Dynamic and instability of submarine avalanches

We perform a laboratory-scale experiment of submarine avalanches on a rough inclined plane. A sediment layer is prepared and thereafter tilted up to an angle lower than the spontaneous avalanche angle. The sediment is scrapped until an avalanche is triggered. Based on the stability diagram of the sediment layer, we investigate different structures for the avalanche front dynamics. First we see a straight front descending the slope, and then a transverse instability occurs. Eventually, a fingering instability shows up similar to rivulets appearing for a viscous fluid flowing down an incline. The mechanisms leading to this new instability and the wavelength selection are discussed.Comment: 4 pages, 6 figures, to appear in the proceedings of Powders and Grains 200

Nonlocal effects in sand flows on an inclined plane

International audienceThe flow of sand on a rough inclined plane is investigated experimentally. We directly show that a jammed layer of grains spontaneously forms below the avalanche. Its properties and its relation with the rheology of the flowing layer of grains are presented and discussed. In a second part, we study the dynamics of erosion and deposition solitary waves in the domain where they are transversally stable. We characterize their shapes and velocity profiles. We relate their translational velocity to the stopping height and to the mass trapped in the avalanche. Finally, we use the velocity profile to get insight into the rheology very close to the jamming limit

Erosion waves: transverse instabilities and fingering

Two laboratory scale experiments of dry and under-water avalanches of non-cohesive granular materials are investigated. We trigger solitary waves and study the conditions under which the front is transversally stable. We show the existence of a linear instability followed by a coarsening dynamics and finally the onset of a fingering pattern. Due to the different operating conditions, both experiments strongly differ by the spatial and time scales involved. Nevertheless, the quantitative agreement between the stability diagram, the wavelengths selected and the avalanche morphology reveals a common scenario for an erosion/deposition process.Comment: 4 pages, 6 figures, submitted to PR

Community-based rehabilitation program for cerebral PALSY (CP) children in North Uganda

Background: CP is a common neurologic disease in children, with a worldwide estimated prevalence of 93 million. Data on the African context are limited. Purpose: This study was aimed at evaluating the efficacy of a mixed outpatient/home physiotherapy program in children with CP admitted to St. Mary's Lacor Hospital (Gulu), the reference center of north Uganda. Methods: This is an observational, uncontrolled, prospective study. All children with CP (aged from 0.5 to 12 years) admitted in the Physiotherapy Unit from January to December 2017 were enrolled. A written consent form (English or Acholi language) was obtained from the mother/ caregiver. Each patient was evaluated at baseline and every two weeks for three months. CP sub-types were defined according to Surveillance of Cerebral Palsy in Europe classification. The child\ub4s abilities were staged through the Gross Motor Function Classification System Expanded and Revised (GMFCS-E&R; scale from I to V, the higher the worse). Changes in motor function were measured through the 66-item version (GMFM-66; scores ranging from 0 to 100, the higher the better). At baseline and subsequent visits, Bobath treatment was applied for 30 minutes by an experienced physiotherapist, who trained the caregiver on customized home exercises following a diary prescription. The functional status reported by the caregiver and the overall compliance were assessed. Changes in GMFCS-E&R and GMFM-66 at 6 and 12 weeks were recorded. The normality of score distributions was tested (Shapiro-Wilks). If confirmed, repeated ANOVA modeling was applied to scores across time points. Results: Fifty-two consecutive children were enrolled (mean age 2.2 years, range 0.5-9.9). Spastic bilateral (19 patients, 36%) and dystonic (16, 31%) were the most common CP sub-types. The main cause of CP were asphyxia during the delivery (26 cases, 50%) and cerebral malaria (10, 19%). Thirty-three/52 cases (67%) presented level V GMFCS-E&R. GMFM-66 mean score at baseline was 19.86 range: 0-52.9. Seventeen/52 (33%) children were assessed at 6 and/or 12 weeks, while 35 (67%) missed at least three study visits (reasons: 28 transportation cost, 2 remote home, 4 other). In 16/17 (94%) patients home exercises were performed correctly. The GMFM-66 mean score increased from 14.8 at baseline to 20.4 and to 24.9 at 6 weeks (p=0.02) and 12 weeks (p=0.00), respectively. The improvement was observed irrespectively from CP sub-type or cause of disability. Conclusion(s): Although on a small number of patients, this study suggests that a mixed outpatient/home physiotherapy program can improve CP disability in compliant children treated in a developing country, like north Uganda. The high drop-out rate and its causes point towards the need for implementing local community programs and/or transport facilities. Implications: These results suggest that a mixed outpatient/home physiotherapy program can benefit children with CP living in developing countries and strengthen the need of a policy aimed at improving the access to the physiotherapy service. In addition, they confirm that neurological damage during the assisted delivery is the major cause of CP in this conte

Patterns and Collective Behavior in Granular Media: Theoretical Concepts

Granular materials are ubiquitous in our daily lives. While they have been a subject of intensive engineering research for centuries, in the last decade granular matter attracted significant attention of physicists. Yet despite a major efforts by many groups, the theoretical description of granular systems remains largely a plethora of different, often contradicting concepts and approaches. Authors give an overview of various theoretical models emerged in the physics of granular matter, with the focus on the onset of collective behavior and pattern formation. Their aim is two-fold: to identify general principles common for granular systems and other complex non-equilibrium systems, and to elucidate important distinctions between collective behavior in granular and continuum pattern-forming systems.Comment: Submitted to Reviews of Modern Physics. Full text with figures (2Mb pdf) avaliable at http://mti.msd.anl.gov/AransonTsimringReview/aranson_tsimring.pdf Community responce is appreciated. Comments/suggestions send to [email protected]

Non-local rheology in dense granular flows -- Revisiting the concept of fluidity

Granular materials belong to the class of amorphous athermal systems, like foams, emulsion or suspension they can resist shear like a solid, but flow like a liquid under a sufficiently large applied shear stress. They exhibit a dynamical phase transition between static and flowing states, as for phase transitions of thermodynamic systems, this rigidity transition exhibits a diverging length scales quantifying the degree of cooperatively. Several experiments have shown that the rheology of granular materials and emulsion is non-local, namely that the stress at a given location does not depend only on the shear rate at this location but also on the degree of mobility in the surrounding region. Several constitutive relations have recently been proposed and tested successfully against numerical and experimental results. Here we use discrete elements simulation of 2D shear flows to shed light on the dynamical mechanism underlying non-locality in dense granular flows

Raccomandazioni per l\u2019esecuzione della Curva Standard da Carico Orale di Glucosio (OGTT) per la diagnosi di Diabete Mellito

The Oral Glucose Tolerance Test (OGTT) is a fractional method which measures the body's ability to metabolize glucose. Despite its large-scale use, the OGTT is still not appropriately performed in most of the Italian laboratories, as proven by our previous recent survey. In particular, we have provided evidence for the variability for execution of the OGTT in Italian laboratories indicating a poor tendency to standardise the procedures and the methodologies. These findings have been a stimulus to promote an effective Nationwide educational campaign, in order to standardise the procedures for the diagnosis of altered glucose metabolism and diabetes. The present document reports therefore the recommendations concerning the OGTT performed for the classification of diabetes. These recommendations do not apply to the execution of the OGTT during pregnancy for diagnosing gestational diabetes mellitus

Second asymptomatic carotid surgery trial (ACST-2): a randomised comparison of carotid artery stenting versus carotid endarterectomy

Background: Among asymptomatic patients with severe carotid artery stenosis but no recent stroke or transient cerebral ischaemia, either carotid artery stenting (CAS) or carotid endarterectomy (CEA) can restore patency and reduce long-term stroke risks. However, from recent national registry data, each option causes about 1% procedural risk of disabling stroke or death. Comparison of their long-term protective effects requires large-scale randomised evidence. Methods: ACST-2 is an international multicentre randomised trial of CAS versus CEA among asymptomatic patients with severe stenosis thought to require intervention, interpreted with all other relevant trials. Patients were eligible if they had severe unilateral or bilateral carotid artery stenosis and both doctor and patient agreed that a carotid procedure should be undertaken, but they were substantially uncertain which one to choose. Patients were randomly allocated to CAS or CEA and followed up at 1 month and then annually, for a mean 5 years. Procedural events were those within 30 days of the intervention. Intention-to-treat analyses are provided. Analyses including procedural hazards use tabular methods. Analyses and meta-analyses of non-procedural strokes use Kaplan-Meier and log-rank methods. The trial is registered with the ISRCTN registry, ISRCTN21144362. Findings: Between Jan 15, 2008, and Dec 31, 2020, 3625 patients in 130 centres were randomly allocated, 1811 to CAS and 1814 to CEA, with good compliance, good medical therapy and a mean 5 years of follow-up. Overall, 1% had disabling stroke or death procedurally (15 allocated to CAS and 18 to CEA) and 2% had non-disabling procedural stroke (48 allocated to CAS and 29 to CEA). Kaplan-Meier estimates of 5-year non-procedural stroke were 2·5% in each group for fatal or disabling stroke, and 5·3% with CAS versus 4·5% with CEA for any stroke (rate ratio [RR] 1·16, 95% CI 0·86–1·57; p=0·33). Combining RRs for any non-procedural stroke in all CAS versus CEA trials, the RR was similar in symptomatic and asymptomatic patients (overall RR 1·11, 95% CI 0·91–1·32; p=0·21). Interpretation: Serious complications are similarly uncommon after competent CAS and CEA, and the long-term effects of these two carotid artery procedures on fatal or disabling stroke are comparable. Funding: UK Medical Research Council and Health Technology Assessment Programme