Settling of an asymmetric dumbbell in a quiescent fluid

We compute the hydrodynamic torque on a dumbbell (two spheres linked by a massless rigid rod) settling in a quiescent fluid at small but finite Reynolds number. The spheres have the same mass densities but different sizes. When the sizes are quite different the dumbbell settles vertically, aligned with the direction of gravity, the largest sphere first. But when the size difference is sufficiently small then its steady-state angle is determined by a competition between the size difference and the Reynolds number. When the sizes of the spheres are exactly equal then fluid inertia causes the dumbbell to settle in a horizontal orientation.Comment: 11 pages, 1 figure, as publishe

Symmetries and the cosmological constant puzzle

We outline the evaluation of the cosmological constant in the framework of the standard field-theoretical treatment of vacuum energy and discuss the relation between the vacuum energy problem and the gauge-group spontaneous symmetry breaking. We suggest possible extensions of the 't Hooft-Nobbenhuis symmetry, in particular, its complexification till duality symmetry and discuss the compatible implementation on gravity. We propose to use the discrete time-reflection transform to formulate a framework in which one can eliminate the huge contributions of vacuum energy into the effective cosmological constant and suggest that the breaking of time--reflection symmetry could be responsible for a small observable value of this constant.Comment: 11 pages, more relevant refs, refining cutoff definition of cosmological constant + eq.for regularized pressure adde

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

Energy balance in lubricated drag-reduced turbulent channel flow

We use direct numerical simulation (DNS) to study drag reduction in a lubricated channel, a flow instance in which a thin layer of lubricating fluid is injected in the near-wall region so as to favour the transportation of a primary fluid. In the present configuration, the two fluids have equal density but different viscosity, so that a viscosity ratio can be defined. To cover a meaningful range of possible situations, we consider five different in the range. All DNS are run using the constant power input (CPI) approach, which prescribes that the flow rate is adjusted according to the actual pressure gradient so as to keep constant the power injected into the flow. The CPI approach has been purposely extended here for the first time to the case of multiphase flows. A phase-field method is used to describe the dynamics of the liquid-liquid interface. We unambiguously show that a significant drag reduction (DR) can be achieved for. Reportedly, the observed DR is a non-monotonic function of and, in the present case, is maximum for (flow-rate increase). Upon a detailed analysis of the energy budgets, we are able to show the existence of two different DR mechanisms. For and, DR is purely due to the effect of the surface tension-a localized elasticity element that separates the two fluids-which, decoupling the wall-normal momentum transfer mechanisms between the primary and the lubricating layer, suppresses turbulence in the lubricating layer (laminarization) and reduces the overall drag. For <[CDATA[\u3bb, turbulence can be sustained in the lubricating layer, because of the increased local Reynolds number. In this case, DR is simply due to the smaller viscosity of the lubricating layer that acts to decrease directly the corresponding wall friction. Finally, we show evidence that an upper bound for exists, for which DR cannot be observed: for, we report a slight drag enhancement, thereby indicating that the turbulence suppression observed in the lubricating layer cannot completely balance the increased friction due to the larger viscosity

Interaction between thermal stratification and turbulence in channel flow

Transport phenomena in high Reynolds number wall-bounded stratified flows are dominated by the interplay between the turbulence structures generated at the wall and the buoyancy-induced large-scale waves populating the channel core. In this study, we want to investigate the flow physics of wall-bounded stratified turbulence at relatively high shear Reynolds number and for mild to moderate stratification level - quantified here by the shear Richardson number varying in the range. By increasing stratification, active turbulence is sustained only in the near-wall region, whereas intermittent turbulence, modulated by the presence of non-turbulent wavy structures (internal gravity waves), is observed at the channel core. In such conditions, the wall-normal transport of momentum and heat is considerably reduced compared with the case of non-stratified turbulence. A careful characterization of the flow-field statistics shows that, despite temperature and wall-normal velocity fluctuations being very large at the channel centre, the mean value of their product - the buoyancy flux - vanishes for. We show that this behaviour is due to the presence of a phase delay between the temperature and the wall-normal velocity signals: when wall-normal velocity fluctuations are large (in magnitude), temperature fluctuations are almost zero, and vice versa. This constitutes a blockage effect to the wall-normal exchange of energy. In addition, we show that the friction factor scales as, and we propose a new scaling for the Nusselt number,. These scaling laws, which seem to be robust over the explored range of parameters, complement and extend previous experimental and numerical data, and are expected to help the development of improved models and parametrizations of stratified flows at large

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

Landscapes and Landforms of Terrestrial and Marine Areas: A Way Forward

The article introduces the aims and topics of the Special Issue 'Landscapes and Landforms of Terrestrial and Marine Areas' showing a variety of approaches and techniques used to integrate terrestrial and marine spatial datasets. The outcomes not only show how innovative and advanced geomorphological mapping techniques can support a more informed sustainable management of coastal environments, but also pave the way for other studies that rely on an improved efficiency in providing 3D landscape visualization from remote multisource and multiscale data

Propagation of capillary waves in two-layer oil-water turbulent flow

We study the dynamics of capillary waves at the interface of a two-layer stratified turbulent channel flow. We use a combined pseudo-spectral/phase field method to solve for the turbulent flow in the two liquid layers and to track the dynamics of the liquid-liquid interface. The two liquid layers have same thickness and same density, but different viscosity. We vary the viscosity of the upper layer (two different values) to mimic a stratified oil-water flow. This allows us to study the interplay between inertial, viscous and surface tension forces in the absence of gravity. In the present set-up, waves are naturally forced by turbulence over a broad range of scales, from the larger scales, whose size is of order of the system scale, down to the smaller dissipative scales. After an initial transient, we observe the emergence of a stationary capillary wave regime, which we study by means of temporal and spatial spectra. The computed frequency and wavenumber power spectra of wave elevation are in line with previous experimental findings and can be explained in the frame of the weak wave turbulence theory. Finally, we show that the dispersion relation, which gives the frequency as a function of the wavenumber , is in good agreement with the well-established theoretical prediction,

Towards the ultimate regime in Rayleigh-Darcy convection

Numerical simulations are used to probe Rayleigh-Darcy convection in fluid-saturated porous media towards the ultimate regime. The present three-dimensional dataset, up to Rayleigh-Darcy number, suggests that the appropriate scaling of the Nusselt number is, fitting the computed data for. Extrapolation of current predictions to the ultimate linear regime yields the asymptotic law, about less than indicated in previous studies. Upon examination of the flow structures near the boundaries, we confirm previous indications of small flow cells hierarchically nesting into supercells, and we show evidence that the supercells at the boundary are the footprints of the megaplumes that dominate the interior part of the flow. The present findings pave the way for more accurate modelling of geophysical systems, with special reference to geological sequestration