Active wetting of epithelial tissues

Development, regeneration and cancer involve drastic transitions in tissue morphology. In analogy with the behavior of inert fluids, some of these transitions have been interpreted as wetting transitions. The validity and scope of this analogy are unclear, however, because the active cellular forces that drive tissue wetting have been neither measured nor theoretically accounted for. Here we show that the transition between 2D epithelial monolayers and 3D spheroidal aggregates can be understood as an active wetting transition whose physics differs fundamentally from that of passive wetting phenomena. By combining an active polar fluid model with measurements of physical forces as a function of tissue size, contractility, cell-cell and cell-substrate adhesion, and substrate stiffness, we show that the wetting transition results from the competition between traction forces and contractile intercellular stresses. This competition defines a new intrinsic lengthscale that gives rise to a critical size for the wetting transition in tissues, a striking feature that has no counterpart in classical wetting. Finally, we show that active shape fluctuations are dynamically amplified during tissue dewetting. Overall, we conclude that tissue spreading constitutes a prominent example of active wetting --- a novel physical scenario that may explain morphological transitions during tissue morphogenesis and tumor progression

Interactivity Improves Usability of Geographic Maps for Visually Impaired People

International audienceTactile relief maps are used by visually impaired people to acquire mental representation of space, but they retain important limitations (limited amount of information, braille text, etc.). Interactive maps may overcome these limitations. However, usability of these two types of maps had never been compared. It is then unknown whether interactive maps are equivalent or even better solutions than traditional raised-line maps. This study presents a comparison of usability of a classical raised-line map vs. an interactive map composed by a multi-touch screen, a raised-line overlay and audio output. Both maps were tested by 24 blind participants. We measured usability as efficiency, effectiveness and satisfaction. Our results show that replacing braille with simple audio-tactile interaction significantly improved efficiency and user satisfaction. Effectiveness was not related to the map type but depended on users' characteristics as well as the category of assessed spatial knowledge. Long-term evaluation of acquired spatial information revealed that maps, whether interactive or not, are useful to build robust survey-type mental representations in blind users. Altogether, these results are encouraging as they show that interactive maps are a good solution for improving map exploration and cognitive mapping in visually impaired people

Damage function for historic paper. Part II: Wear and tear

Background: As a result of use of library and archival documents, defined as reading with handling in the context of general access, mechanical degradation (wear and tear) accumulates. In contrast to chemical degradation of paper, the accumulation of wear and tear is less well studied. Previous work explored the threshold of mechanical degradation at which a paper document is no longer considered to be fit for the purpose of use by a reader, while in this paper we explore the rate of accumulation of such damage in the context of object handling. Results: The degree of polymerisation (DP) of historic paper of European origin from mid-19th–mid-20th Century was shown to affect the rate of accumulation of wear and tear. While at DP > 800, this accumulation no longer depends on the number of handlings (the process is random), a wear-out function could be developed for documents with DP between 300 and 800. For objects with DP < 300, one large missing piece (i.e. such that contains text) developed on average with each instance of handling, which is why we propose this DP value as a threshold value for safe handling. Conclusions: The developed model of accumulation of large missing pieces per number of handlings of a document depending on DP, enables us to calculate the time required for an object to become unfit for use by readers in the context of general access. In the context of the average frequency of document use at The UK National Archives (Kew), this period is 60 years for the category of papers with DP 300, and 450 years for papers with DP 500. At higher DP values, this period of time increases beyond the long-term planning horizon of 500 years, leading to the conclusion that for such papers, accumulation of wear and tear is not a significant collection management concern

“Millennials”: influencia del entorno y desarrollo de sus habilidades en un mercado laboral en plena evolución.

Grado en Administración y Dirección de Empresas con Mención en InternacionalLa Generación Y debe evolucionar en un contexto geopolítico y socioeconómico particular, puesto que varias crisis mundiales han puesto en evidencia los límites del Capitalismo afectando social, económica y profesionalmente a la sociedad. Gracias a Internet, a la globalización y a la educación de sus padres, los “Millennials” han conseguido desarrollar habilidades vitales para triunfar en el mercado laboral y orientarlo hacía un mundo más responsable. Competencias interculturales, inteligencia social, colaboración virtual, resiliencia, pensamiento computacional, trandisciplinaridad, “design-thinking”, son tanto más importantes cuando las empresas deben reinventar sus modelos de negocio poniendo al humano en el centro de sus preocupaciones. Si los “Millennials” no son la generación del cambio, el mundo se dirige hacía una crisis multifacética (ambiental, social, sanitaria y económica). El aumento de la consciencia global sobre los problemas estructurales de nuestra sociedad provoca cambios en el interior de las empresas para sobrevivir en un mundo marcado por un antes y un después.Generation Y must evolve in a particular geopolitical and socio-economic context. Several world crises have highlighted the limits of Capitalism affecting society socially, economically and professionally. Thanks to the Internet, to globalization and to the education of their parents, the Millennials have managed to develop vital skills to succeed in the labor market and to orient it towards a more responsible world. Intercultural skills, social intelligence, virtual collaboration, resilience, computer thinking, trandisciplinarity, design-thinking, are all the more important when companies have to reinvent their business models by putting the human being at the center of their concerns. If the Millennials are not the generation of change, the world is heading towards a multifaceted crisis (environmental, social, health and economic). The increasing global awareness of the structural problems of our society is causing changes within companies to survive in a world marked by a before and after

Osteoclast-mediated resorption primes the skeleton for successful integration during axolotl limb regeneration

Early events during axolotl limb regeneration include an immune response and the formation of a wound epithelium. These events are linked to a clearance of damaged tissue prior to blastema formation and regeneration of the missing structures. Here, we report the resorption of calcified skeletal tissue as an active, cell-driven, and highly regulated event. This process, carried out by osteoclasts, is essential for a successful integration of the newly formed skeleton. Indeed, the extent of resorption is directly correlated with the integration efficiency, and treatment with zoledronic acid resulted in osteoclast function inhibition and failed tissue integration. Moreover, we identified the wound epithelium as a regulator of skeletal resorption, likely releasing signals involved in recruitment/differentiation of osteoclasts. Finally, we reported a correlation between resorption and blastema formation, particularly, a coordination of resorption with cartilage condensation. In sum, our results identify resorption as a major event upon amputation, playing a critical role in the overall process of skeletal regeneration

Comparative Analysis of Saturated and Under-saturated oil Viscosity Correlations using Statistical Tools, Niger Delta Case Study

Crude oil viscosity is one of the most important fluid properties that affects fluid flow behavior; either in pipeline hydraulics or in the porous media (reservoir). Viscosity is a vital physical property that plays a major role in the petroleum industry, the production processing and transportation of oil due to influence on the flow through porous rock, oil wells, multiphase flow through tubing and piping system. Therefore, the need for accurate determination of viscosity for oil and gas applications cannot be overemphasized. Numerous empirical correlations exist in literature for predicting crude oil viscosity but their accuracy is limited based on range of conditions of application, composition of the crude used in developing the correlation, specific range of data and experimental conditions. In the present work, experimental data of oil viscosity from different samples of Nigerian oil reservoirs were statistically compared with correlation predicted viscosity using the most common viscosity empirical correlations. Validity and accuracy of these empirical models has been confirmed for both saturated and under-saturated Niger Delta oil samples. It was observed that for undersaturated oil viscosities, Elshawarky & Alikhan’s correlation gave a better prediction based on the Absolute average percentage error and standard deviation while for the case of saturated oil viscosities Chew and Connally proved to be the closest to the experimental results

Author Correction: Formation of helical membrane tubes around microtubules by single-headed kinesin KIF1A

Correction to: Nature Communications 10.1038/ncomms9025, published online 13 August 2018. This Article contains an error in the first sentence of the ‘KIF1A purification and labelling’ section of the Methods, which incorrectly reads ‘A construct containing the first 382 residues of KIF1A with a His-tag and a Cys residue in the N-terminal, was kindly provided by N. Hirokawa (University of Tokyo, Japan; see ref. 13).’ This should say ‘C-terminus’ instead of ‘N-terminus’. The error has not been fixed in the PDF or HTML versions of the Article

Formation of helical membrane tubes around microtubules by single-headed kinesin KIF1A

The kinesin-3 motor KIF1A is in charge of vesicular transport in neuronal axons. Its single-headed form is known to be very inefficient due to the presence of a diffusive state in the mechanochemical cycle. However, recent theoretical studies have suggested that these motors could largely enhance force generation by working in teams. Here we test this prediction by challenging single-headed KIF1A to extract membrane tubes from giant vesicles along microtubule filaments in a minimal in vitro system. Remarkably, not only KIF1A motors are able to extract tubes but they feature a novel phenomenon: tubes are wound around microtubules forming tubular helices. This finding reveals an unforeseen combination of cooperative force generation and self-organized manoeuvreing capability, suggesting that the diffusive state may be a key ingredient for collective motor performance under demanding traffic conditions. Hence, we conclude that KIF1A is a genuinely cooperative motor, possibly explaining its specificity to axonal trafficking

Steroids and fatty acid esters from Cyperus sexangularis leaf and their antioxidant, anti-inflammatory and anti-elastase properties

SAMPLE AVAILABILITY : Sample of the compounds 1–6 are available from author G.M.M.SUPPLEMENTARY MATERIALS : The observed spectra of compounds 1–6 are available as Figures S1–S6.Cyperus sexangularis (CS) is a plant in the sedges family (Cyperaceae) that grows abundantly in swampy areas. The leaf sheath of plants in the Cyperus genus are mostly used domestically for mat making, while they are implicated for skin treatment in traditional medicine. The plant was investigated for its phytochemical contents as well as its antioxidant, anti-inflammatory and anti-elastase properties. The n-hexane and dichloromethane leaf extracts were chromatographed on a silica gel column to afford compounds 1–6. The compounds were characterized by nuclear magnetic resonance spectroscopy and mass spectrometry. The inhibitory effect of each compound against 2,2-diphenyl-1-picrylhydrazyl (DPPH), nitric oxide (NO) and ferric ion radicals were determined by standard in vitro antioxidant methods. The in vitro anti-inflammatory response was measured using egg albumin denaturation (EAD) assay, while the anti-elastase activity of each compound in human keratinocyte (HaCaT) cells was also monitored. The compounds were characterized as three steroidal derivatives, stigmasterol (1), 17-(1-methyl-allyl)-hexadecahydro-cyclopenta[a]phenanthrene (2) and -sitosterol (3), dodecanoic acid (4) and two fatty acid esters, ethyl nonadecanoate (5) and ethyl stearate (6). Stigmasterol (1) exhibited the best biological properties, with IC50 of 38.18 2.30 g/mL against DPPH, 68.56 4.03 g/mL against NO and 303.58 10.33 AAE/mg against Fe3+. At 6.25 g/mL, stigmasterol inhibited EAD by 50%. This activity was lower when compared to diclofenac (standard), which demonstrated 75% inhibition of the protein at the same concentration. Compounds 1, 3, 4 and 5 showed comparable anti-elastase activity with an IC50 50 g/mL, whereas the activity of ursolic acid (standard) was double fold with an IC50 of 24.80 2.60 g/mL when compared to each of the compounds. In conclusion, this study has identified three steroids (1–3), one fatty acid (4), and two fatty acid esters (5 and 6) in C. sexangularis leaf for the first time. The compounds showed considerable antioxidant, anti-inflammatory and anti-elastase properties. Thus, the findings may serve as a justification for the folkloric use of the plant as a local skin ingredient. It may also serve to validate the biological role of steroids and fatty acid compounds in cosmeceutical formulations.Water Research Commission (WRC), South Africa.https://www.mdpi.com/journal/moleculesam2024Plant Production and Soil ScienceSDG-15:Life on lan