Foams in contact with solid boundaries: equilibrium conditions and conformal invariance

A liquid foam in contact with a solid surface forms a two-dimensional foam on the surface. We derive the equilibrium equations for this 2D foam when the solid surface is curved and smooth, generalising the standard case of flat Hele Shaw cells. The equilibrium conditions at the vertices in 2D, at the edges in 3D, are invariant by conformal transformations. Regarding the films, conformal invariance only holds with restrictions, which we explicit for 3D and flat 2D foams. Considering foams confined in thin interstices between two non parallel plates, normal incidence and Laplace's law lead to an approximate equation relating the plate profile to the conformal map. Solutions are given for the logarithm and power laws in the case of constant pressure. The paper concludes on a comparison with available experimental data.Comment: 10 pages, 7 figure

Topological correlations and asymptotic freedom in cellular aggregates

In random cellular systems, both observation and maximum entropy inference give a specific form to the topological pair correlation: it is bi-affine in the cells number of edges with coefficients depending on the distance between the two cells of the pair. Assuming this form for the pair correlations, we make explicit the conditions of statistical independence at large distance. When, on average, the defects do not contribute, the layer population and the enclosed topological charge both increase polynomially with distance. In dimension 2, the exponent of the leading terms depend on sum rules satisfied, or not, by the maximum entropy coefficients.Comment: Available online at http://www.sciencedirect.co

Stability of the hard-sphere icosahedral quasilattice

The stability of the hard-sphere icosahedral quasilattice is analyzed using the differential formulation of the generalized effective liquid approximation. We find that the icosahedral quasilattice is metastable with respect to the hard-sphere crystal structures. Our results agree with recent findings by McCarley and Ashcroft [Phys. Rev. B {\bf 49}, 15600 (1994)] carried out using the modified weighted density approximation.Comment: 15 pages, 2 figures available from authors upon request, (revtex), submitted to Phys. Rev.

Decorated vertices with 3-edged cells in 2D foams: exact solutions and properties

The energy, area and excess energy of a decorated vertex in a 2D foam are calculated. The general shape of the vertex and its decoration are described analytically by a reference pattern mapped by a parametric Moebius transformation. A single parameter of control allows to describe, in a common framework, different types of decorations, by liquid triangles or 3-sided bubbles, and other non-conventional cells. A solution is proposed to explain the stability threshold in the flower problem.Comment: 13 pages, 17 figure

Phytochemicals as antibiotic alternatives to promote growth and enhance host health

There are heightened concerns globally on emerging drug-resistant superbugs and the lack of new antibiotics for treating human and animal diseases. For the agricultural industry, there is an urgent need to develop strategies to replace antibiotics for food-producing animals, especially poultry and livestock. The 2nd International Symposium on Alternatives to Antibiotics was held at the World Organization for Animal Health in Paris, France, December 12-15, 2016 to discuss recent scientific developments on strategic antibiotic-free management plans, to evaluate regional differences in policies regarding the reduction of antibiotics in animal agriculture and to develop antibiotic alternatives to combat the global increase in antibiotic resistance. More than 270 participants from academia, government research institutions, regulatory agencies, and private animal industries from >25 different countries came together to discuss recent research and promising novel technologies that could provide alternatives to antibiotics for use in animal health and production; assess challenges associated with their commercialization; and devise actionable strategies to facilitate the development of alternatives to antibiotic growth promoters (AGPs) without hampering animal production. The 3-day meeting consisted of four scientific sessions including vaccines, microbial products, phytochemicals, immune-related products, and innovative drugs, chemicals and enzymes, followed by the last session on regulation and funding. Each session was followed by an expert panel discussion that included industry representatives and session speakers. The session on phytochemicals included talks describing recent research achievements, with examples of successful agricultural use of various phytochemicals as antibiotic alternatives and their mode of action in major agricultural animals (poultry, swine and ruminants). Scientists from industry and academia and government research institutes shared their experience in developing and applying potential antibiotic-alternative phytochemicals commercially to reduce AGPs and to develop a sustainable animal production system in the absence of antibiotics.Fil: Lillehoj, Hyun. United States Department of Agriculture. Agricultural Research Service; ArgentinaFil: Liu, Yanhong. University of California; Estados UnidosFil: Calsamiglia, Sergio. Universitat Autònoma de Barcelona; EspañaFil: Fernandez Miyakawa, Mariano Enrique. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Instituto Nacional de Tecnología Agropecuaria. Centro de Investigación en Ciencias Veterinarias y Agronómicas. Instituto de Patobiología; ArgentinaFil: Chi, Fang. Amlan International; Estados UnidosFil: Cravens, Ron L.. Amlan International; Estados UnidosFil: Oh, Sungtaek. United States Department of Agriculture. Agricultural Research Service; ArgentinaFil: Gay, Cyril G.. United States Department of Agriculture. Agricultural Research Service; Argentin

Understanding the Sequence-Dependence of DNA Groove Dimensions: Implications for DNA Interactions

BACKGROUND: The B-DNA major and minor groove dimensions are crucial for DNA-protein interactions. It has long been thought that the groove dimensions depend on the DNA sequence, however this relationship has remained elusive. Here, our aim is to elucidate how the DNA sequence intrinsically shapes the grooves. METHODOLOGY/PRINCIPAL FINDINGS: The present study is based on the analysis of datasets of free and protein-bound DNA crystal structures, and from a compilation of NMR (31)P chemical shifts measured on free DNA in solution on a broad range of representative sequences. The (31)P chemical shifts can be interpreted in terms of the BI↔BII backbone conformations and dynamics. The grooves width and depth of free and protein-bound DNA are found to be clearly related to the BI/BII backbone conformational states. The DNA propensity to undergo BI↔BII backbone transitions is highly sequence-dependent and can be quantified at the dinucleotide level. This dual relationship, between DNA sequence and backbone behavior on one hand, and backbone behavior and groove dimensions on the other hand, allows to decipher the link between DNA sequence and groove dimensions. It also firmly establishes that proteins take advantage of the intrinsic DNA groove properties. CONCLUSIONS/SIGNIFICANCE: The study provides a general framework explaining how the DNA sequence shapes the groove dimensions in free and protein-bound DNA, with far-reaching implications for DNA-protein indirect readout in both specific and non specific interactions

PERIODIC SURFACES IN THE DESCRIPTION OF QUASICRYSTALS

No abstract availabl

Construction of average lattices for quasiperiodic structures by the section method

The construction of an average lattice with bounded modulation, for one dimensional quasiperiodic tilings, is considered from the viewpoint of the higher dimensional space R2. The 1D quasiperiodic tilings are : a) the canonical 1D tiling obtained e.g., by the cut and project method, b) tilings generated by a circle map algorithm, for particular values of the parameters defining the model. In this last case, the construction bridges a gap between the cut and project, or section, methods, and the circle map model, and provides an alternative proof of the quasiperiodic ordering : we build suitable 2D periodic tilings yielding the quasiperiodic ones by section. This geometrical approach gives also an intuitive image of the mechanism of the disappearance of the average latice, and of the quasiperiodic ordering, for generic values of the parameters of the model. The considerations given here may serve as a basis for the construction of average lattices with bounded modulation, if they exist, of higher dimensional tilings.La construction d'un réseau moyen avec une modulation bornée pour des pavages quasipériodiques unidimensionnels est considérée du point de vue de l'espace de dimension supérieure R2. Les pavages quasipériodiques sont: a) le pavage canonique 1D obtenu par exemple par la méthode de coupe et projection, b) des pavages engendrés par un algorithme du cercle pour des valeurs particulières des paramètres définissant le modèle. Dans ce dernier cas, la construction comble un vide entre la méthode de coupe et projection ou de section et le modèle de l'algorithme du cercle et apporte une autre preuve de l'ordre quasipériodique : nous construisons des pavages 2D périodiques appropriés donnant les pavages 1D quasipériodiques par section. Cette approche géométrique donne aussi une image intuitive du mécanisme de la disparition du réseau moyen et de l'ordre quasipériodique pour des valeurs génériques des paramètres du modèle. Les considérations données ici peuvent servir de base à la construction de réseaux moyens avec modulation bornée, s'ils existent, pour des pavages de dimensions supérieures