We present a novel framework to evaluate multi‐agent crowd simulation algorithms based on real‐world observations of crowd movements. A key aspect of our approach is to enable fair comparisons by ...automatically estimating the parameters that enable the simulation algorithms to best fit the given data. We formulate parameter estimation as an optimization problem, and propose a general framework to solve the combinatorial optimization problem for all parameterized crowd simulation algorithms. Our framework supports a variety of metrics to compare reference data and simulation outputs. The reference data may correspond to recorded trajectories, macroscopic parameters, or artist‐driven sketches. We demonstrate the benefits of our framework for example‐based simulation, modeling of cultural variations, artist‐driven crowd animation, and relative comparison of some widely‐used multi‐agent simulation algorithms.
The Hybrid Reciprocal Velocity Obstacle Snape, J.; van den Berg, J.; Guy, S. J. ...
IEEE transactions on robotics,
08/2011, Letnik:
27, Številka:
4
Journal Article
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We present the hybrid reciprocal velocity obstacle for collision-free and oscillation-free navigation of multiple mobile robots or virtual agents. Each robot senses its surroundings and acts ...independently without central coordination or communication with other robots. Our approach uses both the current position and the velocity of other robots to compute their future trajectories in order to avoid collisions. Moreover, our approach is reciprocal and avoids oscillations by explicitly taking into account that the other robots sense their surroundings as well and change their trajectories accordingly. We apply hybrid reciprocal velocity obstacles to iRobot Create mobile robots and demonstrate direct, collision-free, and oscillation-free navigation.
Fast BVH Construction on GPUs Lauterbach, C.; Garland, M.; Sengupta, S. ...
Computer graphics forum,
April 2009, Letnik:
28, Številka:
2
Journal Article
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We present two novel parallel algorithms for rapidly constructing bounding volume hierarchies on manycore GPUs. The first uses a linear ordering derived from spatial Morton codes to build hierarchies ...extremely quickly and with high parallel scalability. The second is a top‐down approach that uses the surface area heuristic (SAH) to build hierarchies optimized for fast ray tracing. Both algorithms are combined into a hybrid algorithm that removes existing bottlenecks in the algorithm for GPU construction performance and scalability leading to significantly decreased build time. The resulting hierarchies are close in to optimized SAH hierarchies, but the construction process is substantially faster, leading to a significant net benefit when both construction and traversal cost are accounted for. Our preliminary results show that current GPU architectures can compete with CPU implementations of hierarchy construction running on multicore systems. In practice, we can construct hierarchies of models with up to several million triangles and use them for fast ray tracing or other applications.
We present a new motion‐compensated hierarchical compression scheme (HMLFC) for encoding light field images (LFI) that is suitable for interactive rendering. Our method combines two different ...approaches, motion compensation schemes and hierarchical compression methods, to exploit redundancies in LFI. The motion compensation schemes capture the redundancies in local regions of the LFI efficiently (local coherence) and the hierarchical schemes capture the redundancies present across the entire LFI (global coherence). Our hybrid approach combines the two schemes effectively capturing both local as well as global coherence to improve the overall compression rate. We compute a tree from LFI using a hierarchical scheme and use phase shifted motion compensation techniques at each level of the hierarchy. Our representation provides random access to the pixel values of the light field, which makes it suitable for interactive rendering applications using a small run‐time memory footprint. Our approach is GPU friendly and allows parallel decoding of LF pixel values. We highlight the performance on the two‐plane parameterized light fields and obtain a compression ratio of 30–800× with a PSNR of 40–45 dB. Overall, we observe a ∼2–5× improvement in compression rates using HMLFC over prior light field compression schemes that provide random access capability. In practice, our algorithm can render new views of resolution 512 × 512 on an NVIDIA GTX‐980 at ∼200 fps.
The amyloid beta (Aβ) peptide is associated with the neurodegenerative and inflammatory changes in brains affected by Alzheimer's disease (AD). We hypothesized that the enteric nervous system also ...produces Aβ in an intestinal component of disease. To test this idea, we compared C57BL/6 wild-type (WT) male and female mice to two models of Alzheimer's disease, amyloid precursor protein (APP)/presenilin 1 (PS1) mice and amyloid precursor protein NL-G-F (AppNL-G-F) mice, at 3, 6, and 12 months of age. Brain Aβ plaque deposition in AppNL-G-F mice preceded that in the APP/PS1 mice, observable by 3 months. Three-month-old female AppNL-G-F mice had decreased intestinal motility compared with WT and APP/PS1 mice. However, 3-month-old female APP/PS1 mice demonstrated increased intestinal permeability compared with WT and AppNL-G-F mice. Both sexes of APP/PS1 and AppNL-G-F mice demonstrated increased colon lipocalin 2 mRNA and insoluble Aβ 1–42 levels at 3 months. These data demonstrate an unrecognized enteric aspect of disease in 2 different mouse models correlating with the earliest brain changes.
•AppNL-G-F and amyloid precursor protein/PS1 mice demonstrated sex and age-dependent dysfunction in intestinal motility and permeability, correlating with colonic proinflammatory changes and amyloid beta (Aβ) levels.•Intestinal dysfunction, inflammation, and Aβ changes correlated with the earliest proinflammatory and Aβ changes in the brains of AppNL-G-F and amyloid precursor protein/PS1 mice.•This study demonstrated a novel aspect of Alzheimer's disease associated with the intestines during early disease.
Aging is a major risk factor for Alzheimer’s disease (AD). Insulin like growth factor-1 receptor (IGF-1R) regulates general aging and lifespan. However, the contribution of IGF-1 to age-related AD ...pathology and progression is highly controversial. Based on our previous work, AβPP/PS1 double transgenic mice, which express human mutant amyloid precursor protein (APP) and presenilin-1 (PS-1), demonstrated a decrease in brain IGF-1 levels when they were crossed with IGF-1 deficient Ames dwarf mice (df/df). Subsequently, a reduction in gliosis, amyloid-β (Aβ) plaque deposition, and Aβ1-40/42 concentrations were observed in this mouse model. This supported the hypothesis that IGF-1 may contribute to progression of disease. To assess the role of IGF-1 in AD, 9-10-month-old male littermate control wild type and AβPP/PS1 mice were randomly divided into 2 treatment groups including control vehicle (DMSO) and picropodophyllin (PPP), a selective, competitive, and reversible IGF-1R inhibitor. The brain penetrant inhibitor was given ip. at 1mg/kg/day. Mice were sacrificed after 7 days of daily injection and the brains, spleens, and livers were collected to quantify histologic and biochemical changes. The PPP-treated AβPP/PS1 mice demonstrated attenuated insoluble Aβ1-40/42 and pro-inflammatory cytokine levels in the temporal cortex including eotaxin, TNF-, IL-1, and IL-1. Additionally, an attenuation in microgliosis and protein p-tyrosine levels were observed due to drug treatment in the hippocampus. Our data suggests IGF-1R signaling is associated with disease progression in this mouse model. More importantly, modulation of the brain IGF-1R signaling pathway, even at mid-life, was enough to attenuate aspects of disease phenotype. This suggests that small molecule therapy targeting the IGF-1R pathway may be viable for late stage disease treatment.
Environmental exposure to air pollution has been linked to a number of health problems including organ rejection, lung damage and inflammation. While the deleterious effects of air pollution in adult ...animals are well documented, the long-term consequences of particulate matter (PM) exposure during animal development are uncertain. In this study we tested the hypothesis that environmental exposure to PM 2.5 μm in diameter in utero promotes long term inflammation and neurodegeneration. We evaluated the behavior of PM exposed animals using several tests and observed deficits in spatial memory without robust changes in anxiety-like behavior. We then examined how this affects the brains of adult animals by examining proteins implicated in neurodegeneration, synapse formation and inflammation by western blot, ELISA and immunohistochemistry. These tests revealed significantly increased levels of COX2 protein in PM2.5 exposed animal brains in addition to changes in synaptophysin and Arg1 proteins. Exposure to PM2.5 also increased the immunoreactivity for GFAP, a marker of activated astrocytes. Cytokine concentrations in the brain and spleen were also altered by PM2.5 exposure. These findings indicate that in utero exposure to particulate matter has long term consequences which may affect the development of both the brain and the immune system in addition to promoting inflammatory change in adult animals.
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•Exposure to PM2.5in utero impaired spatial memory in adult animals with minimal effects on anxiety-like behavior.•Brains harvested from animals exposed to PM2.5in utero had increased protein levels of COX2, Arg1 and synaptophysin.•Modest morphological changes in microglia and astrocytes were observed by immunohistochemistry in PM2.5 exposed animals.•Exposure to PM2.5 altered the levels of numerous cytokines in both the brain and spleen.
Our data indicate that in utero exposure to particulate matter has long term consequences in the adult brain including behavioral alterations, increased COX2 expression and broad changes in cytokine levels.
We present novel parallel algorithms for collision detection and separation distance computation for rigid and deformable models that exploit the computational capabilities of many‐core GPUs. Our ...approach uses thread and data parallelism to perform fast hierarchy construction, updating, and traversal using tight‐fitting bounding volumes such as oriented bounding boxes (OBB) and rectangular swept spheres (RSS). We also describe efficient algorithms to compute a linear bounding volume hierarchy (LBVH) and update them using refitting methods. Moreover, we show that tight‐fitting bounding volume hierarchies offer improved performance on GPU‐like throughput architectures. We use our algorithms to perform discrete and continuous collision detection including self‐collisions, as well as separation distance computation between non‐overlapping models. In practice, our approach (gProximity) can perform these queries in a few milliseconds on a PC with NVIDIA GTX 285 card on models composed of tens or hundreds of thousands of triangles used in cloth simulation, surgical simulation, virtual prototyping and N‐body simulation. Moreover, we observe more than an order of magnitude performance improvement over prior GPU‐based algorithms.
Amyloid β (Aβ) peptide is hypothesized to stimulate microglia to acquire their characteristic proinflammatory phenotype in Alzheimer's disease (AD) brains. The specific mechanisms by which Aβ leads ...to microglial activation remain an area of interest for identifying attractive molecular targets for intervention. Based upon the fact that microglia express the proinflammatory transcription factor, nuclear factor of activated T cells (NFAT), we hypothesized that NFAT activity is required for the Aβ-stimulated microgliosis that occurs during disease.
Primary murine microglia cultures were stimulated with Aβ in the absence or presence of NFAT inhibitors, FK506 and tat-VIVIT peptide, to quantify secretion of cytokines, neurotoxins, or Aβ phagocytosis. A transgenic mouse model of AD, APP/PS1, was treated subcutaneously via mini-osmotic pumps with FK506 or tat-VIVIT to quantify effects on cytokines, microgliosis, plaque load, and memory.
Expression of various NFAT isoforms was verified in primary murine microglia through Western blot analysis. Microglial cultures were stimulated with Aβ fibrils in the absence or presence of the NFAT inhibitors, FK506 and tat-VIVIT, to demonstrate that NFAT activity regulated Aβ phagocytosis, neurotoxin secretion, and cytokine secretion. Delivery of FK506 and tat-VIVIT to transgenic APP/PS1 mice attenuated spleen but not brain cytokine levels. However, FK506 and tat-VIVIT significantly attenuated both microgliosis and Aβ plaque load in treated mice compared to controls. Surprisingly, this did not correlate with changes in memory performance via T-maze testing.
Our findings suggest that development of specific NFAT inhibitors may offer promise as an effective strategy for attenuating the microgliosis and Aβ plaque deposition that occur in AD.
Opinion: Is Twitter a New Way to Learn? Jurivich, Donald A.; Manocha, Gunjan D.
Journal of investigative surgery,
05/2021, Letnik:
34, Številka:
5
Journal Article
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Celotno besedilo
Dostopno za:
DOBA, IJS, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
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