Colloquium: Mechanical formalisms for tissue dynamics

The understanding of morphogenesis in living organisms has been renewed by tremendous progressin experimental techniques that provide access to cell-scale, quantitative information both on theshapes of cells within tissues and on the genes being expressed. This information suggests that ourunderstanding of the respective contributions of gene expression and mechanics, and of their crucialentanglement, will soon leap forward. Biomechanics increasingly benefits from models, which assistthe design and interpretation of experiments, point out the main ingredients and assumptions, andultimately lead to predictions. The newly accessible local information thus calls for a reflectionon how to select suitable classes of mechanical models. We review both mechanical ingredientssuggested by the current knowledge of tissue behaviour, and modelling methods that can helpgenerate a rheological diagram or a constitutive equation. We distinguish cell scale ("intra-cell")and tissue scale ("inter-cell") contributions. We recall the mathematical framework developpedfor continuum materials and explain how to transform a constitutive equation into a set of partialdifferential equations amenable to numerical resolution. We show that when plastic behaviour isrelevant, the dissipation function formalism appears appropriate to generate constitutive equations;its variational nature facilitates numerical implementation, and we discuss adaptations needed in thecase of large deformations. The present article gathers theoretical methods that can readily enhancethe significance of the data to be extracted from recent or future high throughput biomechanicalexperiments.Comment: 33 pages, 20 figures. This version (26 Sept. 2015) contains a few corrections to the published version, all in Appendix D.2 devoted to large deformation

Fenologia de Lafoensia pacari A.St.-Hil. (Lythraceae) em Barra do Garças, Mato Grosso, Brasil Phenology of Lafoensia pacari A.St.-Hil. (Lythraceae) in Barra do Garças, Mato Grosso State, Brazil

Lafoensia pacari A.St.-Hil. é uma espécie da flora do cerrado usada na medicina popular como anti-úlcera, antifúngica, antibactericida, anti-inflamatória, febrífuga, para emagrecimento e no tratamento de pneumonia, dores de estômago e coceiras. Estudou-se a fenologia de L. pacari no cerrado do Parque Estadual da "Serra Azul", região de Barra do Garças-MT (15º 51' 58" S e 52º 15' 37" W), à 645 m de altitude, durante o período de 24 meses. Verificou-se que as fenofases são sazonais, com floração nos meses de abril a agosto, frutificação de junho a setembro, brotação no início da estação chuvosa de outubro a dezembro e queda de folhas de julho a setembro, no final da estação seca.<br>Lafoensia pacari is a species from the Brazilian cerrado used in folk medicine to control ulcers, fungal and bacterial diseases, inflammations, fevers, pneumonia, stomachaches, and itching, as well as to lose weight. L. pacari phenology was studied for 24 months in the cerrado at "Serra Azul" State Park, in the region of Barra do Garças, Mato Grosso State, Brazil (15º 51' 58" S and 52º 15' 37" W), at 645 m altitude. Phenophases are seasonal, with flowering from April to August, fruiting from June to September, sprouting from October to December, during the beginning of the rainy season, and leaf fall from July to September, at the end of the dry season