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MATERIAL I MÈTODES: En el primer estudi es van analitzar els resultats de l’aplicació del Test Combinat (bioquímica materna de primer trimestre (f-β-hCG i PAPP-A) i la mesura de la translucència nucal (TN) d’ambdós fetus a les 11-14 s) per a la detecció de trisomia 21 en 100 gestacions gemel•lars. Es va comparar l’ efectivitat del Test Combinat amb el cribratge exclusivamnet ecogràfic mitjançant la medició de la TN. En un segon temps es van analitzar els resultats obtinguts amb el Test Combinat en 161 gestacions gemel•lars. Es va analitzar també la distribució dels marcadors bioquímics de primer trimestre en funció de la corionicitat i del tipus de reproducció (espontània o assistida). En el segon estudi es van valorar els resultats obtinguts en totes les gestacions gemel•lars (monocorials i dicorials) amb un o ambdós fetus amb una TN extrema (> percentil 99) diagnosticats durant l’ecografia de primer trimestre, en un període de 4 anys. CONCLUSIONS: . Dels resultats del primer estudi es desprèn que l’aplicació del Test Combinat permet en les gestacions gemel•lars, disminuir els falsos positius obtinguts amb l’aplicació del cribratge exclusiu ecogràfic (14.3% de les gestacions vs 5.1%) i que els marcadors bioquímics de primer trimestre presenten uns valors significativament disminuits en les gestacions monocorials respecte a les gestacions dicorials. Els resultats del segon estudi mostren que la prevalença d’una TN extrema és major en els fetus procedents d’una gestació monocorial i que una TN extrema en algun dels fetus s’associa a resultats obstètrics desfavorables (80%) tant en les gestacions monocorials com dicorials. PARAULES CLAU: Gestació gemel•lar; Test Combinat; cribratge de trisomia 21; cribratge de primer trimestre; translucència nucal; translucència nucal augmentada; cariotip normal; defectes estructurals; síndrome de transfusió feto-fetal. / Methods: In the first study, free-β-hCG and PAPP-A were determined at 8-12 weeks and fetal nuchal translucency (NT) was measured at 11-14 weeks in 100 twin pregnancies. The individual risks for trisomy 21 were estimated using NT alone and the Combined Test and the effectiveness of both tests was compared. Subsequently, the results of the combined test were evaluated in 161 twin pregnancies with an assessment on the distribution of the biochemical markers ant NT thickness according to chorionicity and the mode of conception. In the second study a consecutive sample of 206 twin pregnancies (166 dichorionic and 40 monochorionic) were scanned for NT. In those with a NT>99th percentile and a normal karyotype, extensive follow-up was performed and perinatal outcome was recorded. Results:. In the first study, two pregnancies with trisomy 21 were detected by both methods. The false positive rate achieved by NT screening (11.2% of pregnancies) was substantially reduced when first trimester biochemistry was added (5.1%). With the application of the Combined Test in 161 pregnancies, all trisomy 21 pregnancies were identified (3 pregnancies) for a false-positive rate of 6.4%. Fβ-hCG and PAPP-A were significantly decreased in monochorionic pregnancies and PAPP-A was significantly decreased in pregnancies conceived by assisted reproduction. In the second study in 10 pregnancies one of the fetuses had a NT> 99th percentile, 5 DC (1.5%) and 5 MC (6.3%) with a normal karyotype. Among these, six structurally abnormalities were diagnosed (3 in dichorionics and 3 in monochorionics), and two intrauterine fetal demises occurred (1 in dichorionics and 1 in monochorionics). Normal perinatal outcome was observed in two pregnancies, one dichorionic and one monochorionic. Conclusion: The Combined Test maintains the detection rate achieved by NT screening for trisomy 21 in twin pregnancies, but false positive rates are reduced. The differences in the biochemical markers related to chorionicity or the mode of conception must be confirmed in further studies. NT>99th percentile with a normal karyotype was associated with a high rate of fetal abnormalities anf fetal demise irrespective of chorionicity KEY WORDS: Twin pregnancy; Combined Test; Down syndrome screening; first trimester screening; nuchal translucency; increased nuchal translucency; normal karyotype; fetal abnormalities; twin-twin transfusion syndrome

Failure mechanisms in large scale open pit slopes are more complex than could be considered through conventional slope design methods. Pit slope behaviour must be predicted accurately, because for very deep open pits, a small change of slope angle can have serious technical and economic consequences. Failure of hard rock slopes often involves both failure along naturally existing weakness planes and failure of intact rock. Without an advanced understanding of combined rock slope failure mechanisms, the validity of commonly applied methods of large scale slope analysis is questionable. The problem was investigated by means of a toolbox approach, in which a wide range of slope stability analysis methods were used and compared to address specific problems arising during slope design optimisation of the Cadia Hill Open Pit, NSW. In particular, numerical modelling is an advanced tool to obtain insight into potential failure mechanisms and to assist the slope design process. The distinct element method was employed to simulate complex rock slope failure, including fracture extension, progressive step-path failure and brittle failure propagation, which were previously often considered unimportant or too difficult to model. A new, failure-scale-dependent concept for the categorisation of slope failures with six categories ranging from 0 (stable) to 5 (overall slope failure) was suggested to assist risk-based slope design. Parametric slope modelling was conducted to determine the interrelationship between proposed categories and critical slope/discontinuity parameters. Initiation and progression of complex slope failure were simulated and described, which resulted in an advanced understanding of combined slope failure mechanisms and the important role of rock bridges in large scale slope stability. A graphical presentation of the suggested slope failure categories demonstrated their interrelationship to varied slope/discontinuity parameters. Although large scale slope analyses will always involve data-limited systems, this investigation shows that comprehensive, conceptual modelling of slope failure mechanisms can deliver a significantly improved insight into slope behaviour, so that associated slope failure risks can be judged with more confidence. The consideration of combined slope failure mechanisms in the analysis of large scale open pit slopes is essential if slope behaviour is to be realistically modelled.

The Formulary Approach to the Taxation of Transnational Corporations: A Realistic Alternative? Synopsis The central hypotheses of this thesis are: that global formulary apportionment is the most appropriate method for the taxation of transnational corporations (TNCs) in lieu of the present system commonly referred to as the separate accounting/arm's length method; and that it is essential, in order to implement the proposed global formulary model, to create an international organisation which would fulfil, in the taxation field, a role equivalent to that of the World Trade Organisation (WTO) in international trade. The world economy is fast integrating and is increasingly dominated by the activities of transnational enterprises. These activities create a dual tax problem for various revenue authorities seeking to tax gains derived thereon: Firstly, when two or more countries entertain conflicting tax claims on the same base, there arises what is commonly referred to as a double taxation problem. Secondly, an allocation problem arises when different jurisdictions seek to determine the quantum of the gains to be allocated to each jurisdiction for taxation purposes. The traditional regime for solving both the double taxation and the allocation problem is enshrined in a series of bilateral treaties signed between various nations. These are, in general, based on the Organisation for Economic Co-operation and Development (OECD) Model Treaty.1 It is submitted, in this thesis, that while highly successful in an environment characterised by the coexistence of various national taxation systems, the traditional regime lacks the essential attributes suitable to the emerging 'borderless world'. The central theme of this thesis is the allocation problem. The OECD Model attempts to deal with this issue on a bilateral basis. Currently, the allocation problem is resolved through the application of Articles 7 and 9 of the OECD Model. In both instances the solution is based on the 'separate enterprise' standard, also known as the separate entity theory. This separate accounts/arm's length system was articulated in the 1930s when international trade consisted of flows of raw materials and other natural products as well as flows of finished manufactured goods. Such trade is highly visible and may be adequately valued both at the port of departure or at the port of entry in a country. It follows that within this particular system of international trade the application of the arm's length principle was relatively easy and proved to be extremely important in resolving both the double taxation and apportionment problems. Today, however, the conditions under which international trade is conducted are substantially different from those that prevailed until the 1960s. * Firstly, apart from the significant increase in the volume of traditionally traded goods, trade in services now forms the bulk of international exchanges. In addition, the advent of the information age has dramatically increased the importance of specialised information whose value is notoriously difficult to ascertain for taxation purposes. * Secondly, the globalisation phenomenon which gathered momentum over the last two decades has enabled existing TNCs to extend their global operations and has favoured the emergence of new transnational firms. Thus, intra-firm trade conducted outside market conditions accounts for a substantial part of international trade. * Thirdly, further economic integration has been achieved following the end of the Cold War and the acceleration of the globalisation phenomenon. In this new world economic order only TNCs have the necessary resources to take advantage of emerging opportunities. The very essence of a TNC is 'its ability to achieve higher revenues (or lower costs) from its different subsidiaries as a whole compared to the results that would be achieved under separate management on an arm's length basis.'2 Yet, the prevailing system for the taxation of TNCs overlooks this critical characteristic and is therefore incapable of fully capturing, for taxation purposes, the aggregate gains of TNCs. The potential revenue loss arising from the inability of the present system to account for and to allocate synergy gains is substantial. It follows that the perennial questions of international taxation can no longer be addressed within the constraints of the separate entity theory and a narrow definition of national sovereignty. Indeed, in order to mirror the developments occurring in the economic field, taxation needs to move from a national to an international level. Moreover, a profound reform of the system is imperative in order to avoid harmful tax competition between nations and enhance compliance from TNCs. Such a new international tax system needs to satisfy the test of simplicity, equity, efficiency, and administrative ease. To achieve these objectives international cooperation is essential. The hallmark of international cooperation has been the emergence, after World War II, of a range of international organisations designed to facilitate the achievement of certain goals deemed essential by various nations. The need for an organisation to deal specifically with taxation matters is now overwhelming. Consequently, this thesis recommends the creation of an international organisation to administer the proposed system. The main objective of this international organisation would be to initiate and coordinate the multilateral application of a formulary apportionment system which, it is suggested, would deal in a more realistic way with 'the difficult problems of determining the tax base and allocating it appropriately between jurisdictions'.3 The global formulary apportionment methodology is derived from the unitary entity theory. The unitary theory considers a TNC as a single business which, for convenience, is divided into 'purely formal, separately-incorporated subsidiaries'.4 Under the unitary theory the global income of TNCs needs to be computed, then such income is apportioned between the various component parts of the enterprise by way of a formula which reflects the economic contribution of each part to the derivation of profits. The question that arises is whether the world of international taxation is ready for such a paradigm shift. It is arguable that this shift has already occurred albeit cautiously and in very subtle ways. Thus, the latest of the OECD Guidelines on the transfer pricing question provides that 'MNE [Multinational Enterprise] groups retain the freedom to apply methods not described in this Report to establish prices provided those prices satisfy the arm's length principle in accordance with these Guidelines.'5 Arguably, the globalisation process has created 'the specific situation' allowed for by the OECD. This thesis, therefore, explores the relative obsolescence of the bilateral approach to the taxation of TNCs and then suggests that a multilateral system is better adapted to the emerging globalised economy. The fundamental building blocks of the model proposed in this thesis are the following: * First, the administration and coordination of the proposed system is to be achieved by the creation of a specialised tax organisation, called Intertax, to which member countries would devolve a limited part of their fiscal sovereignty. * Second, in order to enable the centralised calculation of TNC's profits, the proposed system requires the formulation of harmonised methods for the measurement of the global profits of TNCs. Therefore, the efforts of the International Accounting Standards Committee (IASC) to produce international accounting standards and harmonised consolidation rules must be recognised and, if needs be, refined and ultimately implemented. * Third, the major function of Intertax would be to determine the commercial profits of TNCs on a standardised basis and to apportion the latter to relevant countries by way of an appropriate formula/formulas. Once this is achieved, each country would be free, starting from its share of commercial profits, to determine the taxable income in accordance with the particular tax base that it adopts and, ultimately, the tax payable within its jurisdiction. In the proposed system, therefore, a particular country would be able to independently set whatever depreciation schedules or investment tax credits it chooses, and adopt whatever tax accounting rules it deems fit relative to its policy objectives. Moreover, this thesis argues that the global formulary apportionment model it proposes is not dramatically opposed to the arm's length principle. Indeed, it suggests that the constant assumption to the contrary, even with regard to the usual formulary apportionment methodology, is extravagant because both methodologies are based on a common endeavour, that is, to give a substantially correct reflex of a TNC's true profits. It has often been objected that global formulary apportionment is arbitrary and ignores market conditions. This thesis addresses such concerns by rejecting the application of a single all-purpose formula. Rather, it recognises that TNCs operating in different industries require different treatment and, therefore, suggests the adoption of different formulas to satisfy specific industry requirements. For example, the formula applicable to a financial institution would be different to that applicable to the pharmaceutical industry. Each formula needs to be based on the fundamental necessity to capture the functions, taking into consideration assets used, and risks assumed within that industry. In addition, if the need arises, each formula should be able to be fine-tuned to fit specific situations. Moreover, it is also pertinent to note that the OECD already accepts 'the selected application of a formula developed by both tax administrations in cooperation with a specific taxpayer or MNE group...such as it might be used in a mutual agreement procedure, advance transfer pricing agreement, or other bilateral or multilateral determination.'6 The system proposed in this thesis can thus be easily reconciled with the separate accounting/arm's length which the OECD so vehemently advocates. Both models have the same preoccupations so that what is herein proposed may simply be characterised as an institutionalised version of the system advocated by the OECD. Multilateral formulary apportionment addresses both the double taxation and the allocation problems in international taxation. It resolves the apportionment question 'without depending on an extraordinary degree of goodwill or compliance from taxpayers.'7 It is therefore submitted that, if applied on a multilateral basis with a minimum of central coordination, it also seriously addresses the double taxation problem. Indeed, it is a flexible method given that different formulas may be devised to suit the needs of TNCs operating in different sectors. Consequently, formulary apportionment understood in this sense, is a realistic alternative to the limitations of the present system.

Diss. (sammanfattning) Stockholm : Karolinska institutet, 2007. / Härtill 5 uppsatser.

Dissertation (Ph.D.) -- University of Texas Southwestern Medical Center at Dallas, 2006. / Vita. Bibliography: p. 132-142.

Diss. (sammanfattning) Linköping : Linköpings universitet, 2007. / Härtill 4 uppsatser.