Iskanje po katalogu digitalne knjižnice

Opis: This article proposes a methodology for the design of double-sided coreless axial flux permanent magnet synchronous machines, which is based on a developed model for calculating the axial component of the magnetic flux density in the middle of the distance between opposite permanent magnets, which also represents the middle of the stator. Values for different geometric parameters represent the input data for the mathematical model in explicit form. The input data are calculated by using a simplified finite element method (FEM), which means that calculations of simplified 3D models are performed. The simplified model consists of two rotor disks with surfacemounted permanent magnets and air between them, instead of stator windings. Such a simplification is possible due to similar values of permeability of the air and copper. For each simplified model of the machine the axial component of the magnetic flux density is analyzed along a line passing through the center of opposite permanent magnets and both rotor disks. Values at the middle of the distance between the opposite permanent magnets are the lowest and are therefore selected for the input data at different stator, rotor disks and permanent magnets (PM) thicknesses. Such input data enable the model to consider the nonlinearity of materials.
Ključne besede: axial flux, analysis, coreless, development, design, explicit form, finite element method, mathematical models, permanent magnet, synchronous
Objavljeno v DKUM: 01.12.2023; Ogledov: 498; Prenosov: 15
Celotno besedilo (2,70 MB)
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Opis: High molecular weight chitosan (HMWCh), quaternised cellulose nanofibrils (qCNF), and their mixture showed antiviral potential in liquid phase, while this effect decreased when applied to facial masks, as studied in our recent work. To gain more insight into material antiviral activity, spin-coated thin films were prepared from each suspension (HMWCh, qCNF) and their mixture with a 1:1 ratio. To understand their mechanism of action, the interactions between these model films with various polar and nonpolar liquids and bacteriophage phi6 (in liquid phase) as a viral surrogate were studied. Surface free energy (SFE) estimates were used as a tool to evaluate the potential adhesion of different polar liquid phases to these films by contact angle measurements (CA) using the sessile drop method. The Fowkes, Owens–Wendt–Rabel–Kealble (OWRK), Wu, and van Oss–Chaudhury–Good (vOGC) mathematical models were used to estimate surface free energy and its polar and dispersive contributions, as well as the Lewis acid and Lewis base contributions. In addition, the surface tension SFT of liquids was also determined. The adhesion and cohesion forces in wetting processes were also observed. The estimated SFE of spin-coated films varied between mathematical models (26–31 mJ/m2) depending on the polarity of the solvents tested, but the correlation between models clearly indicated a significant dominance of the dispersion components that hinder wettability. The poor wettability was also supported by the fact that the cohesive forces in the liquid phase were stronger than the adhesion to the contact surface. In addition, the dispersive (hydrophobic) component dominated in the phi6 dispersion, and since this was also the case in the spin-coated films, it can be assumed that weak physical van der Waals forces (dispersion forces) and hydrophobic interactions occurred between phi6 and the polysaccharide films, resulting in the virus not being in sufficient contact with the tested material during antiviral testing of the material to be inactivated by the active coatings of the polysaccharides used. Regarding the contact killing mechanism, this is a disadvantage that can be overcome by changing the previous material surface (activation). In this way, HMWCh, qCNF, and their mixture can attach to the material surface with better adhesion, thickness, and different shape and orientation, resulting in a more dominant polar fraction of SFE and thus enabling the interactions within the polar part of phi6 dispersion.
Ključne besede: films, surface free energy, SFE mathematical models, phi6, wettability, spreading, interactions
Objavljeno v DKUM: 21.04.2023; Ogledov: 555; Prenosov: 34
Celotno besedilo (3,21 MB)

Opis: Calcium oscillations play an important role in intracellular signal transduction. As a second messenger, ▫$Ca^{2+}$▫ represents a link between several input signals and several target processes in the cell. Whereas the frequency of simple ▫$Ca^{2+}$▫ oscillations enables a selective activation of a specific protein and herewith a particular process, the question arises of how at the same time two or more classes of proteins can be specifically regulated. The question is general and concerns the problem of how one second messenger can transmit more than one signal simultaneously (bow-tie structure of signalling). To investigate whether a complex ▫$Ca^{2+}$▫ signal like bursting, a succession of low-peak and high-peak oscillatory phases, could selectively activate different proteins, several bursting patterns with simplified square pulses were applied in a theoretical model. The results indicate that bursting ▫$Ca^{2+}$▫ oscillations allow a differential regulation of two different calcium-binding proteins, and hence, perform the desired function.
Ključne besede: biophysics, calcium oscillations, cellular dynamics, mathematical models, signalling, bow-tie structures, bursting, decoding
Objavljeno v DKUM: 07.06.2012; Ogledov: 2022; Prenosov: 39
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Opis: We study the impact of stochastic payoff variations with different distributions on the evolution of cooperation in the spatial prisoner's dilemma game. We find that Gaussian-distributed payoff variations are most successful in promoting cooperation irrespective of the temptation to defect. In particular, the facilitative effect of noise on the evolution of cooperation decreases steadily as the frequency of rare events increases. Findings are explained via an analysis of local payoff ranking violations. The relevance of results for economics and sociology is discussed.
Ključne besede: stochastic systems, spatial resonance, stochastic payoff variations, nonlinear systems, noise, spatial dynamics, mathematical models, prisoner's dilemma
Objavljeno v DKUM: 07.06.2012; Ogledov: 2122; Prenosov: 108
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Opis: In airway smooth muscles, kinase/phosphatase-dependent phosphorylation and dephosphorylation of the myosin light chain (MLC) have been revealed by many authors as important steps in calcium ▫$(Ca^{2+})$▫ signalling pathway from the variation of ▫$Ca^{2+}$▫ concentration in cytosol to the force development. Here, a theoretical analysis of the control action of MLC-kinase (MLCK) and MLC-phosphatase (MLCP) in ▫$Ca^{2+}$▫ signalling is presented and related to the general control principles of these enzymes, which were previously studied by Reinhart Heinrich and his co-workers. The kinetic scheme of the mathematical model considers interactions among ▫$Ca^{2+}$▫, calmodulin (CaM) and MLCK and the well-known 4-state actomyosin latch bridge model, whereby a link between them is accomplished by the conservation relation of all species of MLCK. The mathematical model predicts the magnitude and velocity of isometric force in smooth muscles upon transient biphasic ▫$Ca^{2+}$▫ signal. The properties of signal transduction in the system such as the signalling time, signal duration and signal amplitude, which are reflected in the properties of force developed, are studied by the principles of the metabolic control theory. The analysis of our model predictions confirms as shown by Reinhart Heinrich and his co-workers that MLCK controls the amplitude of signal more than its duration, whereas MLCP controls both. Finally, the simulations of elevated total content of MLCK, a typical feature of bronchial muscles of asthmatic subjects and spontaneously hypertensive rats as well as potentiation of MLCP catalytic activity, are carried out and are discussed in view of an increase in the force magnitude.
Ključne besede: cells, calcium, calcium oscillations, myosin light chains, enzyme activities, mathematical models
Objavljeno v DKUM: 07.06.2012; Ogledov: 2348; Prenosov: 33
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