bluuebunny/crossref_metadata_2025 huggingface dataset:
Spatial synchrony of planthopper species with contrasting outbreak behaviour
Authors: Grilli Mariano P.
Published: September 2008

1 We studied the synchrony of two sympatric delphacids species with different outbreak behaviours over a range of 250 km in Argentina.

2 The spatial synchrony in the dynamics of Delphacodes kuscheli and Toya propinqua was quantified by collecting individuals of both species simultaneously at three sampling heights: ground, 1.5 m and 6 m above the ground. Synchrony between paired sampling sites separated by increasing distances was estimated using a nonparametric covariance function.

3 A significant difference was found between the spatial synchrony of the species studied. Delphacodes kuscheli individuals collected at 6 m above the ground showed consistent spatial synchrony over long distances with correlation values declining by 40%. Population dynamics showed declining synchrony as site separation increased. Toya propinqua populations did not show this pattern. This species had a lower mean regional synchrony at at 6 m above the ground, but their ground height synchrony was greater than that observed for D. kuscheli.

4 One possible synchronizing mechanism is seasonality and the dispersal strategies of each species. The main host plants of D. kuscheli are winter cereals sown as pasture for cattle grazing and the synchrony of the crop may affect the general pattern of dispersing individuals of this species. The lack of synchrony observed in T. propinqua populations was probably due to the wider host range of this species.
A mechanistic model based analysis of cotton aphid population dynamics data
Authors: Matis Timothy I. , Parajulee Megha N. , Matis James H. , Shrestha Ram B.
Published: September 2008

1 A 2‐year field study was conducted to generate data on seasonal abundance patterns of cotton aphids Aphis gossypii Glover and to develop a mechanistic model based on cumulative population size. The treatments consisted of three irrigation levels (Low, Medium and High) with 65%, 75% and 85% evapotranspiration replacement and three nitrogen fertility treatments (blanket‐rate‐N, variable‐rate‐N and no nitrogen).

2 A nonlinear regression equation, the analytical solution of a cumulative size mechanistic model, was fitted to each of the 27 individual data sets collected in 2003 and in 2004. The size and time of the peak, the cumulative aphid density, and the birth and death rates were estimated for each population, and each of these five variables was analyzed as a response variable in the analysis of variance.

3 For 2003 (a dry year), the Water (irrigation) main effect was found to be significant for the time of peak, the death rate and the cumulative density. The lower aphid death rate at low water levels might be due to the water stress in plants.

4 For 2004 (a year with moderate precipitation), the Nitrogen main effect was significant for both the birth and death rates. As nitrogen applications were increased, the decrease in both the aphid birth and death rates translates into a decrease in crowding and an increase in aphid survival.

5 The fact that treatment effects may be manifested through birth and death rate parameters in the new mechanistic model opens up new avenues for analyzing population size data of this kind.
Implications for conservation biocontrol of spatio‐temporal relationships between carabid beetles and coleopterous pests in winter oilseed rape
Authors: Warner D. J. , Allen‐Williams L. J. , Warrington S. , Ferguson A. W. , Williams I. H.
Published: September 2008

1 The spatio‐temporal distributions of predatory carabid beetles (Coleoptera: Carabidae) and their potential prey, the larvae of three coleopterous pests, Meligethes aeneus (Fabricius) and Ceutorhynchus spp. [Ceutorhynchus pallidactylus (Marsham), the cabbage stem weevil, and Ceutorhynchus assimilis (Paykull), the cabbage seed weevil], were studied within a crop of winter oilseed rape. The distributions of Collembola were recorded as potential alternative prey. Insect distributions were analysed and compared using Spatial Analysis by Distance Indices.

2 Mature larvae of the pests dropped from the crop canopy to the soil for pupation in temporal succession from May to early July. Their distributions within the crop were irregular and differed with species.

3 Adults of seven species or genera of carabid were abundant and active within the crop during May and June: Nebria brevicollis (Fabricius), Anchomenus dorsalis (Pontoppidan), Loricera pilicornis (Fabricius), Amara similata (Gyllenhal), Asaphidion spp., Pterostichus madidus (Fabricius) and Pterostichus melanarius (Illiger).

4 During May, N. brevicollis was spatially associated with peak numbers of M. aeneus larvae and with Collembola. Anchomenus dorsalis was spatially associated with Ceutorhynchus spp. larvae during two peaks in the abundance of the latter in early and late June. Nebria brevicollis and A. dorsalis coincided in both time and space with larvae of the three coleopterous pests when they were most vulnerable to predation by epigeal predators and are therefore good candidates for conservation biocontrol.

5 The importance of carabid beeetles in the natural enemy complex in winter oilseed rape and their potential for biocontrol of spring and summer pests are discussed in relation to husbandry practices for the crop and its adjacent areas which could be manipulated to promote carabid survival for integrated pest management.
Parasitism and dispersal potential of Sirex noctilio: implications for biological control
Authors: Villacide José M. , Corley Juan C.
Published: September 2008

1 Sirex noctilio F. (Hymenoptera: Siricidae) is a wood‐boring wasp that attacks many pine species, including commercial trees planted throughout the world. Management of its populations is largely based on biological control using the nematode Beddingia siricidicola. Adult females are sterilized by the nematode, but are free to move and attack new trees, promoting nematode dispersal. Although generally successful, wasp management through nematode introductions has sometimes been inadequate.

2 We evaluated the effect of parasitism by B. siricidicola on flight performance of woodwasps under laboratory conditions. Using flight mills, we recorded a total of 46 flight trials over 23 h, obtained from infected and control (uninfected) females.

3 Although all wasps lost weight during flight, parasitized females were significantly smaller and suffered larger weight losses than uninfected females. In addition, total flight distance and velocity were lower in parasitized females.

4 Because nematode infection transmission relies on healthy wasps attacking trees previously visited by nematode‐bearing females, differential dispersal capacity could limit biological control success.
Wheat stem sawfly‐infested plants benefit from parasitism of the herbivorous larvae
Authors: Buteler Micaela , Weaver David K. , Miller Perry R.
Published: September 2008

1 Parasitoids Bracon cephi (Gahan) and Bracon lissogaster Muesebeck and their herbivorous host the wheat stem sawfly Cephus cinctus Norton, a pest of wheat Triticum aestivum, were investigated for yield in T. aestivum grown in the field.

2 Wheat stem sawfly‐infested stems had a higher yield potential than uninfested stems. However, final reproductive output was not significantly different between ears on infested stems that supported complete larval development compared with ears on uninfested stems.

3 Stems containing parasitized larvae and stems containing larvae that died before completing their development had a higher mean number of seeds and seed weight, when accounting for number of fertile spikelets of each ear, than either infested with live larvae and uninfested stems.

4 The results obtained suggest that larval feeding prevented infested stems from attaining their yield potential, and that the negative impact of the pest on wheat yield was reduced when late instar sawfly larvae were parasitized. Even though some feeding occurs before parasitism, this early damage has a comparatively low impact on yield.

5 This is the first study to show a yield benefit and enhanced plant fitness due to the wheat stem sawfly parasitoids B. cephi and B. lissogaster. This results from the maintenance of increased seed number and seed weight in the higher yielding stems that are preferentially infested by this pest.
Diversity and species composition of West African ungulate assemblages: effects of fire, climate and soil
Authors: Klop Erik , Prins Herbert H. T.
Published: September 2008

Aim Anthropogenic fires are a major component of the ecology of rangelands throughout the world. To assess the effects of these fires on the diversity patterns of herbivores, we related gradients in fire occurrence, climate and soil fertility to patterns in alpha and beta diversity of African ungulates.

Location West Africa.

Methods We used a survey‐based approach for ungulates in 37 protected areas in desert, savanna and rain forest habitats throughout West Africa, combined with satellite images of fire occurrence and digital maps of actual evapotranspiration and soil fertility. Alpha diversity was related to the environmental variables using conventional and spatial regression models. We investigated beta diversity using partial Mantel tests and ordination techniques, and by partitioning the variance in assemblage composition into environmental and spatial components.

Results The species richness of grazers showed a quadratic relationship with actual evapotranspiration, whereas that of browsers and frugivores showed a linear relationship. However, in the multiple regression models fire occurrence was the only variable that significantly correlated with the species richness of grazers. Soil fertility was weakly related to overall beta diversity and the species richness of browsers, but was non‐significant in the multiple regression models. Fire occurrence was the most important variable explaining species composition of the overall species set and of grazers, whereas the assemblage composition of browsers and frugivores was explained mostly by actual evapotranspiration.

Main conclusions In contrast to previous studies, our analyses show that moisture and nutrients alone fail to adequately predict the diversity patterns of grazing ungulates. Rather, the species richness and assemblage composition of grazers are largely governed by anthropogenic fires that modify the quality and structure of the grass sward. Diversity patterns of browsers and frugivores are markedly different from grazers and depend mainly on the availability of moisture, which is positively correlated with the availability of foliage and fruits. Our study highlights the importance of incorporating major human‐induced disturbances or habitat alterations into analyses of diversity patterns.
A Psychophysical Evaluation of Inverse Tone Mapping Techniques
Authors: Banterle Francesco , Ledda Patrick , Debattista Kurt , Bloj Marina , Artusi Alessandro , Chalmers Alan
Published: September 2008

In recent years inverse tone mapping techniques have been proposed for enhancing low‐dynamic range (LDR) content for a high‐dynamic range (HDR) experience on HDR displays, and for image based lighting. In this paper, we present a psychophysical study to evaluate the performance of inverse (reverse) tone mapping algorithms. Some of these techniques are computationally expensive because they need to resolve quantization problems that can occur when expanding an LDR image. Even if they can be implemented efficiently on hardware, the computational cost can still be high. An alternative is to utilize less complex operators; although these may suffer in terms of accuracy. Our study investigates, firstly, if a high level of complexity is needed for inverse tone mapping and, secondly, if a correlation exists between image content and quality. Two main applications have been considered: visualization on an HDR monitor and image‐based lighting.
Camera Control in Computer Graphics
Authors: Christie Marc , Olivier Patrick , Normand Jean‐Marie
Published: September 2008

Recent progress in modelling, animation and rendering means that rich, high fidelity virtual worlds are found in many interactive graphics applications. However, the viewer's experience of a 3D world is dependent on the nature of the virtual cinematography, in particular, the camera position, orientation and motion in relation to the elements of the scene and the action. Camera control encompasses viewpoint computation, motion planning and editing. We present a range of computer graphics applications and draw on insights from cinematographic practice in identifying their different requirements with regard to camera control. The nature of the camera control problem varies depending on these requirements, which range from augmented manual control (semi‐automatic) in interactive applications, to fully automated approaches. We review the full range of solution techniques from constraint‐based to optimization‐based approaches, and conclude with an examination of occlusion management and expressiveness in the context of declarative approaches to camera control.
High Performance GPU‐based Proximity Queries using Distance Fields
Authors: Morvan T. , Reimers M. , Samset E.
Published: September 2008

Proximity queries such as closest point computation and collision detection have many applications in computer graphics, including computer animation, physics‐based modelling, augmented and virtual reality. We present efficient algorithms for proximity queries between a closed rigid object and an arbitrary, possibly deformable, polygonal mesh. Using graphics hardware to densely sample the distance field of the rigid object over the arbitrary mesh, we compute minimal proximity and collision response information on the graphics processing unit (GPU) using blending and depth buffering, as well as parallel reduction techniques, thus minimizing the readback bottleneck. Although limited to image‐space resolution, our algorithm provides high and steady performance when compared with other similar algorithms. Proximity queries between arbitrary meshes with hundreds of thousands of triangles and detailed distance fields of rigid objects are computed in a few milliseconds at high‐sampling resolution, even in situations with large overlap.
3D Slit Scanning with Planar Constraints★
Authors: Leotta Matthew J. , Vandergon Austin , Taubin Gabriel
Published: September 2008

We present a planarity constraint and a novel three‐dimensional (3D) point reconstruction algorithm for a multiview laser range slit scanner. The constraint is based on the fact that all observed points on a projected laser line lie on the same plane of laser light in 3D. The parameters of the plane of laser light linearly parametrize a homography between a pair of images of the laser points. This homography can be recovered from point correspondences derived from epipolar geometry. The use of the planar constraint reduces outliers in the reconstruction and allows for the reconstruction of points seen in only one view. We derive an optimal reconstruction of points subject to the planar constraint and compare the accuracy to the suboptimal approach in prior work. We also construct a catadioptric stereo rig with high quality optical components to remove error due to camera synchronization and non‐uniform laser projection. The reconstruction results are compared to prior work that uses inexpensive optics and two cameras.
Diffusion Based Photon Mapping
Authors: Schjøth L. , Sporring J. , Fogh Olsen O.
Published: September 2008

Density estimation employed in multi‐pass global illumination algorithms give cause to a trade‐off problem between bias and noise. The problem is seen most evident as blurring of strong illumination features. In particular, this blurring erodes fine structures and sharp lines prominent in caustics. To address this problem, we introduce a photon mapping algorithm based on nonlinear anisotropic diffusion. Our algorithm adapts according to the structure of the photon map such that smoothing occurs along edges and structures and not across. In this way, we preserve important illumination features, while eliminating noise. We demonstrate the applicability of our algorithm through a series of tests. In the tests, we evaluate the visual and computational performance of our algorithm comparing it to existing popular algorithms.
Adaptive Surface Texture Synthesis Using Round‐Shaped Neighbourhoods
Authors: Chen D. , Dong F.
Published: September 2008

This paper presents a novel surface texture synthesis method, which is capable of producing high‐quality results by performing the synthesis within an effective multi‐resolution scheme using an adaptive texture similarity metric. Compared with related works, our method allows us to directly carry out multi‐resolution synthesis without involving complicated operations such as mesh hierarchy and partitioning on the target surface. Also, the adaptive similarity metric focuses on measuring texture properties at different scales ranging from local to global, allowing for consistency within differently‐sized texture structures. Further, with the introduced round shaped neighbourhoods, we can save considerable amount of computation for the surface texture synthesis over variable texture directions. Experimental results are provided and comparisons are made against other latest works.
Tensor Clustering for Rendering Many‐Light Animations
Authors: Hašan Miloš , Velázquez‐Armendáriz Edgar , Pellacini Fabio , Bala Kavita
Published: September 2008

Rendering animations of scenes with deformable objects, camera motion, and complex illumination, including indirect lighting and arbitrary shading, is a long‐standing challenge. Prior work has shown that complex lighting can be accurately approximated by a large collection of point lights. In this formulation, rendering of animation sequences becomes the problem of efficiently shading many surface samples from many lights across several frames. This paper presents a tensor formulation of the animated many‐light problem, where each element of the tensor expresses the contribution of one light to one pixel in one frame. We sparsely sample rows and columns of the tensor, and introduce a clustering algorithm to select a small number of representative lights to efficiently approximate the animation. Our algorithm achieves efficiency by reusing representatives across frames, while minimizing temporal flicker. We demonstrate our algorithm in a variety of scenes that include deformable objects, complex illumination and arbitrary shading and show that a surprisingly small number of representative lights is sufficient for high quality rendering. We believe out algorithm will find practical use in applications that require fast previews of complex animation.
An Analysis of the In‐Out BRDF Factorization for View‐Dependent Relighting
Authors: Mahajan Dhruv , Tseng Yu‐Ting , Ramamoorthi Ravi
Published: September 2008

Interactive rendering with dynamic natural lighting and changing view is a long‐standing goal in computer graphics. Recently, precomputation‐based methods for all‐frequency relighting have made substantial progress in this direction. Many of the most successful algorithms are based on a factorization of the BRDF into incident and outgoing directions, enabling each term to be precomputed independent of viewing direction, and re‐combined at run‐time. However, there has so far been no theoretical understanding of the accuracy of this factorization, nor the number of terms needed. In this paper, we conduct a theoretical and empirical analysis of the BRDF in‐out factorization. For Phong BRDFs, we obtain analytic results, showing that the number of terms needed grows linearly with the Phong exponent, while the factors correspond closely to spherical harmonic basis functions. More generally, the number of terms is quadratic in the frequency content of the BRDF along the reflected or half‐angle direction. This analysis gives clear practical guidance on the number of factors needed for a given material. Different objects in a scene can each be represented with the correct number of terms needed for that particular BRDF, enabling both accuracy and interactivity.
Real‐time Shading with Filtered Importance Sampling
Authors: Křivánek Jaroslav , Colbert Mark
Published: September 2008

We propose an analysis of numerical integration based on sampling theory, whereby the integration error caused by aliasing is suppressed by pre‐filtering. We derive a pre‐filter for evaluating the illumination integral yielding filtered importance sampling, a simple GPU‐based rendering algorithm for image‐based lighting. Furthermore, we extend the algorithm with real‐time visibility computation. Free from any pre‐computation, the algorithm supports fully dynamic scenes and, above all, is simple to implement.
Ptex: Per‐Face Texture Mapping for Production Rendering
Authors: Burley Brent , Lacewell Dylan
Published: September 2008

Explicit parameterization of subdivision surfaces for texture mapping adds significant cost and complexity to film production. Most parameterization methods currently in use require setup effort, and none are completely general. We propose a new texture mapping method for Catmull‐Clark subdivision surfaces that requires no explicit parameterization. Our method, Ptex, stores a separate texture per quad face of the subdivision control mesh, along with a novel per‐face adjacency map, in a single texture file per surface. Ptex uses the adjacency data to perform seamless anisotropic filtering of multi‐resolution textures across surfaces of arbitrary topology. Just as importantly, Ptex requires no manual setup and scales to models of arbitrary mesh complexity and texture detail. Ptex has been successfully used to texture all of the models in an animated theatrical short and is currently being applied to an entire animated feature. Ptex has eliminated UV assignment from our studio and significantly increased the efficiency of our pipeline.
Lazy Solid Texture Synthesis
Authors: Dong Yue , Lefebvre Sylvain , Tong Xin , Drettakis George
Published: September 2008

Existing solid texture synthesis algorithms generate a full volume of color content from a set of 2D example images. We introduce a new algorithm with the unique ability to restrict synthesis to a subset of the voxels, while enforcing spatial determinism. This is especially useful when texturing objects, since only a thick layer around the surface needs to be synthesized. A major difficulty lies in reducing the dependency chain of neighborhood matching, so that each voxel only depends on a small number of other voxels.

Our key idea is to synthesize a volume from a set of pre‐computed 3D candidates, each being a triple of interleaved 2D neighborhoods. We present an efficient algorithm to carefully select in a pre‐process only those candidates forming consistent triples. This significantly reduces the search space during subsequent synthesis. The result is a new parallel, spatially deterministic solid texture synthesis algorithm which runs efficiently on the GPU.

Our approach generates high resolution solid textures on surfaces within seconds. Memory usage and synthesis time only depend on the output textured surface area. The GPU implementation of our method rapidly synthesizes new textures for the surfaces appearing when interactively breaking or cutting objects.
Geometry‐Aware Framebuffer Level of Detail
Authors: Yang Lei , Sander Pedro V. , Lawrence Jason
Published: September 2008

This paper introduces a framebuffer level of detail algorithm for controlling the pixel workload in an interactive rendering application. Our basic strategy is to evaluate the shading in a low resolution buffer and, in a second rendering pass, resample this buffer at the desired screen resolution. The size of the lower resolution buffer provides a trade‐off between rendering time and the level of detail in the final shading. In order to reduce approximation error we use a feature‐preserving reconstruction technique that more faithfully approximates the shading near depth and normal discontinuities. We also demonstrate how intermediate components of the shading can be selectively resized to provide finer‐grained control over resource allocation. Finally, we introduce a simple control mechanism that continuously adjusts the amount of resizing necessary to maintain a target framerate. These techniques do not require any preprocessing, are straightforward to implement on modern GPUs, and are shown to provide significant performance gains for several pixel‐bound scenes.
Rendering Trees with Indirect Lighting in Real Time
Authors: Boulanger K. , Bouatouch K. , Pattanaik S.
Published: September 2008

High quality lighting is one of the challenges for interactive tree rendering. To this end, this paper presents a lighting model allowing real‐time rendering of trees with convincing indirect lighting. Rather than defining an empirical model to mimic lighting of real trees, we work at a lower level by modeling the spatial distribution of leaves and by assigning them probabilistic properties. We focus mainly on precise low‐frequency lighting that our eyes are more sensitive to and we add high‐frequency details afterwards. The resulting model is efficient and simple to implement on a GPU.
Feature‐guided Image Stippling
Authors: Kim Dongyeon , Son Minjung , Lee Yunjin , Kang Henry , Lee Seungyong
Published: September 2008

This paper presents an automatic method for producing stipple renderings from photographs, following the style of professional hedcut illustrations. For effective depiction of image features, we introduce a novel dot placement algorithm which adapts stipple dots to the local shapes. The core idea is to guide the dot placement along ‘feature flow’ extracted from the feature lines, resulting in a dot distribution that conforms to feature shapes. The sizes of dots are adaptively determined from the input image for proper tone representation. Experimental results show that such feature‐guided stippling leads to the production of stylistic and feature‐emphasizing dot illustrations.
iCheat: A Representation for Artistic Control of Indirect Cinematic Lighting
Authors: Obert Juraj , Křrivánek Jaroslav , Pellacini Fabio , Sýkora Daniel , Pattanaik Sumanta
Published: September 2008

Thanks to an increase in rendering efficiency, indirect illumination has recently begun to be integrated in cinematic lighting design, an application where physical accuracy is less important than careful control of scene appearance. This paper presents a comprehensive, efficient, and intuitive representation for artistic control of indirect illumination. We encode user's adjustments to indirect lighting as scale and offset coefficients of the transfer operator. We take advantage of the nature of indirect illumination and of the edits themselves to efficiently sample and compress them. A major benefit of this sampled representation, compared to encoding adjustments as procedural shaders, is the renderer‐independence. This allowed us to easily implement several tools to produce our final images: an interactive relighting engine to view adjustments, a painting interface to define them, and a final renderer to render high quality results. We demonstrate edits to scenes with diffuse and glossy surfaces and animation.
Compact, Fast and Robust Grids for Ray Tracing
Authors: Lagae Ares , Dutré Philip
Published: September 2008

The focus of research in acceleration structures for ray tracing recently shifted from render time to time to image, the sum of build time and render time, and also the memory footprint of acceleration structures now receives more attention. In this paper we revisit the grid acceleration structure in this setting. We present two efficient methods for representing and building a grid. The compact grid method consists of a static data structure for representing a grid with minimal memory requirements, more specifically exactly one index per grid cell and exactly one index per object reference, and an algorithm for building that data structure in linear time. The hashed grid method reduces memory requirements even further, by using perfect hashing based on row displacement compression. We show that these methods are more efficient in both time and space than traditional methods based on linked lists and dynamic arrays. We also present a more robust grid traversal algorithm. We show that, for applications where time to image or memory usage is important, such as interactive ray tracing and rendering large models, the grid acceleration structure is an attractive alternative.
Combining Confocal Imaging and Descattering
Authors: Fuchs Christian , Heinz Michael , Levoy Marc , Seidel Hans‐Peter , Lensch Hendrik P. A.
Published: September 2008

In translucent objects, light paths are affected by multiple scattering, which is polluting any observation. Confocal imaging reduces the influence of such global illumination effects by carefully focusing illumination and viewing rays from a large aperture to a specific location within the object volume. The selected light paths still contain some global scattering contributions, though. Descattering based on high frequency illumination serves the same purpose. It removes the global component from observed light paths. We demonstrate that confocal imaging and descattering are orthogonal and propose a novel descattering protocol that analyzes the light transport in a neighborhood of light transport paths. In combination with confocal imaging, our descattering method achieves optical sectioning in translucent media with higher contrast and better resolution.
Enhancement of Bright Video Features for HDR Displays
Authors: Didyk P. , Mantiuk R. , Hein M. , Seidel H.P.
Published: September 2008

To utilize the full potential of new high dynamic range (HDR) displays, a system for the enhancement of bright luminous objects in video sequences is proposed. The system classifies clipped (saturated) regions as lights, reflections or diffuse surfaces using a semi‐automatic classifier and then enhances each class of objects with respect to its relative brightness. The enhancement algorithm can significantly stretch the contrast of clipped regions while avoiding amplification of noise and contouring. We demonstrate that the enhanced video is strongly preferred to non‐enhanced video, and it compares favorably to other methods.
Free Form Incident Light Fields
Authors: Unger J. , Gustavson S. , Larsson P. , Ynnerman A.
Published: September 2008

This paper presents methods for photo‐realistic rendering using strongly spatially variant illumination captured from real scenes. The illumination is captured along arbitrary paths in space using a high dynamic range, HDR, video camera system with position tracking. Light samples are rearranged into 4‐D incident light fields (ILF) suitable for direct use as illumination in renderings. Analysis of the captured data allows for estimation of the shape, position and spatial and angular properties of light sources in the scene. The estimated light sources can be extracted from the large 4D data set and handled separately to render scenes more efficiently and with higher quality. The ILF lighting can also be edited for detailed artistic control.
Accelerating Ray Tracing using Constrained Tetrahedralizations
Authors: Lagae Ares , Dutré Philip
Published: September 2008

In this paper we introduce the constrained tetrahedralization as a new acceleration structure for ray tracing. A constrained tetrahedralization of a scene is a tetrahedralization that respects the faces of the scene geometry. The closest intersection of a ray with a scene is found by traversing this tetrahedralization along the ray, one tetrahedron at a time. We show that constrained tetrahedralizations are a viable alternative to current acceleration structures, and that they have a number of unique properties that set them apart from other acceleration structures: constrained tetrahedralizations are not hierarchical yet adaptive; the complexity of traversing them is a function of local geometric complexity rather than global geometric complexity; constrained tetrahedralizations support deforming geometry without any effort; and they have the potential to unify several data structures currently used in global illumination.
Urinary incontinence and use of pads – clinical features and need for help in home care at 11 sites in Europe
Authors: Sørbye Liv Wergeland , Finne‐Soveri Harriet , Ljunggren Gunnar , Topinkova Eva , Garms‐Homolova Vjenka , Jensdóttir Anne Birna , Bernabei Roberto ,   for AdHOC Project Research Group
Published: September 2008

Aim:  The aim of this study was to obtain evidenced‐based knowledge about older persons in home care; we conducted a population‐based study at 11 sites in Europe (2001/2002). This article focuses on urinary incontinence and need for help in home care.

Methods:  A sample of 4010 respondents 65 years or older were assessed by the Resident Assessment Instrument for Home Care. Urinary incontinence was defined as leakage once a week or more including use of catheters.

Results:  A total of 1478 individuals had urinary incontinence, 45% men and 47% women. The use of pads ran from 29% to 52% between the sites. The associates of urinary incontinence were: moderate or severe cognitive impairment, dependency in toileting and other activities of daily living compared with less impaired; urinary infections, obesity and faecal incontinence. Caregivers to persons with urinary incontinence reported burden or stress more often then carers to nonurinary incontinence individuals (OR = 2.2, 95% CI 1.8–2.7).

Conclusions:  To enable older people with incontinence to stay at home with a better quality of life, they need caring assistance during toileting on a regular basis.
Patient‐related barriers to cancer pain management: a systematic exploratory review
Authors: Jacobsen Ramune , Møldrup Claus , Christrup Lona , Sjøgren Per
Published: September 2008

The aim of this review was to systemically explore the current evidence regarding patient‐related barriers to cancer pain management to find new areas that might be important for better understanding of patient barriers’ phenomenon. The method used in this study was a computerised literature search, carried out in Cochrane Library, Medline (through PubMed), Web of Science and EMBASE databases for the period 1994–2005. Thirty‐seven studies, dealing with cognitive, sensory and affective patient‐related barriers, as well as studies, describing patients’ pain communication and their adherence to analgesic regimen were included and analysed. The dominant part of articles studied cognitive patient‐related barriers to cancer pain management, while affective, sensory barriers, as well as pain communication and pain medication adherence were studied in much less extend. However, the findings from different studies regarding relationships between cognitive barriers and pain intensity were not consistent. On the contrary, the quality of pain communication was consistently found to be not satisfactory in some key areas. The associations between more expressed attitudinal as well as sensory barriers and less optimal adherence were also consistent. In conclusions suggestion for the new research areas on patient‐related barriers to cancer pain management are made. Firstly, further research is needed to differentiate the role of cognitive, affective and sensory factors with respect to their impact on pain relief, pain communication and medication adherence. Besides that, validated instruments to assess patients’ pain communication and adherence to analgesic regimen are lacking.
Continuity created by nurses in the perioperative dialogue – a literature review
Authors: Lindwall Lillemor , Von Post Iréne
Published: September 2008

This literature review analyses eight research reports dealing with perioperative dialogues conducted between patients and nurses. The aim of this study was to summarise studies concerned with the perioperative dialogue as an organisation model for bringing safe operative practices and caring into perioperative nursing, by creating continuity for both patients and nurses in perioperative praxis and its research. How do patients and perioperative nurses experience the perioperative dialogue as a model? Perioperative nursing should be perceived as a caring profession emphasising that the focus is on perioperative caring. The perioperative dialogue has a humanistic and caring perspective and presents an ideal model on which to base perioperative nursing. There is general acceptance of the value of the perioperative dialogue for both patients and nurses as means of alleviating suffering and creating a safety nursing, with continuity in the process provided by nursing staff. This study suggests further research and that a means of measuring caring in the perioperative dialogue should be more developed.
Tradition in transition – intergenerational relations with focus on the aged and their family members in a South African context
Authors: Bohman Doris M. , Van Wyk Neltjie C. , Ekman Sirkka‐Liisa
Published: September 2008

This study describes the intergenerational relations influence on the care of the aged in a transitional period expressed by a group of aged South Africans and their family members. Focused ethnographic research was carried out from 2001 to 2006 in a semi‐rural area in central South Africa. Twenty‐nine participants representing 16 families took part in multiple group interviews. The data was supplemented through individual interviews with 10 of the participants as well as home visits, participation in community activities, notes and video recording. The transcribed interview texts were analysed using qualitative content analysis. The study shows aspects of tradition in transition as reciprocal care between generations, the significance of traditional values and the impact of modernization on care. The findings reveal the on going transition in Africa influencing the role of the aged as well as the reciprocal care within the extended family. The study also discloses that in reciprocal relationships, family members do not necessarily have a biological bond and that revaluing of traditions can be seen as a response to social and economic change and as a tool to maintain influence. This ethnographic study contributes knowledge in the field of gerontological care, by illuminating the impact of transition on the role of aged as well as the caring of the aged in the extended family an important issue for health professionals caring for a growing number of older persons in Southern Africa and in countries with a large representation of minority groups from developing countries.
Effect of Tyr‐MIF‐1 peptides on blood ACTH and corticosterone concentration induced by three experimental models of stress
Authors: Bocheva A. , Dzambazova E. , Hadjiolova R. , Traikov L. , Mincheva R. , Bivolarski I.
Published: September 2008

1 Studies, using a wide variety of stressors, have clearly indicated that the pattern of neuroendocrine response is dependent upon the stress stimulus applied.

2 The Tyr‐MIF‐1 family of peptides (Tyr‐MIF‐1s) includes MIF‐1, Tyr‐MIF‐1, Tyr‐W‐MIF‐1 and Tyr‐K‐MIF‐1. These neuropeptides, neuromodulators are able to inhibit the expression of some forms of stress‐induced analgesia.

3 The aim of this study was to compare changes in ACTH and corticosterone (CORT) concentration after various stressors (immobilization, cold and heat), as well as after injection of investigated Tyr‐MIF‐1s peptides.

4 According to our results, hypothalamic‐pituitary‐adrenal (HPA) system was activated by all the stressors applied. Heat and immobilization are stronger stressors, as the exposure of animals to a high ambient temperature and immobilization resulted in the highest rise of plasma ACTH and CORT concentration when compared with cold stress. Moreover, all the investigated peptides from Tyr‐MIF‐1 family, administered after application of stressors, inhibited the elevations in adrenocorticotropic hormone (ACTH) and corticosterone (CORT) plasma concentrations significantly.

5 In conclusion, the various stressors applied seem to induce a different response of the HPA system as judged by quantitative changes in ACTH and CORT release. We suggest that Tyr‐MIF‐1 peptides may possess anti‐stressor effects, as they inhibited stress‐induced rising in two hormones that were investigated.
Growing up with epilepsy: A two‐year investigation of cognitive development in children with new onset epilepsy
Authors: Hermann Bruce P. , Jones Jana E. , Sheth Raj , Koehn Monica , Becker Tara , Fine Jason , Allen Chase A. , Seidenberg Michael
Published: September 2008

Purpose: To characterize patterns and determinants of normal and abnormal cognitive development in children with new onset epilepsy compared to healthy controls.

Methods: Longitudinal (2‐year) cognitive growth was examined in 100 children, age 8–18 years, including healthy controls (n = 48) and children with new onset epilepsy (n = 52). Cognitive maturation was examined as a function of the presence/absence of two neurobehavioral comorbitiies (attention deficit hyperactivity disorder and/or academic problems) identified at the time of epilepsy diagnosis. Groups were compared across a comprehensive neuropsychological battery assessing intelligence, academic achievement, language, memory, executive function, and psychomotor speed.

Results: Children with new onset epilepsy without neurobehavioral comorbidities were comparable to healthy controls at baseline, rate of cognitive development, and follow‐up assessment across all neuropsychological domains. In contrast, the presence of neurobehavioral comorbidities was associated with significantly worse baseline and prospective cognitive trajectories across all cognitive  domains, especially executive functions.

Conclusion: The presence of neurobehavioral comorbidities at the time of epilepsy onset is a major marker of abnormal cognitive development both prior to and after the onset of epilepsy.
Local Bank Financial Constraints and Firm Access to External Finance
Authors: PARAVISINI DANIEL
Published: September 2008

I exploit the exogenous component of a formula‐based allocation of government funds across banks in Argentina to test for financial constraints and underinvestment by local banks. Banks are found to expand lending by $0.66 in response to an additional dollar of external financing. Using novel data to measure risk and return on marginal lending, I show that the profitability of lending does not decline and total borrower debt increases during lending expansions, holding investment opportunities constant. Overall, financial shocks to constrained banks are found to have a quick, persistent, and amplified effect on the aggregate supply of credit.
The Value of Financial Flexibility
Authors: GAMBA ANDREA , TRIANTIS ALEXANDER
Published: September 2008

We develop a model that endogenizes dynamic financing, investment, and cash retention/payout policies in order to analyze the effect of financial flexibility on firm value. We show that the value of financing flexibility depends on the costs of external financing, the level of corporate and personal tax rates that determine the effective cost of holding cash, the firm's growth potential and maturity, and the reversibility of capital. Through simulations, we demonstrate that firms facing financing frictions should simultaneously borrow and lend, and we examine the nature of dynamic debt and liquidity policies and the value associated with corporate liquidity.
Marketwide Private Information in Stocks: Forecasting Currency Returns
Authors: ALBUQUERQUE RUI , DE FRANCISCO EVA , MARQUES LUIS B.
Published: September 2008

We present a model of equity trading with informed and uninformed investors where informed investors trade on firm‐specific and marketwide private information. The model is used to identify the component of order flow due to marketwide private information. Estimated trades driven by marketwide private information display little or no correlation with the first principal component in order flow. Indeed, we find that co‐movement in order flow captures variation mostly in liquidity trades. Marketwide private information obtained from equity market data forecasts industry stock returns, and also currency returns.
Cross‐Asset Speculation in Stock Markets
Authors: BERNHARDT DAN , TAUB BART
Published: September 2008

In practice, heterogeneously informed speculators combine private information about multiple stocks with information in prices, taking into account how their trades influence the inferences of other speculators via prices. We show how this speculation causes prices to be more correlated than asset fundamentals, raising price volatility. The covariance structure of asset fundamentals drives that of prices, while the covariance structure of liquidity trade drives that of order flows. We characterize how speculator profits vary with the distributions of information and liquidity trade across assets and speculators, and relate the cross‐asset factor structure of order flows to that of returns.
The Dog That Did Not Bark: Insider Trading and Crashes
Authors: MARIN JOSE M. , OLIVIER JACQUES P.
Published: September 2008

This paper documents that at the individual stock level, insiders' sales peak many months before a large drop in the stock price, while insiders' purchases peak only the month before a large jump. We provide a theoretical explanation for this phenomenon based on trading constraints and asymmetric information. A key feature of our theory is that rational uninformed investors may react more strongly to the absence of insider sales than to their presence (the “dog that did not bark” effect). We test our hypothesis against competing stories, such as insiders timing their trades to evade prosecution.
“You Can Enter but You Cannot Leave…”: U.S. Securities Markets and Foreign Firms
Authors: MAROSI ANDRÁS , MASSOUD NADIA
Published: September 2008

Although a number of prior papers have argued the benefits to foreign firms of cross‐listing their shares in the U.S., the number of foreign firms exiting U.S. capital markets has been increasing. This has occurred despite the difficulties foreign firms face in deregistering from the Securities and Exchange Commission (SEC). This paper examines the reasons underlying this trend. One of our main findings is that the passage of the Sarbanes‐Oxley Act has reduced the net benefits of a U.S. listing and registration, particularly for smaller foreign firms with lower trading volume and stronger insider control.
Buyer–Supplier Relationships and the Stakeholder Theory of Capital Structure
Authors: BANERJEE SHANTANU , DASGUPTA SUDIPTO , KIM YUNGSAN
Published: September 2008

Firms in bilateral relationships are likely to produce or procure unique products—especially when they are in durable goods industries. Consistent with the arguments of Titman and Titman and Wessels, such firms are likely to maintain lower leverage. We compile a database of firms' principal customers (those that account for at least 10% of sales or are otherwise considered important for business) from the Business Information File of Compustat and find results consistent with the predictions of this theory.