Structure-property relationships from universal signatures of plasticity in disordered solids

When deformed beyond their elastic limits, crystalline solids flow plastically via particle rearrangements localized around structural defects. Disordered solids also flow, but without obvious structural defects. We link structure to plasticity in disordered solids via a microscopic structural quantity, “softness,” designed by machine learning to be maximally predictive of rearrangements. Experimental results and computations enabled us to measure the spatial correlations and strain response of softness, as well as two measures of plasticity: the size of rearrangements and the yield strain. All four quantities maintained remarkable commonality in their values for disordered packings of objects ranging from atoms to grains, spanning seven orders of magnitude in diameter and 13 orders of magnitude in elastic modulus. These commonalities link the spatial correlations and strain response of softness to rearrangement size and yield strain, respectively

Compressions medullaires lentes en milieu Rhumatologique a Lome (Togo)

Patients et méthodes : Il s’est agi d’une étude multicentrique, transversale, menée du 1er janvier au 31 mars 2019 sur dossiers des patients admis en hospitalisation dans les trois services de rhumatologie à Lomé. Le diagnostic positif de syndrome de compression médullaire était clinique. Le diagnostic étiologique a reposé sur des arguments cliniques et paracliniques.Résultats : 165 des 3261 patients examinés (5%) souffraient d’un syndrome de compression médullaire lente. Les 165 patients (84 hommes ; 81 femmes) avaient un âge moyen de 54 ± 17 ans (extrêmes : 2 et 86 ans). La durée moyenne d’évolution était de 20 ± 35 mois (extrêmes : 2j et 18 ans). Les motifs d’hospitalisation étaient une impotence fonctionnelle (80,6%) associée ou non à une cervicalgie (12,9%), à une dorsalgie (15,3%), à une dorsolombalgie (28,8%) et à une lombalgie (46,6%). Les principaux signes cliniques étaient un syndrome rachidien (96,4%) et une parésie ou paralysie (95,2%). Le syndrome de compression médullaire était révélateur de la maladie dans 64,8% des cas. La radiographie standard a été réalisée chez tous les patients (100%), la TDM dans 43,6% des cas et l’IRM dans 16,4%. Les étiologies étaient les causes tumorales malignes (93 ; 56,4%) dominées par les métastases de cancers solides (59 ; 35,7%), les spondylodiscites bactériennes (46 ; 27,8%) dominées par le mal de Pott (40 ; 24,2%) et les affections rachidiennes dégénératives (26 ; 15,8%).Conclusion : Le syndrome de compression médullaire lente est rare en pratique rhumatologique à Lomé. Les étiologies sont dominées par les causes tumorales malignes principalement les métastases de cancers solides. Mots clés : Compression médullaire; Etiologie; Métastases de cancers solides ; Mal de Pott. English abstract: Spinal cord compressions in Rheumatology in Lome (Togo)  Objective: To determine the prevalence and etiologies of slow spinal cord compression syndrome in rheumatology in Lomé. Patients and methods: This was a multicenter, retrospective study, conducted from January 1 to March 31, 2019 on records of patients admitted to hospital in the three rheumatology departments in Lomé. The positive diagnosis of spinal cord syndrome was clinical. The etiological diagnosis was based on clinical and paraclinical arguments. Results: 165 of 3261 patients examined (5%) suffered from slow spinal cord compression syndrome. The 165 patients (84 men; 81 women) had a mean age of 54 ± 17 years (range: 2 and 86 years). The mean duration of evolution was 20 ± 35 months (range: 2 days and 18 years). The reasons for hospitalization were a limitation of the walking distance (85.5%) associated or not with back pain (98.8%), and radiculalgia (89.1%). The main clinical signs were spinal syndrome (96.4%) and paresis or paralysis (95.2%). Spinal cord compression syndrome was indicative of the disease in 64.8% of cases. Standard radiography was performed in all patients (100%), CT in 43.6% of cases and MRI in 16.4%. The aetiologies were malignant tumor causes (56.4%) dominated by metastases of solid cancers (63.4%), bacterial spondylodiscitis (27.8%) dominated by Pott's disease (24.2%) and degenerative spinal diseases (15.8%). Conclusion: Slow spinal cord compression syndrome is rare in rheumatology practice in Lomé. The aetiologies are dominated by malignant tumor causes, mainly metastases from solid cancers. Key words: Spinal cord compression; Etiology; Metastases of solid cancers; Pott's disease