bluuebunny/crossref_metadata_2025 huggingface dataset:
Change in riparian plant community composition along two rivers in northern Sweden
Authors: Nilsson Christer
Published: December 2009

Large-scale spatial variation in vascular plant communities at 62 shoreline sites along the Piteälven and Laisälven–Vindelälven (rivers), in northern Sweden, was examined using two-way indicator species analysis (TWINSPAN). The first four clusters generated for each river were explained by shore substrate and wave and flow action. The Pitealven exhibited a sequence of discrete clusters, whereas along the Laisälven–Vindelälven a high degree of overlap between clusters was found. The results suggest overall “continua,” related to climatic gradients, along both rivers with other superimposed discontinuities related mainly to changes in substrate and flow action.
Cell wall texture in root hairs of the genus Equisetum
Authors: Emons Anne Mie C.
Published: December 2009

Based on cell wall texture of root hairs, two groups can be distinguished within the 10 species of Equisetum listed in Flora Europaea. This distinction coincides with the division of the genus Equisetum into two subgenera: Equisetum (horsetails) and Hippochaete (scouring rushes). All species of the subgenus Equisetum have a helicoidal cell wall texture in young growing root hairs as well as in full-grown hairs. All species of the subgenus Hippochaete deposit an additional inner cell wall layer against this helicoidal layer when elongation has stopped. The microfibrils in this additional layer do not form a helicoidal texture, but are helically arranged, forming a Z-helix. The presence of a helical layer in full-grown hairs is not a prerequisite for growth in soil, but an exclusively helicoidal root hair wall texture might be favourable for life in water. The wall texture is not influenced by the consistency of the substratum.
An ultrastructural study of embryo and endosperm development during in vitro culture of maize ovaries (Zea mays)
Authors: Schel J. H. N. , Kieft H.
Published: December 2009

A culture method is described which allows the continuous supply of fresh liquid medium and which prevents the accumulation of toxic metabolites. Development of maize embryos and endosperm after various periods of in vitro ovary culture was studied by light and electron microscopy. Using this method the ultrastructural features of embryo development in vitro were similar to those of in vivo embryos. In contrast, the formation of endosperm was irregular with the absence of cellularization of the inner endosperm being frequent. In some cases, only the endosperm developed without any indication of embryo formation. In a calcium-depleted medium, embryo development was normal but again, endosperm formation was aberrant. No cells were formed in the central part of the endosperm and near the placental region degeneration took place, resulting in vacuoles with dark inclusions, clumps of rough endoplasmic reticulum membranes, and cellular breakdown. The events occurring after in vitro culture strongly resemble those taking place after intergeneric crosses or crosses between diploid and tetraploid strains. It is concluded that defective endosperm development is probably the main factor for the failure of embryo development.
Soilless culture of vesicular–arbuscular mycorrhizae of cereals: effects of nutrient concentration and nitrogen source
Authors: Thompson J. P.
Published: December 2009

The best productions of mycorrhizal roots from cereals in sand culture treated with four ratios of NO3 to NH4 in three concentrations of a balanced nutrient solution (Hewitt's) were (i) maize – Glomus mosseae: 30–50% colonization and 120–150 m of colonized root per plant from full-strength solution with 95–100% NO3-N; (ii) wheat – G. mosseae: 80–90% colonization from 0.1-strength solution and 40–50 m from 0.25-strength solution with 50–100% NO3-N; (iii) maize – Glomus fasciculatum: 70% and 120 m from 0.25-strength solution with 50% NO3-N; and (iv) wheat – G. fasciculatum: 25 – 30% and 10–15 m from 0.1-strength solution with 50 – 100% NH4-N. The highest nutrient strengths eliminated colonization in wheat or reduced numbers of vesicles and arbuscules. Vesicles were predominant at the lowest nutrient strengths. Ammonium reduced mycorrhizosphere pH, colonization, and sporocarp and ectocarpic spore production. Multiple regression showed best colonization with (i) maize – G. mosseae, pH > 7.4, and best vesicle and arbuscule development with root P < 0.1%; (ii) wheat – G. mosseae, pH 7.2–7.7, root P < 0.055%, and root N > 1.07%; (iii) maize – G. fasciculatum, pH 5.6–6.2, root P < 0.08%, and root N > 1.44%; and (iv) wheat – G. fasciculatum, pH 6.7–6.9. Maize – G. mosseae was grown by the nutrient film technique in 0.1-strength solution with NO3 and rock phosphate. Improving the production of the inoculum from hydroponic culture of cereals is discussed.
Wound age and infection of peach bark by Cytospora leucostoma
Authors: Biggs A. R.
Published: December 2009

Peach bark wounds of varying ages were inoculated with mycelium of Cytospora leucostoma (Pers.) Fr., and colonization frequency and extent were determined. Noninoculated wounds of similar ages and in close proximity to inoculated wounds were also sampled and examined histologically for morphological and histochemical changes associated with nonspecific plant defense reactions, including lignification and formation of lignosuberized tissue and new periderm. Results demonstrated that lignified and lignosuberized tissues significantly decreased the rate of fungal colonization, whereas new periderm with at least three cells thickness of new phellem completely inhibited fungal colonization. The critical period regarding effective periderm formation was between 10 and 14 days postwounding.
A new Harposporium parasitic in bdelloid rotifers
Authors: Barron G. L.
Published: December 2009

Harposporium spirosporum is described as a new hyphomycete attacking bdelloid rotifers in soil. In this species the spiral conidia have sharply pointed ends and lodge in the gullet or mastax of the host to initiate infection.
Nonsteady-state analysis of water flow and capacitance for Agave deserti
Authors: Calkin Howard W. , Nobel Park S.
Published: December 2009

An analog electrical circuit, including both resistances and capacitances for roots, stem, and leaves, was developed for a desert leaf-succulent, Agave deserti. Based on soil water potentials and observed transpiration rates and the influence of leaf, stem, and root relative water content on the water potential of each organ, water potential could be predicted at various locations in the transpiration stream. Simulations indicated that as stomata opened at night for this crassulacean acid-metabolism plant, most of the water initially transpired came from the leaves. Water movement from the soil was greatest throughout the night and the early morning; the maximal water uptake rate from the soil was only about half of the maximum transpiration rate. As drought increased, lower transpiration rates led to smaller water losses, in turn leading to progressively earlier recharge of the leaf capacitance. The substantial and predictable daily changes in plant water potential may have profound effects on physiological processes in the cells near the transpiration stream.
Heteroblastic seedlings of green ash. II. Early development of simple and compound leaves
Authors: Merrill E. K.
Published: December 2009

Simple and compound leaf primordia of green ash seedlings differ in shape from initiation. Simple leaf primordia are flattened until their lamina margins grow out at a primordial length of 150 μm. Compound leaf primordia are rounded and peglike at initiation and lateral leaflet buttresses appear when primordia are 150 μm long. Terminal leaflet margins appear when compound leaf primordia are 200 μm long. At initiation both types of leaf primordia are composed of densely cytoplasmic cells. Vacuolation proceeds so that densely cytoplasmic cells remain only in areas developing blades and leaflets and in procambium. Because simple and compound leaves of green ash differ from initiation, neither leaf type can be considered to result from a change in the ontogeny of the other.
Encoelia pruinosa on Populus tremuloides in Minnesota: occurrence, pathogenicity, and comparison with Colorado isolates
Authors: Juzwik Jennifer , French D. W. , Hinds T. E.
Published: December 2009

The occurrence of Encoelia pruinosa (Ell. & Everh.) Torkelson & Eckblad in Minnesota and its pathogenicity on native Populus tremuloides Michx. were investigated. Isolates from Minnesota were also compared with those from Colorado. The fungus appears to be widely distributed in Minnesota, where apothecia were collected from trembling aspen in eight counties. The optimum temperature for mycelial growth of all isolates was 22 °C. Minnesota isolates of E. pruinosa produced limited sooty-bark cankers on aspen from Minnesota in field inoculations within 2 years. Elongation of cankers in the 3rd year was observed only on the larger diameter inoculated trees. Colonization of recently cut aspen stem sections by Colorado and Minnesota isolates after 2 months was greatest for Colorado isolates. Sections of aspen from Colorado were more readily colonized by E. pruinosa than sections from aspen in Minnesota. It is hypothesized that Colorado isolates of E. pruinosa are more virulent than Minnesota isolates and that Minnesota native aspen is more resistant to colonization by E. purinosa than Colorado native aspen.
A clarification of the Medicago papillosa complex
Authors: Small Ernest
Published: December 2009

The Medicago papillosa complex of northeastern Turkey and the adjacent USSR has been considered to comprise as many as three species. It was found that the diagnostic features attributed to M. papillosa Boiss. var. macrocarpa Boiss. (= M. papillosa subsp. macrocarpa (Boiss.) Urban = M. ignatzii Lesins & Lesins) segregate very well all Turkish plants west of longitude 41° E. Plants of the USSR, commonly labelled M. dzhawakhetica Bordz. (= M. papillosa var. dzhawakhetica (Bordz.) Bordz.), have been alleged to differ from remaining representatives of the M. papillosa complex, especially with respect to the presence of glandular hairs on the fruits. However, no basis was found for recognition of more than one taxon east of longitude 41° E (i. e., inclusive of all Russian plants, and of all Turkish plants east of 41° E). The names accepted in this paper for the western and eastern variants are, respectively, M. papillosa subsp. macrocarpa and M. papillosa subsp. papillosa. Only diploid (2n = 2x = 16) chromosome number determinations have been recorded for M. papillosa subsp. macrocarpa, whereas both diploid and tetraploid counts have been made for M. papillosa subsp. papillosa.
Internal and external infections of fruits and seeds of peppers by Xanthomonas campestris pv. vesicatoria
Authors: Bashan Y. , Okon Y.
Published: December 2009

Fruit infection by Xanthomonas campestris pv. vesicatoria (Doidge 1920) Dye 1978 was monitored by scanning electron microscopy and by bacterial counts. Possible sites for bacterial penetration were through dead flowers and by proliferation of bacteria in the wart (small protuberance) area. Bacterial multiplication was observed in all warts of young, mature, and ripened fruits. Bacterial cells were bound to the fruit surface by fibrillar material. On the fruit surface, bacteria multiplied in small aggregates, submerged in slime. The slime consisted mainly of sucrose units. At later stages of disease development, the slime covered the entire fruit surface in young fruits. Typical scab symptoms appeared only in leaves of inoculated plants, whereas buds, flowers, and fruits of various sizes were symptomless, but later shed; shedding was strongest in young buds. In more mature and ripened fruits, bacterial numbers decreased and there was less shedding. Xanthomonas campestris pv. vesicatoria could be detected, in enrichment culture, in low numbers at the seed site (ovary) in inoculated fruits that did not shed.
Adsorption, in vitro, de l’endopolygalacturonase secrétée par Colletotrichum lindemuthianum sur des parois de deux lignées de haricots isogéniques résistants et sensibles à l'anthracnose
Authors: Sharma R. C. , Barthe J. P. , Lafitte C. , Touzé A.
Published: December 2009

As compared with the cell walls of anthracnose-sensitive beans, the cell walls of resistant beans, with the involvement of Cornell gene, adsorb, when cultivated in vitro, larger quantities of the endopolygalacturonase secreted by the fungus responsible for the disease, Colleotrichum lindemuthianum. This selective adsorption only occurs for the enzyme excreted by the pathogenic fungus. This phenomenon is observed with cell walls from which the constituant glycoproteins inhibitive for the endopolygalacturonase were previously removed. The adsorbing capacity of the two types of cell walls was reduced by a heat treatment (100 °C, 30 min) and the differences between both types of walls for the selective binding with the endopolygalacturonase of C. lindemuthianum are reduced. This suggests that protein(s) are involved in this specific adsorption. Solubilisation of the pectic substances of the walls by an enzymatic treatment strongly reduced the binding capacity of the walls for the endopolygalacturonase. It appears therefore that ionic bindings with the pectic polymers are also involved. The possible implication of this phenomenon in the resistance to anthracnose is discussed. [Translated by the Journal]
Stratigraphy and genesis of the Lake Sixteen peatland, northern Michigan
Authors: Futyma Richard P. , Miller Norton G.
Published: December 2009

The Lake Sixteen peatland is a 400-ha mire consisting principally of low-shrub (Chamaedaphne) bog and lesser areas of tree-covered (Picea – Larix) bog and sedge fen adjacent to a 55-ha alkaline lake. The sediments consist of the following superimposed deposits: gyttja, sedge peat, and Sphagnum–ericad–sedge peat. Near the edges of the peatland, highly humified, sometimes woody peat is present as the basal layer instead of gyttja. Radiocarbon-dated pollen stratigraphies from the lake and four sites in the peatland have elucidated the temporal relationships of the various sediment units and the developmental history of the peatland. During the mid-Holocene, probably in response to a change to cooler, moister climate, early Lake Sixteen underwent an expansion resulting in the deposition of gyttja over an increasingly larger area. About 3000 years BP, a sedge fen developed on the edge of the lake. Low-shrub bog replaced the sedge vegetation as the fen mat expanded into the lake. Swamping of bordering forests also allowed expansion of bog vegetation outward from the basin. Hydrological changes accompanying peat accumulation probably promoted vegetational changes within the peatland and the centrifugal spread of bog vegetation through swamping.
Radial through rotated symmetry of striate pollen of the Acanthaceae
Authors: Vasanthy G. , Pocock Stanley A. J.
Published: December 2009

In Nilgirianthus neilgherrensis (Bedd.) Brem. (tribe Strobilantheae) pollen grains normally have three "polar axially" oriented colpora and pseudocolpi (6 × 3), while a few are two, four, or five aperturate. Exinal features occasionally manifest different degrees of torsion and rotation. An abnormal two-colporate grain exhibits a peculiar 90° rotated symmetry, colpora, pseudocolpi, and sexinal ridges of one hemisphere being perpendicular to the other half. Bravaisia integerrima Standley and B. tubiflora Hemsl. (tribe Trichanthereae) have two-colporate, striate and rotationally symmetric pollen, except for a rare radially symmetric grain of B. integerrima. Two-colporate, striate pollen of Sanchezia lampra Leonard & Smith (tribe Trichanthereae) has also rotated symmetry, but anomalous grains exhibit radial orientation and divergent rotations of exinal features. These divergencies in orientation could be the gradations between polar axial – radial symmetry and 90°-rotated symmetry. This surmise raises several points of discussion such as the role of plasmalemma or factors controlling variable symmetry within a taxon or an anther, effectiveness of rotational symmetry as an harmomegathus, and the significance of the trend, change of symmetry, observed in the striate palynomorphs of different plant lineages and geological periods.
On the ontogeny of the oncus in the pollen grain of Parietaria officinalis ssp. judaica (Urticaceae)
Authors: Seoane-Camba Juan A. , Suárez-Cervera María
Published: December 2009

During the pollen ontogeny of Parietaria officinalis L. ssp. judaica Bég. the apertural zone and operculum are differentiated relatively early and they are well apparent when the microspores are liberated into the thecal cavity. At the late stage of the microspore the endexine becomes ample and granulose in the apertural zone, and a cavity is conspicuous between the operculum and the endexine. On the other hand a structured periplasmic space between the endexine and the plasmalemma is formed. Subsequently the structured periplasmic space becomes thin and a new material, apparently different from the structured one, is produced from the plasmalemma under the apertural zone, as a result of cytoplasmic activity. Finally, the structured periplasmic space is no longer apparent except for a very narrow portion beneath the aperture (Zwischenkörper). Beneath the Zwischenkörper the secondary material, produced by the cytoplasmic activity, becomes globular and constitutes a spherical body that is easily discerned under the transmitted light microscope and which is called the oncus in the classical optical microscopic observation of the fresh pollen grain. By histochemical reactions with periodic acid – Schiff s reagent, Sudan black, and Coomassie brillant blue we have found abundant glucosidic, lipoidal, and proteinaceous material in this globular body.
A GOAL PROGRAMMING APPROACH TO FUZZY LINEAR REGRESSION WITH NON-FUZZY INPUT AND FUZZY OUTPUT DATA
Authors: HASSANPOUR H. , MALEKI H. R. , YAGHOOBI M. A.
Published: December 2009

Many researches have been carried out in fuzzy linear regression since the past three decades. In this paper, a fuzzy linear regression model based on goal programming is proposed. The proposed model takes into account the centers of fuzzy data as an important feature as well as their spreads. Furthermore, the model can deal with both symmetric and non-symmetric data. To show the efficiency of proposed model, it is compared with some earlier methods based on simulation studies and numerical examples. Moreover, the sensitivity of the model to outliers is discussed.
INVESTIGATION OF THE DEFECT STRUCTURE, OPTICAL AND EPR SPECTRA FORCdS:Ti2+ANDCdSe:Ti2+CRYSTAL
Authors: FENG WEN-LIN , ZHENG WEN-CHEN
Published: December 2009

The optical spectral band positions and spin-Hamiltonian parameters (g factors g‖, g⊥and zero-field splitting D) of CdS : Ti2+and CdSe : Ti2+crystals are calculated from the complete diagonalizaion (of energy matrix) method based on a two-spin-orbit parameter model for 3d2ions in trigonal symmetry. In the model, both the contribution to spin-Hamiltonian parameters due to the spin-orbit parameter of central 3d2ions and that of ligand ions are included. The crystal field parameters used in the calculations are obtained from the superposition model which enables correlation of the optical and EPR spectral data with the defect structure of the studied paramagnetic impurity centers in crystals. From the calculations, the defect structures of Ti2+centers in CdS : Ti2+and CdSe : Ti2+are acquired, the signs of zero-field splittings D are suggested, and the optical band positions and spin-Hamiltonian parameters are explained. The results are discussed.
UNCERTAINTY RELATIONS OF STATISTICAL MECHANICS
Authors: VELAZQUEZ LUISBERIS , CURILEF SERGIO
Published: December 2009

Recently, we have presented some simple arguments supporting the existence of a certain complementarity between thermodynamic quantities of temperature and energy, an idea suggested by Bohr and Heinsenberg in the early days of Quantum Mechanics. Such a complementarity is expressed as the impossibility to perform an exact simultaneous determination of the system energy and temperature by using an experimental procedure based on the thermal equilibrium with other system regarded as a measuring apparatus (thermometer). In this work, we provide a simple generalization of the last approach with the consideration of a thermodynamic situation with several control parameters.
DENOUEMENT OF A WORMHOLE–BRANE ENCOUNTER
Authors: RODRIGO ENRICO
Published: December 2009

Higher-dimensional black holes have long been considered within the context of brane worlds. Recently, it was shown that the brane-world ethos also permits the consideration of higher-dimensional wormholes. When such a wormhole, pre-existing in the bulk, impinges upon our universe, taken to be a positive-tension three-brane, it can induce the creation in our universe of a wormhole of ordinary dimensionality. The throat of this wormhole might fully constrict, pinch off, and thus birth a baby universe. Alternatively, the induced wormhole might persist. I show that persistence is more likely and note that the persistent wormhole manifests itself as a particle-like object whose interaction with cosmic matter is purely gravitational. I consider the viability of this object as a dark matter candidate.
A SURVEY OF POLYNOMIAL APPROXIMATION ON THE SPHERE
Authors: DAI FENG , WANG KUNYANG
Published: December 2009

The main purpose of this paper is to survey some of the work on spherical approximation done by the BNU group under the direction of Professor Sun.

The equiconvergent operators of Cesàro means, and their interesting applications are described. The Jackson inequality for spherical polynomials and some moduli of smoothness on the sphere are investigated. The equivalence between moduli of smoothness and K-functionals is also discussed. We also describe several weighted polynomial inequalities on the sphere, including the Remez-type and the Nikolskii-type inequalities, the Marcinkiewicz–Zygmund inequality, the Bernstein-type and the Schur-type inequalities. Positive cubature formulas on the sphere, and their relation to the Marcinkiewicz–Zygmund inequality are also discussed. A survey on recent results on asymptotic orders of the n-widths of Sobolev's classes on the sphere is also given.
ON THE ASYMMETRY OF THE RESIDUE COMPOSITIONS OF THE BINDING SITES ON PROTEIN SURFACES
Authors: IVÁN GÁBOR , SZABADKA ZOLTÁN , GROLMUSZ VINCE
Published: December 2009

By screening all the ligand binding sites in the Protein Data Bank, we have found that while it is geometrically possible that a loop, formed from a protein chain with residues ZYX, would "impersonate" another chain-loop with residues XYZ by a simple twisting of either the loop or the bound ligand, it almost never happens. This fact is rather surprising, and implies a notable asymmetry, since (i) loops in the folded proteins sometimes can be flexible enough to be twisted, but (ii) ligands are almost always extremely mobile before binding to the protein, therefore they can turn around and bind to residue-sequence ZYX as well. Data availability: The supplementary Table 3 lists the appearances of the residue-sequences and their inverses in the binding sites of the whole PDB, and is available at .
SIRIUS PSB: A GENERIC SYSTEM FOR ANALYSIS OF BIOLOGICAL SEQUENCES
Authors: KOH CHUAN HOCK , LIN SHARENE , JEDD GREGORY , WONG LIMSOON
Published: December 2009

Computational tools are essential components of modern biological research. For example, BLAST searches can be used to identify related proteins based on sequence homology, or when a new genome is sequenced, prediction models can be used to annotate functional sites such as transcription start sites, translation initiation sites and polyadenylation sites and to predict protein localization. Here we present Sirius Prediction Systems Builder (PSB), a new computational tool for sequence analysis, classification and searching. Sirius PSB has four main operations: (1) Building a classifier, (2) Deploying a classifier, (3) Search for proteins similar to query proteins, (4) Preliminary and post-prediction analysis. Sirius PSB supports all these operations via a simple and interactive graphical user interface. Besides being a convenient tool, Sirius PSB has also introduced two novelties in sequence analysis. Firstly, genetic algorithm is used to identify interesting features in the feature space. Secondly, instead of the conventional method of searching for similar proteins via sequence similarity, we introduced searching via features' similarity. To demonstrate the capabilities of Sirius PSB, we have built two prediction models — one for the recognition of Arabidopsis polyadenylation sites and another for the subcellular localization of proteins. Both systems are competitive against current state-of-the-art models based on evaluation of public datasets. More notably, the time and effort required to build each model is greatly reduced with the assistance of Sirius PSB. Furthermore, we show that under certain conditions when BLAST is unable to find related proteins, Sirius PSB can identify functionally related proteins based on their biophysical similarities. Sirius PSB and its related supplements are available at:
Motion field texture synthesis
Authors: Ma Chongyang , Wei Li-Yi , Guo Baining , Zhou Kun
Published: December 2009

A variety of animation effects such as herds and fluids contain detailed motion fields characterized by repetitive structures. Such detailed motion fields are often visually important, but tedious to specify manually or expensive to simulate computationally. Due to the repetitive nature, some of these motion fields (e.g. turbulence in fluids) could be synthesized by procedural texturing, but procedural texturing is known for its limited generality.

We apply example-based texture synthesis for motion fields. Our technique is general and can take on a variety of user inputs, including captured data, manual art, and physical/procedural simulation. This data-driven approach enables artistic effects that are difficult to achieve via previous methods, such as heart shaped swirls in fluid animation. Due to the use of texture synthesis, our method is able to populate a large output field from a small input exemplar, imposing minimum user workload. Our algorithm also allows the synthesis of output motion fields not only with the same dimension as the input (e.g. 2D to 2D) but also of higher dimension, such as 3D volumetric outputs from 2D planar inputs. This cross-dimension capability supports a convenient usage scenario, i.e. the user could simply supply 2D images and our method produces a 3D motion field with similar characteristics. The motion fields produced by our method are generic, and could be combined with a variety of large-scale low-resolution motions that are easy to specify either manually or computationally but lack the repetitive structures to be characterized as textures. We apply our technique to a variety of animation phenomena, including smoke, liquid, and group motion.
Image-based street-side city modeling
Authors: Xiao Jianxiong , Fang Tian , Zhao Peng , Lhuillier Maxime , Quan Long
Published: December 2009

We propose an automatic approach to generate street-side 3D photo-realistic models from images captured along the streets at ground level. We first develop a multi-view semantic segmentation method that recognizes and segments each image at pixel level into semantically meaningful areas, each labeled with a specific object class, such as building, sky, ground, vegetation and car. A partition scheme is then introduced to separate buildings into independent blocks using the major line structures of the scene. Finally, for each block, we propose an inverse patch-based orthographic composition and structure analysis method for façade modeling that efficiently regularizes the noisy and missing reconstructed 3D data. Our system has the distinct advantage of producing visually compelling results by imposing strong priors of building regularity. We demonstrate the fully automatic system on a typical city example to validate our methodology.
Efficient affinity-based edit propagation using K-D tree
Authors: Xu Kun , Li Yong , Ju Tao , Hu Shi-Min , Liu Tian-Qiang
Published: December 2009

Image/video editing by strokes has become increasingly popular due to the ease of interaction. Propagating the user inputs to the rest of the image/video, however, is often time and memory consuming especially for large data. We propose here an efficient scheme that allows affinity-based edit propagation to be computed on data containing tens of millions of pixels at interactive rate (in matter of seconds). The key in our scheme is a novel means for approximately solving the optimization problem involved in edit propagation, using adaptive clustering in a high-dimensional, affinity space. Our approximation significantly reduces the cost of existing affinity-based propagation methods while maintaining visual fidelity, and enables interactive stroke-based editing even on high resolution images and long video sequences using commodity computers.
Stretching and wiggling liquids
Authors: Kim Doyub , Song Oh-young , Ko Hyeong-Seok
Published: December 2009

This paper presents a novel framework for simulating the stretching and wiggling of liquids. We demonstrate that complex phase-interface dynamics can be effectively simulated by introducing the Eulerian vortex sheet method, which focuses on the vorticity at the interface (rather than the whole domain). We extend this model to provide user control for the production of visual effects. Then, the generated fluid flow creates complex surface details, such as thin and wiggling fluid sheets. To capture such high-frequency features efficiently, this work employs a denser grid for surface tracking in addition to the (coarser) simulation grid. In this context, the paper proposes a filter, called the liquid-biased filter, which is able to downsample the surface in the high-resolution grid into the coarse grid without unrealistic volume loss resulting from aliasing error. The proposed method, which runs on a single PC, realistically reproduces complex fluid scenes.
Synthetic turbulence using artificial boundary layers
Authors: Pfaff Tobias , Thuerey Nils , Selle Andrew , Gross Markus
Published: December 2009

Turbulent vortices in fluid flows are crucial for a visually interesting appearance. Although there has been a significant amount of work on turbulence in graphics recently, these algorithms rely on the underlying simulation to resolve the flow around objects. We build upon work from classical fluid mechanics to design an algorithm that allows us to accurately precompute the turbulence being generated around an object immersed in a flow. This is made possible by modeling turbulence formation based on an averaged flow field, and relying on universal laws describing the flow near a wall. We precompute the confined vorticity in the boundary layer around an object, and simulate the boundary layer separation during a fluid simulation. Then, a turbulence model is used to identify areas where this separated layer will transition into actual turbulence. We sample these regions with vortex particles, and simulate the further dynamics of the vortices based on these particles. We will show how our method complements previous work on synthetic turbulence, and yields physically plausible results. In addition, we demonstrate that our method can efficiently compute turbulent flows around a variety of objects including cars, whisks, as well as boulders in a river flow. We can even apply our model to precomputed static flow fields, yielding turbulent dynamics without a costly simulation.
Skipping steps in deformable simulation with online model reduction
Authors: Kim Theodore , James Doug L.
Published: December 2009

Finite element simulations of nonlinear deformable models are computationally costly, routinely taking hours or days to compute the motion of detailed meshes. Dimensional model reduction can make simulations orders of magnitude faster, but is unsuitable for general deformable body simulations because it requires expensive precomputations, and it can suppress motion that lies outside the span of a pre-specified low-rank basis. We present an online model reduction method that does not have these limitations. In lieu of precomputation, we analyze the motion of the full model as the simulation progresses, incrementally building a reduced-order nonlinear model, and detecting when our reduced model is capable of performing the next timestep. For these subspace steps, full-model computation is "skipped" and replaced with a very fast (on the order of milliseconds) reduced order step. We present algorithms for both dynamic and quasistatic simulations, and a "throttle" parameter that allows a user to trade off between faster, approximate previews and slower, more conservative results. For detailed meshes undergoing low-rank motion, we have observed speedups of over an order of magnitude with our method.
Sketch2Photo
Authors: Chen Tao , Cheng Ming-Ming , Tan Ping , Shamir Ariel , Hu Shi-Min
Published: December 2009

We present a system that composes a realistic picture from a simple freehand sketch annotated with text labels. The composed picture is generated by seamlessly stitching several photographs in agreement with the sketch and text labels; these are found by searching the Internet. Although online image search generates many inappropriate results, our system is able to automatically select suitable photographs to generate a high quality composition, using a filtering scheme to exclude undesirable images. We also provide a novel image blending algorithm to allow seamless image composition. Each blending result is given a numeric score, allowing us to find an optimal combination of discovered images. Experimental results show the method is very successful; we also evaluate our system using the results from two user studies.
Printing spatially-varying reflectance
Authors: Matusik Wojciech , Ajdin Boris , Gu Jinwei , Lawrence Jason , Lensch Hendrik P. A. , Pellacini Fabio , Rusinkiewicz Szymon
Published: December 2009

Although real-world surfaces can exhibit significant variation in materials --- glossy, diffuse, metallic, etc. --- printers are usually used to reproduce color or gray-scale images. We propose a complete system that uses appropriate inks and foils to print documents with a variety of material properties. Given a set of inks with known Bidirectional Reflectance Distribution Functions (BRDFs), our system automatically finds the optimal linear combinations to approximate the BRDFs of the target documents. Novel gamut-mapping algorithms preserve the relative glossiness between different BRDFs, and halftoning is used to produce patterns to be sent to the printer. We demonstrate the effectiveness of this approach with printed samples of a number of measured spatially-varying BRDFs.
User-assisted intrinsic images
Authors: Bousseau Adrien , Paris Sylvain , Durand Frédo
Published: December 2009

For many computational photography applications, the lighting and materials in the scene are critical pieces of information. We seek to obtainintrinsic images, which decompose a photo into the product of anilluminationcomponent that represents lighting effects and areflectancecomponent that is the color of the observed material. This is an under-constrained problem and automatic methods are challenged by complex natural images. We describe a new approach that enables users to guide an optimization with simple indications such as regions of constant reflectance or illumination. Based on a simple assumption on local reflectance distributions, we derive a new propagation energy that enables a closed form solution using linear least-squares. We achieve fast performance by introducing a novel downsampling that preserves local color distributions. We demonstrate intrinsic image decomposition on a variety of images and show applications.
Depth-of-field rendering with multiview synthesis
Authors: Lee Sungkil , Eisemann Elmar , Seidel Hans-Peter
Published: December 2009

We present a GPU-based real-time rendering method that simulates high-quality depth-of-field effects, similar in quality to multiview accumulation methods. Most real-time approaches have difficulties to obtain good approximations of visibility and view-dependent shading due to the use of a single view image. Our method also avoids the multiple rendering of a scene, but can approximate different views by relying on a layered image-based scene representation. We present several performance and quality improvements, such as early culling, approximate cone tracing, and jittered sampling. Our method achieves artifact-free results for complex scenes and reasonable depth-of-field blur in real time.
Amortized supersampling
Authors: Yang Lei , Nehab Diego , Sander Pedro V. , Sitthi-amorn Pitchaya , Lawrence Jason , Hoppe Hugues
Published: December 2009

We present a real-time rendering scheme that reuses shading samples from earlier time frames to achieve practical antialiasing of procedural shaders. Using a reprojection strategy, we maintain several sets of shading estimates at subpixel precision, and incrementally update these such that for most pixels only one new shaded sample is evaluated per frame. The key difficulty is to prevent accumulated blurring during successive reprojections. We present a theoretical analysis of the blur introduced by reprojection methods. Based on this analysis, we introduce a nonuniform spatial filter, an adaptive recursive temporal filter, and a principled scheme for locally estimating the spatial blur. Our scheme is appropriate for antialiasing shading attributes that vary slowly over time. It works in a single rendering pass on commodity graphics hardware, and offers results that surpass 4x4 stratified supersampling in quality, at a fraction of the cost.
Automatic bounding of programmable shaders for efficient global illumination
Authors: Velázquez-Armendáriz Edgar , Zhao Shuang , Hašan Miloš , Walter Bruce , Bala Kavita
Published: December 2009

This paper describes a technique to automatically adapt programmable shaders for use in physically-based rendering algorithms. Programmable shading provides great flexibility and power for creating rich local material detail, but only allows the material to be queried in one limited way: point sampling. Physically-based rendering algorithms simulate the complex global flow of light through an environment but rely on higher level information about the material properties, such as importance sampling and bounding, to intelligently solve high dimensional rendering integrals.

We propose using a compiler to automatically generate interval versions of programmable shaders that can be used to provide the higher level query functions needed by physically-based rendering without the need for user intervention or expertise. We demonstrate the use of programmable shaders in two such algorithms, multidimensional lightcuts and photon mapping, for a wide range of scenes including complex geometry, materials and lighting.
Removing image artifacts due to dirty camera lenses and thin occluders
Authors: Gu Jinwei , Ramamoorthi Ravi , Belhumeur Peter , Nayar Shree
Published: December 2009

Dirt on camera lenses, and occlusions from thin objects such as fences, are two important types of artifacts in digital imaging systems. These artifacts are not only an annoyance for photographers, but also a hindrance to computer vision and digital forensics. In this paper, we show that both effects can be described by a single image formation model, wherein an intermediate layer (of dust, dirt or thin occluders) both attenuates the incoming light and scatters stray light towards the camera. Because of camera defocus, these artifacts are low-frequency and either additive or multiplicative, which gives us the power to recover the original scene radiance pointwise. We develop a number of physics-based methods to remove these effects from digital photographs and videos. For dirty camera lenses, we propose two methods to estimate the attenuation and the scattering of the lens dirt and remove the artifacts -- either by taking several pictures of a structured calibration pattern beforehand, or by leveraging natural image statistics for post-processing existing images. For artifacts from thin occluders, we propose a simple yet effective iterative method that recovers the original scene from multiple apertures. The method requires two images if the depths of the scene and the occluder layer are known, or three images if the depths are unknown. The effectiveness of our proposed methods are demonstrated by both simulated and real experimental results.
Noise brush
Authors: Chen Jia , Tang Chi-Keung , Wang Jue
Published: December 2009

This paper proposes aninteractiveapproach usingjoint image-noise filteringfor achieving high quality image-noise separation. The core of the system is our novel joint image-noise filter which operates in both image and noise domain, and can effectively separate noise from both high and low frequency image structures. A novel user interface is introduced, which allows the user to interact with both the image and the noise layer, and apply the filter adaptively and locally to achieve optimal results. A comprehensive and quantitative evaluation shows that our interactive system can significantly improve the initial image-noise separation results. Our system can also be deployed in various noise-consistent image editing tasks, where preserving the noise characteristics inherent in the input image is a desired feature.
Edge-preserving multiscale image decomposition based on local extrema
Authors: Subr Kartic , Soler Cyril , Durand Frédo
Published: December 2009

We propose a new model for detail that inherently captures
oscillations
, a key property that distinguishes textures from individual edges. Inspired by techniques in empirical data analysis and morphological image analysis, we use the local extrema of the input image to extract information about oscillations: We define detail as oscillations between local minima and maxima. Building on the key observation that the spatial scale of oscillations are characterized by the density of local extrema, we develop an algorithm for decomposing images into multiple scales of superposed oscillations.

Current edge-preserving image decompositions assume image detail to be low contrast variation. Consequently they apply filters that extract features with increasing contrast as successive layers of detail. As a result, they are unable to distinguish between high-contrast, fine-scale features and edges of similar contrast that are to be preserved. We compare our results with existing edge-preserving image decomposition algorithms and demonstrate exciting applications that are made possible by our new notion of detail.
Debugging GPU stream programs through automatic dataflow recording and visualization
Authors: Hou Qiming , Zhou Kun , Guo Baining
Published: December 2009

We present a novel framework for debugging GPU stream programs through automatic dataflow recording and visualization. Our debugging system can help programmers locate errors that are common in general purpose stream programs but very difficult to debug with existing tools. A stream program is first compiled into an instrumented program using a compiler. This instrumenting compiler automatically adds to the original program dataflow recording code that saves the information of all GPU memory operations into log files. The resulting stream program is then executed on the GPU. With dataflow recording, our debugger automatically detects common memory errors such as out-of-bound access, uninitialized data access, and race conditions -- these errors are extremely difficult to debug with existing tools. When the instrumented program terminates, either normally or due to an error, a dataflow visualizer is launched and it allows the user to examine the memory operation history of all threads and values in all streams. Thus the user can analyze error sources by tracing through relevant threads and streams using the recorded dataflow.

A key ingredient of our debugging framework is
the GPU interrupt
, a novel mechanism that we introduce to support CPU function calls from inside GPU code. We enable interrupts on the GPU by designing a specialized compilation algorithm that translates these interrupts into GPU kernels and CPU management code. Dataflow recording involving disk I/O operations can thus be implemented as interrupt handlers. The GPU interrupt mechanism also allows the programmer to discover errors in more active ways by developing customized debugging functions that can be directly used in GPU code. As examples we show two such functions: assert for data verification and watch for visualizing intermediate results.
Real-time parallel hashing on the GPU
Authors: Alcantara Dan A. , Sharf Andrei , Abbasinejad Fatemeh , Sengupta Shubhabrata , Mitzenmacher Michael , Owens John D. , Amenta Nina
Published: December 2009

We demonstrate an efficient data-parallel algorithm for building large hash tables of millions of elements in real-time. We consider two parallel algorithms for the construction: a classical sparse perfect hashing approach, and cuckoo hashing, which packs elements densely by allowing an element to be stored in one of multiple possible locations. Our construction is a hybrid approach that uses both algorithms. We measure the construction time, access time, and memory usage of our implementations and demonstrate real-time performance on large datasets: for 5 million key-value pairs, we construct a hash table in 35.7 ms using 1.42 times as much memory as the input data itself, and we can access all the elements in that hash table in 15.3 ms. For comparison, sorting the same data requires 36.6 ms, but accessing all the elements via binary search requires 79.5 ms. Furthermore, we show how our hashing methods can be applied to two graphics applications: 3D surface intersection for moving data and geometric hashing for image matching.
Shadow art
Authors: Mitra Niloy J. , Pauly Mark
Published: December 2009

"To them, I said, the truth would be literally nothing but the shadows of the images." -Plato, The Republic

Shadow art is a unique form of sculptural art where the 2D shadows cast by a 3D sculpture are essential for the artistic effect. We introduce computational tools for the creation of shadow art and propose a design process where the user can directly specify the desired shadows by providing a set of binary images and corresponding projection information. Since multiple shadow images often contradict each other, we present a geometric optimization that computes a 3D shadow volume whose shadows best approximate the provided input images. Our analysis shows that this optimization is essential for obtaining physically realizable 3D sculptures. The resulting shadow volume can then be modified with a set of interactive editing tools that automatically respect the often intricate shadow constraints. We demonstrate the potential of our system with a number of complex 3D shadow art sculptures that go beyond what is seen in contemporary art pieces.