221 research outputs found
Renormalized Classical Theory of Quantum Magnets
We derive a renormalized classical spin (RCS) theory for quantum
magnets by constraining a generalized classical theory that includes all
multipolar fluctuations to a reduced CP phase space of dipolar SU()
coherent states. When the spin Hamiltonian is linear in the
spin operators for each lattice site , the RCS
Hamiltonian coincides with the usual classical model
. In the presence
of non-linear terms, however, the RCS theory is more accurate than
. For the many materials modeled by spin Hamiltonians with
(non-linear) single-ion anisotropy terms, the use of the RCS theory is
essential to accurately model phase diagrams and to extract the correct
Hamiltonian parameters from neutron scattering dataComment: 5 pages, 1 figure
The Norwegian eHealth Platform: Development Through Cultivation Strategies and Incremental Changes
publishedVersionNivå
The liminality of trajectory shifts in institutional entrepreneurship
In this paper, we develop a process model of trajectory shifts in institutional entrepreneurship. We focus on the liminal periods experienced by institutional entrepreneurs when they, unlike the rest of the organization, recognize limits in the present and seek to shift a familiar past into an unfamiliar and uncertain future. Such periods involve a situation where the new possible future, not yet fully formed, exists side-by-side with established innovation trajectories. Trajectory shifts are moments of truth for institutional entrepreneurs, but little is known about the underlying mechanisms of how entrepreneurs reflectively deal with liminality to conceive and bring forth new innovation trajectories. Our in-depth case study research at CarCorp traces three such mechanisms (reflective dissension, imaginative projection, and eliminatory exploration) and builds the basis for understanding the liminality of trajectory shifts. The paper offers theoretical implications for the institutional entrepreneurship literature
Dealing with mobility: Understanding access anytime, anywhere
The rapid and accelerating move towards the adoption and use of mobile technologies has increasingly provided people and organisations with the ability to work away from the office and on the move. The new ways of working afforded by these technologies are often characterised in terms of access to information and people ‘anytime, anywhere’. This paper presents a study of mobile workers that highlights different facets of access to remote people and information, and different facets of anytime, anywhere. Four key factors in mobile work are identified from the study: the role of planning, working in ‘dead time’, accessing remote technological and informational resources, and monitoring the activities of remote colleagues. By reflecting on these issues, we can better understand the role of technology and artefact use in mobile work and identify the opportunities for the development of appropriate technological solutions to support mobile workers
Quantum to classical crossover in generalized spin systems -- the temperature-dependent spin dynamics of FeI
Simulating quantum spin systems at finite temperatures is an open challenge
in many-body physics. This work studies the temperature-dependent spin dynamics
of a pivotal compound, FeI, to determine if universal quantum effects can
be accounted for by a phenomenological renormalization of the dynamical spin
structure factor measured by inelastic neutron
scattering. Renormalization schemes based on the quantum-to-classical
correspondence principle are commonly applied at low temperatures to the
harmonic oscillators describing normal modes. However, it is not clear how to
extend this renormalization to arbitrarily high temperatures. Here we introduce
a temperature-dependent normalization of the classical moments, whose magnitude
is determined by imposing the quantum sum rule, i.e. for dipolar magnetic moments. We
show that this simple renormalization scheme significantly improves the
agreement between the calculated and measured for
FeI at all temperatures. Due to the coupled dynamics of dipolar and
quadrupolar moments in that material, this renormalization procedure is
extended to classical theories based on SU(3) coherent states, and by
extension, to any SU(N) coherent state representation of local multipolar
moments.Comment: Associated source code for reproducing calculations available at:
https://github.com/SunnySuite/SunnyContribute
Secondary user relations in emerging mobile computing environments
Mobile technologies are enabling access to information in diverse environ.ments, and are exposing a wider group of individuals to said technology. Therefore, this paper proposes that a wider view of user relations than is usually considered in information systems research is required. Specifically, we examine the potential effects of emerging mobile technologies on end-‐user relations with a focus on the ‘secondary user’, those who are not intended to interact directly with the technology but are intended consumers of the technology’s output. For illustration, we draw on a study of a U.K. regional Fire and Rescue Service and deconstruct mobile technology use at Fire Service incidents. Our findings provide insights, which suggest that, because of the nature of mobile technologies and their context of use, secondary user relations in such emerging mobile environments are important and need further exploration
Quantum physics meets biology
Quantum physics and biology have long been regarded as unrelated disciplines,
describing nature at the inanimate microlevel on the one hand and living
species on the other hand. Over the last decades the life sciences have
succeeded in providing ever more and refined explanations of macroscopic
phenomena that were based on an improved understanding of molecular structures
and mechanisms. Simultaneously, quantum physics, originally rooted in a world
view of quantum coherences, entanglement and other non-classical effects, has
been heading towards systems of increasing complexity. The present perspective
article shall serve as a pedestrian guide to the growing interconnections
between the two fields. We recapitulate the generic and sometimes unintuitive
characteristics of quantum physics and point to a number of applications in the
life sciences. We discuss our criteria for a future quantum biology, its
current status, recent experimental progress and also the restrictions that
nature imposes on bold extrapolations of quantum theory to macroscopic
phenomena.Comment: 26 pages, 4 figures, Perspective article for the HFSP Journa
Actors and networks or agents and structures: towards a realist view of information systems
Actor-network theory (ANT) has achieved a measure of popularity in the analysis of information systems. This paper looks at ANT from the perspective of the social realism of Margaret Archer. It argues that the main issue with ANT from a realist perspective is its adoption of a `flat' ontology, particularly with regard to human beings. It explores the value of incorporating concepts from ANT into a social realist approach, but argues that the latter offers a more productive way of approaching information systems
The future of hybrid imaging—part 2: PET/CT
Since the 1990s, hybrid imaging by means of software and hardware image fusion alike allows the intrinsic combination of functional and anatomical image information. This review summarises the state-of-the-art of dual-modality imaging with a focus on clinical applications. We highlight selected areas for potential improvement of combined imaging technologies and new applications. In the second part, we briefly review the background of dual-modality PET/CT imaging, discuss its main applications and attempt to predict technological and methodological improvements of combined PET/CT imaging. After a decade of clinical evaluation, PET/CT will continue to have a significant impact on patient management, mainly in the area of oncological diseases. By adopting more innovative acquisition schemes and data processing PET/CT will become a fast and dose-efficient imaging method and an integral part of state-of-the-art clinical patient management
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