Unexpected spatial distribution of bubble rearrangements in coarsening foams

Foams are ideal model systems to study stress-driven dynamics, as stress-imbalances within the system are continuously generated by the coarsening process, which unlike thermal fluctuations, can be conveniently quantified by optical means. However, the high turbidity of foams generally hinders the detailed study of the temporal and spatial distribution of rearrangement events, such that definite assessments regarding their contribution to the overall dynamics could not be made so far. In this paper, we use novel light scattering techniques to measure the frequency and position of events within a large sample volume. As recently reported (A. S. Gittings and D. J. Durian, Phys. Rev. E, 2008, 78, 066313), we find that the foam dynamics is determined by two distinct processes: intermittent bubble rearrangements of finite duration and a spatially homogeneous quasicontinuous process. Our experiments show that the convolution of these two processes determines the age-dependence of the mean dynamics, such that relations between intermittent rearrangements and coarsening process can not be established by considering means. By contrast the use of the recently introduced photon correlation imaging technique (A. Duri, D. A. Sessoms, V. Trappe, and L. Cipelletti, Phys. Rev. Lett., 2009, 102, 085702) enables us to assess that the event frequency is directly determined by the strain-rate imposed by the coarsening process. Surprisingly, we also find that, although the distribution of successive events in time is consistent with a random process, the spatial distribution of successive events is not random: rearrangements are more likely to occur within a recently rearranged zone. This implies that a topological rearrangement is likely to lead to an unstable configuration, such that a small amount of coarsening-induced strain is sufficient to trigger another event

Constant Approximation for kk-Median and kk-Means with Outliers via Iterative Rounding

In this paper, we present a new iterative rounding framework for many clustering problems. Using this, we obtain an $(\alpha_1 + \epsilon \leq 7.081 + \epsilon)$-approximation algorithm for $k$-median with outliers, greatly improving upon the large implicit constant approximation ratio of Chen [Chen, SODA 2018]. For $k$-means with outliers, we give an $(\alpha_2+\epsilon \leq 53.002 + \epsilon)$-approximation, which is the first $O(1)$-approximation for this problem. The iterative algorithm framework is very versatile; we show how it can be used to give $\alpha_1$- and $(\alpha_1 + \epsilon)$-approximation algorithms for matroid and knapsack median problems respectively, improving upon the previous best approximations ratios of $8$ [Swamy, ACM Trans. Algorithms] and $17.46$ [Byrka et al, ESA 2015]. The natural LP relaxation for the $k$-median/$k$-means with outliers problem has an unbounded integrality gap. In spite of this negative result, our iterative rounding framework shows that we can round an LP solution to an almost-integral solution of small cost, in which we have at most two fractionally open facilities. Thus, the LP integrality gap arises due to the gap between almost-integral and fully-integral solutions. Then, using a pre-processing procedure, we show how to convert an almost-integral solution to a fully-integral solution losing only a constant-factor in the approximation ratio. By further using a sparsification technique, the additive factor loss incurred by the conversion can be reduced to any $\epsilon > 0$

Evaluation of the effects of short-term amendment with olive mill pomace on some soil properties

The extraction of olive oil produces an enormous quantity of waste, such as olive mill wastewater (OMWW) and olive mill pomace (OMP), The majority of the agricultural wastes, including olive oil mill waste, are used as soil amendments due to their high nutritional value. The purpose of this study was to investigate the effects of the amendment with olive mill pomace from a 3-phase cold-pressed system on the characteristics of the soil pH, electrical conductivity (EC), and organic matter content (OM). The experiment was carried out using increasing rates of olive mill pomace (12.5%, 25%, 50%, 75%, and 100% w/w) plus the control untreated soil in microcosms under laboratory conditions. The results showed that the treatment of soil with olive mill pomace has a significant effect on soil properties (pH, EC, OM, OC, and CaCO3) soil pH was decreased under OMP treatment, especially with high doses of PR4 and PR5, and the electrical conductivity of the soil (EC) was increased, as well as soil carbonate content. Moreover, the soil organic matter content and soil organic carbon content were highly increased under the treatment with OMP. As a result, we can consider the olive mill pomace as a soil fertilizer. Pretreatment of olive mill pomace to reduce acidic pH and salt content before use as a soil amendment is also recommended. © 2022 by the authors

Impact of earthworm activity on the chemical fertility of irrigated soil with urban effluents

The reuse of urban effluents to irrigate the soils of peri-urban grasslands in the vicinity of the town of Setif (northeastern Algeria) is an old and widespread practice. In this context, the present study was conducted to evaluate the effect of the irrigation with urban effluents on the biological and chemical behavior of soils. Effluents analysis showed significant organic and particulate pollution, the latter contributed to earthworm abundance and increased the richness of irrigated soils with nutrients. The analysis of turricules revealed the role of earthworms through the activity of bioturbation in the increase of the rate of organic matter as well as in the bioavailability of the nutrients of the irrigated soils. In space, permanent vegetation cover has played an important role as a biofilter. This was confirmed by the inter-site differences recorded through the measured variables particularly organic ones.Keywords: Natural grasslands, urban effluents, earthworm activity, turricles, organic matte

A high rate flow-focusing foam generator

We use a rigid axisymetric microfluidic flow focusing device to produce monodisperse bubbles, dispersed in a surfactant solution. The gas volume fraction of the dispersion collected out of this device can be as large as 90%, demonstrating that foam with solid-like viscoelastic properties can be produced in this way. The polydispersity of the bubbles is so low that we observe crystallization of our foam. We measure the diameter of the bubbles and compare these data to recent theoretical predictions. The good control over bubble size and foam gas volume fraction shows that our device is a flexible and promising tool to produce calibrated foam at a high flow rate

057 A simple prediction score for significant renal artery stenosis in patients with coronary artery disease

BackgroundRenal artery stenosis (RAS) is a strong independent predictor of mortality in patients (pts) with coronary artery disease (CAD).Aim of studyTo develop and validate a score predicting RAS in patients with CAD.MethodsThree hundred consecutive pts (50 females) with significant CAD underwent abdominal aortography following coronary angiography to screen for significant RAS defined as luminal narrowing of > 50%. Univariate and multivariate analyses were performed comparing pts with and without RAS. Significant factors associated with RAS were included in constructing a score that predicts RAS.The score was internally validated in pts randomly selected from the entire study group (validation group; n=103), using ROC curves and the Hosmer-Lemeshow goodness-of-fit test.ResultsTwenty-seven pts (9%) had a significant RAS. Univariate predictors of significant RAS were: age > 65 years (OR=4.5, p < 0.0001), hypertension (OR=3.6, p=0.001), and female gender (OR=3.6, p=0.015). We found a tendency of more prevalent renal insufficiency (37.1% vs. 21.5%; p=0.05) and the presence of 2 or more significant CAD lesions (70.4% vs. 50.9%; p=0.05) in pts with RAS.Multivariate analysis showed that age > 65 years (OR=4.1%, 95% CI=1.6-10.3, p=0.003) and hypertension (OR=3.1, 95% CI=1.2-7.7, p=0.015) were independent predictors of RAS. The ranged from 0 to 7: 2 points for age > 65 years and hypertension 1 point for female gender, renal insufficiency, and > 3-vessel disease). Internal validation showed a good performance (ROC curve = 0.79 and Chi2 Lemeshow = 3.45). For a score < 2, the negative predictive value is 98%. Applying this criteria, 48.3% of our population would not require systematic abdominal angiography.ConclusionThe performance of our predictive score was good, and significant reduction in the need to perform systematic abdominal aortography could be expected with the use of this score

Deep learning for safety assessment of nuclear power reactors: Reliability, explainability, and research opportunities

Deep learning algorithms provide plausible benefits for efficient prediction and analysis of nuclear reactor safety phenomena. However, research works that discuss the critical challenges with deep learning models from the reactor safety perspective are limited. This article presents the state-of-the-art in deep learning application in nuclear reactor safety analysis, and the inherent limitations in deep learning models. In addition, critical issues such as deep learning model explainability, sensitivity and uncertainty constraints, model reliability, and trustworthiness are discussed from the nuclear safety perspective, and robust solutions to the identified issues are also presented. As a major contribution, a deep feedforward neural network is developed as a surrogate model to predict turbulent eddy viscosity in Reynolds-averaged Navier–Stokes (RANS) simulation. Further, the deep feedforward neural network performance is compared with the conventional Spalart Allmaras closure model in the RANS turbulence closure simulation. In addition, the Shapely Additive Explanation (SHAP) and the local interpretable model-agnostic explanations (LIME) APIs are introduced to explain the deep feedforward neural network predictions. Finally, exciting research opportunities to optimize deep learning-based reactor safety analysis are presented.The work of AA and HA are funded through the Sêr Cymru II 80761-BU-103 project by Welsh European Funding Office (WEFO) under the European Development Fund (ERDF)

Non-Equilibrium in Adsorbed Polymer Layers

High molecular weight polymer solutions have a powerful tendency to deposit adsorbed layers when exposed to even mildly attractive surfaces. The equilibrium properties of these dense interfacial layers have been extensively studied theoretically. A large body of experimental evidence, however, indicates that non-equilibrium effects are dominant whenever monomer-surface sticking energies are somewhat larger than kT, a common case. Polymer relaxation kinetics within the layer are then severely retarded, leading to non-equilibrium layers whose structure and dynamics depend on adsorption kinetics and layer ageing. Here we review experimental and theoretical work exploring these non-equilibrium effects, with emphasis on recent developments. The discussion addresses the structure and dynamics in non-equilibrium polymer layers adsorbed from dilute polymer solutions and from polymer melts and more concentrated solutions. Two distinct classes of behaviour arise, depending on whether physisorption or chemisorption is involved. A given adsorbed chain belonging to the layer has a certain fraction of its monomers bound to the surface, f, and the remainder belonging to loops making bulk excursions. A natural classification scheme for layers adsorbed from solution is the distribution of single chain f values, P(f), which may hold the key to quantifying the degree of irreversibility in adsorbed polymer layers. Here we calculate P(f) for equilibrium layers; we find its form is very different to the theoretical P(f) for non-equilibrium layers which are predicted to have infinitely many statistical classes of chain. Experimental measurements of P(f) are compared to these theoretical predictions.Comment: 29 pages, Submitted to J. Phys.: Condens. Matte

Plastic Response of a 2D Lennard-Jones amorphous solid: Detailed analysis of the local rearrangements at very slow strain-rate

We analyze in details the atomistic response of a model amorphous material submitted to plastic shear in the athermal, quasistatic limit. After a linear stress-strain behavior, the system undergoes a noisy plastic flow. We show that the plastic flow is spatially heterogeneous. Two kinds of plastic events occur in the system: quadrupolar localized rearrangements, and shear bands. The analysis of the individual motion of a particle shows also two regimes: a hyper-diffusive regime followed by a diffusive regime, even at zero temperature