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Análise de Sinais Eletrocardiográficos Atriais Utilizando Componentes Principais e Mapas Auto-Organizáveis. / Atrial Eletrocardiographics Signals Analysis Using Principal Components and Self-Organizing Maps.Coutinho, Paulo Silva 21 November 2008 (has links)
A análise de sinais provenientes de um eletrocardiograma (ECG) pode ser de grande importância para avaliação do comportamento cardíaco de um paciente. Os sinais de ECG possuem características específicas de acordo com os tipos de arritmias e sua classificação depende da morfologia do sinal. Neste trabalho é considerada uma abordagem híbrida utilizando análise de componentes principais (PCA) e mapas auto-organizáveis (SOM) para classificação de agrupamentos provenientes de arritmias como a taquicardia sinusal e, principalmente, fibrilação atrial. Nesse sentido, O PCA é utilizado como um pré-processador buscando suprimir sinais de atividades ventriculares, de maneira que a atividade atrial presente no ECG seja evidenciada sob a forma das ondas f. A Rede Neural SOM, é usada na classificação dos padrões de fibrilação atrial e seus agrupamentos / A análise de sinais provenientes de um eletrocardiograma (ECG) pode ser de grande importância para avaliação do comportamento cardíaco de um paciente. Os sinais de ECG possuem características específicas de acordo com os tipos de arritmias e sua classificação depende da morfologia do sinal. Neste trabalho é considerada uma abordagem híbrida utilizando análise de componentes principais (PCA) e mapas auto-organizáveis (SOM) para classificação de agrupamentos provenientes de arritmias como a taquicardia sinusal e, principalmente, fibrilação atrial. Nesse sentido, O PCA é utilizado como um pré-processador buscando suprimir sinais de atividades ventriculares, de maneira que a atividade atrial presente no ECG seja evidenciada sob a forma das ondas f. A Rede Neural SOM, é usada na classificação dos padrões de fibrilação atrial e seus agrupamentos
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Použití automatického externího defibrilátoru složkami integrovaného záchranného systému - úroveň proškolení hasičů a policistů / The use of an automated external defibrillator by the members of the integrated rescue system - the level of education provided to firemen and policemenStejskalová, Radka January 2018 (has links)
The theme for this thesis is based on the European Resuscitation Council's guidelines for cardiopulmonary resuscitation of 2015. One of the important points of these procedures is the use of an automatic external defibrillator (AED). These devices were developed for informed responders without the knowledge of cardiac rhythm diagnostics and allow to perform an early defibrillation of the heart, before the arrival of emergency services. AED is a sophisticated device that is a part of the equipment of I - firefighters and policemen. Training of these so-called first aid responders performs the local emergency service team. Over the years 2015 and 2016, the majority of the professionally active firefighters and police officers in one selected Czech district who have the automatic external defibrillator in their equipment attended a training in how to use this device. The aim of this thesis is to determine whether the concept of the training courses is sufficient. If the theoretical part is well understandable for the respondents, and whether the practical training is sufficient - not only the actual compressions and ventilation, but also the use of an automatic external defibrillator, or whether it would be appropriate to extend this training. In this research I used a quantitative method - an...
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Spiral-Wave Dynamics in Ionically Realistic Mathematical Models for Human Ventricular TissueNayak, Alok Ranjan January 2013 (has links) (PDF)
There is a growing consensus that life-threatening cardiac arrhythmias like ven- tricular tachycardia (VT) or ventricular fibrillation (VF) arise because of the formation of spiral waves of electrical activation in cardiac tissue; unbroken spiral waves are associated with VT and broken ones with VF. Several experimental studies have shown that in homogeneities in cardiac tissue can have dramatic effects on such spiral waves.
In this thesis we focus on spiral-wave dynamics in mathematical models of human ventricular tissue which contain (a) conduction in homogeneities, (b) ionic in- homogeneities, (c) fibroblasts, (d) Purkinje fibers. We also study the effect of a periodic deformation of the simulation domain on spiral wave-dynamics. Chapter 2 contains our study of “Spiral-Wave Dynamics and Its Control in the Presence of In homogeneities in Two Mathematical Models for Human Cardiac Tissue”; this chapter follows closely parts of a paper we have published [1]. Chapter 3 contains our study of “Spiral-wave dynamics in a Mathematical Model of Human Ventricular Tissue with Myocytes and Fibroblasts”; this chapter follows closely a paper that we have submitted for publication. Chapter 4 contains our study of “Spiral-wave Dynamics in Ionically Realistic Mathematical Models for Human Ventricular Tis- sue: The Effects of Periodic Deformation”; this chapter follows closely a paper that we have submitted for publication. Chapter 5 contains our study of “Spiral-wave dynamics in a Mathematical Model of Human Ventricular Tissue with Myocytes and Purkinje fibers”; this chapter follows closely a paper that we will submit for publication soon.
In chapter 2, we study systematically the AP morphology in a state-of-the-art mathematical model of human ventricular tissue due to ten-Tusscher, Noble, Noble, and Panfilov (the TNNP04 model); we also look at the contribution of individual ionic currents to the AP by partially or completely blocking ion channels associated with the ionic currents. We then carry out systematic studies of plane- wave and circular-wave dynamics in the TNNP04 model for cardiac tissue model. We present a detailed and systematic study of spiral-wave turbulence and spa- tiotemporal chaos in two mathematical models for human cardiac tissue due to (a) ten-Tusscher and Panfilov (the TP06 model) and (b) ten-Tusscher, Noble, Noble, and Panfilov (the TNNP04 model). In particular, we use extensive numerical simulations to elucidate the interaction of spiral waves in these models with conduction and ionic in homogeneities. Our central qualitative result is that, in all these models, the dynamics of such spiral waves depends very sensitively on such in homogeneities. A major goal here is to develop low amplitude defibrillation schemes for the elimination of VT and VF, especially in the presence of in homogeneities that occur commonly in cardiac tissue. Therefore, we study a control scheme that has been suggested for the control of spiral turbulence, via low-amplitude current pulses, in such mathematical models for cardiac tissue; our investigations here are designed to examine the efficacy of such control scheme in the presence of in homogeneities in biophysical realistic models. We find that a scheme that uses control pulses on a spatially extended mesh is more successful in the elimination of spiral turbulence than other control schemes. We discuss the theoretical and experimental implications of our study that have a direct bearing on defibrillation, the control of life-threatening cardiac arrhythmias such as ventricular fibrillation.
In chapter 3, we study the role of cardiac fibroblasts in ventricular tissue; we use the TNNP04 model for the myocyte cell, and the fibroblasts are modelled as passive cells. Cardiac fibroblasts, when coupled functionally with myocytes, can modulate their electrophysiological properties at both cellular and tissue levels. Therefore, it is important to study the effects of such fibroblasts when they are coupled with myocytes. Chapter 3 contains our detailed and systematic study of spiral-wave dynamics in the presence of fibroblasts in both homogeneous and inhomogeneous domains of the TNNP04 model for cardiac tissue. We carry out extensive numerical studies of such modulation of electrophysiological properties in mathematical models for (a) single myocyte fibroblast (MF) units and (b) two-dimensional (2D) arrays of such units; our models build on earlier ones and allow for no, one-way, or two-way MF couplings. Our studies of MF units elucidate the dependence of the action-potential (AP) morphology on parameters such as Ef , the fibroblast resting membrane potential, the fibroblast conductance Gf , and the MF gap-junctional coupling Ggap. Furthermore, we find that our MF composite can show autorhythmic and oscillatory behaviors in addition to an excitable response. Our 2D studies use
(a) both homogeneous and inhomogeneous distributions of fibroblasts, (b) various ranges for parameters such as Ggap, Gf , and Ef , and (c) intercellular couplings that can be no, one-way, and two-way connections of fibroblasts with myocytes. We show, in particular, that the plane-wave conduction velocity CV decreases as a function of Ggap, for no and one-way couplings; however, for two-sided coupling, CV decreases initially and then increases as a function of Ggap, and, eventually, we observe that conduction failure occurs for low values of Ggap. In our homogeneous studies, we find that the rotation speed and stability of a spiral wave can be controlled either by controlling Ggap or Ef . Our studies with fibroblast inhomogeneities show that a spiral wave can get anchored to a local fibroblast inhomogeneity. We also study the efficacy of a low-amplitude control scheme, which has been suggested for the control of spiral-wave turbulence in mathematical models for cardiac tissue, in our MF model both with and without heterogeneities.
In chapter 4, we carry out a detailed, systematic study of spiral-wave dynamics in the presence of periodic deformation (PD) in two state-of-the-art mathematical models of human ventricular tissue, namely, the TNNP04 model and the TP06 model. To the best of our knowledge, our work is the first, systematic study of the dynamics of spiral waves of electrical activation and their transitions, in the presence of PD, in such biophysically realistic mathematical models of cardiac tissue. In our studies, we use three types of initial conditions whose time evolutions lead to the following states in the absence of PD: (a) a single rotating spiral (RS),
(b) a spiral-turbulence (ST) state, with a single meandering spiral, and (c) an ST state with multiple broken spirals for both these models. We then show that the imposition of PD in these three cases leads to a rich variety of spatiotemporal pat- terns in the transmembrane potential including states with (a) an RS state with n-cycle temporal evolution (here n is a positive integer), (b) rotating-spiral states with quasiperiodic (QP) temporal evolution, (c) a state with a single meandering spiral MS, which displays spatiotemporal chaos, (d) an ST state, with multiple bro- ken spirals, and (e) a quiescent state in which all spirals are absorbed (SA). For all three initial conditions, precisely which one of the states is obtained depends on the amplitudes and the frequencies of the PD in the x and y directions. We also suggest specific experiments that can test the results of our simulations. We also study, in the presence of PD, the efficacy of a low-amplitude control scheme that has been suggested, hitherto only without PD, for the control of spiral-wave turbulence, via low-amplitude current pulses applied on a square mesh, in mathematical models for cardiac tissue. We also develop line-mesh and rectangular-mesh variants of this control scheme. We find that square- and line-mesh-based, low-amplitude control schemes suppress spiral-wave turbulence in both the TP06 and TNNP04 models in the absence of PD; however, we show that the line-based scheme works with PD only if the PD is applied along one spatial direction. We then demonstrate that a minor modification of our line-based control scheme can suppress spiral-wave turbulence: in particular, we introduce a rectangular-mesh-based control scheme, in which we add a few control lines perpendicular to the parallel lines of the line- based control scheme; this rectangular-mesh scheme is a significant improvement over the square-mesh scheme because it uses fewer control lines than the one based on a square mesh.
In chapter 5, we have carried out detailed numerical studies of (a) a single unit of an endocardial cell and Purkinje cell (EP) composite and (b) a two-dimensional bilayer, which contains such EP composites at each site. We have considered bio- physically realistic ionic models for human endocardial cells (Ecells) and Purkinje cells (Pcells) to model EP composites. Our study has been designed to elucidate the sensitive dependence, on parameters and initial conditions, of (a) the dynamics of EP composites and (b) the spatiotemporal evolution of spiral waves of electrical activation in EP-bilayer domains. We examine this dependence on myocyte parameters by using the three different parameter sets P1, P2, and P3; to elucidate the initial-condition dependence we vary the time at which we apply the S2 pulse in our S1-S2 protocol; we also investigate the dependence of the spatiotemporal dynamics of our system on the EP coupling Dgap, and on the number of Purkinje- ventricular junctions (PVJs), which are measured here by the ratio R, the ratio of the total number of sites to the number of PVJs in our simulation domain.
Our studies on EP composites show that the frequency of autorhythmic activity of a P cell depends on the diffusive gap-junctional conductance Dgap. We perform a set of simulations to understand the source-sink relation between the E and P cells in an EP composite; such a source-sink relation is an important determinant of wave dynamics at the tissue level. Furthermore, we have studied the restitution properties of an isolated E cell and a composite EP unit to uncover this effect on wave dynamics in 2D, bilayers of EP composites.
Autorhythmicity is an important property of Purkinje cell; it helps to carry electrical signals rapidly from bundle of His to the endocardium. Our investigation of an EP composite shows that the cycle length (CL) of autorhythmic activity decreases, compared to that of an uncoupled Purkinje cell. Furthermore, we find that the APD increases for an EP composite, compared to that of an uncoupled P cell. In our second set of simulations for an EP-composite unit, we have obtained the AP behaviors and the amount of flux that flows from the E to the P cell during the course of the AP. The direction of flow of this flux is an important quantity that identifies which one of these cells act as a source or a sink in this EP composite. We have found that the P cell in an EP composite acts as a stimulation-current source for the E cell in the depolarization phase of the AP, when the stimulus is applied to both cells or to the P cell only. However, the P cell behaves both as a source and a sink when the stimulus is applied to the E cell only. In our third set of simulations for an EP composite unit, we have calculated the restitution of the APD; this plays an important role in deciding the stability of spiral waves in mathematical models for cardiac tissue. Our simulation shows that, for the EP composite with high coupling (Dgap = Dmm~10), the APDR slope decreases, relative to its value for an isolated E cell, for parameter sets P1 and P2, and first increases (for 50 ≤ DI ≤ 100 ms) and then decreases for the parameter set P3 ; however, for low coupling (Dgap = Dmm~100), the variation of the AP D as function of DI, for an EP composite, shows biphasic behavior for all these three parameter sets. We found that the above dynamics in EP cable type domains, with EP composites, depends sensitively on R.
We hope our in silico studies of spiral-wave dynamics in a variety of state-of-the- art ionic models for ventricular tissue will stimulate more experimental studies that examine such dynamics.
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Non-alcoholic fatty liver disease (NAFLD):perspectives to etiology, complications and lipid metabolismKäräjämäki, A. (Aki) 28 November 2017 (has links)
Abstract
Obesity, insulin resistance, type 2 diabetes (T2D) and non-alcoholic fatty liver disease (NAFLD) form a dangerous quartet which threatens human health all over the world. About 25% of adults around the world have NAFLD, which poses risks for cardiovascular and metabolic well-being and may develop into liver cirrhosis and hepatocellular carcinoma. Apart from lifestyle modification, treatment options for NAFLD are scarce.
This thesis presents atrial fibrillation (AF) as a new complication of NAFLD among general population of 958 individuals aged 40-60 years participating in the OPERA study. Even after multiple-adjustments for confounding factors, ultrasound-based NAFLD predicted the development of AF during about 16 years of follow-up. Moreover, the association between AF and liver fibrosis in 76 individuals aged 64-82 years in a cross-sectional setting is presented.
The thesis also shows that individuals with metabolic syndrome (MetS), with or without NAFLD, are at increased risk of cardiovascular events, T2D and the increase of left ventricular mass index in a study population of 958 individuals aged 40-60 years during a 20-year follow-up. In other words, NAFLD without MetS does not seem to expose to these three cardiometabolic complications.
The thesis also shows that rifampicin-activated pregnane X receptor (PXR), a member of the nuclear receptor superfamily of ligand-activated transcription factors with several endobiotic and xenobiotic activators, increases serum levels of cholesterol, phospholipids and certain fatty acids, assessed by nuclear magnetic resonance metabolomics technique, in a randomized, open, placebo-controlled trial among 34 young and healthy individuals. These serum lipids are considered toxic lipids and capable of transforming hepatosteatosis into steatohepatitis and even more severe forms of NAFLD. Moreover, rifampicin-activated PXR has no effect on serum triglycerides, that are non-toxic lipids, or triglyceride accumulation in the liver, assessed by magnetic resonance imaging, in 15 young and healthy individuals.
In conclusion, this thesis advances the knowledge in the pathogenesis, lipid metabolism, complications and heterogeneous nature of NAFLD. These may have implications for patient care and follow-up. / Tiivistelmä
Maailmanlaajuisesti noin 25% täysi-ikäisistä henkilöistä sairastaa alkoholinkäyttöön liittymätöntä rasvamaksaa. Sen tiedetään altistavan sydän- ja verisuonisairauksille, aineenvaihduntahäiriöille, maksakirroosille ja jopa maksasyövälle, mutta elämäntapahoitoa lukuun ottamatta hoitomahdollisuudet ovat toistaiseksi vähäisiä.
Tässä väitöskirjassa osoitetaan ensimmäistä kertaa alkoholinkäyttöön liittymättömän rasvamaksan ennustavan itsenäisesti eteisvärinän ilmaantuvuutta noin 16 vuoden seurannan aikana 958 tavallisen keski-ikäisen ihmisen aineistossa osana OPERA-tutkimusta. Lisäksi väitöskirjassa osoitetaan maksan sidekudosmuodostuksen ja eteisvärinän välillä olevan yhteys poikkileikkausasetelmassa 76 iäkkään ihmisen muodostamassa aineistossa.
Väitöstutkimuksessa havaittiin myös, että metabolista oireyhtymää sairastavilla henkilöillä on suurentunut tyypin 2 diabeteksen, sydän- ja verisuonisairauksien sekä vasemman kammion koon suurentumisen riski noin 20 vuoden seurannan aikana 958 tutkittavan henkilön aineistossa riippumatta siitä, onko heillä alkoholinkäyttöön liittymätön rasvamaksa. Toisin sanoen alkoholin käyttöön liittymätön rasvamaksa ilman metabolista oireyhtymää ei lisää edellä mainittujen kolmen sairauden riskiä.
Väitöstutkimuksessa esitetään lisäksi, että rifampisiinilla aikaansaatu maksan pregnane X -reseptorin aktivaatio johtaa seerumin fosfolipidien, tiettyjen rasvahappojen sekä usean eri kolesterolityypin lisääntymiseen 34 terveen nuoren henkilön aineistossa. Kirjallisuudessa näiden seerumin rasva-aineiden on esitetty aiheuttavan alkoholin käyttöön liittymätöntä maksatulehdusta ja jopa rasvamaksan vakavimpia muotoja. Toisaalta rifampisiini ei lisännyt seerumin triglyseridipitoisuutta eikä aiheuttanut magneettitutkimuksella mitattuna triglyseridien kertymistä maksaan 15 terveen nuoren henkilön aineistossa.
Tämä väitöstutkimus antaa lisätietoa rasvamaksan kehittymisestä, rasva-aineenvaihdunnasta ja komplikaatioista sekä korostaa rasvamaksan monimuotoista luonnetta. Nämä löydökset saattavat parantaa rasvamaksaa sairastavien henkilöiden hoitoa ja seurantaa.
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Avaliação da viabilidade da técnica de acesso ao espaço epicárdico por punção transatrial para ablação epicárdica por catete / Percutaneous transatrial approach to reach the epicardial space for epicardial mapping and ablationAna Claudia Venancio 20 January 2011 (has links)
Fundamentos O acesso percutâneo ao espaço pericárdico pela via transatrial poderia ser uma alternativa ao acesso subxifóide para o mapeamento e ablação de fibras miocárdicas subepicárdicas. O objetivo deste estudo foi avaliar a viabilidade de alcançar o espaço pericárdico normal através do apêndice auricular direito (AAD) por acesso transvenoso. Métodos e Resultados - Um sistema Mullins (8F), originalmente desenvolvido para alcançar o átrio esquerdo (AE) por punção transeptal foi utilizado neste estudo para transfixar o AAD (16) ou AE (1) em 17 suínos, com uma média de 26,9 ± 2,6 kg, e alcançar o espaço pericárdico normal. Um cateter 7F quadripolar com eletrodo distal com 4 ou 8 mm foi introduzido no espaço pericárdico para aplicações de radiofrequência. Em 15 (88%) animais o procedimento foi realizado sem instabilidade hemodinâmica (PA média inicial = 80,4 ± 11.7 mmHg; PA média final = 86,8 ± 9.7 mmHg, p = 0,11). Foi identificado e aspirado derrame pericárdico discreto (28,9 ± 27.6 ml/animal) durante o procedimento. O espaço pericárdico foi acidentalmente acessado por punção do ventrículo direito (VD) em um animal e por punção do anel da valva tricúspide em outro. Ambos apresentaram sangramento xii pericárdico importante e tamponamento cardíaco. Um dispositivo para oclusão do orifício de perfuração foi testado com sucesso em três porcos, dois no AD e um no VD, sem ocorrência de derrame pericárdico significativo. Conclusões O acesso transatrial ao espaço pericárdico pode ser potencialmente útil para mapeamento e ablação de arritmias cardíacas, bem como para drenagem imediata de um tamponamento cardíaco agudo / Background A transvenous access to the pericardial space could provide a convenient route to map and ablate subepicardial myocardial fibers. The aim of this study was to evaluate the feasibility of reaching the normal pericardial space through the right atrial appendage (RAA) by transvenous access. Methods and Results An 8F Mullins system was used to transfix the right atrium (16) and left atrium (1) in 17 pigs with a mean of 26.9 ± 2.6 kg. A 7F quadripolar catheter with 4 or 8 mm distal tip electrode was introduced into the pericardial space to perform epicardial radiofrequency lesions. The pericardial space was successfully reached in 15 (88%) animals without hemodynamic instability (initial mean BP 80.4 ± 11.7 mmHg; final 86.8 ± 9.7 mmHg, p= 0,11). However, a mild pericardial serohemorrhagic effusion was identified and aspirated in all the animals (28.9 ± 27.6 ml/pig) during the procedure. The pericardial space was accidentally accessed through the right ventricle (RV) in one animal and through the tricuspid annulus in another, which presented important pericardial bleeding and cardiac tamponade. The hypothesis that an occlusion device could be useful to close the created atrial xiv orifice was tested successfully in thee pigs (two at RAA and one at RV) and without significant pericardial bleeding. Conclusions The right atrial appendage route might be potentially useful to access the normal pericardial space for mapping and ablating cardiac arrhythmias as well as to drain promptly an acute tamponade
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Ventricular Arrhythmias Complicating Coronary Artery Disease: Recent Trends, Risk Associated with Serum Glucose Levels, and Psychological ImpactTran, Hoang V. 18 June 2018 (has links)
Introduction: Ventricular arrhythmias (VAs) are common after an acute coronary syndrome (ACS) and are associated with worse clinical outcomes. However, little is known about recent trends in their occurrence, their association with serum glucose levels, and their psychological impact in ACS setting.
Methods: We examined 25-year (1986-2011) trends in the incidence rates (IRs) and hospital case-fatality rates (CFRs) of VAs, and the association between serum glucose levels and VAs in patients with an acute myocardial infarction (AMI) in the Worcester Heart Attack Study. Lastly, we examined the relationship between in-hospital occurrence of VAs and 12-month progression of depression and anxiety among hospital survivors of an ACS in the longitudinal TRACE-CORE study.
Results: We found the IRs declined for several major VAs between 1986 and 2011while the hospital CFRs declined in both patients with and without VAs over this period. Elevated serum glucose levels at hospital admission were associated with a higher risk of developing in-hospital VAs. Occurrence of VAs, however, was not associated with worsening progression of symptoms of depression and/or anxiety over a 12-month follow-up period in patients discharged after an ACS.
Conclusions: The burden and impact of VAs in patients with an AMI has declined over time. Elevated serum glucose levels at hospital admission may serve as a predictor for in-hospital occurrence of serious cardiac arrhythmias. In-hospital occurrence of VAs may not be associated with worsening progression of symptoms of depression and anxiety in patients with an ACS.
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Detekce fibrilace síní v EKG / ECG based atrial fibrillation detectionPlch, Vít January 2019 (has links)
This diploma thesis deals with detection of atrial fibrillation from HRV, classification of Poincare map and in the end the divide into two groups, one with detected atrial fibrillation and one not. The result is the decision on which variables are statistically significant for the identification of atrial fibrillations and which are not, and classification of the ECG signals.
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Detekce fibrilace síní v EKG / ECG based atrial fibrillation detectionPlch, Vít January 2019 (has links)
This diploma thesis deals with detection of atrial fibrillation from HRV, classification of Poincare map and in the end the divide into two groups, one with detected atrial fibrillation and one not. The result is the decision on which variables are statistically significant for the identification of atrial fibrillations and which are not, and classification of the ECG signals with Bayes and Lavenberg-Marquardt neural networks. Bayes neural network with 23 neurons in hidden layer is best with F1 measure = 83,6 %, Sensitivity = 88,1 % and Specificity 94,5 %.
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Model fibrilace síní / Atrial fibrillation modelŘedina, Richard January 2021 (has links)
The aim of this master thesis is to create a 3D electroanatomical model of a heart atria, which would be able to perform atrial fibrillation. To control the model, the differential equations of the FitzHugh-Nagumo model were chosen. These equations describe the change of voltage on the cell membrane. The equations have established parameters. The modification of them leads to changes in the behavior of the model. The simulations were performed in the COMSOL Multiphysics environment. In the first step, the simulations were performed on 2D models. Simulations of healthy heart, atrial flutter and atrial fibrillation were created. The acquired knowledge served as a basis for the creation of a 3D model on which atrial fibrillation was simulated on the basis of ectopic activity and reentry mechanism. Convincing results were obtained in accordance with the used literature. The advantages of computational modeling are its availability, zero ethical burden and the ability to simulate even rarer arrhythmias. The disadvantage of the procedure is the need to compromise between accuracy and computational complexity of simulations.
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Bonding Ability Distribution of Fibers in Mechanical Pulp FurnishesReyier Österling, Sofia January 2008 (has links)
This thesis presents a method of measuring the distribution of fiber bonding ability in mechanical pulp furnishes. The method is intended for industrial use, where today only average values are used to describe fiber bonding ability, despite the differences in morphology of the fibers entering the mill. Fiber bonding ability in this paper refers to the mechanical fiber’s flexibility and ability to form large contact areas to other fibers, characteristics required for good paper surfaces and strength. Five mechanical pulps (Pulps A-E), all produced in different processes from Norway spruce (Picea Abies) were fractionated in hydrocyclones with respect to the fiber bonding ability. Five streams were formed from the hydrocyclone fractionation, Streams 1-5. Each stream plus the feed (Stream 0) was fractionated according to fiber length in a Bauer McNett classifier to compare the fibers at equal fiber lengths (Bauer McNett screens 16, 30, 50, and 100 mesh were used). Stream 1 was found to have the highest fiber bonding ability, evaluated as tensile strength and apparent density of long fiber laboratory sheets. External fibrillation and collapse resistance index measured in FiberLabTM, an optical measurement device, also showed this result. Stream 5 was found to have the lowest fiber bonding ability, with a consecutively falling scale between Stream 1 and Stream 5. The results from acoustic emission measurements and cross-sectional scanning electron microscopy analysis concluded the same pattern. The amount of fibers in each hydrocyclone stream was also regarded as a measure of the fibers’ bonding ability in each pulp. The equation for predicted Bonding Indicator (BIN) was calculated by combining, through linear regression, the collapse resistance index and external fibrillation of the P16/R30 fractions for Pulps A and B. Predicted Bonding Indicator was found to correlate well with measured tensile strength. The BIN-equation was then applied also to the data for Pulps C-E, P16/R30, and Pulp A-E, P30/R50, and predicted Bonding Indicator showed good correlations with tensile strength also for these fibers. From the fiber raw data measured by the FiberLabTM instrument, the BIN-equation was used for each individual fiber. This made it possible to calculate a BIN-distribution of the fibers, that is, a distribution of fiber bonding ability. The thesis also shows how the BIN-distributions of fibers can be derived from FiberLabTM measurements of the entire pulp without mechanically separating the fibers by length first, for example in a Bauer McNett classifier. This is of great importance, as the method is intended for industrial use, and possibly as an online-method. Hopefully, the BIN-method will become a useful tool for process evaluations and optimizations in the future. / Den här studien presenterar en metod för att mäta fördelning av fiberbindning i mekaniska massor. Metoden hoppas kunna användas industriellt, där i dagsläget enbart medelvärden används för att mäta fiberbindnings-fördelning, trots råvarans (fibrernas) morfologiska skillnader. Fem mekaniska massor (Massa A-E) från olika massaprocesser men från samma råvara, norsk gran (Picea Abies), har fraktionerats i hydrocykloner med avseende på fiberbindningsförmåga. Från hydrocyklon-fraktioneringen bildades fem strömmar, Ström 1-5. Varje ström plus injektet (Ström 0) fraktionerades också med avseende på fiberlängd i en Bauer McNett för att kunna jämföra fibrerna vid samma fiberlängd (Bauer McNett silplåtarna 16, 30, 50 och 100 mesh användes). Fiberbindingsförmåga i den här studien härrör till fiberns flexibilitet och förmåga att skapa stora kontaktytor med andra fibrer, vilket bidrar till papprets yt- och styrkeegenskaper. Ström 1 visade sig ha den högsta fiberbindningsförmågan, utvärderat som dragstyrka och densitet av långfiberark, samt yttre fibrillering och kollaps resistans index mätt i den optiska analysatorn FiberLabTM. Akustisk emission och tvärsnittsanalyser visade samma resultat. Ström 5 visade sig ha den lägsta fiberbindningsförmågan, med en avtagande skala från Ström 1 till Ström 5. Andelen fibrer från injektet som gick ut med varje hydrocyklon-ström ansågs också vara ett mått på fibrernas bindningsförmåga i varje massa. Genom att kombinera fiberegenskaperna kollaps resistans och yttre fibrillering från den optiska mätningen på varje fiber genom linjär regression, kunde Bindnings Indikator (BIN) predikteras. Medelvärdet av Bindnings Indikator för varje hydrocyklon-ström korrelerar med dragstyrka för långfiber-labark. Det visade sig att predikterad Bindnings Indikator inte bara fungerade för Massa A och Massa B P16/R30 fraktionen, som var de fraktioner som användes i den linjära regressionen, utan även för Massa C-E, P16/R30, och Massa A-E P30/R50 som också visade goda korrelationer med långfiber-dragstyrka när de sattes in i BIN-formeln. BIN-formeln användes sedan för varje enskild fiber, i den rådata som levererats från FiberLabTM. Detta gjorde det möjligt att få en BIN-distribution av fibrerna, d.v.s. en fördelning av fiberbindningsförmåga. Den här rapporten visar också hur det går att få BIN-distributioner också från mätningar på hela massan, för valbara fiberlängder, utan att först mekaniskt separera massan efter fiberlängd. Det är viktigt, då metoden är tänkt att användas som en industriell metod, och eventuellt som en online-metod. Förhoppningsvis kommer BIN-metoden att bli ett användbart verktyg för processutveckling- och optimering i framtiden. / <p>FSCN – Fibre Science and Communication Network</p> / Bonding ability distribution of fibers in mechanical pulp furnishes
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