bluuebunny/crossref_metadata_2025 huggingface dataset:
Opening of the blood–brain barrier during isoflurane anaesthesia
Authors: Tétrault Samuel , Chever Oana , Sik Attila , Amzica Florin
Published: September 2008

In order to produce its desired effect, anaesthesia acts upon neuronal elements by modifying membrane conductances and transmitter interactions. The effect of higher doses of isoflurane, widely used in clinical settings, on the permeability of the blood–brain barrier (BBB) is meanwhile ignored. In this study we investigated the integrity of the BBB during various levels of isoflurane anaesthesia (1% and 3%) in cats by monitoring the extravasation of Evans blue. Simultaneously we measured the electroencephalogram (EEG), with particular emphasis on its direct current (DC) component. High doses of anaesthetic (3%) broke down the BBB in the cortex and thalamus, while milder doses (1%) only opened the BBB in the thalamus. The fluorescent signal of Evans blue was visible over an extravascular length of 23 μm in the cortex and 25 μm in the thalamus, similar to the diffusion of the same dye when the BBB was disrupted with mannitol. The opening of the BBB was associated with (i) a positive DC shift in the EEG measured on the scalp and (ii) an evaluated increase in cerebral volume of 2–2.8%. The opening of the BBB by high doses of isoflurane brings into discussion hitherto unexplored effects of anaesthesia on the brain. The electrophysiological correlate provided by the DC component of the EEG constitutes a promising option for the assessment of the BBB integrity during human anaesthesia.
Mechanisms of platelet‐derived growth factor‐mediated neuroprotection – implications in HIV dementia
Authors: Peng Fuwang , Dhillon Navneet K. , Yao Honghong , Zhu Xuhui , Williams Rachel , Buch Shilpa
Published: September 2008

Platelet‐derived growth factor (PDGF) has been implicated in promoting survival and proliferation of immature neurons, and even protecting neurons from gp120‐induced cytotoxicity. However, the mechanisms involved in neuroprotection are not well understood. In the present study we demonstrate the role of phosphatidylinositol 3‐kinase (PI3K)/Akt signaling in PDGF‐mediated neuroprotection. Pharmacological inhibition of PI3K greatly reduced the ability of PDGF‐BB to block gp120 IIIB‐mediated apoptosis and cell death in human neuroblastoma cells. The role of Akt in PDGF‐mediated protection was further corroborated using a dominant‐negative mutant of Akt, which was able to block the protective effect of PDGF. We next sequentially examined the signals downstream of Akt in PDGF‐mediated protection in human neuroblastoma cells. In cells pretreated with PDGF prior to gp120 there was increased phosphorylation of both GSK‐3β and Bad, an effect that was inhibited by PI3‐kinase inhibitor. Nuclear translocation of NF‐κB, which lies downstream of GSK‐3β, however, remained unaffected in cells treated with PDGF. In addition to inducing phosphorylation of Bad, PDGF‐mediated protection also involved down‐regulation of the proapoptotic protein Bax. Furthermore, PDGF‐mediated protection also involved the inhibition of gp120‐induced release of mitochondrial cytochrome C. Our findings thus underscore the roles of both PI3K/Akt and Bcl family pathways in PDGF‐mediated neuroprotection.
C1 neurons in the rat rostral ventrolateral medulla differentially express vesicular monoamine transporter 2 in soma and axonal compartments
Authors: Sevigny C. P. , Bassi J. , Teschemacher A. G. , Kim K. S. , Williams D. A. , Anderson C. R. , Allen A. M.
Published: September 2008

Vesicular monoamine transporter 2 (VMAT2) packages biogenic amines into large dense core and synaptic vesicles for either somatodendritic or synaptic release from neurons of the CNS. Whilst the distribution of VMAT2 has been well characterized in many catecholaminergic cell groups, its localization amongst C1 adrenergic neurons in the medulla has not been examined in detail. Within the rostral ventrolateral medulla (RVLM), C1 neurons are a group of barosensitive, adrenergic neurons. Rostral C1 cells project to the thoracic spinal cord and are considered sympathetic premotor neurons. The majority of caudal C1 cells project rostrally to regions such as the hypothalamus. The present study sought to quantitate the somatodendritic expression of VMAT2 in C1 neurons, and to assess the subcellular distribution of the transporter. Immunoreactivity for VMAT2 occurred in 31% of C1 soma, with a high proportion of these in the caudal part of the RVLM. Retrograde tracing studies revealed that only two of 43 bulbospinal C1 neurons contained faint VMAT2‐immunoreactivity, whilst 88 ± 5% of rostrally projecting neurons were VMAT2‐positive. A lentivirus, designed to express green fluorescent protein exclusively in noradrenergic and adrenergic neurons, was injected into the RVLM to label C1 neurons. Eighty‐three percent of C1 efferents that occurred in close proximity to sympathetic preganglionic neurons within the T3intermediolateral cell column contained VMAT2‐immunoreactivity. These data demonstrate differential distribution of VMAT2 within different subpopulations of C1 neurons and suggest that this might reflect differences in somatodendritic vs. synaptic release of catecholamines.
Orexin (hypocretin) gene transfer diminishes narcoleptic sleep behavior in mice
Authors: Liu Meng , Thankachan Stephen , Kaur Satvinder , Begum Suraiya , Blanco‐Centurion Carlos , Sakurai Takeshi , Yanagisawa Masashi , Neve Rachael , Shiromani Priyattam J.
Published: September 2008

Gene transfer has proven to be an effective neurobiological tool in a number of neurodegenerative diseases, but it is not known if it can correct a sleep disorder. Narcolepsy is a neurodegenerative sleep disorder linked to the loss of neurons containing the neuropeptide orexin, also known as hypocretin. Here, a replication‐defective herpes simplex virus‐1 amplicon‐based vector was constructed to transfer the gene for mouse prepro‐orexin into mice with a genetic deletion of the orexin gene. After in vitro tests confirmed successful gene transfer into cells, the gene vector was delivered to the lateral hypothalamus of orexin knockout (KO) mice where the orexin peptide was robustly expressed in the somata and processes of numerous neurons, and the peptide product was detected in the cerebrospinal fluid. During the 4‐day life‐span of the vector the incidence of cataplexy declined by 60%, and the levels of rapid eye movement sleep during the second half of the night were similar to levels in wild‐type mice, indicating that narcoleptic sleep–wake behavior in orexin KO mice can be improved by targeted gene transfer.
The Stress‐Buffering Effects of Control on Task Satisfaction and Perceived Goal Attainment: An Experimental Study of the Moderating Influence of Desire for Control
Authors: Parker Stacey L. , Jimmieson Nerina L. , Amiot Catherine E.
Published: September 2008

The purpose of the present study was to examine the extent to which Desire for Control (DFC) interacts with experimental manipulations of demand and control, and the consequences of these interactions on task satisfaction and perceived goal attainment (i.e. task performance and task mastery). It was expected that the proposed stress‐buffering effects of control would be evident only for individuals high in DFC. Moreover, it was anticipated that control may have a stress‐exacerbating effect for those low in DFC. These hypotheses were tested on a sample of 137 first year psychology students who participated in an in‐basket activity under low and high conditions of demand and control. Results revealed that the proposed stress‐buffering effect of control was found only for those high in DFC and a stress‐exacerbating effect of increased control was evident for those low in DFC on task performance and task mastery perceptions. Future research directions and the implications of these findings to applied settings are discussed.

Cette recherche avait pour objet de voir dans quelle mesure le besoin de maîtriser la situation (DFC) interagit avec des manipulations expérimentales portant sur les exigences et le contrôle, ainsi que d’observer les conséquences de ces interactions sur la satisfaction liée à la tâche et à la réussite perçue (relative à la performance et à la maîtrise de la tâche). On a fait l’hypothèse que seuls les individus présentant un haut niveau de DFC verraient leur stress atténué par la possibilité de maîtriser la situation. En outre, on pensait que la maîtrise de la situation pouvait accroître le stress de ceux ayant un faible niveau de DFC. Ces hypothèses ont été mises à l’épreuve sur un échantillon de 137 étudiants de première année de psychologie qui subirent un in‐basket test dans des conditions de haut et de bas niveaux d’exigence et de contrôle. Les résultats montrent que l’atténuation du stress par la maîtrise de la situation n’existe que pour les hauts niveaux de DFC, alors qu’une maîtrise accrue stimule le stress chez les bas niveaux, aussi bien sur la perception de la performance que sur celle de la domination de la tâche. On propose des orientations pour de futures recherches et l’on réfléchit aux retombées de ces résultats sur la vie pratique.
A Cross‐Cultural Look at Assessment Center Practices: Survey Results from Western Europe and North America
Authors: Krause Diana E. , Thornton III George C.
Published: September 2008

No recent survey documents assessment center (AC) practices across several countries. Therefore, we analyse AC practices in a sample of 97 organisations from nine countries in Western Europe and North America. We report findings regarding job analysis, dimensions, exercises, additional diagnostic methods, use of technology, assessor characteristics, contents and methods of assessor training, observational systems, information provided to participants, evaluation of participants’ reactions, data integration, characteristics of feedback, and features after the AC. Finally, we compare our results with prior findings to identify trends over time and point out features of ACs that could be improved.

Face aux défis que soulèvent les centres d’évaluation (AC) dans les organisations internationales, nous proposons un modèle qui rend compte des variations transculturelles dans ces pratiques, variations relevant de données individuelles (la motivation et la qualification des experts en resources humaines), de conditions culturelles (le « contrôle de l’incertitude » et la « distance hiérarchique ») et de réalités institutionnelles (des differences dans le niveau officiel de collectivisme et des divergences en ce qui concerne les normes légales et les lois régissant l’emploi). Ce modèle est exploité pour expliquer les différences dans la planification, l’exécution et l’évaluation des AC dans des organisations situées dans neuf pays d’Europe de l’ouest et d’Amérique du nord. Nous mettons aussi en evidence des tendances sur le long terme dans les pratiques des AC et discutons de l’amélioration de ces pratiques et de l’orientation des futures recherches dans ce domaine.
A review on coping mechanisms against obesity bias in physical activity/education settings
Authors: Li W. , Rukavina P.
Published: September 2008

Obesity bias such as teasing or weight criticism during physical activity can lead to psychological or emotional damage for overweight or obese individuals. The literature indicates that the adverse effects of stigmatization on overweight or obese individuals can be mediated by coping mechanisms. However, little is known about how overweight or obese children and adolescents cope with weight stigma in physical activity/education settings. This paper provides a conceptual analysis of coping mechanisms through reviewing work on weight stigma in psychology literature and discusses the future research directions. The most promising areas for future research include conducting an in‐depth qualitative exploration of overweight or obese individuals' coping mechanisms against obesity bias and studying potential individual and situational factors as moderating variables in physical activity/education settings.
Generating Color Palettes using Intuitive Parameters
Authors: Wijffelaars Martijn , Vliegen Roel , Van Wijk Jarke J. , Van Der Linden Erik‐Jan
Published: September 2008

Color is widely used in data visualization to show data values. The proper selection of colors is critical to convey information correctly. In this paper, we present a technique for generating univariate lightness ordered palettes. These are specified via intuitive input parameters that are used define the appearance of the palette: number of colors, hue, lightness, saturation, contrast and hue range. The settings of the parameters are used to generate curves through CIELUV color space. This color space is used in order to correctly translate the requirements in terms of perceptual properties to a set of colors. The presented palette generation method enables users to specify palettes that have these perceptual properties, such as perceived order, equal perceived distance and equal importance. The technique has been integrated in Magna View, a system for multivariate data visualization.
Animating Causal Overlays
Authors: Bartram Lyn , Yao Miao
Published: September 2008

Most approaches to representing causality, such as the common causal graph, require a separate and static view, but in many cases it is useful to add the dimension of causality to the context of an existing visualization. Building on research from perceptual psychology that shows the perception of causality is a low‐level visual event derived from certain types of motion, we are investigating how to add animated causal representations, called visual causal vectors, onto other visualizations. We refer to these as causal overlays. Our initial experimental results show this approach has great potential but that extra cues are needed to elicit the perception of causality when the motions are overlaid on other graphical objects. In this paper we describe the approach and report on a study that examined two issues of this technique: how to accurately convey the causal flow and how to represent the strength of the causal effect.
Automatic Detection and Visualization of Distinctive Structures in 3D Unsteady Multi‐fields
Authors: Jänicke H. , Böttinger M. , Tricoche X. , Scheuermann G.
Published: September 2008

Current unsteady multi‐field simulation data‐sets consist of millions of data‐points. To efficiently reduce this enormous amount of information, local statistical complexity was recently introduced as a method that identifies distinctive structures using concepts from information theory. Due to high computational costs this method was so far limited to 2D data. In this paper we propose a new strategy for the computation that is substantially faster and allows for a more precise analysis. The bottleneck of the original method is the division of spatio‐temporal configurations in the field (light‐cones) into different classes of behavior. The new algorithm uses a density‐driven Voronoi tessellation for this task that more accurately captures the distribution of configurations in the sparsely sampled high‐dimensional space. The efficient computation is achieved using structures and algorithms from graph theory. The ability of the method to detect distinctive regions in 3D is illustrated using flow and weather simulations.
Concurrent Viewing of Multiple Attribute‐Specific Subspaces
Authors: Sisneros Robert , Johnson C. Ryan , Huang Jian
Published: September 2008

In this work we present a point classification algorithm for multi‐variate data. Our method is based on the concept of attribute subspaces, which are derived from a set of user specified attribute target values. Our classification approach enables users to visually distinguish regions of saliency through concurrent viewing of these subspaces in single images. We also allow a user to threshold the data according to a specified distance from attribute target values. Based on the degree of thresholding, the remaining data points are assigned radii of influence that are used for the final coloring. This limits the view to only those points that are most relevant, while maintaining a similar visual context.
Quality Isosurface Mesh Generation Using an Extended Marching Cubes Lookup Table
Authors: Raman Sundaresan , Wenger Rephael
Published: September 2008

The Marching Cubes Algorithm may return degenerate, zero area isosurface triangles, and often returns isosurface triangles with small areas, edges or angles. We show how to avoid both problems using an extended Marching Cubes lookup table. As opposed to the conventional Marching Cubes lookup table, the extended lookup table differentiates scalar values equal to the isovalue from scalar values greater than the isovalue. The lookup table has 38= 6561 entries, based on three possible labels, ‘−’ or ‘=’ or ‘+’, of each cube vertex. We present an algorithm based on this lookup table which returns an isosurface close to the Marching Cubes isosurface, but without any degenerate triangles or any small areas, edges or angles.
Computing Local Signed Distance Fields for Large Polygonal Models
Authors: Chang B. , Cha D. , Ihm I.
Published: September 2008

The signed distance field for a polygonal model is a useful representation that facilitates efficient computation in many visualization and geometric processing tasks. Often it is more effective to build a local distance field only within a narrow band around the surface that holds local geometric information for the model. In this paper, we present a novel technique to construct a volumetric local signed distance field of a polygonal model. To compute the local field efficiently, exactly those cells that cross the polygonal surface are found first through a new voxelization method, building a list of intersecting triangles for each boundary cell. After their neighboring cells are classified, the triangle lists are exploited to compute the local signed distance field with minimized voxel‐to‐triangle distance computations. While several efficient methods for computing the distance field, particularly those harnessing the graphics processing unit's (GPU's) processing power, have recently been proposed, we focus on a CPU‐based technique, intended to deal flexibly with large polygonal models and high‐resolution grids that are often too bulky for GPU computation.
Interactive Visualization for Memory Reference Traces
Authors: Choudhury A. N. M. Imroz , Potter Kristin C. , Parker Steven G.
Published: September 2008

We present the Memory Trace Visualizer (MTV), a tool that provides interactive visualization and analysis of the sequence of memory operations performed by a program as it runs. As improvements in processor performance continue to outpace improvements in memory performance, tools to understand memory access patterns are increasingly important for optimizing data intensive programs such as those found in scientific computing. Using visual representations of abstract data structures, a simulated cache, and animating memory operations, MTV can expose memory performance bottlenecks and guide programmers toward memory system optimization opportunities. Visualization of detailed memory operations provides a powerful and intuitive way to expose patterns and discover bottlenecks, and is an important addition to existing statistical performance measurements.
Exploratory Visualization of Animal Kinematics Using Instantaneous Helical Axes
Authors: Keefe D. F. , O'Brien T. M. , Baier D. B. , Gatesy S. M. , Brainerd E. L. , Laidlaw D. H.
Published: September 2008

We present novel visual and interactive techniques for exploratory visualization of animal kinematics using instantaneous helical axes (IHAs). The helical axis has been used in orthopedics, biomechanics, and structural mechanics as a construct for describing rigid body motion. Within biomechanics, recent imaging advances have made possible accurate high‐speed measurements of individual bone positions and orientations during experiments. From this high‐speed data, instantaneous helical axes of motion may be calculated. We address questions of effective interactive, exploratory visualization of this high‐speed 3D motion data. A 3D glyph that encodes all parameters of the IHA in visual form is presented. Interactive controls are used to examine the change in the IHA over time and relate the IHA to anatomical features of interest selected by a user. The techniques developed are applied to a stereoscopic, interactive visualization of the mechanics of pig mastication and assessed by a team of evolutionary biologists who found interactive IHA‐based analysis a useful addition to more traditional motion analysis techniques.
Geometry‐driven Visualization of Microscopic Structures in Biology
Authors: Mosaliganti Kishore , Machiraju Raghu , Huang Kun , Leone Gustavo
Published: September 2008

At a microscopic resolution, biological structures are composed of cells, red blood corpuscles (RBCs), cytoplasm and other microstructural components. There is a natural pattern in terms of distribution, arrangement and packing density of these components in biological organization. In this work, we propose to use N‐point correlation functions to guide the analysis and exploration process in microscopic datasets. These functions provide useful feature spaces to aid segmentation and visualization tasks. We show3D visualizations of mouse placenta tissue layers and mouse mammary ducts as well as2D segmentation/tracking of clonal populations. Further confidence in our results stems from validation studies that were performed with manual ground‐truth for segmentation.
Classification and Uncertainty Visualization of Dendritic Spines from Optical Microscopy Imaging
Authors: Janoos Firdaus , Nouansengsy Boonthanome , Xu Xiaoyin , Machiraju Raghu , Wong Stephen T.C.
Published: September 2008

Neuronal dendrites and their spines affect the connectivity of neural networks, and play a significant role in many neurological conditions. Neuronal function is observed to be closely correlated with the appearance, disappearance and morphology of the spines. Automatic 3‐D reconstruction of neurons from light microscopy images, followed by the identification, classification and visualization of dendritic spines is therefore essential for studying neuronal physiology and biophysical properties. In this paper, we present a method to reconstruct dendrites using a surface representation of the dendrite. The 1‐D skeleton of the dendritic surface is then extracted by a medial geodesic function that is robust and topologically correct. This is followed by a Bayesian identification and classification of the spines. The dendrite and spines are visualized in a manner that displays the spines' types and the inherent uncertainty in identification and classification. We also describe a user study conducted to validate the accuracy of the classification and the efficacy of the visualization.
Visual Analysis and Semantic Exploration of Urban LIDAR Change Detection
Authors: Butkiewicz Thomas , Chang Remco , Wartell Zachary , Ribarsky William
Published: September 2008

Many previous approaches to detecting urban change from LIDAR point clouds interpolate the points into rasters, perform pixel‐based image processing to detect changes, and produce 2D images as output. We present a method of LIDAR change detection that maintains accuracy by only using the raw, irregularly spaced LIDAR points, and extracts relevant changes as individual 3D models. We then utilize these models, alongside existing GIS data, within an interactive application that allows the chronological exploration of the changes to an urban environment. A three‐tiered level‐of‐detail system maintains a scale‐appropriate, legible visual representation across the entire range of view scales, from individual changes such as buildings and trees, to groups of changes such as new residential developments, deforestation, and construction sites, and finally to larger regions such as neighborhoods and districts of a city that are emerging or undergoing revitalization. Tools are provided to assist the visual analysis by urban planners and historians through semantic categorization and filtering of the changes presented.
Visual Abstractions of Solvent Pathlines near Protein Cavities
Authors: Bidmon Katrin , Grottel Sebastian , Bös Fabian , Pleiss Jürgen , Ertl Thomas
Published: September 2008

Water is known to play a crucial role in protein structure, flexibility and activity. The use of molecular dynamics simulations allows detailed studies of complex protein‐solvent interactions. Cluster analysis and density‐based approaches have been successfully used for the identification and analysis of conserved water molecules and hydration patterns of proteins. However, appropriate tools for analysing long‐time molecular dynamics simulations with respect to tracking and visualising the paths of solvent molecules are lacking. Our method focuses on visualising the solvent paths entering and leaving cavities of the protein and allows to study the route and dynamics of the exchange of tightly bound internal water molecules with the bulk solvent. The proposed visualisation also represents dynamic properties such as direction and velocity in the solvent. Especially, by clustering similar path‐lines with respect to designated properties the visualisation can be abstracted to represent the principal paths of solvent molecules through the cavities. Its application in the analysis of long‐time scale molecular dynamics simulations not only confirmed conjectures based on previous manual observations made by chance, but also led to novel insights into the dynamical and structural role of water molecules and its interplay with protein structure.
Navigation and Exploration of Interconnected Pathways
Authors: Streit M. , Kalkusch M. , Kashofer K. , Schmalstieg D.
Published: September 2008

Visualizing pathways, i. e. models of cellular functional networks, is a challenging task in computer assisted biomedicine. Pathways are represented as large collections of interwoven graphs, with complex structures present in both the individual graphs and their interconnections. This situation requires the development of novel visualization techniques to allow efficient visual exploration. We present the Caleydo framework, which incorporates a number of approaches to handle such pathways. Navigation in the network of pathways is facilitated by a hierarchical approach which dynamically selects a working set of individual pathways for closer inspection. These pathways are interactively rendered together with visual interconnections in a 2.5D view using graphics hardware acceleration. The layout of individual graphs is not computed automatically, but taken from the KEGG and BioCarta databases, which use layouts that life scientists are familiar with. Therefore they encode essential meta‐information. While the KEGG and BioCarta pathways use a pre‐defined layout, interactions such as linking+brushing, neighborhood search or detail on demand are still fully interactive in Caleydo. We have evaluated Caleydo with pathologists working on the determination of unknown gene functions. Informal experiences confirm that Caleydo is useful in both generating and validating such hypotheses.

Even though the presented techniques are applied to medical pathways, the proposed way of interaction is not limited to cellular processes and therefore has the potential to open new possibilities in other fields of application.
Visual Inspection of Multivariate Graphs
Authors: Pretorius A. Johannes , Van Wijk Jarke J.
Published: September 2008

Most graph visualization techniques focus on the structure of graphs and do not offer support for dealing with node attributes and edge labels. To enable users to detect relations and patterns in terms of data associated with nodes and edges, we present a technique where this data plays a more central role. Nodes and edges are clustered based on associated data. Via direct manipulation users can interactively inspect and query the graph. Questions that can be answered include, “which edge types are activated by specific node attributes?” and, “how and from where can I reach specific types of nodes?” To validate our approach we contrast it with current practice. We also provide several examples where our method was used to study transition graphs that model real‐world systems.
Interactive Exploratory Visualization of 2D Vector Fields
Authors: Isenberg Tobias , Everts Maarten H. , Grubert Jens , Carpendale Sheelagh
Published: September 2008

In this paper we present several techniques to interactively explore representations of 2D vector fields. Through a set of simple hand postures used on large, touch‐sensitive displays, our approach allows individuals to custom‐design glyphs (arrows, lines, etc.) that best reveal patterns of the underlying dataset. Interactive exploration of vector fields is facilitated through freedom of glyph placement, glyph density control, and animation. The custom glyphs can be applied individually to probe specific areas of the data but can also be applied in groups to explore larger regions of a vector field. Re‐positionable sources from which glyphs—animated according to the local vector field—continue to emerge are used to examine the vector field dynamically. The combination of these techniques results in an engaging visualization with which the user can rapidly explore and analyze varying types of 2D vector fields, using a virtually infinite number of custom‐designed glyphs.
Results of a User Study on 2D Hurricane Visualization
Authors: Martin Joel P. , Swan J. Edward , Moorhead Robert J. , Liu Zhanping , Cai Shangshu
Published: September 2008

We present the results from a user study looking at the ability of observers to mentally integrate wind direction and magnitude over a vector field. The data set chosen for the study is an MM5 (PSU/NCAR Mesoscale Model) simulation of Hurricane Lili over the Gulf of Mexico as it approaches the southeastern United States. Nine observers participated in the study. This study investigates the effect of layering on the observer's ability to determine the magnitude and direction of a vector field. We found a tendency for observers to underestimate the magnitude of the vectors and a counter‐clockwise bias when determining the average direction of a vector field. We completed an additional study with two observers to try to uncover the source of the counter‐clockwise bias. These results have direct implications to atmospheric scientists, but may also be able to be applied to other fields that use 2D vector fields.
Evaluation of illustration‐inspired techniques for time‐varying data visualization
Authors: Joshi Alark , Rheingans Penny
Published: September 2008

Illustration‐inspired techniques have provided alternative ways to visualize time‐varying data. Techniques such as speedlines, flow ribbons, strobe silhouettes and opacity‐based techniques provide temporal context to the current timestep being visualized. We evaluated the effectiveness of these illustrative techniques by conducting a user study. We compared the ability of subjects to visually track features using snapshots, snapshots augmented by illustration techniques, animations, and animations augmented by illustration techniques. User accuracy, time required to perform a task, and user confidence were used as measures to evaluate the techniques. The results indicate that the use of illustration‐inspired techniques provides a significant improvement in user accuracy and the time required to complete the task. Subjects performed significantly better on each metric when using augmented animations as compared to augmented snapshots.
Visual Clustering in Parallel Coordinates
Authors: Zhou Hong , Yuan Xiaoru , Qu Huamin , Cui Weiwei , Chen Baoquan
Published: September 2008

Parallel coordinates have been widely applied to visualize high‐dimensional and multivariate data, discerning patterns within the data through visual clustering. However, the effectiveness of this technique on large data is reduced by edge clutter. In this paper, we present a novel framework to reduce edge clutter, consequently improving the effectiveness of visual clustering. We exploit curved edges and optimize the arrangement of these curved edges by minimizing their curvature and maximizing the parallelism of adjacent edges. The overall visual clustering is improved by adjusting the shape of the edges while keeping their relative order. The experiments on several representative datasets demonstrate the effectiveness of our approach.
Interactive Visualization of Multimodal Volume Data for Neurosurgical Tumor Treatment
Authors: Rieder Christian , Ritter Felix , Raspe Matthias , Peitgen Heinz‐Otto
Published: September 2008

We present novel interactive methods for the visualization of multimodal volume data as used in neurosurgical therapy planning. These methods allow surgeons to explore multimodal volumes and focus on functional data and lesions. Computer graphics techniques are proposed to create expressive visualizations at interactive frame rates to reduce time‐consuming and complex interaction with the medical data. Contributions of our work are the distance‐based enhancements of functional data and lesions which allows the surgeon to perceive functional and anatomical structures at once and relate them directly to the intervention. In addition we propose methods for the visual exploration of the path to the structures of interest, to enhance anatomical landmarks, and to provide additional depth indicators. These techniques have been integrated in a visualization prototype that provides interaction capabilities for finding the optimal therapeutic strategy for the neurosurgeon.
Virtual Klingler Dissection: Putting Fibers into Context
Authors: Schultz T. , Sauber N. , Anwander A. , Theisel H. , Seidel H.‐P.
Published: September 2008

Fiber tracking is a standard tool to estimate the course of major white matter tracts from diffusion tensor magnetic resonance imaging (DT‐MRI) data. In this work, we aim at supporting the visual analysis of classical streamlines from fiber tracking by integrating context from anatomical data, acquired by aT1‐weighted MRI measurement. To this end, we suggest a novel visualization metaphor, which is based on data‐driven deformation of geometry and has been inspired by a technique for anatomical fiber preparation known as Klingler dissection. We demonstrate that our method conveys the relation between streamlines and surrounding anatomical features more effectively than standard techniques like slice images and direct volume rendering. The method works automatically, but its GPU‐based implementation allows for additional, intuitive interaction.
A smart stochastic approach for manifolds smoothing
Authors: El Ouafdi A.F. , Ziou D. , Krim H.
Published: September 2008

In this paper, we present a probabilistic approach for 3D object's smoothing. The core idea behind the proposed method is to relate the problem of smoothing objects to that of tracking the transition probability density functions of an underlying random process. We show that such an approach allows for additional insight and sufficient flexibility compared with existing standard smoothing techniques. In particular, we are able to propose a newer, faster, and simpler smoothing approach that retains and enhances important manifold features. Furthermore, it is demonstrated to improve performance over existing smoothing techniques.
Fitting Sharp Features with Loop Subdivision Surfaces
Authors: Ling Ruotian , Wang Wenping , Yan Dongming
Published: September 2008

Various methods have been proposed for fitting subdivision surfaces to different forms of shape data (e.g., dense meshes or point clouds), but none of these methods effectively deals with shapes with sharp features, that is, creases, darts and corners. We present an effective method for fitting a Loop subdivision surface to a dense triangle mesh with sharp features. Our contribution is a new exact evaluation scheme for the Loop subdivision with all types of sharp features, which enables us to compute a fitting Loop subdivision surface for shapes with sharp features in an optimization framework. With an initial control mesh obtained from simplifying the input dense mesh using QEM, our fitting algorithm employs an iterative method to solve a nonlinear least squares problem based on the squared distances from the input mesh vertices to the fitting subdivision surface. This optimization framework depends critically on the ability to express these distances as quadratic functions of control mesh vertices using our exact evaluation scheme near sharp features. Experimental results are presented to demonstrate the effectiveness of the method.
Surface sampling and the intrinsic Voronoi diagram
Authors: Dyer Ramsay , Zhang Hao , Möller Torsten
Published: September 2008

We develop adaptive sampling criteria which guarantee a topologically faithful mesh and demonstrate an improvement and simplification over earlier results, albeit restricted to 2D surfaces. These sampling criteria are based on functions defined by intrinsic properties of the surface: the strong convexity radius and the injectivity radius. We establish inequalities that relate these functions to the local feature size, thus enabling a comparison between the demands of the intrinsic sampling criteria and those based on Euclidean distances and the medial axis.
Provably Good 2D Shape Reconstruction from Unorganized Cross‐Sections
Authors: Memari Pooran , Boissonnat Jean‐Daniel
Published: September 2008

This paper deals with the reconstruction of 2‐dimensional geometric shapes from unorganized 1‐dimensional cross‐sections. We study the problem in its full generality following the approach of Boissonnat and Memari [BM07] for the analogous 3D problem. We propose a new variant of this method and provide sampling conditions to guarantee that the output of the algorithm has the same topology as the original object and is close to it (for the Hausdorff distance).
Streaming Surface Reconstruction Using Wavelets
Authors: Manson J. , Petrova G. , Schaefer S.
Published: September 2008

We present a streaming method for reconstructing surfaces from large data sets generated by a laser range scanner using wavelets. Wavelets provide a localized, multiresolution representation of functions and this makes them ideal candidates for streaming surface reconstruction algorithms. We show how wavelets can be used to reconstruct the indicator function of a shape from a cloud of points with associated normals. Our method proceeds in several steps. We first compute a low‐resolution approximation of the indicator function using an octree followed by a second pass that incrementally adds fine resolution details. The indicator function is then smoothed using a modified octree convolution step and contoured to produce the final surface. Due to the local, multiresolution nature of wavelets, our approach results in an algorithm over 10 times faster than previous methods and can process extremely large data sets in the order of several hundred million points in only an hour.
Deformation‐Driven Shape Correspondence
Authors: Zhang H. , Sheffer A. , Cohen‐Or D. , Zhou Q. , Van Kaick O. , Tagliasacchi A.
Published: September 2008

Non‐rigid 3D shape correspondence is a fundamental and difficult problem. Most applications which require a correspondence rely on manually selected markers. Without user assistance, the performances of existing automatic correspondence methods depend strongly on a good initial shape alignment or shape prior, and they generally do not tolerate large shape variations. We present an automatic feature correspondence algorithm capable of handling large, non‐rigid shape variations, as well as partial matching. This is made possible by leveraging the power of state‐of‐the‐art mesh deformation techniques and relying on a combinatorial tree traversal for correspondence search. The search is deformation‐driven, prioritized by a self‐distortion energy measured on meshes deformed according to a given correspondence. We demonstrate the ability of our approach to naturally match shapes which differ in pose, local scale, part decomposition, and geometric detail through numerous examples.
Dental Inlay and Onlay Construction by Iterative Laplacian Surface Editing
Authors: Steinbrecher Tillmann , Gerth Maik
Published: September 2008

We propose a new method for automatic construction of inlays and onlays. Mesh models from a small tooth library are adapted to the remaining healthy surface of the patient's tooth. In the area above the cavity, the general morphology of the model tooth (fissures, cusp tips, etc) is preserved, but precisely adjusted to the intra‐oral situation. Our approach uses iterative Laplacian Surface Editing to deform the model tooth. This allows the automatic generation of highly individual, functional and anatomically correct inlays/onlays, without having to resort to a large library of different tooth shapes.
Automatic Registration for Articulated Shapes
Authors: Chang Will , Zwicker Matthias
Published: September 2008

We present an unsupervised algorithm for aligning a pair of shapes in the presence of significant articulated motion and missing data, while assuming no knowledge of a template, user‐placed markers, segmentation, or the skeletal structure of the shape. We explicitly sample the motion, which gives a priori the set of possible rigid transformations between parts of the shapes. This transforms the problem into a discrete labeling problem, where the goal is to find an optimal assignment of transformations for aligning the shapes. We then apply graph cuts to optimize a novel cost function, which encodes a preference for a consistent motion assignment from both source to target and target to source. We demonstrate the robustness of our method by aligning several synthetic and real‐world datasets.
Spectral Conformal Parameterization
Authors: Mullen Patrick , Tong Yiying , Alliez Pierre , Desbrun Mathieu
Published: September 2008

We present a spectral approach to automatically and efficiently obtain discrete free‐boundary conformal parameterizations of triangle mesh patches, without the common artifacts due to positional constraints on vertices and without undue bias introduced by sampling irregularity. High‐quality parameterizations are computed through a constrained minimization of a discrete weighted conformal energy by finding the largest eigenvalue/eigenvector of a generalized eigenvalue problem involving sparse, symmetric matrices. We demonstrate that this novel and robust approach improves on previous linear techniques both quantitatively and qualitatively.
A Local/Global Approach to Mesh Parameterization
Authors: Liu Ligang , Zhang Lei , Xu Yin , Gotsman Craig , Gortler Steven J.
Published: September 2008

We present a novel approach to parameterize a mesh with disk topology to the plane in a shape‐preserving manner. Our key contribution is a local/global algorithm, which combines a local mapping of each 3D triangle to the plane, using transformations taken from a restricted set, with a global “stitch” operation of all triangles, involving a sparse linear system. The local transformations can be taken from a variety of families, e.g. similarities or rotations, generating different types of parameterizations. In the first case, the parameterization tries to force each 2D triangle to be an as‐similar‐as‐possible version of its 3D counterpart. This is shown to yield results identical to those of the LSCM algorithm. In the second case, the parameterization tries to force each 2D triangle to be an as‐rigid‐as‐possible version of its 3D counterpart. This approach preserves shape as much as possible. It is simple, effective, and fast, due to pre‐factoring of the linear system involved in the global phase. Experimental results show that our approach provides almost isometric parameterizations and obtains more shape‐preserving results than other state‐of‐the‐art approaches.

We present also a more general “hybrid” parameterization model which provides a continuous spectrum of possibilities, controlled by a single parameter. The two cases described above lie at the two ends of the spectrum. We generalize our local/global algorithm to compute these parameterizations. The local phase may also be accelerated by parallelizing the independent computations per triangle.
Pointwise radial minimization: Hermite interpolation on arbitrary domains
Authors: Floater M. S. , Schulz C.
Published: September 2008

In this paper we propose a new kind of Hermite interpolation on arbitrary domains, matching derivative data of arbitrary order on the boundary. The basic idea stems from an interpretation of mean value interpolation as the pointwise minimization of a radial energy function involving first derivatives of linear polynomials. We generalize this and minimize over derivatives of polynomials of arbitrary odd degree. We analyze the cubic case, which assumes first derivative boundary data and show that the minimization has a unique, infinitely smooth solution with cubic precision. We have not been able to prove that the solution satisfies the Hermite interpolation conditions but numerical examples strongly indicate that it does for a wide variety of planar domains and that it behaves nicely.
Beyond Facts and Figures: The Role of Emotions in Boardroom Dynamics
Authors: Brundin Ethel , Nordqvist Mattias
Published: September 2008

Manuscript Type: Empirical

Research Question/Issue: We address the call for qualitative research in order to better understand the micro‐level dynamics of board work. Our aim is to investigate the role of emotions when board members interact to perform the board's control and service tasks.

Research Findings/Results: Empirical accounts from board meetings and diary notes from a CEO show in detail how emotions work as power energizers and status energizers in boardroom dynamics. We find that short‐term as well as long‐term emotions are a source of energy that affects board work, and that they are influential in the board members' task performance.

Theoretical Implications: We provide process insights with process insights to a field dominated by studies of the structures of corporate governance. We disclose the difference between board expectations and board performance, and offer a new understanding as to how and why this difference emerges. Our results also challenge theories that propose that authenticity of emotional displays is necessary in order to achieve a positive outcome in boardroom interactions. The findings also show that confrontation of negative emotions in boardroom communication may alter the power and status relations among board members.

Practical Implications: Our study shows that the board members who influence processes in the board are those whose emotional energies are built up and transformed as power and status energizers in line with board task expectations. Being aware, and able to understand the subtle working of emotions in board processes are crucial for being an effective board member.
Corporate Social Responsibility and International Development: Critical Assessment
Authors: Frynas Jędrzej G.
Published: September 2008

Manuscript Type: Conceptual

Research Question/Issue: This article critically evaluates recent claims about the positive role that corporate social responsibility (CSR) could play in contributing to international development goals such as poverty alleviation and health improvements.

Research Findings/Results: The article suggests that many recent claims about the positive contribution of CSR to international development are unjustified based on four arguments: (1) lack of empirical evidence; (2) analytical limitations of CSR; (3) the constraints of the business case for CSR; and (4) unresolved governance questions.

Theoretical Implications: On the one hand, the article implies that private firms are unlikely to act as successful development actors without corporate governance reforms, which would align the interests of non‐traditional stakeholders with corporate interests. On the other hand, the article implies that international development priorities may misalign the intrinsic interests of shareholders and company executives.

Practical Implications: The current CSR agenda seems inappropriate for addressing international development goals.