Compatibility of potential reinforcing ceramics with Ni and Fe aluminides

There is a great deal of interest in the possible utilization of intermetallic compounds in advanced high temperature gas turbine engines. These compounds exhibit a variety of promising properties, including reasonable strength, high melting points, relatively low densities, and good corrosion resistance. However, in general, they also show limited ductilities and toughness, and less than optimum creep strengths at elevated temperatures. In addition, in applications involving advanced gas turbine engines, it is often necessary for candidate materials to have large elastic moduli. The present study is part of a program whose objective is to identify a high temperature fiber reinforced composite. The approach adopted was to fabricate laboratory samples of the combinations of materials considered by Misra, in order to determine the extent to which the thermodynamic calculations can predict phase stability. As many of the ceramic phases considered are not currently available in fiber form, they were added as particulates to the alloy matrices. The ways in which the materials were produced and evaluated are described

Neighbourhood mobility in context : household moves and changing neighbourhoods in the Netherlands

Although high levels of population mobility are often viewed as a problem at the neighbourhood level we know relatively little about what makes some neighbourhoods more mobile than others. The main question in this paper is to what extent differences in out-mobility between neighbourhoods can be explained by differences in the share of mobile residents, or whether other neighbourhood characteristics also play a role. To answer this question we focus on the effects of the socioeconomic status and ethnic composition of neighbourhoods and on neighbourhood change. Using data from the Netherlands population registration system and the Housing Demand Survey we model population mobility both at individual and at neighbourhood levels. The aggregate results show that the composition of the housing stock and of the neighbourhood population explain most of the variation in levels of neighbourhood out-mobility. At the same time, although ethnic minority groups in the Netherlands are shown to be relatively immobile, neighbourhoods with higher concentrations of ethnic minority residents have the highest population turnovers. The individual-level models show that people living in neighbourhoods which experience an increase in the percentage of ethnic minorities are more likely to move, except when they belong to an ethnic minority group themselves. The evidence suggests that 'white flight' and 'socio-economic flight' are important factors in neighbourhood change.PostprintPeer reviewe

Gaining Access to Housing in Germany: The Foreign Minority Experience

Housing is a critical component of household well being and the extent to which minority households have achieved parity with Germans is a measure of the extent to which this population is integrated into the larger German society. Specifically we examine whether the housing conditions for immigrants2 has improved between 1985 and 1998 despite the greater barriers to upward mobility for low skill workers arising from industrial restructuring. We use regression models to determine the degree to which socioeconomic differences between the two populations account for variations in the average quality of their housing. Finally, given the low number of vacancies in the German housing market and the disadvantaged position of minorities within it, we are interested in measuring the magnitude of the improvements persons of foreign origin are able to make through residential mobility. Our descriptive analyses reveal that although housing conditions for minorities have improved in absolute terms across a wide array of indicators, only in a few instances has the housing quality gap between Germans and persons of foreign origin narrowed. Further, we find that the housing conditions of minorities remained poorer even after controlling for variables thought to be strong predictors of housing quality (income, age, family size etc..) Finally, persons of foreign origin are becoming increasingly likely to move into the large, often geographically and socially isolated apartment complexes built in the post World War II era.

Quantum effects in the Alcubierre warp drive spacetime

The expectation value of the stress-energy tensor of a free conformally invariant scalar field is computed in a two-dimensional reduction of the Alcubierre ``warp drive'' spacetime. The stress-energy is found to diverge if the apparent velocity of the spaceship exceeds the speed of light. If such behavior occurs in four dimensions, then it appears implausible that ``warp drive'' behavior in a spacetime could be engineered, even by an arbitrarily advanced civilization.Comment: 9 pages, ReVTe

FUNDAMENTAL AND INDUCED BIASES IN TECHNOLOGICAL CHANGE IN CENTRAL CANADIAN AGRICULTURE

A new procedure is developed to estimate innovation possibility frontiers and test for biases in technological change. Using data on four inputs (land, machinery, chemicals and labour) from central Canada (Ontario and Quebec) over the period 1926-1985, we find that the innovations possibilities frontier shifts neutrally over time. This is consistent with Ahmad's model of induced innovations, but is not consistent with de Janvry's application of Ahmad's model to the historical development of Argentine agriculture. Agricultural research in Canada has been conducted with the objective of developing cost minimizing technologies. Empirical support was found for this notion in the development of the innovation possibilities frontier.Innovation possibility frontier, technological change, Research and Development/Tech Change/Emerging Technologies,

Comparing Socio-Spatial Mobility and Its Outcomes in Australia and New Zealand

Households choose places from a hierarchy of options defined by social, economic and environmental contexts and these choices are conditioned by age, family status and economic contexts. While we know a good deal about the choice processes we know somewhat less about the spatial outcomes of these decisions apart from the well-established distance minimization of most moves. Recent research has begun to fill that gap and in this paper I unpack an earlier study of mobility across communities clustered by measures of disadvantage and extend that study to a comparable analysis of mobility in Australia. Specifically, I use the New Zealand Deprivation Index and the SEIFA index in the Household Income and Labour Dynamics Survey in Australia (HILDA) to construct matrices of socio-spatial movement and consider the relationship between in-flows and out-flows, the interaction of moves with age and education and the relationship of initial location with mobility outcomes

Transcriptomic profiling of human breast and melanoma cells selected by migration through narrow constraints

The metastatic spread of cancer cells is a step-wise process that starts with dissociation from primary tumours and local invasion of adjacent tissues. The ability to invade local tissues is the product of several processes, including degradation of extracellular matrices (ECM) and movement of tumour cells through physically-restricting gaps. To identify properties contributing to tumour cells squeezing through narrow gaps, invasive MDA-MB-231 human breast cancer and MDA-MB-435 human melanoma cells were subjected to three successive rounds of selection using cell culture inserts with highly constraining 3 μm pores. For comparison purposes, flow cytometry was also employed to enrich for small diameter MDA-MB-231 cells. RNA-Sequencing (RNA-seq) using the Illumina NextSeq 500 platform was undertaken to characterize how gene expression differed between parental, invasive pore selected or small diameter cells. Gene expression results obtained by RNA-seq were validated by comparing with RT-qPCR. Transcriptomic data generated could be used to determine how alterations that enable cell passage through narrow spaces contribute to local invasion and metastasis

Toward a Science of Sustainability

This report presents an overview of research horizons in sustainability science. Its motivation is to help harness science and technology to foster a transition toward sustainability – toward patterns of development that promote human well-being while conserving the life-support systems of the planet. It builds on but does not explicitly address the vast range of relevant sector-specific and cross-sectoral problem-solving work now underway in fields ranging from green technologies in energy and manufacturing to urban design to agriculture and natural resources. It focuses on the narrower but essential task of characterizing the needs for fundamental work on the core concepts, methods, models, and measurements that, if successful, would support work across all of those sectoral applications by advancing fundamental understanding of the science of sustainability. The report sets forth the workshop’s findings and recommendations on six fundamental questions now facing scholars seeking to harness science and technology to foster sustainability: 1. What are the principal tradeoffs between human well-being and the natural environment, and how are those tradeoffs mediated by the ways in which people use nature? 2. What determines the adaptability of coupled human-environment systems and, more broadly, their vulnerability and robustness/resilience in the face of external shocks and internal dynamics? 3. What shapes the long term trends and transitions that set the stage on which humanenvironment interactions are played out? 4. How can theory and models be formulated that better account for the variation in types or trends of human-environment interactions? 5. How can society most effectively guide or manage human-environment systems toward a sustainability transition? 6. How can the “sustainability” of alternative trajectories of human-environment interactions be usefully and rigorously evaluated