L-systems in Geometric Modeling

We show that parametric context-sensitive L-systems with affine geometry interpretation provide a succinct description of some of the most fundamental algorithms of geometric modeling of curves. Examples include the Lane-Riesenfeld algorithm for generating B-splines, the de Casteljau algorithm for generating Bezier curves, and their extensions to rational curves. Our results generalize the previously reported geometric-modeling applications of L-systems, which were limited to subdivision curves.Comment: In Proceedings DCFS 2010, arXiv:1008.127

The role of metal metabolism and heat shock protein genes on replicative lifespan of the budding yeast, Saccharomyces cerevisiae

A variety of genes that influence aging have been identified in a broad selection of organisms including Saccharomyces cerevisiae (yeast), Caenorhabditis elegans (worms), Drosophila (fruit flies), Macaca Mulatta (rhesus monkeys), and even Homo sapiens. Many of these genes, such the TOR’s, FOXO’s, AKT’s, and S6K’s are conserved across different organisms. All of these genes participate in nutrient sensing networks. Other conserved genetic networks may similarly affect lifespan. In this thesis, I explored genes from an iron metabolism family and a heat shock protein (HSP) gene family that have been identified, but not confirmed, to influence lifespan. Yeast is a reliable model for mitotic (replicative) aging. Using yeast, I tested whether the FET-genes, encoding a family of iron importer-related genes, are required for mitotic lifespan. I also tested whether another family of genes, the yeast SSA HSP70- encoding genes, related to mammalian HSP70s, influence mitotic aging. I primarily used the replicative lifespan (RLS) assay, in which I measured the mitotic capacity of multiple FET and SSA yeast mutants. I hypothesize that aging occurs when iron transport is misregulated, which may lead to an over-reliance on HSPs for lifespan maintenance. The results presented in this thesis support the hypothesis. First, FET3 was primarily involved in lifespan maintenance under normal conditions (2% glucose), while FET5 was primarily involved in the cellular lifespan extension characteristic of caloric restriction (0.01% glucose), a known anti-aging intervention. In addition, SSA2 appeared to facilitate lifespan maintenance in the absence of FET4, while the presence of SSA1 limited lifespan length. That the aging genes identified in this study are involved in iron metabolism or heat stress suggests that protein aggregation or reactive oxidative species production are common processes through which these genes interact

A structural method for assessing self-similarity in plants

International audienceThe important rôle of architecture in the understanding of plants [8, 12, 23] generates a need for investigational tools. Generic tools have already been developed to vizualize plant architecture in three dimensions [20], to model the development of plant structure [6, 20], to measure plant architecture [24] , and to analyze and quantify relations between plant components [11]

Toward a quantification of self-similarity in plants

International audienceSelf-similarity of plants has attracted the attention of biologists for at least 50 years, yet its formal treatment is rare, and no measure for quantifying the degree of self-similarity currently exists. We propose a formal definition and measures of self-similarity, tailored to branching plant structures. To evaluate self-similarity, we make use of an algorithm for computing topological distances between branching systems, developed in computer science. The formalism is illustrated using theoretical branching systems, and applied to analyze self-similarity in two sample plant structures: inflorescences of Syringa vulgaris (lilac) and shoots of Oryza sativa (rice

Representation of fractal curves by means of L systems

This is the author's version of the work. It is posted here for your personal use. Not for redistribution. The definitive Version of Record was published in APL Quote Quad, http://dx.doi.org/10.1145/253417.253348Proceedings of the conference on Designing the future, APL'96; published as an articleFractals can be represented by means of L-systems (Development Grammars), together with a graphic interpretation. Two families of graphic interpretations have been used: turtle graphics and vector graphics. This paper describes an APL2/PC system able to draw fractals represented by L-systems, with both graphic interpretations. A theorem has been proved on the equivalence conditions for both interpretations. Another point shown is the fact that supposed deficiencies in L-systems that have prompted proposals of extensions are really deficiencies in the graphic translation scheme

L-Py: An L-System Simulation Framework for Modeling Plant Architecture Development Based on a Dynamic Language

The study of plant development requires increasingly powerful modeling tools to help understand and simulate the growth and functioning of plants. In the last decade, the formalism of L-systems has emerged as a major paradigm for modeling plant development. Previous implementations of this formalism were made based on static languages, i.e., languages that require explicit definition of variable types before using them. These languages are often efficient but involve quite a lot of syntactic overhead, thus restricting the flexibility of use for modelers. In this work, we present an adaptation of L-systems to the Python language, a popular and powerful open-license dynamic language. We show that the use of dynamic language properties makes it possible to enhance the development of plant growth models: (i) by keeping a simple syntax while allowing for high-level programming constructs, (ii) by making code execution easy and avoiding compilation overhead, (iii) by allowing a high-level of model reusability and the building of complex modular models, and (iv) by providing powerful solutions to integrate MTG data-structures (that are a common way to represent plants at several scales) into L-systems and thus enabling to use a wide spectrum of computer tools based on MTGs developed for plant architecture. We then illustrate the use of L-Py in real applications to build complex models or to teach plant modeling in the classroom