Evolution of social interactions associated with matrix production in Bacillus subtilis biofilms

Bacteria mostly live in collectives, where social interactions are prevalent. In biofilms, groups of surface-attached matrix-bound microbial cells exist and interact. Recent studies demonstrate that experimental evolution can be applied to biofilms to investigate and monitor the alterations in social interactions within the spatial structures. Here, experimental evolution approaches were employed to examine the evolutionary interplay of social activities in relation to the production of the biofilm matrix in pellicle biofilms of Bacillus subtilis, a plant beneficial soil-dwelling bacterium. The significant discoveries in this work are: 1)Biofilms are adequate models to study and monitor the origin and development of social interactions as these provide a tractable system to understand the impact of spatial distribution on microbial evolution. 2)Experimental evolution of biofilms facilitates diversification in clonal populations and results in complex interactions involving cooperative and exploitative behaviours. 3)Evolution of competitive interactions between matrix producers and non-producers results in an enhanced competitive advantage of the non-producers in the biofilm via the release of bacteriophages. 4)The exopolysaccharide (EPS) and protein components (TasA) of B. subtilis biofilms are costly public goods that facilitate the division of labour that is optimal at the genotypic level. 5)Genetic division of labour of costly public goods, EPS and TasA, is diminished by the arose of individuality during experimental evolution that selects for novel biofilm traits. 6)Experimental evolution of matrix producers in the presence of cheaters leads to an alteration in phenotypic heterogeneity that creates an anti-cheating mechanism within the biofilm. The findings presented here demonstrate how interactions in spatially structured environments become diverse, adaptive, maintained, and/or developed into unique biofilm traits, thus, contributing to Sociomicrobiology

Secure Routing and Medium Access Protocols inWireless Multi-hop Networks

While the rapid proliferation of mobile devices along with the tremendous growth of various applications using wireless multi-hop networks have significantly facilitate our human life, securing and ensuring high quality services of these networks are still a primary concern. In particular, anomalous protocol operation in wireless multi-hop networks has recently received considerable attention in the research community. These relevant security issues are fundamentally different from those of wireline networks due to the special characteristics of wireless multi-hop networks, such as the limited energy resources and the lack of centralized control. These issues are extremely hard to cope with due to the absence of trust relationships between the nodes. To enhance security in wireless multi-hop networks, this dissertation addresses both MAC and routing layers misbehaviors issues, with main focuses on thwarting black hole attack in proactive routing protocols like OLSR, and greedy behavior in IEEE 802.11 MAC protocol. Our contributions are briefly summarized as follows. As for black hole attack, we analyze two types of attack scenarios: one is launched at routing layer, and the other is cross layer. We then provide comprehensive analysis on the consequences of this attack and propose effective countermeasures. As for MAC layer misbehavior, we particularly study the adaptive greedy behavior in the context of Wireless Mesh Networks (WMNs) and propose FLSAC (Fuzzy Logic based scheme to Struggle against Adaptive Cheaters) to cope with it. A new characterization of the greedy behavior in Mobile Ad Hoc Networks (MANETs) is also introduced. Finally, we design a new backoff scheme to quickly detect the greedy nodes that do not comply with IEEE 802.11 MAC protocol, together with a reaction scheme that encourages the greedy nodes to become honest rather than punishing them

Secure Routing and Medium Access Protocols inWireless Multi-hop Networks

While the rapid proliferation of mobile devices along with the tremendous growth of various applications using wireless multi-hop networks have significantly facilitate our human life, securing and ensuring high quality services of these networks are still a primary concern. In particular, anomalous protocol operation in wireless multi-hop networks has recently received considerable attention in the research community. These relevant security issues are fundamentally different from those of wireline networks due to the special characteristics of wireless multi-hop networks, such as the limited energy resources and the lack of centralized control. These issues are extremely hard to cope with due to the absence of trust relationships between the nodes. To enhance security in wireless multi-hop networks, this dissertation addresses both MAC and routing layers misbehaviors issues, with main focuses on thwarting black hole attack in proactive routing protocols like OLSR, and greedy behavior in IEEE 802.11 MAC protocol. Our contributions are briefly summarized as follows. As for black hole attack, we analyze two types of attack scenarios: one is launched at routing layer, and the other is cross layer. We then provide comprehensive analysis on the consequences of this attack and propose effective countermeasures. As for MAC layer misbehavior, we particularly study the adaptive greedy behavior in the context of Wireless Mesh Networks (WMNs) and propose FLSAC (Fuzzy Logic based scheme to Struggle against Adaptive Cheaters) to cope with it. A new characterization of the greedy behavior in Mobile Ad Hoc Networks (MANETs) is also introduced. Finally, we design a new backoff scheme to quickly detect the greedy nodes that do not comply with IEEE 802.11 MAC protocol, together with a reaction scheme that encourages the greedy nodes to become honest rather than punishing them

Agent-based models of long-distance trading societies

Studying historical trading societies helps us to identify the institutions (e.g. rules) and characteristics that lead to their success or failure. Historically, long-distance trading societies, as a more particular example of trading societies, have been established in various parts of the world. Many of these societies were successful in certain aspects, and interestingly, a number of these societies were successful, despite having different characteristics and institutions. This thesis aims to identify some of the institutions and characteristics that contributed to their success. We use an agent-based simulation model to identify the key characteristics that impacted the success of two long-distance trading societies. The objective of this study is to develop suitable models of these societies that can be used for systematic studies of their characteristics. Two long-distance trading societies studied in this thesis are the British East India Company and the Armenian traders of New-Julfa, both of which flourished during the 17th and 18th centuries. In this thesis, we conduct a comparative study of the two societies, based on historical evidence and contemporary literature that provide empirical support. Based on the comparative study, we have identified three overarching themes that distinguish these societies: 1) the contractual schemes used and their environmental characteristics; 2) the apprenticeship programmes and vocational schools used; and 3) the institutional mechanisms used. This thesis presents three models developed corresponding to the three themes, based on the presented comparative study of the societies. The first model developed was based on game theory and simulates the impact of contractual schemes and environmental circumstances on the two trading societies’ success. In the contractual scheme, we assessed the impact of payment schemes (e.g. profit-sharing), penalties (e.g. dismissal for wrongdoing), and hiring and firing schemes, in the context of open and closed societies, on the success of the society. As a metric of societal success, we considered rule conformity, sustainability, profitability, and improving societal skills. As a next step, we model the impact of apprenticeship programmes and vocational schools on the societal success (i.e. maintaining societal skill levels, programme completion rate, and increasing societal income). In this model, we consider the impact of different trader and trainer types (e.g. artisans), along with various policies for managing recruits (e.g. training societal members and hiring from other societies). In our last model, we extend the beliefs-desires-intentions (BDI) mental architecture to model the impact of institutional mechanisms (e.g. fairness) on the success of these societies. Beyond creating models (methodological contribution) of these societies to demonstrate the influence of characteristics on the success of the societies, our work provides practical contributions, such as a) insights into the positive impact of profit-sharing on a company’s profitability; b) the aspects that should be considered to have successful apprenticeship programmes; and c) insights into designing societal rules to deal with societies’ lack of transparency

Can teachers’ rewards improve educational outcomes? The role of financial and non-financial rewards

Inspired by the theoretical power of rewards in the labor market, to improve educational outcomes, this paper tests if giving a non-financial reward along with a financial one can result in higher student ex-post outcomes than just a financial incentive. The underlying mechanism by which non-financial reward might work is explored as well. The argument is based on Benabou and Tirole (2002)’s model, that non-financial reward may affect teachers’ self-esteem and, with that, their effort, and thereby the student outcomes after the reward is given. This is accomplished by exploiting a discontinuity in the running variable used to assign the Teaching Excellence Award (AEP for its initials in Spanish). A Sharp Regression Discontinuity Design is used to identify the effect of AEP using data for more than 5,000 math and language teachers. The dataset includes the teaching evaluation score that AEP gives every year to their applicants, the corresponding standardized test score of more than 100,000 students, (SIMCE for its initials in Spanish), school characteristics, and information about motivation and self-perception that teachers self-report in a survey administrated by SIMCE along with the standardized test every year. The results show that rewarding teachers by giving a non-financial reward along with a financial one does not work in the intended way. I find a not statistically significant effect of giving a reward to teachers with outstanding teaching skills and pedagogical knowledge on student test scores, teaching practices, teacher’s self-confidence in a window of three years after the certification process. Lastly, there is no evidence of teacher-student or teacher-school sorting as an ex-post effect of obtaining the certification

The Origins of Shared Intuitions of Justice

Contrary to the common wisdom among criminal law scholars, empirical evidence reveals that people\u27s intuitions of justice are often specific, nuanced, and widely shared. Indeed, with regard to the core harms and evils to which criminal law addresses itself-physical aggression, takings without consent, and deception in transactions-the shared intuitions are stunningly consistent across cultures as well as demographics. It is puzzling that judgments of moral blameworthiness, which seem so complex and subjective, reflect such a remarkable consensus. What could explain this striking result? The authors theorize that one explanation may be an evolved predisposition toward these shared intuitions of justice, arising from the advantages that they provided, including stability, predictability, and the facilitation of beneficial exchange-the cornerstones to cooperative action and its accompanying survival benefits. Recent studies in animal behavior and brain science are consistent with this hypothesis, suggesting that moral judgment not only has biological underpinnings, but also reflects the effects of evolutionary processes on the distinctly human mind. Similarly, the child development literature provides evidence of predictable stages in the development of moral judgment within each individual, from infancy through adulthood, that are universal across all demographics and cultures. The current evidence does not preclude alternative explanations. Shared views of justice might arise, for example, through general social learning. However, a social learning explanation faces a variety of difficulties. It assumes that individuals will adopt norms good for the group at the expense of self-interest. It assumes an undemonstrated human capacity to assess extremely complex issues, such as what will be an efficient norm. It predicts that the significant variation in circumstances among different groups would give rise to commensurately different norms and variation in the effectiveness of teaching them. It is inconsistent with the developmental data that show intuitions of justice appearing early, before social learning of such complexity is possible. And, finally, a general social learning explanation predicts views of justice as accessible, reasoned knowledge, rather than the inaccessible, intuitive knowledge that we know them commonly to be. Whatever the correct explanation for the consensus puzzle, intuitions of justice seem to be an inherent part of being human and this, in turn, can have important implications for criminal law and criminal justice policy

The Origins of Shared Intuitions of Justice

Contrary to the common wisdom among criminal law scholars, the empirical evidence reveals that people\u27s intuitions of justice are often specific, nuanced, and widely shared. Indeed, with regard to the core harms and evils to which criminal law addresses itself – physical aggression, takings without consent, and deception in transactions – the shared intuitions are stunningly consistent, across cultures as well as demographics. It is puzzling that judgments of moral blameworthiness, which seem so complex and subjective, reflect such a remarkable consensus. What could explain this striking result? The authors theorize that one explanation may be an evolved predisposition toward these shared intuitions of justice, arising from the advantages that they provided, including stability, predictability, and the facilitation of beneficial exchange – the cornerstones to cooperative action and its accompanying survival benefits. Recent studies in animal behavior and brain science are consistent with this hypothesis, suggesting that moral judgment-making not only has biological underpinnings, but also reflects the effects of evolutionary processes on the distinctly human mind. Similarly, the child development literature reveals predictable stages in the development of moral judgment within each individual, from infant through adult, that are universal across all demographics and cultures. The current evidence does not preclude alternative explanations entirely. Shared views of justice might arise, for example, through general social learning. However, a social learning explanation faces a variety of difficulties. It assumes individuals will adopt norms good for the group at the expense of self-interest. It assumes an undemonstrated human capacity to assess extremely complex issues, such as what will be an efficient norm. It predicts the existence of only differences in views of justice, to reflect the wide differences among groups, their situations, and cultures producing different efficient norms and different effectiveness in teaching the same. It is inconsistent with the developmental data that show intuitions of justice appearing early, before social learning of such complexity is possible, and that show identical intuitions arising at parallel times despite cultural differences that would affect social learning. And, finally, a general social learning explanation predicts views of justice as accessible, reasoned knowledge, rather than the inaccessible, intuitive knowledge that we know it commonly to be. Whatever the correct explanation for the consensus puzzle, intuitions of justice seem to be an inherent part of being human and this, in turn, can have important implications for criminal law and criminal justice policy. Available for download at http://ssrn.com/abstract=95272

Balancing the Conspiracy’s Books: Inter-Competitor Sales and Price-Fixing Cartels

Price fixing is antithetical to a free-market economy. Competitive markets supply goods and services to consumers at the lowest efficient prices. Unfortunately, many businesses would prefer not to compete because they can increase their profits by conspiring to raise price. By refraining from competition, each firm in a price-fixing cartel can maximize its profits at the expense of its customers. Price-fixing conspiracies injure consumers by reducing output below the efficient level and transferring wealth from consumers to conspirators. Fortunately, cartels are often unstable because each member of the conspiracy can maximize its short-term profits by cheating on the cartel agreement by selling more than its cartel allotment or charging less than the cartel price. Cartels try to create stability through enforcement regimes. In order to deter cheating and to remedy cheating when it occurs, stable cartels need to develop enforcement mechanisms that monitor the sales (and prices) of cartel members, penalize firms that sell more than their cartel allotment, and compensate those who have not received their agreed-upon share of the cartel profits. Common monitoring schemes include firms hiring a third-party auditor or reporting their sales figures to a central cartel manager. When such monitoring detects deviations from the assigned cartel quotas, a cartel ringleader may require those firms that have oversold to funnel money to their cartel partners that have undersold. When cartel managers can solve the enforcement problems inherent in price-fixing conspiracies, cartels can survive for decades. Depending on the size of the market that has been cartelized, price-fixing conspirators can overcharge their consumers by billions of dollars. And while some consumers are being fleeced, other consumers are priced out of the market altogether and denied access to products and services that they would be able to purchase in a truly competitive market. Antitrust law is designed to deter and dismantle price-fixing cartels. Section One of the Sherman Act condemns price-fixing agreements as per se illegal. Section One is both a criminal and a civil statute. If criminally convicted, individuals face up to ten years’ imprisonment. Corporations convicted of price fixing are subject to fines of nine figures or higher. On the civil side, consumers who paid illegally inflated prices can sue for the overcharge. Antitrust damages are automatically tripled, and successful plaintiffs are entitled to their attorneys’ fees and costs. When the threat of enforcement of antitrust laws is genuine, rational firms can be dissuaded from conspiring to fix prices. When firms nonetheless persevere in their price fixing, effective antitrust enforcement can disgorge the ill-gotten gains and compensate the victims of the price-fixing conspiracy. The success of the antitrust regime depends on courts being able to recognize price fixing and to hold price fixers accountable. Unfortunately, courts often do not appreciate the mechanics of cartelization. Most federal judges have not studied the theory and practice of price fixing. They are unfamiliar with the ubiquity of international cartels and the case studies of price fixing in American history. More importantly, judges are generally unversed in how conspirators structure cartel activities to avoid detection or to appear innocent to outsiders untrained in the art of price fixing. This gives actual price fixers confidence that they can conspire to illegally restrain competition while evading liability in court. This Article focuses on the legal significance of competitors buying products from each other. Such inter-competitor sales stabilize price-fixing conspiracies by providing a mechanism to balance the cartel’s books. When one price-fixing conspirator sells more than its cartel quota to its customers, the other conspirator firms that have undersold will demand some form of compensation. Absent some form of reimbursement, an underselling firm may decide the risks of price fixing are not worth the benefits, which are now less than negotiated when its partners are not honoring the letter of the agreement. If one major firm leaves the cartel, the entire enterprise may collapse, and all of the firms may find themselves in a competitive market. To avoid that scenario, some price-fixing conspiracies arrange to have over-sellers purchase products from under-sellers, which funnels money from the former to the latter. This can preserve the life of the cartel, improving the cartel’s coffers at its customers’ expense. If federal judges do not understand how price-fixing conspiracies use inter-competitor sales to enforce their cartel arrangements, then judges may be more prone to dismiss price-fixing claims or grant summary judgment to defendants who have, in fact, conspired to fix prices. This Article seeks to reduce the likelihood of that outcome by explaining how cartels use inter-competitor sales—sometimes called buybacks or true-ups—as a mechanism to balance the cartel’s books. Using a combination of economic analysis and empirical case studies, this Article examines the critical role that buybacks can play—and have played—in price-fixing conspiracies. Part One of this Article lays out the legal framework for proving price fixing through circumstantial evidence. Because direct evidence of price fixing is rarely available, most plaintiffs rely on circumstantial evidence, which requires them both to show that the defendants engaged in parallel pricing and to present “plus factors.” Plus factors are types of evidence that indicate that the parallel conduct is a function of collusion, not of independent decision-making. Through the common-law process, federal courts have recognized over a dozen different plus factors. Part Two discusses how courts have addressed the significance of inter-competitor sales as evidence of a price-fixing conspiracy. Until recently, all federal courts to consider the issue have held inter-competitor sales to be a plus factor. These opinions, however, generally have little discussion about the mechanics of cartelization and how price-fixing conspirators often purchase products from each other as a way to balance accounts among cartel members. Nevertheless, the law seemed reasonably settled. In 2017, however, in Valspar Corp. v. E.I. Du Pont De Nemours & Co., a divided panel of the Third Circuit—claiming a lack of precedent on the issue—held that inter-competitor sales among manufacturers of titanium dioxide had no probative value, and consequently affirmed summary judgment for the defendants, even though the defendants had engaged in thirty-one parallel price increases and other plus factors were present. The Valspar opinion risks upending settled precedent, while claiming that no such precedent exists. Using both economic theory and empirical evidence, Part Three explains why inter-competitor sales are inherently probative of collusion. To be stable in the long run, a price-fixing conspiracy requires a mechanism for cartel members who sell more than their quota to compensate their under-selling cartel partners. Inter-competitor sales provide an ideal compensation instrument because buybacks funnel money from one firm to its rivals without appearing as suspicious as a one-way cash transfer. Inter-firm transactions provide a plausible excuse for why competitors are meeting and discussing the price of their products. Also, buying from rivals removes product from the market in order to create artificial scarcity and, thereby, drives up the market price. Empirically, actual price-fixing cartels have used inter-competitor sales to balance their books. For example, in the early and mid-twentieth century, the international cartels in dyestuffs and aluminum employed company-to-company sales to ensure that each cartel member received its agreed-upon shares of the cartel’s profits. More recently, modern price-fixing conspiracies in citric acid, lysine, and vitamins—which collectively overcharged their customers by billions of dollars—used inter-competitor sales as a cartel enforcement mechanism. Part Four examines the Third Circuit’s Valspar opinion in detail. In discounting inter-competitor sales as a plus factor, the Third Circuit committed several errors. It is important to expose and explain these errors so that future federal judges do not follow in the Third Circuit’s footsteps and replicate these mistakes. For example, the Valspar opinion created the false impression that no precedents or studies exist showing the link between inter-competitor sales and price-fixing conspiracies. It also misanalysed the facts before it, for example, by seeming to treat the presence of intellectual property licensing agreements as sapping inter-competitor sales of their probative value. Ultimately, because the Valspar majority did not understand how price-fixing conspiracies operate, the opinion failed to appreciate the legal significance of inter-competitor sales. Finally, Part Five explains how inter-competitor sales are an important plus factor that help demonstrate that the defendants’ parallel pricing is the product of collusion, not independent decision-making. The presence of inter-competitor sales is a plus factor, in and of itself, because cartels commonly use them as an enforcement device. Such sales also help establish other recognized plus factors, including conduct against the parties’ independent economic interests. Part Five concludes by explaining how the probative value of inter-competitor sales increases significantly under certain conditions, including when the purchasing firm has inventory or excess capacity, when the transactions are correlated with the competing firms reporting their sales data to each other, when the market is characterized by stable market shares, and when the inter-competitor sales take place at non-market prices

Tõhus peit- ja aktiivse ründaja vastu kaitstud turvaline ühisarvutus

Turvaline ühisarvutus on tänapäevase krüptograafia üks tähtsamaid kasutusviise, mis koondab elegantsed matemaatilised lahendused praktiliste rakenduste ehitamiseks, võimaldades mitmel erineval andmeomanikul sooritada oma andmetega suvalisi ühiseid arvutusi, ilma neid andmeid üksteisele avaldamata. Passiivse ründaja vastu turvalised protokollid eeldavad, et kõik osapooled käituvad ausalt. Aktiivse ründaja vastu turvalised protokollid ei lekita privaatseid andmeid sõltumata ründaja käitumisest. Käesolevas töös esitatakse üldine meetod, mis teisendab passiivse ründaja vastu turvalised ühisarvutusprotokollid turvaliseks aktiivse ründaja vastu. Meetod on optimeeritud kolme osapoolega arvutusteks üle algebraliste ringide; praktikas on see väga efektiivne mudel, mis teeb reaalse maailma rakendused teostatavateks. Meetod lisab esialgsele arvutusprotokollile täitmisjärgse verifitseerimisfaasi, mis muudab valesti käitunud osapooltel vahelejäämise vältimise tõenäosuse kaduvväikseks, säilitades esialgse protokolli turvagarantiid. Lisaks uurib käesolev töö rünnete uut eesmärki, mis seisneb mingi ausa osapoole vaate manipuleerimises sellisel viisil, et ta saaks midagi teada teise ausa osapoole privaatsete andmete kohta. Ründaja ise ei tarvitse seda infot üldse teada saada. Sellised ründed on olulised, sest need kohustavad ausat osapoolt tühjendama oma süsteemi teiste osapoolte andmetest, kuid see ülesanne võib olla päris mittetriviaalne. Eelnevalt pakutud verifitseerimismehhanisme täiendatakse nii, et privaatsed andmed oleksid kaitstud ka ausate osapoolte eest. Paljud ühisarvutusplatvormid on varustatud programmeerimiskeelega, mis võimaldab kirjutada privaatsust säilitavaid rakendusi ilma allolevale krüptograafiale mõtlemata. Juhul, kui programm sisaldab tingimuslauseid, kus arvutusharu valik sõltub privaatsetest andmetest, ei tohi ükski osapool haru valikust midagi teada, nii et üldjuhul peavad osapooled täitma kõik harud. Harude suure arvu kor-ral võib arvutuslik lisakulu olla ülisuur, sest enamik vahetulemustest visatakse ära. Käesolevas töös pakutakse selliseid lisakulusid vähendavat optimeerimist.Secure multiparty computation is one of the most important employments of modern cryptography, bringing together elegant mathematical solutions to build up useful practical applications. It allows several distinct data owners to perform arbitrary collaborative computation on their private data without leaking any information to each other. Passively secure protocols assume that all parties follow the protocol rules. Actively secure protocols do not leak private data regardless of the attacker’s behaviour. This thesis presents a generic method for turning passively secure multiparty protocols to actively secure ones. The method is optimized for three party computation over algebraic rings, which has proven to be quite an efficient model, making large real-world applications feasible. Our method adds to the protocol a post-execution verification phase that allows a misbehaving party to escape detection only with negligible probability. It preserves the privacy guarantees of the original protocol. In this thesis, we also study a new adversarial goal in multiparty protocols. The goal is to manipulate the view of some honest party in such a way, that this honest party learns the private data of some other honest party. The adversary itself might not learn this data at all. Such attacks are significant because they create a liability to the first honest party to clean its systems from the second honest party’s data, which may be a highly non-trivial task in practice. We check the security of our verification mechanism in this new model, and we propose some minor modifications that ensure data protection also from the honest parties. Many secure multiparty computation platforms come with a programming language that allows the developer to write privacy-preserving applications without thinking of the underlying cryptography. If a program contains conditional statements where the choice of the computational branch depends on private data, then no party should know which branch has been executed, so in general the parties need to execute all of them. If the number of branches is large, the computational overhead may be enormous, as most of the intermediate results are just discarded. In this thesis, we propose an automatic optimization that reduces this overhead