539 research outputs found
Territories of scarcity and creativity: a critical view of informal settlements and emerging tactics under conditions of scarcity in Nairobi, Kenya and Quito, Ecuador
This thesis explores the processes through which scarcity is constructed in informal settlements and
how conditions emerging within its limits gives way to particular socio-spatial phenomena and
influence the emergence of self-organisation and creative strategies from a non-expert perspective.
At the same time, this thesis deconstructs these emerging tactics (reactive and transformative) in a
diagrammatic way to generate a critical study of their potential for socio-spatial change that goes
beyond the everyday survival.
Most people associate scarcity with “not having enough” of something, most usually of a material
nature. In contrast, this paper is based on the premise that scarcity is a constructed condition,
therefore exploring it beyond its immediate manifestation and illustrating its discursive, distributive
and socio-material components. In this line, the research uses Assemblage Theory as both an
approach and a tool for analysis. This approach allows the research to depart from everyday
narratives of the residents, and gradually evolve into a multi-scalar, non-linear reading of scarcity, by
following leads into different realms and unpacking a series of routine events to uncover their
connections to wider processes and particular elements affecting the settlement and the city as a
whole.
For this purpose, the research is based on a qualitative, flexible and multi-sited methodology, using
different case studies as testing grounds. Collected data stems from a 11-months ethnographic
fieldwork in informal settlements in Ecuador and Kenya, analysing the socio-spatial practices and
strategies deployed by the different actors producing the built environment and arising from
everyday and latent experiences of scarcity. The thesis examines the multi-scalar nature of these
strategies, including self-building and management tactics, the mobilisation of grassroots
organisations, the innovative ways of collaborating deployed by different coalitions and the
reformulation of urban development policies.
As outcomes of the research, the thesis will show illustrative diagrams that allow a better
understanding of, firstly, the construction of scarcity in the built environment beyond its immediate
manifestation and secondly, the way that emerging tactics a) improve existing conditions of scarcity,
b) reinforce the status quo or c) contribute to the worsening of the original condition.
Therefore, this thesis aims to offer lessons with both practical and theoretical considerations, by
firstly, giving an insight into the complexity and transcalar nature of the construction of scarcity in
informal settlements; secondly, by illustrating how acute conditions related to scarcity gives birth to a
plethora of particular phenomena shaping the territory, social relationships and processes; and
thirdly, by identifying specific characteristics within the informal that might allow for new readings of
the city and possibilities for socio-spatial change under conditions of scarcity
Long-term patterns of an interconnected core marine microbiota
Ocean microbes constitute ~ 70% of the marine biomass, are responsible for ~ 50% of the Earth’s primary production and are crucial for global biogeochemical cycles. Marine microbiotas include core taxa that are usually key for ecosystem function. Despite their importance, core marine microbes are relatively unknown, which reflects the lack of consensus on how to identify them. So far, most core microbiotas have been defined based on species occurrence and abundance. Yet, species interactions are also important to identify core microbes, as communities include interacting species. Here, we investigate interconnected bacteria and small protists of the core pelagic microbiota populating a long-term marine-coastal observatory in the Mediterranean Sea over a decade.Versión del edito
An overview of top-down vs. bottom-up models for informal settlement upgrading in South Africa
The paper explores informal settlement upgrading approaches in South Africa and presents a review of top-down vs. bottom-up models, using experience and lessons learned from the Durban metropolitan area. Reflections on past upgrading efforts suggest that top-down policies in South Africa have not been successful to date. By contrast, participatory techniques, such as planning activism, can be used to enhance community empowerment and a sense of local ownership. This paper reveals that although the notion of ‘bottom-up’, participatory methods for community improvement is often discussed in international development discourses, the tools, processes and new knowledge needed to ensure a successful upgrade are under-utilised. Participation and collaboration can mean various things for informal housing upgrading and often the involvement of local communities is limited to providing feedback in already agreed development decisions from local authorities and construction companies. The paper concludes by suggesting directions for ‘co-producing’ knowledge with communities through participatory, action-research methods and integrating these insights into upgrading mechanisms and policies for housing and infrastructure provision. The cumulative impacts emerging from these approaches could aggregate into local, regional, and national environmental, social and economic benefits able to successfully transform urban areas and ensure self-reliance for local populations
Global diversity and distribution of aerobic anoxygenic phototrophs in the tropical and subtropical oceans
The aerobic anoxygenic phototrophic (AAP) bacteria are common in most marine environments but their global diversity and biogeography remain poorly characterized. Here, we analyzed AAP communities across 113 globally-distributed surface ocean stations sampled during the Malaspina Expedition in the tropical and subtropical ocean. By means of amplicon sequencing of the pufM gene, a genetic marker for this functional group, we show that AAP communities along the surface ocean were mainly composed of members of the Halieaceae (Gammaproteobacteria), which were adapted to a large range of environmental conditions, and of different clades of the Alphaproteobacteria, which seemed to dominate under particular circumstances, such as in the oligotrophic gyres. AAP taxa were spatially structured within each of the studied oceans, with communities from adjacent stations sharing more taxonomic similarities. AAP communities were composed of a large pool of rare members and several habitat specialists. When compared to the surface ocean prokaryotic and picoeukaryotic communities, it appears that AAP communities display an idiosyncratic global biogeographical pattern, dominated by selection processes and less influenced by dispersal limitation. Our study contributes to the understanding of how AAP communities are distributed in the horizontal dimension and the mechanisms underlying their distribution across the global surface ocean.Versión del edito
High-Speed Maskless Photolithography for Customized Nanomanufacturing
Achieving high functionality in nanoscale assemblies will require means of deterministically introducing structural complexity. Lithography represents the most effective technology currently at our disposal for creating such structural complexity. In research and in nanomanufacturing, flexibility as well as reasonable throughput and high resolution, are required. For lithographic patterning, photons have numerous advantages over charged particles. Even the disadvantage of lower resolution may soon be circumvented. The maskless photolithography system under development at LumArray Inc., and our plans for future extensions to the deep sub-100nm domain, will be described
Seasonal niche differentiation among closely related marine bacteria
Bacteria display dynamic abundance fluctuations over time in marine environments, where they play key biogeochemical roles. Here, we characterized the seasonal dynamics of marine bacteria in a coastal oligotrophic time series station, tested how similar the temporal niche of closely related taxa is, and what are the environmental parameters modulating their seasonal abundance patterns. We further explored how conserved the niche is at higher taxonomic levels. The community presented recurrent patterns of seasonality for 297 out of 6825 amplicon sequence variants (ASVs), which constituted almost half of the total relative abundance (47%). For certain genera, niche similarity decreased as nucleotide divergence in the 16S rRNA gene increased, a pattern compatible with the selection of similar taxa through environmental filtering. Additionally, we observed evidence of seasonal differentiation within various genera as seen by the distinct seasonal patterns of closely related taxa. At broader taxonomic levels, coherent seasonal trends did not exist at the class level, while the order and family ranks depended on the patterns that existed at the genus level. This study identifies the coexistence of closely related taxa for some bacterial groups and seasonal differentiation for others in a coastal marine environment subjected to a strong seasonality.En prensa8,95
Genetic and phenotypic diversity characterization of natural populations of the parasitoid Parvilucifera sinerae
Parasites exert important top-down control of their host populations. The host−parasite
system formed by Alexandrium minutum (Dinophyceae) and Parvilucifera sinerae (Perkinsozoa)
offers an opportunity to advance our knowledge of parasitism in planktonic communities. In
this study, DNA extracted from 73 clonal strains of P. sinerae, from 10 different locations along the
Atlantic and Mediterranean coasts, was used to genetically characterize this parasitoid at the species
level. All strains showed identical sequences of the small and large subunits and internal transcribed
spacer of the ribosomal RNA, as well as of the β-tubulin genes. However, the phenotypical
characterization showed variability in terms of host invasion, zoospore success, maturation time,
half-maximal infection, and infection rate. This characterization grouped the strains within 3 phenotypic
types distinguished by virulence traits. A particular virulence pattern could not be
ascribed to host-cell bloom appearance or to the location or year of parasite-strain isolation; rather,
some parasitoid strains from the same bloom significantly differed in their virulence traits. Identical
markers such as ITS and β-tubulin genes of P. sinerae strains from different geographic areas
and from different years precludes their use in assessing intra-specific diversity and could indicate
a recent dispersion of this species.Versión del editor2,393
Metastability of (d+n)-dimensional elastic manifolds
We investigate the depinning of a massive elastic manifold with internal
dimensions, embedded in a -dimensional space, and subject to an
isotropic pinning potential The tunneling process is
driven by a small external force We find the zero temperature and
high temperature instantons and show that for the case the
problem exhibits a sharp transition from quantum to classical behavior: At low
temperatures the Euclidean action is constant up to exponentially
small corrections, while for The results are universal and do not depend on the detailed shape
of the trapping potential . Possible applications of the problem to
the depinning of vortices in high- superconductors and nucleation in
-dimensional phase transitions are discussed. In addition, we determine the
high-temperature asymptotics of the preexponential factor for the
-dimensional problem.Comment: RevTeX, 10 pages, 3 figures inserte
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