221 research outputs found

    Facing rapid urbanization: a century of East African Urbanism.

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    East-Africa is one of the least urbanized regions in the world, but living one of the fastest urbanization. Its urban history has roots in the cosmopolitan Swahili culture and common experiences related to British and German colonialism and the East African Community. During the 20th century it has been a great laboratory regarding the effort of ordering growth according to very different political visions and social projects: almost everything has been tested in planning and urban design, with a relevant gradient of determinism in the designing efforts, from total to minimal. The East-Africans are excellent samples of contemporary metropolises facing the unstoppable proliferation of informal growth due to uncontrolled migrations and unsustainable development. Dar es Salaam, Nairobi, Mombasa, Kampala, Kigali and the metropolitan archipelago of Zanzibar have already passed the quota of a million inhabitants and the biggest cities are running million after million, with more than half of this growth occurring informally. From the beginning of their urban history all these cities have faced the issue of hosting different communities with different lifestyles, symbols, rituals, fears and public spaces. Their urban history is a telling overview on the relevance of urban architecture in determining their future. The paper proposes and overview on urban design and planning attempts over the last century proposing a periodization and investigating their influence in driving city growth and in contributing to city resilience through political and ecological changes

    Functional-safety analysis of ASIL decomposition for redundant automotive systems

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    Functional-safety analysis of ASIL decomposition for redundant automotive systems

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    Characterizing hyperbolic spaces and real trees

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    Let X be a geodesic metric space. Gromov proved that there exists k>0 such that if every sufficiently large triangle T satisfies the Rips condition with constant k times pr(T), where pr(T) is the perimeter T, then X is hyperbolic. We give an elementary proof of this fact, also giving an estimate for k. We also show that if all the triangles T in X satisfy the Rips condition with constant k times pr(T), then X is a real tree. Moreover, we point out how this characterization of hyperbolicity can be used to improve a result by Bonk, and to provide an easy proof of the (well-known) fact that X is hyperbolic if and only if every asymptotic cone of X is a real tree.Comment: 13 pages, 3 figures. Comments are welcom

    Central extensions and bounded cohomology

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    It was shown by Gersten that a central extension of a finitely generated group is quasi-isometrically trivial provided that its Euler class is bounded. We say that a finitely generated group GG satisfies Property QITB (quasi-isometrically trivial implies bounded) if the Euler class of any quasi-isometrically trivial central extension of GG is bounded. We exhibit a finitely generated group GG which does not satisfy Property QITB. This answers a question by Neumann and Reeves, and provides partial answers to related questions by Wienhard and Blank. We also prove that Property QITB holds for a large class of groups, including amenable groups, right-angled Artin groups, relatively hyperbolic groups with amenable peripheral subgroups, and 3-manifold groups. Finally, we show that Property QITB holds for every finitely presented group if a conjecture by Gromov on bounded primitives of differential forms holds as well.Comment: 32 pages. v2: Some proofs streamlined in view of recent work of Milizia, revised connection to Gromov's conjectur

    Theorizing Central Asian politics: The state, ideology and power. Introduction.

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    This chapter introduces the reader to the main idea of the book: to move beyond Central Asia as a field reserved to regional studies and towards the opportunities that it provides for theorizing politics. After a review of the scholarly debates and the main literature, it makes the case for a new take on generating theories of the political starting from this region. It concludes by introducing the analyses of the authors chapter by chapter along the three sections of the book: models of governance and power, revealing ideological justifications and reframing the state and order

    The c-terminal extension of a hybrid immunoglobulin A/G heavy chain is responsible for its Golgi-mediated sorting to the vacuole

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    We have assessed the ability of the plant secretory pathway to handle the expression of complex heterologous proteins by investigating the fate of a hybrid immunoglobulin A/G in tobacco cells. Although plant cells can express large amounts of the antibody, a relevant proportion is normally lost to vacuolar sorting and degradation. Here we show that the synthesis of high amounts of IgA/G does not impose stress on the plant secretory pathway. Plant cells can assemble antibody chains with high efficiency and vacuolar transport occurs only after the assembled immunoglobulins have traveled through the Golgi complex. We prove that vacuolar delivery of IgA/G depends on the presence of a cryptic sorting signal in the tailpiece of the IgA/G heavy chain. We also show that unassembled light chains are efficiently secreted as monomers by the plant secretory pathway

    Free ricin A chain, proricin, and native toxin have different cellular fates when expressed in tobacco protoplasts.

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    The catalytic A subunit of ricin can inactivate eukaryotic ribosomes, including those of Ricinus communis where the toxin is naturally produced. How such plant cells avoid intoxication has remained an open question. Here we report the transient expression of a number of ricin A chain-encoding cDNA constructs in tobacco protoplasts. Ricin A chain entered the endoplasmic reticulum lumen, where it was efficiently glycosylated, but it was toxic to the cells and disappeared with time in a brefeldin A-insensitive manner, suggesting reverse translocation to the cytosol and eventual degradation. Proricin (the natural precursor form containing A and B chains joined together by a linker sequence) was glycosylated, transported to the vacuole, and processed to its mature form, but was not toxic. Free ricin A chain and proricin were not secreted, whereas free ricin B chain was found entirely in the extracellular medium. The coexpression of ricin A and B chains resulted in the formation of disulfide-linked, transport-competent heterodimers, which were secreted, with a concomitant reduction in the observed cytotoxicity. These results suggest that the production of ricin as a precursor is essential for its routing to the vacuole and for protection of ricin-producing cells

    Setting Priorities On The Functional Status Of Hydraulic Structures In Mountainous Catchments

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    The frequent inspection of hydraulic structures in mountain catchments is important due to the changing interaction among water-related processes that take place in the context of hydro-meteorological hazards such as debris flow and flash floods. At first level inspections, reports from survey protocols carried out by trained citizen-volunteers are combined to provide an index that represent the status of the structure. The survey protocols aim at identifying needs for cleaning of obstructions or to pre-screen potential problems for a second level inspection or more technical and detailed inspection. Thus, reports are focused on the functional status for the following parameters: condition of the structure at the opening of the streamflow, level of obstruction at the structure and the level of erosion in the streambank. Each parameter is inspected by means of questions to observe while selecting from the available options in the survey protocol. This research presents a web-based tool to support technicians on the use of these reports for setting priorities for the inspection of structures. The decision support methodology is based on the fuzzy logic theory to handle imprecise judgments coming from the visual inspection, analytical hierarchy process (AHP) to weight the different components of each parameter and multi-criteria TOPSIS method to set priorities for the status of the structures according to each parameter. The experiences of actual technicians in using the tool and the feedback on the methodological approach for decision-making are presented from their implementation in a case study in the Fella Basin, Friuli-Venezia-Giulia region, Italy
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