Flexible Paxos: Quorum intersection revisited

Distributed consensus is integral to modern distributed systems. The widely adopted Paxos algorithm uses two phases, each requiring majority agreement, to reliably reach consensus. In this paper, we demonstrate that Paxos, which lies at the foundation of many production systems, is conservative. Specifically, we observe that each of the phases of Paxos may use non-intersecting quorums. Majority quorums are not necessary as intersection is required only across phases. Using this weakening of the requirements made in the original formulation, we propose Flexible Paxos, which generalizes over the Paxos algorithm to provide flexible quorums. We show that Flexible Paxos is safe, efficient and easy to utilize in existing distributed systems. We conclude by discussing the wide reaching implications of this result. Examples include improved availability from reducing the size of second phase quorums by one when the number of acceptors is even and utilizing small disjoint phase-2 quorums to speed up the steady-state

Robust services in dynamic systems

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2005.Includes bibliographical references (p. 191-202).Our growing reliance on online services accessible on the Internet demands highly- available systems that work correctly without interruption. This thesis extends previous work on Byzantine-fault-tolerant replication to meet the new requirements of current Internet services: scalability and the ability to reconfigure the service automatically in the presence of a changing system membership. Our solution addresses two important problems that appear in dynamic replicated services: First, we present a membership service that provides servers and clients in the system with a sequence of consistent views of the system membership (i.e., the set of currently available servers). The membership service is designed to be scalable, and to handle membership changes mostly automatically. Furthermore, the membership service is itself reconfigurable, and tolerates arbitrary faults of a subset of the servers that are implementing it at any instant. The second part of our solution is a generic methodology for transforming replicated services that assume a fixed membership into services that support a dynamic system membership. The methodology uses the output from the membership service to decide when to reconfigure.(cont.) We built two example services using this methodology: a dynamic Byzantine quorum system that supports read and write operations, and a dynamic Byzantine state machine replication system that supports any deterministic service. The final contribution of this thesis is an analytic study that points out an obstacle to the deployment of replicated services based on a dynamic membership. The basic problem is that maintaining redundancy levels for the service state as servers join and leave the system is costly in terms of network bandwidth. To evaluate how dynamic the system membership can be, we developed a model for the cost of state maintenance in dynamic replicated services, and we use measured values from real-world traces to determine possible values for the parameters of the model. We conclude that certain deployments (like a volunteer-based system) are incompatible with the goals of large- scale reliable services. We implemented the membership service and the two example services. Our performance results show that the membership service is scalable, and our replicated services perform well, even during reconfigurations.by Rodrigo Seromenho Miragaia Rodrigues.Ph.D

MEDIATING INDIGENOUS IDENTITY: VIDEO, ADVOCACY, AND KNOWLEDGE IN OAXACA, MEXICO

In the southern Mexican state of Oaxaca, many indigenous communities further their struggles for greater political and cultural autonomy by working with transnational non-governmental organizations (NGOs). Communication technology (what I call comtech) is increasingly vital to these intersecting socio-spatial relations of activism and advocacy. In this dissertation, I examine how comtech offer indigenous individuals and organizations with the means for visualizing their political-cultural agendas. Approaching the access and use of comtech, especially video technologies, as a partial and situated technoscience, I inquire into how and why these activities reconfigure the production and evaluation of authoritative knowledge about indigenous peoples, places, and practices. More specifically, I undertook an organizational ethnography of a small intermediary NGO comprised of individuals who self-identify as indigenous and others who do not, Ojo de Agua Comunicacin Indgena, which endeavors to place communication technologies (especially video equipment) at the disposal of indigenous communities. Through participation-observation and interviews, I explored this groups everyday strategies of networking in the name of assisting indigenous actors access and appropriation of visual technologies. I also pursued interpretive analyses of video-mediated articulations of indigenous knowledge and identity that were enabled by Ojo de Agua. My research indicates that Ojo de Agua has selectively built upon the ambitions and the socio-spatial connections of a government program that emerged from the initiatives of academic advocates, who sought to open new spaces of participation for indigenous peoples. Members of Ojo de Agua have, however, found their goal of service somewhat stymied by a situation that positions them within a flexible labor force of knowledge workers. Their livelihoods as media makers did not allow them (the time or money) to pursue as much altruism and advocacy as they would have liked. Nonetheless, Ojo de Aguas corpus of videos established the group as an alternative and yet authoritative source of visual knowledge of indigenous peoples, places, and practices. This relocation of advocacy is symptomatic of the creative destruction fueled by the neo-liberal economic policies that, for the last thirty years, have been reconfiguring spaces of cooperation and conflict in Latin America

RNA, the Epicenter of Genetic Information

The origin story and emergence of molecular biology is muddled. The early triumphs in bacterial genetics and the complexity of animal and plant genomes complicate an intricate history. This book documents the many advances, as well as the prejudices and founder fallacies. It highlights the premature relegation of RNA to simply an intermediate between gene and protein, the underestimation of the amount of information required to program the development of multicellular organisms, and the dawning realization that RNA is the cornerstone of cell biology, development, brain function and probably evolution itself. Key personalities, their hubris as well as prescient predictions are richly illustrated with quotes, archival material, photographs, diagrams and references to bring the people, ideas and discoveries to life, from the conceptual cradles of molecular biology to the current revolution in the understanding of genetic information. Key Features Documents the confused early history of DNA, RNA and proteins - a transformative history of molecular biology like no other. Integrates the influences of biochemistry and genetics on the landscape of molecular biology. Chronicles the important discoveries, preconceptions and misconceptions that retarded or misdirected progress. Highlights major pioneers and contributors to molecular biology, with a focus on RNA and noncoding DNA. Summarizes the mounting evidence for the central roles of non-protein-coding RNA in cell and developmental biology. Provides a thought-provoking retrospective and forward-looking perspective for advanced students and professional researchers

Technofetishism of posthuman bodies: representations of cyborgs, ghosts, and monsters in contemporary Japanese science fiction film and animation

The thesis uses a feminist approach to explore the representation of the cyborg in Japanese film and animation in relation to gender, the body, and national identity. Whereas the figure of the cyborg is predominantly pervasive in cinematic science fiction, the Japanese popular imagination of cyborgs not only crosses cinematic genre boundaries between monster, disaster, horror, science fiction, and fantasy but also crosses over to the medium of animation. In regard to the academic research on Japanese cinema and animation, there is a serious gap in articulating concepts such as live-action film, animation, gender, and the cyborg. This thesis, therefore, intends to fill the gap by investigating the gendered cyborg through a feminist lens to understand the interplay between gender, the body and the cyborg within historical-social contexts. Consequently, the questions proposed below are the starting point to reassess the relationship between Japanese cinema, animation, and the cyborg. How has Japanese popular culture been obsessed with the figure of the cyborg? What is the relationship between Japanese live-action film and Japanese animation in terms of the popular imagination of the cyborg? In particular, how might we discuss the representation of the cyborg in relation to the concept of national identity and the associated ideology of “Japaneseness”, within the framework of Donna Haraway’s influential cyborg theory and feminist theory? The questions are addressed in the four sections of the thesis to explore the representation of the gendered cyborg. First, I outline the concept of the cyborg as it has been developed in relation to notions of gender and the ‘cyborg’ in Western theory. Secondly, I explore the issues in theorising the science fiction genre in Japanese cinema and animation and then address the problem of defining science fiction in relation to the phenomenon of the cyborg’s genre-crossing. Finally, I provide a contextualising discussion of gender politics and gender roles in Japan in order to justify my use of Western feminist theory as well as discuss the strengths and limitations of such an approach before moving, in the remainder of the thesis, to an examination of a number of case studies drawn from Japanese cinema and animation

A strategic turnaround model for distressed properties

The importance of commercial real estate is clearly shown by the role it plays, worldwide, in the sustainability of economic activities, with a substantial global impact when measured in monetary terms. This study responds to an important gap in the built environment and turnaround literature relating to the likelihood of a successful distressed commercial property financial recovery. The present research effort addressed the absence of empirical evidence by identifying a number of important factors that influence the likelihood of a successful distressed, commercial property financial recovery. Once the important factors that increase the likelihood of recovery have been determined, the results can be used as a basis for turnaround strategies concerning property investors who invest in distressed opportunities. A theoretical turnaround model concerning properties in distress, would be of interest to ‘opportunistic investing’ yield-hungry investors targeting real estate transactions involving ‘turnaround’ potential. Against this background, the main research problem investigated in the present research effort was as follows: Determine the important factors that would increase the likelihood of a successful distressed commercial property financial recovery. A proposed theoretical model was constructed and empirically tested through a questionnaire distributed physically and electronically to a sample of real estate practitioners from across the globe, and who had all been involved, directly or indirectly, with reviving distressed properties. An explanation was provided to respondents of how the questionnaire was developed and how it would be administered. The demographic information pertaining to the 391 respondents was analysed and summarised. The statistical analysis performed to ensure the validity and reliability of the results, was explained to respondents, together with a detailed description of the covariance structural equation modelling method used to verify the proposed theoretical conceptual model. vi The independent variables of the present research effort comprised; Obsolescence Identification, Capital Improvements Feasibility, Tenant Mix, Triple Net Leases, Concessions, Property Management, Contracts, Business Analysis, Debt Renegotiation, Cost-Cutting, Market Analysis, Strategic Planning and Demography, while the dependent variable was The Perceived Likelihood of a Distressed Commercial Property Financial Recovery. After analysis of the findings, a revised model was then proposed and assessed. Both validity and reliability were assessed and resulted in the following factors that potentially influence the dependent variables; Strategy, Concessions, Tenant Mix, Debt Restructuring, Demography, Analyse Alternatives, Capital Improvements Feasibility, Property Management and Net Leases while, after analysis, the dependent variable was replaced by two dependent variables; The Likelihood of a Distressed Property Turnaround and The Likelihood of a Distressed Property Financial Recovery. The results showed that Strategy (comprising of items from Strategic Planning, Business Analysis, Obsolescence Identification and Property Management) and Concessions (comprising of items from Concessions and Triple Net Leases) had a positive influence on both the dependent variables. Property Management (comprising of items from Business Analysis, Property Management, Capital Improvements Feasibility and Tenant Mix) had a positive influence on Financial Turnaround variable while Capital Improvements Feasibility (comprising of items from Capital Improvements Feasibility, Obsolescence Identification and Property Management) had a negative influence on both. Demography (comprising of items only from Demography) had a negative influence on the Financial Recovery variable. The balance of the relationships were depicted as non-significant. The present research effort presents important actions that can be used to influence the turnaround and recovery of distressed real estate. The literature had indicated reasons to recover distressed properties as having wide-ranging economic consequences for the broader communities and the countries in which they reside. The turnaround of distressed properties will not only present financial rewards for opportunistic investors but will have positive effects on the greater community and economy and, thus, social and economic stability. Vii With the emergence of the COVID-19 pandemic crisis, issues with climate change and sustainability, global demographic shifts, changing user requirements, shifts in technology, the threat of obsolescence, urbanisation, globalisation, geo-political tensions, shifting global order, new trends and different generational expectations, it is becoming more apparent that the threat of distressed, abandoned and derelict properties is here to stay, and which will present future opportunities for turnaround, distressed property owners, as well as future worries for urban authorities and municipalities dealing with urban decay. The study concluded with an examination of the perceived limitations of the study as well as presenting a comprehensive range of suggestions for further research.Thesis (PhD) -- Faculty of Engineering, Built Environment and Information Technology, School of the built Environment, 202

A strategic turnaround model for distressed properties

The importance of commercial real estate is clearly shown by the role it plays, worldwide, in the sustainability of economic activities, with a substantial global impact when measured in monetary terms. This study responds to an important gap in the built environment and turnaround literature relating to the likelihood of a successful distressed commercial property financial recovery. The present research effort addressed the absence of empirical evidence by identifying a number of important factors that influence the likelihood of a successful distressed, commercial property financial recovery. Once the important factors that increase the likelihood of recovery have been determined, the results can be used as a basis for turnaround strategies concerning property investors who invest in distressed opportunities. A theoretical turnaround model concerning properties in distress, would be of interest to ‘opportunistic investing’ yield-hungry investors targeting real estate transactions involving ‘turnaround’ potential. Against this background, the main research problem investigated in the present research effort was as follows: Determine the important factors that would increase the likelihood of a successful distressed commercial property financial recovery. A proposed theoretical model was constructed and empirically tested through a questionnaire distributed physically and electronically to a sample of real estate practitioners from across the globe, and who had all been involved, directly or indirectly, with reviving distressed properties. An explanation was provided to respondents of how the questionnaire was developed and how it would be administered. The demographic information pertaining to the 391 respondents was analysed and summarised. The statistical analysis performed to ensure the validity and reliability of the results, was explained to respondents, together with a detailed description of the covariance structural equation modelling method used to verify the proposed theoretical conceptual model. vi The independent variables of the present research effort comprised; Obsolescence Identification, Capital Improvements Feasibility, Tenant Mix, Triple Net Leases, Concessions, Property Management, Contracts, Business Analysis, Debt Renegotiation, Cost-Cutting, Market Analysis, Strategic Planning and Demography, while the dependent variable was The Perceived Likelihood of a Distressed Commercial Property Financial Recovery. After analysis of the findings, a revised model was then proposed and assessed. Both validity and reliability were assessed and resulted in the following factors that potentially influence the dependent variables; Strategy, Concessions, Tenant Mix, Debt Restructuring, Demography, Analyse Alternatives, Capital Improvements Feasibility, Property Management and Net Leases while, after analysis, the dependent variable was replaced by two dependent variables; The Likelihood of a Distressed Property Turnaround and The Likelihood of a Distressed Property Financial Recovery. The results showed that Strategy (comprising of items from Strategic Planning, Business Analysis, Obsolescence Identification and Property Management) and Concessions (comprising of items from Concessions and Triple Net Leases) had a positive influence on both the dependent variables. Property Management (comprising of items from Business Analysis, Property Management, Capital Improvements Feasibility and Tenant Mix) had a positive influence on Financial Turnaround variable while Capital Improvements Feasibility (comprising of items from Capital Improvements Feasibility, Obsolescence Identification and Property Management) had a negative influence on both. Demography (comprising of items only from Demography) had a negative influence on the Financial Recovery variable. The balance of the relationships were depicted as non-significant. The present research effort presents important actions that can be used to influence the turnaround and recovery of distressed real estate. The literature had indicated reasons to recover distressed properties as having wide-ranging economic consequences for the broader communities and the countries in which they reside. The turnaround of distressed properties will not only present financial rewards for opportunistic investors but will have positive effects on the greater community and economy and, thus, social and economic stability. Vii With the emergence of the COVID-19 pandemic crisis, issues with climate change and sustainability, global demographic shifts, changing user requirements, shifts in technology, the threat of obsolescence, urbanisation, globalisation, geo-political tensions, shifting global order, new trends and different generational expectations, it is becoming more apparent that the threat of distressed, abandoned and derelict properties is here to stay, and which will present future opportunities for turnaround, distressed property owners, as well as future worries for urban authorities and municipalities dealing with urban decay. The study concluded with an examination of the perceived limitations of the study as well as presenting a comprehensive range of suggestions for further research.Thesis (PhD) -- Faculty of Engineering, Built Environment and Information Technology, School of the built Environment, 202