Numerical results
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In this article, the results of numerical simulations using computational fluid dynamics (CFD) and a comparison with experiments performed with phase Doppler anemometry are presented. The simulations and experiments were conducted in a realistic model of the human airways, which comprised the throat, trachea and tracheobronchial tree up to the fourth generation. A full inspiration/expiration breathing cycle was used with tidal volumes 0.5 and 1 L, which correspond to a sedentary regime and deep breath, respectively. The length of the entire breathing cycle was 4 s, with inspiration and expiration each lasting 2 s. As a boundary condition for the CFD simulations, experimentally obtained flow rate distribution in 10 terminal airways was used with zero pressure resistance at the throat inlet. CCM+ CFD code (Adapco) was used with an SST k-ω low-Reynolds Number RANS model. The total number of polyhedral control volumes was 2.6 million with a time step of 0.001 s. Comparisons were made at several points in eight cross sections selected according to experiments in the trachea and the left and right bronchi. The results agree well with experiments involving the oscillation (temporal relocation) of flow structures in the majority of the cross sections and individual local positions. Velocity field simulation in several cross sections shows a very unstable flow field, which originates in the tracheal laryngeal jet and propagates far downstream with the formation of separation zones in both left and right airways. The RANS simulation agrees with the experiments in almost all the cross sections and shows unstable local flow structures and a quantitatively acceptable solution for the time-averaged flow field.
- MeSH
- biologické modely * MeSH
- biomechanika MeSH
- bronchy fyziologie MeSH
- časové faktory MeSH
- dýchání * MeSH
- lidé MeSH
- numerická analýza pomocí počítače * MeSH
- plicní ventilace fyziologie MeSH
- trachea fyziologie MeSH
- Check Tag
- lidé MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
- srovnávací studie MeSH
This work is focused on investigation of applicability of two widely used model equations for description of nonlinear standing waves in constant-cross-sectioned resonators. The investigation is based on the comparison of numerical solutions of these model equations with solutions of more accurate model equations whose validity has been verified experimentally in a number of published papers.
- MeSH
- akustika * MeSH
- časové faktory MeSH
- nelineární dynamika * MeSH
- numerická analýza pomocí počítače MeSH
- počítačová simulace MeSH
- pohyb těles MeSH
- reprodukovatelnost výsledků MeSH
- tlak MeSH
- vibrace MeSH
- zvuk * MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
- srovnávací studie MeSH
Správné a spolehlivé vyhodnocení přítomnosti, nebo nepřítomnosti alergen specifických IgE je velmi důležité pro diferenciální diagnostiku alergického onemocnění. K tomuto účelu je k dispozici řada komerčních testů. Existuje jen málo údajů pro posouzení, nakolik jsou v každodenní praxi výsledky těchto různých testů srovnatelné. Záměr: Prozkoumat rozsah srovnatelnosti výsledků stanovení spec. IgE z různých laboratoří. Metody: Bylo vybráno šest diagnostických laboratoří, které používají pět různých metod pro stanovení spec. IgE. Během šesti týdnů byly do každé hodnocené laboratoře zaslány v triplikátech alikvoty 26 sér obsahujících různé koncentrace spec. IgE proti 17 běžným alergenům. Výsledky byly udávány jak ve třídách, tak v číselných hodnotách a byly porovnávány testováním jejich souhlasnosti Kendallovým W non-parametrovým testem. Dále byly testem nejlepší shody porovnány nalezené prahové (cut-off) hodnoty. Byla stanovena reprodukovatelnost profilů přesnosti založených na variačních koeficientech v rámci triplikátů pro všechny výsledky. Výsledky: Celkem bylo analyzováno 7813 výsledků. Souhlas mezi jednotlivými komerčními metodami - až na jednu výjimku - nebyl dobrý. Toto obzvláště platilo pro oblast prahových hodnot, kde většina metod vykazovala značnou nepřesnost. Pharmacia CAP System používaný dvěma laboratořemi vykazoval vysoce srovnatelné výsledky s dobrou přesností. Některé metody byly reprodukovatelné, ale ne správné. Ostatní nebyly ani správné, ani reprodukovatelné. Závěry: Výsledky této studie ukázaly, že ne všechny komerční laboratoře/metody pro stanovení spec. IgE poskytují reprodukovatelné a správné výsledky. U některých ohlášených výsledků bylo zjištěna značná možnost nesprávné diagnózy. Byly označeny metody poskytující citlivé, správné a reprodukovatelné výsledky.
Backround: Accurate and reliable evaluation of the presence or absence of allergen-specific IgE is important in the differential diagnosis of allergic disease. A variety of different commercial tests are available for this purpose. There are few data available to judge how the results of these different tests compare with one another in every use. Objective: To examine prospectively the extent of comparability among specific IgE results from different laboratories. Methods: Six diagnostic laboratories employing five different methods to assay specific IgE were selected. Aliquots from 26 serum samples that contained variable levels of IgE specific to 17 common aeroallergens were sent in triplicate to each study laboratory during a 6-week time period. Results were reported numerically and by class scores and then compared by examining their concordance using Kendall’s W nonparametric statistical test. In addition, cut-off values were compared by a best agreement analysis using reported results. Reproducibility was determined using precision profiles based upon the coefficient of variation among triplicates for each allergen across the range of reported results. Results: In all, 7,813 tests were analyzed. Concordance among different assays in commercial use with one exception was not good. This was particularly true aroud the cut-off region where most assays demonstrated high imprecision. The Pharmacia CAP System used by two different laboratories demonstrated highly comparable results with good precision. Some assays were reproducible but not accurate. Others were neither reproducible nor accurate. Conclusions: The results of this study indicate that not all commercial laboratories/assays for specific IgE provide reproducible and accurate data. Significant potential for misdiagnosis was detected for some reported results. Methods were identifield that do give sensitive, accurate, and reproducible results.
- MeSH
- alergie diagnóza MeSH
- imunoglobulin E krev MeSH
- klinické laboratorní techniky metody přístrojové vybavení statistika a číselné údaje MeSH
- lidé MeSH
- referenční standardy MeSH
- reprodukovatelnost výsledků MeSH
- řízení kvality MeSH
- Check Tag
- lidé MeSH
- Publikační typ
- přehledy MeSH
- srovnávací studie MeSH
Many mutualisms involve inter-specific resource exchanges, making consumer-resource approaches ideal for studying their dynamics. Also in many cases these resources are short lived (e.g. flowers) compared with the population dynamics of their producers and consumers (e.g. plants and insects), which justifies a separation of time scales. As a result, we can derive the numerical response of one species with respect to the abundance of another. For resource consumers, the numerical responses can account for intra-specific competition for mutualistic resources (e.g. nectar), thus connecting competition theory and mutualism mechanistically. For species that depend on services (e.g. pollination, seed dispersal), the numerical responses display saturation of benefits, with service handling times related with rates of resource production (e.g. flower turnover time). In both scenarios, competition and saturation have the same underlying cause, which is that resource production occurs at a finite velocity per individual, but their consumption tracks the much faster rates of population growth characterizing mutualisms. The resulting models display all the basic features seen in many models of facultative and obligate mutualisms, and they can be generalized from species pairs to larger communities.
- MeSH
- biologické modely * MeSH
- ekosystém MeSH
- opylení MeSH
- populační dynamika MeSH
- šíření semen MeSH
- symbióza * MeSH
- zvířata MeSH
- Check Tag
- zvířata MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
Surgical treatment of spine metastases follows only local anatomical and biomechanical objectives. Few cases of actual solitary metastases are rather exceptional, while removal of these metastases and the primary tumor may help to eradicate the process. The aim of our subsequent numerical simulations was to find out the temperature distribution and the volume lesion in a spinal tumor. For this purpose, the parametric three-dimensional numerical model was developed. It was shown that by finite element modeling approach not only the temperature distribution but even the resulted cavity may be estimated. The numerical approach was shown as a strong tool in surgery planning.
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.
Species delineation based on bacterial genomes is an essential part of the research of prokaryotes. In silico genome-to-genome comparison methods are computationally demanding, but much less tedious and error prone than the wet-lab methods. In this paper, we present a novel method for the delineation of bacterial genomes based on genomic signal processing. The proposed method uses numerical representations of whole bacterial genomes, phase signal and cumulated phase signal, from which four parameters are derived for each genome. The parameters characterize a genome and their calculation is independent of the other genomes comprising a delineation dataset. The delineation itself is processed as a calculation of the parameters' average similarity. The method was statistically verified on 1826 bacterial genomes. A similarity threshold of 96% was set based on the receiver operating characteristic curve that featured sensitivity of 99.78% and specificity of 97.25%. Additionally, comparative analysis on another 33 bacterial genomes was conducted using standard delineation tools as these tools were not able to process the dataset of 1826 genomes using desktop computer. The proposed method achieved comparable or better delineation results in comparison with the standard tools. Besides the excellent delineation results, another great advantage of the method is its small computational demands, which enables the delineation of thousands of genomes on a desktop computer. The calculation of the parameters takes tens of minutes for thousands of genomes. Moreover, they can be calculated in advance by creating a database, meaning the delineation itself is then completed in a matter of seconds.
- Publikační typ
- časopisecké články MeSH
Východiska. Léčba karcinomu prsu se v posledním desetiletí významně rozvíjela, nicméně stále zůstává významným sociálním i ekonomickým problémem na celém světě. Volba chirurgického výkonu závisí jednak na léčebném protokolu, jednak na preferenci lékaře. Cílem této studie je zhodnotit namáhání jizvy po rekonstrukci prsu. Metoda. Matematický model ke studování namáhání sešitého kožního laloku použitého při rekonstrukci prsu byl rozdělen na dvě části. V první části byl matematickým modelem zkoumán silikonový implantát. Následně bylo provedeno matematické modelování prsu s implantátem. Výsledky. Maximální geometrický rozdíl u anatomického i kulatého implantátu je umístěn na dolní a horní ploše prsu, zatímco oblast laterální a kolem areoly dosahuje vysoké shody. Největší tenze je lokalizována v místě dvou středových stehů. Maximální síla dosahuje 0,025 N. Cauchy stress equivalent je umístěn kolem bradavky a dosahuje hodnoty 380 kPa. Závěr. Naše výsledky ukazují, že anatomický a kulatý implantát nepřináší stejné zatěžování jizvy. Maximální rozdíl dosahuje 13,4 %, s tím, že kulatý implantát zatěžuje tahem jizvu výrazněji než implantát anatomický.
Background. The treatment of breast cancer has developed a lot during the last decade, nevertheless it still remains a considerable social and economical problem all over the world. The choice of the surgical procedure depends on a patient's protocol and the surgeon's preferences. The aim of this study is to evaluate the stress on the scar after breast reconstruction. Methods. Mathematical modeling of the sutured skin flap used for breast implant placement was divided into the following two steps. At first, material model of the selected silicone implant was identified. Afterwards, the mathematical model of the breast and implant was performed. Results. Maximal geometrical deviation for anatomical and round implant is placed on the lower surface of the breast and upper surface of the breast, while in the area of lateral geometry and the area around the nipple the agreement reaches very high level. The maximal tension is located in two median stitches. The maximal force reaches 0.025 N. The Cauchy stress equivalent is located around the nipple and reaches the value of 380 kPa. Conclusion. From our results it can be seen, that the anatomical and round breast implants do not result in the same stress on the scar. The maximal value difference reaches 13.4% between stress values for these two breast implants and the round implant results in higher loaded scar compared to the anatomical implant.
- MeSH
- analýza metodou konečných prvků statistika a číselné údaje MeSH
- biologické modely MeSH
- chirurgické laloky MeSH
- interpretace obrazu počítačem MeSH
- jizva * MeSH
- lidé MeSH
- mamoplastika MeSH
- mastektomie MeSH
- mechanický stres * MeSH
- nádory prsu chirurgie MeSH
- počítačová simulace MeSH
- počítačové modelování podle konkrétního pacienta MeSH
- prsní implantáty * MeSH
- prsy anatomie a histologie fyziologie MeSH
- teoretické modely MeSH
- zobrazování trojrozměrné MeSH
- Check Tag
- lidé MeSH
- ženské pohlaví MeSH
- Publikační typ
- hodnotící studie MeSH
- práce podpořená grantem MeSH
- srovnávací studie MeSH
