Numerical simulation of droplet impact on wettability-patterned surfaces

© 2020 American Physical Society. Numerical simulations have unexplored potential in the study of droplet impact on nonuniform wettability surfaces. In this paper, we compare numerical and experimental results to investigate the application potential of a volume-of-fluid method utilized in OpenFOAM. The approach implements the Kistler model for the dynamic contact angle of impacting droplets. We begin with an investigation into the influence of the most important solver parameters to optimize the computational setup and reach the best compromise between computational cost and solution errors, as assessed in comparison to experimental results. Next, we verify the accuracy of the predictions for droplet impact on uniformly hydrophilic or superhydrophobic surfaces. Benchmarking the maximal spreading factor, contact, and spreading times, as well as contact-line behavior, we show strong agreement between the present numerical results and the models of Pasandideh-Fard, Phys. Fluids 8, 650 (1996)PHFLE61070-663110.1063/1.868850 and Clanét, J. Fluid Mech. 517, 199 (2004)JFLSA70022-112010.1017/S0022112004000904. Lastly, we demonstrate the capability of the model to accurately predict outcome behaviors of droplets striking distributed-wettability surfaces, which introduce 3D outcome characteristics, even in orthogonal impact. The model successfully predicts droplet splitting and vectoring, as reported in the experiments of Schutzius, Sci. Rep. 4, 7029 (2014)2045-232210.1038/srep07029. Finally, we demonstrate a configuration wherein a droplet centrally strikes a circular disk of different wettability than its surrounding domain. The main contribution of the present paper is a numerical model capable of accurately simulating droplet impact on spatially nonuniform wettability patterns of any foreseeable design

Manipulating Light with Tunable Nanoantennas and Metasurfaces

The extensive progress in nanofabrication techniques enabled innovative methods for molding light at the nanoscale. Subwavelength structured optical elements and, in general, metasurfaces and metamaterials achieved promising results in several research areas, such as holography, microscopy, sensing and nonlinear optics. Still, a demanding challenge is represented by the development of innovative devices with reconfigurable optical properties. Here, we review recent achievements in the field of tunable metasurface. After a brief general introduction about metasurfaces, we will discuss two different mechanisms to implement tunable properties of optical elements at the nanoscale. In particular, we will first focus on phase-transition materials, such as vanadium dioxide, to tune and control the resonances of dipole nanoantennas in the near-infrared region. Finally, we will present a platform based on an AlGaAs metasurface embedded in a liquid crystal matrix that allows the modulation of the generated second harmonic signal

Extraordinary second harmonic generation modulated by divergent strain field in pressurized monolayer domes

The most prominent form of nonlinear optical (NLO) frequency conversion is second harmonic generation (SHG), where incident light interacts with a nonlinear medium producing photons at double the input frequency, which has vast applications in material and biomedical science. Emerging two-dimensional nonlinear optical materials led by transition metal dichalcogenides (TMDs) have fascinating optical and mechanical properties and are highly anticipated to overcome the technical limitations imposed by traditional bulky NLO materials. However, the atomic scale interaction length and low conversion efficiency in TMD materials prevent their further implementation in NLO applications. While some uniaxial strain-engineering studies intensively investigated the anisotropic SHG response in TMDs, they did not realize giant SHG enhancement by exploiting the opto-mechanical characteristics. Herein, we employ proton (H+) irradiation to successfully fabricate large pressurized monolayer TMD domes (d ≥ 10 μm) and conduct a comprehensive investigation and characterization of their SHG performance enhancement. We show that the intensity of SHG is effectively enhanced by around two orders of magnitude at room temperature. Such giant enhancement arises from the distinct separation distance induced by capped pressurized gas and the hemi-spherical morphology, enabling constructive optical interference. Moreover, the unique divergent strain field in TMD domes promotes the first experimental study on the anisotropic nonlinear optical behavior based on biaxial strain conditions in terms of varying strain orientation and relative weights. Our work demonstrates a promising system with enhanced NLO performance and well-preserved biocompatibility, paving a way toward the future nano-scaled quantum optics design and biomedical applications

Dietary administration of D-chiro-inositol attenuates sex-specific metabolic imbalances in the 5xFAD mouse model of Alzheimer’s disease

Increasing evidence shows that hypothalamic dysfunction, insulin resistance, and weight loss precede and progress along with the cognitive decline in sporadic Alzheimer’s Disease (AD) with sex differences. This study aimed to determine the effect of oral dietary administration of D-Chiro-inositol (DCI), an inositol used against insulin resistance associated with polycystic ovary, on the occurrence of metabolic disorders in the transgenic 5xFAD mouse model of AD (FAD: Family Alzheimer's Disease). DCI was administered from 6 to 10 months of age to male and female 5xFAD mice and control (non-Tg) littermates. Energy balance and multiple metabolic and inflammatory parameters in the hypothalamus, liver and plasma were evaluated to assess the central and peripheral effects of DCI. Results indicated that weight loss and reduced food intake in 5xFAD mice were associated with decreased neuropeptides controlling food intake and the appearance of a pro-inflammatory state in the hypothalamus. Oral administration of DCI partially restored energy balance and hypothalamic parameters, highlighting an increased expression of Npy and Agrp and female-specific downregulation of Gfap and Igf1. DCI also partially normalized impaired insulin signaling and circulating insulin, GLP-1, and GIP deficiencies in 5xFAD mice. Principal component analysis of metabolic parameters indicated the presence of a female-specific fatty liver in 5xFAD mice: DCI administration reversed hepatic fat accumulation, β-oxidation, inflammation and increased GOT and GPT levels. Our study depicts that metabolic impairment along with the cognitive decline in a mouse model of AD, which is exacerbated in females, can be ameliorated by oral supplementation with insulin-sensitizing DCI.This research was funded by the European Regional Development Funds-European Union (ERDF-EU) and Fatzheimer project EULAC-HEALTH H2020, grant number EU-LACH16/T010131; Ministerio de Economía, Industria y Competitividad, Gobierno de España, grant number RTC-2016-4983-1; EU-ERDF and Instituto de Salud Carlos III (ISCIII), grant numbers PI19/01577 and PI19/00343; Ministerio de Sanidad, Delegación de Gobierno para el Plan Nacional sobre Drogas, grant numbers 2019/040 and 2020/048; Consejería de Transformación Económica, Industria, Conocimiento y Universidades, Junta de Andalucía, grant number P18-TP-5194, INSERM (Institut National de la Santé et de la Recherche Médicale), Nouvelle Aquitaine Region and ANR (grant numbers ANR-18-CE14-0029 MitObesity, Labex BRAIN ANR-10-LABX-43, ANR-10-EQX-008-1 OPTOPATH, ANR-17-CE14-0007 BABrain, ANR-21-CE14-0018-01_StriaPOM to D.C.). A.J.L.-G. (IFI18/00042) holds an “iPFIS” predoctoral contract from the National System of Health, EU-ERDF-ISCIII. B.P.S (IFI21/00024) holds an “iPFIS” predoctoral contract from the National System of Health, EU-ERDF-ISCIII. P.R. (CP19/00068) holds a ‘’Miguel Servet I” research contract from the National System of Health, EU-ERDF-ISCIII. D.M-V. (FI20/00227) holds a “PFIS” pre-doctoral contract from the National System of Health, EU-ERDF-ISCIII. The microscopy for IBA1 and GFAP immunofluorescence was done in the Bordeaux Imaging Center, a service unit of the CNRS-INSERM and Bordeaux University, member of the national infrastructure France BioImaging supported by the LabEX BRAIN and ANR-10-INBS-04. Partial funding for open access charge: Universidad de Málaga

Endocrine and Metabolic impact of oral ingestion of a carob-pod derived natural syrup containing D-Pinitol: potential use as a novel sweetener in diabetes

The use of added sugars or non-nutritive sweeteners in processed foods and soft drinks are being blamed for multiple complications associated with obesity and diabetes. High fructose content contributes to obesity and liver steatosis, and excessive consumption of non-nutritive sweeteners can generate gut dysbiosis complicating the metabolic control exerted by the liver. Beyond its evolutionary significance in the selection of foods with a high glucose content as an energy source, the fact is that the consumption of sweets produces a hedonic pleasure in our brain. Then, the challenge stands at: how do we control the use of added sugars while providing a safe, palatable, sweet flavour to foods?. The present work explores an alternative approach, in humans and rodents, for sweetening through the use of a simple carob-pod-derived syrup which contains the inositol D-Pinitol. This inositol is known as an insulin sensitizer in muscle capable of keeping glycaemia while avoiding both unnecessary insulin secretion and the conversion of carbohydrates into fat depots .Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech

Manipulating Light with Tunable Nanoantennas and Metasurfaces

The extensive progress in nanofabrication techniques enabled innovative methods for molding light at the nanoscale. Subwavelength structured optical elements and, in general, metasurfaces and metamaterials achieved promising results in several research areas, such as holography, microscopy, sensing and nonlinear optics. Still, a demanding challenge is represented by the development of innovative devices with reconfigurable optical properties. Here, we review recent achievements in the field of tunable metasurface. After a brief general introduction about metasurfaces, we will discuss two different mechanisms to implement tunable properties of optical elements at the nanoscale. In particular, we will first focus on phase-transition materials, such as vanadium dioxide, to tune and control the resonances of dipole nanoantennas in the near-infrared region. Finally, we will present a platform based on an AlGaAs metasurface embedded in a liquid crystal matrix that allows the modulation of the generated second harmonic signal

Impairment of T cell development and acute inflammatory response in HIV-1 Tat transgenic mice

Immune activation and chronic inflammation are hallmark features of HIV infection causing T-cell depletion and cellular immune dysfunction in AIDS. Here, we addressed the issue whether HIV-1 Tat could affect T cell development and acute inflammatory response by generating a transgenic mouse expressing Tat in lymphoid tissue. Tat-Tg mice showed thymus atrophy and the maturation block from DN4 to DP thymic subpopulations, resulting in CD4(+) and CD8(+) T cells depletion in peripheral blood. In Tat-positive thymus, we observed the increased p65/NF-κB activity and deregulated expression of cytokines/chemokines and microRNA-181a-1, which are involved in T-lymphopoiesis. Upon LPS intraperitoneal injection, Tat-Tg mice developed an abnormal acute inflammatory response, which was characterized by enhanced lethality and production of inflammatory cytokines. Based on these findings, Tat-Tg mouse could represent an animal model for testing adjunctive therapies of HIV-1-associated inflammation and immune deregulation

TALIF measurements of atomic oxygen density in L2K plasma wind tunnel

Absolute atomic oxygen concentration measurements using two-photon absorption laser induced fluorescence experimental technique have been carried out in high-enthalpy plasma flow. The measurements have been conducted in L2K hypersonic wind tunnel at DLR. The test campaign is performed at 600 A of arc current in air with a mass flow rate of 36 g/s and a stagnation pressure of 105 Pa. The averaged total enthalpy is ~8.4 MJ/kg and the temperature is assumed to be equal to 4218 K. The investigation has been conducted in the freestream and into the shock layer, i.e., 5 mm upstream from the model surface. The estimation of the atomic oxygen concentration is performed by using relative fluorescence signals considering xenon 6p’[3/2]2 transition as reference gas. The effect of the quenching for the atomic oxygen determines a reduction of the lifetimes τ, i.e., 28.8 ns in the freestream and 11.4 ns into the shock layer. The estimation of the atomic oxygen concentration is performed by using relative fluorescence signals considering xenon as reference gas. The number density is equal to ~3.33 × 1023 m-3 in the freestream and ~15.6 × 1023 m-3 into the shock layer

Two-Photon Laser-Induced Fluorescence Measurements of Atomic Oxygen Density in Hypersonic Plasma Flow

An experimental investigation of high-enthalpy air flow generated by L2K arc-jet facility of DLR is carried out by means of two-photon absorption laser-induced fluorescence (TALIF) measurements of atomic oxygen at O×3p×3P1;2;0 transition. The experiment has been conducted with an arc current of 600 A, a mass flow rate of 36 g∕s, and a total pressure of 105 Pa, resulting in both mass-specific enthalpy of ∼8.4 MJ∕kg and a reservoir temperature of 4200 K. Atomic oxygen has been characterized in terms of translational temperature and absolute number density either in the freestream or behind a shock wave upstream a blunt body. A calibration method based on TALIF measurements of xenon at 6p'[3∕2]2 transition has been used. The results highlight that in the freestream the fluorescence signal exhibits a peak activity lower with respect to that inspected in the shock layer. The measured lifetimes 25.8 ns and 11.4 ns indicate that, in the shock layer, the depletion of the atomic Oxygen excited state occurs mainly via quenching. The analysis of the line broadening of the spectral profile of atomic oxygen reveals an increment of the translational temperature in the shock layer with respect to that measured in the freestream, resulting in 2500 K and 1400 K, respectively. It is found that in the freestream the absolute number density attains ∼5.55E23 m-3 and the presence of the shock wave induces an increment of the number density of ∼26.9E23 m−3, that is, 4.85 times higher than that detected in the freestream