Biomembranes are two-dimensional assemblies of phospholipids that are only a few nanometres thick, but form micrometre-sized structures vital to cellular function. Explicit molecular modelling of ...biologically relevant membrane systems is computationally expensive due to the large number of solvent particles and slow membrane kinetics. Coarse-grained solvent-free membrane models offer efficient sampling but sacrifice realistic kinetics, thereby limiting the ability to predict pathways and mechanisms of membrane processes. Here, we present a framework for integrating coarse-grained membrane models with continuum-based hydrodynamics. This framework facilitates efficient simulation of large biomembrane systems with large timesteps, while achieving realistic equilibrium and non-equilibrium kinetics. It helps to bridge between the nanometer/nanosecond spatiotemporal resolutions of coarse-grained models and biologically relevant time- and lengthscales. As a demonstration, we investigate fluctuations of red blood cells, with varying cytoplasmic viscosities, in 150-milliseconds-long trajectories, and compare kinetic properties against single-cell experimental observations.
The great challenge with biological membrane systems is the wide range of scales involved, from nanometers and picoseconds for individual lipids to the micrometers and beyond millisecond for cellular ...signaling processes. While solvent-free coarse-grained membrane models are convenient for large-scale simulations and promising to provide insight into slow processes involving membranes, these models usually have unrealistic kinetics. One major obstacle is the lack of an equally convenient way of introducing hydrodynamic coupling without significantly increasing the computational cost of the model. To address this, we introduce a framework based on anisotropic Langevin dynamics, for which major in-plane and out-of-plane hydrodynamic effects are modeled via friction and diffusion tensors from analytical or semi-analytical solutions to Stokes hydrodynamic equations. Using this framework, in conjunction with our recently developed membrane model, we obtain accurate dispersion relations for planar membrane patches, both free-standing and in the vicinity of a wall. We briefly discuss how non-equilibrium dynamics is affected by hydrodynamic interactions. We also measure the surface viscosity of the model membrane and discuss the affecting dissipative mechanisms.
Humans dexterously interact with a variety of objects, including those with complex internal dynamics. Even in the simple action of carrying a cup of coffee, the hand not only applies a force to the ...cup, but also indirectly to the liquid, which elicits complex reaction forces back on the hand. Due to underactuation and nonlinearity, the object's dynamic response to an action sensitively depends on its initial state and can display unpredictable, even chaotic behavior. With the overarching hypothesis that subjects strive for predictable object-hand interactions, this study examined how subjects explored and prepared the dynamics of an object for subsequent execution of the target task. We specifically hypothesized that subjects find initial conditions that shorten the transients prior to reaching a stable and predictable steady state. Reaching a predictable steady state is desirable as it may reduce the need for online error corrections and facilitate feed forward control. Alternative hypotheses were that subjects seek to reduce effort, increase smoothness, and reduce risk of failure. Motivated by the task of 'carrying a cup of coffee', a simplified cup-and-ball model was implemented in a virtual environment. Human subjects interacted with this virtual object via a robotic manipulandum that provided force feedback. Subjects were encouraged to first explore and prepare the cup-and-ball before initiating a rhythmic movement at a specified frequency between two targets without losing the ball. Consistent with the hypotheses, subjects increased the predictability of interaction forces between hand and object and converged to a set of initial conditions followed by significantly decreased transients. The three alternative hypotheses were not supported. Surprisingly, the subjects' strategy was more effortful and less smooth, unlike the observed behavior in simple reaching movements. Inverse dynamics of the cup-and-ball system and forward simulations with an impedance controller successfully described subjects' behavior. The initial conditions chosen by the subjects in the experiment matched those that produced the most predictable interactions in simulation. These results present first support for the hypothesis that humans prepare the object to minimize transients and increase stability and, overall, the predictability of hand-object interactions.
Purpose
Several variables can affect work stress. This study aims to model the cause-and-effect relationships among different variables that can predict work stress based on one of the most important ...fuzzy multicriteria decision-making methods used to investigate the cause-and-effect relationships among variables.
Design/methodology/approach
This study was conducted in 2020, including 17 experts in safety management, occupational health and work psychology, based on the fuzzy decision-making trial and evaluation laboratory method as a robust approach to identify the cause-and-effect relationships among different variables.
Findings
Shift work, lack of job satisfaction, mental health, mental overload, fatigue, job security, sleep disorders, environmental discomfort, work pressure, job knowledge (this could mean expertise/level of qualifications/familiarity with the job), work complexity and role conflict were found to be the most significant variables affecting work stress. Moreover, the cause-and-effect model of relationships among variables showed that shift work and lack of job satisfaction are root causes, and mental health, fatigue, mental workload, sleep disorder and environmental discomfort are direct causes.
Originality/value
Although the results of this study demonstrate that work stress can be influenced by 12 different variables, the modeling results show that some variables, such as shift work and lack of job satisfaction, can directly or indirectly impact other variables and thus result in work stress.
The axon initial segment (AIS) is enriched in specific adaptor, cytoskeletal, and transmembrane molecules. During AIS establishment, a membrane diffusion barrier is formed between the axonal and ...somatodendritic domains. Recently, an axonal periodic pattern of actin, spectrin, and ankyrin forming 190-nm-spaced, ring-like structures has been discovered. However, whether this structure is related to the diffusion barrier function is unclear. Here, we performed single-particle tracking time-course experiments on hippocampal neurons during AIS development. We analyzed the mobility of lipid-anchored molecules by high-speed single-particle tracking and correlated positions of membrane molecules with the nanoscopic organization of the AIS cytoskeleton. We observe a strong reduction in mobility early in AIS development. Membrane protein motion in the AIS plasma membrane is confined to a repetitive pattern of ∼190-nm-spaced segments along the AIS axis as early as day in vitro 4, and this pattern alternates with actin rings. Mathematical modeling shows that diffusion barriers between the segments significantly reduce lateral diffusion along the axon.
Although the techniques and perioperative management in modern cardiac surgeries has improved, and mortality and morbidity have decreased dramatically, postoperative cardiac arrest after heart ...surgery (POCHS) is a life-threatening condition that should be assessed and managed precisely.
To determine the mortality rate and causes of death in postoperative cardiac arrest after heart surgery (POCHS).
A total of 3342 patients underwent cardiac surgery from 2010 to 2018 in Isfahan, Iran .142 of them experienced POCHS . POCHS patients were investigated for characteristics, causes of cardiopulmonary arrest, first-line treatment, and mortality. These items were compared between survived and deceased patients to find possible prognostic factors.
The incidence rate of cardiac arrest was 4.2% (142 ones from total of 3342). Success rate of cardiac arrest is 28.8% (41 from 142). Bradycardia was the most common cause of cardiorespiratory arrest (37.3%), followed by cardiogenic shock (30.3%) and ventricular fibrillation (23.2%). Younger patients (58±11.5 versus 62.9±11.3) and those who developed cardiopulmonary arrest due to ventricular fibrillation (42.4% versus 22.2%), bradycardia (21.2% versus 8.8%), and apnea (15.1% versus 6.6%) were more likely to survive, while, those with shock had the worst prognosis (P<0.05). The best response to resuscitation was found among those treated with defibrillator plus ECM (External Cardiac Massage) as compared to the other approaches (P-value=0.003).
Based on the current report, CPR success was found in 28.6% among whom respiratory etiology led to better outcomes than cardiac etiology. The second cause of cardiac arrest is ventricular fibrillation which immediate defibrillation has the best outcome. The highest numerical success in POCHS is combination of ECM with defibrillator.
Abstract
Within carbon fiber manufacturing, the stabilization process is the most time‐ and energy‐intensive process due to the complexity of chemical structure transformation. Therefore, ...optimization is strictly required to enable cost‐efficient stabilization processes. For the first time, a hybrid semi‐parametric model for continuous stabilization is developed to prognose stabilization progress and density of the stabilized fiber. The proposed model takes the process parameters like dwell time, stabilization temperature, and fiber stretching as well as precursor properties, such as fiber density, into account. Finally, the proposed hybrid semi‐parametric model offers a novel plant‐transferable optimization solution for model‐based energy optimization in the stabilization process.
Natural behaviors have redundancy, which implies that humans and animals can achieve their goals with different strategies. Given only observations of behavior, is it possible to infer the control ...objective that the subject is employing? This challenge is particularly acute in animal behavior because we cannot ask or instruct the subject to use a particular strategy. This study presents a three-pronged approach to infer an animal's control objective from behavior. First, both humans and monkeys performed a virtual balancing task for which different control strategies could be utilized. Under matched experimental conditions, corresponding behaviors were observed in humans and monkeys. Second, a generative model was developed that represented two main control objectives to achieve the task goal. Model simulations were used to identify aspects of behavior that could distinguish which control objective was being used. Third, these behavioral signatures allowed us to infer the control objective used by human subjects who had been instructed to use one control objective or the other. Based on this validation, we could then infer objectives from animal subjects. Being able to positively identify a subject's control objective from observed behavior can provide a powerful tool to neurophysiologists as they seek the neural mechanisms of sensorimotor coordination.
AbstractThis study follows the fuzzy analytic hierarchy process to develop a semiquantitative technique to assess the safety risk of construction projects based on effective parameters affecting the ...probability and severity rates. Various studies targeting safety risk assessment in construction projects together with their research characteristics were investigated. In the second step, the initial structure of risk assessment was designed based on a semiquantitative technique of safety risk assessment. In the third step, a three-round Delphi method was employed, and an expert panel comprising 41 project managers and senior authorities of construction projects determined the existing components of the two factors of risk probability and severity. Finally, the weights of the components of risk probability and severity were determined so that their roles in determining the level of final risk could be specified. The normalized weights of probability and severity factors for calculating the semiquantitative safety were 0.48296 and 0.51704, respectively. Moreover, the incident probability factor included the four components of technical inspection, human reliability, incident learning, and hazard detection, with the following weights, respectively: 0.303, 0.364, 0.088, and 0.245. The incident severity factor included the four components of human injury, financial loss, operational interruption, and reputation damage, with the following weights, respectively: 0.369, 0.233, 0.191, and 0.207. The utilization of this technique can help reduce the risk of occupational incidents in construction projects.
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