Numerical analyses
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Developments in environmental modelling ; vol. 20
2nd english ed. xv, 853 s.
- Klíčová slova
- FE Analýza,
- MeSH
- anatomické modely MeSH
- biometrie metody přístrojové vybavení MeSH
- lidé MeSH
- nestabilita kloubu MeSH
- pohyb MeSH
- prospektivní studie MeSH
- protézy kloubů MeSH
- rozsah kloubních pohybů MeSH
- temporomandibulární kloub * anatomie a histologie fyziologie růst a vývoj MeSH
- Check Tag
- lidé MeSH
- Publikační typ
- práce podpořená grantem MeSH
The optimal light dose, heat generation, consequent heat spread and an accurate thermal damage model, are key components of effective laser therapies. Recent advances in nanotechnology offer numerous possibilities on how to increase the efficacy of hyperthermia for tumour treatments. Gold nanoparticles are a promising candidate towards the achievement of this goal owing to their properties for efficiently converting light to heat. In this review, we summarise the numerical tools that are available for theoretical studies of gold-nanoparticle-mediated photo-thermal therapy. The processes that occur in the treatments based on light propagation inside biological tissues and the subsequent temperature distributions are considered first, followed by evaluation of the thermal damage. The fundamental ideas underlying the presented methods are described in addition to their applications in photo-thermal therapy and its effects. The descriptions of extensively used tools for the characterisation of nanoparticles across multiple research fields are also presented for estimating the electromagnetic properties of gold nanoparticles (e.g. discrete dipole approximations, finite-difference time-domain simulations), the Monte Carlo model of light propagation in biological tissues, and the Pennes' bio-heat equation. In addition, the Arrhenius damage evaluation and the cumulative effective minutes normalisation methods are described. Finally, recent in vivo and in vitro results from the rapidly growing field of nanomedicine are presented.
Several constitutive models have been proposed for the description of mechanical behaviour of soft tissues containing collagen fibres. Some of the commonly used approaches accounting for the dispersion of fibre orientations are based on the summation of (mechanical) contributions of differently oriented fibre families. This leads to the need of numerical integration on the sphere surface, and the related numerical consumption is the main disadvantage of this category of constitutive models. The paper is focused on the comparison of various numerical integration methods applied to a specific constitutive model applicable for arterial walls. Robustness and efficiency of several integration rules were tested with respect to application in finite element (FE) codes. Among all the analysed numerical integration rules, the best results were reached by Lebedev quadrature; the related parameters for the specific constitutive model are presented in the paper. The results were implemented into the commercial FE code ANSYS via user subroutines, and their applicability was demonstrated by an example of FE simulation with non-homogenous stress field.
Considering the fact that hemodynamics plays an important role in the patency and overall performance of implanted bypass grafts, this work presents a numerical investigation of pulsatile non-Newtonian blood flow in three different patient-specific aorto-coronary bypasses. The three bypass models are distinguished from each other by the number of distal side-to-side and end-to-side anastomoses and denoted as single, double and triple bypasses. The mathematical model in the form of time-dependent nonlinear system of incompressible Navier-Stokes equations is coupled with the Carreau-Yasuda model describing the shear-thinning property of human blood and numerically solved using the principle of the SIMPLE algorithm and cell-centred finite volume method formulated for hybrid unstructured tetrahedral grids. The numerical results computed for non-Newtonian and Newtonian blood flow in the three aorto-coronary bypasses are compared and analysed with emphasis placed on the distribution of cycle-averaged wall shear stress and oscillatory shear index. As shown in this study, the non-Newtonian blood flow in all of the considered bypass models does not significantly differ from the Newtonian one. Our observations further suggest that, especially in the case of sequential grafts, the resulting flow field and shear stimulation are strongly influenced by the diameter of the vessels involved in the bypassing.
Cílem studie je ukázat, že nově vyvinutá metoda automatické analýzy EEG dokáže rozpoznat abnormální fenomény novorozeneckého EEG a je schopna závažnost odchylky zhodnotit kvantitativně. Analyzovány byly digitální EEG záznamy 36 novorozenců, u nichž bylo EEG vyšetření indikováno z klinických důvodů. Pětiminutové vzorky EEG aktivity ze standardizovaného behaviorálního stavu byly za použití počítačem podporované čtyřstupňové analýzy popsány 312 číselnými položkami, informujícími o amplitudě, výkonu v pěti frekvenčních pásmech, o tvaru signálu a o jeho stálosti či proměnlivosti. Každá z těchto položek byla automaticky porovnána s normativním údajem, získaným vyšetřením 21 zdravých donosených novorozenců, a testována, liší-li se od normy o jednu či o dvě směrodatné odchylky. Počet pacientových položek lišících se od normy byl úměrný závažnosti jeho abnormality. Orientační porovnání výsledků automatické a vizuální analýzy pacientských elektroencefalogramů osvědčilo dobrou shodu. Metoda je příslibem pro klinickou praxi, neboť může významně přispět jak ke zrychlení, tak i k objektivizaci hodnocení novorozeneckého EEG.
The study aims to demonstrate that the newly developed method of automated EEG analysis can detect abnormal phenomena in the neonatal EEG and can quantify the severity of the deviation from the norm. EEG records from 36 neonates with clinically indicated EEG examination were analyzed. Five-minutes samples of EEG activity during a standardized behavioral state were processed using a computer-supported four-stage analysis and described with 312 numerical items, providing the information on amplitude, power in five frequency bands, on signal shape and its stability or variability. Each of these items was automatically compared to normative data acquired from the examination of 21 healthy, full term neonates and tested whether it differs by one or two standard deviations from the norm. The number of patient's items differing from the norm was proportional to the severity of their abnormality. A cursory comparison of the results of automatic and visual analyses of patienť EEG records showed good agreement. The method shows promise for the clinical practice, where it can significantly contribute to both acceleration and greater objectivity of neonatal EEG assessment.
Turing's diffusion-driven instability for the standard two species reaction-diffusion system is only achievable under well-known and rather restrictive conditions on both the diffusion rates and the kinetic parameters, which necessitates the pairing of a self-activator with a self-inhibitor. In this study we generalize the standard two-species model by considering the case where the reactants can bind to an immobile substrate, for instance extra-cellular matrix, and investigate the influence of this dynamics on Turing's diffusion-driven instability. Such systems have been previously studied on the grounds that binding of the self-activator to a substrate may effectively reduce its diffusion rate and thus induce a Turing instability for species with equal diffusion coefficients, as originally demonstrated by Lengyel and Epstein (1992) under the assumption that the bound state dynamics occurs on a fast timescale. We, however, analyse the full system without any separation of timescales and demonstrate that the full system also allows a relaxation of the standard constraints on the reaction kinetics for the Turing instability, increasing the type of interactions that could give rise to spatial patterning. In particular, we show that two self-activators can undertake a diffusively driven instability in the presence of a binding immobile substrate, highlighting that the interactions required of a putative biological Turing instability need not be associated with a self-activator-self-inhibitor morphogen pair.
The aim of this article is 3D analysis of the temporomandibular joint (TMJ) patient, who underwent surgery, during which the right TMJ was resected along with the ramus of mandible and consequently the joint was reconstructed with subtotal replacement. The main goal is to give a suitable formulation of mathematical model, which describes the changes of stresses in TMJ incurred after the surgery. The TMJ is a complex, sensitive and highly mobile joint which works bilaterally so each side influences the contralateral joint and because of this the distribution of the stresses is changed in the healthy joint as well. Detailed knowledge about function these are necessary for clinical application of temporomandibular joint prosthesis and also help us estimate the lifetime of the prosthesis a possibilities of alteration in the contra lateral joint components. The geometry for the 3D models is taken from the CT scan date and its numerical solution is based on the theory of semi-coercive unilateral contact problems in linear elasticity. This article provides medical part with case report, discretion of treatment, than the methods of mathematical modeling and his possibilities are described and finally results are reported.
- MeSH
- analýza metodou konečných prvků MeSH
- anatomické modely MeSH
- biomechanika MeSH
- cysty čelistí patologie radiografie chirurgie MeSH
- lidé MeSH
- mandibula - protézy MeSH
- nemoci temporomandibulárního kloubu patologie radiografie chirurgie MeSH
- počítačová rentgenová tomografie statistika a číselné údaje MeSH
- počítačová simulace MeSH
- senioři MeSH
- temporomandibulární kloub fyziologie patofyziologie chirurgie MeSH
- zobrazování trojrozměrné metody MeSH
- Check Tag
- lidé MeSH
- senioři MeSH
- ženské pohlaví MeSH
- Publikační typ
- časopisecké články MeSH
- kazuistiky MeSH
- práce podpořená grantem MeSH
Motivation: The NCBI database contains mitochondrial DNA (mtDNA) genomes from numerous species. We investigated the presence and locations of inverted repeat sequences (IRs) in these mtDNA sequences, which are known to be important for regulating nuclear genomes. Results: IRs were identified in mtDNA in all species. IR lengths and frequencies correlate with evolutionary age and the greatest variability was detected in subgroups of plants and fungi and the lowest variability in mammals. IR presence is non-random and evolutionary favoured. The frequency of IRs generally decreased with IR length, but not for IRs 24 or 30 bp long, which are 1.5 times more abundant. IRs are enriched in sequences from the replication origin, followed by D-loop, stem-loop and miscellaneous sequences, pointing to the importance of IRs in regulatory regions of mitochondrial DNA. Availability and implementation: Data were produced using Palindrome analyser, freely available on the web at http://bioinformatics.ibp.cz. Contact: vaclav@ibp.cz. Supplementary information: Supplementary data are available at Bioinformatics online.
Acute excessive ethyl alcohol (ethanol) consumption alters cardiac electrophysiology and can evoke cardiac arrhythmias, e.g., in 'holiday heart syndrome'. Ethanol acutely modulates numerous targets in cardiomyocytes, including ion channels, Ca2+-handling proteins and gap junctions. However, the mechanisms underlying ethanol-induced arrhythmogenesis remain incompletely understood and difficult to study experimentally due to the multiple electrophysiological targets involved and their potential interactions with preexisting electrophysiological or structural substrates. Here, we employed cellular- and tissue-level in-silico analyses to characterize the acute effects of ethanol on cardiac electrophysiology and arrhythmogenesis. Acute electrophysiological effects of ethanol were incorporated into human atrial and ventricular cardiomyocyte computer models: reduced INa, ICa,L, Ito, IKr and IKur, dual effects on IK1 and IK,ACh (inhibition at low and augmentation at high concentrations), and increased INCX and SR Ca2+ leak. Multiscale simulations in the absence or presence of preexistent atrial fibrillation or heart-failure-related remodeling demonstrated that low ethanol concentrations prolonged atrial action-potential duration (APD) without effects on ventricular APD. Conversely, high ethanol concentrations abbreviated atrial APD and prolonged ventricular APD. High ethanol concentrations promoted reentry in tissue simulations, but the extent of reentry promotion was dependent on the presence of altered intercellular coupling, and the degree, type, and pattern of fibrosis. Taken together, these data provide novel mechanistic insight into the potential proarrhythmic interactions between a preexisting substrate and acute changes in cardiac electrophysiology. In particular, acute ethanol exposure has concentration-dependent electrophysiological effects that differ between atria and ventricles, and between healthy and diseased hearts. Low concentrations of ethanol can have anti-fibrillatory effects in atria, whereas high concentrations promote the inducibility and maintenance of reentrant atrial and ventricular arrhythmias, supporting a role for limiting alcohol intake as part of cardiac arrhythmia management.
- MeSH
- akční potenciály účinky léků MeSH
- elektrofyziologické jevy účinky léků MeSH
- ethanol škodlivé účinky MeSH
- fibróza MeSH
- iontové kanály metabolismus MeSH
- kardiomyocyty účinky léků metabolismus MeSH
- lidé MeSH
- mezerový spoj účinky léků metabolismus MeSH
- počítačová simulace MeSH
- remodelace cév účinky léků MeSH
- srdce účinky léků patofyziologie MeSH
- srdeční arytmie patologie patofyziologie MeSH
- srdeční síně účinky léků patologie patofyziologie MeSH
- Check Tag
- lidé MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
- Research Support, N.I.H., Extramural MeSH
