Egress Models Research Articles

ESCRT-III-dependent and -independent egress of herpesviruses

Enveloped viruses complete their replication cycle by forming virions that bud from infected cells through membrane scission. The mechanisms by which this is achieved are less well-understood than the well-characterized membrane scission of vesicles budding inwards into the cytosol. The scission of vesicles that bud away from the cytosol is mediated by machinery of the endosomal sorting complexes required for transport (ESCRT)-III, which is highjacked by viruses of several different families. Other groups of viruses can bud independently of ESCRT-III activity. It has not been fully elucidated how the latter achieve this in the absence of host ESCRT-III, but it is known that some viral proteins directly mediate membrane scission. The Herpesviridae constitute a family of highly diverse viruses that bud at the inner nuclear membrane and cytoplasmic membranes in infected cells. Many investigators have attempted to determine the mechanism of membrane scission during herpesvirus budding, and have found this to be complex, not exactly conforming to either of the two methods. The present review attempts to synthesize the disparate findings into a model of herpesvirus egress based on both ESCRT-mediated and viral protein-mediated mechanisms.

Egress Modeling of Evacuation from Railcar - A Case Study

Egress Modeling of Evacuation from Railcar - A Case Study

Design and Implementation of a Quantitative Risk Assessment Model for UK Road Tunnels

One of the critical transportation infrastructures is road tunnels and fire safety is one of the important aspects of their operation. Interaction between the fire, tunnel users, traffic, and fire safety measures influences fires in road tunnels. Therefore, a complex model is required to analyse the risk and quantify the consequences. In this paper, a novel quantitative risk analysis model developed for UK road tunnels is presented consisting of a quantitative consequence analysis model and a quantitative frequency frequency analysis model. The proposed quantitative consequence analysis model is provided through three sub-models; queue model, distribution model, and egress model. The frequency analysis is via an event tree that takes into account the tunnel fire rate in UK road tunnels. After a brief description of this model, the proposed method is illustrated through a case study of an urban road tunnel. The effect of different emergency ventilation systems on societal risk and sensitivity of the model to pre-movement time, accident frequencies involving Heavy Good Vehicles (HGVs), tenability threshold temperature, and different burning vehicles were studied in this case study.

Evaluating building egress safety for the elderly under different urgent-level circumstances in high-density cities: Based on ABEM-enabled simulation

In high-density cities, people usually live in mid-rise or high-rise residential buildings where indoor environments are quite complicated. Safety risks exist not only within homes, but also on the way to egress from residential buildings. As the aging issue becomes severer, it is essential to provide safe egress plans particularly for the elderly who are more fragile to risks and obstacles. Kinds of emergencies might occur in reality, some are hard to predict and extremely dangerous, while some can be warned in advance and would not cause damages immediately. However, previous research seldom considered the different urgent levels of circumstances during the egress process of the elderly. Consequently, this study contributes to proposing an agent-based egress model (ABEM)-based evaluation of building egress safety for the elderly under different urgent-level circumstances by introducing absolute and relative indicators. Absolute indicators evaluate building egress safety for the elderly, relative indicators reveal whether buildings hinder safe egress of the elderly compared with ordinary residents, and indicator weights are decided by AHP method to compute building egress safety index (BESI) as the evaluation results. Case study shows BESI scores of 8.696, 8.941 and 6.290 under three circumstances. BESI scores are valuable references for old home buyers to make decisions. Furthermore, this evaluation approach offers an effective tool to help designers to improve design schemes for safer egress, to assist property managers in updating egress plans and facilities based on new occupancy status in the operation stage, eventually to facilitate the development of healthy residential buildings.

Decreased Innate Migration of Pro-Inflammatory M1 Macrophages through the Mesothelial Membrane Is Affected by Ceramide Kinase and Ceramide 1-P.

The retrograde flow of endometrial tissues deposited into the peritoneal cavity occurs in women during menstruation. Classically (M1) or alternatively (M2) activated macrophages partake in the removal of regurgitated menstrual tissue. The failure of macrophage egress from the peritoneal cavity through the mesothelium leads to chronic inflammation in endometriosis. To study the migration differences of macrophage phenotypes across mesothelial cells, an in vitro model of macrophage egress across a peritoneal mesothelial cell monolayer membrane was developed. M1 macrophages were more sessile, emigrating 2.9-fold less than M2 macrophages. The M1 macrophages displayed a pro-inflammatory cytokine signature, including IL-1α, IL-1β, TNF-α, TNF-β, and IL-12p70. Mass spectrometry sphingolipidomics revealed decreased levels of ceramide-1-phosphate (C1P), an inducer of migration in M1 macrophages, which correlated with its poor migration behavior. C1P is generated by ceramide kinase (CERK) from ceramide, and blocking C1P synthesis via the action of NVP231, a specific CERK chemical inhibitor, prohibited the emigration of M1 and M2 macrophages up to 6.7-fold. Incubation with exogenously added C1P rescued this effect. These results suggest that M1 macrophages are less mobile and have higher retention in the peritoneum due to lower C1P levels, which contributes to an altered peritoneal environment in endometriosis by generating a predominant pro-inflammatory cytokine environment.

Crowd behaviour in Canadian football stadia — Part 1: Data collection

Large crowd sizes at stadia events require an in-depth consideration of human behaviour, since the reliability of egress models in design depends on the confidence of the input data. However, there is little contemporary public data surrounding crowd behaviour, and its implementation into pedestrian movement models, particularly focused on Canadian demographics in stadia. A novel data collection (Part 1) and subsequent egress validation modelling of a Canadian stadium were completed to examine the variability of simulations with behavioural inputs (Part 2). The demographic distribution, pedestrian speed, exit and route choice, and areas of congestion were quantified using high resolution cameras. Behaviourally, pedestrians exited the stadium where they entered which created high levels of cross flow. It was observed that contemporary walking speed profiles for stadia will differentiate from classical profiles especially with reflection of demographic distribution by as much as 31%. Individual walking speeds, while highly variable, impacted overall egress time. Crowd density also being a factor that further reduced their speed.

One-Way Coupling of Fire and Egress Modeling for Realistic Evaluation of Evacuation Process

In the discipline of fire engineering, computational simulation tools are used to evaluate the available safe egress time (ASET) and required safe egress time (RSET) of a building fire. ASET and RSET are often analyzed separately, using computational fluid dynamics (CFD) and crowd dynamics, respectively. Although there are advantages to coupling the ASET and RSET analysis to quantify tenability conditions and reevaluate evacuation time within a building, the coupling process is computationally complex, requiring multiple steps. The coupling setup can be time-consuming, particularly when the results are limited to the modeled scenario. In addition, the procedure is not uniform throughout the industry. This paper presents the successful one-way coupling of CFD and crowd dynamics modeling through a new simplified methodology that captures the impact of fractional effective dose (FED) and reduced visibility from smoke on the individual evacuee’s movement and the human interaction. The simulation tools used were Fire Dynamics Simulator (FDS) and Oasys MassMotion for crowd dynamics. The coupling was carried out with the help of the software development kit of Oasys MassMotion in two different example geometries: an open-plan room and a floor with six rooms and a corridor. The results presented in this paper show that, when comparing an uncoupled and a coupled simulation, the effects of the smoke lead to different crowd density profiles, particularly closer to the exit, which elongates the overall evacuation time. This coupling method can be applied to any geometry because of its flexible and modular framework.

Real-Time Egress Model for Multiplex Buildings under Fire Based on Artificial Neural Network

When fire occurs in a large multiplex building, the direction of smoke and flames is often similar to that of the evacuation of building occupants. This causes evacuation bottlenecks in a specific compartment, especially when the occupant density is very high, which unfortunately often leads to many fatalities and injuries. Thus, the development of an egress model that can ensure the safe evacuation of occupants is required to minimize the number of casualties. In this study, the correlations between fire temperature with visibility and toxic gas concentration were investigated through a fire simulation on a multiplex building, from which databases for training of artificial neural networks (ANN) were created. Based on this, an ANN model that can predict the available safe egress time was developed, and it estimated the available safe egress time (ASET) very accurately. In addition, an egress model that can guide rapid and safe evacuation routes for occupants was proposed, and the rationality of the proposed model was verified in detail through an application example. The proposed model provided the optimal evacuation route with the longest margin of safety in consideration of both ASET and the movement time of occupants under fire.

Influences of wing gate turnstiles' characteristics on pedestrian evacuation based on agent-based egress model.

Wing gate turnstiles are widely used in airports, subway stations, railway stations, movie theaters, parks, etc., and influence the pedestrian evacuation greatly while accidents happen. Thus, doing some researches on how to improve the evacuation speed for wing gate turnstiles are meaningful and necessary. In response to this issue, the influences of the wing gate turnstiles on pedestrian evacuation are investigated by pathfinder in this paper. Pathfinder is an agent-based egress simulator that uses steering behaviors to model occupant motion. First of all, by Pathfinder, two evacuation models with flat-shaped and wedge-shaped hosts wing gate turnstiles, respectively, are established, and the simulations of pedestrian evacuation are carried out by computer. The results show the evacuation speed obtained by the wedge-shaped host is faster than that obtained by the flat-shaped host. Moreover, the longest evacuation time is obtained when the channels' width is 90 cm, and the shortest is obtained when the channels' width is 51.4 cm. For a small number of evacuees, the evacuation time is mainly influenced by the original distributions of the evacuees, however, as the number of the evacuees increases, the evacuation time is mainly influenced by the number of the evacuees. Furthermore, the wing gate turnstiles with widened hosts can get less evacuation time no matter whether the hosts are flat-shaped or wedge-shaped, however, the evacuation-time-saved rate obtained by wedge-shaped host is much higher than that obtained by flat-shaped host. Then, the influences of the wedge angle on the pedestrian evacuation are discussed, and the optimal wedge angle is obtained. The obtained results can not only provide helps for managers to evacuate crowds under emergency, but also offer some assistances for designers to design those gate turnstiles or building exits.

Variability in stadia evacuation under normal, high-motivation, and emergency egress

Egress modelling can be used in stadia design. This modelling describes the movement of pedestrians and crowd flow considering wayfinding and decision making in evacuation and circulation. The accuracy of the modelling is highly dependent on project-specific input data that accurately represents the movement of population with associated human factors considered. Currently, there are few contemporary studies of stadia that consider real egress decision making under a range of stimuli of which practitioners may use to influence their modelling and design process. Herein, a range of evacuation urgencies and their effect on pedestrian decision making and wayfinding in stadia are considered: standard post-game egress, egress under high-motivation conditions, and emergency egress. This is done through carefully collected and recorded observation of real stadia in Canada and obtained third party video for stadiums internationally. To reinforce findings, real case studies of other notable emergencies are also considered. Decision making at all stages of evacuation are analyzed. Results indicate that, based on the cases examined, the egress behaviours differ in relation to the level of urgency, such as high motivation and emergency, and gate densities are higher for high motivation egress by a factor of 1.5. The role of staff in the evacuation process is one of the predominant factors in reducing or extending premovement regardless of the scenario. Associated contemporary behavioural theorems are used to explain differences in movement and decision-making in evacuation scenarios.

A Scenario Simulation - Evaluating Evacuation Analysis for ro-ro Passenger Ship in MV Tai Hwa

The ro-ro passenger ship is a type of passenger ship which is commonly seen in Europe. After the tragedy of MV Estonia, an effective evaluation of escape routes in passenger ship in the initial stage of ship design has been required by International Convention for the Safety of Life at Sea (SOLAS) Convention. To reduce the loss of life in passenger ships at sea, the International Maritime Organization (IMO) has created the revised guidelines on evacuation analyses for new and existing passenger ships. This article followed IMO's mandatory guidelines via using the hydraulic model of emergency egress to scrutinize the evacuation routes, congestion points, and the total evacuation duration of MV Tai Hwa.

Consideration of the Door Opening Process in Pedestrian Flow: Experiments on Door Opening Direction, Door Handle Type, and Limited Visibility

The door is a section prone to bottlenecks and is an important element in the study of pedestrian flow. Therefore, characteristics of doors (e.g., width, location, and the distance between doors) have been taken into consideration in the existing literature related to doors. According to several previous studies, it appears likely that the door opening process (DOP) influences pedestrian flow. However, the number of studies examining the DOP remains small. Therefore, to enhance understanding of pedestrian flow, we examined two door characteristics that could affect the DOP (opening direction (swing door: push or pull) and handle type (knob, lever, and panic bar)) and limited visibility. We conducted a walking experiment to take all variables (10 cases; 10 participants per case) into account. Statistical analysis was performed on the difference in movement times, and the results were as follows: (1) inclusion of the DOP affected pedestrian flow; (2) when visibility was limited, movement times with DOP inclusion increased significantly regardless of the door opening direction and handle type; (3) when the door opening direction was ‘push’, regardless of limited visibility and door handle type, movement times with DOP inclusion were significantly lower; and (4) the door handle type did not result in any significant difference in movement times with DOP inclusion. In addition, we calculated the delay time based on the experiment results, to include the DOP in pedestrian flow (push 1.96–2.88 s, pull 3.91–4.43 s; limited visibility: push 7.38–12.56 s, and pull 12.88–16.35 s). The results of this study could be used as basic data for the development of codes/regulations, engineering guidance, and egress models for doors.

Hospital Evacuation Planning Tool for Assistance Devices (HEPTAD)

SummaryA new software tool, called HEPTAD (Hospital Evacuation Planning Tool for Assistance Devices), designed to aid evacuation planning in hospitals is described and demonstrated in this article. The software can identify regions within a hospital geometry that are inappropriate for patients who require the use of specific movement assistance devices in the event of an emergency evacuation. Using the software, Hospital Emergency Coordinators can reduce the risk of allocating a bed to a patient from which they cannot be evacuated within a safe time. In addition, HEPTAD is designed to be a proof of concept for algorithms that will later be incorporated within the EXODUS egress model. HEPTAD utilises several techniques from autonomous robotics to generate the fastest viable egress route for movement assistance devices from every location in the geometry while considering device spatial constraints (size and shape) and kinematic constraints (maximum speeds, turning radius and holonomicity). It then uses the egress time of this route along with factors from space syntax (isovist and spaciousness) to analyse the emergency vulnerability of every location within the geometry.

Bridging the gap Why we need to enhance current simulation models

Many models that simulate evacuations are state of the art and provide realistic insight to their users. However, simulating everyday situations, such as visitor flow through a museum or passenger flow through an airport, presents marked challenges; existing models reach their limit here. This contribution will introduce and highlight the gap between existing egress models and the difficulties found simulating, for instance, passenger flow or capacity analysis.

Emergency egress for the elderly in care home fire situations

SummaryPractitioners are continuing to develop egress modelling software for the design of the built environment. These models require data about human behaviour and factors for calibration, validation and verification. This study aims to address the specific data and knowledge gap: emergency egress of the elderly. Such data are difficult to collect given privacy and consent concerns, with strong relationships generally being required between residences and researchers. Through the observation of nine fire drills at six Canadian long‐term care (LTC) and retirement homes, specific evacuation actions and behaviour were observed for 37 staff members and information about the evacuation of 56 residents was collected. These drills demonstrated that emergency egress in LTC and retirement homes is highly staff dependent with 72% of residents recorded requiring full assistance at all stages of movement in evacuation, and that the type of announced/unannounced drill and level of resident care will affect the type of data collected. The development of travel speed and pre‐movement is discussed subject to limitation with qualitative behavioural insights of residents that were observed. This study provides valuable methodological discussion on how to conduct behavioural studies in similar highly restricted research environments. Specific attention is given to understanding the considerations that must be made when using fire drills as data sources, and the impact that these can have on using such data for modelling. This study may inform the initial setup and programming of evacuation models from an actions and behavioural perspectives of staff members and residents.

Determining Confidence Intervals, and Convergence, for Parameters in Stochastic Evacuation Models

An issue when using stochastic egress models is how many simulations are required to accurately represent the modelled scenario? Engineers are mostly interested in a representative Total Evacuation Time (TET). However, the convergence of the TET may not ensure that the full range of evacuation dynamics has been adequately represented. The average total egress curve (AC) has been suggested as an improved measure. Unfortunately, defining a confidence interval (CI) for the AC is problematic. CIs can robustly quantify the precision of many statistics and have been used to define convergence in egress modelling and other research fields. This paper presents a novel application of bootstrapping, functional analysis measures (FAMs), and a bisection algorithm, to derive three FAM-based CIs representing the precision of the AC. These CIs were tested using a theoretical model to demonstrate the consistency of the coverage probability, the actual percentage of CIs that contain the theoretical parameter, with the nominal 95% confidence level (NCL). For two of the FAM-based CIs, it was found that the coverage probability was between 94.2% and 95.6% for all tested sample sizes between 10 and 4000 simulations. The third FAM-based CI’s coverage probability was always greater than the NCL and was a conservative estimate, but this presented no problems in practice. A FAM-based CI may suggest if there is more or less variability in an earlier phase of the evacuation. A convergence scheme based on statistical precision, CI widths, is proposed and verified. The method can be extended to other statistics.

TOWARDS EGRESS MODELLING IN VOXEL BUILDING MODELS

Abstract. Egress (or Evacuation) modelling has the purpose to simulate how the people inside a building can move outside in a safe manner and as quick as possible in case of an emergency. The goal can be to assess the safety of an existing building or a building design, to establish evacuation routes and install signage, or even to give real-time guidance to the evacuating crowd during an emergency. In all cases, the availability of a three-dimensional building model allows to generate the necessary input for the egress modelling software. The algorithms for such software can be subdivided into two major categories, working with navigation grids or navigation networks, respectively. The purpose of this paper is to illustrate that voxel-based building models are particularly suited to provide input for both categories. We further illustrate how to process might continue using an algorithm based on (electrical) network analysis, which can be applied in both a gridded and a network-based simulation. We provide preliminary results for the gridded case.

Systematic gene silencing identified Cryptosporidium nucleoside diphosphate kinase and other molecules as targets for suppression of parasite proliferation in human intestinal cells

Cryptosporidiosis is a major cause of diarrheal disease. The only drug approved for cryptosporidiosis has limited efficacy in high-risk populations. Therefore novel drugs are urgently needed. We have identified several enzymes as potential targets for drug development and we have optimized a rapid method to silence genes in Cryptosporidium. In this study, we knocked down expression of the four selected genes: Actin (Act), Apicomplexan DNA-binding protein (Ap2), Rhomboid protein 1 (Rom 1), and nucleoside diphosphate kinase (NDK). After gene silencing, we evaluated the role of each target on parasite development using in vitro models of excystation, invasion, proliferation, and egress. We showed that silencing of Act, Ap2, NDK, and Rom1 reduced invasion, proliferation, and egress of Cryptosporidium. However, silencing of NDK markedly inhibited Cryptosporidium proliferation (~70%). We used an infection model to evaluate the anticryptosporidial activity of ellagic acid (EA), an NDK inhibitor. We showed that EA (EC50 = 15–30 µM) reduced parasite burden without showing human cell toxicity. Here, we demonstrated the usefulness of a rapid silencing method to identify novel targets for drug development. Because EA is a dietary supplement already approved for human use, this compound should be studied as a potential treatment for cryptosporidiosis.

Comparative and functional genomics of the protozoan parasite Babesia divergens highlighting the invasion and egress processes.

Babesiosis is considered an emerging disease because its incidence has significantly increased in the last 30 years, providing evidence of the expanding range of this rare but potentially life-threatening zoonotic disease. Babesia divergens is a causative agent of babesiosis in humans and cattle in Europe. The recently sequenced genome of B. divergens revealed over 3,741 protein coding-genes and the 10.7-Mb high-quality draft become the first reference tool to study the genome structure of B. divergens. Now, by exploiting this sequence data and using new computational tools and assembly strategies, we have significantly improved the quality of the B. divergens genome. The new assembly shows better continuity and has a higher correspondence to B. bovis chromosomes. Moreover, we present a differential expression analysis using RNA sequencing of the two different stages of the asexual lifecycle of B. divergens: the free merozoite capable of invading erythrocytes and the intraerythrocytic parasite stage that remains within the erythrocyte until egress. Comparison of mRNA levels of both stages identified 1,441 differentially expressed genes. From these, around half were upregulated and the other half downregulated in the intraerythrocytic stage. Orthogonal validation by real-time quantitative reverse transcription PCR confirmed the differential expression. A moderately increased expression level of genes, putatively involved in the invasion and egress processes, were revealed in the intraerythrocytic stage compared with the free merozoite. On the basis of these results and in the absence of molecular models of invasion and egress for B. divergens, we have proposed the identified genes as putative molecular players in the invasion and egress processes. Our results contribute to an understanding of key parasitic strategies and pathogenesis and could be a valuable genomic resource to exploit for the design of diagnostic methods, drugs and vaccines to improve the control of babesiosis.

Performance-Based Fire Engineering Design of a Heritage Building: McDougall House Case Study

The application of a performance-based fire engineering design has enabled the conservation of a heritage building in New Zealand. McDougall House is a two-story heritage building which suffered extensive damages during the Canterbury earthquakes in 2010 and 2011. The scope of the conservation plan included the preservation and restoration of the building external façade, the restoration of the ornamental plasterwork ceiling within the Ballroom, the reconstruction of all damaged internal lath and plaster linings, the adaptation of the fireplace, and the reconstruction of the damaged chimney. The fire engineering design adopted is the Verification Method C/VM2 with As Nearly As is Reasonably Practicable consideration for the heritage fabrics of the building. The combination of quantitative and qualitative analyses has demonstrated the building design compliance with the 10 design scenarios of C/VM2. These analyses include the assessment of minimum means of escape and fire protection provisions, the assessment of allowable unprotected areas in the external wall for horizontal fire spread, the assessment of firefighting provisions, the smoke and egress modelling of proposed design fires, and the benefit versus sacrifice analysis on the heritage fabrics. The application of C/VM2 results in an upgrade to the fire safety and fire protection systems of the building while also retaining and enhancing its heritage value.