Physical Basis Research Articles

ST40 electromagnetic predictive studies supported by machine learning applied to experimental database

Nuclear fusion is entering the era of power plant-scale devices, which are now undergoing extensive studies to support the design phase. Plasma disruptions pose a high risk to these classes of devices because of the large stored thermal and magnetic energy which might jeopardize machine integrity and availability. Therefore, disruptions within these devices must be virtually eliminated, and any disruptions which do happen must be highly mitigated. However, the characterisation, prediction and technology used to mitigate disruptions is still an area of active development. In this paper, the authors investigate the disruptions within ST40, with particular attention at the identification of causes and effects associated with disruptions, both from a physics basis and an engineering standpoint. This paper aims at presenting preliminary predictive analyses of ST40 plasma scenarios by exploiting Machine Learning techniques applied to an experimental database populated by plasma pulses executed during the ST40 2021–2022 experimental campaign. The database contains both disrupted and non-disrupted pulses. Using Machine Learning, common features within disruptions are automatically classified and identified, mapping the controllable operational space in terms of plasma displacement and variation of specific plasma internal parameters. The classification was validated by benchmarking the numerical reconstruction of the plasma dynamics with experimental data recovered from the plasma diagnostics. Subsequent Machine Learning analyses allowed the extrapolation of new disrupted plasma configurations for preliminary predictive simulations of the plasma column displacement. Thanks to the numerical simulations performed in MAXFEA environment, it is possible to investigate the plasma vertical displacement both during disrupted and regularly terminated plasma scenarios and to provide lessons to be learnt for the next ST40 experimental campaign and for the design of future ST devices.

Decarbonizing the global steel industry in a resource-constrained future-a systems perspective.

Decarbonizing the global steel industry hinges on three key limited resources: geological carbon storage, zero-emission electricity and end-of-life scrap. Existing system analysis calls for an accelerated expansion of the supply of these resources to meet the assumed ever-increasing steel demand. In this study, we propose a different view on how to decarbonize the global steel industry, based on the principle that resource supply can only expand in line with historical trends and actual construction plans. Our analysis shows that global steel production cannot grow any further within a Paris-compatible carbon budget, resulting in a shortfall of approximately 30% against 2050 demand. This trajectory involves the phasing out of blast furnaces, along with strong growth in scrap recycling and hydrogen-based production. These findings highlight critical yet often overlooked challenges: (i) reducing excess demand while providing essential services, (ii) producing high-grade steel through upcycling scrap, and (iii) ensuring an equitable distribution of limited production across the globe. These perspectives contrast with those of the current agenda, which largely emphasizes the need to invest in new production technologies. Grounded in a physical basis, this analysis offers a complementary perspective for a more balanced debate in policymaking and industrial strategy. This article is part of the discussion meeting issue 'Sustainable metals: science and systems'.

Electromagnetic radiation of granite under dynamic compression

To elucidate the characteristics and mechanism of electromagnetic radiation in granite under impact loading, based on the quasi-static compression tests, this paper conducts dynamic compression experiments on granite using Hopkinson pressure bar and one-stage light-gas gun as loading methods. Combined with experimental and theoretical analyses, the relationship between mechanical and electromagnetic responses under impact loads of different intensities, and the time-domain signals of electromagnetic radiation generated by a single crack under different strain rates are studied. The intensity and frequency of electromagnetic radiation increase with the increasing compressive strain rate. According to the thermal activation theory, it reveals the microscopic mechanism of the transition from intergranular microcracks to transgranular microcracks in terms of strain sensitivity. It also serves as the physical basis for the increase in electromagnetic radiation intensity amplitude and frequency with increasing compressive strain rate. Transgranular microcracks are the primary cause of electromagnetic radiation generated by fractures.

An instructional lab apparatus for quantum experiments with single nitrogen-vacancy centers in diamond

Hands-on experimental experience with quantum systems in the undergraduate physics curriculum provides students with a deeper understanding of quantum physics and equips them for the fast-growing quantum science industry. Here, we present an experimental apparatus for performing quantum experiments with single nitrogen-vacancy (NV) centers in diamond. This apparatus is capable of basic experiments such as single-qubit initialization, rotation, and measurement, as well as more advanced experiments investigating electron–nuclear spin interactions. We describe the basic physics of the NV center and give examples of potential experiments that can be performed with this apparatus. We also discuss the options and inherent trade-offs associated with the choice of diamond samples and hardware. The apparatus described here enables students to write their own experimental control and data analysis software from scratch, all within a single semester of a typical lab course, as well as to inspect the optical components and inner workings of the apparatus. We hope that this work can serve as a standalone resource for any institution that would like to integrate a quantum instructional lab into its undergraduate physics and engineering curriculum.

METHOD FOR INCREASING THE RESOLVING POWER OF AN OPTICAL MICROSCOPE

Purpose. Increasing the resolution and magnification of the optical microscope to expand the possibilities of observation and research in various fields of science and technology. Research methods. Theoretical, experimental. Results. A comparative analysis of the human eye as an optical system and the optical system of a microscope was carried out. It was found that these systems have a similar nature, namely, a separate image of two closely located objects. If we consider the human eye as a light-sensitive matrix, then to determine the resolution of the eye, it is necessary to use the ratio of the average value of the number of light-sensitive elements (rods and cones) that fall on the retina to the area of the retina itself (for the human eye, it is 0.1...0.2 mm). For an optical microscope, it is necessary to separate the concepts of “resolution” and “magnification”. We also mentioned the physical basis of the resolution of optical microscopes. It was shown that for a dry lens the resolution limit for λ = 555 nm is 0.3 μm. One of the ways to increase the resolution is the use of immersion fluids. However, in certain studies its use is inappropriate or impossible. If instead of conventional illuminators (maximum intensity at λ = 555 nm) you use ultraviolet ones (λ = 380…410 nm), then the resolution can be increased several times, and the increase is up to 2000. The disadvantage of using UV illuminators is that it is necessary to use a light filter with direct observation or a monitor with an indirect method to avoid negative effects on the observer’s vision. Scientific novelty. The increased resolution and magnification of the optical microscope when using coherent light sources instead of immersion fluids provides more detailed scientific information and facilitates its processing. Practical value. Using the results of our research allows you to get a more informative image when using coherent light sources.

Laboratory Management; Challenges and Opportunities in FkipUhamka

This study aims to analyze the management of basic physics laboratories at UniversitasMuhammadiyah Prof DR HAMKA and its impact on user performance and satisfaction. Optimal management of basic physics laboratories is very important to support the learning process and student practicums. This study uses a descriptive method with a quantitative approach, where data is collected through questionnaires distributed to lecturers and students who use the laboratory. The results of the study indicate that the management of basic physics laboratories at UniversitasMuhammadiyah Prof DR HAMKA has been running well, but there are still several aspects that need to be improved, such as equipment maintenance, additional facilities, and improving work safety. Data analysis shows that there is a significant relationship between laboratory management and user performance and satisfaction. Good management will improve the efficiency of laboratory use, which in turn will improve academic performance and user satisfaction. Based on the findings, several suggestions are given for further improvement, including planning for periodic maintenance, adding facilities, improving laboratory technician skills, and regular monitoring and evaluation. The implementation of these suggestions is expected to improve the quality of basic physics laboratory management at UniversitasMuhammadiyah Prof. DR HAMKA.

A Theoretical Model for the Hydraulic Permeability of Clayey Sediments Considering the Impact of Pore Fluid Chemistry

The chemistry of the pore fluid within clayey sediments frequently changes in various processes. However, the impacts of pore fluid chemistry have not been well included in the hydraulic permeability model, and the physical bases behind the salinity sensitivity of the hydraulic permeability remains elusive. In this study, a theoretical model for the hydraulic permeability of clayey sediments is proposed, and impacts of the pore fluid chemistry are quantitatively considered by introducing electrokinetic flow theory. Available experimental data were used to verify the theoretical model, and the verified model was further applied as a sensitivity analysis tool to explore more deeply how hydraulic permeability depends on pore fluid chemistry under different conditions. Coupling effects of pore water desalination and the effective stress enhancement on the hydraulic permeability of marine sediments surrounding a depressurization wellbore during hydrate production are discussed. Results and discussion show that the hydraulic permeability reduction is significant only when the electric double layer thickness is comparable to the characteristic pore size, and the reduction becomes more obvious when the ion mobility of the saline solution is smaller and the surface dielectric potential of clay minerals is lower. During gas hydrate production in the ocean, the salinity sensitivity of the hydraulic permeability could become either stronger and weaker, depending on whether the original characteristic pore size of marine sediments is relatively large or small.

Comprehensive assessment of factors affecting the operational reliability of low-voltage asynchronous electric motors of a coal mining complex

THE RELEVANCE of this study lies in solving the problem of reliable functioning of elements of energy systems and ensuring their effective operation during open-pit mining. The paper presents a methodological approach that allows us to assess the level of reliability of low-voltage asynchronous electric motors in a coal mine with complex mining, geological and climatic conditions of production. THE PURPOSE of the work is to quantify the operational factors affecting the service life of an asynchronous electric motor with a short-circuited rotor. Attention is focused on how influencing factors, different in physical basis, among which electrical parameters are highlighted – the coefficient of voltage asymmetry in the reverse sequence, the coefficients of harmonic voltage components and environmental parameters – temperature, air humidity and dustiness, affect the dynamics of changes in the service life of an asynchronous electric motor. Asynchronous electric motors used at one of the enterprises of JSC SUEK in the Trans-Baikal Territory are considered as an object of research. METHODS. The main tool for the implementation of research tasks is computer modeling based on the Matlab software package. RESULTS. The studies were performed on an asynchronous electric motor with a short-circuited rotor with Ph = 3 kW, rated speed 1500 rpm. The simulation of the operating mode of the electric motor under study was performed by changing the experimental parameters: the values of the total coefficient of harmonic voltage components (KU) – from 4 to 12% with a range of 2%; the values of the voltage asymmetry coefficient in the reverse sequence (K2U) – from 0 to 4% with a range of 1%; the ambient temperature (∆Tокr) – from -30°C to +30°C with a range of 10°C; air humidity values (Vc) – 20% and 60%; dust thermal conductivity coefficient values (Kт) – 0,12 and 0,28. Based on the obtained research results, diagrams are constructed that clearly illustrate the dynamics of changes in the service life of an asynchronous electric motor depending on the combination of influencing factors. CONCLUSION. The trends in solving the issues of reliable functioning of a coal mining enterprise with the presence of asynchronous electric motors and ensuring their efficient operation are the most priority, mainly focused on maintaining the stability of technological processes and maintaining the production volumes of a coal mining enterprise. The stability of the electric motor to certain influencing factors is estimated and their critical values are established. Recommendations on the use of asynchronous electric motors are formulated, taking into account their operating conditions.

Investigating the correlation between flow dynamics and flow-induced voltage generation

The conversion of water current to voltage generation through graphene has gained interest in both basic physics and applications such as sensors and electricity generation systems. However, many aspects of the mechanism remain unclear. Recently, quantum-based momentum transfer theories have been reported, but these often do not account for flow conditions. In this study, we investigated the correlation between the flow conditions of a liquid medium and the electrical conduction of graphene through experiments and numerical calculations. Our results suggest that the necessary condition is that the flow must be neither irregular nor purely laminar; instead, graphene responds to the transition process of the fluid. This finding supports the extension of current theories and presents valuable insights for both basic science and industrial applications.

Reentrant DNA shells tune polyphosphate condensate size

The inorganic biopolymer polyphosphate (polyP) occurs in all domains of life and affects myriad cellular processes. A longstanding observation is polyP’s frequent proximity to chromatin, and, in many bacteria, its occurrence as magnesium (Mg2+)-enriched condensates embedded in the nucleoid region, particularly in response to stress. The physical basis of the interaction between polyP, DNA and Mg2+, and the resulting effects on the organization of the nucleoid and polyP condensates, remain poorly understood. Here, using a minimal system of polyP, Mg2+, and DNA, we find that DNA can form shells around polyP-Mg2+ condensates. These shells show reentrant behavior, that is, they form within a window of Mg2+ concentrations, representing a tunable architecture with potential relevance in other multicomponent condensates. This surface association tunes condensate size and DNA morphology in a manner dependent on DNA length and concentration, even at DNA concentrations orders of magnitude lower than found in the cell. Our work also highlights the remarkable capacity of two primordial inorganic species to organize DNA.

Fossil biocalcite remains open to isotopic exchange with seawater for tens of millions of years

Fossilized remains of marine calcifiers constitute the physical basis for reconstructions of both deep ocean and sea-surface temperatures going back millions of years, but paleoclimate records derived from their isotope and trace-element chemistry can be biased by diagenesis. Experiments simulating diagenesis in the presence of an 18O-rich seawater analogue were conducted with modern and 14 Myr old foraminifera (Ammonia sp.) tests to investigate their relative susceptibility to oxygen isotope exchange. The fossilized tests were of exceptional preservation and similar to modern tests in terms of structure and crystalline organization, but had experienced partial loss of embedded organic structures, thus a priori offering fewer preferential pathways for porewaters to penetrate the tests. NanoSIMS imaging revealed that oxygen isotope exchange was pervasive in fossil tests, with isotopic exchange occurring at approximately half the rate of modern tests. The results unequivocally show that fossil biocalcites are metastable and remain more susceptible to isotope exchange than abiotic calcites millions of years after sedimentation and burial.

Membrane Composition Allows the Optimization of Berberine Encapsulation in Liposomes.

Berberine (BBR) is a natural molecule with noteworthy pharmacological properties, including the prevention of antibiotic resistance in Gram-negative bacteria. However, its oral bioavailability is poor, thus resulting in an impaired absorption and efficacy in humans. In combination with other drugs, liposomes have been shown to enhance the availability of the drug, representing a smart delivery system to target tissues and reduce negative side effects. To date, there is a lack of studies on BBR and liposomes that enable the rationalization and molecular-based design of such formulations for future use in humans. In this work, the encapsulation of BBR into liposomes is proposed to overcome current limitations using a combination of experimental and computational assays to rationalize the membrane composition of liposomes that maximizes BBR encapsulation. First, the encapsulation efficiency was measured for several membrane compositions, revealing that it is enhanced by cholesteryl hemisuccinate and, to a lesser extent, by cholesterol. The physical basis of the BBR encapsulation efficiency and permeability was clarified using molecular dynamics simulation: using the lipid composition, one can tune the capability of membranes to attract, i.e., to adsorb, the molecules onto their surface. Overall, these findings suggest a rational strategy to maximize the encapsulation efficiency of liposomes by using negatively charged lipids, thus representing the basis for designing delivery systems for BBR, useful to treat, e.g., antibiotic resistance.

Filamentous fungal pellets as versatile platforms for cell immobilization: developments to date and future perspectives

Filamentous fungi are well-known for their efficiency in producing valuable molecules of industrial significance, but applications of fungal biomass remain relatively less explored despite its abundant and diverse opportunities in biotechnology. One promising application of mycelial biomass is as a platform to immobilize different cell types such as animal, plant, and microbial cells. Filamentous fungal biomass with little to no treatment is a sustainable biomaterial which can also be food safe compared to other immobilization supports which may otherwise be synthetic or heavily processed. Because of these features, the fungal-cell combination can be tailored towards the targeted application and be applied in a variety of fields from bioremediation to biomedicine. Optimization efforts to improve cell loading on the mycelium has led to advancements both in the applied and basic sciences to understand the inter- and intra-kingdom interactions. This comprehensive review compiles for the first time the current state of the art of the immobilization of animal, yeast, microalgae, bacteria, and plant cells in filamentous fungal supports and presents outlook of applications in intensified fermentations, food and biofuel production, and wastewater treatment. Opportunities for further research and development were identified to include elucidation of the physical, chemical, and biological bases of the immobilization mechanisms and co-culture dynamics; expansion of the cell-fungus combinations investigated; exploration of previously unconsidered applications; and demonstration of scaled-up operations. It is concluded that the potential exists to leverage the unique qualities of filamentous fungus as a cellular support in the creation of novel materials and products in support of the circular bioeconomy.

Kepler’s problem of a two-body system perturbed by a third body

One of the most important problems in basic physics and astronomy is studying the motion of planets, satellites, and other celestial bodies. The solution to the two-body problem enables astronomers to predict the orbits of the Moon, satellites, and spaceships around the Earth. The general analytic solution for the three-body problem stands unsolved except in some special cases. This reduces the problem to a two-body problem. In this work, the authors present a closed-form approach to the three-body problem theoretically and numerically based on particle–particle vector analysis. The theoretical approach, which is based on the real Moon–Sun–Earth problem information, illustrates the perturbation of the Moon in the Sun–Earth problem and shows an expected orbital motion with a perturbation in the Sun–Earth orbit due to the revolution of the Moon. The numerical investigation uses the same information to study the same problem and calculate the angular momentums of each pair of objects. The two solutions show good agreement with the well-known Earth-Moon and Sun–Earth momentums. The Moon–Sun orbit is close to an elliptic shape with angular momentum of about 3.27 × 1038 J.s. This approach is the key to future studies for n-body problem solutions.

Virulence-linked adhesin drives mutualist colonization of the bee gut via biofilm formation.

Bacterial biofilms are stable multicellular structures that can enable long term host association. Yet, the role of biofilms in supporting gut mutualism is still not fully understood. Here, we investigate Snodgrassella alvi , a beneficial bacterial symbiont of honey bees, and find that biofilm formation is required for its colonization of the bee gut. We constructed fifteen S. alvi mutants containing knockouts of genes known to promote colonization with putative roles in biofilm formation. Genes required for colonization included staA and staB , encoding trimeric autotransporter adhesins (TAAs) and mltA , encoding a lytic transglycosylase. Intriguingly, TAAs are considered virulence factors in pathogens but support mutualism by the symbiont S. alvi. In vitro , biofilm formation was reduced in Δ staB cells and abolished in the other two mutants. Loss of staA also reduced auto-aggregation and cell-cell connections. Based on structural predictions, StaA/B are massive (>300 nm) TAAs with many repeats in their stalk regions. Further, we find that StaA/B are conserved across Snodgrassella species, suggesting that StaA/B-dependent colonization is characteristic of this symbiont lineage. Finally, staA deletion increases sensitivity to bactericidal antimicrobials, suggesting that the biofilm indirectly buffers against antibiotic stress. In all, the inability of two biofilm-deficient strains (Δ staA and Δ mltA ) to effectively mono-colonize bees indicates that S. alvi biofilm formation is required for colonization of the bee gut. We envision the bee gut system as a genetically tractable model for studying the physical basis of biofilm-mutualist-gut interactions.

ОЙЫН ТЕХНОЛОГИЯСЫНЫҢ ЭЛЕМЕНТТЕРІН ПАЙДАЛАНУ ӘДІСТЕРІ

The article describes the importance of game technology. Discusses the interaction between education and play and how they become effective tools for learning physics. The proposed methods are designed to increase students' interest and make the learning process more effective. Along with education, the student is told that games help develop personal and social skills such as teamwork, leadership, collaborative learning or decision making. And one should not forget the classification of players created by Richard Bartle when using game technology. Because the number of students in one class is usually not small. It is important that it is a fun game for all of them. Let's take a quick look at the games. Hot Potatoes is a game development site. Through this site, we can use tools such as JCloze for creating fill-in-the-blank exercises, JMatch for matching/ordering activities, and Jquiz for creating multiple-choice or short-answer questions. But this site does not consider individual chapters. Generalization is intended for building vectors for students. Scratch is a site where students can create animated videos. This site is not based on specific chapters or even subjects. Games can be created according to everyone's imagination. But due to the limited resources, the games are simple. The article analyzes a computer game for teaching the theory of relativity in physics. During the game, students can understand relative motions and basic principles of relativistic physics. The game explores Newton's laws and inertial motion, but has nothing to do with atomic physics. The article discusses the effectiveness of using games in teaching physics and chemistry in a foreign language. Games help students actively participate in the lesson and develop cognitive, affective, psychomotor skills. The article shows how educational games contribute to the development of cognitive and social skills. Overall, the methods presented in each article demonstrate the many advantages of using games effectively in education. They are aimed at increasing students' activity, deepening their understanding of scientific concepts and improving memory.

Stick-slip unfolding favors self-association of expanded HTT mRNA

In Huntington’s Disease (HD) and related disorders, expansion of CAG trinucleotide repeats produces a toxic gain of function in affected neurons. Expanded huntingtin (expHTT) mRNA forms aggregates that sequester essential RNA binding proteins, dysregulating mRNA processing and translation. The physical basis of RNA aggregation has been difficult to disentangle owing to the heterogeneous structure of the CAG repeats. Here, we probe the folding and unfolding pathways of expHTT mRNA using single-molecule force spectroscopy. Whereas normal HTT mRNAs unfold reversibly and cooperatively, expHTT mRNAs with 20 or 40 CAG repeats slip and unravel non-cooperatively at low tension. Slippage of CAG base pairs is punctuated by concerted rearrangement of adjacent CCG trinucleotides, trapping partially folded structures that readily base pair with another RNA strand. We suggest that the conformational entropy of the CAG repeats, combined with stable CCG base pairs, creates a stick-slip behavior that explains the aggregation propensity of expHTT mRNA.

Mastering the Game: How Level Structure and Game Elements Shape Competency Acquisition

Understanding the dynamics of level structure and game elements in digital educational games is paramount to fostering competency acquisition. How levels are organized within a game, along with the use of various game elements, has a significant impact on the learning outcomes and skill development of individuals. Through the strategic design and implementation of these components, educational games can effectively engage learners and facilitate the acquisition of competencies in multiple domains. In addition to structure, the integration of gamification elements can have a profound impact on learner engagement and sustainable skill acquisition. Therefore, a key element for the success of a serious game is to create appropriate personalization and a balanced relationship between learning and gaming experience. As a result, a mini-game called "Basketball Physics Challenge" has been designed to be integrated into an intelligent, adaptive physical learning game centered around force and motion as part of an ongoing research project. By playing the game "Basketball Physics Challenge", players will apply their understanding of basic physics principles in a realistic, interactive, and virtual setting. An experimental design was used to test the mini-game, in which a gamified and a non-gamified version were used and compared. 20 participants completed the experiment, and their learning progress was meticulously tracked. Using competency-based knowledge space theory, the mini-game facilitated in-game competency assessment, enabled monitoring of learning progress, tailored learning experiences, and provided individualized formative feedback. The pilot was used to develop and implement a competency model that will be the subject of future in-depth studies. The results indicated that the gamified version of the game led to slightly higher engagement and performance levels compared to the non-gamified version, although the difference in learning outcomes between the two versions was not statistically significant. The analysis also showed that an optimal number of levels and a balanced integration of game elements are crucial for maintaining engagement without causing cognitive overload. Furthermore, the order in which the game versions were presented affected player performance, with initial exposure to gamification leading to better outcomes. These findings provide valuable information for the design of educational games and their effectiveness in skill acquisition. This research supports the development of powerful educational technologies that enhance learning through a coherent level structure and meaningful use of game elements that effectively promote learner engagement.

Constitutive modelling in computational geomechanics – 61st Rankine lecture, British Geotechnical Association, 2023

Constitutive models are an essential part of computational modelling in geotechnics; they are at the heart of almost all theoretical predictions of geotechnical structures. How the stress–strain (and perhaps time) response of soil (and rock) is represented in these mathematical models is usually the key to successful prediction of the behaviour of geotechnical structures. However, the important details of these models, particularly the idealisations that are made, may be poorly or incompletely understood, or ignored, sometimes at significant cost to the unwary analyst. Indeed, the capabilities and the shortcomings of these models, especially the more advanced models, are not always easy to ascertain. In some cases, determination of the values of the input parameters is not straightforward. Consequently, it may be difficult to determine which model to select for a particular task. This paper explores some of the more important developments in the constitutive modelling of soils and addresses some of these issues of potential concern. The need for such models and the various attributes and capabilities that the commonly used models possess are reviewed. Also discussed is the issue of matching a particular model to the geotechnical problem at hand, which model attributes are required and why. The intention is to place emphasis on the physical basis of these models, rather than explore their mathematical complexity in detail. Some of the constitutive models encoded in the software packages used routinely in geotechnical practice are reviewed, and discussion is also provided on their specific limitations. Examples of practical applications, involving the solution of boundary and initial value problems, are described to illustrate both the advantages and some of the limitations of both commonly used and highly advanced constitutive models.

Outer hair cells stir cochlear fluids.

We hypothesized that active outer hair cells drive cochlear fluid circulation. The hypothesis was tested by delivering the neurotoxin, kainic acid, to the intact round window of young gerbil cochleae while monitoring auditory responses in the cochlear nucleus. Sounds presented at a modest level significantly expedited kainic acid delivery. When outer-hair-cell motility was suppressed by salicylate, the facilitation effect was compromised. A low-frequency tone was more effective than broadband noise, especially for drug delivery to apical locations. Computational model simulations provided the physical basis for our observation, which incorporated solute diffusion, fluid advection, fluid-structure interaction, and outer-hair-cell motility. Active outer hair cells deformed the organ of Corti like a peristaltic tube to generate apically streaming flows along the tunnel of Corti and basally streaming flows along the scala tympani. Our measurements and simulations coherently indicate that the outer-hair-cell action in the tail region of cochlear traveling waves is for cochlear fluid circulation.