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.

Crowding and Neighborhood Mediation of Urban Density.

ERIC Educational Resources Information Center

Baum, Andrew; And Others

The study of density and crowding has expanded rapidly, due in part to concern about the impact of high density on the quality of life. In this paper results of a study which focused upon the intervening role of neighborhood variables in the experience of urban density are reported. Residents of moderately dense urban areas were surveyed and…

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.

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.

The walking behaviour of pedestrian social groups and its impact on crowd dynamics.

PubMed

Moussaïd, Mehdi; Perozo, Niriaska; Garnier, Simon; Helbing, Dirk; Theraulaz, Guy

2010-04-07

Human crowd motion is mainly driven by self-organized processes based on local interactions among pedestrians. While most studies of crowd behaviour consider only interactions among isolated individuals, it turns out that up to 70% of people in a crowd are actually moving in groups, such as friends, couples, or families walking together. These groups constitute medium-scale aggregated structures and their impact on crowd dynamics is still largely unknown. In this work, we analyze the motion of approximately 1500 pedestrian groups under natural condition, and show that social interactions among group members generate typical group walking patterns that influence crowd dynamics. At low density, group members tend to walk side by side, forming a line perpendicular to the walking direction. As the density increases, however, the linear walking formation is bent forward, turning it into a V-like pattern. These spatial patterns can be well described by a model based on social communication between group members. We show that the V-like walking pattern facilitates social interactions within the group, but reduces the flow because of its "non-aerodynamic" shape. Therefore, when crowd density increases, the group organization results from a trade-off between walking faster and facilitating social exchange. These insights demonstrate that crowd dynamics is not only determined by physical constraints induced by other pedestrians and the environment, but also significantly by communicative, social interactions among individuals.

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)

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.

Evolution of increased adult longevity in Drosophila melanogaster populations selected for adaptation to larval crowding.

PubMed

Shenoi, V N; Ali, S Z; Prasad, N G

2016-02-01

In holometabolous animals such as Drosophila melanogaster, larval crowding can affect a wide range of larval and adult traits. Adults emerging from high larval density cultures have smaller body size and increased mean life span compared to flies emerging from low larval density cultures. Therefore, adaptation to larval crowding could potentially affect adult longevity as a correlated response. We addressed this issue by studying a set of large, outbred populations of D. melanogaster, experimentally evolved for adaptation to larval crowding for 83 generations. We assayed longevity of adult flies from both selected (MCUs) and control populations (MBs) after growing them at different larval densities. We found that MCUs have evolved increased mean longevity compared to MBs at all larval densities. The interaction between selection regime and larval density was not significant, indicating that the density dependence of mean longevity had not evolved in the MCU populations. The increase in longevity in MCUs can be partially attributed to their lower rates of ageing. It is also noteworthy that reaction norm of dry body weight, a trait probably under direct selection in our populations, has indeed evolved in MCU populations. To the best of our knowledge, this is the first report of the evolution of adult longevity as a correlated response of adaptation to larval crowding. © 2015 European Society For Evolutionary Biology. Journal of Evolutionary Biology © 2015 European Society For Evolutionary Biology.

How social influence can undermine the wisdom of crowd effect.

PubMed

Lorenz, Jan; Rauhut, Heiko; Schweitzer, Frank; Helbing, Dirk

2011-05-31

Social groups can be remarkably smart and knowledgeable when their averaged judgements are compared with the judgements of individuals. Already Galton [Galton F (1907) Nature 75:7] found evidence that the median estimate of a group can be more accurate than estimates of experts. This wisdom of crowd effect was recently supported by examples from stock markets, political elections, and quiz shows [Surowiecki J (2004) The Wisdom of Crowds]. In contrast, we demonstrate by experimental evidence (N = 144) that even mild social influence can undermine the wisdom of crowd effect in simple estimation tasks. In the experiment, subjects could reconsider their response to factual questions after having received average or full information of the responses of other subjects. We compare subjects' convergence of estimates and improvements in accuracy over five consecutive estimation periods with a control condition, in which no information about others' responses was provided. Although groups are initially "wise," knowledge about estimates of others narrows the diversity of opinions to such an extent that it undermines the wisdom of crowd effect in three different ways. The "social influence effect" diminishes the diversity of the crowd without improvements of its collective error. The "range reduction effect" moves the position of the truth to peripheral regions of the range of estimates so that the crowd becomes less reliable in providing expertise for external observers. The "confidence effect" boosts individuals' confidence after convergence of their estimates despite lack of improved accuracy. Examples of the revealed mechanism range from misled elites to the recent global financial crisis.

Effect of temporary open-air markets on the sound environment and acoustic perception based on the crowd density characteristics.

PubMed

Meng, Qi; Sun, Yang; Kang, Jian

2017-12-01

The sound environment and acoustic perception of open-air markets, which are very common in high-density urban open spaces, play important roles in terms of the urban soundscape. Based on objective and subjective measurements of a typical temporary open-air market in Harbin city, China, the effects of the temporary open-air market on the sound environment and acoustic perception were studied, considering different crowd densities. It was observed that a temporary open-air market without zoning increases the sound pressure level and subjective loudness by 2.4dBA and 0.21dBA, respectively, compared to the absence of a temporary market. Different from the sound pressure level and subjective loudness, the relationship between crowd density and the perceived acoustic comfort is parabolic. Regarding the effect of a temporary open-air market with different zones on the sound environment and acoustic perception, when the crowd densities were the same, subjective loudness in the fruit and vegetable sales area was always higher than in the food sales area and the clothing sales area. In terms of acoustic comfort, with an increase in crowd density, acoustic comfort in the fruit and vegetable sales area decreased, and acoustic comfort in the food sales area and the clothing sales area exhibited a parabolic change trend of increase followed by decrease. Overall, acoustic comfort can be effectively improved by better planning temporary open-air markets in high-density urban open spaces. Copyright © 2017 Elsevier B.V. All rights reserved.

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.

Adaptation to larval crowding in Drosophila ananassae leads to the evolution of population stability.

PubMed

Dey, Snigdhadip; Bose, Joy; Joshi, Amitabh

2012-05-01

Density-dependent selection is expected to lead to population stability, especially if r and K tradeoff. Yet, there is no empirical evidence of adaptation to crowding leading to the evolution of stability. We show that populations of Drosophila ananassae selected for adaptation to larval crowding have higher K and lower r, and evolve greater stability than controls. We also show that increased population growth rates at high density can enhance stability, even in the absence of a decrease in r, by ensuring that the crowding adapted populations do not fall to very low sizes. We discuss our results in the context of traits known to have diverged between the selected and control populations, and compare our results with previous work on the evolution of stability in D. melanogaster. Overall, our results suggest that density-dependent selection may be an important factor promoting the evolution of relatively stable dynamics in natural populations.

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

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.

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.

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.

46 CFR 171.052 - Passenger heel requirements for pontoon vessels.

Code of Federal Regulations, 2014 CFR

2014-10-01

... on exposed or partially protected waters— (i) 10 foot-degrees with a crowding density of 5 square feet per person (2.15 persons per square meter); and (ii) 7 foot-degrees with a crowding density of 2 square feet per person (5.38 persons per square meter); and (2) For operation on protected waters— (i) 5...

46 CFR 171.052 - Passenger heel requirements for pontoon vessels.

Code of Federal Regulations, 2012 CFR

2012-10-01

... on exposed or partially protected waters— (i) 10 foot-degrees with a crowding density of 5 square feet per person (2.15 persons per square meter); and (ii) 7 foot-degrees with a crowding density of 2 square feet per person (5.38 persons per square meter); and (2) For operation on protected waters— (i) 5...

46 CFR 171.052 - Passenger heel requirements for pontoon vessels.

Code of Federal Regulations, 2011 CFR

2011-10-01

... on exposed or partially protected waters— (i) 10 foot-degrees with a crowding density of 5 square feet per person (2.15 persons per square meter); and (ii) 7 foot-degrees with a crowding density of 2 square feet per person (5.38 persons per square meter); and (2) For operation on protected waters— (i) 5...

46 CFR 171.052 - Passenger heel requirements for pontoon vessels.

Code of Federal Regulations, 2013 CFR

2013-10-01

... on exposed or partially protected waters— (i) 10 foot-degrees with a crowding density of 5 square feet per person (2.15 persons per square meter); and (ii) 7 foot-degrees with a crowding density of 2 square feet per person (5.38 persons per square meter); and (2) For operation on protected waters— (i) 5...

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…

Hopping in the Crowd to Unveil Network Topology.

PubMed

Asllani, Malbor; Carletti, Timoteo; Di Patti, Francesca; Fanelli, Duccio; Piazza, Francesco

2018-04-13

We introduce a nonlinear operator to model diffusion on a complex undirected network under crowded conditions. We show that the asymptotic distribution of diffusing agents is a nonlinear function of the nodes' degree and saturates to a constant value for sufficiently large connectivities, at variance with standard diffusion in the absence of excluded-volume effects. Building on this observation, we define and solve an inverse problem, aimed at reconstructing the a priori unknown connectivity distribution. The method gathers all the necessary information by repeating a limited number of independent measurements of the asymptotic density at a single node, which can be chosen randomly. The technique is successfully tested against both synthetic and real data and is also shown to estimate with great accuracy the total number of nodes.

Hopping in the Crowd to Unveil Network Topology

NASA Astrophysics Data System (ADS)

Asllani, Malbor; Carletti, Timoteo; Di Patti, Francesca; Fanelli, Duccio; Piazza, Francesco

2018-04-01

We introduce a nonlinear operator to model diffusion on a complex undirected network under crowded conditions. We show that the asymptotic distribution of diffusing agents is a nonlinear function of the nodes' degree and saturates to a constant value for sufficiently large connectivities, at variance with standard diffusion in the absence of excluded-volume effects. Building on this observation, we define and solve an inverse problem, aimed at reconstructing the a priori unknown connectivity distribution. The method gathers all the necessary information by repeating a limited number of independent measurements of the asymptotic density at a single node, which can be chosen randomly. The technique is successfully tested against both synthetic and real data and is also shown to estimate with great accuracy the total number of nodes.

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.

Density-dependent natural selection and trade-offs in life history traits.

PubMed

Mueller, L D; Guo, P Z; Ayala, F J

1991-07-26

Theories of density-dependent natural selection state that at extreme population densities evolution produces alternative life histories due to trade-offs. The trade-offs are presumed to arise because those genotypes with highest fitness at high population densities will not also have high fitness at low density and vice-versa. These predictions were tested by taking samples from six populations of Drosophila melanogaster kept at low population densities (r-populations) for nearly 200 generations and placing them in crowded cultures (K-populations). After 25 generations in the crowded cultures, the derived K-populations showed growth rate and productivity that at high densities were elevated relative to the controls, but at low density were depressed.

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.

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.

Jammed Humans in High-Density Crowd Disasters

NASA Astrophysics Data System (ADS)

Bottinelli, Arianna; Sumpter, David; Silverberg, Jesse

When people gather in large groups like those found at Black Friday sales events, pilgrimages, heavy metal concerts, and parades, crowd density often becomes exceptionally high. As a consequence, these events can produce tragic outcomes such as stampedes and ''crowd crushes''. While human collective motion has been studied with active particle simulations, the underlying mechanisms for emergent behavior are less well understood. Here, we use techniques developed to study jammed granular materials to analyze an active matter model inspired by large groups of people gathering at a point of common interest. In the model, a single behavioral rule combined with body-contact interactions are sufficient for the emergence of a self-confined steady state, where particles fluctuate around a stable position. Applying mode analysis to this system, we find evidence for Goldstone modes, soft spots, and stochastic resonance, which may be the preferential mechanisms for dangerous emergent collective motions in crowds.

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

A Hierarchical Bayesian Model for Crowd Emotions

PubMed Central

Urizar, Oscar J.; Baig, Mirza S.; Barakova, Emilia I.; Regazzoni, Carlo S.; Marcenaro, Lucio; Rauterberg, Matthias

2016-01-01

Estimation of emotions is an essential aspect in developing intelligent systems intended for crowded environments. However, emotion estimation in crowds remains a challenging problem due to the complexity in which human emotions are manifested and the capability of a system to perceive them in such conditions. This paper proposes a hierarchical Bayesian model to learn in unsupervised manner the behavior of individuals and of the crowd as a single entity, and explore the relation between behavior and emotions to infer emotional states. Information about the motion patterns of individuals are described using a self-organizing map, and a hierarchical Bayesian network builds probabilistic models to identify behaviors and infer the emotional state of individuals and the crowd. This model is trained and tested using data produced from simulated scenarios that resemble real-life environments. The conducted experiments tested the efficiency of our method to learn, detect and associate behaviors with emotional states yielding accuracy levels of 74% for individuals and 81% for the crowd, similar in performance with existing methods for pedestrian behavior detection but with novel concepts regarding the analysis of crowds. PMID:27458366

Effects of phenotypic plasticity on pathogen transmission in the field in a Lepidoptera-NPV system.

PubMed

Reeson, A F; Wilson, K; Cory, J S; Hankard, P; Weeks, J M; Goulson, D; Hails, R S

2000-08-01

In models of insect-pathogen interactions, the transmission parameter (ν) is the term that describes the efficiency with which pathogens are transmitted between hosts. There are two components to the transmission parameter, namely the rate at which the host encounters pathogens (contact rate) and the rate at which contact between host and pathogen results in infection (host susceptibility). Here it is shown that in larvae of Spodoptera exempta (Lepidoptera: Noctuidae), in which rearing density triggers the expression of one of two alternative phenotypes, the high-density morph is associated with an increase in larval activity. This response is likely to result in an increase in the contact rate between hosts and pathogens. Rearing density is also known to affect susceptibility of S. exempta to pathogens, with the high-density morph showing increased resistance to a baculovirus. In order to determine whether density-dependent differences observed in the laboratory might affect transmission in the wild, a field trial was carried out to estimate the transmission parameter for S. exempta and its nuclear polyhedrosis virus (NPV). The transmission parameter was found to be significantly higher among larvae reared in isolation than among those reared in crowds. Models of insect-pathogen interactions, in which the transmission parameter is assumed to be constant, will therefore not fully describe the S. exempta-NPV system. The finding that crowding can influence transmission in this way has major implications for both the long-term population dynamics and the invasion dynamics of insect-pathogen systems.

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.

Relation of quantity of seed sown and density of seedlings to the development and survival of forest planting stock

Treesearch

W. G. Wahlenberg

1929-01-01

It is obvious that seedlings grown in dense stands can not develop so well as those grown without crowding. Nurserymen naturally wish to avoid injury to their stock from crowding, but they also desire to utilize their soil space as fully as possible. The optimum density of stand for each species and age class of nursery stock can be determined within reasonably close...

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 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.

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.

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.

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…

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…

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.

Molecular Characterization of a Lysozyme Gene and Its Altered Expression Profile in Crowded Beet Webworm (Loxostege sticticalis)

PubMed Central

Kong, Hailong; Lv, Min; Mao, Nian; Wang, Cheng; Cheng, Yunxia; Zhang, Lei; Jiang, Xingfu; Luo, Lizhi

2016-01-01

There is growing evidence that insects living in high-density populations exhibit an increase in immune function to counter a higher risk of disease. This phenomenon, known as density-dependent prophylaxis, has been experimentally tested in a number of insect species. Although density-dependent prophylaxis is especially prevalent in insects exhibiting density-dependent phase polyphenism, the molecular mechanism remains unclear. Our previous study demonstrated that the antibacterial activity of lysozyme is important for this process in the beet webworm Loxostege sticticalis. In this study, a lysozyme cDNA from L. sticticalis was cloned and characterized. The full-length cDNA is 1078 bp long and contains an open reading frame of 426 bp that encodes 142 amino acids. The deduced protein possesses structural characteristics of a typical c-type lysozyme and clusters with c-type lysozymes from other Lepidoptera. LsLysozyme was found to be expressed throughout all developmental stages, showing the highest level in pupae. LsLysozyme was also highly expressed in the midgut and fat body. Elevated LsLysozyme expression was observed in L. sticticalis larvae infected by Beauveria bassiana and in larvae reared under crowding conditions. In addition, the expression level of LsLysozyme in infected larvae reared at a density of 10 larvae per jar was significantly higher compared to those reared at a density of l or 30 larvae per jar. These results suggest that larval crowding affects the gene expression profile of this lysozyme. This study provides additional insight into the expression of an immune-associated lysozyme gene and helps us to better understand the immune response of L. sticticalis under crowding conditions. PMID:27575006

Does Vowel Inventory Density Affect Vowel-to-Vowel Coarticulation?

ERIC Educational Resources Information Center

Mok, Peggy P. K.

2013-01-01

This study tests the output constraints hypothesis that languages with a crowded phonemic vowel space would allow less vowel-to-vowel coarticulation than languages with a sparser vowel space to avoid perceptual confusion. Mandarin has fewer vowel phonemes than Cantonese, but their allophonic vowel spaces are similarly crowded. The hypothesis…

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.

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.

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.

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

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

Monitoring the visitor experience at Buck Island Reef National Monument

Treesearch

Alan R. Graefe; Roger L. Moore

1992-01-01

This paper examines relationships between visitor density levels and perceptions of crowding at a Caribbean coral reef. Reef visitors were more likely to report that the quality of their experience was enhanced, rather than reduced, by their encounters with other visitors. Perceived crowding was related to visitors' previous experience and the location of...

Emergent Structural Mechanisms for High-Density Collective Motion Inspired by Human Crowds

NASA Astrophysics Data System (ADS)

Bottinelli, Arianna; Sumpter, David T. J.; Silverberg, Jesse L.

2016-11-01

Collective motion of large human crowds often depends on their density. In extreme cases like heavy metal concerts and black Friday sales events, motion is dominated by physical interactions instead of conventional social norms. Here, we study an active matter model inspired by situations when large groups of people gather at a point of common interest. Our analysis takes an approach developed for jammed granular media and identifies Goldstone modes, soft spots, and stochastic resonance as structurally driven mechanisms for potentially dangerous emergent collective motion.

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.

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

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

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.

Perceived Crowdedness ina Prison Environment.

ERIC Educational Resources Information Center

Paulus, Paul B.; And Others

This paper presents data bearing on the question of the effects of crowding on indices of stress and on one's perception of being crowded. A palmar sweat measure of stress was employed to examine inmate stress in relation to social and spacial density factors. The data suggest that increasing the number of people in a housing unit (and hence the…

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 scaling of contact rates with population density for the infectious disease models.

PubMed

Hu, Hao; Nigmatulina, Karima; Eckhoff, Philip

2013-08-01

Contact rates and patterns among individuals in a geographic area drive transmission of directly-transmitted pathogens, making it essential to understand and estimate contacts for simulation of disease dynamics. Under the uniform mixing assumption, one of two mechanisms is typically used to describe the relation between contact rate and population density: density-dependent or frequency-dependent. Based on existing evidence of population threshold and human mobility patterns, we formulated a spatial contact model to describe the appropriate form of transmission with initial growth at low density and saturation at higher density. We show that the two mechanisms are extreme cases that do not capture real population movement across all scales. Empirical data of human and wildlife diseases indicate that a nonlinear function may work better when looking at the full spectrum of densities. This estimation can be applied to large areas with population mixing in general activities. For crowds with unusually large densities (e.g., transportation terminals, stadiums, or mass gatherings), the lack of organized social contact structure deviates the physical contacts towards a special case of the spatial contact model - the dynamics of kinetic gas molecule collision. In this case, an ideal gas model with van der Waals correction fits well; existing movement observation data and the contact rate between individuals is estimated using kinetic theory. A complete picture of contact rate scaling with population density may help clarify the definition of transmission rates in heterogeneous, large-scale spatial systems. Copyright © 2013 The Authors. Published by Elsevier Inc. All rights reserved.

Measuring Perceived Crowding for High-Density River Recreation: The Effects of Situational Conditions and Personal Factors

Treesearch

Michael A. Tarrant; H. Ken Cordell; Tamela L. Kibler

1997-01-01

The authors examined the interations of 3 situational vairiables (activity type, location, and encounter type) on 3 predictors of perceived crowding (perceived, preferred, and tolerable encounter levels.) A total of 310 kayakers and canoers and 356 fagters completed on-site and mail-back surveys regarding their trip on the Nantahala River in North Carolina during...

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...

Multiscale Modeling of Diffusion in a Crowded Environment.

PubMed

Meinecke, Lina

2017-11-01

We present a multiscale approach to model diffusion in a crowded environment and its effect on the reaction rates. Diffusion in biological systems is often modeled by a discrete space jump process in order to capture the inherent noise of biological systems, which becomes important in the low copy number regime. To model diffusion in the crowded cell environment efficiently, we compute the jump rates in this mesoscopic model from local first exit times, which account for the microscopic positions of the crowding molecules, while the diffusing molecules jump on a coarser Cartesian grid. We then extract a macroscopic description from the resulting jump rates, where the excluded volume effect is modeled by a diffusion equation with space-dependent diffusion coefficient. The crowding molecules can be of arbitrary shape and size, and numerical experiments demonstrate that those factors together with the size of the diffusing molecule play a crucial role on the magnitude of the decrease in diffusive motion. When correcting the reaction rates for the altered diffusion we can show that molecular crowding either enhances or inhibits chemical reactions depending on local fluctuations of the obstacle density.

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.

Influence of Music on the Behaviors of Crowd in Urban Open Public Spaces

PubMed Central

Meng, Qi; Zhao, Tingting; Kang, Jian

2018-01-01

Sound environment plays an important role in urban open spaces, yet studies on the effects of perception of the sound environment on crowd behaviors have been limited. The aim of this study, therefore, is to explore how music, which is considered an important soundscape element, affects crowd behaviors in urban open spaces. On-site observations were performed at a 100 m × 70 m urban leisure square in Harbin, China. Typical music was used to study the effects of perception of the sound environment on crowd behaviors; then, these behaviors were classified into movement (passing by and walking around) and non-movement behaviors (sitting). The results show that the path of passing by in an urban leisure square with music was more centralized than without music. Without music, 8.3% of people passing by walked near the edge of the square, whereas with music, this percentage was zero. In terms of the speed of passing by behavior, no significant difference was observed with the presence or absence of background music. Regarding the effect of music on walking around behavior in the square, the mean area and perimeter when background music was played were smaller than without background music. The mean speed of those exhibiting walking around behavior with background music in the square was 0.296 m/s slower than when no background music was played. For those exhibiting sitting behavior, when background music was not present, crowd density showed no variation based on the distance from the sound source. When music was present, it was observed that as the distance from the sound source increased, crowd density of those sitting behavior decreased accordingly. PMID:29755390

Influence of Music on the Behaviors of Crowd in Urban Open Public Spaces.

PubMed

Meng, Qi; Zhao, Tingting; Kang, Jian

2018-01-01

Sound environment plays an important role in urban open spaces, yet studies on the effects of perception of the sound environment on crowd behaviors have been limited. The aim of this study, therefore, is to explore how music, which is considered an important soundscape element, affects crowd behaviors in urban open spaces. On-site observations were performed at a 100 m × 70 m urban leisure square in Harbin, China. Typical music was used to study the effects of perception of the sound environment on crowd behaviors; then, these behaviors were classified into movement (passing by and walking around) and non-movement behaviors (sitting). The results show that the path of passing by in an urban leisure square with music was more centralized than without music. Without music, 8.3% of people passing by walked near the edge of the square, whereas with music, this percentage was zero. In terms of the speed of passing by behavior, no significant difference was observed with the presence or absence of background music. Regarding the effect of music on walking around behavior in the square, the mean area and perimeter when background music was played were smaller than without background music. The mean speed of those exhibiting walking around behavior with background music in the square was 0.296 m/s slower than when no background music was played. For those exhibiting sitting behavior, when background music was not present, crowd density showed no variation based on the distance from the sound source. When music was present, it was observed that as the distance from the sound source increased, crowd density of those sitting behavior decreased accordingly.

Environmental Effects on Affect: Density, Noise and Personality.

ERIC Educational Resources Information Center

Bharucha-Reid, Rodabe; Kivak, H. Asuman

1982-01-01

Research findings are reported of a study (N=88 undergraduate males) of molar crowding in urban centers which involved the simultaneous variation of social density, spatial density, noise, and personality as they effect room affect (physical and psychological). Several main effects proved significant. (Author/DC)

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.

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.

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.

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.

Relative density: the key to stocking assessment in regional analysis—a forest survey viewpoint.

Treesearch

Colin D. MacLean

1979-01-01

Relative density is a measure of tree crowding compared to a reference level such as normal density. This stand attribute, when compared to management standards, indicates adequacy of stocking. The Pacific Coast Forest Survey Unit assesses the relative density of each stand sampled by summing the individual density contributions of each tree tallied, thus quantifying...

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.

Spatial Distribution and Sampling Plans for Grapevine Plant Canopy-Inhabiting Scaphoideus titanus (Hemiptera: Cicadellidae) Nymphs.

PubMed

Rigamonti, Ivo E; Brambilla, Carla; Colleoni, Emanuele; Jermini, Mauro; Trivellone, Valeria; Baumgärtner, Johann

2016-04-01

The paper deals with the study of the spatial distribution and the design of sampling plans for estimating nymph densities of the grape leafhopper Scaphoideus titanus Ball in vine plant canopies. In a reference vineyard sampled for model parameterization, leaf samples were repeatedly taken according to a multistage, stratified, random sampling procedure, and data were subjected to an ANOVA. There were no significant differences in density neither among the strata within the vineyard nor between the two strata with basal and apical leaves. The significant differences between densities on trunk and productive shoots led to the adoption of two-stage (leaves and plants) and three-stage (leaves, shoots, and plants) sampling plans for trunk shoots- and productive shoots-inhabiting individuals, respectively. The mean crowding to mean relationship used to analyze the nymphs spatial distribution revealed aggregated distributions. In both the enumerative and the sequential enumerative sampling plans, the number of leaves of trunk shoots, and of leaves and shoots of productive shoots, was kept constant while the number of plants varied. In additional vineyards data were collected and used to test the applicability of the distribution model and the sampling plans. The tests confirmed the applicability 1) of the mean crowding to mean regression model on the plant and leaf stages for representing trunk shoot-inhabiting distributions, and on the plant, shoot, and leaf stages for productive shoot-inhabiting nymphs, 2) of the enumerative sampling plan, and 3) of the sequential enumerative sampling plan. In general, sequential enumerative sampling was more cost efficient than enumerative sampling.

The Gender Pay Gap, Fringe Benefits, and Occupational Crowding.

ERIC Educational Resources Information Center

Solberg, Eric; Laughlin, Teresa

1995-01-01

In estimating earnings equations for seven occupations, when fringe benefits are excluded, women receive significantly lower wages in all but the most female-dominated occupation. Including fringe benefits makes gender significant in only one occupational category. Crowding of one gender into an occupation appears the primary determinant of the…

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.

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

Crowding of Drosophila larvae affects lifespan and other life-history traits via reduced availability of dietary yeast.

PubMed

Klepsatel, Peter; Procházka, Emanuel; Gáliková, Martina

2018-06-19

Conditions experienced during development have often long-lasting effects persisting into adulthood. In Drosophila, it is well-documented that larval crowding influences fitness-related traits such as body size, starvation resistance and lifespan. However, the underlying mechanism of this phenomenon is not well understood. Here, we show that the effects of increased larval density on life-history traits can be explained by decreased yeast availability in the diet during development. Yeast-poor larval diet alters various life-history traits and mimics the effects of larval crowding. In particular, reduced amount of yeast in larval diet prolongs developmental time, reduces body size, increases body fat content and starvation resistance, and prolongs Drosophila lifespan. Conversely, the effects of larval crowding can be rescued by increasing the concentration of the dietary yeast in the diet during development. Altogether, our results show that the well-known effects of larval crowding on life-history traits are mainly caused by the reduced availability of dietary yeasts due to increased larval competition. Copyright © 2018. Published by Elsevier Inc.

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.

Estimating Number of People Using Calibrated Monocular Camera Based on Geometrical Analysis of Surface Area

NASA Astrophysics Data System (ADS)

Arai, Hiroyuki; Miyagawa, Isao; Koike, Hideki; Haseyama, Miki

We propose a novel technique for estimating the number of people in a video sequence; it has the advantages of being stable even in crowded situations and needing no ground-truth data. By analyzing the geometrical relationships between image pixels and their intersection volumes in the real world quantitatively, a foreground image directly indicates the number of people. Because foreground detection is possible even in crowded situations, the proposed method can be applied in such situations. Moreover, it can estimate the number of people in an a priori manner, so it needs no ground-truth data unlike existing feature-based estimation techniques. Experiments show the validity of the proposed method.

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.

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.

Paternal epigenetic effects of population density on locust phase-related characteristics associated with heat-shock protein expression.

PubMed

Chen, Bing; Li, Shaoqin; Ren, Qiang; Tong, Xiwen; Zhang, Xia; Kang, Le

2015-02-01

Many species exhibit transgenerational plasticity by which environmental cues experienced by either parent can be transmitted to their offspring, resulting in phenotypic variants in offspring to match ancestral environments. However, the manner by which paternal experiences affect offspring plasticity through epigenetic inheritance in animals generally remains unclear. In this study, we examined the transgenerational effects of population density on phase-related traits in the migratory locust Locusta migratoria. Using an experimental design that explicitly controls genetic background, we found that the effects of crowd or isolation rearing on phase plasticity could be inherited to the offspring. The isolation of gregarious locusts resulted in reduced weight in offspring eggs and altered morphometric traits in hatchlings, whereas crowding of solitarious locusts exhibited opposite effects. The consequences of density changes were transmitted by both maternal and paternal inheritance, although the expression of paternal effects was not as pronounced as that of maternal effects. Prominent expression of heat-shock proteins (Hsps), such as Hsp90, Hsp70 and Hsp20.6, could be triggered by density changes. Hsps were significantly upregulated upon crowding but downregulated upon isolation. The variation in parental Hsp expression was also transmitted to the offspring, in which the pattern of inheritance was consistent with that of phase characteristics. These results revealed a paternal effect on phase polyphenism and Hsp expression induced by population density, and defined a model system that could be used to study the paternal epigenetic inheritance of environmental changes. © 2015 John Wiley & Sons Ltd.

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

Wilderness experience quality: Effects of use density depend on how experience is conceived

Treesearch

David N. Cole; Troy E. Hall

2012-01-01

Different conceptions of experience and experience quality can explain ambiguous relationships among use density, crowding, experience and experience quality. We employed multiple methods to quantify experiential dimensions at a popular lake in the Alpine Lakes Wilderness, WA. Comparing weekdays to weekends, when use density is typically four times as high, we assessed...

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.

Effect of larval density on food utilization efficiency of Tenebrio molitor (Coleoptera: Tenebrionidae)

USDA-ARS?s Scientific Manuscript database

Rearing conditions, particularly the crowding of larvae, may have a significant impact on production efficiency of some insects produced commercially, such as Tenebrio molitor L. (Coleoptera: Tenebrionidae). Although larval densities are known to affect developmental time and growth in T. molitor, n...

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.

Role of macromolecular crowding and salt ions on the structural-fluctuation of a highly compact configuration of carbonmonoxycytochrome c.

PubMed

Kumar, Rajesh; Sharma, Deepak; Jain, Rishu; Kumar, Sandeep; Kumar, Rajesh

2015-12-01

Carbonmonoxycytochrome c refolds to a native-like compact state (NCO-state), where the non-native Fe(2+)-CO interaction persists. Structural and molecular properties extracted from CD, fluorescence and NMR experiments reveal that the NCO-state shows the generic properties of molten globules. Slow thermal-dissociation of CO transforms the NCO-state to native-state (N-state), where the native Fe(2+)-M80 bond recovers. To determine the role of crowding agents and salt ions on the structural-fluctuation of NCO, the kinetic and thermodynamic parameters for CO-dissociation from NCO (NCO→N+CO) were measured at varying concentrations of crowding agents (dextran 70, dextran 40, ficoll 70) and salt ions (anion: ClO4(-), I(-), Br(-), NO3(-), Cl(-); cation: NH4(+), K(+), Na(+)). As [crowding agent] or [ion] is increased, the rate coefficient of CO-dissociation (kdiss) decreases exponentially. Furthermore, the extent of decrease in kdiss is found to be dependent on (i) size, charge density and charge dispersion of the ion, and (ii) size, shape, and viscosity of the crowding agent. Copyright © 2015 Elsevier B.V. All rights reserved.

Age- and density-dependent prophylaxis in the migratory Mormon cricket Anabrus simplex (Orthoptera: Tettigoniidae)

USDA-ARS?s Scientific Manuscript database

As a result of the increased potential for disease transmission, insects are predicted to show an increased constitutive immunity when crowded. Nymphal Mormon crickets were collected in Montana and reared in the laboratory either solitarily or at densities similar to that experienced by Mormon cric...

Reconciling Apparent Differences between the Responses of Humans and Other Animals to Crowding.

ERIC Educational Resources Information Center

Freedman, Jonathan L.

1979-01-01

In this article, research on nonhuman animals is reviewed to show that there is no discontinuity between humans and other animals. For both, high density is not necessarily harmful. Rather, the effect of high density depends on other factors in the situation. (Author)

Site of maxima of conductivity, temperatures, density of the current and specific capacity of the thermal emission in the HFI-discharge

NASA Astrophysics Data System (ADS)

Gerasimov, A.; Kirpichnikov, A.; Sabirova, F.; Gainullin, R.

2017-11-01

On the basis of theoretical analysis of distributions of the conductivity, current density and specific power of heat release in the high-frequency induction discharge, a law of crowding of maxima of these values has been established.

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.

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).

The trans-generational impact of population density signals on host-parasite interactions.

PubMed

Michel, Jessica; Ebert, Dieter; Hall, Matthew D

2016-11-25

The density of a host population is a key parameter underlying disease transmission, but it also has implications for the expression of disease through its effect on host physiology. In response to higher densities, individuals are predicted to either increase their immune investment in response to the elevated risk of parasitism, or conversely to decrease their immune capacity as a consequence of the stress of a crowded environment. However, an individual's health is shaped by many different factors, including their genetic background, current environmental conditions, and maternal effects. Indeed, population density is often sensed through the presence of info-chemicals in the environment, which may influence a host's interaction with parasites, and also those of its offspring. All of which may alter the expression of disease, and potentially uncouple the presumed link between changes in host density and disease outcomes. In this study, we used the water flea Daphnia magna and its obligate bacterial parasite Pasteuria ramosa, to investigate how signals of high host density impact on host-parasite interactions over two consecutive generations. We found that the chemical signals from crowded treatments induced phenotypic changes in both the parental and offspring generations. In the absence of a pathogen, life-history changes were genotype-specific, but consistent across generations, even when the signal of density was removed. In contrast, the influence of density on infected animals depended on the trait and generation of exposure. When directly exposed to signals of high-density, host genotypes responded differently in how they minimised the severity of disease. Yet, in the subsequent generation, the influence of density was rarely genotype-specific and instead related to ability of the host to minimise the onset of infection. Our findings reveal that population level correlations between host density and infection capture only part of the complex relationship between crowding and the severity of disease. We suggest that besides its role in horizontal transmission, signals of density can influence parasite epidemiology by modifying mechanisms of resistance across multiple generations, and elevating variability via genotype-by-environment interactions. Our results help resolve why some studies are able to find a positive correlation between high density and resistance, while others uncover a negative correlation, or even no direct relationship at all.

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.

A Bio-Inspired, Motion-Based Analysis of Crowd Behavior Attributes Relevance to Motion Transparency, Velocity Gradients, and Motion Patterns

PubMed Central

Raudies, Florian; Neumann, Heiko

2012-01-01

The analysis of motion crowds is concerned with the detection of potential hazards for individuals of the crowd. Existing methods analyze the statistics of pixel motion to classify non-dangerous or dangerous behavior, to detect outlier motions, or to estimate the mean throughput of people for an image region. We suggest a biologically inspired model for the analysis of motion crowds that extracts motion features indicative for potential dangers in crowd behavior. Our model consists of stages for motion detection, integration, and pattern detection that model functions of the primate primary visual cortex area (V1), the middle temporal area (MT), and the medial superior temporal area (MST), respectively. This model allows for the processing of motion transparency, the appearance of multiple motions in the same visual region, in addition to processing opaque motion. We suggest that motion transparency helps to identify “danger zones” in motion crowds. For instance, motion transparency occurs in small exit passages during evacuation. However, motion transparency occurs also for non-dangerous crowd behavior when people move in opposite directions organized into separate lanes. Our analysis suggests: The combination of motion transparency and a slow motion speed can be used for labeling of candidate regions that contain dangerous behavior. In addition, locally detected decelerations or negative speed gradients of motions are a precursor of danger in crowd behavior as are globally detected motion patterns that show a contraction toward a single point. In sum, motion transparency, image speeds, motion patterns, and speed gradients extracted from visual motion in videos are important features to describe the behavioral state of a motion crowd. PMID:23300930

Electromigration Mechanism of Failure in Flip-Chip Solder Joints Based on Discrete Void Formation.

PubMed

Chang, Yuan-Wei; Cheng, Yin; Helfen, Lukas; Xu, Feng; Tian, Tian; Scheel, Mario; Di Michiel, Marco; Chen, Chih; Tu, King-Ning; Baumbach, Tilo

2017-12-20

In this investigation, SnAgCu and SN100C solders were electromigration (EM) tested, and the 3D laminography imaging technique was employed for in-situ observation of the microstructure evolution during testing. We found that discrete voids nucleate, grow and coalesce along the intermetallic compound/solder interface during EM testing. A systematic analysis yields quantitative information on the number, volume, and growth rate of voids, and the EM parameter of DZ*. We observe that fast intrinsic diffusion in SnAgCu solder causes void growth and coalescence, while in the SN100C solder this coalescence was not significant. To deduce the current density distribution, finite-element models were constructed on the basis of the laminography images. The discrete voids do not change the global current density distribution, but they induce the local current crowding around the voids: this local current crowding enhances the lateral void growth and coalescence. The correlation between the current density and the probability of void formation indicates that a threshold current density exists for the activation of void formation. There is a significant increase in the probability of void formation when the current density exceeds half of the maximum value.

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.

A robust method for estimating motorbike count based on visual information learning

NASA Astrophysics Data System (ADS)

Huynh, Kien C.; Thai, Dung N.; Le, Sach T.; Thoai, Nam; Hamamoto, Kazuhiko

2015-03-01

Estimating the number of vehicles in traffic videos is an important and challenging task in traffic surveillance, especially with a high level of occlusions between vehicles, e.g.,in crowded urban area with people and/or motorbikes. In such the condition, the problem of separating individual vehicles from foreground silhouettes often requires complicated computation [1][2][3]. Thus, the counting problem is gradually shifted into drawing statistical inferences of target objects density from their shape [4], local features [5], etc. Those researches indicate a correlation between local features and the number of target objects. However, they are inadequate to construct an accurate model for vehicles density estimation. In this paper, we present a reliable method that is robust to illumination changes and partial affine transformations. It can achieve high accuracy in case of occlusions. Firstly, local features are extracted from images of the scene using Speed-Up Robust Features (SURF) method. For each image, a global feature vector is computed using a Bag-of-Words model which is constructed from the local features above. Finally, a mapping between the extracted global feature vectors and their labels (the number of motorbikes) is learned. That mapping provides us a strong prediction model for estimating the number of motorbikes in new images. The experimental results show that our proposed method can achieve a better accuracy in comparison to others.

Use of the SONET score to evaluate Urgent Care Center overcrowding: a prospective pilot study

PubMed Central

Wang, Hao; Robinson, Richard D; Cowden, Chad D; Gorman, Violet A; Cook, Christopher D; Gicheru, Eugene K; Schrader, Chet D; Jayswal, Rani D; Zenarosa, Nestor R

2015-01-01

Objectives To derive a tool to determine Urgent Care Center (UCC) crowding and investigate the association between different levels of UCC overcrowding and negative patient care outcomes. Design Prospective pilot study. Setting Single centre study in the USA. Participants 3565 patients who registered at UCC during the 21-day study period were included. Patients who had no overcrowding statuses estimated due to incomplete collection of operational variables at the time of registration were excluded in this study. 3139 patients were enrolled in the final data analysis. Primary and secondary outcome measures A crowding estimation tool (SONET: Severely overcrowded, Overcrowded and Not overcrowded Estimation Tool) was derived using the linear regression analysis. The average length of stay (LOS) in UCC patients and the number of left without being seen (LWBS) patients were calculated and compared under the three different levels of UCC crowding. Results Four independent operational variables could affect the UCC overcrowding score including the total number of patients, the number of results pending for patients, the number of patients in the waiting room and the longest time a patient was stationed in the waiting room. In addition, UCC overcrowding was associated with longer average LOS (not overcrowded: 133±76 min, overcrowded: 169±79 min, and severely overcrowded: 196±87 min, p<0.001) and an increased number of LWBS patients (not overcrowded: 0.28±0.69 patients, overcrowded: 0.64±0.98, and severely overcrowded: 1.00±0.97). Conclusions The overcrowding estimation tool (SONET) derived in this study might be used to determine different levels of crowding in a high volume UCC setting. It also showed that UCC overcrowding might be associated with negative patient care outcomes. PMID:25872940

Network dynamics of social influence in the wisdom of crowds.

PubMed

Becker, Joshua; Brackbill, Devon; Centola, Damon

2017-06-27

A longstanding problem in the social, biological, and computational sciences is to determine how groups of distributed individuals can form intelligent collective judgments. Since Galton's discovery of the "wisdom of crowds" [Galton F (1907) Nature 75:450-451], theories of collective intelligence have suggested that the accuracy of group judgments requires individuals to be either independent, with uncorrelated beliefs, or diverse, with negatively correlated beliefs [Page S (2008) The Difference: How the Power of Diversity Creates Better Groups, Firms, Schools, and Societies ]. Previous experimental studies have supported this view by arguing that social influence undermines the wisdom of crowds. These results showed that individuals' estimates became more similar when subjects observed each other's beliefs, thereby reducing diversity without a corresponding increase in group accuracy [Lorenz J, Rauhut H, Schweitzer F, Helbing D (2011) Proc Natl Acad Sci USA 108:9020-9025]. By contrast, we show general network conditions under which social influence improves the accuracy of group estimates, even as individual beliefs become more similar. We present theoretical predictions and experimental results showing that, in decentralized communication networks, group estimates become reliably more accurate as a result of information exchange. We further show that the dynamics of group accuracy change with network structure. In centralized networks, where the influence of central individuals dominates the collective estimation process, group estimates become more likely to increase in error.

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.

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.

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

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.

Agnosic vision is like peripheral vision, which is limited by crowding.

PubMed

Strappini, Francesca; Pelli, Denis G; Di Pace, Enrico; Martelli, Marialuisa

2017-04-01

Visual agnosia is a neuropsychological impairment of visual object recognition despite near-normal acuity and visual fields. A century of research has provided only a rudimentary account of the functional damage underlying this deficit. We find that the object-recognition ability of agnosic patients viewing an object directly is like that of normally-sighted observers viewing it indirectly, with peripheral vision. Thus, agnosic vision is like peripheral vision. We obtained 14 visual-object-recognition tests that are commonly used for diagnosis of visual agnosia. Our "standard" normal observer took these tests at various eccentricities in his periphery. Analyzing the published data of 32 apperceptive agnosia patients and a group of 14 posterior cortical atrophy (PCA) patients on these tests, we find that each patient's pattern of object recognition deficits is well characterized by one number, the equivalent eccentricity at which our standard observer's peripheral vision is like the central vision of the agnosic patient. In other words, each agnosic patient's equivalent eccentricity is conserved across tests. Across patients, equivalent eccentricity ranges from 4 to 40 deg, which rates severity of the visual deficit. In normal peripheral vision, the required size to perceive a simple image (e.g., an isolated letter) is limited by acuity, and that for a complex image (e.g., a face or a word) is limited by crowding. In crowding, adjacent simple objects appear unrecognizably jumbled unless their spacing exceeds the crowding distance, which grows linearly with eccentricity. Besides conservation of equivalent eccentricity across object-recognition tests, we also find conservation, from eccentricity to agnosia, of the relative susceptibility of recognition of ten visual tests. These findings show that agnosic vision is like eccentric vision. Whence crowding? Peripheral vision, strabismic amblyopia, and possibly apperceptive agnosia are all limited by crowding, making it urgent to know what drives crowding. Acuity does not (Song et al., 2014), but neural density might: neurons per deg 2 in the crowding-relevant cortical area. Copyright © 2017 Elsevier Ltd. All rights reserved.

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.

Influences of pea morphology and interacting factors on pea aphid (Homoptera: Aphididae) reproduction.

PubMed

Buchman, N; Cuddington, K

2009-08-01

It has been claimed that plant architecture can alter aphid reproductive rates, but the mechanism driving this effect has not been identified. We studied interactions between plant architecture, aphid density, environmental conditions, and nutrient availability on the reproduction of pea aphids [Acyrthosiphon pisum (Harris)] using four near-isogenic peas (Pisum sativum L.) that differ in morphology. Manipulations of aphid density (1, 5, and 10 adults per plant) allowed us to examine any effects of plant morphology on crowding and consequently reproduction. Pea morphology per se did not alter pea aphid crowding, as measured by mean nearest neighbor distance, and there was no effect on reproduction. In addition, reproduction increased with increasing adult density, indicating positive density dependence. In a separate experiment, peas were fertilized to determine whether differences between nutrient availability of the four different morphologies might drive any observed differences in aphid reproduction. Although plant nitrogen content was altered by fertilization treatments, this did not have an impact on aphid reproduction. Greenhouse experiments, however, suggested that pea morphology can interact with environmental conditions to reduce aphid reproduction under some conditions. We conclude that plant morphology only influences aphid reproduction when environmental conditions are less than optimal.

Effect of Al-trace dimension on Joule heating and current crowding in flip-chip solder joints under accelerated electromigration

NASA Astrophysics Data System (ADS)

Liang, S. W.; Chang, Y. W.; Chen, Chih

2006-04-01

Three-dimensional thermoelectrical simulation was conducted to investigate the influence of Al-trace dimension on Joule heating and current crowding in flip-chip solder joints. It is found that the dimension of the Al-trace effects significantly on the Joule heating, and thus directly determines the mean time to failure (MTTF). Simulated at a stressing current of 0.6A at 70°C, we estimate that the MTTF of the joints with Al traces in 100μm width was 6.1 times longer than that of joints with Al traces in 34μm width. Lower current crowding effect and reduced hot-spot temperature are responsible for the improved MTTF.

Evolution of increased larval competitive ability in Drosophila melanogaster without increased larval feeding rate.

PubMed

Sarangi, Manaswini; Nagarajan, Archana; Dey, Snigdhadip; Bose, Joy; Joshi, Amitabh

2016-09-01

Multiple experimental evolution studies on Drosophila melanogaster in the 1980s and 1990s indicated that enhanced competitive ability evolved primarily through increased larval tolerance to nitrogenous wastes and increased larval feeding and foraging rate, at the cost of efficiency of food conversion to biomass, and this became the widely accepted view of how adaptation to larval crowding evolves in fruitflies.We recently showed that populations of D. ananassae and D. n. nasuta subjected to extreme larval crowding evolved greater competitive ability without evolving higher feeding rates, primarily through a combination of reduced larval duration, faster attainment of minimum critical size for pupation, greater efficiency of food conversion to biomass, increased pupation height and, perhaps, greater urea/ammonia tolerance. This was a very different suite of traits than that seen to evolve under similar selection in D. melanogaster and was closer to the expectations from the theory of K-selection. At that time, we suggested two possible reasons for the differences in the phenotypic correlates of greater competitive ability seen in the studies with D. melanogaster and the other two species. First, that D. ananassae and D. n. nasuta had a very different genetic architecture of traits affecting competitive ability compared to the long-term laboratory populations of D. melanogaster used in the earlier studies, either because the populations of the former two species were relatively recently wild-caught, or by virtue of being different species. Second, that the different evolutionary trajectories in D. ananassae and D. n. nasuta versus D. melanogaster were a reflection of differences in the manner in which larval crowding was imposed in the two sets of selection experiments. The D. melanogaster studies used a higher absolute density of eggs per unit volume of food, and a substantially larger total volume of food, than the studies on D. ananassae and D. n. nasuta. Here, we show that long-term laboratory populations of D. melanogaster, descended from some of the populations used in the earlier studies, evolve essentially the same set of traits as the D. ananassae and D. n. nasuta crowding-adapted populations when subjected to a similar larval density at low absolute volumes of food. As in the case of D. ananassae and D. n. nasuta, and in stark contrast to earlier studies with D. melanogaster, these crowding-adapted populations of D. melanogaster did not evolve greater larval feeding rates as a correlate of increased competitive ability. The present results clearly suggest that the suite of phenotypes through which the evolution of greater competitive ability is achieved in fruitflies depends critically not just on larval density per unit volume of food, but also on the total amount of food available in the culture vials. We discuss these results in the context of an hypothesis about how larval density and the height of the food column in culture vials might interact to alter the fitness costs and benefits of increased larval feeding rates, thus resulting in different routes to the evolution of greater competitive ability, depending on the details of exactly how the larval crowding was implemented.

Crowding during restricted and free viewing

PubMed Central

Wallace, Julian M.; Chiu, Michael K.; Nandy, Anirvan S.; Tjan, Bosco S.

2013-01-01

Crowding impairs the perception of form in peripheral vision. It is likely to be a key limiting factor of form vision in patients without central vision. Crowding has been extensively studied in normally sighted individuals, typically with a stimulus duration of a few hundred milliseconds to avoid eye movements. These restricted testing conditions do not reflect the natural behavior of a patient with central field loss. Could unlimited stimulus duration and unrestricted eye movements change the properties of crowding in any fundamental way? We studied letter identification in the peripheral vision of normally sighted observers in three conditions: (i) a fixation condition with a brief stimulus presentation of 250 ms, (ii) another fixation condition but with an unlimited viewing time, and (iii) an unrestricted eye movement condition with an artificial central scotoma and an unlimited viewing time. In all conditions, contrast thresholds were measured as a function of target-to-flanker spacing, from which we estimated the spatial extent of crowding in terms of critical spacing. We found that presentation duration beyond 250 ms had little effect on critical spacing with stable gaze. With unrestricted eye movements and a simulated central scotoma, we found a large variability in critical spacing across observers, but more importantly, the variability in critical spacing was well correlated with the variability in target eccentricity. Our results assure that the large body of findings on crowding made with briefly presented stimuli remains relevant to conditions where viewing time is unconstrained. Our results further suggest that impaired oculomotor control associated with central vision loss can confound peripheral form vision beyond the limits imposed by crowding. PMID:23563172

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.

Mechanical stretch triggers rapid epithelial cell division through Piezo1.

PubMed

Gudipaty, S A; Lindblom, J; Loftus, P D; Redd, M J; Edes, K; Davey, C F; Krishnegowda, V; Rosenblatt, J

2017-03-02

Despite acting as a barrier for the organs they encase, epithelial cells turn over at some of the fastest rates in the body. However, epithelial cell division must be tightly linked to cell death to preserve barrier function and prevent tumour formation. How does the number of dying cells match those dividing to maintain constant numbers? When epithelial cells become too crowded, they activate the stretch-activated channel Piezo1 to trigger extrusion of cells that later die. However, it is unclear how epithelial cell division is controlled to balance cell death at the steady state. Here we show that mammalian epithelial cell division occurs in regions of low cell density where cells are stretched. By experimentally stretching epithelia, we find that mechanical stretch itself rapidly stimulates cell division through activation of the Piezo1 channel. To stimulate cell division, stretch triggers cells that are paused in early G2 phase to activate calcium-dependent phosphorylation of ERK1/2, thereby activating the cyclin B transcription that is necessary to drive cells into mitosis. Although both epithelial cell division and cell extrusion require Piezo1 at the steady state, the type of mechanical force controls the outcome: stretch induces cell division, whereas crowding induces extrusion. How Piezo1-dependent calcium transients activate two opposing processes may depend on where and how Piezo1 is activated, as it accumulates in different subcellular sites with increasing cell density. In sparse epithelial regions in which cells divide, Piezo1 localizes to the plasma membrane and cytoplasm, whereas in dense regions in which cells extrude, it forms large cytoplasmic aggregates. Because Piezo1 senses both mechanical crowding and stretch, it may act as a homeostatic sensor to control epithelial cell numbers, triggering extrusion and apoptosis in crowded regions and cell division in sparse regions.

Characterizing the uncertainty of classification methods and its impact on the performance of crowdsourcing

NASA Astrophysics Data System (ADS)

Ribera, Javier; Tahboub, Khalid; Delp, Edward J.

2015-03-01

Video surveillance systems are widely deployed for public safety. Real-time monitoring and alerting are some of the key requirements for building an intelligent video surveillance system. Real-life settings introduce many challenges that can impact the performance of real-time video analytics. Video analytics are desired to be resilient to adverse and changing scenarios. In this paper we present various approaches to characterize the uncertainty of a classifier and incorporate crowdsourcing at the times when the method is uncertain about making a particular decision. Incorporating crowdsourcing when a real-time video analytic method is uncertain about making a particular decision is known as online active learning from crowds. We evaluate our proposed approach by testing a method we developed previously for crowd flow estimation. We present three different approaches to characterize the uncertainty of the classifier in the automatic crowd flow estimation method and test them by introducing video quality degradations. Criteria to aggregate crowdsourcing results are also proposed and evaluated. An experimental evaluation is conducted using a publicly available dataset.

Use of the SONET score to evaluate Urgent Care Center overcrowding: a prospective pilot study.

PubMed

Wang, Hao; Robinson, Richard D; Cowden, Chad D; Gorman, Violet A; Cook, Christopher D; Gicheru, Eugene K; Schrader, Chet D; Jayswal, Rani D; Zenarosa, Nestor R

2015-04-14

To derive a tool to determine Urgent Care Center (UCC) crowding and investigate the association between different levels of UCC overcrowding and negative patient care outcomes. Prospective pilot study. Single centre study in the USA. 3565 patients who registered at UCC during the 21-day study period were included. Patients who had no overcrowding statuses estimated due to incomplete collection of operational variables at the time of registration were excluded in this study. 3139 patients were enrolled in the final data analysis. A crowding estimation tool (SONET: Severely overcrowded, Overcrowded and Not overcrowded Estimation Tool) was derived using the linear regression analysis. The average length of stay (LOS) in UCC patients and the number of left without being seen (LWBS) patients were calculated and compared under the three different levels of UCC crowding. Four independent operational variables could affect the UCC overcrowding score including the total number of patients, the number of results pending for patients, the number of patients in the waiting room and the longest time a patient was stationed in the waiting room. In addition, UCC overcrowding was associated with longer average LOS (not overcrowded: 133±76 min, overcrowded: 169±79 min, and severely overcrowded: 196±87 min, p<0.001) and an increased number of LWBS patients (not overcrowded: 0.28±0.69 patients, overcrowded: 0.64±0.98, and severely overcrowded: 1.00±0.97). The overcrowding estimation tool (SONET) derived in this study might be used to determine different levels of crowding in a high volume UCC setting. It also showed that UCC overcrowding might be associated with negative patient care outcomes. 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.

Effect of crowding and confinement on first-passage times: A model study

NASA Astrophysics Data System (ADS)

Antoine, C.; Talbot, J.

2016-06-01

We study the "color dynamics" of a hard-disk fluid confined in an annulus, as well as the corresponding hard-sphere system in three dimensions, using event-driven simulation in order to explore the effect of confinement and self-crowding on the search for targets. We compute the mean first-passage times (MFPTs) of red particles transiting from the outer to the inner boundary as well as those of blue particles passing from the inner to the outer boundary for different packing fractions and geometries. In the steady state the reaction rate, defined as the rate of collision of red particles with the inner boundary, is inversely proportional to the sum of the MFPTs. The reaction rate is wall mediated (ballistic) at low densities and diffusion controlled at higher densities and displays a maximum at intermediate densities. At moderate to high densities, the presence of layering has a strong influence on the search process. The numerical results for the reaction rate and MFPTs are compared with a ballistic model at low densities and a Smoluchowski approach with uniform diffusivities at higher densities. We discuss the reasons for the limited validity of the theoretical approaches. The maximum in the reaction rate is qualitatively well rendered by a Bosanquet-like approach that interpolates between the two regimes. Finally, we compute the position-dependent diffusivity from the MFPTs and observe that it is out of phase with the radial density.

X-ray Reflectivity Study of Ionic Liquids at Electrified Surfaces

NASA Astrophysics Data System (ADS)

Chu, Miaoqi

X-ray reflectivity (XRR) versatile technique that characterize the surface structures. However, due to the lack of phase information of X-ray data, the reconstruction of electron density profile (EDP) from XRR data is an ill-posed inverse problem that requires extra attention. In Chapter 1, several key concepts in XRR data analysis are reviewed. The typical XRR data acquisition procedure and methods of modeling electron density are introduced. The widely used logarithm form of merit function is justified with mathematical deduction and numerical experiment. A scheme that generates artificial reflectivity data with theoretical statistical error but not systematical error is proposed. With the methods and schemes described in Chapter 1, simulated reflectivity data of a simple one-slab model is generated and fitted to test the efficient of EDP reconstruction. By isolating the parameters, the effects of slab width, electron density contrast and maximal wave transfer are studied individually. It?s demonstrated that best-fit/global minima, result reported by most XRR studies, don?t necessary reflect the real EDP. By contrast, mapping the merit function in the parametric space can capture much more details. Additionally, the widely accepted concept about the XRR theoretical spatial resolution (pi/q_{max}) as well the using Patterson function are brought to test. In the perspective of XRR data analysis, this chapter puts forward general rules to design and optimize XRR experiments. It also demonstrates how susceptible the fitting result will be if it?s not done carefully. In Chapter 3, the interface between hydrophobic OTS film and several solvents is studied with XRR in a transmission-cell setup. The solvents, from water, acetone, to alcohol (methanol, ethanol, 1-propanol), to alkane (pentane, hexane and heptane), vary significantly in terms of polarity and hydrogen bonding. However, the XRR data from different solvents are subtle. The methods and principles elicited in previous chapters are employed to extract information about the solid-liquid interface. Electron density depletion due to methyl terminal of solvent molecules (methyl gap) and due to the reduced surface density compared to the bulk density (density gap) are analyzed. In the next Chapter, XRR technique is employed to study the structures and dynamics of room temperature ionic liquids (RTILs) at an electrified surface. RTILs are molten salts at room temperature, consisted purely by anions and cations, with potential applications in energy storage, electro-synthesis, electrodeposition etc. The solvent-free and high charge concentrated novel liquids process many unique properties that not seen in normal dilute salt solution. It is predicted that when a surface isn't highly charged, RTILs form alternating layers of anion/cation to screen the surface charge; when it's highly charged, a crowding layer with ions with like charge forms. The alternating structure has been observed experimentally but not the crowding layer. Following the rules of optimization XRR experiment in Chapter 2, conductive silicon which has small electron density is used which maximize the EDP contrast. This makes it possible to directly observe the formation of crowding layer. The thickness of this crowding layer, charge distributions and compositions as a function of applied voltage. The dynamics of anion/cation reorganization in RTILs determine the power density for RTILs? energy application. In Chapter 5, the time-dependence of the formation and dissipation of the crowding layer is studied with XRR. An ultra-slow dynamic, much longer than the typical RC time constant, is revealed. Comparisons with theoretical predications and experiments studies are made in order to understand the origin of this process. The thesis is summarized in Chapter 6, along with several proposals for future work.

A comparative evaluation of crowding stress on muscle HSP90 and myostatin expression in salmonids

USGS Publications Warehouse

Galt, Nicholas J.; Froehlich, Jacob Michael; McCormick, Stephen; Biga, Peggy R.

2018-01-01

Stress is a major factor that contributes to poor production and animal welfare concerns in aquaculture. As such, a thorough understanding of mechanisms involved in the stress response is imperative to developing strategies to mitigate the negative side effects of stressors, including the impact of high stocking densities on growth. The purpose of this study was to determine how the muscle growth inhibitor, myostatin, and the stress-responsive gene HSP90 are regulated in response to crowding stress in rainbow trout (Oncorhynchus mykiss), cutthroat trout (Oncorhynchus clarki), brook trout (Salvelinus fontinalis), and Atlantic salmon (Salmo salar). All species exhibited higher cortisol and glucose levels following the handling stress, indicating physiological response to the treatment. Additionally, all species, except rainbow trout, exhibited higher HSP90 levels in muscle after a 48 h crowding stress. Crowding stress resulted in a decrease of myostatin-1ain brook trout white muscle but not red muscle, while, myostatin-1a and -2a levels increased in white muscle and myostatin-1b levels increased in red muscle in Atlantic salmon. In rainbow trout, no significant changes were detected in either muscle type, but myostatin-1awas upregulated in both white and red skeletal muscle in the closely related cutthroat trout. The variation in response to crowding suggests a complex and species-specific interaction between stress and the muscle gene regulation in these salmonids. Only Atlantic salmon and cutthroat trout exhibited increased muscle myostatin transcription, and also exhibited the largest increase in circulating glucose in response to crowding. These results suggest that species-specific farming practices should be carefully examined in order to optimize low stress culture conditions.

Effect of Larval Density on Food Utilization Efficiency of Tenebrio molitor (Coleoptera: Tenebrionidae).

PubMed

Morales-Ramos, Juan A; Rojas, M Guadalupe

2015-10-01

Crowding conditions of larvae may have a significant impact on commercial production efficiency of some insects, such as Tenebrio molitor L. (Coleoptera: Tenebrionidae). Although larval densities are known to affect developmental time and growth in T. molitor, no reports were found on the effects of crowding on food utilization. The effect of larval density on food utilization efficiency of T. molitor larvae was studied by measuring efficiency of ingested food conversion (ECI), efficiency of digested food conversion (EDC), and mg of larval weight gain per gram of food consumed (LWGpFC) at increasing larval densities (12, 24, 36, 48, 50, 62, 74, and 96 larvae per dm(2)) over four consecutive 3-wk periods. Individual larval weight gain and food consumption were negatively impacted by larval density. Similarly, ECI, ECD, and LWGpFC were negatively impacted by larval density. Larval ageing, measured as four consecutive 3-wk periods, significantly and independently impacted ECI, ECD, and LWGpFC in a negative way. General linear model analysis showed that age had a higher impact than density on food utilization parameters of T. molitor larvae. Larval growth was determined to be responsible for the age effects, as measurements of larval mass density (in grams of larvae per dm(2)) had a significant impact on food utilization parameters across ages and density treatments (in number of larvae per dm(2)). The importance of mass versus numbers per unit of area as measurements of larval density and the implications of negative effects of density on food utilization for insect biomass production are discussed. Published by Oxford University Press on behalf of Entomological Society of America 2015. This work is written by US Government employees and is in the public domain in the US.

Assembling GHERG: Could "academic crowd-sourcing" address gaps in global health estimates?

PubMed

Rudan, Igor; Campbell, Harry; Marušić, Ana; Sridhar, Devi; Nair, Harish; Adeloye, Davies; Theodoratou, Evropi; Chan, Kit Yee

2015-06-01

In recent months, the World Health Organization (WHO), independent academic researchers, the Lancet and PLoS Medicine journals worked together to improve reporting of population health estimates. The new guidelines for accurate and transparent health estimates reporting (likely to be named GATHER), which are eagerly awaited, represent a helpful move that should benefit the field of global health metrics. Building on this progress and drawing from a tradition of Child Health Epidemiology Reference Group (CHERG)'s successful work model, we would like to propose a new initiative - "Global Health Epidemiology Reference Group" (GHERG). We see GHERG as an informal and entirely voluntary international collaboration of academic groups who are willing to contribute to improving disease burden estimates and respect the principles of the new guidelines - a form of "academic crowd-sourcing". The main focus of GHERG will be to identify the "gap areas" where not much information is available and/or where there is a lot of uncertainty present about the accuracy of the existing estimates. This approach should serve to complement the existing WHO and IHME estimates and to represent added value to both efforts.

Medicaid, family spending, and the financial implications of crowd-out.

PubMed

Dillender, Marcus

2017-05-01

A primary purpose of health insurance is to protect families from medical expenditure risk. Despite this goal and despite the fact that research has found that Medicaid can crowd out private coverage, little is known about the effect of Medicaid on families' spending patterns. This paper implements a simulated instrumental variables strategy with data from the Consumer Expenditure Survey to estimate the effect of an additional family member becoming eligible for Medicaid on family-level health insurance coverage and spending. The results indicate that an additional family member becoming eligible for Medicaid increases the number of people in the family with Medicaid coverage by about 0.135-0.142 and decreases the likelihood that a family has any medical spending in a quarter by 2.7 percentage points. As previous research often finds with different data sets, I find evidence that Medicaid expansions crowd out some private coverage. Unlike most other data sets, the Consumer Expenditure Survey allows for considering the financial implications of crowd-out. The results indicate that families that transition from private coverage to Medicaid are able to spend significantly less on health insurance expenses, meaning Medicaid expansions can be welfare improving for families even when crowd-out occurs. Copyright © 2017 Elsevier B.V. All rights reserved.

Ionizable side chains at catalytic active sites of enzymes.

PubMed

Jimenez-Morales, David; Liang, Jie; Eisenberg, Bob

2012-05-01

Catalytic active sites of enzymes of known structure can be well defined by a modern program of computational geometry. The CASTp program was used to define and measure the volume of the catalytic active sites of 573 enzymes in the Catalytic Site Atlas database. The active sites are identified as catalytic because the amino acids they contain are known to participate in the chemical reaction catalyzed by the enzyme. Acid and base side chains are reliable markers of catalytic active sites. The catalytic active sites have 4 acid and 5 base side chains, in an average volume of 1,072 Å(3). The number density of acid side chains is 8.3 M (in chemical units); the number density of basic side chains is 10.6 M. The catalytic active site of these enzymes is an unusual electrostatic and steric environment in which side chains and reactants are crowded together in a mixture more like an ionic liquid than an ideal infinitely dilute solution. The electrostatics and crowding of reactants and side chains seems likely to be important for catalytic function. In three types of analogous ion channels, simulation of crowded charges accounts for the main properties of selectivity measured in a wide range of solutions and concentrations. It seems wise to use mathematics designed to study interacting complex fluids when making models of the catalytic active sites of enzymes.

Ionizable Side Chains at Catalytic Active Sites of Enzymes

PubMed Central

Jimenez-Morales, David; Liang, Jie

2012-01-01

Catalytic active sites of enzymes of known structure can be well defined by a modern program of computational geometry. The CASTp program was used to define and measure the volume of the catalytic active sites of 573 enzymes in the Catalytic Site Atlas database. The active sites are identified as catalytic because the amino acids they contain are known to participate in the chemical reaction catalyzed by the enzyme. Acid and base side chains are reliable markers of catalytic active sites. The catalytic active sites have 4 acid and 5 base side chains, in an average volume of 1072 Å3. The number density of acid side chains is 8.3 M (in chemical units); the number density of basic side chains is 10.6 M. The catalytic active site of these enzymes is an unusual electrostatic and steric environment in which side chains and reactants are crowded together in a mixture more like an ionic liquid than an ideal infinitely dilute solution. The electrostatics and crowding of reactants and side chains seems likely to be important for catalytic function. In three types of analogous ion channels, simulation of crowded charges accounts for the main properties of selectivity measured in a wide range of solutions and concentrations. It seems wise to use mathematics designed to study interacting complex fluids when making models of the catalytic active sites of enzymes. PMID:22484856

Physiological response of juvenile coho salmon (Oncorhynchus kisutch) and rainbow trout (Salmo gairdneri) to handling and crowding stress in intensive fish culture

USGS Publications Warehouse

Wedemeyer, Gary A.

1976-01-01

Moving 4–5-in. coho salmon (Oncorhynchus kisutch) held in soft (20 ppm CaCO3) water from the relatively light loading density of 0.5 lb/ft3 to 1, 2, or 4 lb/ft3 (density index, DI = 0.1, 0.2, 0.4, 0.8) caused significant stress as indicated by loss of feeding behavior, but only minimal physiological disturbances, as indicated by lack of hyperglycemia or hypochloremia. However, moving them to 6 or 12 lb/ft3 (DI = 1.2, 2.4) caused significant physiological stress which required at least a week for recovery. Smolting coho salmon were physiologically stressed by population densities of 1 lb/ft3 or more and a subclinical corynebacterial kidney infection was activated. Rainbow trout (Salmo gairdneri) (4–5 in.) were physiologically stressed when moved and held at 1 lb/ft3 or more but retained normal feeding behavior. This indicates that handling and crowding stress will be minimized in softwater areas if densities in fish distribution trucks or in ponds or raceways during disease treatments are held to 0.1–0.5 lb/gal.

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.

Theory of molecular crowding in Brownian hard-sphere liquids.

PubMed

Zaccone, Alessio; Terentjev, Eugene M

2012-06-01

We derive an analytical pair potential of mean force for Brownian molecules in the liquid state. Our approach accounts for many-particle correlations of crowding particles of the liquid and for diffusive transport across the spatially modulated local density of crowders in the dense environment. Focusing on the limit of equal-size particles, we show that this diffusive transport leads to additional density- and structure-dependent terms in the interaction potential and to a much stronger attraction (by a factor of ≈4 at average volume fraction of crowders φ{0}=0.25) than in the standard depletion interaction where the diffusive effects are neglected. As an illustration of the theory, we use it to study the size of a polymer chain in a solution of inert crowders. Even in the case of an athermal background solvent, when a classical chain should be fully swollen, we find a sharp coil-globule transition of the ideal chain collapsing at a critical value of the crowder volume fraction φ{c}≈0.145.

Young Adults' Selection and Use of Dependent Coverage under the Affordable Care Act.

PubMed

Chen, Weiwei

2018-01-01

The dependent coverage expansion under the Affordable Care Act (ACA) required health insurance policies that cover dependents to offer coverage for policyholder' children up to age 26. It has been well documented that the provision successfully reduced the uninsured rate among the young adults. However, less is known about whether dependent coverage crowded out other insurance types and whether young adults used dependent coverage as a fill-in-the-gap short-term option. Using data from the Survey of Income and Program Participation 2008 Panel, the paper assesses dependent coverage uptake and duration before and after the ACA provision among young adults aged 19-26 versus those aged 27-30. Regressions for additional coverage outcomes were also performed to estimate the crowd-out rate. It was found that the ACA provision had a significant positive impact on dependent coverage uptake and duration. The estimated crowd-out rate ranges from 27 to 42%, depending on the definition. Most dependent coverage enrollees used the coverage for 1 or 2 years. Differences in dependent coverage uptake and duration remained among racial groups. Less healthy individuals were also less likely to make use of dependent coverage.

Young Adults’ Selection and Use of Dependent Coverage under the Affordable Care Act

PubMed Central

Chen, Weiwei

2018-01-01

The dependent coverage expansion under the Affordable Care Act (ACA) required health insurance policies that cover dependents to offer coverage for policyholder’ children up to age 26. It has been well documented that the provision successfully reduced the uninsured rate among the young adults. However, less is known about whether dependent coverage crowded out other insurance types and whether young adults used dependent coverage as a fill-in-the-gap short-term option. Using data from the Survey of Income and Program Participation 2008 Panel, the paper assesses dependent coverage uptake and duration before and after the ACA provision among young adults aged 19–26 versus those aged 27–30. Regressions for additional coverage outcomes were also performed to estimate the crowd-out rate. It was found that the ACA provision had a significant positive impact on dependent coverage uptake and duration. The estimated crowd-out rate ranges from 27 to 42%, depending on the definition. Most dependent coverage enrollees used the coverage for 1 or 2 years. Differences in dependent coverage uptake and duration remained among racial groups. Less healthy individuals were also less likely to make use of dependent coverage. PMID:29445721

Loop formation of microtubules during gliding at high density

NASA Astrophysics Data System (ADS)

Liu, Lynn; Tüzel, Erkan; Ross, Jennifer L.

2011-09-01

The microtubule cytoskeleton, including the associated proteins, forms a complex network essential to multiple cellular processes. Microtubule-associated motor proteins, such as kinesin-1, travel on microtubules to transport membrane bound vesicles across the crowded cell. Other motors, such as cytoplasmic dynein and kinesin-5, are used to organize the cytoskeleton during mitosis. In order to understand the self-organization processes of motors on microtubules, we performed filament-gliding assays with kinesin-1 motors bound to the cover glass with a high density of microtubules on the surface. To observe microtubule organization, 3% of the microtubules were fluorescently labeled to serve as tracers. We find that microtubules in these assays are not confined to two dimensions and can cross one other. This causes microtubules to align locally with a relatively short correlation length. At high density, this local alignment is enough to create 'intersections' of perpendicularly oriented groups of microtubules. These intersections create vortices that cause microtubules to form loops. We characterize the radius of curvature and time duration of the loops. These different behaviors give insight into how crowded conditions, such as those in the cell, might affect motor behavior and cytoskeleton organization.

Effect of Molecular Crowding on the Response of an Electrochemical DNA Sensor

PubMed Central

Ricci, Francesco; Lai, Rebecca Y.; Heeger, Alan J.; Plaxco, Kevin W.; Sumner, James J.

2009-01-01

E-DNA sensors, the electrochemical equivalent of molecular beacons, appear to be a promising means of detecting oligonucleotides. E-DNA sensors are comprised of a redox-modified (here, methylene blue or ferrocene) DNA stem-loop covalently attached to an interrogating electrode. Because E-DNA signaling arises due to binding-induced changes in the conformation of the stem-loop probe, it is likely sensitive to the nature of the molecular packing on the electrode surface. Here we detail the effects of probe density, target length, and other aspects of molecular crowding on the signaling properties, specificity, and response time of a model E-DNA sensor. We find that the highest signal suppression is obtained at the highest probe densities investigated, and that greater suppression is observed with longer and bulkier targets. In contrast, sensor equilibration time slows monotonically with increasing probe density, and the specificity of hybridization is not significantly affected. In addition to providing insight into the optimization of electrochemical DNA sensors, these results suggest that E-DNA signaling arises due to hybridization-linked changes in the rate, and thus efficiency, with which the redox moiety collides with the electrode and transfers electrons. PMID:17488132

Household crowding is associated with higher allostatic load among the Inuit.

PubMed

Riva, Mylene; Plusquellec, Pierrich; Juster, Robert-Paul; Laouan-Sidi, Elhadji A; Abdous, Belkacem; Lucas, Michel; Dery, Serge; Dewailly, Eric

2014-04-01

Household crowding is an important problem in some aboriginal communities that is reaching particularly high levels among the circumpolar Inuit. Living in overcrowded conditions may endanger health via stress pathophysiology. This study examines whether higher household crowding is associated with stress-related physiological dysregulations among the Inuit. Cross-sectional data on 822 Inuit adults were taken from the 2004 Qanuippitaa? How are we? Nunavik Inuit Health Survey. Chronic stress was measured using the concept of allostatic load (AL) representing the multisystemic biological 'wear and tear' of chronic stress. A summary index of AL was constructed using 14 physiological indicators compiled into a traditional count-based index and a binary variable that contrasted people at risk on at least seven physiological indicators. Household crowding was measured using indicators of household size (total number of people and number of children per house) and overcrowding defined as more than one person per room. Data were analysed using weighted Generalised Estimating Equations controlling for participants' age, sex, income, diet and involvement in traditional activities. Higher household crowding was significantly associated with elevated AL levels and with greater odds of being at risk on at least seven physiological indicators, especially among women and independently of individuals' characteristics. This study demonstrates that household crowding is a source of chronic stress among the Inuit of Nunavik. Differential housing conditions are shown to be a marker of health inequalities among this population. Housing conditions are a critical public health issue in many aboriginal communities that must be investigated further to inform healthy and sustainable housing strategies.

Ionic imbalance, in addition to molecular crowding, abates cytoskeletal dynamics and vesicle motility during hypertonic stress

PubMed Central

Nunes, Paula; Roth, Isabelle; Meda, Paolo; Féraille, Eric; Brown, Dennis; Hasler, Udo

2015-01-01

Cell volume homeostasis is vital for the maintenance of optimal protein density and cellular function. Numerous mammalian cell types are routinely exposed to acute hypertonic challenge and shrink. Molecular crowding modifies biochemical reaction rates and decreases macromolecule diffusion. Cell volume is restored rapidly by ion influx but at the expense of elevated intracellular sodium and chloride levels that persist long after challenge. Although recent studies have highlighted the role of molecular crowding on the effects of hypertonicity, the effects of ionic imbalance on cellular trafficking dynamics in living cells are largely unexplored. By tracking distinct fluorescently labeled endosome/vesicle populations by live-cell imaging, we show that vesicle motility is reduced dramatically in a variety of cell types at the onset of hypertonic challenge. Live-cell imaging of actin and tubulin revealed similar arrested microfilament motility upon challenge. Vesicle motility recovered long after cell volume, a process that required functional regulatory volume increase and was accelerated by a return of extracellular osmolality to isosmotic levels. This delay suggests that, although volume-induced molecular crowding contributes to trafficking defects, it alone cannot explain the observed effects. Using fluorescent indicators and FRET-based probes, we found that intracellular ATP abundance and mitochondrial potential were reduced by hypertonicity and recovered after longer periods of time. Similar to the effects of osmotic challenge, isovolumetric elevation of intracellular chloride concentration by ionophores transiently decreased ATP production by mitochondria and abated microfilament and vesicle motility. These data illustrate how perturbed ionic balance, in addition to molecular crowding, affects membrane trafficking. PMID:26045497

Statistical Deconvolution for Superresolution Fluorescence Microscopy

PubMed Central

Mukamel, Eran A.; Babcock, Hazen; Zhuang, Xiaowei

2012-01-01

Superresolution microscopy techniques based on the sequential activation of fluorophores can achieve image resolution of ∼10 nm but require a sparse distribution of simultaneously activated fluorophores in the field of view. Image analysis procedures for this approach typically discard data from crowded molecules with overlapping images, wasting valuable image information that is only partly degraded by overlap. A data analysis method that exploits all available fluorescence data, regardless of overlap, could increase the number of molecules processed per frame and thereby accelerate superresolution imaging speed, enabling the study of fast, dynamic biological processes. Here, we present a computational method, referred to as deconvolution-STORM (deconSTORM), which uses iterative image deconvolution in place of single- or multiemitter localization to estimate the sample. DeconSTORM approximates the maximum likelihood sample estimate under a realistic statistical model of fluorescence microscopy movies comprising numerous frames. The model incorporates Poisson-distributed photon-detection noise, the sparse spatial distribution of activated fluorophores, and temporal correlations between consecutive movie frames arising from intermittent fluorophore activation. We first quantitatively validated this approach with simulated fluorescence data and showed that deconSTORM accurately estimates superresolution images even at high densities of activated fluorophores where analysis by single- or multiemitter localization methods fails. We then applied the method to experimental data of cellular structures and demonstrated that deconSTORM enables an approximately fivefold or greater increase in imaging speed by allowing a higher density of activated fluorophores/frame. PMID:22677393

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

Psychophysical evidence for the number sense.

PubMed

Burr, David C; Anobile, Giovanni; Arrighi, Roberto

2017-02-19

It is now clear that most animals, including humans, possess an ability to rapidly estimate number. Some have questioned whether this ability arises from dedicated numerosity mechanisms, or is derived indirectly from judgements of density or other attributes. We describe a series of psychophysical experiments, largely using adaptation techniques, which demonstrate clearly the existence of a number sense in humans. The number sense is truly general, extending over space, time and sensory modality, and is closely linked with action. We further show that when multiple cues are present, numerosity emerges as the natural dimension for discrimination. However, when element density increases past a certain level, the elements become too crowded to parse, and the scene is perceived as a texture rather than array of elements. The two different regimes are psychophysically discriminable in that they follow distinct psychophysical laws, and show different dependencies on eccentricity, luminance levels and effects of perceptual grouping. The distinction is important, as the ability to discriminate numerosity, but not texture, correlates with formal maths skills.This article is part of the discussion meeting issue 'The origins of numerical abilities'. © 2017 The Authors.

Optimal ciliary beating patterns

NASA Astrophysics Data System (ADS)

Vilfan, Andrej; Osterman, Natan

2011-11-01

We introduce a measure for energetic efficiency of single or collective biological cilia. We define the efficiency of a single cilium as Q2 / P , where Q is the volume flow rate of the pumped fluid and P is the dissipated power. For ciliary arrays, we define it as (ρQ) 2 / (ρP) , with ρ denoting the surface density of cilia. We then numerically determine the optimal beating patterns according to this criterion. For a single cilium optimization leads to curly, somewhat counterintuitive patterns. But when looking at a densely ciliated surface, the optimal patterns become remarkably similar to what is observed in microorganisms like Paramecium. The optimal beating pattern then consists of a fast effective stroke and a slow sweeping recovery stroke. Metachronal waves lead to a significantly higher efficiency than synchronous beating. Efficiency also increases with an increasing density of cilia up to the point where crowding becomes a problem. We finally relate the pumping efficiency of cilia to the swimming efficiency of a spherical microorganism and show that the experimentally estimated efficiency of Paramecium is surprisingly close to the theoretically possible optimum.

Psychophysical evidence for the number sense

PubMed Central

2018-01-01

It is now clear that most animals, including humans, possess an ability to rapidly estimate number. Some have questioned whether this ability arises from dedicated numerosity mechanisms, or is derived indirectly from judgements of density or other attributes. We describe a series of psychophysical experiments, largely using adaptation techniques, which demonstrate clearly the existence of a number sense in humans. The number sense is truly general, extending over space, time and sensory modality, and is closely linked with action. We further show that when multiple cues are present, numerosity emerges as the natural dimension for discrimination. However, when element density increases past a certain level, the elements become too crowded to parse, and the scene is perceived as a texture rather than array of elements. The two different regimes are psychophysically discriminable in that they follow distinct psychophysical laws, and show different dependencies on eccentricity, luminance levels and effects of perceptual grouping. The distinction is important, as the ability to discriminate numerosity, but not texture, correlates with formal maths skills. This article is part of the discussion meeting issue ‘The origins of numerical abilities’. PMID:29292350

Effects of astaxanthin and emodin on the growth, stress resistance and disease resistance of yellow catfish (Pelteobagrus fulvidraco).

PubMed

Liu, Fei; Shi, Hong-Zhuan; Guo, Qiao-Sheng; Yu, Ye-Bing; Wang, Ai-Ming; Lv, Fu; Shen, Wen-Biao

2016-04-01

Yellow catfish (Pelteobagrus fulvidraco) has become a commercially important fish species in China and eastern Asia. High-density aquaculture has led to congestion and excessive stress and contributed to bacterial infection outbreaks that have caused high mortality. We investigated the effects of dietary supplementation with astaxanthin and emodin alone and in combination on the growth and stress resistance of yellow catfish. After 60 days of feeding, each group of fish (control, astaxanthin, emodin, and astaxanthin plus emodin (combination) groups) was exposed to acute crowding stress for 24 h, and a subsample of fish from the four groups was challenged with the bacterial septicemia pathogen Proteus mirabilis after the end of the crowding stress experiment. Compared with the control, the astaxanthin and emodin groups showed increases in serum total protein (TP), hepatic superoxide dismutase (SOD) activity and hepatic heat shock proteins 70 (HSP70) mRNA levels at 12 and 24 h after the initiation of crowding stress. The combination group exhibited increases in alanine aminotransferase (ALT) activity, aspartate aminotransferase (AST) activity, serum TP, hepatic SOD activity and hepatic HSP70 mRNA levels within 24 h after the initiation of crowding stress. However, decreases relative to the control were observed in the serum cortisol and glucose contents in the three treatment groups at 12 and 24 h after the initiation of crowding stress, in ALT and AST activity in the astaxanthin and emodin group at 24 h after the initiation of crowding stress, and in the serum lysozyme activity, serum alkaline phosphatase (ALP) activity, and hepatic catalase (CAT) and malondialdehyde (MDA) activity in the combination group at 24 h after the initiation of crowding stress. Additionally, the cumulative mortality after P. mirabilis infection was lower in all three treatment groups (57.00%-70.33%) than in the control (77.67%). Dietary supplementation with astaxanthin and emodin decreased the specific growth rate (SGR) and weight gain (WG) of healthy yellow catfish, although significant differences in mortality were not observed. These results indicate that dietary supplementation with 80 mg/kg astaxanthin and 150 mg/kg emodin can improve the anti-oxidative capabilities, hepatic HSP70 levels, and resistance to acute crowding stress of yellow catfish. Finally, an appropriate strategy for enhance yellow catfish stress resistance and disease resistance is proposed. Copyright © 2016 Elsevier Ltd. All rights reserved.

Counteracting estimation bias and social influence to improve the wisdom of crowds.

PubMed

Kao, Albert B; Berdahl, Andrew M; Hartnett, Andrew T; Lutz, Matthew J; Bak-Coleman, Joseph B; Ioannou, Christos C; Giam, Xingli; Couzin, Iain D

2018-04-01

Aggregating multiple non-expert opinions into a collective estimate can improve accuracy across many contexts. However, two sources of error can diminish collective wisdom: individual estimation biases and information sharing between individuals. Here, we measure individual biases and social influence rules in multiple experiments involving hundreds of individuals performing a classic numerosity estimation task. We first investigate how existing aggregation methods, such as calculating the arithmetic mean or the median, are influenced by these sources of error. We show that the mean tends to overestimate, and the median underestimate, the true value for a wide range of numerosities. Quantifying estimation bias, and mapping individual bias to collective bias, allows us to develop and validate three new aggregation measures that effectively counter sources of collective estimation error. In addition, we present results from a further experiment that quantifies the social influence rules that individuals employ when incorporating personal estimates with social information. We show that the corrected mean is remarkably robust to social influence, retaining high accuracy in the presence or absence of social influence, across numerosities and across different methods for averaging social information. Using knowledge of estimation biases and social influence rules may therefore be an inexpensive and general strategy to improve the wisdom of crowds. © 2018 The Author(s).

Understanding the drivers on medical workloads: an analysis of spectators at the Australian Football League.

PubMed

Zeitz, Kathryn; Haghighi, Pari Delir; Burstein, Frada; Williams, Jeffrey

2013-06-01

The present study was designed to further understand the psychosocial drivers of crowds impacting on the demand for healthcare. This involved analysing different spectator crowds for medical usage at mass gatherings; more specifically, did different football team spectators (of the Australian Football League) generate different medical usage rates. In total, 317 games were analysed from 10 venues over 2 years. Data were analysed by the ANOVA and Pearson correlation tests. RESULTS; Spectators who supported different football teams generated statistically significant differences in patient presentation rates (PPR) (F15, 618=1.998, P=0.014). The present study confirmed previous findings that there is a positive correlation between the crowd size and PPR at mass gatherings but found a negative correlation between density and PPR (r = -0.206, n=317, P<0.0005). The present study has attempted to scientifically explore psychosocial elements of crowd behaviour as a driver of demand for emergency medical care. In measuring demand for emergency medical services there is a need to develop a more sophisticated understanding of a variety of drivers in addition to traditional metrics such as temperature, crowd size and other physical elements. In this study we saw that spectators who supported different football teams generated statistically significant differences in PPR. What is known about this topic? Understanding the drivers of emergency medical care is most important in the mass gathering setting. There has been minimal analysis of psychological 'crowd' variables. What does this paper add? This study explores the psychosocial impact of supporting a different team on the PPR of spectators at Australian Football League matches. The value of collecting and analysing these types of data sets is to support more balanced planning, better decision support and knowledge management, and more effective emergency medical demand management. What are the implications for practitioners? This information further expands the body of evidence being created to understand the drivers of emergency medical demand and usage. In addition, it supports the planning and management of emergency medical and health-related requirements by increasing our understanding of the effect of elements of 'crowd' that impact on medical usage and emergency healthcare.

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.

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 vertical pattern of microwave radiation around BTS (Base Transceiver Station) antennae in Hashtgerd township.

PubMed

Nasseri, Simin; Monazzam, Mohammadreza; Beheshti, Meisam; Zare, Sajad; Mahvi, Amirhosein

2013-12-20

New environmental pollutants interfere with the environment and human life along with technology development. One of these pollutants is electromagnetic field. This study determines the vertical microwave radiation pattern of different types of Base Transceiver Station (BTS) antennae in the Hashtgerd city as the capital of Savojbolagh County, Alborz Province of Iran. The basic data including the geographical location of the BTS antennae in the city, brand, operator type, installation and its height was collected from radio communication office, and then the measurements were carried out according to IEEE STD 95. 1 by the SPECTRAN 4060. The statistical analyses were carried out by SPSS16 using Kolmogorov Smirnov test and multiple regression method. Results indicated that in both operators of Irancell and Hamrah-e-Aval (First Operator), the power density rose with an increase in measurement height or decrease in the vertical distance of broadcaster antenna. With mix model test, a significant statistical relationship was observed between measurement height and the average power density in both types of the operators. With increasing measuring height, power density increased in both operators. The study showed installing antennae in a crowded area needs more care because of higher radiation emission. More rigid surfaces and mobile users are two important factors in crowded area that can increase wave density and hence raise public microwave exposure.

The vertical pattern of microwave radiation around BTS (Base Transceiver Station) antennae in Hashtgerd township

PubMed Central

2013-01-01

New environmental pollutants interfere with the environment and human life along with technology development. One of these pollutants is electromagnetic field. This study determines the vertical microwave radiation pattern of different types of Base Transceiver Station (BTS) antennae in the Hashtgerd city as the capital of Savojbolagh County, Alborz Province of Iran. The basic data including the geographical location of the BTS antennae in the city, brand, operator type, installation and its height was collected from radio communication office, and then the measurements were carried out according to IEEE STD 95. 1 by the SPECTRAN 4060. The statistical analyses were carried out by SPSS16 using Kolmogorov Smirnov test and multiple regression method. Results indicated that in both operators of Irancell and Hamrah-e-Aval (First Operator), the power density rose with an increase in measurement height or decrease in the vertical distance of broadcaster antenna. With mix model test, a significant statistical relationship was observed between measurement height and the average power density in both types of the operators. With increasing measuring height, power density increased in both operators. The study showed installing antennae in a crowded area needs more care because of higher radiation emission. More rigid surfaces and mobile users are two important factors in crowded area that can increase wave density and hence raise public microwave exposure. PMID:24359870

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

Disaster Risk Reduction through Innovative Uses of Crowd Sourcing (Invited)

NASA Astrophysics Data System (ADS)

Berger, J.; Greene, M.

2010-12-01

Crowd sourcing can be described as a method of distributed problem-solving. It takes advantage of the power of the crowd, which can in some cases be a community of experts and in other cases the collective insight of a broader range of contributors with varying degrees of domain knowledge. The term crowd sourcing was first used by Jeff Howe in a June 2006 Wired magazine article “The Rise of Crowdsourcing,” and is a combination of the terms “crowd” and “outsourcing.” Some commonly known examples of crowd sourcing, in its broadest sense, include Wikepedia, distributed participatory design projects, and consumer websites such as Yelp and Angie’s List. The popularity and success of early large-scale crowd sourcing activities is made possible through leveraging Web 2.0 technologies that allow for mass participation from distributed individuals. The Earthquake Engineering Research Institute (EERI) in Oakland, California recently participated in two crowd sourcing projects. One was initiated and coordinated by EERI, while in the second case EERI was invited to contribute once the crowd sourcing activity was underway. In both projects there was: 1) the determination of a problem or set of tasks that could benefit immediately from the engagement of an informed volunteer group of professionals; 2) a segmenting of the problem into discrete pieces that could be completed in a short period of time (from ten minutes to four hours); 3) a call to action, where an interested community was made aware of the project; and 4) the collection, aggregation, vetting and ultimately distribution of the results in a relatively short period of time. The first EERI crowd sourcing example was the use of practicing engineers and engineering students in California to help estimate the number of pre-1980 concrete buildings in the high seismic risk counties in the state. This building type is known to perform poorly in earthquakes, and state officials were interested in understanding more about the size of the problem—how many buildings, which jurisdictions. Volunteers signed up for individual jurisdictions and used a variety of techniques to estimate the count. They shared their techniques at meetings and posted their results online. Over 100 volunteers also came together to walk the streets of downtown San Francisco, a city with a particularly large number of these buildings, gathering more data on each building that will be used in a later phase to identify possible mitigation strategies. The second example was EERI’s participation in a response network, GEO-CAN, created in support of the World Bank’s responsibility in the damage assessment of buildings in Port-au-Prince immediately after the January 12, 2010 earthquake. EERI members, primarily earthquake engineers, were invited to speed up critical damage assessment using pre- and post-event aerial imagery. An area of 300 sq km was divided into grids, and grids were then allocated to knowledgeable individuals for analysis. The initial analysis was completed within 96 hours through the participation of over 300 volunteers. Ultimately, over 600 volunteers completed damage assessments for about 30,000 buildings.

A high plant density reduces the ability of maize to use soil nitrogen

PubMed Central

Yan, Peng; Pan, Junxiao; Zhang, Wenjie; Shi, Junfang; Chen, Xinping; Cui, Zhenling

2017-01-01

Understanding the physiological changes associated with high grain yield and high N use efficiency (NUE) is important when increasing the plant density and N rate to develop optimal agronomic management. We tested the hypothesis that high plant densities resulting in crowding stress reduce the ability of plants to use the N supply post-silking, thus decreasing the grain yield and NUE. In 2013 and 2014, a field experiment, with five N-application rates and three plant densities (6.0, 7.5, and 9.0 plants m–2), was conducted in the North China Plain (NCP). The calculated maximum grain yield and agronomic use efficiency (AEN) at a density of 7.5 plants m–2 were 12.4 Mg ha–1 and 39.3 kg kg–1, respectively, which were significantly higher than the values obtained at densities of 6.0 (11.3 Mg ha–1 and 30.2 kg kg–1) and 9.0 plant m–2 (11.7 Mg ha–1 and 27.8 kg kg–1). A high plant density of 9.0 plants m–2 decreased the post-silking N accumulation, leaf N concentration and net photosynthesis, which reduced the post-silking dry matter production, resulting in a low yield and NUE. Although a relatively low grain yield was observed at a density of 9.0 plants m–2, the optimal N rate increased from 150 to 186 kg N ha-1 at a density of 7.5 plants m–2. These results indicate that high plant densities with crowding stress reduce the ability of plants to use soil N during the post-silking period, and high rate of N fertilizer was needed to increase grain yield. We conclude that selecting the appropriate plant density combined with optimal N management could increase grain yields and the NUE in the NCP. PMID:28234970

Impacts of temperature and crowding on sex ratio, fecundity and Wolbachia infection intensity in the copepod, Mesocyclops thermocyclopoides.

PubMed

Wiwatanaratanabutr, Itsanun; Grandjean, Frederic

2016-11-01

Wolbachia are a group of intracellular bacteria that cause reproductive alterations in arthropods. Here, we describe the effects of two environmental factors (crowding and temperature) on phenotypic expression of feminization, the host's fecundity and Wolbachia infection intensity among life cycle stages in the naturally Wolbachia-infected copepod, Mesocyclops thermocyclopoides. The copepod was first found to be co-infected with Wolbachia A- and B-supergroups Wolbachia strains based on wsp primers. The relative Wolbachia infection intensity within individuals was determined using quantitative real-time PCR and was significantly higher in the B-supergroup than in the A-supergroup. Experimental results of temperature effect on bacterial density in each developmental stage revealed a significant decrease in Wolbachia infection intensity following exposure to high temperature (37°C) in both sexes and implied that Wolbachia might survive in room temperature (25°C) better than in high temperature. Experimental results of crowding effects on Wolbachia infection intensity suggested a negative correlation between copepod nauplii and Wolbachia infection intensity. No effect of rearing temperature on the sex ratio was reported although the fecundity was significantly decreased by high temperature. The results showed that Wolbachia infection intensity to be correlated with crowding conditions and was decreased following exposure of elevated temperature. Copyright © 2016 Elsevier Inc. All rights reserved.

Apoptotic death in cerebral hemisphere cells is density dependent and modulated by transient oxygen and glucose deprivation.

PubMed

Yavin, E; Billia, D M

1997-03-01

Flow cytometry, light and fluorescence microscopy, and designated biochemical techniques were used to examine the type of death which occurs in cerebral cortex cells when grown under crowded vs. sparse conditions or after brief anoxia/hypoglycemia. A 4 hr episode of anoxia combined with glucose deprivation enhanced apoptotic cell death as assessed by 4',6-diamidino-2-phenylindole (DAPI) staining and reduced neutral red eye uptake. An additional form of cell death involving exclusion of the nucleus was recorded by time lapse cinematography and DAPI stain. The presence of the endonuclease inhibitor aurintricarboxylic acid (0.1 mM) reduced cell death by 56.6%, while the protein and RNA synthesis inhibitors actinomycin D and cycloheximide (each at 5 micrograms/ml) effectively decreased cell death by 83.3% and 90.6%, respectively. In contrast, 5 mM glutamate had no effect on cell death in accord with the immature state of the cells. Growth of cells under crowded conditions improved cell survival; after 2 h or 4 days in culture, cells seeded at high density (34 microgram cellular DNA/cm2) showed a nearly 3-fold decline in the amount of cell death in comparison to cells seeded at low density (5 micrograms cellular DNA/cm2). At high cell density, anoxic episodes enhanced cell death most likely by preventing a cell density-mediated rescue. Neutral red dye uptake, an index for cell viability, was enhanced with increasing cell density and in vitro maturation, but was reduced in dense cultures exposed to anoxic/hypoglycemic conditions. The data suggest that cell density may play a critical role in brain organogenesis and that anoxic stress is more deleterious in dense than sparse cell assemblies.

The crowding effect and morphometric variability in Echinostoma caproni (Digenea: Echinostomatidae) from ICR mice.

PubMed

Stillson, Lindsey L; Platt, Thomas R

2007-04-01

Population density, or crowding, was examined to determine its effect on the morphometric variability of Echinostoma caproni (Digenea) in ICR mice. Six mice were infected with 25 and 100 metacercariae, and a single mouse was infected with 300 metacercariae. All mice were infected at necropsy 22 days postinfection with recoveries of 77%, 69%, and 7.3%, respectively. Whole mounts were prepared, and 31 characters were evaluated (25 direct measurements and 6 ratios). Univariate and multivariate statistical analysis revealed significant differences between adult worms from all 3 groups. Twenty-seven of 31 characters showed significant within-group differences, with the primary differences between worms from 25/100 versus 300 metacercariae infections. Discriminant function analysis yielded a 100% correct classification based on infection size, which is consistent with studies on distinct species of Echinostoma. The low recovery from the mouse infected with 300 metacercariae suggests inflammatory expulsion of juvenile worms and the possibility of immunity as a factor in the crowding effect. These results suggest that external factors may affect morphometric variability of digenetic trematodes to a larger degree than previously recognized.

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

Resolving stellar populations with crowded field 3D spectroscopy

NASA Astrophysics Data System (ADS)

Kamann, S.; Wisotzki, L.; Roth, M. M.

2013-01-01

We describe a new method of extracting the spectra of stars from observations of crowded stellar fields with integral field spectroscopy (IFS). Our approach extends the well-established concept of crowded field photometry in images into the domain of 3-dimensional spectroscopic datacubes. The main features of our algorithm follow. (1) We assume that a high-fidelity input source catalogue already exists, e.g. from HST data, and that it is not needed to perform sophisticated source detection in the IFS data. (2) Source positions and properties of the point spread function (PSF) vary smoothly between spectral layers of the datacube, and these variations can be described by simple fitting functions. (3) The shape of the PSF can be adequately described by an analytical function. Even without isolated PSF calibrator stars we can therefore estimate the PSF by a model fit to the full ensemble of stars visible within the field of view. (4) By using sparse matrices to describe the sources, the problem of extracting the spectra of many stars simultaneously becomes computationally tractable. We present extensive performance and validation tests of our algorithm using realistic simulated datacubes that closely reproduce actual IFS observations of the central regions of Galactic globular clusters. We investigate the quality of the extracted spectra under the effects of crowding with respect to the resulting signal-to-noise ratios (S/N) and any possible changes in the continuum level, as well as with respect to absorption line spectral parameters, radial velocities, and equivalent widths. The main effect of blending between two nearby stars is a decrease in the S/N in their spectra. The effect increases with the crowding in the field in a way that the maximum number of stars with useful spectra is always ~0.2 per spatial resolution element. This balance breaks down when exceeding a total source density of one significantly detected star per resolution element. We also explore the effects of PSF mismatch and other systematics. We close with an outlook by applying our method to a simulated globular cluster observation with the upcoming MUSE instrument at the ESO-VLT. Based on observations collected at the Centro Astronómico Hispano Alemán (CAHA) at Calar Alto, operated jointly by the Max-Planck Institut für Astronomie and the Instituto de Astrofísica de Andalucía (CSIC).Based on observations made with the NASA/ESA Hubble Space Telescope, and obtained from the Hubble Legacy Archive, which is a collaboration between the Space Telescope Science Institute (STScI/NASA), the Space Telescope European Coordinating Facility (ST-ECF/ESA), and the Canadian Astronomy Data Centre (CADC/NRC/CSA).

Facilitative-Competitive Interactions in an Old-Growth Forest: The Importance of Large-Diameter Trees as Benefactors and Stimulators for Forest Community Assembly

PubMed Central

Fichtner, Andreas; Forrester, David I.; Härdtle, Werner; Sturm, Knut; von Oheimb, Goddert

2015-01-01

The role of competition in tree communities is increasingly well understood, while little is known about the patterns and mechanisms of the interplay between above- and belowground competition in tree communities. This knowledge, however, is crucial for a better understanding of community dynamics and developing adaptive near-natural management strategies. We assessed neighbourhood interactions in an unmanaged old-growth European beech (Fagus sylvatica) forest by quantifying variation in the intensity of above- (shading) and belowground competition (crowding) among dominant and co-dominant canopy beech trees during tree maturation. Shading had on average a much larger impact on radial growth than crowding and the sensitivity to changes in competitive conditions was lowest for crowding effects. We found that each mode of competition reduced the effect of the other. Increasing crowding reduced the negative effect of shading, and at high levels of shading, crowding actually had a facilitative effect and increased growth. Our study demonstrates that complementarity in above- and belowground processes enable F. sylvatica to alter resource acquisition strategies, thus optimising tree radial growth. As a result, competition seemed to become less important in stands with a high growing stock and tree communities with a long continuity of anthropogenic undisturbed population dynamics. We suggest that growth rates do not exclusively depend on the density of potential competitors at the intraspecific level, but on the conspecific aggregation of large-diameter trees and their functional role for regulating biotic filtering processes. This finding highlights the potential importance of the rarely examined relationship between the spatial aggregation pattern of large-diameter trees and the outcome of neighbourhood interactions, which may be central to community dynamics and the related forest ecosystem services. PMID:25803035

Facilitative-competitive interactions in an old-growth forest: the importance of large-diameter trees as benefactors and stimulators for forest community assembly.

PubMed

Fichtner, Andreas; Forrester, David I; Härdtle, Werner; Sturm, Knut; von Oheimb, Goddert

2015-01-01

The role of competition in tree communities is increasingly well understood, while little is known about the patterns and mechanisms of the interplay between above- and belowground competition in tree communities. This knowledge, however, is crucial for a better understanding of community dynamics and developing adaptive near-natural management strategies. We assessed neighbourhood interactions in an unmanaged old-growth European beech (Fagus sylvatica) forest by quantifying variation in the intensity of above- (shading) and belowground competition (crowding) among dominant and co-dominant canopy beech trees during tree maturation. Shading had on average a much larger impact on radial growth than crowding and the sensitivity to changes in competitive conditions was lowest for crowding effects. We found that each mode of competition reduced the effect of the other. Increasing crowding reduced the negative effect of shading, and at high levels of shading, crowding actually had a facilitative effect and increased growth. Our study demonstrates that complementarity in above- and belowground processes enable F. sylvatica to alter resource acquisition strategies, thus optimising tree radial growth. As a result, competition seemed to become less important in stands with a high growing stock and tree communities with a long continuity of anthropogenic undisturbed population dynamics. We suggest that growth rates do not exclusively depend on the density of potential competitors at the intraspecific level, but on the conspecific aggregation of large-diameter trees and their functional role for regulating biotic filtering processes. This finding highlights the potential importance of the rarely examined relationship between the spatial aggregation pattern of large-diameter trees and the outcome of neighbourhood interactions, which may be central to community dynamics and the related forest ecosystem services.

Interspecific Larval Competition Between Aedes albopictus and Aedes japonicus (Diptera: Culicidae) in Northern Virginia

PubMed Central

Armistead, J. S.; Arias, J. R.; Nishimura, N.; Lounibos, L. P.

2008-01-01

Aedes albopictus (Skuse) and Aedes japonicus (Theobald) are two of the most recent and widespread invasive mosquito species to have become established in the United States. The two species co-occur in water-filled artificial containers, where crowding and limiting resources are likely to promote inter- or intraspecific larval competition. The performance of northern Virginia populations of Ae. japonicus and Ae. albopictus competing as larvae under field conditions was evaluated. Per capita rates of population increase for each species were estimated, and the effects of species composition and larval density were determined. In water-containing cups provided with oak leaves, Ae. albopictus larvae exhibited a competitive advantage over Ae. japonicus as a consequence of higher survivorship, shorter developmental time, and a significantly higher estimated population growth rate under conditions of interspecific competition. Intraspecific competition constrained population performance of Ae. albopictus significantly more than competition with Ae. japonicus. In the context of the Lotka-Volterra model of competition, these findings suggest competitive exclusion of Ae. japonicus in those habitats where this species co-occurs with Ae. albopictus. PMID:18714861

Interspecific larval competition between Aedes albopictus and Aedes japonicus (Diptera: Culicidae) in northern Virginia.

PubMed

Armistead, J S; Arias, J R; Nishimura, N; Lounibos, L P

2008-07-01

Aedes albopictus (Skuse) and Aedes japonicus (Theobald) are two of the most recent and widespread invasive mosquito species to have become established in the United States. The two species co-occur in water-filled artificial containers, where crowding and limiting resources are likely to promote inter- or intraspecific larval competition. The performance of northern Virginia populations of Ae. japonicus and Ae. albopictus competing as larvae under field conditions was evaluated. Per capita rates of population increase for each species were estimated, and the effects of species composition and larval density were determined. In water-containing cups provided with oak leaves, Ae. albopictus larvae exhibited a competitive advantage over Ae. japonicus as a consequence of higher survivorship, shorter developmental time, and a significantly higher estimated population growth rate under conditions of interspecific competition. Intraspecific competition constrained population performance of Ae. albopictus significantly more than competition with Ae. japonicus. In the context of the Lotka-Volterra model of competition, these findings suggest competitive exclusion of Ae. japonicus in those habitats where this species co-occurs with Ae. albopictus.

Modeling the growth of individuals in plant populations: local density variation in a strand population of Xanthium strumarium (Asteraceae).

PubMed

Weiner, J; Kinsman, S; Williams, S

1998-11-01

We studied the growth of individual Xanthium strumarium plants growing at four naturally occurring local densities on a beach in Maine: (1) isolated plants, (2) pairs of plants ≤1 cm apart, (3) four plants within 4 cm of each other, and (4) discrete dense clumps of 10-39 plants. A combination of nondestructive measurements every 2 wk and parallel calibration harvests provided very good estimates of the growth in aboveground biomass of over 400 individual plants over 8 wk and afforded the opportunity to fit explicit growth models to 293 of them. There was large individual variation in growth and resultant size within the population and within all densities. Local crowding played a role in determining plant size within the population: there were significant differences in final size between all densities except pairs and quadruples, which were almost identical. Overall, plants growing at higher densities were more variable in growth and final size than plants growing at lower densities, but this was due to increased variation among groups (greater variation in local density and/or greater environmental heterogeneity), not to increased variation within groups. Thus, there was no evidence of size asymmetric competition in this population. The growth of most plants was close to exponential over the study period, but half the plants were slightly better fit by a sigmoidal (logistic) model. The proportion of plants better fit by the logistic model increased with density and with initial plant size. The use of explicit growth models over several growth intervals to describe stand development can provide more biological content and more statistical power than "growth-size" methods that analyze growth intervals separately.

Tidal radii of the globular clusters M 5, M 12, M 13, M 15, M 53, NGC 5053 and NGC 5466 from automated star counts.

NASA Astrophysics Data System (ADS)

Lehmann, I.; Scholz, R.-D.

1997-04-01

We present new tidal radii for seven Galactic globular clusters using the method of automated star counts on Schmidt plates of the Tautenburg, Palomar and UK telescopes. The plates were fully scanned with the APM system in Cambridge (UK). Special account was given to a reliable background subtraction and the correction of crowding effects in the central cluster region. For the latter we used a new kind of crowding correction based on a statistical approach to the distribution of stellar images and the luminosity function of the cluster stars in the uncrowded area. The star counts were correlated with surface brightness profiles of different authors to obtain complete projected density profiles of the globular clusters. Fitting an empirical density law (King 1962) we derived the following structural parameters: tidal radius r_t_, core radius r_c_ and concentration parameter c. In the cases of NGC 5466, M 5, M 12, M 13 and M 15 we found an indication for a tidal tail around these objects (cf. Grillmair et al. 1995).

VizieR Online Data Catalog: Tidal radii of 7 globular clusters (Lehmann+ 1997)

NASA Astrophysics Data System (ADS)

Lehmann, I.; Scholz, R.-D.

1998-02-01

We present new tidal radii for seven Galactic globular clusters using the method of automated star counts on Schmidt plates of the Tautenburg, Palomar and UK telescopes. The plates were fully scanned with the APM system in Cambridge (UK). Special account was given to a reliable background subtraction and the correction of crowding effects in the central cluster region. For the latter we used a new kind of crowding correction based on a statistical approach to the distribution of stellar images and the luminosity function of the cluster stars in the uncrowded area. The star counts were correlated with surface brightness profiles of different authors to obtain complete projected density profiles of the globular clusters. Fitting an empirical density law (King 1962AJ.....67..471K) we derived the following structural parameters: tidal radius rt, core radius rc and concentration parameter c. In the cases of NGC 5466, M 5, M 12, M 13 and M 15 we found an indication for a tidal tail around these objects (cf. Grillmair et al., 1995AJ....109.2553G). (1 data file).

Comfort studies of rail passengers

PubMed Central

Nicol, J. F.; Doré, C.; Weiner, J. S.; Lee, D. E.; Prestidge, S. P.; Andrews, M. J.

1973-01-01

Nicol, J. F., Doré, C., Weiner, J. S., Lee, D. E., Prestidge, S. P., and Andrews, M. J. (1973).British Journal of Industrial Medicine,30, 325-334. Comfort studies of rail passengers. A short series of trials is described in which a specimen car of the new High Density Rolling Stock was laden with passengers at different densities and under different environmental constraints, designed to simulate `shut-down' conditions. The results suggest that the limit for comfort, 21·8°C corrected effective temperature (CET), proposed by Bell and Watts (1971) is reasonable but that temperatures some 3 or 4°C higher can be tolerated without undue discomfort. The physiological limit for safety recommended by Bell and Watts is a CET of 30·6°C. This will be reached in less than 20 minutes if there is a power failure in warm conditions in crowded trains. An undesirable, possibly dangerous, level of discomfort will be experienced by passengers in ventilated but crowded trains after 30 minutes. In any case it is recommended that the globe temperature in a carriage should not exceed 30°C. Images PMID:4753715

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.

Crowdsourcing Vector Surveillance: Using Community Knowledge and Experiences to Predict Densities and Distribution of Outdoor-Biting Mosquitoes in Rural Tanzania.

PubMed

Mwangungulu, Stephen Peter; Sumaye, Robert David; Limwagu, Alex Julius; Siria, Doreen Josen; Kaindoa, Emmanuel Wilson; Okumu, Fredros Oketch

2016-01-01

Lack of reliable techniques for large-scale monitoring of disease-transmitting mosquitoes is a major public health challenge, especially where advanced geo-information systems are not regularly applicable. We tested an innovative crowd-sourcing approach, which relies simply on knowledge and experiences of residents to rapidly predict areas where disease-transmitting mosquitoes are most abundant. Guided by community-based resource persons, we mapped boundaries and major physical features in three rural Tanzanian villages. We then selected 60 community members, taught them basic map-reading skills, and offered them gridded maps of their own villages (grid size: 200m×200m) so they could identify locations where they believed mosquitoes were most abundant, by ranking the grids from one (highest density) to five (lowest density). The ranks were interpolated in ArcGIS-10 (ESRI-USA) using inverse distance weighting (IDW) method, and re-classified to depict areas people believed had high, medium and low mosquito densities. Finally, we used odor-baited mosquito traps to compare and verify actual outdoor mosquito densities in the same areas. We repeated this process for 12 months, each time with a different group of 60 residents. All entomological surveys depicted similar geographical stratification of mosquito densities in areas classified by community members as having high, medium and low vector abundance. These similarities were observed when all mosquito species were combined, and also when only malaria vectors were considered. Of the 12,412 mosquitoes caught, 60.9% (7,555) were from areas considered by community members as having high mosquito densities, 28% (3,470) from medium density areas, and 11.2% (1,387) from low density areas. This study provides evidence that we can rely on community knowledge and experiences to identify areas where mosquitoes are most abundant or least abundant, even without entomological surveys. This crowd-sourcing method could be further refined and validated to improve community-based planning of mosquito control operations at low-cost.

Crowdsourcing Vector Surveillance: Using Community Knowledge and Experiences to Predict Densities and Distribution of Outdoor-Biting Mosquitoes in Rural Tanzania

PubMed Central

Limwagu, Alex Julius; Siria, Doreen Josen; Kaindoa, Emmanuel Wilson; Okumu, Fredros Oketch

2016-01-01

Lack of reliable techniques for large-scale monitoring of disease-transmitting mosquitoes is a major public health challenge, especially where advanced geo-information systems are not regularly applicable. We tested an innovative crowd-sourcing approach, which relies simply on knowledge and experiences of residents to rapidly predict areas where disease-transmitting mosquitoes are most abundant. Guided by community-based resource persons, we mapped boundaries and major physical features in three rural Tanzanian villages. We then selected 60 community members, taught them basic map-reading skills, and offered them gridded maps of their own villages (grid size: 200m×200m) so they could identify locations where they believed mosquitoes were most abundant, by ranking the grids from one (highest density) to five (lowest density). The ranks were interpolated in ArcGIS-10 (ESRI-USA) using inverse distance weighting (IDW) method, and re-classified to depict areas people believed had high, medium and low mosquito densities. Finally, we used odor-baited mosquito traps to compare and verify actual outdoor mosquito densities in the same areas. We repeated this process for 12 months, each time with a different group of 60 residents. All entomological surveys depicted similar geographical stratification of mosquito densities in areas classified by community members as having high, medium and low vector abundance. These similarities were observed when all mosquito species were combined, and also when only malaria vectors were considered. Of the 12,412 mosquitoes caught, 60.9% (7,555) were from areas considered by community members as having high mosquito densities, 28% (3,470) from medium density areas, and 11.2% (1,387) from low density areas. This study provides evidence that we can rely on community knowledge and experiences to identify areas where mosquitoes are most abundant or least abundant, even without entomological surveys. This crowd-sourcing method could be further refined and validated to improve community-based planning of mosquito control operations at low-cost. PMID:27253869

Molecular dynamics simulations of highly crowded amino acid solutions: comparisons of eight different force field combinations with experiment and with each other

PubMed Central

Andrews, Casey T.

2013-01-01

Although it is now commonly accepted that the highly crowded conditions encountered inside biological cells have the potential to significantly alter the thermodynamic properties of biomolecules, it is not known to what extent the thermodynamics of fundamental types of interactions such as salt bridges and hydrophobic interactions are strengthened or weakened by high biomolecular concentrations. As one way of addressing this question we have performed a series of all-atom explicit solvent molecular dynamics (MD) simulations to investigate the effect of increasing solute concentration on the behavior of four types of zwitterionic amino acids in aqueous solution. We have simulated systems containing glycine, valine, phenylalanine or asparagine at concentrations of 50, 100, 200 and 300 mg/ml. Each molecular system has been simulated for 1 μs in order to obtain statistically converged estimates of thermodynamic parameters, and each has been conducted with 8 different force fields and water models; the combined simulation time is 128 μs. The density, viscosity, and dielectric increments of the four amino acids calculated from the simulations have been compared to corresponding experimental measurements. While all of the force fields perform well at reproducing the density increments, discrepancies for the viscosity and dielectric increments raise questions both about the accuracy of the simulation force fields and, in certain cases, the experimental data. We also observe large differences between the various force fields' descriptions of the interaction thermodynamics of salt bridges and, surprisingly, these differences also lead to qualitatively different predictions of their dependences on solute concentration. For the aliphatic interactions of valine sidechains, fewer differences are observed between the force fields, but significant differences are again observed for aromatic interactions of phenylalanine sidechains. Taken together, the results highlight the potential power of using explicit-solvent simulation methods to understand behavior in concentrated systems but also hint at potential difficulties in using these methods to obtain consistent views of behavior in intracellular environments. PMID:24409104

A lack of crowding? Body size does not decrease with density for two behavior-manipulating parasites

USGS Publications Warehouse

Weinersmith, KL; Warinner, Chloe B.; Tan, Virgina; Harris, David J.; Mora, Adrienne B.; Kuris, Armand M.; Lafferty, Kevin D.; Hechinger, Ryan F.

2014-01-01

For trophically transmitted parasites that manipulate the phenotype of their hosts, whether the parasites do or do not experience resource competition depends on such factors as the size of the parasites relative to their hosts, the intensity of infection, the extent to which parasites share the cost of defending against the host’s immune system or manipulating their host, and the extent to which parasites share transmission goals. Despite theoretical expectations for situations in which either no, or positive, or negative density-dependence should be observed, most studies document only negative density-dependence for trophically transmitted parasites. However, this trend may be an artifact of most studies having focused on systems in which parasites are large relative to their hosts. Yet, systems are common where parasites are small relative to their hosts, and these trophically transmitted parasites may be less likely to experience resource limitation. We looked for signs of density-dependence in Euhaplorchis californiensis (EUHA) and Renicola buchanani (RENB), two manipulative trematode parasites infecting wild-caught California killifish (Fundulus parvipinnis). These parasites are small relative to killifish (suggesting resources are not limiting), and are associated with changes in killifish behavior that are dependent on parasite-intensity and that increase predation rates by the parasites’ shared final host (indicating the possibility for cost sharing). We did not observe negative density-dependence in either species, indicating that resources are not limiting. In fact, observed patterns indicate possible mild positive density-dependence for EUHA. Although experimental confirmation is required, our findings suggest that some behavior-manipulating parasites suffer no reduction in size, and may even benefit when "crowded" by conspecifics.

Necessity of guides in pedestrian emergency evacuation

NASA Astrophysics Data System (ADS)

Yang, Xiaoxia; Dong, Hairong; Yao, Xiuming; Sun, Xubin; Wang, Qianling; Zhou, Min

2016-01-01

The role of guide who is in charge of leading pedestrians to evacuate in the case of emergency plays a critical role for the uninformed people. This paper first investigates the influence of mass behavior on evacuation dynamics and mainly focuses on the guided evacuation dynamics. In the extended crowd model proposed in this paper, individualistic behavior, herding behavior and environment influence are all considered for pedestrians who are not informed by the guide. According to the simulation results, herding behavior makes more pedestrians evacuate from the room in the same period of time. Besides, guided crowd demonstrates the same behavior of group dynamics which is characterized by gathering, conflicts and balance. Moreover, simulation results indicate guides with appropriate initial positions and quantity are more conducive to evacuation under a moderate initial density of pedestrians.

Reducing fire hazard: balancing costs and outcomes.

Treesearch

Valerie Rapp

2004-01-01

Massive wildfires in recent years have given urgency to questions of how to reduce fire hazard in Western forests, how to finance the work, and how to use the wood, especially in forests crowded with small trees. Scientists have already developed tools that estimate fire hazard in a forest stand. But hazard is more difficult to estimate at a landscape scale, involving...

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…

Number As a Primary Perceptual Attribute: A Review.

PubMed

Anobile, Giovanni; Cicchini, Guido Marco; Burr, David C

2016-01-01

Although humans are the only species to possess language-driven abstract mathematical capacities, we share with many other animals a nonverbal capacity for estimating quantities or numerosity. For some time, researchers have clearly differentiated between small numbers of items--less than about four--referred to as the subitizing range, and larger numbers, where counting or estimation is required. In this review, we examine more recent evidence suggesting a further division, between sets of items greater than the subitizing range, but sparse enough to be individuated as single items; and densely packed stimuli, where they crowd each other into what is better considered as a texture. These two different regimes are psychophysically discriminable in that they follow distinct psychophysical laws and show different dependencies on eccentricity and on luminance levels. But provided the elements are not too crowded (less than about two items per square degree in central vision, less in the periphery), there is little evidence that estimation of numerosity depends on mechanisms responsive to texture. The distinction is important, as the ability to discriminate numerosity, but not texture, correlates with formal maths skills. © The Author(s) 2015.

Crowd motion segmentation and behavior recognition fusing streak flow and collectiveness

NASA Astrophysics Data System (ADS)

Gao, Mingliang; Jiang, Jun; Shen, Jin; Zou, Guofeng; Fu, Guixia

2018-04-01

Crowd motion segmentation and crowd behavior recognition are two hot issues in computer vision. A number of methods have been proposed to tackle these two problems. Among the methods, flow dynamics is utilized to model the crowd motion, with little consideration of collective property. Moreover, the traditional crowd behavior recognition methods treat the local feature and dynamic feature separately and overlook the interconnection of topological and dynamical heterogeneity in complex crowd processes. A crowd motion segmentation method and a crowd behavior recognition method are proposed based on streak flow and crowd collectiveness. The streak flow is adopted to reveal the dynamical property of crowd motion, and the collectiveness is incorporated to reveal the structure property. Experimental results show that the proposed methods improve the crowd motion segmentation accuracy and the crowd recognition rates compared with the state-of-the-art methods.

New Method for Quantitation of Lipid Droplet Volume From Light Microscopic Images With an Application to Determination of PAT Protein Density on the Droplet Surface.

PubMed

Dejgaard, Selma Y; Presley, John F

2018-06-01

Determination of lipid droplet (LD) volume has depended on direct measurement of the diameter of individual LDs, which is not possible when LDs are small or closely apposed. To overcome this problem, we describe a new method in which a volume-fluorescence relationship is determined from automated analysis of calibration samples containing well-resolved LDs. This relationship is then used to estimate total cellular droplet volume in experimental samples, where the LDs need not be individually resolved, or to determine the volumes of individual LDs. We describe quantitatively the effects of various factors, including image noise, LD crowding, and variation in LD composition on the accuracy of this method. We then demonstrate this method by utilizing it to address a scientifically interesting question, to determine the density of green fluorescent protein (GFP)-tagged Perilipin-Adipocyte-Tail (PAT) proteins on the LD surface. We find that PAT proteins cover only a minority of the LD surface, consistent with models in which they primarily serve as scaffolds for binding of regulatory proteins and enzymes, but inconsistent with models in which their major function is to sterically block access to the droplet surface.

Phenotypic transformation affects associative learning in the desert locust.

PubMed

Simões, Patrício M V; Niven, Jeremy E; Ott, Swidbert R

2013-12-02

In desert locusts, increased population densities drive phenotypic transformation from the solitarious to the gregarious phase within a generation [1-4]. Here we show that when presented with odor-food associations, the two extreme phases differ in aversive but not appetitive associative learning, with solitarious locusts showing a conditioned aversion more quickly than gregarious locusts. The acquisition of new learned aversions was blocked entirely in acutely crowded solitarious (transiens) locusts, whereas appetitive learning and prior learned associations were unaffected. These differences in aversive learning support phase-specific feeding strategies. Associative training with hyoscyamine, a plant alkaloid found in the locusts' habitat [5, 6], elicits a phase-dependent odor preference: solitarious locusts avoid an odor associated with hyoscyamine, whereas gregarious locusts do not. Remarkably, when solitarious locusts are crowded and then reconditioned with the odor-hyoscyamine pairing as transiens, the specific blockade of aversive acquisition enables them to override their prior aversive memory with an appetitive one. Under fierce food competition, as occurs during crowding in the field, this provides a neuroecological mechanism enabling locusts to reassign an appetitive value to an odor that they learned previously to avoid. Copyright © 2013 Elsevier Ltd. All rights reserved.

Continuous theory of active matter systems with metric-free interactions.

PubMed

Peshkov, Anton; Ngo, Sandrine; Bertin, Eric; Chaté, Hugues; Ginelli, Francesco

2012-08-31

We derive a hydrodynamic description of metric-free active matter: starting from self-propelled particles aligning with neighbors defined by "topological" rules, not metric zones-a situation advocated recently to be relevant for bird flocks, fish schools, and crowds-we use a kinetic approach to obtain well-controlled nonlinear field equations. We show that the density-independent collision rate per particle characteristic of topological interactions suppresses the linear instability of the homogeneous ordered phase and the nonlinear density segregation generically present near threshold in metric models, in agreement with microscopic simulations.

Thermospheric mass density model error variance as a function of time scale

NASA Astrophysics Data System (ADS)

Emmert, J. T.; Sutton, E. K.

2017-12-01

In the increasingly crowded low-Earth orbit environment, accurate estimation of orbit prediction uncertainties is essential for collision avoidance. Poor characterization of such uncertainty can result in unnecessary and costly avoidance maneuvers (false positives) or disregard of a collision risk (false negatives). Atmospheric drag is a major source of orbit prediction uncertainty, and is particularly challenging to account for because it exerts a cumulative influence on orbital trajectories and is therefore not amenable to representation by a single uncertainty parameter. To address this challenge, we examine the variance of measured accelerometer-derived and orbit-derived mass densities with respect to predictions by thermospheric empirical models, using the data-minus-model variance as a proxy for model uncertainty. Our analysis focuses mainly on the power spectrum of the residuals, and we construct an empirical model of the variance as a function of time scale (from 1 hour to 10 years), altitude, and solar activity. We find that the power spectral density approximately follows a power-law process but with an enhancement near the 27-day solar rotation period. The residual variance increases monotonically with altitude between 250 and 550 km. There are two components to the variance dependence on solar activity: one component is 180 degrees out of phase (largest variance at solar minimum), and the other component lags 2 years behind solar maximum (largest variance in the descending phase of the solar cycle).

A spatial analysis of social and economic determinants of tuberculosis in Brazil.

PubMed

Harling, Guy; Castro, Marcia C

2014-01-01

We investigated the spatial distribution, and social and economic correlates, of tuberculosis in Brazil between 2002 and 2009 using municipality-level age/sex-standardized tuberculosis notification data. Rates were very strongly spatially autocorrelated, being notably high in urban areas on the eastern seaboard and in the west of the country. Non-spatial ecological regression analyses found higher rates associated with urbanicity, population density, poor economic conditions, household crowding, non-white population and worse health and healthcare indicators. These associations remained in spatial conditional autoregressive models, although the effect of poverty appeared partially confounded by urbanicity, race and spatial autocorrelation, and partially mediated by household crowding. Our analysis highlights both the multiple relationships between socioeconomic factors and tuberculosis in Brazil, and the importance of accounting for spatial factors in analysing socioeconomic determinants of tuberculosis. © 2013 Published by Elsevier Ltd.

Simulation of Molecular Transport in Systems Containing Mobile Obstacles.

PubMed

Polanowski, Piotr; Sikorski, Andrzej

2016-08-04

In this paper, we investigate the movement of molecules in crowded environments with obstacles undergoing Brownian motion by means of extensive Monte Carlo simulations. Our investigations were performed using the dynamic lattice liquid model, which was based on the cooperative movement concept and allowed to mimic systems at high densities where the motion of all elements (obstacles as well as moving particles) were highly correlated. The crowded environments are modeled on a two-dimensional triangular lattice containing obstacles (particles whose mobility was significantly reduced) moving by a Brownian motion. The subdiffusive motion of both elements in the system was analyzed. It was shown that the percolation transition does not exist in such systems in spite of the cooperative character of the particles' motion. The reduction of the obstacle mobility leads to the longer caging of liquid particles by mobile obstacles.

Real-Time Counting People in Crowded Areas by Using Local Empirical Templates and Density Ratios

NASA Astrophysics Data System (ADS)

Hung, Dao-Huu; Hsu, Gee-Sern; Chung, Sheng-Luen; Saito, Hideo

In this paper, a fast and automated method of counting pedestrians in crowded areas is proposed along with three contributions. We firstly propose Local Empirical Templates (LET), which are able to outline the foregrounds, typically made by single pedestrians in a scene. LET are extracted by clustering foregrounds of single pedestrians with similar features in silhouettes. This process is done automatically for unknown scenes. Secondly, comparing the size of group foreground made by a group of pedestrians to that of appropriate LET captured in the same image patch with the group foreground produces the density ratio. Because of the local scale normalization between sizes, the density ratio appears to have a bound closely related to the number of pedestrians who induce the group foreground. Finally, to extract the bounds of density ratios for groups of different number of pedestrians, we propose a 3D human models based simulation in which camera viewpoints and pedestrians' proximity are easily manipulated. We collect hundreds of typical occluded-people patterns with distinct degrees of human proximity and under a variety of camera viewpoints. Distributions of density ratios with respect to the number of pedestrians are built based on the computed density ratios of these patterns for extracting density ratio bounds. The simulation is performed in the offline learning phase to extract the bounds from the distributions, which are used to count pedestrians in online settings. We reveal that the bounds seem to be invariant to camera viewpoints and humans' proximity. The performance of our proposed method is evaluated with our collected videos and PETS 2009's datasets. For our collected videos with the resolution of 320x240, our method runs in real-time with good accuracy and frame rate of around 30 fps, and consumes a small amount of computing resources. For PETS 2009's datasets, our proposed method achieves competitive results with other methods tested on the same datasets [1], [2].

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.

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.

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.

Density-based clustering of small peptide conformations sampled from a molecular dynamics simulation.

PubMed

Kim, Minkyoung; Choi, Seung-Hoon; Kim, Junhyoung; Choi, Kihang; Shin, Jae-Min; Kang, Sang-Kee; Choi, Yun-Jaie; Jung, Dong Hyun

2009-11-01

This study describes the application of a density-based algorithm to clustering small peptide conformations after a molecular dynamics simulation. We propose a clustering method for small peptide conformations that enables adjacent clusters to be separated more clearly on the basis of neighbor density. Neighbor density means the number of neighboring conformations, so if a conformation has too few neighboring conformations, then it is considered as noise or an outlier and is excluded from the list of cluster members. With this approach, we can easily identify clusters in which the members are densely crowded in the conformational space, and we can safely avoid misclustering individual clusters linked by noise or outliers. Consideration of neighbor density significantly improves the efficiency of clustering of small peptide conformations sampled from molecular dynamics simulations and can be used for predicting peptide structures.

Network dynamics of social influence in the wisdom of crowds

PubMed Central

Brackbill, Devon; Centola, Damon

2017-01-01

A longstanding problem in the social, biological, and computational sciences is to determine how groups of distributed individuals can form intelligent collective judgments. Since Galton’s discovery of the “wisdom of crowds” [Galton F (1907) Nature 75:450–451], theories of collective intelligence have suggested that the accuracy of group judgments requires individuals to be either independent, with uncorrelated beliefs, or diverse, with negatively correlated beliefs [Page S (2008) The Difference: How the Power of Diversity Creates Better Groups, Firms, Schools, and Societies]. Previous experimental studies have supported this view by arguing that social influence undermines the wisdom of crowds. These results showed that individuals’ estimates became more similar when subjects observed each other’s beliefs, thereby reducing diversity without a corresponding increase in group accuracy [Lorenz J, Rauhut H, Schweitzer F, Helbing D (2011) Proc Natl Acad Sci USA 108:9020–9025]. By contrast, we show general network conditions under which social influence improves the accuracy of group estimates, even as individual beliefs become more similar. We present theoretical predictions and experimental results showing that, in decentralized communication networks, group estimates become reliably more accurate as a result of information exchange. We further show that the dynamics of group accuracy change with network structure. In centralized networks, where the influence of central individuals dominates the collective estimation process, group estimates become more likely to increase in error. PMID:28607070

Physiological Environment Induces Quick Response – Slow Exhaustion Reactions

PubMed Central

Hiroi, Noriko; Lu, James; Iba, Keisuke; Tabira, Akito; Yamashita, Shuji; Okada, Yasunori; Flamm, Christoph; Oka, Kotaro; Köhler, Gottfried; Funahashi, Akira

2011-01-01

In vivo environments are highly crowded and inhomogeneous, which may affect reaction processes in cells. In this study we examined the effects of intracellular crowding and an inhomogeneity on the behavior of in vivo reactions by calculating the spectral dimension (ds), which can be translated into the reaction rate function. We compared estimates of anomaly parameters obtained from fluorescence correlation spectroscopy (FCS) data with fractal dimensions derived from transmission electron microscopy (TEM) image analysis. FCS analysis indicated that the anomalous property was linked to physiological structure. Subsequent TEM analysis provided an in vivo illustration; soluble molecules likely percolate between intracellular clusters, which are constructed in a self-organizing manner. We estimated a cytoplasmic spectral dimension ds to be 1.39 ± 0.084. This result suggests that in vivo reactions initially run faster than the same reactions in a homogeneous space; this conclusion is consistent with the anomalous character indicated by FCS analysis. We further showed that these results were compatible with our Monte-Carlo simulation in which the anomalous behavior of mobile molecules correlates with the intracellular environment, leading to description as a percolation cluster, as demonstrated using TEM analysis. We confirmed by the simulation that the above-mentioned in vivo like properties are different from those of homogeneously concentrated environments. Additionally, simulation results indicated that crowding level of an environment might affect diffusion rate of reactant. Such knowledge of the spatial information enables us to construct realistic models for in vivo diffusion and reaction systems. PMID:21960972

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.

Revising traditional theory on the link between plant body size and fitness under competition: evidence from old-field vegetation

PubMed Central

Tracey, Amanda J; Aarssen, Lonnie W

2014-01-01

The selection consequences of competition in plants have been traditionally interpreted based on a “size-advantage” hypothesis – that is, under intense crowding/competition from neighbors, natural selection generally favors capacity for a relatively large plant body size. However, this conflicts with abundant data, showing that resident species body size distributions are usually strongly right-skewed at virtually all scales within vegetation. Using surveys within sample plots and a neighbor-removal experiment, we tested: (1) whether resident species that have a larger maximum potential body size (MAX) generally have more successful local individual recruitment, and thus greater local abundance/density (as predicted by the traditional size-advantage hypothesis); and (2) whether there is a general between-species trade-off relationship between MAX and capacity to produce offspring when body size is severely suppressed by crowding/competition – that is, whether resident species with a larger MAX generally also need to reach a larger minimum reproductive threshold size (MIN) before they can reproduce at all. The results showed that MIN had a positive relationship with MAX across resident species, and local density – as well as local density of just reproductive individuals – was generally greater for species with smaller MIN (and hence smaller MAX). In addition, the cleared neighborhoods of larger target species (which had relatively large MIN) generally had – in the following growing season – a lower ratio of conspecific recruitment within these neighborhoods relative to recruitment of other (i.e., smaller) species (which had generally smaller MIN). These data are consistent with an alternative hypothesis based on a ‘reproductive-economy-advantage’ – that is, superior fitness under competition in plants generally requires not larger potential body size, but rather superior capacity to recruit offspring that are in turn capable of producing grand-offspring – and hence transmitting genes to future generations – despite intense and persistent (cross-generational) crowding/competition from near neighbors. Selection for the latter is expected to favor relatively small minimum reproductive threshold size and hence – as a tradeoff – relatively small (not large) potential body size. PMID:24772274

Progress in low-resolution ab initio phasing with CrowdPhase

DOE PAGES

Jorda, Julien; Sawaya, Michael R.; Yeates, Todd O.

2016-03-01

Ab initio phasing by direct computational methods in low-resolution X-ray crystallography is a long-standing challenge. A common approach is to consider it as two subproblems: sampling of phase space and identification of the correct solution. While the former is amenable to a myriad of search algorithms, devising a reliable target function for the latter problem remains an open question. Here, recent developments in CrowdPhase, a collaborative online game powered by a genetic algorithm that evolves an initial population of individuals with random genetic make-up ( i.e. random phases) each expressing a phenotype in the form of an electron-density map, aremore » presented. Success relies on the ability of human players to visually evaluate the quality of these maps and, following a Darwinian survival-of-the-fittest concept, direct the search towards optimal solutions. While an initial study demonstrated the feasibility of the approach, some important crystallographic issues were overlooked for the sake of simplicity. To address these, the new CrowdPhase includes consideration of space-group symmetry, a method for handling missing amplitudes, the use of a map correlation coefficient as a quality metric and a solvent-flattening step. Lastly, performances of this installment are discussed for two low-resolution test cases based on bona fide diffraction data.« less

Progress in low-resolution ab initio phasing with CrowdPhase

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

Jorda, Julien; Sawaya, Michael R.; Yeates, Todd O.

Ab initio phasing by direct computational methods in low-resolution X-ray crystallography is a long-standing challenge. A common approach is to consider it as two subproblems: sampling of phase space and identification of the correct solution. While the former is amenable to a myriad of search algorithms, devising a reliable target function for the latter problem remains an open question. Here, recent developments in CrowdPhase, a collaborative online game powered by a genetic algorithm that evolves an initial population of individuals with random genetic make-up ( i.e. random phases) each expressing a phenotype in the form of an electron-density map, aremore » presented. Success relies on the ability of human players to visually evaluate the quality of these maps and, following a Darwinian survival-of-the-fittest concept, direct the search towards optimal solutions. While an initial study demonstrated the feasibility of the approach, some important crystallographic issues were overlooked for the sake of simplicity. To address these, the new CrowdPhase includes consideration of space-group symmetry, a method for handling missing amplitudes, the use of a map correlation coefficient as a quality metric and a solvent-flattening step. Lastly, performances of this installment are discussed for two low-resolution test cases based on bona fide diffraction data.« less

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

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.

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

Some potentials and limits of the leucocrit test as a fish health assessment method

USGS Publications Warehouse

Wedemeyer, G.A.; Gould, R.W.; Yasutake, W.T.

1983-01-01

The sensitivity of the leucocrit as a stress tolerance and fish health assessment method was evaluated by subjecting juvenile coho salmon, Oncorhynchus kisutch, or steelhead trout, Salmo gairdneri, to standardized crowding, handling, temperature and disease challenges. The leucocrit was a sensitive indicator of the physiological stress resulting from crowding at population densities of 0·2–0·4 kg l−1, and to the stress of handling and to temperature changes. It was relatively insensitive to physiological sampling procedures which supports its continued development as a stress assessment method.In the case of fish diseases, subclinical or active Renibacterium salmoninarum and Yersinia ruckeriinfections had essentially no effect on leucocrit values. In contrast, active Aeromonas salmonicidainfections significantly depressed the leucocrit. However, no change was seen during the subclinical (incubation) phase prior to the development of an epizootic. Thus, the potential of the leucocrit as a fish health assessment method appears limited.

Optimized Diffusion of Run-and-Tumble Particles in Crowded Environments

NASA Astrophysics Data System (ADS)

Bertrand, Thibault; Zhao, Yongfeng; Bénichou, Olivier; Tailleur, Julien; Voituriez, Raphaël

2018-05-01

We study the transport of self-propelled particles in dynamic complex environments. To obtain exact results, we introduce a model of run-and-tumble particles (RTPs) moving in discrete time on a d -dimensional cubic lattice in the presence of diffusing hard-core obstacles. We derive an explicit expression for the diffusivity of the RTP, which is exact in the limit of low density of fixed obstacles. To do so, we introduce a generalization of Kac's theorem on the mean return times of Markov processes, which we expect to be relevant for a large class of lattice gas problems. Our results show the diffusivity of RTPs to be nonmonotonic in the tumbling probability for low enough obstacle mobility. These results prove the potential for the optimization of the transport of RTPs in crowded and disordered environments with applications to motile artificial and biological systems.

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

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

Effects of l-tryptophan on the growth, intestinal enzyme activities and non-specific immune response of sea cucumber (Apostichopus japonicus Selenka) exposed to crowding stress.

PubMed

Zhang, Endong; Dong, Shuanglin; Wang, Fang; Tian, Xiangli; Gao, Qinfeng

2018-04-01

In order to reveal the effects of l-tryptophan (Trp) on the physiology and immune response of sea cucumber (Apostichopus japonicus Selenka) exposed to crowding stress, four density groups of sea cucumbers (i.e. 4, 8, 16 and 32 individuals per 40 L water, represented as L, ML, MH and H) were fed with diets containing 0, 1, 3 and 5% l-tryptophan respectively for 75 days. The results showed that the specific growth rates (SGR) of the sea cucumber fed with diet with 3% Trp (L, 2.1; ML, 1.76; MH, 1.2; H, 0.7) were significantly higher than those fed with basal diet without Trp supplementation (P < .05). Peak amylase activity occurred at H stress density at 3% dietary Trp. Trypsin activity was higher in diet 3% in ML and MH densities than the controls, which increased by 66.4% and 53.8%. However, the lipase activity first increased and then decreased from the stocking density L to H, with highest values of 3% Trp group showed the highest value than other groups. Compared to those fed with the basal diet, sea cucumber fed diets with Trp (3%) had significantly higher phagocytic activities (0.28 OD540/10 6  cells, H) in coelomic fluid and respiratory burst activities (0.105 OD630/10 6  cells, MH) (P < .05). The results suggested that Trp cannot improve superoxide dismutase (SOD) activity at L, ML and MH densities. The alkaline phosphatase activity (AKP) significantly decreased at H stress density. Under the experimental conditions, the present results confirmed that a diet supplemented with 3% Trp was able to enhance intestinal enzyme activities, non-specific immune response and higher growth performance of A. japonicus. Copyright © 2018 Elsevier Ltd. All rights reserved.

Public health aspects of the world's largest mass gathering: The 2013 Kumbh Mela in Allahabad, India.

PubMed

Balsari, Satchit; Greenough, P Gregg; Kazi, Dhruv; Heerboth, Aaron; Dwivedi, Shraddha; Leaning, Jennifer

2016-12-01

India's Kumbh Mela remains the world's largest and longest mass gathering. The 2013 event, where participants undertook a ritual bath, hosted over 70 million Hindu pilgrims during 55 days on a 1936 hectare flood plain at the confluence of the Yamuna and Ganga Rivers. On the holiest bathing days, the population surged. Unlike other religious, cultural, and sports mass gatherings, the Kumbh Mela's administration cannot estimate or limit the participant number. The event created serious and uncommon public health challenges: initiating crowd safety measures where population density and mobility directly contact flowing bodies of water; providing water, sanitation, and hygiene to a population that frequently defecates in the open; and establishing disease surveillance and resource use measures within a temporary health delivery system. We review the world's largest gathering by observing first-hand the public health challenges, plus the preparations for and responses to them. We recommend ways to improve preparedness.

A macromolecular crowding study of RNA folding and activity: polymer pore size matters! (Conference Presentation)

NASA Astrophysics Data System (ADS)

Börner, Richard; Fiorini, Erica; Paudel, Bishnu; Rueda, David; Sigel, Roland K. O.

2016-03-01

Catalytic RNAs, like the group IIB intron ribozyme of S. cerevesiae, require a high magnesium(II) concentration to show folding and function in vitro [1]. In contrast, in vivo conditions are characterized by a highly crowded cellular environment and much lower ion concentration. Molecular crowding agents are a widespread tool to mimic cellular crowding [2]. However, particular physical/chemical properties explaining the crowders influence are mostly not understood. In this study, we gain new insights on how polymer properties like viscosity, pore size etc. influence the activity and folding of a large RNA. We combined bulk activity assays and single-molecule Förster Resonance Energy Transfer experiments, screening the PEG volume fraction (%) and molecular weight (MW). Our results revealed that upon the influence of crowding agents, a compaction of the underlying structure depends on the PEG % and the presence of different PEG MW and % unveiled an optimal pore size in terms of catalytic activity. In summary, an increasing density of the crowding environment shifts the RNA towards the most compact state, but the ribozyme is only active if the crowders network matches its size [4]. We interpret the most compact state as necessary, but not sufficient, to keep the ribozyme active. Financial support from the European Research Council (MIRNA N° 259092, to RKOS), the Swiss National Fund (SNF), and the Forschungskredit Grant of the University of Zürich (FK-14-096 and 15-092 to RB) are gratefully acknowledged. [1] Swisher J.F., Su L.J., Brenowitz M., Anderson V.E., Pyle A.M., J. Mol. Bio., 315, 297-310 (2002). [2] Kilburn D., Roh J.H., Guo L., Briber R.M., Woodson S.A., JACS, 132, 8690-6 (2010). [3] Steiner M., Karunatilaka K.S., Sigel R.K.O., Rueda D., Proc. Natl. Acad. Sci. U.S.A.,105, 13853-8 (2008). [4] aBörner R, Fiorini E, Sigel R.K.O., Chimia, 69, 207-212 (2015).; bFiorini E., Paudel B., Börner R., Rueda D., Sigel R.K.O., submitted. [5] König S.L.B., Hadzic M., Fiorini E., Börner R., Kowerko D., Blanckenhorn W.U., Sigel R.K.O., PLoS ONE, 8, e84157 (2013).

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.

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.

Effects of Crowding and Attention on High-Levels of Motion Processing and Motion Adaptation

PubMed Central

Pavan, Andrea; Greenlee, Mark W.

2015-01-01

The motion after-effect (MAE) persists in crowding conditions, i.e., when the adaptation direction cannot be reliably perceived. The MAE originating from complex moving patterns spreads into non-adapted sectors of a multi-sector adapting display (i.e., phantom MAE). In the present study we used global rotating patterns to measure the strength of the conventional and phantom MAEs in crowded and non-crowded conditions, and when attention was directed to the adapting stimulus and when it was diverted away from the adapting stimulus. The results show that: (i) the phantom MAE is weaker than the conventional MAE, for both non-crowded and crowded conditions, and when attention was focused on the adapting stimulus and when it was diverted from it, (ii) conventional and phantom MAEs in the crowded condition are weaker than in the non-crowded condition. Analysis conducted to assess the effect of crowding on high-level of motion adaptation suggests that crowding is likely to affect the awareness of the adapting stimulus rather than degrading its sensory representation, (iii) for high-level of motion processing the attentional manipulation does not affect the strength of either conventional or phantom MAEs, neither in the non-crowded nor in the crowded conditions. These results suggest that high-level MAEs do not depend on attention and that at high-level of motion adaptation the effects of crowding are not modulated by attention. PMID:25615577

Optimal layout design of obstacles for panic evacuation using differential evolution

NASA Astrophysics Data System (ADS)

Zhao, Yongxiang; Li, Meifang; Lu, Xin; Tian, Lijun; Yu, Zhiyong; Huang, Kai; Wang, Yana; Li, Ting

2017-01-01

To improve the pedestrian outflow in panic situations by suitably placing an obstacle in front of the exit, it is vital to understand the physical mechanism behind the evacuation efficiency enhancement. In this paper, a robust differential evolution is firstly employed to optimize the geometrical parameters of different shaped obstacles in order to achieve an optimal evacuation efficiency. Moreover, it is found that all the geometrical parameters of obstacles could markedly influence the evacuation efficiency of pedestrians, and the best way for achieving an optimal pedestrian outflow is to slightly shift the obstacle from the center of the exit which is consistent with findings of extant literature. Most importantly, by analyzing the profiles of density, velocity and specific flow, as well as the spatial distribution of crowd pressure, we have proven that placing an obstacle in panic situations does not reduce or absorb the pressure in the region of exit, on the contrary, promotes the pressure to a much higher level, hence the physical mechanism behind the evacuation efficiency enhancement is not a pressure decrease in the region of exit, but a significant reduction of high density region by effective separation in space which finally causes the increasing of escape speed and evacuation outflow. Finally, it is clearly demonstrated that the panel-like obstacle is considerably more robust and stable than the pillar-like obstacle to guarantee the enhancement of evacuation efficiency under different initial pedestrian distributions, different initial crowd densities as well as different desired velocities.

VizieR Online Data Catalog: Structure of young stellar clusters. II. (Kuhn+, 2015)

NASA Astrophysics Data System (ADS)

Kuhn, M. A.; Getman, K. V.; Feigelson, E. D.

2015-07-01

We investigate the intrinsic stellar populations (estimated total numbers of OB and pre-main-sequence stars down to 0.1Mȯ) that are present in 17 massive star-forming regions (MSFRs) surveyed by the MYStIX project. The study is based on the catalog of >31000 MYStIX Probable Complex Members with both disk-bearing and disk-free populations, compensating for extinction, nebulosity, and crowding effects. Correction for observational sensitivities is made using the X-ray luminosity function and the near-infrared initial mass function --a correction that is often not made by infrared surveys of young stars. The resulting maps of the projected structure of the young stellar populations, in units of intrinsic stellar surface density, allow direct comparison between different regions. Several regions have multiple dense clumps, similar in size and density to the Orion Nebula Cluster. The highest projected density of ~34000 stars/pc2 is found in the core of the RCW 38 cluster. Histograms of surface density show different ranges of values in different regions, supporting the conclusion of Bressert et al. (B10; 2010MNRAS.409L..54B) that no universal surface-density threshold can distinguish between clustered and distributed star formation. However, a large component of the young stellar population of MSFRs resides in dense environments of 200-10000 stars/pc2 (including within the nearby Orion molecular clouds), and we find that there is no evidence for the B10 conclusion that such dense regions form an extreme "tail" of the distribution. Tables of intrinsic populations for these regions are used in our companion study of young cluster properties and evolution. (3 data files).

A Tracker for Broken and Closely-Spaced Lines

DTIC Science & Technology

1997-10-01

to combine the current level flow estimate and the previous level flow estimate. However, the result is still not good enough for some reasons. First...geometric attributes are not good enough to discriminate line segments, when they are crowded, parallel and closely-spaced to each other. On the other...level information [10]. Still, it is not good at dealing with closely-spaced line segments. Because it requires a proper size of square neighborhood to

Behavioural responses of sardines Sardina pilchardus to simulated purse-seine capture and slipping.

PubMed

Marçalo, A; Araújo, J; Pousão-Ferreira, P; Pierce, G J; Stratoudakis, Y; Erzini, K

2013-09-01

The behavioural effects of confinement of sardine Sardina pilchardus in a purse seine were evaluated through three laboratory experiments simulating the final stages of purse seining; the process of slipping (deliberately allowing fishes to escape) and subsequent exposure to potential predators. Effects of holding time (the time S. pilchardus were held or entangled in the simulation apparatus) and S. pilchardus density were investigated. Experiment 1 compared the effect of a mild fishing stressor (20 min in the net and low S. pilchardus density) with a control (fishing not simulated) while the second and third experiments compared the mild stressor with a severe stressor (40 min in the net and high S. pilchardus density). In all cases, sea bass Dicentrarchus labrax were used as potential predators. Results indicated a significant effect of crowding time and density on the survival and behaviour of slipped S. pilchardus. After simulated fishing, S. pilchardus showed significant behavioural changes including lower swimming speed, closer approaches to predators and higher nearest-neighbour distances (wider school area) than controls, regardless of stressor severity. These results suggest that, in addition to the delayed and unobserved mortality caused by factors related to fishing operations, slipped pelagic fishes can suffer behavioural impairments that may increase vulnerability to predation. Possible sub-lethal effects of behavioural impairment on fitness are discussed, with suggestions on how stock assessment might be modified to account for both unobserved mortality and sub-lethal effects, and possible approaches to provide better estimates of unobserved mortality in the field are provided. © 2013 The Fisheries Society of the British Isles.

Eggs and hatchlings variations in desert locusts: phase related characteristics and starvation tolerance

PubMed Central

Maeno, Koutaro O.; Piou, Cyril; Ould Babah, Mohamed A.; Nakamura, Satoshi

2013-01-01

Locusts are grasshopper species that express phase polyphenism: modifying their behavior, morphology, coloration, life history and physiology in response to crowding. Desert locusts, Schistocerca gregaria, epigenetically modify progeny quality and quantity in response to crowding. Gregarious (crowded) females produce larger but fewer progeny than do solitarious (isolated) ones. The variability of progeny quality within single egg pod and the reasons why gregarious progeny have a better survival rate than solitarious ones remains unclear. This study investigated 1) the effects of rearing density on the variation in egg size within single egg pods 2) the starvation tolerance of hatchlings from mothers with different phases and 3) the physiological differences in hatchling energy reserve. Isolated females produced smaller but more eggs than did crowded ones. The variation in egg size within egg pods was greater in the latter than in the former. A negative relationship between egg size and number of eggs per egg pod was observed for both groups. Under starvation conditions, gregarious hatchlings survived significantly longer than solitarious ones. Among the solitarious hatchlings, the survival time was longer with increased hatchling body size. However, small individuals survived as long as large ones among the gregarious hatchlings. The percentage of water content per fresh body weight was almost equal between the two phases, before and after starvation. In contrast, the percentage of lipid content per dry body weight was significantly higher in gregarious hatchlings than in solitarious ones before starvation, but became almost equal after starvation. These results demonstrate that female locusts not only trade-off to modify their progeny size and number, but also vary progenies' energy reserves. We hypothesize that gregarious females enhance their fitness by producing progeny differently adapted to high environmental variability and particularly to starvation conditions. PMID:24363645

A method to estimate stellar ages from kinematical data

NASA Astrophysics Data System (ADS)

Almeida-Fernandes, F.; Rocha-Pinto, H. J.

2018-05-01

We present a method to build a probability density function (PDF) for the age of a star based on its peculiar velocities U, V, and W and its orbital eccentricity. The sample used in this work comes from the Geneva-Copenhagen Survey (GCS) that contains the spatial velocities, orbital eccentricities, and isochronal ages for about 14 000 stars. Using the GCS stars, we fitted the parameters that describe the relations between the distributions of kinematical properties and age. This parametrization allows us to obtain an age probability from the kinematical data. From this age PDF, we estimate an individual average age for the star using the most likely age and the expected age. We have obtained the stellar age PDF for the age of 9102 stars from the GCS and have shown that the distribution of individual ages derived from our method is in good agreement with the distribution of isochronal ages. We also observe a decline in the mean metallicity with our ages for stars younger than 7 Gyr, similar to the one observed for isochronal ages. This method can be useful for the estimation of rough stellar ages for those stars that fall in areas of the Hertzsprung-Russell diagram where isochrones are tightly crowded. As an example of this method, we estimate the age of Trappist-1, which is a M8V star, obtaining the age of t(UVW) = 12.50(+0.29 - 6.23) Gyr.

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.

Tree mortality from fire and bark beetles following early and late season prescribed fires in a Sierra Nevada mixed conifer forest

Treesearch

Dylan W. Schwilk; Eric E. Knapp; Scott M. Ferrenberg; Jon E. Keeley; Anthony. Caprio

2006-01-01

Over the last century, fire exclusion in the forests of the Sierra Nevada has allowed surface fuels to accumulate and has led to increased tree density. Stand composition has also been altered as shade tolerant tree species crowd out shade intolerant species. To restore forest structure and reduce the risk of large, intense fires, managers have increasingly used...

Phenotypic plasticity in Drosophila cactophilic species: the effect of competition, density, and breeding sites.

PubMed

Fanara, Juan Jose; Werenkraut, Victoria

2017-08-01

Changes in the environmental conditions experienced by naturally occurring populations are frequently accompanied by changes in adaptive traits allowing the organism to cope with environmental unpredictability. Phenotypic plasticity is a major aspect of adaptation and it has been involved in population dynamics of interacting species. In this study, phenotypic plasticity (i.e., environmental sensitivity) of morphological adaptive traits were analyzed in the cactophilic species Drosophila buzzatii and Drosophila koepferae (Diptera: Drosophilidae) considering the effect of crowding conditions (low and high density), type of competition (intraspecific and interspecific competition) and cacti hosts (Opuntia and Columnar cacti). All traits (wing length, wing width, thorax length, wing loading and wing aspect) showed significant variation for each environmental factor considered in both Drosophila species. The phenotypic plasticity pattern observed for each trait was different within and between these cactophilic Drosophila species depending on the environmental factor analyzed suggesting that body size-related traits respond almost independently to environmental heterogeneity. The effects of ecological factors analyzed in this study are discussed in order to elucidate the causal factors investigated (type of competition, crowding conditions and alternative host) affecting the election of the breeding site and/or the range of distribution of these cactophilic species. © 2016 Institute of Zoology, Chinese Academy of Sciences.

Ecological effects of full and partial protection in the crowded Mediterranean Sea: a regional meta-analysis.

PubMed

Giakoumi, Sylvaine; Scianna, Claudia; Plass-Johnson, Jeremiah; Micheli, Fiorenza; Grorud-Colvert, Kirsten; Thiriet, Pierre; Claudet, Joachim; Di Carlo, Giuseppe; Di Franco, Antonio; Gaines, Steven D; García-Charton, José A; Lubchenco, Jane; Reimer, Jessica; Sala, Enric; Guidetti, Paolo

2017-08-21

Marine protected areas (MPAs) are a cornerstone of marine conservation. Globally, the number and coverage of MPAs are increasing, but MPA implementation lags in many human-dominated regions. In areas with intense competition for space and resources, evaluation of the effects of MPAs is crucial to inform decisions. In the human-dominated Mediterranean Sea, fully protected areas occupy only 0.04% of its surface. We evaluated the impacts of full and partial protection on biomass and density of fish assemblages, some commercially important fishes, and sea urchins in 24 Mediterranean MPAs. We explored the relationships between the level of protection and MPA size, age, and enforcement. Results revealed significant positive effects of protection for fisheries target species and negative effects for urchins as their predators benefited from protection. Full protection provided stronger effects than partial protection. Benefits of full protection for fish biomass were only correlated with the level of MPA enforcement; fish density was higher in older, better enforced, and -interestingly- smaller MPAs. Our finding that even small, well-enforced, fully protected areas can have significant ecological effects is encouraging for "crowded" marine environments. However, more data are needed to evaluate sufficient MPA sizes for protecting populations of species with varying mobility levels.

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

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.

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.

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.

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.

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.

Slow-Down in Diffusion in Crowded Protein Solutions Correlates with Transient Cluster Formation.

PubMed

Nawrocki, Grzegorz; Wang, Po-Hung; Yu, Isseki; Sugita, Yuji; Feig, Michael

2017-12-14

For a long time, the effect of a crowded cellular environment on protein dynamics has been largely ignored. Recent experiments indicate that proteins diffuse more slowly in a living cell than in a diluted solution, and further studies suggest that the diffusion depends on the local surroundings. Here, detailed insight into how diffusion depends on protein-protein contacts is presented based on extensive all-atom molecular dynamics simulations of concentrated villin headpiece solutions. After force field adjustments in the form of increased protein-water interactions to reproduce experimental data, translational and rotational diffusion was analyzed in detail. Although internal protein dynamics remained largely unaltered, rotational diffusion was found to slow down more significantly than translational diffusion as the protein concentration increased. The decrease in diffusion is interpreted in terms of a transient formation of protein clusters. These clusters persist on sub-microsecond time scales and follow distributions that increasingly shift toward larger cluster size with increasing protein concentrations. Weighting diffusion coefficients estimated for different clusters extracted from the simulations with the distribution of clusters largely reproduces the overall observed diffusion rates, suggesting that transient cluster formation is a primary cause for a slow-down in diffusion upon crowding with other proteins.

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.

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.

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.

Apparent Sea Level Rise due to Loading of the Atlantic City Pier by Spectators Viewing (1929-1978) Diving Horses

NASA Astrophysics Data System (ADS)

Galvin, C.

2012-12-01

Cyril Galvin, Coastal Engineer Springfield, Virginia 22150 USA Since 1911, the Steel Pier at Atlantic City, New Jersey, has been the site of the Atlantic City tide gauge, except for two intervals: 1911-1921 when the gauge was at the Million Dollar Pier in Atlantic City, and 1985-1991 when the gauge was at the Ventnor Fishing Pier (see Table 2, Zervos, 2009). By design, the Steel Pier was an amusement pier, and its most famous amusement was the Diving Horses: they dove bareback with a woman rider from a platform about 40 feet above sea level. They did that between 1929 and 1978, except for seven years - a post-war period, 1945 to 1953, when diving was suspended. The popularity of the diving horses is recorded on photos of crowds which occupied the bleachers at the seaward end of the pier to view the diving horses. By my count, the crowd pictured in the end papers of the book by Steve Liebowitz (2009) was about 4000 people. Typically, there were multiple shows daily. The weight of the crowd, estimated from the count of the crowd, was about 150 tons. This weight was loaded down on the piles by the crowd of spectators, and unloaded between shows of the diving horses. Most of the piles supporting the pier deck were imbedded in sand newly deposited since 1850. Using Atlantic City sea levels from the PSMSL data base and historical facts from Liebowitz (2009), and beginning with a 1912 start of the tide gauge, the apparent sea level rose at a rate of 3.1mm/yr until 1929 when the horses began diving. With the 1929 start of diving, the apparent sea level rise tripled, averaging 9.4 mm/yr until the act was suspended in 1945. In the 1945-1953 interval, when the horses did not dive (no crowds on the pier), apparent sea level fell (sea level FELL) at a rate of -1.6 mm/yr. The horses resumed diving in 1953, when the apparent sea level resumed at a rate of 4.0mm/yr. This 4.0 mm/yr is identical to the longtime sea level trend (1911-2006) from Zervos (2009) of 3.99mm/yr The history of apparent sea level rise at Steel Pier is consistent with increases caused by loading the pier deck with crowds, and the absence of apparent sea level rise when the pier deck was not loaded by spectators. CG/08Aug 2012

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.

CrowdPhase: crowdsourcing the phase problem

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

Jorda, Julien; Sawaya, Michael R.; Yeates, Todd O., E-mail: yeates@mbi.ucla.edu

The idea of attacking the phase problem by crowdsourcing is introduced. Using an interactive, multi-player, web-based system, participants work simultaneously to select phase sets that correspond to better electron-density maps in order to solve low-resolution phasing problems. The human mind innately excels at some complex tasks that are difficult to solve using computers alone. For complex problems amenable to parallelization, strategies can be developed to exploit human intelligence in a collective form: such approaches are sometimes referred to as ‘crowdsourcing’. Here, a first attempt at a crowdsourced approach for low-resolution ab initio phasing in macromolecular crystallography is proposed. A collaborativemore » online game named CrowdPhase was designed, which relies on a human-powered genetic algorithm, where players control the selection mechanism during the evolutionary process. The algorithm starts from a population of ‘individuals’, each with a random genetic makeup, in this case a map prepared from a random set of phases, and tries to cause the population to evolve towards individuals with better phases based on Darwinian survival of the fittest. Players apply their pattern-recognition capabilities to evaluate the electron-density maps generated from these sets of phases and to select the fittest individuals. A user-friendly interface, a training stage and a competitive scoring system foster a network of well trained players who can guide the genetic algorithm towards better solutions from generation to generation via gameplay. CrowdPhase was applied to two synthetic low-resolution phasing puzzles and it was shown that players could successfully obtain phase sets in the 30° phase error range and corresponding molecular envelopes showing agreement with the low-resolution models. The successful preliminary studies suggest that with further development the crowdsourcing approach could fill a gap in current crystallographic methods by making it possible to extract meaningful information in cases where limited resolution might otherwise prevent initial phasing.« less

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.

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.

An efficient sequential approach to tracking multiple objects through crowds for real-time intelligent CCTV systems.

PubMed

Li, Liyuan; Huang, Weimin; Gu, Irene Yu-Hua; Luo, Ruijiang; Tian, Qi

2008-10-01

Efficiency and robustness are the two most important issues for multiobject tracking algorithms in real-time intelligent video surveillance systems. We propose a novel 2.5-D approach to real-time multiobject tracking in crowds, which is formulated as a maximum a posteriori estimation problem and is approximated through an assignment step and a location step. Observing that the occluding object is usually less affected by the occluded objects, sequential solutions for the assignment and the location are derived. A novel dominant color histogram (DCH) is proposed as an efficient object model. The DCH can be regarded as a generalized color histogram, where dominant colors are selected based on a given distance measure. Comparing with conventional color histograms, the DCH only requires a few color components (31 on average). Furthermore, our theoretical analysis and evaluation on real data have shown that DCHs are robust to illumination changes. Using the DCH, efficient implementations of sequential solutions for the assignment and location steps are proposed. The assignment step includes the estimation of the depth order for the objects in a dispersing group, one-by-one assignment, and feature exclusion from the group representation. The location step includes the depth-order estimation for the objects in a new group, the two-phase mean-shift location, and the exclusion of tracked objects from the new position in the group. Multiobject tracking results and evaluation from public data sets are presented. Experiments on image sequences captured from crowded public environments have shown good tracking results, where about 90% of the objects have been successfully tracked with the correct identification numbers by the proposed method. Our results and evaluation have indicated that the method is efficient and robust for tracking multiple objects (>or= 3) in complex occlusion for real-world surveillance scenarios.

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.

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.

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.

Nonequilibrium Fluctuations and Enhanced Diffusion of a Driven Particle in a Dense Environment

NASA Astrophysics Data System (ADS)

Illien, Pierre; Bénichou, Olivier; Oshanin, Gleb; Sarracino, Alessandro; Voituriez, Raphaël

2018-05-01

We study the diffusion of a tracer particle driven out of equilibrium by an external force and traveling in a dense environment of arbitrary density. The system evolves on a discrete lattice and its stochastic dynamics is described by a master equation. Relying on a decoupling approximation that goes beyond the naive mean-field treatment of the problem, we calculate the fluctuations of the position of the tracer around its mean value on a lattice of arbitrary dimension, and with different boundary conditions. We reveal intrinsically nonequilibrium effects, such as enhanced diffusivity of the tracer induced by both the crowding interactions and the external driving. We finally consider the high-density and low-density limits of the model and show that our approximation scheme becomes exact in these limits.

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/

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.

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.

Investigating molecular crowding within nuclear pores using polarization-PALM

PubMed Central

Fu, Guo; Tu, Li-Chun; Zilman, Anton

2017-01-01

The key component of the nuclear pore complex (NPC) controlling permeability, selectivity, and the speed of nucleocytoplasmic transport is an assembly of natively unfolded polypeptides, which contain phenylalanine-glycine (FG) binding sites for nuclear transport receptors. The architecture and dynamics of the FG-network have been refractory to characterization due to the paucity of experimental methods able to probe the mobility and density of the FG-polypeptides and embedded macromolecules within intact NPCs. Combining fluorescence polarization, super-resolution microscopy, and mathematical analyses, we examined the rotational mobility of fluorescent probes at various locations within the FG-network under different conditions. We demonstrate that polarization PALM (p-PALM) provides a rich source of information about low rotational mobilities that are inaccessible with bulk fluorescence anisotropy approaches, and anticipate that p-PALM is well-suited to explore numerous crowded cellular environments. In total, our findings indicate that the NPC’s internal organization consists of multiple dynamic environments with different local properties. PMID:28949296

The role of orbital dynamics and cloud-cloud collisions in the formation of giant molecular clouds in global spiral structures

NASA Technical Reports Server (NTRS)

Roberts, William W., Jr.; Stewart, Glen R.

1987-01-01

The role of orbit crowding and cloud-cloud collisions in the formation of GMCs and their organization in global spiral structure is investigated. Both N-body simulations of the cloud system and a detailed analysis of individual particle orbits are used to develop a conceptual understanding of how individual clouds participate in the collective density response. Detailed comparisons are made between a representative cloud-particle simulation in which the cloud particles collide inelastically with one another and give birth to and subsequently interact with young star associations and stripped down simulations in which the cloud particles are allowed to follow ballistic orbits in the absence of cloud-cloud collisions or any star formation processes. Orbit crowding is then related to the behavior of individual particle trajectories in the galactic potential field. The conceptual picture of how GMCs are formed in the clumpy ISMs of spiral galaxies is formulated, and the results are compared in detail with those published by other authors.

Dengue Seroprevalence and Risk Factors for Past and Recent Viral Transmission in Venezuela: A Comprehensive Community-Based Study

PubMed Central

Velasco-Salas, Zoraida I.; Sierra, Gloria M.; Guzmán, Diamelis M.; Zambrano, Julio; Vivas, Daniel; Comach, Guillermo; Wilschut, Jan C.; Tami, Adriana

2014-01-01

Dengue transmission in Venezuela has become perennial and a major public health problem. The increase in frequency and magnitude of recent epidemics prompted a comprehensive community-based cross-sectional study of 2,014 individuals in high-incidence neighborhoods of Maracay, Venezuela. We found a high seroprevalence (77.4%), with 10% of people experiencing recent infections. Multivariate logistic regression analysis showed that poverty-related socioeconomic factors (place and duration of residence, crowding, household size, and living in a shack) and factors/constraints related to intradomiciliary potential mosquito breeding sites (storing water and used tires) were linked with a greater risk of acquiring a dengue infection. Our results also suggest that transmission occurs mainly at home. The combination of increasingly crowded living conditions, growing population density, precarious homes, and water storage issues caused by enduring problems in public services in Maracay are the most likely factors that determine the permanent dengue transmission and the failure of vector control programs. PMID:25223944

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.

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…

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

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

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.

High-Performance Energy-Efficient Cool Metal Roof Assemblies Utilizing Building Integrated Renewable Solar Energy Technologies for New and Retrofit Building Construction

DTIC Science & Technology

2014-04-01

technology described in this proposal was first commercialized in 2004. It has been installed in 35 states and 5 countries primarily on residential ...temperatures. o Rainwater harvesting systems help reduce demands on potable water systems and help crowded cities manage stormwater drainage problems...of high density polyisocyanurate rigid insulation board installed over the existing roof and between the sub-purlins with the top layer taped to

Depletion forces drive polymer-like self-assembly in vibrofluidized granular materials†

PubMed Central

Nossal, Ralph

2011-01-01

Ranging from nano- to granular-scales, control of particle assembly can be achieved by limiting the available free space, for example by increasing the concentration of particles (“crowding”) or through their restriction to 2D environments. It is unclear, however, if self-assembly principles governing thermally-equilibrated molecules can also apply to mechanically-excited macroscopic particles in non-equilibrium steady-state. Here we show that low densities of vibrofluidized steel rods, when crowded by high densities of spheres and confined to quasi-2D planes, can self-assemble into linear polymer-like structures. Our 2D Monte Carlo simulations show similar finite sized aggregates in thermally equilibrated binary mixtures. Using theory and simulations, we demonstrate how depletion interactions create oriented “binding” forces between rigid rods to form these “living polymers.” Unlike rod-sphere mixtures in 3D that can demonstrate well-defined equilibrium phases, our mixtures confined to 2D lack these transitions because lower dimensionality favors the formation of linear aggregates, thus suppressing a true phase transition. The qualitative and quantitative agreement between equilibrium and granular patterning for these mixtures suggests that entropy maximization is the determining driving force for bundling. Furthermore, this study uncovers a previously unknown patterning behavior at both the granular and nanoscales, and may provide insights into the role of crowding at interfaces in molecular assembly. PMID:22039392

Mean-time-to-failure study of flip chip solder joints on Cu/Ni(V)/Al thin-film under-bump-metallization

NASA Astrophysics Data System (ADS)

Choi, W. J.; Yeh, E. C. C.; Tu, K. N.

2003-11-01

Electromigration of eutectic SnPb flip chip solder joints and their mean-time-to-failure (MTTF) have been studied in the temperature range of 100 to 140 °C with current densities of 1.9 to 2.75×104 A/cm2. In these joints, the under-bump-metallization (UBM) on the chip side is a multilayer thin film of Al/Ni(V)/Cu, and the metallic bond-pad on the substrate side is a very thick, electroless Ni layer covered with 30 nm of Au. When stressed at the higher current densities, the MTTF was found to decrease much faster than what is expected from the published Black's equation. The failure occurred by interfacial void propagation at the cathode side, and it is due to current crowding near the contact interface between the solder bump and the thin-film UBM. The current crowding is confirmed by a simulation of current distribution in the solder joint. Besides the interfacial void formation, the intermetallic compounds formed on the UBM as well as the Ni(V) film in the UBM have been found to dissolve completely into the solder bump during electromigration. Therefore, the electromigation failure is a combination of the interfacial void formation and the loss of UBM. Similar findings in eutectic SnAgCu flip chip solder joints have also been obtained and compared.

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.

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).

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/.

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.

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

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?

Population size estimation of female sex workers in Iran: Synthesis of methods and results.

PubMed

Sharifi, Hamid; Karamouzian, Mohammad; Baneshi, Mohammad Reza; Shokoohi, Mostafa; Haghdoost, AliAkbar; McFarland, Willi; Mirzazadeh, Ali

2017-01-01

Estimating the number of key populations at risk of HIV is essential for planning, monitoring, and evaluating prevention, care, and treatment programmes. We conducted this study to estimate the number of female sex workers (FSW) in major cities of Iran. We used three population size estimation methods (i.e., wisdom of the crowds, multiplier method, and network scale-up) to calculate the number of FSW in 13 cities in Iran. The wisdom of the crowds and multiplier methods were integrated into a nationwide bio-behavioural surveillance survey in 2015, and the network scale-up method was included in a national survey of the general population in 2014. The median of the three methods was used to calculate the proportion of the adult female population who practice sex work in the 13 cities. These figures were then extrapolated to provide a national population size estimation of FSW across urban areas. The population size of FSW was 91,500 (95% Uncertainty Intervals [UIs] 61,400-117,700), corresponding to 1.43% (95% UIs 0.96-1.84) of the adult (i.e., 15-49 year-old) female population living in these 13 cities. The projected numbers of FSW for all 31 provincial capital cities were 130,800 (95% UIs 87,800-168,200) and 228,700 (95% UIs 153,500-294,300) for all urban settings in Iran. Using methods of comparable rigor, our study provided a data-driven national estimate of the population size of FSW in urban areas of Iran. Our findings provide vital information for enhancing HIV programme planning and lay a foundation for assessing the impact of harm reduction efforts within this marginalized population.

Population size estimation of female sex workers in Iran: Synthesis of methods and results

PubMed Central

Sharifi, Hamid; Karamouzian, Mohammad; Baneshi, Mohammad Reza; Shokoohi, Mostafa; Haghdoost, AliAkbar; McFarland, Willi

2017-01-01

Introduction Estimating the number of key populations at risk of HIV is essential for planning, monitoring, and evaluating prevention, care, and treatment programmes. We conducted this study to estimate the number of female sex workers (FSW) in major cities of Iran. Methods We used three population size estimation methods (i.e., wisdom of the crowds, multiplier method, and network scale-up) to calculate the number of FSW in 13 cities in Iran. The wisdom of the crowds and multiplier methods were integrated into a nationwide bio-behavioural surveillance survey in 2015, and the network scale-up method was included in a national survey of the general population in 2014. The median of the three methods was used to calculate the proportion of the adult female population who practice sex work in the 13 cities. These figures were then extrapolated to provide a national population size estimation of FSW across urban areas. Results The population size of FSW was 91,500 (95% Uncertainty Intervals [UIs] 61,400–117,700), corresponding to 1.43% (95% UIs 0.96–1.84) of the adult (i.e., 15–49 year-old) female population living in these 13 cities. The projected numbers of FSW for all 31 provincial capital cities were 130,800 (95% UIs 87,800–168,200) and 228,700 (95% UIs 153,500–294,300) for all urban settings in Iran. Conclusions Using methods of comparable rigor, our study provided a data-driven national estimate of the population size of FSW in urban areas of Iran. Our findings provide vital information for enhancing HIV programme planning and lay a foundation for assessing the impact of harm reduction efforts within this marginalized population. PMID:28796847

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.

Origins of microstructural transformations in charged vesicle suspensions: the crowding hypothesis.

PubMed

Seth, Mansi; Ramachandran, Arun; Murch, Bruce P; Leal, L Gary

2014-09-02

It is observed that charged unilamellar vesicles in a suspension can spontaneously deflate and subsequently transition to form bilamellar vesicles, even in the absence of externally applied triggers such as salt or temperature gradients. We provide strong evidence that the driving force for this deflation-induced transition is the repulsive electrostatic pressure between charged vesicles in concentrated suspensions, above a critical effective volume fraction. We use volume fraction measurements and cryogenic transmission electron microscopy imaging to quantitatively follow both the macroscopic and microstructural time-evolution of cationic diC18:1 DEEDMAC vesicle suspensions at different surfactant and salt concentrations. A simple model is developed to estimate the extent of deflation of unilamellar vesicles caused by electrostatic interactions with neighboring vesicles. It is determined that when the effective volume fraction of the suspension exceeds a critical value, charged vesicles in a suspension can experience "crowding" due to overlap of their electrical double layers, which can result in deflation and subsequent microstructural transformations to reduce the effective volume fraction of the suspension. Ordinarily in polydisperse colloidal suspensions, particles interacting via a repulsive potential transform into a glassy state above a critical volume fraction. The behavior of charged vesicle suspensions reported in this paper thus represents a new mechanism for the relaxation of repulsive interactions in crowded situations.

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…

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.

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.

The JCMT Plane Survey: early results from the ℓ = 30° field

NASA Astrophysics Data System (ADS)

Moore, T. J. T.; Plume, R.; Thompson, M. A.; Parsons, H.; Urquhart, J. S.; Eden, D. J.; Dempsey, J. T.; Morgan, L. K.; Thomas, H. S.; Buckle, J.; Brunt, C. M.; Butner, H.; Carretero, D.; Chrysostomou, A.; deVilliers, H. M.; Fich, M.; Hoare, M. G.; Manser, G.; Mottram, J. C.; Natario, C.; Olguin, F.; Peretto, N.; Polychroni, D.; Redman, R. O.; Rigby, A. J.; Salji, C.; Summers, L. J.; Berry, D.; Currie, M. J.; Jenness, T.; Pestalozzi, M.; Traficante, A.; Bastien, P.; diFrancesco, J.; Davis, C. J.; Evans, A.; Friberg, P.; Fuller, G. A.; Gibb, A. G.; Gibson, S.; Hill, T.; Johnstone, D.; Joncas, G.; Longmore, S. N.; Lumsden, S. L.; Martin, P. G.; Nguyen Lu'o'ng, Q.; Pineda, J. E.; Purcell, C.; Richer, J. S.; Schieven, G. H.; Shipman, R.; Spaans, M.; Taylor, A. R.; Viti, S.; Weferling, B.; White, G. J.; Zhu, M.

2015-11-01

We present early results from the JCMT (James Clerk Maxwell Telescope) Plane Survey (JPS), which has surveyed the northern inner Galactic plane between longitudes ℓ = 7° and ℓ = 63° in the 850-μm continuum with SCUBA-2 (Submm Common-User Bolometer Array 2), as part of the JCMT Legacy Survey programme. Data from the ℓ = 30° survey region, which contains the massive-star-forming regions W43 and G29.96, are analysed after approximately 40 per cent of the observations had been completed. The pixel-to-pixel noise is found to be 19 mJy beam-1 after a smooth over the beam area, and the projected equivalent noise levels in the final survey are expected to be around 10 mJy beam-1. An initial extraction of compact sources was performed using the FELLWALKER method, resulting in the detection of 1029 sources above a 5σ surface-brightness threshold. The completeness limits in these data are estimated to be around 0.2 Jy beam-1 (peak flux density) and 0.8 Jy (integrated flux density) and are therefore probably already dominated by source confusion in this relatively crowded section of the survey. The flux densities of extracted compact sources are consistent with those of matching detections in the shallower APEX (Atacama Pathfinder Experiment) Telescope Large Area Survey of the Galaxy (ATLASGAL) survey. We analyse the virial and evolutionary state of the detected clumps in the W43 star-forming complex and find that they appear younger than the Galactic-plane average.

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.

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.

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

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

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.

Surface charge- and space-dependent transport of proteins in crowded environments of nanotailored posts.

PubMed

Choi, Chang Kyoung; Fowlkes, Jason D; Retterer, Scott T; Siuti, Piro; Iyer, Sukanya; Doktycz, Mitchel J

2010-06-22

The reaction and diffusion of molecules across barriers and through crowded environments is integral to biological system function and to separation technologies. Ordered, microfabricated post arrays are a promising route to creating synthetic barriers with controlled chemical and physical characteristics. They can be used to create crowded environments, to mimic aspects of cellular membranes, and to serve as engineered replacements of polymer-based separation media. Here, the translational diffusion of fluorescein isothiocyante and various forms of green fluorescent protein (GFP), including "supercharged" variants, are examined in a silicon-based post array environment. The technique of fluorescence recovery after photobleaching (FRAP) is combined with analytical approximations and numerical simulations to assess the relative effects of reaction and diffusion on molecular transport, respectively. FRAP experiments were conducted for 64 different cases where the molecular species, the density of the posts, and the chemical surface charge of the posts were varied. In all cases, the dense packing of the posts hindered the diffusive transport of the fluorescent species. The supercharged GFPs strongly interacted with oppositely charged surfaces. With similar molecular and surface charges, transport is primarily limited by hindered diffusion. For conventional, enhanced GFP in a positively charged surface environment, transport was limited by the coupled action of hindered diffusion and surface interaction with the posts. Quantification of the size-, space-, time-, and charge-dependent translational diffusion in the post array environments can provide insight into natural processes and guide the design and development of selective membrane systems.

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.

A Joint Gaussian Process Model for Active Visual Recognition with Expertise Estimation in Crowdsourcing

PubMed Central

Long, Chengjiang; Hua, Gang; Kapoor, Ashish

2015-01-01

We present a noise resilient probabilistic model for active learning of a Gaussian process classifier from crowds, i.e., a set of noisy labelers. It explicitly models both the overall label noise and the expertise level of each individual labeler with two levels of flip models. Expectation propagation is adopted for efficient approximate Bayesian inference of our probabilistic model for classification, based on which, a generalized EM algorithm is derived to estimate both the global label noise and the expertise of each individual labeler. The probabilistic nature of our model immediately allows the adoption of the prediction entropy for active selection of data samples to be labeled, and active selection of high quality labelers based on their estimated expertise to label the data. We apply the proposed model for four visual recognition tasks, i.e., object category recognition, multi-modal activity recognition, gender recognition, and fine-grained classification, on four datasets with real crowd-sourced labels from the Amazon Mechanical Turk. The experiments clearly demonstrate the efficacy of the proposed model. In addition, we extend the proposed model with the Predictive Active Set Selection Method to speed up the active learning system, whose efficacy is verified by conducting experiments on the first three datasets. The results show our extended model can not only preserve a higher accuracy, but also achieve a higher efficiency. PMID:26924892

The distribution and numbers of cheetah (Acinonyx jubatus) in southern Africa

PubMed Central

Jacobson, Andrew P.; Schoonover, Rebecca F.; Groom, Rosemary J.; Horgan, Jane; Keeping, Derek; Klein, Rebecca; Marnewick, Kelly; Maude, Glyn; Melzheimer, Jörg; Mills, Gus; van der Merwe, Vincent; van der Meer, Esther; van Vuuren, Rudie J.; Wachter, Bettina

2017-01-01

Assessing the numbers and distribution of threatened species is a central challenge in conservation, often made difficult because the species of concern are rare and elusive. For some predators, this may be compounded by their being sparsely distributed over large areas. Such is the case with the cheetah Acinonyx jubatus. The IUCN Red List process solicits comments, is democratic, transparent, widely-used, and has recently assessed the species. Here, we present additional methods to that process and provide quantitative approaches that may afford greater detail and a benchmark against which to compare future assessments. The cheetah poses challenges, but also affords unique opportunities. It is photogenic, allowing the compilation of thousands of crowd-sourced data. It is also persecuted for killing livestock, enabling estimation of local population densities from the numbers persecuted. Documented instances of persecution in areas with known human and livestock density mean that these data can provide an estimate of where the species may or may not occur in areas without observational data. Compilations of extensive telemetry data coupled with nearly 20,000 additional observations from 39 sources show that free-ranging cheetahs were present across approximately 789,700 km2 of Namibia, Botswana, South Africa, and Zimbabwe (56%, 22%, 12% and 10% respectively) from 2010 to 2016, with an estimated adult population of 3,577 animals. We identified a further 742,800 km2 of potential cheetah habitat within the study region with low human and livestock densities, where another ∼3,250 cheetahs may occur. Unlike many previous estimates, we make the data available and provide explicit information on exactly where cheetahs occur, or are unlikely to occur. We stress the value of gathering data from public sources though these data were mostly from well-visited protected areas. There is a contiguous, transboundary population of cheetah in southern Africa, known to be the largest in the world. We suggest that this population is more threatened than believed due to the concentration of about 55% of free-ranging individuals in two ecoregions. This area overlaps with commercial farmland with high persecution risk; adult cheetahs were removed at the rate of 0.3 individuals per 100 km2 per year. Our population estimate for confirmed cheetah presence areas is 11% lower than the IUCN’s current assessment for the same region, lending additional support to the recent call for the up-listing of this species from vulnerable to endangered status. PMID:29250465

The distribution and numbers of cheetah (Acinonyx jubatus) in southern Africa.

PubMed

Weise, Florian J; Vijay, Varsha; Jacobson, Andrew P; Schoonover, Rebecca F; Groom, Rosemary J; Horgan, Jane; Keeping, Derek; Klein, Rebecca; Marnewick, Kelly; Maude, Glyn; Melzheimer, Jörg; Mills, Gus; van der Merwe, Vincent; van der Meer, Esther; van Vuuren, Rudie J; Wachter, Bettina; Pimm, Stuart L

2017-01-01

Assessing the numbers and distribution of threatened species is a central challenge in conservation, often made difficult because the species of concern are rare and elusive. For some predators, this may be compounded by their being sparsely distributed over large areas. Such is the case with the cheetah Acinonyx jubatus. The IUCN Red List process solicits comments, is democratic, transparent, widely-used, and has recently assessed the species. Here, we present additional methods to that process and provide quantitative approaches that may afford greater detail and a benchmark against which to compare future assessments. The cheetah poses challenges, but also affords unique opportunities. It is photogenic, allowing the compilation of thousands of crowd-sourced data. It is also persecuted for killing livestock, enabling estimation of local population densities from the numbers persecuted. Documented instances of persecution in areas with known human and livestock density mean that these data can provide an estimate of where the species may or may not occur in areas without observational data. Compilations of extensive telemetry data coupled with nearly 20,000 additional observations from 39 sources show that free-ranging cheetahs were present across approximately 789,700 km 2 of Namibia, Botswana, South Africa, and Zimbabwe (56%, 22%, 12% and 10% respectively) from 2010 to 2016, with an estimated adult population of 3,577 animals. We identified a further 742,800 km 2 of potential cheetah habitat within the study region with low human and livestock densities, where another ∼3,250 cheetahs may occur. Unlike many previous estimates, we make the data available and provide explicit information on exactly where cheetahs occur, or are unlikely to occur. We stress the value of gathering data from public sources though these data were mostly from well-visited protected areas. There is a contiguous, transboundary population of cheetah in southern Africa, known to be the largest in the world. We suggest that this population is more threatened than believed due to the concentration of about 55% of free-ranging individuals in two ecoregions. This area overlaps with commercial farmland with high persecution risk; adult cheetahs were removed at the rate of 0.3 individuals per 100 km 2 per year. Our population estimate for confirmed cheetah presence areas is 11% lower than the IUCN's current assessment for the same region, lending additional support to the recent call for the up-listing of this species from vulnerable to endangered status.

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.

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

Massive stellar systems: observational challenges and perspectives in the E-ELT era

NASA Astrophysics Data System (ADS)

Bono, G.; Braga, V. F.; Ferraro, I.; Fiorentino, G.; Gilmozzi, R.; Iannicola, G.; Magurno, D.; Matsunaga, N.; Monelli, M.; Rastello, S.

2017-03-01

We introduce the empirical framework concerning optical and near-infrared (NIR) photometry of crowded stellar fields. In particular, we address the impact that linear detectors and analytical PSF played in improving the accuracy and the precision of multi-band color-magnitude diagrams (CMDs). We focus our attention on recent findings based on deep NIR images collected with Adaptive Optics (AO) systems at the 8-10m class telescopes and discuss pros and cons of the different approaches. We also discuss the estimate of the absolute age of globular clusters using a well defined knee along the lower main sequence. We mention the role which the current AO-assisted instruments will have in addressing longstanding astrophysical problems of the Galactic center. Finally, we outline the role of first generation of E-ELT instruments upon photometry and spectroscopy of crowded stellar fields.

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

Kohrs, J.T.

It is popularly reported that rapid population influx due to energy development in the Rocky Mountain states has led to an increase in numerous social disruptions. Professional literature dealing with immigration, population density, crowding, urbanization or new communities does not appear generalizable to rapid population influx in western states. The current study is thus an exploratory one, designed to investigate whether social disruptions over a 15 year period, including institutional admissions, auto accidents, bankruptcies, cost of criminal administration, crime, divorce, fires, infant deaths, school dropouts and welfare recipients occur along with boom growth in Wyoming.

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/

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.

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.

Competitive interaction of Axonopus compressus and Asystasia gangetica under contrasting sunlight intensity.

PubMed

Samedani, B; Juraimi, A S; Anwar, M P; Rafii, M Y; Sheikh Awadz, S H; Anuar, A R

2013-01-01

Axonopus compressus is one of the native soft grass species in oil palm in Malaysia which can be used as a cover crop. The competitive ability of A. compressus to overcome A. gangetica was studied using multiple-density, multiple-proportion replacements series under a glasshouse and full sunlight conditions in a poly bag for 10 weeks. A. compressus produced more dry weight and leaf area when competing against A. gangetica than in monoculture at both densities in the full sunlight and at high density in the shade. Moreover, the relative yield and relative crowding coefficients also indicated A. compressus is a stronger competitor than A. gangetica at both densities in the full sunlight and high density in the shade. It seemed that A. gangetica plants in the shade did not compete with each other and were more competitive against A. compressus as could influence A. compressus height in the shade. It is concluded that although suppression of A. gangetica by A. compressus occurred under full sunlight, irrespective of plant density, this ability reduced under shade as A. compressus density decreased. The result suggests that A. compressus in high density could be considered as a candidate for cover crops under oil palm canopy.

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.).

The development of a quick-running prediction tool for the assessment of human injury owing to terrorist attack within crowded metropolitan environments

PubMed Central

Pope, Daniel J.

2011-01-01

In the aftermath of the London ‘7/7’ attacks in 2005, UK government agencies required the development of a quick-running tool to predict the weapon and injury effects caused by the initiation of a person borne improvised explosive device (PBIED) within crowded metropolitan environments. This prediction tool, termed the HIP (human injury predictor) code, was intended to: — assist the security services to encourage favourable crowd distributions and densities within scenarios of ‘sensitivity’;— provide guidance to security engineers concerning the most effective location for protection systems;— inform rescue services as to where, in the case of such an event, individuals with particular injuries will be located;— assist in training medical personnel concerning the scope and types of injuries that would be sustained as a consequence of a particular attack;— assist response planners in determining the types of medical specialists (burns, traumatic amputations, lungs, etc.) required and thus identify the appropriate hospitals to receive the various casualty types.This document describes the algorithms used in the development of this tool, together with the pertinent underpinning physical processes. From its rudimentary beginnings as a simple spreadsheet, the HIP code now has a graphical user interface (GUI) that allows three-dimensional visualization of results and intuitive scenario set-up. The code is underpinned by algorithms that predict the pressure and momentum outputs produced by PBIEDs within open and confined environments, as well as the trajectories of shrapnel deliberately placed within the device to increase injurious effects. Further logic has been implemented to transpose these weapon effects into forms of human injury depending on where individuals are located relative to the PBIED. Each crowd member is subdivided into representative body parts, each of which is assigned an abbreviated injury score after a particular calculation cycle. The injury levels of each affected body part are then summated and a triage state assigned for each individual crowd member based on the criteria specified within the ‘injury scoring system’. To attain a comprehensive picture of a particular event, it is important that a number of simulations, using what is substantively the same scenario, are undertaken with natural variation being applied to the crowd distributions and the PBIED output. Accurate mathematical representation of such complex phenomena is challenging, particularly as the code must be quick-running to be of use to the stakeholder community. In addition to discussing the background and motivation for the algorithm and GUI development, this document also discusses the steps taken to validate the tool and the plans for further functionality implementation. PMID:21149351

The development of a quick-running prediction tool for the assessment of human injury owing to terrorist attack within crowded metropolitan environments.

PubMed

Pope, Daniel J

2011-01-27

In the aftermath of the London '7/7' attacks in 2005, UK government agencies required the development of a quick-running tool to predict the weapon and injury effects caused by the initiation of a person borne improvised explosive device (PBIED) within crowded metropolitan environments. This prediction tool, termed the HIP (human injury predictor) code, was intended to:--assist the security services to encourage favourable crowd distributions and densities within scenarios of 'sensitivity'; --provide guidance to security engineers concerning the most effective location for protection systems; --inform rescue services as to where, in the case of such an event, individuals with particular injuries will be located; --assist in training medical personnel concerning the scope and types of injuries that would be sustained as a consequence of a particular attack; --assist response planners in determining the types of medical specialists (burns, traumatic amputations, lungs, etc.) required and thus identify the appropriate hospitals to receive the various casualty types. This document describes the algorithms used in the development of this tool, together with the pertinent underpinning physical processes. From its rudimentary beginnings as a simple spreadsheet, the HIP code now has a graphical user interface (GUI) that allows three-dimensional visualization of results and intuitive scenario set-up. The code is underpinned by algorithms that predict the pressure and momentum outputs produced by PBIEDs within open and confined environments, as well as the trajectories of shrapnel deliberately placed within the device to increase injurious effects. Further logic has been implemented to transpose these weapon effects into forms of human injury depending on where individuals are located relative to the PBIED. Each crowd member is subdivided into representative body parts, each of which is assigned an abbreviated injury score after a particular calculation cycle. The injury levels of each affected body part are then summated and a triage state assigned for each individual crowd member based on the criteria specified within the 'injury scoring system'. To attain a comprehensive picture of a particular event, it is important that a number of simulations, using what is substantively the same scenario, are undertaken with natural variation being applied to the crowd distributions and the PBIED output. Accurate mathematical representation of such complex phenomena is challenging, particularly as the code must be quick-running to be of use to the stakeholder community. In addition to discussing the background and motivation for the algorithm and GUI development, this document also discusses the steps taken to validate the tool and the plans for further functionality implementation.

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

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.

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.

Integration of Social Information by Human Groups.

PubMed

Granovskiy, Boris; Gold, Jason M; Sumpter, David J T; Goldstone, Robert L

2015-07-01

We consider a situation in which individuals search for accurate decisions without direct feedback on their accuracy, but with information about the decisions made by peers in their group. The "wisdom of crowds" hypothesis states that the average judgment of many individuals can give a good estimate of, for example, the outcomes of sporting events and the answers to trivia questions. Two conditions for the application of wisdom of crowds are that estimates should be independent and unbiased. Here, we study how individuals integrate social information when answering trivia questions with answers that range between 0% and 100% (e.g., "What percentage of Americans are left-handed?"). We find that, consistent with the wisdom of crowds hypothesis, average performance improves with group size. However, individuals show a consistent bias to produce estimates that are insufficiently extreme. We find that social information provides significant, albeit small, improvement to group performance. Outliers with answers far from the correct answer move toward the position of the group mean. Given that these outliers also tend to be nearer to 50% than do the answers of other group members, this move creates group polarization away from 50%. By looking at individual performance over different questions we find that some people are more likely to be affected by social influence than others. There is also evidence that people differ in their competence in answering questions, but lack of competence is not significantly correlated with willingness to change guesses. We develop a mathematical model based on these results that postulates a cognitive process in which people first decide whether to take into account peer guesses, and if so, to move in the direction of these guesses. The size of the move is proportional to the distance between their own guess and the average guess of the group. This model closely approximates the distribution of guess movements and shows how outlying incorrect opinions can be systematically removed from a group resulting, in some situations, in improved group performance. However, improvement is only predicted for cases in which the initial guesses of individuals in the group are biased. Copyright © 2015 Cognitive Science Society, Inc.

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.

Effects of environmental factors and appendage injury on the wing variation in the cricket Velarifictorus ornatus

PubMed Central

Zhao, Lü-Quan; Zhu, Dao-Hong

2014-01-01

Abstract The effects of environmental factors and appendage injury on the wing variation in Velarifictorus ornatus (Shiraki) (Orthoptera: Gryllidae) were investigated. The percentage of micropters was more than 95% when the nymphs were reared at constant photoperiods, and changing photoperiod did not affect wing variation in V. ornatus at 25 or 30°C. In the crowding experiment, the percentage of macropters was only 11.2% when the nymphs were reared separately at 25°C. In contrast, the percentage of macropters was significantly higher when the rearing density was increased to two nymphs per container and lower when the rearing density was increased to five or 10 nymphs per container. These results indicate that low and high rearing densities induce micropters, but intermediate rearing density stimulates the formation of macropters. Meanwhile, severance of appendages, such as antennae, femora, and tibiae, in the nymph stage exerted a micropterizing effect. The period sensitive to such stresses ranged from 35 to 60 days of nymph development. PMID:25368061

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.

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).

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.

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)

Dengue seroprevalence and risk factors for past and recent viral transmission in Venezuela: a comprehensive community-based study.

PubMed

Velasco-Salas, Zoraida I; Sierra, Gloria M; Guzmán, Diamelis M; Zambrano, Julio; Vivas, Daniel; Comach, Guillermo; Wilschut, Jan C; Tami, Adriana

2014-11-01

Dengue transmission in Venezuela has become perennial and a major public health problem. The increase in frequency and magnitude of recent epidemics prompted a comprehensive community-based cross-sectional study of 2,014 individuals in high-incidence neighborhoods of Maracay, Venezuela. We found a high seroprevalence (77.4%), with 10% of people experiencing recent infections. Multivariate logistic regression analysis showed that poverty-related socioeconomic factors (place and duration of residence, crowding, household size, and living in a shack) and factors/constraints related to intradomiciliary potential mosquito breeding sites (storing water and used tires) were linked with a greater risk of acquiring a dengue infection. Our results also suggest that transmission occurs mainly at home. The combination of increasingly crowded living conditions, growing population density, precarious homes, and water storage issues caused by enduring problems in public services in Maracay are the most likely factors that determine the permanent dengue transmission and the failure of vector control programs. © The American Society of Tropical Medicine and Hygiene.

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.

Social contact patterns of infants in deciding vaccination strategy: a prospective, cross-sectional, single-centre study.

PubMed

Oguz, M M; Camurdan, A D; Aksakal, F N; Akcaboy, M; Altinel Acoglu, E

2018-05-09

Social contact between individuals is believed to be a fundamental cause in the transmission of many respiratory tract infections. Because they have not yet been fully vaccinated, infants are at high risk for contracting whooping cough, influenza and their serious complications. Therefore, determining infant social contact patterns is an important step in protecting them from respiratory tract infection. This study included 1200 healthy infants (<12 months of age). Social contact diaries were used to estimate the frequency and nature of the infants' social contacts. This survey also gathered information regarding the infants' respiratory symptoms and their frequency of attendance at crowded places over a period of 1 week. The diary return rate was 83.8% (N = 1006), and there was a total of 4706 contacts reported for these infants. The median daily contact number per capita was 4 (range 1-18). The median number of contacts with adolescents was 0 (range 0-7). Of the infants, 50.3% had contact with non-household individuals. The mothers had the longest contacts with their babies. Contacts with school children, frequency of attendance at crowded places and age were determined to be significant effective factors for reporting respiratory symptoms. Results suggest that school-age siblings and the mothers should be primarily vaccinated, and parents should keep their babies away from crowded places for protecting their infants.

A Crowd-Sourcing Indoor Localization Algorithm via Optical Camera on a Smartphone Assisted by Wi-Fi Fingerprint RSSI

PubMed Central

Chen, Wei; Wang, Weiping; Li, Qun; Chang, Qiang; Hou, Hongtao

2016-01-01

Indoor positioning based on existing Wi-Fi fingerprints is becoming more and more common. Unfortunately, the Wi-Fi fingerprint is susceptible to multiple path interferences, signal attenuation, and environmental changes, which leads to low accuracy. Meanwhile, with the recent advances in charge-coupled device (CCD) technologies and the processing speed of smartphones, indoor positioning using the optical camera on a smartphone has become an attractive research topic; however, the major challenge is its high computational complexity; as a result, real-time positioning cannot be achieved. In this paper we introduce a crowd-sourcing indoor localization algorithm via an optical camera and orientation sensor on a smartphone to address these issues. First, we use Wi-Fi fingerprint based on the K Weighted Nearest Neighbor (KWNN) algorithm to make a coarse estimation. Second, we adopt a mean-weighted exponent algorithm to fuse optical image features and orientation sensor data as well as KWNN in the smartphone to refine the result. Furthermore, a crowd-sourcing approach is utilized to update and supplement the positioning database. We perform several experiments comparing our approach with other positioning algorithms on a common smartphone to evaluate the performance of the proposed sensor-calibrated algorithm, and the results demonstrate that the proposed algorithm could significantly improve accuracy, stability, and applicability of positioning. PMID:27007379

A Crowd-Sourcing Indoor Localization Algorithm via Optical Camera on a Smartphone Assisted by Wi-Fi Fingerprint RSSI.

PubMed

Chen, Wei; Wang, Weiping; Li, Qun; Chang, Qiang; Hou, Hongtao

2016-03-19

Indoor positioning based on existing Wi-Fi fingerprints is becoming more and more common. Unfortunately, the Wi-Fi fingerprint is susceptible to multiple path interferences, signal attenuation, and environmental changes, which leads to low accuracy. Meanwhile, with the recent advances in charge-coupled device (CCD) technologies and the processing speed of smartphones, indoor positioning using the optical camera on a smartphone has become an attractive research topic; however, the major challenge is its high computational complexity; as a result, real-time positioning cannot be achieved. In this paper we introduce a crowd-sourcing indoor localization algorithm via an optical camera and orientation sensor on a smartphone to address these issues. First, we use Wi-Fi fingerprint based on the K Weighted Nearest Neighbor (KWNN) algorithm to make a coarse estimation. Second, we adopt a mean-weighted exponent algorithm to fuse optical image features and orientation sensor data as well as KWNN in the smartphone to refine the result. Furthermore, a crowd-sourcing approach is utilized to update and supplement the positioning database. We perform several experiments comparing our approach with other positioning algorithms on a common smartphone to evaluate the performance of the proposed sensor-calibrated algorithm, and the results demonstrate that the proposed algorithm could significantly improve accuracy, stability, and applicability of positioning.

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.

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.

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.

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.

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).

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.

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.

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.

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.

Public Relations: Ketchum brands new product with innovative PR strategy.

PubMed

2006-01-01

Novartis Pharmaceuticals tapped publis relations (PR) giant Ketchum earlier this year to spearhead a marketing campaign that would make its new U.S. Food and Drug Administration-approved prescription-based medication, Enablex, stand out among the crowd in over active bladder (OAB) treatment. OAB is a disorder that affects an estimated 33 million Americans making this treatment highly in demand with consumers and highly competitive with other pharmaceutical companies.

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

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

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.

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.

Household-level risk factors for influenza among young children in Dhaka, Bangladesh: a case-control study.

PubMed

Doshi, Saumil; Silk, Benjamin J; Dutt, Dhiman; Ahmed, Moshtaq; Cohen, Adam L; Taylor, Thomas H; Brooks, W Abdullah; Goswami, Doli; Luby, Stephen P; Fry, Alicia M; Ram, Pavani K

2015-06-01

To identify household-level factors associated with influenza among young children in a crowded community in Dhaka, Bangladesh. We conducted a case-control study using existing active surveillance for respiratory illness. Cases were children aged 12-59 months with laboratory-confirmed influenza. Controls were children frequency-matched by age group with no respiratory illness in the prior 6 months. We interviewed caregivers and observed household handwashing behaviour. Soap consumption was estimated by summing weight differences of three bars of soap sequentially left in each household. We measured concentrations of airborne particulate matter <2.5 μg in diameter (PM2.5) in a subset of households. We used logistic regression to estimate adjusted odds ratios (aOR) and 95% confidence intervals (CI). We enrolled 145 cases and 341 controls between March 2009 and April 2010. Case and control household members were observed to wash hands with similar frequency during a 5-h period (mean, 0.64 events vs. 0.63, P = 0.87), and similar daily soap consumption per capita (mean 2.92 grams vs. 2.93, P = 0.92). Case households were more likely than controls to have crowded (≥4 persons) sleeping areas (aOR = 1.67, CI: 1.06-2.63) and cross-ventilated cooking spaces (aOR = 1.75, CI: 1.16-2.63). Case and control households had similar median 24-h geometric mean PM2.5 concentrations in the cooking (69.2 vs. 69.6 μg/m(3), P = 0.45) and sleeping (65.4 vs. 67.4 μg/m(3), P = 0.19) spaces. Handwashing with soap was practiced infrequently and was not associated with paediatric influenza in this community. Interventions aimed at crowded households may reduce influenza incidence in young children. © 2015 John Wiley & Sons Ltd.

Density-dependent regulation of growth of BSC-1 cells in cell culture: control of growth by serum factors.

PubMed Central

Holley, R W; Armour, R; Baldwin, J H; Brown, K D; Yeh, Y C

1977-01-01

BSC-1 cells grow slowly, to high cell density, in medium with 0.1% calf serum. An increase in the serum concentration increases both the growth rate of the cells and the final cell density. The serum can be replaced to some extent by epidermal growth factor (EGF). Initiation of DNA synthesis in BSC-1 cells that have spread into a "wound" in a crowded cell layer requires the addition of a trace of serum or EGF, if the cells have previously been deprived of serum. The binding of 125I-labeled EGF to low-density and high-density BSC-1 cells has been studied. Binding is faster to low-density cells. Cells at low cell density also bind much more EGF per cell than cells at high cell density. The fraction of bound 125I-labeled EGF that is present on the cell surface as intact EGF is larger at low than at high cell density. The results indicate that the number of available EGF receptors per cell decreases drastically as the cell density increases. It is suggested that a decrease in the number of available EGF receptor sites per cell, and the accompanying decrease in sensitivity of the cells to EGF, contributes to density-dependent regulation of growth of these cells. Images PMID:303774

The crowded life is a slow life: Population density and life history strategy.

PubMed

Sng, Oliver; Neuberg, Steven L; Varnum, Michael E W; Kenrick, Douglas T

2017-05-01

The world population has doubled over the last half century. Yet, research on the psychological effects of human population density, once a popular topic, has decreased over the past few decades. Applying a fresh perspective to an old topic, we draw upon life history theory to examine the effects of population density. Across nations and across the U.S. states (Studies 1 and 2), we find that dense populations exhibit behaviors corresponding to a slower life history strategy, including greater future-orientation, greater investment in education, more long-term mating orientation, later marriage age, lower fertility, and greater parental investment. In Studies 3 and 4, experimentally manipulating perceptions of high density led individuals to become more future-oriented. Finally, in Studies 5 and 6, experimentally manipulating perceptions of high density seemed to lead to life-stage-specific slower strategies, with college students preferring to invest in fewer rather than more relationship partners, and an older MTurk sample preferring to invest in fewer rather than more children. This research sheds new insight on the effects of density and its implications for human cultural variation and society at large. (PsycINFO Database Record (c) 2017 APA, all rights reserved).

Competitive Interaction of Axonopus compressus and Asystasia gangetica under Contrasting Sunlight Intensity

PubMed Central

Samedani, B.; Juraimi, A. S.; Anwar, M. P.; Rafii, M. Y.; Sheikh Awadz, S. H.; Anuar, A. R.

2013-01-01

Axonopus compressus is one of the native soft grass species in oil palm in Malaysia which can be used as a cover crop. The competitive ability of A. compressus to overcome A. gangetica was studied using multiple-density, multiple-proportion replacements series under a glasshouse and full sunlight conditions in a poly bag for 10 weeks. A. compressus produced more dry weight and leaf area when competing against A. gangetica than in monoculture at both densities in the full sunlight and at high density in the shade. Moreover, the relative yield and relative crowding coefficients also indicated A. compressus is a stronger competitor than A. gangetica at both densities in the full sunlight and high density in the shade. It seemed that A. gangetica plants in the shade did not compete with each other and were more competitive against A. compressus as could influence A. compressus height in the shade. It is concluded that although suppression of A. gangetica by A. compressus occurred under full sunlight, irrespective of plant density, this ability reduced under shade as A. compressus density decreased. The result suggests that A. compressus in high density could be considered as a candidate for cover crops under oil palm canopy. PMID:24163618

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)

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…

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.

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.

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.

Transparent aligners: An invisible approach to correct mild skeletal class III malocclusion

PubMed Central

Yezdani, A. Arif

2015-01-01

This case report highlights the treatment of a mild skeletal class III malocclusion with an invisible thermoplastic retainer. A 15-year-old female patient presented with a mild skeletal class III malocclusion with a retrognathic maxilla, orthognathic mandible, a low mandibular plane angle with Angle's class III malocclusion with maxillary lateral incisors in anterior cross-bite with crowding of maxillary anteriors, imbricated and rotated mandibular incisors and deep bite. Accurate upper and lower impressions and a bite registration were taken with polyvinyl siloxane rubber base impression material. This was then sent to the lab for the processing of a series of ClearPath aligners. The ClearPath virtual set-up sent from the lab provided the treatment plan and interproximal reduction estimation complete with posttreatment results. This enabled the clinician to actively participate in the treatment plan and provide the necessary suggestions. The ClearPath three-dimensional aligner was found to have effectively corrected the anterior cross-bite and crowding of the maxillary anteriors. PMID:26015738

Bipolar Molecular Outflows within 1pc of Sgr A*:Evidence for Low-mass Star Formation Activity

NASA Astrophysics Data System (ADS)

Yusef-Zadeh, Farhad; Wardle, Mark; Kunneriath, Devaky; Royster, Marc; Wootten, Al; Roberts, Douglas

2018-01-01

The 4 million solar mass black hole, Sgr A*, is expected to suppress star formation because the measured density of the cloud is insufficient for self-gravity to overcome tidal disruption by the black hole's gravitational field. Nevertheless, objects resembling dust-enshrouded young stars and photo-evaporative flows from their disks have been identified within 2pc of Sgr A*. Clear identification of the nature of these objects has been hampered by the Galactic center's distance, 30 magnitudes of foreground extinction, and stellar crowding. Here, we report the discovery of 11 bipolar molecular outflows using ALMA within a projected distance of one pc from Sgr A*. These unambiguous signatures of young protostars manifest as approaching and receding lobes of dense gas swept up by the jets created during the formation and early evolution of low-mass stars. The mean dynamical age of the outflow sources and the rate of star formation are estimated to be ~6500 years and ~5x10^{-4} solar mass per year, respectively. These measurements suggest that star formation could take place in the immediate vicinity of supermassive black holes in the nuclei of external galaxies.

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

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.

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.

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

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.

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

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.

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).

Audible vision for the blind and visually impaired in indoor open spaces.

PubMed

Yu, Xunyi; Ganz, Aura

2012-01-01

In this paper we introduce Audible Vision, a system that can help blind and visually impaired users navigate in large indoor open spaces. The system uses computer vision to estimate the location and orientation of the user, and enables the user to perceive his/her relative position to a landmark through 3D audio. Testing shows that Audible Vision can work reliably in real-life ever-changing environment crowded with people.

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.

Kepler Transit Depths Contaminated By a Phantom Star

NASA Astrophysics Data System (ADS)

Dalba, Paul A.; Muirhead, Philip S.; Croll, Bryce; Kempton, Eliza M.-R.

2017-02-01

We present ground-based observations from the Discovery Channel Telescope (DCT) of three transits of Kepler-445c—a supposed super-Earth exoplanet with properties resembling GJ 1214b—and demonstrate that the transit depth is ˜50% shallower than the depth previously inferred from Kepler spacecraft data. The resulting decrease in planetary radius significantly alters the interpretation of the exoplanet’s bulk composition. Despite the faintness of the M4 dwarf host star, our ground-based photometry clearly recovers each transit and achieves repeatable 1σ precision of ˜0.2% (2 millimags). The transit parameters estimated from the DCT data are discrepant with those inferred from the Kepler data to at least 17σ confidence. This inconsistency is due to a subtle miscalculation of the stellar crowding metric during the Kepler pre-search data conditioning (PDC). The crowding metric, or CROWDSAP, is contaminated by a non-existent phantom star originating in the USNO-B1 catalog and inherited by the Kepler Input Catalog (KIC). Phantom stars in the KIC are likely rare, but they have the potential to affect statistical studies of Kepler targets that use the PDC transit depths for a large number of exoplanets where an individual follow-up observation of each is not possible. The miscalculation of Kepler-445c’s transit depth emphasizes the importance of stellar crowding in the Kepler data, and provides a cautionary tale for the analysis of data from the Transiting Exoplanet Survey Satellite, which will have even larger pixels than Kepler.

Learning to recognize letters in the periphery: Effects of repeated exposure, letter frequency, and letter complexity

PubMed Central

Husk, Jesse S.; Yu, Deyue

2017-01-01

Patients with central vision loss must rely on their peripheral vision for reading. Unfortunately, limitations of peripheral vision, such as crowding, pose significant challenges to letter recognition. As a result, there is a need for developing effective training methods for improving crowded letter recognition in the periphery. Several studies have shown that extensive practice with letter stimuli is beneficial to peripheral letter recognition. Here, we explore stimulus-related factors that might influence the effectiveness of peripheral letter recognition training. Specifically, we examined letter exposure (number of letter occurrences), frequency of letter use in English print, and letter complexity and evaluated their contributions to the amount of improvement observed in crowded letter recognition following training. We analyzed data collected across a range of training protocols. Using linear regression, we identified the best-fitting model and observed that all three stimulus-related factors contributed to improvement in peripheral letter recognition with letter exposure being the most important factor. As an important explanatory variable, pretest accuracy was included in the model as well to avoid estimate biases and was shown to have influence on the relationship between training improvement and letter exposure. When developing training protocols for peripheral letter recognition, it may be beneficial to not only consider the overall length of training, but also to tailor the number of stimulus occurrences for each letter according to its initial performance level, frequency, and complexity. PMID:28265651

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.

Membrane Bending by Protein Crowding

NASA Astrophysics Data System (ADS)

Stachowiak, Jeanne

2014-03-01

From endosomes and synaptic vesicles to the cristae of the mitochondria and the annulus of the nuclear pore, highly curved membranes are fundamental to the structure and physiology of living cells. The established view is that specific families of proteins are able to bend membranes by binding to them. For example, inherently curved proteins are thought to impose their structure on the membrane surface, while membrane-binding proteins with hydrophobic motifs are thought to insert into the membrane like wedges, driving curvature. However, computational models have recently revealed that these mechanisms would require specialized membrane-bending proteins to occupy nearly 100% of a curved membrane surface, an improbable physiological situation given the immense density and diversity of membrane-bound proteins, and the low expression levels of these specialized proteins within curved regions of the membrane. How then does curvature arise within the complex and crowded environment of cellular membranes? Our recent work using proteins involved in clathrin-mediated endocytosis, as well as engineered protein-lipid interactions, has suggested a new hypothesis - that lateral pressure generated by collisions between membrane-bound proteins can drive membrane bending. Specifically, by correlating membrane bending with quantitative optical measurements of protein density on synthetic membrane surfaces and simple physical models of collisions among membrane-bound proteins, we have demonstrated that protein-protein steric interactions can drive membrane curvature. These findings suggest that a simple imbalance in the concentration of membrane-bound proteins across a membrane surface can drive a membrane to bend, providing an efficient mechanism by which essentially any protein can contribute to shaping membranes.

Establishment of a captive all-male group of proboscis monkey (Nasalis larvatus) at the Singapore Zoo.

PubMed

Sha, John Chih Mun; Alagappasamy, Sam; Chandran, Subash; Cho, Khin Maung; Guha, Biswajit

2013-01-01

Surplus male proboscis monkeys at the Singapore Zoo pose a considerable problem for maintenance and maximizing of exhibition potential. In 2008, a new exhibit was constructed to house and display a group of six proboscis monkey males born in Singapore Zoo. To document and monitor the all-male group establishment in the new exhibit, we conducted observations on intragroup interactions between the monkeys, spatial use of their new exhibit, and visitor effects on their behavior. We found contact aggressive interactions between the monkeys to be consistently lower than noncontact aggressive interactions and by week six of introduction to the new exhibit, contact aggression was almost nonevident. Affiliative interactions also developed between individuals in the group, with an interface of aggressive and socioreconcilatory behavior influenced by food competition and a dominance hierarchy. This was evident from significantly higher overall aggression and affiliation during feeding times compared to nonfeeding times, and this was reduced when food competition was mitigated by modifying the feeding regime. We measured the groups' spatial use of the exhibit and the relation to behavior, crowd size, and density. Our results showed that the proboscis monkeys utilized the available exhibit space, were largely unaffected by visitor crowd size and density, and were able to exhibit a variety of natural behaviors, including swimming. Our accomplishment in maintaining and displaying an all-male group of proboscis monkeys in captivity provides viable options for more comprehensive captive management and breeding programs for this endangered species. © 2012 Wiley Periodicals, Inc.

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

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

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.

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…

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.

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...

Effect of Joule heating and current crowding on electromigration in mobile technology

NASA Astrophysics Data System (ADS)

Tu, K. N.; Liu, Yingxia; Li, Menglu

2017-03-01

In the present era of big data and internet of things, the use of microelectronic products in all aspects of our life is manifested by the ubiquitous presence of mobile devices as i-phones and wearable i-products. These devices are facing the need for higher power and greater functionality applications such as in i-health, yet they are limited by physical size. At the moment, software (Apps) is much ahead of hardware in mobile technology. To advance hardware, the end of Moore's law in two-dimensional integrated circuits can be extended by three-dimensional integrated circuits (3D ICs). The concept of 3D ICs has been with us for more than ten years. The challenge in 3D IC technology is dense packing by using both vertical and horizontal interconnections. Mass production of 3D IC devices is behind schedule due to cost because of low yield and uncertain reliability. Joule heating is serious in a dense structure because of heat generation and dissipation. A change of reliability paradigm has advanced from failure at a specific circuit component to failure at a system level weak-link. Currently, the electronic industry is introducing 3D IC devices in mainframe computers, where cost is not an issue, for the purpose of collecting field data of failure, especially the effect of Joule heating and current crowding on electromigration. This review will concentrate on the positive feedback between Joule heating and electromigration, resulting in an accelerated system level weak-link failure. A new driving force of electromigration, the electric potential gradient force due to current crowding, will be reviewed critically. The induced failure tends to occur in the low current density region.

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.

CrowdPhase: crowdsourcing the phase problem

PubMed Central

Jorda, Julien; Sawaya, Michael R.; Yeates, Todd O.

2014-01-01

The human mind innately excels at some complex tasks that are difficult to solve using computers alone. For complex problems amenable to parallelization, strategies can be developed to exploit human intelligence in a collective form: such approaches are sometimes referred to as ‘crowdsourcing’. Here, a first attempt at a crowdsourced approach for low-resolution ab initio phasing in macromolecular crystallography is proposed. A collaborative online game named CrowdPhase was designed, which relies on a human-powered genetic algorithm, where players control the selection mechanism during the evolutionary process. The algorithm starts from a population of ‘individuals’, each with a random genetic makeup, in this case a map prepared from a random set of phases, and tries to cause the population to evolve towards individuals with better phases based on Darwinian survival of the fittest. Players apply their pattern-recognition capabilities to evaluate the electron-density maps generated from these sets of phases and to select the fittest individuals. A user-friendly interface, a training stage and a competitive scoring system foster a network of well trained players who can guide the genetic algorithm towards better solutions from generation to generation via gameplay. CrowdPhase was applied to two synthetic low-resolution phasing puzzles and it was shown that players could successfully obtain phase sets in the 30° phase error range and corresponding molecular envelopes showing agreement with the low-resolution models. The successful preliminary studies suggest that with further development the crowdsourcing approach could fill a gap in current crystallographic methods by making it possible to extract meaningful information in cases where limited resolution might otherwise prevent initial phasing. PMID:24914965

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.

Maintenance cost, toppling risk and size of trees in a self-thinning stand.

PubMed

Larjavaara, Markku

2010-07-07

Wind routinely topples trees during storms, and the likelihood that a tree is toppled depends critically on its allometry. Yet none of the existing theories to explain tree allometry consider wind drag on tree canopies. Since leaf area index in crowded, self-thinning stands is independent of stand density, the drag force per unit land can also be assumed to be independent of stand density, with only canopy height influencing the total toppling moment. Tree stem dimensions and the self-thinning biomass can then be computed by further assuming that the risk of toppling over and stem maintenance per unit land area are independent of stand density, and that stem maintenance cost is a linear function of stem surface area and sapwood volume. These assumptions provide a novel way to understand tree allometry and lead to a self-thinning line relating tree biomass and stand density with a power between -3/2 and -2/3 depending on the ratio of maintenance of sapwood and stem surface. (c) 2010 Elsevier Ltd. All rights reserved.

Density-dependent regulation of growth of BSC-1 cells in cell culture: growth inhibitors formed by the cells.

PubMed Central

Holley, R W; Armour, R; Baldwin, J H

1978-01-01

Inhibitors formed by a monkey epithelial cell line, BSC-1, play an important role in limiting growth at high cell densities. At least three inhibitors are formed: lactic acid, ammonia, and an unidentified inhibitor that may be an unstable protein. The unidentified inhibitor is destroyed by shaking the conditioned medium, by bubbling gas through the medium, or by heating or storing the medium in the absence of cells. The concentrations of lactic acid and ammonia that accumulate in conditioned medium inhibit growth when added to fresh medium. These results, together with earlier studies, indicate that density-dependent regulation of growth of BSC-1 cells results from the combined effects of (a) inhibitors formed by the cells, (b) decreased availability of receptor sites for serum growth factors as the cells become crowded, and (c) limiting concentrations of low molecular weight nutrients in the medium. In contrast, density-dependent regulation of growth in 3T3 mouse embryo fibroblasts results almost entirely from inactivation of serum factors. PMID:273914

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

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

Robust range estimation with a monocular camera for vision-based forward collision warning system.

PubMed

Park, Ki-Yeong; Hwang, Sun-Young

2014-01-01

We propose a range estimation method for vision-based forward collision warning systems with a monocular camera. To solve the problem of variation of camera pitch angle due to vehicle motion and road inclination, the proposed method estimates virtual horizon from size and position of vehicles in captured image at run-time. The proposed method provides robust results even when road inclination varies continuously on hilly roads or lane markings are not seen on crowded roads. For experiments, a vision-based forward collision warning system has been implemented and the proposed method is evaluated with video clips recorded in highway and urban traffic environments. Virtual horizons estimated by the proposed method are compared with horizons manually identified, and estimated ranges are compared with measured ranges. Experimental results confirm that the proposed method provides robust results both in highway and in urban traffic environments.

Robust Range Estimation with a Monocular Camera for Vision-Based Forward Collision Warning System

PubMed Central

2014-01-01

We propose a range estimation method for vision-based forward collision warning systems with a monocular camera. To solve the problem of variation of camera pitch angle due to vehicle motion and road inclination, the proposed method estimates virtual horizon from size and position of vehicles in captured image at run-time. The proposed method provides robust results even when road inclination varies continuously on hilly roads or lane markings are not seen on crowded roads. For experiments, a vision-based forward collision warning system has been implemented and the proposed method is evaluated with video clips recorded in highway and urban traffic environments. Virtual horizons estimated by the proposed method are compared with horizons manually identified, and estimated ranges are compared with measured ranges. Experimental results confirm that the proposed method provides robust results both in highway and in urban traffic environments. PMID:24558344

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.

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

Detecting dominant motion patterns in crowds of pedestrians

NASA Astrophysics Data System (ADS)

Saqib, Muhammad; Khan, Sultan Daud; Blumenstein, Michael

2017-02-01

As the population of the world increases, urbanization generates crowding situations which poses challenges to public safety and security. Manual analysis of crowded situations is a tedious job and usually prone to errors. In this paper, we propose a novel technique of crowd analysis, the aim of which is to detect different dominant motion patterns in real-time videos. A motion field is generated by computing the dense optical flow. The motion field is then divided into blocks. For each block, we adopt an Intra-clustering algorithm for detecting different flows within the block. Later on, we employ Inter-clustering for clustering the flow vectors among different blocks. We evaluate the performance of our approach on different real-time videos. The experimental results show that our proposed method is capable of detecting distinct motion patterns in crowded videos. Moreover, our algorithm outperforms state-of-the-art methods.

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.

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.

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.

Cargo crowding at actin-rich regions along axons causes local traffic jams.

PubMed

Sood, Parul; Murthy, Kausalya; Kumar, Vinod; Nonet, Michael L; Menon, Gautam I; Koushika, Sandhya P

2018-03-01

Steady axonal cargo flow is central to the functioning of healthy neurons. However, a substantial fraction of cargo in axons remains stationary up to several minutes. We examine the transport of precursors of synaptic vesicles (pre-SVs), endosomes and mitochondria in Caenorhabditis elegans touch receptor neurons, showing that stationary cargo are predominantly present at actin-rich regions along the neuronal process. Stationary vesicles at actin-rich regions increase the propensity of moving vesicles to stall at the same location, resulting in traffic jams arising from physical crowding. Such local traffic jams at actin-rich regions are likely to be a general feature of axonal transport since they also occur in Drosophila neurons. Repeated touch stimulation of C. elegans reduces the density of stationary pre-SVs, indicating that these traffic jams can act as both sources and sinks of vesicles. This suggests that vesicles trapped in actin-rich regions are functional reservoirs that may contribute to maintaining robust cargo flow in the neuron. A video abstract of this article can be found at: Video S1; Video S2. © 2017 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

Combining local and global limitations of visual search.

PubMed

Põder, Endel

2017-04-01

There are different opinions about the roles of local interactions and central processing capacity in visual search. This study attempts to clarify the problem using a new version of relevant set cueing. A central precue indicates two symmetrical segments (that may contain a target object) within a circular array of objects presented briefly around the fixation point. The number of objects in the relevant segments, and density of objects in the array were varied independently. Three types of search experiments were run: (a) search for a simple visual feature (color, size, and orientation); (b) conjunctions of simple features; and (c) spatial configuration of simple features (rotated Ts). For spatial configuration stimuli, the results were consistent with a fixed global processing capacity and standard crowding zones. For simple features and their conjunctions, the results were different, dependent on the features involved. While color search exhibits virtually no capacity limits or crowding, search for an orientation target was limited by both. Results for conjunctions of features can be partly explained by the results from the respective features. This study shows that visual search is limited by both local interference and global capacity, and the limitations are different for different visual features.

A novel grid-based mesoscopic model for evacuation dynamics

NASA Astrophysics Data System (ADS)

Shi, Meng; Lee, Eric Wai Ming; Ma, Yi

2018-05-01

This study presents a novel grid-based mesoscopic model for evacuation dynamics. In this model, the evacuation space is discretised into larger cells than those used in microscopic models. This approach directly computes the dynamic changes crowd densities in cells over the course of an evacuation. The density flow is driven by the density-speed correlation. The computation is faster than in traditional cellular automata evacuation models which determine density by computing the movements of each pedestrian. To demonstrate the feasibility of this model, we apply it to a series of practical scenarios and conduct a parameter sensitivity study of the effect of changes in time step δ. The simulation results show that within the valid range of δ, changing δ has only a minor impact on the simulation. The model also makes it possible to directly acquire key information such as bottleneck areas from a time-varied dynamic density map, even when a relatively large time step is adopted. We use the commercial software AnyLogic to evaluate the model. The result shows that the mesoscopic model is more efficient than the microscopic model and provides more in-situ details (e.g., pedestrian movement pattern) than the macroscopic models.

Effect of speed matching on fundamental diagram of pedestrian flow

NASA Astrophysics Data System (ADS)

Fu, Zhijian; Luo, Lin; Yang, Yue; Zhuang, Yifan; Zhang, Peitong; Yang, Lizhong; Yang, Hongtai; Ma, Jian; Zhu, Kongjin; Li, Yanlai

2016-09-01

Properties of pedestrian may change along their moving path, for example, as a result of fatigue or injury, which has never been properly investigated in the past research. The paper attempts to study the speed matching effect (a pedestrian adjusts his velocity constantly to the average velocity of his neighbors) and its influence on the density-velocity relationship (a pedestrian adjust his velocity to the surrounding density), known as the fundamental diagram of the pedestrian flow. By the means of the cellular automaton, the simulation results fit well with the empirical data, indicating the great advance of the discrete model for pedestrian dynamics. The results suggest that the system velocity and flow rate increase obviously under a big noise, i.e., a diverse composition of pedestrian crowd, especially in the region of middle or high density. Because of the temporary effect, the speed matching has little influence on the fundamental diagram. Along the entire density, the relationship between the step length and the average pedestrian velocity is a piecewise function combined two linear functions. The number of conflicts reaches the maximum with the pedestrian density of 2.5 m-2, while decreases by 5.1% with the speed matching.

Pedestrian evacuation at the subway station under fire

NASA Astrophysics Data System (ADS)

Xiao-Xia, Yang; Hai-Rong, Dong; Xiu-Ming, Yao; Xu-Bin, Sun

2016-04-01

With the development of urban rail transit, ensuring the safe evacuation of pedestrians at subway stations has become an important issue in the case of an emergency such as a fire. This paper chooses the platform of line 4 at the Beijing Xuanwumen subway station to study the emergency evacuation process under fire. Based on the established platform, effects of the fire dynamics, different initial pedestrian densities, and positions of fire on evacuation are investigated. According to simulation results, it is found that the fire increases the air temperature and the smoke density, and decreases pedestrians’ visibility and walking velocity. Also, there is a critical initial density at the platform if achieving a safe evacuation within the required 6 minutes. Furthermore, different positions of fire set in this paper have little difference on crowd evacuation if the fire is not large enough. The suggestions provided in this paper are helpful for the subway operators to prevent major casualties. Project supported by the National Natural Science Foundation of China (Grant Nos. 61322307 and 61233001).

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...

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.

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.

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

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.

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.

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.

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

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.

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.

Quantifying rates of cell migration and cell proliferation in co-culture barrier assays reveals how skin and melanoma cells interact during melanoma spreading and invasion.

PubMed

Haridas, Parvathi; Penington, Catherine J; McGovern, Jacqui A; McElwain, D L Sean; Simpson, Matthew J

2017-06-21

Malignant spreading involves the migration of cancer cells amongst other native cell types. For example, in vivo melanoma invasion involves individual melanoma cells migrating through native skin, which is composed of several distinct subpopulations of cells. Here, we aim to quantify how interactions between melanoma and fibroblast cells affect the collective spreading of a heterogeneous population of these cells in vitro. We perform a suite of circular barrier assays that includes: (i) monoculture assays with fibroblast cells; (ii) monoculture assays with SK-MEL-28 melanoma cells; and (iii) a series of co-culture assays initiated with three different ratios of SK-MEL-28 melanoma cells and fibroblast cells. Using immunostaining, detailed cell density histograms are constructed to illustrate how the two subpopulations of cells are spatially arranged within the spreading heterogeneous population. Calibrating the solution of a continuum partial differential equation to the experimental results from the monoculture assays allows us to estimate the cell diffusivity and the cell proliferation rate for the melanoma and the fibroblast cells, separately. Using the parameter estimates from the monoculture assays, we then make a prediction of the spatial spreading in the co-culture assays. Results show that the parameter estimates obtained from the monoculture assays lead to a reasonably accurate prediction of the spatial arrangement of the two subpopulations in the co-culture assays. Overall, the spatial pattern of spreading of the melanoma cells and the fibroblast cells is very similar in monoculture and co-culture conditions. Therefore, we find no clear evidence of any interactions other than cell-to-cell contact and crowding effects. Copyright © 2017 Elsevier Ltd. All rights reserved.

Diffusion, subdiffusion, and localization of active colloids in random post lattices

NASA Astrophysics Data System (ADS)

Morin, Alexandre; Lopes Cardozo, David; Chikkadi, Vijayakumar; Bartolo, Denis

2017-10-01

Combining experiments and theory, we address the dynamics of self-propelled particles in crowded environments. We first demonstrate that motile colloids cruising at constant speed through random lattices undergo a smooth transition from diffusive to subdiffusive to localized dynamics upon increasing the obstacle density. We then elucidate the nature of these transitions by performing extensive simulations constructed from a detailed analysis of the colloid-obstacle interactions. We evidence that repulsion at a distance and hard-core interactions both contribute to slowing down the long-time diffusion of the colloids. In contrast, the localization transition stems solely from excluded-volume interactions and occurs at the void-percolation threshold. Within this critical scenario, equivalent to that of the random Lorentz gas, genuine asymptotic subdiffusion is found only at the critical density where the motile particles explore a fractal maze.

Mesoscopic model for binary fluids

NASA Astrophysics Data System (ADS)

Echeverria, C.; Tucci, K.; Alvarez-Llamoza, O.; Orozco-Guillén, E. E.; Morales, M.; Cosenza, M. G.

2017-10-01

We propose a model for studying binary fluids based on the mesoscopic molecular simulation technique known as multiparticle collision, where the space and state variables are continuous, and time is discrete. We include a repulsion rule to simulate segregation processes that does not require calculation of the interaction forces between particles, so binary fluids can be described on a mesoscopic scale. The model is conceptually simple and computationally efficient; it maintains Galilean invariance and conserves the mass and energy in the system at the micro- and macro-scale, whereas momentum is conserved globally. For a wide range of temperatures and densities, the model yields results in good agreement with the known properties of binary fluids, such as the density profile, interface width, phase separation, and phase growth. We also apply the model to the study of binary fluids in crowded environments with consistent results.

Fluids in porous media. IV. Quench effect on chemical potential.

PubMed

Qiao, C Z; Zhao, S L; Liu, H L; Dong, W

2017-06-21

It appears to be a common sense to measure the crowdedness of a fluid system by the densities of the species constituting it. In the present work, we show that this ceases to be valid for confined fluids under some conditions. A quite thorough investigation is made for a hard sphere (HS) fluid adsorbed in a hard sphere matrix (a quench-annealed system) and its corresponding equilibrium binary mixture. When fluid particles are larger than matrix particles, the quench-annealed system can appear much more crowded than its corresponding equilibrium binary mixture, i.e., having a much higher fluid chemical potential, even when the density of each species is strictly the same in both systems, respectively. We believe that the insight gained from this study should be useful for the design of functionalized porous materials.

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

Kobulnicky, Henry A.; Alexander, Michael J.; Babler, Brian L.

We characterize the completeness of point source lists from Spitzer Space Telescope surveys in the four Infrared Array Camera (IRAC) bandpasses, emphasizing the Galactic Legacy Infrared Mid-Plane Survey Extraordinaire (GLIMPSE) programs (GLIMPSE I, II, 3D, 360; Deep GLIMPSE) and their resulting point source Catalogs and Archives. The analysis separately addresses effects of incompleteness resulting from high diffuse background emission and incompleteness resulting from point source confusion (i.e., crowding). An artificial star addition and extraction analysis demonstrates that completeness is strongly dependent on local background brightness and structure, with high-surface-brightness regions suffering up to five magnitudes of reduced sensitivity to pointmore » sources. This effect is most pronounced at the IRAC 5.8 and 8.0 {mu}m bands where UV-excited polycyclic aromatic hydrocarbon emission produces bright, complex structures (photodissociation regions). With regard to diffuse background effects, we provide the completeness as a function of stellar magnitude and diffuse background level in graphical and tabular formats. These data are suitable for estimating completeness in the low-source-density limit in any of the four IRAC bands in GLIMPSE Catalogs and Archives and some other Spitzer IRAC programs that employ similar observational strategies and are processed by the GLIMPSE pipeline. By performing the same analysis on smoothed images we show that the point source incompleteness is primarily a consequence of structure in the diffuse background emission rather than photon noise. With regard to source confusion in the high-source-density regions of the Galactic Plane, we provide figures illustrating the 90% completeness levels as a function of point source density at each band. We caution that completeness of the GLIMPSE 360/Deep GLIMPSE Catalogs is suppressed relative to the corresponding Archives as a consequence of rejecting stars that lie in the point-spread function wings of saturated sources. This effect is minor in regions of low saturated star density, such as toward the Outer Galaxy; this effect is significant along sightlines having a high density of saturated sources, especially for Deep GLIMPSE and other programs observing closer to the Galactic center using 12 s or longer exposure times.« less

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.

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.

Strained layer relaxation effect on current crowding and efficiency improvement of GaN based LED

NASA Astrophysics Data System (ADS)

Aurongzeb, Deeder

2012-02-01

Efficiency droop effect of GaN based LED at high power and high temperature is addressed by several groups based on career delocalization and photon recycling effect(radiative recombination). We extend the previous droop models to optical loss parameters. We correlate stained layer relaxation at high temperature and high current density to carrier delocalization. We propose a third order model and show that Shockley-Hall-Read and Auger recombination effect is not enough to account for the efficiency loss. Several strained layer modification scheme is proposed based on the model.

Proton clouds to measure long-range contacts between nonexchangeable side chain protons in solid-state NMR.

PubMed

Sinnige, Tessa; Daniëls, Mark; Baldus, Marc; Weingarth, Markus

2014-03-26

We show that selective labeling of proteins with protonated amino acids embedded in a perdeuterated matrix, dubbed 'proton clouds', provides general access to long-range contacts between nonexchangeable side chain protons in proton-detected solid-state NMR, which is important to study protein tertiary structure. Proton-cloud labeling significantly improves spectral resolution by simultaneously reducing proton line width and spectral crowding despite a high local proton density in clouds. The approach is amenable to almost all canonical amino acids. Our method is demonstrated on ubiquitin and the β-barrel membrane protein BamA.

Evolution in population parameters: density-dependent selection or density-dependent fitness?

PubMed

Travis, Joseph; Leips, Jeff; Rodd, F Helen

2013-05-01

Density-dependent selection is one of earliest topics of joint interest to both ecologists and evolutionary biologists and thus occupies an important position in the histories of these disciplines. This joint interest is driven by the fact that density-dependent selection is the simplest form of feedback between an ecological effect of an organism's own making (crowding due to sustained population growth) and the selective response to the resulting conditions. This makes density-dependent selection perhaps the simplest process through which we see the full reciprocity between ecology and evolution. In this article, we begin by tracing the history of studying the reciprocity between ecology and evolution, which we see as combining the questions of evolutionary ecology with the assumptions and approaches of ecological genetics. In particular, density-dependent fitness and density-dependent selection were critical concepts underlying ideas about adaptation to biotic selection pressures and the coadaptation of interacting species. However, theory points to a critical distinction between density-dependent fitness and density-dependent selection in their influences on complex evolutionary and ecological interactions among coexisting species. Although density-dependent fitness is manifestly evident in empirical studies, evidence of density-dependent selection is much less common. This leads to the larger question of how prevalent and important density-dependent selection might really be. Life-history variation in the least killifish Heterandria formosa appears to reflect the action of density-dependent selection, and yet compelling evidence is elusive, even in this well-studied system, which suggests some important challenges for understanding density-driven feedbacks between ecology and evolution.

Computed tomography in pulmonary sarcoidosis

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

Lynch, D.A.; Webb, W.R.; Gamsu, G.

1989-05-01

We studied the high resolution CT (HRCT) scans of 15 patients with biopsy-proven sarcoidosis and correlated the findings with pulmonary function tests (12 patients), 67Ga scans (10 patients), bronchoalveolar lavage (five patients), recent transbronchial biopsy (six patients), and recent open lung biopsy (three patients). The HRCT features included small nodules, thickened interlobular septa, patchy focal increase in lung density, honeycombing, and central conglomeration of vessels and bronchi. Active alveolitis was present by gallium scanning criteria in 5 of 10 cases. By bronchoalveolar lavage criteria, activity was present in three of five cases. Patchy increase in density may correlate with activemore » alveolitis as seen on /sup 67/Ga scanning. High resolution CT was better than chest X-radiography for demonstration of patchy increase in density and for distinguishing nodules from septal thickening. Both nodules and patchy density were partly reversible following therapy. Nodular densities seen on CT correlated with the presence of granulomata on histology. Resting pulmonary function tests correlated poorly with presence and extent of lung disease on HRCT. The presence on HRCT of focal fine nodules, patchy focal increase in lung density, and central crowding of bronchi and vessels should suggest the diagnosis of sarcoidosis. In some patients, HRCT can identify unsuspected parenchymal lung disease and document the reversible components of sarcoid lung disease.« less

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

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 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

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

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.

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

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.

Effect of Molecular Crowding and Ionic Strength on the Isothermal Hybridization of Oligonucleotides

PubMed Central

Markarian, Marie Z.; Schlenoff, Joseph B.

2010-01-01

The isothermal hybridization of complimentary oligonucleotides, 15-mer, 25-mer, 35-mer, and a molecular beacon, was investigated under varying conditions of molecular crowding and ionic strength, using hypochromicity to follow strand pairing and polyethylene glycol as a crowding agent. Thermodynamic analysis of the results revealed the addition of counterions to the oligonucleotide backbones, Δψ, to be dependent on the strand G-C content and the molecular crowding. A decrease in Δψ was observed with both increasing GC% and solution PEG content. In contrast, the number of bound water molecules depended on the activity of Na+, where two regimes were observed. At aNa+⟨0.05 and increasing molecular crowding, water molecules were released into the DNA solutions and oligonucleotide pairing was favored with both increasing hydrophobic forces, while at aNa+≥0.05, water molecules were bound to the strands and the extent of double strand formation decreased with increasing PEG wt%. PMID:20701389

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.

Cost-effective imprinting combining macromolecular crowding and a dummy template for the fast purification of punicalagin from pomegranate husk extract.

PubMed

Sun, Guang-Ying; Wang, Chao; Luo, Yu-Qin; Zhao, Yong-Xin; Yang, Jian; Liu, Zhao-Sheng; Aisa, Haji Akber

2016-05-01

The combination of molecular crowding and virtual imprinting was employed to develop a cost-effective method to prepare molecularly imprinted polymers. By using linear polymer polystyrene as a macromolecular crowding agent, an imprinted polymer recognizable to punicalagin had been successfully synthesized with punicalin as the dummy template. The resulting punicalin-imprinted polymer presented a remarkable selectivity to punicalagin with an imprinting factor of 3.17 even at extremely low consumption of the template (template/monomer ratio of 1:782). In contrast, the imprinted polymer synthesized without crowding agent, did not show any imprinting effect at so low template amount. The imprinted polymers made by combination of molecular crowding and virtual imprinting can be utilized for the fast separation of punicalagin from pomegranate husk extract after optimizing the protocol of solid-phase extraction with the recovery of 85.3 ± 1.2%. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

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.

A Study of Crowd Ability and its Influence on Crowdsourced Evaluation of Design Concepts

DTIC Science & Technology

2014-05-01

identifies the experts from the crowd, under the assumptions that ( 1 ) experts do exist and (2) only experts have consistent evaluations. These assumptions...for design evaluation tasks . Keywords: crowdsourcing, design evaluation, sparse evaluation ability, machine learning ∗Corresponding author. 1 ...intelligence” of a much larger crowd of people with diverse backgrounds [ 1 ]. Crowdsourced evaluation, or the delegation of an eval- uation task to a

On-Site Social Surveys and the Determination of Social Carrying Capacity in Wildland Recreation Management

Treesearch

Patrick C. West

1981-01-01

It has been suggested that on-site surveys of user fail to measure crowding accurately because long time users who knew the area before the "crowds" came tend to feel the most crowded, and thus do not return. Such "displaced" users would not be included in current on-site survey samples. Results from a limited test at the Sylvania Recreation Area...

Influence of Social Media on Crowd Behavior and the Operational Environment

DTIC Science & Technology

2013-05-23

destructiveness, irrationality, emotionality, mental disturbances, lower-class participation, spontaneity, creativeness, and lack of self -control. 13Dr...John M. Kenny, Dr. Clark McPhail, Dr. Peter Waddington, Lt. Sid Heal , Maj. Steve James, Dr. Donald N. Farrer, Dr. Jim Taylor, Capt. Dick Odenthal, Crowd...secondary effect causing overwhelming confusion. As the crowd begins to self -organize, leadership will resonate from within, however, an external source

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.

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.

Anterior maxillary segmental distraction for correction of maxillary hypoplasia and dental crowding in cleft palate patients: a preliminary report.

PubMed

Wang, X-X; Wang, X; Li, Z-L; Yi, B; Liang, C; Jia, Y-L; Zou, B-S

2009-12-01

To evaluate the feasibility of anterior maxillary segmental distraction (AMSD) to correct maxillary hypoplasia and severe dental crowding in cleft lip and palate (CLP) patients, 7 patients (average age 16.4 years) with maxillary hypoplasia, shortened maxillary dental arch length and severe anterior dental crowding secondary to CLP were selected for this study. After anterior maxillary segmental osteotomy, 3 patients were treated using bilateral internal distraction devices, and 4 patients were treated using rigid external distraction devices. Photographs and radiographs were taken to review the improvement in facial profile and occlusion after distraction. An average 10.25 mm anterior maxillary advancement was obtained in all patients after 10-23 days of distraction and 9-16 weeks of consolidation. The sella-nasion-point A (SNA) angle increased from 69.5 degrees to 79.6 degrees. Midface convexity was greatly improved and velopharyngeal competence was preserved. The maxillary dental arch length was greatly increased by 10.1 mm (P<0.01). Dental crowding and malocclusion were corrected by orthodontic treatment. These results show that AMSD can effectively correct the hypoplastic maxilla and severe dental crowding associated with CLP by increasing the midface convexity and dental arch length while preserving velopharyngeal function, and dental crowding can be corrected without requiring tooth extraction.

Estimating the number of sex workers in South Africa: rapid population size estimation.

PubMed

Konstant, Tracey L; Rangasami, Jerushah; Stacey, Maria J; Stewart, Michelle L; Nogoduka, Coceka

2015-02-01

Although recognized as a vulnerable population, there is no national population size estimate for sex workers in South Africa. A rapid sex worker enumeration exercise was undertaken in twelve locations across the country based on principles of participatory mapping and Wisdom of the Crowd. Sites with a range of characteristics were selected, focusing on level of urbanisation, trucking, mining and borders. At each site, sex worker focus groups mapped local hotspots. Interviews with sex workers at identified hotspots were used to estimate the numbers and genders of sex workers working in each. Estimates provided in the literature were combined with enumeration exercise results to define assumptions that could be applied to a national extrapolation. A working estimate was reached of between 131,000 and 182,000 sex worker in South Africa, or between 0.76 and 1 % of the adult female population. The success of the exercise depended on integral involvement of sex worker peer educators and strong ethical considerations.

The Mechanism of Word Crowding

PubMed Central

Yu, Deyue; Akau, Melanie M. U.; Chung, Susana T. L.

2011-01-01

Word reading speed in peripheral vision is slower when words are in close proximity of other words (Chung, 2004). This word crowding effect could arise as a consequence of interaction of low-level letter features between words, or the interaction between high-level holistic representations of words. We evaluated these two hypotheses by examining how word crowding changes for five configurations of flanking words: the control condition — flanking words were oriented upright; scrambled — letters in each flanking word were scrambled in order; horizontal-flip — each flanking word was the left-right mirror-image of the original; letter-flip — each letter of the flanking word was the left-right mirror-image of the original; and vertical-flip — each flanking word was the up-down mirror-image of the original. The low-level letter feature interaction hypothesis predicts similar word crowding effect for all the different flanker configurations, while the high-level holistic representation hypothesis predicts less word crowding effect for all the alternative flanker conditions, compared with the control condition. We found that oral reading speed for words flanked above and below by other words, measured at 10° eccentricity in the nasal field, showed the same dependence on the vertical separation between the target and its flanking words, for the various flanker configurations. The result was also similar when we rotated the flanking words by 90° to disrupt the periodic vertical pattern, which presumably is the main structure in words. The remarkably similar word crowding effect irrespective of the flanker configurations suggests that word crowding arises as a consequence of interactions of low-level letter features. PMID:22079315

Protein diffusion along DNA: on the effect of roadblocks and crowders

NASA Astrophysics Data System (ADS)

Krepel, Dana; Levy, Yaakov

2016-12-01

Rapid recognition by a protein of its DNA target site is achieved through a 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. Both experimental and theoretical studies showed that crowding particles can enhance facilitated diffusion and accelerate search kinetics. This effect may originate from crowding forcing a trade-off between 3D and 1D diffusion. In this study, using coarse-grained molecular dynamic simulations, we investigate how the molecular properties of the crowders may modulate the effect exerted by crowding on a searcher protein. We show that crowders with an affinity to the DNA are less effective search facilitators than particles whose contribution is solely entropic. Crowders that have affinity to DNA may occupy DNA sites and thereby function as obstacles or roadblocks that slow down the searcher protein, and they may also produce a smaller excluded volume effect and so reduce usage of the hopping searching mode in favor of less-effective 3D diffusion in the bulk. We discuss how strong repulsive interactions between the crowding particles themselves may affect the overall dynamics of the crowders and their excluded volume effect. Our study shows that search kinetics and its mechanism are modulated not only by salt concentration and crowding occupancy, but also by the properties of the crowding particles.

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.

Are Individual Differences in Reading Speed Related to Extrafoveal Visual Acuity and Crowding?

PubMed Central

Frömer, Romy; Dimigen, Olaf; Niefind, Florian; Krause, Niels; Kliegl, Reinhold; Sommer, Werner

2015-01-01

Readers differ considerably in their speed of self-paced reading. One factor known to influence fixation durations in reading is the preprocessing of words in parafoveal vision. Here we investigated whether individual differences in reading speed or the amount of information extracted from upcoming words (the preview benefit) can be explained by basic differences in extrafoveal vision—i.e., the ability to recognize peripheral letters with or without the presence of flanking letters. Forty participants were given an adaptive test to determine their eccentricity thresholds for the identification of letters presented either in isolation (extrafoveal acuity) or flanked by other letters (crowded letter recognition). In a separate eye-tracking experiment, the same participants read lists of words from left to right, while the preview of the upcoming words was manipulated with the gaze-contingent moving window technique. Relationships between dependent measures were analyzed on the observational level and with linear mixed models. We obtained highly reliable estimates both for extrafoveal letter identification (acuity and crowding) and measures of reading speed (overall reading speed, size of preview benefit). Reading speed was higher in participants with larger uncrowded windows. However, the strength of this relationship was moderate and it was only observed if other sources of variance in reading speed (e.g., the occurrence of regressive saccades) were eliminated. Moreover, the size of the preview benefit—an important factor in normal reading—was larger in participants with better extrafoveal acuity. Together, these results indicate a significant albeit moderate contribution of extrafoveal vision to individual differences in reading speed. PMID:25789812

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.

Context-based handover of persons in crowd and riot scenarios

NASA Astrophysics Data System (ADS)

Metzler, Jürgen

2015-02-01

In order to control riots in crowds, it is helpful to get ringleaders under control and pull them out of the crowd if one has become an offender. A great support to achieve these tasks is the capability of observing the crowd and ringleaders automatically by using cameras. It also allows a better conservation of evidence in riot control. A ringleader who has become an offender should be tracked across and recognized by several cameras, regardless of whether overlapping camera's fields of view exist or not. We propose a context-based approach for handover of persons between different camera fields of view. This approach can be applied for overlapping as well as for non-overlapping fields of view, so that a fast and accurate identification of individual persons in camera networks is feasible. Within the scope of this paper, the approach is applied to a handover of persons between single images without having any temporal information. It is particularly developed for semiautomatic video editing and a handover of persons between cameras in order to improve conservation of evidence. The approach has been developed on a dataset collected during a Crowd and Riot Control (CRC) training of the German armed forces. It consists of three different levels of escalation. First, the crowd started with a peaceful demonstration. Later, there were violent protests, and third, the riot escalated and offenders bumped into the chain of guards. One result of the work is a reliable context-based method for person re-identification between single images of different camera fields of view in crowd and riot scenarios. Furthermore, a qualitative assessment shows that the use of contextual information can support this task additionally. It can decrease the needed time for handover and the number of confusions which supports the conservation of evidence in crowd and riot scenarios.

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.

Parietal neural prosthetic control of a computer cursor in a graphical-user-interface task.

PubMed

Revechkis, Boris; Aflalo, Tyson N S; Kellis, Spencer; Pouratian, Nader; Andersen, Richard A

2014-12-01

To date, the majority of Brain-Machine Interfaces have been used to perform simple tasks with sequences of individual targets in otherwise blank environments. In this study we developed a more practical and clinically relevant task that approximated modern computers and graphical user interfaces (GUIs). This task could be problematic given the known sensitivity of areas typically used for BMIs to visual stimuli, eye movements, decision-making, and attentional control. Consequently, we sought to assess the effect of a complex, GUI-like task on the quality of neural decoding. A male rhesus macaque monkey was implanted with two 96-channel electrode arrays in area 5d of the superior parietal lobule. The animal was trained to perform a GUI-like 'Face in a Crowd' task on a computer screen that required selecting one cued, icon-like, face image from a group of alternatives (the 'Crowd') using a neurally controlled cursor. We assessed whether the crowd affected decodes of intended cursor movements by comparing it to a 'Crowd Off' condition in which only the matching target appeared without alternatives. We also examined if training a neural decoder with the Crowd On rather than Off had any effect on subsequent decode quality. Despite the additional demands of working with the Crowd On, the animal was able to robustly perform the task under Brain Control. The presence of the crowd did not itself affect decode quality. Training the decoder with the Crowd On relative to Off had no negative influence on subsequent decoding performance. Additionally, the subject was able to gaze around freely without influencing cursor position. Our results demonstrate that area 5d recordings can be used for decoding in a complex, GUI-like task with free gaze. Thus, this area is a promising source of signals for neural prosthetics that utilize computing devices with GUI interfaces, e.g. personal computers, mobile devices, and tablet computers.

Economic Evaluation of the Initiative Control of Tuberculosis in Large Metropolitan Cities in Lima, Peru

DTIC Science & Technology

2016-03-22

crowded, education levels are low, unemployment is high, and there are high rates of crime and violence(112). Peru is located in the South America...Andean region and had an estimated 30 million inhabitants in 2011. According to the World Bank , Peru is classified as an upper middle-income country, as...poor nutritional status, unemployment , and access to basic health services are daily challenges(98). In the following sections, we are going to

Insurance premiums and insurance coverage of near-poor children.

PubMed

Hadley, Jack; Reschovsky, James D; Cunningham, Peter; Kenney, Genevieve; Dubay, Lisa

States increasingly are using premiums for near-poor children in their public insurance programs (Medicaid/SCHIP) to limit private insurance crowd-out and constrain program costs. Using national data from four rounds of the Community Tracking Study Household Surveys spanning the seven years from 1996 to 2003, this study estimates a multinomial logistic regression model examining how public and private insurance premiums affect insurance coverage outcomes (Medicaid/SCHIP coverage, private coverage, and no coverage). Higher public premiums are significantly associated with a lower probability of public coverage and higher probabilities of private coverage and uninsurance; higher private premiums are significantly related to a lower probability of private coverage and higher probabilities of public coverage and uninsurance. The results imply that uninsurance rates will rise if both public and private premiums increase, and suggest that states that impose or increase public insurance premiums for near-poor children will succeed in discouraging crowd-out of private insurance, but at the expense of higher rates of uninsurance. Sustained increases in private insurance premiums will continue to create enrollment pressures on state insurance programs for children.

GEOS-3 ocean current investigation using radar altimeter profiling. [Gulf Stream surface topography

NASA Technical Reports Server (NTRS)

Leitao, C. D.; Huang, N. E.; Parra, C. G.

1978-01-01

Both quasi-stationary and dynamic departures from the marine geoid were successfully detected using altitude measurements from the GEOS-3 radar altimeter. The quasi-stationary departures are observed either as elevation changes in single pass profiles across the Gulf Stream or at the crowding of contour lines at the western and northern areas of topographic maps generated using altimeter data spanning one month or longer. Dynamic features such as current meandering and spawned eddies can be monitored by comparing monthly mean maps. Comparison of altimeter inferred eddies with IR detected thermal rings indicates agreement of the two techniques. Estimates of current velocity are made using derived slope estimates in conjunction with the geostrophic equation.

Synthesis, maturation and extracellular release of procathepsin D as influenced by cell proliferation or transformation.

PubMed

Isidoro, C; Demoz, M; De Stefanis, D; Baccino, F M; Bonelli, G

1995-12-11

The relationship between cell growth and intra- and extracellular accumulation of cathepsin D (CD), a lysosomal endopeptidase involved in cell protein breakdown, was examined in cultures of normal and transformed BALB/c mouse 3T3 fibroblasts grown at various cell densities. In crowded cultures of normal 3T3 cells (doubling time, Td, 53 hr) intracellular CD activity was 2-fold higher than in sparse, rapidly-growing (Td, 27 hr) cultures. In uncrowded (Td, 18 hr) and crowded (Td, 32 hr) cultures of benzo[a]pyrene-transformed cells intracellular CD levels were one third and two thirds, respectively, of those measured in hyperconfluent 3T3 cultures. Regardless of cell density, SV-40-virus-transformed cells (Td, 12 hr) contained one third of CD levels found in hyperconfluent 3T3 cells. Both transformed cell lines released into the medium a higher proportion of CD, compared with their untransformed counterpart, yet the amount secreted was not sufficient to account for the reduced intracellular level of the enzyme. Serum withdrawal induced a marked increase of both intra- and extracellular levels of CD activity. In both normal and virally or chemically transformed 3T3 cells CD comprised a precursor (52 kDa) and processed mature polypeptides; the latter were mostly represented by a 48-kDa peptide, but a minor part was in a double-chain form (31 and 16 kDa respectively). The proportion of mature enzyme vs. precursor was much higher in confluent, slowly-growing cells than in fast-growing cells, whether normal or transformed. In the latter, conversion of mature 48-kDa peptide into the double-chain form occurred more efficiently.

Hydration entropy change from the hard sphere model.

PubMed

Graziano, Giuseppe; Lee, Byungkook

2002-12-10

The gas to liquid transfer entropy change for a pure non-polar liquid can be calculated quite accurately using a hard sphere model that obeys the Carnahan-Starling equation of state. The same procedure fails to produce a reasonable value for hydrogen bonding liquids such as water, methanol and ethanol. However, the size of the molecules increases when the hydrogen bonds are turned off to produce the hard sphere system and the volume packing density rises. We show here that the hard sphere system that has this increased packing density reproduces the experimental transfer entropy values rather well. The gas to water transfer entropy values for small non-polar hydrocarbons is also not reproduced by a hard sphere model, whether one uses the normal (2.8 A diameter) or the increased (3.2 A) size for water. At least part of the reason that the hard sphere model with 2.8 A size water produces too small entropy change is that the size of water is too small for a system without hydrogen bonds. The reason that the 3.2 A model also produces too small entropy values is that this is an overly crowded system and that the free volume introduced in the system by the addition of a solute molecule produces too much of a relief to this crowding. A hard sphere model, in which the free volume increase is limited by requiring that the average surface-to-surface distance between the solute and water molecules is the same as that between the increased-size water molecules, does approximately reproduce the experimental hydration entropy values. Copyright 2002 Elsevier Science B.V.

DDDAMS-based Urban Surveillance and Crowd Control via UAVs and UGVs

DTIC Science & Technology

2015-12-04

for crowd dynamics modeling by incorporating multi-resolution data, where a grid-based method is used to model crowd motion with UAVs’ low -resolution...information and more computational intensive (and time-consuming). Given that the deployment of fidelity selection results in simulation faces computational... low fidelity information FOV y (A) DR x (A) DR y (A) Not detected high fidelity information Table 1: Parameters for UAV and UGV for their detection

Smoke in the Looking Glass: Effects of Discordance between Self- and Peer Rated Crowd Affiliation on Adolescent Anxiety, Depression and Self-Feelings

ERIC Educational Resources Information Center

Brown, B. Bradford; Von Bank, Heather; Steinberg, Laurence

2008-01-01

Peer crowds serve as an identity marker for adolescents, indicating their image and status among peers; but adolescents do not always endorse peer appraisals of crowd affiliation. We report on two studies--one with 924 adolescents in grades 7-12 and a second with a more diverse population of 2,728 students in grades 9-11, followed for 2…

The Face in the Crowd Effect Unconfounded: Happy Faces, Not Angry Faces, Are More Efficiently Detected in Single- and Multiple-Target Visual Search Tasks

ERIC Educational Resources Information Center

Becker, D. Vaughn; Anderson, Uriah S.; Mortensen, Chad R.; Neufeld, Samantha L.; Neel, Rebecca

2011-01-01

Is it easier to detect angry or happy facial expressions in crowds of faces? The present studies used several variations of the visual search task to assess whether people selectively attend to expressive faces. Contrary to widely cited studies (e.g., Ohman, Lundqvist, & Esteves, 2001) that suggest angry faces "pop out" of crowds, our review of…

Identification of primary and secondary UBA footprints on the surface of ubiquitin in cell-mimicking crowded solution.

PubMed

Munari, Francesca; Bortot, Andrea; Zanzoni, Serena; D'Onofrio, Mariapina; Fushman, David; Assfalg, Michael

2017-04-01

Despite significant advancements in our understanding of ubiquitin-mediated signaling, the influence of the intracellular environment on the formation of transient ubiquitin-partner complexes remains poorly explored. In our work, we introduce macromolecular crowding as a first level of complexity toward the imitation of a cellular environment in the study of such interactions. Using NMR spectroscopy, we find that the stereospecific complex of ubiquitin and the ubiquitin-associated domain (UBA) is minimally perturbed by the crowding agent Ficoll. However, in addition to the primary canonical recognition patch on ubiquitin, secondary patches are identified, indicating that in cell-mimicking crowded solution, UBA contacts ubiquitin at multiple sites. © 2017 Federation of European Biochemical Societies.

Observable characteristics associated with alcohol intoxication within licensed entertainment venues in Australia.

PubMed

Coomber, Kerri; Pennay, Amy; Droste, Nicolas; Mayshak, Richelle; Martino, Florentine; Bowe, Steven J; Miller, Peter G

2016-10-01

The aim of the current study was to assess correlates of intoxication in licensed venues in Australia. Covert observations of licensed venues and venue patron in night-time entertainment districts of five Australian cities were conducted. In total, 828 unique cross-sectional observations were completed across 62 bars, nightclubs, and large mainstream pubs. Venues were selected from the main entertainment district of smaller cities and the busiest entertainment districts of larger cities. Outcomes were the estimated percentage of patrons showing any signs of alcohol intoxication and the overall level of intoxication ('high' versus 'none to medium'). Seven predictors of patron intoxication were examined: hour of observation; estimated percentage of male patrons; estimated percentage of patrons <25 years old; venue crowding; presence of observable alcohol promotions; type of alcoholic beverage consumed by the majority of patrons; and, venue type. Time of night (coefficient=11.71, p<.001; OR=9.61, p<.001), percentage of patrons aged <25 (coefficient=0.14, p<.001; OR=1.01, p=.031), and venue crowding (coefficient=4.40, p<.001; OR=1.39, p=.009) had significant positive associations with both signs of intoxication and high levels of intoxication. Nightclubs had a lower percentage of signs of intoxication compared to pubs (coefficient=-10.73, p=.021). Increased percentage of male patrons was associated with increased odds of high-level intoxication (OR=1.05, p=.020). Time of night and proportion of younger patrons had a strong association with patron intoxication adding further support for the strong body of evidence that ceasing service of alcohol earlier in the evening will reduce intoxication levels. Copyright © 2016 Elsevier B.V. All rights reserved.

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.

Crowding of Interacting Fluid Particles in Porous Media through Molecular Dynamics: Breakdown of Universality for Soft Interactions.

PubMed

Schnyder, Simon K; Horbach, Jürgen

2018-02-16

Molecular dynamics simulations of interacting soft disks confined in a heterogeneous quenched matrix of soft obstacles show dynamics which is fundamentally different from that of hard disks. The interactions between the disks can enhance transport when their density is increased, as disks cooperatively help each other over the finite energy barriers in the matrix. The system exhibits a transition from a diffusive to a localized state, but the transition is strongly rounded. Effective exponents in the mean-squared displacement can be observed over three decades in time but depend on the density of the disks and do not correspond to asymptotic behavior in the vicinity of a critical point, thus, showing that it is incorrect to relate them to the critical exponents in the Lorentz model scenario. The soft interactions are, therefore, responsible for a breakdown of the universality of the dynamics.

Does interspecific competition have a moderating effect on Taenia solium transmission dynamics in Southeast Asia?

PubMed

Conlan, James V; Vongxay, Khamphouth; Fenwick, Stanley; Blacksell, Stuart D; Thompson, R C Andrew

2009-09-01

It is well understood that sociocultural practices strongly influence Taenia solium transmission; however, the extent to which interspecific parasite competition moderates Taenia transmission has yet to be determined. This is certainly the case in Southeast Asia where T. solium faces competition in both the definitive host (people) and the intermediate host (pigs). In people, adult worms of T. solium, T. saginata and T. asiatica compete through density-dependent crowding mechanisms. In pigs, metacestodes of T. solium, T. hydatigena and T. asiatica compete through density-dependent immune-mediated interactions. Here, we describe the biological and epidemiological implications of Taenia competition and propose that interspecific competition has a moderating effect on the transmission dynamics of T. solium in the region. Furthermore, we argue that this competitive ecological scenario should be considered in future research and surveillance activities examining T. solium cysticercosis and taeniasis in Southeast Asia.

Two-dimensional enzyme diffusion in laterally confined DNA monolayers.

PubMed

Castronovo, Matteo; Lucesoli, Agnese; Parisse, Pietro; Kurnikova, Anastasia; Malhotra, Aseem; Grassi, Mario; Grassi, Gabriele; Scaggiante, Bruna; Casalis, Loredana; Scoles, Giacinto

2011-01-01

Addressing the effects of confinement and crowding on biomolecular function may provide insight into molecular mechanisms within living organisms, and may promote the development of novel biotechnology tools. Here, using molecular manipulation methods, we investigate restriction enzyme reactions with double-stranded (ds)DNA oligomers confined in relatively large (and flat) brushy matrices of monolayer patches of controlled, variable density. We show that enzymes from the contacting solution cannot access the dsDNAs from the top-matrix interface, and instead enter at the matrix sides to diffuse two-dimensionally in the gap between top- and bottom-matrix interfaces. This is achieved by limiting lateral access with a barrier made of high-density molecules that arrest enzyme diffusion. We put forward, as a possible explanation, a simple and general model that relates these data to the steric hindrance in the matrix, and we briefly discuss the implications and applications of this strikingly new phenomenon.

Thermodynamic properties of water in confined environments: a Monte Carlo study

NASA Astrophysics Data System (ADS)

Gladovic, Martin; Bren, Urban; Urbic, Tomaž

2018-05-01

Monte Carlo simulations of Mercedes-Benz water in a crowded environment were performed. The simulated systems are representative of both composite, porous or sintered materials and living cells with typical matrix packings. We studied the influence of overall temperature as well as the density and size of matrix particles on water density, particle distributions, hydrogen bond formation and thermodynamic quantities. Interestingly, temperature and space occupancy of matrix exhibit a similar effect on water properties following the competition between the kinetic and the potential energy of the system, whereby temperature increases the kinetic and matrix packing decreases the potential contribution. A novel thermodynamic decomposition approach was applied to gain insight into individual contributions of different types of inter-particle interactions. This decomposition proved to be useful and in good agreement with the total thermodynamic quantities especially at higher temperatures and matrix packings, where higher-order potential-energy mixing terms lose their importance.

Crowding of Interacting Fluid Particles in Porous Media through Molecular Dynamics: Breakdown of Universality for Soft Interactions

NASA Astrophysics Data System (ADS)

Schnyder, Simon K.; Horbach, Jürgen

2018-02-01

Molecular dynamics simulations of interacting soft disks confined in a heterogeneous quenched matrix of soft obstacles show dynamics which is fundamentally different from that of hard disks. The interactions between the disks can enhance transport when their density is increased, as disks cooperatively help each other over the finite energy barriers in the matrix. The system exhibits a transition from a diffusive to a localized state, but the transition is strongly rounded. Effective exponents in the mean-squared displacement can be observed over three decades in time but depend on the density of the disks and do not correspond to asymptotic behavior in the vicinity of a critical point, thus, showing that it is incorrect to relate them to the critical exponents in the Lorentz model scenario. The soft interactions are, therefore, responsible for a breakdown of the universality of the dynamics.

Lessons Learned from Crowdsourcing Complex Engineering Tasks.

PubMed

Staffelbach, Matthew; Sempolinski, Peter; Kijewski-Correa, Tracy; Thain, Douglas; Wei, Daniel; Kareem, Ahsan; Madey, Gregory

2015-01-01

Crowdsourcing is the practice of obtaining needed ideas, services, or content by requesting contributions from a large group of people. Amazon Mechanical Turk is a web marketplace for crowdsourcing microtasks, such as answering surveys and image tagging. We explored the limits of crowdsourcing by using Mechanical Turk for a more complicated task: analysis and creation of wind simulations. Our investigation examined the feasibility of using crowdsourcing for complex, highly technical tasks. This was done to determine if the benefits of crowdsourcing could be harnessed to accurately and effectively contribute to solving complex real world engineering problems. Of course, untrained crowds cannot be used as a mere substitute for trained expertise. Rather, we sought to understand how crowd workers can be used as a large pool of labor for a preliminary analysis of complex data. We compared the skill of the anonymous crowd workers from Amazon Mechanical Turk with that of civil engineering graduate students, making a first pass at analyzing wind simulation data. For the first phase, we posted analysis questions to Amazon crowd workers and to two groups of civil engineering graduate students. A second phase of our experiment instructed crowd workers and students to create simulations on our Virtual Wind Tunnel website to solve a more complex task. With a sufficiently comprehensive tutorial and compensation similar to typical crowd-sourcing wages, we were able to enlist crowd workers to effectively complete longer, more complex tasks with competence comparable to that of graduate students with more comprehensive, expert-level knowledge. Furthermore, more complex tasks require increased communication with the workers. As tasks become more complex, the employment relationship begins to become more akin to outsourcing than crowdsourcing. Through this investigation, we were able to stretch and explore the limits of crowdsourcing as a tool for solving complex problems.

The mechanism of word crowding.

PubMed

Yu, Deyue; Akau, Melanie M U; Chung, Susana T L

2012-01-01

Word reading speed in peripheral vision is slower when words are in close proximity of other words (Chung, 2004). This word crowding effect could arise as a consequence of interaction of low-level letter features between words, or the interaction between high-level holistic representations of words. We evaluated these two hypotheses by examining how word crowding changes for five configurations of flanking words: the control condition - flanking words were oriented upright; scrambled - letters in each flanking word were scrambled in order; horizontal-flip - each flanking word was the left-right mirror-image of the original; letter-flip - each letter of the flanking word was the left-right mirror-image of the original; and vertical-flip - each flanking word was the up-down mirror-image of the original. The low-level letter feature interaction hypothesis predicts similar word crowding effect for all the different flanker configurations, while the high-level holistic representation hypothesis predicts less word crowding effect for all the alternative flanker conditions, compared with the control condition. We found that oral reading speed for words flanked above and below by other words, measured at 10° eccentricity in the nasal field, showed the same dependence on the vertical separation between the target and its flanking words, for the various flanker configurations. The result was also similar when we rotated the flanking words by 90° to disrupt the periodic vertical pattern, which presumably is the main structure in words. The remarkably similar word crowding effect irrespective of the flanker configurations suggests that word crowding arises as a consequence of interactions of low-level letter features. Copyright © 2011 Elsevier Ltd. All rights reserved.

Hailstorms over Switzerland: Verification of Crowd-sourced Data

NASA Astrophysics Data System (ADS)

Noti, Pascal-Andreas; Martynov, Andrey; Hering, Alessandro; Martius, Olivia

2016-04-01

The reports of smartphone users, witnessing hailstorms, can be used as source of independent, ground-based observation data on ground-reaching hailstorms with high temporal and spatial resolution. The presented work focuses on the verification of crowd-sourced data collected over Switzerland with the help of a smartphone application recently developed by MeteoSwiss. The precise location, time of hail precipitation and the hailstone size are included in the crowd-sourced data, assessed on the basis of the weather radar data of MeteoSwiss. Two radar-based hail detection algorithms, POH (Probability of Hail) and MESHS (Maximum Expected Severe Hail Size), in use at MeteoSwiss are confronted with the crowd-sourced data. The available data and investigation time period last from June to August 2015. Filter criteria have been applied in order to remove false reports from the crowd-sourced data. Neighborhood methods have been introduced to reduce the uncertainties which result from spatial and temporal biases. The crowd-sourced and radar data are converted into binary sequences according to previously set thresholds, allowing for using a categorical verification. Verification scores (e.g. hit rate) are then calculated from a 2x2 contingency table. The hail reporting activity and patterns corresponding to "hail" and "no hail" reports, sent from smartphones, have been analyzed. The relationship between the reported hailstone sizes and both radar-based hail detection algorithms have been investigated.