Video-based paired comparison to evaluate some cosmetic products under camera movement for dynamic performance.

OBJECTIVE: Until now, standardized evaluation of cosmetic effects was conducted mainly in still conditions such as pictures. In real life, the consumers' experience of their cosmetics' effects is dynamic and some of the benefits can be better observed under movement. In order to capture motion-related performance of cosmetics, we developed a video-based paired comparison on an online platform. METHODS: We validated this new tool through the evaluation of eyeshadow with high light reflection and colour gradation, especially visible under motion according to the observer point of view. This formula was compared with two marketed benchmarks. The three products were applied sequentially on the eyelid of eight Japanese women. Videos were taken in standardized light, speed and face position with a rotating camera around the face. The videos were uploaded on an online secured platform and eyelid 3D effect, highlight and colour gradation were evaluated through paired comparison test by 60 Japanese women from home on their PC or tablets. Those results were compared with picture-based paired comparison by the same observers. RESULTS: Video-based paired comparison provided higher discrimination of products compared to picture-based comparison. CONCLUSION: As compared to still camera acquisition, the evaluation of cosmetics based on videos is closer to real-life experience and can bring higher discrimination, especially for motion-related attributes.

OBJECTIF: Jusqu'à présent, l'évaluation standardisée des effets cosmétiques a été réalisée principalement dans des conditions immobiles telles que des photos. Dans la vie réelle, l'expérience des consommateurs des effets de leurs cosmétiques est dynamique, et certains des avantages peuvent être mieux observés en mouvement. Afin de saisir les performances des produits cosmétiques liées au mouvement, nous avons mis au point une comparaison par paires basée sur des vidéos sur une plateforme en ligne. MÉTHODES: Nous avons validé ce nouvel outil en évaluant un fard à paupières à forte réflexion lumineuse et à gradation de couleurs, particulièrement visible en mouvement selon le point de vue de l'observateur. Cette formule a été comparée à deux références commercialisées. Les trois produits ont été appliqués successivement sur la paupière de huit femmes japonaises. Les vidéos ont été prises dans des conditions de lumière, de vitesse et de position du visage normalisées, avec une caméra tournant autour du visage. Les vidéos ont été téléchargées sur une plateforme sécurisée en ligne, et l'effet 3D des paupières, l'accentuation et la gradation des couleurs ont été évalués au moyen d'un test de comparaison par paires par 60 femmes japonaises depuis leur domicile sur leur PC ou leur tablette. Ces résultats ont été mis en parallèle à une comparaison par paires sur photo par les mêmes observateurs. RÉSULTATS: La comparaison par paires sur vidéo a permis de mieux distinguer les produits par rapport à la comparaison sur photo. CONCLUSION: Par rapport à l'acquisition d'images fixes, l'évaluation des cosmétiques à partir de vidéos est plus proche de l'expérience réelle et peut permettre de mieux distinguer les produits, en particulier pour les attributs liés au mouvement.

Differential Inhibition of HIV Replication by the 12 Interferon Alpha Subtypes.

Type I interferons (IFNs) are a family of cytokines that represent a first line of defense against virus infections. The 12 different IFN-α subtypes share a receptor on target cells and trigger similar signaling cascades. Several studies have collectively shown that this apparent redundancy conceals qualitatively different responses induced by individual subtypes, which display different efficacies of inhibition of HIV replication. Some studies, however, provided evidence that the disparities are quantitative rather than qualitative. Since RNA expression analyses show a large but incomplete overlap of the genes induced, they may support both models. To explore if the IFN-α subtypes induce functionally relevant different anti-HIV activities, we have compared the efficacies of inhibition of all 12 subtypes on HIV spread and on specific steps of the viral replication cycle, including viral entry, reverse transcription, protein synthesis, and virus release. Finding different hierarchies of inhibition would validate the induction of qualitatively different responses. We found that while most subtypes similarly inhibit virus entry, they display distinctive potencies on other early steps of HIV replication. In addition, only some subtypes were able to target effectively the late steps. The extent of induction of known anti-HIV factors helps to explain some, but not all differences observed, confirming the participation of additional IFN-induced anti-HIV effectors. Our findings support the notion that different IFN-α subtypes can induce the expression of qualitatively different antiviral activities. IMPORTANCE The initial response against viruses relies in large part on type I interferons, which include 12 subtypes of IFN-α. These cytokines bind to a common receptor on the cell surface and trigger the expression of incompletely overlapping sets of genes. Whether the anti-HIV responses induced by IFN-α subtypes differ in the extent of expression or in the nature of the genes involved remains debated. Also, RNA expression profiles led to opposite conclusions, depending on the importance attributed to the induction of common or distinctive genes. To explore if relevant anti-HIV activities can be differently induced by the IFN-α subtypes, we compared their relative efficacies on specific steps of the replication cycle. We show that the hierarchy of IFN potencies depends on the step analyzed, supporting qualitatively different responses. This work will also prompt the search for novel IFN-induced anti-HIV factors acting on specific steps of the replication cycle.

Repeatability and reproducibility of a hyperspectral imaging system for in vivo color evaluation.

BACKGROUND: Color imaging is a tried and true method for the evaluation of cosmetic and dermatological effects, but it fails to capture all the information in a scene's spectral reflectance. For this reason, there has been in recent years increasing interest in the use of imaging spectrometers for clinical studies and product evaluation. MATERIAL AND METHODS: We developed a novel HyperSpectral Imager (HSI) able to take in vivo full-face format images as a next generation instrument for skin color measurement and beyond. Here, we report part of the results of our first full-scale validation test of the HSI. We replicated a make-up foundation screening test by applying three products to a panel of 9 models and evaluated the product L∗ , a∗ , b∗ , and ∆E effect immediately after application relative to the bare skin condition. We repeated this test twice in order to study the repeatability of the HSI as an evaluation instrument and during each test two different operators duplicated the data acquisition so we can assess the reproducibility of the measurements. RESULTS: We find that the measurements from the HSI provide repeatability and reproducibility as good or better than those of our previous benchmark devices. CONCLUSION: From these results, we conclude that not only is the HSI suitable for use in color evaluation studies, but also that it gives operational advantages over the previous generation of evaluation instruments, as it provides a spectral measurement combined with good spatial resolution. This allows for analysis of color over an area and post hoc selection of study regions and so opens new possibilities for studies of complex in vivo phenomena which neither non-imaging spectrometers nor conventional cameras can pursue. This study also raises points for future work concerning proper inclusion of instrument uncertainty in comparisons of results between instruments and handling of systematic uncertainties from analyses based on a single area.

Hair transparency decoding in Asia: From stylists' perception to in vitro measurement.

BACKGROUND: The concept of hair transparency has been claimed widely in the Japan (and now it is spreading to Asian) hair color market. Despite the general use of this concept, to date, there is no clear and objective description to accurately explain what it is. In this work, we have decoded and gave clarity to the concept of hair transparency via a technical model (validated for both Japan and China markets) composed of measurable parameters of hair property using a single device. METHODOLOGY AND RESULTS: A comprehensive study composed of various tests was used, starting with a qualitative identification of key parameters via in-depth workshop discussions with over 40 Japanese stylists and a panel of 12 consumers. These identified parameters (luminosity, color visibility, and Shine) were then translated into technically measurable parameters of the hair fiber (Diffused light intensity, ratio of RGB channel intensities of Diffused light, and luster) via a single instrument-Hair SAMBA (a dual-polarized imaging system). Afterward, 10 carefully selected anchor shades were used as visual stimuli in an online pairwise comparison (PC) study with 100 Japanese stylists to generate quantitative transparency perception data of the swatches. Technical parameters of these swatches were measured by SAMBA and consolidated with the PC output, for the creation and validation of the mathematical model. After, with another PC study (N = 100) in China, with seven shades from Japan study and 6 additional Chinese market shades, the applicability of the model in China market was validated. CONCLUSION: We have clarified and quantified the concept of hair transparency through a consumer centric approach and with objective data. Our findings will enable the development of optimum transparent shades which better suits consumer needs. Lastly, we would like to highlight the beauty of digitalization in the study: The digital evaluation pathways chosen allowed us to collect quantitative consumer data from two countries for the creation of a robust model under the impact of COVID-19 and would definitely be the way to go for our future consumer evaluation studies.

A 5-hour follow-up of the impact on ageing facial signs of some foundations in Japanese women through automatically analysed selfie pictures.

OBJECTIVE: To explore the possibility of an automatic grading algorithm to detect and quantify, from selfie pictures, the subtle changes of facial signs brought by the application of a foundation. MATERIAL AND METHODS: A total of 270 Japanese differently aged women (30-54y) living in four different Japanese cities took selfies before, immediately and 5 h after having applied their own foundation, with their own routine. RESULTS: The analysis of 810 selfie pictures revealed (3 times × 270 women) that, prior to applications, all women presented a low grade of facial ageing. In most cases, the severities of less marked facial signs were detected and quantified, found affected by routine at different extents in all age-classes, but more intensely in the older age-class (45-54y) despite their more pronounced signs in bare skin status. In contrast, periorbital wrinkles were detected as more severe in all age-classes at both timing, that is, immediately and 5 h post-application as well as Nasolabial folds 5 h post-application. The amplitude of these positive or negative changes, although found of low amplitude, as decimals of the initial grades, was significantly detected. CONCLUSION: This automatic system appears apt at grading subtle changes in facial ageing signs brought by a foundation and could be a valuable help to the consumers of make-up products, in refining their individual procedure to obtain a more personalized desired facial appearance.

OBJECTIF: Explorer la possibilité pour un algorithme de scorage automatique des signes faciaux de détecter et quantifier sur la base de photographies 'selfies', les changements subtils apportés par l'application et la tenue de fonds de teint. MATÉRIEL ET MÉTHODES: 270 femmes japonaises âgées de 30 à 54 ans et vivant dans 4 villes différentes ont pris des selfies sur la base de leur smartphone avant, immédiatement et 5 heures après avoir appliqué leurs routines cosmétiques incluant leur propre fond de teint. RÉSULTATS: L'analyse des 810 selfies (3 temps×270 femmes) a révélé que, avant application, la plupart des femmes présentent des grades faibles de vieillissement facial. Dans la plupart des cas, les sévérités des signes les moins marqués, détectés et quantifiés, a été trouvée affectée à différents niveaux dans toutes les classes d'âge, mais plus intensément pour les volontaires les plus âgées (45 à 54 ans) en dépit de leurs valeurs plus élevées sur peau nue. A contrario, les rides péri-orbitales ont été mesurées comme plus sévères dans toutes les classes d'âge à tous les temps, c'est-à-dire immédiatement et 5 heures apprès application du fond de teint tandis que le sillon nasogénien a été observé comme plus sévère 5 heures après application. L'amplitude de ces changements positifs ou négatifs, bien que faible avec des valeurs décimales des grades initiaux, a été significativement détectée. CONCLUSIONS: Le système de scorage automatique apparaît capable d'évaluer des changements subtils dans les signes de vieillissement faciaux apportés par l'application de fonds de teint et se révèle une aide intéressante aux consommateurs de produits de maquillage pour affiner leurs routines individuelles afin d'obtenir des résultats plus personnalisés sur l'apparence désirée.

A preliminary study to understand the effects of mask on tinted face cosmetics.

BACKGROUND: The recent COVID-19 pandemic has generalized the use of face mask in public area, and it is now common to wear it for long hours. But face mask interfere with cosmetics, and key concerns for tinted products are staining of the mask and degradation on face. Consumers have modified beauty routine by a decrease of makeup, but are now expecting new products adapted to face mask. Little is known about the mechanisms that affect most the makeup under the face mask, so that further studies are needed to develop adequate evaluation methods and products. In this study, the color transfer on mask and makeup degradation on face are assessed through a mixed approach of consumer and instrumental evaluation. MATERIALS AND METHODS: Two tinted face products (A and B) were applied by half face on 11 Japanese women, who conducted real-life activities with a face mask during 4 hours. Panelists evaluated the stain of their face mask by visual assessment, while the makeup degradation on face was evaluated by color measurement by instrumental method. RESULTS: No difference was observed between the two products for lasting on face, but consumer evaluation showed a better resistance of product A for color transfer on mask. CONCLUSION: The mix of instrumental and consumer evaluation is a promising way to evaluate the makeup degradation on face and color transfer on mask, which are two key factors to develop mask resistant makeup products.

Japanese experiment of a complete and objective automatic grading system of facial signs from selfie pictures: Validation with dermatologists and characterization of changes due to age and sun exposures.

OBJECTIVE: To evaluate the capacity of the automatic detection system to accurately grade, from smartphones' selfie pictures, the severity of ten facial signs in Japanese women and their changes due to age and sun exposures. METHODS: A three-step approach was conducted, based on self-taken selfie images. At first, to check on 310 Japanese women (18-69 years) enrolled in the northerner Hokkaido area (latitude 43.2°N), how, on ten facial signs, the A.I-based automatic grading system may correlate with dermatological assessments, taken as reference. Second, to assess and compare age changes in 310 Japanese and 112 Korean women. Third, as these Japanese panelists were recruited according to their usual behavior toward sun exposure, that is, non-sun-phobic (NSP, N = 114) and sun-phobic (SP, N = 196), and through their regular and early use of a photo-protective product, to characterize the facial photo-damages. RESULTS: (a) On the ten facial signs, detected automatically, nine were found significantly (P < .0001) highly correlated with the evaluations made by three Japanese dermatologists (Wrinkles: r = .75; Sagging: r = .80; Pigmentation: r = .75). (b) The automatic scores showed significant changes with age, by decade, of Wrinkles/Texture, Pigmentation, and Ptosis/Sagging (P < .05). (c) After 45 years, a significantly increased severity of Wrinkles/Texture and Pigmentation was observed in NSP vs. SP women (P < .05). A trend of an increased Ptosis/Sagging (P = .09) was observed. CONCLUSION: This work illustrates, for the first time through investigations conducted at home, some impacts of aging and sun exposures on facial signs of Japanese women. Results significantly confirm the importance of sun avoidance coupled with photo-protective measures. In epidemiological studies, the AI-based system offers a fast, affordable, and confidential approach in detection and quantification of facial signs and their dependence with ages, environments and lifestyles.

VHH characterization.Recombinant VHHs: Production, characterization and affinity.

Among the biological approaches to therapeutics, are the cells, such as CAR-T cells engineered or not, the antibodies armed or not, and the smaller protein scaffolds that can be modified to render them specific of other proteins, à la façon of antibodies. For several years, we explored ways to substitute antibodies by nanobodies (also known as VHHs), the smallest recognizing part of camelids' heavy-chain antibodies: production of those small proteins in host microorganisms, minute analyses, characterization, and qualification of their affinity towards designed targets. Here, we present three standard VHHs described in the literature: anti-albumin, anti-EGF receptor and anti-HER2, a typical cancer cell surface -associated protein. Because they differ slightly in global structure, they are good models to assess our body of analytical methodologies. The VHHs were expressed in several bacteria strains in order to identify and overcome the bottlenecks to obtain homogeneous preparations of this protein. A large panel of biophysical tools, ranging from spectroscopy to mass spectrometry, was here combined to assess VHH structural features and the impact of the disulfide bond. The routes are now ready to move to more complex VHHs raised against specific targets in numerous areas including oncology.

Trap Model for Clogging and Unclogging in Granular Hopper Flows.

Granular flows through narrow outlets may be interrupted by the formation of arches or vaults that clog the exit. These clogs may be destroyed by vibrations. A feature which remains elusive is the broad distribution p(τ) of clog lifetimes τ measured under constant vibrations. Here, we propose a simple model for arch breaking, in which the vibrations are formally equivalent to thermal fluctuations in a Langevin equation; the rupture of an arch corresponds to the escape from an energy trap. We infer the distribution of trap depths from experiments made in two-dimensional hoppers. Using this distribution, we show that the model captures the empirically observed heavy tails in p(τ). These heavy tails flatten at large τ, consistently with experimental observations under weak vibrations. But, here, we find that this flattening is systematic, which casts doubt on the ability of gentle vibrations to restore a finite outflow forever. The trap model also replicates recent results on the effect of increasing gravity on the statistics of clog formation in a static silo. Therefore, the proposed framework points to a common physical underpinning to the processes of clogging and unclogging, despite their different statistics.

Correction: Soft modes and strain redistribution in continuous models of amorphous plasticity: the Eshelby paradigm, and beyond?

Correction for 'Soft modes and strain redistribution in continuous models of amorphous plasticity: the Eshelby paradigm, and beyond?' by Xiangyu Cao et al., Soft Matter, 2018, DOI: 10.1039/c7sm02510f.

Soft modes and strain redistribution in continuous models of amorphous plasticity: the Eshelby paradigm, and beyond?

The deformation of disordered solids relies on swift and localised rearrangements of particles. The inspection of soft vibrational modes can help predict the locations of these rearrangements, while the strain that they actually redistribute mediates collective effects. Here, we study soft modes and strain redistribution in a two-dimensional continuous mesoscopic model based on a Ginzburg-Landau free energy for perfect solids, supplemented with a plastic disorder potential that accounts for shear softening and rearrangements. Regardless of the disorder strength, our numerical simulations show soft modes that are always sharply peaked at the softest point of the material (unlike what happens for the depinning of an elastic interface). Contrary to widespread views, the deformation halo around this peak does not always have a quadrupolar (Eshelby-like) shape. Instead, for finite and narrowly-distributed disorder, it looks like a fracture, with a strain field that concentrates along some easy directions. These findings are rationalised with analytical calculations in the case where the plastic disorder is confined to a point-like 'impurity'. In this case, we unveil a continuous family of elastic propagators, which are identical for the soft modes and for the equilibrium configurations. This family interpolates between the standard quadrupolar propagator and the fracture-like one as the anisotropy of the elastic medium is increased. Therefore, we expect to see a fracture-like propagator when extended regions on the brink of failure have already softened along the shear direction and thus rendered the material anisotropic, but not failed yet. We speculate that this might be the case in carefully aged glasses just before macroscopic failure.

Effects of Inertia on the Steady-Shear Rheology of Disordered Solids.

We study the finite-shear-rate rheology of disordered solids by means of molecular dynamics simulations in two dimensions. By systematically varying the damping strength ζ in the low-temperature limit, we identify two well-defined flow regimes, separated by a thin (temperature-dependent) crossover region. In the overdamped regime, the athermal rheology is governed by the competition between elastic forces and viscous forces, whose ratio gives the Weissenberg number Wi∝ζγ[over ˙]; the macroscopic stress Σ follows the frequently encountered Herschel-Bulkley law Σ=Σ_{0}+ksqrt[Wi], with yield stress Σ_{0}>0. In the underdamped (inertial) regime, dramatic changes in the rheology are observed for low damping: the flow curve becomes nonmonotonic. This change is not caused by longer-lived correlations in the particle dynamics at lower damping; instead, for weak dissipation, the sample heats up considerably due to, and in proportion to, the driving. By thermostating more or less underdamped systems, we are able to link quantitatively the rheology to the kinetic temperature and the shear rate, rescaled with Einstein's vibration frequency.

A Microfluidic Diffusion Cell for Fast and Easy Percutaneous Absorption Assays.

PURPOSE: Percutaneous absorption assays of molecules for pharmaceutical and cosmetology purposes are important to determine the bioavailability of new compounds, once topically applied. The current method of choice is to measure the rate of diffusion through excised human skin using a diffusion cell. This method however entails significant drawbacks such as scarce availability and poor reproducibility of the sample, low sampling rate, and tedious assay setup. METHODS: The objective of the present work is to propose an alternative method that overcomes these issues by integrating an experimental model of the skin (artificial stratum corneum) and online optical sensors into a microfluidic device. RESULTS: The measurement of the diffusion profile followed by the calculation of the permeability coefficients and time lag were performed on seven different molecules and obtained data positively fit with those available from literature on human skin penetration. The coating of the lipid mixture to generate the artificial stratum corneum also proved robust and reproducible. The results show that the proposed device is able to give fast, real-time, accurate, and reproducible data in a user-friendly manner, and can be produced at a large scale. CONCLUSION: These assets should help both the cosmetics and pharmaceutics fields where the skin is the target or a pathway of a formulated compound, by allowing more candidate molecules or formulations to be assessed during the various stages of their development.

Universal and non-universal features in coarse-grained models of flow in disordered solids.

We study the two-dimensional (2D) shear flow of amorphous solids within variants of an elastoplastic model, paying particular attention to spatial correlations and time fluctuations of, e.g., local stresses. The model is based on the local alternation between an elastic regime and plastic events during which the local stress is redistributed. The importance of a fully tensorial description of the stress and of the inclusion of (coarse-grained) convection in the model is investigated; scalar and tensorial models yield similar results, while convection enhances fluctuations and breaks the spurious symmetry between the flow and velocity gradient directions, for instance when shear localisation is observed. Besides, correlation lengths measured with diverse protocols are discussed. One class of such correlation lengths simply scale with the spacing between homogeneously distributed, simultaneous plastic events. This leads to a scaling of the correlation length with the shear rate as γ̇(-1/2) in 2D in the athermal regime, regardless of the details of the model. The radius of the cooperative disk, defined as the near-field region in which plastic events induce a stress redistribution that is not amenable to a mean-field treatment, notably follows this scaling. On the other hand, the cooperative volume measured from the four-point stress susceptibility and its dependence on the system size and the shear rate are model-dependent.

Spatiotemporal correlations between plastic events in the shear flow of athermal amorphous solids.

The slow flow of amorphous solids exhibits striking heterogeneities: swift localised particle rearrangements take place in the midst of a more or less homogeneously deforming medium. Recently, experimental as well as numerical work has revealed spatial correlations between these flow heterogeneities. Here, we use molecular dynamics (MD) simulations to characterise the rearrangements and systematically probe their correlations both in time and in space. In particular, these correlations display a four-fold azimuthal symmetry characteristic of shear stress redistribution in an elastic medium and we unambiguously detect their increase in range with time. With increasing shear rate, correlations become shorter-ranged. In addition, we study a coarse-grained model motivated by the observed flow characteristics and challenge its predictions directly with the MD simulations. While the model captures both macroscopic and local properties rather satisfactorily, the agreement with respect to the spatiotemporal correlations is at most qualitative. The discrepancies provide important insight into relevant physics that is missing in all related coarse-grained models that have been developed for the flow of amorphous materials so far, namely the finite shear wave velocity and the impact of elastic heterogeneities on stress redistribution.

Dimensionless numbers reveal distinct regimes in the structure and dynamics of pedestrian crowds.

In fluid mechanics, dimensionless numbers like the Reynolds number help classify flows. We argue that such a classification is also relevant for crowd flows by putting forward the dimensionless Intrusion and Avoidance numbers, which quantify the intrusions into the pedestrians' personal spaces and the imminency of the collisions that they face, respectively. Using an extensive dataset, we show that these numbers delineate regimes where distinct variables characterize the crowd's arrangement, namely, Euclidean distances at low Avoidance number and times-to-collision at low Intrusion number. On the basis of these findings, a perturbative expansion of the individual pedestrian dynamics is carried out around the noninteracting state, in quite general terms. Simulations confirm that this expansion performs well in its expected regime of applicability.

Enhanced detection of antigen-specific T cells by a multiplexed AIM assay.

Broadly applicable methods to identify and characterize antigen-specific CD4+ and CD8+ T cells are key to immunology research, including studies of vaccine responses and immunity to infectious diseases. We developed a multiplexed activation-induced marker (AIM) assay that presents several advantages compared to single pairs of AIMs. The simultaneous measurement of four AIMs (CD69, 4-1BB, OX40, and CD40L) creates six AIM pairs that define CD4+ T cell populations with partial and variable overlap. When combined in an AND/OR Boolean gating strategy for analysis, this approach enhances CD4+ T cell detection compared to any single AIM pair, while CD8+ T cells are dominated by CD69/4-1BB co-expression. Supervised and unsupervised clustering analyses show differential expression of the AIMs in defined T helper lineages and that multiplexing mitigates phenotypic biases. Paired and unpaired comparisons of responses to infections (HIV and cytomegalovirus [CMV]) and vaccination (severe acute respiratory syndrome coronavirus 2 [SARS-CoV-2]) validate the robustness and versatility of the method.

Spatial cooperativity in microchannel flows of soft jammed materials: a mesoscopic approach.

The flow of amorphous solids results from a combination of elastic deformation and local structural rearrangements, which induce nonlocal elastic deformations. These elements are incorporated into a mechanically consistent mesoscopic model of interacting elastoplastic blocks. We investigate the specific case of channel flow with numerical simulations, paying particular attention to situations of strong confinement. We find that the simple picture of plastic events embedded in an elastic matrix successfully accounts for manifestations of spatial cooperativity. Shear rate fluctuations are observed in seemingly quiescent regions, and the velocity profiles in confined flows at high applied pressure deviate from those expected in the absence of nonlocal effects, in agreement with experimental data. However, we suggest a different physical origin for the large deviations observed when walls have rough surfaces, associated with "bumps" of the particles against the asperities of the walls.

Study of the scale formation mechanism on gold modified with an alkanethiol monolayer.

Scaling is a problem in many industrial processes. To control and minimize it, it is important to understand the dynamics of the scale formation. In this paper, the scale formation was examined on two kinds of gold surfaces. One was a pure metallic gold surface, and the other was a gold surface modified with an alkanethiol self-assembled monolayer. A series of surface characterization experiments were performed to ensure a good understanding of the gold-thiol bond stability in a caustic solution.

From Microscopic Droplets to Macroscopic Crowds: Crossing the Scales in Models of Short-Range Respiratory Disease Transmission, with Application to COVID-19.

Short-range exposure to airborne virus-laden respiratory droplets is an effective transmission route of respiratory diseases, as exemplified by Coronavirus Disease 2019 (COVID-19). In order to assess the risks associated with this pathway in daily-life settings involving tens to hundreds of individuals, the chasm needs to be bridged between fluid dynamical simulations and population-scale epidemiological models. This is achieved by simulating droplet trajectories at the microscale in numerous ambient flows, coarse-graining their results into spatio-temporal maps of viral concentration around the emitter, and coupling these maps to field-data about pedestrian crowds in different scenarios (streets, train stations, markets, queues, and street cafés). At the individual scale, the results highlight the paramount importance of the velocity of the ambient air flow relative to the emitter's motion. This aerodynamic effect, which disperses infectious aerosols, prevails over all other environmental variables. At the crowd's scale, the method yields a ranking of the scenarios by the risks of new infections, dominated by the street cafés and then the outdoor market. While the effect of light winds on the qualitative ranking is fairly marginal, even the most modest air flows dramatically lower the quantitative rates of new infections.