable part of the ions source. As far as protection of the window against deposited films, backstreaming electron bombardment and overheating is concern, we describe the resonant slit in a metallic diagram located downstream the window. This simple component gives a very significant improvement of the microwave coupling and its lifetime

Degenerative lumbar disc disease: in vivo data support the rationale for the selection of appropriate animal models

Since low-back pain is increasing in ageing populations, current research efforts are focused on obtaining a better understanding of the pathophysiology of intervertebral disc degeneration and on developing new therapeutic strategies. This requires adequate and clinically relevant models of the disease process. Ex vivo models can provide insights into isolated aspects of the degenerative/regenerative processes involved; although, ultimately, in vivo models are needed for preclinical translational studies. Such models have been developed in numerous animal species with significant variations in size and disc physiology and their number is considerable. Importantly, the choice of the model has to be tailored to the aim of the study. Given the number of available options, it is important to have a good understanding of the various models of disc degeneration and to be fully aware of their advantages and limitations. After comparing the anatomy and histology of intervertebral discs in animals and humans, the present study provides an overview of the different models of in vivo disc degeneration. It also provides a comprehensive guide with suggested criteria to select the most appropriate animal model in a question-driven manner

Degenerative lumbar disc disease: in vivo data support the rationale for the selection of appropriate animal models

Since low-back pain is increasing in ageing populations, current research efforts are focused on obtaining a better understanding of the pathophysiology of intervertebral disc degeneration and on developing new therapeutic strategies. This requires adequate and clinically relevant models of the disease process. Ex vivo models can provide insights into isolated aspects of the degenerative/regenerative processes involved; although, ultimately, in vivo models are needed for preclinical translational studies. Such models have been developed in numerous animal species with significant variations in size and disc physiology and their number is considerable. Importantly, the choice of the model has to be tailored to the aim of the study. Given the number of available options, it is important to have a good understanding of the various models of disc degeneration and to be fully aware of their advantages and limitations. After comparing the anatomy and histology of intervertebral discs in animals and humans, the present study provides an overview of the different models of in vivo disc degeneration. It also provides a comprehensive guide with suggested criteria to select the most appropriate animal model in a question-driven manner

Correlation between magnetic resonance, X-ray imaging alterations and histological changes in an ovine model of age-related disc degeneration

International audienceSheep are one of the many animal models used to investigate the pathophysiology of disc degeneration and the regenerative strategies for intervertebral disc (IVD) disease. To date, few studies have thoroughly explored ageing of ovine lumbar IVDs. Hence, the objective of the present study was to concomitantly assess the development of spontaneous age-related lumbar IVD degeneration in sheep using X-ray, magnetic resonance imaging (MRI) as well as histological analyses. 8 young ewes ( 48 months old) were included. Disc height, Pfirrmann and modified Pfirrmann grades as well as T2-wsi and T2 times were assessed by X-ray and MRI. The modified Boos score was also determined using histology sections. Pfirrmann (2 to 3) and modified Pfirrmann (2 to 4) grades as well as Boos scores (7 to 13) gradually increased with ageing, while T2-weighted signal intensity (1.18 to 0.75), T2 relaxation time (114.36 to 70.65 ms) and disc height (4.1 to 3.2 mm) decreased significantly. All the imaging modalities strongly correlated with the histology (p < 0.0001). The present study described the suitability of sheep as a model of age-related IVD degeneration by correlation of histological tissue alterations with the changes observed using X-ray and MRI. Given the structural similarities with humans, the study demonstrated that sheep warrant being considered as a pertinent animal model to investigate IVD regenerative strategies without induction of degeneration