6 resultados para FRUSTRATED PYROCHLORES
Resumo:
This paper presents an ethnographic account of jazz music in Athens. The small scene under scrutiny is mainly populated by professional session instrumentalists of the Greek popular music scene who perform jazz as a side activity for their own pleasure. In the process, they construct a conceptual dichotomy between ‘work’ and ‘play’. Drawing on the author’s extended involvement in this scene, and focusing on private interviews with musicians, this article unveils the discourses of cosmopolitanism invoked through local jazz music making. The ethnographic material presented aims to illustrate how even a small subculture can serve as a terrain for contesting cosmopolitan imaginaries.
Resumo:
Orbitally degenerate frustrated spinels, Cd1-xZnxV2O4, with 0 <= x <= 1 were investigated using elastic and inelastic neutron scattering techniques. In the end members with x=0 and 1, a tetragonal distortion (c < a) has been observed upon cooling mediated by a Jahn-Teller distortion that gives rise to orbital ordering. This leads to the formation of spin chains in the ab-plane that upon further cooling, Neel ordering is established due to interchain coupling. In the doped compositions, however, the bulk susceptibility, chi, shows that the macroscopic transitions to cooperative orbital ordering and long-range antiferromagnetic ordering are suppressed. However, the inelastic neutron scattering measurements suggest that the dynamic spin correlations at low temperatures have similar one-dimensional characteristics as those observed in the pure samples. The pair density function analysis of neutron diffraction data shows that the local atomic structure does not become random with doping but rather consists of two distinct environments corresponding to ZnV2O4 and CdV2O4. This indicates that short-range orbital ordering is present which leads to the one-dimensional character of the spin correlations even in the low temperature cubic phase of the doped compositions.
Resumo:
This study examines the relation between selection power and selection labor for information retrieval (IR). It is the first part of the development of a labor theoretic approach to IR. Existing models for evaluation of IR systems are reviewed and the distinction of operational from experimental systems partly dissolved. The often covert, but powerful, influence from technology on practice and theory is rendered explicit. Selection power is understood as the human ability to make informed choices between objects or representations of objects and is adopted as the primary value for IR. Selection power is conceived as a property of human consciousness, which can be assisted or frustrated by system design. The concept of selection power is further elucidated, and its value supported, by an example of the discrimination enabled by index descriptions, the discovery of analogous concepts in partly independent scholarly and wider public discourses, and its embodiment in the design and use of systems. Selection power is regarded as produced by selection labor, with the nature of that labor changing with different historical conditions and concurrent information technologies. Selection labor can itself be decomposed into description and search labor. Selection labor and its decomposition into description and search labor will be treated in a subsequent article, in a further development of a labor theoretic approach to information retrieval.
Resumo:
Background: There is consensus in the literature that the end of life care for patients with chronic illness is suboptimal, but research on the specific needs of this population is limited. Aim: This study aimed to use a mixed methodology and case study approach to explore the palliative care needs of patients with a non-cancer diagnosis from the perspectives of the patient, their significant other and the clinical team responsible for their care. Patients (n 18) had a diagnosis of either end-stage heart failure, renal failure or respiratory disease. Methods: The Short Form 36 and Hospital and Anxiety and Depression Questionnaire were completed by all patients. Unstructured interviews were (n 35) were conducted separately with each patient and then their significant other. These were followed by a focus group discussion (n 18) with the multiprofessional clinical team. Quantitative data were analysed using simple descriptive statistics and simple descriptive statistics. All qualitative data were taped, transcribed and analysed using Colaizzi’s approach to qualitative analysis. Findings: Deteriorating health status was the central theme derived from this analysis. It led to decreased independence, social isolation and family burden. These problems were mitigated by the limited resources at the individual’s disposal and the availability of support from hospital and community services. Generally resources and support were perceived as lacking. All participants in this study expressed concerns regarding the patients’ future and some patients described feelings of depression or acceptance of the inevitability of imminent death. Conclusion: Patients dying from chronic illness in this study had many concerns and unmet clinical needs. Care teams were frustrated by the lack of resources available to them and admitted they were ill-equipped to provide for the individual’s holistic needs. Some clinicians described difficulty in talking openly with the patient and family regarding the palliative nature of their treatment. An earlier and more effective implementation of the palliative care approach is necessary if the needs of patients in the final stages of chronic illness are to be adequately addressed. Pa
Resumo:
Frustration – the inability to simultaneously satisfy all interactions – occurs in a wide range of systems including neural networks, water ice and magnetic systems. An example of the latter is the so called spin-ice in pyrochlore materials [1] which have attracted a lot of interest not least due to the emergence of magnetic monopole defects when the ‘ice rules’ governing the local ordering breaks down [2]. However it is not possible to directly measure the frustrated property – the direction of the magnetic moments – in such spin ice systems with current experimental techniques. This problem can be solved by instead studying artificial spin-ice systems where the molecular magnetic moments are replaced by nanoscale ferromagnetic islands [3-8]. Two different arrangements of the ferromagnetic islands have been shown to exhibit spin ice behaviour: a square lattice maintaining four moments at each vertex [3,8] and the Kagome lattice which has only three moments per vertex but equivalent interactions between them [4-7]. Magnetic monopole defects have been observed in both types of lattices [7-8]. One of the challenges when studying these artificial spin-ice systems is that it is difficult to arrive at the fully demagnetised ground-state [6-8].
Here we present a study of the switching behaviour of building blocks of the Kagome lattice influenced by the termination of the lattice. Ferromagnetic islands of nominal size 1000 nm by 100 nm were fabricated in five island blocks using electron-beam lithography and lift-off techniques of evaporated 18 nm Permalloy (Ni80Fe20) films. Each block consists of a central island with four arms terminated by a different number and placement of ‘injection pads’, see Figure 1. The islands are single domain and magnetised along their long axis. The structures were grown on a 50 nm thick electron transparent silicon nitride membrane to allow TEM observation, which was back-coated with a 5 nm film of Au to prevent charge build-up during the TEM experiments.
To study the switching behaviour the sample was subjected to a magnetic field strong enough to magnetise all the blocks in one direction, see Figure 1. Each block obeys the Kagome lattice ‘ice-rules’ of “2-in, 1-out” or “1-in, 2-out” in this fully magnetised state. Fresnel mode Lorentz TEM images of the sample were then recorded as a magnetic field of increasing magnitude was applied in the opposite direction. While the Fresnel mode is normally used to image magnetic domain structures [9] for these types of samples it is possible to deduce the direction of the magnetisation from the Lorentz contrast [5]. All images were recorded at the same over-focus judged to give good Lorentz contrast.
The magnetisation was found to switch at different magnitudes of the applied field for nominally identical blocks. However, trends could still be identified: all the blocks with any injection pads, regardless of placement and number, switched the direction of the magnetisation of their central island at significantly smaller magnitudes of the applied magnetic field than the blocks without injection pads. It can therefore be concluded that the addition of an injection pad lowers the energy barrier to switching the connected island, acting as a nucleation site for monopole defects. In these five island blocks the defects immediately propagate through to the other side, but in a larger lattice the monopoles could potentially become trapped at a vertex and observed [10].
References
[1] M J Harris et al, Phys Rev Lett 79 (1997) p.2554.
[2] C Castelnovo, R Moessner and S L Sondhi, Nature 451 (2008) p. 42.
[3] R F Wang et al, Nature 439 (2006) 303.
[4] M Tanaka et al, Phys Rev B 73 (2006) 052411.
[5] Y Qi, T Brintlinger and J Cumings, Phys Rev B 77 (2008) 094418.
[6] E Mengotti et al, Phys Rev B 78 (2008) 144402.
[7] S Ladak et al, Nature Phys 6 (2010) 359.
[8] C Phatak et al, Phys Rev B 83 (2011) 174431.
[9] J N Chapman, J Phys D 17 (1984) 623.
[10] The authors gratefully acknowledge funding from the EPSRC under grant number EP/D063329/1.
Resumo:
Summary: This article provides a review of the contribution of Axel Honneth’s model of recognition for critical social work. While Honneth’s tripartite conceptualisation of optimal identity-formation is positively appraised, his analysis of the link between misrecognition, the experience of shame and eventual sense of moral outrage, is contested. Drawing on a range of sources, including the sociology of shame, Honneth’s ideas about the emotional antecedents of emancipatory action are revised to guide critical social work with misrecognised service users.
Findings: The intellectual background to Honneth’s recognition model, emanating from leading German philosophers, is described and its application to social work set out. Even so, Honneth’s model is found to be deficient in one primary regard: its assumption about the emotional antecedents to quests for withheld recognition is misapprehended. In particular, the argument in this article is that the ubiquitous emotion of shame, which Honneth argues flows from misrecognition, must be carefully addressed through the medium of relationship, otherwise it might lead to repressed shame and frustrated attempts at social struggle. To this end, a social work process is delineated for dealing with shame, following episodes of misrecognition.
Applications: Honneth’s model of recognition, along with revised ideas about how to recognise and manage shame, is incorporated into a conceptual framework for critical social work practice. With this renewed understanding of the impact of shame, following misrecognition, social workers should be better equipped conceptually to enable service users to take action for empowerment.