Yielding Is an Absorbing Phase Transition with Vanishing Critical Fluctuations.

The yielding transition in athermal complex fluids can be interpreted as an absorbing phase transition between an elastic, absorbing state with high mesoscopic degeneracy and a flowing, active state. We characterize quantitatively this phase transition in an elastoplastic model under fixed applied shear stress, using a finite-size scaling analysis. We find vanishing critical fluctuations of the order parameter (i.e., the shear rate), and relate this property to the convex character of the phase transition (ß>1). We locate yielding within a family of models akin to fixed-energy sandpile (FES) models, only with long-range redistribution kernels with zero modes that result from mechanical equilibrium. For redistribution kernels with sufficiently fast decay, this family of models belongs to a short-range universality class distinct from the conserved directed percolation class of usual FES, which is induced by zero modes.

"The least significant change on bone mineral density scan increased in patients with higher degrees of obesity".

BACKGROUND: The least significant change (LSC) threshold of 0.03 g/cm² is used to interpret bone mineral density (BMD) scans in the general population. Our working hypothesis was that the current LSC threshold would not be applicable in obese populations. AIMS: The aim of this study was to calculate the LSC in an obese population. METHODS: We performed an interventional study among 120 obesity patients, in whom two measurements of BMD were performed at 3 sites. Pairs of measures were used to calculate the LSC, using the Bland and Altman method. RESULTS: We calculated that the LSC was 0.046 g/cm² at the lumbar spine, 0.069 g/cm² at the femoral neck, and 0.06 g/cm² at the total hip. We also calculated the LSC for each class of obesity and observed an increase in LSC with increasing body mass index (BMI). We calculated a LSC of 0.05 g/cm² in patients with class 2 or class 3 obesity, whereas the LSC in patients with class 1 obesity is similar to the threshold used in the general population. DISCUSSION: In obese population, like BMD, LSC is higher than the threshold value of the general population, and increases with increasing BMI. CONCLUSION: LSC of 0.05 g/cm² could be used in clinical practice in patients with class 2 or 3 obesity. These findings should help to improve the interpretation of BMD scans in these patients and optimize their management. TRIAL REGISTRATION NUMBER: Comité de Protection des Personnes Ile-de France VII, France.

Stomach size in anorexia nervosa: A new challenge?

BACKGROUND & AIMS: Changes in stomach size may impact eating behaviour. A recent study showed gastric dilatation in restrictive eating disorders using computed tomography scans. This study aimed to describe stomach size in the standing position in women with anorexia nervosa (AN). METHODS: Women treated for AN at our institution were retrospectively included if they had undergone upper gastrointestinal radiography (UGR) after the diagnosis of AN. Two control groups (CG1 and CG2) were included, both comprising female patients: CG1 patients were not obese and underwent UGR for digestive symptoms of other aetiologies, and CG2 comprised obese individuals who had UGR before bariatric surgery. A UGR-based Stomach Size Index (SSI), calculated as the ratio of the length of the stomach to the distance between the upper end of the stomach and the top of the iliac crests, was measured in all three groups. Gastromegaly was defined as SSI >1.00. RESULTS: 45 patients suffering from AN (28 with restrictive and 17 with binge/purge subtype), 10 CG1 and 20 CG2 subjects were included in this study. Stomach Size Index was significantly higher in AN (1.27 ± 0.24) than in CG1 (0.80 ± 0.11) and CG2 (0.68 ± 0.09); p < 0.001, but was not significantly different between patients with the restrictive and binge/purge subtypes. Gastromegaly was present in 82.2% of patients with AN and not present in the control groups. In patients with AN, gastromegaly was present in 12/15 patients without digestive symptoms (80.0%) and in 25/30 patients with digestive complaints (83.3%) at time of UGR (p = 0.99). In the AN group, no significant relationship was found between SSI and body mass index. CONCLUSION: Gastromegaly is frequent in AN and could influence AN recovery. This anatomical modification could partially explain the alterations of gastric motility previously reported in AN.

Nonequilibrium Phase Transition to Temporal Oscillations in Mean-Field Spin Models.

We propose a mean-field theory to describe the nonequilibrium phase transition to a spontaneously oscillating state in spin models. A nonequilibrium generalization of the Landau free energy is obtained from the joint distribution of the magnetization and its smoothed stochastic time derivative. The order parameter of the transition is a Hamiltonian, whose nonzero value signals the onset of oscillations. The Hamiltonian and the nonequilibrium Landau free energy are determined explicitly from the stochastic spin dynamics. The oscillating phase is also characterized by a nontrivial overlap distribution reminiscent of a continuous replica symmetry breaking, in spite of the absence of disorder. An illustration is given on an explicit kinetic mean-field spin model.

Dynamics of microstructure anisotropy and rheology of soft jammed suspensions.

We explore the rheology predicted by a recently proposed constitutive model for jammed suspensions of soft elastic particles derived from particle-level dynamics [Cuny et al., Phys. Rev. Lett., 2021, 127, 218003]. Our model predicts that the orientation of the anisotropy of the microstructure, governed by an interplay between advection and contact elasticity, plays a key role at yielding and in flow. It generates normal stress differences contributing significantly to the yield criterion and Trouton ratio. It gives rise to non-trivial transients such as stress overshoots in step increases of shear rate, residual stresses after flow cessation and power-law decay of the shear rate in creep. Finally, it explains the collapse of storage modulus as measured in parallel superposition for a yielded suspension.

Dynapenia in digestive cancer outpatients: association with markers of functional and nutritional status (the FIGHTDIGO study).

BACKGROUND: The FIGHTDIGO study determined the feasibility and acceptability of handgrip strength (HGS) measurement in digestive cancer outpatients. PURPOSE: To assess the relationship between muscle strength and markers of functional and nutritional status in this population. DESIGN: In this prospective study, a total of 201 patients were followed during 6 months and were asked to perform HGS measurement at each hospitalization. Anthropometric measurements, laboratory tests, and performance status (PS) evaluation were collected. The modified Glasgow Prognostic Score (mGPS) was calculated using CRP and albumin levels. Severe malnutrition was defined as body mass index (BMI) < 18 kg/m2 in patients > 70 years old, and BMI < 16 kg/m2 in those < 70 years old. Dynapenia was defined as HGS < 30 kg (men) and < 20 kg (women). Mixed logistic regressions and mixed linear regressions were performed to study factors associated with dynapenia and HGS value, respectively. RESULTS: A total of 879 HGS measurements were analyzed. Dynapenia occurred in 177 measurements (20.1%). BMI and HGS were significantly associated in univariate analysis (p = 0.001). In multivariate analysis, mGPS score (ß = - 0.54 ± 0.31; p = 0.06) and severe malnutrition (ß = - 2.8 ± 1.4; p = 0.08) tended to be associated with HGS. Dynapenia was only associated with functional status impairment in univariate analysis (n = 140/803, 17.4% in ECOG 0 and 1 versus n = 37/76, 58.7% in ECOG 2 and 3; p = 0.002). CONCLUSIONS: Identification of dynapenia using HGS measurement may be useful to predict nutritional vulnerability in digestive cancer outpatients undergoing chemotherapy. Patients could then benefit from nutritional support, adapted physical activity programs, and early therapeutic adjustments. Trial registration ClinicalTrials.gov, NCT02797197.

Association between obesity-related dyspnea in daily living, lung function and body composition analyzed by DXA: a prospective study of 130 patients.

BACKGROUND: Obesity is a risk factor for dyspnea. However, investigations of daily living obesity-related dyspnea are limited and its mechanisms remain unclear. We conducted a cross-sectional study to analyze the relationships between dyspnea in daily living, lung function, and body composition in patients with obesity. METHODS: One-hundred and thirty patients (103 women/27 men), candidate for bariatric surgery, with a mean ± SD Body Mass Index (BMI) of 44.8 ± 6.8 kg/m2 were included. Dyspnea was assessed by the modified Medical Research Council (mMRC) scale. Comorbidities, laboratory parameters, pulmonary function tests, arterial blood gases, six-minute walk test (6MWT), handgrip strength, and DXA body composition were analyzed. RESULTS: Thirty-one percent of patients exhibited disabling dyspnea in daily living (mMRC ≥ 2). Compared with patients without disabling dyspnea (mMRC < 2), significant dyspnea (mMRC ≥ 2) was associated with a lower 6MWT distance (395 ± 103 m vs 457 ± 73 m, p < 0.001), lower lung volumes including Expiratory Reserve Volume (42 ± 28% vs 54 ± 27%, p = 0.024), Vital Capacity (95 ± 14 vs 106 ± 15%, p < 0.001) and Forced expiratory volume in one second (95 ± 13 vs 105 ± 15%, p = 0.002), a higher BMI (48.2 ± 7.7 vs 43.2 ± 5.7 kg/m2, p = 0.001) and a higher percentage of fat mass in the trunk (46 ± 5 vs 44 ± 5 p = 0.012) and android region (52 ± 4 vs 51 ± 4%, p = 0.024). There was no difference regarding comorbidities (except hypertension), laboratory parameters, and sarcopenia markers between patients with (mMRC ≥ 2) and without (mMRC < 2) disabling dyspnea. CONCLUSION: Dyspnea in patients with obesity is associated with a reduction in lung volumes and a higher percentage of fat mass in central body regions. How dyspnea and body composition may change with interventions like physical activity or bariatric surgery remains to be investigated.

Disordered eating as a repercussion of sexual assault: a consequence to consider.

PURPOSE: This study aims at clarifying the links between sexual violence and disordered eating (DE). METHODS: In a sample of 12,638 victims of self-reported sexual violence, we analyzed the situation of 546 victims that declared having developed DE. We assessed the characteristics of the assault (age, type of aggression) and the medical consequences (PTSD, depression, suicide attempts, anxiety disorders, etc.). RESULTS: DE prevalence was 4.3% in the victim sample. The age of the first assault in DE victims was significantly lower than that of the whole population (12 years vs 16 years for median; p < 0.001). A much higher prevalence of sexual assault consequences was present in victims developing DE with odd ratios (OR) for: self-mutilation (OR = 11.5 [8.29-15.95], p < 0.001); depression (OR = 5.7 [4.81-6.86], p < 0.001); self-medication (OR = 5.3 [3.86-7.19], p < 0.001); suicide attempts (OR = 4.5 [3.59-5.67], p < 0.001); post-traumatic stress disorder (OR = 3.8 [2.99-4.78], p < 0.001); anxiety troubles (OR = 5.2 [4.11-6.47], p < 0.001); alcoholism (OR = 4.0 [2.81-5.58], p < 0.001). CONCLUSION: This study confirms the link between DE and sexual violence, especially in childhood, leading to severe psychological consequences. In this context, DE should be envisaged as a coping strategy accompanying emotional dysregulation due to traumatic events, and be treated as such. LEVEL OF EVIDENCE: Level IV: Evidence obtained from multiple time series analysis such as case studies.

Microscopic Theory for the Rheology of Jammed Soft Suspensions.

We develop a constitutive model allowing for the description of the rheology of two-dimensional soft dense suspensions above jamming. Starting from a statistical description of the particle dynamics, we derive, using a set of approximations, a nonlinear tensorial evolution equation linking the deviatoric part of the stress tensor to the strain-rate and vorticity tensors. The coefficients appearing in this equation can be expressed in terms of the packing fraction and of particle-level parameters. This constitutive equation rooted in the microscopic dynamic qualitatively reproduces a number of salient features of the rheology of jammed soft suspensions, including the presence of yield stresses for the shear component of the stress and for the normal stress difference. More complex protocols like the relaxation after a preshear are also considered, showing a smaller stress after relaxation for a stronger preshear.

Prevalence of geophagy and knowledge about its health effects among native Sub-Saharan Africa, Caribbean and South America healthy adults living in France.

Geophagy is widespread among women from Sub-Saharan Africa, South America and the Caribbean and may persist in western countries. This practice may be associated with adverse effects such as anaemia, constipation or intestinal occlusion. We aimed to determine the prevalence of geophagy and the level of knowledge about its health effects among healthy adults originating from these countries and attending a travel medicine and international vaccination consultation in France. Among 101 travellers enrolled in the study, 83 (82.1%) were born in Sub-Saharan Africa and 13 (12.8%) in South America or the Caribbean. The mean duration of residence in France was 15.6 ± 10.4 years. Previous or current geophagy was present in 42 travellers [previous geophagy in 31 (30.7%) and current consumption in 11 (10.9%)]; 38 (90.5%) were women. The rate of awareness of harmful effects of geophagy as the risk of iron-deficient anaemia (18.8%) and soil-transmitted intestinal parasitic infections (11.9%) was low overall. Women with previous or current geophagy more often had history of iron therapy compared to those who never consumed, both during pregnancy (50.0 versus 14.3%; p = 0.0009) and outside pregnancy (47.4 versus 2.8%; p < 0.0001). Despite a long period of residence in France, geophagy was still a current practice among 10.9% of Sub-Saharan, South American and Caribbean travellers, who are poorly informed of its harmful effects. Therefore, specific information tailored to Sub-Saharan, South American and Caribbean about the risks of geophagy should be implemented in western countries.Level of evidence Level V, descriptive cross-sectional survey.

Criticality at a Finite Strain Rate in Fluidized Soft Glassy Materials.

We study the emergence of critical dynamics in the steady shear rheology of fluidized soft glassy materials. Within a mesoscale elastoplastic model accounting for a shear band instability, we show how additional noise can induce a transition from a phase separated to homogeneous flow, accompanied by critical-like fluctuations of the macroscopic shear rate. Both macroscopic quantities and fluctuations exhibit power law behaviors in the vicinity of this transition, consistent with previous experimental findings on vibrated granular media. Altogether, our results suggest a generic scenario for the emergence of criticality when shear weakening mechanisms compete with a fluidizing noise.

Understanding Dense Active Nematics from Microscopic Models.

We study dry, dense active nematics at both particle and continuous levels. Specifically, extending the Boltzmann-Ginzburg-Landau approach, we derive well-behaved hydrodynamic equations from a Vicsek-style model with nematic alignment and pairwise repulsion. An extensive study of the phase diagram shows qualitative agreement between the two levels of description. We find in particular that the dynamics of topological defects strongly depends on parameters and can lead to "arch" solutions forming a globally polar, smecticlike arrangement of Néel walls. We show how these configurations are at the origin of the defect ordered states reported previously. This work offers a detailed understanding of the theoretical description of dense active nematics directly rooted in their microscopic dynamics.

Lack of an equation of state for the nonequilibrium chemical potential of gases of active particles in contact.

We discuss the notion of the nonequilibrium chemical potential in gases of non-interacting active particles filling two compartments separated by a potential energy barrier. Different types of active particles are considered: run-and-tumble particles, active Brownian particles, and active Brownian particles with a stochastic reorientation along an external field. After recalling some analytical results for run-and-rumble particles in one dimension, we focus on the two-dimensional case and obtain a perturbative expression of the density profile in the limit of a fast reorientation dynamics, for the three models of active particles mentioned above. Computing the chemical potentials of the nonequilibrium systems in contact from the knowledge of the stationary probability distribution of the whole system-which agrees with a recently proposed general definition of the chemical potential in nonequilibrium systems in contact-we, generically, find that the chemical potential lacks an equation of state in the sense that it depends on the detailed shape of the potential energy barrier separating the compartments and not only on bulk properties, at odds with equilibrium. This situation is reminiscent of the properties of the mechanical pressure in active systems. We also argue that the Maxwell relation is no longer valid and cannot be used to infer the nonequilibrium chemical potential from the knowledge of the mechanical pressure.

Effective diffusivity of microswimmers in a crowded environment.

The microalga Chlamydomonas Reinhardtii is used here as a model system to study the effect of complex environments on the swimming of micro-organisms. Its motion can be modeled by a run and tumble mechanism so that it describes a persistent random walk from which we can extract an effective diffusion coefficient for the large-time dynamics. In our experiments, the complex medium consists of a series of pillars that are designed in a regular lattice using soft lithography microfabrication. The cells are then introduced in the lattice, and their trajectories within the pillars are tracked and analyzed. The effect of the complex medium on the swimming behavior of microswimmers is analyzed through the measure of relevant statistical observables. In particular, the mean correlation time of direction and the effective diffusion coefficient are shown to decrease when increasing the density of pillars. This provides some basis of understanding for active matter in complex environments.

Feasibility of systematic handgrip strength testing in digestive cancer patients treated with chemotherapy: The FIGHTDIGO study.

BACKGROUND: Handgrip strength (HGS) is a widely studied noninvasive test. Weak strength (dynapenia) seems to be associated with high morbidity and mortality in different populations, notably oncology populations. Despite this, HGS testing is not used in daily practice in oncology. The study was aimed at evaluating the feasibility and acceptability of HGS testing in patients with digestive cancer treated with ambulatory chemotherapy. METHODS: In this prospective, single-center study, enrolled patients were followed for 6 months. Two consecutive bilateral measures were performed with a Jamar dynamometer during each patient's appointments in the unit for intravenous treatment. A questionnaire was completed by patients and medical team members. RESULTS: There were 203 consecutive patients, and 201 were recruited. In all, 1704 of 1716 measurements (99.3%) were performed, and 201 patients (99.0%) performed at least 1 measure; 190 (94.5%) performed all expected measures. One hundred sixty-four of 171 participating patients (95.9%) found the test easy to perform, and 167 (97.7%) did not find the test restrictive. All of the 14 medical team members found the test easy to perform, unrestrictive, and undisruptive in their daily practice. CONCLUSIONS: HGS testing is routinely feasible, inexpensive, and well accepted by patients and medical teams in an ambulatory digestive cancer unit. Cancer 2018;124:1501-6. © 2017 American Cancer Society.

Giant Catalytic Effect of Altruists in Schelling's Segregation Model.

We study the effect of introducing altruistic agents in a Schelling-like model of residential segregation. We find that even an infinitesimal proportion of altruists has dramatic catalytic effects on the collective utility of the system. Altruists provide pathways that move the system away from the suboptimal equilibrium it would reach if the system included only egoist agents, allowing it to reach the optimal steady state.

Dynapenia could predict chemotherapy-induced dose-limiting neurotoxicity in digestive cancer patients.

BACKGROUND: FIGHTDIGO study showed the feasibility and acceptability of handgrip strength (HGS) measure in routine in 201 consecutive patients with digestive cancer treated with ambulatory chemotherapy. The present study focuses on the second aim of FIGHTDIGO study: the relationships between pre-therapeutic dynapenia and chemotherapy-induced Dose-Limiting Toxicities (DLT). METHODS: In this ancillary prospective study, DLT were analyzed in a sub-group of 45 chemotherapy-naive patients. Two bilateral consecutive measures of HGS were performed with a Jamar dynamometer before the first cycle of chemotherapy. Dynapenia was defined as HGS < 30 kg (men) and < 20 kg (women). DLT and/or Dose-Limiting Neurotoxicity (DLN) were defined as any toxicity leading to dose reduction, treatment delays or permanent treatment discontinuation. RESULTS: Two-thirds of chemotherapies were potentially neurotoxic (n = 31 [68.7%]) and 22 patients (48.9%) received FOLFOX (5FU, leucovorin plus oxaliplatin) regimen chemotherapy. Eleven patients (24.4%) had pre-therapeutic dynapenia. The median number of chemotherapy cycles was 10 with a median follow-up of 167 days. Twenty-two patients experienced DLT (48.9%). There was no significant association between pre-therapeutic dynapenia and DLT (p = 0.62). Nineteen patients (42.2%) experienced DLN. In multivariate analysis, dynapenia and tumoral location (stomach, biliary tract or small intestine) were independent risk factors for DLN (HR = 3.5 [1.3; 9.8]; p = 0.02 and HR = 3.6 [1.3; 10.0]; p = 0.01, respectively). CONCLUSIONS: Digestive cancer patients with pre-therapeutic dynapenia seemed to experience more DLN. HGS routine measurement may be a way to screen patients with frailty marker (dynapenia) who would require chemotherapy dose adjustment and adapted physical activity programs. TRIAL REGISTRATION: NCT02797197 June 13, 2016 retrospectively registered.

Nonlinear Rheology in a Model Biological Tissue.

The rheological response of dense active matter is a topic of fundamental importance for many processes in nature such as the mechanics of biological tissues. One prominent way to probe mechanical properties of tissues is to study their response to externally applied forces. Using a particle-based model featuring random apoptosis and environment-dependent division rates, we evidence a crossover from linear flow to a shear-thinning regime with an increasing shear rate. To rationalize this nonlinear flow we derive a theoretical mean-field scenario that accounts for the interplay of mechanical and active noise in local stresses. These noises are, respectively, generated by the elastic response of the cell matrix to cell rearrangements and by the internal activity.

Leaf concentrate compared with skimmed milk as nutritional supplementation for HIV-infected children: a randomized controlled trial in Burundi.

OBJECTIVE: The effectiveness of leaf concentrate powder (LCP) as a nutritional supplement was established in trials conducted among adolescent girls and pregnant women in India. Here we evaluate LCP, compared with skimmed milk powder (SMP), as a supplement for antiretroviral-naïve children living with HIV in a sub-Saharan African country. DESIGN: Randomized controlled, two-arm, 6-month trial comparing effects of isoproteic (5 g) LCP (10 g daily) and SMP (15 g daily) on HIV-1 viral load, CD4+ cell count/percentage, weight/height-for-age, general blood parameters, diarrhoea, respiratory and HIV-related opportunistic infections. SETTING: Bujumbura and Kirundo, Burundi. SUBJECTS: Eighty-three HIV-positive, antiretroviral-naïve children aged 5-14 years: median (range) CD4+ count, 716 (361-1690) cells/mm3; log10 HIV-1 viral load, 4·39 (1·79-6·00). RESULTS: LCP was equivalent to SMP in relation to HIV-specific blood parameters and did not demonstrate superiority over SMP in relation to Hb. Three children in each arm (LCP, 7·1 % (3/42); SMP, 7·3 % (3/41)) proceeded to antiretroviral therapy because their CD4+ counts fell below 350 cells/mm3. Children in the LCP group reported higher levels of appetite and overall health at 6 months. There were no differences in clinical events or any other outcome measures. LCP was less palatable than SMP to the children in this population, but there were few negative perceptions of appearance, texture and taste. CONCLUSIONS: LCP appears to be equivalent to SMP as a nutritional supplement in this population, despite slightly lower palatability. In relation to viral load and CD4+ count, equivalence may indicate no effect in either group. Effectiveness relative to no supplementation remains to be determined.