Mejora de la seguridad y la privacidad de los sistemas biométricos

Tesis doctoral inédita leída en la Universidad Autónoma de Madrid, Escuela Politécnica Superior, Departamento de Tecnología Electrónica y de las Comunicaciones. Fecha de lectura: 02-06-2016This Thesis was printed with the financial support from EPS-UAM and the Biometric Recognition Group-ATVS

Breaching the Barrier: Quantifying Antibiotic Permeability across Gram-negative Bacterial Membranes.

The double-membrane cell envelope of Gram-negative bacteria is a sophisticated barrier that facilitates the uptake of nutrients and protects the organism from toxic compounds. An antibiotic molecule must find its way through the negatively charged lipopolysaccharide layer on the outer surface, pass through either a porin or the hydrophobic layer of the outer membrane, then traverse the hydrophilic peptidoglycan layer only to find another hydrophobic lipid bilayer before it finally enters the cytoplasm, where it typically finds its target. This complex uptake pathway with very different physico-chemical properties is one reason that Gram-negative are intrinsically protected against multiple classes of antibiotic-like molecules, and is likely the main reason that in vitro target-based screening programs have failed to deliver novel antibiotics for these organisms. Due to the lack of general methods available for quantifying the flux of drugs into the cell, little is known about permeation rates, transport pathways and accumulation at the target sites for particular molecules. Here we summarize the current tools available for measuring antibiotic uptake across the different compartments of Gram-negative bacteria

Decolonising Leadership in International Education

ABSTRACT This study articulates the journey, across more than six decades, of one black woman from birth through schooling to international school leadership. The purpose of the study is to open a debate about the challenges faced by women of colour in leadership roles in international schooling to be seen and heard. This is necessary firstly because it is only in the last decade that women of colour have started to be deliberately seen and heard in these roles, and secondly because the matter of colour and gender has largely been invisible in the decolonisation of leadership within international schooling. This act of invisibilisation undermines the perspectives of black women. It can therefore be argued that if such perspectives remain absent from the discourse, the decolonisation of leadership in international schooling cannot begin. This study introduces the reader to the role silence and invisibility play in international school leadership. Using the methodology of autoethnography, I am able to explore decolonisation through personal and professional narratives and show how these narratives uncover the role of silence and invisibility in a life led and attempts to illuminate the drive to decolonise international schools, from the perspective of one woman of colour. The narratives that are structured across the four phases that cover four distinct periods: 1. Colonial period and early life in Guiana (1956-1968) 2. United Kingdom: student and early career (1968-1981) 3. International career in schools and beyond (1981-2010) 4. Return to Europe and beyond (2010 -2021

Topological systems with strong electron-electron interactions

Over the last few decades, topological phases of matter have become an omnipresent topic in modern solid state physics. While conventional phases of matter and the phase transitions between them---like, for example, the transition from water to ice---can be fully understood from local properties of a system, topological phases of matter are characterized by global invariants that can be defined and described within the mathematical framework of topology. An early milestone in the field was the discovery of a peculiar class of materials---later termed topological insulators (TIs)---that exhibit a fully insulating bulk while their surfaces are conducting. The so-called gapless surface states that are responsible for this effect allow for dissipationless transport of electrons along the surfaces of the system and exhibit a surprising robustness against perturbations. Indeed, it turns out that the existence of these surface states is guaranteed by topological---and therefore global---properties of the system, leaving them unaffected by any local imperfections of a particular sample. Soon after the initial ideas had spread, it was realized that not only insulating but also superconducting systems can, at the mean-field level, be described within the framework of topology. One of the most striking features of topological superconductors (TSCs) is the fact that they can host so-called Majorana bound states. These exotic quasiparticles are neither bosons nor fermions but so-called non-Abelian anyons. This means that, upon the spatial exchange of two Majorana bound states, the overall wave function of the system does not simply acquire a phase factor, but undergoes a more complicated rotation in a degenerate manifold of ground states. Apart from their fundamental interest, Majorana bound states---and non-Abelian anyons in general---are considered particularly interesting due to their potential use for quantum computation. Indeed, it was predicted that Majorana bound states could in principle be used as a means to encode and process quantum information in a non-local way. This, in turn, would provide an intrinsic protection against quantum errors, which necessarily occur in any quantum computing device but can be expected to act locally in physically realistic scenarios. Following the seminal works on topological insulators and superconductors, the field has been driven by the desire to access topological phases of matter with increasingly exotic properties. While the original theory of TIs and TSCs was built on single-particle band structure considerations, it has been found that the effects of strong electron-electron interactions can lead to even more exotic phases of matter, many properties of which remain elusive up to date. One of the most remarkable features of strongly interacting phases of matter is the fractionalization of quantum numbers: For example, when a two-dimensional electron gas is driven into the so-called fractional quantum Hall regime, quasiparticle excitations carrying only a fraction of the electronic charge $e$ exist. Another intriguing consequence of strong interactions is the possible emergence of exotic bound states such as parafermions. Indeed, to some extent, parafermions can be seen as the fractionalized cousins of Majorana bound states. With even richer non-Abelian exchange statistics than their conventional counterparts, parafermions are---at least theoretically---predicted to harbor significant potential as building blocks for future quantum computing devices. Motivated both by potential technical applications as well as by fundamental theoretical interest, this Thesis is dedicated to studies of novel topological phases of matter with a particular focus on the effects of strong electron-electron interactions. To begin with, we give an introduction to Majorana bound states and topological superconductors in Chapter 1. While focusing mainly on non-interacting systems, this Chapter introduces some of the basic theoretical concepts that will frequently reappear throughout this Thesis. Next, in Chapters 2 and 3, we move on to strongly interacting phases of matter and study the emergence of parafermions in so-called higher-order TSCs. In particular, in Chapter 2, we construct a theoretical model for a fractional second-order TSC with parafermion corner states at two opposite corners of a rectangular sample. To treat the strong electron-electron interactions analytically, we make use of a coupled-wires construction based on weakly coupled Rashba nanowires. In Chapter 3, we propose an alternative model that can host Majorana and parafermion corner states. Instead of coupled Rashba nanowires, this model is based on coupled quasi-one-dimensional channels arising in bilayer graphene due to electrostatic gating. While the models discussed in Chapters 2 and 3 explicitly break time-reversal symmetry, it turns out that a magnetic field is not a necessary ingredient to obtain a second-order TSC. In Chapter 4, we present a theoretical construction of a time-reversal invariant second-order TSC with Kramers pairs of Majorana corner states. Our model is based on a layered structure consisting of two tunnel-coupled TI layers that are `sandwiched' between two $s$-wave superconductors with a phase difference of $\pi$ between them. The competition between interlayer tunneling and proximity-induced superconductivity can then bring the system into the second-order phase. In this Chapter, we restrict our attention to the non-interacting case for simplicity and brevity. In Chapter 5, we move on to second-order phases in three dimensions and construct a coupled-wires model for a time-reversal invariant second-order topological insulator with helical hinge states. For suitably chosen interwire hoppings, we demonstrate that the system has a fully gapped bulk as well as fully gapped surfaces, but hosts two Kramers pairs of gapless helical hinge states that propagate along a path of hinges determined by the hierarchy of interwire hoppings and the boundary termination of the system. Furthermore, we show that sufficiently strong electron-electron interactions can drive the system into a fractional second-order TI phase with hinge states carrying only a fraction of the electronic charge $e$. Via the coupled-wires approach, all our studies of strongly interacting phases of matter heavily relied on the one-dimensional bosonization formalism. However, many intricate details concerning technical aspects of the bosonization formalism are traditionally glossed over in such studies. For example, in bosonized language, Majorana and parafermion zero modes are usually derived from a semi-classical picture in the limit of infinitely strongly pinned bosonic fields in the bulk of the system, leaving the true spatial profile of the bound states unknown. This is why, in Chapter 6, we take one step back and study the bosonized formulation of the simplest possible toy model for a TSC---the Kitaev chain---in an abundance of technical detail. Next, in Chapters 7 and 8 of this Thesis, we turn our attention to signatures of topological phases of matter, i.e., characteristic features that could be detected in experiments. In Chapter 7, we study an observable that we refer to as the fractional boundary charge. As suggested by the name, boundary charges are excess charges located at the boundary of a system with respect to some average background charge of the bulk. We use a coupled-wires construction to describe the fractional quantum Hall effect (FQHE) at odd filling factors and calculate the fractional boundary charge arising in a Corbino disk geometry. If the hole of the disk is threaded by an external flux, we find that the fractional boundary charge depends linearly on the flux with a quantized slope that is determined by the filling factor. Furthermore, different branches of the FBC directly correspond to different degenerate ground states of the system. Subsequently, in Chapter 8, we shift our attention back to topological superconducting systems and study the effects of dilute classical magnetic impurities a two-dimensional time-reversal invariant TSC with helical Majorana edge states. First, we demonstrate that the spin of a single magnetic impurity close to the edge of the TSC tends to align along the edge. We then compute the Ruderman-Kittel-Kasuya-Yosida (RKKY) interaction between two magnetic impurities placed close to the edge of the TSC. We find that, in the limit of large interimpurity distances, the RKKY interaction between the two impurities is mainly mediated by the Majorana edge states and leads to a ferromagnetic alignment of both spins along the edge. All of these effects are absent in trivial $s$-wave superconductors. As such, spectroscopy of dilute magnetic impurities could be a powerful tool to probe helical TSCs or topological materials with helical edge states in general. Last but not least, in Chapter 9, we turn our attention to systems that exhibit one or more completely dispersionless---or so-called flat---bands. While such a peculiar band structure is interesting already in its own right, flat band systems have attracted particular attention since they can realize a variety of strongly correlated phases of matter. Indeed, since the kinetic energy is completely quenched in the flat band, even arbitrarily weak interactions can drastically modify the properties of the system. The same is true for disorder as well as for `perturbations' due to, e.g., the presence of dilute impurities. This has motivated us to study the RKKY interaction between two classical magnetic impurities in two different one-dimensional lattice models that host flat bands. We start by obtaining exact results for the RKKY interaction in both models by numerical exact diagonalization and find that, in both cases, the RKKY interaction exhibits peculiar features that can directly be traced back to the presence of a flat band. Next, we compare our numerical data to results obtained via different analytical techniques. We discuss how the presence of a flat band can invalidate the conventional RKKY approximation based on non-degenerate second-order perturbation theory and highlight the need for degenerate perturbation theory or even non-perturbative approaches to accurately capture the effect of the flat band

Dangerous Gifts

From Napoleon Bonaparte’s invasion of Egypt in 1798 to the foreign interventions in the ongoing civil wars in Syria, Yemen, and Libya today, global empires or the so-called Great Powers have long assumed the responsibility of bringing security to the Middle East. The past two centuries have witnessed their numerous military occupations to ‘liberate’, ‘secure’, and ‘educate’ local populations. Consulting fresh primary sources collected from some thirty archives in the Middle East, Russia, the United States, and Western Europe, Dangerous Gifts revisits the late eighteenth- and nineteenth-century origins of these imperial security practices. It questions how it all began. Why did Great Power interventions in the Ottoman Levant tend to result in further turmoil and civil wars? Why has the region been embroiled in a paradox—an ever-increasing demand for security despite the increasing supply—ever since? It embeds this highly pertinent genealogical history into an innovative and captivating narrative around the Eastern Question, freeing the latter from the monopoly of Great Power politics, and also foregrounding the experience and agency of the Levantine actors: the gradual yet still forceful opening up of the latter’s economies to global free trade, the asymmetrical implementation of international law from their perspective, and the secondary importance attached to their threat perceptions in a world where political and economic decisions were ultimately made through the filter of global imperial interests

China's Forgotten Revolution: Radical Conservatism in Action, 1927-1949

This dissertation examines Republican China's state-led revolution under the Guomindang. Since the anti-Communist purge in 1927, the party-state had strived to re-energize mass activism and dissolve proletarian political subjectivity with a rightwing program that stressed interclass and national unity. Under Chiang Kai-shek's leadership, the Guomindang put an end to the ideological ambiguity of Sun Yat-sen's national revolution, broke ties the party forged with the Communist International in 1923, and launched an all-round assault on the fledging Chinese Communist Party. Refusing to challenge unequal power relationships domestically and abroad, Guomindang leaders promised to bring China and Asia back to their cultural essence and towards a superior ethical order. Despite its conservative socio-economic agenda, the party retained a radical organizational mode it derived from revolutionary socialism that prized Leninist vanguardism, reliance on mass involvement and cultural transformation. The Chinese nation-state under Guomindang rule experienced a conservative revolution and partook in a global fascist current that swept across Asia, Europe and Latin America during the second quarter of the twentieth century. The distinctiveness of China's conservative revolution is demonstrated in this dissertation through a multilayered study of its ideological formulations, mass mobilization programs, and ability to garner support from outside the Guomindang domestically and abroad. Senior party ideologues among radical conservatives, who produced tracts attacking the Guomindang's Communist allies in the mid-1920s, provided theoretical justifications for the April 1927 purge and heralded the party-state's drastic shift to the right. In the 1930s and 1940s, the Guomindang state deployed the scouting and wartime spiritual mobilization movements to re-channel mass activism towards strengthening the nation's organic unity and consolidating defense against Japanese invasion. Potentially subversive popular demands were diffused through a new focus on refining and rationalizing consumption habits, time management and other social mores. Instead of political participation, popular will found expression in public rituals, physical recreation and cultural entertainments. Conservative revolutionaries were adept in building elite support. The state's goal of disciplining everyday life converged with liberal intellectual fear over a social order collapsing under mob rule. While uncomfortable with some authoritarian behaviors on the Guomindang's part, prominent liberals such as Zhu Guangqian shared the state's priority of reining in an intransigent mass society. Internationally, China's repudiation of Soviet-supported anti-imperialist activities led the Guomindang to appeal to cultural affinities in the overtures it extended to the Indian independence movement. The regime's celebration of Eastern spiritual superiority proved attractive to Pan-Asianists like Rabindranath Tagore and informed exchanges between the Guomindang and Indian National Congress at the height of the Second World War. In highlighting the ascendency of radical conservatism in China and its transnational circulation across Asia, this dissertation sheds light on the distinct qualities, often downplayed in the historical literature, of the Guomindang's revolutionary enterprise vis-à-vis the radical left

Be(com)ing Arab in London: performativity between structures of subjection

This thesis is based upon eighteen months of ethnographic fieldwork in London undertaken between January 2006 and July 2007. It explores the discourses and practices which (re)produce notions of gender, race, ethnicity and class among young people born or raised in London to migrants from Arab states. Instead of taking the existence of an Arab community’ in London as self-evident, this thesis looks critically at the idea of Arab-ness in London and the ways in which it is signified, reiterated and recited. Taking the theorising of performative gender as a starting point I explore the possibilities of a sequential reading of ‘gender’ and ‘race’ and the practices and discourses which produce that which they name ‘Arab woman,’ Arab man,’ ‘British- Arab’. By looking at discourses, practices and political context, ‘ethnicity’ and ‘race’ appear to be less about an inner fixity or even multiple identities, instead they can be significantly attributed to a discursive and corporeal project of survival and social intelligibility between structures of subjection which create imperatives to enact and reproduce notions of ‘race’ and ‘gender’. In this sense it is no longer satisfactory to see ethnicity as something that one possesses – but something that one does and embodies imperfectly, constantly adding, reinforcing and disrupting its presumed structure. Looking at what it means “to do” Arab-ness in London provides opportunities to look at the underlying normative and psychical structures that inform the doing of ethnicity in a particular setting. The shift from foundationalist and “epistemological account[s] of identity to [those] which locate[s] the problematic within practices of signification permits an analysis that takes the epistemological mode itself as one possible and contingent signifying practice” (Butler 1990: 184). Through the Shisha cafe, ‘Arabic nights’, images and narratives I explore the discursive and corporeal acts that signify Arab-ness in London at a particular historical moment

Bricolage Propriety: The Queer Practice of Black Uplift, 1890–1905

Bricolage Propriety: The Queer Practice of Black Uplift, 1890-1905 situates the queer-of-color cultural imaginary in a relatively small nodal point: the United States at the end of the nineteenth century. Through literary analysis and archival research on leading and marginal figures of Post-Reconstruction African American culture, this dissertation considers the progenitorial relationship of late-nineteenth century black uplift novels to modern-day queer theory. Bricolage Propriety builds on work about the sexual politics of early African American literature begun by women-of-color feminists of the late 1980s and early 1990s, including Hazel V. Carby, Ann duCille, and Claudia Tate. A new wave of interest has emerged in the “Post-Bellum/Pre-Harlem” era of African American literary production, but few in queer theory and African American literary study have yet made a connection between this renewed interest and turns in gender and sexuality studies since the late 1990s. Bricolage Propriety attempts to revisit this period of literary production and to update how we think about this period after the emergence of queer-of-color critique, particularly the work of José Esteban Muñoz, Roderick Ferguson, Aliyyah Abdur-Rahman, Tavia Nyong’o, Darieck Scott, Robert Reid-Pharr, Siobahn Somerville, and Mason Stokes. Moreover this project attempts to use its analyses of the gender and sex politics of this literary archive to question queer theory’s novelty, to put antiracism at its center, and to deemphasize the white-gay-male archive’s centrality. The argument offered in Bricolage Propriety narrativizes a usable past of black and queer cultures toward a more efficacious queer and antiracist coalition politics. By implementing race as a form of sexual transgression more fully into queer theory, the critical flexibility and political salience of queer theory can only stand to grow. Published during the emergence of the African American literary genre, the novels of Charles W. Chesnutt, Pauline E. Hopkins, and Sutton E. Griggs provide a critical model for how to think about race as a form of transgressive sexuality; further, these texts show how integral racial representation at the end of the nineteenth century is to our ideas about sexual transgression. In the manner of bricolage — art produced with whatever is at hand — these novelists worked within and outside the dominant culture of their time to theorize black sexual propriety, while challenging that same propriety through key failures and subversions of early African American literary form

Examination of Cultural Significance of Places: Circular Quay, Sydney

This thesis studies the meaning of cultural significance of place, and is concerned with Circular Quay, Sydney, in an attempt to determine the various aspects which contribute to the area’s cultural significance. It sees the area from a wide variety of viewpoints, and uses the area’s diversity as a catalyst for considerations pertaining to the understanding of place generally. It deals with the growing heritage process which has drawn world-wide attention to the phenomenon of place significance, and attempts to show how this process has led to present place evaluation techniques. It considers the acknowledged tools used in assessing place significance, and explores ways of improving and/or augmenting such tools in order to provide the means for assessing cultural significance of place in the second millennium. Circular Quay is an unusual place in many respects. It is the oldest (postcolonial) place in the youngest (and last) major colony, situated in the oldest country in the world. Its status as the site of the First Settlement gives rise to divergent viewpoints, and its post-colonial history has exerted more influence on Australian identity than perhaps any other Australian place. Its physical attributes and setting, once appreciated by both European and Aboriginal cultures as constituting an exceptional natural environment, are once again being appreciated, this time as an extraordinary cultural environment, as we approach the year 2000. Traditional place assessment techniques reside principally in the criteria used to determine whether or not a place possesses a sufficient degree of cultural significance to enable it to be listed in a heritage register. Such criteria have evolved in response to the world’s disappearing heritage, which the various heritage registers attempt to identify so that steps may then be taken to preserve what remains. To date Circular Quay appears on no formal heritage register, although some of the items in the area are listed. This thesis attempts to show how places like Circular Quay can be assessed for their cultural significance, which at present lies outside the scope of the various criteria, and how modified and/or additional criteria can lead to the inclusion of such places in heritage registers