bluuebunny/crossref_metadata_2025 huggingface dataset:
Intrinsic Epidemicity of Streptococcus pneumoniae Depends on Strain Serotype and Antibiotic Susceptibility Pattern
Authors: Domenech de Cellès Matthieu , Opatowski Lulla , Salomon Jérôme , Varon Emmanuelle , Carbon Claude , Boëlle Pierre-Yves , Guillemot Didier
Published: July 2011

Streptococcus pneumoniae
is a major cause of invasive diseases worldwide. It spreads through an interindividual transmission, followed by usually harmless colonization of the host. Possible transmission differences reflecting intrinsic strain features (e.g., serotype and antibiotic susceptibility) have been little studied so far. In this study, we used epidemiological data from an interventional trial of
S. pneumoniae
carriage among kindergartners and developed a mathematical model to estimate the transmission parameters of the different strains isolated during that study. We found small but significant transmissibility differences between the observed serotypes: serotypes 3, 6A, and 19A were found to be the most epidemic, while serotypes 23F, 9V, and 14 were the least epidemic. Further analysis indicated that, within a serotype, susceptible and resistant strains had different abilities to be transmitted. Susceptible-to-resistant transmission rate ratios were computed for five serotypes; susceptible strains were significantly more epidemic than resistant strains for serotypes 6A (mean, 1.02) and 19F (1.05). Serotype 19A resistant strains were not outcompeted by susceptible strains (0.97). Nonsignificant trends were observed for serotypes 6B (1.01) and 15A (0.98). Our results support the existence of heterogeneous abilities of the different serotypes for host-to-host transmission. They also suggest that antibiotic susceptibility within a serotype affects this transmissibility. We conclude that pneumococcal strains should not be considered equally at-risk in terms of transmission. Further quantification of strain-specific epidemic potential is needed, especially in a context of extensive use of conjugate vaccines with the aim of preventing pneumococcal infections.
OXA-198, an Acquired Carbapenem-Hydrolyzing Class D β-Lactamase from Pseudomonas aeruginosa
Authors: El Garch Farid , Bogaerts Pierre , Bebrone Carine , Galleni Moreno , Glupczynski Youri
Published: July 2011

A carbapenem-resistantPseudomonas aeruginosastrain (PA41437) susceptible to expanded-spectrum cephalosporins was recovered from several consecutive lower-respiratory-tract specimens of a patient who developed a ventilator-associated pneumonia while hospitalized in an intensive care unit. Cloning experiments identified OXA-198, a new class D β-lactamase which was weakly related (less than 45% amino acid identity) to other class D β-lactamases. Expression inEscherichia coliTOP10 and inP. aeruginosaPAO1 led to transformants that were resistant to ticarcillin and showed reduced susceptibility to carbapenems and cefepime. TheblaOXA-198gene was harbored by a class 1 integron carried by a ca. 46-kb nontypeable plasmid. This study describes a novel class D β-lactamase involved in carbapenem resistance inP. aeruginosa.
CMX001 Potentiates the Efficacy of Acyclovir in Herpes Simplex Virus Infections
Authors: Prichard Mark N. , Kern Earl R. , Hartline Caroll B. , Lanier E. Randall , Quenelle Debra C.
Published: July 2011

Although acyclovir (ACV) has proven to be of value in the therapy of certain herpes simplex virus (HSV) infections, there is a need for more effective therapies, particularly for serious infections in neonates and immunocompromised individuals, where resistance to this drug can be problematic. CMX001 is an orally bioavailable lipid conjugate of cidofovir that is substantially less nephrotoxic than the parent drug and has excellent antiviral activity against all the human herpesviruses. This compound retains full antiviral activity against ACV-resistant laboratory and clinical isolates. The combined efficacy of CMX001 and ACV was evaluated in a new real-time PCR combination assay, which demonstrated that the combination synergistically inhibited the replication of HSV in cell culture. This was also confirmed in murine models of HSV infection, where the combined therapy with these two drugs synergistically reduced mortality. These results suggest that CMX001 may be effective in the treatment of ACV-resistant HSV infections and as an adjunct therapy in individuals with suboptimal responses to ACV.
Cyclopropavir Inhibits the Normal Function of the Human Cytomegalovirus UL97 Kinase
Authors: James Scott H. , Hartline Caroll B. , Harden Emma A. , Driebe Elizabeth M. , Schupp James M. , Engelthaler David M. , Keim Paul S. , Bowlin Terry L. , Kern Earl R. , Prichard Mark N.
Published: July 2011

Cyclopropavir (CPV) is active against human cytomegalovirus (CMV), as well as both variants of human herpesvirus 6 and human herpesvirus 8. The mechanism of action of CPV against CMV is similar to that of ganciclovir (GCV) in that it is phosphorylated initially by the CMV UL97 kinase, resulting in inhibition of viral DNA synthesis. Resistance to CPV maps to the UL97 kinase but is associated primarily with H520Q mutations and thus retains good antiviral activity against most GCV-resistant isolates. An examination of CMV-infected cultures treated with CPV revealed unusual cell morphology typically associated with the absence of UL97 kinase activity. A surrogate assay for UL97 kinase activity confirmed that CPV inhibited the activity of this enzyme and that its action was similar to the inhibition seen with maribavir (MBV) in this assay. Combination studies using real-time PCR indicated that, like MBV, CPV also antagonized the efficacy of GCV and were consistent with the observed inhibition of the UL97 kinase. Deep sequencing of CPV-resistant laboratory isolates identified a frameshift mutation in UL27, presumably to compensate for a loss of UL97 enzymatic activity. We conclude that the mechanism of action of CPV against CMV is complex and involves both the inhibition of DNA synthesis and the inhibition of the normal activity of the UL97 kinase.
Heat-Labile- and Heat-Stable-Toxoid Fusions (LT
R192G
-STa
P13F
) of Human Enterotoxigenic Escherichia coli Elicit Neutralizing Antitoxin Antibodies
Authors: Liu Mei , Ruan Xiaosai , Zhang Chengxian , Lawson Steve R. , Knudsen David E. , Nataro James P. , Robertson Donald C. , Zhang Weiping
Published: July 2011

Enterotoxigenic
Escherichia coli
(ETEC) strains are a major cause of diarrheal disease in humans and animals. Adhesins and enterotoxins, including heat-labile (LT) and heat-stable (STa) toxins, are the key virulence factors. Antigenic adhesin and LT antigens have been used in developing vaccines against ETEC diarrhea. However, STa has not been included because of its poor immunogenicity and potent toxicity. Our recent study showed that porcine-type STa toxoids became immunogenic and elicited neutralizing anti-STa antibodies after being genetically fused to a full-length porcine-type LT toxoid, LT
R192G
(W. Zhang et al., Infect. Immun. 78:316-325, 2010). In this study, we mutated human-type LT and STa genes, which are highly homologous to porcine-type toxin genes, for a full-length LT toxoid (LT
R192G
) and a full-length STa toxoid (STa
P13F
) and genetically fused them to produce LT
192
-STa
13
toxoid fusions. Mice immunized with LT
192
-STa
13
fusion antigens developed anti-LT and anti-STa IgG (in serum and feces) and IgA antibodies (in feces). Moreover, secretory IgA antibodies from immunized mice were shown to neutralize STa and cholera toxins in T-84 cells. In addition, we fused the STa
13
toxoid at the N terminus and C terminus, between the A1 and A2 peptides, and between the A and B subunits of LT
192
to obtain different fusions in order to explore strategies for enhancing STa immunogenicity. This study demonstrated that human-type LT
192
-STa
13
fusions induce neutralizing antitoxin antibodies and provided important information for developing toxoid vaccines against human ETEC diarrhea.
Human Monocytes Promote Th1 and Th17 Responses to Streptococcus pneumoniae
Authors: Olliver Marie , Hiew Jeffni , Mellroth Peter , Henriques-Normark Birgitta , Bergman Peter
Published: July 2011

Streptococcus pneumoniae
is a leading cause of bacterial pneumonia, meningitis, and sepsis in children. Human immunity to pneumococcal infections has been assumed to depend on anticapsular antibodies. However, recent findings from murine models suggest that alternative mechanisms, dependent on T helper cells, are also involved. Although the immunological events in which T helper cells contribute to acquired immunity have been studied in mice, little is known about how these responses are generated in humans. Therefore, we examined bacterial and host factors involved in the induction of Th1 and Th17 responses, using a coculture model of human monocytes and CD4
+
T cells. We show that monocytes promote effector cytokine production by memory T helper cells, leading to a mixed Th1/Th17 (gamma interferon [IFN-γ]/interleukin-17 [IL-17]) profile. Both T helper cytokines were triggered by purified pneumococcal peptidoglycan; however, the balance between the two immune effector arms depended on bacterial viability. Accordingly, live pneumococci triggered a Th1-biased response via monocyte production of IL-12p40, whereas heat-killed pneumococci triggered a Th17 response through TLR2 signaling. An increased understanding of human T helper responses is essential for the development of novel pneumococcal vaccines designed to elicit cell-mediated immunity.
Cyclic Dimeric GMP Signaling Regulates Intracellular Aggregation, Sessility, and Growth of Ehrlichia chaffeensis
Authors: Kumagai Yumi , Matsuo Junji , Cheng Zhihui , Hayakawa Yoshihiro , Rikihisa Yasuko
Published: July 2011

Cyclic dimeric GMP (c-di-GMP), a bacterial second messenger, is known to regulate bacterial biofilm and sessility. Replication of an obligatory intracellular pathogen,
Ehrlichia chaffeensis
, is characterized by formation of bacterial aggregates called morulae inside membrane-bound inclusions. When
E. chaffeensis
matures into an infectious form, morulae become loose to allow bacteria to exit from host cells to infect adjacent cells.
E. chaffeensis
expresses a sensor kinase, PleC, and a cognate response regulator, PleD, which can produce c-di-GMP. A hydrophobic c-di-GMP antagonist, 2′-
O
-di(
tert
-butyldimethysilyl)-c-di-GMP (CDGA) inhibits
E. chaffeensis
internalization into host cells by facilitating degradation of some bacterial surface proteins via endogenous serine proteases. In the present study, we found that PleC and PleD were upregulated synchronously during exponential growth of bacteria, concomitant with increased morula size. While CDGA did not affect host cells, when infected cells were treated with CDGA, bacterial proliferation was inhibited, morulae became less compact, and the intracellular movement of bacteria was enhanced. Concurrently, CDGA treatment facilitated the extracellular release of bacteria with lower infectivity than those spontaneously released from sham-treated cells. Addition of CDGA to isolated inclusions induced dispersion of the morulae, degradation of an inclusion matrix protein TRP120, and bacterial intrainclusion movement, all of which were blocked by a serine protease inhibitor. These results suggest that c-di-GMP signaling regulates aggregation and sessility of
E. chaffeensis
within the inclusion through stabilization of matrix proteins by preventing the serine protease activity, which is associated with bacterial intracellular proliferation and maturation.
Functional Characterization of EpsC, a Component of the Type II Secretion System, in the Pathogenicity of Vibrio vulnificus
Authors: Hwang Won , Lee Na Yeon , Kim Juri , Lee Mi-Ae , Kim Kun-Soo , Lee Kyu-Ho , Park Soon-Jung
Published: July 2011

EpsC, one of the components comprising the type II secretion system (T2SS), was isolated from a human-pathogenic bacterium,
Vibrio vulnificus
, to evaluate its role in eliciting virulence. An
espC
-deleted mutant of
V. vulnificus
displayed a reduced cytotoxicity to the human cell line HEp-2 and an attenuated virulence in a mouse model. This mutant exhibited dramatic defects in the secretion of diverse extracellular proteins, such as outer membrane proteins, transporters, and the known secreted factors, notably, a hemolysin (VvhA) and an elastase (VvpE). A defect in its secretion of proteins was restored by in
trans
complementation of the intact
epsC
gene. Analyses of cellular fractions revealed that VvhA and VvpE of the
ΔepsC
mutant were not excreted outside the cell but were present mainly in the periplasmic space. Examination of a
V. vulnificus
mutant deficient in TolC, a component of the T1SS, showed that it is not involved in the secretion of VvhA and VvpE but that it is necessary for the secretion of another major toxin of
V. vulnificus
, RtxA. Therefore, the T2SS is required for
V. vulnificus
pathogenicity, which is mediated by at least two secreted factors, VvhA and VvpE, via facilitating the secretion and exposure of these factors to host cells.
New methods for system reliability analysis of soil slopes
Authors: Zhang J. , Zhang L.M. , Tang Wilson H.
Published: July 2011

A slope may have many possible slip surfaces. As sliding along any slip surface can cause slope failure, the system failure probability of a slope is different from the probability of failure along an individual slip surface. In this paper, we first suggest an efficient method for evaluating the system failure probability of a slope that considers a large number of possible slip surfaces. To obtain more insights into the system failure probability of a slope, we also propose a method to identify a few representative slip surfaces most important for system reliability analysis among a large number of potential slip surfaces and to calculate the system failure probability based on these representative slip surfaces. An equation for estimating the bounds of system failure probability based on the failure probability of the most critical slip surface is also suggested. The system failure probability is governed by only a few representative slip surfaces. For a homogenous slope, the failure probability of the most critical slip surface is a good approximation of the system failure probability. For a slope in layered soils, the system failure probability can be significantly larger than the failure probability of the most critical slip surface.
A Bayesian approach for determining velocity and uncertainty estimates from seismic cone penetrometer testing or vertical seismic profiling data
Authors: Pidlisecky Adam , Haines Seth S.
Published: July 2011

Conventional processing methods for seismic cone penetrometer data present several shortcomings, most notably the absence of a robust velocity model uncertainty estimate. We propose a new seismic cone penetrometer testing (SCPT) data-processing approach that employs Bayesian methods to map measured data errors into quantitative estimates of model uncertainty. We first calculate travel-time differences for all permutations of seismic trace pairs. That is, we cross-correlate each trace at each measurement location with every trace at every other measurement location to determine travel-time differences that are not biased by the choice of any particular reference trace and to thoroughly characterize data error. We calculate a forward operator that accounts for the different ray paths for each measurement location, including refraction at layer boundaries. We then use a Bayesian inversion scheme to obtain the most likely slowness (the reciprocal of velocity) and a distribution of probable slowness values for each model layer. The result is a velocity model that is based on correct ray paths, with uncertainty bounds that are based on the data error.
Laboratory testing and microanalysis of colloidal mobilization from a glacial till
Authors: Kunberger T. , Gabr M.A.
Published: July 2011

The effect of the dispersion and piping of clay fines — colloid mobilization — as a means of remediating subsurface contamination was investigated. Prior colloid mobility research has focused on mitigating colloidal movement to reduce contaminant transport or monitoring colloids to determine the extent of mobility and contamination transport. To date, limited work has been performed to evaluate remediation efficiency associated with the removal of clay-sized (colloidal) particles and related sorbed contamination. Laboratory flow-through tests were performed on a glacial till from a radioactive cesium contaminated site. Post-testing analysis comprised mass balance checks, grain-size distribution testing, and microscopic analysis of removed particles. Results showed the potential of initiating and maintaining clay dispersion and piping, thus establishing a means to mobilize colloids and subsequently remove them from the subsurface environment. Beneficial effects of hydraulic gradient and ionic strength manipulations were influenced by soil properties, such as cation exchange capacity, clay content, and average pore diameter. In general, colloid mobilization testing results found that extreme levels of mobilization typically resulted in particle trapping and an overall reduction in colloidal removal, while the effect of more moderate levels was mobilization with increased rates of removal.
Simple assessment of needleleaf and broadleaf chlorophyll content using a flatbed color scanner
Authors: Eitel Jan U.H. , Vierling Lee A. , Long Dan S. , Litvak Marcy , Eitel Karla C.B.
Published: July 2011

Total chlorophyll a and b content (Chlab) of leaves is an important indicator of the photosynthetic capacity, nutritional condition, and health status of plants. Developing low-cost, easily accessible methods for estimating foliar Chlabof needleleaf species would enable a broad range of forestry applications. We evaluated data acquired using an off-the-shelf flatbed color scanner to assess its utility in quantifying needleleaf Chlab. Red and green digital numbers (DN) of the scan image were obtained from needle leaves of oneseed juniper ( Juniperus monosperma (Engelm.) Sarg.) and piñon pine ( Pinus edulis Engelm.) in addition to two broadleaf species for comparison purposes. Values of laboratory-determined Chlab(range 1.5–64.0 µg·cm–2) were then predicted using the DN values from the scanner-imaged needle leaves as a regression estimator. The red or green DN values of the scanner-imaged needle leaves were curvilinearly related to Chlabwith an r2of 0.67 (RMSE = 4.72 µg·cm–2, p < 0.001) for juniper needles and an r2of 0.54 (RMSE = 5.51 µg·cm–2, p < 0.001) for pine needles. Although our results suggest that flatbed scanner derived Chlabestimates are not suitable for applications where highly accurate Chlabestimates are required, the technique is likely to be a useful tool for forest practitioners in managing tree nutrition and health.
Does frequent burning affect longleaf pine (Pinus palustris) bark thickness?
Authors: Wang G. Geoff , Wangen Steve R.
Published: July 2011

Bark thickness plays a critical role in protecting a tree’s cambium from damage by fires. Does frequent surface fire stimulate bark production compared with a fire-suppressed control? Based on data from an ongoing, long-term prescribed fire study, we explored differences in bark thickness from 0 to 200 cm above the ground for longleaf pine ( Pinus palustris P. Mill.) trees on burned and control sites. Biennial prescribed fires, applied between 1973 (stand age = 14 years) and 2006 (stand age = 47 years), significantly reduced diameter at breast height. After adjusting for differences in diameter at breast height, we found no difference in bark thickness of trees from the burn and control sites, except for bark thickness measured at 0 cm aboveground where control sites had significantly thicker bark than burned sites. Results suggest that frequent burning did not stimulate bark production in longleaf pine.
A programmable system for artistic volumetric lighting
Authors: Nowrouzezahrai Derek , Johnson Jared , Selle Andrew , Lacewell Dylan , Kaschalk Michael , Jarosz Wojciech
Published: July 2011

We present a method for generating art-directable volumetric effects, ranging from physically-accurate to non-physical results. Our system mimics the way experienced artists think about volumetric effects by using an intuitive lighting primitive, and decoupling the
modeling
and
shading
of this primitive. To accomplish this, we generalize the physically-based photon beams method to allow arbitrarily programmable simulation and shading phases. This provides an intuitive design space for artists to rapidly explore a wide range of physically-based as well as plausible, but exaggerated, volumetric effects. We integrate our approach into a real-world production pipeline and couple our volumetric effects to surface shading.
Coherent noise for non-photorealistic rendering
Authors: Kass Michael , Pesare Davide
Published: July 2011

A wide variety of non-photorealistic rendering techniques make use of random variation in the placement or appearance of primitives. In order to avoid the "shower-door" effect, this random variation should move with the objects in the scene. Here we present
coherent noise
tailored to this purpose. We compute the coherent noise with a specialized filter that uses the depth and velocity fields of a source sequence. The computation is fast and suitable for interactive applications like games.
Exploration of continuous variability in collections of 3D shapes
Authors: Ovsjanikov Maks , Li Wilmot , Guibas Leonidas , Mitra Niloy J.
Published: July 2011

As large public repositories of 3D shapes continue to grow, the amount of shape variability in such collections also increases, both in terms of the number of different classes of shapes, as well as the geometric variability of shapes within each class. While this gives users more choice for shape selection, it can be difficult to explore large collections and understand the range of variations amongst the shapes. Exploration is particularly challenging for public shape repositories, which are often only loosely tagged and contain neither point-based nor part-based correspondences. In this paper, we present a method for discovering and exploring continuous variability in a collection of 3D shapes without correspondences. Our method is based on a novel navigation interface that allows users to explore a collection of related shapes by deforming a base template shape through a set of intuitive deformation controls. We also help the user to select the most meaningful deformations using a novel technique for learning shape variability in terms of deformations of the template. Our technique assumes that the set of shapes lies near a low-dimensional manifold in a certain descriptor space, which allows us to avoid establishing correspondences between shapes, while being rotation and scaling invariant. We present results on several shape collections taken directly from public repositories.
Probabilistic reasoning for assembly-based 3D modeling
Authors: Chaudhuri Siddhartha , Kalogerakis Evangelos , Guibas Leonidas , Koltun Vladlen
Published: July 2011

Assembly-based modeling is a promising approach to broadening the accessibility of 3D modeling. In assembly-based modeling, new models are assembled from shape components extracted from a database. A key challenge in assembly-based modeling is the identification of relevant components to be presented to the user. In this paper, we introduce a probabilistic reasoning approach to this problem. Given a repository of shapes, our approach learns a probabilistic graphical model that encodes semantic and geometric relationships among shape components. The probabilistic model is used to present components that are semantically and stylistically compatible with the 3D model that is being assembled. Our experiments indicate that the probabilistic model increases the relevance of presented components.
Eulerian solid simulation with contact
Authors: Levin David I. W. , Litven Joshua , Jones Garrett L. , Sueda Shinjiro , Pai Dinesh K.
Published: July 2011

Simulating viscoelastic solids undergoing large, nonlinear deformations in close contact is challenging. In addition to inter-object contact, methods relying on Lagrangian discretizations must handle degenerate cases by explicitly remeshing or resampling the object. Eulerian methods, which discretize space itself, provide an interesting alternative due to the fixed nature of the discretization. In this paper we present a new Eulerian method for viscoelastic materials that features a collision detection and resolution scheme which does not require explicit surface tracking to achieve accurate collision response. Time-stepping with contact is performed by the efficient solution of large sparse quadratic programs; this avoids constraint sticking and other difficulties. Simulation and collision processing can share the same uniform grid, making the algorithm easy to parallelize. We demonstrate an implementation of all the steps of the algorithm on the GPU. The method is effective for simulation of complicated contact scenarios involving multiple highly deformable objects, and can directly simulate volumetric models obtained from medical imaging techniques such as CT and MRI.
Perceptually based tone mapping for low-light conditions
Authors: Kirk Adam G. , O'Brien James F.
Published: July 2011

In this paper we present a perceptually based algorithm for modeling the color shift that occurs for human viewers in low-light scenes. Known as the Purkinje effect, this color shift occurs as the eye transitions from photopic, cone-mediated vision in well-lit scenes to scotopic, rod-mediated vision in dark scenes. At intermediate light levels vision is mesopic with both the rods and cones active. Although the rods have a spectral response distinct from the cones, they still share the same neural pathways. As light levels decrease and the rods become increasingly active they cause a perceived shift in color. We model this process so that we can compute perceived colors for mesopic and scotopic scenes from spectral image data. We also describe how the effect can be approximated from standard high dynamic range RGB images. Once we have determined rod and cone responses, we map them to RGB values that can be displayed on a standard monitor to elicit the intended color perception when viewed photopically. Our method focuses on computing the color shift associated with low-light conditions and leverages current HDR techniques to control the image's dynamic range. We include results generated from both spectral and RGB input images.
Illumination decomposition for material recoloring with consistent interreflections
Authors: Carroll Robert , Ramamoorthi Ravi , Agrawala Maneesh
Published: July 2011

Changing the color of an object is a basic image editing operation, but a high quality result must also preserve natural shading. A common approach is to first compute reflectance and illumination intrinsic images. Reflectances can then be edited independently, and recomposed with the illumination. However, manipulating only the reflectance color does not account for diffuse interreflections, and can result in inconsistent shading in the edited image. We propose an approach for further decomposing illumination into direct lighting, and indirect diffuse illumination from each material. This decomposition allows us to change indirect illumination from an individual material independently, so it matches the modified reflectance color. To address the underconstrained problem of decomposing illumination into multiple components, we take advantage of its smooth nature, as well as user-provided constraints. We demonstrate our approach on a number of examples, where we consistently edit material colors and the associated interreflections.
Microgeometry capture using an elastomeric sensor
Authors: Johnson Micah K. , Cole Forrester , Raj Alvin , Adelson Edward H.
Published: July 2011

We describe a system for capturing microscopic surface geometry. The system extends the retrographic sensor [Johnson and Adelson 2009] to the microscopic domain, demonstrating spatial resolution as small as 2 microns. In contrast to existing microgeometry capture techniques, the system is not affected by the optical characteristics of the surface being measured---it captures the same geometry whether the object is matte, glossy, or transparent. In addition, the hardware design allows for a variety of form factors, including a hand-held device that can be used to capture high-resolution surface geometry in the field. We achieve these results with a combination of improved sensor materials, illumination design, and reconstruction algorithm, as compared to the original sensor of Johnson and Adelson [2009].
CATRA
Authors: Pamplona Vitor F. , Passos Erick B. , Zizka Jan , Oliveira Manuel M. , Lawson Everett , Clua Esteban , Raskar Ramesh
Published: July 2011

We introduce an interactive method to assess cataracts in the human eye by crafting an optical solution that measures the perceptual impact of forward scattering on the foveal region. Current solutions rely on highly-trained clinicians to check the back scattering in the crystallin lens and test their predictions on visual acuity tests. Close-range parallax barriers create collimated beams of light to scan through sub-apertures, scattering light as it strikes a cataract. User feedback generates maps for opacity, attenuation, contrast and sub-aperture point-spread functions. The goal is to allow a general audience to operate a portable high-contrast light-field display to gain a meaningful understanding of their own visual conditions. User evaluations and validation with modified camera optics are performed. Compiled data is used to reconstruct the individual's cataract-affected view, offering a novel approach for capturing information for screening, diagnostic, and clinical analysis.
Efficient maximal poisson-disk sampling
Authors: Ebeida Mohamed S. , Davidson Andrew A. , Patney Anjul , Knupp Patrick M. , Mitchell Scott A. , Owens John D.
Published: July 2011

We solve the problem of generating a uniform Poisson-disk sampling that is both
maximal
and
unbiased
over bounded non-convex domains. To our knowledge this is the first provably correct algorithm with time and space dependent only on the number of points produced. Our method has two phases, both based on classical dart-throwing. The first phase uses a background grid of square cells to rapidly create an unbiased, near-maximal covering of the domain. The second phase completes the maximal covering by calculating the connected components of the remaining uncovered voids, and by using their geometry to efficiently place unbiased samples that cover them. The second phase converges quickly, overcoming a common difficulty in dart-throwing methods. The deterministic memory is
O
(
n
) and the expected running time is
O
(
n
log
n
), where
n
is the output size, the number of points in the final sample. Our serial implementation verifies that the log
n
dependence is minor, and nearly
O
(
n
) performance for both time and memory is achieved in practice. We also present a parallel implementation on GPUs to demonstrate the parallel-friendly nature of our method, which achieves 2.4x the performance of our serial version.
Filtering solid Gabor noise
Authors: Lagae Ares , Drettakis George
Published: July 2011

Solid noise is a fundamental tool in computer graphics. Surprisingly, no existing noise function supports both high-quality antialiasing and continuity across sharp edges. In this paper we show that a slicing approach is required to preserve continuity across sharp edges, and we present a new noise function that supports anisotropic filtering of sliced solid noise. This is made possible by individually filtering the slices of Gabor kernels, which requires the proper treatment of phase. This in turn leads to the introduction of the phase-augmented Gabor kernel and random-phase Gabor noise, our new noise function. We demonstrate that our new noise function supports both high-quality anti-aliasing and continuity across sharp edges, as well as anisotropy.
GlobFit
Authors: Li Yangyan , Wu Xiaokun , Chrysathou Yiorgos , Sharf Andrei , Cohen-Or Daniel , Mitra Niloy J.
Published: July 2011

Given a noisy and incomplete point set, we introduce a method that simultaneously recovers a set of locally fitted primitives along with their global mutual relations. We operate under the assumption that the data corresponds to a man-made engineering object consisting of basic primitives, possibly repeated and globally aligned under common relations. We introduce an algorithm to directly couple the local and global aspects of the problem. The local fit of the model is determined by how well the inferred model agrees to the observed data, while the global relations are iteratively learned and enforced through a constrained optimization. Starting with a set of initial RANSAC based locally fitted primitives, relations across the primitives such as orientation, placement, and equality are progressively learned and conformed to. In each stage, a set of feasible relations are extracted among the candidate relations, and then aligned to, while best fitting to the input data. The global coupling corrects the primitives obtained in the local RANSAC stage, and brings them to precise global alignment. We test the robustness of our algorithm on a range of synthesized and scanned data, with varying amounts of noise, outliers, and non-uniform sampling, and validate the results against ground truth, where available.
High-quality spatio-temporal rendering using semi-analytical visibility
Authors: Gribel Carl Johan , Barringer Rasmus , Akenine-Möller Tomas
Published: July 2011

We present a novel visibility algorithm for rendering motion blur with per-pixel anti-aliasing. Our algorithm uses a number of line samples over a rectangular group of pixels, and together with the time dimension, a two-dimensional spatio-temporal visibility problem needs to be solved per line sample. In a coarse culling step, our algorithm first uses a bounding volume hierarchy to rapidly remove geometry that does not overlap with the current line sample. For the remaining triangles, we approximate each triangle's depth function, along the line and along the time dimension, with a number of patch triangles. We resolve for the final color using an analytical visibility algorithm with depth sorting, simple occlusion culling, and clipping. Shading is decoupled from visibility, and we use a shading cache for efficient reuse of shaded values. In our results, we show practically noise-free renderings of motion blur with high-quality spatial anti-aliasing and with competitive rendering times. We also demonstrate that our algorithm, with some adjustments, can be used to accurately compute motion blurred ambient occlusion.
Temporal light field reconstruction for rendering distribution effects
Authors: Lehtinen Jaakko , Aila Timo , Chen Jiawen , Laine Samuli , Durand Frédo
Published: July 2011

Traditionally, effects that require evaluating multidimensional integrals for each pixel, such as motion blur, depth of field, and soft shadows, suffer from noise due to the variance of the high-dimensional integrand. In this paper, we describe a general reconstruction technique that exploits the anisotropy in the temporal light field and permits efficient reuse of samples between pixels, multiplying the effective sampling rate by a large factor. We show that our technique can be applied in situations that are challenging or impossible for previous anisotropic reconstruction methods, and that it can yield good results with very sparse inputs. We demonstrate our method for simultaneous motion blur, depth of field, and soft shadows.
A quantized-diffusion model for rendering translucent materials
Authors: D'Eon Eugene , Irving Geoffrey
Published: July 2011

We present a new BSSRDF for rendering images of translucent materials. Previous diffusion BSSRDFs are limited by the accuracy of classical diffusion theory. We introduce a modified diffusion theory that is more accurate for highly absorbing materials and near the point of illumination. The new diffusion solution accurately decouples single and multiple scattering. We then derive a novel, analytic, extended-source solution to the multilayer search-light problem by quantizing the diffusion Green's function. This allows the application of the diffusion multipole model to material layers several orders of magnitude thinner than previously possible and creates accurate results under high-frequency illumination. Quantized diffusion provides both a new physical foundation and a variable-accuracy construction method for sum-of-Gaussians BSSRDFs, which have many useful properties for efficient rendering and appearance capture. Our BSSRDF maps directly to previous real-time rendering algorithms. For film production rendering, we propose several improvements to previous hierarchical point cloud algorithms by introducing a new radial-binning data structure and a doubly-adaptive traversal strategy.
Interactive and anisotropic geometry processing using the screened Poisson equation
Authors: Chuang Ming , Kazhdan Michael
Published: July 2011

We present a general framework for performing geometry filtering through the solution of a screened Poisson equation. We show that this framework can be efficiently adapted to a changing Riemannian metric to support curvature-aware filtering and describe a parallel and streaming multigrid implementation for solving the system. We demonstrate the practicality of our approach by developing an interactive system for mesh editing that allows for exploration of a large family of curvature-guided, anisotropic filters.
Expression flow for 3D-aware face component transfer
Authors: Yang Fei , Wang Jue , Shechtman Eli , Bourdev Lubomir , Metaxas Dimitri
Published: July 2011

We address the problem of correcting an undesirable expression on a face photo by transferring local facial components, such as a smiling mouth, from another face photo of the same person which has the desired expression. Direct copying and blending using existing compositing tools results in semantically unnatural composites, since expression is a global effect and the local component in one expression is often incompatible with the shape and other components of the face in another expression. To solve this problem we present Expression Flow, a 2D flow field which can warp the target face globally in a natural way, so that the warped face is compatible with the new facial component to be copied over. To do this, starting with the two input face photos, we jointly construct a pair of 3D face shapes with the same identity but different expressions. The expression flow is computed by projecting the difference between the two 3D shapes back to 2D. It describes how to warp the target face photo to match the expression of the reference photo. User studies suggest that our system is able to generate face composites with much higher fidelity than existing methods.
Exploring photobios
Authors: Kemelmacher-Shlizerman Ira , Shechtman Eli , Garg Rahul , Seitz Steven M.
Published: July 2011

We present an approach for generating face animations from large image collections of the same person. Such collections, which we call
photobios
, sample the appearance of a person over changes in pose, facial expression, hairstyle, age, and other variations. By optimizing the order in which images are displayed and cross-dissolving between them, we control the motion through face space and create compelling animations (e.g., render a smooth transition from frowning to smiling). Used in this context, the
cross dissolve
produces a very strong motion effect; a key contribution of the paper is to explain this effect and analyze its operating range. The approach operates by creating a graph with faces as nodes, and similarities as edges, and solving for walks and shortest paths on this graph. The processing pipeline involves face detection, locating fiducials (eyes/nose/mouth), solving for pose, warping to frontal views, and image comparison based on Local Binary Patterns. We demonstrate results on a variety of datasets including time-lapse photography, personal photo collections, and images of celebrities downloaded from the Internet. Our approach is the basis for the Face Movies feature in Google's Picasa.
Discrete element textures
Authors: Ma Chongyang , Wei Li-Yi , Tong Xin
Published: July 2011

A variety of phenomena can be characterized by repetitive small scale elements within a large scale domain. Examples include a stack of fresh produce, a plate of spaghetti, or a mosaic pattern. Although certain results can be produced via manual placement or procedural/physical simulation, these methods can be labor intensive, difficult to control, or limited to specific phenomena.

We present discrete element textures, a data-driven method for synthesizing repetitive elements according to a small input exemplar and a large output domain. Our method preserves both individual element properties and their aggregate distributions. It is also general and applicable to a variety of phenomena, including different dimensionalities, different element properties and distributions, and different effects including both artistic and physically realistic ones. We represent each element by one or multiple samples whose positions encode relevant element attributes including position, size, shape, and orientation. We propose a sample-based neighborhood similarity metric and an energy optimization solver to synthesize desired outputs that observe not only input exemplars and output domains but also optional constraints such as physics, orientation fields, and boundary conditions. As a further benefit, our method can also be applied for editing existing element distributions.
Example-based image color and tone style enhancement
Authors: Wang Baoyuan , Yu Yizhou , Xu Ying-Qing
Published: July 2011

Color and tone adjustments are among the most frequent image enhancement operations. We define a color and tone style as a set of explicit or implicit rules governing color and tone adjustments. Our goal in this paper is to learn implicit color and tone adjustment rules from examples. That is, given a set of examples, each of which is a pair of corresponding images before and after adjustments, we would like to discover the underlying mathematical relationships optimally connecting the color and tone of corresponding pixels in all image pairs. We formally define tone and color adjustment rules as mappings, and propose to approximate complicated spatially varying nonlinear mappings in a piecewise manner. The reason behind this is that a very complicated mapping can still be locally approximated with a low-order polynomial model. Parameters within such low-order models are trained using data extracted from example image pairs. We successfully apply our framework in two scenarios, low-quality photo enhancement by transferring the style of a high-end camera, and photo enhancement using styles learned from photographers and designers.
MeshFlow
Authors: Denning Jonathan D. , Kerr William B. , Pellacini Fabio
Published: July 2011

The construction of polygonal meshes remains a complex task in Computer Graphics, taking tens of thousands of individual operations over several hours of modeling time. The complexity of modeling in terms of number of operations and time makes it difficult for artists to understand all details of how meshes are constructed. We present
MeshFlow
, an interactive system for visualizing mesh construction sequences.
MeshFlow
hierarchically clusters mesh editing operations to provide viewers with an overview of the model construction while still allowing them to view more details on demand. We base our clustering on an analysis of the frequency of repeated operations and implement it using substituting regular expressions. By filtering operations based on either their type or which vertices they affect,
MeshFlow
also ensures that viewers can interactively focus on the relevant parts of the modeling process. Automatically generated graphical annotations visualize the clustered operations. We have tested
MeshFlow
by visualizing five mesh sequences each taking a few hours to model, and we found it to work well for all. We have also evaluated
MeshFlow
with a case study using modeling students. We conclude that our system provides useful visualizations that are found to be more helpful than video or document-form instructions in understanding mesh construction.
Local Laplacian filters
Authors: Paris Sylvain , Hasinoff Samuel W. , Kautz Jan
Published: July 2011

The Laplacian pyramid is ubiquitous for decomposing images into multiple scales and is widely used for image analysis. However, because it is constructed with spatially invariant Gaussian kernels, the Laplacian pyramid is widely believed as being unable to represent edges well and as being ill-suited for edge-aware operations such as edge-preserving smoothing and tone mapping. To tackle these tasks, a wealth of alternative techniques and representations have been proposed, e.g., anisotropic diffusion, neighborhood filtering, and specialized wavelet bases. While these methods have demonstrated successful results, they come at the price of additional complexity, often accompanied by higher computational cost or the need to post-process the generated results. In this paper, we show state-of-the-art edge-aware processing using standard Laplacian pyramids. We characterize edges with a simple threshold on pixel values that allows us to differentiate large-scale edges from small-scale details. Building upon this result, we propose a set of image filters to achieve edge-preserving smoothing, detail enhancement, tone mapping, and inverse tone mapping. The advantage of our approach is its simplicity and flexibility, relying only on simple point-wise nonlinearities and small Gaussian convolutions; no optimization or post-processing is required. As we demonstrate, our method produces consistently high-quality results, without degrading edges or introducing halos.
Domain transform for edge-aware image and video processing
Authors: Gastal Eduardo S. L. , Oliveira Manuel M.
Published: July 2011

We present a new approach for performing high-quality edge-preserving filtering of images and videos in real time. Our solution is based on a transform that defines an isometry between curves on the 2D image manifold in 5D and the real line. This transform preserves the geodesic distance between points on these curves, adaptively warping the input signal so that 1D edge-preserving filtering can be efficiently performed in linear time. We demonstrate three realizations of 1D edge-preserving filters, show how to produce high-quality 2D edge-preserving filters by iterating 1D-filtering operations, and empirically analyze the convergence of this process. Our approach has several desirable features: the use of 1D operations leads to considerable speedups over existing techniques and potential memory savings; its computational cost is not affected by the choice of the filter parameters; and it is the first edge-preserving filter to work on color images at arbitrary scales in real time, without resorting to subsampling or quantization. We demonstrate the versatility of our domain transform and edge-preserving filters on several real-time image and video processing tasks including edge-preserving filtering, depth-of-field effects, stylization, recoloring, colorization, detail enhancement, and tone mapping.