Parametric Design of Minimal Mass Tensegrity Bridges Under Yielding and Buckling Constraints

This paper investigates the use of the most fundamental elements; cables for tension and bars for compression, in the search for the most efficient bridges. Stable arrangements of these elements are called tensegrity structures. We show herein the minimal mass arrangement of these basic elements to satisfy both yielding and buckling constraints. We show that the minimal mass solution for a simply-supported bridge subject to buckling constraints matches Michell's 1904 paper which treats the case of only yield constraints, even though our boundary conditions differ. The necessary and sufficient condition is given for the minimal mass bridge to lie totally above (or below) deck. Furthermore this condition depends only on material properties. If one ignores joint mass, and considers only bridges above deck level, the optimal complexity (number of elements in the bridge) tends toward infinity (producing a material continuum). If joint mass is considered then the optimal complexity is finite. The optimal (minimal mass) bridge below deck has the smallest possible complexity (and therefore cheaper to build), and under reasonable material choices, yields the smallest mass bridge.Comment: 56 pages, 25 figures, 13 tables. Internal Report 2014-1: University of California, San Diego, 201

Measuring walking accessibility to public transport for the elderly: the case of Naples

Demographic ageing represents an essential challenge for local authorities and public transport providers. Decision-makers should not ignore the speci c needs of this weak segment of the population and should implement appropriate policies. This paper develops a GIS-based method to analyse public transport accessibility of elderly people to support policies and planning strategies. To test the proposed method, we propose an application to the city of Naples in Italy. We selected this study case because it represents an example of high population density, complex urban structure and low level of quality of life, especially for the elderly. The application to the city of Naples showed that the urban accessibility changes dramatically for different age segments. Results also reveal patterns of public transport coverage that are signi cantly low particularly in suburban settings. The structure of this paper is organised into four sections: in the rst section, we introduce the main topic of mobility of elderly; in the second section, we describe and discuss the GIS-based method proposed; in the third section, we report on the application to the city of Naples; in the last section, we analyse the results and discuss future research developments

Experimental investigation of the softening-stiffening response of tensegrity prisms under compressive loading

The present paper is concerned with the formulation of new assembly methods of bi-material tensegrity prisms, and the experimental characterization of the compressive response of such structures. The presented assembly techniques are easy to implement, including a string-first approach in the case of ordinary tensegrity prisms, and a base-first approach in the case of systems equipped with rigid bases. The experimental section shows that the compressive response of tensegrity prisms switches from stiffening to softening under large displacements, in dependence on the current values of suitable geometric and prestress variables. Future research lines regarding the mechanical modeling of tensegrity prisms and their use as building blocks of nonlinear periodic lattices and acoustic metamaterials are discussed

A strategy for the design of skyrmion racetrack memories

Magnetic storage based on racetrack memory is very promising for the design of ultra-dense, low-cost and low-power storage technology. Information can be coded in a magnetic region between two domain walls or, as predicted recently, in topological magnetic objects known as skyrmions. Here, we show the technological advantages and limitations of using Bloch and Neel skyrmions manipulated by spin current generated within the ferromagnet or via the spin-Hall effect arising from a non-magnetic heavy metal underlayer. We found that the Neel skyrmion moved by the spin-Hall effect is a very promising strategy for technological implementation of the next generation of skyrmion racetrack memories (zero field, high thermal stability, and ultra-dense storage). We employed micromagnetics reinforced with an analytical formulation of skyrmion dynamics that we developed from the Thiele equation. We identified that the excitation, at high currents, of a breathing mode of the skyrmion limits the maximal velocity of the memory

Adapting to ageing: a mixed methods study of the role of Selection, Optimisation and Compensation in the maintenance of high wellbeing

Objectives: Selection, Optimization and Compensation (SOC) may contribute to successful aging by helping older people maximize wellbeing in the context of physical decline. To explore this hypothesis, and to investigate the potential for narrative analysis to improve understanding of SOC, we analyze interviews conducted with 15 members of the 6-Day Sample, a cohort of Scots born in 1936. Method: Interviewees were chosen based on their physical function and wellbeing scores. Interviews were analyzed to investigate ‘SOC talk’, i.e. older people’s talk about SOC behaviors in everyday life. Types and amounts of SOC talk were quantified, and talk was narratively analyzed. We hypothesized that older people who engaged in more SOC talk would have higher wellbeing. Results: Older people who engaged in high levels of SOC talk had high wellbeing despite low physical function. Those who engaged in little SOC talk had low wellbeing despite higher physical function. Discussion: The concept of successful aging is valuable in part because of its narrative quality: one must strive to keep one’s life story developing despite physical decline and other losses. We provide evidence, from the perspectives of older people themselves, of the ways in which SOC may play a role in that process

Testing a gravity-based accessibility instrument to engage stakeholders into integrated LUT planning

The paper starts from the concern that while there is a large body of literature focusing on the theoretical definitions and measurements of accessibility, the extent to which such measures are used in planning practice is less clear. Previous reviews of accessibility instruments have in fact identified a gap between the clear theoretical assumptions and the infrequent applications of accessibility instruments in spatial and transport planning. In this paper we present the results of a structured-workshop involving private and public stakeholders to test usability of gravity-based accessibility measures (GraBaM) to assess integrated land-use and transport policies. The research is part of the COST Action TU1002 “Accessibility Instruments for Planning Practice” during which different accessibility instruments where tested for different case studies. Here we report on the empirical case study of Rome

The learning process of accessibility instrument developers: Testing the tools in planning practice

Many planning support tools have recently been developed aimed at measuring and mod- elling accessibility (Accessibility Instrument or AI). The main difficulty for tool developers is designing an AI that is at the same time technically rigorous and usable in practice. Measuring accessibility is indeed a complex task, and AI outputs are difficult to communi- cate to target end-users, in particular, because these users are professionals from several disciplines with different languages and areas of expertise, such as urban geographers, spa- tial planners, transport planners, and budgeting professionals. In addition to this, AI devel- opers seem to have little awareness of the needs of AI end-users, which in turn tend to have limited ability for using these tools. Against this complex background, our research focuses on the viewpoint of AI developers, with two aims: (1) to provide insights into how AI devel- opers perceive their tools and (2) to understand how their perceptions might change after testing their AI with end-users. With this in mind, an analysis of 15 case studies was per- formed: groups of end-users tested different AI in structured workshops. Before and after the workshops, two questionnaires explored the AI developers’ perceptions on the tools and their usability. The paper demonstrates that the workshops with end-users were crit- ical for developers to appreciate the importance of specific characteristics the tool should have, namely practical relevance, flexibility, and ease of use. The study provides evidence that AI developers were prone to change their perceptions about AI after interacting directly with end-users

Giardia Cyst Wall Protein 1 Is a Lectin That Binds to Curled Fibrils of the GalNAc Homopolymer

The infectious and diagnostic stage of Giardia lamblia (also known as G. intestinalis or G. duodenalis) is the cyst. The Giardia cyst wall contains fibrils of a unique β-1,3-linked N-acetylgalactosamine (GalNAc) homopolymer and at least three cyst wall proteins (CWPs) composed of Leu-rich repeats (CWPLRR) and a C-terminal conserved Cys-rich region (CWPCRR). Our goals were to dissect the structure of the cyst wall and determine how it is disrupted during excystation. The intact Giardia cyst wall is thin (~400 nm), easily fractured by sonication, and impermeable to small molecules. Curled fibrils of the GalNAc homopolymer are restricted to a narrow plane and are coated with linear arrays of oval-shaped protein complex. In contrast, cyst walls of Giardia treated with hot alkali to deproteinate fibrils of the GalNAc homopolymer are thick (~1.2 µm), resistant to sonication, and permeable. The deproteinated GalNAc homopolymer, which forms a loose lattice of curled fibrils, is bound by native CWP1 and CWP2, as well as by maltose-binding protein (MBP)-fusions containing the full-length CWP1 or CWP1LRR. In contrast, neither MBP alone nor MBP fused to CWP1CRR bind to the GalNAc homopolymer. Recombinant CWP1 binds to the GalNAc homopolymer within secretory vesicles of Giardia encysting in vitro. Fibrils of the GalNAc homopolymer are exposed during excystation or by treatment of heat-killed cysts with chymotrypsin, while deproteinated fibrils of the GalNAc homopolymer are degraded by extracts of Giardia cysts but not trophozoites. These results show the Leu-rich repeat domain of CWP1 is a lectin that binds to curled fibrils of the GalNAc homopolymer. During excystation, host and Giardia proteases appear to degrade bound CWPs, exposing fibrils of the GalNAc homopolymer that are digested by a stage-specific glycohydrolase. Author SummaryWhile the walls of plants and fungi contain numerous sugar homopolymers (cellulose, chitin, and β-1,3-glucans) and dozens of proteins, the cyst wall of Giardia is relatively simple. The Giardia wall contains a unique homopolymer of β-1,3-linked N-acetylgalactosamine (GalNAc) and at least three cyst wall proteins (CWPs), each of which is composed of Leu-rich repeats and a C-terminal Cys-rich region. The three major discoveries here are: 1) Fibrils of the GalNAc homopolymer are curled and form a lattice that is compressed into a narrow plane by bound protein in intact cyst walls. 2) Leu-rich repeats of CWP1 form a novel lectin domain that is specific for fibrils of the GalNAc homopolymer, which can be isolated by methods used to deproteinate fungal walls. 3) A cyst-specific glycohydrolase is able to degrade deproteinated fibrils of the GalNAc homopolymer. We incorporate these findings into a new curled fiber and lectin model of the intact Giardia cyst wall and a protease and glycohydrolase model of excystation.National Institutes of Health (AI048082, AI44070, GM31318, RR1088

Classifying day and night station areas: application of the node-place model in Greater London

In many countries around the world, cities are looking for ways to promote the integration of public transport and urban development or “transit-oriented development” (TOD). Often, however, these integration attempts are limited to a particular station site, instead of being based on a comprehensive strategy encompassing the whole urban region and public transportation network. This is especially true in the case of Greater London, where the transformation of station areas lacks a much broader space and time horizons vision. With the aim of supporting long-term integrated land-use and transport strategies at the regional scale, this paper analyses and classifies the station areas system in Greater London. In fact, TOD has also been widely advocated and applied in London; however, so far no study has systematically developed a TOD typology in the London context. This paper fills this gap using an approach based on the node-place model, introduced by Bertolini (1996, 1999) to chart ‘node’ and ‘place’ components for station catchment areas. The main innovation of this application of the node-place is that it is applied in the day hours and the night hours, considering the opening hours of the London Tube. Using GIS, the paper proposes a system of indicators for the day and night hours, including network connectivity (‘node values’) and geographically detailed data on amenity levels, job and employment densities (‘place values’). Drawing on these confrontations, opportunities for (i) land-use densification within catchment areas or (ii) increased network connectivity of the stations are suggested both for the day and night hours, supporting the 24hours London economy