The Mekong Delta Research Project as a Tool for Building a Pedagogical Approach

As an opportunity to discuss “Teaching in Research,” at EDAR’s Fourth Rencontre, I will be sharing my past experience in teaching without a Ph.D. and why I have decided to invest in obtaining a Ph.D. I shall discuss the differences between teaching with and without a Ph.D., and how a Ph.D. would serve to better define my contribution as an educator. Whereas the first part of the paper addresses the questions of the corresponding relationship between teaching and research, the body regards a discussion of the start of my Ph.D. research, and how my topic is currently positioned as a means of bridging the gap between a contextual territory and how it may be reframed to explain a hypothesis or theoretical viewpoint. As an urban designer who quickly transitioned into a career in teaching at university, the extent of my pedagogical approach was limited due to how knowledge was further obtained – through an ad-hoc accumulation of knowledge found in books, journals, and articles. In hindsight, there was a lack of critical knowledge direction and theoretical approach (found in a curriculum), that would offer more guidance and shed light into relevant schools of thought, and pedagogical approaches related to my research interests. Without experiencing the rigor of knowledge building via the Ph.D. research process, a-priori assumptions on pedagogy offered no additional perspectives to a given theory. The paper argues the reason why arriving at a complete Ph.D. research project would allow one to gain the required tools into becoming a more qualified professor. The rigorous and iterative process of re-organizing information to build one’s framing of a situation at hand creates one’s critical stance or hypothesis, whereby to address present and future challenges in the field. A Ph.D. can unlock the tools necessary pedagogically, to build the kind of criticality desirable in an academic. My research topic in the Mekong Delta currently serves as a process for building my pedagogical knowledge and understanding. The Mekong Delta traverses six Asian countries starting from the Tibetan plateau and ending in the South China Sea, which positions it in relation to multiple urban-rural realities. With increasingly unpredictable tropical climates, changing river flows and coastal levels; water resources in South East Asia are increasingly squeezed as nearly 70% of freshwater is channeled into industrial uses in agriculture and food production-related processes. The settlements in the Mekong rely on access to vast landscape resources, including access to water, currently treated as an open and limitless resource. The natural assets of the Delta’s ecological landscape have been increasingly harvested by processes of industrialization and urbanization, resulting in a kind of diffused organization between settlement patterns, water systems, and agricultural fields. The current proposal is a study of the relationship between the peri-urban regions and the Deltaic water systems. Rapid sea-level rise in the Delta is the cause of drought and salination of the once fertile soils. Artificial alterations of the rivers and estuaries are increasingly tempering with the Delta’s ability to naturally support the cultivation of landscapes, significantly decreasing fertile land for agriculture, aquaculture and other food production. The research proposes to territorially reveal the process leading to such detrimental conditions of the Delta and to shed light on reversal processes in adaptation for the future. The research project will only be more applicable as a teaching tool if it bridges the gap between global issues, theoretical concepts and concrete examples found in local realities. The theoretical phenomena in which I am further investigating in the Mekong Delta regards Desakota, defined by Prof. Terry McGee. Moreover, my theoretical perspective and territorial approach are based on Prof. Paola Vigano’s Citta Diffusa model; whereby existing patterns of dispersed urban settlements are rooted in an isotropic valorization of water networks and related ecosystems. These serve as my pedagogical approach and hypothetical position for addressing the Mekong’s territories. An analytical approach to mapping territory is proposed as a means to produce knowledge about how the territory has transformed over time. And the reframing of the currently separate processes of water infrastructure, and Desakota expansion shall be revealed from the local perspective. The hope is that the first-hand experience gained in building the thesis project would foster a critical understanding, through the process of linking a concrete territorial situation to existing urban theory. A completed Ph.D. would offer a means of teaching specifically based on my pedagogical approach; with a newfound theoretical perspective whereby to frame and deconstruct existing theoretical works in the field.

Perturbative Techniques in Hadron Collider Physics

Paolo Torrielli

High-energy particle physics is going through a crucial moment of its history, one in which it can finally aspire to give a precise answer to some of the fundamental questions it has been conceived for. On the one side, the theoretical picture describing the elementary strong and electroweak interactions below the TeV scale, the Standard Model, has been well consolidated over the decades by the observation and the precise characterization of its constituents. On the other hand, the enormous technological potentialities nowadays available, and the skills accumulated in decades of collider experiments with increasingly high complexity, render for the first time plausible the possibility of addressing complicated and conceptually deep questions like the ones at hand. The best incarnation of this high level of sophistication is the CERN Large Hadron Collider (LHC), the most powerful experimental apparatus ever built, which is designed to shed light on the true nature of fundamental interactions at energies never attained before, and which has already started to open a new era in physics with the recent discovery of the longed-for Higgs boson, a true milestone for the human knowledge as well as one of the most important discoveries in the modern epoch. The knowledge that has been and is going to be reached in these crucial years would of course not be conceivable without a deep interplay between the theoretical and the experimental efforts. In particular, on the theoretical side, not only there are wide groups of researchers devoted to building possible extensions to the Standard Model, which draws the guidelines of current and future experiments, but also there is a vast community whose research is rather aimed at the precise predictions of all the physical observables that could be measured at colliders, and at the systematic improvement of the approximations that currently constrain such predictions. On top of representing the state-of-the-art of the human understanding of the properties that regulate elementary-particle interactions and of the formalisms that describe them, the developments of this line of research have an immediate and significant impact on experiments. Firstly, these detailed calculations are the very theoretical predictions against which experimental data are compared, so they are crucial in establishing the validity or not of the theories according to which they are performed. Secondly, the signals one wants to extract from data at modern colliders are so tiny and difficult to single out that the experimental searches themselves need be supplemented by a detailed work of theoretical modelling and simulation. In this respect, high-precision computations play an essential role in all analysis strategies devised by experimental collaborations, and in many aspects of the detector calibration. It is clear that, for theoretical computations to be useful in experimental analyses and simulations, the predictions they yield should be reliable for all possible configurations of the particles to be detected. Thus the key feature for the present theoretical collider physics is not particularly the computation of observables with high precision only in a limited region of the phase space, but the capability of combining (‘matching’) in a consistent way different approaches, each of which is reliable in a particular kinematic regime. With this perspective, matching techniques represent one of the most promising and successful theoretical frameworks currently available, and are considered as eminently valuable tools both on the theoretical and on the experimental sides. Matched computations are based on a perturbation-theory approach for the description of configurations in which the scattering products are well separated and/or highly energetic: in particular the precision currently attained for all but a few of the relevant processes within the Standard Model is the next-to-leading order (NLO) in powers of the strong quantum-chromodynamics (QCD) coupling constant αS; for the description of configurations in which the particles outgoing the collisions are close to each other and/or have low energy, it can be shown that the perturbation-theory expansion breaks down, and then a complementary method, like the parton shower Monte Carlo (PSMC), has instead to be employed. The task of matching is precisely that of giving a prediction that interpolates between the two approaches in a smooth and theoretically-consistent way. This thesis is focused on MC@NLO, a high-energy physics formalism capable of matching computations performed at the NLO in QCD to PSMC generators, in such a way as to retain the virtues of both approaches while discarding their mutual deficiencies. In particular, the thesis reports on the work successfully achieved in extending MC@NLO from its original numerical implementation, tailored on the HERWIG PSMC, to the other main PSMC programs currently employed by experimental collaborations, PYTHIA and Herwig++, confirming the advocated universality of the method. Differences in the various realizations are explained in detail both at the formal level and through the simulation of various Standard-Model reactions. Moreover we describe how the MC@NLO framework has been developed so as to render its implementation automatic with respect to the physics process one is about to simulate: beyond yielding an enormous increase in its potential for present and future collider phenomenology, and upgrading the standard of precision for high-energy computations to the NLO+PSMC level, this development allows for the first time the application of the MC@NLO formalism to a huge number of relevant and highly complicated reactions, through an implementation which is also easily usable by people well-outside the community of experts in QCD calculations. As example of this new version, called aMC@NLO, recent results are presented for complex scattering processes, involving four or five final-state particles. Finally, possible extensions of the framework to theories beyond the Standard Model, like the supersymmetric version of QCD, are briefly introduced.

EPFL2012

Changes in Employment Localization and Accessibility

Pierre-Emmanuel Dessemontet

Until about the end of WWII, the territorial organization of the economy could be expressed along a very strong center-periphery gradient, with industries and services concentrated in cities while the countryside supplied agricultural products. Since the industrial revolution, industrial regions had emerged essentially in mining regions which perturbed this very simple scheme, but without fundamentally modifying it. In the first half of the 20th century, with the advent of mass transportation and of the individual car, the residential functions started to deconcentrate and residential suburbs developed. However, as a general rule, most non-agricultural economic functions remained tightly attached to the city core and its immediate surroundings, and with them their jobs. These structures were accounted for by various theoretical models, of which the Von Thunen land-rent model family, the Weber models of industrial localization and regional specialization, and the Christaller model of hierarchical city networks were the most prominent. However, since 1945, those jobs have seen their territorial distribution shift. First, the importance of agriculture dwindled, to the profit first of industrial activities, then of services. Land-hungry activities, such as the industry and logistical activities vacated the urban centers in search for ample space, which they generally found in suburban settings under the guise of industrial zones. But they weren't alone at deconcentrating. Retail and personal services tended to follow their customers in the suburbs. During the last quarter of the 20th century, selected suburbs evolved from purely residential or industrial functions to more complete economic ones, integrating retail, high tech and professional services. By 1990, the phenomenon was largely recognized in North America, where those job-intensive suburbs were nicknamed edge cities. Empirical studies showed convincingly that the same patterns of job and functional deconcentration were found in the whole world and especially in western countries. Job suburbanization is contemporary with major spatial and functional economical upheavals. The economy, for instance, evolved from the fordist integrated economical model dominated by very large companies internalizing most of their functions in a vertical, hierarchical relationship pattern to a post-fordist disintegrated model where companies concentrate on their core competencies and subcontract in a horizontal, contractual manner their non-core needs. Economical spatial deconcentration is also contemporary with the current version of globalization, materialized by the emergence of global cities and metropolises which keep constant communication flow between themselves, in a horizontal manner, and which are less and less dependent on their hinterland for their economical survival and development. Likewise, the economy becomes more and more informational, relying on knowledge, immaterial services, instant worldwide communication, and the production of sophisticated products for which worldwide shipping costs became negligible, and for which the location needs shifted from access to markets to access to qualified workers. While globalization, metropolization and the post-fordist economical transition have been thoroughly studied, job suburbanization has not been the focus of such an interest from the scientific community. Consequently, we lack empirical evidence and theoretical advances which would help us to better understand how the economy spatially evolved since 1945 and where the world is heading if the trends seen since 1945 are maintained. The prime goal of this work is to provide a better understanding of the way the economy spatially evolved at the intra-metropolitan scale, based on the example of Switzerland, a fairly exemplary western country. The work is divided in three major parts – an introductory one, an empirical one, and a inferential one. The core hypothesis of this work is that as the individual car became ubiquitous, proximal relations were progressively supplanted by accessibility relations. We surmise that job distributions and their evolution can be explained by accessibility patterns and change, which are in turn dependent on a number of factors – the population distribution, the structure and state of the road network, the state of the car technology, and the time commuters are ready to travel to go to work. The first three chapters aim at defining our object of study in chapter 1, to give an understanding of the country on which we will be working and of the data at our disposal in chapter 2, and a working definition of what constitutes a job center in chapter 3, where major distinctions between urban, mixed, suburban, exurban, touristic centers and edgeless space are introduced which accompanies us for the rest of the work. The next four chapters constitute the empirical part of the work. Chapter 4 seeks at describing as precisely as possible the territorial evolution of the Swiss economy since WWII, studying it at nine different points in time from 1939 to 2008. Chapter 5 takes a long-term view of the same series of data and seeks to detect, describe and explain the trends which are unearthed by this larger view. Chapter 6 concentrates on the latter half of the period under review and studies the distributions along more precise branch divisions, as well as miscellaneous other classifications according to added value and productivity, interaction needs, job qualification and creativity. Chapter 7 concentrates on the command and control structure of the economy as seen through the spatial relations entertained by headquarters and their subsidiaries, by Swiss and foreign multinationals, by the public and private sector. Finally, chapters 8 and 9 undertake the inferential part of our work, and aim at testing our core hypothesis of a statistically demonstrable link between accessibility, which is defined and thoroughly studied in its historical dimension in chapter 8, and a measure of job quality. Chapter 9, the last of the work, takes this core hypothesis to the statistical test. The results of this work are multiple. First of all, it shows that the spatial structure of the economy indeed transitioned from a very strong center-periphery organization in 1939, when two thirds of all non-agricultural jobs were located in urban centers, about a quarter in the country-side and the rest in numerous small industrial villages, to a vastly different structure in 2008 with less than half such jobs located in urban centers while suburban centers capitalize about a quarter of them, the rest being distributed mainly in edgeless space – industrial villages having somewhat lost in importance. This work shows that the spatial components of the economical structure have also greatly evolved. While in 1939 urban centers concentrated most of the economic functions and all of the commanding ones, spatial specialization has been relentless since then, and especially since the last quarter of the 20th century. Suburban centers have grown, but also gained in quality, especially in the high tech and the professional services sectors, and in commanding functions: as of 2008, they hosted more jobs in headquarters than in subsidiaries. In parallel, cities have tended to specialize on some key sectors of the economy: finance and governmental services at large, accompanied by personal services catering for the new urban elite. Taken altogether those developments pick at the prevailing spatial economic theories and show a major departure from the Christallerian model. Anecdotal evidence shows that by and large suburban centers seem not located haphazardly in the larger suburban belt, but are concentrated on several specific point within it, namely the higher accessibility areas, especially highway junctions and interchanges. This hints at the possibility that high accessibility is a determinant of job localization. In the course of this work we demonstrated first that accessibility is more dependent on road network changes that to other parameters such as population distribution, technological changes and attitude changes towards commuting, and that the accessibility changes due to road network evolutions display far stronger local accessibility gradients. Secondly, we demonstrated the existence of a link between accessibility and job density taken as a measure of job quality, after taking into account the effects of spatial autocorrelation. Much of the unexplained variance shown by a global regression model can be modeled away as regional effects when using a geographically weighted regression, so that the combination of regional effects and accessibility accounts for a major part of the job density variance. Finally, the introduction of time lags between accessibility conditions and job densities hinted at the possibility that a causal link exists between the two, accessibility changes preceding, and maybe then causing, job density changes: in short, this work shows that accessibility by car is a major determinant of job localization.

EPFL2011

Theoretical and Experimental Studies of Dendritic Metacommunities

Francesco Carrara

The present thesis deals with the understanding of the origins and the mechanisms of maintenance of biodiversity in natural landscapes, in particular by identifying key processes that define large-scale patterns of abundance and diversity. Biological communities often occur in spatially structured habitats where connectivity directly affects dispersal and metacommunity processes. Recent theoretical work suggests that dispersal constrained by the connectivity of specific habitat structures affects diversity patterns and species interactions. This is particularly relevant in dendritic networks epitomized by fluvial ecological corridors. This thesis addresses whether connectivity alone can explain observed features of biodiversity and selectively promote different components of community composition in river-like landscapes, such as local species richness or the among-community similarity. The relevance of this thesis lies in the major ecological challenges posed by the topic, and its fundamental importance to conservation biology. The studies pursued herein are also deemed relevant because of the influence of the spatial connectivity and dispersal on population dynamics and of the relevance of biodiversity to ecosystem functioning. Mechanisms of species coexistence were investigated with a blend of theoretical tools (broadly related to statistical mechanics and the theory of stochastic processes) and experimental work using laboratory microbial communities. The research tools ranged from aspects of modern coexistence theory in a local perspective to the recent concept of the metacommunity in spatial ecology, within a unified framework. The study of biodiversity in riverine ecosystems guided by observational data has been addressed by combining theoretical metacommunity models with laboratory experiments. The results are diverse. First, they show experimentally that connectivity per se shapes key components of biodiversity in metacommunities. Local dispersal in isotropic lattice landscapes homogenizes local species richness and leads to pronounced spatial persistence. By contrast, dispersal along dendritic landscapes leads to higher variability in local diversity and among-community composition. Although headwaters exhibit relatively lower species richness, they are crucial for the maintenance of regional biodiversity. By suitably arranging patch sizes within river-like networks the effect of local habitat capacity (i.e., the patch size) and dendritic connectivity on biodiversity can be experimentally disentangled in aquatic microcosm metacommunities. It is shown in this thesis that species coexistence and community assembly depend on intricate, non-trivial interactions of local community capacity and network positioning. Furthermore, an interaction of spatial arrangement of habitat capacity and dispersal along river-like networks also affects a key ecosystem descriptor, namely regional evenness. High regional evenness in community composition is found only in landscapes preserving geomorphological scaling properties of patch sizes. In riverine environments some of the rarer species sustained regionally more abundant populations and were better able to track their own niche requirements compared to landscapes with homogeneous patch size or landscapes with spatially uncorrelated patch size. All the experimental results were supported and extended by a theoretical analysis where the above mechanisms have been generalized. This thesis provides the first direct experimental evidence that spatially constrained dendritic connectivity is a key factor for community composition and population persistence in riverine landscapes. As such, this thesis assesses a longstanding issue in spatial community ecology. It offers unique insights into the ecological forces structuring natural communities in a key ecosytem, and demonstrates principles that can be further tested in theoretical metacommunity models possibly to be extended to real riverine ecosystems. Taken together, the analyses show how the structure of ecological networks interacts with the spatial environmental matrix in determining biodiversity patterns and the functioning of biological communities. The analyses also suggest that altering the natural linkage between dendritic connectivity and patch size strongly affects community properties at multiple scales. The first part of this thesis (chapters 2 and 3) addresses key aspects of biodiversity-ecosystem functioning research where the combination of theory-guided experiments and theoretical investigations shows how a stochastic implementation of population dynamics proves fundamental for key community properties such as species persistence and community stability. The diversity-productivity and diversity-stability relationships are explored. Both experimental findings and the results of a stochastic model fitted to the experimental interaction matrix, suggest the emergence of strong stabilizing forces when species from different functional groups interact in the same environment, increasing species coexistence and community biomass production. The last part (chapter 6) provides a synthesis of this thesis work, in that it aims at unifying aspects from niche-theory, usually adopted in spatially implicit models, with those characteristic of a spatially explicit context from a typical real-life mountainous regions. It is dedicated to the possible explanation for a macroecological pattern routinely observed from organisms in different domains of life, that is, the mid-elevational peak in local species richness. Guided by empirical observations on diversity of macroinvertebrates in Swiss river basins, a theoretical ansatz is provided which is deemed to capture the essential geomorphological drivers and controls relating species-fitness to altitude. A set of overarching conclusions and perspectives for future research are discussed in the concluding chapter.

EPFL2013