Deciphering the crowd: modeling and identification of pedestrian group motion.

PubMed

Yücel, Zeynep; Zanlungo, Francesco; Ikeda, Tetsushi; Miyashita, Takahiro; Hagita, Norihiro

2013-01-14

Associating attributes to pedestrians in a crowd is relevant for various areas like surveillance, customer profiling and service providing. The attributes of interest greatly depend on the application domain and might involve such social relations as friends or family as well as the hierarchy of the group including the leader or subordinates. Nevertheless, the complex social setting inherently complicates this task. We attack this problem by exploiting the small group structures in the crowd. The relations among individuals and their peers within a social group are reliable indicators of social attributes. To that end, this paper identifies social groups based on explicit motion models integrated through a hypothesis testing scheme. We develop two models relating positional and directional relations. A pair of pedestrians is identified as belonging to the same group or not by utilizing the two models in parallel, which defines a compound hypothesis testing scheme. By testing the proposed approach on three datasets with different environmental properties and group characteristics, it is demonstrated that we achieve an identification accuracy of 87% to 99%. The contribution of this study lies in its definition of positional and directional relation models, its description of compound evaluations, and the resolution of ambiguities with our proposed uncertainty measure based on the local and global indicators of group relation.

Deciphering the Crowd: Modeling and Identification of Pedestrian Group Motion

PubMed Central

Yücel, Zeynep; Zanlungo, Francesco; Ikeda, Tetsushi; Miyashita, Takahiro; Hagita, Norihiro

2013-01-01

Associating attributes to pedestrians in a crowd is relevant for various areas like surveillance, customer profiling and service providing. The attributes of interest greatly depend on the application domain and might involve such social relations as friends or family as well as the hierarchy of the group including the leader or subordinates. Nevertheless, the complex social setting inherently complicates this task. We attack this problem by exploiting the small group structures in the crowd. The relations among individuals and their peers within a social group are reliable indicators of social attributes. To that end, this paper identifies social groups based on explicit motion models integrated through a hypothesis testing scheme. We develop two models relating positional and directional relations. A pair of pedestrians is identified as belonging to the same group or not by utilizing the two models in parallel, which defines a compound hypothesis testing scheme. By testing the proposed approach on three datasets with different environmental properties and group characteristics, it is demonstrated that we achieve an identification accuracy of 87% to 99%. The contribution of this study lies in its definition of positional and directional relation models, its description of compound evaluations, and the resolution of ambiguities with our proposed uncertainty measure based on the local and global indicators of group relation. PMID:23344382

Detecting and Analyzing Multiple Moving Objects in Crowded Environments with Coherent Motion Regions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cheriyadat, Anil M.

Understanding the world around us from large-scale video data requires vision systems that can perform automatic interpretation. While human eyes can unconsciously perceive independent objects in crowded scenes and other challenging operating environments, automated systems have difficulty detecting, counting, and understanding their behavior in similar scenes. Computer scientists at ORNL have a developed a technology termed as "Coherent Motion Region Detection" that invloves identifying multiple indepedent moving objects in crowded scenes by aggregating low-level motion cues extracted from moving objects. Humans and other species exploit such low-level motion cues seamlessely to perform perceptual grouping for visual understanding. The algorithm detectsmore » and tracks feature points on moving objects resulting in partial trajectories that span coherent 3D region in the space-time volume defined by the video. In the case of multi-object motion, many possible coherent motion regions can be constructed around the set of trajectories. The unique approach in the algorithm is to identify all possible coherent motion regions, then extract a subset of motion regions based on an innovative measure to automatically locate moving objects in crowded environments.The software reports snapshot of the object, count, and derived statistics ( count over time) from input video streams. The software can directly process videos streamed over the internet or directly from a hardware device (camera).« less

Simulating dynamical features of escape panic

NASA Astrophysics Data System (ADS)

Helbing, Dirk; Farkas, Illés; Vicsek, Tamás

2000-09-01

One of the most disastrous forms of collective human behaviour is the kind of crowd stampede induced by panic, often leading to fatalities as people are crushed or trampled. Sometimes this behaviour is triggered in life-threatening situations such as fires in crowded buildings; at other times, stampedes can arise during the rush for seats or seemingly without cause. Although engineers are finding ways to alleviate the scale of such disasters, their frequency seems to be increasing with the number and size of mass events. But systematic studies of panic behaviour and quantitative theories capable of predicting such crowd dynamics are rare. Here we use a model of pedestrian behaviour to investigate the mechanisms of (and preconditions for) panic and jamming by uncoordinated motion in crowds. Our simulations suggest practical ways to prevent dangerous crowd pressures. Moreover, we find an optimal strategy for escape from a smoke-filled room, involving a mixture of individualistic behaviour and collective `herding' instinct.

Congestion detection of pedestrians using the velocity entropy: A case study of Love Parade 2010 disaster

NASA Astrophysics Data System (ADS)

Huang, Lida; Chen, Tao; Wang, Yan; Yuan, Hongyong

2015-12-01

Gatherings of large human crowds often result in crowd disasters such as the Love Parade Disaster in Duisburg, Germany on July 24, 2010. To avoid these tragedies, video surveillance and early warning are becoming more and more significant. In this paper, the velocity entropy is first defined as the criterion for congestion detection, which represents the motion magnitude distribution and the motion direction distribution simultaneously. Then the detection method is verified by the simulation data based on AnyLogic software. To test the generalization performance of this method, video recordings of a real-world case, the Love Parade disaster, are also used in the experiments. The velocity histograms of the foreground object in the videos are extracted by the Gaussian Mixture Model (GMM) and optical flow computation. With a sequential change-point detection algorithm, the velocity entropy can be applied to detect congestions of the Love Parade festival. It turned out that without recognizing and tracking individual pedestrian, our method can detect abnormal crowd behaviors in real-time.

Anomalous transport in the crowded world of biological cells

NASA Astrophysics Data System (ADS)

Höfling, Felix; Franosch, Thomas

2013-04-01

A ubiquitous observation in cell biology is that the diffusive motion of macromolecules and organelles is anomalous, and a description simply based on the conventional diffusion equation with diffusion constants measured in dilute solution fails. This is commonly attributed to macromolecular crowding in the interior of cells and in cellular membranes, summarizing their densely packed and heterogeneous structures. The most familiar phenomenon is a sublinear, power-law increase of the mean-square displacement (MSD) as a function of the lag time, but there are other manifestations like strongly reduced and time-dependent diffusion coefficients, persistent correlations in time, non-Gaussian distributions of spatial displacements, heterogeneous diffusion and a fraction of immobile particles. After a general introduction to the statistical description of slow, anomalous transport, we summarize some widely used theoretical models: Gaussian models like fractional Brownian motion and Langevin equations for visco-elastic media, the continuous-time random walk model, and the Lorentz model describing obstructed transport in a heterogeneous environment. Particular emphasis is put on the spatio-temporal properties of the transport in terms of two-point correlation functions, dynamic scaling behaviour, and how the models are distinguished by their propagators even if the MSDs are identical. Then, we review the theory underlying commonly applied experimental techniques in the presence of anomalous transport like single-particle tracking, fluorescence correlation spectroscopy (FCS) and fluorescence recovery after photobleaching (FRAP). We report on the large body of recent experimental evidence for anomalous transport in crowded biological media: in cyto- and nucleoplasm as well as in cellular membranes, complemented by in vitro experiments where a variety of model systems mimic physiological crowding conditions. Finally, computer simulations are discussed which play an important role in testing the theoretical models and corroborating the experimental findings. The review is completed by a synthesis of the theoretical and experimental progress identifying open questions for future investigation.

Perceiving Group Behavior: Sensitive Ensemble Coding Mechanisms for Biological Motion of Human Crowds

ERIC Educational Resources Information Center

Sweeny, Timothy D.; Haroz, Steve; Whitney, David

2013-01-01

Many species, including humans, display group behavior. Thus, perceiving crowds may be important for social interaction and survival. Here, we provide the first evidence that humans use ensemble-coding mechanisms to perceive the behavior of a crowd of people with surprisingly high sensitivity. Observers estimated the headings of briefly presented…

Anomalous, non-Gaussian tracer diffusion in crowded two-dimensional environments

NASA Astrophysics Data System (ADS)

Ghosh, Surya K.; Cherstvy, Andrey G.; Grebenkov, Denis S.; Metzler, Ralf

2016-01-01

A topic of intense current investigation pursues the question of how the highly crowded environment of biological cells affects the dynamic properties of passively diffusing particles. Motivated by recent experiments we report results of extensive simulations of the motion of a finite sized tracer particle in a heterogeneously crowded environment made up of quenched distributions of monodisperse crowders of varying sizes in finite circular two-dimensional domains. For given spatial distributions of monodisperse crowders we demonstrate how anomalous diffusion with strongly non-Gaussian features arises in this model system. We investigate both biologically relevant situations of particles released either at the surface of an inner domain or at the outer boundary, exhibiting distinctly different features of the observed anomalous diffusion for heterogeneous distributions of crowders. Specifically we reveal an asymmetric spreading of tracers even at moderate crowding. In addition to the mean squared displacement (MSD) and local diffusion exponent we investigate the magnitude and the amplitude scatter of the time averaged MSD of individual tracer trajectories, the non-Gaussianity parameter, and the van Hove correlation function. We also quantify how the average tracer diffusivity varies with the position in the domain with a heterogeneous radial distribution of crowders and examine the behaviour of the survival probability and the dynamics of the tracer survival probability. Inter alia, the systems we investigate are related to the passive transport of lipid molecules and proteins in two-dimensional crowded membranes or the motion in colloidal solutions or emulsions in effectively two-dimensional geometries, as well as inside supercrowded, surface adhered cells.

Foot force models of crowd dynamics on a wobbly bridge

PubMed Central

Belykh, Igor; Jeter, Russell; Belykh, Vladimir

2017-01-01

Modern pedestrian and suspension bridges are designed using industry standard packages, yet disastrous resonant vibrations are observed, necessitating multimillion dollar repairs. Recent examples include pedestrian-induced vibrations during the opening of the Solférino Bridge in Paris in 1999 and the increased bouncing of the Squibb Park Bridge in Brooklyn in 2014. The most prominent example of an unstable lively bridge is the London Millennium Bridge, which started wobbling as a result of pedestrian-bridge interactions. Pedestrian phase locking due to footstep phase adjustment is suspected to be the main cause of its large lateral vibrations; however, its role in the initiation of wobbling was debated. We develop foot force models of pedestrians’ response to bridge motion and detailed, yet analytically tractable, models of crowd phase locking. We use biomechanically inspired models of crowd lateral movement to investigate to what degree pedestrian synchrony must be present for a bridge to wobble significantly and what is a critical crowd size. Our results can be used as a safety guideline for designing pedestrian bridges or limiting the maximum occupancy of an existing bridge. The pedestrian models can be used as “crash test dummies” when numerically probing a specific bridge design. This is particularly important because the U.S. code for designing pedestrian bridges does not contain explicit guidelines that account for the collective pedestrian behavior. PMID:29296679

Foot force models of crowd dynamics on a wobbly bridge.

PubMed

Belykh, Igor; Jeter, Russell; Belykh, Vladimir

2017-11-01

Modern pedestrian and suspension bridges are designed using industry standard packages, yet disastrous resonant vibrations are observed, necessitating multimillion dollar repairs. Recent examples include pedestrian-induced vibrations during the opening of the Solférino Bridge in Paris in 1999 and the increased bouncing of the Squibb Park Bridge in Brooklyn in 2014. The most prominent example of an unstable lively bridge is the London Millennium Bridge, which started wobbling as a result of pedestrian-bridge interactions. Pedestrian phase locking due to footstep phase adjustment is suspected to be the main cause of its large lateral vibrations; however, its role in the initiation of wobbling was debated. We develop foot force models of pedestrians' response to bridge motion and detailed, yet analytically tractable, models of crowd phase locking. We use biomechanically inspired models of crowd lateral movement to investigate to what degree pedestrian synchrony must be present for a bridge to wobble significantly and what is a critical crowd size. Our results can be used as a safety guideline for designing pedestrian bridges or limiting the maximum occupancy of an existing bridge. The pedestrian models can be used as "crash test dummies" when numerically probing a specific bridge design. This is particularly important because the U.S. code for designing pedestrian bridges does not contain explicit guidelines that account for the collective pedestrian behavior.

How cognitive heuristics can explain social interactions in spatial movement.

PubMed

Seitz, Michael J; Bode, Nikolai W F; Köster, Gerta

2016-08-01

The movement of pedestrian crowds is a paradigmatic example of collective motion. The precise nature of individual-level behaviours underlying crowd movements has been subject to a lively debate. Here, we propose that pedestrians follow simple heuristics rooted in cognitive psychology, such as 'stop if another step would lead to a collision' or 'follow the person in front'. In other words, our paradigm explicitly models individual-level behaviour as a series of discrete decisions. We show that our cognitive heuristics produce realistic emergent crowd phenomena, such as lane formation and queuing behaviour. Based on our results, we suggest that pedestrians follow different cognitive heuristics that are selected depending on the context. This differs from the widely used approach of capturing changes in behaviour via model parameters and leads to testable hypotheses on changes in crowd behaviour for different motivation levels. For example, we expect that rushed individuals more often evade to the side and thus display distinct emergent queue formations in front of a bottleneck. Our heuristics can be ranked according to the cognitive effort that is required to follow them. Therefore, our model establishes a direct link between behavioural responses and cognitive effort and thus facilitates a novel perspective on collective behaviour. © 2016 The Author(s).

How cognitive heuristics can explain social interactions in spatial movement

PubMed Central

Köster, Gerta

2016-01-01

The movement of pedestrian crowds is a paradigmatic example of collective motion. The precise nature of individual-level behaviours underlying crowd movements has been subject to a lively debate. Here, we propose that pedestrians follow simple heuristics rooted in cognitive psychology, such as ‘stop if another step would lead to a collision’ or ‘follow the person in front’. In other words, our paradigm explicitly models individual-level behaviour as a series of discrete decisions. We show that our cognitive heuristics produce realistic emergent crowd phenomena, such as lane formation and queuing behaviour. Based on our results, we suggest that pedestrians follow different cognitive heuristics that are selected depending on the context. This differs from the widely used approach of capturing changes in behaviour via model parameters and leads to testable hypotheses on changes in crowd behaviour for different motivation levels. For example, we expect that rushed individuals more often evade to the side and thus display distinct emergent queue formations in front of a bottleneck. Our heuristics can be ranked according to the cognitive effort that is required to follow them. Therefore, our model establishes a direct link between behavioural responses and cognitive effort and thus facilitates a novel perspective on collective behaviour. PMID:27581483

Uncertainty in a spatial evacuation model

NASA Astrophysics Data System (ADS)

Mohd Ibrahim, Azhar; Venkat, Ibrahim; Wilde, Philippe De

2017-08-01

Pedestrian movements in crowd motion can be perceived in terms of agents who basically exhibit patient or impatient behavior. We model crowd motion subject to exit congestion under uncertainty conditions in a continuous space and compare the proposed model via simulations with the classical social force model. During a typical emergency evacuation scenario, agents might not be able to perceive with certainty the strategies of opponents (other agents) owing to the dynamic changes entailed by the neighborhood of opponents. In such uncertain scenarios, agents will try to update their strategy based on their own rules or their intrinsic behavior. We study risk seeking, risk averse and risk neutral behaviors of such agents via certain game theory notions. We found that risk averse agents tend to achieve faster evacuation time whenever the time delay in conflicts appears to be longer. The results of our simulations also comply with previous work and conform to the fact that evacuation time of agents becomes shorter once mutual cooperation among agents is achieved. Although the impatient strategy appears to be the rational strategy that might lead to faster evacuation times, our study scientifically shows that the more the agents are impatient, the slower is the egress time.

Structure preserving clustering-object tracking via subgroup motion pattern segmentation

NASA Astrophysics Data System (ADS)

Fan, Zheyi; Zhu, Yixuan; Jiang, Jiao; Weng, Shuqin; Liu, Zhiwen

2018-01-01

Tracking clustering objects with similar appearances simultaneously in collective scenes is a challenging task in the field of collective motion analysis. Recent work on clustering-object tracking often suffers from poor tracking accuracy and terrible real-time performance due to the neglect or the misjudgment of the motion differences among objects. To address this problem, we propose a subgroup motion pattern segmentation framework based on a multilayer clustering structure and establish spatial constraints only among objects in the same subgroup, which entails having consistent motion direction and close spatial position. In addition, the subgroup segmentation results are updated dynamically because crowd motion patterns are changeable and affected by objects' destinations and scene structures. The spatial structure information combined with the appearance similarity information is used in the structure preserving object tracking framework to track objects. Extensive experiments conducted on several datasets containing multiple real-world crowd scenes validate the accuracy and the robustness of the presented algorithm for tracking objects in collective scenes.

Application of Integral Optical Flow for Determining Crowd Movement from Video Images Obtained Using Video Surveillance Systems

NASA Astrophysics Data System (ADS)

Chen, H.; Ye, Sh.; Nedzvedz, O. V.; Ablameyko, S. V.

2018-03-01

Study of crowd movement is an important practical problem, and its solution is used in video surveillance systems for preventing various emergency situations. In the general case, a group of fast-moving people is of more interest than a group of stationary or slow-moving people. We propose a new method for crowd movement analysis using a video sequence, based on integral optical flow. We have determined several characteristics of a moving crowd such as density, speed, direction of motion, symmetry, and in/out index. These characteristics are used for further analysis of a video scene.

Effects of soft interactions and bound mobility on diffusion in crowded environments: a model of sticky and slippery obstacles

NASA Astrophysics Data System (ADS)

Stefferson, Michael W.; Norris, Samantha L.; Vernerey, Franck J.; Betterton, Meredith D.; E Hough, Loren

2017-08-01

Crowded environments modify the diffusion of macromolecules, generally slowing their movement and inducing transient anomalous subdiffusion. The presence of obstacles also modifies the kinetics and equilibrium behavior of tracers. While previous theoretical studies of particle diffusion have typically assumed either impenetrable obstacles or binding interactions that immobilize the particle, in many cellular contexts bound particles remain mobile. Examples include membrane proteins or lipids with some entry and diffusion within lipid domains and proteins that can enter into membraneless organelles or compartments such as the nucleolus. Using a lattice model, we studied the diffusive movement of tracer particles which bind to soft obstacles, allowing tracers and obstacles to occupy the same lattice site. For sticky obstacles, bound tracer particles are immobile, while for slippery obstacles, bound tracers can hop without penalty to adjacent obstacles. In both models, binding significantly alters tracer motion. The type and degree of motion while bound is a key determinant of the tracer mobility: slippery obstacles can allow nearly unhindered diffusion, even at high obstacle filling fraction. To mimic compartmentalization in a cell, we examined how obstacle size and a range of bound diffusion coefficients affect tracer dynamics. The behavior of the model is similar in two and three spatial dimensions. Our work has implications for protein movement and interactions within cells.

Towards Complete, Geo-Referenced 3d Models from Crowd-Sourced Amateur Images

NASA Astrophysics Data System (ADS)

Hartmann, W.; Havlena, M.; Schindler, K.

2016-06-01

Despite a lot of recent research, photogrammetric reconstruction from crowd-sourced imagery is plagued by a number of recurrent problems. (i) The resulting models are chronically incomplete, because even touristic landmarks are photographed mostly from a few "canonical" viewpoints. (ii) Man-made constructions tend to exhibit repetitive structure and rotational symmetries, which lead to gross errors in the 3D reconstruction and aggravate the problem of incomplete reconstruction. (iii) The models are normally not geo-referenced. In this paper, we investigate the possibility of using sparse GNSS geo-tags from digital cameras to address these issues and push the boundaries of crowd-sourced photogrammetry. A small proportion of the images in Internet collections (≍ 10 %) do possess geo-tags. While the individual geo-tags are very inaccurate, they nevertheless can help to address the problems above. By providing approximate geo-reference for partial reconstructions they make it possible to fuse those pieces into more complete models; the capability to fuse partial reconstruction opens up the possibility to be more restrictive in the matching phase and avoid errors due to repetitive structure; and collectively, the redundant set of low-quality geo-tags can provide reasonably accurate absolute geo-reference. We show that even few, noisy geo-tags can help to improve architectural models, compared to puristic structure-from-motion only based on image correspondence.

a Gaussian Process Based Multi-Person Interaction Model

NASA Astrophysics Data System (ADS)

Klinger, T.; Rottensteiner, F.; Heipke, C.

2016-06-01

Online multi-person tracking in image sequences is commonly guided by recursive filters, whose predictive models define the expected positions of future states. When a predictive model deviates too much from the true motion of a pedestrian, which is often the case in crowded scenes due to unpredicted accelerations, the data association is prone to fail. In this paper we propose a novel predictive model on the basis of Gaussian Process Regression. The model takes into account the motion of every tracked pedestrian in the scene and the prediction is executed with respect to the velocities of all interrelated persons. As shown by the experiments, the model is capable of yielding more plausible predictions even in the presence of mutual occlusions or missing measurements. The approach is evaluated on a publicly available benchmark and outperforms other state-of-the-art trackers.

Anomalous Diffusion of Single Particles in Cytoplasm

PubMed Central

Regner, Benjamin M.; Vučinić, Dejan; Domnisoru, Cristina; Bartol, Thomas M.; Hetzer, Martin W.; Tartakovsky, Daniel M.; Sejnowski, Terrence J.

2013-01-01

The crowded intracellular environment poses a formidable challenge to experimental and theoretical analyses of intracellular transport mechanisms. Our measurements of single-particle trajectories in cytoplasm and their random-walk interpretations elucidate two of these mechanisms: molecular diffusion in crowded environments and cytoskeletal transport along microtubules. We employed acousto-optic deflector microscopy to map out the three-dimensional trajectories of microspheres migrating in the cytosolic fraction of a cellular extract. Classical Brownian motion (BM), continuous time random walk, and fractional BM were alternatively used to represent these trajectories. The comparison of the experimental and numerical data demonstrates that cytoskeletal transport along microtubules and diffusion in the cytosolic fraction exhibit anomalous (nonFickian) behavior and posses statistically distinct signatures. Among the three random-walk models used, continuous time random walk provides the best representation of diffusion, whereas microtubular transport is accurately modeled with fractional BM. PMID:23601312

Structure, function and folding of phosphoglycerate kinase are strongly perturbed by macromolecular crowding.

NASA Astrophysics Data System (ADS)

Samiotakis, Antonios; Dhar, Apratim; Ebbinghaus, Simon; Nienhaus, Lea; Homouz, Dirar; Gruebele, Martin; Cheung, Margaret

2010-10-01

We combine experiment and computer simulation to show how macromolecular crowding dramatically affects the structure, function and folding landscape of phosphoglycerate kinase (PGK). Fluorescence labeling shows that compact states of yeast PGK are populated as the amount of crowding agents (Ficoll 70) increases. Coarse-grained molecular simulations reveal three compact ensembles: C (crystal structure), CC (collapsed crystal) and Sph (spherical compact). With an adjustment for viscosity, crowded wild type PGK and fluorescent PGK are about 15 times or more active in 200 mg/ml Ficoll than in aqueous solution. Our results suggest a new solution to the classic problem of how the ADP and diphosphoglycerate binding sites of PGK come together to make ATP: rather than undergoing a hinge motion, the ADP and substrate sites are already located in proximity under crowded conditions that mimic the in vivo conditions under which the enzyme actually operates.

A method of emotion contagion for crowd evacuation

NASA Astrophysics Data System (ADS)

Cao, Mengxiao; Zhang, Guijuan; Wang, Mengsi; Lu, Dianjie; Liu, Hong

2017-10-01

The current evacuation model does not consider the impact of emotion and personality on crowd evacuation. Thus, there is large difference between evacuation results and the real-life behavior of the crowd. In order to generate more realistic crowd evacuation results, we present a method of emotion contagion for crowd evacuation. First, we combine OCEAN (Openness, Extroversion, Agreeableness, Neuroticism, Conscientiousness) model and SIS (Susceptible Infected Susceptible) model to construct the P-SIS (Personalized SIS) emotional contagion model. The P-SIS model shows the diversity of individuals in crowd effectively. Second, we couple the P-SIS model with the social force model to simulate emotional contagion on crowd evacuation. Finally, the photo-realistic rendering method is employed to obtain the animation of crowd evacuation. Experimental results show that our method can simulate crowd evacuation realistically and has guiding significance for crowd evacuation in the emergency circumstances.

Non-universal tracer diffusion in crowded media of non-inert obstacles.

PubMed

Ghosh, Surya K; Cherstvy, Andrey G; Metzler, Ralf

2015-01-21

We study the diffusion of a tracer particle, which moves in continuum space between a lattice of excluded volume, immobile non-inert obstacles. In particular, we analyse how the strength of the tracer-obstacle interactions and the volume occupancy of the crowders alter the diffusive motion of the tracer. From the details of partitioning of the tracer diffusion modes between trapping states when bound to obstacles and bulk diffusion, we examine the degree of localisation of the tracer in the lattice of crowders. We study the properties of the tracer diffusion in terms of the ensemble and time averaged mean squared displacements, the trapping time distributions, the amplitude variation of the time averaged mean squared displacements, and the non-Gaussianity parameter of the diffusing tracer. We conclude that tracer-obstacle adsorption and binding triggers a transient anomalous diffusion. From a very narrow spread of recorded individual time averaged trajectories we exclude continuous type random walk processes as the underlying physical model of the tracer diffusion in our system. For moderate tracer-crowder attraction the motion is found to be fully ergodic, while at stronger attraction strength a transient disparity between ensemble and time averaged mean squared displacements occurs. We also put our results into perspective with findings from experimental single-particle tracking and simulations of the diffusion of tagged tracers in dense crowded suspensions. Our results have implications for the diffusion, transport, and spreading of chemical components in highly crowded environments inside living cells and other structured liquids.

Taming Crowded Visual Scenes

DTIC Science & Technology

2014-08-12

Nolan Warner, Mubarak Shah. Tracking in Dense Crowds Using Prominenceand Neighborhood Motion Concurrence, IEEE Transactions on Pattern Analysis...of  computer  vision,   computer   graphics  and  evacuation  dynamics  by  providing  a  common  platform,  and  provides...areas  that  includes  Computer  Vision,  Computer   Graphics ,  and  Pedestrian   Evacuation  Dynamics.  Despite  the

Crowd Modeling in Military Simulations: Requirements Analysis, Survey, and Design Study

DTIC Science & Technology

2003-04-01

Survey, Crowd Simulation Federate 16. SECURITY CLASSIFICATION OF: 17. LIMITATION 18. NUMBER 19a. NAME OF RESPONSIBLE PERSON OF ABSTRACT OF PAGES John L...models of crowds and crowd behavior are essentially absent from current production military simulations. The absence of models of crowds in military...understanding of cognitive psychology, including better connection of cognition to behavior, is essential to provide a psychological basis for crowd models

Two-stage perceptual learning to break visual crowding.

PubMed

Zhu, Ziyun; Fan, Zhenzhi; Fang, Fang

2016-01-01

When a target is presented with nearby flankers in the peripheral visual field, it becomes harder to identify, which is referred to as crowding. Crowding sets a fundamental limit of object recognition in peripheral vision, preventing us from fully appreciating cluttered visual scenes. We trained adult human subjects on a crowded orientation discrimination task and investigated whether crowding could be completely eliminated by training. We discovered a two-stage learning process with this training task. In the early stage, when the target and flankers were separated beyond a certain distance, subjects acquired a relatively general ability to break crowding, as evidenced by the fact that the breaking of crowding could transfer to another crowded orientation, even a crowded motion stimulus, although the transfer to the opposite visual hemi-field was weak. In the late stage, like many classical perceptual learning effects, subjects' performance gradually improved and showed specificity to the trained orientation. We also found that, when the target and flankers were spaced too finely, training could only reduce, rather than completely eliminate, the crowding effect. This two-stage learning process illustrates a learning strategy for our brain to deal with the notoriously difficult problem of identifying peripheral objects in clutter. The brain first learned to solve the "easy and general" part of the problem (i.e., improving the processing resolution and segmenting the target and flankers) and then tackle the "difficult and specific" part (i.e., refining the representation of the target).

The effect of eccentricity and spatiotemporal energy on motion silencing.

PubMed

Choi, Lark Kwon; Bovik, Alan C; Cormack, Lawrence K

2016-01-01

The now well-known motion-silencing illusion has shown that salient changes among a group of objects' luminances, colors, shapes, or sizes may appear to cease when objects move rapidly (Suchow & Alvarez, 2011). It has been proposed that silencing derives from dot spacing that causes crowding, coherent changes in object color or size, and flicker frequencies combined with dot spacing (Choi, Bovik, & Cormack, 2014; Peirce, 2013; Turi & Burr, 2013). Motion silencing is a peripheral effect that does not occur near the point of fixation. To better understand the effect of eccentricity on motion silencing, we measured the amount of motion silencing as a function of eccentricity in human observers using traditional psychophysics. Fifteen observers reported whether dots in any of four concentric rings changed in luminance over a series of rotational velocities. The results in the human experiments showed that the threshold velocity for motion silencing almost linearly decreases as a function of log eccentricity. Further, we modeled the response of a population of simulated V1 neurons to our stimuli. We found strong matches between the threshold velocities on motion silencing observed in the human experiment and those seen in the energy model of Adelson and Bergen (1985). We suggest the plausible explanation that as eccentricity increases, the combined motion-flicker signal falls outside the narrow spatiotemporal frequency response regions of the modeled receptive fields, thereby reducing flicker visibility.

A comparison of form processing involved in the perception of biological and nonbiological movements

PubMed Central

Thurman, Steven M.; Lu, Hongjing

2016-01-01

Although there is evidence for specialization in the human brain for processing biological motion per se, few studies have directly examined the specialization of form processing in biological motion perception. The current study was designed to systematically compare form processing in perception of biological (human walkers) to nonbiological (rotating squares) stimuli. Dynamic form-based stimuli were constructed with conflicting form cues (position and orientation), such that the objects were perceived to be moving ambiguously in two directions at once. In Experiment 1, we used the classification image technique to examine how local form cues are integrated across space and time in a bottom-up manner. By comparing with a Bayesian observer model that embodies generic principles of form analysis (e.g., template matching) and integrates form information according to cue reliability, we found that human observers employ domain-general processes to recognize both human actions and nonbiological object movements. Experiments 2 and 3 found differential top-down effects of spatial context on perception of biological and nonbiological forms. When a background does not involve social information, observers are biased to perceive foreground object movements in the direction opposite to surrounding motion. However, when a background involves social cues, such as a crowd of similar objects, perception is biased toward the same direction as the crowd for biological walking stimuli, but not for rotating nonbiological stimuli. The model provided an accurate account of top-down modulations by adjusting the prior probabilities associated with the internal templates, demonstrating the power and flexibility of the Bayesian approach for visual form perception. PMID:26746875

Simulation of counterflow pedestrian dynamics using spheropolygons

NASA Astrophysics Data System (ADS)

Alonso-Marroquín, Fernando; Busch, Jonathan; Chiew, Coraline; Lozano, Celia; Ramírez-Gómez, Álvaro

2014-12-01

Pedestrian dynamic models are typically designed for comfortable walking or slightly congested conditions and typically use a single disk or combination of three disks for the shape of a pedestrian. Under crowd conditions, a more accurate pedestrian shape has advantages over the traditional single or three-disks model. We developed a method for simulating pedestrian dynamics in a large dense crowd of spheropolygons adapted to the cross section of the chest and arms of a pedestrian. Our numerical model calculates pedestrian motion from Newton's second law, taking into account viscoelastic contact forces, contact friction, and ground-reaction forces. Ground-reaction torque was taken to arise solely from the pedestrians' orientation toward their preferred destination. Simulations of counterflow pedestrians dynamics in corridors were used to gain insight into a tragic incident at the Madrid Arena pavilion in Spain, where five girls were crushed to death. The incident took place at a Halloween Celebration in 2012, in a long, densely crowded hallway used as entrance and exit at the same time. Our simulations reconstruct the mechanism of clogging in the hallway. The hypothetical case of a total evacuation order was also investigated. The results highlights the importance of the pedestrians' density and the effect of counterflow in the onset of avalanches and clogging and provides an estimation of the number of injuries based on a calculation of the contact-force network between the pedestrians.

Simulation of counterflow pedestrian dynamics using spheropolygons.

PubMed

Alonso-Marroquín, Fernando; Busch, Jonathan; Chiew, Coraline; Lozano, Celia; Ramírez-Gómez, Álvaro

2014-12-01

Pedestrian dynamic models are typically designed for comfortable walking or slightly congested conditions and typically use a single disk or combination of three disks for the shape of a pedestrian. Under crowd conditions, a more accurate pedestrian shape has advantages over the traditional single or three-disks model. We developed a method for simulating pedestrian dynamics in a large dense crowd of spheropolygons adapted to the cross section of the chest and arms of a pedestrian. Our numerical model calculates pedestrian motion from Newton's second law, taking into account viscoelastic contact forces, contact friction, and ground-reaction forces. Ground-reaction torque was taken to arise solely from the pedestrians' orientation toward their preferred destination. Simulations of counterflow pedestrians dynamics in corridors were used to gain insight into a tragic incident at the Madrid Arena pavilion in Spain, where five girls were crushed to death. The incident took place at a Halloween Celebration in 2012, in a long, densely crowded hallway used as entrance and exit at the same time. Our simulations reconstruct the mechanism of clogging in the hallway. The hypothetical case of a total evacuation order was also investigated. The results highlights the importance of the pedestrians' density and the effect of counterflow in the onset of avalanches and clogging and provides an estimation of the number of injuries based on a calculation of the contact-force network between the pedestrians.

Intelligence Surveillance And Reconnaissance Full Motion Video Automatic Anomaly Detection Of Crowd Movements: System Requirements For Airborne Application

DTIC Science & Technology

The collection of Intelligence , Surveillance, and Reconnaissance (ISR) Full Motion Video (FMV) is growing at an exponential rate, and the manual... intelligence for the warfighter. This paper will address the question of how can automatic pattern extraction, based on computer vision, extract anomalies in

Research on Evacuation Based on Social Force Model

NASA Astrophysics Data System (ADS)

Liu, W.; Deng, Z.; Li, W.; Lin, J.

2017-09-01

Crowded centers always cause personnel casualties in evacuation operations. Stampede events often occur by hit, squeeze and crush due to panic. It is of vital important to alleviate such situation. With the deepening of personnel evacuation research, more and more researchers are committed to study individual behaviors and self-organization phenomenon in evacuation process. The study mainly includes: 1, enrich the social force model from different facets such as visual, psychological, external force to descript more realistic evacuation; 2, research on causes and effects of self - organization phenomenon. In this paper, we focus on disorder motion that occurs in the crowded indoor publics, especially the narrow channel and safety exits and other special arteries. We put forward the improved social force model to depict pedestrians' behaviors, an orderly speed-stratification evacuation method to solve disorder problem, and shape-changed export to alleviate congestion. The result of this work shows an improvement of evacuation efficiency by 19.5 %. Guiding pedestrians' direction to slow down the influence of social forces has a guidance function in improving the efficiency of indoor emergency evacuation.

Searching for High Proper Motion Sources Towards the Galactic Center using Convolution Neural Networks

NASA Astrophysics Data System (ADS)

Giongo Fernandes, Alexandre; Benjamin, Robert A.; Babler, Brian

2018-01-01

Two sets of infrared images of the Galactic Center region (|L|< 1 degree and |B| < 0.75 degrees) taken by the Spitzer Space Telescope in IRAC 3.6 micron and 4.5 micron bands are searched for high proper motion objects (> 100 mas/year). The two image sets come from GALCEN observations in 2005 and GLIMPSE proper observations in 2015 with matched observation modes. We use three different methods to search for these objects in extremely crowded fields: (1) comparing matched point source lists, (2) crowd sourcing by several college introductory astronomy classes in the state of Wisconsin (700 volunteers), and (3) convolutional neural networks trained using objects from the previous two methods. Before our search six high proper objects were known, four of which were found by the VVV near-infrared Galactic plane survey. We compare and describe our methods for this search, and present a preliminary catalog of high proper motions objects.

Peripheral Vision of Youths with Low Vision: Motion Perception, Crowding, and Visual Search

PubMed Central

Tadin, Duje; Nyquist, Jeffrey B.; Lusk, Kelly E.; Corn, Anne L.; Lappin, Joseph S.

2012-01-01

Purpose. Effects of low vision on peripheral visual function are poorly understood, especially in children whose visual skills are still developing. The aim of this study was to measure both central and peripheral visual functions in youths with typical and low vision. Of specific interest was the extent to which measures of foveal function predict performance of peripheral tasks. Methods. We assessed central and peripheral visual functions in youths with typical vision (n = 7, ages 10–17) and low vision (n = 24, ages 9–18). Experimental measures used both static and moving stimuli and included visual crowding, visual search, motion acuity, motion direction discrimination, and multitarget motion comparison. Results. In most tasks, visual function was impaired in youths with low vision. Substantial differences, however, were found both between participant groups and, importantly, across different tasks within participant groups. Foveal visual acuity was a modest predictor of peripheral form vision and motion sensitivity in either the central or peripheral field. Despite exhibiting normal motion discriminations in fovea, motion sensitivity of youths with low vision deteriorated in the periphery. This contrasted with typically sighted participants, who showed improved motion sensitivity with increasing eccentricity. Visual search was greatly impaired in youths with low vision. Conclusions. Our results reveal a complex pattern of visual deficits in peripheral vision and indicate a significant role of attentional mechanisms in observed impairments. These deficits were not adequately captured by measures of foveal function, arguing for the importance of independently assessing peripheral visual function. PMID:22836766

Peripheral vision of youths with low vision: motion perception, crowding, and visual search.

PubMed

Tadin, Duje; Nyquist, Jeffrey B; Lusk, Kelly E; Corn, Anne L; Lappin, Joseph S

2012-08-24

Effects of low vision on peripheral visual function are poorly understood, especially in children whose visual skills are still developing. The aim of this study was to measure both central and peripheral visual functions in youths with typical and low vision. Of specific interest was the extent to which measures of foveal function predict performance of peripheral tasks. We assessed central and peripheral visual functions in youths with typical vision (n = 7, ages 10-17) and low vision (n = 24, ages 9-18). Experimental measures used both static and moving stimuli and included visual crowding, visual search, motion acuity, motion direction discrimination, and multitarget motion comparison. In most tasks, visual function was impaired in youths with low vision. Substantial differences, however, were found both between participant groups and, importantly, across different tasks within participant groups. Foveal visual acuity was a modest predictor of peripheral form vision and motion sensitivity in either the central or peripheral field. Despite exhibiting normal motion discriminations in fovea, motion sensitivity of youths with low vision deteriorated in the periphery. This contrasted with typically sighted participants, who showed improved motion sensitivity with increasing eccentricity. Visual search was greatly impaired in youths with low vision. Our results reveal a complex pattern of visual deficits in peripheral vision and indicate a significant role of attentional mechanisms in observed impairments. These deficits were not adequately captured by measures of foveal function, arguing for the importance of independently assessing peripheral visual function.

Spatial-size scaling of pedestrian groups under growing density conditions

NASA Astrophysics Data System (ADS)

Zanlungo, Francesco; Brščić, Dražen; Kanda, Takayuki

2015-06-01

We study the dependence on crowd density of the spatial size, configuration, and velocity of pedestrian social groups. We find that, in the investigated density range, the extension of pedestrian groups in the direction orthogonal to that of motion decreases linearly with the pedestrian density around them, both for two- and three-person groups. Furthermore, we observe that at all densities, three-person groups walk slower than two-person groups, and the latter are slower than individual pedestrians, the differences in velocities being weakly affected by density. Finally, we observe that three-person groups walk in a V-shaped formation regardless of density, with a distance between the pedestrians in the front and back again almost independent of density, although the configuration appears to be less stable at higher densities. These findings may facilitate the development of more realistic crowd dynamics models and simulators.

Anomalous dynamics of intruders in a crowded environment of mobile obstacles

PubMed Central

Sentjabrskaja, Tatjana; Zaccarelli, Emanuela; De Michele, Cristiano; Sciortino, Francesco; Tartaglia, Piero; Voigtmann, Thomas; Egelhaaf, Stefan U.; Laurati, Marco

2016-01-01

Many natural and industrial processes rely on constrained transport, such as proteins moving through cells, particles confined in nanocomposite materials or gels, individuals in highly dense collectives and vehicular traffic conditions. These are examples of motion through crowded environments, in which the host matrix may retain some glass-like dynamics. Here we investigate constrained transport in a colloidal model system, in which dilute small spheres move in a slowly rearranging, glassy matrix of large spheres. Using confocal differential dynamic microscopy and simulations, here we discover a critical size asymmetry, at which anomalous collective transport of the small particles appears, manifested as a logarithmic decay of the density autocorrelation functions. We demonstrate that the matrix mobility is central for the observed anomalous behaviour. These results, crucially depending on size-induced dynamic asymmetry, are of relevance for a wide range of phenomena ranging from glassy systems to cell biology. PMID:27041068

Crowd macro state detection using entropy model

NASA Astrophysics Data System (ADS)

Zhao, Ying; Yuan, Mengqi; Su, Guofeng; Chen, Tao

2015-08-01

In the crowd security research area a primary concern is to identify the macro state of crowd behaviors to prevent disasters and to supervise the crowd behaviors. The entropy is used to describe the macro state of a self-organization system in physics. The entropy change indicates the system macro state change. This paper provides a method to construct crowd behavior microstates and the corresponded probability distribution using the individuals' velocity information (magnitude and direction). Then an entropy model was built up to describe the crowd behavior macro state. Simulation experiments and video detection experiments were conducted. It was verified that in the disordered state, the crowd behavior entropy is close to the theoretical maximum entropy; while in ordered state, the entropy is much lower than half of the theoretical maximum entropy. The crowd behavior macro state sudden change leads to the entropy change. The proposed entropy model is more applicable than the order parameter model in crowd behavior detection. By recognizing the entropy mutation, it is possible to detect the crowd behavior macro state automatically by utilizing cameras. Results will provide data support on crowd emergency prevention and on emergency manual intervention.

Investigating the effects of methodological expertise and data randomness on the robustness of crowd-sourced SfM terrain models

NASA Astrophysics Data System (ADS)

Ratner, Jacqueline; Pyle, David; Mather, Tamsin

2015-04-01

Structure-from-motion (SfM) techniques are now widely available to quickly and cheaply generate digital terrain models (DTMs) from optical imagery. Topography can change rapidly during disaster scenarios and change the nature of local hazards, making ground-based SfM a particularly useful tool in hazard studies due to its low cost, accessibility, and potential for immediate deployment. Our study is designed to serve as an analogue to potential real-world use of the SfM method if employed for disaster risk reduction purposes. Experiments at a volcanic crater in Santorini, Greece, used crowd-sourced data collection to demonstrate the impact of user expertise and randomization of SfM data on the resultant DTM. Three groups of participants representing variable expertise levels utilized 16 different camera models, including four camera phones, to collect 1001 total photos in one hour of data collection. Datasets collected by each group were processed using the free and open source software VisualSFM. The point densities and overall quality of the resultant SfM point clouds were compared against each other and also against a LiDAR dataset for reference to the industry standard. Our results show that the point clouds are resilient to changes in user expertise and collection method and are comparable or even preferable in data density to LiDAR. We find that 'crowd-sourced' data collected by a moderately informed general public yields topography results comparable to those produced with data collected by experts. This means that in a real-world scenario involving participants with a diverse range of expertise levels, topography models could be produced from crowd-sourced data quite rapidly and to a very high standard. This could be beneficial to disaster risk reduction as a relatively quick, simple, and low-cost method to attain a rapidly updated knowledge of terrain attributes, useful for the prediction and mitigation of many natural hazards.

Walking on a moving surface: energy-optimal walking motions on a shaky bridge and a shaking treadmill can reduce energy costs below normal.

PubMed

Joshi, Varun; Srinivasan, Manoj

2015-02-08

Understanding how humans walk on a surface that can move might provide insights into, for instance, whether walking humans prioritize energy use or stability. Here, motivated by the famous human-driven oscillations observed in the London Millennium Bridge, we introduce a minimal mathematical model of a biped, walking on a platform (bridge or treadmill) capable of lateral movement. This biped model consists of a point-mass upper body with legs that can exert force and perform mechanical work on the upper body. Using numerical optimization, we obtain energy-optimal walking motions for this biped, deriving the periodic body and platform motions that minimize a simple metabolic energy cost. When the platform has an externally imposed sinusoidal displacement of appropriate frequency and amplitude, we predict that body motion entrained to platform motion consumes less energy than walking on a fixed surface. When the platform has finite inertia, a mass- spring-damper with similar parameters to the Millennium Bridge, we show that the optimal biped walking motion sustains a large lateral platform oscillation when sufficiently many people walk on the bridge. Here, the biped model reduces walking metabolic cost by storing and recovering energy from the platform, demonstrating energy benefits for two features observed for walking on the Millennium Bridge: crowd synchrony and large lateral oscillations.

Walking on a moving surface: energy-optimal walking motions on a shaky bridge and a shaking treadmill can reduce energy costs below normal

PubMed Central

Joshi, Varun; Srinivasan, Manoj

2015-01-01

Understanding how humans walk on a surface that can move might provide insights into, for instance, whether walking humans prioritize energy use or stability. Here, motivated by the famous human-driven oscillations observed in the London Millennium Bridge, we introduce a minimal mathematical model of a biped, walking on a platform (bridge or treadmill) capable of lateral movement. This biped model consists of a point-mass upper body with legs that can exert force and perform mechanical work on the upper body. Using numerical optimization, we obtain energy-optimal walking motions for this biped, deriving the periodic body and platform motions that minimize a simple metabolic energy cost. When the platform has an externally imposed sinusoidal displacement of appropriate frequency and amplitude, we predict that body motion entrained to platform motion consumes less energy than walking on a fixed surface. When the platform has finite inertia, a mass- spring-damper with similar parameters to the Millennium Bridge, we show that the optimal biped walking motion sustains a large lateral platform oscillation when sufficiently many people walk on the bridge. Here, the biped model reduces walking metabolic cost by storing and recovering energy from the platform, demonstrating energy benefits for two features observed for walking on the Millennium Bridge: crowd synchrony and large lateral oscillations. PMID:25663810

Fractional motion model for characterization of anomalous diffusion from NMR signals.

PubMed

Fan, Yang; Gao, Jia-Hong

2015-07-01

Measuring molecular diffusion has been used to characterize the properties of living organisms and porous materials. NMR is able to detect the diffusion process in vivo and noninvasively. The fractional motion (FM) model is appropriate to describe anomalous diffusion phenomenon in crowded environments, such as living cells. However, no FM-based NMR theory has yet been established. Here, we present a general formulation of the FM-based NMR signal under the influence of arbitrary magnetic field gradient waveforms. An explicit analytic solution of the stretched exponential decay format for NMR signals with finite-width Stejskal-Tanner bipolar pulse magnetic field gradients is presented. Signals from a numerical simulation matched well with the theoretical prediction. In vivo diffusion-weighted brain images were acquired and analyzed using the proposed theory, and the resulting parametric maps exhibit remarkable contrasts between different brain tissues.

Fractional motion model for characterization of anomalous diffusion from NMR signals

NASA Astrophysics Data System (ADS)

Fan, Yang; Gao, Jia-Hong

2015-07-01

Measuring molecular diffusion has been used to characterize the properties of living organisms and porous materials. NMR is able to detect the diffusion process in vivo and noninvasively. The fractional motion (FM) model is appropriate to describe anomalous diffusion phenomenon in crowded environments, such as living cells. However, no FM-based NMR theory has yet been established. Here, we present a general formulation of the FM-based NMR signal under the influence of arbitrary magnetic field gradient waveforms. An explicit analytic solution of the stretched exponential decay format for NMR signals with finite-width Stejskal-Tanner bipolar pulse magnetic field gradients is presented. Signals from a numerical simulation matched well with the theoretical prediction. In vivo diffusion-weighted brain images were acquired and analyzed using the proposed theory, and the resulting parametric maps exhibit remarkable contrasts between different brain tissues.

An Information Perception-Based Emotion Contagion Model for Fire Evacuation

NASA Astrophysics Data System (ADS)

Liu, Ting Ting; Liu, Zhen; Ma, Minhua; Xuan, Rongrong; Chen, Tian; Lu, Tao; Yu, Lipeng

2017-03-01

In fires, people are easier to lose their mind. Panic will lead to irrational behavior and irreparable tragedy. It has great practical significance to make contingency plans for crowd evacuation in fires. However, existing studies about crowd simulation always paid much attention on the crowd density, but little attention on emotional contagion that may cause a panic. Based on settings about information space and information sharing, this paper proposes an emotional contagion model for crowd in panic situations. With the proposed model, a behavior mechanism is constructed for agents in the crowd and a prototype of system is developed for crowd simulation. Experiments are carried out to verify the proposed model. The results showed that the spread of panic not only related to the crowd density and the individual comfort level, but also related to people's prior knowledge of fire evacuation. The model provides a new way for safety education and evacuation management. It is possible to avoid and reduce unsafe factors in the crowd with the lowest cost.

On the Role of Entropy in the Protein Folding Process

NASA Astrophysics Data System (ADS)

Hoppe, Travis

2011-12-01

A protein's ultimate function and activity is determined by the unique three-dimensional structure taken by the folding process. Protein malfunction due to misfolding is the culprit of many clinical disorders, such as abnormal protein aggregations. This leads to neurodegenerative disorders like Huntington's and Alzheimer's disease. We focus on a subset of the folding problem, exploring the role and effects of entropy on the process of protein folding. Four major concepts and models are developed and each pertains to a specific aspect of the folding process: entropic forces, conformational states under crowding, aggregation, and macrostate kinetics from microstate trajectories. The exclusive focus on entropy is well-suited for crowding studies, as many interactions are nonspecific. We show how a stabilizing entropic force can arise purely from the motion of crowders in solution. In addition we are able to make a a quantitative prediction of the crowding effect with an implicit crowding approximation using an aspherical scaled-particle theory. In order to investigate the effects of aggregation, we derive a new operator expansion method to solve the Ising/Potts model with external fields over an arbitrary graph. Here the external fields are representative of the entropic forces. We show that this method reduces the problem of calculating the partition function to the solution of recursion relations. Many of the methods employed are coarse-grained approximations. As such, it is useful to have a viable method for extracting macrostate information from time series data. We develop a method to cluster the microstates into physically meaningful macrostates by grouping similar relaxation times from a transition matrix. Overall, the studied topics allow us to understand deeper the complicated process involving proteins.

The effects of bound state motion on macromolecular diffusion

NASA Astrophysics Data System (ADS)

Hough, Loren; Stefferson, Michael; Norris, Samantha; Maguire, Laura; Vernerey, Franck; Betterton, Meredith

The diffusion of macromolecules is modified in crowded environments by both inert obstacles and interaction sites. Molecules are generally slowed in their movement inducing transient anomalous subdiffusion. Obstacles also modify the kinetics and equilibrium behavior of interaction between mobile proteins. In some biophysical contexts, bound molecules can still experience mobility, for example transcription factors sliding along DNA, membrane proteins with some entry and diffusion within lipid domains, or proteins that can enter into non-membrane bound compartments such as the nucleolus. We used lattice and continuum models to study the diffusive behavior of tracer particles which bind to obstacles and can diffuse within them. We show that binding significantly alters the motion of tracers. The type and degree of motion while bound is a key determinant of the tracer mobility. Our work has implications for protein-protein movement and interactions within living cells, including those involving intrinsically disordered proteins.

Correlation Imaging Reveals Specific Crowding Dynamics of Kinesin Motor Proteins

NASA Astrophysics Data System (ADS)

Miedema, Daniël M.; Kushwaha, Vandana S.; Denisov, Dmitry V.; Acar, Seyda; Nienhuis, Bernard; Peterman, Erwin J. G.; Schall, Peter

2017-10-01

Molecular motor proteins fulfill the critical function of transporting organelles and other building blocks along the biopolymer network of the cell's cytoskeleton, but crowding effects are believed to crucially affect this motor-driven transport due to motor interactions. Physical transport models, like the paradigmatic, totally asymmetric simple exclusion process (TASEP), have been used to predict these crowding effects based on simple exclusion interactions, but verifying them in experiments remains challenging. Here, we introduce a correlation imaging technique to precisely measure the motor density, velocity, and run length along filaments under crowding conditions, enabling us to elucidate the physical nature of crowding and test TASEP model predictions. Using the kinesin motor proteins kinesin-1 and OSM-3, we identify crowding effects in qualitative agreement with TASEP predictions, and we achieve excellent quantitative agreement by extending the model with motor-specific interaction ranges and crowding-dependent detachment probabilities. These results confirm the applicability of basic nonequilibrium models to the intracellular transport and highlight motor-specific strategies to deal with crowding.

A system for learning statistical motion patterns.

PubMed

Hu, Weiming; Xiao, Xuejuan; Fu, Zhouyu; Xie, Dan; Tan, Tieniu; Maybank, Steve

2006-09-01

Analysis of motion patterns is an effective approach for anomaly detection and behavior prediction. Current approaches for the analysis of motion patterns depend on known scenes, where objects move in predefined ways. It is highly desirable to automatically construct object motion patterns which reflect the knowledge of the scene. In this paper, we present a system for automatically learning motion patterns for anomaly detection and behavior prediction based on a proposed algorithm for robustly tracking multiple objects. In the tracking algorithm, foreground pixels are clustered using a fast accurate fuzzy K-means algorithm. Growing and prediction of the cluster centroids of foreground pixels ensure that each cluster centroid is associated with a moving object in the scene. In the algorithm for learning motion patterns, trajectories are clustered hierarchically using spatial and temporal information and then each motion pattern is represented with a chain of Gaussian distributions. Based on the learned statistical motion patterns, statistical methods are used to detect anomalies and predict behaviors. Our system is tested using image sequences acquired, respectively, from a crowded real traffic scene and a model traffic scene. Experimental results show the robustness of the tracking algorithm, the efficiency of the algorithm for learning motion patterns, and the encouraging performance of algorithms for anomaly detection and behavior prediction.

Gauging Through the Crowd: A Crowd-Sourcing Approach to Urban Rainfall Measurement and Storm Water Modeling Implications

NASA Astrophysics Data System (ADS)

Yang, Pan; Ng, Tze Ling

2017-11-01

Accurate rainfall measurement at high spatial and temporal resolutions is critical for the modeling and management of urban storm water. In this study, we conduct computer simulation experiments to test the potential of a crowd-sourcing approach, where smartphones, surveillance cameras, and other devices act as precipitation sensors, as an alternative to the traditional approach of using rain gauges to monitor urban rainfall. The crowd-sourcing approach is promising as it has the potential to provide high-density measurements, albeit with relatively large individual errors. We explore the potential of this approach for urban rainfall monitoring and the subsequent implications for storm water modeling through a series of simulation experiments involving synthetically generated crowd-sourced rainfall data and a storm water model. The results show that even under conservative assumptions, crowd-sourced rainfall data lead to more accurate modeling of storm water flows as compared to rain gauge data. We observe the relative superiority of the crowd-sourcing approach to vary depending on crowd participation rate, measurement accuracy, drainage area, choice of performance statistic, and crowd-sourced observation type. A possible reason for our findings is the differences between the error structures of crowd-sourced and rain gauge rainfall fields resulting from the differences between the errors and densities of the raw measurement data underlying the two field types.

Microscopic information processing and communication in crowd dynamics

NASA Astrophysics Data System (ADS)

Henein, Colin Marc; White, Tony

2010-11-01

Due, perhaps, to the historical division of crowd dynamics research into psychological and engineering approaches, microscopic crowd models have tended toward modelling simple interchangeable particles with an emphasis on the simulation of physical factors. Despite the fact that people have complex (non-panic) behaviours in crowd disasters, important human factors in crowd dynamics such as information discovery and processing, changing goals and communication have not yet been well integrated at the microscopic level. We use our Microscopic Human Factors methodology to fuse a microscopic simulation of these human factors with a popular microscopic crowd model. By tightly integrating human factors with the existing model we can study the effects on the physical domain (movement, force and crowd safety) when human behaviour (information processing and communication) is introduced. In a large-room egress scenario with ample exits, information discovery and processing yields a crowd of non-interchangeable individuals who, despite close proximity, have different goals due to their different beliefs. This crowd heterogeneity leads to complex inter-particle interactions such as jamming transitions in open space; at high crowd energies, we found a freezing by heating effect (reminiscent of the disaster at Central Lenin Stadium in 1982) in which a barrier formation of naïve individuals trying to reach blocked exits prevented knowledgeable ones from exiting. Communication, when introduced, reduced this barrier formation, increasing both exit rates and crowd safety.

Diffusing diffusivity: Rotational diffusion in two and three dimensions

NASA Astrophysics Data System (ADS)

Jain, Rohit; Sebastian, K. L.

2017-06-01

We consider the problem of calculating the probability distribution function (pdf) of angular displacement for rotational diffusion in a crowded, rearranging medium. We use the diffusing diffusivity model and following our previous work on translational diffusion [R. Jain and K. L. Sebastian, J. Phys. Chem. B 120, 3988 (2016)], we show that the problem can be reduced to that of calculating the survival probability of a particle undergoing Brownian motion, in the presence of a sink. We use the approach to calculate the pdf for the rotational motion in two and three dimensions. We also propose new dimensionless, time dependent parameters, αr o t ,2 D and αr o t ,3 D, which can be used to analyze the experimental/simulation data to find the extent of deviation from the normal behavior, i.e., constant diffusivity, and obtain explicit analytical expressions for them, within our model.

A neurophysiologically plausible population code model for feature integration explains visual crowding.

PubMed

van den Berg, Ronald; Roerdink, Jos B T M; Cornelissen, Frans W

2010-01-22

An object in the peripheral visual field is more difficult to recognize when surrounded by other objects. This phenomenon is called "crowding". Crowding places a fundamental constraint on human vision that limits performance on numerous tasks. It has been suggested that crowding results from spatial feature integration necessary for object recognition. However, in the absence of convincing models, this theory has remained controversial. Here, we present a quantitative and physiologically plausible model for spatial integration of orientation signals, based on the principles of population coding. Using simulations, we demonstrate that this model coherently accounts for fundamental properties of crowding, including critical spacing, "compulsory averaging", and a foveal-peripheral anisotropy. Moreover, we show that the model predicts increased responses to correlated visual stimuli. Altogether, these results suggest that crowding has little immediate bearing on object recognition but is a by-product of a general, elementary integration mechanism in early vision aimed at improving signal quality.

Exploiting Motion Capture to Enhance Avoidance Behaviour in Games

NASA Astrophysics Data System (ADS)

van Basten, Ben J. H.; Jansen, Sander E. M.; Karamouzas, Ioannis

Realistic simulation of interacting virtual characters is essential in computer games, training and simulation applications. The problem is very challenging since people are accustomed to real-world situations and thus, they can easily detect inconsistencies and artifacts in the simulations. Over the past twenty years several models have been proposed for simulating individuals, groups and crowds of characters. However, little effort has been made to actually understand how humans solve interactions and avoid inter-collisions in real-life. In this paper, we exploit motion capture data to gain more insights into human-human interactions. We propose four measures to describe the collision-avoidance behavior. Based on these measures, we extract simple rules that can be applied on top of existing agent and force based approaches, increasing the realism of the resulting simulations.

Visualization and Rule Validation in Human-Behavior Representation

ERIC Educational Resources Information Center

Moya, Lisa Jean; McKenzie, Frederic D.; Nguyen, Quynh-Anh H.

2008-01-01

Human behavior representation (HBR) models simulate human behaviors and responses. The Joint Crowd Federate [TM] cognitive model developed by the Virginia Modeling, Analysis, and Simulation Center (VMASC) and licensed by WernerAnderson, Inc., models the cognitive behavior of crowds to provide credible crowd behavior in support of military…

The effect of macromolecular crowding on the electrostatic component of barnase-barstar binding: a computational, implicit solvent-based study.

PubMed

Qi, Helena W; Nakka, Priyanka; Chen, Connie; Radhakrishnan, Mala L

2014-01-01

Macromolecular crowding within the cell can impact both protein folding and binding. Earlier models of cellular crowding focused on the excluded volume, entropic effect of crowding agents, which generally favors compact protein states. Recently, other effects of crowding have been explored, including enthalpically-related crowder-protein interactions and changes in solvation properties. In this work, we explore the effects of macromolecular crowding on the electrostatic desolvation and solvent-screened interaction components of protein-protein binding. Our simple model enables us to focus exclusively on the electrostatic effects of water depletion on protein binding due to crowding, providing us with the ability to systematically analyze and quantify these potentially intuitive effects. We use the barnase-barstar complex as a model system and randomly placed, uncharged spheres within implicit solvent to model crowding in an aqueous environment. On average, we find that the desolvation free energy penalties incurred by partners upon binding are lowered in a crowded environment and solvent-screened interactions are amplified. At a constant crowder density (fraction of total available volume occupied by crowders), this effect generally increases as the radius of model crowders decreases, but the strength and nature of this trend can depend on the water probe radius used to generate the molecular surface in the continuum model. In general, there is huge variation in desolvation penalties as a function of the random crowder positions. Results with explicit model crowders can be qualitatively similar to those using a lowered "effective" solvent dielectric to account for crowding, although the "best" effective dielectric constant will likely depend on multiple system properties. Taken together, this work systematically demonstrates, quantifies, and analyzes qualitative intuition-based insights into the effects of water depletion due to crowding on the electrostatic component of protein binding, and it provides an initial framework for future analyses.

The Effect of Macromolecular Crowding on the Electrostatic Component of Barnase–Barstar Binding: A Computational, Implicit Solvent-Based Study

PubMed Central

Qi, Helena W.; Nakka, Priyanka; Chen, Connie; Radhakrishnan, Mala L.

2014-01-01

Macromolecular crowding within the cell can impact both protein folding and binding. Earlier models of cellular crowding focused on the excluded volume, entropic effect of crowding agents, which generally favors compact protein states. Recently, other effects of crowding have been explored, including enthalpically-related crowder–protein interactions and changes in solvation properties. In this work, we explore the effects of macromolecular crowding on the electrostatic desolvation and solvent-screened interaction components of protein–protein binding. Our simple model enables us to focus exclusively on the electrostatic effects of water depletion on protein binding due to crowding, providing us with the ability to systematically analyze and quantify these potentially intuitive effects. We use the barnase–barstar complex as a model system and randomly placed, uncharged spheres within implicit solvent to model crowding in an aqueous environment. On average, we find that the desolvation free energy penalties incurred by partners upon binding are lowered in a crowded environment and solvent-screened interactions are amplified. At a constant crowder density (fraction of total available volume occupied by crowders), this effect generally increases as the radius of model crowders decreases, but the strength and nature of this trend can depend on the water probe radius used to generate the molecular surface in the continuum model. In general, there is huge variation in desolvation penalties as a function of the random crowder positions. Results with explicit model crowders can be qualitatively similar to those using a lowered “effective” solvent dielectric to account for crowding, although the “best” effective dielectric constant will likely depend on multiple system properties. Taken together, this work systematically demonstrates, quantifies, and analyzes qualitative intuition-based insights into the effects of water depletion due to crowding on the electrostatic component of protein binding, and it provides an initial framework for future analyses. PMID:24915485

Mexican waves in an excitable medium.

PubMed

Farkas, I; Helbing, D; Vicsek, T

2002-09-12

The Mexican wave, or La Ola, which rose to fame during the 1986 World Cup in Mexico, surges through the rows of spectators in a stadium as those in one section leap to their feet with their arms up, and then sit down again as the next section rises to repeat the motion. To interpret and quantify this collective human behaviour, we have used a variant of models that were originally developed to describe excitable media such as cardiac tissue. Modelling the reaction of the crowd to attempts to trigger the wave reveals how this phenomenon is stimulated, and may prove useful in controlling events that involve groups of excited people.

Crowding Induces Complex Ergodic Diffusion and Dynamic Elongation of Large DNA Molecules

PubMed Central

Chapman, Cole D.; Gorczyca, Stephanie; Robertson-Anderson, Rae M.

2015-01-01

Despite the ubiquity of molecular crowding in living cells, the effects of crowding on the dynamics of genome-sized DNA are poorly understood. Here, we track single, fluorescent-labeled large DNA molecules (11, 115 kbp) diffusing in dextran solutions that mimic intracellular crowding conditions (0–40%), and determine the effects of crowding on both DNA mobility and conformation. Both DNAs exhibit ergodic Brownian motion and comparable mobility reduction in all conditions; however, crowder size (10 vs. 500 kDa) plays a critical role in the underlying diffusive mechanisms and dependence on crowder concentration. Surprisingly, in 10-kDa dextran, crowder influence saturates at ∼20% with an ∼5× drop in DNA diffusion, in stark contrast to exponentially retarded mobility, coupled to weak anomalous subdiffusion, with increasing concentration of 500-kDa dextran. Both DNAs elongate into lower-entropy states (compared to random coil conformations) when crowded, with elongation states that are gamma distributed and fluctuate in time. However, the broadness of the distribution of states and the time-dependence and length scale of elongation length fluctuations depend on both DNA and crowder size with concentration having surprisingly little impact. Results collectively show that mobility reduction and coil elongation of large crowded DNAs are due to a complex interplay between entropic effects and crowder mobility. Although elongation and initial mobility retardation are driven by depletion interactions, subdiffusive dynamics, and the drastic exponential slowing of DNA, up to ∼300×, arise from the reduced mobility of larger crowders. Our results elucidate the highly important and widely debated effects of cellular crowding on genome-sized DNA. PMID:25762333

Can (should) theories of crowding be unified?

PubMed Central

Agaoglu, Mehmet N.; Chung, Susana T. L.

2016-01-01

Objects in clutter are difficult to recognize, a phenomenon known as crowding. There is little consensus on the underlying mechanisms of crowding, and a large number of models have been proposed. There have also been attempts at unifying the explanations of crowding under a single model, such as the weighted feature model of Harrison and Bex (2015) and the texture synthesis model of Rosenholtz and colleagues (Balas, Nakano, & Rosenholtz, 2009; Keshvari & Rosenholtz, 2016). The goal of this work was to test various models of crowding and to assess whether a unifying account can be developed. Adopting Harrison and Bex's (2015) experimental paradigm, we asked observers to report the orientation of two concentric C-stimuli. Contrary to the predictions of their model, observers' recognition accuracy was worse for the inner C-stimulus. In addition, we demonstrated that the stimulus paradigm used by Harrison and Bex has a crucial confounding factor, eccentricity, which limits its usage to a very narrow range of stimulus parameters. Nevertheless, reporting the orientations of both C-stimuli in this paradigm proved very useful in pitting different crowding models against each other. Specifically, we tested deterministic and probabilistic versions of averaging, substitution, and attentional resolution models as well as the texture synthesis model. None of the models alone was able to explain the entire set of data. Based on these findings, we discuss whether the explanations of crowding can (should) be unified. PMID:27936273

Exits in order: How crowding affects particle lifetimes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Penington, Catherine J.; Simpson, Matthew J.; Baker, Ruth E.

2016-06-28

Diffusive processes are often represented using stochastic random walk frameworks. The amount of time taken for an individual in a random walk to intersect with an absorbing boundary is a fundamental property that is often referred to as the particle lifetime, or the first passage time. The mean lifetime of particles in a random walk model of diffusion is related to the amount of time required for the diffusive process to reach a steady state. Mathematical analysis describing the mean lifetime of particles in a standard model of diffusion without crowding is well known. However, the lifetime of agents inmore » a random walk with crowding has received much less attention. Since many applications of diffusion in biology and biophysics include crowding effects, here we study a discrete model of diffusion that incorporates crowding. Using simulations, we show that crowding has a dramatic effect on agent lifetimes, and we derive an approximate expression for the mean agent lifetime that includes crowding effects. Our expression matches simulation results very well, and highlights the importance of crowding effects that are sometimes overlooked.« less

Anomalous diffusion of brain metabolites evidenced by diffusion-weighted magnetic resonance spectroscopy in vivo

PubMed Central

Marchadour, Charlotte; Brouillet, Emmanuel; Hantraye, Philippe; Lebon, Vincent; Valette, Julien

2012-01-01

Translational displacement of molecules within cells is a key process in cellular biology. Molecular motion potentially depends on many factors, including active transport, cytosol viscosity and molecular crowding, tortuosity resulting from cytoskeleton and organelles, and restriction barriers. However, the relative contribution of these factors to molecular motion in the cytoplasm remains poorly understood. In this work, we designed an original diffusion-weighted magnetic resonance spectroscopy strategy to probe molecular motion at subcellular scales in vivo. This led to the first observation of anomalous diffusion, that is, dependence of the apparent diffusion coefficient (ADC) on the diffusion time, for endogenous intracellular metabolites in the brain. The observed increase of the ADC at short diffusion time yields evidence that metabolite motion is characteristic of hindered random diffusion rather than active transport, for time scales up to the dozen milliseconds. Armed with this knowledge, data modeling based on geometrically constrained diffusion was performed. Results suggest that metabolite diffusion occurs in a low-viscosity cytosol hindered by ∼2-μm structures, which is consistent with known intracellular organization. PMID:22929443

Kinetic models for crowd dynamics. Comment on "Human behaviours in evacuation crowd dynamics: From modelling to "big data" toward crisis management" by N. Bellomo et al.

NASA Astrophysics Data System (ADS)

Banasiak, J.

2016-09-01

There has been a hierarchy of models of crowd behaviour. One can consider the crowd at the so called microscopic level, as a collection of individuals, and derive its description in the form of a (large) system of ordinary differential equations describing the position and velocity of each individual, in parallel to the Newton's description of matter, see e.g. [10]. Another possibility is to describe crowd, in analogy to fluid dynamics, by providing its density and velocity at a given point, see e.g. [11,12]. At the same time, it is recognized that crowd is 'living, social' system that is prone to exhibit rare, not easily predictable, behaviour in response to stress induced by the perception of danger, or of the action of specific agents, see e.g. [1,2]. This high probability of the occurrence of events that are far from average, makes the crowd behaviour similar to the processes with fat-tailed distribution of events. Such unlikely events have been metaphorically termed black swans in [14], or Lévy flights in [13]. While microscopic and macroscopic models can capture many features of crowd dynamics, including obstacles, see [3,8], such models are described by differential equations that inherently are local in space. At the same time, black swan events are often caused by non-local interactions such as self-organization, learning or adherence to some averaged group behaviour. It is known that such interactions are well described by mean field models best represented by integro-differential equations, such as the Boltzmann equation of the rarefied gas theory. This has made plausible to introduce crowd models at the intermediate, (meso) scale by describing the crowd by the one particle distribution function that gives the density of individuals at any particular state; that is, at a given point in the domain and moving with a specific velocity.

The interplay of intrinsic disorder and macromolecular crowding on α-synuclein fibril formation

NASA Astrophysics Data System (ADS)

Shirai, Nobu C.; Kikuchi, Macoto

2016-02-01

α-synuclein (α-syn) is an intrinsically disordered protein which is considered to be one of the causes of Parkinson's disease. This protein forms amyloid fibrils when in a highly concentrated solution. The fibril formation of α-syn is induced not only by increases in α-syn concentration but also by macromolecular crowding. In order to investigate the coupled effect of the intrinsic disorder of α-syn and macromolecular crowding, we construct a lattice gas model of α-syn in contact with a crowding agent reservoir based on statistical mechanics. The main assumption is that α-syn can be expressed as coarse-grained particles with internal states coupled with effective volume; and disordered states are modeled by larger particles with larger internal entropy than other states. Thanks to the simplicity of the model, we can exactly calculate the number of conformations of crowding agents, and this enables us to prove that the original grand canonical ensemble with a crowding agent reservoir is mathematically equivalent to a canonical ensemble without crowding agents. In this expression, the effect of macromolecular crowding is absorbed in the internal entropy of disordered states; it is clearly shown that the crowding effect reduces the internal entropy. Based on Monte Carlo simulation, we provide scenarios of crowding-induced fibril formation. We also discuss the recent controversy over the existence of helically folded tetramers of α-syn, and suggest that macromolecular crowding is the key to resolving the controversy.

Thermodynamics of Macromolecular Association in Heterogeneous Crowding Environments: Theoretical and Simulation Studies with a Simplified Model.

PubMed

Ando, Tadashi; Yu, Isseki; Feig, Michael; Sugita, Yuji

2016-11-23

The cytoplasm of a cell is crowded with many different kinds of macromolecules. The macromolecular crowding affects the thermodynamics and kinetics of biological reactions in a living cell, such as protein folding, association, and diffusion. Theoretical and simulation studies using simplified models focus on the essential features of the crowding effects and provide a basis for analyzing experimental data. In most of the previous studies on the crowding effects, a uniform crowder size is assumed, which is in contrast to the inhomogeneous size distribution of macromolecules in a living cell. Here, we evaluate the free energy changes upon macromolecular association in a cell-like inhomogeneous crowding system via a theory of hard-sphere fluids and free energy calculations using Brownian dynamics trajectories. The inhomogeneous crowding model based on 41 different types of macromolecules represented by spheres with different radii mimics the physiological concentrations of macromolecules in the cytoplasm of Mycoplasma genitalium. The free energy changes of macromolecular association evaluated by the theory and simulations were in good agreement with each other. The crowder size distribution affects both specific and nonspecific molecular associations, suggesting that not only the volume fraction but also the size distribution of macromolecules are important factors for evaluating in vivo crowding effects. This study relates in vitro experiments on macromolecular crowding to in vivo crowding effects by using the theory of hard-sphere fluids with crowder-size heterogeneity.

An entropy model to measure heterogeneity of pedestrian crowds using self-propelled agents

NASA Astrophysics Data System (ADS)

Rangel-Huerta, A.; Ballinas-Hernández, A. L.; Muñoz-Meléndez, A.

2017-05-01

An entropy model to characterize the heterogeneity of a pedestrian crowd in a counter-flow corridor is presented. Pedestrians are modeled as self-propelled autonomous agents that are able to perform maneuvers to avoid collisions based on a set of simple rules of perception and action. An observer can determine a probability distribution function of the displayed behavior of pedestrians based only on external information. Three types of pedestrian are modeled, relaxed, standard and hurried pedestrians depending on their preferences of turn and non-turn when walking. Thus, using these types of pedestrians two crowds can be simulated: homogeneous and heterogeneous crowds. Heterogeneity is measured in this research based on the entropy in function of time. For that, the entropy of a homogeneous crowd comprising standard pedestrians is used as reference. A number of simulations to measure entropy of pedestrian crowds were conducted by varying different combinations of types of pedestrians, initial simulation conditions of macroscopic flow, as well as density of the crowd. Results from these simulations show that our entropy model is sensitive enough to capture the effect of both the initial simulation conditions about the spatial distribution of pedestrians in a corridor, and the composition of a crowd. Also, a relevant finding is that entropy in function of density presents a phase transition in the critical region.

A simple quantitative model of macromolecular crowding effects on protein folding: Application to the murine prion protein(121-231)

NASA Astrophysics Data System (ADS)

Bergasa-Caceres, Fernando; Rabitz, Herschel A.

2013-06-01

A model of protein folding kinetics is applied to study the effects of macromolecular crowding on protein folding rate and stability. Macromolecular crowding is found to promote a decrease of the entropic cost of folding of proteins that produces an increase of both the stability and the folding rate. The acceleration of the folding rate due to macromolecular crowding is shown to be a topology-dependent effect. The model is applied to the folding dynamics of the murine prion protein (121-231). The differential effect of macromolecular crowding as a function of protein topology suffices to make non-native configurations relatively more accessible.

Comparison of emergency department crowding scores: a discrete-event simulation approach.

PubMed

Ahalt, Virginia; Argon, Nilay Tanık; Ziya, Serhan; Strickler, Jeff; Mehrotra, Abhi

2018-03-01

According to American College of Emergency Physicians, emergency department (ED) crowding occurs when the identified need for emergency services exceeds available resources for patient care in the ED, hospital, or both. ED crowding is a widely reported problem and several crowding scores are proposed to quantify crowding using hospital and patient data as inputs for assisting healthcare professionals in anticipating imminent crowding problems. Using data from a large academic hospital in North Carolina, we evaluate three crowding scores, namely, EDWIN, NEDOCS, and READI by assessing strengths and weaknesses of each score, particularly their predictive power. We perform these evaluations by first building a discrete-event simulation model of the ED, validating the results of the simulation model against observations at the ED under consideration, and utilizing the model results to investigate each of the three ED crowding scores under normal operating conditions and under two simulated outbreak scenarios in the ED. We conclude that, for this hospital, both EDWIN and NEDOCS prove to be helpful measures of current ED crowdedness, and both scores demonstrate the ability to anticipate impending crowdedness. Utilizing both EDWIN and NEDOCS scores in combination with the threshold values proposed in this work could provide a real-time alert for clinicians to anticipate impending crowding, which could lead to better preparation and eventually better patient care outcomes.

The role of fluctuations and interactions in pedestrian dynamics

NASA Astrophysics Data System (ADS)

Corbetta, Alessandro; Meeusen, Jasper; Benzi, Roberto; Lee, Chung-Min; Toschi, Federico

Understanding quantitatively the statistical behaviour of pedestrians walking in crowds is a major scientific challenge of paramount societal relevance. Walking humans exhibit a rich (stochastic) dynamics whose small and large deviations are driven, among others, by own will as well as by environmental conditions. Via 24/7 automatic pedestrian tracking from multiple overhead Microsoft Kinect depth sensors, we collected large ensembles of pedestrian trajectories (in the order of tens of millions) in different real-life scenarios. These scenarios include both narrow corridors and large urban hallways, enabling us to cover and compare a wide spectrum of typical pedestrian dynamics. We investigate the pedestrian motion measuring the PDFs, e.g. those of position, velocity and acceleration, and at unprecedentedly high statistical resolution. We consider the dependence of PDFs on flow conditions, focusing on diluted dynamics and pair-wise interactions (''collisions'') for mutual avoidance. By means of Langevin-like models we provide models for the measured data, inclusive typical fluctuations and rare events. This work is part of the JSTP research programme ``Vision driven visitor behaviour analysis and crowd management'' with Project Number 341-10-001, which is financed by the Netherlands Organisation for Scientific Research (NWO).

Autonomous detection of crowd anomalies in multiple-camera surveillance feeds

NASA Astrophysics Data System (ADS)

Nordlöf, Jonas; Andersson, Maria

2016-10-01

A novel approach for autonomous detection of anomalies in crowded environments is presented in this paper. The proposed models uses a Gaussian mixture probability hypothesis density (GM-PHD) filter as feature extractor in conjunction with different Gaussian mixture hidden Markov models (GM-HMMs). Results, based on both simulated and recorded data, indicate that this method can track and detect anomalies on-line in individual crowds through multiple camera feeds in a crowded environment.

Is Buffer a Good Proxy for a Crowded Cell-Like Environment? A Comparative NMR Study of Calmodulin Side-Chain Dynamics in Buffer and E. coli Lysate

PubMed Central

Latham, Michael P.; Kay, Lewis E.

2012-01-01

Biophysical studies of protein structure and dynamics are typically performed in a highly controlled manner involving only the protein(s) of interest. Comparatively fewer such studies have been carried out in the context of a cellular environment that typically involves many biomolecules, ions and metabolites. Recently, solution NMR spectroscopy, focusing primarily on backbone amide groups as reporters, has emerged as a powerful technique for investigating protein structure and dynamics in vivo and in crowded “cell-like” environments. Here we extend these studies through a comparative analysis of Ile, Leu, Val and Met methyl side-chain motions in apo, Ca2+-bound and Ca2+, peptide-bound calmodulin dissolved in aqueous buffer or in E. coli lysate. Deuterium spin relaxation experiments, sensitive to pico- to nano-second time-scale processes and Carr-Purcell-Meiboom-Gill relaxation dispersion experiments, reporting on millisecond dynamics, have been recorded. Both similarities and differences in motional properties are noted for calmodulin dissolved in buffer or in lysate. These results emphasize that while significant insights can be obtained through detailed “test-tube” studies, experiments performed under conditions that are “cell-like” are critical for obtaining a comprehensive understanding of protein motion in vivo and therefore for elucidating the relation between motion and function. PMID:23118958

Modified two-layer social force model for emergency earthquake evacuation

NASA Astrophysics Data System (ADS)

Zhang, Hao; Liu, Hong; Qin, Xin; Liu, Baoxi

2018-02-01

Studies of crowd behavior with related research on computer simulation provide an effective basis for architectural design and effective crowd management. Based on low-density group organization patterns, a modified two-layer social force model is proposed in this paper to simulate and reproduce a group gathering process. First, this paper studies evacuation videos from the Luan'xian earthquake in 2012, and extends the study of group organization patterns to a higher density. Furthermore, taking full advantage of the strength in crowd gathering simulations, a new method on grouping and guidance is proposed while using crowd dynamics. Second, a real-life grouping situation in earthquake evacuation is simulated and reproduced. Comparing with the fundamental social force model and existing guided crowd model, the modified model reduces congestion time and truly reflects group behaviors. Furthermore, the experiment result also shows that a stable group pattern and a suitable leader could decrease collision and allow a safer evacuation process.

Multiple scales modelling approaches to social interaction in crowd dynamics and crisis management. Comment on "Human behaviours in evacuation crowd dynamics: From modelling to "big data" toward crisis management" by Nicola Bellomo et al.

NASA Astrophysics Data System (ADS)

Trucu, Dumitru

2016-09-01

In this comprehensive review concerning the modelling of human behaviours in crowd dynamics [3], the authors explore a wide range of mathematical approaches spanning over multiple scales that are suitable to describe emerging crowd behaviours in extreme situations. Focused on deciphering the key aspects leading to emerging crowd patterns evolutions in challenging times such as those requiring an evacuation on a complex venue, the authors address this complex dynamics at both microscale (individual level), mesoscale (probability distributions of interacting individuals), and macroscale (population level), ultimately aiming to gain valuable understanding and knowledge that would inform decision making in managing crisis situations.

CrowdMapping: A Crowdsourcing-Based Terminology Mapping Method for Medical Data Standardization.

PubMed

Mao, Huajian; Chi, Chenyang; Huang, Boyu; Meng, Haibin; Yu, Jinghui; Zhao, Dongsheng

2017-01-01

Standardized terminology is the prerequisite of data exchange in analysis of clinical processes. However, data from different electronic health record systems are based on idiosyncratic terminology systems, especially when the data is from different hospitals and healthcare organizations. Terminology standardization is necessary for the medical data analysis. We propose a crowdsourcing-based terminology mapping method, CrowdMapping, to standardize the terminology in medical data. CrowdMapping uses a confidential model to determine how terminologies are mapped to a standard system, like ICD-10. The model uses mappings from different health care organizations and evaluates the diversity of the mapping to determine a more sophisticated mapping rule. Further, the CrowdMapping model enables users to rate the mapping result and interact with the model evaluation. CrowdMapping is a work-in-progress system, we present initial results mapping terminologies.

Comparison of reconstructed rapid prototyping models produced by 3-dimensional printing and conventional stone models with different degrees of crowding.

PubMed

Wan Hassan, Wan Nurazreena; Yusoff, Yusnilawati; Mardi, Noor Azizi

2017-01-01

Rapid prototyping models can be reconstructed from stereolithographic digital study model data to produce hard-copy casts. In this study, we aimed to compare agreement and accuracy of measurements made with rapid prototyping and stone models for different degrees of crowding. The Z Printer 450 (3D Systems, Rock Hill, SC) reprinted 10 sets of models for each category of crowding (mild, moderate, and severe) scanned using a structured-light scanner (Maestro 3D, AGE Solutions, Pisa, Italy). Stone and RP models were measured using digital calipers for tooth sizes in the mesiodistal, buccolingual, and crown height planes and for arch dimension measurements. Bland-Altman and paired t test analyses were used to assess agreement and accuracy. Clinical significance was set at ±0.50 mm. Bland-Altman analysis showed the mean bias of measurements between the models to be within ±0.15 mm (SD, ±0.40 mm), but the 95% limits of agreement exceeded the cutoff point of ±0.50 mm (lower range, -0.81 to -0.41 mm; upper range, 0.34 to 0.76 mm). Paired t tests showed statistically significant differences for all planes in all categories of crowding except for crown height in the moderate crowding group and arch dimensions in the mild and moderate crowding groups. The rapid prototyping models were not clinically comparable with conventional stone models regardless of the degree of crowding. Copyright © 2017 American Association of Orthodontists. Published by Elsevier Inc. All rights reserved.

Detecting multiple moving objects in crowded environments with coherent motion regions

DOEpatents

Cheriyadat, Anil M.; Radke, Richard J.

2013-06-11

Coherent motion regions extend in time as well as space, enforcing consistency in detected objects over long time periods and making the algorithm robust to noisy or short point tracks. As a result of enforcing the constraint that selected coherent motion regions contain disjoint sets of tracks defined in a three-dimensional space including a time dimension. An algorithm operates directly on raw, unconditioned low-level feature point tracks, and minimizes a global measure of the coherent motion regions. At least one discrete moving object is identified in a time series of video images based on the trajectory similarity factors, which is a measure of a maximum distance between a pair of feature point tracks.

Empirical study of a unidirectional dense crowd during a real mass event

NASA Astrophysics Data System (ADS)

Zhang, X. L.; Weng, W. G.; Yuan, H. Y.; Chen, J. G.

2013-06-01

Many tragic crowd disasters have happened across the world in recent years, such as the Phnom Penh stampede in Cambodia, crowd disaster in Mina/Makkah, and the Love Parade disaster in Germany, showing that management of mass events is a tough task for organizers. The study of unidirectional flow, one of the most common forms of motion in mass activities, is essential for safe organization of such events. In this paper, the properties of unidirectional flow in a crowded street during a real mass event in China are quantitatively investigated with sophisticated active infrared counters and an image processing method. A complete dataset of flow rates during the whole celebration is recorded, and a time series analysis gives new insight into such activities. The spatial analysis shows that the velocity and density of the crowd are inhomogeneous due to the boundary effect, whereas the flux is uniform. The estimated capacity of the street indicates that the maximum flow rate under normal condition should be between 1.73 and 1.98 /m/s, which is in good agreement with several field studies available in the existing literature. In consideration of the significant deviation among different studies, fundamental diagrams of dense crowds are also re-verified, and the results here are consistent with those from other field studies of unidirectional flow, but different from the bidirectional and experimental results. It is suggested that the data from multidirectional flow and experiments cannot be directly applied to unidirectional dense flow in a real mass event. The results also imply that the density of a similar unidirectional marching crowd should be controlled to be under 5 /m2, which can produce optimal efficiency and have more possibility to ensure safety. The field study data given here provide a good example of a database for crowd studies.

Comparison of the International Crowding Measure in Emergency Departments (ICMED) and the National Emergency Department Overcrowding Score (NEDOCS) to measure emergency department crowding: pilot study.

PubMed

Boyle, Adrian; Abel, Gary; Raut, Pramin; Austin, Richard; Dhakshinamoorthy, Vijayasankar; Ayyamuthu, Ravi; Murdoch, Iona; Burton, Joel

2016-05-01

There is uncertainty about the best way to measure emergency department crowding. We have previously developed a consensus-based measure of crowding, the International Crowding Measure in Emergency Departments (ICMED). We aimed to obtain pilot data to evaluate the ability of a shortened form of the ICMED, the sICMED, to predict senior emergency department clinicians' concerns about crowding and danger compared with a very well-studied measure of emergency department crowding, the National Emergency Department Overcrowding Score (NEDOCS). We collected real-time observations of the sICMED and NEDOCS and compared these with clinicians' perceptions of crowding and danger on a visual analogue scale. Data were collected in four emergency departments in the East of England. Associations were explored using simple regression, random intercept models and models accounting for correlation between adjacent time points. We conducted 82 h of observation in 10 observation sets. Naive modelling suggested strong associations between sICMED and NEDOCS and clinician perceptions of crowding and danger. Further modelling showed that, due to clustering, the association between sICMED and danger persisted, but the association between these two measures and perception of crowding was no longer statistically significant. Both sICMED and NEDOCS can be collected easily in a variety of English hospitals. Further studies are required but initial results suggest both scores may have potential use for assessing crowding variation at long timescales, but are less sensitive to hour-by-hour variation. Correlation in time is an important methodological consideration which, if ignored, may lead to erroneous conclusions. Future studies should account for such correlation in both design and analysis. Published by the BMJ Publishing Group Limited. For permission to use (where not already granted under a licence) please go to http://www.bmj.com/company/products-services/rights-and-licensing/

Neural dynamics of grouping and segmentation explain properties of visual crowding.

PubMed

Francis, Gregory; Manassi, Mauro; Herzog, Michael H

2017-07-01

Investigations of visual crowding, where a target is difficult to identify because of flanking elements, has largely used a theoretical perspective based on local interactions where flanking elements pool with or substitute for properties of the target. This successful theoretical approach has motivated a wide variety of empirical investigations to identify mechanisms that cause crowding, and it has suggested practical applications to mitigate crowding effects. However, this theoretical approach has been unable to account for a parallel set of findings that crowding is influenced by long-range perceptual grouping effects. When the target and flankers are perceived as part of separate visual groups, crowding tends to be quite weak. Here, we describe how theoretical mechanisms for grouping and segmentation in cortical neural circuits can account for a wide variety of these long-range grouping effects. Building on previous work, we explain how crowding occurs in the model and explain how grouping in the model involves connected boundary signals that represent a key aspect of visual information. We then introduce new circuits that allow nonspecific top-down selection signals to flow along connected boundaries or within a surface contained by boundaries and thereby induce a segmentation that can separate the visual information corresponding to the flankers from the visual information corresponding to the target. When such segmentation occurs, crowding is shown to be weak. We compare the model's behavior to 5 sets of experimental findings on visual crowding and show that the model does a good job explaining the key empirical findings. (PsycINFO Database Record (c) 2017 APA, all rights reserved).

Formulation of human-structure interaction system models for vertical vibration

NASA Astrophysics Data System (ADS)

Caprani, Colin C.; Ahmadi, Ehsan

2016-09-01

In this paper, human-structure interaction system models for vibration in the vertical direction are considered. This work assembles various moving load models from the literature and proposes extension of the single pedestrian to a crowd of pedestrians for the FE formulation for crowd-structure interaction systems. The walking pedestrian vertical force is represented as a general time-dependent force, and the pedestrian is in turn modelled as moving force, moving mass, and moving spring-mass-damper. The arbitrary beam structure is modelled using either a formulation in modal coordinates or finite elements. In each case, the human-structure interaction (HSI) system is first formulated for a single walking pedestrian and then extended to consider a crowd of pedestrians. Finally, example applications for single pedestrian and crowd loading scenarios are examined. It is shown how the models can be used to quantify the interaction between the crowd and bridge structure. This work should find use for the evaluation of existing and new footbridges.

Is emergency department crowding associated with increased “bounceback” admissions?

PubMed Central

Hsia, Renee Y.; Asch, Steven M.; Weiss, Robert E.; Zingmond, David; Gabayan, Gelareh; Liang, Li-Jung; Han, Weijuan; McCreath, Heather; Sun, Benjamin C.

2013-01-01

Objective Emergency department (ED) crowding is linked with poor quality of care and worse outcomes, including higher mortality. With the growing emphasis on hospital performance measures, there is additional concern whether inadequate care during crowded periods increases a patient’s likelihood of subsequent inpatient admission. We sought to determine if ED crowding during the index visit was associated with these “bounceback” admissions. Methods We used comprehensive, non-public, statewide ED and inpatient discharge data from the California Office of Statewide Health Planning and Development from 2007 to identify index outpatient ED visits and bounceback admissions within seven days. We further used ambulance diversion data collected from California local emergency medical services agencies to identify crowded days using intra-hospital daily diversion hour quartiles. Using a hierarchical logistic regression model, we then determined if patients visiting on crowded days were more likely to have a subsequent bounceback admission. Results We analyzed 3,368,527 index visits across 202 hospitals, of which 596,471 (17.7%) observations were on crowded days. We found no association between ED crowding and bounceback admissions. This lack of relationship persisted in both a discrete (high/low) model (OR 1.01, 95% CI 0.99, 1.02) and a secondary model using ambulance diversion hours as a continuous predictor (OR 1.00, 95% CI 1.00, 1.00). Conclusions Crowding as measured by ambulance diversion does not have an association with hospitalization within 7 days of an ED visit discharge. Therefore, bounceback admission may be a poor measure of delayed or worsened quality of care due to crowding. PMID:24036997

College Crowd-In: How Private Donations Positively Affect Alumni Giving

ERIC Educational Resources Information Center

Gottfried, Michael A.

2008-01-01

The issue of donor behavior and crowding out has been pertinent in the economics literature, both theoretically and empirically. Aggregate research has not been decisive, nor have many studies analyzed education institutions. I begin with a theoretical model of crowding-out versus crowding-in donor behavior. I then employ a fixed effects…

Visualizing Protein Interactions and Dynamics: Evolving a Visual Language for Molecular Animation

ERIC Educational Resources Information Center

Jenkinson, Jodie; McGill, Gael

2012-01-01

Undergraduate biology education provides students with a number of learning challenges. Subject areas that are particularly difficult to understand include protein conformational change and stability, diffusion and random molecular motion, and molecular crowding. In this study, we examined the relative effectiveness of three-dimensional…

A Neurophysiologically Plausible Population Code Model for Feature Integration Explains Visual Crowding

PubMed Central

van den Berg, Ronald; Roerdink, Jos B. T. M.; Cornelissen, Frans W.

2010-01-01

An object in the peripheral visual field is more difficult to recognize when surrounded by other objects. This phenomenon is called “crowding”. Crowding places a fundamental constraint on human vision that limits performance on numerous tasks. It has been suggested that crowding results from spatial feature integration necessary for object recognition. However, in the absence of convincing models, this theory has remained controversial. Here, we present a quantitative and physiologically plausible model for spatial integration of orientation signals, based on the principles of population coding. Using simulations, we demonstrate that this model coherently accounts for fundamental properties of crowding, including critical spacing, “compulsory averaging”, and a foveal-peripheral anisotropy. Moreover, we show that the model predicts increased responses to correlated visual stimuli. Altogether, these results suggest that crowding has little immediate bearing on object recognition but is a by-product of a general, elementary integration mechanism in early vision aimed at improving signal quality. PMID:20098499

A crowd of pedestrian dynamics - The perspective of physics. Comment on "Human behaviours in evacuation crowd dynamics: From modelling to "big data" toward crisis management" by Nicola Bellomo et al.

NASA Astrophysics Data System (ADS)

Miguel, António F.

2016-09-01

Walking is the most basic form of transportation. A good understanding of pedestrian's dynamics is essential in meeting the mobility and accessibility needs of people by providing a safe and quick walking flow [1]. Advances in the dynamics of pedestrians in crowds are of great theoretical and practical interest, as they lead to new insights regarding the planning of pedestrian facilities, crowd management, or evacuation analysis. Nicola Bellomo's et al. article [2] is a very timely review of the related research on modelling approaches, computational simulations, decision-making and crisis response. It also includes an attempt to accurately define commonly used terms, as well as a critical analysis of crowd dynamics and safety problems. As noted by the authors, ;models and simulations offer a virtual representation of real dynamics; that are essential to understand and predict the ;behavioural dynamics of crowds; [2]. As a physicist, I would like to put forward some additional theoretical and practical contributions that could be interesting to explore, regarding the perspective of physics on about human crowd dynamics (panic as a specific form of behaviour excluded).

A control theoretical approach to crowd management. Comment on "Human behaviours in evacuation crowd dynamics: From modelling to "big data" toward crisis management" by Nicola Bellomo et al.

NASA Astrophysics Data System (ADS)

Borzí, Alfio; Caponigro, Marco

2016-09-01

The formulation of mathematical models for crowd dynamics is one current challenge in many fields of applied sciences. It involves the modelization of the complex behavior of a large number of individuals. In particular, the difficulty lays in describing emerging collective behaviors by means of a relatively small number of local interaction rules between individuals in a crowd. Clearly, the individual's free will involved in decision making processes and in the management of the social interactions cannot be described by a finite number of deterministic rules. On the other hand, in large crowds, this individual indeterminacy can be considered as a local fluctuation averaged to zero by the size of the crowd. While at the microscopic scale, using a system of coupled ODEs, the free will should be included in the mathematical description (e.g. with a stochastic term), the mesoscopic and macroscopic scales, modeled by PDEs, represent a powerful modelling tool that allows to neglect this feature and provide a reliable description. In this sense, the work by Bellomo, Clarke, Gibelli, Townsend, and Vreugdenhil [2] represents a mathematical-epistemological contribution towards the design of a reliable model of human behavior.

Collective learning dynamics in behavioral crowds. Comment on "Human behaviours in evacuation crowd dynamics: From modeling to "big data" toward crisis management" by Nicola Bellomo et al.

NASA Astrophysics Data System (ADS)

Burini, D.

2016-09-01

A recent literature on crowd dynamics [9,10] has enlightened that the management of crisis situations needs models able to depict social behaviors and, in particular, the spread of emotional feelings such as stress by panic situation.

From crowd modeling to safety problems. Comment on "Human behaviours in evacuation crowd dynamics: From modelling to "big data" toward crisis management" by Nicola Bellomo et al.

NASA Astrophysics Data System (ADS)

Elaiw, Ahmed

2016-09-01

Paper [3] presents a survey and a critical analysis on models of crowd dynamics derived to support crisis management related to safety problems. This is an important topic which can have an important impact on the wellbeing of our society. We are very interested in this topic as we operate in a country, Saudi Arabia, where huge crowds can be present and that stress conditions can be occasionally induced by non predictable events. In these situations the problem of crisis management is of fundamental importance.

Analytical Modelling of the Spread of Disease in Confined and Crowded Spaces

NASA Astrophysics Data System (ADS)

Goscé, Lara; Barton, David A. W.; Johansson, Anders

2014-05-01

Since 1927 and until recently, most models describing the spread of disease have been of compartmental type, based on the assumption that populations are homogeneous and well-mixed. Recent models have utilised agent-based models and complex networks to explicitly study heterogeneous interaction patterns, but this leads to an increasing computational complexity. Compartmental models are appealing because of their simplicity, but their parameters, especially the transmission rate, are complex and depend on a number of factors, which makes it hard to predict how a change of a single environmental, demographic, or epidemiological factor will affect the population. Therefore, in this contribution we propose a middle ground, utilising crowd-behaviour research to improve compartmental models in crowded situations. We show how both the rate of infection as well as the walking speed depend on the local crowd density around an infected individual. The combined effect is that the rate of infection at a population scale has an analytically tractable non-linear dependency on crowd density. We model the spread of a hypothetical disease in a corridor and compare our new model with a typical compartmental model, which highlights the regime in which current models may not produce credible results.

Intra-specific competition (crowding) of giant sequoias (Sequoiadendron giganteum)

USGS Publications Warehouse

Stohlgren, Thomas J.

1993-01-01

Information on the size and location of 1916 giant sequoias (Sequoiadendron giganteum (Lindl.) Buchholz) in Muir Grove, Sequoia National Park, in the southern Sierra Nevada of California was used to assess intra-specific crowding. Study objectives were to: (1) determine which parameters associated with intra-specific competition (i.e. size and distance to nearest neighbor, crowding/root system area overlap, or number of neighbors) might be important in spatial pattern development, growth, and survivorship of established giant sequoias; (2) quantify the level of intra-specific crowding of different sized live sequoias based on a model of estimated overlapping root system areas (i.e. an index of relative crowding); (3) compare the level of intra-specific crowding of similarly sized live and dead giant sequoias (less than 30 cm diameter at breast height (dbh) at the time of inventory (1969). Mean distances to the nearest live giant sequoia neighbor were not significantly different (at α = 0.05) for live and dead sequoias in similar size classes. A zone of influence competition model (i.e. index of crowding) based on horizontal overlap of estimated root system areas was developed for 1753 live sequoias. The model, based only on the spatial arrangement of live sequoias, was then tested on dead sequoias of less than 30 cm dbh (n = 163 trees; also recorded in 1969). The dead sequoias had a significantly higher crowding index than 561 live trees of similar diameter. Results showed that dead sequoias of less than 16.6 cm dbh had a significantly greater mean number of live neighbors and mean crowding index than live sequoias of similar size. Intra-specific crowding may be an important mechanism in determining the spatial distribution of sequoias in old-growth forests.

Class III malocclusion with complex problems of lateral open bite and severe crowding successfully treated with miniscrew anchorage and lingual orthodontic brackets.

PubMed

Yanagita, Takeshi; Kuroda, Shingo; Takano-Yamamoto, Teruko; Yamashiro, Takashi

2011-05-01

In this article, we report the successful use of miniscrews in a patient with an Angle Class III malocclusion, lateral open bite, midline deviation, and severe crowding. Simultaneously resolving such problems with conventional Class III treatment is difficult. In this case, the treatment procedure was even more challenging because the patient preferred to have lingual brackets on the maxillary teeth. As a result, miniscrews were used to facilitate significant asymmetric tooth movement in the posterior and downward directions; this contributed to the camouflage of the skeletal mandibular protrusion together with complete resolution of the severe crowding and lateral open bite. Analysis of the jaw motion showed that irregularities in chewing movement were also resolved, and a stable occlusion was achieved. Improvements in the facial profile and dental arches remained stable at the 18-month follow-up. Copyright © 2011 American Association of Orthodontists. Published by Mosby, Inc. All rights reserved.

Modeling detour behavior of pedestrian dynamics under different conditions

NASA Astrophysics Data System (ADS)

Qu, Yunchao; Xiao, Yao; Wu, Jianjun; Tang, Tao; Gao, Ziyou

2018-02-01

Pedestrian simulation approach has been widely used to reveal the human behavior and evaluate the performance of crowd evacuation. In the existing pedestrian simulation models, the social force model is capable of predicting many collective phenomena. Detour behavior occurs in many cases, and the important behavior is a dominate factor of the crowd evacuation efficiency. However, limited attention has been attracted for analyzing and modeling the characteristics of detour behavior. In this paper, a modified social force model integrated by Voronoi diagram is proposed to calculate the detour direction and preferred velocity. Besides, with the consideration of locations and velocities of neighbor pedestrians, a Logit-based choice model is built to describe the detour direction choice. The proposed model is applied to analyze pedestrian dynamics in a corridor scenario with either unidirectional or bidirectional flow, and a building scenario in real-world. Simulation results show that the modified social force model including detour behavior could reduce the frequency of collision and deadlock, increase the average speed of the crowd, and predict more practical crowd dynamics with detour behavior. This model can also be potentially applied to understand the pedestrian dynamics and design emergent management strategies for crowd evacuations.

Crowd dynamics and safety. Reply to comments on "Human behaviours in evacuation crowd dynamics: From modelling to "big data" toward crisis management"

NASA Astrophysics Data System (ADS)

Bellomo, N.; Clarke, D.; Gibelli, L.; Townsend, P.; Vreugdenhil, B. J.

2016-09-01

The survey [13] presents an overview and critical analysis of the existing literature on the modeling of crowd dynamics related to crisis management toward the search of safety conditions. Out of this general review some rationale on research perspectives have been brought to the attention of the reader.

New insights into turbulent pedestrian movement pattern in crowd-quakes

NASA Astrophysics Data System (ADS)

Ma, J.; Song, W. G.; Lo, S. M.; Fang, Z. M.

2013-02-01

Video recordings right before the Love Parade disaster have been quantitatively analyzed to explore the bursts of unusual crowd movement patterns, crowd-quakes. The pedestrian movement pattern in this incident was special for the reason that it happened in a congested counter flow scenario, where stopped pedestrians were involved. No one was believed to have pushed others intentionally at the beginning, however, under this situation, the body contacts among the pedestrians still induced a force spread, which then led to velocity fluctuation. As indicated by the individual velocity-related features, the densely crowded pedestrian movement displayed turbulent flow features. Further analyzing the overall flow field, we also found that the pedestrian flow field shared typical patterns with turbulent fluid flow. As a result of the turbulent state, different clusters of pedestrians displayed different velocity features. Thus crowd pressure which took into account the velocity and density information was proved to be a good indicator of crowd disasters. Based on these essential features of pedestrian crowd-quakes, a minimal model, i.e., a pedestrian crowd-quake model, was established. Effects including pedestrian gait, stress conservation level and personal intention to escape were explored.

Communication: Distinguishing between short-time non-Fickian diffusion and long-time Fickian diffusion for a random walk on a crowded lattice

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ellery, Adam J.; Simpson, Matthew J.; Baker, Ruth E.

2016-05-07

The motion of cells and molecules through biological environments is often hindered by the presence of other cells and molecules. A common approach to modeling this kind of hindered transport is to examine the mean squared displacement (MSD) of a motile tracer particle in a lattice-based stochastic random walk in which some lattice sites are occupied by obstacles. Unfortunately, stochastic models can be computationally expensive to analyze because we must average over a large ensemble of identically prepared realizations to obtain meaningful results. To overcome this limitation we describe an exact method for analyzing a lattice-based model of the motionmore » of an agent moving through a crowded environment. Using our approach we calculate the exact MSD of the motile agent. Our analysis confirms the existence of a transition period where, at first, the MSD does not follow a power law with time. However, after a sufficiently long period of time, the MSD increases in proportion to time. This latter phase corresponds to Fickian diffusion with a reduced diffusivity owing to the presence of the obstacles. Our main result is to provide a mathematically motivated, reproducible, and objective estimate of the amount of time required for the transport to become Fickian. Our new method to calculate this crossover time does not rely on stochastic simulations.« less

DEKF system for crowding estimation by a multiple-model approach

NASA Astrophysics Data System (ADS)

Cravino, F.; Dellucca, M.; Tesei, A.

1994-03-01

A distributed extended Kalman filter (DEKF) network devoted to real-time crowding estimation for surveillance in complex scenes is presented. Estimation is carried out by extracting a set of significant features from sequences of images. Feature values are associated by virtual sensors with the estimated number of people using nonlinear models obtained in an off-line training phase. Different models are used, depending on the positions and dimensions of the crowded subareas detected in each image.

Active particles in complex and crowded environments

DOE PAGES

Bechinger, Clemens; Di Leonardo, Roberto; Löwen, Hartmut; ...

2016-11-23

Differently from passive Brownian particles, active particles, also known as self-propelled Brownian particles or microswimmers and nanoswimmers, are capable of taking up energy from their environment and converting it into directed motion. Because of this constant flow of energy, their behavior can be explained and understood only within the framework of nonequilibrium physics. In the biological realm, many cells perform directed motion, for example, as a way to browse for nutrients or to avoid toxins. Inspired by these motile microorganisms, researchers have been developing artificial particles that feature similar swimming behaviors based on different mechanisms. These man-made micromachines and nanomachinesmore » hold a great potential as autonomous agents for health care, sustainability, and security applications. Finally, with a focus on the basic physical features of the interactions of self-propelled Brownian particles with a crowded and complex environment, this comprehensive review will provide a guided tour through its basic principles, the development of artificial self-propelling microparticles and nanoparticles, and their application to the study of nonequilibrium phenomena, as well as the open challenges that the field is currently facing.« less

Pair mobility functions for rigid spheres in concentrated colloidal dispersions: Stresslet and straining motion couplings

NASA Astrophysics Data System (ADS)

Su, Yu; Swan, James W.; Zia, Roseanna N.

2017-03-01

Accurate modeling of particle interactions arising from hydrodynamic, entropic, and other microscopic forces is essential to understanding and predicting particle motion and suspension behavior in complex and biological fluids. The long-range nature of hydrodynamic interactions can be particularly challenging to capture. In dilute dispersions, pair-level interactions are sufficient and can be modeled in detail by analytical relations derived by Jeffrey and Onishi [J. Fluid Mech. 139, 261-290 (1984)] and Jeffrey [Phys. Fluids A 4, 16-29 (1992)]. In more concentrated dispersions, analytical modeling of many-body hydrodynamic interactions quickly becomes intractable, leading to the development of simplified models. These include mean-field approaches that smear out particle-scale structure and essentially assume that long-range hydrodynamic interactions are screened by crowding, as particle mobility decays at high concentrations. Toward the development of an accurate and simplified model for the hydrodynamic interactions in concentrated suspensions, we recently computed a set of effective pair of hydrodynamic functions coupling particle motion to a hydrodynamic force and torque at volume fractions up to 50% utilizing accelerated Stokesian dynamics and a fast stochastic sampling technique [Zia et al., J. Chem. Phys. 143, 224901 (2015)]. We showed that the hydrodynamic mobility in suspensions of colloidal spheres is not screened, and the power law decay of the hydrodynamic functions persists at all concentrations studied. In the present work, we extend these mobility functions to include the couplings of particle motion and straining flow to the hydrodynamic stresslet. The couplings computed in these two articles constitute a set of orthogonal coupling functions that can be utilized to compute equilibrium properties in suspensions at arbitrary concentration and are readily applied to solve many-body hydrodynamic interactions analytically.

Modeling social crowds. Comment on "Human behaviours in evacuation crowd dynamics: From modelling to "big data" toward crisis management" by Nicola Bellomo et al.

NASA Astrophysics Data System (ADS)

Poyato, David; Soler, Juan

2016-09-01

The study of human behavior is a complex task, but modeling some aspects of this behavior is an even more complicated and exciting idea. From crisis management to decision making in evacuation protocols, understanding the complexity of humans in stress situations is more and more demanded in our society by obvious reasons [5,6,8,12]. In this context, [4] deals with crowd dynamics with special attention to evacuation.

Household crowding associated with childhood otitis media hospitalisations in New Zealand.

PubMed

Bowie, Christopher; Pearson, Amber L; Campbell, Malcolm; Barnett, Ross

2014-06-01

To examine the association between hospitalisations for otitis media and area-level measures of household crowding among children in New Zealand. Counts of hospital admissions for otitis media by census area unit were offset against population data from the 2006 national census. Area-level household crowding, exposure to tobacco smoke in the home, equivalised income and individual-level characteristics age and sex were adjusted for. To examine effect modification by ethnicity, three separate poisson models were examined for the total, Māori and non-Māori populations. Household crowding was significantly associated with hospital admissions for otitis media after adjustment in all three models. Neighbourhoods with the highest compared to the lowest proportion of crowded homes exhibited incidence rate ratios of 1.25 (95%CI 1.12-1.37) in the total population, 1.59 (95%CI 1.21-2.04) in the Māori restricted model and 1.17 (95%CI 1.06-1.32) in the non-Māori restricted model. Otitis media hospitalisations are associated with area-level measures of household crowding and other risk factors in this ecological study. The largest increase in otitis media incidence relative to neighbourhood rates of household crowding was exhibited among Māori cases of otitis media. This study adds weight to the growing body of literature linking infectious disease risk to overcrowding in the home. © 2014 The Authors. ANZJPH © 2014 Public Health Association of Australia.

Crowding and experience-use history: a study of the moderating effect of place attachment among water-based recreationists.

PubMed

Budruk, Megha; Wilhem Stanis, Sonja A; Schneider, Ingrid E; Heisey, Jennifer J

2008-04-01

Effective recreation resource management relies on understanding visitor perceptions and behaviors. Given current and increasing pressures on water resources, understanding crowding evaluations seems important. Beyond crowding, however, variables that possibly relate to or influence crowding are of interest and in particular, place attachment and experience-use history (EUH). As EUH is related to place attachment and likely affects crowding, this study explored the moderating effect of place attachment dimensions on the relationships between EUH and visitor crowding evaluations. Water based recreationists at a U.S. Army Corps of Engineers site were contacted onsite and asked questions related to experience-use history, crowding evaluations, place attachment, and activity participation. Anglers and campers at the site identified similar crowding perceptions and place attachments. Only one of eight models tested revealed a moderating effect. Specifically, place identity moderated the relationship between the total times visited in the past twelve months and expected crowding among anglers. As such, the quest continues to understand the relationship among these important variables.

Mitigating randomness of consumer preferences under certain conditional choices

NASA Astrophysics Data System (ADS)

Bothos, John M. A.; Thanos, Konstantinos-Georgios; Papadopoulou, Eirini; Daveas, Stelios; Thomopoulos, Stelios C. A.

2017-05-01

Agent-based crowd behaviour consists a significant field of research that has drawn a lot of attention in recent years. Agent-based crowd simulation techniques have been used excessively to forecast the behaviour of larger or smaller crowds in terms of certain given conditions influenced by specific cognition models and behavioural rules and norms, imposed from the beginning. Our research employs conditional event algebra, statistical methodology and agent-based crowd simulation techniques in developing a behavioural econometric model about the selection of certain economic behaviour by a consumer that faces a spectre of potential choices when moving and acting in a multiplex mall. More specifically we try to analyse the influence of demographic, economic, social and cultural factors on the economic behaviour of a certain individual and then we try to link its behaviour with the general behaviour of the crowds of consumers in multiplex malls using agent-based crowd simulation techniques. We then run our model using Generalized Least Squares and Maximum Likelihood methods to come up with the most probable forecast estimations, regarding the agent's behaviour. Our model is indicative about the formation of consumers' spectre of choices in multiplex malls under the condition of predefined preferences and can be used as a guide for further research in this area.

Convex Formulations of Learning from Crowds

NASA Astrophysics Data System (ADS)

Kajino, Hiroshi; Kashima, Hisashi

It has attracted considerable attention to use crowdsourcing services to collect a large amount of labeled data for machine learning, since crowdsourcing services allow one to ask the general public to label data at very low cost through the Internet. The use of crowdsourcing has introduced a new challenge in machine learning, that is, coping with low quality of crowd-generated data. There have been many recent attempts to address the quality problem of multiple labelers, however, there are two serious drawbacks in the existing approaches, that are, (i) non-convexity and (ii) task homogeneity. Most of the existing methods consider true labels as latent variables, which results in non-convex optimization problems. Also, the existing models assume only single homogeneous tasks, while in realistic situations, clients can offer multiple tasks to crowds and crowd workers can work on different tasks in parallel. In this paper, we propose a convex optimization formulation of learning from crowds by introducing personal models of individual crowds without estimating true labels. We further extend the proposed model to multi-task learning based on the resemblance between the proposed formulation and that for an existing multi-task learning model. We also devise efficient iterative methods for solving the convex optimization problems by exploiting conditional independence structures in multiple classifiers.

Dynamics of crowd disasters: An empirical study

NASA Astrophysics Data System (ADS)

Helbing, Dirk; Johansson, Anders; Al-Abideen, Habib Zein

2007-04-01

Many observations of the dynamics of pedestrian crowds, including various self-organization phenomena, have been successfully described by simple many-particle models. For ethical reasons, however, there is a serious lack of experimental data regarding crowd panic. Therefore, we have analyzed video recordings of the crowd disaster in Mina/Makkah during the Hajj in 1426H on 12 January 2006. They reveal two subsequent, sudden transitions from laminar to stop-and-go and “turbulent” flows, which question many previous simulation models. While the transition from laminar to stop-and-go flows supports a recent model of bottleneck flows [D. Helbing , Phys. Rev. Lett. 97, 168001 (2006)], the subsequent transition to turbulent flow is not yet well understood. It is responsible for sudden eruptions of pressure release comparable to earthquakes, which cause sudden displacements and the falling and trampling of people. The insights of this study into the reasons for critical crowd conditions are important for the organization of safer mass events. In particular, they allow one to understand where and when crowd accidents tend to occur. They have also led to organizational changes, which have ensured a safe Hajj in 1427H.

Generating Pedestrian Trajectories Consistent with the Fundamental Diagram Based on Physiological and Psychological Factors

PubMed Central

Narang, Sahil; Best, Andrew; Curtis, Sean; Manocha, Dinesh

2015-01-01

Pedestrian crowds often have been modeled as many-particle system including microscopic multi-agent simulators. One of the key challenges is to unearth governing principles that can model pedestrian movement, and use them to reproduce paths and behaviors that are frequently observed in human crowds. To that effect, we present a novel crowd simulation algorithm that generates pedestrian trajectories that exhibit the speed-density relationships expressed by the Fundamental Diagram. Our approach is based on biomechanical principles and psychological factors. The overall formulation results in better utilization of free space by the pedestrians and can be easily combined with well-known multi-agent simulation techniques with little computational overhead. We are able to generate human-like dense crowd behaviors in large indoor and outdoor environments and validate the results with captured real-world crowd trajectories. PMID:25875932

The Sense-It App: A Smartphone Sensor Toolkit for Citizen Inquiry Learning

ERIC Educational Resources Information Center

Sharples, Mike; Aristeidou, Maria; Villasclaras-Fernández, Eloy; Herodotou, Christothea; Scanlon, Eileen

2017-01-01

The authors describe the design and formative evaluation of a sensor toolkit for Android smartphones and tablets that supports inquiry-based science learning. The Sense-it app enables a user to access all the motion, environmental and position sensors available on a device, linking these to a website for shared crowd-sourced investigations. The…

Long-range dependence and time-clustering behavior in pedestrian movement patterns in stampedes: The Love Parade case-study

NASA Astrophysics Data System (ADS)

Lian, Liping; Song, Weiguo; Richard, Yuen Kwok Kit; Ma, Jian; Telesca, Luciano

2017-03-01

Pedestrian stampede happened more and more often during these years, such as Love Parade disaster in Germany 2010, trampling in Shanghai bund 2014 and crowd stampede in pilgrimages. Love Parade disaster 2010 stands out for well recorded videos, which are HD quality and available for researchers. There were totally seven surveillance cameras capturing the whole festival progress and the video we study is just before the disaster happened. Pedestrian motion was special and a small disturbance would lead the group to an avalanche in this kind of critical situation. Here we focus on the individual movement pattern. The trajectories of each pedestrian involved were extracted by a mean-shift algorithm. We analyzed the space-time patterns of the pedestrians involved in the Love Parade stampede by using the detrended fluctuation analysis and the coefficient of variation. Our results reveal that the pedestrians' movement in crowd-quakes is persistent in space, globally time-clusterized but locally regular or quasi-periodic behavior. Pedestrian movement was treated as stop and go state by point process-based representation. When the threshold increases, this means that the "go" state is longer and pedestrians keep on walking in several consecutive time frames; this is difficult in crowded situations and lead to special time-clustering behavior of the sequence of "go" events. The study reveals pedestrian motion characteristics in critical situations, which will enhance the understanding of pedestrian behaviors and supply early warning features for not only Love Parade Disaster, but also other similar large events.

Rhythmic crowd bobbing on a grandstand simulator

NASA Astrophysics Data System (ADS)

Comer, A. J.; Blakeborough, A.; Williams, M. S.

2013-01-01

It is widely accepted that concerted human activity such as bouncing or bobbing can excite cantilever grandstands. Crowd coordination can be unwitting and may be exacerbated by structural motion caused by resonant structural response. This is an area of uncertainty in the design and analysis of modern grandstands. This paper presents experimental measurement and analysis of rhythmic crowd bobbing loads obtained from tests on a grandstand simulator with two distinct support conditions; (a) rigid, and; (b) flexible. It was found that significant structural vibration at the bobbing frequency did not increase the effective bobbing load. Structural motion at the bobbing frequency caused a reduction in the dynamic load factor (DLF) at the frequency of the second harmonic while those at the first and third harmonics were unaffected. Two plausible reasons for this are: (a) the bobbing group were unable to supply significant energy to the system at the frequency of the second harmonic; (b) the bobbing group altered their bobbing style to reduce the response of the grandstand simulator. It was deduced that the bobbing group did not absorb energy from the dynamic system. Furthermore, dynamic load factors for groups of test subjects bobbing on a rigid structure were typically greater than those of synthesised groups derived from individuals bobbing alone, possibly due to group effects such as audio and visual stimuli from neighbouring test subjects. Last, the vibration levels experienced by the test subjects appear to be below levels likely to cause discomfort. This is to be expected as the test subjects were themselves controlling the magnitude and duration of vibration for the bobbing tests considered.

Motion-guided attention promotes adaptive communications during social navigation.

PubMed

Lemasson, B H; Anderson, J J; Goodwin, R A

2013-03-07

Animals are capable of enhanced decision making through cooperation, whereby accurate decisions can occur quickly through decentralized consensus. These interactions often depend upon reliable social cues, which can result in highly coordinated activities in uncertain environments. Yet information within a crowd may be lost in translation, generating confusion and enhancing individual risk. As quantitative data detailing animal social interactions accumulate, the mechanisms enabling individuals to rapidly and accurately process competing social cues remain unresolved. Here, we model how motion-guided attention influences the exchange of visual information during social navigation. We also compare the performance of this mechanism to the hypothesis that robust social coordination requires individuals to numerically limit their attention to a set of n-nearest neighbours. While we find that such numerically limited attention does not generate robust social navigation across ecological contexts, several notable qualities arise from selective attention to motion cues. First, individuals can instantly become a local information hub when startled into action, without requiring changes in neighbour attention level. Second, individuals can circumvent speed-accuracy trade-offs by tuning their motion thresholds. In turn, these properties enable groups to collectively dampen or amplify social information. Lastly, the minority required to sway a group's short-term directional decisions can change substantially with social context. Our findings suggest that motion-guided attention is a fundamental and efficient mechanism underlying collaborative decision making during social navigation.

Mathematical Capture of Human Crowd Behavioral Data for Computational Model Building, Verification, and Validation

DTIC Science & Technology

2011-03-21

throughout the experimental runs. Reliable and validated measures of anxiety ( Spielberger , 1983), as well as custom-constructed questionnaires about...Crowd modeling and simulation technologies. Transactions on modeling and computer simulation, 20(4). Spielberger , C. D. (1983

The Resolved Stellar Populations Early Release Science Program

NASA Astrophysics Data System (ADS)

Gilbert, Karoline; Weisz, Daniel; Resolved Stellar Populations ERS Program Team

2018-06-01

The Resolved Stellar Populations Early Release Science Program (PI D. Weisz) will observe Local Group targets covering a range of stellar density and star formation histories, including a globular cluster, and ultra-faint dwarf galaxy, and a star-forming dwarf galaxy. Using observations of these diverse targets we will explore a broad science program: we will measure star formation histories, the sub-solar stellar initial mass function, and proper motions, perform studies of evolved stars, and map extinction in the target fields. Our observations will be of high archival value for other science such as calibrating stellar evolution models, studying variable stars, and searching for metal-poor stars. We will determine optimal observational setups and develop data reduction techniques that will be common to JWST studies of resolved stellar populations. We will also design, test, and release point spread function (PSF) fitting software specific to NIRCam and NIRISS, required for the crowded stellar regime. Prior to the Cycle 2 Call for Proposals, we will release PSF fitting software, matched HST and JWST catalogs, and clear documentation and step-by-step tutorials (such as Jupyter notebooks) for reducing crowded stellar field data and producing resolved stellar photometry catalogs, as well as for specific resolved stellar photometry science applications.

Modeling persistence of motion in a crowded environment: The diffusive limit of excluding velocity-jump processes

NASA Astrophysics Data System (ADS)

Gavagnin, Enrico; Yates, Christian A.

2018-03-01

Persistence of motion is the tendency of an object to maintain motion in a direction for short time scales without necessarily being biased in any direction in the long term. One of the most appropriate mathematical tools to study this behavior is an agent-based velocity-jump process. In the absence of agent-agent interaction, the mean-field continuum limit of the agent-based model (ABM) gives rise to the well known hyperbolic telegraph equation. When agent-agent interaction is included in the ABM, a strictly advective system of partial differential equations (PDEs) can be derived at the population level. However, no diffusive limit of the ABM has been obtained from such a model. Connecting the microscopic behavior of the ABM to a diffusive macroscopic description is desirable, since it allows the exploration of a wider range of scenarios and establishes a direct connection with commonly used statistical tools of movement analysis. In order to connect the ABM at the population level to a diffusive PDE at the population level, we consider a generalization of the agent-based velocity-jump process on a two-dimensional lattice with three forms of agent interaction. This generalization allows us to take a diffusive limit and obtain a faithful population-level description. We investigate the properties of the model at both the individual and population levels and we elucidate some of the models' key characteristic features. In particular, we show an intrinsic anisotropy inherent to the models and we find evidence of a spontaneous form of aggregation at both the micro- and macroscales.

Macromolecular crowding impacts on the diffusion and conformation of DNA hairpins

NASA Astrophysics Data System (ADS)

Stiehl, Olivia; Weidner-Hertrampf, Kathrin; Weiss, Matthias

2015-01-01

Biochemical reactions in crowded fluids differ significantly from those in dilute solutions. Both, excluded-volume interactions with surrounding macromolecules ("crowders") and an enhanced rebinding of reaction partners due to crowding-induced viscoelasticity and subdiffusion have been hypothesized to shift chemical equilibria towards the associated state. We have explored the impact of both cues in an experimentally tunable system by monitoring the steady-state fraction of open DNA hairpins in crowded fluids with varying viscoelastic characteristics but similar occupied volume fractions. As a result, we observed an increased fraction of closed DNA hairpins in viscoelastic crowded fluids. Our observations compare favorably to a simple statistical model that considers both facets of crowding, while preferential interactions between crowders and DNA hairpins appear to have little influence.

Patterns of residential crowding among Hispanics in later life: immigration, assimilation, and housing market factors.

PubMed

Burr, Jeffrey A; Mutchler, Jan E; Gerst, Kerstin

2010-11-01

We describe patterns of residential crowding among older Hispanics and non-Hispanic Whites. We also examine hypotheses about the relationship of residential crowding with assimilation (language and duration of residence) and housing market characteristics. We employ a multilevel research design, using data from the 2000 U.S. Census of Population. Hierarchical linear models are utilized to estimate the association between residential crowding and both individual and housing market factors. Approximately one third of older Hispanics in metropolitan areas live in crowded housing compared with only one tenth of older non-Hispanic Whites. Foreign-born older persons report higher levels of crowding than U.S.-born older persons. Residential crowding differences between older Hispanics and non-Hispanics are not eliminated after controls are included. Older Hispanics who report better English language skills and a longer duration of residence in the United States live in less crowded housing. We do not find evidence for a relationship between crowding and residential segregation, but we find consistent evidence for an association between residential crowding and relative size of the Hispanic population. The forces that shape household composition and access to housing among older Hispanics appear to result in higher levels of residential crowding for this population.

The Density Functional Theory of Flies: Predicting distributions of interacting active organisms

NASA Astrophysics Data System (ADS)

Kinkhabwala, Yunus; Valderrama, Juan; Cohen, Itai; Arias, Tomas

On October 2nd, 2016, 52 people were crushed in a stampede when a crowd panicked at a religious gathering in Ethiopia. The ability to predict the state of a crowd and whether it is susceptible to such transitions could help prevent such catastrophes. While current techniques such as agent based models can predict transitions in emergent behaviors of crowds, the assumptions used to describe the agents are often ad hoc and the simulations are computationally expensive making their application to real-time crowd prediction challenging. Here, we pursue an orthogonal approach and ask whether a reduced set of variables, such as the local densities, are sufficient to describe the state of a crowd. Inspired by the theoretical framework of Density Functional Theory, we have developed a system that uses only measurements of local densities to extract two independent crowd behavior functions: (1) preferences for locations and (2) interactions between individuals. With these two functions, we have accurately predicted how a model system of walking Drosophila melanogaster distributes itself in an arbitrary 2D environment. In addition, this density-based approach measures properties of the crowd from only observations of the crowd itself without any knowledge of the detailed interactions and thus it can make predictions about the resulting distributions of these flies in arbitrary environments, in real-time. This research was supported in part by ARO W911NF-16-1-0433.

Flexibility damps macromolecular crowding effects on protein folding dynamics: Application to the murine prion protein (121-231)

NASA Astrophysics Data System (ADS)

Bergasa-Caceres, Fernando; Rabitz, Herschel A.

2014-01-01

A model of protein folding kinetics is applied to study the combined effects of protein flexibility and macromolecular crowding on protein folding rate and stability. It is found that the increase in stability and folding rate promoted by macromolecular crowding is damped for proteins with highly flexible native structures. The model is applied to the folding dynamics of the murine prion protein (121-231). It is found that the high flexibility of the native isoform of the murine prion protein (121-231) reduces the effects of macromolecular crowding on its folding dynamics. The relevance of these findings for the pathogenic mechanism are discussed.

Crowding Effects in Vehicular Traffic

PubMed Central

Combinido, Jay Samuel L.; Lim, May T.

2012-01-01

While the impact of crowding on the diffusive transport of molecules within a cell is widely studied in biology, it has thus far been neglected in traffic systems where bulk behavior is the main concern. Here, we study the effects of crowding due to car density and driving fluctuations on the transport of vehicles. Using a microscopic model for traffic, we found that crowding can push car movement from a superballistic down to a subdiffusive state. The transition is also associated with a change in the shape of the probability distribution of positions from a negatively-skewed normal to an exponential distribution. Moreover, crowding broadens the distribution of cars’ trap times and cluster sizes. At steady state, the subdiffusive state persists only when there is a large variability in car speeds. We further relate our work to prior findings from random walk models of transport in cellular systems. PMID:23139762

Empirical study on social groups in pedestrian evacuation dynamics

NASA Astrophysics Data System (ADS)

von Krüchten, Cornelia; Schadschneider, Andreas

2017-06-01

Pedestrian crowds often include social groups, i.e. pedestrians that walk together because of social relationships. They show characteristic configurations and influence the dynamics of the entire crowd. In order to investigate the impact of social groups on evacuations we performed an empirical study with pupils. Several evacuation runs with groups of different sizes and different interactions were performed. New group parameters are introduced which allow to describe the dynamics of the groups and the configuration of the group members quantitatively. The analysis shows a possible decrease of evacuation times for large groups due to self-ordering effects. Social groups can be approximated as ellipses that orientate along their direction of motion. Furthermore, explicitly cooperative behaviour among group members leads to a stronger aggregation of group members and an intermittent way of evacuation.

Hyperbolic scaling and computing in social crowds: Comment on "Human behaviours in evacuation crowd dynamics: From modelling to "big data" toward crisis management" by Nicola Bellomo et al.

NASA Astrophysics Data System (ADS)

Outada, Nisrine

2016-09-01

I have read with great interest the paper [5] where the authors present an overview and critical analysis of the literature on the modeling of the crowd dynamics with special attention to evacuation dynamics. The approach developed is based on suitable development of methods of the kinetic theory. Interactions, which lead to the decision choice, are modeled by theoretical tools of stochastic evolutionary game theory [11,12]. However, the paper [5] provides not only a survey focused on topics of great interest for our society, but also it looks ahead to a variety of interesting and challenging mathematical problems. Specifically, I am interested in the derivation of macroscopic (hydrodynamic) models from the underlying description given from the kinetic theory approach, more specifically by the kinetic theory for active particles [8]. A general reference on crowd modeling is the recently published book [10].

Emergency department crowding in Singapore: Insights from a systems thinking approach.

PubMed

Schoenenberger, Lukas K; Bayer, Steffen; Ansah, John P; Matchar, David B; Mohanavalli, Rajagopal L; Lam, Sean Sw; Ong, Marcus Eh

2016-01-01

Emergency Department crowding is a serious and international health care problem that seems to be resistant to most well intended but often reductionist policy approaches. In this study, we examine Emergency Department crowding in Singapore from a systems thinking perspective using causal loop diagramming to visualize the systemic structure underlying this complex phenomenon. Furthermore, we evaluate the relative impact of three different policies in reducing Emergency Department crowding in Singapore: introduction of geriatric emergency medicine, expansion of emergency medicine training, and implementation of enhanced primary care. The construction of the qualitative causal loop diagram is based on consultations with Emergency Department experts, direct observation, and a thorough literature review. For the purpose of policy analysis, a novel approach, the path analysis, is applied. The path analysis revealed that both the introduction of geriatric emergency medicine and the expansion of emergency medicine training may be associated with undesirable consequences contributing to Emergency Department crowding. In contrast, enhancing primary care was found to be germane in reducing Emergency Department crowding; in addition, it has apparently no negative side effects, considering the boundary of the model created. Causal loop diagramming was a powerful tool for eliciting the systemic structure of Emergency Department crowding in Singapore. Additionally, the developed model was valuable in testing different policy options.

iCrowd: agent-based behavior modeling and crowd simulator

NASA Astrophysics Data System (ADS)

Kountouriotis, Vassilios I.; Paterakis, Manolis; Thomopoulos, Stelios C. A.

2016-05-01

Initially designed in the context of the TASS (Total Airport Security System) FP-7 project, the Crowd Simulation platform developed by the Integrated Systems Lab of the Institute of Informatics and Telecommunications at N.C.S.R. Demokritos, has evolved into a complete domain-independent agent-based behavior simulator with an emphasis on crowd behavior and building evacuation simulation. Under continuous development, it reflects an effort to implement a modern, multithreaded, data-oriented simulation engine employing latest state-of-the-art programming technologies and paradigms. It is based on an extensible architecture that separates core services from the individual layers of agent behavior, offering a concrete simulation kernel designed for high-performance and stability. Its primary goal is to deliver an abstract platform to facilitate implementation of several Agent-Based Simulation solutions with applicability in several domains of knowledge, such as: (i) Crowd behavior simulation during [in/out] door evacuation. (ii) Non-Player Character AI for Game-oriented applications and Gamification activities. (iii) Vessel traffic modeling and simulation for Maritime Security and Surveillance applications. (iv) Urban and Highway Traffic and Transportation Simulations. (v) Social Behavior Simulation and Modeling.

Associative Interactions in Crowded Solutions of Biopolymers Counteract Depletion Effects.

PubMed

Groen, Joost; Foschepoth, David; te Brinke, Esra; Boersma, Arnold J; Imamura, Hiromi; Rivas, Germán; Heus, Hans A; Huck, Wilhelm T S

2015-10-14

The cytosol of Escherichia coli is an extremely crowded environment, containing high concentrations of biopolymers which occupy 20-30% of the available volume. Such conditions are expected to yield depletion forces, which strongly promote macromolecular complexation. However, crowded macromolecule solutions, like the cytosol, are very prone to nonspecific associative interactions that can potentially counteract depletion. It remains unclear how the cytosol balances these opposing interactions. We used a FRET-based probe to systematically study depletion in vitro in different crowded environments, including a cytosolic mimic, E. coli lysate. We also studied bundle formation of FtsZ protofilaments under identical crowded conditions as a probe for depletion interactions at much larger overlap volumes of the probe molecule. The FRET probe showed a more compact conformation in synthetic crowding agents, suggesting strong depletion interactions. However, depletion was completely negated in cell lysate and other protein crowding agents, where the FRET probe even occupied slightly more volume. In contrast, bundle formation of FtsZ protofilaments proceeded as readily in E. coli lysate and other protein solutions as in synthetic crowding agents. Our experimental results and model suggest that, in crowded biopolymer solutions, associative interactions counterbalance depletion forces for small macromolecules. Furthermore, the net effects of macromolecular crowding will be dependent on both the size of the macromolecule and its associative interactions with the crowded background.

Crowding Effects on the Formation and Maintenance of Nuclear Bodies: Insights from Molecular-Dynamics Simulations of Simple Spherical Model Particles

PubMed Central

Cho, Eun Jin; Kim, Jun Soo

2012-01-01

The physics of structure formation and maintenance of nuclear bodies (NBs), such as nucleoli, Cajal bodies, promyelocytic leukemia bodies, and speckles, in a crowded nuclear environment remains largely unknown. We investigate the role of macromolecular crowding in the formation and maintenance of NBs using computer simulations of a simple spherical model, called Lennard-Jones (LJ) particles. LJ particles form a one-phase, dilute fluid when the intermolecular interaction is weaker than a critical value, above which they phase separate and form a condensed domain. We find that when volume-exclusive crowders exist in significant concentrations, domain formation is induced even for weaker intermolecular interactions, and the effect is more pronounced with increasing crowder concentration. Simulation results show that a previous experimental finding that promyelocytic leukemia bodies disappear in the less-crowded condition and reassemble in the normal crowded condition can be interpreted as a consequence of the increased intermolecular interactions between NB proteins due to crowding. Based on further analysis of the simulation results, we discuss the acceleration of macromolecular associations that occur within NBs, and the delay of diffusive transport of macromolecules within and out of NBs when the crowder concentration increases. This study suggests that in a polydisperse nuclear environment that is enriched with a variety of macromolecules, macromolecular crowding not only plays an important role in the formation and maintenance of NBs, but also may perform some regulatory functions in response to alterations in the crowding conditions. PMID:22947858

Continuum modelling of pedestrian flows - Part 2: Sensitivity analysis featuring crowd movement phenomena

NASA Astrophysics Data System (ADS)

Duives, Dorine C.; Daamen, Winnie; Hoogendoorn, Serge P.

2016-04-01

In recent years numerous pedestrian simulation tools have been developed that can support crowd managers and government officials in their tasks. New technologies to monitor pedestrian flows are in dire need of models that allow for rapid state-estimation. Many contemporary pedestrian simulation tools model the movements of pedestrians at a microscopic level, which does not provide an exact solution. Macroscopic models capture the fundamental characteristics of the traffic state at a more aggregate level, and generally have a closed form solution which is necessary for rapid state estimation for traffic management purposes. This contribution presents a next step in the calibration and validation of the macroscopic continuum model detailed in Hoogendoorn et al. (2014). The influence of global and local route choice on the development of crowd movement phenomena, such as dissipation, lane-formation and stripe-formation, is studied. This study shows that most self-organization phenomena and behavioural trends only develop under very specific conditions, and as such can only be simulated using specific parameter sets. Moreover, all crowd movement phenomena can be reproduced by means of the continuum model using one parameter set. This study concludes that the incorporation of local route choice behaviour and the balancing of the aptitude of pedestrians with respect to their own class and other classes are both essential in the correct prediction of crowd movement dynamics.

Further steps in the modeling of behavioural crowd dynamics, good news for safe handling. Comment on "Human behaviours in evacuation crowd dynamics: From modelling to "big data" toward crisis management" by Nicola Bellomo et al.

NASA Astrophysics Data System (ADS)

Knopoff, Damián A.

2016-09-01

The recent review paper [4] constitutes a valuable contribution on the understanding, modeling and simulation of crowd dynamics in extreme situations. It provides a very comprehensive revision about the complexity features of the system under consideration, scaling and the consequent justification of the used methods. In particular, macro and microscopic models have so far been used to model crowd dynamics [9] and authors appropriately explain that working at the mesoscale is a good choice to deal with the heterogeneous behaviour of walkers as well as with the difficulty of their deterministic identification. In this way, methods based on the kinetic theory and statistical dynamics are employed, more precisely the so-called kinetic theory for active particles [7]. This approach has successfully been applied in the modeling of several complex dynamics, with recent applications to learning [2,8] that constitutes the key to understand communication and is of great importance in social dynamics and behavioral sciences.

Multiscale diffusion of a molecular probe in a crowded environment: a concept

NASA Astrophysics Data System (ADS)

Currie, Megan; Thao, Chang; Timerman, Randi; Welty, Robb; Berry, Brenden; Sheets, Erin D.; Heikal, Ahmed A.

2015-08-01

Living cells are crowded with macromolecules and organelles. Yet, it is not fully understood how macromolecular crowding affects the myriad of biochemical reactions, transport and the structural stability of biomolecules that are essential to cellular function and survival. These molecular processes, with or without electrostatic interactions, in living cells are therefore expected to be distinct from those carried out in test tube in dilute solutions where excluded volumes are absent. Thus there is an urgent need to understand the macromolecular crowding effects on cellular and molecular biophysics towards quantitative cell biology. In this report, we investigated how biomimetic crowding affects both the rotational and translation diffusion of a small probe (rhodamine green, RhG). For biomimetic crowding agents, we used Ficoll-70 (synthetic polymer), bovine serum albumin and ovalbumin (proteins) at various concentrations in a buffer at room temperature. As a control, we carried out similar measurements on glycerolenriched buffer as an environment with homogeneous viscosity as a function of glycerol concentration. The corresponding bulk viscosity was measured independently to test the validity of the Stokes-Einstein model of a diffusing species undergoing a random walk. For rotational diffusion (ps-ns time scale), we used time-resolved anisotropy measurements to examine potential binding of RhG as a function of the crowding agents (surface structure and size). For translational diffusion (μs-s time scale), we used fluorescence correlation spectroscopy for single-molecule fluctuation analysis. Our results allow us to examine the diffusion model of a molecular probe in crowded environments as a function of concentration, length scale, homogeneous versus heterogeneous viscosity, size and surface structures. These biomimetic crowding studies, using non-invasive fluorescence spectroscopy methods, represent an important step towards understanding cellular biophysics and quantitative cell biology.

The CrowdMag App - turning your smartphone into a travelling magnetic observatory

NASA Astrophysics Data System (ADS)

Saltus, Richard; Nair, Manoj

2017-04-01

In 2014, we started the "CrowdMag" Project to collect vector magnetic data from digital magnetometers in smartphones. In October 2014, we released our first-generation Android and iOS apps. Currently, the CrowdMag Project has more than 15,000 enthusiastic users contributing more than 12 million magnetic data points from around the world. NOAA's National Centers for Environmental Information (NCEI), in partnership with the University of Colorado's Cooperative Institute for Research in the Environmental Sciences (CIRES) develops magnetic field models to aid navigation, resource exploration and scientific research. We use observatories, satellites and ship/airborne surveys to measure the magnetic data. However, the measurements leave gaps in coverage, particularly for short-wavelength urban noise. Our ultimate goal is to use data from the CrowdMag Project to improve global magnetic data coverage. Here we present some early results from the analysis of the crowdsourced magnetic data. A global magnetic model derived solely based on CrowdMag data is generally consistent with satellite-derived models such as World Magnetic Model. A unique contribution of the CrowdMag Project is the collection of ground level magnetic data in densely populated regions with an unprecedented spatial resolution. For example, we show a magnetic map (by binning the data collected into 100x100m cells) of central Boulder using 170,000 data points collected by about 60 devices over the duration October 2014- January 2016. The median magnetic field value is consistent with the expected magnitude of the Earth's background magnetic field. The standard deviation of the CrowdMag total field (F) values is much higher than the expected natural (i.e., diurnal and geologic) magnetic field variation. However, the phone's magnetometer is sensitive enough to capture the larger magnitude magnetic signature from the urban magnetic sources. We discuss the reliability of crowdsourced magnetic maps and their applications to navigation, global models, and local geologic or environmental investigations.

Double Trouble at High Density: Cross-Level Test of Resource-Related Adaptive Plasticity and Crowding-Related Fitness

PubMed Central

Gergs, André; Preuss, Thomas G.; Palmqvist, Annemette

2014-01-01

Population size is often regulated by negative feedback between population density and individual fitness. At high population densities, animals run into double trouble: they might concurrently suffer from overexploitation of resources and also from negative interference among individuals regardless of resource availability, referred to as crowding. Animals are able to adapt to resource shortages by exhibiting a repertoire of life history and physiological plasticities. In addition to resource-related plasticity, crowding might lead to reduced fitness, with consequences for individual life history. We explored how different mechanisms behind resource-related plasticity and crowding-related fitness act independently or together, using the water flea Daphnia magna as a case study. For testing hypotheses related to mechanisms of plasticity and crowding stress across different biological levels, we used an individual-based population model that is based on dynamic energy budget theory. Each of the hypotheses, represented by a sub-model, is based on specific assumptions on how the uptake and allocation of energy are altered under conditions of resource shortage or crowding. For cross-level testing of different hypotheses, we explored how well the sub-models fit individual level data and also how well they predict population dynamics under different conditions of resource availability. Only operating resource-related and crowding-related hypotheses together enabled accurate model predictions of D. magna population dynamics and size structure. Whereas this study showed that various mechanisms might play a role in the negative feedback between population density and individual life history, it also indicated that different density levels might instigate the onset of the different mechanisms. This study provides an example of how the integration of dynamic energy budget theory and individual-based modelling can facilitate the exploration of mechanisms behind the regulation of population size. Such understanding is important for assessment, management and the conservation of populations and thereby biodiversity in ecosystems. PMID:24626228

Effects of macromolecular crowding on biochemical reaction equilibria: a molecular thermodynamic perspective.

PubMed

Hu, Zhongqiao; Jiang, Jianwen; Rajagopalan, Raj

2007-09-01

A molecular thermodynamic model is developed to investigate the effects of macromolecular crowding on biochemical reactions. Three types of reactions, representing protein folding/conformational isomerization, coagulation/coalescence, and polymerization/association, are considered. The reactants, products, and crowders are modeled as coarse-grained spherical particles or as polymer chains, interacting through hard-sphere interactions with or without nonbonded square-well interactions, and the effects of crowder size and chain length as well as product size are examined. The results predicted by this model are consistent with experimentally observed crowding effects based on preferential binding or preferential exclusion of the crowders. Although simple hard-core excluded-volume arguments do in general predict the qualitative aspects of the crowding effects, the results show that other intermolecular interactions can substantially alter the extent of enhancement or reduction of the equilibrium and can even change the direction of the shift. An advantage of the approach presented here is that competing reactions can be incorporated within the model.

What Macromolecular Crowding Can Do to a Protein

PubMed Central

Kuznetsova, Irina M.; Turoverov, Konstantin K.; Uversky, Vladimir N.

2014-01-01

The intracellular environment represents an extremely crowded milieu, with a limited amount of free water and an almost complete lack of unoccupied space. Obviously, slightly salted aqueous solutions containing low concentrations of a biomolecule of interest are too simplistic to mimic the “real life” situation, where the biomolecule of interest scrambles and wades through the tightly packed crowd. In laboratory practice, such macromolecular crowding is typically mimicked by concentrated solutions of various polymers that serve as model “crowding agents”. Studies under these conditions revealed that macromolecular crowding might affect protein structure, folding, shape, conformational stability, binding of small molecules, enzymatic activity, protein-protein interactions, protein-nucleic acid interactions, and pathological aggregation. The goal of this review is to systematically analyze currently available experimental data on the variety of effects of macromolecular crowding on a protein molecule. The review covers more than 320 papers and therefore represents one of the most comprehensive compendia of the current knowledge in this exciting area. PMID:25514413

Folding free energy surfaces of three small proteins under crowding: validation of the postprocessing method by direct simulation

NASA Astrophysics Data System (ADS)

Qin, Sanbo; Mittal, Jeetain; Zhou, Huan-Xiang

2013-08-01

We have developed a ‘postprocessing’ method for modeling biochemical processes such as protein folding under crowded conditions (Qin and Zhou 2009 Biophys. J. 97 12-19). In contrast to the direct simulation approach, in which the protein undergoing folding is simulated along with crowders, the postprocessing method requires only the folding simulation without crowders. The influence of the crowders is then obtained by taking conformations from the crowder-free simulation and calculating the free energies of transferring to the crowders. This postprocessing yields the folding free energy surface of the protein under crowding. Here the postprocessing results for the folding of three small proteins under ‘repulsive’ crowding are validated by those obtained previously by the direct simulation approach (Mittal and Best 2010 Biophys. J. 98 315-20). This validation confirms the accuracy of the postprocessing approach and highlights its distinct advantages in modeling biochemical processes under cell-like crowded conditions, such as enabling an atomistic representation of the test proteins.

Crowd Simulation Incorporating Agent Psychological Models, Roles and Communication

DTIC Science & Technology

2005-01-01

system (PMFserv) that implements human behavior models from a range of ability, stress, emotion , decision theoretic and motivation sources. An...autonomous agents, human behavior models, culture and emotions 1. Introduction There are many applications of computer animation and simulation where...We describe a new architecture to integrate a psychological model into a crowd simulation system in order to obtain believable emergent behaviors

Vision-Based Autonomous Sensor-Tasking in Uncertain Adversarial Environments

DTIC Science & Technology

2015-01-02

motion segmentation and change detection in crowd behavior. In particular we investigated Finite Time Lyapunov Exponents, Perron Frobenius Operator and...deformation tensor [11]. On the other hand, eigenfunctions of, the Perron Frobenius operator can be used to detect Almost Invariant Sets (AIS) which are... Perron Frobenius operator. Finally, Figure 1.12d shows the ergodic partitions (EP) obtained based on the eigenfunctions of the Koopman operator

Nonlinear Motion Tracking by Deep Learning Architecture

NASA Astrophysics Data System (ADS)

Verma, Arnav; Samaiya, Devesh; Gupta, Karunesh K.

2018-03-01

In the world of Artificial Intelligence, object motion tracking is one of the major problems. The extensive research is being carried out to track people in crowd. This paper presents a unique technique for nonlinear motion tracking in the absence of prior knowledge of nature of nonlinear path that the object being tracked may follow. We achieve this by first obtaining the centroid of the object and then using the centroid as the current example for a recurrent neural network trained using real-time recurrent learning. We have tweaked the standard algorithm slightly and have accumulated the gradient for few previous iterations instead of using just the current iteration as is the norm. We show that for a single object, such a recurrent neural network is highly capable of approximating the nonlinearity of its path.

Active and passive transport of cargo in a corrugated channel: A lattice model study

NASA Astrophysics Data System (ADS)

Dey, Supravat; Ching, Kevin; Das, Moumita

2018-04-01

Inside cells, cargos such as vesicles and organelles are transported by molecular motors to their correct locations via active motion on cytoskeletal tracks and passive, Brownian diffusion. During the transportation of cargos, motor-cargo complexes (MCCs) navigate the confining and crowded environment of the cytoskeletal network and other macromolecules. Motivated by this, we study a minimal two-state model of motor-driven cargo transport in confinement and predict transport properties that can be tested in experiments. We assume that the motion of the MCC is directly affected by the entropic barrier due to confinement if it is in the passive, unbound state but not in the active, bound state where it moves with a constant bound velocity. We construct a lattice model based on a Fokker Planck description of the two-state system, study it using a kinetic Monte Carlo method and compare our numerical results with analytical expressions for a mean field limit. We find that the effect of confinement strongly depends on the bound velocity and the binding kinetics of the MCC. Confinement effectively reduces the effective diffusivity and average velocity, except when it results in an enhanced average binding rate and thereby leads to a larger average velocity than when unconfined.

Water-mediated influence of a crowded environment on internal vibrations of a protein molecule.

PubMed

Kuffel, Anna; Zielkiewicz, Jan

2016-02-14

The influence of crowding on the protein inner dynamics is examined by putting a single protein molecule close to one or two neighboring protein molecules. The presence of additional molecules influences the amplitudes of protein fluctuations. Also, a weak dynamical coupling of collective velocities of surface atoms of proteins separated by a layer of water is detected. The possible mechanisms of these phenomena are described. The cross-correlation function of the collective velocities of surface atoms of two proteins was decomposed into the Fourier series. The amplitude spectrum displays a peak at low frequencies. Also, the results of principal component analysis suggest that the close presence of an additional protein molecule influences the high-amplitude, low-frequency modes in the most prominent way. This part of the spectrum covers biologically important protein motions. The neighbor-induced changes in the inner dynamics of the protein may be connected with the changes in the velocity power spectrum of interfacial water. The additional protein molecule changes the properties of solvation water and in this way it can influence the dynamics of the second protein. It is suggested that this phenomenon may be described, at first approximation, by a damped oscillator driven by an external random force. This model was successfully applied to conformationally rigid Choristoneura fumiferana antifreeze protein molecules.

A Method for Molecular Dynamics on Curved Surfaces

PubMed Central

Paquay, Stefan; Kusters, Remy

2016-01-01

Dynamics simulations of constrained particles can greatly aid in understanding the temporal and spatial evolution of biological processes such as lateral transport along membranes and self-assembly of viruses. Most theoretical efforts in the field of diffusive transport have focused on solving the diffusion equation on curved surfaces, for which it is not tractable to incorporate particle interactions even though these play a crucial role in crowded systems. We show here that it is possible to take such interactions into account by combining standard constraint algorithms with the classical velocity Verlet scheme to perform molecular dynamics simulations of particles constrained to an arbitrarily curved surface. Furthermore, unlike Brownian dynamics schemes in local coordinates, our method is based on Cartesian coordinates, allowing for the reuse of many other standard tools without modifications, including parallelization through domain decomposition. We show that by applying the schemes to the Langevin equation for various surfaces, we obtain confined Brownian motion, which has direct applications to many biological and physical problems. Finally we present two practical examples that highlight the applicability of the method: 1) the influence of crowding and shape on the lateral diffusion of proteins in curved membranes; and 2) the self-assembly of a coarse-grained virus capsid protein model. PMID:27028633

A Method for Molecular Dynamics on Curved Surfaces

NASA Astrophysics Data System (ADS)

Paquay, Stefan; Kusters, Remy

2016-03-01

Dynamics simulations of constrained particles can greatly aid in understanding the temporal and spatial evolution of biological processes such as lateral transport along membranes and self-assembly of viruses. Most theoretical efforts in the field of diffusive transport have focussed on solving the diffusion equation on curved surfaces, for which it is not tractable to incorporate particle interactions even though these play a crucial role in crowded systems. We show here that it is possible to combine standard constraint algorithms with the classical velocity Verlet scheme to perform molecular dynamics simulations of particles constrained to an arbitrarily curved surface, in which such interactions can be taken into account. Furthermore, unlike Brownian dynamics schemes in local coordinates, our method is based on Cartesian coordinates allowing for the reuse of many other standard tools without modifications, including parallelisation through domain decomposition. We show that by applying the schemes to the Langevin equation for various surfaces, confined Brownian motion is obtained, which has direct applications to many biological and physical problems. Finally we present two practical examples that highlight the applicability of the method: (i) the influence of crowding and shape on the lateral diffusion of proteins in curved membranes and (ii) the self-assembly of a coarse-grained virus capsid protein model.

Application of crowd-sourced data to multi-scale evolutionary exposure and vulnerability models

NASA Astrophysics Data System (ADS)

Pittore, Massimiliano

2016-04-01

Seismic exposure, defined as the assets (population, buildings, infrastructure) exposed to earthquake hazard and susceptible to damage, is a critical -but often neglected- component of seismic risk assessment. This partly stems from the burden associated with the compilation of a useful and reliable model over wide spatial areas. While detailed engineering data have still to be collected in order to constrain exposure and vulnerability models, the availability of increasingly large crowd-sourced datasets (e. g. OpenStreetMap) opens up the exciting possibility to generate incrementally evolving models. Integrating crowd-sourced and authoritative data using statistical learning methodologies can reduce models uncertainties and also provide additional drive and motivation to volunteered geoinformation collection. A case study in Central Asia will be presented and discussed.

Macromolecular Crowding Regulates the Gene Expression Profile by Limiting Diffusion

DOE PAGES

Golkaram, Mahdi; Hellander, Stefan; Drawert, Brian; ...

2016-11-28

We seek to elucidate the role of macromolecular crowding in transcription and translation. It is well known that stochasticity in gene expression can lead to differential gene expression and heterogeneity in a cell population. Recent experimental observations by Tan et al. have improved our understanding of the functional role of macromolecular crowding. It can be inferred from their observations that macromolecular crowding can lead to robustness in gene expression, resulting in a more homogeneous cell population. We introduce a spatial stochastic model to provide insight into this process. Our results show that macromolecular crowding reduces noise (as measured by themore » kurtosis of the mRNA distribution) in a cell population by limiting the diffusion of transcription factors (i.e. removing the unstable intermediate states), and that crowding by large molecules reduces noise more efficiently than crowding by small molecules. Finally, our simulation results provide evidence that the local variation in chromatin density as well as the total volume exclusion of the chromatin in the nucleus can induce a homogenous cell population« less

Study on Human-structure Dynamic Interaction in Civil Engineering

NASA Astrophysics Data System (ADS)

Gao, Feng; Cao, Li Lin; Li, Xing Hua

2018-06-01

The research of human-structure dynamic interaction are reviewed. Firstly, the influence of the crowd load on structural dynamic characteristics is introduced and the advantages and disadvantages of different crowd load models are analyzed. Then, discussing the influence of structural vibration on the human-induced load, especially the influence of different stiffness structures on the crowd load. Finally, questions about human-structure interaction that require further study are presented.

Current crowding issues on nanoscale planar organic transistors for spintronics applications.

PubMed

Verduci, Tindara; Chaumy, Guillaume; Dayen, Jean-Francois; Leclerc, Nicolas; Devaux, Eloïse; Stoeckel, Marc-Antoine; Orgiu, Emanuele; Samorì, Paolo; Doudin, Bernard

2018-06-12

The predominance of interface resistance makes current crowding ubiquitous in short channel organic electronics devices but its impact on spin transport has never been considered. We investigate electrochemically-doped nanoscale PBTTT short channel devices and observe the smallest reported values of crowding lengths, found for sub-100 nm electrodes separation. These observed values are nevertheless exceeding the spin diffusion lengths reported in the literature. We discuss here how current crowding can be taken into account in the framework of the Fert-Jaffrès model of spin current propagation in heterostructures, and predict that the anticipated resulting values of magnetoresistance can be significantly reduced. Current crowding therefore impacts spin transport applications and interpretation of the results on spin valve devices. © 2018 IOP Publishing Ltd.

Household Crowding During Childhood and Long-Term Education Outcomes.

PubMed

Lopoo, Leonard M; London, Andrew S

2016-06-01

Household crowding, or having more household members than rooms in one's residence, could potentially affect a child's educational attainment directly through a number of mechanisms. We use U.S. longitudinal data from the Panel Study of Income Dynamics to derive new measures of childhood crowding and estimate negative associations between crowding during one's high school years and, respectively, high school graduation by age 19 and maximum education at age 25. These negative relationships persist in multivariate models in which we control for the influence of a variety of factors, including socioeconomic status and housing-cost burden. Given the importance of educational attainment for a range of midlife and later-life outcomes, this study suggests that household crowding during one's high school years is an engine of cumulative inequality over the life course.

A least-effort principle based model for heterogeneous pedestrian flow considering overtaking behavior

NASA Astrophysics Data System (ADS)

Liu, Chi; Ye, Rui; Lian, Liping; Song, Weiguo; Zhang, Jun; Lo, Siuming

2018-05-01

In the context of global aging, how to design traffic facilities for a population with a different age composition is of high importance. For this purpose, we propose a model based on the least effort principle to simulate heterogeneous pedestrian flow. In the model, the pedestrian is represented by a three-disc shaped agent. We add a new parameter to realize pedestrians' preference to avoid changing their direction of movement too quickly. The model is validated with numerous experimental data on unidirectional pedestrian flow. In addition, we investigate the influence of corridor width and velocity distribution of crowds on unidirectional heterogeneous pedestrian flow. The simulation results reflect that widening corridors could increase the specific flow for the crowd composed of two kinds of pedestrians with significantly different free velocities. Moreover, compared with a unified crowd, the crowd composed of pedestrians with great mobility differences requires a wider corridor to attain the same traffic efficiency. This study could be beneficial in providing a better understanding of heterogeneous pedestrian flow, and quantified outcomes could be applied in traffic facility design.

Concentrated Solutions of Single-Chain Nanoparticles: A Simple Model for Intrinsically Disordered Proteins under Crowding Conditions.

PubMed

Moreno, Angel J; Lo Verso, Federica; Arbe, Arantxa; Pomposo, José A; Colmenero, Juan

2016-03-03

By means of large-scale computer simulations and small-angle neutron scattering (SANS), we investigate solutions of single-chain nanoparticles (SCNPs), covering the whole concentration range from infinite dilution to melt density. The analysis of the conformational properties of the SCNPs reveals that these synthetic nano-objects share basic ingredients with intrinsically disordered proteins (IDPs), as topological polydispersity, generally sparse conformations, and locally compact domains. We investigate the role of the architecture of the SCNPs in their collapse behavior under macromolecular crowding. Unlike in the case of linear macromolecules, which experience the usual transition from self-avoiding to Gaussian random-walk conformations, crowding leads to collapsed conformations of SCNPs resembling those of crumpled globules. This behavior is already found at volume fractions (about 30%) that are characteristic of crowding in cellular environments. The simulation results are confirmed by the SANS experiments. Our results for SCNPs--a model system free of specific interactions--propose a general scenario for the effect of steric crowding on IDPs: collapse from sparse conformations at high dilution to crumpled globular conformations in cell environments.

VizieR Online Data Catalog: Massive stars in 30 Dor (Schneider+, 2018)

NASA Astrophysics Data System (ADS)

Schneider, F. R. N.; Sana, H.; Evans, C. J.; Bestenlehner, J. M.; Castro, N.; Fossati, L.; Grafener, G.; Langer, N.; Ramirez-Agudelo, O. H.; Sabin-Sanjulian, C.; Simon-Diaz, S.; Tramper, F.; Crowther, P. A.; de Koter, A.; de Mink, S. E.; Dufton, P. L.; Garcia, M.; Gieles, M.; Henault-Brunet, V.; Herrero, A.; Izzard, R. G.; Kalari, V.; Lennon, D. J.; Apellaniz, J. M.; Markova, N.; Najarro, F.; Podsiadlowski, P.; Puls, J.; Taylor, W. D.; van Loon, J. T.; Vink, J. S.; Norman, C.

2018-02-01

Through the use of the Fibre Large Array Multi Element Spectrograph (FLAMES) on the Very Large Telescope (VLT), the VLT-FLAMES Tarantula Survey (VFTS) has obtained optical spectra of ~800 massive stars in 30 Dor, avoiding the core region of the dense star cluster R136 because of difficulties with crowding. Repeated observations at multiple epochs allow determination of the orbital motion of potentially binary objects. For a sample of 452 apparently single stars, robust stellar parameters-such as effective temperatures, luminosities, surface gravities, and projected rotational velocities-are determined by modeling the observed spectra. Composite spectra of visual multiple systems and spectroscopic binaries are not considered here because their parameters cannot be reliably inferred from the VFTS data. To match the derived atmospheric parameters of the apparently single VFTS stars to stellar evolutionary models, we use the Bayesian code Bonnsai. (2 data files).

Collective motion of active Brownian particles with polar alignment.

PubMed

Martín-Gómez, Aitor; Levis, Demian; Díaz-Guilera, Albert; Pagonabarraga, Ignacio

2018-04-04

We present a comprehensive computational study of the collective behavior emerging from the competition between self-propulsion, excluded volume interactions and velocity-alignment in a two-dimensional model of active particles. We consider an extension of the active brownian particles model where the self-propulsion direction of the particles aligns with the one of their neighbors. We analyze the onset of collective motion (flocking) in a low-density regime (10% surface area) and show that it is mainly controlled by the strength of velocity-alignment interactions: the competition between self-propulsion and crowding effects plays a minor role in the emergence of flocking. However, above the flocking threshold, the system presents a richer pattern formation scenario than analogous models without alignment interactions (active brownian particles) or excluded volume effects (Vicsek-like models). Depending on the parameter regime, the structure of the system is characterized by either a broad distribution of finite-sized polar clusters or the presence of an amorphous, highly fluctuating, large-scale traveling structure which can take a lane-like or band-like form (and usually a hybrid structure which is halfway in between both). We establish a phase diagram that summarizes collective behavior of polar active brownian particles and propose a generic mechanism to describe the complexity of the large-scale structures observed in systems of repulsive self-propelled particles.

Polymer Chain Conformation and Dynamical Confinement in a Model One-Component Nanocomposite

NASA Astrophysics Data System (ADS)

Mark, C.; Holderer, O.; Allgaier, J.; Hübner, E.; Pyckhout-Hintzen, W.; Zamponi, M.; Radulescu, A.; Feoktystov, A.; Monkenbusch, M.; Jalarvo, N.; Richter, D.

2017-07-01

We report a neutron-scattering investigation on the structure and dynamics of a single-component nanocomposite based on SiO2 particles that were grafted with polyisoprene chains at the entanglement limit. By skillful labeling, we access both the monomer density in the corona as well as the conformation of the grafted chains. While the corona profile follows a r-1 power law, the conformation of a grafted chain is identical to that of a chain in a reference melt, implying a high mutual penetration of the coronas from different particles. The brush crowding leads to topological confinement of the chain dynamics: (i) At local scales, the segmental dynamics is unchanged compared to the reference melt, while (ii) at the scale of the chain, the dynamics appears to be slowed down; (iii) by performing a mode analysis in terms of end-fixed Rouse chains, the slower dynamics is tracked to topological confinement within the cone spanned by the adjacent grafts; (iv) by adding 50% matrix chains, the topological confinement sensed by the grafted chain is lifted partially and the apparent chain motion is accelerated. We observe a crossover from pure Rouse motion at short times to topological confined motion beyond the time when the segmental mean squared displacement has reached the distance to the next graft.

Human behaviours in evacuation crowd dynamics: From modelling to "big data" toward crisis management

NASA Astrophysics Data System (ADS)

Bellomo, N.; Clarke, D.; Gibelli, L.; Townsend, P.; Vreugdenhil, B. J.

2016-09-01

This paper proposes an essay concerning the understanding of human behaviours and crisis management of crowds in extreme situations, such as evacuation through complex venues. The first part focuses on the understanding of the main features of the crowd viewed as a living, hence complex system. The main concepts are subsequently addressed, in the second part, to a critical analysis of mathematical models suitable to capture them, as far as it is possible. Then, the third part focuses on the use, toward safety problems, of a model derived by the methods of the mathematical kinetic theory and theoretical tools of evolutionary game theory. It is shown how this model can depict critical situations and how these can be managed with the aim of minimizing the risk of catastrophic events.

Peer crowd affiliation as a segmentation tool for young adult tobacco use.

PubMed

Lisha, Nadra E; Jordan, Jeffrey W; Ling, Pamela M

2016-10-01

In California, young adult tobacco prevention is of prime importance; 63% of smokers start by the age of 18 years, and 97% start by the age of 26 years. We examined social affiliation with 'peer crowd' (eg, Hipsters) as an innovative way to identify high-risk tobacco users. Cross-sectional surveys were conducted in 2014 (N=3368) among young adult bar patrons in 3 California cities. We examined use rates of five products (cigarettes, e-cigarettes, hookah, cigars and smokeless tobacco) by five race/ethnicity categories. Peer crowd affiliation was scored based on respondents' selecting pictures of young adults representing those most and least likely to be in their friend group. Respondents were classified into categories based on the highest score; the peer crowd score was also examined as a continuous predictor. Logistic regression models with each tobacco product as the outcome tested the unique contribution of peer crowd affiliation, controlling for race/ethnicity, age, sex, sexual orientation and city. Respondents affiliating with Hip Hop and Hipster peer crowds reported significantly higher rates of tobacco use. As a categorical predictor, peer crowd was related to tobacco use, independent of associations with race/ethnicity. As a continuous predictor, Hip Hop peer crowd affiliation was also associated with tobacco use, and Young Professional affiliation was negatively associated, independent of demographic factors. Tobacco product use is not the same across racial/ethnic groups or peer crowds, and peer crowd predicts tobacco use independent of race/ethnicity. Antitobacco interventions targeting peer crowds may be an effective way to reach young adult tobacco users. NCT01686178, Pre-results. Published by the BMJ Publishing Group Limited. For permission to use (where not already granted under a licence) please go to http://www.bmj.com/company/products-services/rights-and-licensing/.

Does Prison Crowding Predict Higher Rates of Substance Use Related Parole Violations? A Recurrent Events Multi-Level Survival Analysis.

PubMed

Ruderman, Michael A; Wilson, Deirdra F; Reid, Savanna

2015-01-01

This administrative data-linkage cohort study examines the association between prison crowding and the rate of post-release parole violations in a random sample of prisoners released with parole conditions in California, for an observation period of two years (January 2003 through December 2004). Crowding overextends prison resources needed to adequately protect inmates and provide drug rehabilitation services. Violence and lack of access to treatment are known risk factors for drug use and substance use disorders. These and other psychosocial effects of crowding may lead to higher rates of recidivism in California parolees. Rates of parole violation for parolees exposed to high and medium levels of prison crowding were compared to parolees with low prison crowding exposure. Hazard ratios (HRs) with 95% confidence intervals (CIs) were estimated using a Cox model for recurrent events. Our dataset included 13070 parolees in California, combining individual level parolee data with aggregate level crowding data for multilevel analysis. Comparing parolees exposed to high crowding with those exposed to low crowding, the effect sizes from greatest to least were absconding violations (HR 3.56 95% CI: 3.05-4.17), drug violations (HR 2.44 95% CI: 2.00-2.98), non-violent violations (HR 2.14 95% CI: 1.73-2.64), violent and serious violations (HR 1.88 95% CI: 1.45-2.43), and technical violations (HR 1.86 95% CI: 1.37-2.53). Prison crowding predicted higher rates of parole violations after release from prison. The effect was magnitude-dependent and particularly strong for drug charges. Further research into whether adverse prison experiences, such as crowding, are associated with recidivism and drug use in particular may be warranted.

Does Prison Crowding Predict Higher Rates of Substance Use Related Parole Violations? A Recurrent Events Multi-Level Survival Analysis

PubMed Central

Ruderman, Michael A.; Wilson, Deirdra F.; Reid, Savanna

2015-01-01

Objective This administrative data-linkage cohort study examines the association between prison crowding and the rate of post-release parole violations in a random sample of prisoners released with parole conditions in California, for an observation period of two years (January 2003 through December 2004). Background Crowding overextends prison resources needed to adequately protect inmates and provide drug rehabilitation services. Violence and lack of access to treatment are known risk factors for drug use and substance use disorders. These and other psychosocial effects of crowding may lead to higher rates of recidivism in California parolees. Methods Rates of parole violation for parolees exposed to high and medium levels of prison crowding were compared to parolees with low prison crowding exposure. Hazard ratios (HRs) with 95% confidence intervals (CIs) were estimated using a Cox model for recurrent events. Our dataset included 13070 parolees in California, combining individual level parolee data with aggregate level crowding data for multilevel analysis. Results Comparing parolees exposed to high crowding with those exposed to low crowding, the effect sizes from greatest to least were absconding violations (HR 3.56 95% CI: 3.05–4.17), drug violations (HR 2.44 95% CI: 2.00–2.98), non-violent violations (HR 2.14 95% CI: 1.73–2.64), violent and serious violations (HR 1.88 95% CI: 1.45–2.43), and technical violations (HR 1.86 95% CI: 1.37–2.53). Conclusions Prison crowding predicted higher rates of parole violations after release from prison. The effect was magnitude-dependent and particularly strong for drug charges. Further research into whether adverse prison experiences, such as crowding, are associated with recidivism and drug use in particular may be warranted. PMID:26492490

The impact of crowd noise on officiating in muay thai: achieving external validity in an experimental setting.

PubMed

Myers, Tony; Balmer, Nigel

2012-01-01

Numerous factors have been proposed to explain the home advantage in sport. Several authors have suggested that a partisan home crowd enhances home advantage and that this is at least in part a consequence of their influence on officiating. However, while experimental studies examining this phenomenon have high levels of internal validity (since only the "crowd noise" intervention is allowed to vary), they suffer from a lack of external validity, with decision-making in a laboratory setting typically bearing little resemblance to decision-making in live sports settings. Conversely, observational and quasi-experimental studies with high levels of external validity suffer from low levels of internal validity as countless factors besides crowd noise vary. The present study provides a unique opportunity to address these criticisms, by conducting a controlled experiment on the impact of crowd noise on officiating in a live tournament setting. Seventeen qualified judges officiated on thirty Thai boxing bouts in a live international tournament setting featuring "home" and "away" boxers. In each bout, judges were randomized into a "noise" (live sound) or "no crowd noise" (noise-canceling headphones and white noise) condition, resulting in 59 judgments in the "no crowd noise" and 61 in the "crowd noise" condition. The results provide the first experimental evidence of the impact of live crowd noise on officials in sport. A cross-classified statistical model indicated that crowd noise had a statistically significant impact, equating to just over half a point per bout (in the context of five round bouts with the "10-point must" scoring system shared with professional boxing). The practical significance of the findings, their implications for officiating and for the future conduct of crowd noise studies are discussed.

The Impact of Crowd Noise on Officiating in Muay Thai: Achieving External Validity in an Experimental Setting

PubMed Central

Myers, Tony; Balmer, Nigel

2012-01-01

Numerous factors have been proposed to explain the home advantage in sport. Several authors have suggested that a partisan home crowd enhances home advantage and that this is at least in part a consequence of their influence on officiating. However, while experimental studies examining this phenomenon have high levels of internal validity (since only the “crowd noise” intervention is allowed to vary), they suffer from a lack of external validity, with decision-making in a laboratory setting typically bearing little resemblance to decision-making in live sports settings. Conversely, observational and quasi-experimental studies with high levels of external validity suffer from low levels of internal validity as countless factors besides crowd noise vary. The present study provides a unique opportunity to address these criticisms, by conducting a controlled experiment on the impact of crowd noise on officiating in a live tournament setting. Seventeen qualified judges officiated on thirty Thai boxing bouts in a live international tournament setting featuring “home” and “away” boxers. In each bout, judges were randomized into a “noise” (live sound) or “no crowd noise” (noise-canceling headphones and white noise) condition, resulting in 59 judgments in the “no crowd noise” and 61 in the “crowd noise” condition. The results provide the first experimental evidence of the impact of live crowd noise on officials in sport. A cross-classified statistical model indicated that crowd noise had a statistically significant impact, equating to just over half a point per bout (in the context of five round bouts with the “10-point must” scoring system shared with professional boxing). The practical significance of the findings, their implications for officiating and for the future conduct of crowd noise studies are discussed. PMID:23049520

Universal Power Law Governing Pedestrian Interactions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Karamouzas, Ioannis; Skinner, Brian; Guy, Stephen J.

2014-12-01

Human crowds often bear a striking resemblance to interacting particle systems, and this has prompted many researchers to describe pedestrian dynamics in terms of interaction forces and potential energies. The correct quantitative form of this interaction, however, has remained an open question. Here, we introduce a novel statistical-mechanical approach to directly measure the interaction energy between pedestrians. This analysis, when applied to a large collection of human motion data, reveals a simple power-law interaction that is based not on the physical separation between pedestrians but on their projected time to a potential future collision, and is therefore fundamentally anticipatory inmore » nature. Remarkably, this simple law is able to describe human interactions across a wide variety of situations, speeds, and densities. We further show, through simulations, that the interaction law we identify is sufficient to reproduce many known crowd phenomena.« less

The wisdom of the crowd playing The Price Is Right.

PubMed

Lee, Michael D; Zhang, Shunan; Shi, Jenny

2011-07-01

In The Price Is Right game show, players compete to win a prize, by placing bids on its price. We ask whether it is possible to achieve a "wisdom of the crowd" effect, by combining the bids to produce an aggregate price estimate that is superior to the estimates of individual players. Using data from the game show, we show that a wisdom of the crowd effect is possible, especially by using models of the decision-making processes involved in bidding. The key insight is that, because of the competitive nature of the game, what people bid is not necessarily the same as what they know. This means better estimates are formed by aggregating latent knowledge than by aggregating observed bids. We use our results to highlight the usefulness of models of cognition and decision-making in studying the wisdom of the crowd, which are often approached only from non-psychological statistical perspectives.

Visual crowding illustrates the inadequacy of local vs. global and feedforward vs. feedback distinctions in modeling visual perception

PubMed Central

Clarke, Aaron M.; Herzog, Michael H.; Francis, Gregory

2014-01-01

Experimentalists tend to classify models of visual perception as being either local or global, and involving either feedforward or feedback processing. We argue that these distinctions are not as helpful as they might appear, and we illustrate these issues by analyzing models of visual crowding as an example. Recent studies have argued that crowding cannot be explained by purely local processing, but that instead, global factors such as perceptual grouping are crucial. Theories of perceptual grouping, in turn, often invoke feedback connections as a way to account for their global properties. We examined three types of crowding models that are representative of global processing models, and two of which employ feedback processing: a model based on Fourier filtering, a feedback neural network, and a specific feedback neural architecture that explicitly models perceptual grouping. Simulations demonstrate that crucial empirical findings are not accounted for by any of the models. We conclude that empirical investigations that reject a local or feedforward architecture offer almost no constraints for model construction, as there are an uncountable number of global and feedback systems. We propose that the identification of a system as being local or global and feedforward or feedback is less important than the identification of a system's computational details. Only the latter information can provide constraints on model development and promote quantitative explanations of complex phenomena. PMID:25374554

Emergency department throughput, crowding, and financial outcomes for hospitals.

PubMed

Handel, Daniel A; Hilton, Joshua A; Ward, Michael J; Rabin, Elaine; Zwemer, Frank L; Pines, Jesse M

2010-08-01

Emergency department (ED) crowding has been identified as a major public health problem in the United States by the Institute of Medicine. ED crowding not only is associated with poorer patient outcomes, but it also contributes to lost demand for ED services when patients leave without being seen and hospitals must go on ambulance diversion. However, somewhat paradoxically, ED crowding may financially benefit hospitals. This is because ED crowding allows hospitals to maximize occupancy with well-insured, elective patients while patients wait in the ED. In this article, the authors propose a more holistic model of hospital flow and revenue that contradicts this notion and offer suggestions for improvements in ED and hospital management that may not only reduce crowding and improve quality, but also increase hospital revenues. Also proposed is that increased efficiency and quality in U.S. hospitals will require changes in systematic microeconomic and macroeconomic incentives that drive the delivery of health services in the United States. Finally, the authors address several questions to propose mutually beneficial solutions to ED crowding that include the realignment of hospital incentives, changing culture to promote flow, and several ED-based strategies to improve ED efficiency.

Multiple Diffusion Mechanisms Due to Nanostructuring in Crowded Environments

PubMed Central

Sanabria, Hugo; Kubota, Yoshihisa; Waxham, M. Neal

2007-01-01

One of the key questions regarding intracellular diffusion is how the environment affects molecular mobility. Mostly, intracellular diffusion has been described as hindered, and the physical reasons for this behavior are: immobile barriers, molecular crowding, and binding interactions with immobile or mobile molecules. Using results from multi-photon fluorescence correlation spectroscopy, we describe how immobile barriers and crowding agents affect translational mobility. To study the hindrance produced by immobile barriers, we used sol-gels (silica nanostructures) that consist of a continuous solid phase and aqueous phase in which fluorescently tagged molecules diffuse. In the case of molecular crowding, translational mobility was assessed in increasing concentrations of 500 kDa dextran solutions. Diffusion of fluorescent tracers in both sol-gels and dextran solutions shows clear evidence of anomalous subdiffusion. In addition, data from the autocorrelation function were analyzed using the maximum entropy method as adapted to fluorescence correlation spectroscopy data and compared with the standard model that incorporates anomalous diffusion. The maximum entropy method revealed evidence of different diffusion mechanisms that had not been revealed using the anomalous diffusion model. These mechanisms likely correspond to nanostructuring in crowded environments and to the relative dimensions of the crowding agent with respect to the tracer molecule. Analysis with the maximum entropy method also revealed information about the degree of heterogeneity in the environment as reported by the behavior of diffusive molecules. PMID:17040979

Global and local magnetic mapping using CrowdMag data

NASA Astrophysics Data System (ADS)

Saltus, R.; Nair, M. C.

2016-12-01

NOAA's National Centers for Environmental Information (NCEI), in partnership with the University of Colorado's CIRES develop magnetic field models to aid navigation, resource exploration and scientific research. We use observatories, satellites and ship/airborne surveys to map and model the Earth's magnetic field. However, the available measurements leave gaps in coverage, particularly for short-wavelength anomalies associated with man-made infrastructure ("urban noise"). In 2014, we started a project to address these gaps through the collection of vector magnetic data from digital magnetometers in smartphones. In October 2014, we released the "CrowdMag" Android and iOS apps for harvesting data from phones. Currently, the CrowdMag project has more than 10,000 enthusiastic users contributing more than 12 million magnetic data measurements from around the world. We present the first analysis results from the crowdsourced magnetic data. A global magnetic model derived solely from CrowdMag data is consistent to degree and order 4 with satellite-derived models such as World Magnetic Model. A unique contribution of CrowdMag project is the collection of ground level magnetic data in densely populated regions with an unprecedented spatial resolution. To demonstrate, we generated a magnetic map (by binning the data collected in 200x200m cells) of central Boulder, Colorado using 170,000 data points collected by about 60 devices over the duration October 2014- January 2016. The median value is consistent with the expected magnitude of the Earth's background magnetic field. The standard deviation of the CrowdMag total field (F) values is much higher than the expected natural (i.e., diurnal and geologic) magnetic field variation. However, the phone's magnetometer is sensitive enough to capture the larger magnitude magnetic signature from the urban magnetic sources. We discuss the potential reliability of crowdsourced magnetic maps and their applications to navigation and other applications.

A new coarse-grained model for E. coli cytoplasm: accurate calculation of the diffusion coefficient of proteins and observation of anomalous diffusion.

PubMed

Hasnain, Sabeeha; McClendon, Christopher L; Hsu, Monica T; Jacobson, Matthew P; Bandyopadhyay, Pradipta

2014-01-01

A new coarse-grained model of the E. coli cytoplasm is developed by describing the proteins of the cytoplasm as flexible units consisting of one or more spheres that follow Brownian dynamics (BD), with hydrodynamic interactions (HI) accounted for by a mean-field approach. Extensive BD simulations were performed to calculate the diffusion coefficients of three different proteins in the cellular environment. The results are in close agreement with experimental or previously simulated values, where available. Control simulations without HI showed that use of HI is essential to obtain accurate diffusion coefficients. Anomalous diffusion inside the crowded cellular medium was investigated with Fractional Brownian motion analysis, and found to be present in this model. By running a series of control simulations in which various forces were removed systematically, it was found that repulsive interactions (volume exclusion) are the main cause for anomalous diffusion, with a secondary contribution from HI.

Topological and behavioral disorder in collective motion

NASA Astrophysics Data System (ADS)

Quint, David

2014-03-01

A major underlying assumption in many studies on the collective motion of self-propelled agents has been that the environment is continuous, isotropic and ordered and agents are all identical. In the natural world there are many examples of disordered environments or heterogeneous swarms where collective motion can exist. Examples include bats that navigate natural caverns via echolocation, schools of fish that maneuver through dark and light areas, microbial colonies that move about in heterogeneous soil, quorum sensing bacteria, crowds of people that are evacuating a building and traffic flow in major cities. In general disorder can arise from two basic sources that inhibit/augment both movement and information flow, those that represent physical obstacles (i.e topological), (extrinsic), and those that arise from behavioral heterogeneties within the swarm itself (intrinsic). In either case, extrinsic or intrinsic, disorder can be quenched or dynamic in space or time or both. To understand the effect of the various forms of disorder that can be present in the environment of the agents, we study both discrete and continuous 2 d agent based models that utilize only local interactions and study the transition to the collectively moving state as a function of the amount of disorder or behavioral heterogeneities present in the environment. I will present our recent results and discuss the effect that disorder has on collective motion and the general physical mechanisms that swarms, either real or artificial, could utilize in order to overcome disorder in their environment.

Crowding in Cellular Environments at an Atomistic Level from Computer Simulations

PubMed Central

2017-01-01

The effects of crowding in biological environments on biomolecular structure, dynamics, and function remain not well understood. Computer simulations of atomistic models of concentrated peptide and protein systems at different levels of complexity are beginning to provide new insights. Crowding, weak interactions with other macromolecules and metabolites, and altered solvent properties within cellular environments appear to remodel the energy landscape of peptides and proteins in significant ways including the possibility of native state destabilization. Crowding is also seen to affect dynamic properties, both conformational dynamics and diffusional properties of macromolecules. Recent simulations that address these questions are reviewed here and discussed in the context of relevant experiments. PMID:28666087

Does This Make Me Look Fat? Peer Crowd and Peer Contributions to Adolescent Girls' Weight Control Behaviors

ERIC Educational Resources Information Center

Mackey, Eleanor Race; La Greca, Annette M.

2008-01-01

Based on the Theory of Reasoned Action, this study evaluated a "socialization" model linking girls' peer crowd affiliations (e.g., Jocks, Populars) with their own weight concern, perceived peer weight norms, and weight control behaviors. An alternative "selection" model was also evaluated. Girls (N = 236; M age = 15.95 years) from diverse ethnic…

POI Summarization by Aesthetics Evaluation From Crowd Source Social Media.

PubMed

Qian, Xueming; Li, Cheng; Lan, Ke; Hou, Xingsong; Li, Zhetao; Han, Junwei

2018-03-01

Place-of-Interest (POI) summarization by aesthetics evaluation can recommend a set of POI images to the user and it is significant in image retrieval. In this paper, we propose a system that summarizes a collection of POI images regarding both aesthetics and diversity of the distribution of cameras. First, we generate visual albums by a coarse-to-fine POI clustering approach and then generate 3D models for each album by the collected images from social media. Second, based on the 3D to 2D projection relationship, we select candidate photos in terms of the proposed crowd source saliency model. Third, in order to improve the performance of aesthetic measurement model, we propose a crowd-sourced saliency detection approach by exploring the distribution of salient regions in the 3D model. Then, we measure the composition aesthetics of each image and we explore crowd source salient feature to yield saliency map, based on which, we propose an adaptive image adoption approach. Finally, we combine the diversity and the aesthetics to recommend aesthetic pictures. Experimental results show that the proposed POI summarization approach can return images with diverse camera distributions and aesthetics.

Steric contribution of macromolecular crowding to the time and activation energy for preprotein translocation across the endoplasmic reticulum membrane

NASA Astrophysics Data System (ADS)

Vélez Pérez, José Antonio; Guzmán, Orlando; Navarro-García, Fernando

2013-07-01

Protein translocation from the cytosol to the endoplasmic reticulum (ER) or vice versa, an essential process for cell function, includes the transport of preproteins destined to become secretory, luminal, or integral membrane proteins (translocation) or misfolded proteins returned to the cytoplasm to be degraded (retrotranslocation). An important aspect in this process that has not been fully studied is the molecular crowding at both sides of the ER membrane. By using models of polymers crossing a membrane through a pore, in an environment crowded by either static or dynamic spherical agents, we computed the following transport properties: the free energy, the activation energy, the force, and the transport times for translocation and retrotranslocation. Using experimental protein crowding data for the cytoplasm and ER sides, we showed that dynamic crowding, which resembles biological environments where proteins are translocated or retrotranslocated, increases markedly all the physical properties of translocation and retrotranslocation as compared with translocation in a diluted system. By contrast, transport properties in static crowded systems were similar to those in diluted conditions. In the dynamic regime, the effects of crowding were more notorious in the transport times, leading to a huge difference for large chains. We indicate that this difference is the result of the synergy between the free energy and the diffusivity of the translocating chain. That synergy leads to translocation rates similar to experimental measures in diluted systems, which indicates that the effects of crowding can be measured. Our data also indicate that effects of crowding cannot be neglected when studying translocation because protein dynamic crowding has a relevant steric contribution, which changes the properties of translocation.

Quantitative comparison between crowd models for evacuation planning and evaluation

NASA Astrophysics Data System (ADS)

Viswanathan, Vaisagh; Lee, Chong Eu; Lees, Michael Harold; Cheong, Siew Ann; Sloot, Peter M. A.

2014-02-01

Crowd simulation is rapidly becoming a standard tool for evacuation planning and evaluation. However, the many crowd models in the literature are structurally different, and few have been rigorously calibrated against real-world egress data, especially in emergency situations. In this paper we describe a procedure to quantitatively compare different crowd models or between models and real-world data. We simulated three models: (1) the lattice gas model, (2) the social force model, and (3) the RVO2 model, and obtained the distributions of six observables: (1) evacuation time, (2) zoned evacuation time, (3) passage density, (4) total distance traveled, (5) inconvenience, and (6) flow rate. We then used the DISTATIS procedure to compute the compromise matrix of statistical distances between the three models. Projecting the three models onto the first two principal components of the compromise matrix, we find the lattice gas and RVO2 models are similar in terms of the evacuation time, passage density, and flow rates, whereas the social force and RVO2 models are similar in terms of the total distance traveled. Most importantly, we find that the zoned evacuation times of the three models to be very different from each other. Thus we propose to use this variable, if it can be measured, as the key test between different models, and also between models and the real world. Finally, we compared the model flow rates against the flow rate of an emergency evacuation during the May 2008 Sichuan earthquake, and found the social force model agrees best with this real data.

Simulation of emotional contagion using modified SIR model: A cellular automaton approach

NASA Astrophysics Data System (ADS)

Fu, Libi; Song, Weiguo; Lv, Wei; Lo, Siuming

2014-07-01

Emotion plays an important role in the decision-making of individuals in some emergency situations. The contagion of emotion may induce either normal or abnormal consolidated crowd behavior. This paper aims to simulate the dynamics of emotional contagion among crowds by modifying the epidemiological SIR model to a cellular automaton approach. This new cellular automaton model, entitled the “CA-SIRS model”, captures the dynamic process ‘susceptible-infected-recovered-susceptible', which is based on SIRS contagion in epidemiological theory. Moreover, in this new model, the process is integrated with individual movement. The simulation results of this model show that multiple waves and dynamical stability around a mean value will appear during emotion spreading. It was found that the proportion of initial infected individuals had little influence on the final stable proportion of infected population in a given system, and that infection frequency increased with an increase in the average crowd density. Our results further suggest that individual movement accelerates the spread speed of emotion and increases the stable proportion of infected population. Furthermore, decreasing the duration of an infection and the probability of reinfection can markedly reduce the number of infected individuals. It is hoped that this study will be helpful in crowd management and evacuation organization.

Reduced native state stability in crowded cellular environment due to protein-protein interactions.

PubMed

Harada, Ryuhei; Tochio, Naoya; Kigawa, Takanori; Sugita, Yuji; Feig, Michael

2013-03-06

The effect of cellular crowding environments on protein structure and stability is a key issue in molecular and cellular biology. The classical view of crowding emphasizes the volume exclusion effect that generally favors compact, native states. Here, results from molecular dynamics simulations and NMR experiments show that protein crowders may destabilize native states via protein-protein interactions. In the model system considered here, mixtures of villin head piece and protein G at high concentrations, villin structures become increasingly destabilized upon increasing crowder concentrations. The denatured states observed in the simulation involve partial unfolding as well as more subtle conformational shifts. The unfolded states remain overall compact and only partially overlap with unfolded ensembles at high temperature and in the presence of urea. NMR measurements on the same systems confirm structural changes upon crowding based on changes of chemical shifts relative to dilute conditions. An analysis of protein-protein interactions and energetic aspects suggests the importance of enthalpic and solvation contributions to the crowding free energies that challenge an entropic-centered view of crowding effects.

A random walk model for the migration of Strongylus vulgaris in the intestinal arteries of the horse.

PubMed

Aref, S

1982-01-01

A study of the migration of fourth stage larvae of the parasite Strongylus vulgaris in the intestinal arteries of the horse is presented. It is established, that the larvae migrate along the arteries in almost straight lines. It is suggested that this is primarily due to their ability to sense the curvature of the vessel wall, and not, as might have been expected, because of an ability to sense the direction of blood flow. A larva will sometimes alter its direction of motion when encountering a small off-branching artery. This behaviour suggests, that the migration of S. vulgaris larvae can be modeled as a one-dimensional discrete random walk on a long time scale. This model is simpler than any deterministic model and, in particular, does not require the existence of a predilection site. The available data is not, however, sufficient for a convincing, quantitative test of the model. The proposed reluctance of the larvae to bend into off-branching arteries is used to explain the crowding of larvae in the cranial mesenteric artery.

A generic method for evaluating crowding in the emergency department.

PubMed

Eiset, Andreas Halgreen; Erlandsen, Mogens; Møllekær, Anders Brøns; Mackenhauer, Julie; Kirkegaard, Hans

2016-06-14

Crowding in the emergency department (ED) has been studied intensively using complicated non-generic methods that may prove difficult to implement in a clinical setting. This study sought to develop a generic method to describe and analyse crowding from measurements readily available in the ED and to test the developed method empirically in a clinical setting. We conceptualised a model with ED patient flow divided into separate queues identified by timestamps for predetermined events. With temporal resolution of 30 min, queue lengths were computed as Q(t + 1) = Q(t) + A(t) - D(t), with A(t) = number of arrivals, D(t) = number of departures and t = time interval. Maximum queue lengths for each shift of each day were found and risks of crowding computed. All tests were performed using non-parametric methods. The method was applied in the ED of Aarhus University Hospital, Denmark utilising an open cohort design with prospectively collected data from a one-year observation period. By employing the timestamps already assigned to the patients while in the ED, a generic queuing model can be computed from which crowding can be described and analysed in detail. Depending on availability of data, the model can be extended to include several queues increasing the level of information. When applying the method empirically, 41,693 patients were included. The studied ED had a high risk of bed occupancy rising above 100 % during day and evening shift, especially on weekdays. Further, a 'carry over' effect was shown between shifts and days. The presented method offers an easy and generic way to get detailed insight into the dynamics of crowding in an ED.

The maximum intelligible range of the human voice

NASA Astrophysics Data System (ADS)

Boren, Braxton

This dissertation examines the acoustics of the spoken voice at high levels and the maximum number of people that could hear such a voice unamplified in the open air. In particular, it examines an early auditory experiment by Benjamin Franklin which sought to determine the maximum intelligible crowd for the Anglican preacher George Whitefield in the eighteenth century. Using Franklin's description of the experiment and a noise source on Front Street, the geometry and diffraction effects of such a noise source are examined to more precisely pinpoint Franklin's position when Whitefield's voice ceased to be intelligible. Based on historical maps, drawings, and prints, the geometry and material of Market Street is constructed as a computer model which is then used to construct an acoustic cone tracing model. Based on minimal values of the Speech Transmission Index (STI) at Franklin's position, Whitefield's on-axis Sound Pressure Level (SPL) at 1 m is determined, leading to estimates centering around 90 dBA. Recordings are carried out on trained actors and singers to determine their maximum time-averaged SPL at 1 m. This suggests that the greatest average SPL achievable by the human voice is 90-91 dBA, similar to the median estimates for Whitefield's voice. The sites of Whitefield's largest crowds are acoustically modeled based on historical evidence and maps. Based on Whitefield's SPL, the minimal STI value, and the crowd's background noise, this allows a prediction of the minimally intelligible area for each site. These yield maximum crowd estimates of 50,000 under ideal conditions, while crowds of 20,000 to 30,000 seem more reasonable when the crowd was reasonably quiet and Whitefield's voice was near 90 dBA.

Avenues for crowd science in Hydrology.

NASA Astrophysics Data System (ADS)

Koch, Julian; Stisen, Simon

2016-04-01

Crowd science describes research that is conducted with the participation of the general public (the crowd) and gives the opportunity to involve the crowd in research design, data collection and analysis. In various fields, scientists have already drawn on underused human resources to advance research at low cost, with high transparency and large acceptance of the public due to the bottom up structure and the participatory process. Within the hydrological sciences, crowd research has quite recently become more established in the form of crowd observatories to generate hydrological data on water quality, precipitation or river flow. These innovative observatories complement more traditional ways of monitoring hydrological data and strengthen a community-based environmental decision making. However, the full potential of crowd science lies in internet based participation of the crowd and it is not yet fully exploited in the field of Hydrology. New avenues that are not primarily based on the outsourcing of labor, but instead capitalize the full potential of human capabilities have to emerge. In multiple realms of solving complex problems, like image detection, optimization tasks, narrowing of possible solutions, humans still remain more effective than computer algorithms. The most successful online crowd science projects Foldit and Galaxy Zoo have proven that the collective of tens of thousands users could clearly outperform traditional computer based science approaches. Our study takes advantage of the well trained human perception to conduct a spatial sensitivity analysis of land-surface variables of a distributed hydrological model to identify the most sensitive spatial inputs. True spatial performance metrics, that quantitatively compare patterns, are not trivial to choose and their applicability is often not universal. On the other hand humans can quickly integrate spatial information at various scales and are therefore a trusted competence. We selected zooniverse, the most popular crowd science platform where over a million registered users contribute to various research projects, to build a survey of the human perception. The survey will be shown during the interactive discussion, but moreover for building future avenues of crowd science in Hydrology the following questions should be discussed: (1) What hydrological problems are suitable for an internet based crowd science application? (2) How to abstract the complex problem to a medium that appeals to the crowd? (3) How to secure good science with reliable results? (4) Can the crowd replace existing and established computer based applications like parameter optimization or forecasting at all?

On the scaling problem and micro-macro derivation of crowd models. Comment on "Human behaviours in evacuation crowd dynamics: From modelling to "big data" toward crisis management" by Nicola Bellomo et al.

NASA Astrophysics Data System (ADS)

Chouhad, Nadia

2016-09-01

A personal comment on a scientific paper is unavoidably related to the personal education and bias. This statement allows me to apologize about the fact that my comment mainly focuses on a somewhat narrow field, namely to analytic topics related to modeling behavioral crowds. The remarks in the following aim also to induce further research suggestions from the authors of paper [3]. In more detail I bring to the attention of the authors of [3] and I look forward to their reply in view of future activity in this field: The micro-macro derivation of hydrodynamic type models should lead to hyperbolic type models, where the propagation speed of perturbation is finite, see [4]. However, it would be interesting understanding how far parabolic type models [6], and their possible modifications, can be accepted as an approximation of physical reality [8].

Conceptualizing intragroup and intergroup dynamics within a controlled crowd evacuation.

PubMed

Elzie, Terra; Frydenlund, Erika; Collins, Andrew J; Robinson, R Michael

2015-01-01

Social dynamics play a critical role in successful pedestrian evacuations. Crowd modeling research has made progress in capturing the way individual and group dynamics affect evacuations; however, few studies have simultaneously examined how individuals and groups interact with one another during egress. To address this gap, the researchers present a conceptual agent-based model (ABM) designed to study the ways in which autonomous, heterogeneous, decision-making individuals negotiate intragroup and intergroup behavior while exiting a large venue. A key feature of this proposed model is the examination of the dynamics among and between various groupings, where heterogeneity at the individual level dynamically affects group behavior and subsequently group/group interactions. ABM provides a means of representing the important social factors that affect decision making among diverse social groups. Expanding on the 2013 work of Vizzari et al., the researchers focus specifically on social factors and decision making at the individual/group and group/group levels to more realistically portray dynamic crowd systems during a pedestrian evacuation. By developing a model with individual, intragroup, and intergroup interactions, the ABM provides a more representative approximation of real-world crowd egress. The simulation will enable more informed planning by disaster managers, emergency planners, and other decision makers. This pedestrian behavioral concept is one piece of a larger simulation model. Future research will build toward an integrated model capturing decision-making interactions between pedestrians and vehicles that affect evacuation outcomes.

Rahman Prize Lecture: Lattice Boltzmann simulation of complex states of flowing matter

NASA Astrophysics Data System (ADS)

Succi, Sauro

Over the last three decades, the Lattice Boltzmann (LB) method has gained a prominent role in the numerical simulation of complex flows across an impressively broad range of scales, from fully-developed turbulence in real-life geometries, to multiphase flows in micro-fluidic devices, all the way down to biopolymer translocation in nanopores and lately, even quark-gluon plasmas. After a brief introduction to the main ideas behind the LB method and its historical developments, we shall present a few selected applications to complex flow problems at various scales of motion. Finally, we shall discuss prospects for extreme-scale LB simulations of outstanding problems in the physics of fluids and its interfaces with material sciences and biology, such as the modelling of fluid turbulence, the optimal design of nanoporous gold catalysts and protein folding/aggregation in crowded environments.

Modeling and simulation of explosion effectiveness as a function of blast and crowd characteristics

NASA Astrophysics Data System (ADS)

Usmani, Zeeshan-Ul-Hassan

Suicide bombing has become one of the most lethal and favorite modus operandi of terrorist organizations around the world. On average, there is a suicide bombing attack every six days somewhere in the world. While various attempts have been made to assess the impact of explosions on structures and military personnel, little has been done on modeling the impact of a blast wave on a crowd in civilian settings. The assessment of an explosion's effect on a crowd can lead to better management of disasters, triage of patients, locating blast victims under the debris, development of protective gear, and safe distance recommendations to reduce the casualties. The overall goal of this work is to predict the magnitude of injuries and lethality on humans from a blast-wave with various explosive and crowd characteristics, and to compare, contrast, and analyze the performance of explosive and injury models against the real-life data of suicide bombing incidents. This thesis introduces BlastSim---a physics based stationary multi-agent simulation platform to model and simulate a suicide bombing event. The agents are constrained by the physical characteristics and mechanics of the blast wave. The BlastSim is programmed to test, analyze, and validate the results of different model combinations under various conditions with different sets of parameters, such as the crowd and explosive characteristics, blockage and human shields, fragmentation and the bomber's position, in 2-dimensional and 3-dimensional environments. The suicide bombing event can be re-created for forensic analysis. The proposed model combinations show a significant performance---the Harold Brode explosive model with Catherine Lee injury model using the blockage stands out consistently to be the best with an overall cumulative accuracy of 87.6%. When comparing against actual data, overall, prediction accuracy can be increased by 71% using this model combination. The J. Clutter with Reflection explosive model using Charles Stewart injury model with blockage works best for confined-space incidents with an accuracy of 80%. Blockage in a crowd can increase the accuracy by 17% for all models. Line-of-sight with an attacker, rushing towards an exit, announcing the threat of a suicide bombing, sitting inside a vehicle or building, and standing closer to a wall or a rigid surface were found to be the most lethal choices both during and after an attack. The findings can have implications for emergency response and counter terrorism.

Evaluation of Proteins' Rotational Diffusion Coefficients from Simulations of Their Free Brownian Motion in Volume-Occupied Environments.

PubMed

Długosz, Maciej; Antosiewicz, Jan M

2014-01-14

We have investigated the rotational dynamics of hen egg white lysozyme in monodisperse aqueous solutions of concentrations up to 250 mg/mL, using a rigid-body Brownian dynamics method that accurately accounts for anisotropies of diffusing objects. We have examined the validity of the free diffusion concept in the analysis of computer simulations of volume-occupied molecular solutions. We have found that, when as the only intermolecular interaction, the excluded volume effect is considered, rotational diffusion of molecules adheres to the free diffusion model. Further, we present a method based on the exact (in the case of the free diffusion) analytic forms of autocorrelation functions of particular vectors rigidly attached to diffusing objects, which allows one to obtain from results of molecular simulations the three principal rotational diffusion coefficients characterizing rotational Brownian motion of an arbitrarily shaped rigid particle for an arbitrary concentration of crowders. We have applied this approach to trajectories resulting from Brownian dynamics simulations of hen egg white lysozyme solutions. We show that the apparent anisotropy of proteins' rotational motions increases with an increasing degree of crowding. Finally, we demonstrate that even if the hydrodynamic anisotropy of molecules is neglected and molecules are simulated using their average translational and rotational diffusion coefficients, excluded volume effects still lead to their anisotropic rotational dynamics.

A Smartphone Camera-Based Indoor Positioning Algorithm of Crowded Scenarios with the Assistance of Deep CNN.

PubMed

Jiao, Jichao; Li, Fei; Deng, Zhongliang; Ma, Wenjing

2017-03-28

Considering the installation cost and coverage, the received signal strength indicator (RSSI)-based indoor positioning system is widely used across the world. However, the indoor positioning performance, due to the interference of wireless signals that are caused by the complex indoor environment that includes a crowded population, cannot achieve the demands of indoor location-based services. In this paper, we focus on increasing the signal strength estimation accuracy considering the population density, which is different to the other RSSI-based indoor positioning methods. Therefore, we propose a new wireless signal compensation model considering the population density, distance, and frequency. First of all, the number of individuals in an indoor crowded scenario can be calculated by our convolutional neural network (CNN)-based human detection approach. Then, the relationship between the population density and the signal attenuation is described in our model. Finally, we use the trilateral positioning principle to realize the pedestrian location. According to the simulation and tests in the crowded scenarios, the proposed model increases the accuracy of the signal strength estimation by 1.53 times compared to that without considering the human body. Therefore, the localization accuracy is less than 1.37 m, which indicates that our algorithm can improve the indoor positioning performance and is superior to other RSSI models.

Theoretical study on interaction of cytochrome f and plastocyanin complex by a simple coarse-grained model with molecular crowding effect

NASA Astrophysics Data System (ADS)

Nakagawa, Satoshi; Kurniawan, Isman; Kodama, Koichi; Arwansyah, Muhammad Saleh; Kawaguchi, Kazutomo; Nagao, Hidemi

2018-03-01

We present a simple coarse-grained model with the molecular crowding effect in solvent to investigate the structure and dynamics of protein complexes including association and/or dissociation processes and investigate some physical properties such as the structure and the reaction rate from the viewpoint of the hydrophobic intermolecular interactions of protein complex. In the present coarse-grained model, a function depending upon the density of hydrophobic amino acid residues in a binding area of the complex is introduced, and the function involves the molecular crowding effect for the intermolecular interactions of hydrophobic amino acid residues between proteins. We propose a hydrophobic intermolecular potential energy between proteins by using the density-dependent function. The present coarse-grained model is applied to the complex of cytochrome f and plastocyanin by using the Langevin dynamics simulation to investigate some physical properties such as the complex structure, the electron transfer reaction rate constant from plastocyanin to cytochrome f and so on. We find that for proceeding the electron transfer reaction, the distance between metals in their active sites is necessary within about 18 Å. We discuss some typical complex structures formed in the present simulation in relation to the molecular crowding effect on hydrophobic interactions.

Crowded and Sparse Domains in Object Recognition: Consequences for Categorization and Naming

ERIC Educational Resources Information Center

Gale, Tim M.; Laws, Keith R.; Foley, Kerry

2006-01-01

Some models of object recognition propose that items from structurally crowded categories (e.g., living things) permit faster access to superordinate semantic information than structurally dissimilar categories (e.g., nonliving things), but slower access to individual object information when naming items. We present four experiments that utilize…

Crowding, sex ratio and horn evolution in a South African beetle community.

PubMed

Pomfret, Joanne C; Knell, Robert J

2008-02-07

Sexually selected ornaments and weapons are exceptionally variable, even between closely related species. It has long been recognized that some of this diversity can be explained by differences in mating systems between species, but there remains substantial variation between species with similar mating systems. We investigated the roles of sex ratio (measured as operational sex ratio, OSR) and population density (measured as mean male crowding, a measure indicating the average number of conspecific males that an individual male animal will encounter) in determining horn presence in a community of South African dung beetles. Analysis of data from 14 species using a generalized least-squares model incorporating phylogenetic influences found that both OSR and mean crowding were significant predictors of horn presence, with hornless species tending to show female-biased sex ratios and high levels of crowding. The influence of mean crowding on horn diversity between species probably reflects the difficulty of guarding and monopolizing females when many competitors are present, meaning that males who adopt 'scramble' tactics tend to be favoured.

Crowding by a single bar: probing pattern recognition mechanisms in the visual periphery.

PubMed

Põder, Endel

2014-11-06

Whereas visual crowding does not greatly affect the detection of the presence of simple visual features, it heavily inhibits combining them into recognizable objects. Still, crowding effects have rarely been directly related to general pattern recognition mechanisms. In this study, pattern recognition mechanisms in visual periphery were probed using a single crowding feature. Observers had to identify the orientation of a rotated T presented briefly in a peripheral location. Adjacent to the target, a single bar was presented. The bar was either horizontal or vertical and located in a random direction from the target. It appears that such a crowding bar has very strong and regular effects on the identification of the target orientation. The observer's responses are determined by approximate relative positions of basic visual features; exact image-based similarity to the target is not important. A version of the "standard model" of object recognition with second-order features explains the main regularities of the data. © 2014 ARVO.

New insights into the crowd characteristics in Mina

NASA Astrophysics Data System (ADS)

Wang, J. Y.; Weng, W. G.; Zhang, X. L.

2014-11-01

The significance of the study of the characteristics of crowd behavior is indubitable for safely organizing mass activities. There is insufficient material to conduct such research. In this paper, the Mina crowd disaster is quantitatively re-investigated. Its instantaneous velocity field is extracted from video material based on the cross-correlation algorithm. The properties of the stop-and-go waves, including fluctuation frequencies, wave propagation speeds, characteristic speeds, and time and space averaged velocity variances, are analyzed in detail. Thus, the database of the stop-and-go wave features is enriched, which is very important to crowd studies. The ‘turbulent’ flows are investigated with the proper orthogonal decomposition (POD) method which is widely used in fluid mechanics. And time series and spatial analysis are conducted to investigate the characteristics of the ‘turbulent’ flows. In this paper, the coherent structures and movement process are described by the POD method. The relationship between the jamming point and crowd path is analyzed. And the pressure buffer recognized in this paper is consistent with Helbing's high-pressure region. The results revealed here may be helpful for facilities design, modeling crowded scenarios and the organization of large-scale mass activities.

Household Crowding and Food Insecurity Among Inuit Families With School-Aged Children in the Canadian Arctic

PubMed Central

Muckle, Gina; Dewailly, Éric; Jacobson, Joseph L.; Jacobson, Sandra W.; Ayotte, Pierre; Riva, Mylène

2015-01-01

Objectives. We examined the relation of household crowding to food insecurity among Inuit families with school-aged children in Arctic Quebec. Methods. We analyzed data collected between October 2005 and February 2010 from 292 primary caregiver–child dyads from 14 Inuit communities. We collected information about household conditions, food security, and family socioeconomic characteristics by interviews. We used logistic regression models to examine the association between household crowding and food insecurity. Results. Nearly 62% of Inuit families in the Canadian Arctic resided in more crowded households, placing them at risk for food insecurity. About 27% of the families reported reducing the size of their children’s meals because of lack of money. The likelihood of reducing the size of children’s meals was greater in crowded households (odds ratio = 3.73; 95% confidence interval = 1.96, 7.12). After we adjusted for different socioeconomic characteristics, results remained statistically significant. Conclusions. Interventions operating across different levels (community, regional, national) are needed to ensure food security in the region. Targeting families living in crowded conditions as part of social and public health policies aiming to reduce food insecurity in the Arctic could be beneficial. PMID:25602890

Household crowding and food insecurity among Inuit families with school-aged children in the Canadian Arctic.

PubMed

Ruiz-Castell, Maria; Muckle, Gina; Dewailly, Éric; Jacobson, Joseph L; Jacobson, Sandra W; Ayotte, Pierre; Riva, Mylène

2015-03-01

We examined the relation of household crowding to food insecurity among Inuit families with school-aged children in Arctic Quebec. We analyzed data collected between October 2005 and February 2010 from 292 primary caregiver-child dyads from 14 Inuit communities. We collected information about household conditions, food security, and family socioeconomic characteristics by interviews. We used logistic regression models to examine the association between household crowding and food insecurity. Nearly 62% of Inuit families in the Canadian Arctic resided in more crowded households, placing them at risk for food insecurity. About 27% of the families reported reducing the size of their children's meals because of lack of money. The likelihood of reducing the size of children's meals was greater in crowded households (odds ratio=3.73; 95% confidence interval=1.96, 7.12). After we adjusted for different socioeconomic characteristics, results remained statistically significant. Interventions operating across different levels (community, regional, national) are needed to ensure food security in the region. Targeting families living in crowded conditions as part of social and public health policies aiming to reduce food insecurity in the Arctic could be beneficial.

The Decomposed Affiliation Exposure Model: A Network Approach to Segregating Peer Influences from Crowds and Organized Sports.

PubMed

Fujimoto, Kayo; Wang, Peng; Valente, Thomas W

2013-08-01

Self-identification with peer crowds (jocks, popular kids, druggies, etc.) has an important influence on adolescent substance use behavior. However, little is known about the impact of the shared nature of crowd identification on different stages of adolescent drinking behavior, or the way crowd identification interacts with participation in school-sponsored sports activities. This study examines drinking influences from (1) peers with shared crowd identities, and (2) peers who jointly participate in organized sports at their school (activity members). This study introduces a new network analytic approach that can disentangle the effects of crowd identification and sports participation on individual behavior. Using survey data from adolescents in five high schools in a predominantly a Hispanic/Latino district (N=1,707), this article examines the association between social influences and each stage of drinking behavior (intention to drink, lifetime, past-month, and binge drinking) by conducting an ordinal regression analysis. The results show that both shared identities and joint participation were associated with all stages of drinking, controlling for friends' influence. Additionally, shared identification overlapped with joint participation was associated with more frequent drinking. Related policy implications are discussed.

Automatic trajectory measurement of large numbers of crowded objects

NASA Astrophysics Data System (ADS)

Li, Hui; Liu, Ye; Chen, Yan Qiu

2013-06-01

Complex motion patterns of natural systems, such as fish schools, bird flocks, and cell groups, have attracted great attention from scientists for years. Trajectory measurement of individuals is vital for quantitative and high-throughput study of their collective behaviors. However, such data are rare mainly due to the challenges of detection and tracking of large numbers of objects with similar visual features and frequent occlusions. We present an automatic and effective framework to measure trajectories of large numbers of crowded oval-shaped objects, such as fish and cells. We first use a novel dual ellipse locator to detect the coarse position of each individual and then propose a variance minimization active contour method to obtain the optimal segmentation results. For tracking, cost matrix of assignment between consecutive frames is trainable via a random forest classifier with many spatial, texture, and shape features. The optimal trajectories are found for the whole image sequence by solving two linear assignment problems. We evaluate the proposed method on many challenging data sets.

Dynamical density functional theory for microswimmers

NASA Astrophysics Data System (ADS)

Menzel, Andreas M.; Saha, Arnab; Hoell, Christian; Löwen, Hartmut

2016-01-01

Dynamical density functional theory (DDFT) has been successfully derived and applied to describe on one hand passive colloidal suspensions, including hydrodynamic interactions between individual particles. On the other hand, active "dry" crowds of self-propelled particles have been characterized using DDFT. Here, we go one essential step further and combine these two approaches. We establish a DDFT for active microswimmer suspensions. For this purpose, simple minimal model microswimmers are introduced. These microswimmers self-propel by setting the surrounding fluid into motion. They hydrodynamically interact with each other through their actively self-induced fluid flows and via the common "passive" hydrodynamic interactions. An effective soft steric repulsion is also taken into account. We derive the DDFT starting from common statistical approaches. Our DDFT is then tested and applied by characterizing a suspension of microswimmers, the motion of which is restricted to a plane within a three-dimensional bulk fluid. Moreover, the swimmers are confined by a radially symmetric trapping potential. In certain parameter ranges, we find rotational symmetry breaking in combination with the formation of a "hydrodynamic pumping state," which has previously been observed in the literature as a result of particle-based simulations. An additional instability of this pumping state is revealed.

Quality Analysis of Open Street Map Data

NASA Astrophysics Data System (ADS)

Wang, M.; Li, Q.; Hu, Q.; Zhou, M.

2013-05-01

Crowd sourcing geographic data is an opensource geographic data which is contributed by lots of non-professionals and provided to the public. The typical crowd sourcing geographic data contains GPS track data like OpenStreetMap, collaborative map data like Wikimapia, social websites like Twitter and Facebook, POI signed by Jiepang user and so on. These data will provide canonical geographic information for pubic after treatment. As compared with conventional geographic data collection and update method, the crowd sourcing geographic data from the non-professional has characteristics or advantages of large data volume, high currency, abundance information and low cost and becomes a research hotspot of international geographic information science in the recent years. Large volume crowd sourcing geographic data with high currency provides a new solution for geospatial database updating while it need to solve the quality problem of crowd sourcing geographic data obtained from the non-professionals. In this paper, a quality analysis model for OpenStreetMap crowd sourcing geographic data is proposed. Firstly, a quality analysis framework is designed based on data characteristic analysis of OSM data. Secondly, a quality assessment model for OSM data by three different quality elements: completeness, thematic accuracy and positional accuracy is presented. Finally, take the OSM data of Wuhan for instance, the paper analyses and assesses the quality of OSM data with 2011 version of navigation map for reference. The result shows that the high-level roads and urban traffic network of OSM data has a high positional accuracy and completeness so that these OSM data can be used for updating of urban road network database.

Can visco-elastic phase separation, macromolecular crowding and colloidal physics explain nuclear organisation?

PubMed

Iborra, Francisco J

2007-04-12

The cell nucleus is highly compartmentalized with well-defined domains, it is not well understood how this nuclear order is maintained. Many scientists are fascinated by the different set of structures observed in the nucleus to attribute functions to them. In order to distinguish functional compartments from non-functional aggregates, I believe is important to investigate the biophysical nature of nuclear organisation. The various nuclear compartments can be divided broadly as chromatin or protein and/or RNA based, and they have very different dynamic properties. The chromatin compartment displays a slow, constrained diffusional motion. On the other hand, the protein/RNA compartment is very dynamic. Physical systems with dynamical asymmetry go to viscoelastic phase separation. This phase separation phenomenon leads to the formation of a long-lived interaction network of slow components (chromatin) scattered within domains rich in fast components (protein/RNA). Moreover, the nucleus is packed with macromolecules in the order of 300 mg/ml. This high concentration of macromolecules produces volume exclusion effects that enhance attractive interactions between macromolecules, known as macromolecular crowding, which favours the formation of compartments. In this paper I hypothesise that nuclear compartmentalization can be explained by viscoelastic phase separation of the dynamically different nuclear components, in combination with macromolecular crowding and the properties of colloidal particles. I demonstrate that nuclear structure can satisfy the predictions of this hypothesis. I discuss the functional implications of this phenomenon.

Crowdedness Mediates the Effect of Social Identification on Positive Emotion in a Crowd: A Survey of Two Crowd Events

PubMed Central

Novelli, David; Drury, John; Reicher, Stephen; Stott, Clifford

2013-01-01

Exposure to crowding is said to be aversive, yet people also seek out and enjoy crowded situations. We surveyed participants at two crowd events to test the prediction of self-categorization theory that variable emotional responses to crowding are a function of social identification with the crowd. In data collected from participants who attended a crowded outdoor music event (n = 48), identification with the crowd predicted feeling less crowded; and there was an indirect effect of identification with the crowd on positive emotion through feeling less crowded. Identification with the crowd also moderated the relation between feeling less crowded and positive emotion. In data collected at a demonstration march (n = 112), identification with the crowd predicted central (most dense) location in the crowd; and there was an indirect effect of identification with the crowd on positive emotion through central location in the crowd. Positive emotion in the crowd also increased over the duration of the crowd event. These findings are in line with the predictions of self-categorization theory. They are inconsistent with approaches that suggest that crowding is inherently aversive; and they cannot easily be explained through the concept of ‘personal space’. PMID:24236079

Biomolecular interactions modulate macromolecular structure and dynamics in atomistic model of a bacterial cytoplasm.

PubMed

Yu, Isseki; Mori, Takaharu; Ando, Tadashi; Harada, Ryuhei; Jung, Jaewoon; Sugita, Yuji; Feig, Michael

2016-11-01

Biological macromolecules function in highly crowded cellular environments. The structure and dynamics of proteins and nucleic acids are well characterized in vitro, but in vivo crowding effects remain unclear. Using molecular dynamics simulations of a comprehensive atomistic model cytoplasm we found that protein-protein interactions may destabilize native protein structures, whereas metabolite interactions may induce more compact states due to electrostatic screening. Protein-protein interactions also resulted in significant variations in reduced macromolecular diffusion under crowded conditions, while metabolites exhibited significant two-dimensional surface diffusion and altered protein-ligand binding that may reduce the effective concentration of metabolites and ligands in vivo. Metabolic enzymes showed weak non-specific association in cellular environments attributed to solvation and entropic effects. These effects are expected to have broad implications for the in vivo functioning of biomolecules. This work is a first step towards physically realistic in silico whole-cell models that connect molecular with cellular biology.

Brownian motion, old and new, and Irwin's role in my academic life

NASA Astrophysics Data System (ADS)

Lindenberg, Katja

2015-03-01

Irwin Oppenheim's early work on Langevin equations, master equations, and Brownian motion was one of the earliest and strongest reasons for my change of direction from my PhD work in condensed matter theory to my later and lifelong interest in Brownian motion and, more broadly, statistical mechanics. I will talk about some of my most recent work on subdiffusion, a form of anomalous diffusion that describes random motions in crowded or disordered media where motions are hindered by the medium. On a personal note, I knew Irwin for decades, from the time before he had a family (he was a sworn bachelor...until he met his wife) until shortly before his death. For many years, first alone and then with family, Irwin would spend some portion of the cold Boston winter in warm La Jolla, and we would always get together during these visits. For a period of a number of years we decided to take advantage of these visits to write the definitive text in traditional Thermodynamics. We did not make it past about 2/3 of the project, but it was a great learning experience for me while it lasted. Irwin's knowledge and understanding of the subject were breathtaking.

Crowd computing: using competitive dynamics to develop and refine highly predictive models.

PubMed

Bentzien, Jörg; Muegge, Ingo; Hamner, Ben; Thompson, David C

2013-05-01

A recent application of a crowd computing platform to develop highly predictive in silico models for use in the drug discovery process is described. The platform, Kaggle™, exploits a competitive dynamic that results in model optimization as the competition unfolds. Here, this dynamic is described in detail and compared with more-conventional modeling strategies. The complete and full structure of the underlying dataset is disclosed and some thoughts as to the broader utility of such 'gamification' approaches to the field of modeling are offered. Copyright © 2013 Elsevier Ltd. All rights reserved.

The association between crowding and mortality in admitted pediatric patients from mixed adult-pediatric emergency departments in Korea.

PubMed

Cha, Won Chul; Shin, Sang Do; Cho, Jin Sung; Song, Kyoung Jun; Singer, Adam J; Kwak, Young Ho

2011-12-01

We aimed to investigate the effect of crowding on the hospital mortality of pediatric patients from adult-pediatric mixed emergency departments (EDs). We used the National Emergency Department Information System database, which included demographic, clinical, diagnostic, and procedural information with all emergency patients visiting to 116 EDs from Korea since 2004. We enrolled EDs with mean length of stay of more than 6 hours. Study period was from January 2006 to December 2008. Pediatric patients younger than 15 years admitted from these EDs were study targets. We calculated the mean patient volume (mean number of patients in the ED) over 8-hour shift for each hospital. When the volume reached the highest quartile, the period was considered as crowded. Patients who came during the overcrowded period were defined as the crowded group. We performed a Kaplan-Meier analysis, and hazard ratio and 95% confidence intervals (95% CIs) were calculated using a Cox proportional hazards regression model. A total of 34 EDs and 125,031 admitted pediatric patients were included; 74,152 (59.3%) were male, and the mean age was 3.84 (95% CI, 3.82-3.86) years; 35,924 (28.7%) were determined as the crowded group. The 30-day mortality rates were 0.4% and 0.3% (P = 0.063) for the crowded group and for the noncrowded group, respectively. The hazard ratio for hospital mortality of the crowded group was 1.230 (95% CI, 1.019-1.558). The ED crowding was associated with increased hazard for hospital mortality for pediatric patients in mixed EDs.

Experimental study on small group behavior and crowd dynamics in a tall office building evacuation

NASA Astrophysics Data System (ADS)

Ma, Yaping; Li, Lihua; Zhang, Hui; Chen, Tao

2017-05-01

It is well known that a large percentage of occupants in a building are evacuated together with their friends, families, and officemates, especially in China. Small group behaviors are therefore critical for crowd movement. This paper aims to study the crowd dynamic considering different social relations and the impacts of small groups on crowd dynamics in emergency evacuation. Three experiments are conducted in an 11-storey office building. In the first two experiments, all participants are classmates and know each other well. They are evacuated as individuals or pairs. In the third experiment, social relations among the participants are complex. Participants consist of 8 families, 6 lovers and several individuals. Space-time features, speed characteristics and density-speed relations for each experiment are analyzed and compared. Results conclude that small group behaviors can make positive impacts on crowd dynamics when evacuees know each other and are cooperative. This conclusion is also testified by four verified experiments. In the third experiment, speeds of evacuees are lowest. Small groups form automatically with the presence of intimate social relations. Small groups in this experiment slow down the average speed of the crowd and make disturbance on the crowd flow. Small groups in this case make negative impacts on the movement of the crowd. It is because that evacuees do not know each other and they are competitive to each other. Characteristics of different types of small groups are also investigated. Experimental data can provide foundational parameters for evacuation model development and are helpful for building designers.

Eyes on crowding: crowding is preserved when responding by eye and similarly affects identity and position accuracy.

PubMed

Yildirim, Funda; Meyer, Vincent; Cornelissen, Frans W

2015-02-16

Peripheral vision guides recognition and selection of targets for eye movements. Crowding—a decline in recognition performance that occurs when a potential target is surrounded by other, similar, objects—influences peripheral object recognition. A recent model study suggests that crowding may be due to increased uncertainty about both the identity and the location of peripheral target objects, but very few studies have assessed these properties in tandem. Eye tracking can integrally provide information on both the perceived identity and the position of a target and therefore could become an important approach in crowding studies. However, recent reports suggest that around the moment of saccade preparation crowding may be significantly modified. If these effects were to generalize to regular crowding tasks, it would complicate the interpretation of results obtained with eye tracking and the comparison to results obtained using manual responses. For this reason, we first assessed whether the manner by which participants responded—manually or by eye—affected their performance. We found that neither recognition performance nor response time was affected by the response type. Hence, we conclude that crowding magnitude was preserved when observers responded by eye. In our main experiment, observers made eye movements to the location of a tilted Gabor target while we varied flanker tilt to manipulate target-flanker similarity. The results indicate that this similarly affected the accuracy of peripheral recognition and saccadic target localization. Our results inform about the importance of both location and identity uncertainty in crowding. © 2015 ARVO.

Social dynamics in emergency evacuations: Disentangling crowd's attraction and repulsion effects

NASA Astrophysics Data System (ADS)

Haghani, Milad; Sarvi, Majid

2017-06-01

The social dynamics of crowds in emergency escape scenarios have been conventionally modelled as the net effect of virtual forces exerted by the crowd on each individual (as self-driven particles), with the magnitude of the influence formulated as decreasing functions of inter-individual distances and the direction of effect assumed to be transitioning from repulsion to attraction by distance. Here, we revisit this conventional assumption using laboratory experimental data. We show based on robust econometric hypothesis-testing methods that individuals' perception of other escapees differs based on whether those individuals are jamming around exit destinations or are on the move towards the destinations. Also, for moving crowds, it differs based on whether the escape destination chosen by the moving flow is visible or invisible to the individual. The presence of crowd jams around a destination, also the movement of crowd flows towards visible destinations are both perceived on average as repulsion (or disutility) effects (with the former showing significantly larger magnitude than the latter). The movement of crowd flows towards an invisible destination, however, is on average perceived as attraction (or utility) effect. Yet, further hypothesis testing showed that neither of those effects in isolation determines adequately whether an individual would merge with or diverge from the crowd. Rather, the social interaction factors act (at significant levels) in conjunction with the physical factors of the environments (including spatial distances to exit destinations and destinations' visibility). In brief, our finding disentangles the conditions under which individuals are more likely to show mass behaviour from the situations where they are more likely to break from the herd. It identifies two factors that moderate the perception of social interactions, ;crowds' jam/movement status; and ;environmental setup;. Our results particularly challenge the taxonomy of attraction-repulsion social interaction forces defined purely based on the distance of the individual to the surrounding crowd, by showing that crowds could be in far distance and yet be perceived as repulsion effect, or they could be in close distance and yet act as attraction effect.

CrowdWater - Can people observe what models need?

NASA Astrophysics Data System (ADS)

van Meerveld, I. H. J.; Seibert, J.; Vis, M.; Etter, S.; Strobl, B.

2017-12-01

CrowdWater (www.crowdwater.ch) is a citizen science project that explores the usefulness of crowd-sourced data for hydrological model calibration and prediction. Hydrological models are usually calibrated based on observed streamflow data but it is likely easier for people to estimate relative stream water levels, such as the water level above or below a rock, than streamflow. Relative stream water levels may, therefore, be a more suitable variable for citizen science projects than streamflow. In order to test this assumption, we held surveys near seven different sized rivers in Switzerland and asked more than 450 volunteers to estimate the water level class based on a picture with a virtual staff gauge. The results show that people can generally estimate the relative water level well, although there were also a few outliers. We also asked the volunteers to estimate streamflow based on the stick method. The median estimated streamflow was close to the observed streamflow but the spread in the streamflow estimates was large and there were very large outliers, suggesting that crowd-based streamflow data is highly uncertain. In order to determine the potential value of water level class data for model calibration, we converted streamflow time series for 100 catchments in the US to stream level class time series and used these to calibrate the HBV model. The model was then validated using the streamflow data. The results of this modeling exercise show that stream level class data are useful for constraining a simple runoff model. Time series of only two stream level classes, e.g. above or below a rock in the stream, were already informative, especially when the class boundary was chosen towards the highest stream levels. There was hardly any improvement in model performance when more than five water level classes were used. This suggests that if crowd-sourced stream level observations are available for otherwise ungauged catchments, these data can be used to constrain a simple runoff model and to generate simulated streamflow time series from the level observations.

Blindsight modulation of motion perception.

PubMed

Intriligator, James M; Xie, Ruiman; Barton, Jason J S

2002-11-15

Monkey data suggest that of all perceptual abilities, motion perception is the most likely to survive striate damage. The results of studies on motion blindsight in humans, though, are mixed. We used an indirect strategy to examine how responses to visible stimuli were modulated by blind-field stimuli. In a 26-year-old man with focal striate lesions, discrimination of visible optic flow was enhanced about 7% by blind-field flow, even though discrimination of optic flow in the blind field alone (the direct strategy) was at chance. Pursuit of an imagined target using peripheral cues showed reduced variance but not increased gain with blind-field cues. Preceding blind-field prompts shortened reaction times to visible targets by about 10 msec, but there was no attentional crowding of visible stimuli by blind-field distractors. A similar efficacy of indirect blind-field optic flow modulation was found in a second patient with residual vision after focal striate damage, but not in a third with more extensive medial occipito-temporal damage. We conclude that indirect modulatory strategies are more effective than direct forced-choice methods at revealing residual motion perception after focal striate lesions.

Modeling a Mathematical to Quantify the Degree of Emergency Department Crowding

NASA Astrophysics Data System (ADS)

Chang, Y.; Pan, C.; Wen, J.

2012-12-01

The purpose of this study is to deduce a function from the admissions/discharge rate of patient flow to estimate a "Critical Point" that provides a reference for warning systems in regards to crowding in the emergency department (ED) of a hospital or medical clinic. In this study, a model of "Input-Throughput-Output" was used in our established mathematical function to evaluate the critical point. The function was defined as ∂ρ/∂t=-K×∂ρ/∂x , where ρ= number of patients per unit distance (also called density), t= time, x= distance, K= distance of patients movement per unit time. Using the average K of ED crowding, we could initiate the warning system at appropriate time and plan necessary emergency response to facilitate the patient process more smoothly. It was concluded that ED crowding can be quantified using the average value of K, and the value can be used as a reference for medical staff to give optimal emergency medical treatment to patients. Therefore, additional practical work should be launched to collect more precise quantitative data.

Aggregating and Predicting Sequence Labels from Crowd Annotations

PubMed Central

Nguyen, An T.; Wallace, Byron C.; Li, Junyi Jessy; Nenkova, Ani; Lease, Matthew

2017-01-01

Despite sequences being core to NLP, scant work has considered how to handle noisy sequence labels from multiple annotators for the same text. Given such annotations, we consider two complementary tasks: (1) aggregating sequential crowd labels to infer a best single set of consensus annotations; and (2) using crowd annotations as training data for a model that can predict sequences in unannotated text. For aggregation, we propose a novel Hidden Markov Model variant. To predict sequences in unannotated text, we propose a neural approach using Long Short Term Memory. We evaluate a suite of methods across two different applications and text genres: Named-Entity Recognition in news articles and Information Extraction from biomedical abstracts. Results show improvement over strong baselines. Our source code and data are available online1. PMID:29093611

Optimal Measurement Interval for Emergency Department Crowding Estimation Tools.

PubMed

Wang, Hao; Ojha, Rohit P; Robinson, Richard D; Jackson, Bradford E; Shaikh, Sajid A; Cowden, Chad D; Shyamanand, Rath; Leuck, JoAnna; Schrader, Chet D; Zenarosa, Nestor R

2017-11-01

Emergency department (ED) crowding is a barrier to timely care. Several crowding estimation tools have been developed to facilitate early identification of and intervention for crowding. Nevertheless, the ideal frequency is unclear for measuring ED crowding by using these tools. Short intervals may be resource intensive, whereas long ones may not be suitable for early identification. Therefore, we aim to assess whether outcomes vary by measurement interval for 4 crowding estimation tools. Our eligible population included all patients between July 1, 2015, and June 30, 2016, who were admitted to the JPS Health Network ED, which serves an urban population. We generated 1-, 2-, 3-, and 4-hour ED crowding scores for each patient, using 4 crowding estimation tools (National Emergency Department Overcrowding Scale [NEDOCS], Severely Overcrowded, Overcrowded, and Not Overcrowded Estimation Tool [SONET], Emergency Department Work Index [EDWIN], and ED Occupancy Rate). Our outcomes of interest included ED length of stay (minutes) and left without being seen or eloped within 4 hours. We used accelerated failure time models to estimate interval-specific time ratios and corresponding 95% confidence limits for length of stay, in which the 1-hour interval was the reference. In addition, we used binomial regression with a log link to estimate risk ratios (RRs) and corresponding confidence limit for left without being seen. Our study population comprised 117,442 patients. The time ratios for length of stay were similar across intervals for each crowding estimation tool (time ratio=1.37 to 1.30 for NEDOCS, 1.44 to 1.37 for SONET, 1.32 to 1.27 for EDWIN, and 1.28 to 1.23 for ED Occupancy Rate). The RRs of left without being seen differences were also similar across intervals for each tool (RR=2.92 to 2.56 for NEDOCS, 3.61 to 3.36 for SONET, 2.65 to 2.40 for EDWIN, and 2.44 to 2.14 for ED Occupancy Rate). Our findings suggest limited variation in length of stay or left without being seen between intervals (1 to 4 hours) regardless of which of the 4 crowding estimation tools were used. Consequently, 4 hours may be a reasonable interval for assessing crowding with these tools, which could substantially reduce the burden on ED personnel by requiring less frequent assessment of crowding. Copyright © 2017 American College of Emergency Physicians. Published by Elsevier Inc. All rights reserved.

Theoretical mechanics: crowd synchrony on the Millennium Bridge.

PubMed

Strogatz, Steven H; Abrams, Daniel M; McRobie, Allan; Eckhardt, Bruno; Ott, Edward

2005-11-03

Soon after the crowd streamed on to London's Millennium Bridge on the day it opened, the bridge started to sway from side to side: many pedestrians fell spontaneously into step with the bridge's vibrations, inadvertently amplifying them. Here we model this unexpected and now notorious phenomenon--which was not due to the bridge's innovative design as was first thought--by adapting ideas originally developed to describe the collective synchronization of biological oscillators such as neurons and fireflies. Our approach should help engineers to estimate the damping needed to stabilize other exceptionally crowded footbridges against synchronous lateral excitation by pedestrians.

A double dissociation of the acuity and crowding limits to letter identification, and the promise of improved visual screening

PubMed Central

Song, Shuang; Levi, Dennis M.; Pelli, Denis G.

2014-01-01

Here, we systematically explore the size and spacing requirements for identifying a letter among other letters. We measure acuity for flanked and unflanked letters, centrally and peripherally, in normals and amblyopes. We find that acuity, overlap masking, and crowding each demand a minimum size or spacing for readable text. Just measuring flanked and unflanked acuity is enough for our proposed model to predict the observer's threshold size and spacing for letters at any eccentricity. We also find that amblyopia in adults retains the character of the childhood condition that caused it. Amblyopia is a developmental neural deficit that can occur as a result of either strabismus or anisometropia in childhood. Peripheral viewing during childhood due to strabismus results in amblyopia that is crowding limited, like peripheral vision. Optical blur of one eye during childhood due to anisometropia without strabismus results in amblyopia that is acuity limited, like blurred vision. Furthermore, we find that the spacing:acuity ratio of flanked and unflanked acuity can distinguish strabismic amblyopia from purely anisometropic amblyopia in nearly perfect agreement with lack of stereopsis. A scatter diagram of threshold spacing versus acuity, one point per patient, for several diagnostic groups, reveals the diagnostic power of flanked acuity testing. These results and two demonstrations indicate that the sensitivity of visual screening tests can be improved by using flankers that are more tightly spaced and letter like. Finally, in concert with Strappini, Pelli, Di Pace, and Martelli (submitted), we jointly report a double dissociation between acuity and crowding. Two clinical conditions—anisometropic amblyopia and apperceptive agnosia—each selectively impair either acuity A or the spacing:acuity ratio S/A, not both. Furthermore, when we specifically estimate crowding, we find a double dissociation between acuity and crowding. Models of human object recognition will need to accommodate this newly discovered independence of acuity and crowding. PMID:24799622

Emergent vortices in populations of colloidal rollers

PubMed Central

Bricard, Antoine; Caussin, Jean-Baptiste; Das, Debasish; Savoie, Charles; Chikkadi, Vijayakumar; Shitara, Kyohei; Chepizhko, Oleksandr; Peruani, Fernando; Saintillan, David; Bartolo, Denis

2015-01-01

Coherent vortical motion has been reported in a wide variety of populations including living organisms (bacteria, fishes, human crowds) and synthetic active matter (shaken grains, mixtures of biopolymers), yet a unified description of the formation and structure of this pattern remains lacking. Here we report the self-organization of motile colloids into a macroscopic steadily rotating vortex. Combining physical experiments and numerical simulations, we elucidate this collective behaviour. We demonstrate that the emergent-vortex structure lives on the verge of a phase separation, and single out the very constituents responsible for this state of polar active matter. Building on this observation, we establish a continuum theory and lay out a strong foundation for the description of vortical collective motion in a broad class of motile populations constrained by geometrical boundaries. PMID:26088835

The Effect of Attractive Interactions and Macromolecular Crowding on Crystallins Association

PubMed Central

Wei, Jiachen; Dobnikar, Jure; Curk, Tine; Song, Fan

2016-01-01

In living systems proteins are typically found in crowded environments where their effective interactions strongly depend on the surrounding medium. Yet, their association and dissociation needs to be robustly controlled in order to enable biological function. Uncontrolled protein aggregation often causes disease. For instance, cataract is caused by the clustering of lens proteins, i.e., crystallins, resulting in enhanced light scattering and impaired vision or blindness. To investigate the molecular origins of cataract formation and to design efficient treatments, a better understanding of crystallin association in macromolecular crowded environment is needed. Here we present a theoretical study of simple coarse grained colloidal models to characterize the general features of how the association equilibrium of proteins depends on the magnitude of intermolecular attraction. By comparing the analytic results to the available experimental data on the osmotic pressure in crystallin solutions, we identify the effective parameters regimes applicable to crystallins. Moreover, the combination of two models allows us to predict that the number of binding sites on crystallin is small, i.e. one to three per protein, which is different from previous estimates. We further observe that the crowding factor is sensitive to the size asymmetry between the reactants and crowding agents, the shape of the protein clusters, and to small variations of intermolecular attraction. Our work may provide general guidelines on how to steer the protein interactions in order to control their association. PMID:26954357

Crowd evacuation model based on bacterial foraging algorithm

NASA Astrophysics Data System (ADS)

Shibiao, Mu; Zhijun, Chen

To understand crowd evacuation, a model based on a bacterial foraging algorithm (BFA) is proposed in this paper. Considering dynamic and static factors, the probability of pedestrian movement is established using cellular automata. In addition, given walking and queue times, a target optimization function is built. At the same time, a BFA is used to optimize the objective function. Finally, through real and simulation experiments, the relationship between the parameters of evacuation time, exit width, pedestrian density, and average evacuation speed is analyzed. The results show that the model can effectively describe a real evacuation.

Neural dynamics of object-based multifocal visual spatial attention and priming: Object cueing, useful-field-of-view, and crowding

PubMed Central

Foley, Nicholas C.; Grossberg, Stephen; Mingolla, Ennio

2015-01-01

How are spatial and object attention coordinated to achieve rapid object learning and recognition during eye movement search? How do prefrontal priming and parietal spatial mechanisms interact to determine the reaction time costs of intra-object attention shifts, inter-object attention shifts, and shifts between visible objects and covertly cued locations? What factors underlie individual differences in the timing and frequency of such attentional shifts? How do transient and sustained spatial attentional mechanisms work and interact? How can volition, mediated via the basal ganglia, influence the span of spatial attention? A neural model is developed of how spatial attention in the where cortical stream coordinates view-invariant object category learning in the what cortical stream under free viewing conditions. The model simulates psychological data about the dynamics of covert attention priming and switching requiring multifocal attention without eye movements. The model predicts how “attentional shrouds” are formed when surface representations in cortical area V4 resonate with spatial attention in posterior parietal cortex (PPC) and prefrontal cortex (PFC), while shrouds compete among themselves for dominance. Winning shrouds support invariant object category learning, and active surface-shroud resonances support conscious surface perception and recognition. Attentive competition between multiple objects and cues simulates reaction-time data from the two-object cueing paradigm. The relative strength of sustained surface-driven and fast-transient motion-driven spatial attention controls individual differences in reaction time for invalid cues. Competition between surface-driven attentional shrouds controls individual differences in detection rate of peripheral targets in useful-field-of-view tasks. The model proposes how the strength of competition can be mediated, though learning or momentary changes in volition, by the basal ganglia. A new explanation of crowding shows how the cortical magnification factor, among other variables, can cause multiple object surfaces to share a single surface-shroud resonance, thereby preventing recognition of the individual objects. PMID:22425615

Neural dynamics of object-based multifocal visual spatial attention and priming: object cueing, useful-field-of-view, and crowding.

PubMed

Foley, Nicholas C; Grossberg, Stephen; Mingolla, Ennio

2012-08-01

How are spatial and object attention coordinated to achieve rapid object learning and recognition during eye movement search? How do prefrontal priming and parietal spatial mechanisms interact to determine the reaction time costs of intra-object attention shifts, inter-object attention shifts, and shifts between visible objects and covertly cued locations? What factors underlie individual differences in the timing and frequency of such attentional shifts? How do transient and sustained spatial attentional mechanisms work and interact? How can volition, mediated via the basal ganglia, influence the span of spatial attention? A neural model is developed of how spatial attention in the where cortical stream coordinates view-invariant object category learning in the what cortical stream under free viewing conditions. The model simulates psychological data about the dynamics of covert attention priming and switching requiring multifocal attention without eye movements. The model predicts how "attentional shrouds" are formed when surface representations in cortical area V4 resonate with spatial attention in posterior parietal cortex (PPC) and prefrontal cortex (PFC), while shrouds compete among themselves for dominance. Winning shrouds support invariant object category learning, and active surface-shroud resonances support conscious surface perception and recognition. Attentive competition between multiple objects and cues simulates reaction-time data from the two-object cueing paradigm. The relative strength of sustained surface-driven and fast-transient motion-driven spatial attention controls individual differences in reaction time for invalid cues. Competition between surface-driven attentional shrouds controls individual differences in detection rate of peripheral targets in useful-field-of-view tasks. The model proposes how the strength of competition can be mediated, though learning or momentary changes in volition, by the basal ganglia. A new explanation of crowding shows how the cortical magnification factor, among other variables, can cause multiple object surfaces to share a single surface-shroud resonance, thereby preventing recognition of the individual objects. Copyright © 2012 Elsevier Inc. All rights reserved.

THE OPEP COARSE-GRAINED PROTEIN MODEL: FROM SINGLE MOLECULES, AMYLOID FORMATION, ROLE OF MACROMOLECULAR CROWDING AND HYDRODYNAMICS TO RNA/DNA COMPLEXES

PubMed Central

Sterpone, Fabio; Melchionna, Simone; Tuffery, Pierre; Pasquali, Samuela; Mousseau, Normand; Cragnolini, Tristan; Chebaro, Yassmine; Saint-Pierre, Jean-Francois; Kalimeri, Maria; Barducci, Alessandro; Laurin, Yohan; Tek, Alex; Baaden, Marc; Nguyen, Phuong Hoang; Derreumaux, Philippe

2015-01-01

The OPEP coarse-grained protein model has been applied to a wide range of applications since its first release 15 years ago. The model, which combines energetic and structural accuracy and chemical specificity, allows studying single protein properties, DNA/RNA complexes, amyloid fibril formation and protein suspensions in a crowded environment. Here we first review the current state of the model and the most exciting applications using advanced conformational sampling methods. We then present the current limitations and a perspective on the on-going developments. PMID:24759934

The Shape of Protein Crowders is a Major Determinant of Protein Diffusion

PubMed Central

Balbo, Jessica; Mereghetti, Paolo; Herten, Dirk-Peter; Wade, Rebecca C.

2013-01-01

As a model for understanding how molecular crowding influences diffusion and transport of proteins in cellular environments, we combined experimental and theoretical approaches to study the diffusion of proteins in highly concentrated protein solutions. Bovine serum albumin and γ-Globulin were chosen as molecular crowders and as tracers. These two proteins are representatives of the main types of plasma protein and have different shapes and sizes. Solutions consisting of one or both proteins were studied. The self-diffusion coefficients of the fluorescently labeled tracer proteins were measured by means of fluorescence correlation spectroscopy at a total protein concentration of up to 400 g/L. γ-Globulin is found to have a stronger influence as a crowder on the tracer self-diffusion coefficient than Bovine serum albumin. Brownian dynamics simulations show that the excluded volume and the shape of the crowding protein have a significantly stronger influence on translational and rotational diffusion coefficients, as well as transient oligomerization, than hydrodynamic or direct interactions. Anomalous subdiffusion, which is not observed at the experimental fluorescence correlation spectroscopy timescales (>100 μs), appears only at very short timescales (<1 μs) in the simulations due to steric effects of the proteins. We envision that the combined experimental and computational approach employed here can be developed to unravel the different biophysical contributions to protein motion and interaction in cellular environments by systematically varying protein properties such as molecular weight, size, shape, and electrostatic interactions. PMID:23561534

Home advantage and referee bias in European football.

PubMed

Goumas, Chris

2014-01-01

Home advantage is well documented in a wide range of team sports including association football (soccer). Home team crowd support has been shown to be a likely causal factor and its influence on referee decision-making appears to play a significant role. Match data from the 2009/2010 and 2010/2011 seasons of the Union of European Football Associations (UEFA) Champions League and Europa League were used to investigate referee bias in terms of the association between match location (home vs. away) and disciplinary sanctions used by football referees. The adjusted mean number of yellow cards received by home and away teams and the ratios of these means were estimated from Poisson regression models. After controlling for within-match measures of attacking dominance referees in the Champions League and Europa League issued 25% (p<0.001) and 10% (p=0.002) more yellow cards, respectively, to away teams than to home teams. The higher level of home team bias in the Champions League appeared to be mainly due to higher crowd densities. In a combined analysis of both UEFA leagues the magnitude of referee bias increased with increasing crowd density (p<0.001). Crowd size and crowd proximity were not associated with referee bias after controlling for crowd density. These results provide further evidence that crowd support influences referee decisions. Failure to control for within-match team performance may over-estimate the extent of referee bias in terms of the number of disciplinary sanctions used.

A grouping method based on grid density and relationship for crowd evacuation simulation

NASA Astrophysics Data System (ADS)

Li, Yan; Liu, Hong; Liu, Guang-peng; Li, Liang; Moore, Philip; Hu, Bin

2017-05-01

Psychological factors affect the movement of people in the competitive or panic mode of evacuation, in which the density of pedestrians is relatively large and the distance among them is small. In this paper, a crowd is divided into groups according to their social relations to simulate the actual movement of crowd evacuation more realistically and increase the attractiveness of the group based on social force model. The force of group attraction is the synthesis of two forces; one is the attraction of the individuals generated by their social relations to gather, and the other is that of the group leader to the individuals within the group to ensure that the individuals follow the leader. The synthetic force determines the trajectory of individuals. The evacuation process is demonstrated using the improved social force model. In the improved social force model, the individuals with close social relations gradually present a closer and coordinated action while following the leader. In this paper, a grouping algorithm is proposed based on grid density and relationship via computer simulation to illustrate the features of the improved social force model. The definition of the parameters involved in the algorithm is given, and the effect of relational value on the grouping is tested. Reasonable numbers of grids and weights are selected. The effectiveness of the algorithm is shown through simulation experiments. A simulation platform is also established using the proposed grouping algorithm and the improved social force model for crowd evacuation simulation.

Advanced Demonstration of Motion Correction for Ship-to-Ship Passive Inspections

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ziock, Klaus-Peter; Boehnen, Chris Bensing; Ernst, Joseph

2013-09-30

Passive radiation detection is a key tool for detecting illicit nuclear materials. In maritime applications it is most effective against small vessels where attenuation is of less concern. Passive imaging provides: discrimination between localized (threat) and distributed (non-threat) sources, removal of background fluctuations due to nearby shorelines and structures, source localization to an individual craft in crowded waters, and background subtracted spectra. Unfortunately, imaging methods cannot be easily applied in ship-to-ship inspections because relative motion of the vessels blurs the results over many pixels, significantly reducing sensitivity. This is particularly true for the smaller water craft where passive inspections aremore » most valuable. In this project we performed tests and improved the performance of an instrument (developed earlier under, “Motion Correction for Ship-to-Ship Passive Inspections”) that uses automated tracking of a target vessel in visible-light images to generate a 3D radiation map of the target vessel from data obtained using a gamma-ray imager.« less

Processive movement of single kinesins on crowded microtubules visualized using quantum dots

PubMed Central

Seitz, Arne; Surrey, Thomas

2006-01-01

Kinesin-1 is a processive molecular motor transporting cargo along microtubules. Inside cells, several motors and microtubule-associated proteins compete for binding to microtubules. Therefore, the question arises how processive movement of kinesin-1 is affected by crowding on the microtubule. Here we use total internal reflection fluorescence microscopy to image in vitro the runs of single quantum dot-labelled kinesins on crowded microtubules under steady-state conditions and to measure the degree of crowding on a microtubule at steady-state. We find that the runs of kinesins are little affected by high kinesin densities on a microtubule. However, the presence of high densities of a mutant kinesin that is not able to step efficiently reduces the average speed of wild-type kinesin, while hardly changing its processivity. This indicates that kinesin waits in a strongly bound state on the microtubule when encountering an obstacle until the obstacle unbinds and frees the binding site for kinesin's next step. A simple kinetic model can explain quantitatively the behaviour of kinesin under both crowding conditions. PMID:16407972

Public engagement in 3D flood modelling through integrating crowd sourced imagery with UAV photogrammetry to create a 3D flood hydrograph.

NASA Astrophysics Data System (ADS)

Bond, C. E.; Howell, J.; Butler, R.

2016-12-01

With an increase in flood and storm events affecting infrastructure the role of weather systems, in a changing climate, and their impact is of increasing interest. Here we present a new workflow integrating crowd sourced imagery from the public with UAV photogrammetry to create, the first 3D hydrograph of a major flooding event. On December 30th 2015, Storm Frank resulted in high magnitude rainfall, within the Dee catchment in Aberdeenshire, resulting in the highest ever-recorded river level for the Dee, with significant impact on infrastructure and river morphology. The worst of the flooding occurred during daylight hours and was digitally captured by the public on smart phones and cameras. After the flood event a UAV was used to shoot photogrammetry to create a textured elevation model of the area around Aboyne Bridge on the River Dee. A media campaign aided crowd sourced digital imagery from the public, resulting in over 1,000 images submitted by the public. EXIF data captured by the imagery of the time, date were used to sort the images into a time series. Markers such as signs, walls, fences and roads within the images were used to determine river level height through the flood, and matched onto the elevation model to contour the change in river level. The resulting 3D hydrograph shows the build up of water on the up-stream side of the Bridge that resulted in significant scouring and under-mining in the flood. We have created the first known data based 3D hydrograph for a river section, from a UAV photogrammetric model and crowd sourced imagery. For future flood warning and infrastructure management a solution that allows a realtime hydrograph to be created utilising augmented reality to integrate the river level information in crowd sourced imagery directly onto a 3D model, would significantly improve management planning and infrastructure resilience assessment.

Peer Crowds in Singapore

ERIC Educational Resources Information Center

Sim, Tick Ngee; Yeo, Geck Hong

2012-01-01

This study examined peer crowds in the Singapore context. A total of 598 Secondary 1 and 2 adolescents were asked to identify the crowds they perceived to exist in their schools and to describe these crowds' characteristics. The adolescents had no difficulty identifying crowds, generating a total of 1,534 crowds. Among the crowds identified, seven…

Biomolecular interactions modulate macromolecular structure and dynamics in atomistic model of a bacterial cytoplasm

PubMed Central

Yu, Isseki; Mori, Takaharu; Ando, Tadashi; Harada, Ryuhei; Jung, Jaewoon; Sugita, Yuji; Feig, Michael

2016-01-01

Biological macromolecules function in highly crowded cellular environments. The structure and dynamics of proteins and nucleic acids are well characterized in vitro, but in vivo crowding effects remain unclear. Using molecular dynamics simulations of a comprehensive atomistic model cytoplasm we found that protein-protein interactions may destabilize native protein structures, whereas metabolite interactions may induce more compact states due to electrostatic screening. Protein-protein interactions also resulted in significant variations in reduced macromolecular diffusion under crowded conditions, while metabolites exhibited significant two-dimensional surface diffusion and altered protein-ligand binding that may reduce the effective concentration of metabolites and ligands in vivo. Metabolic enzymes showed weak non-specific association in cellular environments attributed to solvation and entropic effects. These effects are expected to have broad implications for the in vivo functioning of biomolecules. This work is a first step towards physically realistic in silico whole-cell models that connect molecular with cellular biology. DOI: http://dx.doi.org/10.7554/eLife.19274.001 PMID:27801646

Exploring the crowding-satisfaction relationship between day and overnight users in the lower Colorado River Basin, Texas

Treesearch

Yung-Ping Tseng; Gerard T. Kyle; C. Scott Shafer; Alan R. Graefe; Timothy A. Bradle

2009-01-01

As the boating population and number of boats in use have grown in the United States, boaters' perceptions of density at recreation sites and the associated impacts on their experience (e.g., satisfaction) are becoming increasingly important. This paper explores a recreational boating crowding-satisfaction model derived from previous work using safety and...

Multi-species coexistence in Lotka-Volterra competitive systems with crowding effects.

PubMed

Gavina, Maica Krizna A; Tahara, Takeru; Tainaka, Kei-Ichi; Ito, Hiromu; Morita, Satoru; Ichinose, Genki; Okabe, Takuya; Togashi, Tatsuya; Nagatani, Takashi; Yoshimura, Jin

2018-01-19

Classical Lotka-Volterra (LV) competition equation has shown that coexistence of competitive species is only possible when intraspecific competition is stronger than interspecific competition, i.e., the species inhibit their own growth more than the growth of the other species. Note that density effect is assumed to be linear in a classical LV equation. In contrast, in wild populations we can observed that mortality rate often increases when population density is very high, known as crowding effects. Under this perspective, the aggregation models of competitive species have been developed, adding the additional reduction in growth rates at high population densities. This study shows that the coexistence of a few species is promoted. However, an unsolved question is the coexistence of many competitive species often observed in natural communities. Here, we build an LV competition equation with a nonlinear crowding effect. Our results show that under a weak crowding effect, stable coexistence of many species becomes plausible, unlike the previous aggregation model. An analysis indicates that increased mortality rate under high density works as elevated intraspecific competition leading to the coexistence. This may be another mechanism for the coexistence of many competitive species leading high species diversity in nature.

Polymer Crowding in Confined Polymer-Nanoparticle Mixtures

NASA Astrophysics Data System (ADS)

Davis, Wyatt J.; Denton, Alan R.

Crowding can influence the conformations and thus functionality of macromolecules in quasi-two-dimensional environments, such as DNA or proteins confined to a cell membrane. We explore such crowding within a model of polymers as penetrable ellipses, whose shapes are governed by the statistics of a 2D random walk. The principal radii of the polymers fluctuate according to probability distributions of the eigenvalues of the gyration tensor. Within this coarse-grained model, we perform Monte Carlo simulations of mixtures of polymers and hard nanodisks, including trial changes in polymer conformation (shape and orientation). Penetration of polymers by nanodisks is incorporated with a free energy cost predicted by polymer field theory. Over ranges of size ratio and nanodisk density, we analyze the influence of crowding on polymer shape by computing eigenvalue distributions, mean radius of gyration, and mean asphericity of the polymer. We compare results with predictions of free-volume theory and with corresponding results in three dimensions. Our approach may help to interpret recent (and motivate future) experimental studies of biopolymers interacting with cell membranes, with relevance for drug delivery and gene therapy. This work was supported by the National Science Foundation under Grant No. DMR-1106331.

Self-crowding of AMPA receptors in the excitatory postsynaptic density can effectuate anomalous receptor sub-diffusion.

PubMed

Gupta, Rahul

2018-02-01

AMPA receptors (AMPARs) and their associations with auxiliary transmembrane proteins are bulky structures with large steric-exclusion volumes. Hence, self-crowding of AMPARs, depending on the local density, may affect their lateral diffusion in the postsynaptic membrane as well as in the highly crowded postsynaptic density (PSD) at excitatory synapses. Earlier theoretical studies considered only the roles of transmembrane obstacles and the AMPAR-binding submembranous scaffold proteins in shaping receptor diffusion within PSD. Using lattice model of diffusion, the present study investigates the additional impacts of self-crowding on the anomalousity and effective diffusion coefficient (Deff) of AMPAR diffusion. A recursive algorithm for avoiding false self-blocking during diffusion simulation is also proposed. The findings suggest that high density of AMPARs in the obstacle-free membrane itself engenders strongly anomalous diffusion and severe decline in Deff. Adding transmembrane obstacles to the membrane accentuates the anomalousity arising from self-crowding due to the reduced free diffusion space. Contrarily, enhanced AMPAR-scaffold binding, either through increase in binding strength or scaffold density or both, ameliorates the anomalousity resulting from self-crowding. However, binding has differential impacts on Deff depending on the receptor density. Increase in binding causes consistent decrease in Deff for low and moderate receptor density. For high density, binding increases Deff as long as it reduces anomalousity associated with intense self-crowding. Given a sufficiently strong binding condition when diffusion acquires normal behavior, further increase in binding causes decrease in Deff. Supporting earlier experimental observations are mentioned and implications of present findings to the experimental observations on AMPAR diffusion are also drawn.

Bayesian network model of crowd emotion and negative behavior

NASA Astrophysics Data System (ADS)

Ramli, Nurulhuda; Ghani, Noraida Abdul; Hatta, Zulkarnain Ahmad; Hashim, Intan Hashimah Mohd; Sulong, Jasni; Mahudin, Nor Diana Mohd; Rahman, Shukran Abd; Saad, Zarina Mat

2014-12-01

The effects of overcrowding have become a major concern for event organizers. One aspect of this concern has been the idea that overcrowding can enhance the occurrence of serious incidents during events. As one of the largest Muslim religious gathering attended by pilgrims from all over the world, Hajj has become extremely overcrowded with many incidents being reported. The purpose of this study is to analyze the nature of human emotion and negative behavior resulting from overcrowding during Hajj events from data gathered in Malaysian Hajj Experience Survey in 2013. The sample comprised of 147 Malaysian pilgrims (70 males and 77 females). Utilizing a probabilistic model called Bayesian network, this paper models the dependence structure between different emotions and negative behaviors of pilgrims in the crowd. The model included the following variables of emotion: negative, negative comfortable, positive, positive comfortable and positive spiritual and variables of negative behaviors; aggressive and hazardous acts. The study demonstrated that emotions of negative, negative comfortable, positive spiritual and positive emotion have a direct influence on aggressive behavior whereas emotion of negative comfortable, positive spiritual and positive have a direct influence on hazardous acts behavior. The sensitivity analysis showed that a low level of negative and negative comfortable emotions leads to a lower level of aggressive and hazardous behavior. Findings of the study can be further improved to identify the exact cause and risk factors of crowd-related incidents in preventing crowd disasters during the mass gathering events.

Integration agent-based models and GIS as a virtual urban dynamic laboratory

NASA Astrophysics Data System (ADS)

Chen, Peng; Liu, Miaolong

2007-06-01

Based on the Agent-based Model and spatial data model, a tight-coupling integrating method of GIS and Agent-based Model (ABM) is to be discussed in this paper. The use of object-orientation for both spatial data and spatial process models facilitates their integration, which can allow exploration and explanation of spatial-temporal phenomena such as urban dynamic. In order to better understand how tight coupling might proceed and to evaluate the possible functional and efficiency gains from such a tight coupling, the agent-based model and spatial data model are discussed, and then the relationships affecting spatial data model and agent-based process models interaction. After that, a realistic crowd flow simulation experiment is presented. Using some tools provided by general GIS systems and a few specific programming languages, a new software system integrating GIS and MAS as a virtual laboratory applicable for simulating pedestrian flows in a crowd activity centre has been developed successfully. Under the environment supported by the software system, as an applicable case, a dynamic evolution process of the pedestrian's flows (dispersed process for the spectators) in a crowds' activity center - The Shanghai Stadium has been simulated successfully. At the end of the paper, some new research problems have been pointed out for the future.

People detection in crowded scenes using active contour models

NASA Astrophysics Data System (ADS)

Sidla, Oliver

2009-01-01

The detection of pedestrians in real-world scenes is a daunting task, especially in crowded situations. Our experience over the last years has shown that active shape models (ASM) can contribute significantly to a robust pedestrian detection system. The paper starts with an overview of shape model approaches, it then explains our approach which builds on top of Eigenshape models which have been trained using real-world data. These models are placed over candidate regions and matched to image gradients using a scoring function which integrates i) point distribution, ii) local gradient orientations iii) local image gradient strengths. A matching and shape model update process is iteratively applied in order to fit the flexible models to the local image content. The weights of the scoring function have a significant impact on the ASM performance. We analyze different settings of scoring weights for gradient magnitude, relative orientation differences, distance between model and gradient in an experiment which uses real-world data. Although for only one pedestrian model in an image computation time is low, the number of necessary processing cycles which is needed to track many people in crowded scenes can become the bottleneck in a real-time application. We describe the measures which have been taken in order to improve the speed of the ASM implementation and make it real-time capable.

Time-dependent spectral analysis of interactions within groups of walking pedestrians and vertical structural motion using wavelets

NASA Astrophysics Data System (ADS)

Bocian, M.; Brownjohn, J. M. W.; Racic, V.; Hester, D.; Quattrone, A.; Gilbert, L.; Beasley, R.

2018-05-01

A multi-scale and multi-object interaction phenomena can arise when a group of walking pedestrians crosses a structure capable of exhibiting dynamic response. This is because each pedestrian is an autonomous dynamic system capable of displaying intricate behaviour affected by social, psychological, biomechanical and environmental factors, including adaptations to the structural motion. Despite a wealth of mathematical models attempting to describe and simulate coupled crowd-structure system, their applicability can generally be considered uncertain. This can be assigned to a number of assumptions made in their development and the scarcity or unavailability of data suitable for their validation, in particular those associated with pedestrian-pedestrian and pedestrian-structure interaction. To alleviate this problem, data on behaviour of individual pedestrians within groups of six walkers with different spatial arrangements are gathered simultaneously with data on dynamic structural response of a footbridge, from a series of measurements utilising wireless motion monitors. Unlike in previous studies on coordination of pedestrian behaviour, the collected data can serve as a proxy for pedestrian vertical force, which is of critical importance from the point of view of structural stability. A bivariate analysis framework is proposed and applied to these data, encompassing wavelet transform, synchronisation measures based on Shannon entropy and circular statistics. A topological pedestrian map is contrived showing the strength and directionality of between-subjects interactions. It is found that the coordination in pedestrians' vertical force depends on the spatial collocation within a group, but it is generally weak. The relationship between the bridge and pedestrian behaviour is also analysed, revealing stronger propensity for pedestrians to coordinate their force with the structural motion rather than with each other.

Consensus-based Recommendations for Research Priorities Related to Interventions to Safeguard Patient Safety in the Crowded Emergency Department

PubMed Central

Fee, Christopher; Hall, Kendall; Morrison, J. Bradley; Stephens, Robert; Cosby, Karen; Fairbanks, Rollin (Terry) J.; Youngberg, Barbara; Lenehan, Gail; Abualenain, Jameel; O’Connor, Kevin; Wears, Robert

2012-01-01

This article describes the results of the Interventions to Safeguard Safety breakout session of the 2011 Academic Emergency Medicine (AEM) consensus conference entitled “Interventions to Assure Quality in the Crowded Emergency Department.” Using a multistep nominal group technique, experts in emergency department (ED) crowding, patient safety, and systems engineering defined knowledge gaps and priority research questions related to the maintenance of safety in the crowded ED. Consensus was reached for seven research priorities related to interventions to maintain safety in the setting of a crowded ED. Included among these are: 1) How do routine corrective processes and compensating mechanism change during crowding? 2) What metrics should be used to determine ED safety? 3) How can checklists ensure safer care and what factors contribute to their success or failure? 4) What constitutes safe staffing levels / ratios? 5) How can we align emergency medicine (EM)-specific patient safety issues with national patient safety issues? 6) How can we develop metrics and skills to recognize when an ED is getting close to catastrophic overload conditions? and 7) What can EM learn from experts and modeling from fields outside of medicine to develop innovative solutions? These priorities have the potential to inform future clinical and human factors research and extramural funding decisions related to this important topic. PMID:22168192

A natural and readily available crowding agent: NMR studies of proteins in hen egg white.

PubMed

Martorell, Gabriel; Adrover, Miquel; Kelly, Geoff; Temussi, Piero Andrea; Pastore, Annalisa

2011-05-01

In vitro studies of biological macromolecules are usually performed in dilute, buffered solutions containing one or just a few different biological macromolecules. Under these conditions, the interactions among molecules are diffusion limited. On the contrary, in living systems, macromolecules of a given type are surrounded by many others, at very high total concentrations. In the last few years, there has been an increasing effort to study biological macromolecules directly in natural crowded environments, as in intact bacterial cells or by mimicking natural crowding by adding proteins, polysaccharides, or even synthetic polymers. Here, we propose the use of hen egg white (HEW) as a simple natural medium, with all features of the media of crowded cells, that could be used by any researcher without difficulty and inexpensively. We present a study of the stability and dynamics behavior of model proteins in HEW, chosen as a prototypical, readily accessible natural medium that can mimic cytosol. We show that two typical globular proteins, dissolved in HEW, give NMR spectra very similar to those obtained in dilute buffers, although dynamic parameters are clearly affected by the crowded medium. The thermal stability of one of these proteins, measured in a range comprising both heat and cold denaturation, is also similar to that in buffer. Our data open new possibilities to the study of proteins in natural crowded media. Copyright © 2010 Wiley-Liss, Inc.

Combing bacterial turbulence.

NASA Astrophysics Data System (ADS)

Sokolov, Andrey; Nishiguchi, Daiki; Aronson, Igor

Living systems represented by ensembles of motile organisms demonstrate a transition from a chaotic motion to a highly ordered state. Examples of such living systems include suspensions of bacteria, schools of fish, flocks of birds and even crowds of people. In spite of significant differences in interacting mechanisms and motion scales, ordered living systems have many similarities: short-range alignment of organism, turbulent-like motion, emergence of large-scale flows and dynamic vortices. In this work, we rectify a turbulent dynamics in suspensions of swimming bacteria Bacillus subtilis by imposing periodical constraints on bacterial motion. Bacteria, swimming between periodically placed microscopic vertical pillars, may self-organize in a stable lattice of vortices. We demonstrate the emergence of a strong anti-ferromagnetic order of bacterial vortices in a rectangular lattice of pillars. Hydrodynamic interaction between vortices increases the stability of an emerged pattern. The highest stability of vortices in the anti-ferromagnetic lattice and the fastest vortices speed were observed in structures with the periods comparable with a correlation length of bacterial unconstrained motion. A.S and I.A were supported by the US DOE, Office of Basic Energy Sciences, Division of Materials Science And Engineering, under contract No. DE AC02-06CH11357 and D.N was supported by ALPS and JSPS Grant No. 26-9915.

Social identification moderates the effect of crowd density on safety at the Hajj.

PubMed

Alnabulsi, Hani; Drury, John

2014-06-24

Crowd safety is a major concern for those attending and managing mass gatherings, such as the annual Hajj or pilgrimage to Mecca (also called Makkah). One threat to crowd safety at such events is crowd density. However, recent research also suggests that psychological membership of crowds can have positive benefits. We tested the hypothesis that the effect of density on safety might vary depending on whether there is shared social identification in the crowd. We surveyed 1,194 pilgrims at the Holy Mosque, Mecca, during the 2012 Hajj. Analysis of the data showed that the negative effect of crowd density on reported safety was moderated by social identification with the crowd. Whereas low identifiers reported reduced safety with greater crowd density, high identifiers reported increased safety with greater crowd density. Mediation analysis suggested that a reason for these moderation effects was the perception that other crowd members were supportive. Differences in reported safety across national groups (Arab countries and Iran compared with the rest) were also explicable in terms of crowd identification and perceived support. These findings support a social identity account of crowd behavior and offer a novel perspective on crowd safety management.

Social identification moderates the effect of crowd density on safety at the Hajj

PubMed Central

Alnabulsi, Hani; Drury, John

2014-01-01

Crowd safety is a major concern for those attending and managing mass gatherings, such as the annual Hajj or pilgrimage to Mecca (also called Makkah). One threat to crowd safety at such events is crowd density. However, recent research also suggests that psychological membership of crowds can have positive benefits. We tested the hypothesis that the effect of density on safety might vary depending on whether there is shared social identification in the crowd. We surveyed 1,194 pilgrims at the Holy Mosque, Mecca, during the 2012 Hajj. Analysis of the data showed that the negative effect of crowd density on reported safety was moderated by social identification with the crowd. Whereas low identifiers reported reduced safety with greater crowd density, high identifiers reported increased safety with greater crowd density. Mediation analysis suggested that a reason for these moderation effects was the perception that other crowd members were supportive. Differences in reported safety across national groups (Arab countries and Iran compared with the rest) were also explicable in terms of crowd identification and perceived support. These findings support a social identity account of crowd behavior and offer a novel perspective on crowd safety management. PMID:24927593

Crowded growth leads to the spontaneous evolution of semistable coexistence in laboratory yeast populations.

PubMed

Frenkel, Evgeni M; McDonald, Michael J; Van Dyken, J David; Kosheleva, Katya; Lang, Gregory I; Desai, Michael M

2015-09-08

Identifying the mechanisms that create and maintain biodiversity is a central challenge in biology. Stable diversification of microbial populations often requires the evolution of differences in resource utilization. Alternatively, coexistence can be maintained by specialization to exploit spatial heterogeneity in the environment. Here, we report spontaneous diversification maintained by a related but distinct mechanism: crowding avoidance. During experimental evolution of laboratory Saccharomyces cerevisiae populations, we observed the repeated appearance of "adherent" (A) lineages able to grow as a dispersed film, in contrast to their crowded "bottom-dweller" (B) ancestors. These two types stably coexist because dispersal reduces interference competition for nutrients among kin, at the cost of a slower maximum growth rate. This tradeoff causes the frequencies of the two types to oscillate around equilibrium over the course of repeated cycles of growth, crowding, and dispersal. However, further coevolution of the A and B types can perturb and eventually destroy their coexistence over longer time scales. We introduce a simple mathematical model of this "semistable" coexistence, which explains the interplay between ecological and evolutionary dynamics. Because crowded growth generally limits nutrient access in biofilms, the mechanism we report here may be broadly important in maintaining diversity in these natural environments.

Prominent effects and neural correlates of visual crowding in a neurodegenerative disease population.

PubMed

Yong, Keir X X; Shakespeare, Timothy J; Cash, Dave; Henley, Susie M D; Nicholas, Jennifer M; Ridgway, Gerard R; Golden, Hannah L; Warrington, Elizabeth K; Carton, Amelia M; Kaski, Diego; Schott, Jonathan M; Warren, Jason D; Crutch, Sebastian J

2014-12-01

Crowding is a breakdown in the ability to identify objects in clutter, and is a major constraint on object recognition. Crowding particularly impairs object perception in peripheral, amblyopic and possibly developing vision. Here we argue that crowding is also a critical factor limiting object perception in central vision of individuals with neurodegeneration of the occipital cortices. In the current study, individuals with posterior cortical atrophy (n=26), typical Alzheimer's disease (n=17) and healthy control subjects (n=14) completed centrally-presented tests of letter identification under six different flanking conditions (unflanked, and with letter, shape, number, same polarity and reverse polarity flankers) with two different target-flanker spacings (condensed, spaced). Patients with posterior cortical atrophy were significantly less accurate and slower to identify targets in the condensed than spaced condition even when the target letters were surrounded by flankers of a different category. Importantly, this spacing effect was observed for same, but not reverse, polarity flankers. The difference in accuracy between spaced and condensed stimuli was significantly associated with lower grey matter volume in the right collateral sulcus, in a region lying between the fusiform and lingual gyri. Detailed error analysis also revealed that similarity between the error response and the averaged target and flanker stimuli (but not individual target or flanker stimuli) was a significant predictor of error rate, more consistent with averaging than substitution accounts of crowding. Our findings suggest that crowding in posterior cortical atrophy can be regarded as a pre-attentive process that uses averaging to regularize the pathologically noisy representation of letter feature position in central vision. These results also help to clarify the cortical localization of feature integration components of crowding. More broadly, we suggest that posterior cortical atrophy provides a neurodegenerative disease model for exploring the basis of crowding. These data have significant implications for patients with, or who will go on to develop, dementia-related visual impairment, in whom acquired excessive crowding likely contributes to deficits in word, object, face and scene perception. © The Author (2014). Published by Oxford University Press on behalf of the Guarantors of Brain.

Prominent effects and neural correlates of visual crowding in a neurodegenerative disease population

PubMed Central

Shakespeare, Timothy J.; Cash, Dave; Henley, Susie M. D.; Nicholas, Jennifer M.; Ridgway, Gerard R.; Golden, Hannah L.; Warrington, Elizabeth K.; Carton, Amelia M.; Kaski, Diego; Schott, Jonathan M.; Warren, Jason D.; Crutch, Sebastian J.

2014-01-01

Crowding is a breakdown in the ability to identify objects in clutter, and is a major constraint on object recognition. Crowding particularly impairs object perception in peripheral, amblyopic and possibly developing vision. Here we argue that crowding is also a critical factor limiting object perception in central vision of individuals with neurodegeneration of the occipital cortices. In the current study, individuals with posterior cortical atrophy (n = 26), typical Alzheimer’s disease (n = 17) and healthy control subjects (n = 14) completed centrally-presented tests of letter identification under six different flanking conditions (unflanked, and with letter, shape, number, same polarity and reverse polarity flankers) with two different target-flanker spacings (condensed, spaced). Patients with posterior cortical atrophy were significantly less accurate and slower to identify targets in the condensed than spaced condition even when the target letters were surrounded by flankers of a different category. Importantly, this spacing effect was observed for same, but not reverse, polarity flankers. The difference in accuracy between spaced and condensed stimuli was significantly associated with lower grey matter volume in the right collateral sulcus, in a region lying between the fusiform and lingual gyri. Detailed error analysis also revealed that similarity between the error response and the averaged target and flanker stimuli (but not individual target or flanker stimuli) was a significant predictor of error rate, more consistent with averaging than substitution accounts of crowding. Our findings suggest that crowding in posterior cortical atrophy can be regarded as a pre-attentive process that uses averaging to regularize the pathologically noisy representation of letter feature position in central vision. These results also help to clarify the cortical localization of feature integration components of crowding. More broadly, we suggest that posterior cortical atrophy provides a neurodegenerative disease model for exploring the basis of crowding. These data have significant implications for patients with, or who will go on to develop, dementia-related visual impairment, in whom acquired excessive crowding likely contributes to deficits in word, object, face and scene perception. PMID:25351740

Alleviation of mandibular anterior crowding with copper-nickel-titanium vs nickel-titanium wires: a double-blind randomized control trial.

PubMed

Pandis, Nikolaos; Polychronopoulou, Argy; Eliades, Theodore

2009-08-01

The purpose of this study was to investigate the efficiency of copper-nickel-titanium (CuNiTi) vs nickel-titanium (NiTi) archwires in resolving crowding of the anterior mandibular dentition. Sixty patients were included in this single-center, single-operator, double-blind randomized trial. All patients were bonded with the In Ovation-R self-ligating bracket (GAC, Central Islip, NY) with a 0.022-in slot, and the amount of crowding of the mandibular anterior dentition was assessed by using the irregularity index. The patients were randomly allocated into 2 groups of 30 patients, each receiving a 0.016-in CuNiTi 35 degrees C (Ormco, Glendora, Calif) or a 0.016-in NiTi (ModernArch, Wyomissing, Pa) wire. The type of wire selected for each patient was not disclosed to the provider or the patient. The date that each patient received a wire was recorded, and all patients were followed monthly for a maximum of 6 months. Demographic and clinical characteristics between the 2 wire groups were compared with the t test or the chi-square test and the Fisher exact test. Time to resolve crowding was explored with statistical methods for survival analysis, and alignment rate ratios for wire type and crowding level were calculated with Cox proportional hazards multivariate modeling. The type of wire (CuNiTi vs NiTi) had no significant effect on crowding alleviation (129.4 vs 121.4 days; hazard ratio, 1.3; P >0.05). Severe crowding (>5 on the irregularity index) showed a significantly higher probability of crowding alleviation duration relative to dental arches with a score of <5 (138.5 vs 113.1 days; hazard ratio, 2.2; P=0.02). The difference of the loading pattern of wires in laboratory and clinical conditions might effectively eliminate the laboratory-derived advantage of CuNiTi wires.

Self-crowding of AMPA receptors in the excitatory postsynaptic density can effectuate anomalous receptor sub-diffusion

PubMed Central

Gupta, Rahul

2018-01-01

AMPA receptors (AMPARs) and their associations with auxiliary transmembrane proteins are bulky structures with large steric-exclusion volumes. Hence, self-crowding of AMPARs, depending on the local density, may affect their lateral diffusion in the postsynaptic membrane as well as in the highly crowded postsynaptic density (PSD) at excitatory synapses. Earlier theoretical studies considered only the roles of transmembrane obstacles and the AMPAR-binding submembranous scaffold proteins in shaping receptor diffusion within PSD. Using lattice model of diffusion, the present study investigates the additional impacts of self-crowding on the anomalousity and effective diffusion coefficient (Deff) of AMPAR diffusion. A recursive algorithm for avoiding false self-blocking during diffusion simulation is also proposed. The findings suggest that high density of AMPARs in the obstacle-free membrane itself engenders strongly anomalous diffusion and severe decline in Deff. Adding transmembrane obstacles to the membrane accentuates the anomalousity arising from self-crowding due to the reduced free diffusion space. Contrarily, enhanced AMPAR-scaffold binding, either through increase in binding strength or scaffold density or both, ameliorates the anomalousity resulting from self-crowding. However, binding has differential impacts on Deff depending on the receptor density. Increase in binding causes consistent decrease in Deff for low and moderate receptor density. For high density, binding increases Deff as long as it reduces anomalousity associated with intense self-crowding. Given a sufficiently strong binding condition when diffusion acquires normal behavior, further increase in binding causes decrease in Deff. Supporting earlier experimental observations are mentioned and implications of present findings to the experimental observations on AMPAR diffusion are also drawn. PMID:29444074

Structured crowding and its effects on enzyme catalysis.

PubMed

Ma, Buyong; Nussinov, Ruth

2013-01-01

Macromolecular crowding decreases the diffusion rate, shifts the equilibrium of protein-protein and protein-substrate interactions, and changes protein conformational dynamics. Collectively, these effects contribute to enzyme catalysis. Here we describe how crowding may bias the conformational change and dynamics of enzyme populations and in this way affect catalysis. Crowding effects have been studied using artificial crowding agents and in vivo-like environments. These studies revealed a correlation between protein dynamics and function in the crowded environment. We suggest that crowded environments be classified into uniform crowding and structured crowding. Uniform crowding represents random crowding conditions created by synthetic particles with a narrow size distribution. Structured crowding refers to the highly coordinated cellular environment, where proteins and other macromolecules are clustered and organized. In structured crowded environments the perturbation of protein thermal stability may be lower; however, it may still be able to modulate functions effectively and dynamically. Dynamic, allosteric enzymes could be more sensitive to cellular perturbations if their free energy landscape is flatter around the native state; on the other hand, if their free energy landscape is rougher, with high kinetic barriers separating deep minima, they could be more robust. Above all, cells are structured; and this holds both for the cytosol and for the membrane environment. The crowded environment is organized, which limits the search, and the crowders are not necessarily inert. More likely, they too transmit allosteric effects, and as such play important functional roles. Overall, structured cellular crowding may lead to higher enzyme efficiency and specificity.

Internal curvature signal and noise in low- and high-level vision

PubMed Central

Grabowecky, Marcia; Kim, Yee Joon; Suzuki, Satoru

2011-01-01

How does internal processing contribute to visual pattern perception? By modeling visual search performance, we estimated internal signal and noise relevant to perception of curvature, a basic feature important for encoding of three-dimensional surfaces and objects. We used isolated, sparse, crowded, and face contexts to determine how internal curvature signal and noise depended on image crowding, lateral feature interactions, and level of pattern processing. Observers reported the curvature of a briefly flashed segment, which was presented alone (without lateral interaction) or among multiple straight segments (with lateral interaction). Each segment was presented with no context (engaging low-to-intermediate-level curvature processing), embedded within a face context as the mouth (engaging high-level face processing), or embedded within an inverted-scrambled-face context as a control for crowding. Using a simple, biologically plausible model of curvature perception, we estimated internal curvature signal and noise as the mean and standard deviation, respectively, of the Gaussian-distributed population activity of local curvature-tuned channels that best simulated behavioral curvature responses. Internal noise was increased by crowding but not by face context (irrespective of lateral interactions), suggesting prevention of noise accumulation in high-level pattern processing. In contrast, internal curvature signal was unaffected by crowding but modulated by lateral interactions. Lateral interactions (with straight segments) increased curvature signal when no contextual elements were added, but equivalent interactions reduced curvature signal when each segment was presented within a face. These opposing effects of lateral interactions are consistent with the phenomena of local-feature contrast in low-level processing and global-feature averaging in high-level processing. PMID:21209356

Effect of handling, confinement and crowding in HSP70 production in Pachygrapsus marmoratus, a model species for climate change experiments

NASA Astrophysics Data System (ADS)

Vinagre, Catarina; Madeira, Diana; Narciso, Luís; Cabral, Henrique N.; Diniz, Mário S.

2012-08-01

The aim of this study was to investigate the effect of handling, confinement and crowding on HSP70 production in an intertidal crab. HSP70 has been widely used as a biochemical indicator of thermal stress; however studies on the effect of experimental conditions and handling on HSP70 expression are very scarce. The response of marbled crab, Pachygrapsus marmoratus, collected in the Portuguese coast, was investigated through an experiment in captivity, where 42 juveniles (10-19 mm of carapace width) were confined in an experimental container (60 × 42 × 10 cm) and exposed to three treatments: 1) increasing temperatures and periodic handling, 2) only to periodic handling and 3) no handling, for 12 h. The objective of this work was to investigate whether the HSP70 production measured in an increasing temperature experiment is a response to temperature alone or whether manipulation, confinement and crowding during the experiment also increase HSP70 production. Three individuals were sampled after t = 0, t = 4, t = 6, t = 8, t = 10 and t = 12 h, for the quantification of HSP70 production in the hemolymph, in the three trials. It was concluded that while temperature has a significant effect on HSP70 production, periodic handling does not, nor does confinement to the experimental container or crowding. It can thus be concluded that experimental conditions and handling are not parasitic variables in experiments with this species considering increasing temperatures. P. marmoratus can thus be used as a model species in climate warming experiments involving handling, confinement and crowding.

Effect of form of obstacle on speed of crowd evacuation

NASA Astrophysics Data System (ADS)

Yano, Ryosuke

2018-03-01

This paper investigates the effect of the form of an obstacle on the time that a crowd takes to evacuate a room, using a toy model. Pedestrians are modeled as active soft matter moving toward a point with intended velocities. An obstacle is placed in front of the exit, and it has one of four shapes: a cylindrical column, a triangular prism, a quadratic prism, or a diamond prism. Numerical results indicate that the evacuation-completion time depends on the shape of the obstacle. Obstacles with a circular cylinder (C.C.) shape yield the shortest evacuation-completion time in the proposed model.

Unrecognized astrometric confusion in the Galactic Centre

NASA Astrophysics Data System (ADS)

Plewa, P. M.; Sari, R.

2018-06-01

The Galactic Centre is a crowded stellar field and frequent unrecognized events of source confusion, which involve undetected faint stars, are expected to introduce astrometric noise on a sub-mas level. This confusion noise is the main non-instrumental effect limiting the astrometric accuracy and precision of current near-infrared imaging observations and the long-term monitoring of individual stellar orbits in the vicinity of the central supermassive black hole. We self-consistently simulate the motions of the known and the yet unidentified stars to characterize this noise component and show that a likely consequence of source confusion is a bias in estimates of the stellar orbital elements, as well as the inferred mass and distance of the black hole, in particular if stars are being observed at small projected separations from it, such as the star S2 during pericentre passage. Furthermore, we investigate modelling the effect of source confusion as an additional noise component that is time-correlated, demonstrating a need for improved noise models to obtain trustworthy estimates of the parameters of interest (and their uncertainties) in future astrometric studies.

Crowd Behavior Algorithm Development for COMBAT XXI

DTIC Science & Technology

2017-05-30

This study cost the Department of Defense approximately $176,000 expended by TRAC in Fiscal Years 15-17. Prepared on 30 May 2017 TRAC Project Code...modeling to study impacts of military operations in urban terrain. Impacts of crowds on military operations can include those lethality, mobility...de- pendent on the particular socio-economic, political, and cultural environment of the region being studied in the scenario. Our research has found

Risk of large-scale evacuation based on the effectiveness of rescue strategies under different crowd densities.

PubMed

Wang, Jinghong; Lo, Siuming; Wang, Qingsong; Sun, Jinhua; Mu, Honglin

2013-08-01

Crowd density is a key factor that influences the moving characteristics of a large group of people during a large-scale evacuation. In this article, the macro features of crowd flow and subsequent rescue strategies were considered, and a series of characteristic crowd densities that affect large-scale people movement, as well as the maximum bearing density when the crowd is extremely congested, were analyzed. On the basis of characteristic crowd densities, the queuing theory was applied to simulate crowd movement. Accordingly, the moving characteristics of the crowd and the effects of typical crowd density-which is viewed as the representation of the crowd's arrival intensity in front of the evacuation passageways-on rescue strategies was studied. Furthermore, a "risk axle of crowd density" is proposed to determine the efficiency of rescue strategies in a large-scale evacuation, i.e., whether the rescue strategies are able to effectively maintain or improve evacuation efficiency. Finally, through some rational hypotheses for the value of evacuation risk, a three-dimensional distribution of the evacuation risk is established to illustrate the risk axle of crowd density. This work aims to make some macro, but original, analysis on the risk of large-scale crowd evacuation from the perspective of the efficiency of rescue strategies. © 2012 Society for Risk Analysis.

Peer Crowd Identification and Adolescent Health Behaviors: Results From a Statewide Representative Study.

PubMed

Jordan, Jeffrey W; Stalgaitis, Carolyn A; Charles, John; Madden, Patrick A; Radhakrishnan, Anjana G; Saggese, Daniel

2018-02-01

Peer crowds are macro-level subcultures that share similarities across geographic areas. Over the past decade, dozens of studies have explored the association between adolescent peer crowds and risk behaviors, and how they can inform public health efforts. However, despite the interest, researchers have not yet reported on crowd size and risk levels from a representative sample, making it difficult for practitioners to apply peer crowd science to interventions. The current study reports findings from the first statewide representative sample of adolescent peer crowd identification and health behaviors. Weighted data were analyzed from the 2015 Virginia Youth Survey of Health Behaviors ( n = 4,367). Peer crowds were measured via the I-Base Survey™, a photo-based peer crowd survey instrument. Frequencies and confidence intervals of select behaviors including tobacco use, substance use, nutrition, physical activity, and violence were examined to identify high- and low-risk crowds. Logistic regression was used to calculate adjusted odds ratios for each crowd and behavior. Risky behaviors clustered in two peer crowds. Hip Hop crowd identification was associated with substance use, violence, and some depression and suicidal behaviors. Alternative crowd identification was associated with increased risk for some substance use behaviors, depression and suicide, bullying, physical inactivity, and obesity. Mainstream and, to a lesser extent, Popular, identities were associated with decreased risk for most behaviors. Findings from the first representative study of peer crowds and adolescent behavior identify two high-risk groups, providing critical insights for practitioners seeking to maximize public health interventions by targeting high-risk crowds.

Assessing product image quality for online shopping

NASA Astrophysics Data System (ADS)

Goswami, Anjan; Chung, Sung H.; Chittar, Naren; Islam, Atiq

2012-01-01

Assessing product-image quality is important in the context of online shopping. A high quality image that conveys more information about a product can boost the buyer's confidence and can get more attention. However, the notion of image quality for product-images is not the same as that in other domains. The perception of quality of product-images depends not only on various photographic quality features but also on various high level features such as clarity of the foreground or goodness of the background etc. In this paper, we define a notion of product-image quality based on various such features. We conduct a crowd-sourced experiment to collect user judgments on thousands of eBay's images. We formulate a multi-class classification problem for modeling image quality by classifying images into good, fair and poor quality based on the guided perceptual notions from the judges. We also conduct experiments with regression using average crowd-sourced human judgments as target. We compute a pseudo-regression score with expected average of predicted classes and also compute a score from the regression technique. We design many experiments with various sampling and voting schemes with crowd-sourced data and construct various experimental image quality models. Most of our models have reasonable accuracies (greater or equal to 70%) on test data set. We observe that our computed image quality score has a high (0.66) rank correlation with average votes from the crowd sourced human judgments.

High fidelity simulations of infrared imagery with animated characters

NASA Astrophysics Data System (ADS)

Näsström, F.; Persson, A.; Bergström, D.; Berggren, J.; Hedström, J.; Allvar, J.; Karlsson, M.

2012-06-01

High fidelity simulations of IR signatures and imagery tend to be slow and do not have effective support for animation of characters. Simplified rendering methods based on computer graphics methods can be used to overcome these limitations. This paper presents a method to combine these tools and produce simulated high fidelity thermal IR data of animated people in terrain. Infrared signatures for human characters have been calculated using RadThermIR. To handle multiple character models, these calculations use a simplified material model for the anatomy and clothing. Weather and temperature conditions match the IR-texture used in the terrain model. The calculated signatures are applied to the animated 3D characters that, together with the terrain model, are used to produce high fidelity IR imagery of people or crowds. For high level animation control and crowd simulations, HLAS (High Level Animation System) has been developed. There are tools available to create and visualize skeleton based animations, but tools that allow control of the animated characters on a higher level, e.g. for crowd simulation, are usually expensive and closed source. We need the flexibility of HLAS to add animation into an HLA enabled sensor system simulation framework.

Statistical analysis of passenger-crowding in bus transport network of Harbin

NASA Astrophysics Data System (ADS)

Hu, Baoyu; Feng, Shumin; Li, Jinyang; Zhao, Hu

2018-01-01

Passenger flow data is indispensable but rare in the study of public transport networks. In this study, we focus on the passenger-crowding characteristics of the bus transport network of Harbin (BTN-H) based on passenger flow investigation. The three frequency histograms for all the uplinks and downlinks in Harbin are presented, including passengers on the bus at each section, crowding coefficients, and position parameters of crowded sections. The differences in crowding position are analyzed on each route. The distributions of degree and crowding degree (in directed space L) follow an exponential law. The new finding indicates that there are many stations with few crowded sections and a few stations with many crowded sections. The distributions of path length and crowded length (in directed space P) are presented based on the minimum transfer times, and it is found that they can be fitted by a composite Gaussian function and a Gaussian function, respectively. The stations and paths can be divided into three crowd levels. We conclude that BTN-H is crowded from a network-based perspective.

Collective Motion in Behaviorally Heterogeneous Systems

NASA Astrophysics Data System (ADS)

Copenhagen, Katherine

Collective motion is a widespread phenomenon in nature where individuals actively propel themselves, gather together and move as a group. Some examples of collective motion are bird flocks, fish schools, bacteria swarms, cell clusters, and crowds of people. Many models seek to understand the effects of activity in collective systems including things such as environmental disorder, density, and interaction details primarily at infinite size limits and with uniform populations. In this dissertation I investigate the effects of finite sizes and behavioral heterogeneity as it exists in nature. Behavioral heterogeneity can originate from several different sources. Mixed populations of individuals can have inherently different behaviors such as mutant bacteria, injured fish, or agents that prefer individualistic behavior over coordinated motion. Alternatively, agents may modify their own behavior based on some local environmental dependency, such as local substrate, or density. In cases such as mutant cheaters in bacteria or malfunctioning drones in swarms, mixed populations of behaviorally heterogeneous agents can be modelled as arising in the form of aligning and non-aligning agents. When this kind of heterogeneity is introduced, there is a critical carrying capacity of non-aligners above which the system is unable to form a cohesive ordered group. However, if the cohesion of the group is relaxed to allow for fracture, the system will actively sort out non-aligning agents the system will exist at a critical non-aligner fraction. A similar heterogeneity could result in a mixture of high and low noise individuals. In this case there is also a critical carry capacity beyond which the system is unable to reach an ordered state, however the nature of this transition depends on the model details. Agents which are part of an ordered collective may vary their behavior as the group changes environments such as a flock of birds flying into a cloud. Using a unique model of a flock where the group behaves as a rigid disk reveals interesting behaviors as the system crosses a boundary between interfaces. The collective rotates and reorients or becomes stuck on the boundary as it crosses. I also investigate the effects of variable behavior depending on local density, and find that a frustration driven transient rotational phase arises in clusters where agents with low local density move faster than those with high local density as in cell clusters. All together I have shown that behavioral heterogeneity in collective motion can lead to unique phases and behaviors that are not seen in their homogeneous counterparts.

Gravity dependent processes and intracellular motion

NASA Technical Reports Server (NTRS)

Todd, Paul

1991-01-01

Most organelles large enough to sediment or to undergo isothermal settling within eukaryotic cells are held in position by one or more components of the cytoskeleton. The interior of eukaryotic cells is considered to be very crowded, and the evaluation of natural-convective processes is very difficult. In a most simple view, the cell may be considered as consisting of four immiscible phases among which solutes are exchanged causing steep concentration gradients and thermodynamic conditions far from equilibrium. Extracellular gravity-related forces may include natural convection due to solute gradients external to single cells or the work performed by swimming, ciliated, or elongating cells.

A structural study of [CpM(CO)3H] (M = Cr, Mo and W) by single-crystal X-ray diffraction and DFT calculations: sterically crowded yet surprisingly flexible molecules.

PubMed

Burchell, Richard P L; Sirsch, Peter; Decken, Andreas; McGrady, G Sean

2009-08-14

The single-crystal X-ray structures of the complexes [CpCr(CO)3H] 1, [CpMo(CO)3H] 2 and [CpW(CO)3H] 3 are reported. The results indicate that 1 adopts a structure close to a distorted three-legged piano stool geometry, whereas a conventional four-legged piano stool arrangement is observed for 2 and 3. Further insight into the equilibrium geometries and potential energy surfaces of all three complexes was obtained by DFT calculations. These show that in the gas phase complex 1 also prefers a geometry close to a four-legged piano stool in line with its heavier congeners, and implying strong packing forces at work for 1 in the solid state. Comparison with their isolelectronic group 7 tricarbonyl counterparts [CpM(CO)3] (M = Mn 4 and Re 5) illustrates that 1, 2 and 3 are sterically crowded complexes. However, a surprisingly soft bending potential is evident for the M-H moiety, whose order (1 approximately = 2 < 3) correlates with the M-H bond strength rather than with the degree of congestion at the metal centre, indicating electronic rather than steric control of the potential. The calculations also reveal cooperative motions of the hydride and carbonyl ligands in the M(CO)3H unit, which allow the M-H moiety to move freely, in spite of the closeness of the four basal ligands, helping to explain the surprising flexibility of the crowded coordination sphere observed for this family of high CN complexes.

Extracting foreground ensemble features to detect abnormal crowd behavior in intelligent video-surveillance systems

NASA Astrophysics Data System (ADS)

Chan, Yi-Tung; Wang, Shuenn-Jyi; Tsai, Chung-Hsien

2017-09-01

Public safety is a matter of national security and people's livelihoods. In recent years, intelligent video-surveillance systems have become important active-protection systems. A surveillance system that provides early detection and threat assessment could protect people from crowd-related disasters and ensure public safety. Image processing is commonly used to extract features, e.g., people, from a surveillance video. However, little research has been conducted on the relationship between foreground detection and feature extraction. Most current video-surveillance research has been developed for restricted environments, in which the extracted features are limited by having information from a single foreground; they do not effectively represent the diversity of crowd behavior. This paper presents a general framework based on extracting ensemble features from the foreground of a surveillance video to analyze a crowd. The proposed method can flexibly integrate different foreground-detection technologies to adapt to various monitored environments. Furthermore, the extractable representative features depend on the heterogeneous foreground data. Finally, a classification algorithm is applied to these features to automatically model crowd behavior and distinguish an abnormal event from normal patterns. The experimental results demonstrate that the proposed method's performance is both comparable to that of state-of-the-art methods and satisfies the requirements of real-time applications.

Macromolecular Crowding Studies of Amino Acids Using NMR Diffusion Measurements and Molecular Dynamics Simulations

NASA Astrophysics Data System (ADS)

Virk, Amninder; Stait-Gardner, Timothy; Willis, Scott; Torres, Allan; Price, William

2015-02-01

Molecular crowding occurs when the total concentration of macromolecular species in a solution is so high that a considerable proportion of the volume is physically occupied and therefore not accessible to other molecules. This results in significant changes in the solution properties of the molecules in such systems. Macromolecular crowding is ubiquitous in biological systems due to the generally high intracellular protein concentrations. The major hindrance to understanding crowding is the lack of direct comparison of experimental data with theoretical or simulated data. Self-diffusion is sensitive to changes in the molecular weight and shape of the diffusing species, and the available diffusion space (i.e., diffusive obstruction). Consequently, diffusion measurements are a direct means for probing crowded systems including the self-association of molecules. In this work, nuclear magnetic resonance measurements of the self-diffusion of four amino acids (glycine, alanine, valine and phenylalanine) up to their solubility limit in water were compared directly with molecular dynamics simulations. The experimental data were then analyzed using various models of aggregation and obstruction. Both experimental and simulated data revealed that the diffusion of both water and the amino acids were sensitive to the amino acid concentration. The direct comparison of the simulated and experimental data afforded greater insights into the aggregation and obstruction properties of each amino acid.

A hybrid model for traffic flow and crowd dynamics with random individual properties.

PubMed

Schleper, Veronika

2015-04-01

Based on an established mathematical model for the behavior of large crowds, a new model is derived that is able to take into account the statistical variation of individual maximum walking speeds. The same model is shown to be valid also in traffic flow situations, where for instance the statistical variation of preferred maximum speeds can be considered. The model involves explicit bounds on the state variables, such that a special Riemann solver is derived that is proved to respect the state constraints. Some care is devoted to a valid construction of random initial data, necessary for the use of the new model. The article also includes a numerical method that is shown to respect the bounds on the state variables and illustrative numerical examples, explaining the properties of the new model in comparison with established models.

Multiple Level Crowding: Crowding at the Object Parts Level and at the Object Configural level.

PubMed

Kimchi, Ruth; Pirkner, Yossef

2015-01-01

In crowding, identification of a peripheral target in the presence of nearby flankers is worse than when the target appears alone. Prevailing theories hold that crowding occurs because of integration or "pooling" of low-level features at a single, relatively early stage of visual processing. Recent studies suggest that crowding can occur also between high-level object representations. The most relevant findings come from studies with faces and may be specific to faces. We examined whether crowding can occur at the object configural level in addition to part-level crowding, using nonface objects. Target (a disconnected square or diamond made of four elements) identification was measured at varying eccentricities. The flankers were similar either to the target parts or to the target configuration. The results showed crowding in both cases: Flankers interfered with target identification such that identification accuracy decreased with an increase in eccentricity, and no interference was observed at the fovea. Crowding by object parts, however, was weaker and had smaller spatial extent than crowding by object configurations; we related this finding to the relationship between crowding and perceptual organization. These results provide strong evidence that crowding occurs not only between object parts but also between configural representations of objects. © The Author(s) 2015.

Third molar impaction and agenesis: influence on anterior crowding.

PubMed

Esan, Temitope; Schepartz, Lynne A

2017-02-01

Background Third molar influence on anterior crowding is controversial, but they are assumed to play a major role in compromising dental arch space. Aim To evaluate the relationship among impaction, agenesis and crowding in black South African males. Subjects and method Mandibles and maxillae of 535 black South African males in the Raymond A. Dart Collection of Human Skeletons, University of the Witwatersrand were examined for anterior crowding and third molar agenesis and impaction. Dental crowding was determined using Little's irregularity index. Results Individuals with impaction showed more moderate-to-extreme crowding than those with agenesis. Bilateral third molar presence was more frequently associated with ideal-to-minimal crowding. Weak positive but significant correlations between crowding and impaction were found (mandible, ρ = 0.154, p = 0.000; maxilla ρ = 0.130, p = 0.000). The direction was the opposite for bilateral presence of molars (mandible, ρ = -0.135, p = 0.02; maxilla, ρ = -0.111, p = 0.010). Odds of mandibular crowding were greatest in individuals with impaction (OR = 3.22, CI = 1.716-6.05, p < 0.001). Maxillary results were similar. Conclusion Third molar impaction plays a role in anterior crowding. Third molar presence was not associated with anterior crowding, while agenesis did not explain absence of crowding.

Lessons from Fraxinus, a crowd-sourced citizen science game in genomics

PubMed Central

Rallapalli, Ghanasyam; Saunders, Diane GO; Yoshida, Kentaro; Edwards, Anne; Lugo, Carlos A; Collin, Steve; Clavijo, Bernardo; Corpas, Manuel; Swarbreck, David; Clark, Matthew; Downie, J Allan; Kamoun, Sophien

2015-01-01

In 2013, in response to an epidemic of ash dieback disease in England the previous year, we launched a Facebook-based game called Fraxinus to enable non-scientists to contribute to genomics studies of the pathogen that causes the disease and the ash trees that are devastated by it. Over a period of 51 weeks players were able to match computational alignments of genetic sequences in 78% of cases, and to improve them in 15% of cases. We also found that most players were only transiently interested in the game, and that the majority of the work done was performed by a small group of dedicated players. Based on our experiences we have built a linear model for the length of time that contributors are likely to donate to a crowd-sourced citizen science project. This model could serve a guide for the design and implementation of future crowd-sourced citizen science initiatives. DOI: http://dx.doi.org/10.7554/eLife.07460.001 PMID:26219214

Implications of privacy needs and interpersonal distancing mechanisms for space station design

NASA Technical Reports Server (NTRS)

Harrison, A. A.; Sommer, R.; Struthers, N.; Hoyt, K.

1985-01-01

Privacy needs, or the need of people to regulate their degree of contact with one another, and interpersonal distancing mechanisms, which serve to satisfy these needs, are common in all cultures. Isolation, confinement, and other conditions accociated with space flight may at once accentuate privacy needs and limit the availability of certain common interpersonal contact. Loneliness occurs when people have less contact with one another than they desire. Crowding occurs when people have more contact with one another than they desire. Crowding, which is considered the greater threat to members of isolated and confined groups, can contribute to stress, a low quality of life, and poor performance. Drawing on the general literature on privacy, personal space, and interpersonal distancing, and on specialized literature on life aboard spacecraft and in spacecraft-analogous environments, a quantitative model for understanding privacy, interpersonal distancing, loneliness, and crowding was developed and the practical implications of this model for space station design were traced.

Look into Crowds.

ERIC Educational Resources Information Center

Christian Education Movement, London (England).

This booklet is designed to help British teachers introduce concepts of crowds to young students. Elementary school students will better understand issues of crowd behavior such as rural to urban migration and crowding in urban areas if they realize that all crowds are composed of individual human beings. Teachers can help students become familiar…

Effects of Crowding in Prisons.

ERIC Educational Resources Information Center

Paulus, Paul B.; And Others

Research on crowding in prisons is reviewed. Studies have shown that crowding in prisons can increase blood pressure, palmar sweat, illness complaints, and aggression. The number of people per housing unit appears to be more important than space per person. Tolerance for crowding was found to decrease with the experience of crowding. Research on…

Adolescent peer crowds and patterns of belief in the boundaries of personal authority.

PubMed

Daddis, Christopher

2010-10-01

Patterns of authority beliefs were examined among peer crowds in 598 middle school (M=12.97 years), early high school (M=15.10 years), and late high school adolescents (M=18.25 years). Participants reported beliefs regarding the boundaries of personal authority across personal, prudential, conventional, moral, and multifaceted issues. As expected, analyses revealed persistent differences in belief patterns among crowds within each age group. Tough and Alternative crowds asserted personal authority across all issues, while Prep and Outcast crowds endorsed parental authority. Jock, Hip Hop, and Normal crowds presented with shared-control patterns, but each crowd ceded and asserted authority over different issues. Discussion focused on crowds' roles in the development of group differences in the boundaries of personal authority.

Contemporary understanding of riots: Classical crowd psychology, ideology and the social identity approach.

PubMed

Stott, Clifford; Drury, John

2016-04-01

This article explores the origins and ideology of classical crowd psychology, a body of theory reflected in contemporary popularised understandings such as of the 2011 English 'riots'. This article argues that during the nineteenth century, the crowd came to symbolise a fear of 'mass society' and that 'classical' crowd psychology was a product of these fears. Classical crowd psychology pathologised, reified and decontextualised the crowd, offering the ruling elites a perceived opportunity to control it. We contend that classical theory misrepresents crowd psychology and survives in contemporary understanding because it is ideological. We conclude by discussing how classical theory has been supplanted in academic contexts by an identity-based crowd psychology that restores the meaning to crowd action, replaces it in its social context and in so doing transforms theoretical understanding of 'riots' and the nature of the self. © The Author(s) 2016.

Differential hemispheric and visual stream contributions to ensemble coding of crowd emotion

PubMed Central

Im, Hee Yeon; Albohn, Daniel N.; Steiner, Troy G.; Cushing, Cody A.; Adams, Reginald B.; Kveraga, Kestutis

2017-01-01

In crowds, where scrutinizing individual facial expressions is inefficient, humans can make snap judgments about the prevailing mood by reading “crowd emotion”. We investigated how the brain accomplishes this feat in a set of behavioral and fMRI studies. Participants were asked to either avoid or approach one of two crowds of faces presented in the left and right visual hemifields. Perception of crowd emotion was improved when crowd stimuli contained goal-congruent cues and was highly lateralized to the right hemisphere. The dorsal visual stream was preferentially activated in crowd emotion processing, with activity in the intraparietal sulcus and superior frontal gyrus predicting perceptual accuracy for crowd emotion perception, whereas activity in the fusiform cortex in the ventral stream predicted better perception of individual facial expressions. Our findings thus reveal significant behavioral differences and differential involvement of the hemispheres and the major visual streams in reading crowd versus individual face expressions. PMID:29226255

Factors influencing experience in crowds - The participant perspective.

PubMed

Filingeri, Victoria; Eason, Ken; Waterson, Patrick; Haslam, Roger

2017-03-01

Humans encounter crowd situations on a daily basis, resulting in both negative and positive experiences. Understanding how to optimise the participant experience of crowds is important. In the study presented in this paper, 5 focus groups were conducted (35 participants, age range: 21-71 years) and 55 crowd situations observed (e.g. transport hubs, sport events, retail situations). Influences on participant experience in crowds identified by the focus groups and observations included: physical design of crowd space and facilities (layout, queuing strategies), crowd movement (monitoring capacity, pedestrian flow), communication and information (signage, wayfinding), comfort and welfare (provision of facilities, environmental comfort), and public order. It was found that important aspects affecting participant experience are often not considered systematically in the planning of events or crowd situations. The findings point to human factors aspects of crowds being overlooked, with the experiences of participants often poor. Copyright © 2016. Published by Elsevier Ltd.

De-Trending K2 Exoplanet Targets for High Spacecraft Motion

NASA Astrophysics Data System (ADS)

Saunders, Nicholas; Luger, Rodrigo; Barnes, Rory

2018-01-01

After the failure of two reaction wheels, the Kepler space telescope lost its fine pointing ability and entered a new phase of observation, K2. Targets observed by K2 have high motion relative to the detector and K2 light curves have higher noise than Kepler observations. Despite the increased noise, systematics removal pipelines such as K2SFF and EVEREST have enabled continued high-precision transiting planet science with the telescope, resulting in the detection of hundreds of new exoplanets. However, as the spacecraft begins to run out of fuel, sputtering will drive large and random variations in pointing that can prevent detection of exoplanets during the remaining 5 campaigns. In general, higher motion will spread the stellar point spread function (PSF) across more pixels during a campaign, which increases the number of degrees of freedom in the noise component and significantly reduces the de-trending power of traditional systematics removal methods. We use a model of the Kepler CCD combined with pixel-level information of a large number of stars across the detector to improve the performance of the EVEREST pipeline at high motion. We also consider the problem of increased crowding for static apertures in the high-motion regime and develop pixel response function (PRF)-fitting techniques to mitigate contamination and maximize the de-trending power. We assess the performance of our code by simulating sputtering events and assessing exoplanet detection efficiency with transit injection/recovery tests. We find that targets with roll amplitudes of up to 8 pixels, approximately 15 times K2 roll, can be de-trended within 2 to 3 factors of current K2 photometric precision for stars up to 14th magnitude. Achieved recovery precision allows detection of small planets around 11th and 12th magnitude stars. These methods can be applied to the light curves of K2 targets for existing and future campaigns to ensure that precision exoplanet science can still be performed despite increased motion. We further discuss how these methods can be applied to upcoming space telescope missions, such as the Transiting Exoplanet Survey Satellite (TESS), to improve future detection and characterization of exoplanet candidates.

Advancing the citizen scientist's contributions to documenting and understanding natural hazards: a proof of concept for linking crowdsourced and remotely sensed data on landslide hazards in El Salvador

NASA Astrophysics Data System (ADS)

Anderson, E. R.; Griffin, R.; Markert, K. N.

2017-12-01

Scientists, practitioners, policymakers, and citizen groups, share a role in ensuring "that all sectors have access to, understand and can use scientific information for better informed decision-making" (Sendai Framework 2015-2030). When it comes to understanding hazards and exposure, inventories on disaster events are often limited. Thus, there are many opportunities for citizen scientists to engage in improving the collective understanding—and ultimately reduction—of disaster risk. Landslides are very difficult to forecast on spatial and temporal scales meaningful for early warning and evacuation. Heuristic hazard mapping methods are very common in regional hazard zonation and rely on expert knowledge of previous events and local conditions, but they often lack a temporal component. As new data analysis packages are becoming more open and accessible, probabilistic approaches that consider high resolution spatial and temporal dimensions are becoming more common, but this is only possible when rich inventories of landslide events exist. The work presented offers a proof of concept on incorporating crowd-sourced data to improve landslide hazard model performance. Starting with a national inventory of 90 catalogued landslides in El Salvador for a study period of 1998 to 2011, we simulate the addition of over 600 additional crowd-sourced landslide events that would have been identified through human interpretation of high resolution imagery in the Google Earth time slider feature. There is a noticeable improvement in performance statistics between static heuristic hazard models and probabilistic models that incorporate the events identified by the "crowd." Such a dynamic incorporation of crowd-sourced data on hazard events is not so far-fetched. Given the engagement of "local observers" in El Salvador who augment in situ hydro-meteorological measurements, the growing access to Earth observation data to the lay person, and immense interest behind connecting citizen scientists to remote sensing data through hackathons such as the NASA Space Apps Challenges, we envision a much more dynamic, collective understanding of landslide hazards. Here we present a better scenario of what we could have known had data from the crowd been incorporated into probabilistic hazard models on a regular basis.

Introduction

NASA Astrophysics Data System (ADS)

Flomenbom, Ophir; Castañeda-Priego, Ramón; Peeters, François

2014-11-01

In this document, we present the Special Issue's projects; these include reviews and articles about mathematical solutions and formulations of single-file dynamics (SFD), yet also its computational modeling, experimental evidence, and value in explaining real life occurrences. In particular, we introduce projects focusing on electron dynamics on liquid helium in channels with changing width, on the zig-zag configuration in files with longitudinal movement, on expanding files, on both heterogeneous and slow files, on files with external forces, and on the importance of the interaction potential shape on the particle dynamics along the file. Applications of SFD are of intrinsic value in life sciences, biophysics, physics, and materials science, since they can explain a large diversity of many-body systems, e.g., biological channels, biological motors, membranes, crowding, electron motion in proteins, etc. These systems are explained in all the projects that participate in this topical issue. This Special Issue can therefore intrigue, inspire and advance scientifically young people, yet also those scientists that actively work in this field.

Order and disorder in traffic and self-driven many-particle systems

NASA Astrophysics Data System (ADS)

Helbing, Dirk

2002-07-01

During the last decade, physicists have identified various spatio-temporal patterns of motion in vehicle and pedestrian traffic. Moreover, by applying and extending methods from statistical physics and non-linear dynamics, these have been successfully explained by means of self-driven many-particle models. Some of the questions now understood are the following: Why are vehicles sometimes stopped by so-called "phantom traffic jams," although they all like to drive fast? What are the mechanisms behind stop-and-go traffic? Why are there several different kinds of congestion, and how are they related? Why do most traffic jams occur considerably before the road capacity is reached? Can a temporary reduction of the traffic volume cause a lasting traffic jam? What is the origin of fluctuations in traffic systems and which consequences do they have? Why do pedestrians moving in opposite directions normally organize in lanes, while nervous crowds are "freezing by heating?" Why do panicking pedestrians produce dangerous deadlocks?

Physicochemical code for quinary protein interactions in Escherichia coli

PubMed Central

Mu, Xin; Choi, Seongil; Lang, Lisa; Mowray, David; Danielsson, Jens; Oliveberg, Mikael

2017-01-01

How proteins sense and navigate the cellular interior to find their functional partners remains poorly understood. An intriguing aspect of this search is that it relies on diffusive encounters with the crowded cellular background, made up of protein surfaces that are largely nonconserved. The question is then if/how this protein search is amenable to selection and biological control. To shed light on this issue, we examined the motions of three evolutionary divergent proteins in the Escherichia coli cytoplasm by in-cell NMR. The results show that the diffusive in-cell motions, after all, follow simplistic physical−chemical rules: The proteins reveal a common dependence on (i) net charge density, (ii) surface hydrophobicity, and (iii) the electric dipole moment. The bacterial protein is here biased to move relatively freely in the bacterial interior, whereas the human counterparts more easily stick. Even so, the in-cell motions respond predictably to surface mutation, allowing us to tune and intermix the protein’s behavior at will. The findings show how evolution can swiftly optimize the diffuse background of protein encounter complexes by just single-point mutations, and provide a rational framework for adjusting the cytoplasmic motions of individual proteins, e.g., for rescuing poor in-cell NMR signals and for optimizing protein therapeutics. PMID:28536196

Incisor malalignment and the risk of periodontal disease progression.

PubMed

Alsulaiman, Ahmed A; Kaye, Elizabeth; Jones, Judith; Cabral, Howard; Leone, Cataldo; Will, Leslie; Garcia, Raul

2018-04-01

The objective of this study was to investigate the association between incisor crowding, irregularity, and periodontal disease progression in the anterior teeth. Data collected over 35 years from men enrolled in the Veterans Affairs Dental Longitudinal Study included information concerning pocket depth and alveolar bone loss. Plaster casts of the maxillary (n = 400) and mandibular (n = 408) arches were available for baseline measurements. Periodontal disease in the anterior teeth was defined as per arch sum of pathologic pocket depth and sum of teeth with any alveolar bone loss in the anterior sextants. Incisor malalignment status was defined by the anterior tooth size-arch length discrepancy index and Little's Irregularity Index. Adjusted mixed effects linear models computed the beta (β) estimates and 95% confidence intervals (95% CI) of the amounts of change in periodontal disease outcomes by the level of malalignment. In the anterior maxillary arch, crowding and spacing were significantly associated with an increased per-arch sum of pathologic pocket depth (β, 0.70 mm; 95% CI, 0.20-1.21, and β, 0.49 mm; 95% CI, 0.06-0.91, respectively). In the anterior mandibular arch, incisor crowding and irregularity were significantly associated with an increased per-arch sum of pathologic pocket depth (mild crowding: β, 0.47 mm; 95% CI, 0.01-0.93; severe irregularity: β, 0.94 mm; 95% CI, 0.50-1.38), and the sum number of teeth with alveolar bone loss (mild and moderate-to-severe crowding: β, 0.45 teeth; 95% CI, 0.08-0.82; and β, 0.45 teeth; 95% CI, 0.13-0.83, respectively; moderate irregularity: β, 0.34 teeth; 95% CI, 0.06-0.62). Certain incisor malalignment traits (ie, maxillary incisor crowding, maxillary incisor spacing, mandibular incisor mild crowding, mandibular incisor moderate-to-severe crowding, mandibular incisor moderate irregularity, and mandibular incisor severe irregularity) are associated with significant periodontal disease progression. Copyright © 2017 American Association of Orthodontists. Published by Elsevier Inc. All rights reserved.

The KIT Motion-Language Dataset.

PubMed

Plappert, Matthias; Mandery, Christian; Asfour, Tamim

2016-12-01

Linking human motion and natural language is of great interest for the generation of semantic representations of human activities as well as for the generation of robot activities based on natural language input. However, although there have been years of research in this area, no standardized and openly available data set exists to support the development and evaluation of such systems. We, therefore, propose the Karlsruhe Institute of Technology (KIT) Motion-Language Dataset, which is large, open, and extensible. We aggregate data from multiple motion capture databases and include them in our data set using a unified representation that is independent of the capture system or marker set, making it easy to work with the data regardless of its origin. To obtain motion annotations in natural language, we apply a crowd-sourcing approach and a web-based tool that was specifically build for this purpose, the Motion Annotation Tool. We thoroughly document the annotation process itself and discuss gamification methods that we used to keep annotators motivated. We further propose a novel method, perplexity-based selection, which systematically selects motions for further annotation that are either under-represented in our data set or that have erroneous annotations. We show that our method mitigates the two aforementioned problems and ensures a systematic annotation process. We provide an in-depth analysis of the structure and contents of our resulting data set, which, as of October 10, 2016, contains 3911 motions with a total duration of 11.23 hours and 6278 annotations in natural language that contain 52,903 words. We believe this makes our data set an excellent choice that enables more transparent and comparable research in this important area.

Cogestion and recreation site demand: a model of demand-induced quality effects

USGS Publications Warehouse

Douglas, Aaron J.; Johnson, Richard L.

1993-01-01

This analysis focuses on problems of estimating site-specific dollar benefits conferred by outdoor recreation sites in the face of congestion costs. Encounters, crowding effects and congestion costs have often been treated by natural resource economists in a piecemeal fashion. In the current paper, encounters and crowding effects are treated systematically. We emphasize the quantitative impact of congestion costs on site-specific estimates of benefits conferred by improvements in outdoor recreation sites. The principal analytic conclusion is that techniques that streamline on data requirements produce biased estimates of benefits conferred by site improvements at facilities with significant crowding effects. The principal policy recommendation is that the Federal and state agencies should collect and store information on visitation rates, encounter levels and congestion costs at various outdoor recreation sites.

Stochastic reaction-diffusion algorithms for macromolecular crowding

NASA Astrophysics Data System (ADS)

Sturrock, Marc

2016-06-01

Compartment-based (lattice-based) reaction-diffusion algorithms are often used for studying complex stochastic spatio-temporal processes inside cells. In this paper the influence of macromolecular crowding on stochastic reaction-diffusion simulations is investigated. Reaction-diffusion processes are considered on two different kinds of compartmental lattice, a cubic lattice and a hexagonal close packed lattice, and solved using two different algorithms, the stochastic simulation algorithm and the spatiocyte algorithm (Arjunan and Tomita 2010 Syst. Synth. Biol. 4, 35-53). Obstacles (modelling macromolecular crowding) are shown to have substantial effects on the mean squared displacement and average number of molecules in the domain but the nature of these effects is dependent on the choice of lattice, with the cubic lattice being more susceptible to the effects of the obstacles. Finally, improvements for both algorithms are presented.

Emergency Department Crowding and Time at the Bedside: A Wearable Technology Feasibility Study.

PubMed

Castner, Jessica; Suffoletto, Heidi

2018-04-25

ED crowding is a public health crisis, limiting quality and access to lifesaving care. The purpose of this study was to (1) evaluate the feasibility of radio-frequency identification tags to measure clinician-patient contact and (2) to test the relationship between ED occupancy and clinician-patient contact time. In this 4-week observational study, radio-frequency identification tags were worn by emergency clinicians in a 21-bay urban teaching hospital emergency department. The time-motion data were merged with electronic medical repository patient information (N = 3,237) to adjust for occupancy, age, gender, and acuity. Qualitative themes were generated from focus group (N = 39) debriefings of the quantitative results. Data were collected on 56,342 total clinician events. Adjusting for patient age, increasing ED occupancy increased the number of times the attending physician entered and left the patient room (b = 0 .008, 95% confidence interval [CI] = [0.001-0.016], P = 0.03). There was no relationship for patient gender, triage acuity, shift at arrival, disposition to home, or discharge diagnosis category with either total minutes or number of encounters per patient visit. No time-motion and occupancy associations were observed for nurses, residents, or nurse practitioners/physician assistants. Debriefings indicated occupancy influenced the quality of care, despite maintaining the same quantity of contact time. The physical environment and clinician privacy concerns limit the feasibility of wearable tracking technology in the emergency setting. Attending physician care becomes more fragmented with increasing ED occupancy. Other clinicians report changes in the quality of care, whereas the quantity of time and encounters were unchanged with occupancy rates. Copyright © 2018 Elsevier Inc. All rights reserved.

Effects of face feature and contour crowding in facial expression adaptation.

PubMed

Liu, Pan; Montaser-Kouhsari, Leila; Xu, Hong

2014-12-01

Prolonged exposure to a visual stimulus, such as a happy face, biases the perception of subsequently presented neutral face toward sad perception, the known face adaptation. Face adaptation is affected by visibility or awareness of the adapting face. However, whether it is affected by discriminability of the adapting face is largely unknown. In the current study, we used crowding to manipulate discriminability of the adapting face and test its effect on face adaptation. Instead of presenting flanking faces near the target face, we shortened the distance between facial features (internal feature crowding), and reduced the size of face contour (external contour crowding), to introduce crowding. We are interested in whether internal feature crowding or external contour crowding is more effective in inducing crowding effect in our first experiment. We found that combining internal feature and external contour crowding, but not either of them alone, induced significant crowding effect. In Experiment 2, we went on further to investigate its effect on adaptation. We found that both internal feature crowding and external contour crowding reduced its facial expression aftereffect (FEA) significantly. However, we did not find a significant correlation between discriminability of the adapting face and its FEA. Interestingly, we found a significant correlation between discriminabilities of the adapting and test faces. Experiment 3 found that the reduced adaptation aftereffect in combined crowding by the external face contour and the internal facial features cannot be decomposed into the effects from the face contour and facial features linearly. It thus suggested a nonlinear integration between facial features and face contour in face adaptation.

Anatomy of the Crowd4Discovery crowdfunding campaign.

PubMed

Perlstein, Ethan O

2013-01-01

Crowdfunding allows the public to fund creative projects, including curiosity-driven scientific research. Last Fall, I was part of a team that raised $25,460 from an international coalition of "micropatrons" for an open, pharmacological research project called Crowd4Discovery. The goal of Crowd4Discovery is to determine the precise location of amphetamines inside mouse brain cells, and we are sharing the results of this project on the Internet as they trickle in. In this commentary, I will describe the genesis of Crowd4Discovery, our motivations for crowdfunding, an analysis of our fundraising data, and the nuts and bolts of running a crowdfunding campaign. Science crowdfunding is in its infancy but has already been successfully used by an array of scientists in academia and in the private sector as both a supplement and a substitute to grants. With traditional government sources of funding for basic scientific research contracting, an alternative model that couples fundraising and outreach - and in the process encourages more openness and accountability - may be increasingly attractive to researchers seeking to diversify their funding streams.

Hindered Diffusion in Polymeric Solutions Studied by Fluorescence Correlation Spectroscopy

PubMed Central

Zustiak, Silviya P.; Nossal, Ralph; Sackett, Dan L.

2011-01-01

Diffusion of molecules in the crowded and charged interior of the cell has long been of interest for understanding cellular processes. Here, we introduce a model system of hindered diffusion that includes both crowding and binding. In particular, we obtained the diffusivity of the positively charged protein, ribonuclease A (RNase), in solutions of dextrans of various charges (binding) and concentrations (crowding), as well as combinations of both, in a buffer of physiological ionic strength. Using fluorescence correlation spectroscopy, we observed that the diffusivity of RNase was unaffected by the presence of positively charged or neutral dextrans in the dilute regime but was affected by crowding at higher polymer concentrations. Conversely, protein diffusivity was significantly reduced by negatively charged dextrans, even at 0.4 μM (0.02% w/v) dextran. The diffusivity of RNase decreased with increasing concentrations of negative dextran, and the amount of bound RNase increased until it reached a plateau of ∼80% bound RNase. High salt concentrations were used to establish the electrostatic nature of the binding. Binding of RNase to the negatively charged dextrans was further confirmed by ultrafiltration. PMID:21723836

CROWDING-OUT OF GIANTS BY DWARFS: AN ORIGIN FOR THE LACK OF COMPANION PLANETS IN HOT JUPITER SYSTEMS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ogihara, Masahiro; Inutsuka, Shu-ichiro; Kobayashi, Hiroshi, E-mail: ogihara@nagoya-u.jp

2013-11-20

We investigate the formation of close-in terrestrial planets from planetary embryos under the influence of a hot Jupiter (HJ) using gravitational N-body simulations that include gravitational interactions between the gas disk and the terrestrial planet (e.g., type I migration). Our simulations show that several terrestrial planets efficiently form outside the orbit of the HJ, making a chain of planets, and all of them gravitationally interact directly or indirectly with the HJ through resonance, which leads to inward migration of the HJ. We call this mechanism of induced migration of the HJ ''crowding-out''. The HJ is eventually lost through collision withmore » the central star, and only several terrestrial planets remain. We also find that the efficiency of the crowding-out effect depends on the model parameters; for example, the heavier the disk is, the more efficient the crowding-out is. When planet formation occurs in a massive disk, the HJ can be lost to the central star and is never observed. On the other hand, for a less massive disk, the HJ and terrestrial planets can coexist; however, the companion planets may be below the detection limit of current observations. In both cases, systems with a HJ and terrestrial planets have little chance of detection. Therefore, our model naturally explains the lack of companion planets in HJ systems regardless of the disk mass. In effect, our model provides a theoretical prediction for future observations; additional planets can be discovered just outside the HJ, and their masses should generally be small.« less

Leadership, consensus decision making and collective behaviour in humans

PubMed Central

Dyer, John R.G.; Johansson, Anders; Helbing, Dirk; Couzin, Iain D.; Krause, Jens

2008-01-01

This paper reviews the literature on leadership in vertebrate groups, including recent work on human groups, before presenting the results of three new experiments looking at leadership and decision making in small and large human groups. In experiment 1, we find that both group size and the presence of uninformed individuals can affect the speed with which small human groups (eight people) decide between two opposing directional preferences and the likelihood of the group splitting. In experiment 2, we show that the spatial positioning of informed individuals within small human groups (10 people) can affect the speed and accuracy of group motion. We find that having a mixture of leaders positioned in the centre and on the edge of a group increases the speed and accuracy with which the group reaches their target. In experiment 3, we use large human crowds (100 and 200 people) to demonstrate that the trends observed from earlier work using small human groups can be applied to larger crowds. We find that only a small minority of informed individuals is needed to guide a large uninformed group. These studies build upon important theoretical and empirical work on leadership and decision making in animal groups. PMID:19073481

The sound of the crowd: auditory information modulates the perceived emotion of a crowd based on bodily expressions.

PubMed

McHugh, Joanna E; Kearney, Gavin; Rice, Henry; Newell, Fiona N

2012-02-01

Although both auditory and visual information can influence the perceived emotion of an individual, how these modalities contribute to the perceived emotion of a crowd of characters was hitherto unknown. Here, we manipulated the ambiguity of the emotion of either a visual or auditory crowd of characters by varying the proportions of characters expressing one of two emotional states. Using an intersensory bias paradigm, unambiguous emotional information from an unattended modality was presented while participants determined the emotion of a crowd in an attended, but different, modality. We found that emotional information in an unattended modality can disambiguate the perceived emotion of a crowd. Moreover, the size of the crowd had little effect on these crossmodal influences. The role of audiovisual information appears to be similar in perceiving emotion from individuals or crowds. Our findings provide novel insights into the role of multisensory influences on the perception of social information from crowds of individuals. PsycINFO Database Record (c) 2012 APA, all rights reserved

Systematically biological prioritizing remediation sites based on datasets of biological investigations and heavy metals in soil

NASA Astrophysics Data System (ADS)

Lin, Wei-Chih; Lin, Yu-Pin; Anthony, Johnathen

2015-04-01

Heavy metal pollution has adverse effects on not only the focal invertebrate species of this study, such as reduction in pupa weight and increased larval mortality, but also on the higher trophic level organisms which feed on them, either directly or indirectly, through the process of biomagnification. Despite this, few studies regarding remediation prioritization take species distribution or biological conservation priorities into consideration. This study develops a novel approach for delineating sites which are both contaminated by any of 5 readily bioaccumulated heavy metal soil contaminants and are of high ecological importance for the highly mobile, low trophic level focal species. The conservation priority of each site was based on the projected distributions of 6 moth species simulated via the presence-only maximum entropy species distribution model followed by the subsequent application of a systematic conservation tool. In order to increase the number of available samples, we also integrated crowd-sourced data with professionally-collected data via a novel optimization procedure based on a simulated annealing algorithm. This integration procedure was important since while crowd-sourced data can drastically increase the number of data samples available to ecologists, still the quality or reliability of crowd-sourced data can be called into question, adding yet another source of uncertainty in projecting species distributions. The optimization method screens crowd-sourced data in terms of the environmental variables which correspond to professionally-collected data. The sample distribution data was derived from two different sources, including the EnjoyMoths project in Taiwan (crowd-sourced data) and the Global Biodiversity Information Facility (GBIF) ?eld data (professional data). The distributions of heavy metal concentrations were generated via 1000 iterations of a geostatistical co-simulation approach. The uncertainties in distributions of the heavy metals were then quantified based on the overall consistency between realizations. Finally, Information-Gap Decision Theory (IGDT) was applied to rank the remediation priorities of contaminated sites in terms of both spatial consensus of multiple heavy metal realizations and the priority of specific conservation areas. Our results show that the crowd-sourced optimization algorithm developed in this study is effective at selecting suitable data from crowd-sourced data. By using this technique the available sample data increased to a total number of 96, 162, 72, 62, 69 and 62 or, that is, 2.6, 1.6, 2.5, 1.6, 1.2 and 1.8 times that originally available through the GBIF professionally-assembled database. Additionally, for all species considered the performance of models, in terms of test-AUC values, based on the combination of both data sources exceeded those models which were based on a single data source. Furthermore, the additional optimization-selected data lowered the overall variability, and therefore uncertainty, of model outputs. Based on the projected species distributions, our results revealed that around 30% of high species hotspot areas were also identified as contaminated. The decision-making tool, IGDT, successfully yielded remediation plans in terms of specific ecological value requirements, false positive tolerance rates of contaminated areas, and expected decision robustness. The proposed approach can be applied both to identify high conservation priority sites contaminated by heavy metals, based on the combination of screened crowd-sourced and professionally-collected data, and in making robust remediation decisions.

Task-irrelevant fear enhances amygdala-FFG inhibition and decreases subsequent face processing.

PubMed

Schulte Holthausen, Barbara; Habel, Ute; Kellermann, Thilo; Schelenz, Patrick D; Schneider, Frank; Christopher Edgar, J; Turetsky, Bruce I; Regenbogen, Christina

2016-09-01

Facial threat is associated with changes in limbic activity as well as modifications in the cortical face-related N170. It remains unclear if task-irrelevant threat modulates the response to a subsequent facial stimulus, and whether the amygdala's role in early threat perception is independent and direct, or modulatory. In 19 participants, crowds of emotional faces were followed by target faces and a rating task while simultaneous EEG-fMRI were recorded. In addition to conventional analyses, fMRI-informed EEG analyses and fMRI dynamic causal modeling (DCM) were performed. Fearful crowds reduced EEG N170 target face amplitudes and increased responses in a fMRI network comprising insula, amygdala and inferior frontal cortex. Multimodal analyses showed that amygdala response was present ∼60 ms before the right fusiform gyrus-derived N170. DCM indicated inhibitory connections from amygdala to fusiform gyrus, strengthened when fearful crowds preceded a target face. Results demonstrated the suppressing influence of task-irrelevant fearful crowds on subsequent face processing. The amygdala may be sensitive to task-irrelevant fearful crowds and subsequently strengthen its inhibitory influence on face-responsive fusiform N170 generators. This provides spatiotemporal evidence for a feedback mechanism of the amygdala by narrowing attention in order to focus on potential threats. © The Author (2016). Published by Oxford University Press. For Permissions, please email: journals.permissions@oup.com.

Organometallic rotaxane dendrimers with fourth-generation mechanically interlocked branches.

PubMed

Wang, Wei; Chen, Li-Jun; Wang, Xu-Qing; Sun, Bin; Li, Xiaopeng; Zhang, Yanyan; Shi, Jiameng; Yu, Yihua; Zhang, Li; Liu, Minghua; Yang, Hai-Bo

2015-05-05

Mechanically interlocked molecules, such as catenanes, rotaxanes, and knots, have applications in information storage, switching devices, and chemical catalysis. Rotaxanes are dumbbell-shaped molecules that are threaded through a large ring, and the relative motion of the two components along each other can respond to external stimuli. Multiple rotaxane units can amplify responsiveness, and repetitively branched molecules--dendrimers--can serve as vehicles for assembly of many rotaxanes on single, monodisperse compounds. Here, we report the synthesis of higher-generation rotaxane dendrimers by a divergent approach. Linkages were introduced as spacer elements to reduce crowding and to facilitate rotaxane motion, even at the congested periphery of the compounds up to the fourth generation. The structures were characterized by 1D multinuclear ((1)H, (13)C, and (31)P) and 2D NMR spectroscopy, MALDI-TOF-MS, gel permeation chromatography (GPC), and microscopy-based methods including atomic force microscopy (AFM) and transmission electron microscopy (TEM). AFM and TEM studies of rotaxane dendrimers vs. model dendrimers show that the rotaxane units enhance the rigidity and reduce the tendency of these assemblies to collapse by self-folding. Surface functionalization of the dendrimers with ferrocenes as termini produced electrochemically active assemblies. The preparation of dendrimers with a well-defined topological structure, enhanced rigidity, and diverse functional groups opens previously unidentified avenues for the application of these materials in molecular electronics and materials science.

Modeling Epidemics Spreading on Social Contact Networks.

PubMed

Zhang, Zhaoyang; Wang, Honggang; Wang, Chonggang; Fang, Hua

2015-09-01

Social contact networks and the way people interact with each other are the key factors that impact on epidemics spreading. However, it is challenging to model the behavior of epidemics based on social contact networks due to their high dynamics. Traditional models such as susceptible-infected-recovered (SIR) model ignore the crowding or protection effect and thus has some unrealistic assumption. In this paper, we consider the crowding or protection effect and develop a novel model called improved SIR model. Then, we use both deterministic and stochastic models to characterize the dynamics of epidemics on social contact networks. The results from both simulations and real data set conclude that the epidemics are more likely to outbreak on social contact networks with higher average degree. We also present some potential immunization strategies, such as random set immunization, dominating set immunization, and high degree set immunization to further prove the conclusion.

Modeling Epidemics Spreading on Social Contact Networks

PubMed Central

ZHANG, ZHAOYANG; WANG, HONGGANG; WANG, CHONGGANG; FANG, HUA

2016-01-01

Social contact networks and the way people interact with each other are the key factors that impact on epidemics spreading. However, it is challenging to model the behavior of epidemics based on social contact networks due to their high dynamics. Traditional models such as susceptible-infected-recovered (SIR) model ignore the crowding or protection effect and thus has some unrealistic assumption. In this paper, we consider the crowding or protection effect and develop a novel model called improved SIR model. Then, we use both deterministic and stochastic models to characterize the dynamics of epidemics on social contact networks. The results from both simulations and real data set conclude that the epidemics are more likely to outbreak on social contact networks with higher average degree. We also present some potential immunization strategies, such as random set immunization, dominating set immunization, and high degree set immunization to further prove the conclusion. PMID:27722037

Measures of crowding in the emergency department: a systematic review.

PubMed

Hwang, Ula; McCarthy, Melissa L; Aronsky, Dominik; Asplin, Brent; Crane, Peter W; Craven, Catherine K; Epstein, Stephen K; Fee, Christopher; Handel, Daniel A; Pines, Jesse M; Rathlev, Niels K; Schafermeyer, Robert W; Zwemer, Frank L; Bernstein, Steven L

2011-05-01

Despite consensus regarding the conceptual foundation of crowding, and increasing research on factors and outcomes associated with crowding, there is no criterion standard measure of crowding. The objective was to conduct a systematic review of crowding measures and compare them in conceptual foundation and validity. This was a systematic, comprehensive review of four medical and health care citation databases to identify studies related to crowding in the emergency department (ED). Publications that "describe the theory, development, implementation, evaluation, or any other aspect of a 'crowding measurement/definition' instrument (qualitative or quantitative)" were included. A "measurement/definition" instrument is anything that assigns a value to the phenomenon of crowding in the ED. Data collected from papers meeting inclusion criteria were: study design, objective, crowding measure, and evidence of validity. All measures were categorized into five measure types (clinician opinion, input factors, throughput factors, output factors, and multidimensional scales). All measures were then indexed to six validation criteria (clinician opinion, ambulance diversion, left without being seen (LWBS), times to care, forecasting or predictions of future crowding, and other). There were 2,660 papers identified by databases; 46 of these papers met inclusion criteria, were original research studies, and were abstracted by reviewers. A total of 71 unique crowding measures were identified. The least commonly used type of crowding measure was clinician opinion, and the most commonly used were numerical counts (number or percentage) of patients and process times associated with patient care. Many measures had moderate to good correlation with validation criteria. Time intervals and patient counts are emerging as the most promising tools for measuring flow and nonflow (i.e., crowding), respectively. Standardized definitions of time intervals (flow) and numerical counts (nonflow) will assist with validation of these metrics across multiple sites and clarify which options emerge as the metrics of choice in this "crowded" field of measures. © 2011 by the Society for Academic Emergency Medicine.

Intracellular crowding effects on the self-association of the bacterial cell division protein FtsZ.

PubMed

Naddaf, Lamis; Sayyed-Ahmad, Abdallah

2014-12-15

The dimerization rate of the bacterial cell division protein FtsZ is strongly affected by the intracellular crowding. Yet the complexity of the intracellular environment makes it difficult to investigate via all-atom molecular dynamics or other detailed theoretical methods. We study the crowding effect on FtsZ dimerization which is the first step of an oligomerization process that results in more elaborate supramolecular structures. In particular, we consider the effect of intracellular crowding on the reaction rates, and their dependence on the different concentrations of crowding agents. We achieved this goal by using Brownian dynamics (BD) simulation techniques and a modified post-processing approach in which we decompose the rate constant in crowded media as a product of the rate constant in the dilute solution times a factor that incorporates the crowding effect. The latter factor accounts for the diffusion reduction and crowder induced energy. In addition we include the crowding effects on water viscosity in the BD simulations of crowded media. We finally show that biomolecular crowding has a considerable effect on the FtsZ dimerization by increasing the dimerization rate constant from 2.6×10(7)M(-1)s(-1) in the absence of crowders to 1.0×10(8)M(-1)s(-1) at crowding level of 0.30. Copyright © 2014 Elsevier Inc. All rights reserved.

Better the Martian you know? Trust in the crowd vs. trust in the machine when using a Martian Citizen Science platform

NASA Astrophysics Data System (ADS)

Sprinks, James Christopher; Wardlaw, Jessica; Houghton, Robert; Bamford, Steven; Marsh, Stuart

2016-10-01

Citizen science platforms allow untrained volunteers to take part in scientific research across a range of disciplines, and often involve the analysis of remotely sensed imagery. The data collected by increasingly advanced and automated instruments has made planetary science a prime candidate for, and user of, citizen science online platforms. In order to process this large volume of information, such systems are increasingly performed in conjunction with data-mining analysis software, with varying configurations of computer and volunteer contribution. Despite citizen science being a relatively new approach, there has been a growing field of research considering the practice in its own right beyond the scientific problems they address, with studies involving interface HCI, platform functionality, and motivation particularly adding to a growing body of citizen science scholarship.Through iterations of the FP7 iMars project's 'Mars in Motion' platform, the work presented studied the effect that guidance information had on volunteers' accuracy and trust. Whilst analysing imagery for change, volunteers were told whether automated change detection software or the consensus of other citizen scientists had found change, with this information varying in terms of accuracy. Results showed that volunteers' ability to both identify change and the type of feature undergoing change was improved when both the software result and crowd opinion guidance information provided had a greater accuracy. However, when guidance information was less accurate volunteers' level of trust fell at a sharper rate when it came from the crowd than when it came from the algorithm, and participants reported more frustration - a counter-intuitive result compared to existing research. Citizen science practitioners need to consider the information they provide to volunteers and how they present it; the results of software analysis or the consensus of a crowd need to be conclusive and above all accurate in order to improve both the performance and engagement of their volunteer community.The research leading to these results has received funding from the European Union's Seventh Framework Programme (FP7/2007-2013) under iMars grant agreement 607379.

Music-reading training alleviates crowding with musical notation.

PubMed

Wong, Yetta Kwailing; Wong, Alan C-N

2016-06-01

Crowding refers to the disrupted recognition of an object by nearby distractors. Prior work has shown that real-world music-reading experts experience reduced crowding specifically for musical stimuli. However, it is unclear whether music-reading training reduced the magnitude of crowding or whether individuals showing less crowding are more likely to learn and excel in music reading later. To examine the first possibility, we tested whether crowding can be alleviated by music-reading training in the laboratory. Intermediate-level music readers completed 8 hr of music-reading training within 2 weeks. Their threshold duration for reading musical notes dropped by 44.1% after training to a level comparable with that of extant expert music readers. Importantly, crowding was reduced with musical stimuli but not with the nonmusical stimuli Landolt Cs. In sum, the reduced crowding for musical stimuli in expert music readers can be explained by music-reading training.

Tooth eruption sequence and dental crowding: a case-control study

PubMed Central

Moshkelgosha, Vahid; Khosravifard, Negar; Golkari, Ali

2014-01-01

When cases of dental crowding are identified and diagnosed promptly, interceptive orthodontics is particularly successful. Aim: To assess the differences in the eruption sequence of the mandibular canine and first premolar teeth in children with and without dental crowding. Materials and Methods: Children who attended the Shiraz Dental School's orthodontic clinic (Iran) from September to December 2012 were enrolled in this case-control study. Tooth size arch length discrepancy (TSALD) of all 8-10 year olds was calculated from patients’ dental models. Thirty-six children were randomly selected from those with TSALD of equal or less than 4mm (those with crowding). Each selected case was matched for sex and age with another child (as control) with TSALD>−4mm attending the same clinic, in the same time period. The existing panoramic radiographs were traced and the eruption percentages were measured for mandibular canine and first premolar teeth. The mean difference between canine and first premolar eruption percentages was compared between the case and control groups using the SPSS (version PASW 18) software and a paired sample t-test. Results: Canine and first premolar eruption percentages in the case group were 65.82±13.00 and 78.92±10.15 percent, respectively. The mean eruption percentages for canines and first premolars of the control group were 74.12±14.55 and 75.47±11.60 percent, respectively. There was a significant difference in pre-eruptive positions of canine and first premolar teeth in those with moderate to severe crowding when compared to the control group (p<0.001). Conclusion: These findings may improve the early diagnosis of children with high risk of developing moderate to severe crowding during mixed dentition. PMID:25110582

Time series model for forecasting the number of new admission inpatients.

PubMed

Zhou, Lingling; Zhao, Ping; Wu, Dongdong; Cheng, Cheng; Huang, Hao

2018-06-15

Hospital crowding is a rising problem, effective predicting and detecting managment can helpful to reduce crowding. Our team has successfully proposed a hybrid model combining both the autoregressive integrated moving average (ARIMA) and the nonlinear autoregressive neural network (NARNN) models in the schistosomiasis and hand, foot, and mouth disease forecasting study. In this paper, our aim is to explore the application of the hybrid ARIMA-NARNN model to track the trends of the new admission inpatients, which provides a methodological basis for reducing crowding. We used the single seasonal ARIMA (SARIMA), NARNN and the hybrid SARIMA-NARNN model to fit and forecast the monthly and daily number of new admission inpatients. The root mean square error (RMSE), mean absolute error (MAE) and mean absolute percentage error (MAPE) were used to compare the forecasting performance among the three models. The modeling time range of monthly data included was from January 2010 to June 2016, July to October 2016 as the corresponding testing data set. The daily modeling data set was from January 4 to September 4, 2016, while the testing time range included was from September 5 to October 2, 2016. For the monthly data, the modeling RMSE and the testing RMSE, MAE and MAPE of SARIMA-NARNN model were less than those obtained from the single SARIMA or NARNN model, but the MAE and MAPE of modeling performance of SARIMA-NARNN model did not improve. For the daily data, all RMSE, MAE and MAPE of NARNN model were the lowest both in modeling stage and testing stage. Hybrid model does not necessarily outperform its constituents' performances. It is worth attempting to explore the reliable model to forecast the number of new admission inpatients from different data.

Setting up crowd science projects.

PubMed

Scheliga, Kaja; Friesike, Sascha; Puschmann, Cornelius; Fecher, Benedikt

2016-11-29

Crowd science is scientific research that is conducted with the participation of volunteers who are not professional scientists. Thanks to the Internet and online platforms, project initiators can draw on a potentially large number of volunteers. This crowd can be involved to support data-rich or labour-intensive projects that would otherwise be unfeasible. So far, research on crowd science has mainly focused on analysing individual crowd science projects. In our research, we focus on the perspective of project initiators and explore how crowd science projects are set up. Based on multiple case study research, we discuss the objectives of crowd science projects and the strategies of their initiators for accessing volunteers. We also categorise the tasks allocated to volunteers and reflect on the issue of quality assurance as well as feedback mechanisms. With this article, we contribute to a better understanding of how crowd science projects are set up and how volunteers can contribute to science. We suggest that our findings are of practical relevance for initiators of crowd science projects, for science communication as well as for informed science policy making. © The Author(s) 2016.

Peer-group affiliation and adolescent self-esteem: an integration of ego-identity and symbolic-interaction theories.

PubMed

Brown, B B; Lohr, M J

1987-01-01

To evaluate expectations derived from ego-identity theory and symbolic-interaction theories about the association between self-concept and peer-group affiliations in adolescence, we examined the self-esteem of 221 7th through 12th graders associated by peers with one of five major school crowds and 106 students relatively unknown by classmates and not associated with any school crowd. Among crowd members, self-esteem was directly related to the position of one's crowd in the peer-group status hierarchy (based on both peer-rated and self-perceived crowd affiliation). Outsiders' self-esteem differed in relation to the accuracy of their reflected appraisal of and the salience they attached to crowd affiliation. Crowd members as a whole exhibited higher self-esteem than outsiders as a whole. Differences, however, were mediated by crowd status, salience of crowd affiliation, and the accuracy of reflected appraisals. An adequate interpretation of the findings required an integration of Festinger's (1954, 1957) social comparisons and cognitive-dissonance theories, Cooley's (1902) notions of reflected appraisal, and Newman and Newman's (1976) extrapolations from ego-identity theory.

The crowding factor method applied to parafoveal vision

PubMed Central

Ghahghaei, Saeideh; Walker, Laura

2016-01-01

Crowding increases with eccentricity and is most readily observed in the periphery. During natural, active vision, however, central vision plays an important role. Measures of critical distance to estimate crowding are difficult in central vision, as these distances are small. Any overlap of flankers with the target may create an overlay masking confound. The crowding factor method avoids this issue by simultaneously modulating target size and flanker distance and using a ratio to compare crowded to uncrowded conditions. This method was developed and applied in the periphery (Petrov & Meleshkevich, 2011b). In this work, we apply the method to characterize crowding in parafoveal vision (<3.5 visual degrees) with spatial uncertainty. We find that eccentricity and hemifield have less impact on crowding than in the periphery, yet radial/tangential asymmetries are clearly preserved. There are considerable idiosyncratic differences observed between participants. The crowding factor method provides a powerful tool for examining crowding in central and peripheral vision, which will be useful in future studies that seek to understand visual processing under natural, active viewing conditions. PMID:27690170

Changing attitudes toward smoking and smoking susceptibility through peer crowd targeting: more evidence from a controlled study.

PubMed

Moran, Meghan Bridgid; Sussman, Steve

2015-01-01

Peer crowd identification consistently predicts an adolescent's smoking behavior. As such, several interventions have targeted adolescents and young adults based on their identification with a specific crowd (e.g., Hipsters). This study uses a controlled experimental design to isolate and test the effect of peer crowd targeting in an antismoking ad on antismoking attitudes and smoking susceptibility. Two hundred and thirty-nine adolescents, age 13-15 years, completed a baseline survey and then viewed an antismoking ad targeting one of eight crowds; 1 week later they completed a posttest. Participants were assessed on antismoking attitudes and smoking susceptibility. Adolescents who strongly identified with the crowd targeted by the ad reported stronger antismoking attitudes and lower levels of smoking susceptibility. Those who disidentified with the crowd targeted in the ad exhibited not statistically significant increases in smoking susceptibility and weaker antismoking attitudes at posttest. These findings indicate that targeting youths based on their peer crowd is a useful strategy for antismoking interventions. Additional research should further examine whether youths who disidentify with the targeted crowd in an ad exhibit reactance against the message.

Hysteretic dynamics of active particles in a periodic orienting field

PubMed Central

Romensky, Maksym; Scholz, Dimitri; Lobaskin, Vladimir

2015-01-01

Active motion of living organisms and artificial self-propelling particles has been an area of intense research at the interface of biology, chemistry and physics. Significant progress in understanding these phenomena has been related to the observation that dynamic self-organization in active systems has much in common with ordering in equilibrium condensed matter such as spontaneous magnetization in ferromagnets. The velocities of active particles may behave similar to magnetic dipoles and develop global alignment, although interactions between the individuals might be completely different. In this work, we show that the dynamics of active particles in external fields can also be described in a way that resembles equilibrium condensed matter. It follows simple general laws, which are independent of the microscopic details of the system. The dynamics is revealed through hysteresis of the mean velocity of active particles subjected to a periodic orienting field. The hysteresis is measured in computer simulations and experiments on unicellular organisms. We find that the ability of the particles to follow the field scales with the ratio of the field variation period to the particles' orientational relaxation time, which, in turn, is related to the particle self-propulsion power and the energy dissipation rate. The collective behaviour of the particles due to aligning interactions manifests itself at low frequencies via increased persistence of the swarm motion when compared with motion of an individual. By contrast, at high field frequencies, the active group fails to develop the alignment and tends to behave like a set of independent individuals even in the presence of interactions. We also report on asymptotic laws for the hysteretic dynamics of active particles, which resemble those in magnetic systems. The generality of the assumptions in the underlying model suggests that the observed laws might apply to a variety of dynamic phenomena from the motion of synthetic active particles to crowd or opinion dynamics. PMID:26040594

Multipurpose surgical robot as a laparoscope assistant.

PubMed

Nelson, Carl A; Zhang, Xiaoli; Shah, Bhavin C; Goede, Matthew R; Oleynikov, Dmitry

2010-07-01

This study demonstrates the effectiveness of a new, compact surgical robot at improving laparoscope guidance. Currently, the assistant guiding the laparoscope camera tends to be less experienced and requires physical and verbal direction from the surgeon. Human guidance has disadvantages of fatigue and shakiness leading to inconsistency in the field of view. This study investigates whether replacing the assistant with a compact robot can improve the stability of the surgeon's field of view and also reduce crowding at the operating table. A compact robot based on a bevel-geared "spherical mechanism" with 4 degrees of freedom and capable of full dexterity through a 15-mm port was designed and built. The robot was mounted on the standard railing of the operating table and used to manipulate a laparoscope through a supraumbilical port in a porcine model via a joystick controlled externally by a surgeon. The process was videotaped externally via digital video recorder and internally via laparoscope. Robot position data were also recorded within the robot's motion control software. The robot effectively manipulated the laparoscope in all directions to provide a clear and consistent view of liver, small intestine, and spleen. Its range of motion was commensurate with typical motions executed by a human assistant and was well controlled with the joystick. Qualitative analysis of the video suggested that this method of laparoscope guidance provides highly stable imaging during laparoscopic surgery, which was confirmed by robot position data. Because the robot was table-mounted and compact in design, it increased standing room around the operation table and did not interfere with the workspace of other surgical instruments. The study results also suggest that this robotic method may be combined with flexible endoscopes for highly dexterous visualization with more degrees of freedom.

Semantic priming from crowded words.

PubMed

Yeh, Su-Ling; He, Sheng; Cavanagh, Patrick

2012-06-01

Vision in a cluttered scene is extremely inefficient. This damaging effect of clutter, known as crowding, affects many aspects of visual processing (e.g., reading speed). We examined observers' processing of crowded targets in a lexical decision task, using single-character Chinese words that are compact but carry semantic meaning. Despite being unrecognizable and indistinguishable from matched nonwords, crowded prime words still generated robust semantic-priming effects on lexical decisions for test words presented in isolation. Indeed, the semantic-priming effect of crowded primes was similar to that of uncrowded primes. These findings show that the meanings of words survive crowding even when the identities of the words do not, suggesting that crowding does not prevent semantic activation, a process that may have evolved in the context of a cluttered visual environment.

Conflict management by hamadryas baboons (Papio hamadryas hamadryas) during crowding: a tension-reduction strategy.

PubMed

Judge, P G; Griffaton, N S; Fincke, A M

2006-10-01

Primates change a variety of behavioral responses during short-term exposure to crowding. Under crowded conditions, rates of aggression, submissive behavior, and affiliative behavior may increase or decrease. Different patterns of change among these three categories of response have been interpreted as various coping "strategies" for managing the increased risk of conflict under crowded conditions. Grooming is of particular interest because this behavior is known to have a calming influence on the recipient and could be used to manage conflict under tense situations. A captive group of nine hamadryas baboons (Papio hamadryas hamadryas) composed of two harems was observed under short-term crowding to determine whether this species adopts conflict-management strategies similar to those described in other primates. The aggression, submission, affiliation, and displacement activities of the six adults in the group (two males and four females) were recorded, and behaviors in their small indoor quarters was compared with baseline behaviors in the outdoor section of their enclosure, which had over 10 times more space. Repeated-measures analysis of variance (ANOVA) was used to compare behavioral rates during crowding with baseline rates recorded immediately after crowding and during matched controls collected at the same time of day as the crowding sessions. Aggression and submission rates did not change significantly across conditions. Huddling together and proximity increased during crowding, and females increased grooming of their harem male during crowding. Displacement activities (e.g., pacing and self-grooming) increased during crowding, but scratching, an indicator of anxiety in primates, did not. The pattern of behavior exhibited by this group conforms to an active "tension-reduction" strategy in which animals successfully reduce the higher risk of aggression during crowding.

Electromyographic characteristic of orbicularis oris in patients with dental crowding in permanent occlusion.

PubMed

Dmytrenko, Maryna I; Kuroiedowa, Vira D

2016-01-01

electromyographic indices were developed for complex analysis of functional condition of orbicularis oris. to study electromyographic indices of orbicularis oris in patients with dental crowding in permanent occlusion. thirty four patients with malocclusion and a severe degree of severity of dental crowding (15 males, 19 females, aged 16-29 years) who underwent orthodontic examination. The treatment group was divided into three: Group Ia comprised 11 subjects with mandibular crowding (mean age 19,27 ± 1,08 years); group Ib, 10 patients with maxillary dental crowding (mean age 20,10 ± 1,60 years) and group Ic, 13 subjects with both maxillary and mandibular crowding (mean age 20,15 ± 1,45 years). The control group consisted of 10 patients with malocclusions but without dental crowding (mean age 20,70 ± 1,32 years). The findings were compared with similar indices in subjects with normal occlusion (mean age 21,3 ± 1,25 years). The index of orbicularis oris activity (ACTIV,%) was determined for each patient. A Student's t-test was used to analyze statistical difference between different groups. patients having crowding of maxillary teeth showed greater activity of muscles of the upper lip during maximum voluntary clenching (АCTІV= -0,99±7,44%). Activity of the muscles of the lower lip in patients with crowding of mandibular teeth (АСTІV=20,52±4,22%) and crowding of maxillary and mandibular teeth (АСTІV=17,93±4,33%) is prevailing. аctivity of the orbicularis oris in patients with malocclusion, complicated by dental crowding depend on clinical localization of crowding.

Electromyographic characteristic of orbicularis oris in patients with dental crowding in permanent occlusion.

PubMed

Dmytrenko, Maryna I; Kuroiedowa, Vira D

electromyographic indices were developed for complex analysis of functional condition of orbicularis oris. to study electromyographic indices of orbicularis oris in patients with dental crowding in permanent occlusion. thirty four patients with malocclusion and a severe degree of severity of dental crowding (15 males, 19 females, aged 16-29 years) who underwent orthodontic examination. The treatment group was divided into three: Group Ia comprised 11 subjects with mandibular crowding (mean age 19,27 ± 1,08 years); group Ib, 10 patients with maxillary dental crowding (mean age 20,10 ± 1,60 years) and group Ic, 13 subjects with both maxillary and mandibular crowding (mean age 20,15 ± 1,45 years). The control group consisted of 10 patients with malocclusions but without dental crowding (mean age 20,70 ± 1,32 years). The findings were compared with similar indices in subjects with normal occlusion (mean age 21,3 ± 1,25 years). The index of orbicularis oris activity (ACTIV,%) was determined for each patient. A Student's t-test was used to analyze statistical difference between different groups. patients having crowding of maxillary teeth showed greater activity of muscles of the upper lip during maximum voluntary clenching (АCTІV= -0,99±7,44%). Activity of the muscles of the lower lip in patients with crowding of mandibular teeth (АСTІV=20,52±4,22%) and crowding of maxillary and mandibular teeth (АСTІV=17,93±4,33%) is prevailing. аctivity of the orbicularis oris in patients with malocclusion, complicated by dental crowding depend on clinical localization of crowding.

The Effect of Aging and Attention on Visual Crowding and Surround Suppression of Perceived Contrast Threshold.

PubMed

Malavita, Menaka S; Vidyasagar, Trichur R; McKendrick, Allison M

2017-02-01

The purpose of this study was to study how, in midperipheral vision, aging affects visual processes that interfere with target detection (crowding and surround suppression) and to determine whether the performance on such tasks are related to visuospatial attention as measured by visual search. We investigated the effect of aging on crowding and suppression in detection of a target in peripheral vision, using different types of flanking stimuli. Both thresholds were also obtained while varying the position of the flanker (placed inside or outside of target, relative to fixation). Crowding thresholds were also estimated with spatial uncertainty (jitter). Additionally, we included a visual search task comprising Gabor stimuli to investigate whether performance is related to top-down attention. Twenty young adults (age, 18-32 years; mean age, 26.1 years; 10 males) and 19 older adults (age, 60-74 years; mean age, 70.3 years; 10 males) participated in the study. Older adults showed more surround suppression than the young (F[1,37] = 4.21; P < 0.05), but crowding was unaffected by age. In the younger group, the position of the flanker influenced the strength of crowding, but not the strength of suppression (F[1,39] = 4.11; P < 0.05). Crowding was not affected by spatial jitter of the stimuli. Neither crowding nor surround suppression was predicted by attentional efficiency measured in the visual search task. There was also no significant correlation between crowding and surround suppression. We show that aging does not affect visual crowding but does increase surround suppression of contrast, suggesting that crowding and surround suppression may be distinct visual phenomena. Furthermore, strengths of crowding and surround suppression did not correlate with each other nor could they be predicted by efficiency of visual search.

Semantic-based surveillance video retrieval.

PubMed

Hu, Weiming; Xie, Dan; Fu, Zhouyu; Zeng, Wenrong; Maybank, Steve

2007-04-01

Visual surveillance produces large amounts of video data. Effective indexing and retrieval from surveillance video databases are very important. Although there are many ways to represent the content of video clips in current video retrieval algorithms, there still exists a semantic gap between users and retrieval systems. Visual surveillance systems supply a platform for investigating semantic-based video retrieval. In this paper, a semantic-based video retrieval framework for visual surveillance is proposed. A cluster-based tracking algorithm is developed to acquire motion trajectories. The trajectories are then clustered hierarchically using the spatial and temporal information, to learn activity models. A hierarchical structure of semantic indexing and retrieval of object activities, where each individual activity automatically inherits all the semantic descriptions of the activity model to which it belongs, is proposed for accessing video clips and individual objects at the semantic level. The proposed retrieval framework supports various queries including queries by keywords, multiple object queries, and queries by sketch. For multiple object queries, succession and simultaneity restrictions, together with depth and breadth first orders, are considered. For sketch-based queries, a method for matching trajectories drawn by users to spatial trajectories is proposed. The effectiveness and efficiency of our framework are tested in a crowded traffic scene.

Swimming motility plays a key role in the stochastic dynamics of cell clumping

NASA Astrophysics Data System (ADS)

Qi, Xianghong; Nellas, Ricky B.; Byrn, Matthew W.; Russell, Matthew H.; Bible, Amber N.; Alexandre, Gladys; Shen, Tongye

2013-04-01

Dynamic cell-to-cell interactions are a prerequisite to many biological processes, including development and biofilm formation. Flagellum induced motility has been shown to modulate the initial cell-cell or cell-surface interaction and to contribute to the emergence of macroscopic patterns. While the role of swimming motility in surface colonization has been analyzed in some detail, a quantitative physical analysis of transient interactions between motile cells is lacking. We examined the Brownian dynamics of swimming cells in a crowded environment using a model of motorized adhesive tandem particles. Focusing on the motility and geometry of an exemplary motile bacterium Azospirillum brasilense, which is capable of transient cell-cell association (clumping), we constructed a physical model with proper parameters for the computer simulation of the clumping dynamics. By modulating mechanical interaction (‘stickiness’) between cells and swimming speed, we investigated how equilibrium and active features affect the clumping dynamics. We found that the modulation of active motion is required for the initial aggregation of cells to occur at a realistic time scale. Slowing down the rotation of flagellar motors (and thus swimming speeds) is correlated to the degree of clumping, which is consistent with the experimental results obtained for A. brasilense.

International perspectives on emergency department crowding.

PubMed

Pines, Jesse M; Hilton, Joshua A; Weber, Ellen J; Alkemade, Annechien J; Al Shabanah, Hasan; Anderson, Philip D; Bernhard, Michael; Bertini, Alessio; Gries, André; Ferrandiz, Santiago; Kumar, Vijaya Arun; Harjola, Veli-Pekka; Hogan, Barbara; Madsen, Bo; Mason, Suzanne; Ohlén, Gunnar; Rainer, Timothy; Rathlev, Niels; Revue, Eric; Richardson, Drew; Sattarian, Mehdi; Schull, Michael J

2011-12-01

The maturation of emergency medicine (EM) as a specialty has coincided with dramatic increases in emergency department (ED) visit rates, both in the United States and around the world. ED crowding has become a public health problem where periodic supply and demand mismatches in ED and hospital resources cause long waiting times and delays in critical treatments. ED crowding has been associated with several negative clinical outcomes, including higher complication rates and mortality. This article describes emergency care systems and the extent of crowding across 15 countries outside of the United States: Australia, Canada, Denmark, Finland, France, Germany, Hong Kong, India, Iran, Italy, The Netherlands, Saudi Arabia, Catalonia (Spain), Sweden, and the United Kingdom. The authors are local emergency care leaders with knowledge of emergency care in their particular countries. Where available, data are provided about visit patterns in each country; however, for many of these countries, no national data are available on ED visits rates or crowding. For most of the countries included, there is both objective evidence of increases in ED visit rates and ED crowding and also subjective assessments of trends toward higher crowding in the ED. ED crowding appears to be worsening in many countries despite the presence of universal health coverage. Scandinavian countries with robust systems to manage acute care outside the ED do not report crowding is a major problem. The main cause for crowding identified by many authors is the boarding of admitted patients, similar to the United States. Many hospitals in these countries have implemented operational interventions to mitigate crowding in the ED, and some countries have imposed strict limits on ED length of stay (LOS), while others have no clear plan to mitigate crowding. An understanding of the causes and potential solutions implemented in these countries can provide a lens into how to mitigate ED crowding in the United States through health policy interventions and hospital operational changes. © 2011 by the Society for Academic Emergency Medicine.

Association between shelter crowding and incidence of sleep disturbance among disaster evacuees: a retrospective medical chart review study.

PubMed

Kawano, Takahisa; Nishiyama, Kei; Morita, Hiroshi; Yamamura, Osamu; Hiraide, Atsuchi; Hasegawa, Kohei

2016-01-13

We determined whether crowding at emergency shelters is associated with a higher incidence of sleep disturbance among disaster evacuees and identified the minimum required personal space at shelters. Retrospective review of medical charts. 30 shelter-based medical clinics in Ishinomaki, Japan, during the 46 days following the Great Eastern Japan Earthquake and Tsunami in 2011. Shelter residents who visited eligible clinics. Based on the result of a locally weighted scatter-plot smoothing technique assessing the relationship between the mean space per evacuee and cumulative incidence of sleep disturbance at the shelter, eligible shelters were classified into crowded and non-crowded shelters. The cumulative incidence per 1000 evacuees was compared between groups, using a Mann-Whitney U test. To assess the association between shelter crowding and the daily incidence of sleep disturbance per 1000 evacuees, quasi-least squares method adjusting for potential confounders was used. The 30 shelters were categorised as crowded (mean space per evacuee <5.0 m(2), 9 shelters) or non-crowded (≥ 5.0 m(2), 21 shelters). The study included 9031 patients. Among the eligible patients, 1079 patients (11.9%) were diagnosed with sleep disturbance. Mean space per evacuee during the study period was 3.3 m(2) (SD, 0.8 m(2)) at crowded shelters and 8.6 m(2) (SD, 4.3 m(2)) at non-crowded shelters. The median cumulative incidence of sleep disturbance did not differ between the crowded shelters (2.3/1000 person-days (IQR, 1.6-5.4)) and non-crowded shelters (1.9/1000 person-days (IQR, 1.0-2.8); p=0.20). In contrast, after adjusting for potential confounders, crowded shelters had an increased daily incidence of sleep disturbance (2.6 per 1000 person-days; 95% CI 0.2 to 5.0/1000 person-days, p=0.03) compared to that at non-crowded shelters. Crowding at shelters may exacerbate sleep disruptions in disaster evacuees; therefore, appropriate evacuation space requirements should be considered. Published by the BMJ Publishing Group Limited. For permission to use (where not already granted under a licence) please go to http://www.bmj.com/company/products-services/rights-and-licensing/

Numerical Simulation of Evacuation Process in Malaysia By Using Distinct-Element-Method Based Multi-Agent Model

NASA Astrophysics Data System (ADS)

Abustan, M. S.; Rahman, N. A.; Gotoh, H.; Harada, E.; Talib, S. H. A.

2016-07-01

In Malaysia, not many researches on crowd evacuation simulation had been reported. Hence, the development of numerical crowd evacuation process by taking into account people behavioral patterns and psychological characteristics is crucial in Malaysia. On the other hand, tsunami disaster began to gain attention of Malaysian citizens after the 2004 Indian Ocean Tsunami that need quick evacuation process. In relation to the above circumstances, we have conducted simulations of tsunami evacuation process at the Miami Beach of Penang Island by using Distinct Element Method (DEM)-based crowd behavior simulator. The main objectives are to investigate and reproduce current conditions of evacuation process at the said locations under different hypothetical scenarios for the efficiency study of the evacuation. The sim-1 is initial condition of evacuation planning while sim-2 as improvement of evacuation planning by adding new evacuation area. From the simulation result, sim-2 have a shorter time of evacuation process compared to the sim-1. The evacuation time recuded 53 second. The effect of the additional evacuation place is confirmed from decreasing of the evacuation completion time. Simultaneously, the numerical simulation may be promoted as an effective tool in studying crowd evacuation process.

Estimating the Critical Point of Crowding in the Emergency Department for the Warning System

NASA Astrophysics Data System (ADS)

Chang, Y.; Pan, C.; Tseng, C.; Wen, J.

2011-12-01

The purpose of this study is to deduce a function from the admissions/discharge rate of patient flow to estimate a "Critical Point" that provides a reference for warning systems in regards to crowding in the emergency department (ED) of a hospital or medical clinic. In this study, a model of "Input-Throughput-Output" was used in our established mathematical function to evaluate the critical point. The function is defined as dPin/dt=dwait/dt+Cp×B+ dPout/dt where Pin= number of registered patients, Pwait= number of waiting patients, Cp= retention rate per bed (calculated for the critical point), B= number of licensed beds in the treatment area, and Pout= number of patients discharged from the treatment area. Using the average Cp of ED crowding, we could start the warning system at an appropriate time and then plan for necessary emergency response to facilitate the patient process more smoothly. It was concluded that ED crowding could be quantified using the average value of Cp and the value could be used as a reference for medical staff to give optimal emergency medical treatment to patients. Therefore, additional practical work should be launched to collect more precise quantitative data.

Demotivating incentives and motivation crowding out in charitable giving

PubMed Central

Chao, Matthew

2017-01-01

Research has shown that extrinsic incentives can crowd out intrinsic motivation in many contexts. Despite this, many nonprofits offer conditional thank-you gifts, such as mugs or tote bags, in exchange for donations. In collaboration with a nonprofit, this study implements a direct mail field experiment and demonstrates that thank-you gifts reduced donation rates in a fundraising campaign. Attention-based multiattribute choice models suggest that this is because prospective donors shift attention to the salient gift offer, causing them to underweight less salient intrinsic motives. Attention to the gift may also cause individuals to adopt a more cost–benefit mindset, further de-emphasizing intrinsic motives. Consistent with these hypotheses, crowding out was driven by those who donated higher amounts in the previous year (i.e., those who likely had higher intrinsic motivation). In a complementary online experiment, thank-you gifts also reduced donation rates but only when the gift was visually salient. This corroborates the mediating role of attention in crowding out. Taken together, the laboratory and field results demonstrate that this fundraising technique can be demotivating in some contexts and that this may occur through an attention-based mechanism. PMID:28655844

Demotivating incentives and motivation crowding out in charitable giving.

PubMed

Chao, Matthew

2017-07-11

Research has shown that extrinsic incentives can crowd out intrinsic motivation in many contexts. Despite this, many nonprofits offer conditional thank-you gifts, such as mugs or tote bags, in exchange for donations. In collaboration with a nonprofit, this study implements a direct mail field experiment and demonstrates that thank-you gifts reduced donation rates in a fundraising campaign. Attention-based multiattribute choice models suggest that this is because prospective donors shift attention to the salient gift offer, causing them to underweight less salient intrinsic motives. Attention to the gift may also cause individuals to adopt a more cost-benefit mindset, further de-emphasizing intrinsic motives. Consistent with these hypotheses, crowding out was driven by those who donated higher amounts in the previous year (i.e., those who likely had higher intrinsic motivation). In a complementary online experiment, thank-you gifts also reduced donation rates but only when the gift was visually salient. This corroborates the mediating role of attention in crowding out. Taken together, the laboratory and field results demonstrate that this fundraising technique can be demotivating in some contexts and that this may occur through an attention-based mechanism.

Learning Supervised Topic Models for Classification and Regression from Crowds.

PubMed

Rodrigues, Filipe; Lourenco, Mariana; Ribeiro, Bernardete; Pereira, Francisco C

2017-12-01

The growing need to analyze large collections of documents has led to great developments in topic modeling. Since documents are frequently associated with other related variables, such as labels or ratings, much interest has been placed on supervised topic models. However, the nature of most annotation tasks, prone to ambiguity and noise, often with high volumes of documents, deem learning under a single-annotator assumption unrealistic or unpractical for most real-world applications. In this article, we propose two supervised topic models, one for classification and another for regression problems, which account for the heterogeneity and biases among different annotators that are encountered in practice when learning from crowds. We develop an efficient stochastic variational inference algorithm that is able to scale to very large datasets, and we empirically demonstrate the advantages of the proposed model over state-of-the-art approaches.

AggNet: Deep Learning From Crowds for Mitosis Detection in Breast Cancer Histology Images.

PubMed

Albarqouni, Shadi; Baur, Christoph; Achilles, Felix; Belagiannis, Vasileios; Demirci, Stefanie; Navab, Nassir

2016-05-01

The lack of publicly available ground-truth data has been identified as the major challenge for transferring recent developments in deep learning to the biomedical imaging domain. Though crowdsourcing has enabled annotation of large scale databases for real world images, its application for biomedical purposes requires a deeper understanding and hence, more precise definition of the actual annotation task. The fact that expert tasks are being outsourced to non-expert users may lead to noisy annotations introducing disagreement between users. Despite being a valuable resource for learning annotation models from crowdsourcing, conventional machine-learning methods may have difficulties dealing with noisy annotations during training. In this manuscript, we present a new concept for learning from crowds that handle data aggregation directly as part of the learning process of the convolutional neural network (CNN) via additional crowdsourcing layer (AggNet). Besides, we present an experimental study on learning from crowds designed to answer the following questions. 1) Can deep CNN be trained with data collected from crowdsourcing? 2) How to adapt the CNN to train on multiple types of annotation datasets (ground truth and crowd-based)? 3) How does the choice of annotation and aggregation affect the accuracy? Our experimental setup involved Annot8, a self-implemented web-platform based on Crowdflower API realizing image annotation tasks for a publicly available biomedical image database. Our results give valuable insights into the functionality of deep CNN learning from crowd annotations and prove the necessity of data aggregation integration.

Crowding and hopping in a protein’s diffusive transport on DNA

NASA Astrophysics Data System (ADS)

Koslover, Elena F.; Díaz de la Rosa, Mario; Spakowitz, Andrew J.

2017-02-01

Diffusion is a ubiquitous phenomenon that impacts virtually all processes that involve random fluctuations, and as such, the foundational work of Smoluchowski has proven to be instrumental in addressing innumerable problems. Here, we focus on a critical biological problem that relies on diffusive transport and is analyzed using a probabilistic treatment originally developed by Smoluchowski. The search of a DNA binding protein for its specific target site is believed to rely on non-specific binding to DNA with transient hops along the chain. In this work, we address the impact of protein crowding along the DNA on the transport of a DNA-binding protein. The crowders dramatically alter the dynamics of the protein while bound to the DNA, resulting in single-file transport that is subdiffusive in nature. However, transient unbinding and hopping results in a long-time behavior (shown to be superdiffusive) that is qualitatively unaffected by the crowding on the DNA. Thus, hopping along the chain mitigates the role that protein crowding has in restricting the translocation dynamics along the chain. The superdiffusion coefficient is influenced by the quantitative values of the effective binding rate, which is influenced by protein crowding. We show that vacancy fraction and superdiffusion coefficient exhibits a non-monotonic relationship under many circumstances. We leverage analytical theory and dynamic Monte Carlo simulations to address this problem. With several additional contributions, the core of our modeling work adopts a reaction-diffusion framework that is based on Smoluchowski’s original work.

Crowding in central vision in normally sighted and visually impaired [corrected] children aged 4 to 8 years: the influence of age and test design.

PubMed

Huurneman, Bianca; Boonstra, F Nienke; Cillessen, Antonius H N; van Rens, Ger; Cox, Ralf F A

2012-06-01

To investigate crowding ratios in children with a visual impairment due to ocular disease (n = 58) and normally sighted children (n = 75) aged 4 to 8 years using several variants of two clinically available tests with different optotype spacing (fixed or proportional to the optotype size). Crowding ratios, calculated by dividing the single acuity by the linear acuity, were measured binocularly with the C-test and the LH line chart. Ratios >1.00 indicate crowding. The charts with fixed spacing revealed significantly higher crowding ratios for visually impaired children than normally sighted children (both for measurements at 40 cm and 5 m). The age-related reduction of the crowding ratios seen in normally sighted children when tested with near-vision charts with fixed spacing was not present in the visually impaired group. Visually impaired children with nystagmus showed higher crowding ratios than visually impaired children without nystagmus. The chart with proportional intersymbol spacing (ISS) did not reveal differences between the normally sighted and visually impaired children; nor did it show group, age, or nystagmus effects. Visually impaired children showed higher crowding ratios than normally sighted children when measured with charts with fixed ISS. This study illustrates that test design and target/flanker interference as a manifestation of crowding are critical issues to bear in mind when assessing crowding ratios in children.

Actin Filament Elasticity and Retrograde Flow Shape the Force-Velocity Relation of Motile Cells

PubMed Central

Zimmermann, Juliane; Brunner, Claudia; Enculescu, Mihaela; Goegler, Michael; Ehrlicher, Allen; Käs, Josef; Falcke, Martin

2012-01-01

Cells migrate through a crowded environment during processes such as metastasis or wound healing, and must generate and withstand substantial forces. The cellular motility responses to environmental forces are represented by their force-velocity relation, which has been measured for fish keratocytes but remains unexplained. Even pN opposing forces slow down lamellipodium motion by three orders of magnitude. At larger opposing forces, the retrograde flow of the actin network accelerates until it compensates for polymerization, and cell motion stalls. Subsequently, the lamellipodium adapts to the stalled state. We present a mechanism quantitatively explaining the cell's force-velocity relation and its changes upon application of drugs that hinder actin polymerization or actomyosin-based contractility. Elastic properties of filaments, close to the lamellipodium leading edge, and retrograde flow shape the force-velocity relation. To our knowledge, our results shed new light on how these migratory responses are regulated, and on the mechanics and structure of the lamellipodium. PMID:22339865

High frame rate imaging based photometry. Photometric reduction of data from electron-multiplying charge coupled devices (EMCCDs)

NASA Astrophysics Data System (ADS)

Harpsøe, K. B. W.; Jørgensen, U. G.; Andersen, M. I.; Grundahl, F.

2012-06-01

Context. The EMCCD is a type of CCD that delivers fast readout times and negligible readout noise, making it an ideal detector for high frame rate applications which improve resolution, like lucky imaging or shift-and-add. This improvement in resolution can potentially improve the photometry of faint stars in extremely crowded fields significantly by alleviating crowding. Alleviating crowding is a prerequisite for observing gravitational microlensing in main sequence stars towards the galactic bulge. However, the photometric stability of this device has not been assessed. The EMCCD has sources of noise not found in conventional CCDs, and new methods for handling these must be developed. Aims: We aim to investigate how the normal photometric reduction steps from conventional CCDs should be adjusted to be applicable to EMCCD data. One complication is that a bias frame cannot be obtained conventionally, as the output from an EMCCD is not normally distributed. Also, the readout process generates spurious charges in any CCD, but in EMCCD data, these charges are visible as opposed to the conventional CCD. Furthermore we aim to eliminate the photon waste associated with lucky imaging by combining this method with shift-and-add. Methods: A simple probabilistic model for the dark output of an EMCCD is developed. Fitting this model with the expectation-maximization algorithm allows us to estimate the bias, readout noise, amplification, and spurious charge rate per pixel and thus correct for these phenomena. To investigate the stability of the photometry, corrected frames of a crowded field are reduced with a point spread function (PSF) fitting photometry package, where a lucky image is used as a reference. Results: We find that it is possible to develop an algorithm that elegantly reduces EMCCD data and produces stable photometry at the 1% level in an extremely crowded field. Based on observation with the Danish 1.54 m telescope at ESO La Silla Observatory.

Facilitated aggregation of FG nucleoporins under molecular crowding conditions.

PubMed

Milles, Sigrid; Huy Bui, Khanh; Koehler, Christine; Eltsov, Mikhail; Beck, Martin; Lemke, Edward A

2013-02-01

Intrinsically disordered and phenylalanine-glycine-rich nucleoporins (FG Nups) form a crowded and selective transport conduit inside the NPC that can only be transited with the help of nuclear transport receptors (NTRs). It has been shown in vitro that FG Nups can assemble into two distinct appearances, amyloids and hydrogels. If and how these phenomena are linked and if they have a physiological role still remains unclear. Using a variety of high-resolution fluorescence and electron microscopic (EM) tools, we reveal that crowding conditions mimicking the NPC environment can accelerate the aggregation and amyloid formation speed of yeast and human FG Nups by orders of magnitude. Aggregation can be inhibited by NTRs, providing a rationale on how the cell might control amyloid formation of FG Nups. The superb spatial resolving power of EM also reveals that hydrogels are enlaced amyloid fibres, and these findings have implications for existing transport models and for NPC assembly.

Facilitated aggregation of FG nucleoporins under molecular crowding conditions

PubMed Central

Milles, Sigrid; Huy Bui, Khanh; Koehler, Christine; Eltsov, Mikhail; Beck, Martin; Lemke, Edward A

2013-01-01

Intrinsically disordered and phenylalanine–glycine-rich nucleoporins (FG Nups) form a crowded and selective transport conduit inside the NPC that can only be transited with the help of nuclear transport receptors (NTRs). It has been shown in vitro that FG Nups can assemble into two distinct appearances, amyloids and hydrogels. If and how these phenomena are linked and if they have a physiological role still remains unclear. Using a variety of high-resolution fluorescence and electron microscopic (EM) tools, we reveal that crowding conditions mimicking the NPC environment can accelerate the aggregation and amyloid formation speed of yeast and human FG Nups by orders of magnitude. Aggregation can be inhibited by NTRs, providing a rationale on how the cell might control amyloid formation of FG Nups. The superb spatial resolving power of EM also reveals that hydrogels are enlaced amyloid fibres, and these findings have implications for existing transport models and for NPC assembly. PMID:23238392

Crowd noise as a cue in referee decisions contributes to the home advantage.

PubMed

Unkelbach, Christian; Memmert, Daniel

2010-08-01

The home advantage is one of the best established phenomena in sports (Courneya & Carron, 1992), and crowd noise has been suggested as one of its determinants (Nevill & Holder, 1999). However, the psychological processes that mediate crowd noise influence and its contribution to the home advantage are still unclear. We propose that crowd noise correlates with the criteria referees have to judge. As crowd noise is a valid cue, referee decisions are strongly influenced by crowd noise. Yet, when audiences are not impartial, a home advantage arises. Using soccer as an exemplar, we show the relevance of this influence in predicting outcomes of real games via a database analysis. Then we experimentally demonstrate the influence of crowd noise on referees' yellow cards decisions in soccer. Finally, we discuss why the focus on referee decisions is useful, and how more experimental research could benefit investigations of the home advantage.

Ensemble Perception of Dynamic Emotional Groups.

PubMed

Elias, Elric; Dyer, Michael; Sweeny, Timothy D

2017-02-01

Crowds of emotional faces are ubiquitous, so much so that the visual system utilizes a specialized mechanism known as ensemble coding to see them. In addition to being proximally close, members of emotional crowds, such as a laughing audience or an angry mob, often behave together. The manner in which crowd members behave-in sync or out of sync-may be critical for understanding their collective affect. Are ensemble mechanisms sensitive to these dynamic properties of groups? Here, observers estimated the average emotion of a crowd of dynamic faces. The members of some crowds changed their expressions synchronously, whereas individuals in other crowds acted asynchronously. Observers perceived the emotion of a synchronous group more precisely than the emotion of an asynchronous crowd or even a single dynamic face. These results demonstrate that ensemble representation is particularly sensitive to coordinated behavior, and they suggest that shared behavior is critical for understanding emotion in groups.

Noncanonical structures and their thermodynamics of DNA and RNA under molecular crowding: beyond the Watson-Crick double helix.

PubMed

Sugimoto, Naoki

2014-01-01

How does molecular crowding affect the stability of nucleic acid structures inside cells? Water is the major solvent component in living cells, and the properties of water in the highly crowded media inside cells differ from that in buffered solution. As it is difficult to measure the thermodynamic behavior of nucleic acids in cells directly and quantitatively, we recently developed a cell-mimicking system using cosolutes as crowding reagents. The influences of molecular crowding on the structures and thermodynamics of various nucleic acid sequences have been reported. In this chapter, we discuss how the structures and thermodynamic properties of nucleic acids differ under various conditions such as highly crowded environments, compartment environments, and in the presence of ionic liquids, and the major determinants of the crowding effects on nucleic acids are discussed. The effects of molecular crowding on the activities of ribozymes and riboswitches on noncanonical structures of DNA- and RNA-like quadruplexes that play important roles in transcription and translation are also described. © 2014 Elsevier Inc. All rights reserved.

Multiscale Spectroscopy of Diffusing Molecules in Crowded Environments

NASA Astrophysics Data System (ADS)

Heikal, Ahmed A.

2015-06-01

Living cells are known to be crowded with organelles, biomembranes, and macromolecules such as proteins, DNA, RNA, and actin filaments. It is believed that such macromolecular crowding affect biomolecular diffusion, protein-protein and protein-substrate interaction, and protein folding. In this contribution, I will discuss our recent results on rotational and translational diffusion of small and large molecules in crowded environments using time-resolved anisotropy and fluorescence correlation spectroscopy methods. In these studies, rhodamine green and enhanced green fluorescent protein are used as fluorescent probes diffusing in buffers enriched with biomimetic crowding agents such as Ficoll-70, bovine serum albumin (BSA), and ovalbumin. Controlled experiments on pure and glycerol-rich buffers were carried out as environments with variable, homogeneous viscosity. Our results indicate that the microviscosity differs from the corresponding bulk viscosity, depending on the nature of crowding agents (i.e., proteins versus polymers), the concentration of crowding agents and spatio-temporal scaling of our experimental approach. Our findings provide a foundation for fluorescence-based studies of diffusion and binding of biomolecules in the crowded milieu of living cells.

Recovery of a crowded object by masking the flankers: Determining the locus of feature integration

PubMed Central

Chakravarthi, Ramakrishna; Cavanagh, Patrick

2009-01-01

Object recognition is a central function of the visual system. As a first step, the features of an object are registered; these independently encoded features are then bound together to form a single representation. Here we investigate the locus of this “feature integration” by examining crowding, a striking breakdown of this process. Crowding, an inability to identify a peripheral target surrounded by flankers, results from “excessive integration” of target and flanker features. We presented a standard crowding display with a target C flanked by four flanker C's in the periphery. We then masked only the flankers (but not the target) with one of three kinds of masks—noise, metacontrast, and object substitution—each of which interferes at progressively higher levels of visual processing. With noise and metacontrast masks (low-level masking), the crowded target was recovered, whereas with object substitution masks (high-level masking), it was not. This places a clear upper bound on the locus of interference in crowding suggesting that crowding is not a low-level phenomenon. We conclude that feature integration, which underlies crowding, occurs prior to the locus of object substitution masking. Further, our results indicate that the integrity of the flankers, but not their identification, is crucial for crowding to occur. PMID:19810785

Crowd behaviour during high-stress evacuations in an immersive virtual environment

PubMed Central

Kapadia, Mubbasir; Thrash, Tyler; Sumner, Robert W.; Gross, Markus; Helbing, Dirk; Hölscher, Christoph

2016-01-01

Understanding the collective dynamics of crowd movements during stressful emergency situations is central to reducing the risk of deadly crowd disasters. Yet, their systematic experimental study remains a challenging open problem due to ethical and methodological constraints. In this paper, we demonstrate the viability of shared three-dimensional virtual environments as an experimental platform for conducting crowd experiments with real people. In particular, we show that crowds of real human subjects moving and interacting in an immersive three-dimensional virtual environment exhibit typical patterns of real crowds as observed in real-life crowded situations. These include the manifestation of social conventions and the emergence of self-organized patterns during egress scenarios. High-stress evacuation experiments conducted in this virtual environment reveal movements characterized by mass herding and dangerous overcrowding as they occur in crowd disasters. We describe the behavioural mechanisms at play under such extreme conditions and identify critical zones where overcrowding may occur. Furthermore, we show that herding spontaneously emerges from a density effect without the need to assume an increase of the individual tendency to imitate peers. Our experiments reveal the promise of immersive virtual environments as an ethical, cost-efficient, yet accurate platform for exploring crowd behaviour in high-risk situations with real human subjects. PMID:27605166

Crowd behaviour during high-stress evacuations in an immersive virtual environment.

PubMed

Moussaïd, Mehdi; Kapadia, Mubbasir; Thrash, Tyler; Sumner, Robert W; Gross, Markus; Helbing, Dirk; Hölscher, Christoph

2016-09-01

Understanding the collective dynamics of crowd movements during stressful emergency situations is central to reducing the risk of deadly crowd disasters. Yet, their systematic experimental study remains a challenging open problem due to ethical and methodological constraints. In this paper, we demonstrate the viability of shared three-dimensional virtual environments as an experimental platform for conducting crowd experiments with real people. In particular, we show that crowds of real human subjects moving and interacting in an immersive three-dimensional virtual environment exhibit typical patterns of real crowds as observed in real-life crowded situations. These include the manifestation of social conventions and the emergence of self-organized patterns during egress scenarios. High-stress evacuation experiments conducted in this virtual environment reveal movements characterized by mass herding and dangerous overcrowding as they occur in crowd disasters. We describe the behavioural mechanisms at play under such extreme conditions and identify critical zones where overcrowding may occur. Furthermore, we show that herding spontaneously emerges from a density effect without the need to assume an increase of the individual tendency to imitate peers. Our experiments reveal the promise of immersive virtual environments as an ethical, cost-efficient, yet accurate platform for exploring crowd behaviour in high-risk situations with real human subjects. © 2016 The Authors.

Mechanism of Facilitated Diffusion during a DNA Search in Crowded Environments.

PubMed

Krepel, Dana; Gomez, David; Klumpp, Stefan; Levy, Yaakov

2016-11-03

The key feature explaining the rapid recognition of a DNA target site by its protein lies in the combination of one- and three-dimensional (1D and 3D) diffusion, which allows efficient scanning of the many alternative sites. This facilitated diffusion mechanism is expected to be affected by cellular conditions, particularly crowding, given that up to 40% of the total cellular volume may by occupied by macromolecules. Using coarse-grained molecular dynamics and Monte Carlo simulations, we show that the crowding particles can enhance facilitated diffusion and accelerate search kinetics. This effect originates from a trade-off between 3D and 1D diffusion. The 3D diffusion coefficient is lower under crowded conditions, but it has little influence because the excluded volume effect of molecular crowding restricts its use. Largely prevented from using 3D diffusion, the searching protein dramatically increases its use of the hopping search mode, which results in a higher linear diffusion coefficient. The coefficient of linear diffusion also increases under crowded conditions as a result of increased collisions between the crowding particles and the searching protein. Overall, less 3D diffusion coupled with an increase in the use of the hopping and speed of 1D diffusion results in faster search kinetics under crowded conditions. Our study shows that the search kinetics and mechanism are modulated not only by the crowding occupancy but also by the properties of the crowding particles and the salt concentration.

Initial validation of the International Crowding Measure in Emergency Departments (ICMED) to measure emergency department crowding.

PubMed

Boyle, Adrian; Coleman, James; Sultan, Yasmin; Dhakshinamoorthy, Vijayasankar; O'Keeffe, Jacqueline; Raut, Pramin; Beniuk, Kathleen

2015-02-01

Emergency department (ED) crowding is recognised as a major public health problem. While there is agreement that ED crowding harms patients, there is less agreement about the best way to measure ED crowding. We have previously derived an eight-point measure of ED crowding by a formal consensus process, the International Crowding Measure in Emergency Departments (ICMED). We aimed to test the feasibility of collecting this measure in real time and to partially validate this measure. We conducted a cross-sectional study in four EDs in England. We conducted independent observations of the measure and compared these with senior clinician's perceptions of crowding and safety. We obtained 84 measurements spread evenly across the four EDs. The measure was feasible to collect in real time except for the 'Left Before Being Seen' variable. Increasing numbers of violations of the measure were associated with increasing clinician concerns. The area under the receiver operating characteristic curve was 0.80 (95% CI 0.72 to 0.90) for predicting crowding and 0.74 (95% CI 0.60 to 0.89) for predicting danger. The optimal number of violations for predicting crowding was three, with a sensitivity of 91.2 (95% CI 85.1 to 97.2) and a specificity of 100.0 (92.9-100). The measure predicted clinician concerns better than individual variables such as occupancy. The ICMED can easily be collected in multiple EDs with different information technology systems. The ICMED seems to predict clinician's concerns about crowding and safety well, but future work is required to validate this before it can be advocated for widespread use. Published by the BMJ Publishing Group Limited. For permission to use (where not already granted under a licence) please go to http://group.bmj.com/group/rights-licensing/permissions.

Some aspects on kinetic modeling of evacuation dynamics. Comment on "Human behaviours in evacuation crowd dynamics: From modelling to "big data" toward crisis management" by Nicola Bellomo et al.

NASA Astrophysics Data System (ADS)

Calvo, Juan; Nieto, Juanjo

2016-09-01

The management of human crowds in extreme situations is a complex subject which requires to take into account a variety of factors. To name a few, the understanding of human behaviour, the psychological and behavioural features of individuals, the quality of the venue and the stress level of the pedestrian need to be addressed in order to select the most appropriate action during an evacuation process on a complex venue. In this sense, the mathematical modeling of such complex phenomena can be regarded as a very useful tool to understand and predict these situations. As presented in [4], mathematical models can provide guidance to the personnel in charge of managing evacuation processes, by means of helping to design a set of protocols, among which the most appropriate during a given critical situation is then chosen.

Comparing State- Versus Facility-Level Effects on Crowding in U.S. Correctional Facilities

ERIC Educational Resources Information Center

Steiner, Benjamin; Wooldredge, John

2008-01-01

The literature on prison crowding underscores the potential importance of both state- and facility-level effects on crowding, although empirical research has not assessed these relative effects because of the sole focus on states as units of analysis. This article describes findings from bi-level analyses of crowding across 459 state-operated…

Death Rates, Psychiatric Commitments, Blood Pressure, and Perceived Crowding as a Function of Institutional Crowding.

ERIC Educational Resources Information Center

Paulus, Paul; And Others

1978-01-01

Emphasis was directed toward three factors: (1) social density; (2) spatial density; and (3) overall institutional population level. In prisons, higher population years yielded higher death rates and higher rates of psychiatric commitments. Blood pressure was higher in more crowded housing. Degree of perceived crowding was related to space per…

Why Peer Crowds Matter: Incorporating Youth Subcultures and Values in Health Education Campaigns.

PubMed

Moran, Meghan B; Walker, Matthew W; Alexander, Tesfa N; Jordan, Jeffrey W; Wagner, Dana E

2017-03-01

Grounded on research showing that peer crowds vary in risk behavior, several recent health behavior interventions, including the US Food and Drug Administration's Fresh Empire campaign, have targeted high-risk peer crowds. We establish the scientific foundations for using this approach. We introduce peer crowd targeting as a strategy for culturally targeting health behavior interventions to youths. We use social identity and social norms theory to explicate the theoretical underpinnings of this approach. We describe Fresh Empire to demonstrate how peer crowd targeting functions in a campaign and critically evaluate the benefits and limitations of this approach. By replacing unhealthy behavioral norms with desirable, healthy lifestyles, peer crowd-targeted interventions can create a lasting impact that resonates in the target audience's culture.

Cross-cultural differences in tolerance for crowding: fact or fiction?

PubMed

Evans, G W; Lepore, S J; Allen, K M

2000-08-01

It is widely believed that cultures vary in their tolerance for crowding. There is, however, little evidence to substantiate this belief, coupled with serious shortcomings in the extant literature. Tolerance for crowding has been confused with cultural differences in personal space preferences along with perceived crowding. Furthermore, the few studies that have examined cultural variability in reactions to crowding have compared subgroup correlations, which is not equivalent to a statistical interaction. Although the authors found a statistical interaction indicating that Asian Americans and Latin Americans differ in the way they perceive crowding in comparison to their fellow Anglo-American and African American citizens, all four ethnic groups suffer similar, negative psychological distress sequelae of high-density housing. These results hold independently of household income.

Modeling of knowledge transmission by considering the level of forgetfulness in complex networks

NASA Astrophysics Data System (ADS)

Cao, Bin; Han, Shui-hua; Jin, Zhen

2016-06-01

In this study, we establish a general model by considering the level of forgetfulness during knowledge transmission in complex networks, where the level of forgetfulness depends mainly on the number in a crowd who possess knowledge, while the saturated incidence is also considered. In theory, we analyze the stability of the equilibrium points and the transmission threshold R0 is also given. If R0 > 1, then knowledge can ​be transmitted, but if not, it will become completely extinct. In addition, we performed some numerical simulations to verify the reasonability of the theoretical analysis. The results of the simulations also suggest ​that the proportion of the crowd with knowledge will be increased under a better cultural atmosphere.

Bioconvection and front formation of Paramecium tetraurelia

NASA Astrophysics Data System (ADS)

Kitsunezaki, So; Komori, Rie; Harumoto, Terue

2007-10-01

We have investigated the bioconvection of Paramecium tetraurelia in high-density suspensions made by centrifugal concentration. When a suspension is kept at rest in a Hele-Shaw cell, a crowded front of paramecia is formed in the vicinity of the bottom and it propagates gradually toward the water-air interface. Fluid convection occurs under this front, and it is driven persistently by the upward swimming of paramecia. The roll structures of the bioconvection become turbulent with an increase in the depth of the suspension; they also change rapidly as the density of paramecia increases. Our experimental results suggest that lack of oxygen in the suspension causes the active individual motions of paramecia to induce the formation of this front.

Collective workload organization in confined excavation of granular media

NASA Astrophysics Data System (ADS)

Monaenkova, Daria; Linevich, Vadim; Goodisman, Michael A.; Goldman, Daniel I.

2015-03-01

Many social insects collectively construct large nests in complex substrates; such structures are often composed of narrow tunnels. The benefits of collective construction, including reduced construction costs per worker come with challenges of navigation in crowded, confined spaces. Here we study the workforce organization of groups of S. invicta fire ants creating tunnels in wet granular media. We monitor the activity levels of marked (painted) workers-defined as a number of tunnel visits over 12 hours- during initiation of tunnels. The activity levels are described by a Lorenz curve with a Gini coefficient of ~ 0 . 7 indicating that a majority of the excavation is performed by a minority of workers. We hypothesize that this workload distribution is beneficial for excavation in crowded conditions, and use a 2D cellular automata (CA) model to reproduce behaviors of the excavating ants. CA simulations reveal that tunnel construction rates decrease in groups of equally active animals compared to groups with the natural workload distribution. We use predictions of the CA model to organize collective excavation of granular material by teams of digging robots, and use the robots to test hypotheses of crowded excavation in the physical world. We acknowledge support of National Science Foundation, Physics of Living Systems division.

To Evaluate the Correlation Between Skeletal and Dental Parameters to the Amount of Crowding in Class II Div. 1 Malocclusions.

PubMed

Singh, Shivani; Shivaprakash, G

2017-09-01

Crowding of teeth is one of the most common problem that motivates the patient to seek orthodontic treatment. Determination of etiology of crowding could have a significant effect on treatment planning and prognosis of Class II malocclusion. Aim of this study was to evaluate the relationship of skeletal and dental parameters to amount of dental crowding in patients with Class II Divison 1 (div.1) malocclusion. Pretreatment lateral cephalograms and dental casts of 60 patients with skeletal Class II malocclusion were collected for the study. The sample was divided into two groups according to severity of pretreatment mandibular crowding. Group I consisted of cases with crowding ≥3 mm and Group II with crowding <3 mm. Lateral cephalograms for each patient was manually traced and skeletal parameters (effective maxillary and mandibular length, mandibular plane angle, Y Axis, lower anterior face height) and dental parameters (axial inclination of lower incisor, inclination of lower incisor to mandibular plane, interincisal angle) were measured. Unpaired t-test was used for intergroup comparison and relationship between different measurements was investigated using Pearson correlation coefficient. Among the skeletal parameters measured, only effective mandibular length exhibited statistically significant difference between the two groups. No statistically significant difference was found between the two groups for any of the dental parameters. Significant inverse correlation was found between mandibular crowding and effective mandibular length. Subjects with Class II div.1 malocclusion and moderate to severe mandibular crowding have significantly smaller effective mandibular base length than subjects with the same malocclusion and slight mandibular crowding.

Density estimation in aerial images of large crowds for automatic people counting

NASA Astrophysics Data System (ADS)

Herrmann, Christian; Metzler, Juergen

2013-05-01

Counting people is a common topic in the area of visual surveillance and crowd analysis. While many image-based solutions are designed to count only a few persons at the same time, like pedestrians entering a shop or watching an advertisement, there is hardly any solution for counting large crowds of several hundred persons or more. We addressed this problem previously by designing a semi-automatic system being able to count crowds consisting of hundreds or thousands of people based on aerial images of demonstrations or similar events. This system requires major user interaction to segment the image. Our principle aim is to reduce this manual interaction. To achieve this, we propose a new and automatic system. Besides counting the people in large crowds, the system yields the positions of people allowing a plausibility check by a human operator. In order to automatize the people counting system, we use crowd density estimation. The determination of crowd density is based on several features like edge intensity or spatial frequency. They indicate the density and discriminate between a crowd and other image regions like buildings, bushes or trees. We compare the performance of our automatic system to the previous semi-automatic system and to manual counting in images. By counting a test set of aerial images showing large crowds containing up to 12,000 people, the performance gain of our new system will be measured. By improving our previous system, we will increase the benefit of an image-based solution for counting people in large crowds.

Face features and face configurations both contribute to visual crowding.

PubMed

Sun, Hsin-Mei; Balas, Benjamin

2015-02-01

Crowding refers to the inability to recognize an object in peripheral vision when other objects are presented nearby (Whitney & Levi Trends in Cognitive Sciences, 15, 160-168, 2011). A popular explanation of crowding is that features of the target and flankers are combined inappropriately when they are located within an integration field, thus impairing target recognition (Pelli, Palomares, & Majaj Journal of Vision, 4(12), 12:1136-1169, 2004). However, it remains unclear which features of the target and flankers are combined inappropriately to cause crowding (Levi Vision Research, 48, 635-654, 2008). For example, in a complex stimulus (e.g., a face), to what extent does crowding result from the integration of features at a part-based level or at the level of global processing of the configural appearance? In this study, we used a face categorization task and different types of flankers to examine how much the magnitude of visual crowding depends on the similarity of face parts or of global configurations. We created flankers with face-like features (e.g., the eyes, nose, and mouth) in typical and scrambled configurations to examine the impacts of part appearance and global configuration on the visual crowding of faces. Additionally, we used "electrical socket" flankers that mimicked first-order face configuration but had only schematic features, to examine the extent to which global face geometry impacted crowding. Our results indicated that both face parts and configurations contribute to visual crowding, suggesting that face similarity as realized under crowded conditions includes both aspects of facial appearance.

Crowding, visual awareness, and their respective neural loci

PubMed Central

Shin, Kilho; Chung, Susana T. L.; Tjan, Bosco S.

2017-01-01

In peripheral vision, object identification can be impeded when a target object is flanked by other objects. This phenomenon of crowding has been attributed to basic processes associated with image encoding by the visual system, but the neural origin of crowding is not known. Determining whether crowding depends on subjective awareness of the flankers can provide information on the neural origin of crowding. However, recent studies that manipulated flanker awareness have yielded conflicting results. In the current study, we suppressed flanker awareness with two methods: interocular suppression (IOS) and adaptation-induced blindness (AIB). We tested two different types of stimuli: gratings and letters. With IOS, we found that the magnitude of crowding increased as the number of physical flankers increased, even when the observers did not report seeing any of the flankers. In contrast, when flanker awareness was manipulated with AIB, the magnitude of crowding increased with the number of perceived flankers. Our results show that whether crowding is contingent on awareness of the flankers depends on the method used to suppress awareness. In addition, our results imply that the locus of crowding is upstream from the neural locus of IOS and close to or downstream from that of AIB. Neurophysiology and neuroimaging studies jointly implicate mid-to-high level visual processing stages for IOS, while direct evidence regarding the neural locus of AIB is limited. The most consistent interpretation of our empirical findings is to place the neural locus of crowding at an early cortical site, such as V1 or V2. PMID:28549353

Computational Replication of the Primary Isotope Dependence of Secondary Kinetic Isotope Effects in Solution Hydride-Transfer Reactions: Supporting the Isotopically Different Tunneling Ready State Conformations.

PubMed

Derakhshani-Molayousefi, Mortaza; Kashefolgheta, Sadra; Eilers, James E; Lu, Yun

2016-06-30

We recently reported a study of the steric effect on the 1° isotope dependence of 2° KIEs for several hydride-transfer reactions in solution (J. Am. Chem. Soc. 2015, 137, 6653). The unusual 2° KIEs decrease as the 1° isotope changes from H to D, and more in the sterically hindered systems. These were explained in terms of a more crowded tunneling ready state (TRS) conformation in D-tunneling, which has a shorter donor-acceptor distance (DAD) than in H-tunneling. To examine the isotopic DAD difference explanation, in this paper, following an activated motion-assisted H-tunneling model that requires a shorter DAD in a heavier isotope transfer process, we computed the 2° KIEs at various H/D positions at different DADs (2.9 Å to 3.5 Å) for the hydride-transfer reactions from 2-propanol to the xanthylium and thioxanthylium ions (Xn(+) and TXn(+)) and their 9-phenyl substituted derivatives (Ph(T)Xn(+)). The calculated 2° KIEs match the experiments and the calculated DAD effect on the 2° KIEs fits the observed 1° isotope effect on the 2° KIEs. These support the motion-assisted H-tunneling model and the isotopically different TRS conformations. Furthermore, it was found that the TRS of the sterically hindered Ph(T)Xn(+) system does not possess a longer DAD than that of the (T)Xn(+) system. This predicts a no larger 1° KIE in the former system than in the latter. The observed 1° KIE order is, however, contrary to the prediction. This implicates the stronger DAD-compression vibrations coupled to the bulky Ph(T)Xn(+) reaction coordinate.

A fuzzy-theory-based method for studying the effect of information transmission on nonlinear crowd dispersion dynamics

NASA Astrophysics Data System (ADS)

Fu, Libi; Song, Weiguo; Lo, Siuming

2017-01-01

Emergencies involved in mass events are related to a variety of factors and processes. An important factor is the transmission of information on danger that has an influence on nonlinear crowd dynamics during the process of crowd dispersion. Due to much uncertainty in this process, there is an urgent need to propose a method to investigate the influence. In this paper, a novel fuzzy-theory-based method is presented to study crowd dynamics under the influence of information transmission. Fuzzy functions and rules are designed for the ambiguous description of human states. Reasonable inference is employed to decide the output values of decision making such as pedestrian movement speed and directions. Through simulation under four-way pedestrian situations, good crowd dispersion phenomena are achieved. Simulation results under different conditions demonstrate that information transmission cannot always induce successful crowd dispersion in all situations. This depends on whether decision strategies in response to information on danger are unified and effective, especially in dense crowds. Results also suggest that an increase in drift strength at low density and the percentage of pedestrians, who choose one of the furthest unoccupied Von Neumann neighbors from the dangerous source as the drift direction at high density, is helpful in crowd dispersion. Compared with previous work, our comprehensive study improves an in-depth understanding of nonlinear crowd dynamics under the effect of information on danger.

Two's a crowd? Crowding effect in a parasitic castrator drives differences in reproductive resource allocation in single vs double infections.

PubMed

Fong, Caitlin R; Moron, Nancy A; Kuris, Armand M

2017-04-01

The 'crowding effect' is a result of competition by parasites within a host for finite resources. Typically, the severity of this effect increases with increasing numbers of parasites within a host and manifests in reduced body size and thus fitness. Evidence for the crowding effect is mixed - while some have found negative effects, others have found a positive effect of increased parasite load on parasite fitness. Parasites are consumers with diverse trophic strategies reflected in their life history traits. These distinctions are useful to predict the effects of crowding. We studied a parasitic castrator, a parasite that usurps host reproductive energy and renders the host sterile. Parasitic castrators typically occur as single infections within hosts. With multiple parasitic castrators, we expect strong competition and evidence of crowding. We directly assess the effect of crowding on reproductive success in a barnacle population infected by a unique parasitic castrator, Hemioniscus balani, an isopod parasite that infects and blocks reproduction of barnacles. We find (1) strong evidence of crowding in double infections, (2) increased frequency of double infections in larger barnacle hosts with more resources and (3) perfect compensation in egg production, supporting strong space limitation. Our results document that the effects of crowding are particularly severe for this parasitic castrator, and may be applicable to other castrators that are also resource or space limited.

Automated Student Model Improvement

ERIC Educational Resources Information Center

Koedinger, Kenneth R.; McLaughlin, Elizabeth A.; Stamper, John C.

2012-01-01

Student modeling plays a critical role in developing and improving instruction and instructional technologies. We present a technique for automated improvement of student models that leverages the DataShop repository, crowd sourcing, and a version of the Learning Factors Analysis algorithm. We demonstrate this method on eleven educational…

Finding Optimal Apertures in Kepler Data

NASA Astrophysics Data System (ADS)

Smith, Jeffrey C.; Morris, Robert L.; Jenkins, Jon M.; Bryson, Stephen T.; Caldwell, Douglas A.; Girouard, Forrest R.

2016-12-01

With the loss of two spacecraft reaction wheels precluding further data collection for the Kepler primary mission, even greater pressure is placed on the processing pipeline to eke out every last transit signal in the data. To that end, we have developed a new method to optimize the Kepler Simple Aperture Photometry (SAP) photometric apertures for both planet detection and minimization of systematic effects. The approach uses a per cadence modeling of the raw pixel data and then performs an aperture optimization based on signal-to-noise ratio and the Kepler Combined Differential Photometric Precision (CDPP), which is a measure of the noise over the duration of a reference transit signal. We have found the new apertures to be superior to the previous Kepler apertures. We can now also find a per cadence flux fraction in aperture and crowding metric. The new approach has also been proven to be robust at finding apertures in K2 data that help mitigate the larger motion-induced systematics in the photometry. The method further allows us to identify errors in the Kepler and K2 input catalogs.

Coupling of three-dimensional field and human thermoregulatory models in a crowded enclosure

DOE Office of Scientific and Technical Information (OSTI.GOV)

Xue, H.; Kang, Z.J.; Bong, T.Y.

1999-11-12

Health, comfort, and energy conservation are important factors to consider in the design of a building and its HVAC systems. Advanced tools are required to evaluate parameters regarding airflow, temperature, and humidity ratio in buildings, with the end results being better indoor air quality and thermal environment as well as increased confidence in the performance of buildings. A numerical model coupling the three-dimensional field and human thermoregulatory models is proposed and developed. A high-Re {kappa}-{epsilon} turbulence model is used for the field simulation. A modified 25-mode model of human thermoregulation is adopted to predict human thermal response in physiological parameters,more » such as body temperature and body heat loss. Distributions of air velocity, temperature, and moisture content are demonstrated in a crowded enclosure with mechanical ventilation under two ventilation rates. The results are analyzed and discussed. The coupling model is useful in assisting and verifying ventilation and air-conditioning system designs.« less

The impact of crowd control measures on the occurrence of stampedes during Mass Gatherings: The Hajj experience.

PubMed

Alaska, Yasser A; Aldawas, Abdulaziz D; Aljerian, Nawfal A; Memish, Ziad A; Suner, Selim

Mass gatherings present enormous challenges for emergency preparedness. Planners must anticipate and prepare for communicable and non-communicable disease outbreaks, illnesses, and injuries to participants, crowd control, and disaster responses to unforeseen natural or man-made threats. The Hajj, the largest annually recurring mass gathering event on earth. It attracts about 3 million pilgrims from over 180 countries who assemble in Mecca over a 1-week period. A literature review was conducted using Medline and OVID, while searching for published data concerning human stampedes and crowd control measures implemented to prevent human stampedes. The review was further extended to include media reports and published numbers and reports about Hajj from the Saudi Arabian government, in both the English and Arabic languages. Because millions of pilgrims undertake their religious ritual within strict constraints in term of space and time; this rigour and strictness have led to a series of large crowd disasters over several years, thus putting pressure on the authorities. In the past few years, the government of Saudi Arabia have put an enormous effort to solve this difficulty using state of the art innovative scientific means. The use of crowd simulation models, assessment of the best ways of grouping and scheduling pilgrims, crowd management and control engineering technologies, luggage management, video monitoring, and changes in the construction of the transport system for the event. A large gathering such as the Hajj still holds an increasing risk for future disasters. International collaboration and continued vigilance in planning efforts remains an integral part of these annual preparations. The development of educational campaigns for pilgrims regarding the possible dangers is also crucial. Lessons gleaned from experiences at the Hajj may influence planning for mass gatherings of any kind, worldwide. Copyright © 2016 Elsevier Ltd. All rights reserved.

Verification Games: Crowd-Sourced Formal Verification

DTIC Science & Technology

2016-03-01

VERIFICATION GAMES : CROWD-SOURCED FORMAL VERIFICATION UNIVERSITY OF WASHINGTON MARCH 2016 FINAL TECHNICAL REPORT...DATES COVERED (From - To) JUN 2012 – SEP 2015 4. TITLE AND SUBTITLE VERIFICATION GAMES : CROWD-SOURCED FORMAL VERIFICATION 5a. CONTRACT NUMBER FA8750...clarification memorandum dated 16 Jan 09. 13. SUPPLEMENTARY NOTES 14. ABSTRACT Over the more than three years of the project Verification Games : Crowd-sourced

The Crowd in Mind and Crowded Minds: An Experimental Investigation of Crowding Effects on Students' Views Regarding Tuition Fees in Germany

ERIC Educational Resources Information Center

Hellmann, Jens H.; Jucks, Regina

2017-01-01

In higher education, just amounts of tuition fees are often a topic of heated debate among different groups such as students, university teachers, administrative staff, and policymakers. We investigated whether unpleasant situations that students often experience at university due to social crowding can affect students' views on the justified…

Developmental Changes during Childhood in Single-Letter Acuity and Its Crowding by Surrounding Contours

ERIC Educational Resources Information Center

Jeon, Seong Taek; Hamid, Joshua; Maurer, Daphne; Lewis, Terri L.

2010-01-01

Crowding refers to impaired target recognition caused by surrounding contours. We investigated the development of crowding in central vision by comparing single-letter and crowding thresholds in groups of 5-year-olds, 8-year-olds, 11-year-olds, and adults. The task was to discriminate the orientation of a Sloan letter E. Single-letter thresholds,…

Crowd-driven Ecosystem for Evolutionary Design

DTIC Science & Technology

2012-07-28

also embeds social media connections to maximize crowd engagement. Within such an environment, experts and non- traditional contributors (crowd) can...process.” The CEED platform also embeds social media connections to maximize crowd engagement. When completed, the software developed under the...track a project of interest online through other social media (namely RSS, Facebook, and Twitter) as well as on the vehicleforge website itself

Social Network Analysis of Crowds

DTIC Science & Technology

2009-08-06

crowd responses to non-lethal weapons d tan sys ems – Prior, existing social relationships – Real time social interactions – Formal/informal...Crowd Behavior Testbed Layout Video Cameras on Trusses Importance of Social Factors • Response to non-lethal weapons fire depends on social ... relationships among crowd members – Pre-existing Personal Relationships – Ongoing Real Time Social Interactions – Formal/Informal Hierarchies • Therefore

Crowding is size and eccentricity dependent.

PubMed

Gurnsey, Rick; Roddy, Gabrielle; Chanab, Waël

2011-06-17

Crowding is a form of lateral interaction in which flanking items interfere with the detection or discrimination of a target stimulus. It is believed that crowding is a property of peripheral vision only and that no crowding occurs at fixation. If these two claims are true, then there must be a change in the nature of crowding interactions across the visual field. In three different tasks, we determined target size and flanker separation at threshold for eccentricities of 0 to 16° in the lower visual field for 7 relative separations (1.25 to 8 times target size). In all three tasks, the magnitude of crowding increases with eccentricity; there was no crowding at fixation and extreme crowding at 16°. Using a novel double-scaling procedure, we show that the non-foveal data in all three tasks can be characterized as shifted versions of the same psychometric function such that different sections of the function characterize data at each eccentricity. This pattern of results can be understood in terms of size-dependent responses to the target and distance-dependent interference from the flankers. The data suggest that the distance-dependent interference increases with eccentricity.

The influence of crowd density on the sound environment of commercial pedestrian streets.

PubMed

Meng, Qi; Kang, Jian

2015-04-01

Commercial pedestrian streets are very common in China and Europe, with many situated in historic or cultural centres. The environments of these streets are important, including their sound environments. The objective of this study is to explore the relationships between the crowd density and the sound environments of commercial pedestrian streets. On-site measurements were performed at the case study site in Harbin, China, and a questionnaire was administered. The sound pressure measurements showed that the crowd density has an insignificant effect on sound pressure below 0.05 persons/m2, whereas when the crowd density is greater than 0.05 persons/m2, the sound pressure increases with crowd density. The sound sources were analysed, showing that several typical sound sources, such as traffic noise, can be masked by the sounds resulting from dense crowds. The acoustic analysis showed that crowd densities outside the range of 0.10 to 0.25 persons/m2 exhibited lower acoustic comfort evaluation scores. In terms of audiovisual characteristics, the subjective loudness increases with greater crowd density, while the acoustic comfort decreases. The results for an indoor underground shopping street are also presented for comparison. Copyright © 2014 Elsevier B.V. All rights reserved.

An evaluation of self-esteem and quality of life in orthodontic patients: effects of crowding and protrusion.

PubMed

Jung, Min-Ho

2015-09-01

To evaluate the effect of dental crowding and lip protrusion on self-esteem and quality of life (QOL) in female orthodontic patients with Class I malocclusion. The study sample consisted of 201 patients (mean age 22.6 ± 3.0 years) who sought orthodontic treatment. All the patients were evaluated before treatment in terms of their degree of dental crowding and lip protrusion. Rosenberg's Self-Esteem Scale and the Orthognathic Quality of Life Questionnaire (OQLQ) were used to determine self-esteem and QOL and to evaluate whether these values were related to malocclusion severity. The results indicated that severe crowding and severe protrusion can result in lower self-esteem and poorer QOL (P < .05) than mild crowding and protrusion in Class I malocclusion. In the oral function component of the OQLQ, the severity of protrusion did not have significant effect. In Class I malocclusion, patients with mild crowding or protrusion had significantly better self-esteem and QOL scores than severe crowding or protrusion patients.

High Incidence of Progressive Postnatal Cerebellar Enlargement in Costello Syndrome: Brain Overgrowth Associated with HRAS Mutations as the Likely Cause of Structural Brain and Spinal Cord Abnormalities

PubMed Central

Gripp, Karen W.; Hopkins, Elisabeth; Doyle, Daniel; Dobyns, William B.

2010-01-01

Costello syndrome is a rasopathy caused by germline mutations in the proto-oncogene HRAS. Its presentation includes failure-to-thrive with macrocephaly, characteristic facial features, hypertrophic cardiomyopathy, papillomata, malignant tumors, and cognitive impairment. In a systematic review we found absolute or relative macrocephaly (100%), ventriculomegaly (50%), and other abnormalities on brain and spinal cord imaging studies in 27/28 individuals. Posterior fossa crowding with cerebellar tonsillar herniation (CBTH) was noted in 27/28 (96%), and in 10/17 (59%) with serial studies posterior fossa crowding progressed. Sequelae of posterior fossa crowding and CBTH included hydrocephalus requiring shunt or ventriculostomy (25%), Chiari 1 malformation (32%) and syrinx formation (25%). Our data reveal macrocephaly with progressive frontal bossing and CBTH, documenting an ongoing process rather than a static congenital anomaly. Comparison of images obtained in young infants to subsequent studies demonstrated postnatal development of posterior fossa crowding. This process of evolving megalencephaly and cerebellar enlargement is in keeping with mouse model data, delineating abnormal genesis of neurons and glia, resulting in an increased number of astrocytes and enlarged brain volume. In Costello syndrome and macrocephaly-capillary malformation syndrome disproportionate brain growth is the main factor resulting in postnatal CBTH and Chiari 1 malformation. PMID:20425820

Perceptual Learning in Children With Infantile Nystagmus: Effects on Visual Performance.

PubMed

Huurneman, Bianca; Boonstra, F Nienke; Goossens, Jeroen

2016-08-01

To evaluate whether computerized training with a crowded or uncrowded letter-discrimination task reduces visual impairment (VI) in 6- to 11-year-old children with infantile nystagmus (IN) who suffer from increased foveal crowding, reduced visual acuity, and reduced stereopsis. Thirty-six children with IN were included. Eighteen had idiopathic IN and 18 had oculocutaneous albinism. These children were divided in two training groups matched on age and diagnosis: a crowded training group (n = 18) and an uncrowded training group (n = 18). Training occurred two times per week during 5 weeks (3500 trials per training). Eleven age-matched children with normal vision were included to assess baseline differences in task performance and test-retest learning. Main outcome measures were task-specific performance, distance and near visual acuity (DVA and NVA), intensity and extent of (foveal) crowding at 5 m and 40 cm, and stereopsis. Training resulted in task-specific improvements. Both training groups also showed uncrowded and crowded DVA improvements (0.10 ± 0.02 and 0.11 ± 0.02 logMAR) and improved stereopsis (670 ± 249″). Crowded NVA improved only in the crowded training group (0.15 ± 0.02 logMAR), which was also the only group showing a reduction in near crowding intensity (0.08 ± 0.03 logMAR). Effects were not due to test-retest learning. Perceptual learning with or without distractors reduces the extent of crowding and improves visual acuity in children with IN. Training with distractors improves near vision more than training with single optotypes. Perceptual learning also transfers to DVA and NVA under uncrowded and crowded conditions and even stereopsis. Learning curves indicated that improvements may be larger after longer training.

Fluorescence Dynamics of a FRET Probe Designed for Crowding Studies.

PubMed

Currie, Megan; Leopold, Hannah; Schwarz, Jacob; Boersma, Arnold J; Sheets, Erin D; Heikal, Ahmed A

2017-06-15

Living cells are crowded with macromolecules and organelles. As a result, there is an urgent need for molecular sensors for quantitative, site-specific assessment of the macromolecular crowding effects on a myriad of biochemical processes toward quantitative cell biology and biophysics. Here we investigate the excited-state dynamics and translational diffusion of a novel FRET sensor (mCerulean-linker-mCitrine) in a buffer (PBS, pH 7.4) at room temperature. Complementary experiments were carried out on free CFP, YFP, and the cleaved FRET probe as controls. The wavelength-dependent fluorescence lifetime measurements of the donor and acceptor in the FRET probe, using the time-correlated single-photon counting technique, indicate an energy transfer efficiency of 6.8 ± 0.9% in PBS, with distinct excited-state dynamics from the recombinant CFP and YFP. The estimated mCerulean-mCitrine distance in this FRET probe is 7.7 ± 0.2 nm. The energy transfer efficiency increases (11.5 ± 0.9%) as the concentration of Ficoll-70 increases over the range of 0-300 g/L with an estimated mCerulean-mCitrine distance of 6.1 ± 0.2 nm. Complementary time-resolved anisotropy measurements suggest that the rotational diffusion of hetero-FRET in PBS is sensitive to the energy transfer from the donor to the acceptor. The results also suggest that the linker, -(GSG) 6 A(EAAAK) 6 A(GSG) 6 A(EAAAK) 6 A(GSG) 6 -, is rather flexible, and the observed rotational dynamics is likely to be due to a segmental mobility of the FRET pairs rather than an overall tumbling motion of a rigid probe. Comparative studies on a new construct of a FRET probe with a shorter, more flexible linker, mCerulean-(GSG) 18 -mCitrine, reveal enhanced energy transfer efficiency. On the millisecond time scale, fluorescence fluctuation analyses of the acceptor (excited at 488 nm) provide a means to examine the translational diffusion coefficient of the FRET probe. The results also suggest that the linker is flexible in this FRET probe, and the observed diffusion coefficient is faster than predicted as compared to the cleaved FRET probe. Our results serve as a point of reference for this FRET probe in a buffer toward its full potential as a sensor for macromolecular crowding in living cells and tissues.

A Research Agenda to Assure Equity During Periods of Emergency Department Crowding

PubMed Central

Hwang, Ula; Weber, Ellen J.; Richardson, Lynne D.; Sweet, Vicki; Todd, Knox; Abraham, Gallane; Ankel, Felix

2012-01-01

The effect of emergency department (ED) crowding on equitable care is the least studied of the domains of quality as defined by the Institute of Medicine (IOM). Inequities in access and treatment throughout the health care system are well documented in all fields of medicine. While there is little evidence demonstrating that inequity is worsened by crowding, theory and evidence from social science disciplines, as well as known barriers to care for vulnerable populations, would suggest that crowding will worsen inequities. To design successful interventions, however, it is important to first understand how crowding can result in disparities and base interventions on these mechanisms. A research agenda is proposed to understand mechanisms that may threaten equity during periods of crowding and design and test potential interventions that may ensure the equitable aspect of quality of care. PMID:22168197

Identification of Crowding Stress Tolerance Co-Expression Networks Involved in Sweet Corn Yield

PubMed Central

Choe, Eunsoo; Drnevich, Jenny; Williams, Martin M.

2016-01-01

Tolerance to crowding stress has played a crucial role in improving agronomic productivity in field corn; however, commercial sweet corn hybrids vary greatly in crowding stress tolerance. The objectives were to 1) explore transcriptional changes among sweet corn hybrids with differential yield under crowding stress, 2) identify relationships between phenotypic responses and gene expression patterns, and 3) identify groups of genes associated with yield and crowding stress tolerance. Under conditions of crowding stress, three high-yielding and three low-yielding sweet corn hybrids were grouped for transcriptional and phenotypic analyses. Transcriptional analyses identified from 372 to 859 common differentially expressed genes (DEGs) for each hybrid. Large gene expression pattern variation among hybrids and only 26 common DEGs across all hybrid comparisons were identified, suggesting each hybrid has a unique response to crowding stress. Over-represented biological functions of DEGs also differed among hybrids. Strong correlation was observed between: 1) modules with up-regulation in high-yielding hybrids and yield traits, and 2) modules with up-regulation in low-yielding hybrids and plant/ear traits. Modules linked with yield traits may be important crowding stress response mechanisms influencing crop yield. Functional analysis of the modules and common DEGs identified candidate crowding stress tolerant processes in photosynthesis, glycolysis, cell wall, carbohydrate/nitrogen metabolic process, chromatin, and transcription regulation. Moreover, these biological functions were greatly inter-connected, indicating the importance of improving the mechanisms as a network. PMID:26796516

Perceptual learning in children with visual impairment improves near visual acuity.

PubMed

Huurneman, Bianca; Boonstra, F Nienke; Cox, Ralf F A; van Rens, Ger; Cillessen, Antonius H N

2013-09-17

This study investigated whether visual perceptual learning can improve near visual acuity and reduce foveal crowding effects in four- to nine-year-old children with visual impairment. Participants were 45 children with visual impairment and 29 children with normal vision. Children with visual impairment were divided into three groups: a magnifier group (n = 12), a crowded perceptual learning group (n = 18), and an uncrowded perceptual learning group (n = 15). Children with normal vision also were divided in three groups, but were measured only at baseline. Dependent variables were single near visual acuity (NVA), crowded NVA, LH line 50% crowding NVA, number of trials, accuracy, performance time, amount of small errors, and amount of large errors. Children with visual impairment trained during six weeks, two times per week, for 30 minutes (12 training sessions). After training, children showed significant improvement of NVA in addition to specific improvements on the training task. The crowded perceptual learning group showed the largest acuity improvements (1.7 logMAR lines on the crowded chart, P < 0.001). Only the children in the crowded perceptual learning group showed improvements on all NVA charts. Children with visual impairment benefit from perceptual training. While task-specific improvements were observed in all training groups, transfer to crowded NVA was largest in the crowded perceptual learning group. To our knowledge, this is the first study to provide evidence for the improvement of NVA by perceptual learning in children with visual impairment. (http://www.trialregister.nl number, NTR2537.).

Computational modeling and statistical analyses on individual contact rate and exposure to disease in complex and confined transportation hubs

NASA Astrophysics Data System (ADS)

Wang, W. L.; Tsui, K. L.; Lo, S. M.; Liu, S. B.

2018-01-01

Crowded transportation hubs such as metro stations are thought as ideal places for the development and spread of epidemics. However, for the special features of complex spatial layout, confined environment with a large number of highly mobile individuals, it is difficult to quantify human contacts in such environments, wherein disease spreading dynamics were less explored in the previous studies. Due to the heterogeneity and dynamic nature of human interactions, increasing studies proved the importance of contact distance and length of contact in transmission probabilities. In this study, we show how detailed information on contact and exposure patterns can be obtained by statistical analyses on microscopic crowd simulation data. To be specific, a pedestrian simulation model-CityFlow was employed to reproduce individuals' movements in a metro station based on site survey data, values and distributions of individual contact rate and exposure in different simulation cases were obtained and analyzed. It is interesting that Weibull distribution fitted the histogram values of individual-based exposure in each case very well. Moreover, we found both individual contact rate and exposure had linear relationship with the average crowd densities of the environments. The results obtained in this paper can provide reference to epidemic study in complex and confined transportation hubs and refine the existing disease spreading models.

The VMC survey. XXVIII. Improved measurements of the proper motion of the Galactic globular cluster 47 Tucanae

NASA Astrophysics Data System (ADS)

Niederhofer, Florian; Cioni, Maria-Rosa L.; Rubele, Stefano; Schmidt, Thomas; Bekki, Kenji; de Grijs, Richard; Emerson, Jim; Ivanov, Valentin D.; Oliveira, Joana M.; Petr-Gotzens, Monika G.; Ripepi, Vincenzo; Sun, Ning-Chen; van Loon, Jacco Th.

2018-05-01

We use deep multi-epoch point-spread function (PSF) photometry taken with the Visible and Infrared Survey Telescope for Astronomy (VISTA) to measure and analyze the proper motions of stars within the Galactic globular cluster 47 Tucanae (47 Tuc, NGC 104). The observations are part of the ongoing near-infrared VISTA survey of the Magellanic Cloud system (VMC). The data analyzed in this study correspond to one VMC tile, which covers a total sky area of 1.77 deg2. Absolute proper motions with respect to 9070 background galaxies are calculated from a linear regression model applied to the positions of stars in 11 epochs in the Ks filter. The data extend over a total time baseline of about 17 months. We found an overall median proper motion of the stars within 47 Tuc of (μαcos(δ), μδ) = (+5.89 ± 0.02 (statistical) ± 0.13 (systematic), -2.14 ± 0.02 (statistical) ± 0.08 (systematic)) mas yr-1, based on the measurements of 35 000 individual sources between 5' and 42' from the cluster center. We compared our result to the proper motions from the newest US Naval Observatory CCD Astrograph Catalog (UCAC5), which includes data from the Gaia data release 1. Selecting cluster members ( 2700 stars), we found a median proper motion of (μαcos(δ), μδ) = (+5.30 ± 0.03 (statistical) ± 0.70 (systematic), -2.70 ± 0.03 (statistical) ± 0.70 (systematic)) mas yr-1. Comparing the results with measurements in the literature, we found that the values derived from the VMC data are consistent with the UCAC5 result, and are close to measurements obtained using the Hubble Space Telescope. We combined our proper motion results with radial velocity measurements from the literature and reconstructed the orbit of 47 Tuc, finding that the cluster is on an orbit with a low ellipticity and is confined within the inner 7.5 kpc of the Galaxy. We show that the use of an increased time baseline in combination with PSF-determined stellar centroids in crowded regions significantly improves the accuracy of the method. In future works, we will apply the methods described here to more VMC tiles to study in detail the kinematics of the Magellanic Clouds. Based on observations made with VISTA at the Paranal Observatory under program ID 179.B-2003.

Peer Crowd Identification and Indoor Artificial UV Tanning Behavioral Tendencies

PubMed Central

STAPLETON, JEROD; TURRISI, ROB; HILLHOUSE, JOEL

2014-01-01

In this study, the relation between peer crowd identification and indoor tanning behavioral tendencies was examined. Participants were 174 undergraduate students at a large university in the USA. Results indicated peer crowd identification was significantly associated with indoor artificial UV tanning behavioral tendencies (attitudes, normative beliefs, past year use and intentions) independent of gender and skin type. Participants who identified with the popular peer crowd were at the greatest risk for indoor tanning UV exposure while identification with the brain crowd was protective against such behavior. The findings are discussed in terms of implications for future skin cancer intervention efforts. PMID:18809645

An evaluation of self-esteem and quality of life in orthodontic patients: Effects of crowding and protrusion.

PubMed

Jung, Min-Ho

2014-12-31

Objective: To evaluate the effect of dental crowding and lip protrusion on self-esteem and quality of life (QOL) in female orthodontic patients with Class I malocclusion. Materials and Methods: The study sample consisted of 201 patients (mean age 22.6 ± 3.0 years) who sought orthodontic treatment. All the patients were evaluated before treatment in terms of their degree of dental crowding and lip protrusion. Rosenberg's Self-Esteem Scale and the Orthognathic Quality of Life Questionnaire (OQLQ) were used to determine self-esteem and QOL and to evaluate whether these values were related to malocclusion severity. Results: The results indicated that severe crowding and severe protrusion can result in lower self-esteem and poorer QOL (P < .05) than mild crowding and protrusion in Class I malocclusion. In the oral function component of the OQLQ, the severity of protrusion did not have significant effect. Conclusions: In Class I malocclusion, patients with mild crowding or protrusion had significantly better self-esteem and QOL scores than severe crowding or protrusion patients.

A crowdful of letters: disentangling the role of similarity, eccentricity and spatial frequencies in letter crowding.

PubMed

Zahabi, Sacha; Arguin, Martin

2014-04-01

The present study investigated the joint impact of target-flanker similarity and of spatial frequency content on the crowding effect in letter identification. We presented spatial frequency filtered letters to neurologically intact non-dyslexic readers while manipulating target-flanker distance, target eccentricity and target-flanker confusability (letter similarity metric based on published letter confusion matrices). The results show that high target-flanker confusability magnifies crowding. They also reveal an intricate pattern of interactions of the spatial frequency content of the stimuli with target eccentricity, flanker distance and similarity. The findings are congruent with the notion that crowding results from the inappropriate pooling of target and flanker features and that this integration is more likely to match a response template at a subsequent decision stage with similar than dissimilar flankers. In addition, the evidence suggests that crowding from similar flankers is biased towards relatively high spatial frequencies and that crowding shifts towards lower spatial frequencies as target eccentricity is increased. Copyright © 2014 Elsevier B.V. All rights reserved.

Inter-area correlations in the ventral visual pathway reflect feature integration

PubMed Central

Freeman, Jeremy; Donner, Tobias H.; Heeger, David J.

2011-01-01

During object perception, the brain integrates simple features into representations of complex objects. A perceptual phenomenon known as visual crowding selectively interferes with this process. Here, we use crowding to characterize a neural correlate of feature integration. Cortical activity was measured with functional magnetic resonance imaging, simultaneously in multiple areas of the ventral visual pathway (V1–V4 and the visual word form area, VWFA, which responds preferentially to familiar letters), while human subjects viewed crowded and uncrowded letters. Temporal correlations between cortical areas were lower for crowded letters than for uncrowded letters, especially between V1 and VWFA. These differences in correlation were retinotopically specific, and persisted when attention was diverted from the letters. But correlation differences were not evident when we substituted the letters with grating patches that were not crowded under our stimulus conditions. We conclude that inter-area correlations reflect feature integration and are disrupted by crowding. We propose that crowding may perturb the transformations between neural representations along the ventral pathway that underlie the integration of features into objects. PMID:21521832

Development of adolescents' peer crowd identification in relation to changes in problem behaviors.

PubMed

Doornwaard, Suzan M; Branje, Susan; Meeus, Wim H J; ter Bogt, Tom F M

2012-09-01

This 5-wave longitudinal study, which included 1,313 Dutch adolescents, examined the development of peer crowd identification in relation to changes in problem behaviors. Adolescents from 2 age cohorts annually reported their identification with 7 peer crowds and their levels of internalizing and externalizing problem behaviors. Univariate latent growth curve analyses revealed declines (i.e., "Hip Hoppers" and "Metal Heads") or declines followed by stabilization (i.e., "Nonconformists") in identification with nonconventional crowds and increases (i.e., "Elites" and "Brains") or declines followed by stabilization (i.e., "Normals" and "Jocks") in identification with conventional crowds. Multivariate latent growth curve analyses indicated that stronger and more persistent identifications with nonconventional crowds were generally associated with more problem behaviors throughout adolescence. In contrast, stronger and more persistent identifications with conventional crowds were generally associated with fewer problem behaviors throughout adolescence with the notable exception of Brains, who showed a mixed pattern. Though characterized by fewer externalizing problems, this group did report more anxiety problems. These findings and their implications are discussed. PsycINFO Database Record (c) 2012 APA, all rights reserved.

Crowding by Invisible Flankers

PubMed Central

Ho, Cristy; Cheung, Sing-Hang

2011-01-01

Background Human object recognition degrades sharply as the target object moves from central vision into peripheral vision. In particular, one's ability to recognize a peripheral target is severely impaired by the presence of flanking objects, a phenomenon known as visual crowding. Recent studies on how visual awareness of flanker existence influences crowding had shown mixed results. More importantly, it is not known whether conscious awareness of the existence of both the target and flankers are necessary for crowding to occur. Methodology/Principal Findings Here we show that crowding persists even when people are completely unaware of the flankers, which are rendered invisible through the continuous flash suppression technique. Contrast threshold for identifying the orientation of a grating pattern was elevated in the flanked condition, even when the subjects reported that they were unaware of the perceptually suppressed flankers. Moreover, we find that orientation-specific adaptation is attenuated by flankers even when both the target and flankers are invisible. Conclusions These findings complement the suggested correlation between crowding and visual awareness. What's more, our results demonstrate that conscious awareness and attention are not prerequisite for crowding. PMID:22194919

Negative feedback in ants: crowding results in less trail pheromone deposition

PubMed Central

Czaczkes, Tomer J.; Grüter, Christoph; Ratnieks, Francis L. W.

2013-01-01

Crowding in human transport networks reduces efficiency. Efficiency can be increased by appropriate control mechanisms, which are often imposed externally. Ant colonies also have distribution networks to feeding sites outside the nest and can experience crowding. However, ants do not have external controllers or leaders. Here, we report a self-organized negative feedback mechanism, based on local information, which downregulates the production of recruitment signals in crowded parts of a network by Lasius niger ants. We controlled crowding by manipulating trail width and the number of ants on a trail, and observed a 5.6-fold reduction in the number of ants depositing trail pheromone from least to most crowded conditions. We also simulated crowding by placing glass beads covered in nest-mate cuticular hydrocarbons on the trail. After 10 bead encounters over 20 cm, forager ants were 45 per cent less likely to deposit pheromone. The mechanism of negative feedback reported here is unusual in that it acts by downregulating the production of a positive feedback signal, rather than by direct inhibition or the production of an inhibitory signal. PMID:23365196

The effects of crowding agents Dextran-70k and PEG-8k on actin structure and unfolding reaction

NASA Astrophysics Data System (ADS)

Gagarskaia, Iuliia A.; Povarova, Olga I.; Uversky, Vladimir N.; Kuznetsova, Irina M.; Turoverov, Konstantin K.

2017-07-01

Recently, an increasing number of studies on proteins' structure, stability and folding are trying to bring the experimental conditions closer to those existing in a living cell, namely to the conditions of macromolecular crowding. In vitro such conditions are typically imitated by the ;inert; highly water-soluble polymers with different hydrodynamic dimensions. In this work, the effects of crowded milieu on the structure and conformational stability of actin, which is a key component of the muscle contraction system, was examined. The crowded milieu was simulated by high concentrations of PEG-8k or Dextran-70k. It was revealed that both crowding agents decelerated but not inhibited actin unfolding and made a compact state of inactivated actin thermodynamically more favorable in comparison with the unfolded state. At the same time, the high viscosity of the solution of crowding agents slowed down all processes and especially inactivated actin formation, since it involves the interaction of 14-16 partially unfolded actin molecules. The effects of crowding agent were larger when its hydrodynamic dimensions were closer to the size of globular actin.

Nanopore detection of DNA molecules in crowded neutral polymer solutions

NASA Astrophysics Data System (ADS)

Sharma, Rajesh Kumar; Dai, Liang; Doyle, Patrick; Garaj, Slaven

Nanopore sensing is a precise technique for analysis of the structure and dynamics of individual biomolecules in different environments, and has even become a prominent technique for next-gen DNA sequencing. In the nanopore sensor, an individual DNA molecule is electrophoretically translocated through a single, nanometer-scaled pore in a solid-state membrane separating two chambers filled with electrolyte. The conformation of the molecule is deduced from modulations in the ionic current through the pore during the translocation event. Using nanopores, we investigated the dynamics of the DNA molecules in a crowded solution of neutral polymers of different sizes and concentrations. The translocation dynamics depends significantly on the size and concentration of the polymers, as different contributions to the electrophoretic and entropic forces on the DNA molecules come into play. This setup offers an excellent, tuneable model-system for probing biologically relevant questions regarding the behaviour of DNA molecules in highly confined and crowded environments. Singapore-MIT Alliance for Research and Technology.

Take-up of public insurance and crowd-out of private insurance under recent CHIP expansions to higher income children.

PubMed

Gresenz, Carole Roan; Edgington, Sarah E; Laugesen, Miriam; Escarce, José J

2012-10-01

To analyze the effects of states' expansions of Children's Health Insurance Program (CHIP) eligibility to children in higher income families on health insurance coverage outcomes. 2002-2009 Current Population Survey linked to multiple secondary data sources. Instrumental variables estimation of linear probability models. Outcomes are whether the child had any public insurance, any private insurance, or no insurance coverage during the year. Among children in families with incomes between two and four times the federal poverty line (FPL), four enrolled in CHIP for every 100 who became eligible. Roughly half of the newly eligible children who took up public insurance were previously uninsured. The upper bound "crowd-out" rate was estimated to be 46 percent. The CHIP expansions to children in higher income families were associated with limited uptake of public coverage. Our results additionally suggest that there was crowd-out of private insurance coverage. © Health Research and Educational Trust.

Crowdsourcing 101: a few basics to make you the leader of the pack.

PubMed

Parvanta, Claudia; Roth, Yannig; Keller, Heidi

2013-03-01

Crowdsourcing is a problem-solving approach that taps the knowledge, energy, and creativity of a global, online community. Like marketing, crowdsourcing originated and continues to evolve in the private sector. Health communicators and social marketers can use crowdsourcing across the research-development-dissemination process. This article provides an overview of crowdsourcing and how it can be used to speed up and enhance social marketing and health communication. Nielsen's 1/9/90% model is presented as a guide for engaging appropriate crowds for tasks throughout the development process. The four Fs that motivate online contributors--Fun, Feeling good (fulfillment), Fame, and Fortune--are also presented as ways of incentivizing crowd engagement and matching the incentive to the task at hand. Crowdsourcing resources, such as curating agencies, websites, and crowd labor markets, can be tremendous force multipliers. If done strategically, crowdsourcing has the promise of giving well-researched and creative social marketing results for less money and in less time than traditional methods.

Molecular simulation investigation of the nanorheology of an entangled polymer melt

NASA Astrophysics Data System (ADS)

Karim, Mir; Khare, Rajesh; Indei, Tsutomu; Schieber, Jay

2014-03-01

Knowledge of the ``local rheology'' is important for viscoelastic systems that contain significant structural and dynamic heterogeneities, such as cellular and extra-cellular crowded environments. For homogeneous viscoelastic media, a study of probe particle motion provides information on the microstructural evolution of the medium in response to the probe particle motion. Over the last two decades, probe particle rheology has emerged as a leading experimental technique for capturing local rheology of complex fluids. In recent work [M. Karim, S. C. Kohale, T. Indei, J. D. Schieber, and R. Khare, Phys. Rev. E86, 051501 (2012)], we showed that this approach can be used in molecular dynamics (MD) simulations to study the nanoscale viscoelastic properties of an unentangled polymer melt; an important conclusion of that work was that medium and particle inertia play a crucial role in analysis of the particle rheology simulation data. MD simulations have a natural advantage that they enable study of deformation and dynamics over a small length scale around the moving probe particle. In this work, the approach is extended to compare the motion of a nanoscale probe in melts of entangled and unentangled chains. The simulations will be used to elucidate the differences between the local responses of these media to the probe particle motion. In particular, results will be presented for the differences in the resultant velocity and stress fields as well as any possible structural asymmetry developed around the moving probe particle in the entangled and unentangled cases.

On Crowd-verification of Biological Networks

PubMed Central

Ansari, Sam; Binder, Jean; Boue, Stephanie; Di Fabio, Anselmo; Hayes, William; Hoeng, Julia; Iskandar, Anita; Kleiman, Robin; Norel, Raquel; O’Neel, Bruce; Peitsch, Manuel C.; Poussin, Carine; Pratt, Dexter; Rhrissorrakrai, Kahn; Schlage, Walter K.; Stolovitzky, Gustavo; Talikka, Marja

2013-01-01

Biological networks with a structured syntax are a powerful way of representing biological information generated from high density data; however, they can become unwieldy to manage as their size and complexity increase. This article presents a crowd-verification approach for the visualization and expansion of biological networks. Web-based graphical interfaces allow visualization of causal and correlative biological relationships represented using Biological Expression Language (BEL). Crowdsourcing principles enable participants to communally annotate these relationships based on literature evidences. Gamification principles are incorporated to further engage domain experts throughout biology to gather robust peer-reviewed information from which relationships can be identified and verified. The resulting network models will represent the current status of biological knowledge within the defined boundaries, here processes related to human lung disease. These models are amenable to computational analysis. For some period following conclusion of the challenge, the published models will remain available for continuous use and expansion by the scientific community. PMID:24151423

Localization of Protein Aggregation in Escherichia coli Is Governed by Diffusion and Nucleoid Macromolecular Crowding Effect

PubMed Central

Coquel, Anne-Sophie; Jacob, Jean-Pascal; Primet, Mael; Demarez, Alice; Dimiccoli, Mariella; Julou, Thomas; Moisan, Lionel

2013-01-01

Aggregates of misfolded proteins are a hallmark of many age-related diseases. Recently, they have been linked to aging of Escherichia coli (E. coli) where protein aggregates accumulate at the old pole region of the aging bacterium. Because of the potential of E. coli as a model organism, elucidating aging and protein aggregation in this bacterium may pave the way to significant advances in our global understanding of aging. A first obstacle along this path is to decipher the mechanisms by which protein aggregates are targeted to specific intercellular locations. Here, using an integrated approach based on individual-based modeling, time-lapse fluorescence microscopy and automated image analysis, we show that the movement of aging-related protein aggregates in E. coli is purely diffusive (Brownian). Using single-particle tracking of protein aggregates in live E. coli cells, we estimated the average size and diffusion constant of the aggregates. Our results provide evidence that the aggregates passively diffuse within the cell, with diffusion constants that depend on their size in agreement with the Stokes-Einstein law. However, the aggregate displacements along the cell long axis are confined to a region that roughly corresponds to the nucleoid-free space in the cell pole, thus confirming the importance of increased macromolecular crowding in the nucleoids. We thus used 3D individual-based modeling to show that these three ingredients (diffusion, aggregation and diffusion hindrance in the nucleoids) are sufficient and necessary to reproduce the available experimental data on aggregate localization in the cells. Taken together, our results strongly support the hypothesis that the localization of aging-related protein aggregates in the poles of E. coli results from the coupling of passive diffusion-aggregation with spatially non-homogeneous macromolecular crowding. They further support the importance of “soft” intracellular structuring (based on macromolecular crowding) in diffusion-based protein localization in E. coli. PMID:23633942

Modeling electrokinetics in ionic liquids: General

DOE PAGES

Wang, Chao; Bao, Jie; Pan, Wenxiao; ...

2017-04-01

Using direct numerical simulations, we provide a thorough study regarding the electrokinetics of ionic liquids. In particular, modified Poisson–Nernst–Planck equations are solved to capture the crowding and overscreening effects characteristic of an ionic liquid. For modeling electrokinetic flows in an ionic liquid, the modified Poisson-Nernst-Planck equations are coupled with Navier–Stokes equations to study the coupling of ion transport, hydrodynamics, and electrostatic forces. Specifically, we consider the ion transport between two parallel charged surfaces, charging dynamics in a nanopore, capacitance of electric double-layer capacitors, electroosmotic flow in a nanochannel, electroconvective instability on a plane ion-selective surface, and electroconvective flow on amore » curved ionselective surface. Lastly, we also discuss how crowding and overscreening and their interplay affect the electrokinetic behaviors of ionic liquids in these application problems.« less

Simulation study of pedestrian flow in a station hall during the Spring Festival travel rush

NASA Astrophysics Data System (ADS)

Wang, Lei; Zhang, Qian; Cai, Yun; Zhang, Jianlin; Ma, Qingguo

2013-05-01

The Spring Festival is the most important festival in China. How can passengers go home smoothly and quickly during the Spring Festival travel rush, especially when emergencies of terrible winter weather happen? By modifying the social force model, we simulated the pedestrian flow in a station hall. The simulation revealed casualties happened when passengers escaped from panic induced by crowd turbulence. The results suggest that passenger numbers, ticket checking patterns, baggage volumes, and anxiety can affect the speed of passing through the waiting corridor. Our approach is meaningful in understanding the feature of a crowd moving and can be served to reproduce mass events. Therefore, it not only develops a realistic modeling of pedestrian flow but also is important for a better preparation of emergency management.

A bivalent scale for measuring crowding among deer hunters

USGS Publications Warehouse

Gigliotti, Larry M.; Chase, Loren

2014-01-01

One factor that may influence satisfaction in outdoor recreation is crowding, which historically has been defined as a negative evaluation of the density of other participants. While this definition is suitable for most scenarios, there are circumstances where encounters with others in the area are evaluated positively and thus contribute to the satisfaction of the participant. To adequately describe this phenomenon we suggest a more inclusive measurement of crowding that allows for both positive and negative evaluations of participant density to more accurately explore the relationship between crowding and satisfaction. We identified a sub-group of deer hunters who negatively evaluated the low density of other hunters, which reduced their satisfaction with their overall hunting experience. The methodology for measuring crowding in recreation research may have an important effect in identifying the relationship crowding has with other relevant variables as well as management implications.

Engaging the public in healthcare decision-making: results from a Citizens' Jury on emergency care services.

PubMed

Scuffham, P A; Moretto, N; Krinks, R; Burton, P; Whitty, J A; Wilson, A; Fitzgerald, G; Littlejohns, P; Kendall, E

2016-11-01

Policies addressing ED crowding have failed to incorporate the public's perspectives; engaging the public in such policies is needed. This study aimed at determining the public's recommendations related to alternative models of care intended to reduce crowding, optimising access to and provision of emergency care. A Citizens' Jury was convened in Queensland, Australia, to consider priority setting and resource allocation to address ED crowding. Twenty-two jurors were recruited from the electoral roll, who were interested and available to attend the jury from 15 to 17 June 2012. Juror feedback was collected via a survey immediately following the end of the jury. The jury considered that all patients attending the ED should be assessed with a minority of cases diverted for assistance elsewhere. Jurors strongly supported enabling ambulance staff to treat patients in their homes without transporting them to the ED, and allowing non-medical staff to treat some patients without seeing a doctor. Jurors supported (in principle) patient choice over aspects of their treatment (when, where and type of health professional) with some support for patients paying towards treatment but unanimous opposition for patients paying to be prioritised. Most of the jurors were satisfied with their experience of the Citizens' Jury process, but some jurors perceived the time allocated for deliberations as insufficient. These findings suggest that the general public may be open to flexible models of emergency care. The jury provided clear recommendations for direct public input to guide health policy to tackle ED crowding. Published by the BMJ Publishing Group Limited. For permission to use (where not already granted under a licence) please go to http://www.bmj.com/company/products-services/rights-and-licensing/.

Non-Brownian diffusion in lipid membranes: Experiments and simulations.

PubMed

Metzler, R; Jeon, J-H; Cherstvy, A G

2016-10-01

The dynamics of constituents and the surface response of cellular membranes-also in connection to the binding of various particles and macromolecules to the membrane-are still a matter of controversy in the membrane biophysics community, particularly with respect to crowded membranes of living biological cells. We here put into perspective recent single particle tracking experiments in the plasma membranes of living cells and supercomputing studies of lipid bilayer model membranes with and without protein crowding. Special emphasis is put on the observation of anomalous, non-Brownian diffusion of both lipid molecules and proteins embedded in the lipid bilayer. While single component, pure lipid bilayers in simulations exhibit only transient anomalous diffusion of lipid molecules on nanosecond time scales, the persistence of anomalous diffusion becomes significantly longer ranged on the addition of disorder-through the addition of cholesterol or proteins-and on passing of the membrane lipids to the gel phase. Concurrently, experiments demonstrate the anomalous diffusion of membrane embedded proteins up to macroscopic time scales in the minute time range. Particular emphasis will be put on the physical character of the anomalous diffusion, in particular, the occurrence of ageing observed in the experiments-the effective diffusivity of the measured particles is a decreasing function of time. Moreover, we present results for the time dependent local scaling exponent of the mean squared displacement of the monitored particles. Recent results finding deviations from the commonly assumed Gaussian diffusion patterns in protein crowded membranes are reported. The properties of the displacement autocorrelation function of the lipid molecules are discussed in the light of their appropriate physical anomalous diffusion models, both for non-crowded and crowded membranes. In the last part of this review we address the upcoming field of membrane distortion by elongated membrane-binding particles. We discuss how membrane compartmentalisation and the particle-membrane binding energy may impact the dynamics and response of lipid membranes. This article is part of a Special Issue entitled: Biosimulations edited by Ilpo Vattulainen and Tomasz Róg. Copyright © 2016 The Authors. Published by Elsevier B.V. All rights reserved.

Crowd-sourced assessment of technical skills: an adjunct to urology resident surgical simulation training.

PubMed

Holst, Daniel; Kowalewski, Timothy M; White, Lee W; Brand, Timothy C; Harper, Jonathan D; Sorenson, Mathew D; Kirsch, Sarah; Lendvay, Thomas S

2015-05-01

Crowdsourcing is the practice of obtaining services from a large group of people, typically an online community. Validated methods of evaluating surgical video are time-intensive, expensive, and involve participation of multiple expert surgeons. We sought to obtain valid performance scores of urologic trainees and faculty on a dry-laboratory robotic surgery task module by using crowdsourcing through a web-based grading tool called Crowd Sourced Assessment of Technical Skill (CSATS). IRB approval was granted to test the technical skills grading accuracy of Amazon.com Mechanical Turk™ crowd-workers compared to three expert faculty surgeon graders. The two groups assessed dry-laboratory robotic surgical suturing performances of three urology residents (PGY-2, -4, -5) and two faculty using three performance domains from the validated Global Evaluative Assessment of Robotic Skills assessment tool. After an average of 2 hours 50 minutes, each of the five videos received 50 crowd-worker assessments. The inter-rater reliability (IRR) between the surgeons and crowd was 0.91 using Cronbach's alpha statistic (confidence intervals=0.20-0.92), indicating an agreement level between the two groups of "excellent." The crowds were able to discriminate the surgical level, and both the crowds and the expert faculty surgeon graders scored one senior trainee's performance above a faculty's performance. Surgery-naive crowd-workers can rapidly assess varying levels of surgical skill accurately relative to a panel of faculty raters. The crowds provided rapid feedback and were inexpensive. CSATS may be a valuable adjunct to surgical simulation training as requirements for more granular and iterative performance tracking of trainees become mandated and commonplace.

The Hip Hop peer crowd: An opportunity for intervention to reduce tobacco use among at-risk youth.

PubMed

Walker, Matthew W; Navarro, Mario A; Hoffman, Leah; Wagner, Dana E; Stalgaitis, Carolyn A; Jordan, Jeffrey W

2018-07-01

Peer crowds, peer groups with macro-level connections and shared norms that transcend geography and race/ethnicity, have been linked to risky health behaviors. Research has demonstrated that Hip Hop peer crowd identification, which is common among multicultural youth, is associated with increased risk of tobacco use. To address this, the FDA Center for Tobacco Products created Fresh Empire, the first national tobacco education campaign tailored for Hip Hop youth aged 12-17 who are multicultural (Hispanic, African American, Asian-Pacific Islander, or Multiracial). As part of campaign development, peer crowd (Hip Hop, Mainstream, Popular, Alternative, Country) and cigarette smoking status were examined for the first time with a nationally recruited sample. Youth were recruited via targeted social media advertisements. Participants aged 13-17 (n = 5153) self-reported peer crowd identification via the I-Base Survey™ and cigarette smoking status. Differences in smoking status by peer crowd were examined using chi-square and followed up with z-tests to identify specific differences. Alternative youth were most at risk of cigarette smoking, followed by Hip Hop. Specifically, Hip Hop youth were significantly less likely to be Non-susceptible Non-triers than Popular, Mainstream, and Country youth, and more likely to be Experimenters than Popular and Mainstream youth. Representative studies show that Alternative is relatively small compared to other high-risk crowds, such as the Hip Hop peer crowd. The current research underscores the potential utility of interventions tailored to larger at-risk crowds for campaigns like Fresh Empire. Published by Elsevier Ltd.

Effect of stimulus configuration on crowding in strabismic amblyopia.

PubMed

Norgett, Yvonne; Siderov, John

2017-11-01

Foveal vision in strabismic amblyopia can show increased levels of crowding, akin to typical peripheral vision. Target-flanker similarity and visual-acuity test configuration may cause the magnitude of crowding to vary in strabismic amblyopia. We used custom-designed visual acuity tests to investigate crowding in observers with strabismic amblyopia. LogMAR was measured monocularly in both eyes of 11 adults with strabismic or mixed strabismic/anisometropic amblyopia using custom-designed letter tests. The tests used single-letter and linear formats with either bar or letter flankers to introduce crowding. Tests were presented monocularly on a high-resolution display at a test distance of 4 m, using standardized instructions. For each condition, five letters of each size were shown; testing continued until three letters of a given size were named incorrectly. Uncrowded logMAR was subtracted from logMAR in each of the crowded tests to highlight the crowding effect. Repeated-measures ANOVA showed that letter flankers and linear presentation individually resulted in poorer performance in the amblyopic eyes (respectively, mean normalized logMAR = 0.29, SE = 0.07, mean normalized logMAR = 0.27, SE = 0.07; p < 0.05) and together had an additive effect (mean = 0.42, SE = 0.09, p < 0.001). There was no difference across the tests in the fellow eyes (p > 0.05). Both linear presentation and letter rather than bar flankers increase crowding in the amblyopic eyes of people with strabismic amblyopia. These results suggest the influence of more than one mechanism contributing to crowding in linear visual-acuity charts with letter flankers.

Macromolecular crowding: chemistry and physics meet biology (Ascona, Switzerland, 10-14 June 2012).

PubMed

Foffi, G; Pastore, A; Piazza, F; Temussi, P A

2013-08-02

More than 60 years of biochemical and biophysical studies have accustomed us to think of proteins as highly purified entities that act in isolation, more or less freely diffusing until they find their cognate partner to bind to. While in vitro experiments that reproduce these conditions largely remain the only way to investigate the intrinsic properties of molecules, this approach ignores an important factor: in their natural milieu , proteins are surrounded by several other molecules of different chemical nature, and this crowded environment can considerably modify their behaviour. About 40% of the cellular volume on average is occupied by all sorts of molecules. Furthermore, biological macromolecules live and operate in an extremely structured and complex environment within the cell (endoplasmic reticulum, Golgi apparatus, cytoskeletal structures, etc). Hence, to further complicate the picture, the interior of the cell is by no means a simply crowded medium, rather, a most crowded and confining one. In recent times, several approaches have been developed in the attempt to take into account important factors such as the ones mentioned above, at both theoretical and experimental levels, so that this field of research is now emerging as one of the most thriving in molecular and cell biology (see figure 1). [Formula: see text] Figure 1. Left: number of articles containing the word 'crowding' as a keyword limited to the biological and chemical science domains (source: ISI Web of Science). The arrow flags the 2003 'EMBO Workshop on Biological Implications of Macromolecular Crowding' (Embo, 2012). Right: number of citations to articles containing the word 'crowding' limited to the same domains (bars) and an exponential regression curve (source: Elsevier Scopus). To promote the importance of molecular crowding and confinement and provide researchers active in this field an interdisciplinary forum for meeting and exchanging ideas, we recently organized an international conference held in Ascona from 10 to 14 June 2012. In the unique scenario of the Maggiore lake and absorbed in the magic atmosphere of the Centro Stefano Franscini (CSF) at Monte Verità, we enjoyed three-and-a-half days of intense and inspiring activity, where not only many of the most prominent scientists working on macromolecular crowding, but also experts in closely related fields such as colloids and soft matter presented their work. The meeting was intended and has been organized to bring theoreticians and experimentalists together in the attempt to promote an active dialogue. Moreover, we wanted different disciplines to be represented, notably physics and chemistry, besides biology, as cross-fertilization is proving an increasingly fundamental source of inspiration and advancement. This issue of Physical Biology (PB) features a selection of the oral contributions presented at the conference, expanded in the form of research or review articles. PB, one of the scientific journals of the Institute of Physics (IOP), is one of the most dynamic and lively forums active at the interface between biology on one side, and physics and mathematics on the other. As its mission is stated by IOP, PB 'focuses on research in which physics-based approaches lead to new insights into biological systems at all scales of space and time, and all levels of complexity'. For these reasons, and also in view of its high reputation and broad readership, PB appears to be the ideal place for disseminating the thriving pieces of research presented at the conference. We are extremely grateful to PB and its kind and efficient editorial staff who helped make this issue a great scientific follow-up to the conference. The opening lecture of the conference, the first of four day-opening keynote lectures, was given by Allen P Minton from NIH (USA), possibly the most influential among the pioneers in the field. He provided a lucid and well-thought-out overview of the concept of macromolecular crowding through an exhaustive chronological account of the major milestones. It is clear that the concept of excluded volume as a key factor remains central to the concept of molecular crowding. As a consequence, simple descriptive paradigms borrowed essentially from colloid physics may still provide useful tools to understand the subtle effects of crowding and confinement in living matter. The contiguity between crowding, colloids and soft matter further emerged as an important concept in the course of the conference in several theoretical lectures and a few experimental ones. Dave Thirumalai, from the University of Maryland (USA), one of the most active theoreticians in the field of theoretical biophysics, outlined scaling theories, concepts from colloid literature and different simulation techniques to describe scenarios for crowding-induced changes in the structure and dynamics of proteins and RNA. In particular, he showed the importance of the shape of crowding particles in affecting folding oligomerization of amyloidogenic peptides. Johannes Schöneberg, from IMPRS, Mathematics Institute (Germany), illustrated ReaDDy , a newly developed particle-based simulation software tool for reaction-diffusion dynamics, developed in the group of Frank Noe at EMPRS. He showed that ReaDDy makes it possible to bridge the gap between soft matter and molecular dynamics (MD) simulations on the one hand and particle-based stochastic reaction-diffusion simulations on the other. We asked Johannes to organize a tutorial session to lead interested participants into the package and 'get their hands wet' under the guidance of the developers. The tutorial session was indeed successful and the broad possibilities offered by the simulation toolkit appeared to be clear to the participants. Paolo De Los Rios, from the Ecole Polytechnique Fédérale de Lausanne (EPFL, Switzerland), examined the complexity of the effects caused by crowding conditions from the point of view of statistical physics. Starting from a modification of the well-known Smoluchowski approach to calculate the encounter rate of diffusion-limited reactions, he showed how more realistic situations accounting for crowding effects could be treated equally well on the same theoretical grounds. This talk marked an important point in the conference as it reinforced the idea that simple models of theoretical physics still have the power to provide inspiring results in spite of the intrinsic simplifications of such theoretical approaches. Along the same lines, Nicolas Dorsaz, from the University of Cambridge (UK), proposed an extension of the Smoluchowski framework that incorporates repulsive and attracting interactions between the reactants. This approach was illustrated by reaction rates obtained from event-driven Brownian dynamics and dynamical Monte Carlo simulations. Another striking example of the physical subtleties associated with modelling crowding effects was provided by Jeffrey Skolnick, from the Georgia Institute of Technology (USA). He examined the role of hydrodynamic interactions in the self-organization of biological assemblies in the presence of crowding. His results strongly suggest that hydrodynamic interactions greatly affect the kinetics of self-assembly reactions, so that including them in the picture appears crucial for understanding the dynamics of biological systems in vivo . Margareth Cheung, from the University of Houston (USA), emphasized that how the crowded environment inside a cell affects the structural conformation of a protein with a spherical shape is a vital question because the geometry of proteins and protein-protein complexes are far from globules in vivo . Her work demonstrates the malleability of 'native' proteins and implies that crowding-induced shape changes may be important for protein function and malfunction in vivo . Huan-Xiang Zhou, from the Florida State University (USA), focused on atomistic simulations of protein folding and binding under crowding conditions. His lab has developed a post-processing method that allows the atomistic representation of proteins in folding and binding processes under crowding. A comparison with experimental results was also presented. Other lecturers pointed out that there are still aspects not entirely explored in the effects of both crowding and confinement. As suggested in the talk by Gary Pielak, from the University of North Carolina (USA), the currently used synthetic crowding agents are far from being satisfactory in replicating naturally occurring effects associated with crowded environments. For example, non-specific binding seems to play a subtle role in the cell, as natural macromolecules can induce both stabilization and destabilization when used as crowders. It is indeed possible to fine-tune the effect of proteins, as crowders, on the stability of other proteins. Another aspect that became clear is that new, more powerful methods need to be developed to study the effect of crowding, but even more to compare crowding and confinement. Indeed, it appeared clear from the lecture by Pierandrea Temussi, from the University of Naples (Italy), that a reliable comparison of the effects of crowding and confinement on the stability of proteins can only be based on the measurement of the whole stability curve of the same protein. Controversial aspects do not pertain only to the influence of crowding on protein stability, but also to aggregation phenomena in natural fluids. Domenico Sanfelice, from NIMR (London, UK), reported an interesting case of the apparent influence of crowding on aggregation. Hen egg white, a possible natural medium to study macromolecules in crowded conditions can dramatically increase the aggregation kinetics of proteins with an inbuilt tendency to associate. By carefully dissecting the phenomenology, it was shown that only part of this effect is due to crowding, while another factor playing an important role is the interaction with proteins from the milieu . In other words, high-molecular-weight glycoproteins can act as efficient molecular seeds for aggregation. A special topic of great relevance in the conference appeared to be the direct study of crowding in living systems. Alan Verkman, from the University of California, San Francisco (USA), one of the world's leading scientific personalities in the field of experimental investigation of crowding and confinement, was invited to give the second plenary lecture devoted to the experimental study of crowding effects in vivo . In his keynote lecture, Dr Verkman led us on a wide and compelling tour, exploring the main experimental approaches to study molecular crowding in and around cells. After a thorough examination of methods such as fluorescence recovery after photo-bleaching, fluorescence correlation spectroscopy, photo-activation localization microscopy and stochastic reconstruction microscopy, he concluded that the general consensus emerging from experimental studies is that the notion of universally anomalous diffusion in and around cells as a consequence of molecular crowding may not be correct, and that the slowing of diffusion in cells is less marked than has been widely assumed and can be simply described through a five- to sixfold reduction of the normal diffusion coefficient. A Soranno, from the University of Zürich (Switzerland), described how, by employing FRET measurements, it is possible to quantify the effect of molecular crowding on the dimensions of the highly charged, intrinsically disordered protein human prothymosin alpha. For a large variety of polymeric crowders (PEG, PVP, Ficoll, Dextran, PVA, PAA), a collapse of the polypeptide chain is observed with increasing polymer size and polymer concentration. The largest extent of collapse is observed for polymer radii comparable to the dimensions of the protein, in agreement with theoretical considerations. For his contribution, A Soranno was awarded the CSF Award for the best contributed talk. In his most inspiring talk, Clifford Brangwynne, from Princeton University (USA), drew attention to very important objects, namely Ribonucleoprotein (RNP) bodies. These are non-membrane-bound macromolecular assemblies that form from the dynamic interactions of RNA and proteins. The assembly of RNP bodies may sensitively depend on the biophysical features of the surrounding cytoplasm, including the degree of crowding, transport coefficients and mechanical properties. This dependency may have important implications for the RNA processing reactions involved in fundamental biological processes such as developmental cell growth. Remarkably, Brangwynne showed how RNPs behave in the cell as liquid droplets, pointing to a possible entirely new means that the cell could use to control and fine-tune its internal processes, in fact, more than that, a completely unexplored, new state of organization of living matter, and a functional one. Giuseppe Zaccai, from Institut Laue Langevin, Grenoble (France), showed that protein dynamics is more sensitive than structure to environmental factors such as crowding, solvent, temperature or pressure. Furthermore, he convincingly explained how neutron scattering provides unique experimental data to underpin MD calculations in this context. Following up on environment-induced modulations of protein functional dynamics, Ruth Nussinov, from Tel Aviv University (Israel), addressed the important problem of whether cellular signals can travel long distances in a crowded environment. She proposed a model based on the evolution of at least three properties: a modular functional organization of the cellular network, sequences in some key regions of proteins, such as linkers or loops, and compact interactions between proteins, possibly favoured by a crowded environment. The workshop ended on a keynote lecture by Jean-Marie Lehn, from the Université de Strasbourg (France). Lehn, 1987 Nobel Laureate in chemistry, offered a 'supramolecular view' of the field of molecular interactions. Supramolecular chemistry explores the design of systems undergoing self-organization , i.e. systems capable of generating well-defined functional supramolecular architectures by self-assembling from their components, thus behaving as programmed chemical systems . Chemistry may therefore be considered an information science , the science of informed matter. Supramolecular chemistry is intrinsically a dynamic chemistry in view of the ability of the interactions connecting the molecular components of a supramolecular entity and the resulting ability of supramolecular species to exchange their constituents. The same holds for molecular chemistry when the molecular entity contains covalent bonds that may form and break reversibly, so as to allow a continuous change in constitution by the reorganization and exchange of building blocks. These features define a constitutional dynamic chemistry (CDC) on both the molecular and supramolecular levels. CDC takes advantage of dynamic constitutional diversity to allow variation and selection in response to either internal or external factors to achieve adaptation . The merging of the features-information and programmability, dynamics and reversibility, constitution and structural diversity-points towards the emergence of adaptive and evolutive chemistry . The whole workshop could have not taken place without the help of the Centro Stefano Franscini. The CSF is the congress centre of the Swiss Federal Institute of Technology of Zurich (ETH Zurich) and has been situated at Monte Verità since 1989. It is an ideal meeting point for all members of the international scientific community who wish to discuss the state-of-the-art and new challenges of any field of research. The CSF supports 20-25 international conferences every year and, since 2010, up to ten winter doctoral schools 1 . The competence and professionalism of the staff were at the same level of beauty and inspiring character as that of Monte Verità. A meeting of this sort, if successful, leaves the audience with more open questions than settled answers, and this was definitely the case for Crowding 2012. Excluded volume is clearly a fundamental concept that has allowed crowding, a very familiar concept in soft matter, to enter into the domain of biological sciences. However, the complexity of the biological milieu calls for more refined descriptions. What is the role of electrostatic and electrodynamic interactions? What is the role of hydrodynamics interactions? To what extent does the strong spatial inhomogeneity (clustering of molecules, cellular compartmentalization, etc) have to be taken into account? Or, more generally, what are the minimal elements that prove crucial to describe reactions within a cell? How does the diffusion proceed (diffusion, slow diffusion, sub-diffusion) given that the experimental evidences are still controversial? In conclusion, we knew that allowing scientists with very different backgrounds and ideas to mingle was a hazardous attempt. Despite that, the workshop turned out to be a very successful experiment, which was highly enjoyed both by the participants and the organizers. Discussions sparked regularly among ever-changing groups, comprising senior scientists and students, despite the rather tight schedule, adding to the sense of fulfilment ignited by the outstanding level of the presentations. Given the success of the meeting Crowding 2012, a new event has been organized and will take place on the same themes during fall 2013, this time in the beautiful scenery of the Loire valley in France. The workshop 'Macromolecular crowding effects in cell biology: models and experiments' will be held on the CNRS campus in Orléans, France, on 24-25 October 2013. More information can be found on the workshop website: http://dirac.cnrs-orleans.fr/∼piazza/. 1 Source: www.csf.ethz.ch/

Macromolecular crowding: chemistry and physics meet biology (Ascona, Switzerland, 10-14 June 2012)

NASA Astrophysics Data System (ADS)

Foffi, G.; Pastore, A.; Piazza, F.; Temussi, P. A.

2013-08-01

More than 60 years of biochemical and biophysical studies have accustomed us to think of proteins as highly purified entities that act in isolation, more or less freely diffusing until they find their cognate partner to bind to. While in vitro experiments that reproduce these conditions largely remain the only way to investigate the intrinsic properties of molecules, this approach ignores an important factor: in their natural milieu , proteins are surrounded by several other molecules of different chemical nature, and this crowded environment can considerably modify their behaviour. About 40% of the cellular volume on average is occupied by all sorts of molecules. Furthermore, biological macromolecules live and operate in an extremely structured and complex environment within the cell (endoplasmic reticulum, Golgi apparatus, cytoskeletal structures, etc). Hence, to further complicate the picture, the interior of the cell is by no means a simply crowded medium, rather, a most crowded and confining one. In recent times, several approaches have been developed in the attempt to take into account important factors such as the ones mentioned above, at both theoretical and experimental levels, so that this field of research is now emerging as one of the most thriving in molecular and cell biology (see figure 1). Figure 1. Figure 1. Left: number of articles containing the word 'crowding' as a keyword limited to the biological and chemical science domains (source: ISI Web of Science). The arrow flags the 2003 'EMBO Workshop on Biological Implications of Macromolecular Crowding' (Embo, 2012). Right: number of citations to articles containing the word 'crowding' limited to the same domains (bars) and an exponential regression curve (source: Elsevier Scopus). To promote the importance of molecular crowding and confinement and provide researchers active in this field an interdisciplinary forum for meeting and exchanging ideas, we recently organized an international conference held in Ascona from 10 to 14 June 2012. In the unique scenario of the Maggiore lake and absorbed in the magic atmosphere of the Centro Stefano Franscini (CSF) at Monte Verità, we enjoyed three-and-a-half days of intense and inspiring activity, where not only many of the most prominent scientists working on macromolecular crowding, but also experts in closely related fields such as colloids and soft matter presented their work. The meeting was intended and has been organized to bring theoreticians and experimentalists together in the attempt to promote an active dialogue. Moreover, we wanted different disciplines to be represented, notably physics and chemistry, besides biology, as cross-fertilization is proving an increasingly fundamental source of inspiration and advancement. This issue of Physical Biology (PB) features a selection of the oral contributions presented at the conference, expanded in the form of research or review articles. PB, one of the scientific journals of the Institute of Physics (IOP), is one of the most dynamic and lively forums active at the interface between biology on one side, and physics and mathematics on the other. As its mission is stated by IOP, PB 'focuses on research in which physics-based approaches lead to new insights into biological systems at all scales of space and time, and all levels of complexity'. For these reasons, and also in view of its high reputation and broad readership, PB appears to be the ideal place for disseminating the thriving pieces of research presented at the conference. We are extremely grateful to PB and its kind and efficient editorial staff who helped make this issue a great scientific follow-up to the conference. The opening lecture of the conference, the first of four day-opening keynote lectures, was given by Allen P Minton from NIH (USA), possibly the most influential among the pioneers in the field. He provided a lucid and well-thought-out overview of the concept of macromolecular crowding through an exhaustive chronological account of the major milestones. It is clear that the concept of excluded volume as a key factor remains central to the concept of molecular crowding. As a consequence, simple descriptive paradigms borrowed essentially from colloid physics may still provide useful tools to understand the subtle effects of crowding and confinement in living matter. The contiguity between crowding, colloids and soft matter further emerged as an important concept in the course of the conference in several theoretical lectures and a few experimental ones. Dave Thirumalai, from the University of Maryland (USA), one of the most active theoreticians in the field of theoretical biophysics, outlined scaling theories, concepts from colloid literature and different simulation techniques to describe scenarios for crowding-induced changes in the structure and dynamics of proteins and RNA. In particular, he showed the importance of the shape of crowding particles in affecting folding oligomerization of amyloidogenic peptides. Johannes Schöneberg, from IMPRS, Mathematics Institute (Germany), illustrated ReaDDy , a newly developed particle-based simulation software tool for reaction-diffusion dynamics, developed in the group of Frank Noe at EMPRS. He showed that ReaDDy makes it possible to bridge the gap between soft matter and molecular dynamics (MD) simulations on the one hand and particle-based stochastic reaction-diffusion simulations on the other. We asked Johannes to organize a tutorial session to lead interested participants into the package and 'get their hands wet' under the guidance of the developers. The tutorial session was indeed successful and the broad possibilities offered by the simulation toolkit appeared to be clear to the participants. Paolo De Los Rios, from the Ecole Polytechnique Fédérale de Lausanne (EPFL, Switzerland), examined the complexity of the effects caused by crowding conditions from the point of view of statistical physics. Starting from a modification of the well-known Smoluchowski approach to calculate the encounter rate of diffusion-limited reactions, he showed how more realistic situations accounting for crowding effects could be treated equally well on the same theoretical grounds. This talk marked an important point in the conference as it reinforced the idea that simple models of theoretical physics still have the power to provide inspiring results in spite of the intrinsic simplifications of such theoretical approaches. Along the same lines, Nicolas Dorsaz, from the University of Cambridge (UK), proposed an extension of the Smoluchowski framework that incorporates repulsive and attracting interactions between the reactants. This approach was illustrated by reaction rates obtained from event-driven Brownian dynamics and dynamical Monte Carlo simulations. Another striking example of the physical subtleties associated with modelling crowding effects was provided by Jeffrey Skolnick, from the Georgia Institute of Technology (USA). He examined the role of hydrodynamic interactions in the self-organization of biological assemblies in the presence of crowding. His results strongly suggest that hydrodynamic interactions greatly affect the kinetics of self-assembly reactions, so that including them in the picture appears crucial for understanding the dynamics of biological systems in vivo . Margareth Cheung, from the University of Houston (USA), emphasized that how the crowded environment inside a cell affects the structural conformation of a protein with a spherical shape is a vital question because the geometry of proteins and protein-protein complexes are far from globules in vivo . Her work demonstrates the malleability of 'native' proteins and implies that crowding-induced shape changes may be important for protein function and malfunction in vivo . Huan-Xiang Zhou, from the Florida State University (USA), focused on atomistic simulations of protein folding and binding under crowding conditions. His lab has developed a post-processing method that allows the atomistic representation of proteins in folding and binding processes under crowding. A comparison with experimental results was also presented. Other lecturers pointed out that there are still aspects not entirely explored in the effects of both crowding and confinement. As suggested in the talk by Gary Pielak, from the University of North Carolina (USA), the currently used synthetic crowding agents are far from being satisfactory in replicating naturally occurring effects associated with crowded environments. For example, non-specific binding seems to play a subtle role in the cell, as natural macromolecules can induce both stabilization and destabilization when used as crowders. It is indeed possible to fine-tune the effect of proteins, as crowders, on the stability of other proteins. Another aspect that became clear is that new, more powerful methods need to be developed to study the effect of crowding, but even more to compare crowding and confinement. Indeed, it appeared clear from the lecture by Pierandrea Temussi, from the University of Naples (Italy), that a reliable comparison of the effects of crowding and confinement on the stability of proteins can only be based on the measurement of the whole stability curve of the same protein. Controversial aspects do not pertain only to the influence of crowding on protein stability, but also to aggregation phenomena in natural fluids. Domenico Sanfelice, from NIMR (London, UK), reported an interesting case of the apparent influence of crowding on aggregation. Hen egg white, a possible natural medium to study macromolecules in crowded conditions can dramatically increase the aggregation kinetics of proteins with an inbuilt tendency to associate. By carefully dissecting the phenomenology, it was shown that only part of this effect is due to crowding, while another factor playing an important role is the interaction with proteins from the milieu . In other words, high-molecular-weight glycoproteins can act as efficient molecular seeds for aggregation. A special topic of great relevance in the conference appeared to be the direct study of crowding in living systems. Alan Verkman, from the University of California, San Francisco (USA), one of the world's leading scientific personalities in the field of experimental investigation of crowding and confinement, was invited to give the second plenary lecture devoted to the experimental study of crowding effects in vivo . In his keynote lecture, Dr Verkman led us on a wide and compelling tour, exploring the main experimental approaches to study molecular crowding in and around cells. After a thorough examination of methods such as fluorescence recovery after photo-bleaching, fluorescence correlation spectroscopy, photo-activation localization microscopy and stochastic reconstruction microscopy, he concluded that the general consensus emerging from experimental studies is that the notion of universally anomalous diffusion in and around cells as a consequence of molecular crowding may not be correct, and that the slowing of diffusion in cells is less marked than has been widely assumed and can be simply described through a five- to sixfold reduction of the normal diffusion coefficient. A Soranno, from the University of Zürich (Switzerland), described how, by employing FRET measurements, it is possible to quantify the effect of molecular crowding on the dimensions of the highly charged, intrinsically disordered protein human prothymosin alpha. For a large variety of polymeric crowders (PEG, PVP, Ficoll, Dextran, PVA, PAA), a collapse of the polypeptide chain is observed with increasing polymer size and polymer concentration. The largest extent of collapse is observed for polymer radii comparable to the dimensions of the protein, in agreement with theoretical considerations. For his contribution, A Soranno was awarded the CSF Award for the best contributed talk. In his most inspiring talk, Clifford Brangwynne, from Princeton University (USA), drew attention to very important objects, namely Ribonucleoprotein (RNP) bodies. These are non-membrane-bound macromolecular assemblies that form from the dynamic interactions of RNA and proteins. The assembly of RNP bodies may sensitively depend on the biophysical features of the surrounding cytoplasm, including the degree of crowding, transport coefficients and mechanical properties. This dependency may have important implications for the RNA processing reactions involved in fundamental biological processes such as developmental cell growth. Remarkably, Brangwynne showed how RNPs behave in the cell as liquid droplets, pointing to a possible entirely new means that the cell could use to control and fine-tune its internal processes, in fact, more than that, a completely unexplored, new state of organization of living matter, and a functional one. Giuseppe Zaccai, from Institut Laue Langevin, Grenoble (France), showed that protein dynamics is more sensitive than structure to environmental factors such as crowding, solvent, temperature or pressure. Furthermore, he convincingly explained how neutron scattering provides unique experimental data to underpin MD calculations in this context. Following up on environment-induced modulations of protein functional dynamics, Ruth Nussinov, from Tel Aviv University (Israel), addressed the important problem of whether cellular signals can travel long distances in a crowded environment. She proposed a model based on the evolution of at least three properties: a modular functional organization of the cellular network, sequences in some key regions of proteins, such as linkers or loops, and compact interactions between proteins, possibly favoured by a crowded environment. The workshop ended on a keynote lecture by Jean-Marie Lehn, from the Université de Strasbourg (France). Lehn, 1987 Nobel Laureate in chemistry, offered a 'supramolecular view' of the field of molecular interactions. Supramolecular chemistry explores the design of systems undergoing self-organization , i.e. systems capable of generating well-defined functional supramolecular architectures by self-assembling from their components, thus behaving as programmed chemical systems . Chemistry may therefore be considered an information science , the science of informed matter. Supramolecular chemistry is intrinsically a dynamic chemistry in view of the ability of the interactions connecting the molecular components of a supramolecular entity and the resulting ability of supramolecular species to exchange their constituents. The same holds for molecular chemistry when the molecular entity contains covalent bonds that may form and break reversibly, so as to allow a continuous change in constitution by the reorganization and exchange of building blocks. These features define a constitutional dynamic chemistry (CDC) on both the molecular and supramolecular levels. CDC takes advantage of dynamic constitutional diversity to allow variation and selection in response to either internal or external factors to achieve adaptation . The merging of the features—information and programmability, dynamics and reversibility, constitution and structural diversity—points towards the emergence of adaptive and evolutive chemistry . The whole workshop could have not taken place without the help of the Centro Stefano Franscini. The CSF is the congress centre of the Swiss Federal Institute of Technology of Zurich (ETH Zurich) and has been situated at Monte Verità since 1989. It is an ideal meeting point for all members of the international scientific community who wish to discuss the state-of-the-art and new challenges of any field of research. The CSF supports 20-25 international conferences every year and, since 2010, up to ten winter doctoral schools1. The competence and professionalism of the staff were at the same level of beauty and inspiring character as that of Monte Verità. A meeting of this sort, if successful, leaves the audience with more open questions than settled answers, and this was definitely the case for Crowding 2012. Excluded volume is clearly a fundamental concept that has allowed crowding, a very familiar concept in soft matter, to enter into the domain of biological sciences. However, the complexity of the biological milieu calls for more refined descriptions. What is the role of electrostatic and electrodynamic interactions? What is the role of hydrodynamics interactions? To what extent does the strong spatial inhomogeneity (clustering of molecules, cellular compartmentalization, etc) have to be taken into account? Or, more generally, what are the minimal elements that prove crucial to describe reactions within a cell? How does the diffusion proceed (diffusion, slow diffusion, sub-diffusion) given that the experimental evidences are still controversial? In conclusion, we knew that allowing scientists with very different backgrounds and ideas to mingle was a hazardous attempt. Despite that, the workshop turned out to be a very successful experiment, which was highly enjoyed both by the participants and the organizers. Discussions sparked regularly among ever-changing groups, comprising senior scientists and students, despite the rather tight schedule, adding to the sense of fulfilment ignited by the outstanding level of the presentations. Given the success of the meeting Crowding 2012, a new event has been organized and will take place on the same themes during fall 2013, this time in the beautiful scenery of the Loire valley in France. The workshop 'Macromolecular crowding effects in cell biology: models and experiments' will be held on the CNRS campus in Orléans, France, on 24-25 October 2013. More information can be found on the workshop website: http://dirac.cnrs-orleans.fr/~piazza/. 1Source: www.csf.ethz.ch/

Cities, Crowding and Crime

ERIC Educational Resources Information Center

Trotter, Robert J.

1974-01-01

This article considers the effects of human crowding in light of recent tests and observations. Factors such as sex, age, culture, socio-economic standing, frustration, and interpersonal physical distance are examined. Results indicate that crowding contributes to social problems and crime. (TK)

Crowd Sourcing for Challenging Technical Problems and Business Model

NASA Technical Reports Server (NTRS)

Davis, Jeffrey R.; Richard, Elizabeth

2011-01-01

Crowd sourcing may be defined as the act of outsourcing tasks that are traditionally performed by an employee or contractor to an undefined, generally large group of people or community (a crowd) in the form of an open call. The open call may be issued by an organization wishing to find a solution to a particular problem or complete a task, or by an open innovation service provider on behalf of that organization. In 2008, the Space Life Sciences Directorate (SLSD), with the support of Wyle Integrated Science and Engineering, established and implemented pilot projects in open innovation (crowd sourcing) to determine if these new internet-based platforms could indeed find solutions to difficult technical challenges. These unsolved technical problems were converted to problem statements, also called "Challenges" or "Technical Needs" by the various open innovation service providers, and were then posted externally to seek solutions. In addition, an open call was issued internally to NASA employees Agency wide (10 Field Centers and NASA HQ) using an open innovation service provider crowd sourcing platform to post NASA challenges from each Center for the others to propose solutions). From 2008 to 2010, the SLSD issued 34 challenges, 14 externally and 20 internally. The 14 external problems or challenges were posted through three different vendors: InnoCentive, Yet2.com and TopCoder. The 20 internal challenges were conducted using the InnoCentive crowd sourcing platform designed for internal use by an organization. This platform was customized for NASA use and promoted as NASA@Work. The results were significant. Of the seven InnoCentive external challenges, two full and five partial awards were made in complex technical areas such as predicting solar flares and long-duration food packaging. Similarly, the TopCoder challenge yielded an optimization algorithm for designing a lunar medical kit. The Yet2.com challenges yielded many new industry and academic contacts in bone imaging, microbial detection and even the use of pharmaceuticals for radiation protection. The internal challenges through NASA@Work drew over 6000 participants across all NASA centers. Challenges conducted by each NASA center elicited ideas and solutions from several other NASA centers and demonstrated rapid and efficient participation from employees at multiple centers to contribute to problem solving. Finally, on January 19, 2011, the SLSD conducted a workshop on open collaboration and innovation strategies and best practices through the newly established NASA Human Health and Performance Center (NHHPC). Initial projects will be described leading to a new business model for SLSD.

Molecular crowding of collagen: a pathway to produce highly-organized collagenous structures.

PubMed

Saeidi, Nima; Karmelek, Kathryn P; Paten, Jeffrey A; Zareian, Ramin; DiMasi, Elaine; Ruberti, Jeffrey W

2012-10-01

Collagen in vertebrate animals is often arranged in alternating lamellae or in bundles of aligned fibrils which are designed to withstand in vivo mechanical loads. The formation of these organized structures is thought to result from a complex, large-area integration of individual cell motion and locally-controlled synthesis of fibrillar arrays via cell-surface fibripositors (direct matrix printing). The difficulty of reproducing such a process in vitro has prevented tissue engineers from constructing clinically useful load-bearing connective tissue directly from collagen. However, we and others have taken the view that long-range organizational information is potentially encoded into the structure of the collagen molecule itself, allowing the control of fibril organization to extend far from cell (or bounding) surfaces. We here demonstrate a simple, fast, cell-free method capable of producing highly-organized, anistropic collagen fibrillar lamellae de novo which persist over relatively long-distances (tens to hundreds of microns). Our approach to nanoscale organizational control takes advantage of the intrinsic physiochemical properties of collagen molecules by inducing collagen association through molecular crowding and geometric confinement. To mimic biological tissues which comprise planar, aligned collagen lamellae (e.g. cornea, lamellar bone or annulus fibrosus), type I collagen was confined to a thin, planar geometry, concentrated through molecular crowding and polymerized. The resulting fibrillar lamellae show a striking resemblance to native load-bearing lamellae in that the fibrils are small, generally aligned in the plane of the confining space and change direction en masse throughout the thickness of the construct. The process of organizational control is consistent with embryonic development where the bounded planar cell sheets produced by fibroblasts suggest a similar confinement/concentration strategy. Such a simple approach to nanoscale organizational control of structure not only makes de novo tissue engineering a possibility, but also suggests a clearer pathway to organization for fibroblasts than direct matrix printing. Copyright © 2012 Elsevier Ltd. All rights reserved.

How color, regularity, and good Gestalt determine backward masking.

PubMed

Sayim, Bilge; Manassi, Mauro; Herzog, Michael

2014-06-18

The strength of visual backward masking depends on the stimulus onset asynchrony (SOA) between target and mask. Recently, it was shown that the conjoint spatial layout of target and mask is as crucial as SOA. Particularly, masking strength depends on whether target and mask group with each other. The same is true in crowding where the global spatial layout of the flankers and target-flanker grouping determine crowding strength. Here, we presented a vernier target followed by different flanker configurations at varying SOAs. Similar to crowding, masking of a red vernier target was strongly reduced for arrays of 10 green compared with 10 red flanking lines. Unlike crowding, single green lines flanking the red vernier showed strong masking. Irregularly arranged flanking lines yielded stronger masking than did regularly arranged lines, again similar to crowding. While cuboid flankers reduced crowding compared with single lines, this was not the case in masking. We propose that, first, masking is reduced when the flankers are part of a larger spatial structure. Second, spatial factors counteract color differences between the target and the flankers. Third, complex Gestalts, such as cuboids, seem to need longer processing times to show ungrouping effects as observed in crowding. Strong parallels between masking and crowding suggest similar underlying mechanism; however, temporal factors in masking additionally modulate performance, acting as an additional grouping cue. © 2014 ARVO.

Crowd-Funding: A New Resource Cooperation Mode for Mobile Cloud Computing.

PubMed

Zhang, Nan; Yang, Xiaolong; Zhang, Min; Sun, Yan

2016-01-01

Mobile cloud computing, which integrates the cloud computing techniques into the mobile environment, is regarded as one of the enabler technologies for 5G mobile wireless networks. There are many sporadic spare resources distributed within various devices in the networks, which can be used to support mobile cloud applications. However, these devices, with only a few spare resources, cannot support some resource-intensive mobile applications alone. If some of them cooperate with each other and share their resources, then they can support many applications. In this paper, we propose a resource cooperative provision mode referred to as "Crowd-funding", which is designed to aggregate the distributed devices together as the resource provider of mobile applications. Moreover, to facilitate high-efficiency resource management via dynamic resource allocation, different resource providers should be selected to form a stable resource coalition for different requirements. Thus, considering different requirements, we propose two different resource aggregation models for coalition formation. Finally, we may allocate the revenues based on their attributions according to the concept of the "Shapley value" to enable a more impartial revenue share among the cooperators. It is shown that a dynamic and flexible resource-management method can be developed based on the proposed Crowd-funding model, relying on the spare resources in the network.

Crowd-Funding: A New Resource Cooperation Mode for Mobile Cloud Computing

PubMed Central

Zhang, Min; Sun, Yan

2016-01-01

Mobile cloud computing, which integrates the cloud computing techniques into the mobile environment, is regarded as one of the enabler technologies for 5G mobile wireless networks. There are many sporadic spare resources distributed within various devices in the networks, which can be used to support mobile cloud applications. However, these devices, with only a few spare resources, cannot support some resource-intensive mobile applications alone. If some of them cooperate with each other and share their resources, then they can support many applications. In this paper, we propose a resource cooperative provision mode referred to as "Crowd-funding", which is designed to aggregate the distributed devices together as the resource provider of mobile applications. Moreover, to facilitate high-efficiency resource management via dynamic resource allocation, different resource providers should be selected to form a stable resource coalition for different requirements. Thus, considering different requirements, we propose two different resource aggregation models for coalition formation. Finally, we may allocate the revenues based on their attributions according to the concept of the "Shapley value" to enable a more impartial revenue share among the cooperators. It is shown that a dynamic and flexible resource-management method can be developed based on the proposed Crowd-funding model, relying on the spare resources in the network. PMID:28030553

Global Dynamic Exposure and the OpenBuildingMap

NASA Astrophysics Data System (ADS)

Schorlemmer, D.; Beutin, T.; Hirata, N.; Hao, K. X.; Wyss, M.; Cotton, F.; Prehn, K.

2015-12-01

Detailed understanding of local risk factors regarding natural catastrophes requires in-depth characterization of the local exposure. Current exposure capture techniques have to find the balance between resolution and coverage. We aim at bridging this gap by employing a crowd-sourced approach to exposure capturing focusing on risk related to earthquake hazard. OpenStreetMap (OSM), the rich and constantly growing geographical database, is an ideal foundation for us. More than 2.5 billion geographical nodes, more than 150 million building footprints (growing by ~100'000 per day), and a plethora of information about school, hospital, and other critical facility locations allow us to exploit this dataset for risk-related computations. We will harvest this dataset by collecting exposure and vulnerability indicators from explicitly provided data (e.g. hospital locations), implicitly provided data (e.g. building shapes and positions), and semantically derived data, i.e. interpretation applying expert knowledge. With this approach, we can increase the resolution of existing exposure models from fragility classes distribution via block-by-block specifications to building-by-building vulnerability. To increase coverage, we will provide a framework for collecting building data by any person or community. We will implement a double crowd-sourced approach to bring together the interest and enthusiasm of communities with the knowledge of earthquake and engineering experts. The first crowd-sourced approach aims at collecting building properties in a community by local people and activists. This will be supported by tailored building capture tools for mobile devices for simple and fast building property capturing. The second crowd-sourced approach involves local experts in estimating building vulnerability that will provide building classification rules that translate building properties into vulnerability and exposure indicators as defined in the Building Taxonomy 2.0 developed by the Global Earthquake Model (GEM). These indicators will then be combined with a hazard model using the GEM OpenQuake engine to compute a risk model. The free/open framework we will provide can be used on commodity hardware for local to regional exposure capturing and for communities to understand their earthquake risk.

Crowdsourcing for identification of polyp-free segments in virtual colonoscopy videos

NASA Astrophysics Data System (ADS)

Park, Ji Hwan; Mirhosseini, Seyedkoosha; Nadeem, Saad; Marino, Joseph; Kaufman, Arie; Baker, Kevin; Barish, Matthew

2017-03-01

Virtual colonoscopy (VC) allows a physician to virtually navigate within a reconstructed 3D colon model searching for colorectal polyps. Though VC is widely recognized as a highly sensitive and specific test for identifying polyps, one limitation is the reading time, which can take over 30 minutes per patient. Large amounts of the colon are often devoid of polyps, and a way of identifying these polyp-free segments could be of valuable use in reducing the required reading time for the interrogating radiologist. To this end, we have tested the ability of the collective crowd intelligence of non-expert workers to identify polyp candidates and polyp-free regions. We presented twenty short videos flying through a segment of a virtual colon to each worker, and the crowd was asked to determine whether or not a possible polyp was observed within that video segment. We evaluated our framework on Amazon Mechanical Turk and found that the crowd was able to achieve a sensitivity of 80.0% and specificity of 86.5% in identifying video segments which contained a clinically proven polyp. Since each polyp appeared in multiple consecutive segments, all polyps were in fact identified. Using the crowd results as a first pass, 80% of the video segments could in theory be skipped by the radiologist, equating to a significant time savings and enabling more VC examinations to be performed.

Macromolecular Crowding Induces Spatial Correlations That Control Gene Expression Bursting Patterns.

PubMed

Norred, S Elizabeth; Caveney, Patrick M; Chauhan, Gaurav; Collier, Lauren K; Collier, C Patrick; Abel, Steven M; Simpson, Michael L

2018-05-18

Recent superresolution microscopy studies in E. coli demonstrate that the cytoplasm has highly variable local concentrations where macromolecular crowding plays a central role in establishing membrane-less compartmentalization. This spatial inhomogeneity significantly influences molecular transport and association processes central to gene expression. Yet, little is known about how macromolecular crowding influences gene expression bursting-the episodic process where mRNA and proteins are produced in bursts. Here, we simultaneously measured mRNA and protein reporters in cell-free systems, showing that macromolecular crowding decoupled the well-known relationship between fluctuations in the protein population (noise) and mRNA population statistics. Crowded environments led to a 10-fold increase in protein noise even though there were only modest changes in the mRNA population and fluctuations. Instead, cell-like macromolecular crowding created an inhomogeneous spatial distribution of mRNA ("spatial noise") that led to large variability in the protein production burst size. As a result, the mRNA spatial noise created large temporal fluctuations in the protein population. These results highlight the interplay between macromolecular crowding, spatial inhomogeneities, and the resulting dynamics of gene expression, and provide insights into using these organizational principles in both cell-based and cell-free synthetic biology.

Effects of Lower Third Molar Angulation and Position on Lower Arch Crowding.

PubMed

Selmani, Mimoza E; Gjorgova, Julijana; Selmani, Manushaqe E; Shkreta, Mirsad; Duci, Shkelzen B

2016-01-01

The role of the third molars in lower arch crowding has been debated for more than a century. The aim of this study was to determine the relationship between lower arch crowding and the presence of angulation and position of lower third molar. The measurements of the dental arch were made in 120 subjects aged 16 to 21 years, with average age to 18 years. The subjects were divided into two groups: Class I normal occlusion comprised 35 male and 25 female with mean age 18.87years, whereas Class I crowding comprised 27 males and 33 females with mean age 18.5 years. The dental pantomogram (DPT) were used to calculate the ratio of retromolar space (Ganss ratio), angulation of third molar to second molar and third molar to the base of the mandible. The results showed that measurements of Ganss ratio, third molar angulation to the base of the mandible, and third molar to second molar inclination, was statistically significant between crowded and normal groups. It can be concluded that there was a strong relationship between angulation and position of third molars and lower arch crowding. Key words: Third molars, angulation, lower arch, crowding

Macromolecular crowding effect upon in vitro enzyme kinetics: mixed activation-diffusion control of the oxidation of NADH by pyruvate catalyzed by lactate dehydrogenase.

PubMed

Balcells, Cristina; Pastor, Isabel; Vilaseca, Eudald; Madurga, Sergio; Cascante, Marta; Mas, Francesc

2014-04-17

Enzyme kinetics studies have been usually designed as dilute solution experiments, which differ substantially from in vivo conditions. However, cell cytosol is crowded with a high concentration of molecules having different shapes and sizes. The consequences of such crowding in enzymatic reactions remain unclear. The aim of the present study is to understand the effect of macromolecular crowding produced by dextran of different sizes and at diverse concentrations in the well-known reaction of oxidation of NADH by pyruvate catalyzed by L-lactate dehydrogenase (LDH). Our results indicate that the reaction rate is determined by both the occupied volume and the relative size of dextran obstacles with respect to the enzyme present in the reaction. Moreover, we analyzed the influence of macromolecular crowding on the Michaelis-Menten constants, vmax and Km. The obtained results show that only high concentrations and large sizes of dextran reduce both constants suggesting a mixed activation-diffusion control of this enzymatic reaction due to the dextran crowding action. From our knowledge, this is the first experimental study that depicts mixed activation-diffusion control in an enzymatic reaction due to the effect of crowding.

The Appreciation of Humor By Males and Females During Conditions of Crowding Experimentally Induced.

ERIC Educational Resources Information Center

Prerost, Frank J.; Brewer, Robert E.

1980-01-01

Subjects rated the humor of jokes under conditions of high and low spatial density. Crowding was found to significantly diminish appreciation of three types of humor. Significant sex differences in reactivity to crowding were found. (Author/CS)

Estimating the number of people in crowded scenes

NASA Astrophysics Data System (ADS)

Kim, Minjin; Kim, Wonjun; Kim, Changick

2011-01-01

This paper presents a method to estimate the number of people in crowded scenes without using explicit object segmentation or tracking. The proposed method consists of three steps as follows: (1) extracting space-time interest points using eigenvalues of the local spatio-temporal gradient matrix, (2) generating crowd regions based on space-time interest points, and (3) estimating the crowd density based on the multiple regression. In experimental results, the efficiency and robustness of our proposed method are demonstrated by using PETS 2009 dataset.

Nyala and Bushbuck I: A Competing Species Model.

ERIC Educational Resources Information Center

Fay, Temple H.; Greeff, Johanna C.

1999-01-01

Introduces a model of differential equations for students--a very real overpopulation problem is occurring in the Ndumu Game Reserve in KwaZulu-Natal, South Africa, where one species of antelope, the Nyala, is crowding out another species, the Bushbuck. Constructs a competing species model to mathematically describe what is occurring in Ndumu.…

The effect of macromolecular crowding on the structure of the protein complex superoxide dismutase

NASA Astrophysics Data System (ADS)

Rajapaksha Mudalige, Ajith Rathnaweera

Biological environments contain between 7 - 40% macromolecules by volume. This reduces the available volume for macromolecules and elevates the osmotic pressure relative to pure water. Consequently, biological macromolecules in their native environments tend to adopt more compact and dehydrated conformations than those in vitro. This effect is referred to as macromolecular crowding and constitutes an important physical difference between native biological environments and the simple solutions in which biomolecules are usually studied. We used small angle scattering (SAS) to measure the effects of macromolecular crowding on the size of a protein complex, superoxide dismutase (SOD). Crowding was induced using 400 MW polyethylene glycol (PEG), triethylene glycol (TEG), methyl-alpha-glucoside (alpha-MG) and trimethylamine N-oxide (TMAO). Parallel small angle neutron scattering (SANS) and small angle X-ray scattering (SAXS) allowed us to unambiguously attribute apparent changes in radius of gyration to changes in the structure of SOD. For a 40% PEG solution, we find that the volume of SOD was reduced by 9%. SAS coupled with osmotic pressure measurements allowed us to estimate a compressibility modulus for SOD. We believe this to be the first time the osmotic compressibility of a protein complex was measured. Molecular Dynamics (MD) simulations are widely used to obtain insights on biomolecular processes. However, it is not clear whether MD is capable of predicting subtle effects of macromolecular crowding. We used our experimentally observed compressibility of SOD to evaluate the ability of MD to predict macromolecular crowding. Effects of macromolecular crowding due to PEG on SOD were modeled using an all atom MD simulation with the CHARMM forcefield and the crystallographically resolved structures of SOD and PEG. Two parallel MD simulations were performed for SOD in water and SOD in 40% PEG for over 150~ns. Over the period of the simulation the SOD structure in 40% PEG did not change compared to the SOD structure in water. It therefore appears that under the conditions of our simulations MD could not describe the experimentally observed effects of macromolecular crowding. In a separate project, we measured the rate of diffusive transport in excised porcine corneal stroma using FCS for fluorescent labeled dextran molecules with hydrodynamic radii ranging from 1.3 to 34 nm. Dextran molecules diffuse more slowly in cornea as compared to buffer solution. The reduction in diffusion coefficient is modest however (67% smaller), and is uniform over the range of sizes that we measured. Diffusion coefficients measured parallel vs. perpendicular to the collagen lamellae were indistinguishable. This indicates that diffusion in the corneal stroma is not highly anisotropic. Delivery of therapeutic agents to the eye requires efficient transport through cellular and extracellular barriers. Our measurements bring important insights into how macromolecular and nanoparticle therapeutics might permeate through the eyes.

Modulation of calmodulin plasticity by the effect of macromolecular crowding.

PubMed

Homouz, Dirar; Sanabria, Hugo; Waxham, M Neal; Cheung, Margaret S

2009-09-04

In vitro biochemical reactions are most often studied in dilute solution, a poor mimic of the intracellular space of eukaryotic cells, which are crowded with mobile and immobile macromolecules. Such crowded conditions exert volume exclusion and other entropic forces that have the potential to impact chemical equilibria and reaction rates. In this article, we used the well-characterized and ubiquitous molecule calmodulin (CaM) and a combination of theoretical and experimental approaches to address how crowding impacts CaM's conformational plasticity. CaM is a dumbbell-shaped molecule that contains four EF hands (two in the N-lobe and two in the C-lobe) that each could bind Ca(2+), leading to stabilization of certain substates that favor interactions with other target proteins. Using coarse-grained molecular simulations, we explored the distribution of CaM conformations in the presence of crowding agents. These predictions, in which crowding effects enhance the population of compact structures, were then confirmed in experimental measurements using fluorescence resonance energy transfer techniques of donor- and acceptor-labeled CaM under normal and crowded conditions. Using protein reconstruction methods, we further explored the folding-energy landscape and examined the structural characteristics of CaM at free-energy basins. We discovered that crowding stabilizes several different compact conformations, which reflects the inherent plasticity in CaM's structure. From these results, we suggest that the EF hands in the C-lobe are flexible and can be thought of as a switch, while those in the N-lobe are stiff, analogous to a rheostat. New combinatorial signaling properties may arise from the product of the differential plasticity of the two distinct lobes of CaM in the presence of crowding. We discuss the implications of these results for modulating CaM's ability to bind Ca(2+) and target proteins.

Modeling urban coastal flood severity from crowd-sourced flood reports using Poisson regression and Random Forest

NASA Astrophysics Data System (ADS)

Sadler, J. M.; Goodall, J. L.; Morsy, M. M.; Spencer, K.

2018-04-01

Sea level rise has already caused more frequent and severe coastal flooding and this trend will likely continue. Flood prediction is an essential part of a coastal city's capacity to adapt to and mitigate this growing problem. Complex coastal urban hydrological systems however, do not always lend themselves easily to physically-based flood prediction approaches. This paper presents a method for using a data-driven approach to estimate flood severity in an urban coastal setting using crowd-sourced data, a non-traditional but growing data source, along with environmental observation data. Two data-driven models, Poisson regression and Random Forest regression, are trained to predict the number of flood reports per storm event as a proxy for flood severity, given extensive environmental data (i.e., rainfall, tide, groundwater table level, and wind conditions) as input. The method is demonstrated using data from Norfolk, Virginia USA from September 2010 to October 2016. Quality-controlled, crowd-sourced street flooding reports ranging from 1 to 159 per storm event for 45 storm events are used to train and evaluate the models. Random Forest performed better than Poisson regression at predicting the number of flood reports and had a lower false negative rate. From the Random Forest model, total cumulative rainfall was by far the most dominant input variable in predicting flood severity, followed by low tide and lower low tide. These methods serve as a first step toward using data-driven methods for spatially and temporally detailed coastal urban flood prediction.

Citizen Science and Crowdsourcing as effective STEM Education and Engagement activities for Diverse Audiences: case studies featured in THE CROWD & THE CLOUD public TV series.

NASA Astrophysics Data System (ADS)

Haines-Stiles, G.; Abdalati, W.; Akuginow, E.

2017-12-01

Citizen science and crowdsourcing are relatively unfamiliar terms to the general public, including parents, children and teachers, as seen in focus groups convened by the NSF-funded THE CROWD & THE CLOUD public television series. Once aware, however, of the potential of today's citizen science—often relying on smartphones, apps and innovative sensors—both citizens and professional scientists become excited and seek to learn more. CROWD & CLOUD, premiering on PBS stations in April 2017, hosted by former NASA Chief Scientist Waleed Abdalati, and streaming at CrowdAndCloud.org, features a wide range of projects supported by NASA, NOAA, USGS, EPA and other Federal agencies. Some, such as EyesOnALZ, a startup which aims to accelerate research on Alzheimer's disease, adapt a crowdsourcing model first developed to help analyze data returned by NASA's Stardust spacecraft. Early results from its "StallCatchers" puzzle-game show both high quality data and have been shown to cut one year's worth of academic labor down to one month of effort by "the crowd." While longstanding citizen science projects such as Audubon's Christmas Bird Count (starting in 1900) have proven their worth, Smartfin—embedding sensors in surfboard fins—is taking advantage of recent technical innovations to track sea surface temperatures and ocean acidification, with their accuracy validated by the Scripps Institution of Oceanography. The NASA-supported GLOBE Observer mosquito habitat mapper project uses a $6 microscope attached to a smartphone to aid in species identification. Some projects tap adult volunteers, but many, such as USGS's Nature's Notebook, also appeal to youngsters. In Albuquerque local teens track invasive species and help refuge managers, usefully supplementing the sole salaried ranger. In the Rockaways, New York, high school students plant pollinator gardens and promote ecosystem resilience following Superstorm Sandy. This presentation will feature short videos demonstrating the wide variety of "Citizen Science in the Digital Age" and present a first look at findings from CROWD & CLOUD's External Evaluation (Rockman et al) including extensive surveys, web analytics and interviews with career scientists, citizen science practitioners, and members of the general public.

Crowding and Density

ERIC Educational Resources Information Center

Design and Environment, 1972

1972-01-01

Three-part report pinpointing problems and uncovering solutions for the dual concepts of density (ratio of people to space) and crowding (psychological response to density). Section one, A Primer on Crowding,'' reviews new psychological and social findings; section two, Density in the Suburbs,'' shows conflict between status quo and increased…

The Effects of Molecular Crowding on the Structure and Stability of G-Quadruplexes with an Abasic Site

PubMed Central

Fujimoto, Takeshi; Nakano, Shu-ichi; Miyoshi, Daisuke; Sugimoto, Naoki

2011-01-01

Both cellular environmental factors and chemical modifications critically affect the properties of nucleic acids. However, the structure and stability of DNA containing abasic sites under cell-mimicking molecular crowding conditions remain unclear. Here, we investigated the molecular crowding effects on the structure and stability of the G-quadruplexes including a single abasic site. Structural analysis by circular dichroism showed that molecular crowding by PEG200 did not affect the topology of the G-quadruplex structure with or without an abasic site. Thermodynamic analysis further demonstrated that the degree of stabilization of the G-quadruplex by molecular crowding decreased with substitution of an abasic site for a single guanine. Notably, we found that the molecular crowding effects on the enthalpy change for G-quadruplex formation had a linear relationship with the abasic site effects depending on its position. These results are useful for predicting the structure and stability of G-quadruplexes with abasic sites in the cell-mimicking conditions. PMID:21949901

High pressures in room evacuation processes and a first approach to the dynamics around unconscious pedestrians

NASA Astrophysics Data System (ADS)

Cornes, F. E.; Frank, G. A.; Dorso, C. O.

2017-10-01

Clogging raises as the principal phenomenon during many evacuation processes of pedestrians in an emergency situation. As people push to escape from danger, compression forces may increase to harming levels. Many individuals might fall down, while others will try to dodge the fallen people, or, simply pass through them. We studied the dynamics of the crowd for these situations, in the context of the "social force model". We modeled the unconscious (fallen) pedestrians as inanimate bodies that can be dodged (or not) by the surrounding individuals. We found that new morphological structures appear along the evacuating crowd. Under specific conditions, these structures may enhance the evacuation performance. The pedestrian's willings for either dodging or passing through the unconscious individuals play a relevant role in the overall evacuation performance.

Modeling electrokinetics in ionic liquids: General

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang, Chao; Bao, Jie; Pan, Wenxiao

2017-04-07

Using direct numerical simulations we provide a thorough study on the electrokinetics of ionic liquids. In particular, the modfied Poisson-Nernst-Planck (MPNP) equations are solved to capture the crowding and overscreening effects that are the characteristics of an ionic liquid. For modeling electrokinetic flows in an ionic liquid, the MPNP equations are coupled with the Navier-Stokes equations to study the coupling of ion transport, hydrodynamics, and electrostatic forces. Specifically, we consider the ion transport between two parallel plates, charging dynamics in a 2D straight-walled pore, electro-osmotic ow in a nano-channel, electroconvective instability on a plane ion-selective surface, and electroconvective ow onmore » a curved ion-selective surface. We discuss how the crowding and overscreening effects and their interplay affect the electrokinetic behaviors of ionic liquids in these application problems.« less

ReaDDy - A Software for Particle-Based Reaction-Diffusion Dynamics in Crowded Cellular Environments

PubMed Central

Schöneberg, Johannes; Noé, Frank

2013-01-01

We introduce the software package ReaDDy for simulation of detailed spatiotemporal mechanisms of dynamical processes in the cell, based on reaction-diffusion dynamics with particle resolution. In contrast to other particle-based reaction kinetics programs, ReaDDy supports particle interaction potentials. This permits effects such as space exclusion, molecular crowding and aggregation to be modeled. The biomolecules simulated can be represented as a sphere, or as a more complex geometry such as a domain structure or polymer chain. ReaDDy bridges the gap between small-scale but highly detailed molecular dynamics or Brownian dynamics simulations and large-scale but little-detailed reaction kinetics simulations. ReaDDy has a modular design that enables the exchange of the computing core by efficient platform-specific implementations or dynamical models that are different from Brownian dynamics. PMID:24040218

Analysis of genetic polymorphisms in skeletal Class I crowding.

PubMed

Ting, Tung Yuen; Wong, Ricky Wing Kit; Rabie, A Bakr M

2011-07-01

Dental crowding is a problem for both adolescents and adults in modern society. The purpose of this research was to identify single nucleotide polymorphisms (SNPs) responsible for crowding in subjects with skeletal Class I relationships. The case subjects consisted of healthy Chinese people living in Hong Kong with skeletal Class I relationships and at least 5 mm of crowding in either arch. The control subjects met the same requirements but lacked crowding or spacing. SNP genotyping was performed on the MassARRAY platform. The chi-square test was used to compare genotype and allele type distributions between the case and the control groups. Logistic regression was used to calculate odds ratios with 95% confidence intervals, and the effects of age and sex for each SNP. Analyses of linkage disequilibrium and haplotype associations between SNPs were performed with software. Five SNPs were found to be significantly different in genotype or allele type distributions. SNP rs372024 was significantly associated with crowding (P = 0.004). Two SNPs, rs3764746 and rs3795170, on the EDA gene were found to be associated marginally. SNPs rs1005464 and rs15705 also exhibited marginal association with crowding. The effects of associated SNPs remained significant after adjustments for age and sex factors. This study suggests an association for the genes EDA and XEDAR in dental crowding in the Hong Kong Chinese population. Copyright © 2011 American Association of Orthodontists. Published by Mosby, Inc. All rights reserved.

Rapid visual perception of interracial crowds: Racial category learning from emotional segregation.

PubMed

Lamer, Sarah Ariel; Sweeny, Timothy D; Dyer, Michael Louis; Weisbuch, Max

2018-05-01

Drawing from research on social identity and ensemble coding, we theorize that crowd perception provides a powerful mechanism for social category learning. Crowds include allegiances that may be distinguished by visual cues to shared behavior and mental states, providing perceivers with direct information about social groups and thus a basis for learning social categories. Here, emotion expressions signaled group membership: to the extent that a crowd exhibited emotional segregation (i.e., was segregated into emotional subgroups), a visible characteristic (race) that incidentally distinguished emotional subgroups was expected to support categorical distinctions. Participants were randomly assigned to view interracial crowds in which emotion differences between (black vs. white) subgroups were either small (control condition) or large (emotional segregation condition). On each trial, participants saw crowds of 12 faces (6 black, 6 white) for roughly 300 ms and were asked to estimate the average emotion of the entire crowd. After all trials, participants completed a racial categorization task and self-report measure of race essentialism. As predicted, participants exposed to emotional segregation (vs. control) exhibited stronger racial category boundaries and stronger race essentialism. Furthermore, such effects accrued via ensemble coding, a visual mechanism that summarizes perceptual information: emotional segregation strengthened participants' racial category boundaries to the extent that segregation limited participants' abilities to integrate emotion across racial subgroups. Together with evidence that people observe emotional segregation in natural environments, these findings suggest that crowd perception mechanisms support racial category boundaries and race essentialism. (PsycINFO Database Record (c) 2018 APA, all rights reserved).

How the visual aspects can be crucial in reading acquisition? The intriguing case of crowding and developmental dyslexia.

PubMed

Gori, Simone; Facoetti, Andrea

2015-01-14

Developmental dyslexia (DD) is the most common neurodevelopmental disorder (about 10% of children across cultures) characterized by severe difficulties in learning to read. According to the dominant view, DD is considered a phonological processing impairment that might be linked to a cross-modal, letter-to-speech sound integration deficit. However, new theories-supported by consistent data-suggest that mild deficits in low-level visual and auditory processing can lead to DD. This evidence supports the probabilistic and multifactorial approach for DD. Among others, an interesting visual deficit that is often associated with DD is excessive visual crowding. Crowding is defined as difficulty in the ability to recognize objects when surrounded by similar items. Crowding, typically observed in peripheral vision, could be modulated by attentional processes. The direct consequence of stronger crowding on reading is the inability to recognize letters when they are surrounded by other letters. This problem directly translates to reading at a slower speed and being more prone to making errors while reading. Our aim is to review the literature supporting the important role of crowding in DD. Moreover, we are interested in proposing new possible studies in order to clarify whether the observed excessive crowding could be a cause rather than an effect of DD. Finally, we also suggest possible remediation and even prevention programs that could be based on reducing the crowding in children with or at risk for DD without involving any phonological or orthographic training. © 2015 ARVO.

Use Level and Encounters: Important Variables of Perceived Crowding Among Nonspecialized Recreationists.

ERIC Educational Resources Information Center

Hammitt, William E.; And Others

1984-01-01

Use level, visual encounters, crowding expectations, and feelings were examined by regression techniques to explain perceived crowding among innertube floaters. Degree of user specialization and specificity for any given activity and place is offered as an explanation for the discrepancy from previous findings. (Author/DF)

Locus of Peer Influence: Social Crowd and Best Friend.

ERIC Educational Resources Information Center

Urberg, Kathryn A.

1992-01-01

The relative influence of best friends and social crowds of 324 older adolescents (eleventh graders) on cigarette smoking was examined to determine influences as a function of sex, conformity, and friendship mutuality. Best friends, rather than social crowd, appeared to be the major influence in this group. (SLD)

Why Peer Crowds Matter: Incorporating Youth Subcultures and Values in Health Education Campaigns

PubMed Central

Walker, Matthew W.; Alexander, Tesfa N.; Jordan, Jeffrey W.; Wagner, Dana E.

2017-01-01

Grounded on research showing that peer crowds vary in risk behavior, several recent health behavior interventions, including the US Food and Drug Administration’s Fresh Empire campaign, have targeted high-risk peer crowds. We establish the scientific foundations for using this approach. We introduce peer crowd targeting as a strategy for culturally targeting health behavior interventions to youths. We use social identity and social norms theory to explicate the theoretical underpinnings of this approach. We describe Fresh Empire to demonstrate how peer crowd targeting functions in a campaign and critically evaluate the benefits and limitations of this approach. By replacing unhealthy behavioral norms with desirable, healthy lifestyles, peer crowd–targeted interventions can create a lasting impact that resonates in the target audience’s culture. PMID:28103067

A mathematical method for the turbulent behavior of crowds using agent particles

NASA Astrophysics Data System (ADS)

Ohnishi, Teruaki

2016-08-01

Among the people moving as a group there appear social and psychological forces together with physical forces such as friction and resistance. With the definition that the field of the crowd is the region of those forces continuously extending with varying strength, and with the pre-requisite that the spatial distribution of the crowd, i.e., the distribution of the field, varies according to the hydrodynamic rule by the Navier-Stokes equation, a methodology was proposed to describe the behavior of the crowd composed of many agent particles as the movement of a compressible, turbulent fluid. A numerical calculation was exemplified for the dynamic behavior and spatial distribution of crowds during movements when there appears a conflict between groups with different characters, imaging for instance the medieval battle of Breitenfeld.

Macromolecular Crowding Induces Spatial Correlations That Control Gene Expression Bursting Patterns

DOE PAGES

Norred, Sarah Elizabeth; Caveney, Patrick M.; Chauhan, Gaurav; ...

2018-04-24

Recent superresolution microscopy studies in E. coli demonstrate that the cytoplasm has highly variable local concentrations where macromolecular crowding plays a central role in establishing membrane-less compartmentalization. This spatial inhomogeneity significantly influences molecular transport and association processes central to gene expression. Yet, little is known about how macromolecular crowding influences gene expression bursting—the episodic process where mRNA and proteins are produced in bursts. Here, we simultaneously measured mRNA and protein reporters in cell-free systems, showing that macromolecular crowding decoupled the well-known relationship between fluctuations in the protein population (noise) and mRNA population statistics. Crowded environments led to a 10-fold increasemore » in protein noise even though there were only modest changes in the mRNA population and fluctuations. Instead, cell-like macromolecular crowding created an inhomogeneous spatial distribution of mRNA (“spatial noise”) that led to large variability in the protein production burst size. As a result, the mRNA spatial noise created large temporal fluctuations in the protein population. Furthermore, these results highlight the interplay between macromolecular crowding, spatial inhomogeneities, and the resulting dynamics of gene expression, and provide insights into using these organizational principles in both cell-based and cell-free synthetic biology.« less

Macromolecular Crowding Induces Spatial Correlations That Control Gene Expression Bursting Patterns

DOE Office of Scientific and Technical Information (OSTI.GOV)

Norred, Sarah Elizabeth; Caveney, Patrick M.; Chauhan, Gaurav

Recent superresolution microscopy studies in E. coli demonstrate that the cytoplasm has highly variable local concentrations where macromolecular crowding plays a central role in establishing membrane-less compartmentalization. This spatial inhomogeneity significantly influences molecular transport and association processes central to gene expression. Yet, little is known about how macromolecular crowding influences gene expression bursting—the episodic process where mRNA and proteins are produced in bursts. Here, we simultaneously measured mRNA and protein reporters in cell-free systems, showing that macromolecular crowding decoupled the well-known relationship between fluctuations in the protein population (noise) and mRNA population statistics. Crowded environments led to a 10-fold increasemore » in protein noise even though there were only modest changes in the mRNA population and fluctuations. Instead, cell-like macromolecular crowding created an inhomogeneous spatial distribution of mRNA (“spatial noise”) that led to large variability in the protein production burst size. As a result, the mRNA spatial noise created large temporal fluctuations in the protein population. Furthermore, these results highlight the interplay between macromolecular crowding, spatial inhomogeneities, and the resulting dynamics of gene expression, and provide insights into using these organizational principles in both cell-based and cell-free synthetic biology.« less

Effect of crowd size on patient volume at a large, multipurpose, indoor stadium.

PubMed

De Lorenzo, R A; Gray, B C; Bennett, P C; Lamparella, V J

1989-01-01

A prediction of patient volume expected at "mass gatherings" is desirable in order to provide optimal on-site emergency medical care. While several methods of predicting patient loads have been suggested, a reliable technique has not been established. This study examines the frequency of medical emergencies at the Syracuse University Carrier Dome, a 50,500-seat indoor stadium. Patient volume and level of care at collegiate basketball and football games as well as rock concerts, over a 7-year period were examined and tabulated. This information was analyzed using simple regression and nonparametric statistical methods to determine level of correlation between crowd size and patient volume. These analyses demonstrated no statistically significant increase in patient volume for increasing crowd size for basketball and football events. There was a small but statistically significant increase in patient volume for increasing crowd size for concerts. A comparison of similar crowd size for each of the three events showed that patient frequency is greatest for concerts and smallest for basketball. The study suggests that crowd size alone has only a minor influence on patient volume at any given event. Structuring medical services based solely on expected crowd size and not considering other influences such as event type and duration may give poor results.

Relevance and limitations of crowding, fractal, and polymer models to describe nuclear architecture.

PubMed

Huet, Sébastien; Lavelle, Christophe; Ranchon, Hubert; Carrivain, Pascal; Victor, Jean-Marc; Bancaud, Aurélien

2014-01-01

Chromosome architecture plays an essential role for all nuclear functions, and its physical description has attracted considerable interest over the last few years among the biophysics community. These researches at the frontiers of physics and biology have been stimulated by the demand for quantitative analysis of molecular biology experiments, which provide comprehensive data on chromosome folding, or of live cell imaging experiments that enable researchers to visualize selected chromosome loci in living or fixed cells. In this review our goal is to survey several nonmutually exclusive models that have emerged to describe the folding of DNA in the nucleus, the dynamics of proteins in the nucleoplasm, or the movements of chromosome loci. We focus on three classes of models, namely molecular crowding, fractal, and polymer models, draw comparisons, and discuss their merits and limitations in the context of chromosome structure and dynamics, or nuclear protein navigation in the nucleoplasm. Finally, we identify future challenges in the roadmap to a unified model of the nuclear environment. © 2014 Elsevier Inc. All rights reserved.

Cellular automaton model of crowd evacuation inspired by slime mould

NASA Astrophysics Data System (ADS)

Kalogeiton, V. S.; Papadopoulos, D. P.; Georgilas, I. P.; Sirakoulis, G. Ch.; Adamatzky, A. I.

2015-04-01

In all the living organisms, the self-preservation behaviour is almost universal. Even the most simple of living organisms, like slime mould, is typically under intense selective pressure to evolve a response to ensure their evolution and safety in the best possible way. On the other hand, evacuation of a place can be easily characterized as one of the most stressful situations for the individuals taking part on it. Taking inspiration from the slime mould behaviour, we are introducing a computational bio-inspired model crowd evacuation model. Cellular Automata (CA) were selected as a fully parallel advanced computation tool able to mimic the Physarum's behaviour. In particular, the proposed CA model takes into account while mimicking the Physarum foraging process, the food diffusion, the organism's growth, the creation of tubes for each organism, the selection of optimum tube for each human in correspondence to the crowd evacuation under study and finally, the movement of all humans at each time step towards near exit. To test the model's efficiency and robustness, several simulation scenarios were proposed both in virtual and real-life indoor environments (namely, the first floor of office building B of the Department of Electrical and Computer Engineering of Democritus University of Thrace). The proposed model is further evaluated in a purely quantitative way by comparing the simulation results with the corresponding ones from the bibliography taken by real data. The examined fundamental diagrams of velocity-density and flow-density are found in full agreement with many of the already published corresponding results proving the adequacy, the fitness and the resulting dynamics of the model. Finally, several real Physarum experiments were conducted in an archetype of the aforementioned real-life environment proving at last that the proposed model succeeded in reproducing sufficiently the Physarum's recorded behaviour derived from observation of the aforementioned biological laboratory experiments.

CA-LOD: Collision Avoidance Level of Detail for Scalable, Controllable Crowds

NASA Astrophysics Data System (ADS)

Paris, Sébastien; Gerdelan, Anton; O'Sullivan, Carol

The new wave of computer-driven entertainment technology throws audiences and game players into massive virtual worlds where entire cities are rendered in real time. Computer animated characters run through inner-city streets teeming with pedestrians, all fully rendered with 3D graphics, animations, particle effects and linked to 3D sound effects to produce more realistic and immersive computer-hosted entertainment experiences than ever before. Computing all of this detail at once is enormously computationally expensive, and game designers as a rule, have sacrificed the behavioural realism in favour of better graphics. In this paper we propose a new Collision Avoidance Level of Detail (CA-LOD) algorithm that allows games to support huge crowds in real time with the appearance of more intelligent behaviour. We propose two collision avoidance models used for two different CA-LODs: a fuzzy steering focusing on the performances, and a geometric steering to obtain the best realism. Mixing these approaches allows to obtain thousands of autonomous characters in real time, resulting in a scalable but still controllable crowd.

Crowding-out effect of coal industry investment in coal mining area: taking Shanxi province in China as a case.

PubMed

Li, Li; Lei, Yalin; Xu, Qun; Wu, Sanmang; Yan, Dan; Chen, Jiabin

2017-10-01

The rapid development of coal industry in Shanxi province in China has important effects on its economic development. A large amount of money has been invested into the coal industry and other related industries during the recent years. However, research on the investment effect of Shanxi's coal industry was rare. In order to analyze the investment effect of coal industry, based on the crowding-out effect model, cointegration test, and the data available in Shanxi Statistical Yearbooks, this paper calculates the effect between coal industry investment and other 17 industry investment. The results show that the investment of coal industry produces crowding-out effect on food industry, building materials industry, and machinery industry. Increasing 1% of the coal industry investment can reduce 0.25% of the food industry investment, or 0.6% of building materials industry investment, or 0.52% of the machinery industry investment, which implies that Shanxi province should adjust coal industrial structure, promote the balance development of coal industry and other industries, so as to promote its economic growth.

Crowding measures associated with the quality of emergency department care: a systematic review.

PubMed

Stang, Antonia S; Crotts, Jennifer; Johnson, David W; Hartling, Lisa; Guttmann, Astrid

2015-06-01

Despite the substantial body of literature on emergency department (ED) crowding, to the best of our knowledge, there is no agreement on the measure or measures that should be used to quantify crowding. The objective of this systematic review was to identify existing measures of ED crowding that have been linked to quality of care as defined by the Institute of Medicine (IOM) quality domains (safe, effective, patient-centered, efficient, timely, and equitable). Six major bibliographic databases were searched from January 1980 to January 2012, and hand searches were conducted of relevant journals and conference proceedings. Observational studies (cross-sectional, cohort, and case-control), quality improvement studies, quasi-experimental (e.g., before/after) studies, and randomized controlled trials were considered for inclusion. Studies that did not provide measures of ED crowding were excluded. Studies that did not provide quantitative data on the link between crowding measures and quality of care were also excluded. Two independent reviewers assessed study eligibility, completed data extraction, and assessed study quality using the Newcastle-Ottawa Quality Assessment Scale (NOS) for observational studies and a modified version of the NOS for cross-sectional studies. The search identified 7,413 articles. Thirty-two articles were included in the review: six cross-sectional, one case-control, 23 cohort, and two retrospective reviews of performance improvement data. Methodologic quality was moderate, with weaknesses in the reporting of study design and methodology. Overall, 15 of the crowding measures studied had quantifiable links to quality of care. The three measures most frequently linked to quality of care were the number of patients in the waiting room, ED occupancy (percentage of overall ED beds filled), and the number of admitted patients in the ED awaiting inpatient beds. None of the articles provided data on the link between crowding measures and the IOM domains reflecting equitable and efficient care. The results of this review provide data on the association between ED crowding measures and quality of care. Three simple crowding measures have been linked to quality of care in multiple publications. © 2015 by the Society for Academic Emergency Medicine.

Accelerated recovery of Atlantic salmon (Salmo salar) from effects of crowding by swimming.

PubMed

Veiseth, Eva; Fjaera, Svein Olav; Bjerkeng, Bjørn; Skjervold, Per Olav

2006-07-01

The effects of post-crowding swimming velocity (0, 0.35, and 0.70 m/s) and recovery time (1.5, 6, and 12 h) on physiological recovery and processing quality parameters of adult Atlantic salmon (Salmo salar) were determined. Atlantic salmon crowded to a density similar to that of a commercial slaughter process (>200 kg/m(3), 40 min) were transferred to a swimming chamber for recovery treatment. Osmolality and concentrations of cortisol, glucose and lactate in blood plasma were used as physiological stress indicators, whereas image analyses of extent and duration of rigor contraction, and fillet gaping were used as measures of processing quality. Crowded salmon had a 5.8-fold higher plasma cortisol concentration than control salmon (P<0.05). The elevated plasma cortisol concentration was reduced by increasing the swimming velocity, and had returned to control levels after 6 h recovery at high water velocity. Similar effects of swimming velocity were observed for plasma osmolality and lactate concentration. A lower plasma glucose concentration was present in crowded than in control fish (P<0.05), although a typical post-stress elevation in plasma glucose was observed after the recovery treatments. Lower muscle pH was found in crowded compared with control salmon (P<0.05), but muscle pH returned to control levels after 6 h recovery at intermediate and high swimming velocities and after 12 h in the low velocity group. Crowding caused an early onset of rigor mortis contraction. However, subjecting crowded salmon to active swimming for 6 h before slaughter delayed the onset of rigor mortis contraction from 2.5 to 7.5 h post mortem. The extent of rigor mortis contraction was also affected by crowding and post-stress swimming activity (P<0.05), and the largest degree of contraction was found in crowded salmon. In conclusion, active swimming accelerated the return of plasma cortisol, hydromineral balance, and the energy metabolism of adult Atlantic salmon to pre-stress levels. Moreover, an active swimming period delayed the onset of rigor mortis contraction, which has a positive technological implication for the salmon processing industry.

Improvement of imprinting effect of ionic liquid molecularly imprinted polymers by use of a molecular crowding agent.

PubMed

Jia, Man; Yang, Jian; Sun, Ya Kun; Bai, Xi; Wu, Tao; Liu, Zhao Sheng; Aisa, Haji Akber

2018-01-01

We aimed to improve the imprinting effect of ionic liquid molecularly imprinted polymers (MIPs) by use of a molecular crowding agent. The ionic liquid 1-vinyl-3-ethylimidazolium tetrafluoroborate ([VEIm][BF 4 ]) was used as the functional monomer and aesculetin was used as the template molecule in a crowding environment, which was made up of a tetrahydrofuran solution of polystyrene. The ionic liquid MIPs that were prepared in the crowding environment displayed an enhanced imprinting effect. NMR peak shifts of active hydrogen of aesculetin suggested that interaction between the functional monomer and the template could be increased by the use of a crowding agent in the self-assembly process. The retention and selectivity of aesculetin were affected greatly by high molecular crowding, the amount of high molecular weight crowding agent, and the ratio of [VEIm][BF 4 ] to aesculetin. The optimal MIPs were used as solid-phase extraction sorbents to extract aesculetin from Cichorium glandulosum. A calibration curve was obtained with aesculetin concentrations from 0.0005 to 0.05 mg mL -1 (correlation coefficient R 2 of 0.9999, y = 1519x + 0.0923). The limit of quantification was 0.12 μg mL -1 , and the limit of detection was 0.05 μg mL -1 . The absolute recovery of aesculetin was (80 ± 2)% (n = 3), and the purity of aesculetin was (92 ± 0.5)% (n = 5). As a conclusion, molecular crowding is an effective approach to obtain ionic liquid MIPs with high selectivity even in a polar solvent environment.

Action Recognition in a Crowded Environment

PubMed Central

Nieuwenhuis, Judith; Bülthoff, Isabelle; Barraclough, Nick; de la Rosa, Stephan

2017-01-01

So far, action recognition has been mainly examined with small point-light human stimuli presented alone within a narrow central area of the observer’s visual field. Yet, we need to recognize the actions of life-size humans viewed alone or surrounded by bystanders, whether they are seen in central or peripheral vision. Here, we examined the mechanisms in central vision and far periphery (40° eccentricity) involved in the recognition of the actions of a life-size actor (target) and their sensitivity to the presence of a crowd surrounding the target. In Experiment 1, we used an action adaptation paradigm to probe whether static or idly moving crowds might interfere with the recognition of a target’s action (hug or clap). We found that this type of crowds whose movements were dissimilar to the target action hardly affected action recognition in central and peripheral vision. In Experiment 2, we examined whether crowd actions that were more similar to the target actions affected action recognition. Indeed, the presence of that crowd diminished adaptation aftereffects in central vision as wells as in the periphery. We replicated Experiment 2 using a recognition task instead of an adaptation paradigm. With this task, we found evidence of decreased action recognition accuracy, but this was significant in peripheral vision only. Our results suggest that the presence of a crowd carrying out actions similar to that of the target affects its recognition. We outline how these results can be understood in terms of high-level crowding effects that operate on action-sensitive perceptual channels. PMID:29308177

The Wisdom of the Crowd in Combinatorial Problems

ERIC Educational Resources Information Center

Yi, Sheng Kung Michael; Steyvers, Mark; Lee, Michael D.; Dry, Matthew J.

2012-01-01

The "wisdom of the crowd" phenomenon refers to the finding that the aggregate of a set of proposed solutions from a group of individuals performs better than the majority of individual solutions. Most often, wisdom of the crowd effects have been investigated for problems that require single numerical estimates. We investigate whether the effect…

Perceptions of Crowding: Predicting at the Residence, Neighborhood, and City Levels.

ERIC Educational Resources Information Center

Schmidt, Donald E.; And Others

1979-01-01

Details the results of a large-scale field study aimed at testing two theories on human crowding. Found that psychological factors are increasingly important for the prediction of crowding as one moved from the immediate residence to the less immediate city level. Implications, limitations and further results are discussed. (Author/MA)

Perceived crowding at Boston Harbor Islands National Park Area

Treesearch

Megha Budruk; Robert E. Manning; William A. Valliere; Benjamin Wang

2002-01-01

The increasing popularity of outdoor recreation has led to concerns about the level and types of visitor use that can be accommodated in parks and related areas without causing unacceptable impacts to the recreation experience. Such impacts represent the social component of carrying capacity, and include perceived crowding. Crowding within recreation environments has...

Socialization of Social Anxiety in Adolescent Crowds

ERIC Educational Resources Information Center

Van Zalk, Nejra; Van Zalk, Maarten Herman Walter; Kerr, Margaret

2011-01-01

In this study, we looked at whether social anxiety is socialized, or influenced by peers' social anxiety, more in some peer crowds than others. Adolescents in crowds with eye-catching appearances such as Goths and Punks (here termed "Radical"), were compared with three comparison groups. Using data from 796 adolescents (353 girls and 443 boys; M…

Peer Crowd Affiliation and Internalizing Distress in Childhood and Adolescence: A Longitudinal Follow-Back Study.

ERIC Educational Resources Information Center

Prinstein, Mitchell J.; La Greca, Annette M.

2002-01-01

Examined concurrent and longitudinal associations between peer crowd affiliation and internalized distress in a sample of 246 youth. Found that adolescents' report of peer crowd affiliation was concurrently associated with self-concept and levels of internalizing distress. Follow-back analyses revealed that "Populars/Jocks" had…

Curriculum-Guided Crowd Sourcing of Assessments in a Developing Country

ERIC Educational Resources Information Center

Zualkernan, Imran A.; Raza, Anjana; Karim, Asad

2012-01-01

Success of Wikipedia has opened a number of possibilities for crowd sourcing learning resources. However, not all crowd sourcing initiatives are successful. For developing countries, adoption factors like lack of infrastructure and poor teacher training can have an impact on success of such systems. This paper presents an exploratory study to…

Achieving external validity in home advantage research: generalizing crowd noise effects

PubMed Central

Myers, Tony D.

2014-01-01

Different factors have been postulated to explain the home advantage phenomenon in sport. One plausible explanation investigated has been the influence of a partisan home crowd on sports officials' decisions. Different types of studies have tested the crowd influence hypothesis including purposefully designed experiments. However, while experimental studies investigating crowd influences have high levels of internal validity, they suffer from a lack of external validity; decision-making in a laboratory setting bearing little resemblance to decision-making in live sports settings. This focused review initially considers threats to external validity in applied and theoretical experimental research. Discussing how such threats can be addressed using representative design by focusing on a recently published study that arguably provides the first experimental evidence of the impact of live crowd noise on officials in sport. The findings of this controlled experiment conducted in a real tournament setting offer a level of confirmation of the findings of laboratory studies in the area. Finally directions for future research and the future conduct of crowd noise studies are discussed. PMID:24917839

Mobile mapping of sporting event spectators using bluetooth sensors: tour of flanders 2011.

PubMed

Versichele, Mathias; Neutens, Tijs; Goudeseune, Stephanie; van Bossche, Frederik; van de Weghe, Nico

2012-10-22

Accurate spatiotemporal information on crowds is a necessity for a better management in general and for the mitigation of potential security risks. The large numbers of individuals involved and their mobility, however, make generation of this information non-trivial. This paper proposes a novel methodology to estimate and map crowd sizes using mobile Bluetooth sensors and examines to what extent this methodology represents a valuable alternative to existing traditional crowd density estimation methods. The proposed methodology is applied in a unique case study that uses Bluetooth technology for the mobile mapping of spectators of the Tour of Flanders 2011 road cycling race. The locations of nearly 16,000 cell phones of spectators along the race course were registered and detailed views of the spatiotemporal distribution of the crowd were generated. Comparison with visual head counts from camera footage delivered a detection ratio of 13.0 ± 2.3%, making it possible to estimate the crowd size. To our knowledge, this is the first study that uses mobile Bluetooth sensors to count and map a crowd over space and time.

Mobile Mapping of Sporting Event Spectators Using Bluetooth Sensors: Tour of Flanders 2011

PubMed Central

Versichele, Mathias; Neutens, Tijs; Goudeseune, Stephanie; van Bossche, Frederik; van de Weghe, Nico

2012-01-01

Accurate spatiotemporal information on crowds is a necessity for a better management in general and for the mitigation of potential security risks. The large numbers of individuals involved and their mobility, however, make generation of this information non-trivial. This paper proposes a novel methodology to estimate and map crowd sizes using mobile Bluetooth sensors and examines to what extent this methodology represents a valuable alternative to existing traditional crowd density estimation methods. The proposed methodology is applied in a unique case study that uses Bluetooth technology for the mobile mapping of spectators of the Tour of Flanders 2011 road cycling race. The locations of nearly 16,000 cell phones of spectators along the race course were registered and detailed views of the spatiotemporal distribution of the crowd were generated. Comparison with visual head counts from camera footage delivered a detection ratio of 13.0 ± 2.3%, making it possible to estimate the crowd size. To our knowledge, this is the first study that uses mobile Bluetooth sensors to count and map a crowd over space and time. PMID:23202044

Macromolecular crowding-assisted fabrication of liquid-crystalline imprinted polymers.

PubMed

Zhang, Chen; Zhang, Jing; Huang, Yan-Ping; Liu, Zhao-Sheng

2015-04-01

A macromolecular crowding-assisted liquid-crystalline molecularly imprinted monolith (LC-MIM) was prepared successfully for the first time. The imprinted stationary phase was synthesized with polymethyl methacrylate (PMMA) or polystyrene (PS) as the crowding agent, 4-cyanophenyl dicyclohexyl propylene (CPCE) as the liquid-crystal monomer, and hydroquinidine as the pseudo-template for the chiral separation of cinchona alkaloids in HPLC. A low level of cross-linker (26%) has been found to be sufficient to achieve molecular recognition on the crowding-assisted LC-MIM due to the physical cross-linking of mesogenic groups in place of chemical cross-linking, and baseline separation of quinidine and quinine could be achieved with good resolution (R(s) = 2.96), selectivity factor (α = 2.16), and column efficiency (N = 2650 plates/m). In contrast, the LC-MIM prepared without crowding agents displayed the smallest diastereoselectivity (α = 1.90), while the crowding-assisted MIM with high level of cross-linker (80%) obtained the greatest selectivity factor (α = 7.65), but the lowest column efficiency (N = 177 plates/m).

Hemoglobin diffusion and the dynamics of oxygen capture by red blood cells.

PubMed

Longeville, Stéphane; Stingaciu, Laura-Roxana

2017-09-05

Translational diffusion of macromolecules in cell is generally assumed to be anomalous due high macromolecular crowding of the milieu. Red blood cells are a special case of cells filled quasi exclusively (95% of the dry weight of the cell) with an almost spherical protein: hemoglobin. Hemoglobin diffusion has since a long time been recognized as facilitating the rate of oxygen diffusion through a solution. We address in this paper the question on how hemoglobin diffusion in the red blood cells can help the oxygen capture at the cell level and hence to improve oxygen transport. We report a measurement by neutron spin echo spectroscopy of the diffusion of hemoglobin in solutions with increasing protein concentration. We show that hemoglobin diffusion in solution can be described as Brownian motion up to physiological concentration and that hemoglobin diffusion in the red blood cells and in solutions at similar concentration are the same. Finally, using a simple model and the concentration dependence of the diffusion of the protein reported here, we show that hemoglobin concentration observed in human red blood cells ([Formula: see text]330 g.L -1 ) corresponds to an optimum for oxygen transport for individuals under strong activity.

Hemoglobin diffusion and the dynamics of oxygen capture by red blood cells

DOE PAGES

Longeville, Stéphane; Stingaciu, Laura-Roxana

2017-09-05

Translational diffusion of macromolecules in cell is generally assumed to be anomalous due high macromolecular crowding of the milieu. Red blood cells are a special case of cells filled quasi exclusively (95% of the dry weight of the cell) with an almost spherical protein: hemoglobin. Hemoglobin diffusion has since a long time been recognized as facilitating the rate of oxygen diffusion through a solution. We address in this paper the question on how hemoglobin diffusion in the red blood cells can help the oxygen capture at the cell level and hence to improve oxygen transport. We report a measurement bymore » neutron spin echo spectroscopy of the diffusion of hemoglobin in solutions with increasing protein concentration. We show that hemoglobin diffusion in solution can be described as Brownian motion up to physiological concentration and that hemoglobin diffusion in the red blood cells and in solutions at similar concentration are the same. Finally, using a simple model and the concentration dependence of the diffusion of the protein reported here, we show that hemoglobin concentration observed in human red blood cells (≃330 g.L -1) corresponds to an optimum for oxygen transport for individuals under strong activity.« less

Hemoglobin diffusion and the dynamics of oxygen capture by red blood cells

DOE Office of Scientific and Technical Information (OSTI.GOV)

Longeville, Stéphane; Stingaciu, Laura-Roxana

Translational diffusion of macromolecules in cell is generally assumed to be anomalous due high macromolecular crowding of the milieu. Red blood cells are a special case of cells filled quasi exclusively (95% of the dry weight of the cell) with an almost spherical protein: hemoglobin. Hemoglobin diffusion has since a long time been recognized as facilitating the rate of oxygen diffusion through a solution. We address in this paper the question on how hemoglobin diffusion in the red blood cells can help the oxygen capture at the cell level and hence to improve oxygen transport. We report a measurement bymore » neutron spin echo spectroscopy of the diffusion of hemoglobin in solutions with increasing protein concentration. We show that hemoglobin diffusion in solution can be described as Brownian motion up to physiological concentration and that hemoglobin diffusion in the red blood cells and in solutions at similar concentration are the same. Finally, using a simple model and the concentration dependence of the diffusion of the protein reported here, we show that hemoglobin concentration observed in human red blood cells (≃330 g.L -1) corresponds to an optimum for oxygen transport for individuals under strong activity.« less

Localization switching of a large object in a crowded cavity: A rigid/soft object prefers surface/inner positioning.

PubMed

Shew, Chwen-Yang; Oda, Soutaro; Yoshikawa, Kenichi

2017-11-28

For living cells in the real world, a large organelle is commonly positioned in the inner region away from membranes, such as the nucleus of eukaryotic cells, the nucleolus of nuclei, mitochondria, chloroplast, Golgi body, etc. It contradicts the expectation by the current depletion-force theory in that the larger particle should be excluded from the inner cell space onto cell boundaries in a crowding media. Here we simply model a sizable organelle as a soft-boundary large particle allowing crowders, which are smaller hard spheres in the model, to intrude across its boundary. The results of Monte Carlo simulation indicate that the preferential location of the larger particle switches from the periphery into the inner region of the cavity by increasing its softness. An integral equation theory is further developed to account for the structural features of the model, and the theoretical predictions are found consistent with our simulation results.

Localization switching of a large object in a crowded cavity: A rigid/soft object prefers surface/inner positioning

NASA Astrophysics Data System (ADS)

Shew, Chwen-Yang; Oda, Soutaro; Yoshikawa, Kenichi

2017-11-01

For living cells in the real world, a large organelle is commonly positioned in the inner region away from membranes, such as the nucleus of eukaryotic cells, the nucleolus of nuclei, mitochondria, chloroplast, Golgi body, etc. It contradicts the expectation by the current depletion-force theory in that the larger particle should be excluded from the inner cell space onto cell boundaries in a crowding media. Here we simply model a sizable organelle as a soft-boundary large particle allowing crowders, which are smaller hard spheres in the model, to intrude across its boundary. The results of Monte Carlo simulation indicate that the preferential location of the larger particle switches from the periphery into the inner region of the cavity by increasing its softness. An integral equation theory is further developed to account for the structural features of the model, and the theoretical predictions are found consistent with our simulation results.

Pitfalls and Potentials of Crowd Science: a Meta-Analysis of Contextual Influences

NASA Astrophysics Data System (ADS)

Klippel, A.; Sparks, K.; Wallgrün, J. O.

2015-08-01

Crowd science is becoming an integral part of research in many disciplines. The research discussed in this paper lies at the intersection of spatial and behavioral sciences, two of the greatest beneficiaries of crowd science. As a young methodological development, crowd science needs attention from the perspective of a rigorous evaluation of the data collected to explore potentials as well as limitations (pitfalls). Our research has addressed a variety of contextual effects on the validity of crowdsourced data such as cultural, linguistic, regional, as well as methodological differences that we will discuss here in light of semantics.

The Ionosphere's Pocket Litter: Exploiting Crowd-Sourced Observations

NASA Astrophysics Data System (ADS)

Miller, E. S.; Frissell, N. A.; Kaeppler, S. R.; Demajistre, R.; Knuth, A. A.

2015-12-01

One of the biggest challenges faced in developing and testing our understanding of the ionosphere is acquiring data that characterizes the latitudinal and longitudinal variability of the ionosphere. While there are extensive networks of ground sites that sample the vertical distribution, we have rather poor coverage over the oceans and in parts of the southern hemisphere. Our ability to validate the ionospheric models is limited by the lack of point measurements and those measurements that essentially constitute characterization of horizontal gradients. In this talk, we discuss and demonstrate the use of various types of crowd-sourced information that enables us to extend our coverage over these regions. We will discuss new sources of these data, concepts for new experiments and the use of these data in assimilative models. We note that there are new, low cost options for obtaining data that broaden the participation beyond the aeronomy/ionospheric community.

Linking crowding, visual span, and reading.

PubMed

He, Yingchen; Legge, Gordon E

2017-09-01

The visual span is hypothesized to be a sensory bottleneck on reading speed with crowding thought to be the major sensory factor limiting the size of the visual span. This proposed linkage between crowding, visual span, and reading speed is challenged by the finding that training to read crowded letters reduced crowding but did not improve reading speed (Chung, 2007). Here, we examined two properties of letter-recognition training that may influence the transfer to improved reading: the spatial arrangement of training stimuli and the presence of flankers. Three groups of nine young adults were trained with different configurations of letter stimuli at 10° in the lower visual field: a flanked-local group (flanked letters localized at one position), a flanked-distributed group (flanked letters distributed across different horizontal locations), and an isolated-distributed group (isolated and distributed letters). We found that distributed training, but not the presence of flankers, appears to be necessary for the training benefit to transfer to increased reading speed. Localized training may have biased attention to one specific, small area in the visual field, thereby failing to improve reading. We conclude that the visual span represents a sensory bottleneck on reading, but there may also be an attentional bottleneck. Reducing the impact of crowding can enlarge the visual span and can potentially facilitate reading, but not when adverse attentional bias is present. Our results clarify the association between crowding, visual span, and reading.

Linking crowding, visual span, and reading

PubMed Central

He, Yingchen; Legge, Gordon E.

2017-01-01

The visual span is hypothesized to be a sensory bottleneck on reading speed with crowding thought to be the major sensory factor limiting the size of the visual span. This proposed linkage between crowding, visual span, and reading speed is challenged by the finding that training to read crowded letters reduced crowding but did not improve reading speed (Chung, 2007). Here, we examined two properties of letter-recognition training that may influence the transfer to improved reading: the spatial arrangement of training stimuli and the presence of flankers. Three groups of nine young adults were trained with different configurations of letter stimuli at 10° in the lower visual field: a flanked-local group (flanked letters localized at one position), a flanked-distributed group (flanked letters distributed across different horizontal locations), and an isolated-distributed group (isolated and distributed letters). We found that distributed training, but not the presence of flankers, appears to be necessary for the training benefit to transfer to increased reading speed. Localized training may have biased attention to one specific, small area in the visual field, thereby failing to improve reading. We conclude that the visual span represents a sensory bottleneck on reading, but there may also be an attentional bottleneck. Reducing the impact of crowding can enlarge the visual span and can potentially facilitate reading, but not when adverse attentional bias is present. Our results clarify the association between crowding, visual span, and reading. PMID:28973564

Third molars and dental crowding: different opinions of orthodontists and oral surgeons among Italian practitioners.

PubMed

Gavazzi, Michela; De Angelis, Donato; Blasi, Sergio; Pesce, Paolo; Lanteri, Valentina

2014-11-22

The role of third molars as a cause of incisor crowding, especially in the lower arch, continues to be controversial. The aim of this work is to compare opinions of Italian oral surgeons and orthodontists on this topic. One hundred ninety-three Italian practitioners of the Society of Orthodontics (SIDO) and the Italian Society of Oral Surgery (SICOI) were asked to fill out an online questionnaire made up of six questions. Practitioners were asked to express their opinion on the relation between upper and lower third molar eruption and anterior crowding. One hundred sixty-six members of both societies completed the online research survey; response rate (RR) was 86%. There were no statistically significant differences between the two groups (P > 0.005). Both agree not to believe that third molars create a force responsible for anterior crowding in the upper (82.5% orthodontists, 83.8% surgeons) and in the lower arch (52.6% orthodontists, 63.8% surgeons). Both agree also not to consider the upper (89.7% orthodontists, 82.1% surgeons) and lower (58.8% orthodontists, 63.2% surgeons) third molar extraction useful to prevent crowding. Italian orthodontists and oral surgeons have the same opinion on the role of the third molar in causing anterior crowding. The majority of both groups of clinicians do not consider their preventive extraction useful in order to prevent anterior crowding.

Solving the worldwide emergency department crowding problem - what can we learn from an Israeli ED?

PubMed

Pines, Jesse M; Bernstein, Steven L

2015-01-01

ED crowding is a prevalent and important issue facing hospitals in Israel and around the world, including North and South America, Europe, Australia, Asia and Africa. ED crowding is associated with poorer quality of care and poorer health outcomes, along with extended waits for care. Crowding is caused by a periodic mismatch between the supply of ED and hospital resources and the demand for patient care. In a recent article in the Israel Journal of Health Policy Research, Bashkin et al. present an Ishikawa diagram describing several factors related to longer length of stay (LOS), and higher levels of ED crowding, including management, process, environmental, human factors, and resource issues. Several solutions exist to reduce ED crowding, which involve addressing several of the issues identified by Bashkin et al. This includes reducing the demand for and variation in care, and better matching the supply of resources to demands in care in real time. However, what is needed to reduce crowding is an institutional imperative from senior leadership, implemented by engaged ED and hospital leadership with multi-disciplinary cross-unit collaboration, sufficient resources to implement effective interventions, access to data, and a sustained commitment over time. This may move the culture of a hospital to facilitate improved flow within and across units and ultimately improve quality and safety over the long-term.

Stochastic simulation tools and continuum models for describing two-dimensional collective cell spreading with universal growth functions

NASA Astrophysics Data System (ADS)

Jin, Wang; Penington, Catherine J.; McCue, Scott W.; Simpson, Matthew J.

2016-10-01

Two-dimensional collective cell migration assays are used to study cancer and tissue repair. These assays involve combined cell migration and cell proliferation processes, both of which are modulated by cell-to-cell crowding. Previous discrete models of collective cell migration assays involve a nearest-neighbour proliferation mechanism where crowding effects are incorporated by aborting potential proliferation events if the randomly chosen target site is occupied. There are two limitations of this traditional approach: (i) it seems unreasonable to abort a potential proliferation event based on the occupancy of a single, randomly chosen target site; and, (ii) the continuum limit description of this mechanism leads to the standard logistic growth function, but some experimental evidence suggests that cells do not always proliferate logistically. Motivated by these observations, we introduce a generalised proliferation mechanism which allows non-nearest neighbour proliferation events to take place over a template of r≥slant 1 concentric rings of lattice sites. Further, the decision to abort potential proliferation events is made using a crowding function, f(C), which accounts for the density of agents within a group of sites rather than dealing with the occupancy of a single randomly chosen site. Analysing the continuum limit description of the stochastic model shows that the standard logistic source term, λ C(1-C), where λ is the proliferation rate, is generalised to a universal growth function, λ C f(C). Comparing the solution of the continuum description with averaged simulation data indicates that the continuum model performs well for many choices of f(C) and r. For nonlinear f(C), the quality of the continuum-discrete match increases with r.

Stochastic simulation tools and continuum models for describing two-dimensional collective cell spreading with universal growth functions.

PubMed

Jin, Wang; Penington, Catherine J; McCue, Scott W; Simpson, Matthew J

2016-10-07

Two-dimensional collective cell migration assays are used to study cancer and tissue repair. These assays involve combined cell migration and cell proliferation processes, both of which are modulated by cell-to-cell crowding. Previous discrete models of collective cell migration assays involve a nearest-neighbour proliferation mechanism where crowding effects are incorporated by aborting potential proliferation events if the randomly chosen target site is occupied. There are two limitations of this traditional approach: (i) it seems unreasonable to abort a potential proliferation event based on the occupancy of a single, randomly chosen target site; and, (ii) the continuum limit description of this mechanism leads to the standard logistic growth function, but some experimental evidence suggests that cells do not always proliferate logistically. Motivated by these observations, we introduce a generalised proliferation mechanism which allows non-nearest neighbour proliferation events to take place over a template of [Formula: see text] concentric rings of lattice sites. Further, the decision to abort potential proliferation events is made using a crowding function, f(C), which accounts for the density of agents within a group of sites rather than dealing with the occupancy of a single randomly chosen site. Analysing the continuum limit description of the stochastic model shows that the standard logistic source term, [Formula: see text], where λ is the proliferation rate, is generalised to a universal growth function, [Formula: see text]. Comparing the solution of the continuum description with averaged simulation data indicates that the continuum model performs well for many choices of f(C) and r. For nonlinear f(C), the quality of the continuum-discrete match increases with r.

Brownian motion on random dynamical landscapes

NASA Astrophysics Data System (ADS)

Suñé Simon, Marc; Sancho, José María; Lindenberg, Katja

2016-03-01

We present a study of overdamped Brownian particles moving on a random landscape of dynamic and deformable obstacles (spatio-temporal disorder). The obstacles move randomly, assemble, and dissociate following their own dynamics. This landscape may account for a soft matter or liquid environment in which large obstacles, such as macromolecules and organelles in the cytoplasm of a living cell, or colloids or polymers in a liquid, move slowly leading to crowding effects. This representation also constitutes a novel approach to the macroscopic dynamics exhibited by active matter media. We present numerical results on the transport and diffusion properties of Brownian particles under this disorder biased by a constant external force. The landscape dynamics are characterized by a Gaussian spatio-temporal correlation, with fixed time and spatial scales, and controlled obstacle concentrations.

Crowd-Sourcing (Semantically) Structured Multilingual Educational Content (CoSMEC)

ERIC Educational Resources Information Center

Tarasowa, Darya; Auer, Sören; Khalili, Ali; Unbehauen, Jörg

2014-01-01

The support of multilingual content becomes crucial for educational platforms due to the benefits it offers. In this paper we propose a concept that allows content authors to use the power of the crowd to create (semantically) structured multilingual educational content out of their material. To enable the collaboration of the crowd, we expand our…

YaQ: an architecture for real-time navigation and rendering of varied crowds.

PubMed

Maïm, Jonathan; Yersin, Barbara; Thalmann, Daniel

2009-01-01

The YaQ software platform is a complete system dedicated to real-time crowd simulation and rendering. Fitting multiple application domains, such as video games and VR, YaQ aims to provide efficient algorithms to generate crowds comprising up to thousands of varied virtual humans navigating in large-scale, global environments.

Measures of wilderness trip satisfaction and user perceptions of crowding

Treesearch

Chad P. Dawson; Alan E. Watson

2000-01-01

The inverse relationship between user perceptions of crowding and satisfaction with the wilderness experience was studied in three national wilderness areas in Oregon (1991) and in four state wilderness areas in the Adirondack Park of New York State (1997). User perceptions of crowding were correlated (low negative coefficients) with user satisfaction on the wilderness...

Kinetic theory of situated agents applied to pedestrian flow in a corridor

NASA Astrophysics Data System (ADS)

Rangel-Huerta, A.; Muñoz-Meléndez, A.

2010-03-01

A situated agent-based model for simulation of pedestrian flow in a corridor is presented. In this model, pedestrians choose their paths freely and make decisions based on local criteria for solving collision conflicts. The crowd consists of multiple walking agents equipped with a function of perception as well as a competitive rule-based strategy that enables pedestrians to reach free access areas. Pedestrians in our model are autonomous entities capable of perceiving and making decisions. They apply socially accepted conventions, such as avoidance rules, as well as individual preferences such as the use of specific exit points, or the execution of eventual comfort turns resulting in spontaneous changes of walking speed. Periodic boundary conditions were considered in order to determine the density-average walking speed, and the density-average activity with respect to specific parameters: comfort angle turn and frequency of angle turn of walking agents. The main contribution of this work is an agent-based model where each pedestrian is represented as an autonomous agent. At the same time the pedestrian crowd dynamics is framed by the kinetic theory of biological systems.

Is the crowd better as an assistant or a replacement in ontology engineering? An exploration through the lens of the Gene Ontology.

PubMed

Mortensen, Jonathan M; Telis, Natalie; Hughey, Jacob J; Fan-Minogue, Hua; Van Auken, Kimberly; Dumontier, Michel; Musen, Mark A

2016-04-01

Biomedical ontologies contain errors. Crowdsourcing, defined as taking a job traditionally performed by a designated agent and outsourcing it to an undefined large group of people, provides scalable access to humans. Therefore, the crowd has the potential to overcome the limited accuracy and scalability found in current ontology quality assurance approaches. Crowd-based methods have identified errors in SNOMED CT, a large, clinical ontology, with an accuracy similar to that of experts, suggesting that crowdsourcing is indeed a feasible approach for identifying ontology errors. This work uses that same crowd-based methodology, as well as a panel of experts, to verify a subset of the Gene Ontology (200 relationships). Experts identified 16 errors, generally in relationships referencing acids and metals. The crowd performed poorly in identifying those errors, with an area under the receiver operating characteristic curve ranging from 0.44 to 0.73, depending on the methods configuration. However, when the crowd verified what experts considered to be easy relationships with useful definitions, they performed reasonably well. Notably, there are significantly fewer Google search results for Gene Ontology concepts than SNOMED CT concepts. This disparity may account for the difference in performance - fewer search results indicate a more difficult task for the worker. The number of Internet search results could serve as a method to assess which tasks are appropriate for the crowd. These results suggest that the crowd fits better as an expert assistant, helping experts with their verification by completing the easy tasks and allowing experts to focus on the difficult tasks, rather than an expert replacement. Copyright © 2016 Elsevier Inc. All rights reserved.

The allocation of attention and working memory in visual crowding.

PubMed

Bacigalupo, Felix; Luck, Steven J

2015-06-01

When the distance between a visual target and nearby flankers falls below a critical distance, target discrimination declines precipitously. This is called "crowding." Many researchers have proposed that selective attention plays a role in crowding. However, although some research has examined the effects of directing attention toward versus away from the targets, no previous research has assessed how attentional allocation varies as a function of target-flanker distance in crowding. Here, we used ERPs to assess the operation of attention during crowding, focusing on the attention-related N2pc component. We used a typical crowding task in which participants were asked to report the category (vowel/consonant) of a lateralized target letter flanked by distractor letters at different distances. We tested the hypothesis that attention fails when the target-flanker distance becomes too small for attention to operate effectively. Consistent with this hypothesis, we found that N2pc amplitude was maximal at intermediate target-flanker distances and decreased substantially when crowding became severe. In addition, we examined the sustained posterior contralateral negativity (SPCN), which reflects the amount of information being maintained in working memory. Unlike the N2pc component, the SPCN increased in amplitude at small target-flanker distances, suggesting that observers stored information about the target and flankers in working memory when attention failed to select the target. Together, the N2pc and SPCN results suggest that attention and working memory play distinctive roles in crowding: Attention operates to minimize interference from the flankers at intermediate target-flanker distances, whereas working memory may be recruited when attention fails to select the target at small target-flanker distances.

STS-109 Crew Return Ceremony at Ellington Field

NASA Image and Video Library

2002-03-13

Photographic documentation of the STS-109 Crew Return Ceremony. The events take place at Hangar 990 at Ellington Field. Views include: Overall view of crewmembers [09319]; View of crewmembers standing on stage talking to group [09320]; Unidentified crewmember waving to crowd [09321]; Unidentified crewmember autographing photo [09322]; Mission Specialist Michael J. Massimino holding crew photo as he talks to child in group [09323]; Pilot Duane G. Carey signing a crew photo for a visitor [09324]; Unidentified crewmember signing a photo for visitor [09325]; Commander Scott D. Altman talking to child in group [09326]; Unidentified crewmember giving a photo to visitor [09327]; Crewmembers exiting plane [09328]; Duane G. Carey shaking hands with visitor. Astronaut Scott Altman smiling in the background [09329); Astronaut Jim Newman kissing his child [09330]; Jim Newman holding his daughter as his son grabs at his pant leg [09331]; Close-up view of Payload Commander John Grunsfeld holding his daughter [09332]; Duane G. Carey standing with family members [09333]; Close-up view of Duane G. Carey placing his hand on a child's head as he is talking to him [09334]; Overall view of spectator watching ceremony [09335]; Close-up view of speaker during ceremony [09336]; Close-up view of Scott Altman speaking to crowd [09337]; Close-up view of a young spectator at ceremony [09338]; Close-up view of Duane G. Carey speaking to the crowd [09339]; Close-up view of Mission Specialist Nancy J. Currie speaking to the crowd [09340]; Close-up view of John M. Grunsfield speaking to the crowd [09341]; Close-up view of Mission Specialist Richard M. Linnehan speaking to the crowd [09342]; Close-up view of James H. Newman speaking to the crowd [09343]; Close-up view of Michael J. Massimino speaking to the crowd [09344

Modeling 2D and 3D diffusion.

PubMed

Saxton, Michael J

2007-01-01

Modeling obstructed diffusion is essential to the understanding of diffusion-mediated processes in the crowded cellular environment. Simple Monte Carlo techniques for modeling obstructed random walks are explained and related to Brownian dynamics and more complicated Monte Carlo methods. Random number generation is reviewed in the context of random walk simulations. Programming techniques and event-driven algorithms are discussed as ways to speed simulations.

Explaining effervescence: Investigating the relationship between shared social identity and positive experience in crowds

PubMed Central

Hopkins, Nick; Reicher, Stephen D.; Khan, Sammyh S.; Tewari, Shruti; Srinivasan, Narayanan; Stevenson, Clifford

2016-01-01

We investigated the intensely positive emotional experiences arising from participation in a large-scale collective event. We predicted such experiences arise when those attending a collective event are (1) able to enact their valued collective identity and (2) experience close relations with other participants. In turn, we predicted both of these to be more likely when participants perceived crowd members to share a common collective identity. We investigated these predictions in a survey of pilgrims (N = 416) attending a month-long Hindu pilgrimage festival in north India. We found participants' perceptions of a shared identity amongst crowd members had an indirect effect on their positive experience at the event through (1) increasing participants' sense that they were able to enact their collective identity and (2) increasing the sense of intimacy with other crowd members. We discuss the implications of these data for how crowd emotion should be conceptualised. PMID:25787295

Explaining effervescence: Investigating the relationship between shared social identity and positive experience in crowds.

PubMed

Hopkins, Nick; Reicher, Stephen D; Khan, Sammyh S; Tewari, Shruti; Srinivasan, Narayanan; Stevenson, Clifford

2016-01-01

We investigated the intensely positive emotional experiences arising from participation in a large-scale collective event. We predicted such experiences arise when those attending a collective event are (1) able to enact their valued collective identity and (2) experience close relations with other participants. In turn, we predicted both of these to be more likely when participants perceived crowd members to share a common collective identity. We investigated these predictions in a survey of pilgrims (N = 416) attending a month-long Hindu pilgrimage festival in north India. We found participants' perceptions of a shared identity amongst crowd members had an indirect effect on their positive experience at the event through (1) increasing participants' sense that they were able to enact their collective identity and (2) increasing the sense of intimacy with other crowd members. We discuss the implications of these data for how crowd emotion should be conceptualised.

School Crowding, Year-Round Schooling, and Mobile Classroom Use: Evidence from North Carolina

ERIC Educational Resources Information Center

McMullen, Steven C.; Rouse, Kathryn E.

2012-01-01

This study exploits a unique policy environment and a large panel dataset to evaluate the impact of school crowding on student achievement in Wake County, NC. We also estimate the effects of two education policy initiatives that are often used to address crowding: multi-track year-round calendars and mobile classrooms. We estimate a multi-level…

Effect of experience, expectation and resource availability on perceptions of crowding among trout anglers in Pennsylvania

Treesearch

Craig A. Miller

1995-01-01

Crowding research has suggested expectancy theory as one explanation to perceptions of crowding expressed by participants in outdoor recreation activities. Expectancy theory states that an individual enters into an activity with a preconceived set of expectations for the outcome of the experience. In this study, anglers fishing on the opening day of Pennsylvania's...

Crowding at Cape Lookout National Seashore: an examination of the influence of visitor characteristics on encounter norms and perceived crowding

Treesearch

David Alan Graefe; Hans Vogelsong

2009-01-01

Outdoor recreation researchers have typically defined "crowding" as a negative evaluation of the social atmosphere of an area. According to normative theory, individuals have standards (norms) regarding the appropriateness of different levels and types of recreational use. The purpose of this study was to examine the influences of visitor characteristics on...

Open-Phylo: a customizable crowd-computing platform for multiple sequence alignment

PubMed Central

2013-01-01

Citizen science games such as Galaxy Zoo, Foldit, and Phylo aim to harness the intelligence and processing power generated by crowds of online gamers to solve scientific problems. However, the selection of the data to be analyzed through these games is under the exclusive control of the game designers, and so are the results produced by gamers. Here, we introduce Open-Phylo, a freely accessible crowd-computing platform that enables any scientist to enter our system and use crowds of gamers to assist computer programs in solving one of the most fundamental problems in genomics: the multiple sequence alignment problem. PMID:24148814

Does Temporal Integration Occur for Unrecognizable Words in Visual Crowding?

PubMed Central

Zhou, Jifan; Lee, Chia-Lin; Li, Kuei-An; Tien, Yung-Hsuan; Yeh, Su-Ling

2016-01-01

Visual crowding—the inability to see an object when it is surrounded by flankers in the periphery—does not block semantic activation: unrecognizable words due to visual crowding still generated robust semantic priming in subsequent lexical decision tasks. Based on the previous finding, the current study further explored whether unrecognizable crowded words can be temporally integrated into a phrase. By showing one word at a time, we presented Chinese four-word idioms with either a congruent or incongruent ending word in order to examine whether the three preceding crowded words can be temporally integrated to form a semantic context so as to affect the processing of the ending word. Results from both behavioral (Experiment 1) and Event-Related Potential (Experiment 2 and 3) measures showed congruency effect in only the non-crowded condition, which does not support the existence of unconscious multi-word integration. Aside from four-word idioms, we also found that two-word (modifier + adjective combination) integration—the simplest kind of temporal semantic integration—did not occur in visual crowding (Experiment 4). Our findings suggest that integration of temporally separated words might require conscious awareness, at least under the timing conditions tested in the current study. PMID:26890366

Developing an emergency department crowding dashboard: A design science approach.

PubMed

Martin, Niels; Bergs, Jochen; Eerdekens, Dorien; Depaire, Benoît; Verelst, Sandra

2017-08-30

As an emergency department (ED) is a complex adaptive system, the analysis of continuously gathered data is valuable to gain insight in the real-time patient flow. To support the analysis and management of ED operations, relevant data should be provided in an intuitive way. Within this context, this paper outlines the development of a dashboard which provides real-time information regarding ED crowding. The research project underlying this paper follows the principles of design science research, which involves the development and study of artifacts which aim to solve a generic problem. To determine the crowding indicators that are desired in the dashboard, a modified Delphi study is used. The dashboard is implemented using the open source Shinydashboard package in R. A dashboard is developed containing the desired crowding indicators, together with general patient flow characteristics. It is demonstrated using a dataset of a Flemish ED and fulfills the requirements which are defined a priori. The developed dashboard provides real-time information on ED crowding. This information enables ED staff to judge whether corrective actions are required in an effort to avoid the adverse effects of ED crowding. Copyright © 2017 Elsevier Ltd. All rights reserved.

Emergency department crowding: a point in time.

PubMed

Schneider, Sandra M; Gallery, Michael E; Schafermeyer, Robert; Zwemer, Frank L

2003-08-01

This is a pilot study designed to assess the feasibility of a point prevalence study to assess the degree of crowding in hospital emergency departments (EDs). In addition, we sought to measure the degree of physical crowding and personnel shortage in our sample. A mail survey was sent to a random sample of 250 EDs chosen from a database compiled by the American College of Emergency Physicians of 5,064 EDs in the United States. In addition to demographic information, respondents were asked to count the patients and staff in their EDs at 7 PM local time on Monday, March 12, 2001 (index time). The response rate was 36%. At the index time, there was an average of 1.1 patients per treatment space, and 52% of EDs reported more than 1 patient per treatment space. There was also evidence of personnel shortage, with a mean of 4.2 patients per registered nurse and 49% of EDs having each registered nurse caring for more than 4 patients. There was a mean of 9.7 patients per physician. Sixty-eight percent of EDs had each physician caring for more than 6 patients. There was crowding present in all geographic areas and all hospital types (teaching-nonteaching status of the hospital). Consistent with the crowded conditions, 11% of institutions were on ambulance diversion and not accepting new acute patients. Delays in transfer of admitted patients out of the ED contributed to the physical crowding. Twenty-two percent of patients in the ED were already admitted and were awaiting transfer to an inpatient bed; 73% of EDs were boarding 2 or more inpatients. The amount of crowding quantified by this point prevalence study was confirmed by the amount of crowding reported for the previous week: 48% of EDs were boarding inpatients during the previous week for a mean of 8.9 hours, 4.2 days per week; 31% had been on diversion; 59% had been routinely using their halls for patients; 38% had been doubling their rooms; and 47% had been using nonclinical space for patient care. Our low response rate limits this pilot study. Nonetheless, this study, as well as others, demonstrates that EDs throughout the United States are severely crowded. Such crowding raises concerns about the ability of EDs to respond to mass casualty or volume surges.

Conceptual design of an orbital debris collector

NASA Technical Reports Server (NTRS)

Odonoghue, Peter (Editor); Brenton, Brian; Chambers, Ernest; Schwind, Thomas; Swanhart, Christopher; Williams, Thomas

1991-01-01

The current Lower Earth Orbit (LEO) environment has become overly crowded with space debris. An evaluation of types of debris is presented in order to determine which debris poses the greatest threat to operation in space, and would therefore provide a feasible target for removal. A target meeting these functional requirements was found in the Cosmos C-1B Rocket Body. These launchers are spent space transporters which constitute a very grave risk of collision and fragmentation in LEO. The motion and physical characteristics of these rocket bodies have determined the most feasible method of removal. The proposed Orbital Debris Collector (ODC) device is designed to attach to the Orbital Maneuvering Vehicle (OMV), which provides all propulsion, tracking, and power systems. The OMV/ODC combination, the Rocket Body Retrieval Vehicle (RBRV), will match orbits with the rocket body, use a spin table to match the rotational motion of the debris, capture it, despin it, and remove it from orbit by allowing it to fall into the Earth's atmosphere. A disposal analysis is presented to show how the debris will be deorbited into the Earth's atmosphere. The conceptual means of operation of a sample mission is described.

Sculpting Pickering Emulsion Droplets by Arrest and Jamming

NASA Astrophysics Data System (ADS)

Burke, Christopher; Wei, Zengyi; Caggioni, Marco; Spicer, Patrick; Atherton, Tim

Pickering emulsion droplets can be arrested into non-spherical shapes--useful for applications such as active delivery--through a general mechanism of deformation followed by absorption of additional colloidal particles onto the interface, relaxation of the droplet caused by surface tension and arrest at some point due to crowding of the particles. We perform simulations of the arrest process to clarify the relative importance of diffusive rearrangement of particles and collective forcing due to surface evolution. Experiment and theory are compared, giving insight into the stability of the resulting capsules and the robustness of the production process for higher-throughput production in, for example, microfluidic systems. We adapt theoretical tools from the jamming literature to better understand the arrested configurations and long timescale evolution of the system: using linear programming and a penalty function approach, we identify unjamming motions in kinetically arrested states. We propose a paradigm of ``metric jamming'' to describe the limiting behavior of this class of system: a structure is metric-jammed if it is stable with respect to collective motion of the particles as well as evolution of the hypersurface on which the packing is embedded. Supported by a Cottrell Award from the Research Corporation for Science Advancement.

Visualizing protein interactions and dynamics: evolving a visual language for molecular animation.

PubMed

Jenkinson, Jodie; McGill, Gaël

2012-01-01

Undergraduate biology education provides students with a number of learning challenges. Subject areas that are particularly difficult to understand include protein conformational change and stability, diffusion and random molecular motion, and molecular crowding. In this study, we examined the relative effectiveness of three-dimensional visualization techniques for learning about protein conformation and molecular motion in association with a ligand-receptor binding event. Increasingly complex versions of the same binding event were depicted in each of four animated treatments. Students (n = 131) were recruited from the undergraduate biology program at University of Toronto, Mississauga. Visualization media were developed in the Center for Molecular and Cellular Dynamics at Harvard Medical School. Stem cell factor ligand and cKit receptor tyrosine kinase were used as a classical example of a ligand-induced receptor dimerization and activation event. Each group completed a pretest, viewed one of four variants of the animation, and completed a posttest and, at 2 wk following the assessment, a delayed posttest. Overall, the most complex animation was the most effective at fostering students' understanding of the events depicted. These results suggest that, in select learning contexts, increasingly complex representations may be more desirable for conveying the dynamic nature of cell binding events.

Mixed emotions: Sensitivity to facial variance in a crowd of faces.

PubMed

Haberman, Jason; Lee, Pegan; Whitney, David

2015-01-01

The visual system automatically represents summary information from crowds of faces, such as the average expression. This is a useful heuristic insofar as it provides critical information about the state of the world, not simply information about the state of one individual. However, the average alone is not sufficient for making decisions about how to respond to a crowd. The variance or heterogeneity of the crowd--the mixture of emotions--conveys information about the reliability of the average, essential for determining whether the average can be trusted. Despite its importance, the representation of variance within a crowd of faces has yet to be examined. This is addressed here in three experiments. In the first experiment, observers viewed a sample set of faces that varied in emotion, and then adjusted a subsequent set to match the variance of the sample set. To isolate variance as the summary statistic of interest, the average emotion of both sets was random. Results suggested that observers had information regarding crowd variance. The second experiment verified that this was indeed a uniquely high-level phenomenon, as observers were unable to derive the variance of an inverted set of faces as precisely as an upright set of faces. The third experiment replicated and extended the first two experiments using method-of-constant-stimuli. Together, these results show that the visual system is sensitive to emergent information about the emotional heterogeneity, or ambivalence, in crowds of faces.

The effects of shape crowding on grasping.

PubMed

Chen, Juan; Jayawardena, Sanasi; Goodale, Melvyn Alan

2015-03-10

Crowding refers to the deleterious effect of nearby objects on the identification of a target in the peripheral visual field. A recent study (Chen, Sperandio, & Goodale, 2015) showed that when a three-dimensional (3D) disk was crowded by disks of different sizes, participants could scale their grip aperture to the size of the target, even when they could not perceive its size. It is still unclear, however, whether or not grasping can also escape to some degree the crowding of other object features, such as shape. To test this, we presented 3D rectangular blocks in isolation or crowded by other blocks in the periphery. The target and flanking blocks had the same surface area but different dimensions. Participants were required either to grasp the target block across its width or to estimate its width. We found that, consistent with what we observed earlier with size, participants can also scale their grasp to the width of the target block even when they could not perceive its width. To further explore whether or not the effect of crowding on grasping depends on how proficient people are with their right hand, we had right-handed participants perform the same test but with their left hand. We found that left-hand grasping did not escape the crowding effect on shape perception at all. Taken together, our results suggest that people can also use invisible shape information to guide actions and that this ability depends on the proficiency of the action. © 2015 ARVO.

Real-time micro-modelling of city evacuations

NASA Astrophysics Data System (ADS)

Löhner, Rainald; Haug, Eberhard; Zinggerling, Claudio; Oñate, Eugenio

2018-01-01

A methodology to integrate geographical information system (GIS) data with large-scale pedestrian simulations has been developed. Advances in automatic data acquisition and archiving from GIS databases, automatic input for pedestrian simulations, as well as scalable pedestrian simulation tools have made it possible to simulate pedestrians at the individual level for complete cities in real time. An example that simulates the evacuation of the city of Barcelona demonstrates that this is now possible. This is the first step towards a fully integrated crowd prediction and management tool that takes into account not only data gathered in real time from cameras, cell phones or other sensors, but also merges these with advanced simulation tools to predict the future state of the crowd.

Examining visitors' behavioral intentions and behaviors in a Taiwan National Park

Treesearch

Chieh-Lu Li; Garry E. Chick

2011-01-01

In 2007-2008, some visitors to Taroko National Park in Taiwan were surveyed to allow testing of a behavioral prediction model in the context of national park recreation. This model includes three constructs: values (a cultural anthropology factor), perceptions of service quality (service marketing factors), and perceptions of crowding (a national park recreation factor...

Democracy under Uncertainty: The Wisdom of Crowds and the Free-Rider Problem in Group Decision Making

ERIC Educational Resources Information Center

Kameda, Tatsuya; Tsukasaki, Takafumi; Hastie, Reid; Berg, Nathan

2011-01-01

We introduce a game theory model of individual decisions to cooperate by contributing personal resources to group decisions versus by free riding on the contributions of other members. In contrast to most public-goods games that assume group returns are linear in individual contributions, the present model assumes decreasing marginal group…

The Fluid-Mosaic Model of Membrane Structure: still relevant to understanding the structure, function and dynamics of biological membranes after more than 40 years.

PubMed

Nicolson, Garth L

2014-06-01

In 1972 the Fluid-Mosaic Membrane Model of membrane structure was proposed based on thermodynamic principals of organization of membrane lipids and proteins and available evidence of asymmetry and lateral mobility within the membrane matrix [S. J. Singer and G. L. Nicolson, Science 175 (1972) 720-731]. After over 40years, this basic model of the cell membrane remains relevant for describing the basic nano-structures of a variety of intracellular and cellular membranes of plant and animal cells and lower forms of life. In the intervening years, however, new information has documented the importance and roles of specialized membrane domains, such as lipid rafts and protein/glycoprotein complexes, in describing the macrostructure, dynamics and functions of cellular membranes as well as the roles of membrane-associated cytoskeletal fences and extracellular matrix structures in limiting the lateral diffusion and range of motion of membrane components. These newer data build on the foundation of the original model and add new layers of complexity and hierarchy, but the concepts described in the original model are still applicable today. In updated versions of the model more emphasis has been placed on the mosaic nature of the macrostructure of cellular membranes where many protein and lipid components are limited in their rotational and lateral motilities in the membrane plane, especially in their natural states where lipid-lipid, protein-protein and lipid-protein interactions as well as cell-matrix, cell-cell and intracellular membrane-associated protein and cytoskeletal interactions are important in restraining the lateral motility and range of motion of particular membrane components. The formation of specialized membrane domains and the presence of tightly packed integral membrane protein complexes due to membrane-associated fences, fenceposts and other structures are considered very important in describing membrane dynamics and architecture. These structures along with membrane-associated cytoskeletal and extracellular structures maintain the long-range, non-random mosaic macro-organization of membranes, while smaller membrane nano- and submicro-sized domains, such as lipid rafts and protein complexes, are important in maintaining specialized membrane structures that are in cooperative dynamic flux in a crowded membrane plane. This Article is Part of a Special Issue Entitled: Membrane Structure and Function: Relevance in the Cell's Physiology, Pathology and Therapy. © 2013.

Occlusal traits of deciduous dentition of preschool children of Indian children

PubMed Central

Bahadure, Rakesh N.; Thosar, Nilima; Gaikwad, Rahul

2012-01-01

Objectives: To assess the occlusal relationship, canine relationship, crowding, primate spaces, and anterior spacing in both maxillary and mandibular arches of primary dentition of Indian children of Wardha District and also to study the age-wise differences in occlusal characteristics. Materials and Methods: A total of 1053 (609 males and 444 females) children of 3-5 year age group with complete primary dentition were examined for occlusal relationship, canine relationship, crowding, primate spaces, and anterior spacing in both maxillary and mandibular arches. Results: The data after evaluation showed significant values for all parameters except mandibular anterior spacing, which was 47.6%. Mild crowding was prevalent at 5 year age group and moderate crowding was common at 3 year-age group. Conclusion: Evaluated parameters such as terminal molar relationship and canine relationship were predominantly progressing toward to normal but contacts and crowding status were contributing almost equal to physiologic anterior spacing. Five-year-age group showed higher values with respect to all the parameters. PMID:23633806

Acute and chronic gregarisation are associated with distinct DNA methylation fingerprints in desert locusts.

PubMed

Mallon, Eamonn B; Amarasinghe, Harindra E; Ott, Swidbert R

2016-10-18

Desert locusts (Schistocerca gregaria) show a dramatic form of socially induced phenotypic plasticity known as phase polyphenism. In the absence of conspecifics, locusts occur in a shy and cryptic solitarious phase. Crowding with conspecifics drives a behavioural transformation towards gregariousness that occurs within hours and is followed by changes in physiology, colouration and morphology, resulting in the full gregarious phase syndrome. We analysed methylation-sensitive amplified fragment length polymorphisms (MS-AFLP) to compare the effect of acute and chronic crowding on DNA methylation in the central nervous system. We find that crowd-reared and solitary-reared locusts show markedly different neural MS-AFLP fingerprints. However, crowding for a day resulted in neural MS-AFLP fingerprints that were clearly distinct from both crowd-reared and uncrowded solitary-reared locusts. Our results indicate that changes in DNA methylation associated with behavioural gregarisation proceed through intermediate states that are not simply partial realisations of the endpoint states.

How can macromolecular crowding inhibit biological reactions? The enhanced formation of DNA nanoparticles

PubMed Central

Hou, Sen; Trochimczyk, Piotr; Sun, Lili; Wisniewska, Agnieszka; Kalwarczyk, Tomasz; Zhang, Xuzhu; Wielgus-Kutrowska, Beata; Bzowska, Agnieszka; Holyst, Robert

2016-01-01

In contrast to the already known effect that macromolecular crowding usually promotes biological reactions, solutions of PEG 6k at high concentrations stop the cleavage of DNA by HindIII enzyme, due to the formation of DNA nanoparticles. We characterized the DNA nanoparticles and probed the prerequisites for their formation using multiple techniques such as fluorescence correlation spectroscopy, dynamic light scattering, fluorescence analytical ultracentrifugation etc. In >25% PEG 6k solution, macromolecular crowding promotes the formation of DNA nanoparticles with dimensions of several hundreds of nanometers. The formation of DNA nanoparticles is a fast and reversible process. Both plasmid DNA (2686 bp) and double-stranded/single-stranded DNA fragment (66bp/nt) can form nanoparticles. We attribute the enhanced nanoparticle formation to the depletion effect of macromolecular crowding. This study presents our idea to enhance the formation of DNA nanoparticles by macromolecular crowding, providing the first step towards a final solution to efficient gene therapy. PMID:26903405

How can macromolecular crowding inhibit biological reactions? The enhanced formation of DNA nanoparticles.

PubMed

Hou, Sen; Trochimczyk, Piotr; Sun, Lili; Wisniewska, Agnieszka; Kalwarczyk, Tomasz; Zhang, Xuzhu; Wielgus-Kutrowska, Beata; Bzowska, Agnieszka; Holyst, Robert

2016-02-23

In contrast to the already known effect that macromolecular crowding usually promotes biological reactions, solutions of PEG 6k at high concentrations stop the cleavage of DNA by HindIII enzyme, due to the formation of DNA nanoparticles. We characterized the DNA nanoparticles and probed the prerequisites for their formation using multiple techniques such as fluorescence correlation spectroscopy, dynamic light scattering, fluorescence analytical ultracentrifugation etc. In >25% PEG 6k solution, macromolecular crowding promotes the formation of DNA nanoparticles with dimensions of several hundreds of nanometers. The formation of DNA nanoparticles is a fast and reversible process. Both plasmid DNA (2686 bp) and double-stranded/single-stranded DNA fragment (66 bp/nt) can form nanoparticles. We attribute the enhanced nanoparticle formation to the depletion effect of macromolecular crowding. This study presents our idea to enhance the formation of DNA nanoparticles by macromolecular crowding, providing the first step towards a final solution to efficient gene therapy.