381023 research outputs found
Sort by
Recent advances in tremors in dogs and cats
No full textTremors in dogs and cats have been faintly investigated in veterinary neurology. There are poorly known tremors in dogs and cats, that require further description. Additionally, it is controversial whether further investigations such as advanced imaging is indicated in some types of tremor. Little is further known about the treatment and outcome of these tremors. Especially in cats, it is unknown which diseases are the most common causes of tremors. In this thesis, several of the aforementioned questions are attempted to be answered with an aim to elucidate these often enigmatic neurological signs in dogs and cats. This thesis is divided in the following chapters. In the general introduction (chapter 1) a narrative review is provided discussing the currently known tremors in dogs and cats based on up-to-date veterinary literature. This chapter alsocontains a clinical and practical approach of tremors and contains a series of videos of tremors in dogs and cats. The scientific aims (chapter 2) of this thesis are presented in this section. The results of this thesis are presented, and they are divided in 7 chapters. In chapter 3 the signalment, semiology, magnetic reasoning imaging (MRI) findings and outcomes of dogs with idiopathic episodic head tremor (IEHT) and structural episodic head tremor (SEHT) were investigated. We found that SEHT exists in dogs and can be associated with a structural lesion in the thalamus or/and mesencephalic aqueduct. Structural episodic head tremor is usually manifested in older dogs with accompanying neurological deficits compared to IEHT dogs. In chapter 4, dystonic head tremor as a sign of paroxysmal dyskinesia was investigated in dogs. We recognised dystonic head tremor as a part of semiology in 43.6 % of dogs with paroxysmal dyskinesia. Poodle or Poodle-cross breeds were the most commonly affected breeds. In chapter 5, episodic mandibular tremor, that is teeth chattering, was investigated in dogs and cats in hospital populations as well as in an open public survey. We recognised an idiopathic episodic mandibular tremor in dogs and cats as a novel possible benign movement disorder. These dogs and cats did not have any other underlying neurologic disease and other accompanying neurological signs. Cavalier King Charles Spaniels were overrepresented. In chapter 6, the tremor phenotype, diagnostic test findings, treatment and outcome of dogs with orthostatic tremors and orthostatic tremor-plus were investigated. We found that orthostatic tremor was common in young giant or large breeds, and that also orthostatic tremor – plus exists in dogs which can be concomitant or associated with other neurological diseases. In chapter 7, the study evaluates the prevalence of underlying aetiologies and describes the clinical features of a large cohort of cats with tremors. We found that the most common diseases causing tremors in cats include degenerative encephalopathy, feline infectious peritonitis, congenital portosystemic shunt, intoxication and polyneuropathy. In chapter 8, we investigated in-depth the clinical features of tremors in cats with hepatic encephalopathy and congenital portosystemic shunts or post-attenuation neurologic syndrome. We found that tremors of variable phenotype occur in cats with a portosystemic shunt. In some cats tremors can be the main presenting complaint. In conclusion, the studies included in this thesis provide new information on tremors in dogs and cats. Further prospective studies are necessary to further increase our knowledge of tremors in dogs and cats
Mathematical models for robust and collaborative transport optimization
No full textHet belang van transport en logistiek in zowel de historische als de huidige samenleving is moeilijk te overschatten. Deze sectoren zijn verantwoordelijk voor een aanzienlijk deel van de globale economie, maar zijn daartegenover ook verantwoordelijk voor een groot deel van de globale CO₂ uitstoot. Dit betekent dat elke mogelijke verbetering in de operationele efficiëntie in deze sectoren een significante impact kan hebben in zowel economische waarde als de toestand van het klimaat. Een manier om de efficiëntie te verbeteren is door de integratie van verschillende niveaus binnen de logistieke keten en de samenwerking tussen de verschillende betrokken partijen. Op deze manier is verdere optimalisatie mogelijk en kunnen door het uitwisselen van informatie en middelen betere planningen opgesteld worden dan wanneer elke partij individueel zou werken. Een ander belangrijk aspect in het berekenen van routes en planningen in transport en logistiek is robuustheid. In de praktijk zijn veel processen, zoals reistijden in het drukke verkeer, laad- en lostijden, of last-minute aanpassingen van bestellingen, onderhevig aan onzekerheid. Door dit in rekening te brengen in de wiskundige modellen kan er op geanticipeerd worden en kan het falen van een planning vermeden worden
Enhancing requirements clarity : analyzing potential ambiguity in user stories
No full textAgile Software Development (ASD) has become increasingly prevalent in the past two decades, emphasizing flexibility and adaptability to meet evolving market demands and accelerate project delivery. Effective communication within Agile teams is paramount, as any misunderstandings can lead to various challenges, including non-compliant software solutions and increased development costs. Moreover, cultural differences, spanning language, norms, and communication styles, can exacerbate these challenges, leading to cultural misperceptions, ambiguous misunderstandings, and divergent interpretations and documentations. Addressing these complexities is essential for promoting collaboration and ensuring project success.
To facilitate collaboration between IT and business stakeholders, Agile methodologies advocate the use of lightweight documentation, often in the form of user stories. However, as natural language-based artifacts, user stories are inherently prone to ambiguity, posing risks to software quality. Ambiguity in user stories manifests in various patterns and analyzing it is a complex task. Nonetheless, investing efforts in refining the quality of user stories is essential, as it can mitigate the risk of higher costs in later development stages while enhancing software quality and expediting the development process.
This doctoral project consists of four substantive chapters, framed by an introductory and a concluding chapter, addressing the overarching research question: How can potential sources of ambiguity in user stories be identified and what is a comprehensive and effective approach to address this problem? To answer this question, a qualitative interpretive methodology was employed through a systematic literature mapping. This approach provided a deeper understanding of how user story research has been conducted, facilitating informed decision-making and guiding future research endeavors. Further extraction was performed using inferential generalization in a systematic literature review to identify different manifestations of ambiguity in a set of user stories. A framework for analyzing ambiguity in a set of user stories is introduced and initially tested using a controlled experiment to evaluate its potential usability for identifying ambiguity. To enhance performance, a tool-supported method was developed by leveraging NLP techniques. This method not only identifies ambiguity but also refines user stories flagged as “potentially ambiguous”.
The efficacy of the AmbiTRUS tool was evaluated through usability testing with professionals in requirements engineering and business analysis. The results of each empirical study support the effectiveness of AmbiTRUS in identifying ambiguity in a set of user stories. Specifically, AmbiTRUS has proven effective in identifying different manifestations of ambiguity at various linguistic levels, helping users quickly analyze and refine problematic user stories. From an academic perspective, Chapter 2 reveals that ambiguity in user stories is a scarcely addressed but relevant topic, with a few solutions reaching the prototype stage. Chapter 3 identifies different manifestations of ambiguity across linguistic levels. From a practical perspective, Chapters 4 and 5 present a comprehensive framework, integrated into the tool-supported method (AmbiTRUS tool), to facilitate ambiguity analysis and requirements refinement. The studies demonstrate that AmbiTRUS is effective and user-friendly, with a high likelihood of regular use as an ambiguity-checking mechanism. Consequently, this dissertation makes a dual contribution to both academia and industry by extending the understanding of ambiguity in a set of user stories and providing a comprehensive and effective tool to facilitate requirement analysis
Pore-scale imaging of solute and colloid transport
No full textStromingen doorheen de ondergrond spelen een grote rol voor een breed scala aan wetenschappelijke, industriële en milieutoepassingen en leveren een belangrijke bijdrage aan bijvoorbeeld grondstoffenbeheer en de duurzame ontwikkelingsdoelstellingen. Om het gedrag van de vloeistofstromingen op reservoirschaal te voorspellen wordt gewoonlijk gebruik gemaakt van numerieke modellen waar het poreuze medium beschouwd wordt als een materiaal met continue eigenschappen op de meter schaal. Dit soort eigenschappen weerspiegelen het gedrag van de vloeistof in de porieruimte en worden vaak bepaald met laboratorium experimenten of veldmetingen die niet altijd representatief zijn voor het volledige reservoir. Daarom kan een beter begrip van het complexe 3D gedrag van transport van opgeloste stoffen en colloïden op de porie schaal helpen om deze modellen te verbeteren. Maar ondanks de aanzienlijke vooruitgang in het bestuderen van transport op de porie schaal met geavanceerde beeldvormings- en modelleringstechnieken, blijft het een uitdaging om de transport processen in complexe driedimensionale poreuze structuren te visualiseren en kwantificeren met rechtstreekse beeldvorming omdat hiervoor een hoge beeld- en tijdsresolutie cruciaal zijn. In dit proefschrift worden deze uitdagingen aangepakt en wordt het transport van opgeloste stoffen en colloïden bestudeerd door de processen rechtstreeks te visualiseren op porie schaal met tijdsgeresolveerde X-stralen tomografie
Advanced three-dimensional insight leads the way to ultrasound-guided interventional cardiology in horses
No full textCatheter-based procedures are commonly performed in humans and small animals to characterize
and treat cardiac disease. Diagnostic catheterisations include blood pressure measurements,
myocardial biopsy or electrophysiological studies, while therapeutic procedures include valve
implantation, defect closure or arrhythmia ablation. The implementation of these catheter-based
interventions in equine cardiology is hampered by several aspects, such as vascular access, imaging
guidance and the availability of appropriate medical devices. In contrast to human and small animal
medicine, fluoroscopy does not provide adequate guidance for catheter placement in equine
cardiology. There is a major need to explore other imaging modalities for guiding catheter-based
procedures, thus facilitating the development of catheterisations adapted to the equine anatomy
and physiology. This way, opportunities can be created to unravel the pathophysiology behind a
variety of cardiac diseases and to expand the diagnostic and therapeutic possibilities within equine
cardiology.
Chapter 1 gives an overview of the catheter-based interventions performed in human and small
animal medicine for structural and electrophysiological indications. Associated preprocedural and
procedural imaging modalities are discussed, with fluoroscopy being the main imaging modality, and
three-dimensional electroanatomical mapping (3D EAM), transoesophageal and intracardiac
echocardiography (TOE and ICE) as complementary modalities or stand-alone alternatives for
procedural guidance. In humans and small animals, vascular access is usually obtained via the
femoral vein. To access the left atrium and ventricle in a minimally-invasive way, transseptal
puncture is used to attain a favourable stable positioning of catheters in the left heart.
Periprocedural antithrombotic treatment is dependent on the treated disease, concurrent
conditions and whether the left or right heart is accessed. The field of equine interventional
cardiology shows a much more limited range of catheter-based interventions, which mostly focus
on electrophysiological procedures (e.g. transvenous electrical cardioversion, 3D-EAM and
radiofrequency ablation). Reports of interventions for structural heart disease are scarce. Guidance
is predominantly performed using transthoracic echocardiography (TTE), and 3D EAM for
electrophysiological procedures, as fluoroscopy provides insufficient guidance with a high radiation
exposure. However, echocardiography is restricted by interference of the lungs, ribs and body
conformation, and is based on a two-dimensional (2D) imaging plane visualising the complex 3D
structure of the equine heart. The majority of the catheterisations are performed in the right heart.
Left heart catheterisations are rarely reported and if performed an arterial retrograde approach is
used. Transseptal puncture had never been performed in horses, and no guidelines exist regarding
periprocedural antithrombotic treatment in the context of cardiac catheterisations.
As the lack of appropriate detailed imaging guidance is a major reason for the limited availability of
cardiac catheterisations in horses, the general aim of this thesis was to explore the possibilities of
echocardiographic guidance for cardiac catheterisations in horses. Chapters 3 and 4 focus on
obtaining better anatomical insights into the equine heart, as a thorough understanding of the
cardiac anatomy is needed to understand how catheters can be manipulated and how the
echocardiographic image can be correlated to the cardiac anatomy. In Chapter 3, the macroscopic
characteristics of the coronary sinus, great and middle cardiac vein and the fossa ovalis were
explored. Important findings were the presence of a valve at the entrance of the coronary sinus
(Thebesian valve) and numerous valves in the great cardiac vein, which can hamper insertion of
devices. Fossa ovalis dimensions were variable but correlated with body weight and aortic size. Such
variations might affect transseptal puncture. Chapter 4 addressed the second objective of this
doctoral thesis, namely to obtain enhanced 3D anatomical insight in the equine heart by creating a
3D equine cardiac computer model representing the in vivo anatomy. Two methods to obtain a 3D
dataset of the equine heart were explored. The method based on computed tomography of
polyurethane casted hearts produced a highly detailed model, however compliant cardiac
structures were disproportionally expanded by the foam. The second method, consisting of an in
vivo contrast-enhanced computed tomography of ponies provided an anatomically correct but
slightly less detailed model. For the purpose of developing an equine cardiac ultrasound simulator,
the model based on the contrast-enhanced computed tomography of ponies was preferred as it
represented best the in vivo situation.
Using the equine cardiac ultrasound simulator, Chapter 5 addressed the third objective of this
thesis to develop novel images for ICE to create a roadmap of the right heart. Views were first
developed on the simulator, after which they were validated in six horses. Views were focused on
the tributaries of the cranial vena cava at the thoracic inlet, both atria, the pulmonary veins, aorta
and pulmonary artery. Catheter manipulations were similar in the simulator and the live horses. The
newly developed images are essential to navigate through the equine heart during interventional
procedures. In addition, the usefulness of the simulator to define new echocardiographic views with
enhanced anatomical insight was shown, thereby reducing the need for experimental animals. The
clinical usefulness of ICE in two cases of morphological variations of the interatrial septum was
explored in Chapter 6. The complementary use of ICE, 2D TTE and 3D TTE allowed for detailed
characterisation of a patent foramen ovale in one horse, with evidence of a left-to-right shunt with
limited haemodynamic implications. In the other horse, ICE allowed to exclude the presence of a
patent foramen ovale. This demonstrates the added value of ICE in a clinical setting.
A fourth objective of this thesis was to develop a transseptal puncture technique adapted to horses
and guided by ICE. First, in Chapter 7, a transseptal puncture technique was developed based on
radiofrequency application on a guidewire to puncture the fossa ovalis under echocardiographic
guidance. Two different approaches were explored, namely the jugular vein approach and the
transhepatic approach. Transseptal puncture was successful in 17/18 horses, with a 15/16 success
rate for the jugular vein approach and a 5/8 success rate for the transhepatic approach. Atrial
arrhythmias occurred in 13/18 horses during puncture. Transthoracic echocardiography provided
guidance for major catheter manipulations in the heart, but ICE was essential in guiding the precise
manipulations performed during the actual puncture. The study showed the feasibility of
ultrasound-guided transseptal puncture in horses. To investigate the occurrence of postprocedural
complications and closure of the iatrogenic atrial septal defect (iASD) after puncture, a transseptal
puncture using the jugular vein approach was performed in 11 horses in the subsequent study
(Chapter 8). The puncture was successful in all horses with a median duration of 22 [10-104]
minutes. In 4 horses, balloon dilation of the puncture site was needed to allow introduction of the
transseptal sheath into the left atrium. Atrial arrhythmias occurred in 9 horses, including atrial
premature depolarisations, atrial tachycardia and atrial fibrillation. Intracardiac echocardiographic
follow-up demonstrated spontaneous closure of iASD in all horses within 14±9 days, ranging from 1
to 35 days. Horses were treated with enoxaparin during the follow-up period, which could be
monitored with point-of-care analysis of activated clotting time (ACT). However, the ACT values
could not be related with anti-factor Xa activity.
Finally, the last objective was to investigate the feasibility to guide multiple catheters to specific
positions in the four cardiac chambers using TTE guidance (Chapter 9). Catheter positioning in the
right heart and left ventricle was successfully guided in the majority of the horses while catheter
positioning in the left atrium, and especially the pulmonary veins, was challenging to guide
echocardiographically. Apart from 2D TTE, 3D TTE functionalities such as 3D volume imaging and
biplane imaging proved to be useful to guide the catheter to the moderator band and His bundle,
respectively. Left parasternal echocardiography and ICE were not systematically assessed for their
usefulness during catheter guidance, and might provide improved guidance of catheter positioning
in the left atrium.
In conclusion, this thesis has shown that in-depth 3D anatomical insight into the equine heart is
essential to understand catheter manipulation, to select devices adapted to the specific equine
anatomy, and to understand how a 2D echocardiographic image is rendered from the 3D cardiac
structure. The 3D computer model and equine cardiac ultrasound simulator are of great value for
this purpose. The simulator might in future be enhanced by including specific cardiac pathologies,
cardiac contractions, flow and cardiac valves. Furthermore, although echocardiography has its
known limitations, its different modalities have an enormous potential in equine interventional
cardiology. Transthoracic echocardiography provides overview of major catheter manipulations,
while ICE can be used for very detailed procedures such as the transseptal puncture. Further work
is needed regarding the use of left parasternal TTE for catheter guidance and ICE imaging from
within the left atrium. The advent of 3D ICE creates perspectives for 3D interventional guidance
needed for complex procedures. The transseptal puncture provides a minimally-invasive gateway
towards the left heart, thus allowing the exploration of the pulmonary veins in the context of AF or
the feasibility of novel interventional treatments. Further optimisation of the transseptal puncture
to allow a swift puncture with minimized risk for thromboembolic events will be needed to allow for
an efficient implementation within catheter-based procedures. In addition, as the number of
catheterisations performed in horses will be rising, further research is needed to evaluate the
benefit of antithrombotic treatment to limit the thromboembolic risk. With these advancements,
diagnostic and therapeutic possibilities for horses suffering from different cardiac diseases can be
expanded
Decentralised linked data architectures for the transport domain
No full textInteroperabiliteit van gegevens vormt de kern van de EU-datastrategie voor zowel de publieke als de private sector. In dit proefschrift worden gedecentraliseerde en kostenefficiënte systeemarchitecturen voorgesteld en bestudeerd, gebaseerd op Linked Data technologieën, gericht op (maar niet beperkt tot) het transportdomein. Drie belangrijke use cases worden behandeld, namelijk het beheer van fietsparkeerinfrastructuur, het publiceren van dienstregelingen voor openbaar vervoer en technische compatibiliteit tussen voertuigen en de EU spoorweginfrastructuur. De oplossingen die in dit proefschrift worden beschreven, zijn en worden nog steeds gebruikt in productieomgevingen en laten een hoge mate van adoptie zien. Ze hebben ook bijgedragen aan de vormgeving van EU-wetgeving, zoals in het geval van gegevens over de spoorweginfrastructuur. Deze oplossingen leveren het bewijs dat Linked Data technologieën geschikt zijn voor gebruik in praktische en realistische omgevingen, terwijl semantische en technische interoperabiliteitsuitdagingen worden aangepakt
The security of energy supplies between Turkey and the EU : the case of renewable energy
No full textThe thesis is an examination of the regulation of the security of supply focusing on the case of renewable energy at three levels (the international, the EU and the national, namely Turkey). Following the introductory chapter, the second chapter outlines the institutional set-up of energy agencies and their roles in ensuring the security of supply by encouraging the production and use of renewable energy. Detailed attention is given to IRENA and IEA. The third chapter describes the principal actors in the regulation of the energy market at the EU level, including the EU institutions and ACER. The fourth chapter describes the Turkish energy market's structure and principal actors. The fifth chapter highlights various challenges and flaws in the regulation of the energy markets with regard to renewable energy sources at three different levels, along with the novel contributions that this research brings to the field.
A significant component and purpose of this research involves making recommendations for legal improvements related to the legislation and regulation directly affecting renewable energy and the security of energy supply. In this context, international, multilateral and bilateral agreements are analyzed in detail, including several court cases. Therefore, the findings of this dissertation research aim to contribute to international, regional, and national legal and policy decisions in this area.
The study compares a range of legal means in the EU and Turkey in this area, including EU directives, regulations and treaties, such as the Energy Charter Treaty and other legal decisions. The analysis aids in assessing how the legal instruments can be used in securing energy supply and renewable energy, utilizing the example of the EU's relationship with Turkey and scrutinizes Turkey's interaction and position in its domestic legislation towards the EU and global energy markets while illuminating the reasons for conflicting legislation and other measures.
The methodology for the research includes legal research and analysis, institutional and academic document research at the EU and the Turkish levels. Primary sources supporting the research findings include laws and regulations, case law, treaties and policy documents. Secondary sources range from academic articles and books in the fields of energy policy and law. The core focus of the current study is on the legal aspects of renewable energy and the security of energy supply in energy markets. However, other relevant political and technical aspects of the subject are covered in a limited context within the research boundaries.
The thesis demonstrates that the current energy market regulation has substantial challenges and flaws at three levels in terms of supply security and renewable energy regulation. The research findings show what legal mechanisms and factors appear problematic in the achievement of the security of energy supply and renewable energy aims at both the EU and the Turkish levels. This research has the potential to impact Turkey's future security of energy supply and the development of renewable energy legislation, which is currently being shaped as a part of the EU membership process
Modeling weighted and temporal graphs : methods and evaluation
No full textHet doel van mijn promotieonderzoek is om kennis te halen uit gegevens die zijn weergegeven als grafieken (netwerken) en nauwkeurige voorspellingen te doen. Dit soort onderzoek heeft toepassingen in bijvoorbeeld sociale netwerkanalyse, biologische netwerken en aanbevelingssystemen. Traditionele methoden gebruiken vaak statische grafieken, maar hiermee missen we belangrijke informatie, zoals de gewichten van verbindingen (edges) of tijdstempels van interacties. In dit onderzoek stel ik methoden voor om complexe interactiepatronen op het niveau van de verbindingen in modellen te verwerken. Het onderzoek richt zich op het voorspellen van nieuwe verbindingen (Link Prediction), het kwantificeren van onzekerheid, en simulatie.
Een toepassing hiervan is het gebruik van gewogen grafiekmodellen voor het voorspellen van het volgende nummer in muziekspeellijsten. Daarnaast heb ik technieken ontwikkeld, geïnspireerd door Survival Analysis en Point Processes, om rekening te houden met de tijdsgebonden evolutie van netwerken. Tot slot heb ik de impact van Negative Sampling onderzocht en bekeken hoe dit de evaluatie van statistische modellen voor complexe netwerken beïnvloedt