Uplifted spirits, earthbound machines : studies on artists and the dream of flight, 1900-1935

Doctoral dissertation, Academy of Fine Arts

Experimental thermal hydraulic studies on the enhancement of safety of LWRs

The safe use of nuclear power plants (NPPs) requires a deep understanding of the functioning of physical processes and systems involved. Studies on thermal hydraulics have been carried out in various separate effects and integral test facilities at Lappeenranta University of Technology (LUT) either to ensure the functioning of safety systems of light water reactors (LWR) or to produce validation data for the computer codes used in safety analyses of NPPs. Several examples of safety studies on thermal hydraulics of the nuclear power plants are discussed. Studies are related to the physical phenomena existing in different processes in NPPs, such as rewetting of the fuel rods, emergency core cooling (ECC), natural circulation, small break loss-of-coolant accidents (SBLOCA), non-condensable gas release and transport, and passive safety systems. Studies on both VVER and advanced light water reactor (ALWR) systems are included. The set of cases include separate effects tests for understanding and modeling a single physical phenomenon, separate effects tests to study the behavior of a NPP component or a single system, and integral tests to study the behavior of the whole system. In the studies following steps can be found, not necessarily in the same study. Experimental studies as such have provided solutions to existing design problems. Experimental data have been created to validate a single model in a computer code. Validated models are used in various transient analyses of scaled facilities or NPPs. Integral test data are used to validate the computer codes as whole, to see how the implemented models work together in a code. In the final stage test results from the facilities are transferred to the NPP scale using computer codes. Some of the experiments have confirmed the expected behavior of the system or procedure to be studied; in some experiments there have been certain unexpected phenomena that have caused changes to the original design to avoid the recognized problems. This is the main motivation for experimental studies on thermal hydraulics of the NPP safety systems. Naturally the behavior of the new system designs have to be checked with experiments, but also the existing designs, if they are applied in the conditions that differ from what they were originally designed for. New procedures for existing reactors and new safety related systems have been developed for new nuclear power plant concepts. New experiments have been continuously needed.

Exploring the strategic impact of technological change - Studies on the role of Internet in magazine publishing

Over the past few decades, turbulent change has characterized the situation in the media industry. It has been noted that digitalization and new media are strongly influencing the industry: it is changing the existing market dynamics and requires new strategies. Prior research on the impact of digitalization and the Internet has emphasized news-focused media such as newspaper publishing and broadcasting, yet magazine publishing is very seldom the focus of the research. This study examines how the Internetimpacts magazine publishing. The work presents a multi-level analysis on the role and impact of the Internet on magazine products, companies and industry. The study is founded on strategic management, technology management and media economics literature. This study consists of two parts. The first part introduces the research topic and discusses the overall results of the study. The second part comprises five research publications. Qualitative research methods are used throughout. The results of the study indicate that the Internet has not had a disruptive effect on magazine publishing, and that its strategic implications could rather be considered complementary to the print magazine and the business as a whole. It seems that the co-specialized assets, together with market-related competencies and unchanged core competence have protected established firms from the disruptive effect of the new technology in magazine publishing. In addition, it seems that the Internet offers a valuable possibility to build and nourish customer relationships. The study contributes tomedia management and economics research by moving from product- or industry-level investigations towards a strategic-management perspective.

Supply chain integration: studies on linking customer responsiveness and operational efficiency in logistics policy planning

Abstract The research problem in the thesis deals with improving the responsiveness and efficiency of logistics service processes between a supplier and its customers. The improvement can be sought by customizing the services and increasing the coordination of activities between the different parties in the supply chain. It is argued that to achieve coordination the parties have to have connections on several levels. In the framework employed in this research, three contexts are conceptualized at which the linkages can be planned: 1) the service policy context, 2) the process coordination context, and 3) the relationship management context. The service policy context consists of the planning methods by which a supplier analyzes its customers' logistics requirements and matches them with its own operational environment and efficiency requirements. The main conclusion related to the service policy context is that it is important to have a balanced selection of both customer-related and supplier-related factors in the analysis. This way, while the operational efficiency is planned a sufficient level of service for the most important customers is assured. This kind of policy planning involves taking multiple variables into the analysis, and there is a need to develop better tools for this purpose. Some new approaches to deal with this are presented in the thesis.The process coordination context and the relationship management context deal with the issues of how the implementation of the planned service policies can be facilitated in an inter-organizational environment. Process coordination includes typically such mechanisms as control rules, standard procedures and programs, but inhighly demanding circumstances more integrative coordination mechanisms may be necessary. In the thesis the coordination problems in third-party logistics relationship are used as an example of such an environment. Relationship management deals with issues of how separate companies organize their relationships to improve the coordination of their common processes. The main implication related to logistics planning is that by integrating further at the relationship level, companies can facilitate the use of the most efficient coordination mechanisms and thereby improve the implementation of the selected logistics service policies. In the thesis, a case of a logistics outsourcing relationship is used to demonstrate the need to address the relationship issues between the service provider andthe service buyer before the outsourcing can be done.The dissertation consists of eight research articles and a summarizing report. The principal emphasis in the articles is on the service policy planning context, which is the main theme of six articles. Coordination and relationship issues are specifically addressed in two of the papers.

Studies on integrating kinematic design method with mechanical systems simulation techniques

Theultimate goal of any research in the mechanism/kinematic/design area may be called predictive design, ie the optimisation of mechanism proportions in the design stage without requiring extensive life and wear testing. This is an ambitious goal and can be realised through development and refinement of numerical (computational) technology in order to facilitate the design analysis and optimisation of complex mechanisms, mechanical components and systems. As a part of the systematic design methodology this thesis concentrates on kinematic synthesis (kinematic design and analysis) methods in the mechanism synthesis process. The main task of kinematic design is to find all possible solutions in the form of structural parameters to accomplish the desired requirements of motion. Main formulations of kinematic design can be broadly divided to exact synthesis and approximate synthesis formulations. The exact synthesis formulation is based in solving n linear or nonlinear equations in n variables and the solutions for the problem areget by adopting closed form classical or modern algebraic solution methods or using numerical solution methods based on the polynomial continuation or homotopy. The approximate synthesis formulations is based on minimising the approximation error by direct optimisation The main drawbacks of exact synthesis formulationare: (ia) limitations of number of design specifications and (iia) failure in handling design constraints- especially inequality constraints. The main drawbacks of approximate synthesis formulations are: (ib) it is difficult to choose a proper initial linkage and (iib) it is hard to find more than one solution. Recentformulations in solving the approximate synthesis problem adopts polynomial continuation providing several solutions, but it can not handle inequality const-raints. Based on the practical design needs the mixed exact-approximate position synthesis with two exact and an unlimited number of approximate positions has also been developed. The solutions space is presented as a ground pivot map but thepole between the exact positions cannot be selected as a ground pivot. In this thesis the exact synthesis problem of planar mechanism is solved by generating all possible solutions for the optimisation process ¿ including solutions in positive dimensional solution sets - within inequality constraints of structural parameters. Through the literature research it is first shown that the algebraic and numerical solution methods ¿ used in the research area of computational kinematics ¿ are capable of solving non-parametric algebraic systems of n equations inn variables and cannot handle the singularities associated with positive-dimensional solution sets. In this thesis the problem of positive-dimensional solutionsets is solved adopting the main principles from mathematical research area of algebraic geometry in solving parametric ( in the mathematical sense that all parameter values are considered ¿ including the degenerate cases ¿ for which the system is solvable ) algebraic systems of n equations and at least n+1 variables.Adopting the developed solution method in solving the dyadic equations in direct polynomial form in two- to three-precision-points it has been algebraically proved and numerically demonstrated that the map of the ground pivots is ambiguousand that the singularities associated with positive-dimensional solution sets can be solved. The positive-dimensional solution sets associated with the poles might contain physically meaningful solutions in the form of optimal defectfree mechanisms. Traditionally the mechanism optimisation of hydraulically driven boommechanisms is done at early state of the design process. This will result in optimal component design rather than optimal system level design. Modern mechanismoptimisation at system level demands integration of kinematic design methods with mechanical system simulation techniques. In this thesis a new kinematic design method for hydraulically driven boom mechanism is developed and integrated in mechanical system simulation techniques. The developed kinematic design method is based on the combinations of two-precision-point formulation and on optimisation ( with mathematical programming techniques or adopting optimisation methods based on probability and statistics ) of substructures using calculated criteria from the system level response of multidegree-of-freedom mechanisms. Eg. by adopting the mixed exact-approximate position synthesis in direct optimisation (using mathematical programming techniques) with two exact positions and an unlimitednumber of approximate positions the drawbacks of (ia)-(iib) has been cancelled.The design principles of the developed method are based on the design-tree -approach of the mechanical systems and the design method ¿ in principle ¿ is capable of capturing the interrelationship between kinematic and dynamic synthesis simultaneously when the developed kinematic design method is integrated with the mechanical system simulation techniques.

Technology selection and group decision support systems: Case studies on supporting strategic technology selection processes

The objective of the dissertation is to increase understanding and knowledge in the field where group decision support system (GDSS) and technology selection research overlap in the strategic sense. The purpose is to develop pragmatic, unique and competent management practices and processes for strategic technology assessment and selection from the whole company's point of view. The combination of the GDSS and technology selection is approached from the points of view of the core competence concept, the lead user -method, and different technology types. In this research the aim is to find out how the GDSS contributes to the technology selection process, what aspects should be considered when selecting technologies to be developed or acquired, and what advantages and restrictions the GDSS has in the selection processes. These research objectives are discussed on the basis of experiences and findings in real life selection meetings. The research has been mainly carried outwith constructive, case study research methods. The study contributes novel ideas to the present knowledge and prior literature on the GDSS and technology selection arena. Academic and pragmatic research has been conducted in four areas: 1) the potential benefits of the group support system with the lead user -method,where the need assessment process is positioned as information gathering for the selection of wireless technology development projects; 2) integrated technology selection and core competencies management processes both in theory and in practice; 3) potential benefits of the group decision support system in the technology selection processes of different technology types; and 4) linkages between technology selection and R&D project selection in innovative product development networks. New type of knowledge and understanding has been created on the practical utilization of the GDSS in technology selection decisions. The study demonstrates that technology selection requires close cooperation between differentdepartments, functions, and strategic business units in order to gather the best knowledge for the decision making. The GDSS is proved to be an effective way to promote communication and co-operation between the selectors. The constructs developed in this study have been tested in many industry fields, for example in information and communication, forest, telecommunication, metal, software, and miscellaneous industries, as well as in non-profit organizations. The pragmatic results in these organizations are some of the most relevant proofs that confirm the scientific contribution of the study, according to the principles of the constructive research approach.

R&D Performance Analysis: Case Studies on the Challenges and Promotion of the Evaluation and Measurement of R&D

Due to the intense international competition, demanding, and sophisticated customers, and diverse transforming technological change, organizations need to renew their products and services by allocating resources on research and development (R&D). Managing R&D is complex, but vital for many organizations to survive in the dynamic, turbulent environment. Thus, the increased interest among decision-makers towards finding the right performance measures for R&D is understandable. The measures or evaluation methods of R&D performance can be utilized for multiple purposes; for strategic control, for justifying the existence of R&D, for providing information and improving activities, as well as for the purposes of motivating and benchmarking. The earlier research in the field of R&D performance analysis has generally focused on either the activities and considerable factors and dimensions - e.g. strategic perspectives, purposes of measurement, levels of analysis, types of R&D or phases of R&D process - prior to the selection of R&Dperformance measures, or on proposed principles or actual implementation of theselection or design processes of R&D performance measures or measurement systems. This study aims at integrating the consideration of essential factors anddimensions of R&D performance analysis to developed selection processes of R&D measures, which have been applied in real-world organizations. The earlier models for corporate performance measurement that can be found in the literature, are to some extent adaptable also to the development of measurement systemsand selecting the measures in R&D activities. However, it is necessary to emphasize the special aspects related to the measurement of R&D performance in a way that make the development of new approaches for especially R&D performance measure selection necessary: First, the special characteristics of R&D - such as the long time lag between the inputs and outcomes, as well as the overall complexity and difficult coordination of activities - influence the R&D performance analysis problems, such as the need for more systematic, objective, balanced and multi-dimensional approaches for R&D measure selection, as well as the incompatibility of R&D measurement systems to other corporate measurement systems and vice versa. Secondly, the above-mentioned characteristics and challenges bring forth the significance of the influencing factors and dimensions that need to be recognized in order to derive the selection criteria for measures and choose the right R&D metrics, which is the most crucial step in the measurement system development process. The main purpose of this study is to support the management and control of the research and development activities of organizations by increasing the understanding of R&D performance analysis, clarifying the main factors related to the selection of R&D measures and by providing novel types of approaches and methods for systematizing the whole strategy- and business-based selection and development process of R&D indicators.The final aim of the research is to support the management in their decision making of R&D with suitable, systematically chosen measures or evaluation methods of R&D performance. Thus, the emphasis in most sub-areas of the present research has been on the promotion of the selection and development process of R&D indicators with the help of the different tools and decision support systems, i.e. the research has normative features through providing guidelines by novel types of approaches. The gathering of data and conducting case studies in metal and electronic industry companies, in the information and communications technology (ICT) sector, and in non-profit organizations helped us to formulate a comprehensive picture of the main challenges of R&D performance analysis in different organizations, which is essential, as recognition of the most importantproblem areas is a very crucial element in the constructive research approach utilized in this study. Multiple practical benefits regarding the defined problemareas could be found in the various constructed approaches presented in this dissertation: 1) the selection of R&D measures became more systematic when compared to the empirical analysis, as it was common that there were no systematic approaches utilized in the studied organizations earlier; 2) the evaluation methods or measures of R&D chosen with the help of the developed approaches can be more directly utilized in the decision-making, because of the thorough consideration of the purpose of measurement, as well as other dimensions of measurement; 3) more balance to the set of R&D measures was desired and gained throughthe holistic approaches to the selection processes; and 4) more objectivity wasgained through organizing the selection processes, as the earlier systems were considered subjective in many organizations. Scientifically, this dissertation aims to make a contribution to the present body of knowledge of R&D performance analysis by facilitating dealing with the versatility and challenges of R&D performance analysis, as well as the factors and dimensions influencing the selection of R&D performance measures, and by integrating these aspects to the developed novel types of approaches, methods and tools in the selection processes of R&D measures, applied in real-world organizations. In the whole research, facilitation of dealing with the versatility and challenges in R&D performance analysis, as well as the factors and dimensions influencing the R&D performance measure selection are strongly integrated with the constructed approaches. Thus, the research meets the above-mentioned purposes and objectives of the dissertation from the scientific as well as from the practical point of view.

Project Success through Effective Decisions: Case Studies on Project Goal Setting, Success Evaluation and Managerial Decision Making

The objective of the thesis is to structure and model the factors that contribute to and can be used in evaluating project success. The purpose of this thesis is to enhance the understanding of three research topics. The goal setting process, success evaluation and decision-making process are studied in the context of a project, business unitand its business environment. To achieve the objective three research questionsare posed. These are 1) how to set measurable project goals, 2) how to evaluateproject success and 3) how to affect project success with managerial decisions.The main theoretical contribution comes from deriving a synthesis of these research topics which have mostly been discussed apart from each other in prior research. The research strategy of the study has features from at least the constructive, nomothetical, and decision-oriented research approaches. This strategy guides the theoretical and empirical part of the study. Relevant concepts and a framework are composed on the basis of the prior research contributions within the problem area. A literature review is used to derive constructs of factors withinthe framework. They are related to project goal setting, success evaluation, and decision making. On the basis of this, the case study method is applied to complement the framework. The empirical data includes one product development program, three construction projects, as well as one organization development, hardware/software, and marketing project in their contexts. In two of the case studiesthe analytic hierarchy process is used to formulate a hierarchical model that returns a numerical evaluation of the degree of project success. It has its origin in the solution idea which in turn has its foundation in the notion of projectsuccess. The achieved results are condensed in the form of a process model thatintegrates project goal setting, success evaluation and decision making. The process of project goal setting is analysed as a part of an open system that includes a project, the business unit and its competitive environment. Four main constructs of factors are suggested. First, the project characteristics and requirements are clarified. The second and the third construct comprise the components of client/market segment attractiveness and sources of competitive advantage. Together they determine the competitive position of a business unit. Fourth, the relevant goals and the situation of a business unit are clarified to stress their contribution to the project goals. Empirical evidence is gained on the exploitation of increased knowledge and on the reaction to changes in the business environment during a project to ensure project success. The relevance of a successful project to a company or a business unit tends to increase the higher the reference level of project goals is set. However, normal performance or sometimes performance below this normal level is intentionally accepted. Success measures make project success quantifiable. There are result-oriented, process-oriented and resource-oriented success measures. The study also links result measurements to enablers that portray the key processes. The success measures can be classified into success domains determining the areas on which success is assessed. Empiricalevidence is gained on six success domains: strategy, project implementation, product, stakeholder relationships, learning situation and company functions. However, some project goals, like safety, can be assessed using success measures that belong to two success domains. For example a safety index is used for assessing occupational safety during a project, which is related to project implementation. Product safety requirements, in turn, are connected to the product characteristics and thus to the product-related success domain. Strategic success measures can be used to weave the project phases together. Empirical evidence on their static nature is gained. In order-oriented projects the project phases are oftencontractually divided into different suppliers or contractors. A project from the supplier's perspective can represent only a part of the ¿whole project¿ viewed from the client's perspective. Therefore static success measures are mostly used within the contractually agreed project scope and duration. Proof is also acquired on the dynamic use of operational success measures. They help to focus on the key issues during each project phase. Furthermore, it is shown that the original success domains and success measures, their weights and target values can change dynamically. New success measures can replace the old ones to correspond better with the emphasis of the particular project phase. This adjustment concentrates on the key decision milestones. As a conclusion, the study suggests a combination of static and dynamic success measures. Their linkage to an incentive system can make the project management proactive, enable fast feedback and enhancethe motivation of the personnel. It is argued that the sequence of effective decisions is closely linked to the dynamic control of project success. According to the used definition, effective decisions aim at adequate decision quality and decision implementation. The findings support that project managers construct and use a chain of key decision milestones to evaluate and affect success during aproject. These milestones can be seen as a part of the business processes. Different managers prioritise the key decision milestones to a varying degree. Divergent managerial perspectives, power, responsibilities and involvement during a project offer some explanation for this. Finally, the study introduces the use ofHard Gate and Soft Gate decision milestones. The managers may use the former milestones to provide decision support on result measurements and ad hoc critical conditions. In the latter milestones they may make intermediate success evaluation also on the basis of other types of success measures, like process and resource measures.

Studies on coordination of systems development process

This thesis examines coordination of systems development process in a contemporary software producing organization. The thesis consists of a series of empirical studies in which the actions, conceptions and artifacts of practitioners are analyzed using a theory-building case study research approach. The three phases of the thesis provide empirical observations on different aspects of systemsdevelopment. In the first phase is examined the role of architecture in coordination and cost estimation in multi-site environment. The second phase involves two studies on the evolving requirement understanding process and how to measure this process. The third phase summarizes the first two phases and concentrates on the role of methods and how practitioners work with them. All the phases provide evidence that current systems development method approaches are too naïve in looking at the complexity of the real world. In practice, development is influenced by opportunity and other contingent factors. The systems development processis not coordinated using phases and tasks defined in methods providing universal mechanism for managing this process like most of the method approaches assume.Instead, the studies suggest that managing systems development process happens through coordinating development activities using methods as tools. These studies contribute to the systems development methods by emphasizing the support of communication and collaboration between systems development participants. Methods should not describe the development activities and phases in a detail level, butshould include the higher level guidance for practitioners on how to act in different systems development environments.

Macroporous Scaffolds for Bone Engineering. Studies on Cell Culture and Ectopic Bone Formation

Bone engineering is a rapidly developing area of reconstructive medicine where bone inducing factors and/or cells are combined with a scaffold material to regenerate the structure and function of the original tissue. The aim of this study was to compare the suitability of different macroporous scaffold types for bone engineering applications. The two scaffold categories studied were a) the mechanically strong and stable titanium fiber meshes and b) the elastic and biodegradable porous polymers. Furthermore, bioactive modifications were applied to these basic scaffold types, and their effect on the osteogenic responses was evaluated in cell culture and ectopic bone formation studies. The osteogenic phenotype of cultured cell-scaffold constructs was heightened with a sol-gel derived titania coating, but not with a mixed titania-silica coating. The latter coating also resulted in delayed ectopic bone formation in bone marrow stromal cell seeded scaffolds. However, the better bone contact in early implantation times and more even bone tissue distribution at later times indicated enhanced osteoconductivity of both the coated scaffold types. Overall, the most promising bone engineering results were obtained with titania coated fiber meshes. Elastic and biodegradable poly(ε-caprolactone/D,L-lactide) based scaffolds were also developed in this study. The degradation rates of the scaffolds in vitro were governed by the hydrophilicity of the polymer matrix, and the porous architecture was controlled by the amount and type of porogen used. A continuous phase macroporosity was obtained using a novel CaCl2 • 6H2O porogen. Dynamic culture conditions increased cell invasion, but decreased cell numbers and osteogenicity, within the scaffolds. Osteogenic differentiation in static cultures and ectopic bone formation in cell seeded scaffolds were enhanced in composites, with 30 wt-% of bioactive glass filler.

Neuropeptide Y at the cellular level – Studies on PreproNPY L7P Polymorphism and the Mitochondrial Form of NPY

Neuropeptide Y (NPY) is a widely expressed neurotransmitter in the central and peripheral nervous systems. Thymidine 1128 to cytocine substitution in the signal sequence of the preproNPY results in a single amino acid change where leucine is changed to proline. This L7P change leads to a conformational change of the signal sequence which can have an effect on the intracellular processing of NPY. The L7P polymorphism was originally associated with higher total and LDL cholesterol levels in obese subjects. It has also been associated with several other physiological and pathophysiological responses such as atherosclerosis and T2 diabetes. However, the changes on the cellular level due to the preproNPY signal sequence L7P polymorphism were not known. The aims of the current thesis were to study the effects of the [p.L7]+[p.L7] and the [p.L7]+[p.P7] genotypes in primary cultured and genotyped human umbilical vein endothelial cells (HUVEC), in neuroblastoma (SK-N-BE(2)) cells and in fibroblast (CHO-K1) cells. Also, the putative effects of the L7P polymorphism on proliferation, apoptosis and LDL and nitric oxide metabolism were investigated. In the course of the studies a fragment of NPY targeted to mitochondria was found. With the putative mitochondrial NPY fragment the aim was to study the translational preferences and the mobility of the protein. The intracellular distribution of NPY between the [p.L7]+[p.L7] and the [p.L7]+[p.P7] genotypes was found to be different. NPY immunoreactivity was prominent in the [p.L7]+[p.P7] cells while the proNPY immunoreactivity was prominent in the [p.L7]+[p.L7] genotype cells. In the proliferation experiments there was a difference in the [p.L7]+[p.L7] genotype cells between early and late passage (aged) cells; the proliferation was raised in the aged cells. NPY increased the growth of the cells with the [p.L7]+[p.P7] genotype. Apoptosis did not seem to differ between the genotypes, but in the aged cells with the [p.L7]+[p.L7] genotype, LDL uptake was found to be elevated. Furthermore, the genotype seemed to have a strong effect on the nitric oxide metabolism. The results indicated that the mobility of NPY protein inside the cells was increased within the P7 containing constructs. The existence of the mitochondria targeted NPY fragment was verified, and translational preferences were proved to be due to the origin of the cells. Cell of neuronal origin preferred the translation of mature NPY (NPY1-36) when compared to the non neuronal cells that translated both, NPY and the mitochondrial fragment of NPY. The mobility of the mitochondrial fragment was found to be minimal. The functionality of the mitochondrial NPY fragment remains to be investigated. L7P polymorphism in the preproNPY causes a series of intracellular changes. These changes may contribute to the state of cellular senescence, vascular tone and lead to endothelial dysfunction and even to increased susceptibility to diseases, like atherosclerosis and T2 diabetes.

Bile duct stones, strictures and iatrogenic lesions: studies on early diagnosis and treatment.

Aims: This study was carried out to investigate the role of common liver function tests, and the degree of common bile duct dilatation in the differential diagnosis of extrahepatic cholestasis, as well as the occurrence, diagnosis and treatment of iatrogenic bile duct injuries. In bile duct injuries, special attention was paid to gender and severity distribution and long-term results. Patients and methods: All consecutive patients with diagnosed common bile duct stones or malignant strictures in ERCP between August 2000 and November 2003. Common liver function tests were measured in the morning before ERCP on all of these 212 patients, and their common bile duct diameter was measured from ERCP films. Between January 1995 and April 2002, 3736 laparoscopic cholecystectomies were performed and a total of 32 bile duct injuries were diagnosed. All pre-, per-, and postoperative data were collected retrospectively; and the patients were also interviewed by phone. Results: Plasma bilirubin proved to be the best discriminator between CBD stones and malignant strictures (p≤0.001 compared to other liver function tests and degree of common bile duct dilatation). The same effect was seen in Receiver Operating Characteristics curves (AUC 0.867). With a plasma bilirubin cut-off value of 145 μmol/l, four out of five patients could be classified correctly. The degree of common bile duct dilatation proved to be worthless in differential diagnostics. After laparoscopic cholecystectomy the total risk for bile duct injury was 0.86%, including cystic duct leaks. 86% of severe injuries and 88% of injuries requiring operative treatment were diagnosed in females. All the cystic duct leakages and 87% of the strictures were treated endoscopically. Good long-term results were seen in 84% of the whole study population. Conclusions: Plasma bilirubin is the most effective liver function test in differential diagnosis between CBD stones and malignant strictures. The only value of common bile duct dilatation is its ability to verify the presence of extrahepatic cholestasis. Female gender was associated with higher number of iatrogenic bile duct injuries, and in particular, most of the major complications occur in females. Most of the cystic duct leaks and common bile duct strictures can be treated endoscopically. The long-term results in our institution are at an internationally acceptable level.