Soft matter physics of the ground beneath our feet.

The soft part of the Earth's surface - the ground beneath our feet - constitutes the basis for life and natural resources, yet a general physical understanding of the ground is still lacking. In this critical time of climate change, cross-pollination of scientific approaches is urgently needed to better understand the behavior of our planet's surface. The major topics in current research in this area cross different disciplines, spanning geosciences, and various aspects of engineering, material sciences, physics, chemistry, and biology. Among these, soft matter physics has emerged as a fundamental nexus connecting and underpinning many research questions. This perspective article is a multi-voice effort to bring together different views and approaches, questions and insights, from researchers that work in this emerging area, the soft matter physics of the ground beneath our feet. In particular, we identify four major challenges concerned with the dynamics in and of the ground: (I) modeling from the grain scale, (II) near-criticality, (III) bridging scales, and (IV) life. For each challenge, we present a selection of topics by individual authors, providing specific context, recent advances, and open questions. Through this, we seek to provide an overview of the opportunities for the broad Soft Matter community to contribute to the fundamental understanding of the physics of the ground, strive towards a common language, and encourage new collaborations across the broad spectrum of scientists interested in the matter of the Earth's surface.

Development of broad modulus profile upon polymer-polymer interface formation between immiscible glassy-rubbery domains.

Interfaces of glassy materials such as thin films, blends, and composites create strong unidirectional gradients to the local heterogeneous dynamics that can be used to elucidate the length scales and mechanisms associated with the dynamic heterogeneity of glasses. We focus on bilayer films of two different polymers with very different glass transition temperatures ([Formula: see text]) where previous work has demonstrated a long-range (∼200 nm) profile in local [Formula: see text] is established between immiscible glassy and rubbery polymer domains when the polymer-polymer interface is formed to equilibrium. Here, we demonstrate that an equally long-ranged gradient in local modulus [Formula: see text] is established when the polymer-polymer interface ([Formula: see text]5 nm) is formed between domains of glassy polystyrene (PS) and rubbery poly(butadiene) (PB), consistent with previous reports of a broad [Formula: see text] profile in this system. A continuum physics model for the shear wave propagation caused by a quartz crystal microbalance across a PB/PS bilayer film is used to measure the viscoelastic properties of the bilayer during the evolution of the PB/PS interface showing the development of a broad gradient in local modulus [Formula: see text] spanning [Formula: see text]180 nm between the glassy and rubbery domains of PS and PB. We suggest these broad profiles in [Formula: see text] and [Formula: see text] arise from a coupling of the spectrum of vibrational modes across the polymer-polymer interface as a result of acoustic impedance matching of sound waves with [Formula: see text] nm during interface broadening that can then trigger density fluctuations in the neighboring domain.

Ticks' attraction to electrically charged hosts.

Ticks are blood-feeding parasites with limited locomotion, known for transmitting multiple pathogens to vertebrates. England et al. suggest that ticks can be easily pulled, via electrostatic induction, toward charged hosts with fluffy coats that are prone to accumulate higher electrostatic potentials. Thus, static electricity may influence ticks' ecology and management.

Considerations in Children and Adolescents Related to Coronavirus Disease 2019 (COVID-19).

Pediatric post-acute sequelae of SARS-CoV-2 (PASC) or "long COVID" are a complex multisystemic disease that affects children's physical, social, and mental health. PASC has a variable presentation, time course, and severity and can affect children even with mild or asymptomatic acute COVID-19 symptoms. Screening for PASC in children with a history of SARS-CoV-2 infection is important for early detection and intervention. A multifaceted treatment approach and utilization of multidisciplinary care, if available, are beneficial in managing the complexities of PASC. Lifestyle interventions, physical rehabilitation, and mental health management are important treatment approaches to improve pediatric PASC patients' quality of life.

Limited evidence that emergency department care is more costly than other outpatient settings for low-acuity conditions: a systematic review.

PURPOSE: Caring for patients with low-acuity conditions in Emergency Departments (ED) is often thought to cost more than treating those patients in other ambulatory settings. Understanding the relative cost of care between settings has critical implications for healthcare policy and system design. METHODS: We conducted a systematic review of papers comparing the cost of care for low-acuity and ambulatory care sensitive conditions in ED and other outpatient settings. We searched PubMed, EMBASE, CINAHL, and Web of Science for peer reviewed papers, plus Google for grey literature. We conducted duplicate screening and data extraction, and quality assessment of included studies using an adapted SIGN checklist for economic studies. We calculated an unweighted mean charge ratio across studies and summarized our findings in narrative and tabular format. RESULTS: We identified one study comparing costs. 18 studies assessed physician or facility charges, conducted in the United States, United Kingdom, and Canada, including cohort analyses (5), charge analyses (5), survey (1), and database searches (5) assessing populations ranging from 370 participants to 60 million. Charge ratios ranged from 0.60 to 13.45 with an unweighted mean of 4.20. Most (12) studies were of acceptable quality. CONCLUSION: No studies since 2001 assess the comparative costs of ED versus non-ED care for low-acuity ambulatory conditions. Physician and facility charges for ED care are higher than in other ambulatory settings for low-acuity conditions. Empirical evidence is lacking to support that ED care is more costly than similar care in other ambulatory settings.

RéSUMé: OBJECTIFS: La prise en charge des patients souffrant d'affections de faible gravité dans les services d'urgence est souvent considérée comme plus coûteuse que la prise en charge de ces mêmes patients dans d'autres structures ambulatoires. Comprendre le coût relatif des soins entre les différents environnements a des implications cruciales pour la politique des soins de santé et la conception des systèmes. MéTHODES: Nous avons procédé à un examen systématique des documents comparant le coût des soins pour les affections à faible gravité et les affections sensibles aux soins ambulatoires dans les services d'urgence et dans d'autres établissements de soins ambulatoires. Nous avons effectué des recherches dans PubMed, EMBASE, CINAHL et Web of Science pour les articles évalués par des pairs, ainsi que dans Google pour la littérature grise. Nous avons procédé à une double sélection et à une extraction des données, ainsi qu'à une évaluation de la qualité des études incluses à l'aide d'une liste de contrôle SIGN adaptée aux études économiques. Nous avons calculé un ratio moyen non pondéré pour l'ensemble des études et avons résumé nos conclusions sous forme de texte et de tableau. RéSULTATS: Nous avons identifié une étude comparant les coûts. 18 études ont évalué les frais des médecins ou des établissements, menées aux États-Unis, au Royaume-Uni et au Canada, y compris des analyses de cohortes (5), des analyses de frais (5), des enquêtes (1) et des recherches dans des bases de données (5) évaluant des populations allant de 370 participants à 60 millions de personnes. Les taux d'imputation allaient de 0,60 à 13,45, avec une moyenne non pondérée de 4,20. La plupart des études (12) étaient de qualité acceptable. CONCLUSION: Depuis 2001, aucune étude n'a évalué les coûts comparatifs des soins aux urgences par rapport aux soins hors urgences pour les affections ambulatoires de faible gravité. Les honoraires des médecins et des établissements pour les soins aux urgences sont plus élevés que dans d'autres structures ambulatoires pour les affections de faible gravité. Il n'existe pas de données empiriques permettant d'affirmer que les soins aux urgences sont plus coûteux que des soins similaires dispensés dans d'autres structures ambulatoires.

Test characteristics of ultrasound for the diagnosis of peritonsillar abscess: A systematic review and meta-analysis.

BACKGROUND: Distinguishing peritonsillar abscess (PTA) from peritonsillar cellulitis using clinical assessment is challenging as many features overlap for both conditions, and physical examination is only about 75% sensitive and 50% specific for diagnosing PTA. The primary objective of this systematic review was to determine the test characteristics of ultrasound for diagnosing PTA when compared to a reference standard of computed tomography or acquisition of pus via needle aspiration or incision and drainage. METHODS: This systematic review was performed in accordance with the Preferred Reporting Items for a Systematic Review and Meta-analysis of Diagnostic Test Accuracy (PRISMA-DTA) guidelines. We searched seven databases from 1960 to November 2022. Two independent reviewers completed study selection, data extraction, and QUADAS-2 risk-of-bias assessment. We used a bivariate random-effects model to calculate pooled sensitivity, specificity, positive likelihood ratio (LR+), and negative likelihood ratio (LR-). We also conducted subgroup analyses on radiology ultrasound compared to point-of-care ultrasound (POCUS) and intraoral compared to transcervical scanning techniques. RESULTS: From 339 citations, we identified 18 studies for inclusion. Because one study only reported positive cases of PTA (thereby preventing the calculation of specificity), it was excluded from the analysis, so the analysis included a total of 17 studies with 812 patients, of whom 541 had PTA. Pooled bivariate sensitivity was 86% (95% confidence interval [CI] 78%-91%), specificity 76% (95% CI 67%-82%), LR+ 3.51 (95% CI 2.59-4.89), and LR- 0.19 (95% CI 0.12-0.30). On subgroup analysis, radiology-performed ultrasound had a sensitivity and specificity of 89% and 71%, compared to POCUS, which had a sensitivity and specificity of 74% and 79%. Comparing the two different techniques, intraoral had a sensitivity and specificity of 91% and 75% while transcervical had a sensitivity and specificity of 80% and 81%. CONCLUSIONS: Ultrasound demonstrates high sensitivity for ruling out PTA, but it only has moderate specificity for ruling in the diagnosis.

A Review of Current Evaluation and Management Strategies in Pediatric Postacute Sequelae of COVID-19.

Pediatric postacute sequelae of COVID-19 (pPASC), or long COVID, is a complex, heterogeneous, multisystem syndrome that leads to disruption in the lives of children and adolescents for months, and possibly years, after recovery from acute SARS-CoV-2 (severe acute respiratory syndrome coronavirus 2) infection. While the underlying pathophysiologic mechanisms of PASC are still under investigation, clinicians are facing the immediate challenges of treating these patients. In this article, we provide an overview of the current multidisciplinary evaluation of patients with pPASC. We also offer guidance on the medical, psychological, and rehabilitative management strategies based on experience with both pPASC and patients with other postviral syndromes. [Pediatr Ann. 2022;51(11):e421-e425.].

Extracting forces from noisy dynamics in dusty plasmas.

Extracting environmental forces from noisy data is a common yet challenging task in complex physical systems. Machine learning (ML) represents a robust approach to this problem, yet is mostly tested on simulated data with known parameters. Here we use supervised ML to extract the electrostatic, dissipative, and stochastic forces acting on micron-sized charged particles levitated in an argon plasma (dusty plasma). By tracking the subpixel motion of particles in subsequent images, we successfully estimated these forces from their random motion. The experiments contained important sources of non-Gaussian noise, such as drift and pixel locking, representing a data mismatch from methods used to analyze simulated data with purely Gaussian noise. Our model was trained on simulated particle trajectories that included all of these artifacts, and used more than 100 dynamical and statistical features, resulting in a prediction with 50% better accuracy than conventional methods. Finally, in systems with two interacting particles, the model provided noncontact measurements of the particle charge and Debye length in the plasma environment.

The lifetime of charged dust in the atmosphere.

Wind-blown dust plays a critical role in numerous geophysical and biological systems, yet current models fail to explain the transport of coarse-mode particles (>5 µm) to great distances from their sources. For particles larger than a few microns, electrostatic effects have been invoked to account for longer-than-predicted atmospheric residence times. Although much effort has focused on elucidating the charging processes, comparatively little effort has been expended understanding the stability of charge on particles once electrified. Overall, electrostatic-driven transport requires that charge remain present on particles for days to weeks. Here, we present a set of experiments designed to explore the longevity of electrostatic charge on levitated airborne particles after a single charging event. Using an acoustic levitator, we measured the charge on particles of different material compositions suspended in atmospheric conditions for long periods of time. In dry environments, the total charge on particles decayed in over 1 week. The decay timescale decreased to days in humid environments. These results were independent of particle material and charge polarity. However, exposure to UV radiation could both increase and decrease the decay time depending on polarity. Our work suggests that the rate of charge decay on airborne particles is solely determined by ion capture from the air. Furthermore, using a one-dimensional sedimentation model, we predict that atmospheric dust of order 10 µm will experience the largest change in residence time due to electrostatic forces.

Minimum Leidenfrost Temperature on Smooth Surfaces.

During the Leidenfrost effect, a thin insulating vapor layer separates an evaporating liquid from a hot solid. Here we demonstrate that Leidenfrost vapor layers can be sustained at much lower temperatures than those required for formation. Using a high-speed electrical technique to measure the thickness of water vapor layers over smooth, metallic surfaces, we find that the explosive failure point is nearly independent of material and fluid properties, suggesting a purely hydrodynamic mechanism determines this threshold. For water vapor layers of several millimeters in size, the minimum temperature for stability is ≈140 °C, corresponding to an average vapor layer thickness of 10-20 µm.