VictorJuiz/thesis huggingface dataset:
Duality theory for optimal mechanism design
Keywords: approximation algorithms
duality
optimal auctions
revenue maximization
game theory
mechanism design

In this work we present a general duality-theory framework for revenue maximization in additive Bayesian auctions involving multiple items and many bidders whose values for the goods follow arbitrary continuous joint distributions over some multi-dimensional real interval. Although the single-item case has been resolved in a very elegant way by the seminal work of Myerson [1981], optimal solutions involving more items still remain elusive. The framework extends linear programming duality and complementarity to constraints with partial derivatives. The dual system reveals the natural geometric nature of the problem and highlights its connection with the theory of bipartite graph matchings.
We demonstrate the power of the framework by applying it to various special monopoly settings where a seller of multiple heterogeneous goods faces a buyer with independent item values drawn from various distributions of interest, to design both exact and approximately optimal selling mechanisms. Previous optimal solutions were only known for up to two and three goods, and a very limited range of distributional priors. The duality framework is used not only for proving optimality, but perhaps more importantly, for deriving the optimal mechanisms themselves.
Some of our main results include: the proposal of a simple deterministic mechanism, which we call Straight-Jacket Auction (SJA) and is defined in a greedy, recursive way through natural geometric constraints, for many uniformly distributed goods, where exact optimality is proven for up to six items and general optimality is conjectured; a scheme of sufficient conditions for exact optimality for two-good settings and general independent distributions; a technique for upper-bounding the optimal revenue for arbitrarily many goods, with an application to uniform and exponential priors; and the proof that offering deterministically all items in a single full bundle is the optimal way of selling multiple exponentially i.i.d. items.
Reliable peer to peer grid middleware
Keywords: SAM-GRID
cloud
middleware
DHT
grid
distributed systems
chord
distributed hash table
peer to peer

Grid computing systems are suffering from reliability and scalability problems caused by their reliance on centralised middleware. In this thesis, we argue that peer to peer middleware could help alleviate these problems. We show that peer to peer techniques can be used to provide reliable storage systems, which can be used as the basis for peer to peer grid middleware. We examine and develop new methods of providing reliable peer to peer storage, giving a new algorithm for this purpose, and assessing its performance through a combination of analysis and simulation. We then give an architecture for a peer to peer grid information system based on this work. Performance evaluation of this information system shows that it improves scalability when compared to the original centralised system, and that it withstands the failure of participant nodes without a significant reduction in quality of service. New contributions include dynamic replication, a new method for maintaining reliable storage in a Distributed Hash Table, which we show allows for the creation of more reliable, higher performance systems with lower bandwidth usage than current techniques. A new analysis of the reliability of distributed storage systems is also presented, which shows for the first time that replica placement has a significant effect on reliability. A simulation of the performance of distributed storage systems provides for the first time a quantitative performance comparison between different placement patterns. Finally, we show how these reliable storage techniques can be applied to grid computing systems, giving a new architecture for a peer to peer grid information service for the SAM-Grid system. We present a thorough performance evaluation of a prototype implementation of this architecture. Many of these contributions have been published at peer reviewed conferences.
Real exchange rate volatility in the long-run growth process
Keywords: unconventional credit policy
financial frictions
home bias
imperfect asset substitutability
real exchange rate volatility
moral hazard

The objective of this thesis is to examine real exchange rate volatility, with a particular focus on investigating the causes of exchange rate jumps. While the predominant approach in the literature is to examine the interaction between nominal rigidities and nominal shocks, this thesis examines the volatility that arises from real rigidities and shocks. Trying to better understand the transmission of real shocks to the exchange rate is a worthwhile task, given the substantial evidence that these shocks and rigidities are important for explaining other economic fluctuations.
This thesis develops theoretical models that examine the contributions of specific real rigidities to exchange rate volatility. Chapter 1 introduces our baseline specification - a frictionless model, with the exception of capital adjustment costs. This baseline generates very mild exchange rate fluctuations. Additional rigidities are required to generate volatility of the magnitude that is typically observed. Chapter 2 finds that introducing imperfect asset substitutability - specifically, home asset bias - goes a little towards achieving this. When investors are biased, the exchange rate must adjust by more to equilibrate asset markets. This greater burden of adjustment on the exchange rate along the short run path typically translates to larger jumps after shocks. Similarly, Chapter 3 shows that augmenting the baseline with banks and financial frictions raises exchange rate volatility. The key point is that, in the presence of financial frictions, there is a risk premium that widens after negative shocks, increasing the required adjustment of the exchange rate. A fourth chapter extends Chapter 3 and shows that unconventional credit policy, while beneficial in some respects, nonetheless entails nontrivial costs because it invites moral hazard by encouraging banks to be more highly leveraged, which increases exchange rate and consumption volatility.
So, the overall message is that, in the presence of plausible real frictions - including (i) capital adjustment costs, (ii) imperfect asset substitutability, and (iii) financial frictions - real shocks can generate a plausibly significant degree of real exchange rate volatility. This thus posits an additional explanation of exchange rate jumps that complements the predominantly monetary literature.
A laboratory study of the Marchetti dilatometer
Keywords: dilatometer

The purpose of this study was twofold: to design, construct and commission a testing chamber for the calibration of in-situ devices in clay and to use the chamber to carry out a programme of research into the factors affecting the results of the Marchetti dilatometer test. A calibration chamber system was developed which was capable of producing one metre high by one metre diameter cylindrical beds of clay. The preparation technique involved an initial phase of one-dimensional consolidation in a rigid tube, followed by a second phase of consolidation in a chamber with independent stress control. The stress control was achieved through water-filled flexible membranes in the side and at the base of the chamber. Reasonably uniform distributions of the water content and the undrained strength were obtained from investigations carried out in each clay bed after they had been tested. The Marchetti dilatometer is an in-situ testing device the results of which have been interpreted chiefly through empirical correlations based on the results of field tests. The interpretation has mainly involved the use of two readings, and , though recently a third reading , has been introduced. Dilatometer tests were carried out in nine clay beds. The stress history and stress state of each clay bed were systematically varied in the test programme to allow their individual effects on the dilatometer readings to be assessed. The study revealed that in clay the dilatometer reading is controlled by the undrained strength and the horizontal stress and was independent of the degree of overconsolidation. Through use of this result it was shown that the applicability of many of the empirical correlations presently used to evaluate the dilatometer readings is restricted to deposits with one-dimensional stress histories. It was also found that was dependent on the undrained strength and that the reading was close to the total horizontal stress of the sample though the latter finding does not appear to be supported by the few field results that are available. The results have highlighted the redundancy of the reading for property evaluation. It was found that a timed sequence of , and readings could be used to detect the variation of the consolidation properties between clay beds. In addition to the tests in clay, the results of 31 dilatometer tests carried out in a calibration chamber for sand have also been analysed. An inter-relationship between , and was found suggesting that they were all measuring the same soil response; that of the pressure required to open a cavity in the sand. The reading was shown to be dependent on the horizontal stress and the state parameter, though this dependence could not be exploited to back calculate the horizontal stress. Overconsolidation of the sand specimens had no significant influence on the readings.
Sustainable development, climate change, and renewable energy in rural Central America
Keywords: Political Ecology
Climate Change Adaptation
Common Property Resources
Climate Change Mitigation
Poverty Alleviation
Renewable Energy

Can rural renewable energy projects simultaneously meet the multiple goals of sustainable development, climate change mitigation and climate change adaptation? If so, under what conditions? Rural communities throughout Latin America have increasingly suffered the impacts of climate change and few policies exist to help them adapt to these impacts. The basic infrastructure and services that they frequently lack can be provided by low carbon technologies, potentially funded by international carbon finance flows that could enable the Millennium Development Goals of economic growth and poverty alleviation to be met while minimizing carbon emissions. This research will focus on this interrelationship among development, climate change mitigation and climate change adaptation policies and practices using political ecology to analyse community renewable energy projects in rural Central America.
I assess fifteen community-owned renewable energy projects in Guatemala and Nicaragua to analyse whether current renewable energy projects are achieving these goals in an integrated way. The projects were established primarily as development, emissions reductions, climate change adaptation and disaster relief. The projects are evaluated on economic, development and climate change indicators that include sustainable development, poverty alleviation, emissions reductions, and climate vulnerability. I examine how the type of common property governance, local historical and environmental background and project implementation process influence the project success in meeting multiple objectives of climate adaptation, mitigation and development. Research methods include participatory poverty assessment techniques, semi-structured interviews, stakeholder analysis, and a combination of rapid and participatory methods. The analysis of sustainable development and vulnerability used the Sustainable Livelihoods Approach methodologies and emissions reductions were calculated using standard carbon reduction methodologies.
The results show that, under certain conditions, renewable energy projects can simultaneously meet these three objectives, and thus that responses to climate change can be integrated with poverty alleviation and sustainable development. Small scale hydroelectric and solar systems can reduce emissions, enable adaptation and help local livelihoods although there are numerous problems that limit the success of projects including poor design, inequitable distribution of benefits, and poorly designed governance and maintenance structures.
DNA motor-protein hybrids for molecular transport and self-organisation
Keywords: bionanotechnology

Kinesin is a molecular motor which walks on microtubule tracks in the eukaryotic cytoskeleton. It transports cargo but is also involved in cytoskeletal organisation. This thesis demonstrates fusing kinesin and DNA to construct a molecular transport system using self-organised tracks and to study the mechanics of the minimal motor unit of kinesin.
The programmability of DNA allows for the formation of nanostructures with controllable interactions. Kinesin is conjugated to various DNA nanostructures to accomplish different tasks. Instructions encoded into DNA sequences are used to direct the assembly of a polar array of microtubules, to control the loading, active concentration and unloading of cargo on this track network and to trigger the disassembly of the network. Fluorescence microscopy was used to observe these microtubule arrays and the movement of cargo. It was found that the DNA signals used to control the unloading of cargo and the disassembly of the network had to be actively transported, rather than relying on diffusion, for effective delivery of the signal. This work lead to a first author publication, Wollman et al. (2013).
DNA was also used to study kinesin by linking defined numbers of minimal functional motor units, single kinesin heads, into teams of 4-12 heads and observing their movement along microtubules via fluorescent labelling. A minimum of 5 heads were required for sustained movement, in agreement with the predictions of Hancock and Howard (1998). The velocity of teams increased with more heads, up to 8, and then a decrease was observed in teams with more heads.
Structural and functional studies of cell surface receptors
Keywords: fibronectin leucine-rich transmembrane proteins
cell surface receptors
structural biology
protein-protein interactions
T-cell receptors

Receptor proteins on the surfaces of cells equip them to communicate with each other and to sense and interact with their environment. One receptor family, the αβ T-cell receptors (TCRs), allow T lymphocytes to detect and respond to pathogens via interactions with antigen-presenting major histocompatibility complex (MHC) molecules on target cells. A degree of TCR cross-reactivity (e.g. through structural similarity between peptide-MHC (pMHC) complexes) is essential to account for all possible pathogens, but can also lead to the misinterpretation of self antigens as foreign, and thereby elicit an autoimmune response, resulting in diseases such as multiple sclerosis (MS). Structural studies of pMHC and TCR-pMHC complexes have been key to developing of an understanding of the molecular basis of TCR cross reactivity, and the first strand of this thesis describes attempts to express and purify a highly cross-reactive MS patient-derived TCR for structural characterisation. The formation, purification and crystallisation of a TCR-self pMHC complex including another autoreactive TCR is also described.
Another family of receptors, the fibronectin leucine-rich transmembrane proteins (FLRTs), has been implicated in roles in embryonic development including cell sorting and adhesion. In the second strand of this thesis, the nature of homotypic interactions between FLRTs, which may underlie adhesion between FLRT transfected cells, is investigated. Biophysical analyses demonstrate that these interactions may be mediated by the extracellular leucine-rich repeat (LRR) domain, and crystal structures of all three FLRT LRR domains suggest how interactions between them may underlie FLRT self-association at the cell surface. Residues which contribute to these interactions are conserved across different members of the FLRT family and different species. These findings confirm that FLRTs induce homotypic cell-cell adhesion, and suggest that this behaviour is mediated by self association at the cell surface via the LRR domain.
Studies in identification and control
Keywords: time-delay control
continuous-time control
Self-tuning control
minimum-variance control
optimal control
adaptive control

The optimal steady-state control, and suboptimal adaptive control, of disturbed single-input-output systems are introduced, and the class of systems considered is defined. It is noted that the stochastic tracking problem divides into a deterministic tracking problem and a stochastic regulator problem; the solutions to these two problems are shown to be independent but formally similar. The continuous regulator problem is approached via both frequency and time domain methods: the former method is extended to cover unstable systems; the latter method is extended to include systems with input delay. The two regulators are shown to be externally equivalent. The frequency domain method is briefly described for discrete systems, and shown to include the minimum variance regulator of Åström and Peterka as a special case. Some systems which allow measurement noise to be treated as a system disturbance for the purposes of optimal controller design are investigated. A novel class of control laws is described in both continuous and discrete time; in the same way as the minimum variance regulator forms the basis of the self-tuning regulator of Åström and Wittenmark, these minimum variance controllers from the basis of a self-tuning controller. These minimum variance controllers have a number of advantages over the minimum-variance regulator, and are open to a number of interpretations including: a model following control law, and an extension of classical control laws to systems with delay. The optimality of this class of control laws is investigated, and analogies drawn with the previously considered k-step-ahead control laws; some examples are given to illustrate the method. An adaptive control law combining the above minimum variance controllers with a linear least-squares algorithm is proposed and shown to be self-tuning. These self-tuning controllers are only slightly more complex than the self-tuning regulator of Åström and Wittenmark, but have a number of advantages. Intuitive justification is given for the conjecture that some methods of Ljung, developed for the analysis of the self-tuning regulator, are applicable to the self-tuning controller. Simulated examples are given which compare and contrast the performance of the self-tuning controller with that of the self-tuning regulator. The first steps towards a quasi-continuous self-tuning controller are outlined.
Interplay of the osmotic environment and a fibronectin fragment in intervertebral disc cell metabolism
Keywords: intervertebral disc
fibronectin fragment
osmolarity
MMP

Breakdown of the disc extracellular matrix is thought to arise from increased activity of matrix metalloproteinases (MMPs). Aggrecan, one of the major disc matrix macromolecules, is degraded through action of MMPs and aggrecanases and its concentration falls early in the degeneration process. Loss of the constituent glycosaminoglycans (GAGs), which are osmotically active, leads to a decrease in osmotic pressure and subsequently to a fall in tissue hydration. Apart from the major biomechanical consequences, fall in extracellular osmolarity is known to influence cell function. Apart from aggrecan, other macromolecules such as fibronectin are also broken down by MMPs. Fibronectin fragments (Fnfs) have been identified in degenerate discs. Such Fnfs have been found to stimulate production and activity of MMPs in articular cartilage but little is known about the effect of these fragments on disc cells.
The aim of the work was thus to determine whether Fnf stimulated expression of MMPs and hence induced aggrecan breakdown and loss in the disc and whether extracellular osmolarity influenced this potential response. NP cells or explants were harvested from adult bovine caudal discs. They were cultured in DMEM culture medium over a range of osmolarities with or without Fnf treatment. Profiles of gene expression of MMPs and their inhibitors and effect of changes in osmolarity on expression of selected MMPs were determined. The effect of Fnf on responses of cells and tissue explants from the central region of the disc, the nucleus pulposus (NP) and the role of changes in extracellular osmolarity in relation to GAG loss and expression of selected MMPs was then examined both at the protein level and by gene profiling using a microarray.
My results showed that expression of MMPs by disc cells is regulated by extracellular osmolarity rather than the 30 kD Fnf, with the level of some MMPs secreted by disc cells and involved in degradation of disc matrix rising as osmolarity falls. These results could explain in part the finding that MMP expression increases with degree of disc degeneration i.e. with loss of aggrecan and fall in extracellular osmolarity. These also suggested that a fall in osmolarity could induce a degenerative cascade with proteolytic digestion of aggrecan leading to a fall in osmolarity and hence a further increase in proteinase expression and matrix degradation.
Studies of intestinal inflammation: the roles of IL-23R, gamma-delta T-cells and IL-21i
Keywords: IL-23
IL-21
intestine
colitis
T-cell

The aetiology of the inflammatory bowel diseases ulcerative colitis and Crohn’s disease remains uncertain. Genetic studies and model systems strongly implicate components of the IL-23/type-17 axis in the pathogenesis of disease, but the cellular and molecular mediators are uncertain. Using an IL-23Rgfp reporter mouse we analysed the cellular expression of IL-23R in homeostasis and disease. Whereas steady state expression in the intestine was dominated by a collection of unconventional lymphoid cells including gamma delta T-cells, we found rapid accumulation of IL-23R+CD4+-/-
mice developing increased bacterial colonisation and severe colitis, shown to be driven by increased Th1/IFN-;gamma& responses. These studies provide novel insights into aspects of IL-23 driven cellular and molecular pathways in homeostasis and inflammation in the intestine, with implications for future therapeutic approaches to IBD.