652 research outputs found
Laboratory simulation of cometary x rays using a high-resolution microcalorimeter
X-ray emission following charge exchange has been studied on the University
of California Lawrence Livermore National Laboratory electron beam ion traps
EBIT-I and EBIT-II using a high-resolution microcalorimeter. The measured
spectra include the K-shell emission from hydrogenlike and heliumlike C, N, O,
and Ne needed for simulations of cometary x-ray emission. A comparison of the
spectra produced in the interaction of O8+ with N2 and CH4 is presented that
illustrates the dependence of the observed spectrum on the interaction gas.Comment: 11 pages, 2 figure
Moral reasoning and homosexuality: the acceptability of arguments about lesbian and gay issues
In the political arena, lesbian and gay issues have typically been contested on grounds of human rights, but with variable success. Using a moral developmental framework, the purpose of this study was to explore preferences for different types of moral arguments when thinking about moral dilemmas around lesbian and gay issues. The analysis presented here comprised data collected from 545 students at UK universities, who completed a questionnaire, part of which comprised a moral dilemma task. Findings of the study showed that respondents do not apply moral reasoning consistently, and do not (clearly) favour human rights reasoning when thinking about lesbian and gay issues. Respondents tended to favour reasoning supporting existing social structures and frameworks, therefore this study highlights the importance of structural change in effecting widespread attitude change in relation to lesbian and gay rights issues. The implications of the findings for moral education are also discussed.</p
Magnetic and thermal properties of 4f-3d ladder-type molecular compounds
We report on the low-temperature magnetic susceptibilities and specific heats
of the isostructural spin-ladder molecular complexes L[M(opba)]_{3\cdot
xDMSOHO, hereafter abbreviated with LM (where L =
La, Gd, Tb, Dy, Ho and M = Cu, Zn). The results show that the Cu containing
complexes (with the exception of LaCu) undergo long range magnetic
order at temperatures below 2 K, and that for GdCu this ordering is
ferromagnetic, whereas for TbCu and DyCu it is probably
antiferromagnetic. The susceptibilities and specific heats of TbCu
and DyCu above have been explained by means of a model
taking into account nearest as well as next-nearest neighbor magnetic
interactions. We show that the intraladder L--Cu interaction is the predominant
one and that it is ferromagnetic for L = Gd, Tb and Dy. For the cases of Tb, Dy
and Ho containing complexes, strong crystal field effects on the magnetic and
thermal properties have to be taken into account. The magnetic coupling between
the (ferromagnetic) ladders is found to be very weak and is probably of dipolar
origin.Comment: 13 pages, 15 figures, submitted to Phys. Rev.
Quantum Computing with NMR
A review of progress in NMR quantum computing and a brief survey of the
literatureComment: Commissioned by Progress in NMR Spectroscopy (95 pages, no figures
Recommended from our members
The interplay between formal and informal elements in analysing situations of role conflict among construction participants
The interplay of formal and informal factors in construction teams influences the enactment of
roles and the individuals who fulfil those roles. With a specific focus on a phenomenon called role
conflict, the aim is to explore if and how the interaction of formal and informal elements would
lead to situations of role conflict. This phenomenon proved to lead to frustration, tension and
employee burnout. An analytical model of role interaction was developed, which disentangles
formal and informal elements that shape role interactions. Qualitative data was collected through
semi-structured interviews, project documents and observations. Four cases of role conflict are
presented here. Contract, as a formal element, and participantâs values and interests, as informal
elements, appeared to be the most important factor shaping participantsâ expectations and
behaviours. The analysis in this study showed that if a participant who faces role conflict is able
to influence the formal elements in favour of his or her informal elements, then he or she may
experience less frustration. At a more general level, the results suggest that increasing formality can increase participantsâ frustration, which then would decrease the likelihood of collaboration. As the theoretical contribution, this research extends organizational role theory to deal with informal and formal aspects. Taking into account formal sources enables the study of how roles are institutionally governed while including informal sources allows for the idea that some of the aspects of the role, even in the context of work role, are socially constructed
Basic concepts in quantum computation
Section headings: 1 Qubits, gates and networks 2 Quantum arithmetic and
function evaluations 3 Algorithms and their complexity 4 From interferometers
to computers 5 The first quantum algorithms 6 Quantum search 7 Optimal phase
estimation 8 Periodicity and quantum factoring 9 Cryptography 10 Conditional
quantum dynamics 11 Decoherence and recoherence 12 Concluding remarksComment: 37 pages, lectures given at les Houches Summer School on "Coherent
Matter Waves", July-August 199
Optimal estimation of qubit states with continuous time measurements
We propose an adaptive, two steps strategy, for the estimation of mixed qubit
states. We show that the strategy is optimal in a local minimax sense for the
trace norm distance as well as other locally quadratic figures of merit. Local
minimax optimality means that given identical qubits, there exists no
estimator which can perform better than the proposed estimator on a
neighborhood of size of an arbitrary state. In particular, it is
asymptotically Bayesian optimal for a large class of prior distributions.
We present a physical implementation of the optimal estimation strategy based
on continuous time measurements in a field that couples with the qubits.
The crucial ingredient of the result is the concept of local asymptotic
normality (or LAN) for qubits. This means that, for large , the statistical
model described by identically prepared qubits is locally equivalent to a
model with only a classical Gaussian distribution and a Gaussian state of a
quantum harmonic oscillator.
The term `local' refers to a shrinking neighborhood around a fixed state
. An essential result is that the neighborhood radius can be chosen
arbitrarily close to . This allows us to use a two steps procedure by
which we first localize the state within a smaller neighborhood of radius
, and then use LAN to perform optimal estimation.Comment: 32 pages, 3 figures, to appear in Commun. Math. Phy
Dynamical stability of infinite homogeneous self-gravitating systems: application of the Nyquist method
We complete classical investigations concerning the dynamical stability of an
infinite homogeneous gaseous medium described by the Euler-Poisson system or an
infinite homogeneous stellar system described by the Vlasov-Poisson system
(Jeans problem). To determine the stability of an infinite homogeneous stellar
system with respect to a perturbation of wavenumber k, we apply the Nyquist
method. We first consider the case of single-humped distributions and show
that, for infinite homogeneous systems, the onset of instability is the same in
a stellar system and in the corresponding barotropic gas, contrary to the case
of inhomogeneous systems. We show that this result is true for any symmetric
single-humped velocity distribution, not only for the Maxwellian. If we
specialize on isothermal and polytropic distributions, analytical expressions
for the growth rate, damping rate and pulsation period of the perturbation can
be given. Then, we consider the Vlasov stability of symmetric and asymmetric
double-humped distributions (two-stream stellar systems) and determine the
stability diagrams depending on the degree of asymmetry. We compare these
results with the Euler stability of two self-gravitating gaseous streams.
Finally, we determine the corresponding stability diagrams in the case of
plasmas and compare the results with self-gravitating systems
The impact of music festival attendance on young people's psychological and social well being
Although the social, emotional, physical and cognitive benefits of engagement in music are well known, little research has been conducted on the psychological benefits of music in the context of music festivals. This article draws on theoretical constructs from the field of positive psychology to interpret the impact of music festival attendance on participants' psychological and social well-being. Qualitative and quantitative data were collected from a focus group and questionnaire survey with young festival-goers aged 18-29 years. Four facets of the music festival experience were identified that were associated with well-being outcomes. These are explored and discussed with reference both to participants' focus group comments and statistical analysis of questionnaire responses. A conceptual model is presented in order to guide further research in this area, and enable both festival organizers and attendees to take optimal advantage of the potential of music festivals to impact positively on young adults' psychological and social well-being
A narrative analysis of career transition themes and outcomes using chaos theory as a guiding metaphor
In a rapidly changing world of work little research exists on mid-career transitions. We investigated these using the open-systems approach of chaos theory as a guiding metaphor and conducted interviews with seven mid-career individuals chosen for their experience of a significant mid-career transition. Four common themes were identified through narrative analysis, where âfalse startsâ to a career were a common experience prior to finding a career âfitâ. Career transitions, precipitated by a trigger state and/or event such as a period of disillusionment, were an important part of this âfinding a fitâ process. Overall, career success outcomes were shaped by a combination of chaos elements: chance, unplanned events, and non-linearity of resultant outcomes. We discuss implications for future research and for practice
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