Some issues concerning Large-Eddy Simulation of inertial particle dispersion in turbulent bounded flows

The problem of an accurate Eulerian-Lagrangian modeling of inertial particle dispersion in Large Eddy Simulation (LES) of turbulent wall-bounded flows is addressed. We run Direct Numerical Simulation (DNS) for turbulent channel flow at shear Reynolds numbers equal to 150 and 300 and corresponding a-priori and a-posteriori LES on differently coarse grids. We then tracked swarms of different inertia particles and we examined the influence of filtering and of Sub-Grid Scale (SGS) modeling for the fluid phase on particle velocity and concentration statistics. We also focused on how particle preferential segregation is predicted by LES. Results show that even ``well-resolved'' LES is unable to reproduce the physics as demonstrated by DNS, both for particle accumulation at the wall and for particle preferential segregation. Inaccurate prediction is observed for the entire range of particles considered in this study, even when the particle response time is much larger than the flow timescales not resolved in LES. Both a-priori and a-posteriori tests indicate that recovering the level of fluid and particle velocity fluctuations is not enough to have accurate prediction of near-wall accumulation and local segregation. This may suggest that reintroducing the correct amount of higher-order moments of the velocity fluctuations is also a key point for SGS closure models for the particle equation. Another important issue is the presence of possible flow Reynolds number effects on particle dispersion. Our results show that, in small Reynolds number turbulence and in the case of heavy particles, the shear fluid velocity is a suitable scaling parameter to quantify these effects

Second primary squamous cell carcinomas treated with trans oral robotic surgery: Oncological and functional results.

Recovery of swallowing in patients treated with trans-oral robotic surgery (TORS) is in general considered as favorable. However, patients afflicted with a secondary primary carcinoma of the head and neck may be more vulnerable to swallowing dysfunctions after trans-oral surgery as a consequence of previous treatments. This is a retrospective monocentric study on patients undergoing TORS for second primary squamous cell carcinoma between 2013 and 2017 (follow-up until June 2021). Swallowing performance was assessed via the functional outcome swallowing scale (FOSS). Also, overall survival (OS), disease-free survival (DS) and disease-specific survival (DSS) were evaluated. Eighteen patients (median 62 years) underwent TORS with curative intent for T1-2 oropharyngeal and supraglottic secondary primaries. The average follow-up was of 52 months. All cases were resected R0 using TORS. 84% of patients had a post-treatment FOSS score equal or better upon last follow-up compared with pre-treatment. Only one patient required a percutaneous gastrostomy long term. DSS/DFS/OS at 5 years was 94%, 60%, and 67%, respectively. The main cause of death was metachronous pulmonary neoplasia. Our study demonstrates encouraging results in terms of swallowing recovery in patients undergoing TORS for selected secondary primaries of the oropharynx and supraglottic larynx. Further studies into trans-oral surgery for this condition seem therefore warranted. Level of Evidence: Case series; Level 4

Landslides, a Key Landform in the Global Geological Heritage

Landslides are important components of global geoheritage, but awareness of their significance and value in such terms seems scanty in the scientific community. Landslides are normally identified among various features of geological and geomorphological interest, and often considered a source of hazard. However, they are seldom identified as geosites and as part of geoheritage. This paper aims at filling these gaps by highlighting the importance of landslides in the global geoheritage. After a short introduction on the values and criteria to define landforms as geosites, based on literature review, we show to what extent landslides have been defined as geomorphosites and as part of geoheritage around the world. We then outline three aspects that should be specifically considered in the identification of landslides as geomorphosites, namely 1) past and present climate changes, 2) anthropic signature, and 3) risk perception. Finally, we describe four cases of spectacular landslides that serve as significant examples worldwide

Statistical properties of an ideal subgrid-scale correction for Lagrangian particle tracking in turbulent channel flow

One issue associated with the use of Large-Eddy Simulation (LES) to investigate the dispersion of small inertial particles in turbulent flows is the accuracy with which particle statistics and concentration can be reproduced. The motion of particles in LES fields may differ significantly from that observed in experiments or direct numerical simulation (DNS) because the force acting on the particles is not accurately estimated, due to the availability of the only filtered fluid velocity, and because errors accumulate in time leading to a progressive divergence of the trajectories. This may lead to different degrees of inaccuracy in the prediction of statistics and concentration. We identify herein an ideal subgrid correction of the a-priori LES fluid velocity seen by the particles in turbulent channel flow. This correction is computed by imposing that the trajectories of individual particles moving in filtered DNS fields exactly coincide with the particle trajectories in a DNS. In this way the errors introduced by filtering into the particle motion equations can be singled out and analyzed separately from those due to the progressive divergence of the trajectories. The subgrid correction term, and therefore the filtering error, is characterized in the present paper in terms of statistical moments. The effects of the particle inertia and of the filter type and width on the properties of the correction term are investigated.Comment: 15 pages,24 figures. Submitted to Journal of Physics: Conference Serie

Curcumin and type 2 diabetes mellitus : Prevention and treatment

Type 2 diabetes mellitus (T2DM) is an ensemble of metabolic diseases that has reached pandemic dimensions all over the world. The multifactorial nature of the pathology makes patient management, which includes lifelong drug therapy and lifestyle modification, extremely challenging. It is well known that T2DM is a preventable disease, therefore lowering the incidence of new T2DM cases could be a key strategy to reduce the global impact of diabetes. Currently, there is growing evidence on the efficacy of the use of medicinal plants supplements for T2DM prevention and management. Among these medicinal plants, curcumin is gaining a growing interest in the scientific community. Curcumin is a bioactive molecule present in the rhizome of the Curcuma longa plant, also known as turmeric. Curcumin has different pharmacological and biological effects that have been described by both in vitro and in vivo studies, and include antioxidant, cardio-protective, anti-inflammatory, anti-microbial, nephro-protective, anti-neoplastic, hepato-protective, immunomodulatory, hypoglycaemic and anti-rheumatic effects. In animal models, curcumin extract delays diabetes development, improves \u3b2-cell functions, prevents \u3b2-cell death, and decreases insulin resistance. The present review focuses on pre-clinical and clinical trials on curcumin supplementation in T2DM and discusses the peculiar mechanisms by which curcumin might ameliorate diabetes management

The quantum Hall effect in graphene samples and the relativistic Dirac effective action

We study the Euclidean effective action per unit area and the charge density for a Dirac field in a two--dimensional spatial region, in the presence of a uniform magnetic field perpendicular to the 2D--plane, at finite temperature and density. In the limit of zero temperature we reproduce, after performing an adequate Lorentz boost, the Hall conductivity measured for different kinds of graphene samples, depending upon the phase choice in the fermionic determinant.Comment: Conclusions extended. References added. 9 pages. 1 figur

Deposits, composition and technological behavior of fluxes for ceramic tiles

The ceramic tile industry is a big consumer of feldspathic rocks and further raw materials able to act as flux during firing. This demand is currently fed with the recourse to a wide range of sources of igneous, sedimentary, metamorphic and metasomatic origin. The main geological features of flux deposits actually exploited by the ceramic industry are reviewed. The chemical and mineralogical composition is described to have a general picture of raw fluxes as well as average data and compositional perimeter for deposits of different origin. Overall beneficiation routes are drawn to trace the compositional path from deposit to commercial flux. The technological behavior in tile-making is shortly overviewed and new experimental data are provided on flux fusibility (by hot-stage microscopy). A chart is proposed to discriminate fluxes according to different fusibility

Role of large-scale advection and small-scale turbulence on vertical migration of gyrotactic swimmers

In this work, we use direct-numerical-simulation-based Eulerian-Lagrangian simulations to investigate the dynamics of small gyrotactic swimmers in free-surface turbulence. We consider open-channel flow turbulence in which bottom-heavy swimmers are dispersed. Swimmers are characterized by different vertical stability, so that some realign to swim upward with a characteristic time smaller than the Kolmogorov timescale, while others possess a reorientation time longer than the Kolmogorov timescale. We cover one order of magnitude in the flow Reynolds number and two orders of magnitude in the stability number, which is a measure of bottom heaviness. We observe that large-scale advection dominates vertical motion when the stability number, scaled on the local Kolmogorov timescale of the flow, is larger than unity: This condition is associated to enhanced migration toward the surface, particularly at low Reynolds number, when swimmers can rise through surface renewal motions that originate directly from the bottom boundary turbulent bursts. Conversely, small-scale effects become more important when the Kolmogorov-based stability number is below unity: Under this condition, migration toward the surface is hindered, particularly at high Reynolds, when bottom-boundary bursts are less effective in bringing bulk fluid to the surface. In an effort to provide scaling arguments to improve predictions of models for motile microorganisms in turbulent water bodies, we demonstrate that a Kolmogorov-based stability number around unity represents a threshold beyond which swimmer capability to reach the free surface and form clusters saturates

Recommendations for Medical Education in Taiwan

The purpose of the new project presented in these pages is to offer an innovative approach to the study of the evolution of Coptic literature and, more specifically, to the corpus of writings produced in Egypt between the third and the late eleventh centuries, and expressed in the different dialects of the Coptic language. Its aim is to provide a new perspective on the cultural landscape of Christian Egypt by interweaving literary, historical, codicological and archaeological data, and producing a series of scholarly tools, till now unavailable, in a digital environment, including an archaeological Atlas of late antique and early mediaeval Coptic literature that will be searchable at different chronological, regional and thematic levels. As part of the above-described research activities and goals, a complete catalogue of the Coptic papyrus codices preserved in the Museo Egizio will be produced, as well as an edition of their titles and scribal subscriptions. The fragmentary codices in question, purchased in Egypt by Bernardino Drovetti in the 1820s, are a unique example of an entire well-preserved late antique institutional library – very likely originally belonging to the cathedral of This/Thinis – reflecting the literary tastes and dogmatic orientations before what can be defined as the ninth-century Coptic book revolution, which significantly changed bookmaking in Christian Egypt. The library of Thi(ni)s is a crucial and transitional instance in the history of Coptic books, which saw on the one hand the creation of new codicological and palaeographical features and on the other the progressive emergence of multiple-text codices

Intrinsic filtering errors of Lagrangian particle tracking in LES flow fields

Large-Eddy Simulations (LES) of two-phase turbulent flows exhibit quantitative differences in particle statistics if compared to Direct Numerical Simulations (DNS) which, in the context of the present study, is considered the exact reference case. Differences are primarily due to filtering, a fundamental intrinsic feature of LES. Filtering the fluid velocity field yields approximate computation of the forces acting on particles and, in turn, trajectories that are inaccurate when compared to those of DNS. In this paper, we focus precisely on the filtering error for which we quantify a lower bound. To this aim, we use a DNS database of inertial particle dispersion in turbulent channel flow and we perform a-priori tests in which the error purely due to filtering is singled out removing error accumulation effects, which would otherwise lead to progressive divergence between DNS and LES particle trajectories. By applying filters of different type and width at varying particle inertia, we characterize the statistical properties of the filtering error as a function of the wall distance. Results show that filtering error is stochastic and has a non-Gaussian distribution. In addition, the distribution of the filtering error depends strongly on the wall-normal coordinate being maximum in the buffer region. Our findings provide insight on the effect of subgrid-scale velocity field on the force driving the particles, and establish the requirements which a LES model must satisfy to predict correctly the velocity and the trajectory of inertial particles.Comment: 39 pages, 1 table, 12 figures, submitted to Physics of Fluid