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Thermopriming induces genome-wide differential gene expression and alternative splicing patterns, and establishes a ‘splicing memory’ that helps plants to survive subsequent and otherwise lethal heat stress., Abiotic and biotic stresses limit crop productivity. Exposure to a non-lethal stress, referred to as priming, can allow plants to survive subsequent and otherwise lethal conditions; the priming effect persists even after a prolonged stress-free period. However, the molecular mechanisms underlying priming are not fully understood. Here, we investigated the molecular basis of heat-shock memory and the role of priming in Arabidopsis thaliana. Comprehensive analysis of transcriptome-wide changes in gene expression and alternative splicing in primed and non-primed plants revealed that alternative splicing functions as a novel component of heat-shock memory. We show that priming of plants with a non-lethal heat stress results in de-repression of splicing after a second exposure to heat stress. By contrast, non-primed plants showed significant repression of splicing. These observations link ‘splicing memory’ to the ability of plants to survive subsequent and otherwise lethal heat stress. This newly discovered priming-induced splicing memory may represent a general feature of heat-stress responses in plants and other organisms as many of the key components are conserved among eukaryotes. Furthermore, this finding could facilitate the development of novel approaches to improve plant survival under extreme heat stress.

The networking of individual artificial molecular motors into collective actuation systems is a promising approach for the design of active materials working out of thermodynamic equilibrium. Here, we report the first mechanical studies on active polymer gels built by integrating light-driven rotary molecular motors as reticulation units in polymer networks. We correlate the volume ratio before and after light irradiation with the change of the elastic modulus, and we reveal the universal maximum mechanical efficiency of such gels related to their critical overlap concentration before chemical reticulation. We also show the major importance of heterogeneities in the macroscopic contraction process and we confirm that these materials can increase their internal energy by the motorized winding of their polymer chains.

InAs/AlAs$_{x}$Sb$_{1-x}$ quantum wells are investigated for their potential as hot carrier solar cells. Continuous wave power and temperature dependent photoluminescence indicate a transition in the dominant hot carrier relaxation process from conventional phonon-mediated carrier relaxation below 90 K to a regime where inhibited radiative recombination dominates the hot carrier relaxation at elevated temperatures. At temperatures below 90 K photoluminescence measurements are consistent with type-I quantum wells that exhibit hole localization associated with alloy/interface fluctuations. At elevated temperatures hole delocalization reveals the true type-II band alignment; where it is observed that inhibited radiative recombination due to the spatial separation of the charge carriers dominates hot carrier relaxation. This decoupling of phonon-mediated relaxation results in robust hot carriers at higher temperatures even at lower excitation powers. These results indicate type-II quantum wells offer potential as practical hot carrier systems., Comment: 7 pages, 6 figures, submitted to "Progress in Photovoltaics: Research and Applications"

International audience; View identi¯cation is the basal process for solid reconstruc- tion from engineering drawings. A new method is presented to label various views from a section-involved drawing and identify geometric planes through the object at which the sections are to be located. In the approach, a graph repre- sentation is developed for describing multiple relationships among various views in the 2D drawing space, and a rea- soning technique based on evidence theory is implemented to validate view relations that are used to fold views and sections in the 3D object space. This is the ¯rst automated approach which can handle multiple sections in diverse ar- rangements, especially accommodating the aligned section for the ¯rst time. Experimental results are given to show that the proposed solution makes a breakthrough in the ¯eld and builds a promising basis for further expansibility, although it is not a complete one.

International audience; This paper proposes a geometric iteration algorithm for computing point projection and inversion on planar parametriccurves based on local biarc approximation. The iteration begins with initial estimation of the projection of theprescribed test point. For each iteration, we construct a biarc that locally approximates a segment on the originalcurve starting from the current projective point. Then we compute the projective point for the next iteration, as well asthe parameter corresponding to it, by projecting the test point onto this biarc. The iterative process terminates whenthe projective point satisfies the required precision. Examples demonstrate that our algorithm converges faster and isless dependent on the choice of the initial value compared to the traditional geometric iteration algorithms based onsingle-point approximation.

Solving combinatorial optimization problems via their reduction to Boolean MinSAT is an emerging generic problem solving approach. In this paper we extend MinSAT with many-valued variables, and refer to the new formalism as Many-Valued MinSAT. For Many-Valued MinSAT, we describe an exact solver, Mv-MinSatz, which builds on the Boolean branch-and-bound solver MinSatz, and exploits the domain information of many-valued variables. Moreover, we also define efficient and robust encodings from optimization problems with many-valued variables to MinSAT. The empirical results provide evidence of the good performance of the new encodings, and of Many-Valued MinSAT over Boolean MinSAT on relevant optimization problems.

International audience; Polar NURBS surface is a kind of periodic NURBS surface, one boundary of which shrinks to a degenerate polarpoint. The specific topology of its control-point mesh offers the ability to represent a cap-like surface, which iscommon in geometric modeling. However, there is a critical and challenging problem that hinders its application:curvature continuity at the extraordinary singular pole. We first propose a sufficient and necessary condition ofcurvature continuity at the pole. Then, we present constructive methods for the two key problems respectively:how to construct a polar NURBS surface with curvature continuity and how to reform an ordinary polar NURBSsurface to curvature continuous. The algorithms only depend on the symbolic representation and operations ofNURBS, and they introduce no restrictions on the degree or the knot vectors. Examples and comparisons demonstratethe applications of the curvature-continuous polar NURBS surface in hole-filling and free-shape modeling.

International audience; Rapid retrieval of specified items in a large amount of multi-dimensional data has become an urgent and challenging topic for improving the effectiveness of data searching and analysis approaches. In order to help users quickly re-find the desired items, we present a novel multi-perspective visual retrieval method which is totally different from traditional visualizations for searching results, such as list-based techniques. In our prototype, customized dimensions are generated adaptively which enables users to fast approach to the desired targets from multiple perspectives. We also design several display modes to layout the items by introducing degree-of-interest(DOI) ranking, which is implicitly defined by the geometric relationships of different dimensions. The display modes includes the Cluster Mode using importance-driven dimensionality reduction techniques, the Radial Mode diffusing the items into separate directions, the Uniform Mode evolved by Archimedean Spiral which keeps items non-overlapping and the Custom Mode for deep analysis. Moreover, we combine Focus + Context, Visual Cues which presents item properties, Collaborative Filtering and animations to recommend results according to the features users are interested in. Finally, we evaluate our method in different scenarios: text message retrospection, desktop search and web browsing history retrieval. The experiments show that our method is flexible, extensible, and efficient.

Blue noise sampling is an important component in many graphics applications, but existing techniques consider mainly the spatial positions of samples, making them less effective when handling problems with non-spatial features. Examples include biological distribution in which plant spacing is influenced by non-positional factors such as tree type and size, photon mapping in which photon flux and direction are not a direct function of the attached surface, and point cloud sampling in which the underlying surface is unknown a priori. These scenarios can benefit from blue noise sample distributions, but cannot be adequately handled by prior art. Inspired by bilateral filtering, we propose a bilateral blue noise sampling strategy. Our key idea is a general formulation to modulate the traditional sample distance measures, which are determined by sample position in spatial domain, with a similarity measure that considers arbitrary per sample attributes. This modulation leads to the notion of bilateral blue noise whose properties are influenced by not only the uniformity of the sample positions but also the similarity of the sample attributes. We describe how to incorporate our modulation into various sample analysis and synthesis methods, and demonstrate applications in object distribution, photon density estimation, and point cloud sub-sampling.

As a novel type of real-time social networking service, microblogging has already become ubiquitous and an irreplaceable tool. Tracking in the pulse of retweeting propagation is important and meaningful. In this paper, we investigate how information propagation in a specific microblogging platform evolves to identify relevant patterns and understand dynamic attributes of information propagation and the underlying sociological motivations. More specifically, based on the node-link diagram, we propose three efficient strategies to map the multiple attributes of information propagation graph to appropriate visual elements. For revealing the dynamic attributes, we propose two models: the depth-varying and the time-varying parallel data model to illustrate the temporal evolution efficiently. We also present a novel method by combining the traditional scatter plot with Hough transformation to represent the distribution of propagation instances and trace the propagation speeds. We integrate our methods to a visual mining tool and develop several interactive features. We demonstrate how our approaches improve the understanding of the propagation graph from a visual perspective by employing propagation datasets collected from Sina Weibo, the largest microblogging service provider in mainland China. Meanwhile, this visual mining tool has been evaluated by data analysts and successfully used in Sina Corporation as a helpful assistant to them.

International audience; It is a fundamental problem to calculate Jacobiancoefficients of constraint equations in assembly constraintsolving because most approaches to solving an assemblyconstraint system will finally resort to a numerical iterativemethod that requires the first-order derivatives of theconstraint equations. The most-used method of derivingthe Jacobian coefficients is to use virtual rotation whichis originally presented to derive the equations of motionof constrained mechanical systems. However, when Eulerparameters are adopted as the state variables to represent thetransformation matrix, using the virtual rotation will yielderroneous formulae of Jacobian coefficients. The reason isthat Euler parameters are incompatible with virtual rotation.In this paper, correct formulae of Jacobian coefficients ofgeometric constraints with respect to Euler parameters arepresented in both Cartesian coordinates and relative generalizedcoordinates. Experimental results show that ourproposed formulae make Newton-Raphson iterative methodconverge faster and more stable.

International audience; In this paper, an incremental method is proposed for solving under-constrainedassembly problems under interactive environment. During an assembling process, adesigner adds or removes some constraints, changes the design parameters, ormaneuvers some bodies frequently. For each operation, we identify and solve theaffected biconnected subgraph in the constraint graph using the cut-joint method. Astrategy is provided to construct the joint reference frames from the former assemblyconfiguration. After solving the biconnected subgraph, rigid transformation is utilizedto propagate the changes until all subgraphs are visited. Examples are provided toillustrate the effectiveness of the method proposed in the paper.

International audience; This paper proposes a method to analyze the geometry and semantic information of2D vector floor plans, and reconstruct the corresponding 3D building modelsautomatically. First, the Shape-opening graph (SOG) is introduced to recognizeStructural Components (SCs) and describe the relationships between SCs and openingswhich are architectural components separating spaces. A priority principle algorithmis developed to replace openings with wall equivalent lines for the purpose of laterloop searching. Then, we present an odd-even-based edge breaking algorithm topreprocess wall lines in order to search loops directly and exactly. After that, all theinterior-space contours, which are in fact rooms or aisles, and exterior boundarycontour can be obtained. With the hierarchical component tree presented, thetopological relations of the whole building can be obtained. Finally, 3D models can begenerated after extruding loops to the wall height and cutting openings from the walls.A drawing with several floor plans can also be reconstructed to multi-floor buildingafter aligning their dimensions. Moreover, the intermediate result after analyzing the2D floor plan can be the input of other architectural software to generate 3D models.

International audience; Path planning is a fundamental problem, especially for various AEC applications, such as architecturaldesign, indoor and outdoor navigation, and emergency evacuation. However, the conventionalapproaches mainly operate path planning on 2D drawings or building layouts by simply considering geometricinformation, while losing abundant semantic information of building components. To address thisissue, this paper introduces a new method to cope with path planning for 3D indoor space through an IFC(Industry Foundation Classes) file as input. As a major data exchange standard for Building InformationModeling (BIM), the IFC standard is capable of restoring both geometric information and rich semanticinformation of building components to support lifecycle data sharing. The method consists of three mainsteps: (1) extracting both geometric and semantic information of building components defined withinthe IFC file, (2) discretizing and mapping the extracted information into a planar grid, (3) and finally findingthe shortest path based on the mapping for path planning using Fast Marching Method. The paperaims to process different kinds of building components and their corresponding properties to obtain richsemantic information that can enhance applications of path planning. In addition, the IFC-based distributeddata sharing and management is implemented for path planning. The paper also presents someexperiments to demonstrate the accuracy, efficiency and adaptability of the method. Video demonstrationis available from http://cgcad.thss.tsinghua.edu.cn/liuyushen/ifcpath/.

International audience; Assembly searching technologies are important for the improvement of design reusability. However, existing methods require that assemblies possess high-level information, and thus cannot be applied in lightweight assemblies. In this paper, we propose a novel relaxed lightweight assembly retrieval approach based on a vector space model (VSM). By decomposing the assemblies represented in a watertight polygon mesh into bags of parts, and considering the queries as a vague specification of a set of parts, the resilient ranking strategy in VSM is successfully applied in the assembly retrieval. Furthermore, we take the scale-sensitive similarities between parts into the evaluation of matching values, and extend the original VSM to a relaxed matching framework. This framework allows users to input any fuzzy queries, is capable of measuring the results quantitatively, and performs well in retrieving assemblies with specified characteristics. To accelerate the online matching procedure, a typical parts based matching process, as well as a greedy strategy based matching algorithm is presented and integrated in the framework, which makes our system achieve interactive performance. We demonstrate the efficiency and effectiveness of our approach through various experiments on the prototype system.

International audience; For large simulation data, Parallel Marching Cubes algorithm is efficient and commonly used to extract isosurfaces in 3D scalar field. However, the isosurface meshes are sometimes too dense and it is difficult for scientists to specify the areas they are interested in. In this paper, we provide them a new way to define mesh importance for decimation using transfer functions and visualize large simulation data in case the normal visualization methods cannot handle due to memory limit. We also introduce a parallel isosurface simplification framework which uses pyramid peeling to extract the decimated meshes progressively without generating the original surface. Since the implementation uses OpenCL which is oriented to heterogeneous computing, our method can be applied to different parallel systems and scientists can see the visualization results while doing simulations. Finally, we evaluate the performances of our algorithm and use different scientific datasets to show the efficiency of our method.

International audience; Particle systems are important building block for simulating vivid and detail-rich effects in virtual world. One of the most difficult aspects of particle systems has been detecting collisions between particlesand mesh surface. Due to the huge computation, a variety of proxy-based approaches have been proposed recently to perform visually correct simulation. However, all either limit the complexity of the scene, fail toguarantee non-penetration, or are too slow for real-time use with many particles. In this paper, we propose anew octree-based proxy for colliding particles with meshes on the GPU. Our approach works by subdividingthe scene mesh with an octree in which each leaf node associates with a representative normal correspondingto the normals of the triangles that intersect the node. We present a view-visible method, which is suitable forboth closed and non-closed models, to label the empty leaf nodes adjacent to nonempty ones with appropriateback/front property, allowing particles to collide with both sides of the scene mesh. We show how collisionscan be performed robustly on this proxy structure in place of the original mesh, and describe an extension thatallows for fast traversal of the octree structure on the GPU. The experiments show that the proposed methodis fast enough for real-time performance with millions of particles interacting with complex scenes.

Despite their similarities, MaxSAT and MinSAT use different encodings and solving techniques to cope with optimization problems. In this paper we describe a new weighted partial MinSAT solver, define original MinSAT encodings for relevant combinatorial problems, propose a new testbed for evaluating MinSAT, report on an empirical investigation comparing MinSAT with MaxSAT, and provide new insights into the duality between MinSAT and MaxSAT. © 2013 Springer-Verlag.

International audience; no abstract

MinSAT is the problem of finding a truth assignment that minimizes the number of satisfied clauses in a CNF formula. When we distinguish between hard and soft clauses, and soft clauses have an associated weight, then the problem, called Weighted Partial MinSAT, consists in finding a truth assignment that satisfies all the hard clauses and minimizes the sum of weights of satisfied soft clauses. In this paper we define a novel encoding from Weighted Partial MinSAT into Weighted Partial MaxSAT, which is also valid for encoding Weighted Partial MaxSAT into Weighted Partial MinSAT. Moreover, we report on an empirical investigation that shows that our encoding significantly outperforms existing encodings on weighted and unweighted Min2SAT and Min3SAT instances.

We define solving techniques for the Minimum Satisfiability Problem (MinSAT), propose an efficient branch-and-bound algorithm to solve the Weighted Partial MinSAT problem, and report on an empirical evaluation of the algorithm on Min-3SAT, MaxClique, and combinatorial auction problems. Techniques solving MinSAT are substantially different from those for the Maximum Satisfiability Problem (MaxSAT). Our results provide empirical evidence that solving combinatorial optimization problems by reducing them to MinSAT may be substantially faster than reducing them to MaxSAT, and even competitive with specific algorithms. We also use MinSAT to study an interesting correlation between the minimum number and the maximum number of satisfied clauses of a SAT instance., Nous proposons, dans cet article, de placer le problème de satisfiabilité minimale (MinSAT) sur le devant de la scène. Pour cela, un algorithme efficace de type {em branch-and-bound} pour résoudre le problème MinSAT partiel avec pondération est introduit, permettant du même coup une évaluation empirique de cet algorithme pour les cas Min-3SAT aléatoires, MaxClique et pour les problèmes d'enchères combinatoires. Les techniques employées pour résoudre MinSAT se démarquent de celles utilisées pour le problème de satisfiabilité maximale (MaxSAT), qui a lui été très étudié. Nos résultats démontrent de manière empirique que, notamment sur les problèmes d'enchères combinatoires, une réduction du problème initial à MinSAT peut être plus intéressante qu'une réduction à MaxSAT, ou même que l'utilisation de méthodes dédiées. Nous étendons par ailleurs ce travail en montrant une corrélation entre le nombre minimal et le nombre maximal de clauses satisfaites dans une instance SAT aléatoire donnée.

International audience; This paper proposes a second order geometric iteration algorithm for point projection and inversion on parametric surfaces. The iteration starts from an initial projection estimation. In each iteration, we construct a second order osculating torus patch to the parametric surface at the previous projection. Then we project the test point onto the torus patch to compute the next projection and its parameter. This iterative process is terminated when the parameter satisfies the required precision. Experiments demonstrate the convergence speed of our algorithm.

International audience; Solid reconstruction from engineering drawings is one of the efficient technologies to product solid models. The B-rep oriented approach provides a practical way for reconstructing a wide range of objects. However, its major limitation is the computational complexity involved in the search for all valid faces from the intermediate wire-frame, especially for objects with complicated face topologies. In previous work, we presented a hint-based algorithm to recognize quadric surfaces from orthographic views and generate a hybrid wire-frame as the intermediate model of our B-rep oriented method. As a key stage in the process of solid reconstructing, we propose an algorithm to convert the hybrid wire-frame to the final B-rep model by extracting all the rest faces of planes based on graph theory. The entities lying on the same planar surface are first collected in a plane graph. After all the cycles are traced in a simplified edge-adjacency matrix of the graph, the face loops of the plane are formed by testing loop containment and assigning loop directions. Finally, the B-rep model is constructed by sewing all the plane faces based on the M¨obius rule. The method can efficiently construct 2- manifold objects with a variety of face topologies, which is illustrated by results of implementation

National audience; An algorithm to construct biarcs that not only match the interpolation requirement of the point positions and tangent vectors but also lie on one side of the constraint line is proposed. For C-type biarc interpolation with the line constraint , firstly twelve inequalities in total are provided according to different position relationships between the constraint line and the interpolation requirement. These inequalities are used to check if biarcs lie on one side of the constraint line. If there exist many biarcs satisfying both the interpolation requirement and the line constraint , the optimal biarc can be obtained by solving a minimum problem. Otherwise , one extra point is added to make it possible to obtain biarcs. For S-type biarc interpolation with the line constraint , some results are also listed.

National audience; Solid reconstruction from engineering drawings is one of the efficient technologies to product solid models, which has become one of the important research topics in both computer graphics and artificial intelligence. The problem of solid reconstruction from engineering drawings is captured. The taxonomy for solid reconstruction techniques is presented with the typical algorithms reviewed. After comparing the application areas of the algorithms, the open research issues are analyzed. Finally, the future work in the research field is also pointed out.

International audience; The reconstruction of 3D objects from 2D orthographic views is crucial for maintaining and further developing existing product designs. A B-rep oriented method for reconstructing curved objects from three orthographic views is presented by employing a hybrid wire-frame in place of an intermediate wire-frame. The Link-Relation Graph (LRG) is introduced as a multi-graph representation of orthographic views, and quadric surface features (QSFs) are defined by special basic patterns of LRG as well as aggregation rules. By hint-based pattern matching in the LRGs of three orthographic views in an order of priority, the corresponding QSFs are recognized, and the geometry and topology of quadric surfaces are recovered simultaneously. This method can handle objects with interacting quadric surfaces and avoids the combinatorial search for tracing all the quadric surfaces in an intermediate wire-frame by the existing methods. Several examples are provided.

International audience; A new algorithm for Boolean operations on general planar polygons is presented. It is available for general planar polygons (manifold or non-manifold, with or without holes). Edges of the two general polygons are subdivided at the intersection points and touching points. Thus, the boundaryof the Boolean operation resultant polygon is made of some whole edges of the polygons after the subdivision process. We use the simplex theory to build the basic mathematical model of the new algorithm. The subordination problem between an edge and a polygon is reduced to a problem of determining whether a point is on some edges of some simplices or inside the simplices, and the associated simplicial chain of the resultant polygon is just an assembly of some simplices and their coefficients of the two polygons after the subdivision process. Examples show that the running time required bythe new algorithm is less than one-third of that bythe Rivero and Feito algorithm.

Observed northern extratropical land greening is consistent with anthropogenic forcings, where greenhouse gases play a dominant role, but not with simulations that include only natural forcings and internal climate variability.

International audience; Dynamic partial differential equation (PDE) parametric curves which can be expressed as a coupled system of two hyperbolic equations are developed. In curve design, dynamic PDE parametric curves can be modified intuitively and are more flexible than ordinary differential equation (ODE) curves. The calculation of dynamic PDE parametric curves must recur to numerical methods and a three-level finite difference scheme is proposed. Approximation and stability properties for the scheme are proved and convergence property is derived. An example of interpolating PDE curves is presented as an application of dynamic PDE parametric curves.