Infrainguinal bypass grafting is an established method in the treatment of patients with femoropopliteal and crural occlusive disease leading to critical lower limb ischaemia (CLI). However, complications related to surgical procedure are not negligible and percutaneous transluminal angioplasty (PTA) has emerged as an alternative. The present thesis covers some aspects of infrainguinal PTA in patients with chronic severe lower limb ischaemia. The records of 217 patients undergoing 272 PTA procedures at various infrainguinal arterial segments were analysed. The indication for intervention was subcritical ischaemia in 76 limbs and critical ischaemia in 177 limbs. The role of duplex ultrasound examination in the selection of patients for PTA was retrospectively evaluated following a prospective validation of the method against angiography. A technically successful PTA was achieved in 89%. The overall 30-day mortality was 2.7%. No patient underwent amputation directly related to failed PTA. The primary success rates at 12 and 60 months following femoropopliteal PTA were 40% and 27% compared, to 51% and 36% in limbs undergoing crural artery PTA. Primary success rate in limbs with SFA occlusion longer than 5 cm was only 12% after 5 years, compared to 32% if the occlusion was equal or less than 5 cm in length (p<0.01). In patients undergoing distal PTA through patent infrainguinal grafts, the primary and primary assisted patency rates at 3 years were 32% and 53%, respectively. The sensitivity of duplex scanning in the selection of lesions for PTA was less satisfactory in the popliteal and crural arteries compared to the superficial femoral arteries. In conclusion, the results of infrainguinal PTA performed for treatment of subcritical or CLI seemed to be inferior to the results of surgical interventions reported in the literature. However, due to the fact that the PTA procedure does not preclude the performance of bypass grafting, it might be an alternative to surgical intervention in limbs with stenotic or short occlusive lesions.

The local corrosion behavior of duplex stainless steel (DSS)is affected by a wide variety of factors. Localized corrosionof DSS frequently starts at micrometer scale inclusions orprecipitates, which are often segregated in theaustenite-ferrite boundary regions. Moreover, due to thepartitioning of the key alloying elements of ferrite (Cr andMo) and austenite (N and Ni), the local interactions betweenthe phases must also be considered. The aim of this doctoral study was to increase the knowledgeabout the local dissolution behavior of DSS in acidic-chlorideenvironments. The recent developments of new local probingtechniques have opened a new frontier in corrosion science,providing valuable local information not accessible in thepast. The local techniques used include electrochemicalscanning tunneling microscopy (EC-STM), scanning probe forcemicroscopy (SKPFM), magnetic force microscopy (MFM), andscanning Auger electron Spectroscopy (SAES), all withmicrometer or sub-micrometer resolution. With EC-STM, it was possible to monitor local dissolutionprocesses on DSS in situ, and in real time. MFM was capable ofimaging the phase distribution in DSS without the need of thetraditional surface etching, while SKPFM revealed that theVolta potential difference between the two phases wasmeasurable and significant. SAES showed that the compositiongradient at the phase boundaries is narrower than 2µm. Different types of DSSs have been studied, from low-alloyedDSS to superduplex. Higher contents of Cr, Mo and Nstrengthened both phases as well as the phase boundaries,resulting in phases having similar corrosion resistance thatshowed a more uniform dissolution behavior. However, the Voltapotential difference between the phases proved to be of thesame order for all the DSSs studied. Austenite was in generalassociated to regions displaying a more noble Volta potentialthan ferrite, resulting in a higher dissolution rate of theferrite next to the austenite phase. <b>Key words:</b>In situ, local dissolution, electrochemical,STM, SKPFM, MFM, SAES, duplex stainless steel, acidic-chloridesolution.

Treatment for varicose veins (VV) is insufficiently evidence based and recurrence rates are high. The aim of this thesis was to study the long-term results after VV surgery, risk factors for recurrences and the effect of preoperative duplex scanning on recurrence rate, quality of life (QoL) and costs. In a follow-up study 89 patients with 100 legs operated on for VV 6–10 years earlier were re-examined with duplex, in 13 cases also with varicography. 57% had incompetent vessels in the groin visible with duplex, equally well defined by varicography. Residual branches could not be differentiated from new vessel formation. The recurrence rate did not correlate to the surgeon’s level of experience or perioperative difficulties at primary surgery. In a prospective randomized study 293 patients (343 legs) were operated on for primary VV with or without preoperative duplex. Duplex was done postoperatively, at 2 months and 2 years. QoL was measured with SF-36 preoperatively, at 1 month, 1 year and 2 years. After 2 years the number of reoperations were 2 in the group with preoperative duplex and 14 in the group without (p=0.002). Incompetent veins were seen in the saphenofemoral or saphenopopliteal junction in 19 and 53 legs respectively (p&lt;0.001). Preoperative QoL was worse in the VV patients compared to a reference population, and was normalised 2 years postoperatively. The improved surgical result in the duplex group was not reflected in a significantly higher QoL. The lower costs for redo surgery in the duplex group did not offset the costs for duplex, partly due to more extensive primary surgery. A significant proportion of recurrences after 2 years was new vessel formation and progression of disease. Preoperative perforating vein incompetence did not influence recurrence rate, and was abolished without specific interruption in 60% at 2 years postoperatively.

Good toughness properties in base and weld material enable the use of duplex stainless steels (DSS) in critical applications. DSS offer high strength compared to common austenitic stainless steels. The high strength can be utilized to reduce the wall thickness and accordingly accomplish reduction of cost, welding time and transportation weight, contributing to ecological and energy savings. Although DSS have been used successfully in many applications the last decades, the full utilisation in pressure vessels has been restricted due to conservative design rules. The consequences of failure in a pressure vessel are often very severe and it is accordingly important to verify a high ductility and fracture toughness. In this study fracture toughness data has been generated that has been used to analyse the brittle failure model in the European pressure vessel code EN 13445. The evaluation of the results has been made successfully by the master curve analysis, previously applied to ferritic steels. The master curve analysis includes calculation of a reference temperature, which can be correlated to an impact toughness transition temperature. A correlation between fracture and impact toughness results is necessary for a practically applicable design code. The heat distribution and austenite reformation have been modelled to verify satisfactory toughness properties in the heat affected zone. A similar model was used to evaluate the nucleation and diffusional growth of sigma phase during isothermal heat treatment or continuous cooling. For future stainless steel development, the availability of satisfactory correlations between composition, microstructure and mechanical properties are essential to optimize alloy design. Stainless steel data has been analysed to find approximate relations between mechanical properties and the chemical composition, grain size, ferrite content, product thickness and solution hardening size misfit parameter. The solution hardening effect was successfully predicted by the Labusch-Nabarro relation and multiple regression analyses were used to evaluate hardening equations for stainless steel. / QC 20100920

One of the greatest challenges facing the nuclear power industry is the final disposition of nuclear waste. To meet the needs of the nuclear power industry, a new fuel assembly design, called DUPLEX, has been developed which provides higher fuel burnups, burns transuranic waste while reducing minor actinides, reduces the long term radiotoxicity of spent nuclear fuel, and was developed for use in current light water reactors. The DUPLEX design considered in this thesis is based on a seed and blanket unit (SBU) configuration, where the seed region contains standard UO2 fuel, and the blanket region contains an inert matrix (Pu,Np,Am)O2-MgO-ZrO2 fuel. The research efforts of this thesis are first to consider the higher burnup effects on DUPLEX assembly thermal-hydraulic performance and thermal safety margin over the assembly’s expected operational lifetime. In order to accomplish this, an existing burnup-dependent thermal-hydraulic methodology for conventional homogeneous fuel assemblies has been updated to meet the modeling needs specific to SBU-type assemblies. The developed framework dramatically expands the capabilities of the latest thermal-hydraulic evaluation framework such that the most promising and unique DUPLEX fuel design can be evaluated. As part of this updated methodology, the posed DUPLEX design is evaluated with respect to the minimum departure from nucleate boiling ratio, peak fuel temperatures for both regions, and the peak cladding temperatures, under ANS Condition I, II, and III transient events with the thermal-hydraulic code VIPRE-01. Due to difficulty in the fabrication and handling of minor actinide dioxides, documented thermal conductivity values for the considered IMF design are unavailable. In order to develop a representative thermal conductivity model for use in VIPRE-01, an extensive literature survey on the thermal conductivity of (Pu,Np,Am)O2-MgO-ZrO2 component materials and a comprehensive review of combinatory models was performed. Using the updated methodology, VIPRE-01 is used to perform steady-state and transient thermal hydraulic analyses for the DUPLEX fuel assembly. During loss-of-flow accident scenarios, the DUPLEX design is shown to meet imposed safety criteria. However, using the most conservative thermal conductivity modeling approach for (Pu,Np,Am)O2-MgO-ZrO2, the blanket region fuel temperatures remain only slightly below the design limit.

<p>MicroRNAs (miRNAs) are small RNAs that have important roles in post-transcriptional gene regulation in a wide range of species. This regulation is controlled by having miRNAs directly bind to a target messenger RNA (mRNA), causing it to be destabilized and degraded, or translationally repressed. Identifying miRNA targets has been a large area of focus for study; however, a lack of generally high-throughput experiments to validate direct miRNA targeting has been a limiting factor. To overcome these limitations, computational methods have become crucial for understanding and predicting miRNA-gene target interactions.</p><p>While a variety of computational tools exist for predicting miRNA targets, many of them are focused on a similar feature set for their prediction. These commonly used features are complementarity to 5'seed of miRNAs and evolutionary conservation. Unfortunately, not all miRNA target sites are conserved or adhere to canonical seed complementarity. Seeking to address these limitations, several studies have included energy features of mRNA:miRNA duplex formation as alternative features. However, different independent evaluations reported conflicting results on the reliability of energy-based predictions. Here, we reassess the usefulness of energy features for mammalian target prediction, aiming to relax or eliminate the need for perfect seed matches and conservation requirement.</p><p>We detect significant differences of energy features at experimentally supported human miRNA target sites and at genome-wide interaction sites to Argonaute (AGO) protein family members, which are essential parts of the miRNA machinery complex. This trend is confirmed on data sets that assay the effect of miRNAs on mRNA and protein expression changes, where a statistically significant change in expression is noted when compared to the control. Furthermore, our method also allows for prediction of strictly imperfect sites, as well as non-conserved targets.</p><p>Recently, new methods for identifying direct miRNA binding have been developed, which provides us with additional sources of information for miRNA target prediction. While some computational target predictions tools have begun to incorporate this information, they still rely on the presence of a seed match in the AGO-bound windows without accounting for the possibility of variations. </p><p>We investigate the usefulness of the site level direct binding evidence in miRNA target identification and propose a model that incorporates multiple different features along with the AGO-interaction data. Our method outperforms both an ad hoc strategy of seed match searches as well as an existing target prediction tool, while still allowing for predictions of sites other than a long perfect seed match. Additionally, we show supporting evidence for a class of non-canonical sites as bound targets. Our model can be extended to predict additional types of imperfect sites, and can also be readily modified to include additional features that may produce additional improvements.</p> / Dissertation

The austenitic stainless steel 316L has been compared to duplex stainless steels to be able to highlight a choice of material for manufacturing of spare tanks used for cooling water at nuclear power stations on the Swedish west coast. In this report 316L and the duplex stainless steels 2205, 2304 and LDX 2404 have been compared according to corrosion resistance, strength, manufacturing aspects and prices. The steels arranged by increasing corrosion resistance: 316L &lt; 2304 &lt; LDX 2404 &lt; 2205. The steels arranged by increasing strength (considering the thickness of the plates needed for construction): 316L &lt; 2304 &lt; LDX 2404 and 2205. The steels arranged by increasing price/tank: 2304 &lt; LDX 2404 &lt; 2205 &lt; 316L. One of the duplex stainless steels is recommended rather than the austenitic stainless steel 316L. In terms of price 2304 is preferable to 2205 and LDX 2404. When it comes to corrosion resistance 2205 is superior to 2304 and can sometimes be considered as unnecessary good and therefore not relevant for this application.

Bakgrund: Venduplex har på senare år vuxit fram som den mest använda metoden vid diagnostik av venös insufficiens eftersom det är en ofarlig, kostnadseffektiv, non-invasiv metod med hög sensitivitet och specificitet där både den anatomiska placeringen av insufficiensen samt den funktionella förändringen av venen kan påvisas direkt vid undersökningen. Olika manövrar kan genomföras för att påfresta venklaffarna och därmed framkalla en eventuell reflux, men det är oklart om de olika manövrerna kan påverka den reflux som provoceras fram och därmed också påverkar bedömningen av insufficiensgraden. Syfte: Syftet med studien var att undersöka om det förelåg skillnad i graderingen av insufficiensen samt om den maximala refluxhastigheten påverkades beroende på vilken manöver som användes för att framkalla en reflux. Metod: 20 v. saphena magna mitt på låret med påvisad reflux deltog i studien. Två upprepade mätningar genomfördes där venklaffarna provocerades med hjälp av en blodtrycksmanschett över vaden, med en manuell kompression över låret samt med en manuell kompression över vaden. Resultat: Den maximala refluxhastigheten blev 0,33±0,20m/s när en blodtrycksmanschett över vaden användes, 0,31±0,22m/s när en manuell handkompression över vaden användes samt 0,17±0,16m/s när en manuell lårkompression genomfördes. Slutsats: Ingen signifikant skillnad på maximal refluxhastighet kunde konstateras när en automatisk uppblåsbar blodtrycksmanschett över vaden jämfördes med en manuell handkompression över vaden. En signifikant högre maximal refluxhastighet konstaterades när en manuell vadkompression jämfördes med en manuell lårkompression.

Duplex stainless steels have a microstructure that consists of almost equal shares of austenite and ferrite, which leads to excellent material properties. During production and processing, the steel can be exposed to high temperatures which leads to the development of a third (sigma) phase, and thus to a change in material properties. The objective of this research is to assess the material damage in thermally degraded 2205 duplex stainless steel using nonlinear ultrasonics (NLU). Seven 2205 duplex stainless steel specimens are thermally degraded at 700 C for a series of different time durations. Nonlinear Ultrasonic measurements are conducted in a pitch-catch setup to avoid any adverse nonlinear influences of reflections and wave interference. The material nonlinearity parameter, beta, is then obtained by directly applying the fast Fourier Transform (FFT) to the measured time-domain signal. The results show that the nonlinearity parameter beta increases to a peak at 30 minutes aging time, then droppes to a low at 360 minutes and then increases again for increasing thermal damage. This demonstrates that the nonlinearity parameter has the potential to be used as a quantitative tool to estimate thermal damage in a specimen.

<p>The local corrosion behavior of duplex stainless steel (DSS)is affected by a wide variety of factors. Localized corrosionof DSS frequently starts at micrometer scale inclusions orprecipitates, which are often segregated in theaustenite-ferrite boundary regions. Moreover, due to thepartitioning of the key alloying elements of ferrite (Cr andMo) and austenite (N and Ni), the local interactions betweenthe phases must also be considered.</p><p>The aim of this doctoral study was to increase the knowledgeabout the local dissolution behavior of DSS in acidic-chlorideenvironments. The recent developments of new local probingtechniques have opened a new frontier in corrosion science,providing valuable local information not accessible in thepast. The local techniques used include electrochemicalscanning tunneling microscopy (EC-STM), scanning probe forcemicroscopy (SKPFM), magnetic force microscopy (MFM), andscanning Auger electron Spectroscopy (SAES), all withmicrometer or sub-micrometer resolution.</p><p>With EC-STM, it was possible to monitor local dissolutionprocesses on DSS in situ, and in real time. MFM was capable ofimaging the phase distribution in DSS without the need of thetraditional surface etching, while SKPFM revealed that theVolta potential difference between the two phases wasmeasurable and significant. SAES showed that the compositiongradient at the phase boundaries is narrower than 2µm.</p><p>Different types of DSSs have been studied, from low-alloyedDSS to superduplex. Higher contents of Cr, Mo and Nstrengthened both phases as well as the phase boundaries,resulting in phases having similar corrosion resistance thatshowed a more uniform dissolution behavior. However, the Voltapotential difference between the phases proved to be of thesame order for all the DSSs studied. Austenite was in generalassociated to regions displaying a more noble Volta potentialthan ferrite, resulting in a higher dissolution rate of theferrite next to the austenite phase.</p><p><b>Key words:</b>In situ, local dissolution, electrochemical,STM, SKPFM, MFM, SAES, duplex stainless steel, acidic-chloridesolution.</p>