1,282 research outputs found

    Crustal evolution inferred from Apollo magnetic measurements

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    Magnetic field and solar wind plasma density measurements were analyzed to determine the scale size characteristics of remanent fields at the Apollo 12, 15, and 16 landing sites. Theoretical model calculations of the field-plasma interaction, involving diffusion of the remanent field into the solar plasma, were compared to the data. The information provided by all these experiments shows that remanent fields over most of the lunar surface are characterized by spatial variations as small as a few kilometers. Large regions (50 to 100 km) of the lunar crust were probably uniformly magnetized during early crustal evolution. Bombardment and subsequent gardening of the upper layers of these magnetized regions left randomly oriented, smaller scale (5 to 10 km) magnetic sources close to the surface. The larger scale size fields of magnitude approximately 0.1 gammas are measured by the orbiting subsatellite experiments and the small scale sized remanent fields of magnitude approximately 100 gammas are measured by the surface experiments

    Approximate analysis and stability of pressure oscillations in ramjets

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    This paper summarizes work accomplished during the past five years on analysis of stability related to recent experimental results on combustion instabilities in dump combustors. The primary purpose is to provide the information in a form useful to those concerned with design and development of operational systems. Thus most substantial details are omitted; the material is presented in a qualitative fashion

    Degeneracies in trapped two-component Fermi gases

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    We report on previously unobserved inter-system degeneracies in two-component equal-mass Fermi gases with interspecies zero-range interactions under isotropic harmonic confinement. Over the past 10 years, two-component Fermi gases consisting of n1n_1 spin-up and n2n_2 spin-down atoms with interspecies zero-range interactions have become a paradigm for modeling condensed matter systems, nuclear matter and neutron matter. We show that the eigen energies of the (n1+1,n21)(n_1+1,n_2-1) system are degenerate with the eigen energies of the (n1,n2)(n_1,n_2) system for any s-wave scattering length asa_s, including infinitely large, positive and negative asa_s. The existence of the inter-system degeneracies is demonstrated explicitly for few-body systems with n1+n2=4,5n_1+n_2=4, 5 and 6. The degeneracies and associated symmetries are explained within a group theoretical framework.Comment: 5 pages with 4 figures + 5 pages of supplemental materia

    Labour after Land Reform: The Precarious Livelihoods of Former Farmworkers in Zimbabwe

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    What happens to labour when major redistributive land reform restructures a system of settler colonial agriculture? This article examines the livelihoods of former farmworkers on large‐scale commercial farms who still live in farm compounds after Zimbabwe's land reform. Through a mix of surveys and in‐depth biographical interviews, four different types of livelihood are identified, centred on differences in land access. These show how diverse, but often precarious, livelihoods are being carved out, representing the ‘fragmented classes of labour’ in a restructured agrarian economy. The analysis highlights the tensions between gaining new freedoms, notably through access to land, and being subject to new livelihood vulnerabilities. The findings are discussed in relation to wider questions about the informalization of the economy and the role of labour and employment in a post‐settler agrarian economy, where the old ‘farmworker’ label no longer applies

    Corporate governance and financial constraints on strategic turnarounds

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    The paper extends the Robbins and Pearce (1992) two-stage turnaround response model to include governance factors. In addition to the retrenchment and recovery, the paper proposes the addition of a realignment stage, referring specifically to the re-alignment of expectations of principal and agent groups. The realignment stage imposes a threshold that must be crossed before the retrenchment and hence recovery stage can be entered. Crossing this threshold is problematic to the extent that the interests of governance-stakeholder groups diverge in a crisis situation. The severity of the crisis impacts on the bases of strategy contingent asset valuation leading to the fragmentation of stakeholder interests. In some cases the consequence may be that management are prevented from carrying out turnarounds by governance constraints. The paper uses a case study to illustrate these dynamics, and like the Robbins and Pearce study, it focuses on the textile industry. A longitudinal approach is used to show the impact of the removal of governance constraints. The empirical evidence suggests that such financial constraints become less serious to the extent that there is a functioning market for corporate control. Building on governance research and turnaround literature, the paper also outlines the general case necessary and sufficient conditions for successful turnarounds

    Challenges in the Quest for Keystones

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    Identifying keystone species is difficult-but essential to understanding bow loss of species will affect ecosystems

    Molecular, phenotypic, and sample-associated data to describe pluripotent stem cell lines and derivatives

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    The use of induced pluripotent stem cells (iPSC) derived from independent patients and sources holds considerable promise to improve the understanding of development and disease. However, optimized use of iPSC depends on our ability to develop methods to efficiently qualify cell lines and protocols, monitor genetic stability, and evaluate self-renewal and differentiation potential. To accomplish these goals, 57 stem cell lines from 10 laboratories were differentiated to 7 different states, resulting in 248 analyzed samples. Cell lines were differentiated and characterized at a central laboratory using standardized cell culture methodologies, protocols, and metadata descriptors. Stem cell and derived differentiated lines were characterized using RNA-seq, miRNA-seq, copy number arrays, DNA methylation arrays, flow cytometry, and molecular histology. All materials, including raw data, metadata, analysis and processing code, and methodological and provenance documentation are publicly available for re-use and interactive exploration at https://www.synapse.org/pcbc. The goal is to provide data that can improve our ability to robustly and reproducibly use human pluripotent stem cells to understand development and disease

    Do leaders matter? : Chinese politics, leadership transition and the 17th Party Congress

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    The opaque nature of decision making in China has generated considerable interest in the internecine machinations of elite politics. Particularly, but not only, when it comes to issues of leadership transition, considerations of factional formation and conflict come to the fore. This is partly to explain the transition process itself, but also out of concern for how new leaders might change the direction of Chinese policy. This paper suggests that whilst leaders and leadership changes do matter, they matter less than they once did. This is partly a result of the de-ideologicization and increasing diverse nature of elite interests and group formation. But it is also partly a result of the changed nature of China’s political economy; in short, there is less desire and less ability for new leaders to impose a clear paradigm shift

    Nation, Migration, Identity: Learning from the Cross-Strait Context

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    It has been argued that globalisation, with its flexible landscapes of production, consumption and mobility, has favoured the emergence of new forms of belonging and identity that are not necessarily built on such principles of the nation state. In this paper, we argue that this process is more likely to happen when movements occur between states that are not in conflictual relations with each other. When the relations between two nations are shaped by conflicts, for instance due to disputes about sovereignty over a territory, nationalism may remain a crucial factor shaping identification and belonging of those who move between the two territories. In this paper, by taking the case of migrants moving between the People’s Republic of China and Taiwan, we will shed light on how the issue of “unresolved sovereignty” may eventually lead these actors to reinforce nationalist ideals and identities in their daily narratives and practices, instead of favouring the generation of hybrid identities
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