Simple Systems Research Articles

HIGH-DIMENSIONAL STOCHASTIC DESIGN OPTIMIZATION UNDER DEPENDENT RANDOM VARIABLES BY A DIMENSIONALLY DECOMPOSED GENERALIZED POLYNOMIAL CHAOS EXPANSION

Newly restructured generalized polynomial chaos expansion (GPCE) methods for high-dimensional design optimization in the presence of input random variables with arbitrary, dependent probability distributions are reported. The methods feature a dimensionally decomposed GPCE (DD-GPCE) for statistical moment and reliability analyses associated with a high-dimensional stochastic response; a novel synthesis between the DD-GPCE approximation and score functions for estimating the first-order design sensitivities of the statistical moments and failure probability; and a standard gradient-based optimization algorithm, constructing the single-step DD-GPCE and multipoint single-step DD-GPCE (MPSS-DD-GPCE) methods. In these new design methods, the multivariate orthonormal basis functions are assembled consistent with the chosen degree of interaction between input variables and the polynomial order, thus facilitating to deflate the curse of dimensionality to the extent possible. In addition, when coupled with score functions, the DD-GPCE approximation leads to analytical formulae for calculating the design sensitivities. More importantly, the statistical moments, failure probability, and their design sensitivities are determined concurrently from a single stochastic analysis or simulation. Numerical results affirm that the proposed methods yield accurate and computationally efficient optimal solutions of mathematical problems and design solutions for simple mechanical systems. Finally, the success in conducting stochastic shape optimization of a bogie side frame with 41 random variables demonstrates the power of the MPSS-DD-GPCE method in solving industrial-scale engineering design problems.

Visualizing Loss of Plasma Membrane Lipid Asymmetry Using Annexin V Staining.

Loss of plasma membrane lipid asymmetry contributes to many cellular functions and responses, including apoptosis, blood coagulation, and cell fusion. In this protocol, we describe the use of fluorescently labeled annexin V to detect loss of lipid asymmetry in the plasma membrane of adherent living cells by fluorescence microscopy. The approach provides a simple, sensitive, and reproducible method to detect changes in lipid asymmetry but is limited by low sample throughput. The protocol can also be adapted to other fluorescently labeled lipid-binding proteins or peptide probes. To validate the lipid binding properties of such probes, we additionally describe here the preparation and use of giant unilamellar vesicles as simple model membrane systems that have a size comparable to cells. Key features Monitoring loss of lipid asymmetry in the plasma membrane via confocal microscopy. Protocol can be applied to any type of cell that is adherent in culture, including primary cells. Assay can be adapted to other fluorescently labeled lipid-binding proteins or peptide probes. Giant unilamellar vesicles serve as a tool to validate the lipid binding properties of such probes. Graphical overview Imaging the binding of fluorescent annexin V to adherent mammalian cells and giant vesicles by confocal microscopy. Annexin V labeling is a useful method for detecting a loss of plasma membrane lipid asymmetry in cells (top image, red); DAPI can be used to identify nuclei (top image, blue). Giant vesicles are used as a tool to validate the lipid binding properties of annexin V to anionic lipids (lower image, red).

EVOLUTIONARY PATH OF CONSCIOUSNESS AND REASON: COGNITOME FROM A PHILOSOPHICAL PERSPECTIVE

The ability of an organism to experience subjective states is an object of research for many disciplines of science. This article seeks to consider consciousness on the foundation of advances in neuroscience, cognitive science, anthropology, and philosophy. Particular attention is given to the concept of “cognitome” suggested by K.V. Anokhin. We agree with understanding conscious activity as a particular ability of an organism, which cannot be reduced to a mass of simpler systems. However, we believe that subjective ability for the cognition or “anticipatory reflection” of the environment must be considered under the history of natural evolution. We suggest that a particular interference pattern that emerges from the activity of neural domain systems can be a foundation for a critical enhancement of a system’s efficiency and cause further evolution of cognitive systems. This theory is coherent with the most elaborated neuroscientific explanations of consciousness and can explain the direct match between the neural system’s dynamics and states of subjective reality.

Один из подходов решения противоречивых задач «мягкого моделирования» управления медицинским учреждением

The article is devoted to the problem of both classification of contradictory conditions in management problems in medical institutions and their solution using the method of committees. In previous studies, it was found that medical problems require the use of “soft modeling” methods, which is often reduced to solving systems of linear equations and inequalities due to its difficulty in formalizing. This is where restrictions of various kinds arise. The purpose of the work. The purpose of this work is to study the contradictions in solving the problems of management of medical institutions, as well as the possibility of eliminating them using the committee method, as well as the approach of building the most joint subsystems. Materials and methods. It is proposed to use the method of maximally joint subsystems modified for the design of the problem, due to the probability of the model, that is, when the state vector is considered to be some random vector (random variable). Here, a situation arises related to the uncertainty principle, which is well solved with the help of the p-committee. The considered methods show effectiveness, since the approximate solution of an incompatible system turns out to be quite close to the true one. However, the classification of contradictions reveals new problems related to the dimension and number of members of the minimum committee. The results of the study. In the course of formulating the types of contradictions, it becomes clear that the problem of the number of members of the committee is reduced to the already solved problem of building maximally joint subsystems. Which, on the one hand, fully justifies the approach considered by the authors, and on the other hand makes it quite simple in the conditions of modern digitalization, since solving systems of linear inequalities is not time-consuming for modern computer programs. Discussion and conclusion. The results obtained allow us to assert that the use of “soft modeling” in the management of medical institutions is simpler, since it is reduced to clear and simple systems of inequalities, albeit incompatible, but this problem is solved using the method of committees. Howe¬ver, it is worth noting that in the end the problem has simple solutions when using convex functions, and the question remains open, in the general case.

Characterization of non-covalent contacts in mono- and di-halo substituted acetaldehydes: probing the substitution effects of electron donating and withdrawing groups.

In the current work, a systematic evaluation of the different types of non-covalent interactions (NCIs) in acetaldehyde dimers, including dimers of mono-halo (XCH2CHO)2, di-halo (X2CHCHO)2 and tri-halo substituted (X3CCHO)2 acetaldehydes via the associated stabilization energy of these dimers has been performed. Furthermore, a topological analysis of the electron density based on the quantum theory of atoms in molecules (QTAIM) and non-covalent interaction reduced density gradient (NCI-RDG) isosurfaces has also been performed to evaluate the nature of these NCIs. The geometrical and electronic characteristics have been evaluated via the presence of different electron-donating groups (EDGs) and electron-withdrawing groups (EWGs) or substituents in dimers of these molecules, namely, XCH(Y)CHO and X2C(Y)CHO (wherein X = -F, -Cl, and -Br and Y = -SO3H, -CN, -NO2, -NH2, -CH3, -OCH3, and -SMe3). The C-H⋯O, C-H⋯X, X⋯X, X⋯O and C⋯O tetrel bonded contacts have been recognized to play an important role in the stabilization of the formed dimers. This study also establishes the fact that the overall stability of the dimeric assemblies is governed by the contributions from the mutual and complex interplay of a variety of interactions in the investigated dimers. Hence considerations based on strong H-bond donor-acceptor characteristics hold relevance for simple systems only, but slight alteration in the electronic environment can affect the overall stabilization energies of the system being investigated and the nature of the interactions that contribute towards the same.

Perancangan Sistem Keamanan Perumahan Menggunakan Face Recognition Berbasis Android

Environmental security is an important issue that must be considered, relying on the physical strength of security officers to stand guard 24 hours is not enough, an information and communication technology-based system is needed to assist security officers and neighborhood residents in monitoring the environment and its surroundings from possible disturbances of good crime. from outside as well as from within the environment itself. Based on these environmental security issues, the authors were inspired to design a residential security system application using the face recognition method. The main objective of this research is to help the environmental security system in housing. Data collection methods used are interviews, observation and literature study. The results of this study are residential security system applications using Android-based face recognition. This residential security system application is designed with simple systems and features to make it easier for the user. The Face Recognition method makes it easier for security officers to carry out their duties to recognize people who enter and leave housing. This security system application is designed to help residential residents, especially security officers, to be able to detect known and unknown people in housing.

한국 대학교육의 정책적 변화에 대한 비판

This study looked at the higher education law from the perspective of university education as well as school education to explore authenticity. Starting with the Higher Education Act, which was first enforced in 1998, among the Higher Education Acts revised and enacted until 2022, we will focus on systems that have become a policy change point or have had a significant impact on higher education. Through this, the problem was overviewed and a solution was sought. Korea has achieved policy and institutional improvements through various institutional reforms, and has demonstrated the power of Korean education that could not be found anywhere else in the international community. However, at this point, it is necessary to review the flow of higher education in the past and discuss the policy direction to find consistency and originality in the future. It is also pointed out as a problem that the majority of studies take a bottom-up approach to designing simple policies or systems or implementing them efficiently. In order to find the original meaning of university, major courses of various characteristics must be developed and operated, and learner-centered self-directed learning must be realized. A cquisition o f a c reative p roblem-solving p rocess a s w ell a s t he a bility t o u tilize i t a nd t he exploration of self are privileges of university education, so future university policies should be promoted in this direction. Lastly, active support for the formation of a network of policy researchers is needed at the government level so that higher education researchers can maximize their expertise and expand the scope of higher education research. Finally, in order to solve the problems of university education, the process of change was reviewed centering on the higher education law, which is most direct to the field of university education, policy changes in future university education were examined, and alternatives to university education in the future were presented. In this respect, I would like to give meaning to this study.

A novel cascade resorption system for high temperature thermochemical energy storage and large temperature lift energy upgradation

The discrepancy between energy supply and demand can be overcome by sorption based thermochemical energy storage system. Thermochemical energy storage system based on metal hydrides is an attractive option due to cyclic stability and high energy storage density. In the present study a novel cascade resorption system is proposed and analyzed for high temperature energy storage. The cascade resorption system uses Mg-50 wt% LaNi5 for energy storage due to its high reaction enthalpy and hydrogen absorption capacity whereas LaNi5 and LaNi4.7Al0.3 are used for hydrogen storage. The temperature at which energy is recovered is increased by two stage cascading desorption method. Therefore, a large magnitude of energy upgradation is possible. An energy upgradation of 52 °C is obtained using the cascade resorption system when the energy source and regeneration temperatures are at 300 and 80 °C, respectively. Thermodynamic analysis shows that the COP and energy storage density of 0.419 and 141.323 kJ/kg, respectively are obtained. In the end, cascade resorption system is compared with the simple resorption system and discussed the relative merits of cascade system. The energy upgradation of 18 and 23 °C is obtained using two simple resorption systems.

Reducing accidental losses of aviation kerosene in simplified aircraft central fueling systems

The issues of reducing losses of aviation kerosene during its pumping in systems of centralized refueling of aircraft with fuel, in which pipes and equipment of collapsible pipelines are used, are considered. Comparative data on possible leaks through the sealing units of pipe joints with MPT couplings and welded joints are shown. A technique for determining the parameters and the number of U-shaped compensators for unloading from thermal stresses of straight horizontal sections of collapsible pipelines kits connected by welding is presented. Modeling was carried out to establish the influence of various initial data on temperature deformations and the compensating ability of U-shaped expansion joints. Dependences have been obtained to determine the compensating capacity of U-shaped expansion joints without preliminary stretching (compression) by half of the longitudinal deformation, depending on the length of the overhang and the width of the flange for pipelines PST-100 and PST-150M. Keywords: collapsible pipelines; centralized refueling of aircraft; temperature deformation of pipelines; U-shaped compensator; allowable deformation of the compensator.

Application of alvarado scoring system in diagnosis of acute appendicitis

Acute appendicitis is a common cause of abdominal pain and can be difficult to diagnose, especially during the early stages. There is still appreciable morbidity and occasionally mortality which may be related to the failure of making an early diagnosis (1) As a result of their concern these surgeons create for themselves 'a surgical security zone which allows them to accept a 15-30% negative laparotomy rate with impunity (2), Although various aids exist to facilitate more accurate diagnosis and reduce the rate of negative appendectomy, many are complex. Whereas simple scoring systems have been available for some time, they have not been widely tested. The aim of this study was conducted to assess one of these scoring systems which were described by Alvarado in 19851(1), by comparing it to the histopathology results of operated patients. This retrospective study of consecutive patients admitted to the surgical ward at Benghazi Aljala hospital with suspicion of having acute appendicitis during the period of January 2008 to January 2010. The Alvarado scoring system was computed from admission notes and records correlated with histopathology, all cases with insufficient data or no histopathology result were excluded from the study Out of 153 patients, 90 underwent appendectomy with the intention to treat appendicitis and diagnosis was confirmed in 80 patients. The reliability of the system was assessed by calculating the negative appendectomy rate and positive predictive value which was 85%, and the normal appendectomy frequency was 12%. Alvarado scoring system is an easy, cheap, and useful tool in the preoperative diagnosis of acute appendicitis and can work effectively in routine practice.

Effects of the long-range neutrino-mediated force in atomic phenomena

As known, electron vacuum polarisation by nuclear Coulomb field produces the Uehling potential with the range . Similarly, neutrino vacuum polarisation by the Z boson field produces a long-range potential with a very large range . Measurements of macroscopic effects produced by the potential give limits on the effective interaction constant which exceed Fermi constant by many orders of magnitude, while limits from the spectroscopy of simple atomic systems are approaching the Standard Model predictions. In this paper, we consider limits on from hydrogen, muonium, positronium, deuteron and molecular hydrogen. Constraints are also obtained on fifth force parameterised by Yukawa-type potential mediated by a scalar particle.

Supervised learning of a chemistry functional with damped dispersion

Kohn–Sham density functional theory is widely used in chemistry, but no functional can accurately predict the whole range of chemical properties, although recent progress by some doubly hybrid functionals comes close. Here, we optimized a singly hybrid functional called CF22D with higher across-the-board accuracy for chemistry than most of the existing non-doubly hybrid functionals by using a flexible functional form that combines a global hybrid meta-nonseparable gradient approximation that depends on density and occupied orbitals with a damped dispersion term that depends on geometry. We optimized this energy functional by using a large database and performance-triggered iterative supervised training. We combined several databases to create a very large, combined database whose use demonstrated the good performance of CF22D on barrier heights, isomerization energies, thermochemistry, noncovalent interactions, radical and nonradical chemistry, small and large systems, simple and complex systems and transition-metal chemistry.

Neurobiological reduction: From cellular explanations of behavior to interventions.

Scientific reductionism, the view that higher level functions can be explained by properties at some lower-level or levels, has been an assumption of nervous system analyses since the acceptance of the neuron doctrine in the late 19th century, and became a dominant experimental approach with the development of intracellular recording techniques in the mid-20th century. Subsequent refinements of electrophysiological approaches and the continual development of molecular and genetic techniques have promoted a focus on molecular and cellular mechanisms in experimental analyses and explanations of sensory, motor, and cognitive functions. Reductionist assumptions have also influenced our views of the etiology and treatment of psychopathologies, and have more recently led to claims that we can, or even should, pharmacologically enhance the normal brain. Reductionism remains an area of active debate in the philosophy of science. In neuroscience and psychology, the debate typically focuses on the mind-brain question and the mechanisms of cognition, and how or if they can be explained in neurobiological terms. However, these debates are affected by the complexity of the phenomena being considered and the difficulty of obtaining the necessary neurobiological detail. We can instead ask whether features identified in neurobiological analyses of simpler aspects in simpler nervous systems support current molecular and cellular approaches to explaining systems or behaviors. While my view is that they do not, this does not invite the opposing view prevalent in dichotomous thinking that molecular and cellular detail is irrelevant and we should focus on computations or representations. We instead need to consider how to address the long-standing dilemma of how a nervous system that ostensibly functions through discrete cell to cell communication can generate population effects across multiple spatial and temporal scales to generate behavior.

Oxygen Vacancy‐Mediated Exciton Effect in Hierarchical BiOBr Enables Dichotomy of Energy Transfer and Electron Transfer in Photocatalysis

AbstractUsing solar energy through green and simple artificial photosynthesis systems are considered as a promising way to solve the energy and environmental crisis. However, one of the important primary steps of photosynthesis, i.e., energy transfer, is long being ignored especially in inorganic semiconducting systems due to the small exciton binding energies. Herein, the simultaneous interrogation of the charge transfer and energy transfer steps in a photoexcitation process is proposed by utilizing few‐layered nanosheet‐assembled hierarchical BiOBr nanotubes with rich oxygen vacancies (OVs) as efficient multifunctional photocatalysts. Benefiting from the integrated 1D/2D structure and abundant OV defects, the excitonic effect strikes a delicate balance in the optimized BiOBr photocatalyst, showing not only improved charge carrier separation and transfer but also enhanced exciton generation. As a result, the hierarchical BiOBr nanotubes exhibit high efficiency toward photocatalytic CO2 reduction with an impressive CO evolution rate of 135.6 µmol g−1 h−1 without cocatalyst or photosensitizer. The dominant reactive oxygen species of singlet oxygen (1O2) are discriminated for the first time, which originated from an energy transfer process, with electrophilic character, whereas the minor effect of superoxide anion radical (•O2−) with a nucleophilic rate‐determining step in the photocatalytic aerobic oxidation of sulfides.

A meta-heuristic optimization-based approach for 3D simplified parametric analysis of embedded soil-foundation systems undergoing coupled horizontal-rocking vibrations

This paper presents a novel modeling approach based on meta-heuristic optimization for constructing adaptive lumped-parameter models to approximate the dynamic response of a shallow foundation in layered soil considering coupled horizontal and rocking vibrations. The developed model is adaptive to complexities of impedance functions for different types of layered soil deposits. The optimal parameters of the proposed model are computed using three optimization algorithms, with the forensic-based investigation outperforming the others and being chosen as the best optimization strategy for numerical investigations. A parametric study of foundation characteristics and soil properties on frequency response curves, including magnification factors and phase angle, is performed to comprehensively verify the proposed model’s appropriateness. The findings reveal that dynamic responses of the proposed simplified systems are perfectly consistent with those computed using existing impedances and worldwide-recognized software in both frequency and time domains. It shall be concluded that the proposed model is compatible with different soil profiles and more effective than existing models in approximating the unbounded behavior of layered soil. Furthermore, it offers great potential to implement the time-history analysis of interacting systems subjected to forced vibrations and seismic motions in commercial software based on the proposed model for engineering practice.

Achieving win-win outcomes for biodiversity and yield through diversified farming

To leverage agriculture's potential to better benefit both people and nature, policymakers need clear messages about which farming practices positively impact biodiversity and yields, and when trade-offs arise. Existing reviews analyse effects of different agricultural practices on either biodiversity or yield, without considering interactions. Here, we applied multinomial and quantile regression models to synthesize global evidence of synergies and trade-offs between biodiversity and yield, using 764 paired observations (from 43 studies across 18 countries) comparing diversified and simplified farming systems. Results show that farmland diversification led to win-win outcomes for biodiversity and yield in 23% of cases, while a win for biodiversity coupled with a loss in yield was the most likely outcome (28% of cases). Yield and biodiversity responses were negatively correlated, meaning that diversifying farming systems solely in pursuit of production goals is unlikely to lead to markedly better outcomes for biodiversity, or vice-versa. Yet certain situations made win-win significantly more likely, including when crop and animal production, or multiple diversification practices (e.g., intercropping and cover crops), were combined, when no agrochemicals were applied, when diversification occurred in temperate climates, and when diversification enhanced below-ground taxa. Win-win was also more likely than lose-lose when biodiversity was measured as richness or richness-evenness, but not abundance, suggesting that in certain contexts diversified farming can effectively enhance species diversity while increasing agricultural yields. Overall, crop commodity group and bioclimatic location were amongst the most important contextual factors influencing the likelihood of a synergy or trade-off between biodiversity and yield, and diversification that accounts for these is less likely to lead to unexpected outcomes. Our novel method and up-to-date review show that farmland diversification frequently leads to better outcomes for biodiversity and/or agricultural production when compared to monocultures and farmland stripped of natural vegetation, opening a pathway to more sustainable agricultural production.

Scaling-Up of Thin-Film Photoelectrodes for Solar Water Splitting Based on Atomic Layer Deposition.

Atomic layer deposition (ALD) is an established method to prepare protective layers for Si-based photoelectrodes for photoelectrochemical (PEC) water splitting. Although ALD has been widely used in microelectronics and photovoltaics, it remains a great challenge to design simple and effective ALD systems to deposit large and uniform protective films for Si-based photoelectrodes with industrial sizes. This paper describes the design and realization of a simple ALD chamber configuration for photoelectrodes with large sizes, in which the influence of a gas redistributor over the gas flow and heat transfer during film growth was revealed by computational fluid dynamics simulations and experimental investigations. A simple circular baffle-type redistributor was proposed to establish a uniform gas flow field throughout the ALD reactor, resulting in a uniform temperature profile. With this simple baffle redistributor, the large-area Al2O3 monitor film (46 nm thickness) reached a good nonuniformity (Nu %) of 0.88% over a large area of 256 cm2. This design enables the fabrication of large-scale photocathodes from standard industrial-grade 166 mm Si(100) wafers (276 cm2) by depositing 50 nm TiO2 protective films with Nu % less than 5%. The obtained photocathode achieves a saturation current of 6.45 A with a hydrogen production rate of 43.2 mL/min under outdoor illumination. This work elucidates how flow pattern and heat transfer may influence the deposition of protective layers over large photoelectrodes, providing guidance for future industrial applications of PEC water splitting.

Notch signaling sculpts the stem cell niche.

Adult stem cells depend on their niches for regulatory signaling that controls their maintenance, division, and their progeny differentiation. While communication between various types of stem cells and their niches is becoming clearer, the process of stem cell niche establishment is still not very well understood. Model genetic organisms provide simplified systems to address various complex questions, for example, how is a stem cell niche formed? What signaling cascades induce the stem cell niche formation? Are the mechanisms of stem cell niche formation conserved? Notch signaling is an evolutionarily conserved pathway first identified in fruit flies, crucial in fate acquisition and spatiotemporal patterning. While the core logic behind its activity is fairly simple and requires direct cell-cell interaction, it reaches an astonishing complexity and versatility by combining its different modes of action. Subtleties such as equivalency between communicating cells, their physical distance, receptor and ligand processing, and endocytosis can have an effect on the way the events unfold, and this review explores some important general mechanisms of action, later on focusing on its involvement in stem cell niche formation. First, looking at invertebrates, we will examine how Notch signaling induces the formation of germline stem cell niche in male and female Drosophila. In the developing testis, a group of somatic gonadal precursor cells receive Delta signals from the gut, activating Notch signaling and sealing their fate as niche cells even before larval hatching. Meanwhile, the ovarian germline stem cell niche is built later during late larval stages and requires a two-step process that involves terminal filament formation and cap cell specification. Intriguingly, double security mechanisms of Notch signaling activation coordinated by the soma or the germline control both steps to ensure the robustness of niche assembly. Second, in the vast domains of mammalian cellular signaling, there is an emerging picture of Notch being an active player in a variety of tissues in health and disease. Notch involvement has been shown in stem cell niche establishment in multiple organs, including the brain, muscle, and intestine, where the stem cell niches are essential for the maintenance of adult stem cells. But adult stem cells are not the only cells looking for a home. Cancer stem cells use Notch signaling at specific stages to gain an advantage over endogenous tissue and overpower it, at the same time acquiring migratory and invasive abilities to claim new tissues (e.g., bone) as their territory. Moreover, in vitro models such as organoids reveal similar Notch employment when it comes to the developing stem cell niches. Therefore, a better understanding of the processes regulating stem cell niche assembly is key for the fields of stem cell biology and regenerative medicines.

Hitting Times and Positions in Rare Events

We establish abstract limit theorems which provide sufficient conditions for a sequence $(A_{l})$ of rare events in an ergodic probability preserving dynamical system to exhibit Poisson asymptotics, and for the consecutive positions inside the $A_{l}$ to be asymptotically iid (spatiotemporal Poisson limits). The limit theorems only use information on what happens to $A_{l}$ before some time $\tau_{l}$ which is of order $o(1/\mu(A_{l}))$. In particular, no assumptions on the asymptotic behavior of the system akin to classical mixing conditions are used. We also discuss some general questions about the asymptotic behaviour of spatial and spatiotemporal processes, and illustrate our results in a setup of simple prototypical systems.

Dynamical fractal and anomalous noise in a clean magnetic crystal

Fractals-objects with noninteger dimensions-occur in manifold settings and length scales in nature. In this work, we identify an emergent dynamical fractal in a disorder-free, stoichiometric, and three-dimensional magnetic crystal in thermodynamic equilibrium. The phenomenon is born from constraints on the dynamics of the magnetic monopole excitations in spin ice, which restrict them to move on the fractal. This observation explains the anomalous exponent found in magnetic noise experiments in the spin ice compound Dy2Ti2O7, and it resolves a long-standing puzzle about its rapidly diverging relaxation time. The capacity of spin ice to exhibit such notable phenomena suggests that there will be further unexpected discoveries in the cooperative dynamics of even simple topological many-body systems.