Evolution in prostheses for sprinters with lower-limb amputation

Depuis une quinzaine d'années, les progrès techniques en appareillage ont été le facteur déterminant de la progression des performances des sportifs amputés de membre inférieur. Pour l'amputé tibial, la prothèse de course comprend un manchon gel et une emboîture solidarisés par un accrochage distal ou un vide virtuel. Par ses qualités dynamiques, le pied en fibre de carbone, garni de pointes, assure des performances remarquables. Pour l'amputé fémoral, équipé des mêmes pieds prothétiques, le genou est à biellettes et à contrôle des phases d'appui et pendulaire. Par rapport au coureur valide, le temps d'appui sur le membre appareillé est raccourci tandis que celui sur le membre sain est allongé. L'asymétrie du sprint de l'amputé tibial est discrète. C'est le travail des extenseurs de hanche qui est la principale compensation au déficit de propulsion dû à l'amputation. Chez l'amputé fémoral, l'absence de genou aggrave l'asymétrie. L'extension totale du genou prothétique, précoce en fin de phase oscillante et persistant pendant toute la phase d'appui, impose une compensation par une augmentation d'extension de la hanche controlatérale. Les transferts de charge de travail entre côté amputé et sain, par l'intermédiaire d'une hyperlordose lombaire, mettent en jeu le bassin, le tronc et les épaules. Les amputés sportifs font progresser la recherche en appareillage. Leurs orthoprothésistes acquièrent avec eux un savoir-faire dont bénéficient leurs patients non-sportifs.For about 15 years, technical advances in prosthetic treatment have been the main factor in the increased performance of athletes with lower-limb amputation. For trans-tibial amputation, the prosthesis for sprinting is composed of a gel liner and a socket joined by a locking or virtual vacuum liner. Because of these dynamic properties, the carbon prosthetic foot equipped with tacks ensures outstanding performance. For trans-femoral amputation, a hydraulic swing and a stance control unit are added to the same prosthesis. In comparison with the able-bodied runner, athletes with amputation have smaller loading times in the prosthetic limb and larger ones in the sound limb. The length of the energy-storing prosthetic foot is determined by the “up-on-the-toes” running gait. The sprinting gait with trans-tibial amputation is almost symmetrical. The hip extensor effort is the main compensation of propulsion reduction with lower-limb amputation. With trans-femoral amputation, the lack of knee increases the asymmetry. The total prosthetic knee extension (early in late-swing phase and lasting during total stance phase) compensates with extension of both hips, especially the opposite one. The amputation and sound limb load transfer with lumbar hyperlordosis concern the pelvis, trunk and shoulders. Because of athletes with amputation, research in prosthetic treatment has progressed. The development of orthotics and prostheses for such athletes has benefited non-athletes with amputation

PHARAO Laser Source Flight Model: Design and Performances

In this paper, we describe the design and the main performances of the PHARAO laser source flight model. PHARAO is a laser cooled cesium clock specially designed for operation in space and the laser source is one of the main sub-systems. The flight model presented in this work is the first remote-controlled laser system designed for spaceborne cold atom manipulation. The main challenges arise from mechanical compatibility with space constraints, which impose a high level of compactness, a low electric power consumption, a wide range of operating temperature and a vacuum environment. We describe the main functions of the laser source and give an overview of the main technologies developed for this instrument. We present some results of the qualification process. The characteristics of the laser source flight model, and their impact on the clock performances, have been verified in operational conditions.Comment: Accepted for publication in Review of Scientific Instrument

A Unified Theoretical Description of the Thermodynamical Properties of Spin Crossover with Magnetic Interactions

After the discovery of the phenomena of light-induced excited spin state trapping (LIESST), the functional properties of metal complexes have been studied intensively. Among them, cooperative phenomena involving low spin-high spin (spin-crossover) transition and magnetic ordering have attracted interests, and it has become necessary to formulate a unified description of both phenomena. In this work, we propose a model in which they can be treated simultaneously by extending the Wajnflasz-Pick model including a magnetic interaction. We found that this new model is equivalent to Blume-Emery-Griffiths (BEG) Hamiltonian with degenerate levels. This model provides a unified description of the thermodynamic properties associated with various types of systems, such as spin-crossover (SC) solids and Prussian blue analogues (PBA). Here, the high spin fraction and the magnetization are the order parameters describing the cooperative phenomena of the model. We present several typical temperature dependences of the order parameters and we determine the phase diagram of the system using the mean-field theory and Monte Carlo simulations. We found that the magnetic interaction drives the SC transition leading to re-entrant magnetic and first-order SC transitions.Comment: 30pages, 11figure

Collective effects in spin-crossover chains with exchange interaction

The collective properties of spin-crossover chains are studied. Spin-crossover compounds contain ions with a low-spin ground state and low lying high-spin excited states and are of interest for molecular memory applications. Some of them naturally form one-dimensional chains. Elastic interaction and Ising exchange interaction are taken into account. The transfer-matrix approach is used to calculate the partition function, the fraction of ions in the high-spin state, the magnetization, susceptibility, etc., exactly. The high-spin-low-spin degree of freedom leads to collective effects not present in simple spin chains. The ground-state phase diagram is mapped out and compared to the case with Heisenberg exchange interaction. The various phases give rise to characteristic behavior at nonzero temperatures, including sharp crossovers between low- and high-temperature regimes. A Curie-Weiss law for the susceptibility is derived and the paramagnetic Curie temperature is calculated. Possible experiments to determine the exchange coupling are discussed.Comment: 9 pages, 13 color figures, published versio

Atmospheric methane during the last four glacial-interglacial cycles: Rapid changes and their link with Antarctic temperature

Atmospheric methane (CH₄) recorded in Antarctic ice cores represents the closest ice proxy available for Greenland temperature changes beyond times when Greenland climate records are available. The record over four climatic cycles from the Vostok ice core offers the opportunity to study the phase relationship between Greenland and Antarctic climate changes through detailed CH₄ profiles. Combining American and French analytical efforts, we have improved the time resolution of the existing CH₄ record from Petit et al. [1999] . Spectral analyses reveal high- and low-frequency variability (including a strong precessional component). The phase relationship between CH₄ and the Antarctic temperature proxy (δD) shows a systematic lag of CH₄ versus temperature by 1100 ± 200 years, on long timescales (50–400 kyr) and a more complex behavior over shorter timescales (i.e., ≤25 kyr), suggesting that Dansgaard/Oeschger-type of climatic variability and associated interhemispheric linkage are robust features of late Quaternary climate

The Migration Policy Simulation: Engaging stakeholders in Austria’s migration future by linking an agent-based model with a policy exercise

This report fulfils the ABM2Policy project Deliverable 2.2: A scientific report describing the protocol and outcomes of the migration-focused gamification exercise and the usefulness of an agent-based model for policy assessment. The goals guiding the research of the ABM2Policy project are twofold: i) to advance macroeconomic agent-based model (ABM) methodology for a realistic and verifiable analysis of migration as an external economic shock to the Austrian national economy, and ii) to explore the usefulness of an ABM combined with a gamified user-interface to support the Austrian migration policymaking discussions and to enhance stakeholder engagement. This Deliverable reports on the second project goal. The ABM was ‘gamified’ by developing a model-based policy exercise (PE) in the complex policy setting of climate migration to Austria. The results of the simulations of a macroeconomic ABM informed (role-playing) stakeholder deliberations, and in some instances, consensus emerged on complex climate migration policy issues. The PE brought to the fore the diverse and often conflicting viewpoints regarding migration through a process of discussion and negotiation, which in turn helped the participants understand the complexities of migration issues in the Austrian context. Overall, the PE participants assessed the game to be an effective tool for gaining knowledge and understanding of the policy process on environmental migration. The preliminary trials show promise in combining an ABM with a PE to support stakeholder deliberations on the migration policy process. The next step is to conduct a similar policy exercise with relevant Austrian stakeholders, e.g., political party members and public officials, to inform actual policy processes

Restriction of HIV-1 Replication in Monocytes Is Abolished by Vpx of SIVsmmPBj

Background: Human primary monocytes are refractory to infection with the human immunodeficiency virus 1 (HIV-1) or transduction with HIV-1-derived vectors. In contrast, efficient single round transduction of monocytes is mediated by vectors derived from simian immunodeficiency virus of sooty mangabeys (SIVsmmPBj), depending on the presence of the viral accessory protein Vpx. Methods and Findings: Here we analyzed whether Vpx of SIVsmmPBj is sufficient for transduction of primary monocytes by HIV-1-derived vectors. To enable incorporation of PBj Vpx into HIV-1 vector particles, a HA-Vpr/Vpx fusion protein was generated. Supplementation of HIV-1 vector particles with this fusion protein was not sufficient to facilitate transduction of human monocytes. However, monocyte transduction with HIV-1-derived vectors was significantly enhanced after delivery of Vpx proteins by virus-like particles (VLPs) derived from SIVsmmPBj. Moreover, pre-incubation with Vpx-containing VLPs restored replication capacity of infectious HIV-1 in human monocytes. In monocytes of non-human primates, single-round transduction with HIV-1 vectors was enabled. Conclusion: Vpx enhances transduction of primary human and even non-human monocytes with HIV-1-derived vectors, only if delivered in the background of SIVsmmPBj-derived virus-like particles. Thus, for accurate Vpx function the presence of SIVsmmPBj capsid proteins might be required. Vpx is essential to overcome a block of early infection steps in primary monocytes

The influence of localised size reorganisation on short-duration bidispersed granular flows

We investigate experimentally the runout resulting from the collapse of a granular column containing two particle species that differ in size only. The experimental configuration is strictly twodimensional (only one particle per width of the experimental tank) and we explore both the role of the initial arrangement and proportion of the two particle sizes in the column, using high-speed videography, and by determining the centres of mass of the big and small particles in the initial column and the final deposit. The duration of the experiment is sufficiently short that large-scale segregation does not occur, however, we find a clear dependence of runout on both initial mixture arrangement and proportion for all conditions. We investigated this observation through detailed analysis of the flow front motion, and identify a characteristic "stopping" phase when dissipation dominates, and we apply a shallow layer model at the flow front to show how the initial mixture arrangement and proportion influence the effective coefficient of friction during emplacement. We find that a bidispersed mixture can induce a larger friction on emplacement than a monodispersed mixture, and the highest coefficient of friction was found for a well-mixed initial arrangement of particles at the proportion that shows maximum horizontal spreading of the flow. These observations suggest that downwards percolation of fine particles takes place at the front of the collapsing column, and so localised size segregation processes at the flow front can control flow mobility. This effect is likely to be important in controlling the mobility of large geophysical flows that occur on finite time scales, and whose deposits typically show granular segregation at the front and edges but not throughout the entire deposit