Pour lutter efficacement contre les phénomènes de fraude et d'évasion fiscales internationales favorisés par l'opacité des juridictions offshores et l'attractivité des paradis fiscaux, Je législateur a eu recours aux présomptions. Cette technique juridique a pour caractéristique de modifier la dialectique de la preuve en faveur de l'administration, qui n'est plus tenue de faire la démonstration de la fraude ou de l'évasion, mais seulement d'un ou de plusieurs faits connexes à l'infraction frauduleuse ou au fait d'optimisation fiscale abusive. En pratique, le législateur a souvent eu recours à des présomptions à la force renforcée, renversant directement le fardeau de la preuve sur le contribuable qui est d'emblée tenu d'établir la preuve d'un fait connexe exonératoire à l'infraction ou au fait abusif. Pour muscler leur efficacité, le législateur a également introduit des présomptions irréfragables, au couperet définitif. Les présomptions simples caractérisées par une clause anti-abus centrée sur l'objet ont pour particularité de faire peser sur le contribuable la charge d'une preuve qualitativement supérieure. Ces présomptions, dont l'actionnement est conditionné à la preuve d'un fait connexe par l'administration, représentent une catégorie hétérodoxe de dispositifs présomptif renforcés, obligeant le contribuable à faire un effort d'analyse sur les finalités des opérations, ce qui revient à lui faire supporter la charge de la preuve de l'absence d'abus de droit. L'emploi des présomptions se heurte essentiellement aux droits et liberté économiques communautaire et conventionnels, obligeant Je législateur à adapter les dispositifs présomptifs à ces contraintes. / In order to struggle efficiently against tax avoidance and tax evasion tendencies, enhanced by offshore jurisdictions, often lacking transparency, and tax havens with their attractive conditions, the lawmaker has enabled rebuttable and conclusive presumptions to be used in suing cases. These legal tricks favour Tax administrations in winning the argument, since those are no longer required to bring compelling evidence of tax avoidance or tax evasion. It is enough to prove a fraud, an offence or an aggressive tax optimisation process with one or several connected facts. In practice, the lawmaker is often using strengthened standards on presumption to reverse the burden of proof onto the taxpayer, who therefore must provide evidence for any exemptions from responsibility regarding the alleged offence or abuse. To improve these tools efficiency, the lawmaker has also designed conclusive ( or irrebuttable) presumptions. Usual presumptions are characterised by their emphasis on anti-abuse clauses, which oblige taxpayers to bring stronger evidences in lawsuit. For Tax authorities, these are part of a legal arsenal using connected facts against the defensor who carries the burden of proof related to tax monitoring operations in the absence of abuse of rights.

The subject of this thesis is particularly the issue of domestic reverse charge procedure as a tool in the fight against tax evasion on value added tax (VAT) and its planned expansion. The reverse charge is not the only tool in the fight against evasion of VAT in the Czech Republic. The thesis therefore analyzed and used other tools. These instruments are inspection report, institute an unreliable payer, liability for unpaid VAT and EET. In conclusion, there is the comparison of individual instruments.

This thesis deals with tools against tax evasion of value added tax. The main aim of this work is to analyse tools that either have been implemented in the Czech Republic and the European Union already, or, it is being planned to be introduced in the near future, and then, to evaluate their impact and effectiveness. Theoretical points and analysis of the tools take the first part of this thesis. It is a description of the principle of the functioning of value added tax, definition of tax evasion, legislative regulation of value added tax, and current forms of tax evasion. In the second part, every tool is being analysed, described the basic principles of the functioning, legislative regulation, and analysis of its advantages and disadvantages. It deals with VAT control report, electronic records of sales, reverse charge, concept of liability, comprehensive reporting and VIES.

This study aimed to examine if there was a difference in how likely a victim is to click on a phishing email’s links based on the content of the email, the tone and language used and the structure of the code. This likelihood also includes the email’s ability to bypass spam filters.  Method: The method used to examine this was a simulated phishing attack. Six different phishing templates were created and sent out via the Gophish framework to target groups of students (from Halmstad University), from a randomized pool of 20.000 users. The phishing emails contained a link to a landing page (hosted via a virtual machine) which tracked user status. The templates were: Covid19 Pre-Attempt, Spotify Friendly CSS, Spotify Friendly Button, Spotify Aggressive CSS, Spotify Aggressive Button, Student Union. Results: Covid19 Pre-Attempt: 72.6% initial spam filter evasion, 45.8% spam filter evasion, 4% emails opened and 100% links clicked. Spotify Friendly CSS: 50% initial spam filter evasion, 38% spam filter evasion, 26.3% emails opened and 0% links clicked. Spotify Friendly Button: 59% initial spam filter evasion, 28.8% spam filter evasion, 5.8% emails opened and 0 %links clicked. Spotify Aggressive CSS: 50% initial spam filter evasion, 38% spam filter evasion, 10.5% emails opened, and 100% links clicked. Spotify Aggressive Button: 16% initial spam filter evasion, 25% spam filter evasion, 0% emails opened and 0% emails clicked. Student Union: 40% initial spam filter evasion, 75% spam filter evasion, 33.3% emails opened and 100% links clicked. Conclusion: Differently structured emails have different capabilities for bypassing spam filters and for deceiving users. Language and tone appears to affect phishing email efficacy; the results suggest that an aggressive and authoritative tone heightens a phishing email’s ability to deceive users, but seems to not affect its ability to bypass spam filters to a similar degree. Authenticity appears to affect email efficacy; the results showed a difference in deception efficacy if an email was structured like that of a genuine sender. Appealing to emotions such as stress and fear appears to increase the phishing email’s efficacy in deceiving a user. / Syftet med denna studie var att undersöka om det fanns en skillnad i hur troligt det är att ett offer klickar på länkarna till ett phishing-e-postmeddelande, baserat på innehållet i e-postmeddelandet, tonen och språket som används och kodens struktur. Denna sannolikhet inkluderar även e-postens förmåga att kringgå skräppostfilter. Metod: Metoden som användes var en simulerad phishing-attack. Sex olika phishing-mallar skapades och skickades ut via Gophish-ramverket till målgruppen bestående av studenter (från Halmstads universitet), från en slumpmässig pool med 20 000 användare. Phishing-e-postmeddelandena innehöll en länk till en målsida (hostad via en virtuell maskin) som spårade användarstatus. Mallarna var: Covid19 Pre-Attempt, Spotify Friendly CSS, Spotify Friendly Button, Spotify Aggressive CSS, Spotify Aggressive Button, Student Union. Resultat: Covid19 förförsök: 72,6% kringgick det primära spamfiltret, 45,8% kringgick det sekundära spamfiltret, 4% e-postmeddelanden öppnade och 100% länkar klickade Spotify Friendly CSS: 50% kringgick det primära spamfiltret, 38% kringgick det sekundära spamfiltret, 26,3% e-postmeddelanden öppnade och 0% länkar klickade. Spotify Friendly Button: 59% kringgick det primära spamfiltret, 28,8% kringgick det sekundära spamfiltret, 5.8% e-postmeddelanden öppnade och 0% länkar klickade. Spotify Aggressive CSS: 50% kringgick det primära spamfiltret, 38% kringgick det sekundära spamfiltret, 10,5% e-post öppnade och 100% länkar klickade. Spotify Aggressive Button: 16% kringgick det primära spamfiltret, 25% kringgick det sekundära spamfiltret, 0% e-postmeddelanden öppnade och 0% e-postmeddelanden klickade. Studentkåren: 40% kringgick det primära spamfiltret, 75% kringgick det sekundära spamfiltret, 33,3% e-postmeddelanden öppnade och 100% länkar klickade. Slutsats: Olika strukturerade e-postmeddelanden har olika funktioner för att kringgå skräppostfilter och för att lura användare. Språk och ton tycks påverka effektiviteten för epost-phishing. Resultaten tyder på att en aggressiv och auktoritär ton ökar phishing-epostmeddelandets förmåga att lura användare, men verkar inte påverka dess förmåga att kringgå skräppostfilter i motsvarande grad. Autenticitet verkar påverka e-postens effektivitet, då resultaten visade en skillnad i effektivitet om ett e-postmeddelande var strukturerat som en äkta avsändare. Att adressera känslor som stress och rädsla verkar öka phishing-e-postens effektivitet när det gäller att lura en användare.

published_or_final_version / abstract / toc / Transport Policy and Planning / Master / Master of Arts in Transport Policy and Planning

Taxes are major source of public funds to finance government expenditures. Tax authorities impose different kind of taxes and employ many agents to collect taxes effectively. Some dutiful taxpayers will undoubtedly pay their tax liabilities while many others will not. The Internal Revenue Service in the United States reports that the estimate of income tax liability not collected is about 17, which translates into 345 billion for 2001. It is important to make a distinction between tax evasion and tax avoidance. The distinguishing characteristic of evasion is illegality. Whether the reason for not paying tax liability is avoidance or evasion, economic models of taxation need to be changed in the light of these realities. In this study, I analyze some of the economic problems of tax evasion/avoidance. In the first chapter, I discuss the relationship between number of tax audits, tax administration reform and tax compliance in Turkey. In recent years, many developing countries have carried out reforms in their tax administration to increase their efficiency in collecting taxes. In 2005, the tax authority in Turkey established Tax Office Directorates (T.O.D.s) in 29 provinces for the purpose of controlling the underground economy, improving taxpayer assistance, and increasing auditing efficiency. By using the panel data on province level tax returns, my analysis answers two questions. First, I examine the effect of audits on reported income and reported tax liability. By controlling for the detectibility of evasion and other socioeconomic variables, I find that audits have the same effectiveness in increasing reported income and reported tax liability. Second, I investigate the effect of establishing T.O.D.s in 29 provinces on compliance in those provinces. I find that T.O.D.s are effective at the extensive margin rather than the intensive margin. Thus, establishing T.O.D.s had no significant effect on the compliance level of existing taxpayers while it increased the number of tax returns significantly. In the second chapter, I analyze the excess burden on income tax when tax avoidance matters. I present a simple static labor supply model with endogenous asset choice. Then, I examine how tax avoidance through asset trading a ects the labor supply response and the excess burden of income tax. Furthermore, I discuss the implications of the tax policy analysis and show that a failure to account for avoidance responses may lead to errors when estimating how tax reform affects labor supply, tax revenue, and the welfare cost of taxation. Because of tax avoidance through tax arbitrage, the progressivity of a given tax system will be less than what the formal tax system implies. In the third chapter,we study the Marginal Cost of Funds in the existence of tax evasion. We develop a general equilibrium model of tax evasion, including the expected utility of taxpayers and three different revenue-raising government policies. In this rich model environment, we analytically derive the marginal cost of funds (MCF) for the alternative policy instruments. We consider two main fiscal reforms: the revision in the nonlinear tax scheme and the changes in enforcement mechanism (the audit and penalty rates). First, we derive the MCF for the tax reform and find its key determinants. The derived MCF is greater than the previous ones since it includes a "risk-bearing cost" as well as tax distortion. The reform in enforcement mechanism generates MCFs in different forms. Two more MCFs with respect to audit and penalty rates are presented. Finally, we compare these three different MCFs in numerical example and provide some policy implications. / text

The pathogen Streptococcus pyogenes is a significant cause of human morbidity and mortality. Most of the work in this thesis is focused on streptococcal virulence factor IdeS, but the thesis also features work on SpeB, another streptococcal virulence factor. Both IdeS and SpeB are secreted cysteine proteases and both have previously been shown to degrade human IgG. IgG is the only known substrate for IdeS while SpeB is a more promiscuous protease with a larger number of identified substrates. A significant part of the data presented in this thesis is the result of designing and optimizing methods to detect and accurately measure the proteolytic degradation of IgG. Methods aimed at measuring the binding interactions between enzyme and substrate have also been frequently utilized. I show that IdeS is a monomeric protease, as opposed to previously published data that suggested it to be dimeric. IdeS cleaves the two heavy chains of IgG in a two-step reaction and I demonstrate that the first cleavage is magnitudes faster than the second one. This means that IdeS is a more efficient enzyme than previously thought. The difference in rate cannot completely be explained by a loss of affinity between IdeS and IgG after the cleavage of the first heavy chain. The velocity of IdeS is further increased by the presence of human Cystatin C, via an unknown mechanism. Cystatin C is normally a protease inhibitor and it having an opposite effect is puzzling.The synthesis and evaluation of novel inhibitors are also described. Peptide analogues mimicking the sequence surrounding the scissile bond on IgG - with an amino acid replaced with a more rigid motif - act as specific, but low-affinity, inhibitors of IdeS. The peptide analogues’ inhibitory capacity for SpeB and papain was also assayed.When it comes to SpeB, I show that it does not have IgG as a substrate under physiological conditions, in contrast to what was previously thought. This thesis does not only present findings on the IgG degrading capacity of IdeS and SpeB but also include data on fundamental enzymatic properties for these proteases.

Vibrio splendidus LGP32 est une bactérie pathogène associée aux épisodes de mortalités estivales qui affectent la production d'huître Crassostrea gigas depuis des décennies. Nous avons montré ici que la porine OmpU était un effecteur majeur de l'interaction V. splendidus / C. gigas. Nous avons pour cela construit un mutant ΔompU de V. splendidus. Celui-ci nous a permis de mo ntrer l'implication de OmpU (i) dans la résistance de V. splendidus aux antimicrobiens, incluant ceux de l'huître, (ii) dans la « fitness » chez l'huître, et (iii) dans la virulence en infections expérimentales (mortalités de 56 % pour le sauvage versus pour le 11% mutant). En accord avec ces résultats, nous avons montré que la délétion de ompU modifiait la sécrétion de protéines dont l'expression est contrôlée par les voies de régulation de la virulence (ToxR) et de l'intégrité membranaire (SigmaE). Par ailleurs, nous avons montré que OmpU jouait un rôle essentiel dans la reconnaissance par les hémocytes. En effet, (i) in vivo, les gènes hémocytaires répondent différemment à l'infection par le Vibrio sauvage ou ΔompU, et (ii) in vitro, OmpU est nécessaire à l'invasion hémocytaire par V. splendidus. Cette invasion utilise la phagocytose dépendante de l'intégrine b et la SOD extracellulaire du plasma d'huître comme opsonine qui lie OmpU. Ainsi, OmpU est un facteur de virulence majeur qui permet l'infection des hémocytes dans lesquels il est capable de survivre en inhibant la formation de radicaux oxygénés et de vacuoles acides. La résistance du Vibrio aux antimicrobiens hémocytaires de l'huître, elle-même dépendante de OmpU, est probablement un élément supplémentaire favorable à la survie intra-cellulaire. / Vibrio splendidus LGP32 is a bacterial pathogen associated to the summer mortality outbreaks that have affected the production of Crassostrea gigas oysters over the past decades. We showed here that the OmpU porin is a major effector of the V. splendidus / C. gigas interaction. For that, we have constructed a ΔompU mutant of V. splendidus, and shown that the OmpU porin is implicated (i) in the resistance of V. splendidus to antimicrobials, including those of oyster, (ii) in its in vivo fitness, and (iii) in its virulence in oyster experimental infections (mortalities have been reduced from 56 % to 11 % upon mutation). In agreement, we have shown that the ompU deletion modified the expression of secreted proteins controlled by the virulence (ToxR) and the membrane integrity (SigmaE) regulation pathways. Furthermore, we have shown that OmpU has a major role in the recognition of V. splendidus by oyster hemocytes. Indeed, (i) in vivo, hemocyt e genes displayed differential responses to an infection with the wild-type or the ΔompU mutant, and (ii) in vitro, OmpU was necessary for hemocyte invasion by V. splendidus. This invasion process required the hemocyte b-integrin and the oyster plasma extracellular SOD, which was found to act as an opsonin recognizing OmpU. Thus, OmpU is a major virulence factor that allows infection of hemocytes in which V. splendidus is able to survive by inhibiting the production of reactive oxygen species and the formation of acidic vacuoles. Resistance of V. splendidus to hemocyte antimicrobials, which is also OmpU-dependant, is probably an additional determinant of V. splendidus intracellular survival.

Within the field of multi-agent systems theory, we study the problems of consensus and pursuit-evasion. In our study of the consensus problem, we first provide some theoretical results and then consider the problem of consensus on SO(3) or attitude synchronization. In Chapter 2, for agents with states in R^m, we present two theorems along the lines of Lyapunov’s second method that, under different conditions, guarantee asymptotic state consensus in multi-agent systems where the interconnection topologies are switching. The first theorem is formulated by using the states of the agents in the multi-agent system, whereas the second theorem is formulated by using the pairwise states for pairs of agents in the multi-agent system. In Chapter 3, the problem of consensus on SO(3) for a multi-agent system with directed and switching interconnection topologies is addressed. We provide two different types of kinematic control laws for a broad class of local representations of SO(3). The first control law consists of a weighted sum of pairwise differences between positions of neighboring agents, expressed as coordinates in a local representation. The structure of the control law is well known in the consensus community for being used in systems of agents in the Euclidean space, and here we show that the same type of control law can be used in the context of consensus on SO(3). In a later part of this chapter, based on the kinematic control laws, we introduce torque control laws for a system of rigid bodies in space and show that the system reaches consensus when these control laws are used. Chapter 4 addresses the problem of consensus on SO(3) for networks of uncalibrated cameras. Under the assumption that each agent uses a camera in order to measure its rotation, we prove convergence to the consensus set for two types of kinematic control laws, where only conjugate rotation matrices are available for the agents. In these conjugate rotations, the rotation matrix can be seen as distorted by the (unknown) intrinsic parameters of the camera. For the conjugate rotations we introduce distorted versions of well known local parameterizations of SO(3) and show consensus by using control laws that are similar to the ones in Chapter 3, with the difference that the distorted local representations are used instead. In Chapter 5, we study the output consensus problem for homogeneous systems of agents with linear continuous time-invariant dynamics. We derive control laws that solve the problem, while minimizing a cost functional of the control signal. Instead of considering a fixed communication topology for the system, we derive the optimal control law without any restrictions on the topology. We show that for all linear output controllable homogeneous systems, the optimal control law uses only relative information but requires the connectivity graph to be complete and in general requires measurements of the state errors. We identify cases where the optimal control law is only based on output errors. In Chapter 6, we address the multi-pursuer version of the visibility pursuit-evasion problem in polygonal environments. By discretizing the problem and applying a Mixed Integer Linear Programming (MILP) framework, we are able to address problems requiring so called recontamination and also impose additional constraints, such as connectivity between the pursuers. The proposed MILP formulation is less conservative than solutions based on graph discretizations of the environment, but still somewhat more conservative than the original underlying problem. It is well known that MILPs, as well as multi-pursuer pursuit-evasion problems, are NP-hard. Therefore we apply an iterative Receding Horizon Control (RHC) scheme, where a number of smaller MILPs are solved over shorter planning horizons. The proposed approach is illustrated by a number of solved examples. / <p>QC 20140327</p>

"Mémoire présenté à la Faculté des études supérieures En vue de l'obtention du grade de maîtrise en droit" / Un auteur a dit: «L'association d'idée avec la girafe se présente immédiatement à l'esprit, en donner une définition est difficile, mais chacun reconnaît l'animal». Tel est le cas pour la notion de contrat international qui apparaît souvent comme évidente, mais lorsqu'il est question de donner une définition précise la tâche s'avére complexe. L'internationalité du contrat a fait l'objet de plusieurs études et recherches dans le but de délimiter cette notion. La doctrine et la jurisprudence ont élaboré deux méthodes de qualification: économique et juridique; sans pour autant définir le contrat international de façon nette, claire et précise. Le but visé par cette étude est d'essayer d'établir le lien entre la possibilité de fraude à la loi et la problématique de la définition du contrat international; par le biais d'une étude comparative entre le droit civil (français, québécois, tunisien), la common law (Royaume-Uni, Canada, États-Unis), le droit dans les pays à commerce d'État et le droit conventionel. / One author said : «L'association d'idée avec la girafe se présente immédiatement l'esprit, en donner une définition est difficile mais chacun reconnaît l'animal». This is the case for the notion of international contract, whose definition is often presumed to be self-evident, but in reality constructing a precise definition is a very complicated task. The international nature of a contract has been the subject of many studies and much research has been dedicated to this topic, aIl with the goal of formulating a clear definition. Legal doctrine and jurisprudence have succeeded in qualifying international contract as legal or economic without actually defining it in any constant, clear or precise manner. The aim of this study is to make an attempt at establishing a link between possible evasion of the law and the problem of defining international contract; this will b e a chieved v ia a comparative s tudy of c ivill aw (France, Quebec, Tunisia), common law (United Kingdom, Canada, United States) law in countries where the economy is state-run and international treaty law.