Application of a simplifying model to the breakage of different materials in an air jet mill

Cet article est paru de nouveau en 2012 dans la revue "International journal of mineral processing", special issue Comminution 2009, (ESCC 2009 - European Symposium on Comminution and Classification, Espoo, Finland, September 15-18, 2009) vol. 112-113, pp. 7-12. (L'article de référence reste celui de 2011 pour les citations bibliographiques).International audienceThis paper describes the application of a unifying `master curve' model for single impact size reduction in an air jet mill. Based on a dimensional analysis and a modified fracture mechanical theory, it enables to relate the weight percentage of broken particles under sieve cut size to the mean sieve cut size of the studied material, the net kinetic energy provided to the material, the number of impacts and a global parameter f(Mat). Altogether 11 sieve cuts of different materials are impacted in an experimental air jet mill. Minimum breakage energies are derived and are shown to vary with a power function of the sieve cut size. The simplifying model is then successfully applied and enables to derive the fMat. parameters. In our situation, the experimental data do not show a direct relationship between fMat. and the minimum breakage energy and sieve cut size for all the materials

Modifying upper-limb inter-joint coordination in healthy subjects by training with a robotic exoskeleton

Background: The possibility to modify the usually pathological patterns of coordination of the upper-limb in stroke survivors remains a central issue and an open question for neurorehabilitation. Despite robot-led physical training could potentially improve the motor recovery of hemiparetic patients, most of the state-of-the-art studies addressing motor control learning, with artificial virtual force fields, only focused on the end-effector kinematic adaptation, by using planar devices. Clearly, an interesting aspect of studying 3D movements with a robotic exoskeleton, is the possibility to investigate the way the human central nervous system deals with the natural upper-limb redundancy for common activities like pointing or tracking tasks. Methods: We asked twenty healthy participants to perform 3D pointing or tracking tasks under the effect of inter-joint velocity dependant perturbing force fields, applied directly at the joint level by a 4-DOF robotic arm exoskeleton. These fields perturbed the human natural inter-joint coordination but did not constrain directly the end-effector movements and thus subjects capability to perform the tasks. As a consequence, while the participants focused on the achievement of the task, we unexplicitly modified their natural upper-limb coordination strategy. We studied the force fields direct effect on pointing movements towards 8 targets placed in the 3D peripersonal space, and we also considered potential generalizations on 4 distinct other targets. Post-effects were studied after the removal of the force fields (wash-out and follow up). These effects were quantified by a kinematic analysis of the pointing movements at both end-point and joint levels, and by a measure of the final postures. At the same time, we analysed the natural inter-joint coordination through PCA. Results: During the exposition to the perturbative fields, we observed modifications of the subjects movement kinematics at every level (joints, end-effector, and inter-joint coordination). Adaptation was evidenced by a partial decrease of the movement deviations due to the fields, during the repetitions, but it occurred only on 21% of the motions. Nonetheless post-effects were observed in 86% of cases during the wash-out and follow up periods (right after the removal of the perturbation by the fields and after 30 minutes of being detached from the exoskeleton). Important inter-individual differences were observed but with small variability within subjects. In particular, a group of subjects showed an over-shoot with respect to the original unexposed trajectories (in 30% of cases), but the most frequent consequence (in 55% of cases) was the partial persistence of the modified upper-limb coordination, adopted at the time of the perturbation. Temporal and spatial generalizations were also evidenced by the deviation of the movement trajectories, both at the end-effector and at the intermediate joints and the modification of the final pointing postures towards targets which were never exposed to any field. Conclusions: Such results are the first quantified characterization of the effects of modification of the upper-limb coordination in healthy subjects, by imposing modification through viscous force fields distributed at the joint level, and could pave the way towards opportunities to rehabilitate pathological arm synergies with robots

Do robotic and non-robotic arm movement training drive motor recovery after stroke by a common neural mechanism? Experimental evidence and a computational model.

Different dose-matched, upper extremity rehabilitation training techniques, including robotic and non-robotic techniques, can result in similar improvement in movement ability after stroke, suggesting they may elicit a common drive for recovery. Here we report experimental results that support the hypothesis of a common drive, and develop a computational model of a putative neural mechanism for the common drive. We compared weekly motor control recovery during robotic and unassisted movement training techniques after chronic stroke (n = 27), as assessed with quantitative measures of strength, speed, and coordination. The results showed that recovery in both groups followed an exponential time course with a time constant of about 4-5 weeks. Despite the greater range and speed of movement practiced by the robot group, motor recovery was very similar between the groups. The premise of the computational model is that improvements in motor control are caused by improvements in the ability to activate spared portions of the damaged corticospinal system, as learned by a biologically plausible search algorithm. Robot-assisted and unassisted training would in theory equally drive this search process

Rapid Displacement of Dengue Virus Type 1 by Type 4, Pacific Region, 2007–2009

Since 2000–2001, dengue virus type 1 has circulated in the Pacific region. However, in 2007, type 4 reemerged and has almost completely displaced the strains of type 1. If only 1 serotype circulates at any time and is replaced approximately every 5 years, DENV-3 may reappear in 2012

The high burden of hospitalizations for primary EBV infection: a 6-year prospective survey in a French hospital

AbstractPrimary Epstein-Barr virus infection (PEI) is acquired increasingly later in life in developed countries, involving a growing number of adults. No studies have examined the effect of age on PEI. We conducted a prospective, single-centre, noninterventional survey to assess the clinical and economic effects of PEI care according to age. We included all serology-confirmed cases observed in all departments of a large regional hospital. Clinical and biologic data, therapeutics and costs of care were examined. Over a 6-year period, we included 292 subjects (148 children and 144 adults) with a median age of 15.4 years (range 9 months to 79 years). Adults were hospitalized more often (83% vs. 60%) and for longer periods of time (median 4 days vs. 2 days) than children (p ≤ 0.0001 for both). Two adults required a secondary transfer into the intensive care unit, although no children did. Typically, adults showed higher levels of activated lymphocytes and liver abnormalities. They also required the use of systemic corticosteroids more often (45% vs. 23%, p < 0.0001) and for longer periods of time (median 7 days vs. 3 days, p 0.02) than children. Overall, the costs were significantly higher for adults than for children (median, €1940 vs. €1130, p < 0.0001), mainly because of the frequency and duration of hospitalizations. Age increases the immune response and clinical severity of PEI, resulting in substantial additional costs for the community. Better recognition of the disease in adults could shorten the average length of hospital stay

Transcriptome analysis of antigenic variation in Plasmodium falciparum - var silencing is not dependent on antisense RNA

BACKGROUND: Plasmodium falciparum, the causative agent of the most severe form of malaria, undergoes antigenic variation through successive presentation of a family of antigens on the surface of parasitized erythrocytes. These antigens, known as Plasmodium falciparum erythrocyte membrane protein 1 (PfEMP1) proteins, are subject to a mutually exclusive expression system, and are encoded by the multigene var family. The mechanism whereby inactive var genes are silenced is poorly understood. To investigate transcriptional features of this mechanism, we conducted a microarray analysis of parasites that were selected to express different var genes by adhesion to chondroitin sulfate A (CSA) or CD36. RESULTS: In addition to oligonucleotides for all predicted protein-coding genes, oligonucleotide probes specific to each known var gene of the FCR3 background were designed and added to the microarray, as well as tiled sense and antisense probes for a subset of var genes. In parasites selected for adhesion to CSA, one full-length var gene (var2csa) was strongly upregulated, as were sense RNA molecules emanating from the 3' end of a limited subset of other var genes. No global relationship between sense and antisense production of var genes was observed, but notably, some var genes had coincident high levels of both antisense and sense transcript. CONCLUSION: Mutually exclusive expression of PfEMP1 proteins results from transcriptional silencing of non-expressed var genes. The distribution of steady-state sense and antisense RNA at var loci are not consistent with a silencing mechanism based on antisense silencing of inactive var genes. Silencing of var loci is also associated with altered regulation of genes distal to var loci

MHD in von Kármán swirling flows, development and first run of the sodium experiment

URL: http://www-spht.cea.fr/articles/s01/004 MHD dans les écoulements de von Kármán | Collaboration VKSNATO Science Series II 26, 35-50 (2001). NATO Advanced Research Workshop, Dynamo and Dynamics, A Mathematical ChallengeWe describe the motivations, development and first run of the Von Kármán Sodium (VKS) experiment built to study high Reynolds number magnetohydrodynamics and applications to the dynamo effect. The flow is optimized using water experiments at scale 1/2 and kinematic dynamo simulations. In VKS run1, induction measurements are made in the presence of an externally applied field. Results are reported concerning the geometry of the induced field and its fluctuations in time

Recovery in Stroke Rehabilitation through the Rotation of Preferred Directions Induced by Bimanual Movements: A Computational Study

Stroke patients recover more effectively when they are rehabilitated with bimanual movement rather than with unimanual movement; however, it remains unclear why bimanual movement is more effective for stroke recovery. Using a computational model of stroke recovery, this study suggests that bimanual movement facilitates the reorganization of a damaged motor cortex because this movement induces rotations in the preferred directions (PDs) of motor cortex neurons. Although the tuning curves of these neurons differ during unimanual and bimanual movement, changes in PD, but not changes in modulation depth, facilitate such reorganization. In addition, this reorganization was facilitated only when encoding PDs are rotated, but decoding PDs are not rotated. Bimanual movement facilitates reorganization because this movement changes neural activities through inter-hemispheric inhibition without changing cortical-spinal-muscle connections. Furthermore, stronger inter-hemispheric inhibition between motor cortices results in more effective reorganization. Thus, this study suggests that bimanual movement is effective for stroke rehabilitation because this movement rotates the encoding PDs of motor cortex neurons

Optimization of Topical Therapy for Leishmania major Localized Cutaneous Leishmaniasis Using a Reliable C57BL/6 Model

When initiating the cutaneous disease named cutaneous leishmaniasis (CL), Leishmania parasites develop within the parasitophorous vacuoles of phagocytes residing in and/or recruited to the dermis, a process leading to more or less chronic dermis and epidermis-damaging inflammatory processes. Topical treatment of CL could be a mainstay in its management. Any improvements of topicals, such as new vehicles and shorter optimal contact regimes, could facilitate their use as an ambulatory treatment. Recently, WR279396, a third-generation aminoglycoside ointment, was designed with the aim to provide stability and optimal bioavailability for the molecules expected to target intracellular Leishmania. Two endpoints were expected to be reached: i) accelerated clearance of the maximal number of parasites, and ii) accelerated and stable repair processes without scars. A mouse model of CL was designed: it relies on the intradermal inoculation of luciferase-expressing Leishmania, allowing for in vivo bioluminescence imaging of the parasite load fluctuation, which can then be quantified simultaneously with the onset and resolution of clinical signs. These quantitative readout assays, deployed in real time, provide robust methods to rapidly assess efficacy of drugs/compounds i) to screen treatment modalities and ii) allow standardized comparison of different therapeutic agents

A homozygous FANCM mutation underlies a familial case of non-syndromic primary ovarian insufficiency

Primary Ovarian Insufficiency (P01) affects 1% of women under forty. Exome sequencing of two Finnish sisters with non-syndromic P01 revealed a homozygous mutation in FANCM, leading to a truncated protein (p.GIn1701*). FANCM is a DNA-damage response gene whose heterozygous mutations predispose to breast cancer. Compared to the mother's cells, the patients' lymphocytes displayed higher levels of basal and mitomycin C (MMC)-induced chromosomal abnormalities. Their lymphoblasts were hypersensitive to MMC and MMC-induced monoubiquitination of FANCD2 was impaired. Genetic complementation of patient's cells with wild-type FANCM improved their resistance to MMC re-establishing FANCD2 monoubiquitination. FANCM was more strongly expressed in human fetal germ cells than in somatic cells. FANCM protein was preferentially expressed along the chromosomes in pachytene cells, which undergo meiotic recombination. This mutation may provoke meiotic defects leading to a depleted follicular stock, as in Fancrril- mice. Our findings document the first Mendelian phenotype due to a biallelic FANCM mutation