Time Hierarchy Research Articles

Enhancing the Graduate Medical Education Clinical Learning Environment Through Community of Practice Forums.

An optimal clinical learning environment (CLE) is associated with improved learning and patient care outcomes. Significant concerns exist about the state of the CLE in graduate medical education (GME). Research suggests GME programming falls short in interpersonal aspects of training that promote trainee engagement and psychological safety. Furthermore, published educational interventions in the CLE lack adequate theoretical backing to inform a rational approach to interventions in the CLE that could address these important problems.The authors apply the 2002 work of Etienne Wenger on communities of practice (COP) to address these GME CLE concerns. To distinguish this COP intervention from earlier theoretical work on COPs, the authors refer to this management concept as "COP forums." COP forums favorably influence the GME CLE through effects that complement experiential learning in patient care. COP forums support trainee psychological safety, mentorship from near peers, and opportunities to innovate-effects that can serve as a counterbalance to the time pressures, hierarchy, and compliance culture often experienced in the clinical environment. Deliverables of COP forums, including practice innovation and trainee self-efficacy, can favorably impact organization-wide performance and engagement.This article describes the historical position of COP forums in the evolution of COP theory and outlines the basic structure and function of COP forums. It contrasts COP forums to other COP-related concepts to explain their relevance to the GME CLE. Examples of innovative GME COP forums illustrate the structure and function of these interventions. Finally, the authors call for more research on the impact of COP forums on the GME CLE. To avoid confusion, such scholarship must account for the ongoing evolution of the larger COP framework and target specific dimensions of the theory most pertinent to the medical education research question at hand.

Oscillatory phenomena in electrophysiological networks: The coupling between cell bioelectricity and transcription

Morphogenetic regulation during embryogenesis and regeneration rely on information transfer and coordination between different regions. Here, we explore theoretically the coupling between bioelectrical and transcriptional oscillations at the individual cell and multicellular levels. The simulations, based on a set of ion channels and intercellular gap junctions, show that bioelectrical and transcriptional waves can electrophysiologically couple distant regions of a model network in phase and antiphase oscillatory states that include synchronization phenomena. In this way, different multicellular regionalizations can be encoded by cell potentials that oscillate between depolarized and polarized states, thus allowing a spatio-temporal coding. Because the electric potential patterns characteristic of development and regeneration are correlated with the spatial distributions of signaling ions and molecules, bioelectricity can act as a template for slow biochemical signals following a hierarchy of experimental times. In particular, bioelectrical gradients that couple cell potentials to transcription rates give to each single cell a rough idea of its location in the multicellular ensemble, thus controlling local differentiation processes that switch on and off crucial parts of the genome.

Building capacity through networking

Networks are an ally for higher educators: providing them an avenue to connect beyond the boundaries of space, time, and institutional hierarchy, to build professional capacity. This paper reports on an ethics approved mixed methods study on the value of networking to develop capacity for teaching with technologies. Data were collected via the means of anonymous online questionnaire and semi-structured interviews. There were 218 valid questionnaire responses and 31 interviews with participants from 23 countries worldwide. The value creation framework by Wenger, Trayner and deLaat (2011) was the main reference concept for data collection, analysis and reporting. The findings show that higher educators create value in networks to build capacity to teach with technologies by taking the role of Lurker, Seeker or Leader.

Three-state mathematical model for the assessment of DCMU-treated photosystem II heterogeneity.

Photosystem II (PSII) is one of the main pigment-protein complexes of photosynthesis which is highly sensitive to unfavorable environmental factors. The heterogeneity of PSII properties is essential for the resistance of autotrophic organisms to stress factors. Assessment of the PSII heterogeneity may be used in environmental monitoring for on-line detection of contamination of the environment. We propose an approach to assess PSII oxygen-evolving complex and light-harvesting antenna heterogeneity that is based on mathematical modeling of the shape of chlorophyll a fluorescence rise of 3-(3,4-dichlorophenyl)-1,1-dimethylurea-treated samples. The hierarchy of characteristic times of the processes considered in the model makes it possible to reduce the model to a system of three ordinary differential equations. The analytic solution of the reduced three-state model is expressed as a sum of two exponential functions, and it exactly reproduces the solution of the complete system within the time range from microseconds to hundreds of milliseconds. The combination of several such models for reaction centers with different properties made it possible to use it as an instrument to study PSII heterogeneity. PSII heterogeneity was studied for Chlamydomonas at different intensities of actinic light, for Scenedesmus under short-term heating, and for Chlorella grown in nitrate-enriched and nitrate-depleted media.

Variational analysis and AI algorithm implementation of free energy landscapes of molecular system

Accurate description of the free energy landscape (FES) is the basis for understanding complex molecular systems, and for further realizing molecular design, manufacture and industrialization. Major challenges include multiple metastable states, which usually are separated by high potential barriers and are not linearly separable, and may exist at multiple levels of time and spatial scales. Consequently FES is not suitable for analytical analysis and brute force simulation. To address these challenges, many enhanced sampling methods have been developed. However, utility of them usually involves many empirical choices, which hinders research advancement, and also makes error control very unimportant. Although variational calculus has been widely applied and achieved great success in physics, engineering and statistics, its application in complex molecular systems has just begun with the development of neural networks. This brief review is to summarize the background, major developments, current limitations, and prospects of applying variation in this field. It is hoped to facilitate the AI algorithm development for complex molecular systems in general, and to promote the further methodological development in this line of research in particular.

TOWARDS THEORETICAL MODELLING OF DISTRIBUTION OF MATTER IN UNIVERSE

The description of the distribution of matter in the universe requires not only accurate observations but also adequate approaches to their theoretical interpretation. This paper proposes a method of parameterization of distributions with a morphologically complex topology using structural invariants (for example, Euler), based on which it is possible to distinguish clusters with different topologies (in the observation plane). Based on the introduced classification and appropriate scaling, it becomes possible to estimate the distribution of matter, for example, within the framework of the mean-field model. To study the kinetics of the evolution of matter distribution, it is proposed to introduce the appropriate ordering parameter, which is built based on the calibrating and current values of the Euler-Poincaré invariants. This approach, by constructing phase diagrams for the ordering parameter, allows you to track the details of the kinetics of the evolution of matter distributions, studying, in particular, the temporal hierarchy of relaxation times of intermediate states. The temporal kinetics of this approach are described using simple kinetic equations that describe the relaxation of the ordering parameter field, and the values of invariants determined with the help of appropriate measurements (observations) appear as initial conditions. This approach can be seen as an alternative to other approaches to parameterization of structurally complex systems, such as Voronoi methods, graphs, etc. A comparative analysis of the results of various alternative approaches to the parameterization of topologically complex distributions of matter, which will be conducted in the future, should contribute to the deepening of existing ideas about the nature of the distribution of matter in the Universe.

Positivity of the Symmetric Group Characters Is as Hard as the Polynomial Time Hierarchy

Abstract We prove that deciding the vanishing of the character of the symmetric group is $\textsf{C}_= \textsf{P}$-complete. We use this hardness result to prove that the absolute value and also the square of the character are not contained in $\textsf{#P}$, unless the polynomial hierarchy collapses to the second level. This rules out the existence of any (unsigned) combinatorial description for the square of the characters. As a byproduct of our proof, we conclude that deciding positivity of the character is $\textsf{PP}$-complete under many-one reductions, and hence $\textsf{PH}$-hard under Turing reductions.

Local problems on grids from the perspective of distributed algorithms, finitary factors, and descriptive combinatorics

We present an intimate connection among the following fields:(a)distributed local algorithms: coming from the area of computer science,(b)finitary factors of iid processes: coming from the area of analysis of randomized processes,(c)descriptive combinatorics: coming from the area of combinatorics and measure theory. In particular, we study locally checkable problems on grids from all three perspectives. Most of our results are for perspective (b) where we prove time hierarchy theorems similar to those known in the field (a) Chang and Pettie (2017) [16]. This approach, which borrows techniques from fields (a) and (c), implies a number of results about the possible complexities of finitary factor solutions. Among others, it answers three open questions of Holroyd et al. (2017) [46] or the more general question of Brandt et al. Brandt (2017) [9] who asked for a formal connection between the fields (a) and (b).In general, we hope that our treatment will help to view all three perspectives as a part of a common theory of locality, in which we follow the insightful paper of Bernshteyn (2023) [6].

The fractal scale-invariant structure of a temporal hierarchy in the relaxation and energy dissipation processes in a visco-elastic/capillary-porous medium

The phenomena of elastic aftereffects during loading/unloading of viscoelastic and capillary-porous bodies, relaxation of their stresses is accompanied by the energy accumulation and dissipation to be taken into account in the theory of oscillations which also considers the behavior of materials when the force is applied to them. The elastic aftereffect and stress relaxation forms ostensibly opposite energy processes. In the first case, under constant load deformation, the work increases in course of time, and in the second case, under constant load deformation, the work (energy) decreases. While researching on the energy dissipation in the conditions of oscillations application, i.e. within the frame of internal friction theories, one can find that some theories are based on the dependence of friction on the oscillations’ velocity, other ones establish the dependence of friction on the amplitude. Research papers are based on the hypothesis of M.M. Davydenkov, according to which the energy when subjected to oscillations depends on the amplitude and does not depend on the velocity. According to E.S. Sorokin, the theory of internal friction is poorly consistent with the theories describing the inherited properties of materials (viscoelastic and capillary-porous ones). A tendency is observed: the better a theory reflects hereditary properties, the worse this theory is adapted to describe energy losses due to oscillations.In this paper, an attempt has been made to harmonize both these theories and numerous experiments on the destruction of materials described in the academic literature. It turns out that in order to remove contradictions, it is necessary to take into account the dependence of body deformation changing in the course of time.It is shown that the hierarchy of times determining shear and bulk relaxation in viscoelastic/capillary-porous medium has a fractal (scale-invariant) structure. It was observed that the presence of time fractality eases the modeling of viscoelastic/capillary-porous bodies resulting in the universal relaxation function of a rather simple kind. In particular, for the scale-invariant distribution of relaxation characteristics medium, the application of algebraic relaxation law for viscoelastic/capillary-porous materials is possible: this resulting in rheological models and state equations with the derivatives of fractional order.

Мodulus of Elasticity as a Function of a Process in Hereditary Mechanics

The article considers the problem of determining the modulus of elasticity for polymer materials. The measurement process of these materials is considerably complex, mainly due to the fact that they comply with the laws of viscoelasticity. The Boltzmann — Volterra method is applied to the consideration of the behavior of a hereditarily elastic body, namely, to synthetic threads. We revealed that the elastic modulus for polymer materials is not a constant value and depends on the frequency of exposure during the deformation of the material. It is particularly noted that the modulus of elasticity is not a function of the state, but a function of the process. In this regard, it is necessary to consider various modes of deformation, namely static, acoustic, and dynamic modes. The Boltzmann heredity principle is utilized to provide a clear understanding of the concepts of static, dynamic, and acoustic modulus of elasticity. Furthermore, the applicability of the Boltzmann equation to dynamic mechanical processes is analyzed using two methods — the hierarchy of relaxation times and the method of linearization. In addition, the concept of the interaction core of static and dynamic parts of deformation is introduced. This concept helps to explain the relationship between the static and dynamic moduli of elasticity and their impact on material properties.

Spatiotemporal heterogeneity and impact factors of hepatitis B and C in China from 2010 to 2018: Bayesian space-time hierarchy model.

Viral hepatitis is a global public health problem, and China still faces great challenges to achieve the WHO goal of eliminating hepatitis. This study focused on hepatitis B and C, aiming to explore the long-term spatiotemporal heterogeneity of hepatitis B and C incidence in China from 2010 to 2018 and quantify the impact of socioeconomic factors on their risk through Bayesian spatiotemporal hierarchical model. The results showed that the risk of hepatitis B and C had significant spatial and temporal heterogeneity. The risk of hepatitis B showed a slow downward trend, and the high-risk provinces were mainly distributed in the southeast and northwest regions, while the risk of hepatitis C had a clear growth trend, and the high-risk provinces were mainly distributed in the northern region. In addition, for hepatitis B, illiteracy and hepatitis C prevalence were the main contributing factors, while GDP per capita, illiteracy rate and hepatitis B prevalence were the main contributing factors to hepatitis C. This study analyzed the spatial and temporal heterogeneity of hepatitis B and C and their contributing factors, which can serve as a basis for monitoring efforts. Meanwhile, the data provided by this study will contribute to the effective allocation of resources to eliminate viral hepatitis and the design of interventions at the provincial level.

Statistical complexity and the road to equilibrium in many-body chaotic quantum systems.

In this work we revisit the problem of equilibration in isolated many-body interacting quantum systems. We pay particular attention to quantum chaotic Hamiltonians, and rather than focusing on the properties of the asymptotic states and how they adhere to the predictions of the Eigenstate Thermalization Hypothesis, we focus on the equilibration process itself, i.e., the road to equilibrium. Along the road to equilibrium the diagonal ensembles obey an emergent form of the second law of thermodynamics and we provide an information theoretic proof of this fact. With this proof at hand we show that the road to equilibrium is nothing but a hierarchy in time of diagonal ensembles. Furthermore, introducing the notions of statistical complexity and the entropy-complexity plane, we investigate the uniqueness of the road to equilibrium in a generic many-body system by comparing its trajectories in the entropy-complexity plane to those generated by a random Hamiltonian. Finally, by treating the random Hamiltonian as a perturbation we analyzed the stability of entropy-complexity trajectories associated with the road to equilibrium for a chaotic Hamiltonian and different types of initial states.

Capturing Bisimulation-Invariant Exponential-Time Complexity Classes

Otto's Theorem characterises the bisimulation-invariant PTIME queries over graphs as exactly those that can be formulated in the polyadic mu-calculus, hinging on the Immerman-Vardi Theorem which characterises PTIME (over ordered structures) by First-Order Logic with least fixpoints. This connection has been extended to characterise bisimulation-invariant EXPTIME by an extension of the polyadic mu-calculus with functions on predicates, making use of Immerman's characterisation of EXPTIME by Second-Order Logic with least fixpoints. In this paper we show that the bisimulation-invariant versions of all classes in the exponential time hierarchy have logical counterparts which arise as extensions of the polyadic mu-calculus by higher-order functions. This makes use of the characterisation of k-EXPTIME by Higher-Order Logic (of order k+1) with least fixpoints, due to Freire and Martins.

Predictability of Population Fluctuations

Population dynamics is affected by environmental fluctuations (such as climate variations), which have a characteristic correlation time. Strikingly, the time scale of predictability can be larger for the population dynamics than for the underlying environmental fluctuations. Here, we present a general mechanism leading to this increase in predictability. We considered colored environmental fluctuation acting on a population close to equilibrium. In this framework, we derived the temporal auto and cross-correlation functions for the environmental and population fluctuations. We found a general correlation time hierarchy led by the environmental-population correlation time, closely followed by the population autocorrelation time. The increased predictability of the population fluctuations arises as an increase in its autocorrelation and cross-correlation times. These increases are enhanced by the slow damping of the population fluctuations, which has an integrative effect on the impact of correlated environmental fluctuations. Therefore, population fluctuation predictability is enhanced when the damping time of the population fluctuation is larger than the environmental fluctuations. This general mechanism can be quite frequent in nature, and it largely increases the perspectives of making reliable predictions of population fluctuations.

Construction System Failures: Frame Notation of Project Pathogens and their Propagation Across Time and System Hierarchy

AbstractA construction system is an organizational and technological system that produces buildings or civil engineering structures for human use by fabricating and installing materials into an integrated structure according to design specifications. Failures of such construction systems materialize in various forms, including defective design, rework, and dysfunctional building systems. Frequent accidents and building defects in the construction sector clearly indicate that our society still needs to improve the safety of construction systems. Research studies on how major accidents and minor defects occur are often conducted in isolation by different researchers, and existing system safety concepts and frameworks are not necessarily suited to handling the dynamic nature of temporary multiple organizations (TMOs)—a feature that characterizes the uniqueness of construction projects. We need a framework that can better describe failures specific to construction, and capture the wide spectrum of these failures. Here, we build on concepts from system safety research to develop a graphical notation with “frames” and system hierarchy as the main components to illustrate how pathogens are generated and propagated by defective processes and end up embedded in the physical structure.

Multifunctions of α‐Synuclein Explained by Its Dynamic Heterogeneous Conformations with a Hierarchy of Transition Times

α‐Synuclein plays essential roles in synaptic vesicle homeostasis and neurotransmitter release through the interaction with membrane, while α‐synuclein aggregates have been associated with several neurodegenerative diseases, especially Parkinson’s disease. The different roles of α‐synuclein could be attributed to the heterogenous conformations adopted by this intrinsically disordered protein. To demystify the physiological functions of α‐synuclein and understand its pathogenic mechanism of Parkinson’s disease, characterizing the monomeric structural ensemble and identifying the aggregation‐prone and non‐aggregation‐prone structures are of particular importance. Here, we use inter‐residue distance distributions derived from time‐resolved FRET experiments as constraints to guide discrete molecular dynamics simulations of α‐synuclein monomer. We explore the conformational space of α‐synuclein and verify the generated conformational ensemble by additional experiments including far‐UV circular dichroism spectrum and cross‐linking mass spectrometry. We find that some conformational states of α‐synuclein are surprisingly stable displaying dynamic transitions less than milliseconds. A comprehensive analysis of the conformational ensemble uncovers important structural features and potential conformations that are critical to stabilize the monomeric state or induce different oligomerization pathways.

Temporal and Spatial Heterogeneity of PM2.5 Related to Meteorological and Socioeconomic Factors across China during 2000-2018.

In recent years, air pollution caused by PM2.5 in China has become increasingly severe. This study applied a Bayesian space–time hierarchy model to reveal the spatiotemporal heterogeneity of the PM2.5 concentrations in China. In addition, the relationship between meteorological and socioeconomic factors and their interaction with PM2.5 during 2000–2018 was investigated based on the GeoDetector model. Results suggested that the concentration of PM2.5 across China first increased and then decreased between 2000 and 2018. Geographically, the North China Plain and the Yangtze River Delta were high PM2.5 pollution areas, while Northeast and Southwest China are regarded as low-risk areas for PM2.5 pollution. Meanwhile, in Northern and Southern China, the population density was the most important socioeconomic factor affecting PM2.5 with q values of 0.62 and 0.66, respectively; the main meteorological factors affecting PM2.5 were air temperature and vapor pressure, with q values of 0.64 and 0.68, respectively. These results are conducive to our in-depth understanding of the status of PM2.5 pollution in China and provide an important reference for the future direction of PM2.5 pollution control.

Hierarchy of relaxation times in supramolecular polymer model networks.

Supramolecular polymer gels are an evolving class of soft materials with a vast number of properties that can be tuned to desired applications. Despite continuous advances concerning polymer synthesis, sustainability or adaptability, a consistent understanding of the interplay between structure, dynamics, and diffusion processes within transient networks is lacking. In this study, the hierarchy of several relaxation processes is investigated, starting from a microscopic perspective of a single sticker dissociation event up to the center-of-mass diffusion of a star-shaped polymer building block on different length scales, as well as the resulting macroscopic mechanical response to applied external stress. In addition to that, a second focus is placed on the gel micro-structure that is analyzed by light scattering. Conversion of the dynamic light scattering (DLS) inverse length scale into real space allows for a combination of relaxation times with those obtained by forced Rayleigh scattering (FRS). For these investigations, a model-type metallo-supramolecular network consisting of narrowly dispersed tetra-arm poly(ethylene glycol)-terpyridine macromolecules that are interconnected via complexation with zinc ions is chosen. Assembling the obtained activation energies reveals that all complex dissociation-governed relaxation processes exhibit similar activation energies.

The polynomial hierarchy of functions and its levels

We give recursion-theoretic characterizations of all levels of the polynomial hierarchy of time and of the hierarchy itself. We characterize both, the □nP and the ΣnP levels. In this work, only composition and recursion schemes are used. We identify the recursion scheme which added to FPtime leads to the full polynomial hierarchy.

The complexity of finding temporal separators under waiting time constraints

In this work, we investigate the computational complexity of Restless Temporal(s,z)-Separation, where we are asked whether it is possible to destroy all restless temporal paths between two distinct vertices s and z by deleting at most k vertices from a temporal graph. A temporal graph has a fixed vertex set but the edges have (discrete) time stamps. A restless temporal path uses edges with non-decreasing time stamps and the time spent at each vertex must not exceed a given duration Δ.Restless Temporal(s,z)-Separation naturally generalizes the NP-hard Temporal(s,z)-Separation problem. We show that Restless Temporal(s,z)-Separation is complete for Σ2P, a complexity class located in the second level of the polynomial time hierarchy. We further provide some insights in the parameterized complexity of Restless Temporal(s,z)-Separation parameterized by the separator size k.