To see the other types of publications on this topic, follow the link: Friction in biological systems.
Journal articles on the topic 'Friction in biological systems'
Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles
Consult the top 50 journal articles for your research on the topic 'Friction in biological systems.'
Next to every source in the list of references, there is an 'Add to bibliography' button. Press on it, and we will generate automatically the bibliographic reference to the chosen work in the citation style you need: APA, MLA, Harvard, Chicago, Vancouver, etc.
You can also download the full text of the academic publication as pdf and read online its abstract whenever available in the metadata.
Browse journal articles on a wide variety of disciplines and organise your bibliography correctly.
1
WIERZCHOLSKI, Krzysztof, and Andrzej MISZCZAK. "IMPACT OF ADHESION AND VISCOSITY FORCES ON FRICTION VARIATIONS IN BIO-TRIBOLOGICAL SYSTEMS." Tribologia 278, no. 2 (May 1, 2018): 139–51. http://dx.doi.org/10.5604/01.3001.0012.6987.
Full textAbstract:
The classical theory of lubrication holds that the lubricant dynamic viscosity increments cause the increments of hydrodynamic pressure, as well as friction forces and wear. In the case of high values of hydrodynamic pressure, it very often has a significant impact on the friction coefficient. New achievements in the field of micro-and nano-tribology provide for new hypotheses on the decrements and increments of the friction coefficient in the case of the lubricant viscosity increments. Experimental investigations have shown that, even in the case of decrements of the friction coefficient with the lubricant viscosity increments, such decrements are very often lower than simultaneous hydrodynamic pressure increments which results in the friction force increments with the lubricant viscosity increments. In biological friction nods, we can observe a varied impact of the biological lubricant viscosity on the friction force and friction coefficient values. The abovementioned impact is caused by the adhesion and cohesion forces occurring between the biological fluid particles flowing around the phospholipid bilayer on the superficial layer of the cartilage with varied wettability and hydrogen ion concentration. The wettability (We) and power hydrogen ion concentration (pH) have a significant impact on the physiological fluid or biological lubricant viscosity variations and, as a result, on the friction forces and friction coefficient. This paper describes the abovementioned impact and the process of friction forces and friction coefficients variations in biological friction nods.
2
Tramsen, Halvor T., Stanislav N. Gorb, Hao Zhang, Poramate Manoonpong, Zhendong Dai, and Lars Heepe. "Inversion of friction anisotropy in a bio-inspired asymmetrically structured surface." Journal of The Royal Society Interface 15, no. 138 (January 2018): 20170629. http://dx.doi.org/10.1098/rsif.2017.0629.
Full textAbstract:
Friction anisotropy is an important property of many surfaces that usually facilitate the generation of motion in a preferred direction. Such surfaces are very common in biological systems and have been the templates for various bio-inspired materials with similar tribological properties. So far friction anisotropy is considered to be the result of an asymmetric arrangement of surface nano- and microstructures. However, here we show by using bio-inspired sawtooth-structured surfaces that the anisotropic friction properties are not only controlled by an asymmetric surface topography, but also by the ratio of the sample–substrate stiffness, the aspect ratio of surface structures, and by the substrate roughness. Systematically modifying these parameters, we were able to demonstrate a broad range of friction anisotropies, and for specific sample–substrate combinations even an inversion of the anisotropy. This result highlights the complex interrelation between the different material and topographical parameters on friction properties and sheds new light on the conventional design paradigm of tribological systems. Finally, this result is also of great importance for understanding functional principles of biological materials and surfaces, as such inversion of friction anisotropy may correlate with gait pattern and walking behaviour in climbing animals, which in turn may be used in robotic applications.
3
Nosonovsky, Michael, and Bharat Bhushan. "Thermodynamics of surface degradation, self-organization and self-healing for biomimetic surfaces." Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences 367, no. 1893 (April 28, 2009): 1607–27. http://dx.doi.org/10.1098/rsta.2009.0009.
Full textAbstract:
Friction is a dissipative irreversible process; therefore, entropy is produced during frictional contact. The rate of entropy production can serve as a measure of degradation (e.g. wear). However, in many cases friction leads to self-organization at the surface. This is because the excess entropy is either driven away from the surface, or it is released at the nanoscale, while the mesoscale entropy decreases. As a result, the orderliness at the surface grows. Self-organization leads to surface secondary structures either due to the mutual adjustment of the contacting surfaces (e.g. by wear) or due to the formation of regular deformation patterns, such as friction-induced slip waves caused by dynamic instabilities. The effect has practical applications, since self-organization is usually beneficial because it leads to friction and wear reduction (minimum entropy production rate at the self-organized state). Self-organization is common in biological systems, including self-healing and self-cleaning surfaces. Therefore, designing a successful biomimetic surface requires an understanding of the thermodynamics of frictional self-organization. We suggest a multiscale decomposition of entropy and formulate a thermodynamic framework for irreversible degradation and for self-organization during friction. The criteria for self-organization due to dynamic instabilities are discussed, as well as the principles of biomimetic self-cleaning, self-lubricating and self-repairing surfaces by encapsulation and micro/nanopatterning.
4
Sekhar, JA. "Tunable coefficient of friction with surface texturing in materials engineering and biological systems." Current Opinion in Chemical Engineering 19 (March 2018): 94–106. http://dx.doi.org/10.1016/j.coche.2017.12.002.
Full text
5
Qian, Shanhua, Liguo Liu, Zifeng Ni, and Yong Luo. "Experimental investigation of the dynamic properties of natural cartilage under reciprocating sliding at two typical rubbing pairs." Proceedings of the Institution of Mechanical Engineers, Part J: Journal of Engineering Tribology 233, no. 9 (March 21, 2019): 1318–26. http://dx.doi.org/10.1177/1350650119836815.
Full textAbstract:
Natural cartilage is a multiporous viscoelastic biological material with extremely high water content and a macroscopically curved surface. Due to the sampling frequency limitations of typical data systems, the dynamic properties of the contact of cartilage against other surfaces, including rubbing surface characteristics and coefficient of friction, is still not completely understood. In this study, cartilage samples were retrieved from 18- to 24-month-old bovine femora. Contact displacement and coefficient of friction of two typical rubbing pairs of for cartilage-on-glass and cartilage-on-cartilage were recorded using a UMT-2 testing rig using a high sampling frequency data system. A five-point sliding average method was adopted to analyze the experimental data. The results showed that contact displacement comprised cartilage deformation and nominal rubbing profile. Cartilage deformation increased nonlinearly with time while nominal rubbing profile was associated with the rubbing configuration and appeared to be a factor in the low surface sample configuration. Higher cartilage deformation resulted in more load being carried by the solid phase and coefficient of friction with the time as a whole, but the surface characteristics played a role in determining the coefficient of friction in the cartilage-on-cartilage configuration but a lesser role for cartilage-on-glass. Therefore, surface characteristics have a clear role in defining the dynamic properties of natural viscoelastic soft biological materials and these research results will help to evaluate in future the frictional properties of artificial cartilage biomaterials.
6
Enders, S., N. Barbakadse, S. N. Gorb, and E. Arzt. "Exploring Biological Surfaces by Nanoindentation." Journal of Materials Research 19, no. 3 (March 2004): 880–87. http://dx.doi.org/10.1557/jmr.2004.19.3.880.
Full textAbstract:
With the help of instrumented indentation, the mechanical behavior of a variety of biological systems was studied: the waxy zone of the pitcher plant (Nephenthes alata) adapted for attachment prevention, the head-to-thorax articulation system of a beetle (Pachnoda marginata) as an example of friction minimization, and the wing arresting system of the dung beetle (Geotrupes stercorarius) adapted for mechanical interlocking. We demonstrate that nanoindentation can successfully be applied to compliant and highly structured biological composite materials. Measuring the mechanical performance of these surfaces can provide important information for understanding the overall functioning of these systems. Tests on fresh and dried samples show the influence of desiccation on the results and point out the importance of native conditions during the measurements. However, these preliminary results also point to current limits of the test method and the need for adapting it and current theories to meet the specific requirements of biological materials.
7
Reddy, J. Mohan, and Horacio Apolayo. "Friction Correction Factor For Center‐Pivot Irrigation Systems." Journal of Irrigation and Drainage Engineering 114, no. 1 (February 1988): 183–85. http://dx.doi.org/10.1061/(asce)0733-9437(1988)114:1(183).
Full text
8
Shivalinga, BM, H. Jyothikiran, Sachin Bansal, and Azeem Farhan. "A Comparison of Frictional Resistance between Active and Passive Self-ligating Brackets with Conventional Bracket Systems." World Journal of Dentistry 2, no. 4 (2011): 302–8. http://dx.doi.org/10.5005/jp-journals-10015-1102.
Full textAbstract:
ABSTRACT Friction, though, is an inseparable and undeniable orthodontic entity that should be minimized, if not eliminated, for obtaining an optimal biological tissue response. Aim The present study compared the frictional resistance of active (time- 2, In-Ovation R) and passive (Damon SL-2, Smart clip) self-ligating brackets with conventional titanium, fiberglass and ceramic brackets under dry and wet conditions with artificial saliva using universal testing machine. Methods Modified Tidy's jig was constructed to simulate clinical situation. A total of 200 samples were tested. Specimens were divided into two categories which were run under dry and wet conditions, using artificial saliva. Around 10 samples of each active and passive selfligating brackets were dry run and 10 others were used in wet conditions. Around 10 samples of each ceramic, titanium and fiberglass brackets were run using elastomeric ties in both dry and wet conditions and 10 each of them using stainless steel ligatures under dry and wet conditions. Results The study revealed that the least frictional resistance was demonstrated by the brackets in the following order, i.e. passive selfligating brackets, active self-ligating brackets, titanium, fiberglass and ceramic brackets in both dry and wet conditions. Conclusion The self-ligating brackets seem to be promising in quenching the thirst of orthodontist to have a bracket that is functionally efficient with reduced friction, esthetically pleasing, reduced treatment and chairside time, combined with better oral hygiene maintenance and patient comfort because of absence of ligation.
9
van den Boogaart, Luc M., Julian K. A. Langowski, and Guillermo J. Amador. "Studying Stickiness: Methods, Trade-Offs, and Perspectives in Measuring Reversible Biological Adhesion and Friction." Biomimetics 7, no. 3 (September 15, 2022): 134. http://dx.doi.org/10.3390/biomimetics7030134.
Full textAbstract:
Controlled, reversible attachment is widely spread throughout the animal kingdom: from ticks to tree frogs, whose weights span from 2 mg to 200 g, and from geckos to mosquitoes, who stick under vastly different situations, such as quickly climbing trees and stealthily landing on human hosts. A fascinating and complex interplay of adhesive and frictional forces forms the foundation of attachment of these highly diverse systems to various substrates. In this review, we present an overview of the techniques used to quantify the adhesion and friction of terrestrial animals, with the aim of informing future studies on the fundamentals of bioadhesion, and motivating the development and adoption of new or alternative measurement techniques. We classify existing methods with respect to the forces they measure, including magnitude and source, i.e., generated by the whole body, single limbs, or by sub-structures. Additionally, we compare their versatility, specifically what parameters can be measured, controlled, and varied. This approach reveals critical trade-offs of bioadhesion measurement techniques. Beyond stimulating future studies on evolutionary and physicochemical aspects of bioadhesion, understanding the fundamentals of biological attachment is key to the development of biomimetic technologies, from soft robotic grippers to gentle surgical tools.
10
Aihara, Kazuyuki, and Hideyuki Suzuki. "Theory of hybrid dynamical systems and its applications to biological and medical systems." Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences 368, no. 1930 (November 13, 2010): 4893–914. http://dx.doi.org/10.1098/rsta.2010.0237.
Full textAbstract:
In this introductory article, we survey the contents of this Theme Issue. This Theme Issue deals with a fertile region of hybrid dynamical systems that are characterized by the coexistence of continuous and discrete dynamics. It is now well known that there exist many hybrid dynamical systems with discontinuities such as impact, switching, friction and sliding. The first aim of this Issue is to discuss recent developments in understanding nonlinear dynamics of hybrid dynamical systems in the two main theoretical fields of dynamical systems theory and control systems theory. A combined study of the hybrid systems dynamics in the two theoretical fields might contribute to a more comprehensive understanding of hybrid dynamical systems. In addition, mathematical modelling by hybrid dynamical systems is particularly important for understanding the nonlinear dynamics of biological and medical systems as they have many discontinuities such as threshold-triggered firing in neurons, on–off switching of gene expression by a transcription factor, division in cells and certain types of chronotherapy for prostate cancer. Hence, the second aim is to discuss recent applications of hybrid dynamical systems in biology and medicine. Thus, this Issue is not only general to serve as a survey of recent progress in hybrid systems theory but also specific to introduce interesting and stimulating applications of hybrid systems in biology and medicine. As the introduction to the topics in this Theme Issue, we provide a brief history of nonlinear dynamics and mathematical modelling, different mathematical models of hybrid dynamical systems, the relationship between dynamical systems theory and control systems theory, examples of complex behaviour in a simple neuron model and its variants, applications of hybrid dynamical systems in biology and medicine as a road map of articles in this Theme Issue and future directions of hybrid systems modelling.
11
Erazo, Christian, Martin E. Homer, Petri T. Piiroinen, and Mario Di Bernardo. "Dynamic Cell Mapping Algorithm for Computing Basins of Attraction in Planar Filippov Systems." International Journal of Bifurcation and Chaos 27, no. 12 (November 2017): 1730041. http://dx.doi.org/10.1142/s0218127417300415.
Full textAbstract:
Discontinuities are a common feature of physical models in engineering and biological systems, e.g. stick-slip due to friction, electrical relays or gene regulatory networks. The computation of basins of attraction of such nonsmooth systems is challenging and requires special treatments, especially regarding numerical integration. In this paper, we present a numerical routine for computing basins of attraction (BA) in nonsmooth systems with sliding, (so-called Filippov systems). In particular, we extend the Simple Cell Mapping (SCM) method to cope with the presence of sliding solutions by exploiting an event-driven numerical integration routine specifically written for Filippov systems. Our algorithm encompasses a method for dynamic construction of the cell state space so that a lower number of integration steps are required. Moreover, we incorporate an adaptive strategy of the simulation time to render more efficiently the computation of basins of attraction. We illustrate the effectiveness of our algorithm by computing basins of attraction of a sliding control problem and a dry-friction oscillator.
12
Zhuravel, D., D. Milko, and A. Bondar. "Use of biological oils for agricultural machinery." Mehanization and electrification of agricultural, no. 10(109) (2019): 151–59. http://dx.doi.org/10.37204/0131-2189-2019-10-15.
Full textAbstract:
Purpose. Improvement of tribotechnical properties of organic oil to ensure the reliable operation of nodes and units of functional systems of mobile agricultural machinery. Methods. The methods of estimation of tribotechnical properties of lubricants of biological origin were used. Results. The methodology of improvement of tribotechnical properties of biological oil for mobile agricultural machinery is considered. As a result of the conducted researches it is established that materials that work in the environment of biological lubricants have the best resistance to wear, in addition, the wear in the environment of biological oils is practically independent of the tribosystem load. However, organic oil is prone to negative processes that lead to polymerization and oxidation. To improve the tribotechnical properties of organic oil, it is necessary to introduce special additives and additives in it, which will allow to level these processes. Conclusions. 1. It is established that the use of blended oil is promising. The widespread use of vegetable oil in the production of lubricants will solve some of the complex environmental problems. 2. The chemical and tribotechnical properties of organic oil are better than those of mineral oils, but they are inferior to the resistance to oxidation, so it is advisable to introduce multifunctional additives and additives to improve its basic characteristics. However, additives to organic oils have structural components of different origin, they are unsystematized and have no scientific justification to ensure the wear resistance of the surface layers of friction pairs of nodes and aggregates of mobile machinery. 3. As a result of the researches it was established that the wear of the samples for friction steam “spool – the valve body” decreased in the environments: rapeseed oil by 62.5%, and with 1.0% by the addition of ICF-18 by 75%; of sunflower oil by 62.5%, and with 1.0% by the addition of MKF-18 by 80%. Keywords: agricultural technology, the reliability of functional systems, tribotechnical properties, metalplating additives, biological fluids, lubricants, units and aggregates.
13
Wang, Hongyun, and Hong Zhou. "Stokes Efficiency of Molecular Motor-Cargo Systems." Abstract and Applied Analysis 2008 (2008): 1–13. http://dx.doi.org/10.1155/2008/241736.
Full textAbstract:
A molecular motor utilizes chemical free energy to generate a unidirectional motion through the viscous fluid. In many experimental settings and biological settings, a molecular motor is elastically linked to a cargo. The stochastic motion of a molecular motor-cargo system is governed by a set of Langevin equations, each corresponding to an individual chemical occupancy state. The change of chemical occupancy state is modeled by a continuous time discrete space Markov process. The probability density of a motor-cargo system is governed by a two-dimensional Fokker-Planck equation. The operation of a molecular motor is dominated by high viscous friction and large thermal fluctuations from surrounding fluid. The instantaneous velocity of a molecular motor is highly stochastic: the past velocity is quickly damped by the viscous friction and the new velocity is quickly excited by bombardments of surrounding fluid molecules. Thus, the theory for macroscopic motors should not be applied directly to molecular motors without close examination. In particular, a molecular motor behaves differently working against a viscous drag than working against a conservative force. The Stokes efficiency was introduced to measure how efficiently a motor uses chemical free energy to drive against viscous drag. For a motor without cargo, it was proved that the Stokes efficiency is bounded by 100% [H. Wang and G. Oster, (2002)]. Here, we present a proof for the general motor-cargo system.
14
Šugárová, Jana, Peter Šugár, and Martin Frnčík. "Friction Evaluation of Laser Textured Tool Steel Surfaces." Acta Mechanica et Automatica 11, no. 2 (June 1, 2017): 129–34. http://dx.doi.org/10.1515/ama-2017-0020.
Full textAbstract:
AbstractSurface textures can be defined as a regularly arranged micro-depressions or grooves with defined shape and dimensions. These textures, if they are manufactured by laser ablation process, contribute to a significant improvement of the tribological, optical or various biological properties. The aim of this paper is to analyze the influence of the surface textures prepared by laser surface texturing (LST) at the friction coefficient value measured on the tool (90MnCrV8 steel) – workpiece (S235JRG1 steel) interface. Planar frontal surfaces of compression platens have been covered by parabolic dimple-like depressions with different dimensions. The morphological analysis of such manufactured depressions has been performed by laser scanning microscopy. Influence of such created textures on the tribological properties of the contact pair has been analyzed by the ring compression test method in the terms of hydrodynamic lubrication regime. The experimental research shown that by applying of surface textures with defined shape and dimensions and using an appropriate liquid lubricant at the same time, the coefficient of contact friction can be reduced nearly to the half of its original value.
15
Bhushan, Bharat. "Nanotribology and nanomechanics in nano/biotechnology." Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences 366, no. 1870 (January 11, 2008): 1499–537. http://dx.doi.org/10.1098/rsta.2007.2170.
Full textAbstract:
Owing to larger surface area in micro/nanoelectromechanical systems (MEMS/NEMS), surface forces such as adhesion, friction, and meniscus and viscous drag forces become large when compared with inertial and electromagnetic forces. There is a need to develop lubricants and identify lubrication methods that are suitable for MEMS/NEMS. For BioMEMS/BioNEMS, adhesion between biological molecular layers and the substrate, and friction and wear of biological layers may be important, and methods to enhance adhesion between biomolecules and the device surface need to be developed. There is a need for development of a fundamental understanding of adhesion, friction/stiction, wear, the role of surface contamination and environment, and lubrication. MEMS/NEMS materials need to exhibit good mechanical and tribological properties on the micro/nanoscale. Most mechanical properties are known to be scale dependent. Therefore, the properties of nanoscale structures need to be measured. Component-level studies are required to provide a better understanding of the tribological phenomena occurring in MEMS/NEMS. The emergence of micro/nanotribology and atomic force microscopy-based techniques has provided researchers with a viable approach to address these problems. This paper presents an overview of micro/nanoscale adhesion, friction, and wear studies of materials and lubrication studies for MEMS/NEMS and BioMEMS/BioNEMS. It also presents a review of scale-dependent mechanical properties, and stress and deformation analysis of nanostructures.
16
Grimble, D. W., S. Theodossiades, H. Rahnejat, and M. Wilby. "Tribology of rough ultra-film contacts in drug delivery devices." Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science 222, no. 11 (November 1, 2008): 2209–16. http://dx.doi.org/10.1243/09544062jmes1047.
Full textAbstract:
Elastomeric seals are extensively used in an assortment of drug delivery devices, such as syringes and pressurized metered dose inhalers. Although tribology of rubber seals and o-rings is reasonably well understood in engineering applications, the drug mixtures and formulations do not enjoy the required rheology to ensure coherent hydrodynamic action. In fact formation of uninterrupted hydrodynamic films is not actually sought in drug delivery devices, which often contain mixtures that are volatile when exposed to the environment. Furthermore, while engineering devices are often driven to overcome friction, many drug delivery systems are actuated manually and frequently by frail individuals. Therefore, the tribological problem is quite complex with many biological and environmental constraints. This paper highlights a parametric friction model for combined adhesive friction due to asperity interactions and non-Newtonian viscous action of the formulation. The model predicts the hysteretic behaviour of elastomeric seal contacts and conforms reasonably well to the experimental measurements of the same through actuation and release of inhaler valves.
17
Harun, Zambri, Ashraf Amer Abbas, Bagus Nugroho, Leon Chan, and Sohif Mat. "Surface Roughness Effects Studies in Transportation Industries." Jurnal Kejuruteraan si1, no. 7 (November 30, 2018): 87–90. http://dx.doi.org/10.17576/jkukm-2018-si1(7)-11.
Full textAbstract:
Aerodynamic and skin friction effects are two main factors determining fuel efficiencies in the transportation industry. In any of transportation areas, either road transport, railway, maritime or aerospace, fuel efficiency has become interesting and sometimes sensitive topics. Data were from experimental studies, simulations as well as news and discussions in engineering bulletins dan</em> <em>fuel efficiency, i.e. skin friction. Studies in skin friction are very important because skin friction drag account the majority of drag in a streamlined body e.g. tankers. The use of biomimetic, i.e. the study of the structures and functions of biological systems in the design of engineering systems has attracted a lot of attentions in the last few decades. Mimicking the arrangement and pattern on shark scales and how owls quietly fly has contributed to progress in various engineering fields. Simulation works are carried out especially to reduce costs and to obtain estimation of drags prior to experiment works. However, current computational resources only allow turbulent flows to be simulated at low and medium Reynolds numbers - far below that of engineering flows. This has lead researchers to develop empirical models which can be used for practical engineering applications so that engineers are able to obtain a estimate of the drag on the surface. Throughout the years, many models have been proposed but none has been universally reliable. Indeed, the turbulent flow over rough surfaces is a complex field of research and much is still to be discovered.
18
Andreucci, Carlos Aurelio, Elza M. M. Fonseca, and Renato N. Jorge. "Bio-lubricant Properties Analysis of Drilling an Innovative Design of Bioactive Kinetic Screw into Bone." Designs 7, no. 1 (February 1, 2023): 21. http://dx.doi.org/10.3390/designs7010021.
Full textAbstract:
Biotribology is applied to study the friction, wear, and lubrication of biological systems or natural phenomena under relative motion in the human body. It is a multidisciplinary field and tribological processes impact all aspects of our daily life. Tribological processes may occur after the implantation of an artificial device in the human body with a wide variety of sliding and frictional interfaces. Blood is a natural bio-lubricant experiencing laminar flow at the lower screw velocities associated with drilling implants into bone, being a viscoelastic fluid with viscous and fluid characteristics. The viscosity comes from the blood plasma, while the elastic properties are from the deformation of red blood cells. In this study, drilling parameters according to material properties obtained by Finite Element Analysis are given. The influence of blood on the resulting friction between the surfaces is demonstrated and correlated with mechanical and biological consequences, identifying an innovative approach to obtaining a new lubricant parameter for bone drilling analysis. The lubrication parameter (HN) found within the limitations of conditions used in this study is 10.7 × 10−7 for both cortical bone (D1) and spongy bone (D4). A thermal-structural analysis of the densities of the soft bone (D4) and hard bone (D1) shows differences in only the equivalent stress values due to the differences in respective Young moduli. The natural occurrences of blood as a lubricant in bone-screw perforations are poorly investigated in the literature and its effects are fundamental in osseointegration. This work aims to elucidate the relevance of the study of blood as a lubricant in drilling and screwing implants into bone at lower speeds.
19
Liwo, Adam, Cezary Czaplewski, Adam K. Sieradzan, Agnieszka G. Lipska, Sergey A. Samsonov, and Rajesh K. Murarka. "Theory and Practice of Coarse-Grained Molecular Dynamics of Biologically Important Systems." Biomolecules 11, no. 9 (September 11, 2021): 1347. http://dx.doi.org/10.3390/biom11091347.
Full textAbstract:
Molecular dynamics with coarse-grained models is nowadays extensively used to simulate biomolecular systems at large time and size scales, compared to those accessible to all-atom molecular dynamics. In this review article, we describe the physical basis of coarse-grained molecular dynamics, the coarse-grained force fields, the equations of motion and the respective numerical integration algorithms, and selected practical applications of coarse-grained molecular dynamics. We demonstrate that the motion of coarse-grained sites is governed by the potential of mean force and the friction and stochastic forces, resulting from integrating out the secondary degrees of freedom. Consequently, Langevin dynamics is a natural means of describing the motion of a system at the coarse-grained level and the potential of mean force is the physical basis of the coarse-grained force fields. Moreover, the choice of coarse-grained variables and the fact that coarse-grained sites often do not have spherical symmetry implies a non-diagonal inertia tensor. We describe selected coarse-grained models used in molecular dynamics simulations, including the most popular MARTINI model developed by Marrink’s group and the UNICORN model of biological macromolecules developed in our laboratory. We conclude by discussing examples of the application of coarse-grained molecular dynamics to study biologically important processes.
20
Yoshihito, Osada. "Polymer Gels as Artificial Soft Tissue1, "Высокомолекулярные соединения. Серия С"." Высокомолекулярные соединения С, no. 1 (2017): 5–13. http://dx.doi.org/10.7868/s2308114717010022.
Full textAbstract:
Abstract - Soft tissue consists a main body of biological systems. It is made of hydrogels mainly composed of extra cellular matrix (ECM), which is the three-dimensional highly organized and inter-woven network of proteins and polysaccharides. ECM has three symbolic roles. They are pertinent and excellent mechanical performance, extremely low friction, and effective and selective transportation of solute molecules for cell viability. One of the important goals for gel science would be to design and create hydrogels with critical parameters, which natural tissues possess and eventually to replace them with artificial one.
21
Borzì, Alfio, and Suttida Wongkaew. "Modeling and control through leadership of a refined flocking system." Mathematical Models and Methods in Applied Sciences 25, no. 02 (November 24, 2014): 255–82. http://dx.doi.org/10.1142/s0218202515500098.
Full textAbstract:
A new refined flocking model that includes self-propelling, friction, attraction and repulsion, and alignment features is presented. This model takes into account various behavioral phenomena observed in biological and social systems. In addition, the presence of a leader is included in the system in order to develop a control strategy for the flocking model to accomplish desired objectives. Specifically, a model predictive control scheme is proposed that requires the solution of a sequence of open-loop optimality systems. An accurate Runge–Kutta scheme to discretize the optimality systems and a nonlinear conjugate gradient solver are implemented and discussed. Numerical experiments are performed that investigate the properties of the refined flocking model and demonstrate the ability of the control strategy to drive the flocking system to attain a desired target configuration and to follow a given trajectory.
22
Ditsche, Petra, and Adam Summers. "Learning from Northern clingfish ( Gobiesox maeandricus ): bioinspired suction cups attach to rough surfaces." Philosophical Transactions of the Royal Society B: Biological Sciences 374, no. 1784 (September 9, 2019): 20190204. http://dx.doi.org/10.1098/rstb.2019.0204.
Full textAbstract:
While artificial suction cups only attach well to smooth surfaces, the Northern clingfish can attach to surfaces ranging from nanoscale smooth to rough stone. This ability is highly desirable for technical applications. The morphology of the fish's suction disc and its ability to attach to rough and slimy surfaces have been described before, and here we aim to close gaps in the biomechanical understanding, and transfer the biomechanical principles to technical suction cups. We demonstrate that the margin of the suction disc is the critical feature enabling attachment to rough surfaces. Second, friction measurements show that friction of the disc rim is increased on rough substrates and contributes to high tenacity. Increased friction causes a delay in failure of the suction cup and increases the attachment force. We were able to implement these concepts to develop the first suction cups bioinspired by Northern clingfish. These cups attach with tenacities up to 70 kPa on surfaces as rough as 270 µm grain size. The application of this technology is promising in fields such as surgery, industrial production processes and whale tagging. This article is part of the theme issue ‘Transdisciplinary approaches to the study of adhesion and adhesives in biological systems'.
23
Grützmacher, Philipp G., Francisco J. Profito, and Andreas Rosenkranz. "Multi-Scale Surface Texturing in Tribology—Current Knowledge and Future Perspectives." Lubricants 7, no. 11 (October 28, 2019): 95. http://dx.doi.org/10.3390/lubricants7110095.
Full textAbstract:
Surface texturing has been frequently used for tribological purposes in the last three decades due to its great potential to reduce friction and wear. Although biological systems advocate the use of hierarchical, multi-scale surface textures, most of the published experimental and numerical works have mainly addressed effects induced by single-scale surface textures. Therefore, it can be assumed that the potential of multi-scale surface texturing to further optimize friction and wear is underexplored. The aim of this review article is to shed some light on the current knowledge in the field of multi-scale surface textures applied to tribological systems from an experimental and numerical point of view. Initially, fabrication techniques with their respective advantages and disadvantages regarding the ability to create multi-scale surface textures are summarized. Afterwards, the existing state-of-the-art regarding experimental work performed to explore the potential, as well as the underlying effects of multi-scale textures under dry and lubricated conditions, is presented. Subsequently, numerical approaches to predict the behavior of multi-scale surface texturing under lubricated conditions are elucidated. Finally, the existing knowledge and hypotheses about the underlying driven mechanisms responsible for the improved tribological performance of multi-scale textures are summarized, and future trends in this research direction are emphasized.
24
Labonte, David, and Walter Federle. "Scaling and biomechanics of surface attachment in climbing animals." Philosophical Transactions of the Royal Society B: Biological Sciences 370, no. 1661 (February 5, 2015): 20140027. http://dx.doi.org/10.1098/rstb.2014.0027.
Full textAbstract:
Attachment devices are essential adaptations for climbing animals and valuable models for synthetic adhesives. A major unresolved question for both natural and bioinspired attachment systems is how attachment performance depends on size. Here, we discuss how contact geometry and mode of detachment influence the scaling of attachment forces for claws and adhesive pads, and how allometric data on biological systems can yield insights into their mechanism of attachment. Larger animals are expected to attach less well to surfaces, due to their smaller surface-to-volume ratio, and because it becomes increasingly difficult to distribute load uniformly across large contact areas. In order to compensate for this decrease of weight-specific adhesion, large animals could evolve overproportionally large pads, or adaptations that increase attachment efficiency (adhesion or friction per unit contact area). Available data suggest that attachment pad area scales close to isometry within clades, but pad efficiency in some animals increases with size so that attachment performance is approximately size-independent. The mechanisms underlying this biologically important variation in pad efficiency are still unclear. We suggest that switching between stress concentration (easy detachment) and uniform load distribution (strong attachment) via shear forces is one of the key mechanisms enabling the dynamic control of adhesion during locomotion.
25
Vitali, Silvia, Vittoria Sposini, Oleksii Sliusarenko, Paolo Paradisi, Gastone Castellani, and Gianni Pagnini. "Langevin equation in complex media and anomalous diffusion." Journal of The Royal Society Interface 15, no. 145 (August 2018): 20180282. http://dx.doi.org/10.1098/rsif.2018.0282.
Full textAbstract:
The problem of biological motion is a very intriguing and topical issue. Many efforts are being focused on the development of novel modelling approaches for the description of anomalous diffusion in biological systems, such as the very complex and heterogeneous cell environment. Nevertheless, many questions are still open, such as the joint manifestation of statistical features in agreement with different models that can also be somewhat alternative to each other, e.g. continuous time random walk and fractional Brownian motion. To overcome these limitations, we propose a stochastic diffusion model with additive noise and linear friction force (linear Langevin equation), thus involving the explicit modelling of velocity dynamics. The complexity of the medium is parametrized via a population of intensity parameters (relaxation time and diffusivity of velocity), thus introducing an additional randomness, in addition to white noise, in the particle's dynamics. We prove that, for proper distributions of these parameters, we can get both Gaussian anomalous diffusion, fractional diffusion and its generalizations.
26
Dаnishevskyy, V. V., and A. M. Gaidar. "ОPTIMAL PLACEMENT OF FRICTION DAMPERS FOR THE SEISMIC PROTECTION OF FRAME BUILDINGS USING THE PARTICLE SWARM OPTIMIZATION." Bulletin of Odessa State Academy of Civil Engineering and Architecture, no. 80 (September 3, 2020): 34–42. http://dx.doi.org/10.31650/2415-377x-2020-80-34-42.
Full textAbstract:
Abstract. A challenging problem of Civil Engineering is the protection of buildings against dynamic loads and earthquake impacts. The advanced solutions employ lightweight structures equipped with special damping devices. These devices can be active or passive and their application depends on the investments for the project. The active devices change their properties depending on the structural response and they are the most expensive ones. On the other hand, passive devices are essentially cheaper and, in many cases, require minimal costs of installation and maintenance. Last decades, passive friction dampers are widely used for the earthquake protection of multi-storey buildings. The friction dampers make use of the effect of solid friction to dissipate the mechanical energy and to reduce the amplitude of the vibration of the structure. The friction is developed between two solid bodies sliding in relation to one another. As usual, pairs of metal, polymer or concrete components can be utilized. Determination of the optimal location of the friction dampers inside the building presents a complicated task for the practical design. In this paper, a new approach is developed basing on the method of particle swarm optimization (PSO). The PSO method presents an artificial simulation of the phenomenon of collective intelligence, which is observed in many decentralized biological systems like ant colonies, bee swarms, flocks of birds and even social groups of human individuals. As an illustrative example, the 2D model of a ten-storey concrete frame building is considered. The purpose of the analysis is to minimize the objective function, which is the amplitude of the displacements of the top of the structure in a case of the resonance dynamic load with a frequency of the first normal mode. Non-stationary dynamic analysis is performed by the finite elements method using the program package «LIRA-SAPR» and its module «Dynamic-plus». The software implementation of the PSO procedure is developed using the open-source computer algebra system «Maxima». The optimal placement of friction dampers is determined providing the minimal displacements of the frame. The developed approach can be further extended to various problems of the optimal design of buildings and structures.
27
Flemming, H. C., and J. Wingender. "Relevance of microbial extracellular polymeric substances (EPSs) - Part II: Technical aspects." Water Science and Technology 43, no. 6 (March 1, 2001): 9–16. http://dx.doi.org/10.2166/wst.2001.0328.
Full textAbstract:
Extracellular polymeric substances (EPSs) are involved in both detrimental and beneficial consequences of microbial aggregates such as biofilms, flocs and biological sludges. In biofouling, they are responsible for the increase of friction resistance, change of surface properties such as hydrophobicity, roughness, colour, etc. In biocorrosion of metals they are involved by their ability to bind metal ions. In bioweathering, they contribute by their complexing properties to the dissolution of minerals. The EPSs represent a sorption site for pollutants such as heavy metal ions and organic molecules. This can lead to a burden in wastewater sludge; on the other hand, the sorption properties can be used for water purification. Other biotechnological uses of EPS exploit their contribution to viscosity, e.g., in food, paints and oil-drilling ‘muds’; their hydrating properties are also used in cosmetics and pharmaceuticals. Furthermore, EPSs may have potential uses as biosurfactants, e.g., in tertiary oilproduction, and as biological glue. EPSs are an interesting component of all biofilm systems and still hold a large biotechnological potential.
28
Branco, Ana C., Andreia S. Oliveira, Inês Monteiro, Pedro Nolasco, Diana C. Silva, Célio G. Figueiredo-Pina, Rogério Colaço, and Ana P. Serro. "PVA-Based Hydrogels Loaded with Diclofenac for Cartilage Replacement." Gels 8, no. 3 (February 24, 2022): 143. http://dx.doi.org/10.3390/gels8030143.
Full textAbstract:
Polyvinyl alcohol (PVA) hydrogels have been widely studied for cartilage replacement due to their biocompatibility, chemical stability, and ability to be modified such that they approximate natural tissue behavior. Additionally, they may also be used with advantages as local drug delivery systems. However, their properties are not yet the most adequate for such applications. This work aimed to develop new PVA-based hydrogels for this purpose, displaying improved tribomechanical properties with the ability to control the release of diclofenac (DFN). Four types of PVA-based hydrogels were prepared via freeze-thawing: PVA, PVA/PAA (by polyacrylic acid (PAA) addition), PVA/PAA+PEG (by polyethylene glycol (PEG) immersion), and PVA/PAA+PEG+A (by annealing). Their morphology, water uptake, mechanical and rheological properties, wettability, friction coefficient, and drug release behavior were accessed. The irritability of the best-performing material was investigated. The results showed that the PAA addition increased the swelling and drug release amount. PEG immersion led to a more compact structure and significantly improved the material’s tribomechanical performance. The annealing treatment led to the material with the most suitable properties: besides presenting a low friction coefficient, it further enhanced the mechanical properties and ensured a controlled DFN release for at least 3 days. Moreover, it did not reveal irritability potential for biological tissues.
29
Thierron, W. "The Flexural Rigidity of Polyester-fibre–Cotton Yarns Produced on the Ring-, Rotor-, and Friction-spinning Systems." Journal of The Textile Institute 76, no. 6 (November 1985): 454–58. http://dx.doi.org/10.1080/00405008508658961.
Full text
30
Chernyavskiy, A. M., T. M. Ruzmatov, A. V. Fomichev, A. E. Medvedev, Yu M. Prikhodko, V. M. Fomin, V. P. Fomichev, K. A. Lomanovich, and A. M. Karaskov. "Experimental evaluation of mechanical heart support system based on viscous friction disc pump." Russian Journal of Transplantology and Artificial Organs 19, no. 1 (April 14, 2017): 28–34. http://dx.doi.org/10.15825/1995-1191-2017-1-28-34.
Full textAbstract:
Aim. Experimental evaluation of the viscous friction disk pump efficiency, studying the relationship between inter-disk clearance and sizes of input and output ports and pump performance parameters.Materials and methods. To assess the characteristics and to optimize the disk friction pump design the pump model and experimental stand were created. Pump dimensions were set on the basis of medical and biological requirements for mechanical heart support systems and with due consideration of the experimental studies of our colleagues from Pennsylvania. Flow volume of the working fluid was measured by float rotameter Krohne VA-40 with measurement error of not more than 1%. The pressure values in the hydrodynamic circuit were measured using a monitor manufactured by Biosoft-M. Expansion device allowed changing the flow resistance of the system simulating the total peripheral resistance of the circulatory system.Results. Linear direct correlation between the pump performance and the pressure drop of liquid being created at the inlet and outlet of the pump was obtained. The required flow rate (5–7 l/min) and pressure (90–100 mmHg) were reached when the rotor speed was in the range of 2500–3000 rev/min. It has been shown that the increase of the inlet diameter to 15 mm has not resulted in a significant increase in the pump performance, and that the highest efficiency values can be obtained for the magnitude of inter-disk gap of 0.4–0.5 mm.Conclusion. Designed and manufactured experimental disc pump model for pumping fluid has showed the fundamental possibility to use this model as a system for mechanical support of the heart.
31
Orozco-Hernández, Giovany, Pablo Guzmán Durán, and William Aperador. "Tribocorrosion Evaluation of Nb2O5, TiO2, and Nb2O5 + TiO2 Coatings for Medical Applications." Lubricants 9, no. 5 (May 1, 2021): 49. http://dx.doi.org/10.3390/lubricants9050049.
Full textAbstract:
Materials used in biomedicine for purposes of long-time stay inside the body presents diverse sort of problems like cytotoxicity, wear, biocompatibility, and ion liberation along time. This paper presents the characterization of corrosion-wear combined phenomena on Nb2O5, TiO2, and Nb2O5 + TiO2 coatings with future applications as biomaterials. After the films’ production process using magnetron sputtering technique, they were characterized through an optic, scanning electron, and atomic force microscopy to evaluate their morphology, structure, and surface damage suffered by the synergy between wear and corrosion phenomena. The life in service of the implant was evaluated in terms of the coating behavior against inside body conditions like charge, wear, and electrochemical degradation. This test was made with electrochemical measurements in simulated biological fluid combined with the wear characterization implementing a potentiostat and a tribometer in a linear wear configuration with a bone pin. As a result, the different electrochemical responses of the films were evidenced by polarization curves and equivalent circuits of the systems. The coefficient of friction and surface degradation were also obtained and evaluated. Comparing the properties of the systems, we conclude that TiO2 coatings have better behavior in terms of the wear-corrosion synergy phenomena while the systems with Nb present pitting corrosion.
32
Cairoli, Andrea, Rainer Klages, and Adrian Baule. "Weak Galilean invariance as a selection principle for coarse-grained diffusive models." Proceedings of the National Academy of Sciences 115, no. 22 (May 14, 2018): 5714–19. http://dx.doi.org/10.1073/pnas.1717292115.
Full textAbstract:
How does the mathematical description of a system change in different reference frames? Galilei first addressed this fundamental question by formulating the famous principle of Galilean invariance. It prescribes that the equations of motion of closed systems remain the same in different inertial frames related by Galilean transformations, thus imposing strong constraints on the dynamical rules. However, real world systems are often described by coarse-grained models integrating complex internal and external interactions indistinguishably as friction and stochastic forces. Since Galilean invariance is then violated, there is seemingly no alternative principle to assess a priori the physical consistency of a given stochastic model in different inertial frames. Here, starting from the Kac–Zwanzig Hamiltonian model generating Brownian motion, we show how Galilean invariance is broken during the coarse-graining procedure when deriving stochastic equations. Our analysis leads to a set of rules characterizing systems in different inertial frames that have to be satisfied by general stochastic models, which we call “weak Galilean invariance.” Several well-known stochastic processes are invariant in these terms, except the continuous-time random walk for which we derive the correct invariant description. Our results are particularly relevant for the modeling of biological systems, as they provide a theoretical principle to select physically consistent stochastic models before a validation against experimental data.
33
Alanazi, Meznah M., Awatif A. Hendi, Qadeer Raza, Muhammad Abdul Rehman, Muhammad Zubair Akbar Qureshi, Bagh Ali, and Nehad Ali Shah. "Numerical Computation of Hybrid Morphologies of Nanoparticles on the Dynamic of Nanofluid: The Case of Blood-Based Fluid." Axioms 12, no. 2 (February 6, 2023): 163. http://dx.doi.org/10.3390/axioms12020163.
Full textAbstract:
The movement of biological fluids in the human body is a premium field of interest to overcome growing biomedical challenges. Blood behavior shows different behavior in capillaries, veins, and arteries during circulation. In this paper, a new mathematical relation for the nano-layer of biological fluids flows with the effect of TiO2 and Ag hybrid nanoparticles was developed. Further, we explain the engineering phenomena of biological fluids and the role of hybrid nanoparticles in the blood vessel system. The improvement of drug delivery systems by using low seepage Reynolds number was associated with expansion/contraction and was discussed in detail through the rectangular domain. Using similarity transformation, the governing equations were converted into non-linear ordinary differential equations, and the mathematical problem was solved by employing the numerical shooting method. Plots of momentum, temperature, skin friction coefficient, as well as the Nusselt number on different non-dimensionless parameters are displayed via lower/upper porous walls of the channel. It was analyzed that the walls of the channel showed different results on magnetized physical parameters. Values of thermophoresis and the Brownian motion flow of the heat transfer rate gradually increased on the upper wall and decreased on the lower wall of the channel. The important thing is that the hybrid nanoparticles, rather than nano, were more useful for improving thermal conductivity, heat transfer rate, and the nano-layer.
34
Roach, Ty N. F., Peter Salamon, James Nulton, Bjarne Andresen, Ben Felts, Andreas Haas, Sandi Calhoun, Nathan Robinett, and Forest Rohwer. "Application of Finite-Time and Control Thermodynamics to Biological Processes at Multiple Scales." Journal of Non-Equilibrium Thermodynamics 43, no. 3 (July 26, 2018): 193–210. http://dx.doi.org/10.1515/jnet-2018-0008.
Full textAbstract:
AbstractAn overall synthesis of biology and non-equilibrium thermodynamics remains a challenge at the interface between the physical and life sciences. Herein, theorems from finite-time and control thermodynamics are applied to biological processes to indicate which biological strategies will succeed over different time scales. In general, living systems maximize power at the expense of efficiency during the early stages of their development while proceeding at slower rates to maximize efficiency over longer time scales. The exact combination of yield and power depends upon the constraints on the system, the degrees of freedom in question, and the time scales of the processes. It is emphasized that biological processes are not driven by entropy production but, rather, by informed exergy flow. The entropy production is the generalized friction that is minimized insofar as the constraints allow. Theorems concerning thermodynamic path length and entropy production show that there is a direct tradeoff between the efficiency of a process and the process rate. To quantify this tradeoff, the concepts of compensated heat and waste heat are introduced. Compensated heat is the exergy dissipated, which is necessary for a process to satisfy constraints. Conversely, waste heat is exergy that is dissipated as heat, but does not provide a compensatory increase in rate or other improvement. We hypothesize that it is waste heat that is minimized through natural selection. This can be seen in the strategies employed at several temporal and spatial scales, including organismal development, ecological succession, and long-term evolution. Better understanding the roles of compensated heat and waste heat in biological processes will provide novel insight into the underlying thermodynamic mechanisms involved in metabolism, ecology, and evolution.
35
Adetunla, Adedotun, Sunday Afolalu, Tien-Chien Jen, and Ayodele Ogundana. "The Roles of Surfactant in Tribology Applications of Recent Technology; an overview." E3S Web of Conferences 391 (2023): 01021. http://dx.doi.org/10.1051/e3sconf/202339101021.
Full textAbstract:
In managing friction, wear, and lubricant qualities such as emulsification, demulsification, bio resistance, oxidation resistance, rust prevention, and corrosion resistance, surfactants play a crucial role in tribology. This is an important topic for the development of new materials and gadgets, particularly those created at the Nano-scale. The tribological characteristics of cutting fluids, lubricant performance in relation to steel surfaces, bio lubricants, and novel materials and approaches to friction and wear reduction will all be covered in this most recent edition. Numerous industries place a high priority on surface science and tribology. Almost all consumer and industrial products are manufactured and used with the aid of sophisticated surface and tribological knowledge.Amphiphilic molecules are those that function as surface-active agents or surfactants. Their tails are hydrophobic while their heads are polar, or hydrophilic. They are dispersible in both water and organic solvents. This article introduces surfactants' nature and physical traits with a focus on their importance in modern science and technology. The primary property of surfactant molecules is the ability to self-assemble into micelles, which gives us a way to apply surfactants. The study of the surfactants results in a number of practical application areas, including food, health and personal care goods, biological systems, mineral and petroleum processing, and even nanotechnology. The organisms, food manufacturing, crop protection, personal care products, mineral and petroleum processing, and other practical application areas serve as examples of what these in turn give rise to a range of operational application domains.
36
Ya'ish, F., A. Waton, H. B'Durga, and A. Nanu. "OSTEOCUTANEOUS RADIAL FOREARM FREE FLAPS: PROPHYLACTIC FIXATION OF DONOR SITE USING LOCKING PLATE AUGMENTED WITH MINERAL CEMENT." Hand Surgery 16, no. 02 (January 2011): 215–22. http://dx.doi.org/10.1142/s0218810411005400.
Full textAbstract:
Prophylactic plating of donor site in osteocutaneous radial forearm free flaps have demonstrated improvement in fracture rates. Previous series used conventional plating systems which rely on plate-bone friction forces to generate stability and can result in iatrogenic fractures if not accurately contoured. Locking plates have superior stability and do not require contouring. This retrospective series reports our experience using locking plate fixation augmented with calcium phosphate mineral cement. Twenty patients' records were reviewed; 13 were alive and reviewed clinically. Mean radiological follow-up was 28.2 months. Two deceased patients had donor site fractures diagnosed on the first postoperative radiograph. These fractures were related to technical fixation errors and failure to apply correct locking fixation principles. None of the other patients with proper locking fixation had fractures or metalwork related complications. We believe that locking fixation augmented with mineral cement can provide more biological stability and enhance restoration of bone structural strength.
37
Sobamowo, M. G., A. T. Akinshilo, and A. A. Yinusa. "Thermo-Magneto-Solutal Squeezing Flow of Nanofluid between Two Parallel Disks Embedded in a Porous Medium: Effects of Nanoparticle Geometry, Slip and Temperature Jump Conditions." Modelling and Simulation in Engineering 2018 (June 3, 2018): 1–18. http://dx.doi.org/10.1155/2018/7364634.
Full textAbstract:
The various applications of squeezing flow between two parallel surfaces such as those that are evident in manufacturing industries, polymer processing, compression, power transmission, lubricating system, food processing, and cooling amongst others call for further study on the effects of various parameters on the flow phenomena. In the present study, effects of nanoparticle geometry, slip, and temperature jump conditions on thermo-magneto-solutal squeezing flow of nanofluid between two parallel disks embedded in a porous medium are investigated, analyzed, and discussed. Similarity variables are used to transform the developed governing systems of nonlinear partial differential equations to systems of nonlinear ordinary differential equations. Homotopy perturbation method is used to solve the systems of the nonlinear ordinary differential equations. In order to verify the accuracy of the developed analytical solutions, the results of the homotopy perturbation method are compared with the results of the numerical method using the shooting method coupled with the fourth-order Runge–Kutta, and good agreements are established. Through the approximate analytical solutions, parametric studies are carried out to investigate the effects of nanoparticle size and shape, Brownian motion parameter, nanoparticle parameter, thermophoresis parameter, Hartmann number, Lewis number and pressure gradient parameters, slip, and temperature jump boundary conditions on thermo-solutal and hydromagnetic behavior of the nanofluid. This study will enhance and advance the understanding of nanofluidics such as energy conservation, friction reduction, and micromixing of biological samples.
38
Usol’tseva, Nadezhda V., and Antonina I. Smirnova. "Liquid Crystals as Lubricants." Lubricants 7, no. 12 (December 9, 2019): 111. http://dx.doi.org/10.3390/lubricants7120111.
Full textAbstract:
The review summarizes the literature data and the authors’ own research results on the application of liquid crystals in tribology. It has been shown that both thermotropic (calamitic, discotic, cholesteric) and lyotropic (surfactants, chromonics) mesogens as tribological additives are able to optimize the properties of lubricating compositions when introduced even at low concentrations to oils and greases. A wide possibility of varying the chemical structure of mesogens and studying the relationship between their structure and tribological properties can be used for the desired (programmed) change of the quality of tribotechnical processes. The synergism of the combined use of mesogenic esters of cholesterol and carbon nanostructures as additives in improving tribological properties has been established. The use of synthetic lubricants in biological systems still requires further research as the experimental results obtained on models of joint prostheses in vitro conditions are significantly worse than the results obtained in vivo. Considering the annual loss of billions of US dollars worldwide due to the low efficiency of friction processes in the industry and the resulting wear, liquid crystals and the systems based on them can be the most effective way to optimize these processes. The present review will be useful for researchers and industrialists.
39
Roux, Benoît, Toby Allen, Simon Bernèche, and Wonpil Im. "Theoretical and computational models of biological ion channels." Quarterly Reviews of Biophysics 37, no. 1 (February 2004): 15–103. http://dx.doi.org/10.1017/s0033583504003968.
Full textAbstract:
1. Introduction 172. Dynamics of many-body systems 192.1 Effective dynamics of reduced systems 212.2 The constraint of thermodynamic equilibrium 242.3 Mean-field theories 253. Solvation free energy and electrostatics 273.1 Microscopic view of the Born model 273.2 Ion–Ion interactions in bulk solution 293.3 Continuum electrostatics and the PB equation 293.4 Limitations of continuum dielectric models 323.5 The dielectric barrier 333.6 The transmembrane potential and the PB-V equation 354. Statistical mechanical equilibrium theory 404.1 Multi-ion PMF 404.2 Equilibrium probabilities of occupancy 434.3 Coupling to the membrane potential 444.4 Ionic selectivity 484.5 Reduction to a one-dimensional (1D) free-energy profile 495. From MD toI–V: a practical guide 505.1 Extracting the essential ingredients from MD 515.1.1 Channel conductance from equilibrium and non-equilibrium MD 515.1.2 PMF techniques 525.1.3 Friction and diffusion coefficient techniques 535.1.4 About computational times 555.2 Ion permeation models 565.2.1 The 1D-NP electrodiffusion theory 565.2.2 Discrete-state Markov chains 575.2.3 The GCMC/BD algorithm 585.2.4 PNP electrodiffusion theory 626. Computational studies of ion channels 636.1 Computational studies of gA 656.1.1 Free-energy surface for K+ permeation 666.1.2 Mean-force decomposition 696.1.3 Cation-binding sites 696.1.4 Channel conductance 706.1.5 Selectivity 726.2 Computational studies of KcsA 726.2.1 Multi-ion free-energy surface and cation-binding sites 736.2.2 Channel conductance 746.2.3 Mechanism of ion conduction 776.2.4 Selectivity 786.3 Computational studies of OmpF 796.3.1 The need to compare the different level of approximations 796.3.2 Equilibrium protein fluctuations and ion distribution 806.3.3 Non-equilibrium ion fluxes 806.3.4 Reversal potential and selectivity 846.4 Successes and limitations 876.4.1 Channel structure 876.4.2 Ion-binding sites 876.4.3 Ion conduction 886.4.4 Ion selectivity 897. Conclusion 908. Acknowledgments 939. References 93The goal of this review is to establish a broad and rigorous theoretical framework to describe ion permeation through biological channels. This framework is developed in the context of atomic models on the basis of the statistical mechanical projection-operator formalism of Mori and Zwanzig. The review is divided into two main parts. The first part introduces the fundamental concepts needed to construct a hierarchy of dynamical models at different level of approximation. In particular, the potential of mean force (PMF) as a configuration-dependent free energy is introduced, and its significance concerning equilibrium and non-equilibrium phenomena is discussed. In addition, fundamental aspects of membrane electrostatics, with a particular emphasis on the influence of the transmembrane potential, as well as important computational techniques for extracting essential information from all-atom molecular dynamics (MD) simulations are described and discussed. The first part of the review provides a theoretical formalism to ‘translate’ the information from the atomic structure into the familiar language of phenomenological models of ion permeation. The second part is aimed at reviewing and contrasting results obtained in recent computational studies of three very different channels; the gramicidin A (gA) channel, which is a narrow one-ion pore (at moderate concentration), the KcsA channel from Streptomyces lividans, which is a narrow multi-ion pore, and the outer membrane matrix porin F (OmpF) from Escherichia coli, which is a trimer of three β-barrel subunits each forming wide aqueous multi-ion pores. Comparison with experiments demonstrates that current computational models are approaching semi-quantitative accuracy and are able to provide significant insight into the microscopic mechanisms of ion conduction and selectivity. We conclude that all-atom MD with explicit water molecules can represent important structural features of complex biological channels accurately, including such features as the location of ion-binding sites along the permeation pathway. We finally discuss the broader issue of the validity of ion permeation models and an outlook to the future.
40
Adetunla, Adedotun, Sunday Afolalu, Tien-Chien Jen, and Ayodele Ogundana. "The Roles of Surfactant in Tribology Applications of Recent Technology: An overview." E3S Web of Conferences 391 (2023): 01012. http://dx.doi.org/10.1051/e3sconf/202339101012.
Full textAbstract:
In managing friction, wear, and lubricant qualities such as emulsification, demulsification, bio resistance, oxidation resistance, rust prevention, and corrosion resistance, surfactants play a crucial role in tribology. This is an important topic for the development of new materials and gadgets, particularly those created at the Nano-scale. The tribological characteristics of cutting fluids, lubricant performance in relation to steel surfaces, bio lubricants, and novel materials and approaches to friction and wear reduction will all be covered in this most recent edition. Numerous industries place a high priority on surface science and tribology. Almost all consumer and industrial products are manufactured and used with the aid of sophisticated surface and tribological knowledge. Amphiphilic molecules are those that function as surface-active agents or surfactants. Their tails are hydrophobic while their heads are polar, or hydrophilic. They are dispersible in both water and organic solvents. This article introduces surfactants’ nature and physical traits with a focus on their importance in modern science and technology. The primary property of surfactant molecules is the ability to self-assemble into micelles, which gives us a way to apply surfactants. The study of the surfactants results in a number of practical application areas, including food, health and personal care goods, biological systems, mineral and petroleum processing, and even nanotechnology. The organisms, food manufacturing, crop protection, personal care products, mineral and petroleum processing, and other practical application areas serve as examples of what these in turn give rise to a range of operational application domains.
41
Li, Junfeng, Songyu Chen, and Minjie Sun. "Design and fabrication of a crawling robot based on a soft actuator." Smart Materials and Structures 30, no. 12 (November 9, 2021): 125018. http://dx.doi.org/10.1088/1361-665x/ac2e1b.
Full textAbstract:
Abstract Inspired by biological systems, soft crawling robots provide unique advantages in terms of resilience and adaptive shaping during robotic motion. However, soft robots actuated by motors and pumps are usually heavy, noisy and bulky. In this paper, based on the principle of liquid-vapor changes of ethanol, a novel soft crawling robot that demonstrates more silent actuation and lighter weight compared with other robots is proposed. To increase the crawling speed of the robot, silicone mixed with liquid metal with a volume ratio of 20% is used to fabricate the actuators. The deformation of the actuator is analyzed and can be predicted using a theoretical model. To obtain effective crawling performance, a crawling locomotion sequence consisting of the three different parts (central, head and tail) based on the variable friction mechanism of actuators B and C is presented. The experimental results demonstrate that the robot can achieve forward movement on a horizontal surface and along vertical pipes and sticks. This study will provide further inspiration and guidance for the future development of crawling robots.
42
Røn, Troels, Irakli Javakhishvili, Søren Hvilsted, Katja Jankova, and Seunghwan Lee. "Self-restoring polymer brushes under tribological stress and the biomedical applications." MRS Advances 1, no. 27 (2016): 1971–76. http://dx.doi.org/10.1557/adv.2016.345.
Full textAbstract:
ABSTRACTFor biological and mechanical systems involving moving parts, surface slipperiness is often a critical attribute for their optimal functions. Surface grafting with hydrophilic polymers is a powerful means to render materials slippery in aqueous environment. In “inverted grafting-to approach”, the hydrophilic polymer chains of amphiphilic diblock copolymers dispersed within a poly(dimethylsiloxane) (PDMS) network are selectively segregated upon exposure to aqueous solution. This allows formation of extremely stable brush-like polymer layers. Tribological application of inverted grafting-to approach was successfully demonstrated with PDMS-block-poly(acrylic acid) (PDMS-b-PAA) dispersed within thin PDMS films on PDMS blocks by showing friction coefficients (µ) of ca 10-2 to 10-3, depending on the load, pH and buffer salinity in the absence of other external re-supply of PAA chains. Further manipulations of the thin PDMS film incorporating PDMS-b-PAA to optimize the tribological properties are presented. Lastly, first trials to employ PAA-grafted PDMS surface to generate in-vitro mucosae model are also presented and discussed.
43
Данилова, Д. В., О. Г. Зиновенко, Н. В. Новак, О. В. Федоринчик, and Н. В. Цикра. "Features of Mechanical Treatment of Root Canals with Rotating Tool Systems S-Profile." Стоматология. Эстетика. Инновации, no. 4 (December 20, 2021): 421–38. http://dx.doi.org/10.34883/pi.2021.5.4.009.
Full textAbstract:
Обзорная статья посвящена проблеме выбора оптимальных вращающихся инструментов для механической обработки корневых каналов. В статье описаны представители файлов с s-образным поперечным сечением. Такой дизайн рабочей части обеспечивает инструментам хорошую режущую эффективность, уменьшенную силу трения, способность выводить дентинные опилки в апикальном направлении. Однако системы файлов с s-образным поперечным сечением, выпущенные разными производителями, существенно отличаются друг от друга. Для более ранних версий вращающихся инструментов s-стиля характерны линейки, состоящие из 4–5 инструментов, что обуславливает многоступенчатый подход к обработке корневых каналов. Современные вращающиеся инструменты, базовые комплекты которых состоят в среднем из 3 файлов, позволяют производить манипуляции 2–3 инструментами. Кроме того, улучшенные механические свойства благодаря специальной термической обработке никельтитанового сплава позволяют применять данные файлы многократно, а также в каналах со сложной анатомией. Преобладающая 04-конусность данных инструментов соответствует принципам рационального препарирования корневого канала и биологической целесообразности. The review article is devoted to the problem of choosing the optimal rotating instruments for mechanical processing of root canals. The article describes representatives of files with an s-shaped cross-section. This design of the working part provides the instruments with good cutting efficiency, reduced friction force, and the ability to remove dentin chips in the apical direction. However, s-shaped file systems from different manufacturers differ significantly from each other. Earlier versions of the s-style rotary instruments feature a ruler of 4 to 5 instruments, resulting in a multi- step approach to root canal treatment. Modern rotating instruments, the basic sets of which consist, on average, of 3 files, allow manipulation of 2–3 instruments. In addition, the improved mechanicalproperties, due to the special heat treatment of the nickel-titanium alloy, make it possible to use these files multiple times, as well as in canals with complex anatomy. The predominant 04 taper of these instruments corresponds to the principles of rational root canal preparation and biological expediency.
44
Gilley, James R. "Discussion of “ Friction Correction Factor for Center‐Pivot Irrigation Systems ” by J. Mohan Reddy and Horacio Apolayo (February, 1988, Vol. 114, No. 1)." Journal of Irrigation and Drainage Engineering 115, no. 4 (August 1989): 769–70. http://dx.doi.org/10.1061/(asce)0733-9437(1989)115:4(769).
Full text
45
Akulenko, L., N. Bolotnik, D. Leshchenko, and E. Palii. "ON INERTIAL MOTION OF AN ABSOLUTELY RIGID BODY ON A THREE-DEGREE SUSPENSION WITH LINKS OF FINITE LENGTH." Mechanics And Mathematical Methods 2, no. 2 (December 2020): 6–17. http://dx.doi.org/10.31650/2618-0650-2020-2-2-6-17.
Full textAbstract:
Papers on the dynamics of an absolutely rigid body with a fixed point generally assume that the mechanical system has three degrees of freedom. This is the situation when the body is attached to a fixed base by a ball-and-socket joint. On engineering systems one often encounters rigid bodies attached to a base by a two-degrees-of-freedom joint, consisting of a fixed axis and a movable one, which are mutually perpendicular. Such systems have two degrees of freedom, but the set of kinematically possible motions is quite rich. Dynamic analysis of the motion of a rigid body with a two-degree hinge in a force field is an integral part of the description of the action of mechanical actions of robotic systems. In recent decades, an increasingly closed role in the dynamics of rigid body systems has been played by manipulation robots consisting of a sequential chain of rigid links and controlled by means of torque drives in articulated joints. The same class of objects can be attributed to many biological systems that imitate, for example, the movements of a person or animal (walking, running, jumping). Two-link systems have a variety of practical applications and an almost equally wide range of areas of theoretical research. We note, in particular, the analysis of free and forced plane-parallel motion of a bundle of two rigid bodies connected by an ideal cylindrical hinge and simulating a composite satellite in outer space, a two-link manipulator, and an element of a crushing machine. The dynamic behavior of a rigid body in the gimbal suspension is a system, which can be interpreted as two-degree manipulator and used an element of more complex robotic structures. The linear mathematical model of two-link manipulator free oscillations with viscous friction in both its joints is a system, which reduces to the calculation scheme of double pendulum and allows the construction of exact analytical solution in the partial case. According to the research methodology, the proposed paper is close to works, where the motion by inertia of a plane two–rigid body hinged system was studied and devoted to the study of the motion of an absolutely rigid body on a power-to-power joint.
46
Jakeer, Shaik, Sathishkumar Veerappampalayam Easwaramoorthy, Seethi Reddy Reddisekhar Reddy, and Hayath Thameem Basha. "Numerical and Machine Learning Approach for Fe3O4-Au/Blood Hybrid Nanofluid Flow in a Melting/Non-Melting Heat Transfer Surface with Entropy Generation." Symmetry 15, no. 8 (July 28, 2023): 1503. http://dx.doi.org/10.3390/sym15081503.
Full textAbstract:
The physiological system loses thermal energy to nearby cells via the bloodstream. Such energy loss can result in sudden death, severe hypothermia, anemia, high or low blood pressure, and heart surgery. Gold and iron oxide nanoparticles are significant in cancer treatment. Thus, there is a growing interest among biomedical engineers and clinicians in the study of entropy production as a means of quantifying energy dissipation in biological systems. The present study provides a novel implementation of an intelligent numerical computing solver based on an MLP feed-forward backpropagation ANN with the Levenberg–Marquard algorithm to interpret the Cattaneo–Christov heat flux model and demonstrate the effect of entropy production and melting heat transfer on the ferrohydrodynamic flow of the Fe3O4-Au/blood Powell–Eyring hybrid nanofluid. Similarity transformation studies symmetry and simplifies PDEs to ODEs. The MATLAB program bvp4c is used to solve the nonlinear coupled ordinary differential equations. Graphs illustrate the impact of a wide range of physical factors on variables, including velocity, temperature, entropy generation, local skin friction coefficient, and heat transfer rate. The artificial neural network model engages in a process of data selection, network construction, training, and evaluation through the use of mean square error. The ferromagnetic parameter, porosity parameter, distance from origin to magnetic dipole, inertia coefficient, dimensionless Curie temperature ratio, fluid parameters, Eckert number, thermal radiation, heat source, thermal relaxation parameter, and latent heat of the fluid parameter are taken as input data, and the skin friction coefficient and heat transfer rate are taken as output data. A total of sixty data collections were used for the purpose of testing, certifying, and training the ANN model. From the results, it is found that the fluid temperature declines when the thermal relaxation parameter is improved. The latent heat of the fluid parameter impacts the entropy generation and Bejan number. There is a less significant impact on the heat transfer rate of the hybrid nanofluid over the sheet on the melting heat transfer parameter.
47
Nikiforova, N. S., and A. V. Konnov. "PILES BEARING CAPACITY IN PERMAFROST SOILS UNDER CLIMATE CHANGE." Construction and Geotechnics 12, no. 3 (December 15, 2021): 14–24. http://dx.doi.org/10.15593/2224-9826/2021.3.02.
Full textAbstract:
The one of the main natural systems in the Russian Federation that are exposed to global warming is the permafrost zone. The temperature of permafrost soils changes, the seasonal thaw zone increases, the process of permafrost degradation is started, influencing the strength characteristics of the soils. The study was aimed to assess the climate change in terms of the impact on the bearing capacity of the soil base under buildings and structures built in the 1960s and 1980s on the Principle I (maintaining the permafrost state of the soil). On the basis of published archival and forecast data on the increase rate in the active layer thickness and the rising temperature trends of permafrost soils for seven geographical regions of Russia (North of the European part, North of Western Siberia, Middle Siberia, Yakutia, Southern Siberia, Baikal region and North-East of Russia) a reduction in the bearing capacity of the standard reinforced concrete pile (35´35 cm section, 10 m long) was determined. The study revealed that for now in most regions the reduction in the bearing capacity of the pile is on average level (10-20 %). However a high (>30 %) decrease is expected by 2050. The temperature distribution in the soil mass was modelled in the Frost 3D program for the conditions of Norilsk, considering the thermal influence of the building. Numerical modelling was performed for a period of time until the middle of the XXI century. In the base of a building the resulting significant settlement of the thawing soil under its own weight can lead to the occurrence of negative friction forces. This effect must be taken into account when calculating pile foundations.
48
Bérut, Antoine, Hugo Chauvet, Valérie Legué, Bruno Moulia, Olivier Pouliquen, and Yoël Forterre. "Gravisensors in plant cells behave like an active granular liquid." Proceedings of the National Academy of Sciences 115, no. 20 (April 30, 2018): 5123–28. http://dx.doi.org/10.1073/pnas.1801895115.
Full textAbstract:
Plants are able to sense and respond to minute tilt from the vertical direction of the gravity, which is key to maintain their upright posture during development. However, gravisensing in plants relies on a peculiar sensor made of microsize starch-filled grains (statoliths) that sediment and form tiny granular piles at the bottom of the cell. How such a sensor can detect inclination is unclear, as granular materials like sand are known to display flow threshold and finite avalanche angle due to friction and interparticle jamming. Here, we address this issue by combining direct visualization of statolith avalanches in plant cells and experiments in biomimetic cells made of microfluidic cavities filled with a suspension of heavy Brownian particles. We show that, despite their granular nature, statoliths move and respond to the weakest angle, as a liquid clinometer would do. Comparison between the biological and biomimetic systems reveals that this liquid-like behavior comes from the cell activity, which agitates statoliths with an apparent temperature one order of magnitude larger than actual temperature. Our results shed light on the key role of active fluctuations of statoliths for explaining the remarkable sensitivity of plants to inclination. Our study also provides support to a recent scenario of gravity perception in plants, by bridging the active granular rheology of statoliths at the microscopic level to the macroscopic gravitropic response of the plant.
49
Macias-Fauria, Marc, Paul Jepson, Nikita Zimov, and Yadvinder Malhi. "Pleistocene Arctic megafaunal ecological engineering as a natural climate solution?" Philosophical Transactions of the Royal Society B: Biological Sciences 375, no. 1794 (January 27, 2020): 20190122. http://dx.doi.org/10.1098/rstb.2019.0122.
Full textAbstract:
Natural climate solutions (NCS) in the Arctic hold the potential to be implemented at a scale able to substantially affect the global climate. The strong feedbacks between carbon-rich permafrost, climate and herbivory suggest an NCS consisting of reverting the current wet/moist moss and shrub-dominated tundra and the sparse forest–tundra ecotone to grassland through a guild of large herbivores. Grassland-dominated systems might delay permafrost thaw and reduce carbon emissions—especially in Yedoma regions, while increasing carbon capture through increased productivity and grass and forb deep root systems. Here we review the environmental context of megafaunal ecological engineering in the Arctic; explore the mechanisms through which it can help mitigate climate change; and estimate its potential—based on bison and horse, with the aim of evaluating the feasibility of generating an ecosystem shift that is economically viable in terms of carbon benefits and of sufficient scale to play a significant role in global climate change mitigation. Assuming a megafaunal-driven ecosystem shift we find support for a megafauna-based arctic NCS yielding substantial income in carbon markets. However, scaling up such projects to have a significant effect on the global climate is challenging given the large number of animals required over a short period of time. A first-cut business plan is presented based on practical information—costs and infrastructure—from Pleistocene Park (northeastern Yakutia, Russia). A 10 yr experimental phase incorporating three separate introductions of herds of approximately 1000 individuals each is costed at US$114 million, with potential returns of approximately 0.3–0.4% yr −1 towards the end of the period, and greater than 1% yr −1 after it. Institutional friction and the potential role of new technologies in the reintroductions are discussed. This article is part of the theme issue ‘Climate change and ecosystems: threats, opportunities and solutions'.
50
Zafar, S. S., Ayman Alfaleh, A. Zaib, Farhan Ali, M. Faizan, Ahmed M. Abed, Samia Elattar, and M. Ijaz Khan. "Simulation of Prandtl Nanofluid in the Mixed Convective Flow of Activation Energy with Gyrotactic Microorganisms: Numerical Outlook Features of Micro-Machines." Micromachines 14, no. 3 (February 27, 2023): 559. http://dx.doi.org/10.3390/mi14030559.
Full textAbstract:
The physiological systems and biological applications that have arisen during the past 15 years depend heavily on the microscale and nanoscale fluxes. Microchannels have been utilized to develop new diagnostic assays, examine cell adhesion and molecular transport, and replicate the fluid flow microenvironment of the circulatory system. The various uses of MHD boundary flow in engineering and technology are extensive, ranging from MHD power generators and the polymer industry to MHD flow meters and pumps and the spinning of filaments. In this investigation, the (Magnetohydrodynamic) MHD flow of Prandtl nanofluid is investigated along with mixed convection, energy activation, microorganism, and chemical reaction. The flow model is considered through partial differential equations in dimensionless form which is then integrated numerically via considering the Bvp4c technique. The outcome is numerous emerging physical parameters over velocity profile, temperature, mass concentration, and microorganism with the separate pertinent quantities such as the Prandtl fluid parameter, elastic fluid parameter, magnetic field, mixed convection parameter, activation energy, chemical reaction, Brownian motion, thermophoretic force, Prandtl number, and Schmidt number. The friction factor, rate of heat transfer and Sherwood number, and density of microbes are revealed numerically and graphically. The outcomes indicate that the Prandtl fluid parameter and elastic fluid parameter tend to enhance the velocity profile. It is also noted that the Prandtl fluid parameter depreciates the thermal rate with the addition of the concentration profile while the opposite trend is recorded for activation energy. Obtained numerical outcomes are correspondingly compared with the current statistics in limiting cases and a close match is obtained.