969 research outputs found
Non-vanishing Berry Phase in Chiral Insulators
The binary compounds FeSi, RuSi, and OsSi are chiral insulators crystallizing
in the space group P2_13 which is cubic. By means of ab initio calculations we
find for these compounds a non-vanishing electronic Berry phase, the sign of
which depends on the handedness of the crystal. There is thus the possibility
that the Berry phase signals the existence of a macroscopic electric
polarization due to the electrons. We show that this is indeed so if a small
external magnetic field is applied in the [111]-direction. The electric
polarization is oscillatory in the magnetic field and possesses a signature
that distinguishes the handedness of the crystal. Our findings add to the
discussion of topological classifications of insulators and are significant for
spintronics applications, and in particular, for a deeper understanding of
skyrmions in insulators
Combining brain-computer interfaces and assistive technologies: state-of-the-art and challenges
In recent years, new research has brought the field of EEG-based Brain-Computer Interfacing (BCI) out of its infancy and into a phase of relative maturity through many demonstrated prototypes such as brain-controlled wheelchairs, keyboards, and computer games. With this proof-of-concept phase in the past, the time is now ripe to focus on the development of practical BCI technologies that can be brought out of the lab and into real-world applications. In particular, we focus on the prospect of improving the lives of countless disabled individuals through a combination of BCI technology with existing assistive technologies (AT). In pursuit of more practical BCIs for use outside of the lab, in this paper, we identify four application areas where disabled individuals could greatly benefit from advancements in BCI technology, namely,âCommunication and Controlâ, âMotor Substitutionâ, âEntertainmentâ, and âMotor Recoveryâ. We review the current state of the art and possible future developments, while discussing the main research issues in these four areas. In particular, we expect the most progress in the development of technologies such as hybrid BCI architectures, user-machine adaptation algorithms, the exploitation of usersâ mental states for BCI reliability and confidence measures, the incorporation of principles in human-computer interaction (HCI) to improve BCI usability, and the development of novel BCI technology including better EEG devices
Optimisation of off-highway truck fuel consumption through mine haul road design
This study aims to optimise the fuel consumption of Caterpillar 785D off-highway trucks as used by the project sponsor at an open cut coal mining operation in Queensland, Australia.
This was achieved by:
- Researching mine design and operational factors influencing fuel consumption of off-highway trucks
- Identifying variables and haul road design scenarios relevant to the project sponsorâs particular operation
- Creating a data collection program to obtain and combine relevant condition monitoring data from multiple sources
- Analysing the data for variations in fuel consumption
- Quantifying fuel consumption in different haul road scenarios
Fuel consumption rates were found for three scenarios, ascending ramps, stop-start driving and idling. Mining engineers can use these quantities to predict fuel costs incurred by various ramp grades and lengths, truck queuing, intersections and other similar road features. Fuel costs can be compared to construction and production costs to determine optimal road designs. An additional tool was created to assist with the calculation of fuel costs over the life of a ramp. This tool demonstrates how these costs are affected by ramp grade.
The methodology could be expanded to other truck models or operations in the future. In addition to optimising fuel consumption, condition monitoring data could also be used to optimise other production, design or maintenance tasks
Magnetization Dissipation in Ferromagnets from Scattering Theory
The magnetization dynamics of ferromagnets are often formulated in terms of
the Landau-Lifshitz-Gilbert (LLG) equation. The reactive part of this equation
describes the response of the magnetization in terms of effective fields,
whereas the dissipative part is parameterized by the Gilbert damping tensor. We
formulate a scattering theory for the magnetization dynamics and map this
description on the linearized LLG equation by attaching electric contacts to
the ferromagnet. The reactive part can then be expressed in terms of the static
scattering matrix. The dissipative contribution to the low-frequency
magnetization dynamics can be described as an adiabatic energy pumping process
to the electronic subsystem by the time-dependent magnetization. The Gilbert
damping tensor depends on the time derivative of the scattering matrix as a
function of the magnetization direction. By the fluctuation-dissipation
theorem, the fluctuations of the effective fields can also be formulated in
terms of the quasistatic scattering matrix. The theory is formulated for
general magnetization textures and worked out for monodomain precessions and
domain wall motions. We prove that the Gilbert damping from scattering theory
is identical to the result obtained by the Kubo formalism.Comment: 15 pages, 1 figur
BNCI systems as a potential assistive technology: ethical issues and participatory research in the BrainAble project
This paper highlights aspects related to current research and thinking about ethical issues in relation to Brain Computer Interface (BCI) and Brain-Neuronal Computer Interfaces (BNCI) research through the experience of one particular project, BrainAble, which is exploring and developing the potential of these technologies to enable people with complex disabilities to control computers. It describes how ethical practice has been developed both within the multidisciplinary research team and with participants. Results: The paper presents findings in which participants shared their views of the project prototypes, of the potential of BCI/BNCI systems as an assistive technology, and of their other possible applications. This draws attention to the importance of ethical practice in projects where high expectations of technologies, and representations of âideal typesâ of disabled users may reinforce stereotypes or drown out participant âvoicesâ. Conclusions: Ethical frameworks for research and development in emergent areas such as BCI/BNCI systems should be based on broad notions of a âduty of careâ while being sufficiently flexible that researchers can adapt project procedures according to participant needs. They need to be frequently revisited, not only in the light of experience, but also to ensure they reflect new research findings and ever more complex and powerful technologies
More than a cognitive experience: unfamiliarity, invalidation, and emotion in organizational learning
Literature on organizational learning (OL) lacks an integrative framework that captures the emotions involved as OL proceeds. Drawing on personal construct theory, we suggest that organizations learn where their members reconstrue meaning around questions of strategic significance for the organization. In this 5-year study of an electronics company, we explore the way in which emotions change as members perceive progress or a lack of progress around strategic themes. Our framework also takes into account whether OL involves experiences that are familiar or unfamiliar and the implications for emotions. We detected similar patterns of emotion arising over time for three different themes in our data, thereby adding to OL perspectives that are predominantly cognitive in orientation
Experimental Induction of Odontoblast Differentiation and Stimulation During Preparative Processes
In vivo implantation experiments have shown that ethylenediaminetetraaceticacid(EDTA)-soluble frac tions of dentin stimulate reparative dentinogenesis . When isolated embryonic dental papillae were cultured in the presence of these dentin constituents, odontoblast cytological and functional differentiation could be initiated and maintained in the absence of an enamel organ. These effects were attributed to the presence of TGF-/1- related molecules [TGF-/11 or bone morphogenetic protein -2a (BMP-2a)] which had to be used in combination with an EDT A-soluble fraction of dentin in order to specifically affect competent preodontoblasts . These EDT A-soluble constituents present in dentin could be replaced by heparin or fibronectin which both have been reported to interact with TGF-/1. The association of such defined matrix components with a TGF-/1-related molecule represents a biologically active complex triggering odontoblast functional differentiation.
In response to caries, odontoblasts modulate their secretory activity and are stimulated to elaborate reactionary dentin. This might be induced by active molecules such as IGF, TGF-6 or BMP which are liberated from dentin consecutively to the demineralization process.
Reparative dentinogenesis is distinct from reactionary dentinogenesis and more complex since it implicates the differentiation of precursor cells present in the dental papilla. The developmental history of these cells is different from that of the physiological predontoblasts in developing teeth. The nature of these stem cells and the mechanism of their induction still remain open questions
âHe's Still the Winner in My Mindâ: Maintaining the Collective Identity in Sport through Social Creativity and Group Affirmation
Social Creativity and Group Affirmation are two strategies by which individuals that identify with a sporting activity, team, group or individual may protect that sense of identification in light of negative events. This paper explores the use of such strategies through examining reactions to doping allegations surrounding Lance Armstrong to explain how members of two brand communities (one based on the brand of Armstrong as cyclist and the other on the brand of Armstrong as cancer survivor) maintain a sense of allegiance. Through undertaking a netnographic approach, six strategies were identified by members of these communities, three of which could be identified as Social Creativity Strategies (Lance Armstrong as âsuperhumanâ, the notion of cycling as a âlevel playing fieldâ, Armstrong as scapegoat) and three as Group Affirmation (Armstrong as a continuing inspiration, the Armstrong legacy, and denial). The two brand communities demonstrated differing patterns of maintenance, with those within the cycling community focusing more upon Social Creativity strategies, whereas those members of the Armstrong as cancer survivor brand tended to focus upon Group Affirmation strategies
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Recovering from stillbirth: the effects of making and sharing memories on maternal mental health
Objective: This study examined whether the experience of creating and sharing memories of their babies is associated with mothersâ mental health after stillbirth, taking account of factors previously shown to be important. Background: Mothers of stillborn babies are usually offered the opportunity to spend time with and create memories of their babies. However, evidence on whether this leads to better mental health outcomes is equivocal. One possible explanation is that the impact of making memories is mediated by the extent to which women subsequently share these memories. Methods: Cross-sectional questionnaire study. Mothers (N = 162) of stillborn babies completed online questionnaires of how memories were made and shared, satisfaction with memory-making and sharing, professional and social support, and symptoms of depression, anxiety and PTSD. Results: The majority of mothers made and shared memories. The number of different memory-making activities was not associated with mental health outcomes. However, the degree to which mothers shared their memories was associated with fewer PTSD symptoms. Regression analyses showed that good mental health was most strongly associated with time since stillbirth, perceived professional support, sharing of memories and less wish to talk more about the baby. Conclusion: This study confirms research showing that time since stillbirth and perceived professional support is associated with better mental health following stillbirth and for the first time shows the importance of opportunities to share memories of the baby. Variation in sharing opportunities may contribute to inconsistencies in the association between making memories and mental health following stillbirth
Metal-insulator transition in vanadium dioxide nanobeams: probing sub-domain properties of strongly correlated materials
Many strongly correlated electronic materials, including high-temperature
superconductors, colossal magnetoresistance and metal-insulator-transition
(MIT) materials, are inhomogeneous on a microscopic scale as a result of domain
structure or compositional variations. An important potential advantage of
nanoscale samples is that they exhibit the homogeneous properties, which can
differ greatly from those of the bulk. We demonstrate this principle using
vanadium dioxide, which has domain structure associated with its dramatic MIT
at 68 degrees C. Our studies of single-domain vanadium dioxide nanobeams reveal
new aspects of this famous MIT, including supercooling of the metallic phase by
50 degrees C; an activation energy in the insulating phase consistent with the
optical gap; and a connection between the transition and the equilibrium
carrier density in the insulating phase. Our devices also provide a
nanomechanical method of determining the transition temperature, enable
measurements on individual metal-insulator interphase walls, and allow general
investigations of a phase transition in quasi-one-dimensional geometry.Comment: 9 pages, 3 figures, original submitted in June 200
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