Dissertations / Theses on the topic 'Bypass'

Dissertação de Mestrado Integrado em Medicina Veterinária<br>A obstrução ureteral por nefrolitíase ocorre ocasionalmente no gato e parece ter incidência crescente na população felina. O seu diagnóstico é feito com base nos sinais clínicos, análises bioquímicas, com destaque para a medição de ureia e creatinina, e recorrendo a meios complementares de diagnóstico como a radiografia e a ecografia. Para o seu tratamento, pode-se recorrer numa primeira abordagem a uma terapêutica médica, no entanto, esta é muitas vezes ineficaz, pelo que geralmente há necessidade de intervir cirurgicamente. Tradicionalmente a nefrolitíase tem sido resolvida através de técnicas com elevado grau de complicações, tais como a ureteronefrectomia, nefrotomia, pielolitotomia, ureterotomia, ureteroneocistostomia e o transplante renal. Contudo, técnicas inovadoras e menos invasivas têm surgido. Entre elas, está o bypass ureteral subcutâneo, uma técnica recentemente introduzida em Portugal. Este trabalho visa a descrição detalhada desta técnica no gato em 35 intervenções abordadas no Hospital Veterinário do Restelo. Foram calculadas as taxas de mortalidade e de complicações observadas e descritas as principais complicações associadas, assim como as medidas de correção implementadas.<br>ABSTRACT - Subcutaneous Ureteral Bypass: retrospective study - Ureteral obstruction due to nephrolithiasis occasionally is a common disease of domestic cat and seems to be increasing in the feline population. Diagnosis is based on clinical signs, blood work, especially for urea and creatinine, and using complementary diagnostic tests such as X-ray and ultrasound. For treatment, one may start with medical treatment, however, this is often ineffective. Therefore there is usually the need for surgical intervention. Nephrolithiasis has been traditionally resolved by techniques involving high complication rates, such as ureteronephrectomy, nephrostomy, pyelolithotomy, ureterotomy, ureteroneocystostomy and kidney transplantation. However, innovative and less invasive techniques have emerged. These include the subcutaneous ureteral bypass, a recently introduced technique in Portugal. This study aims to describe in detail the use of this technique in cats including 35 interventions addressed at the Hospital Veterinário do Restelo. The mortality and complications rates observed were calculated and the main complications associated were described, as well as the corrective measures implemented.

Methods: Patients were randomised to off-pump coronary artery bypass grafting (OPCAB) or conventional coronary artery bypass grafting with cardiopulmonary bypass (CABG-CPB). Small intestine function was assessed by differential four sugars (0=methyl-D-glucose, D-xylose, L-rhamnose, and Lactulose) permeability and absorption tests before surgery, at day 1 and day 5 post-surgery. Liver function was assessed before and at the end of surgery by monoethylglycinexyhdide (MEGX)/Iidocaine ratios after injection of 1 mg/kg bolus of lidocaine and by serial measurements of transaminases (AST and ALT), bilirubin, and alkaline phosphatase (ALP).

Zusammenfassung Gefäßerkrankungen und Diabetes mellitus nehmen als Krankheiten der modernen Zivilisation zu. Sie gehen oft mit dem Risiko einer Amputation einher. Trotz verbesserter Therapie aufgrund des medizinischen Fortschritts steigen die Amputationsraten. Besonders gefährdet sind Patienten mit Diabetes mellitus. Aufgrund des besonderen Atherosklerosebefallsmusters mit Verschluss der kruralen Gefäße bei relativer Aussparung der Oberschenkel- und Fußarterien erzielen pedale Bypässe bei diabetischen Patienten besonders gute Ergebnisse im Hinblick auf die Wiederherstellung der Fußdurchblutung. Ein pedaler Bypass kann eine drohende Amputation oft verhindern. Voraussetzungen für eine pedale Bypass-Operation sind umfassende anatomische Kenntnisse über die Variabilität der Arterien im Operationsgebiet. Die vorliegende Arbeit befasst sich mit den Gefäßvariationen an Unterschenkel und Fuß. Mit unterschiedlichen Methoden wurden Alkohol-fixierte (n=12) und Thiel-fixierte (n=10) Beinpräparate auf arterielle Variabilität untersucht. Die Alkohol-fixierten Präparate wurden makroskopisch präpariert und fotografisch dokumentiert, außerdem erfolgte eine Probenentnahme zur histologischen Untersuchung der Atherosklerosegrade in verschiedenen Gefäßregionen (n=32) und die Herstellung von zwei Dauerpräparaten. An Thiel-fixiertem Material wurde die Digitale Subtraktionsangiographie (DSA) getestet. Folgende Fragestellungen waren zu beantworten: 1. Welche Variationen der Blutgefäße finden sich für den Unterschenkel und Fuß? Wie kommunizieren die Gefäße zwischen Fußsohle und Fußrücken? 2. Wie können kleinste Gefäße am Fuß präpariert und fotografisch dokumentiert werden? 3. Lässt sich an fixiertem Leichenmaterial eine Digitale Subtraktionsangiographie durchzuführen? 4. Zeigen proximale und distale Blutgefäße des Beines einen unterschiedlichen Befall der Atherosklerose? 5. Welche Bedeutung hat die Herstellung von Dauerpräparaten für den studentischen Unterricht? 6. Welche Bedeutung hat die makroskopische Anatomie für die Klinik? Die Ergebnisse und Schlussfolgerungen sind: 1. Während der makroskopischen Präparation fanden sich folgende Variationen: Trifurkation, Truncus tibiofibularis anterior mit hohem Abgang der A. tibialis posterior und Abgang der A. tibialis anterior aus der A. fibularis, eine sehr dominante A. fibularis bei schwach ausgeprägter A. tibialis posterior, ein Arcus plantaris durch den zweiten intermetatarsalen Spalt laufend, kräftig ausgebildete A. plantaris profunda, kräftiger tiefer Ast der A. plantaris medialis, stark ausgeprägte A. arcuata. Die den Arcus plantaris versorgenden Arterien, vor allem die A. plantaris lateralis und die A. plantaris profunda, variieren stark in ihrer Ausprägung. Sie sind Teil der „Ringanastomose”, die eine Durchblutung des Fußes über die Verbindungen verschiedener Gefäße zwischen Fußsohle und Fußrücken gewährleistet. Neben der A. plantaris profunda, die auch als Ramus perforans I bezeichnet wird, gibt es zwischen den Aa. metatarsales plantares und dorsales Verbindungen, die Rr. perforantes II-IV, die bei schwach ausgeprägter A. plantaris profunda die Gefäßversorgung sicherstellen und entsprechend stärker ausgebildet sein können. Die A. fibularis kann über ihre kommunizierenden Äste, dem Ramus perforans zur A. dorsalis pedis oder dem Ramus communicans zur A. tibialis posterior, an der arteriellen Versorgung der Fußsohle beteiligt sein. Bei schwacher Ausbildung der A. tibialis posterior und/oder A. tibialis anterior kann diese durch die A. fibularis als phylogenetisch ältestes und damit konstantestes Gefäß der drei Unterschenkelarterien sogar teilweise oder vollständig ersetzt werden. Die „Ringanastomose“ hat für die Gefäßchirurgie eine große Bedeutung. Beim popliteodistalen Bypass orientiert sich die Wahl des distalen Anschlussgefäßes daran, über welches Gefäß sich der Arcus plantaris angiographisch füllt. Eine Kollateralbildung beim Erwachsenen infolge atherosklerotischer Veränderungen über ursprünglich embryologische Gegebenheiten ist denkbar. 2. Die makroskopische Präparation kleinster Gefäße am Fuß wird durch die Injektion der roten Injektionslösung Microfil® erleichtert. Zur fotografischen Dokumentation ist eine Farbmarkierung der Arterien von außen notwendig, um den Gefäßverlauf sichtbar zu machen. 3. Digitale Subtraktionsangiographie an Leichenmaterial ist nur an Thiel-fixiertem Material möglich, da diese Methode die Gewebeverhältnisse in ihrer natürlichen Konsistenz erhält. Das Einbinden der Schleusen und die Injektion von Kontrastmittel in das Gefäßsystem sind durchführbar, weil die Gefäßlumina durchgängig bleiben. Alkohol- oder Formaldehyd-fixiertes Material ist für diese Zwecke ungeeignet, da das Gewebe aushärtet und in den Gefäßen befindliche Blutreste koagulieren. Dadurch wird eine Kontrastmittel-Injektion unmöglich. 4. Dass histologische Färbungen an langzeitfixiertem Material möglich sind, konnte bestätigt werden. Nach Modifikation der Färbevorschriften erlauben sie die Bewertung des Atherosklerosegrades. Der schwerste Befall mit Grad 4 befindet sich in den Arterien der Kniekehle. Die Fußarterien sind mit Grad 2 geringer befallen. 5. Dauerpräparate verbleiben in der anatomischen Lehrsammlung bzw. im Fundus von Anschauungsmaterial. Sie werden zukünftig zur Demonstration anatomischer Strukturen im Rahmen klinischer Kurse und im Studentenunterricht verwendet. 6. Die Anatomie als Grundlagenfach der Medizin hat in der Lehre einen hohen Stellenwert und in allen Studienabschnitten eine hohe klinische Relevanz. Gemeinsame Lehrveranstaltungen von Anatomie und Klinik wecken bei Studenten großes Interesse und fördern die Motivation. Im Rahmen der ärztlichen Aus- und Weiterbildung werden in klinischen Kursen am Institut für Anatomie beispielsweise Untersuchungsmethoden und Operationsbedingungen simuliert. Kliniker wiederholen, festigen oder vertiefen ihre anatomischen Kenntnisse. Vor allem die chirurgischen Fächer profitieren von diesen praktischen Trainingsmöglichkeiten. Wie die Arbeit am Beispiel der Gefäßchirurgie zeigt, bedingt eine gute Zusammenarbeit zwischen Anatomie und Klinik eine sichere klinische Praxis und eine lebendige Anatomie mit klinischen Bezügen<br>Summary Vascular diseases and diabetes mellitus show rising frequency in the Western world and are often accompanied by amputation. The amputation rate is still increasing despite major developments in diagnostics and therapy. Especially patients with diabetes mellitus are at high risk. Because of the special pattern with more severe atherosclerosis in the crural vessels than in the femoral and pedal arteries, the pedal bypass surgery provides excellent vessel patency and limb salvage rates in diabetic patients and can often prevent amputation. A solid knowledge about anatomical variations in the operating area is a precondition for bypass operations. This dissertation deals with variations of arteries from the lower leg and foot. Lower legs from alcohol-fixed and Thiel-fixed cadavers were examined with different methods: The alcohol-fixed legs (n=12) were dissected macroscopically for variations of the arteries and documented by photographes. Samples along the vessel course (n=32) were taken for histological evaluation of the atherosclerotic degrees. Two legs were plastinated with polyethylene glycol. The Thiel-fixed legs (n=10) were tested for digital subtraction angiography (DSA). The following questions had to be answered: 1. Which arterial variations can be found for the lower leg and foot? How do the vessels communicate between the sole and the dorsum of the foot? 2. How are small foot vessels dissected for photographical documentation? 3. Can Thiel-fixed material be used for DSA? 4. Do proximal and distal vessels show different degrees of atherosclerosis? 5. Which relevance does plastination have for the medical education? 6. How important is Gross anatomy for the clinicians? Results and conclusions: 1. The following variations occurred: trifurcation, anterior tibiofibular truncus with high branching from the posterior tibial artery and the anterior tibial artery originating from the fibular artery, dominant fibular artery, plantar arch running through the second interosseus space, dominant deep plantar artery, dominant deep branch of the medial plantar artery, prominent arcuate artery. The arteries for the plantar arch, supplying most of the foot arteries, show a high diversification. They are part of the “ring anastomosis” which assures a good blood supply via different vessels connecting the dorsum and the sole of the foot. Beside the deep plantar artery, also named as “perforating branch I”, there are other connecting branches between the plantar and dorsal metatarsal arteries - the perforating braches II, III and IV. These branches are highly developed in case of an undeveloped deep plantar artery. The fibular artery can be involved in the blood supply of the foot via a communicating branch to the posterior tibial artery and the perforating branch to the dorsalis pedis artery. The fibular artery, which is phylogenetically the oldest crural vessel, can be highly developed in case of inferior anterior tibial artery and/or posterior tibial artery. The “ring anastomosis” is very important for vascular surgery. The inflow and outflow vessels of a popliteodistal bypass are chosen after angiography of the plantar arch showing the vessel for the supply of the plantar arch. 2. Macroscopical dissection of very small foot vessels can be facilitated by injection of a special plastic, Microfil®-solution. The arteries have to be additionally coloured by help of special markers for photographical documentation. 3. DSA can just be done with Thiel-fixed material. Thiel-fixation allows DSA because maintained in situ conditions. The blood is not coagulated and the vessels stay patent for contrast medium. Alcohol-fixed or formaldehyde-fixed material is not suitable for DSA because of clotted blood in the vessels impeding injection of contrast agent. 4. It is confirmed that histological examination is possible with long fixed material. After modification of the staining protocol the sections could be used for evaluation of the atherosclerotic degree. The popliteal arteries are more affected with degree 4 in comparison to the foot arteries with degree 2. 5. Plastinates are displayed in the anatomical collection of the Institute for Anatomy. They will be used for anatomical demonstrations in the lessons of students and in clinical courses. 6. Anatomy as basic knowledge is very important for teaching medical students and has a high clinical relevance in every phase of the medical course. Interdisciplinary lessons between anatomy and clinical disciplines awake interest and motivate students. Advanced medical training is obtained at the Institute for Anatomy by simulating endoscopic examination and developing new surgical techniques. Clinicians repeat, stabilize and deepen their anatomical knowledge. Especially surgeons benefit from these training possibilities. Using the example of vascular bypass surgery the present dissertation shows the value of a good cooperation between anatomy and clinic to provide a safe clinical practice and a lively anatomy with clinical references

[Truncated abstract] Cardiac surgery involving cardiopulmonary bypass is a complex procedure that results in significant changes to blood coagulation, fibrinolytic biochemistry, platelet number and function, and the vasculature. These are due to pharmacological agents which are administered, haemodilution and contact of the blood with artificial surfaces. Consequently there are significant risks of thrombosis and haemorrhage associated with this procedure. The research presented in this thesis utilises in vitro, in vivo, and a novel ex vivo model to investigate the nature of the haemostatic defect induced by cardiopulmonary bypass. The components studied include the drugs heparin, protamine sulphate, and aprotinin, different types of bypass circuitry (including heparin bonded circuits) and procedures such as acute normovolaemic haemodilution. Patient variables, such as Factor V Leiden, are also studied. Each of these components is assessed for the effects on a number of laboratory measures of haemostasis including activated partial thromboplastin time, prothrombin time, activated protein C ratio, antithrombin concentration, heparin concentration, thrombin-antithrombin complex formation, prothrombin fragment 1+2 formation, markers of platelet surface activation and secretion, activated clotting time, haemoglobin concentration and coagulation factor assays.

Antalet personer som klassificeras som överviktiga ökar i stadig takt och antalet personer som lider av fetma har fördubblats sedan 1980. Kraftig övervikt och fetma medför komplikationer som påverkar livskvaliteten hos personer negativt. Då individer har svårigheter med att gå ned i vikt på naturlig väg övervägs genomförandet av en gastric bypass. Livskvalitet är något varje människa upplever subjektivt och innefattar psykisk och fysisk hälsa, sociala relationer och känsla av självständighet. Syftet med studien är att beskriva livskvaliteten hos patienter som genomgått en gastric bypass. Metoden som valdes var litteraturstudie studien och utfördes enligt Polit &amp; Becks (2012) niostegsmodell. Artiklarna söktes fram i PubMed och CINAHL och data ifrån 16 sammanställdes. Resultatet delades in i livskvalitet med underrubrikerna fysisk livskvalitet och psykisk livskvalitet. Resultatet visar att gastric bypass är ett effektivt sätt för att gå ner i vikt, förebygga överviktsrelaterade symtom samt att höja livskvaliteten. Mentala besvär förekommer hos många patienter och det är viktigt att belysa det efter ingreppet. Slutsats livskvaliteten höjs i samband med att patienter går ned i vikt.

Turbofan engines are normally bench-tested with a standard flared bellmouth intake. This is different from the aircraft situation. As a result, an engine installation may experience a degree of inlet flow distortion not normally present during tests. It is, therefore, very desirable to understand the effect of any radial inlet total pressure loss on turbofan engine performance. Steady-state radial inlet distortion may occur, for example, as a result of boundary layers. An early awareness on distortion tolerance is very important to enable the prediction of surge margin. However, synthesis of turbofan performance with distortion is currently not available. This work therefore, investigates in detail the modelling of the fan component of low bypass-ratio turbofan engines within an engine performance simulation program. For example, the air flow in turbofan engines is split after the fan between the core gas generator and the bypass flow. A fan model must be able to simulate the required flow and thermodynamic parameters to the core and bypass flows at fan exit. Conventional fan models, however, are restricted to a fixed bypass ratio versus non-dimensional speed schedule at which the fan has been rig-tested. The fan component also experiences a varying degree of inlet total pressure distortion. Existing engine simulation fan models are unable to quantify this effect on fan performance and on engine performance. The turbofan modelling work conducted here is preceded by an analysis of rig data of Low Bypass Ratio (LBPR) turbo-fan engines to give a firm background basis. The engine modelling uses the component-based iterative solution method for gas turbine performance calculations. Two key outcomes of the work are the following. Firstly, LBPR fans have large circumferential fan exit flow variations as well as radial variations. This includes total temperature profiles which are an order of magnitude higher than those for High Bypass Ratio Fans (HBPR) fans. Secondly, it is inconclusive, at a given non-dimensional speed and flow function, as to whether fan exit profiles are independent of BPR. The fan radial profile modelling starts from an existing modification of a conventional compressor characteristic but also models in 2-D with dependency on the fan exit radial position. The inlet distortion fan model uses a throughflow streamline curvature for radial performance prediction coupled to the 2-D-LBPR fan model. Against this background, a new fan characteristic model has been devised for LBPR fans. In addition, a new inlet distortion performance model has been developed which is able to predict engine performance changes with radial inlet total pressure distortion.

Ischaemic heart disease (IHD) is the leading cause of death worldwide and according to the World Health Organisation the number of patients with IHD will reach 19 million by 2020 if current trends continue. While coronary artery bypass graft (CABG) surgery remains the treatment of choice for the severest form of the disease, the detrimental effects of peri-operative myocardial injury particularly in the form of myocardial ischaemia-reperfusion injury (IRI) accounts for significant levels of morbidity and mortality particularly in high-risk patients. The past four decades have seen advances in cardioprotective strategies especially within the disciplines of cardioplegia and anaesthesia. Despite this, improvements in patient survival have been limited. Researchers and clinicians alike have called for novel ways of protecting the heart, directing their attention to cellular and mitochondrial pathways which may hold the key to improving survival. This thesis covers a fascinating exploration into the cardioprotective effects brought about by the inhibition of the mitochondrial permeability transition pore (mPTP) using cyclosporin A (CsA), as well as the role of remote ischaemic preconditioning (RIPC) in limiting the extent of myocardial injury in the setting of complex cardiac bypass surgery. In summary, this thesis examines both pharmacological and non-pharmacological strategies for protecting the heart in the setting of cardiac surgery. Despite decades of advancement in research within this field, the consequences of ischaemia-reperfusion injury remain ever-present. As a result, it is hoped that the research in this thesis will make a positive contribution to the body of evidence currently available for the benefit of patients with IHD.

<p> This thesis explores the spiritual-bypass phenomenon identified by John Welwood and how it can be a defense against wholeness as defined in Jungian psychology. Using hermeneutic and heuristic methodologies, and drawing on depth psychological theories, the author discusses the various forms of spiritual bypass and the underlying shadow dynamics, such as emotional repression. The author examines the nature of psychological and spiritual development through states and stages of consciousness development, healthy transcendence versus unhealthy transcendence, and the Jungian process of individuation toward wholeness. The research also explores contributing factors to spiritual bypass including the effect of early childhood attachment style and demonstrates the significance of integrating psychological development in a spiritual path. Finally, the author provides suggestions for therapists working with clients who may be in spiritual bypass.</p>

Obesity is increasingly recognised as a major health threat in the developed world, with more than 120 million people worldwide classified as clinically obese. Increased weight causes increased morbidity and mortality due to its association with cardiovascular disease, diabetes and certain cancers. Bariatric surgery is currently the most efficacious treatment for morbid obesity and has the best long-term outcomes. Bariatric surgery is not without risks. Some of the early risks include postoperative bleeding, anastomotic leaks, and venous thromboembolism. Late complications include marginal ulcer formation, nutritional deficiencies and small bowel obstruction. The latter may be caused by internal hernia formation. In this thesis, an analysis of the causes of small bowel obstruction after laparoscopic Roux-en-Y gastric bypass (LRYGB) is presented, looking specifically at internal hernia formation. A detailed account of the presentation and radiological findings of internal hernia following laparoscopic gastric bypass is provided. The impact of altering surgical technique on the occurrence of internal hernia is analysed: an Observational Clinical Human Reliability Assessment (OCHRA) tool was used for root cause analysis of internal hernia following gastric bypass and in the final study, the employment of a new technique demonstrated significant reduction in the incidence of internal hernia.

Este trabalho foi realizado no âmbito da conclusão do Mestrado Integrado em Medicina Veterinária, e encontra-se dividido em três partes. A primeira parte é referente à casuística acompanhada no decorrer do estágio curricular, no período de 2 de setembro de 2019 até 29 de fevereiro de 2020, no Hospital Veterinário do Restelo. A segunda parte consiste numa revisão bibliográfica referente ao tema “bypass ureteral subcutâneo na ureterolitíase felina”. Na terceira parte é realizada a apresentação de um caso clínico e a sua discussão. A ureterolitíase é a principal causa de obstrução ureteral em gatos. A colocação do bypass ureteral subcutâneo é uma técnica relativamente recente, que tem vindo a substituir as técnicas cirúrgicas convencionais na resolução ureterolitíase em gatos, sendo considerada o tratamento de eleição para gatos com obstrução ureteral; Subcutaneous ureteral bypass in feline ureterolithiasis Abstract: This thesis was carried out within the scope of the conclusion of the Master’s Degree in Veterinary Medicine, and is divided into three parts. The first part refers to the casuistry followed during the curricular internship, from September 2, 2019 to February 29, 2020, at the Hospital Veterinário do Restelo. The second part consists of a bibliographic review on the subject “subcutaneous ureteral bypass in feline ureterolithiasis”. In the third part there is a presentation of a clinical case and its discussion. Ureterolithiasis is the main cause of ureteral obstruction in cats. Subcutaneous ureteral bypass placement is a relatively recent technique, which has been replacing conventional surgical techniques in resolving ureterolithiasis in cats, being considered the treatment of choice for cats with ureteral obstruction.

Tunnel Seismic Prediction (TSP) is a geophysical investigation method used to predict the rock conditions ahead of the tunnel face. The method has been used in different types of rock and rock conditions. The Swedish Transport Administration, Trafikverket, has used the investigation method in multiple locations in the large infrastructure project E4 The Stockholm Bypass. The method is however rather new to Swedish rock conditions, and there is therefore a need to evaluate the method to assess its strengths and weaknesses. In this thesis, the TSP method is compared to other investigation methods used in the Stockholm Bypass project at the location Sätra-Kungshatt where the tunnels cross underneath Lake Mälaren. The investigation methods include geological mapping and Measurement While Drilling (MWD). The TSP results are also compared to the engineering geological prognosis. An evaluation of how the seismic primary and secondary waves, Vp and Vs, correlates to rock quality was carried out, and a linear regression analysis was performed to determine if the wave velocities found using the TSP method correlate with the Q value retrieved through the geological mapping. It was found that the TSP method is capable of detecting weaker zones of rock mass, however no correlation between the wave velocities and the Q value used to describe the quality of the rock mass was found. When comparing the TSP results to the MWD results, it was found that the methods could be used as complements to each other as the different methods sometimes detected weakness zones where the other method did not. As the geology in this location of Stockholm Bypass overall was found to be complex with rather poor rock mass quality, it could be concluded that the TSP method might be better suited for less complex geology where the contrast in rock quality is greater.<br>Tunnel Seismic Prediction (TSP) är en geofysisk undersökningsmetod för att tillhandhålla en prognos av berget framför tunnelstuffen. Metoden har använts i olika typer av berg och bergförhållanden. I Sverige har metoden använts av Trafikverket vid flertalet tillfällen i infrastrukturprojektet E4 Förbifart Stockholm. Metoden är dock relativt ny för de svenska bergförhållandena, vilket gör att det finns ett behov av att utvärdera metodens styrkor och svagheter i dessa förhållanden. I detta masterprojekt har resultaten som tillhandahållits från TSP-metoden jämförts med resultat från andra undersökningsmetoder som använts vid vattenpassagen vid Sätra-Kungshatt där tunneln korsar under Mälaren. Dessa undersökningsmetoder inkluderar geologisk kartering och Measurement While Drilling (MWD). TSP-resultaten har även jämförts med den ingenjörsgeologiska prognosen för området. Vikt har lagts på hur den seismiska primärvågen, Vp, och sekundärvågen, Vs, förhåller sig till den karterade bergkvaliteten. En regressionsanalys har även utförts för att avgöra om resultaten från TSP-metoden korrelerar med resultaten från den geologiska karteringen. Jämförelsen mellan de olika undersökningsmetoderna visade på att TSP kan påvisa svaghetszoner i bergmassan. Dock kunde ingen korrelation mellan våghastigheterna och Q värdet påvisas. Jämförelsen mellan TSP och MWD visade att de båda metoderna generellt visade liknande resultat. Dock kunde vissa avvikelser mellan resultaten från metoderna hittas, vilket göra att metoderna skulle kunna användas som komplement till varandra. Detta då de olika metoderna ibland kunde identifiera svaghetszoner som den andra metoden inte kunde identifiera. De svåra geologiska förhållandena på platsen kan ha bidragit till att TSP-resultaten över lag är relativt svårtolkade, vilket gör att TSP-metoden möjligtvis är bättre lämpad för mindre komplexa bergförhållanden där kontrasten mellan bra och dålig bergkvalitet är tydligare.

Thesis (M. S.)--Mechanical Engineering, Georgia Institute of Technology, 2005.<br>David N. Ku, Committee Chair ; Alexander Rachev, Committee Co-Chair ; Elliot L. Chaikof, Committee Member. Includes bibliographical references.

This study proposes the use of a pipe line system to transport the inflow sediment to a reservoir through the dam, and discharge it downstream. The system is powered by the available head at the dam. It aims at restoring the original sediment transport regime of the river (i.e. before the dam was built). The idea is fundamentally sound because of the much more efficient sediment transport characteristics of pipes compared to that of open channels. The necessary theory for the hydraulic design of such a system was simply not available and is developed in this study. The work of numerous previous investigators is summarized in the final results and in the developed equation which allows for the calculation of the capacity transport concentration of sediments in pipes. This equation, coupled with the most accepted head loss equation, and the continuity principle, allows for the hydraulic design of systems transporting grannular material. The calculation procedures were fitted into computer programs. In addition to computer programs, design charts where developed which allow for quick application as well as visualization of the developed concepts. It was concluded that the proposed system is fundamentally feasible. Although no economic analysis was conducted, indicators show that it is also economically favorable.

Coronary artery disease is the leading cause of death in North America. The invasiveness of its treatment depends on its severity; less severe disease can be treated pharmacologically or surgically without significantly different outcomes, but coronary artery bypass grafting (CABG) clearly reduces mortality among medium- and high-risk patients compared to percutaneous and non-surgical intervention. Although the majority of patients undergoing surgical revascularization emerge without severe postoperative complications, a significant portion of patients encounter a postoperative complication known as low cardiac output syndrome which can quadruple the overall mortality rate for CABG. Intraoperative ischemia reperfusion injury is a major factor in the development of low cardiac output syndrome; so effective intraoperative myocardial protection is central to reducing its incidence, and represents an opportunity to considerably improve patient outcomes. The introductory chapter of this thesis describes the origin and role of reactive oxygen species (ROS) in myocardial ischemia-reperfusion injury. In addition, it introduces key strategies targeted to reduce ROS-mediated myocardial ischemia-reperfusion injury, highlighting key clinical studies that translated these strategies to reduce the severity of ischemia-reperfusion injury during CABG. The central hypothesis of the clinical project on which this thesis is based states that propofol reduces the incidence of low cardiac output syndrome subsequent to CABG with CPB by decreasing the magnitude of 15-F₂t-isoprostane generation during ischemia-reperfusion. The second chapter introduces propofol, and will review previous studies that explore its cardioprotective potential. The experimental section of this thesis describes the development of a quantitative technique for propofol analysis in whole blood, and its application in a dose finding study that define the parameters for achieving experimentally relevant concentrations of propofol during cardiopulmonary bypass. These two studies were fundamental to the development of a clinical study evaluating ROS generation and the incidence low cardiac output syndrome in patients undergoing CABG surgery. Preliminary results that address the central hypothesis are subsequently presented, along with an alternative proposed mechanism for propofol-mediated cardioprotection. This thesis will conclude with a summary of findings and a description of several future studies aimed at testing, generating, and evaluating new hypotheses.

The purposes of this study were to explore the relationships between uncertainty and quality of life indicators in patients recovering from coronary artery bypass graft (CABG) surgery and to investigate the differences in uncertainty and quality of life indicators between primary CABG patients and reoperation patients. The indicators of quality of life selected for this study were the patient's perception of health status and life satisfaction. A convenience sample of 41 primary CABG patients and 11 reoperation patients who were five to ten months postoperative completed the Mishel Uncertainty in Illness Scale (Community Version) (MUISCV), the General Health Rating Index (GHRI), the Cantril Self-Anchoring Scale, and a patient information sheet. Uncertainty, past life satisfaction, and present life satisfaction did not significantly differ between the primary and reoperation patients. Both groups of patients perceived moderately low uncertainty, and were moderately satisfied with their present lives. Trends in the ratings of past, present, and future life satisfaction suggested that CABG surgery was associated with an improvement in life satisfaction and optimism for the future in both primary CABG patients and reoperation patients. Reoperation patients' perceptions of health status and projections of future life satisfaction were significantly less favorable than those of the primary CABG patients suggesting that the quality of life following CABG surgery is lower for the reoperation patients. Uncertainty was significantly negatively associated with perceptions of health status, present life satisfaction, and future life satisfaction. This finding suggests that higher uncertainty is associated with a lower quality of life in CABG patients who are five to ten months postoperative. The findings were discussed in relation to theoretical expectations, other research studies, and the methodological problems inherent in the study. Implications of the findings for nursing practice were suggested. Recommendations for future research were made.<br>Applied Science, Faculty of<br>Nursing, School of<br>Graduate

Despite the scientific, technological and surgical improvements of the past 50 years organ dysfunction following elective paediatric cardiac surgery utilising cardiopulmonary bypass continues to account for increased complications, often leading to a protracted course in hospital with a longer stay in intensive care and the potential for irreversible organ damage long term. Furthermore, paediatric cardiac surgeons are routinely undertaking more complex operations with a shift from palliation to early correction. This has resulted in younger children being subjected to longer periods on the bypass machine with increased effects on vital organs. This thesis describes two clinical studies designed to further assess and characterise peri-operative cardiac, renal and pulmonary function in children undergoing elective cardiac repair at a tertiary referral centre in Scotland, UK. In the first instance a prospective, observational study was undertaken in forty-five children to examine the use of tissue Doppler imaging in the assessment of peri-operative cardiac function, its relationship to myocardial injury and clinical outcome. Tissue Doppler parameters were obtained using a Vivid 7 ultrasound scanner with a 7-MHz probe pre-operatively, on admission to paediatric intensive care and on day one. Myocardial injury was assessed using Troponin-I on the first post-operative day by a commercially available chemiluminescent immunoassay. In twenty children within this group peri-operative renal function was also investigated using standard estimates of glomerular filtration rate, namely creatinine clearance measured by the kinetic Jaffe method during the first and second twelve hour post-operative periods, in comparison to serum creatinine and the novel biomarker cystatin C. Routine plasma retained pre-operatively and on days 0, 1, 2 and 3 post-operatively was used to measure serum cystatin C and creatinine using a particle-enhanced nephelometric immunoassay and the Roche Creatinine Plus enzymatic assay respectively. The association between cystatin C and recorded perfusion parameters including bypass duration, pump flow, haematocrit, oxygen delivery and Troponin-I was investigated. Peri-operative pulmonary function was evaluated through a phase IV, randomised, double-blind, placebo controlled trial. In total, twenty four children were randomised to receive oral sildenafil or equivalent volume placebo four times the day before surgery. Blood samples were collected peri-operatively to measure serum cyclic guanosine monophosphate with a commercially available competitive enzyme immunoassay. Haemodynamic data and echocardiography were acquired at two and twenty four hours post-operatively including pulmonary vascular resistance index and bi-ventricular contractility. Post-operative oxygenation was also determined at the same time by oxygen delivery and oxygenation index. In Chapter 2, peri-operative cardiac function as assessed by tissue Doppler imaging was examined. The results of this study demonstrated that pre-operatively, bi-ventricular systolic function in the study group was reduced compared with normal controls, displaying a significant step-wise decrease with increasing complexity of lesion. This picture persisted post-operatively predominantly in the right ventricle and was significantly associated with the extent of myocardial injury. Impaired peri-operative left ventricular function correlated with clinical outcomes. In Chapter 3, peri-operative renal function as assessed by cystatin C and its association with parameters of perfusion was examined. The results of this study demonstrated that in comparison to serum creatinine, cystatin C had a superior correlation with glomerular filtration rate in the early post-operative period. An elevated level of this biomarker was significantly associated with bypass duration, minimum pump flow and post-operative myocardial injury. Haematocrit was not directly linked to renal dysfunction in this study although evidence of a critical dysoxic threshold within the kidney was suggested indirectly through oxygen delivery calculations. In Chapter 4, peri-operative pulmonary function and vascular reactivity in association with the pre-operative administration of oral sildenafil (0.5mg/kg, six hourly) was examined. The results of this trial demonstrated that compared to placebo, pre-operative sildenafil resulted in modest elevations of serum cyclic guanosine monophosphate, limited effects on pulmonary vascular resistance index, significant reductions in peri-operative bi-ventricular contractility, significant reductions in post-operative oxygen delivery and a trend for increasing ventilatory support. In summary, the current thesis has demonstrated that in children undergoing corrective cardiac surgery peri-operative bi-ventricular function can be accurately assessed by tissue Doppler imaging which to date has had limited use in this patient group. With regards to renal function, cystatin C was shown to be a better estimate of glomerular filtration rate and a more sensitive marker of early renal dysfunction in children after surgery. Furthermore, cystatin C identified a transient post-operative renal impairment, the magnitude of which was associated with duration of bypass, pump flow and myocardial injury. In relation to pulmonary function, this research identified that pre-operative administration of oral sildenafil to children undergoing cardiac surgery produced limited effects on pulmonary vascular resistance but was associated with reduced ventricular contractility and post-operative oxygenation raising significant concerns over its routine clinical use.

Bakgrund: Övervikt blir allt vanligare vilket även resulterat i ett ökat antal Gastric Bypass (GBP) operationer. Dessa individer påverkades inte bara fysiskt negativt, det var även en påfrestning för välbefinnandet. För vissa individer sågs GBP som deras sista möjlighet till ett hälsosamt liv Syfte: Syftet med studien är att belysa vad patienter upplever ökar hälsan i sin vardag efter en Gastric Bypass. Metod: Fem självbiografier analyserades med hjälp av en kvalitativ analys beskriven av Dahlborg-Lyckhage. Resultat: Analysen visade på vikten av ett adekvat stöd för en känsla av ökat välbefinnande. Det fanns tre typer av stöd: närstående, stödgrupper och religion. Operationen ses som en möjlighet att börja om med ett nytt ”jag” och en ny hälsosammare livsstil. Dessvärre försvann inte alltid matbegäret. För att tillfredställa begäret vände sig vissa till alkohol och droger. För att undvika detta beteende behövde patienten realistiska mål för att säkerställa en hälsosam återhämtning. Diskussion: För att försäkra sig om patientens välbefinnande var ett adekvat stöd viktigt. Sjuksköterskan bör informera patienten om stödgrupper samt beteenden som kunde orsaka beroende. Slutsats: Resultatet gav en bra grund för förståelse av vad GBP patienter var i behov av efter operationen för att uppnå en god känsla av hälsa.<br>Background: Obesity has been rapidly increasing and so has the number of Gastric Bypass (GBP) surgeries. Not only was the individuals’ physical health affected negatively, the perceived health took its toll as well. For some individuals GBP was a last resort to a healthy life. Aim: The aim of this study is to illustrate what patients perceive increase health in their daily life after Gastric Bypass. Method: Five autobiographies were analyzed using a qualitative analysis described by Dahlborg-Lyckhage. Result:  The analysis showed the importance of support after GBP. It consisted of three different types: acquaintances, support groups and religion. The surgery was considered a new beginning, with a new “you” and a new healthier lifestyle. Unfortunately the food urges didn’t always disappear. To satisfy the urges some turned to alcohol and drugs. To avoid this kind of behavior patients needed realistic goals to ensure a healthy recovery. Discussion: To ensure the patient well-being it was important to ensure the patient has proper support. The nurse should inform the patient about support groups as well as the risks of addiction. Conclusion: The result illustrated what GBP patients need in order to obtain health after surgery.

Fetma är allt vanligare idag, och de senaste åren har förekomsten av fetma ökat och bara i Sverige kan en halv miljon vuxna anses lida av fetma och 2.5 miljoner vara överviktiga. Gastric bypass är en kirurgisk behandling mot övervikt som har fyrdubblats inom en femårs period. En bättre livskvalitet har i olika kvantitativa studier kunnat påvisas efter viktminskning, men osäkert hur livskvaliteten ökar efter kirurgi då det ofta speglas negativt i media. I de kvantitativa studierna kan inga nyanser av upplevelser urskiljas. Syftet med denna undersökning var därför att beskriva den subjektiva upplevelsen hos personer som genomgått en gastric bypass. En empirisk studie gjordes med öppna frågor och en kvalitativ innehållsanalys med en induktiv ansats. Resultatet av studien styrker den tidigare forskning som gjorts, då informanterna beskriver en ökad livskvalitet och förbättrad hälsa såväl fysiskt som psykiskt. Operationen har förbättrat informanternas självbild och bidragit till en ökad frihetskänsla. Det tydliggörs hur informanterna upplevt sig vara stigmatiserade och de har skämts för sin fetma. De negativa erfarenheter som framkommit, såsom dumping, har inte haft setts som ett stort problem, utan viktnedgången och de positiva hälsoeffekterna har dominerat. I diskussionen framkommer hur viktigt det är att öka förståelsen för individens problematik samt hur viktig sjuksköterskans roll är att hjälpa individen att tillgodogöra sig aktuell information. Vidare diskuteras att om förväntningarna är orealistiska skapas en större besvikelse vilket eventuellt kan leda till ett missnöje. Det är viktigt att en operation inte ses som en helhetslösning utan som ett verktyg.<br>Program: Sjuksköterskeutbildning

Objectives: To assess neurocognitive function after Coronary Artery Bypass Grafting (CABG); to compare and contrast pre- and post-operative test results and to characterise the degree of change in neurocognitive profiles. To identify neuropsychological patterns associated with different impairment models such as hypoxia and stroke. Methods: A comprehensive neuropsychological battery of tests was administered to a small number of individuals undergoing CABG at pre and post operative stage. In order to minimise practice effects, alternate tests were employed for memory, verbal and visuo-spatial functions. Mood measures were included. Results: There were six variables that indicated significant changes. These changes were in Processing Motor Speed, Verbal Executive function, Verbal, Visual learning and Memory, Verbal functions and Visuospatial functions. There was an overall improvement on mood after CABG. Conclusions: There were different neuropsychological sequelae - considering hypoxia and stroke impairment models - in the participants undergoing CABG via Cardiopulmonary Bypass (CPB). Neuropsychological deficits and improvements were identified.

Cardiopulmonary Bypass (CPB) isolates the heart from the circulatory system. As a result, Coronary Artery Bypass Graft (CABG) surgery has become a common treatment for coronary artery disease (CAD) relieving angina and improving health related quality of life (HRQOL) and mood. However, CABG has been associated with Central Nervous System (CNS) dysfunction and successful surgery can be marred by cognitive impairment and/or poor HRQOL/ mood.

SAMMANFATTNING Bakgrund Fetma och övervikt definieras som ett onormalt överskott på fett som inverkar på en persons hälsa. Antalet överviktiga i världen har nästan fördubblats sedan 1980-talet och i Sverige beräknas tio procent av befolkningen lida av fetma. Att lida av övervikt och fetma kan innebära att en individ lättare drabbas av följdsjukdomar såsom hjärt- kärlsjukdomar, diabetes typ 2 samt vissa typer av cancer. Det finns flera orsaker till fetma, varav några av dessa är hereditet, livsstil och farmakologiska biverkningar. Idag kan fetma behandlas med hjälp av olika metoder. Överviktskirurgi har snabbt kommit att bli en av standardbehandlingarna för vuxna med grav fetma. Gastric bypass är idag ett av de ledande ingreppen inom denna typ av kirurgi. I Sverige genomförs cirka 8600 operationer om året. För att få genomgå en gastric bypass krävs det att individen uppfyller vissa kriterier. Bland annat ska seriösa försök till viktnedgång ha genomförts. Syfte Syftet var att belysa livskvaliteten hos individer som genomgått gastric bypass. Metod En litteraturbaserad studie valdes att genomföras. I studien har femton vetenskapliga artiklar inkluderats som alla tagits fram via databasen PubMed. Inklusionskriterier var att artiklarna skulle vara skrivna på svenska, norska eller engelska, vara genomförda på vuxna människor över 19 år samt vara publicerade de senaste tio åren. Samtliga artiklar har granskats utifrån ett bedömningsunderlag. Resultat I resultatet framkom att livskvaliteten skattades högre en tid efter gastric bypass för att sedan minska något. Många var nöjda med och skulle göra om operationen igen. Den fysiska funktionen och aktiviteten ökade samt sågs förbättringar i komorbiditeter såsom diabetes, hyperlipidemi, gastroesofagal reflux, hypertoni, smärta och sömnapné. Illamående och ofrivillig kräkning var vanligt förekommande besvär en månad efter operationen. Vanliga komplikationer efter ingreppet var striktur och internt bråck. Individer som drabbats av komplikationer rapporterade en lägre livskvalitet över tid. Efter ingreppet sågs en ökad självkänsla och tillfredsställelse med sin kropp. Tillstånd som depression och ångest förbättrades och sexlivet skattades högre efter gastric bypass. Hetsätning minskade och bland många förekom ingen hetsätning alls efter ingreppet. En studie visade dock på att oregelbundna episoder av hetsätning eller att ätande nattetid förekom efter gastric bypass. Slutsats En förbättring av livskvaliteten sågs efter gastric bypass, både ur ett fysiskt och psykiskt perspektiv. Dock förekom svårigheter med kosthållning och komplikationer postoperativt hos ett antal individer. Trots detta skattades ingreppet vara övervägande positivt. Nyckelord: Fetma, Gastric bypass, Fysisk livskvalitet, Psykisk livskvalitet

<p>Fetman i Sverige har under de senaste två decennierna ökat kraftigt. Till följd av detta är hälsokostnaderna relaterat till fetma ansenliga och förväntas öka ytterligare om ingenting görs åt problemet. I denna studie studeras prevention och gastric bypass som alternativa behandlingsmetoder mot fetma sett ur ett samhällsekonomiskt perspektiv. Tre hypotetiska kohorter utvecklas; status quo, effektiv prevention i ungdomsåren samt individer som utvecklar svår fetma opereras med gastric bypass. Dessa kohorter följs under åldern 20-64 år där kostnader och effekter observeras med hjälp av en beslutsträdsmodell. Både gastric bypass och prevention påvisas vara kostnadseffektiva behandlingsmetoder mot fetma. Gastric Bypass visas vara mer effektiv än en studerad befolkningsinriktad preventionsåtgärd. Slutligen påvisas att effektiva högriskpreventioner kan bidra med en högre samhällsnytta än gastric bypass operationer.</p><p> </p><p>Nyckelord: Fetma, Gastric Bypass, Prevention</p><p> </p><br><p>The prevalence of obesity has increased rapidly the past two decades. As a consequence the health expenditures related to obesity are high and are expected to increase if nothing is done.</p><p>The objective of this thesis was to study whether prevention in early years or gastric bypass is the preference from a societal perspective as an intervention to obesity. I develop three hypothetical cohorts; status quo, effective prevention in early years and people whom develop obesity have gastric bypass surgery. The cohorts are followed from age 20 to age 64 where costs and effects are observed using a decision tree model. The results were that both gastric bypass and prevention in early years are found to be cost-effective treatments to obesity. Gastric bypass is found being more effective than a studied population-based prevention. Effective high-risk preventive methods can contribute to a higher benefit to society than a gastric bypass surgery.</p><p> </p><p>Keyword: Obesity, Gastric Bypass, Prevention</p><p> </p>

Bypass transition, i.e. transition of a boundary layer at subcritical Reynolds numbers, has been studied. Fundamental studies of the phenomenon as such have been performed side by side with experiments aimed at controlling, i.e. delaying, transition. The experiments have been performed in three different flow facilities, two with air as the working fluid (a plane channel flow and a wind-tunnel) and one with water (a water channel). From the water channel data the well known low-speed streaks appearing in a boundary layer under a turbulent free stream are found to be correlated with upward motion in the boundary layer. The streaks are found to scale in proportion to the boundary-layer thickness in both the streamwise and wall-normal directions. The streamwise length is around hundred boundary-layer thicknesses. It is found that the secondary instability of the streaks grows slower for disturbances consisting of less than four wavelengths, as compared to continuous wavetrains. Elongated low-speed structures are controlled, first in the plane channel flow and then by a reactive system in the wind-tunnel. In the channel, the breakdown of generated streaks is delayed by applying localized suction under the regions of low velocity. Measurements of the disturbance environment withand without control applied show that both the growth of the secondary instability and its spreading in the spanwise direction are reduced when applying the control. In order to be successful, the control has to be applied to a narrow region (about 1/10th of a streak width) around the position of minimum velocity. The reactive system in the windtunnel, comprising four upstream sensors and four suction ports downstream, inhibits the growth of the amplitude of the streaks for a certain distance downstream of the suction ports. After the inhibited growth the disturbances start to grow again and far downstream the streak amplitude returns to close to the uncontrolled values.<br>QC 20100527

Syfte: Syftet var att utifrån litteratur beskriva livskvaliteten hos patienter som genomgått en gastric bypass-operation samt att granska kvaliteten på urvalsmetoden i de ingående artiklarna. Bakgrund: Övervikt och fetma har ökat markant världen över vilket är ett stort hälsoproblem. Fetma medför en rad hälsorisker och kan påverka livskvaliteten negativt. Gastric bypass är en operation som genomförs för att uppnå viktminskning samt förbättra livskvalitet hos denna patientgrupp. Metod: Litteraturstudien hade en deskriptiv design. Vetenskapliga artiklar söktes i PubMed och 13 inkluderades i studien, dessa artiklar bearbetades och sammanfattades. Huvudresultat: Det har visat sig att livskvaliteten efter en gastric bypass operation förändras. Den fysiska dimensionen av begreppet ökar markant medans den mentala dimensionen har en knapp ökning och tenderar att återgå till den preoperativa utgångspunkten vid ett- och tvåårsuppföljningar. Slutsats: Livskvaliteten efter en gastric bypass ökar men inom begreppet finner författarna markanta skillnader mellan den fysiska och mentala komponenten. Alla individer har individuella behov och det åligger sjuksköterskan att identifiera och tillgodose dessa för att individens ska kunna uppnå en högre livskvalitet även i den mentala komponenten.<br>The aim: The aim of this study was to describe quality of life in patients who had undergone a gastric bypass surgery and examine the quality of the included articles sample. Objective: Overweight and obesity has increased radically worldwide and is a large health problem. Obesity comes with a number of health risks and might have a negative impact on quality of life. Obese patients undergo gastric bypass surgery to achieve weight loss and improve their quality of life. Methods: This study had a descriptive design. Scientific articles were found by searching in PubMed. Thirteen articles where included in the study, these where processed and summarized. Findings: After a gastric bypass surgery it has been discovered that quality of life changes. The physical dimension of the concept increases markedly while the mental dimension has a slight increase and tends to return to the preoperative starting point for one-and two-year follow-ups. Conclusion: Quality of life after gastric bypass increases but within the concept the authors find significant differences between the physical and mental component. Every individual has individual needs, and it is up to the nurse to identify and meet these to achieve a higher quality of life in the mental component.

The permanent cell cycle arrest known as cellular senescence is a major block to tumorigenesis. Currently the effects of latent senescence signaling on disease progression, response to therapy and outcome are poorly understood. Furthermore, the role of microRNAs in the regulation of senescence remains to be fully elucidated. For immortalisation to occur replicative senescence must be bypassed usually by activating a telomere maintenance mechanism (TMM). However, the expression differences between TMMs are also poorly understood. To address these questions a combination of gene expression and miRNA microarray profiling, virtual drug and siRNA kinase screening were utilised. These findings highlight the distinct roles of secretory and damage associated senescence pathways in disease progression and in response to therapy. Examination of the differentially expressed genes between TMMs also highlighted a differentially expressed gene expression network surrounding TERT, regulated by c-Myc and TCEAL7 in TMMs. These findings give further insight into the complex regulation network surrounding senescence signaling during tumorigenesis.

Which criteria to pay attention to is important when finding the optimal pigging frequency. This thesis illustrates the forces acting on a bypass pig in operation. Expressions for both the frictional force and wax removal force have been presented. Results presented in this thesis show that the frictional forces are much higher than the forces for wax removal. The most important factor for the contact forces for a cleaning pig seems to be due to the oversize of the discs. However, it is difficult to obtain accurate values for the friction force without experimental data. The insulating effect of wax deposition on the overall heat transfer has been confirmed by analytical calculation. Results do also show that the simulation software Hysys do not account for wax deposition when estimation the U-value. Pressure drop calculations for a pipe with wax deposition have been done. Results show that the roughness of wax has a large influence on the pressure drop in a pipeline. Ageing of wax leads to higher wax removal forces and may decrease the removal efficiency for a cleaning pig. Pigging operations should happen at a given frequency to prevent wax from hardening. It would be beneficial to have more knowledge about wall adhesion and ageing for the given composition when estimation the wax removal forces