2,119 research outputs found
Ethical difficulties in clinical practice : experiences of European doctors
Background: Ethics support services are growing in Europe to help doctors in dealing with ethical difficulties.
Currently, insufficient attention has been focused on the experiences of doctors who have faced ethical
difficulties in these countries to provide an evidence base for the development of these services.
Methods: A survey instrument was adapted to explore the types of ethical dilemma faced by European
doctors, how they ranked the difficulty of these dilemmas, their satisfaction with the resolution of a recent
ethically difficult case and the types of help they would consider useful. The questionnaire was translated and
given to general internists in Norway, Switzerland, Italy and the UK.
Results: Survey respondents (n = 656, response rate 43%) ranged in age from 28 to 82 years, and averaged
25 years in practice. Only a minority (17.6%) reported having access to ethics consultation in individual
cases. The ethical difficulties most often reported as being encountered were uncertain or impaired decisionmaking
capacity (94.8%), disagreement among caregivers (81.2%) and limitation of treatment at the end of
life (79.3%). The frequency of most ethical difficulties varied among countries, as did the type of issue
considered most difficult. The types of help most often identified as potentially useful were professional
reassurance about the decision being correct (47.5%), someone capable of providing specific advice
(41.1%), help in weighing outcomes (36%) and clarification of the issues (35.9%). Few of the types of help
expected to be useful varied among countries.
Conclusion: Cultural differences may indeed influence how doctors perceive ethical difficulties. The type of
help needed, however, did not vary markedly. The general structure of ethics support services would not have
to be radically altered to suit cultural variations among the surveyed countries
Dynamic rotor mode in antiferromagnetic nanoparticles
We present experimental, numerical, and theoretical evidence for a new mode
of antiferromagnetic dynamics in nanoparticles. Elastic neutron scattering
experiments on 8 nm particles of hematite display a loss of diffraction
intensity with temperature, the intensity vanishing around 150 K. However, the
signal from inelastic neutron scattering remains above that temperature,
indicating a magnetic system in constant motion. In addition, the precession
frequency of the inelastic magnetic signal shows an increase above 100 K.
Numerical Langevin simulations of spin dynamics reproduce all measured neutron
data and reveal that thermally activated spin canting gives rise to a new type
of coherent magnetic precession mode. This "rotor" mode can be seen as a
high-temperature version of superparamagnetism and is driven by exchange
interactions between the two magnetic sublattices. The frequency of the rotor
mode behaves in fair agreement with a simple analytical model, based on a high
temperature approximation of the generally accepted Hamiltonian of the system.
The extracted model parameters, as the magnetic interaction and the axial
anisotropy, are in excellent agreement with results from Mossbauer
spectroscopy
Three Dimensional Polarimetric Neutron Tomography of Magnetic Fields
Through the use of Time-of-Flight Three Dimensional Polarimetric Neutron
Tomography (ToF 3DPNT) we have for the first time successfully demonstrated a
technique capable of measuring and reconstructing three dimensional magnetic
field strengths and directions unobtrusively and non-destructively with the
potential to probe the interior of bulk samples which is not amenable
otherwise.
Using a pioneering polarimetric set-up for ToF neutron instrumentation in
combination with a newly developed tailored reconstruction algorithm, the
magnetic field generated by a current carrying solenoid has been measured and
reconstructed, thereby providing the proof-of-principle of a technique able to
reveal hitherto unobtainable information on the magnetic fields in the bulk of
materials and devices, due to a high degree of penetration into many materials,
including metals, and the sensitivity of neutron polarisation to magnetic
fields. The technique puts the potential of the ToF time structure of pulsed
neutron sources to full use in order to optimise the recorded information
quality and reduce measurement time.Comment: 12 pages, 4 figure
Predictability of large future changes in a competitive evolving population
The dynamical evolution of many economic, sociological, biological and
physical systems tends to be dominated by a relatively small number of
unexpected, large changes (`extreme events'). We study the large, internal
changes produced in a generic multi-agent population competing for a limited
resource, and find that the level of predictability actually increases prior to
a large change. These large changes hence arise as a predictable consequence of
information encoded in the system's global state.Comment: 10 pages, 3 figure
Striped periodic minimizers of a two-dimensional model for martensitic phase transitions
In this paper we consider a simplified two-dimensional scalar model for the
formation of mesoscopic domain patterns in martensitic shape-memory alloys at
the interface between a region occupied by the parent (austenite) phase and a
region occupied by the product (martensite) phase, which can occur in two
variants (twins). The model, first proposed by Kohn and Mueller, is defined by
the following functional: where
is periodic in and almost everywhere.
Conti proved that if then the minimal specific
energy scales like ,
as . In the regime , we improve Conti's results, by computing exactly the
minimal energy and by proving that minimizers are periodic one-dimensional
sawtooth functions.Comment: 29 pages, 3 figure
Forecasting the price of gold
This article seeks to evaluate the appropriateness of a variety of existing forecasting techniques (17 methods) at providing accurate and statistically significant forecasts for gold price. We report the results from the nine most competitive techniques. Special consideration is given to the ability of these techniques to provide forecasts which outperforms the random walk (RW) as we noticed that certain multivariate models (which included prices of silver, platinum, palladium and rhodium, besides gold) were also unable to outperform the RW in this case. Interestingly, the results show that none of the forecasting techniques are able to outperform the RW at horizons of 1 and 9 steps ahead, and on average, the exponential smoothing model is seen providing the best forecasts in terms of the lowest root mean squared error over the 24-month forecasting horizons. Moreover, we find that the univariate models used in this article are able to outperform the Bayesian autoregression and Bayesian vector autoregressive models, with exponential smoothing reporting statistically significant results in comparison with the former models, and classical autoregressive and the vector autoregressive models in most cases
Ferritins: furnishing proteins with iron
Ferritins are a superfamily of iron oxidation, storage and mineralization proteins found throughout the animal, plant, and microbial kingdoms. The majority of ferritins consist of 24 subunits that individually fold into 4-α-helix bundles and assemble in a highly symmetric manner to form an approximately spherical protein coat around a central cavity into which an iron-containing mineral can be formed. Channels through the coat at inter-subunit contact points facilitate passage of iron ions to and from the central cavity, and intrasubunit catalytic sites, called ferroxidase centers, drive Fe2+ oxidation and O2 reduction. Though the different members of the superfamily share a common structure, there is often little amino acid sequence identity between them. Even where there is a high degree of sequence identity between two ferritins there can be major differences in how the proteins handle iron. In this review we describe some of the important structural features of ferritins and their mineralized iron cores and examine in detail how three selected ferritins oxidise Fe2+ in order to explore the mechanistic variations that exist amongst ferritins. We suggest that the mechanistic differences reflect differing evolutionary pressures on amino acid sequences, and that these differing pressures are a consequence of different primary functions for different ferritins
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