4,518 research outputs found
Heterotopia in Networked Learning: Beyond the Shadow Side of Participation in Learning Communities
As it has evolved, networked learning (NL) has come to emphasise the importance of the collaborative learning aspects and possibilities of online learning. The importance assumed for 'collaboration based' forms of participation within NL has almost become ubiquitous and is frequently seen as an unquestionable good aspect - a utopian view of participation which does not acknowledge the 'shadow side' of participation in learning. In the paper we examine some of the darker sides of collaborative participation which in its extreme manifestations can be experienced as normative and, we suggest, a form of tyranny of the dominant and which instead of having a liberating effect, reinforces a form of oppression and control. We argue this is most likely to be the case in the absence of reflexivity and understanding of different ways and approaches to participation. We go on to suggest an alternative and potentially more productive perspective which, after Foucault, is a heterotopian one. A perspective that acknowledges and assumes disruption and which disturbs our customary notion of ourselves. Participation in heterotopian spaces is disturbing and ambiguous, but it offers a space in which to imagine, to desire and act differently
Microstructure and mechanical properties of thermomechanically processed C-Si-Mn steels
Comparison of the microstructures formed in the specimens produced by corresponding schedules in the dilatometer and by laboratory rolling has shown that a higher level of retained austenite was achieved in dilatometer specimens, whereas in rolled specimens a higher amount of martensite was present instead of retained austenite
Abnormal negative feedback processing in first episode schizophrenia: evidence from an oculomotor rule switching task
Background. Previous studies have shown that patients with schizophrenia are impaired on executive tasks,
where positive and negative feedbacks are used to update task rules or switch attention. However, research to date
using saccadic tasks has not revealed clear deficits in task switching in these patients. The present study used an
oculomotor ‘ rule switching ’ task to investigate the use of negative feedback when switching between task rules in
people with schizophrenia.
Method. A total of 50 patients with first episode schizophrenia and 25 healthy controls performed a task in which the association between a centrally presented visual cue and the direction of a saccade could change from trial to trial. Rule changes were heralded by an unexpected negative feedback, indicating that the cue-response mapping
had reversed.
Results. Schizophrenia patients were found to make increased errors following a rule switch, but these were almost entirely the result of executing saccades away from the location at which the negative feedback had been presented on the preceding trial. This impairment in negative feedback processing was independent of IQ.
Conclusions. The results not only confirm the existence of a basic deficit in stimulus–response rule switching in
schizophrenia, but also suggest that this arises from aberrant processing of response outcomes, resulting in a failure to appropriately update rules. The findings are discussed in the context of neurological and pharmacological
abnormalities in the conditions that may disrupt prediction error signalling in schizophrenia
Nucleon momentum distribution in deuteron and other nuclei within the light-front dynamics method
The relativistic light-front dynamics (LFD) method has been shown to give a
correct description of the most recent data for the deuteron monopole and
quadrupole charge form factors obtained at the Jefferson Laboratory for elastic
electron-deuteron scattering for six values of the squared momentum transfer
between 0.66 and 1.7 (GeV/c). The good agreement with the data is in
contrast with the results of the existing non-relativistic approaches. In this
work we firstly make a complementary test of the LFD applying it to calculate
another important characteristic, the nucleon momentum distribution of
the deuteron using six invariant functions instead of two
(- and -waves) in the nonrelativistic case. The comparison with the
-scaling data shows the decisive role of the function which at
500 MeV/c exceeds all other -functions (as well as the - and
-waves) for the correct description of of the deuteron in the
high-momentum region. Comparison with other calculations using - and
-waves corresponding to various nucleon-nucleon potentials is made.
Secondly, using clear indications that the high-momentum components of
in heavier nuclei are related to those in the deuteron, we develop an approach
within the natural orbital representation to calculate in -nuclei
on the basis of the deuteron momentum distribution. As examples, in
He, C and Fe are calculated and good agreement with the
-scaling data is obtained.Comment: 16 pages, 6 figures, corrected, to appear in Phys. Rev. C in February
200
Fast nucleon emission as a probe of the isospin momentum dependence
In this article we investigate the structure of the non-local part of the
symmetry term, that leads to a splitting of the effective masses of protons and
neutrons in asymmetric matter. Based on microscopic transport simulations we
suggest some rather sensitive observables in collisions of neutron-rich
(unstable) ions at intermediate () energies. In particular we focus the
attention on pre-equilibrium nucleon emissions. We discuss interesting
correlations between the N/Z content of the fast emitted particles and their
rapidity or transverse momentum, that show a nice dependence on the
prescription used for the effective mass splitting.Comment: 5 pages, 6 figures, revtex
A study of the strengthening mechanism in the thermomechanically processed TRIP/TWIP steel
The strengthening mechanism responsible for the unique combination of ultimate tensile strength and elongation in a multiphase Fe-0.2C-1.5Mn-1.2Si-0.3Mo-0.6Al-0.02Nb (wt%) steel was studied. The microstructures with different volume fraction of polygonal fenite, bainite and retained austenite were simulated by controlled thermomechanical processing. The interupted tensile test was used to study the bainitic ferrite, retained austenite and polygonal ferrite behavior as a function of plastic strain. X-ray analysis was used to characterize the volume fraction and carbon content of retained austenite. TEM and heat-tinting were utilized to analyze the effect of bainitic fenite morphology on the strain induced transformation of retained austenite and retained austenite twinning as a function of strain in the bulk material. The study has shown that the austenite twinning mechanism is more preferable than the transformation induced plasticity mechanism during the early stages of deformation for a microstructure containing I5% polygonal ferrite, while the transformation induced plasticity effect is the main mechanism in when there is 50% of polygonal ferrite in the microstructure. The baillitic fenite morphology affects the deformation mode of retained austenite during straining. The polygonal fenite behavior during straining depends on dislocation substructure tonned due to the deformation and the additional mobile dislocations caused by the TRIP effect. TRIP and TWIP effects depend not only on the chemical and mechanical stability of retained austenite, but also on the interaction of the phases during straining.<br /
Learning From Early Attempts to Generalize Darwinian Principles to Social Evolution
Copyright University of Hertfordshire & author.Evolutionary psychology places the human psyche in the context of evolution, and addresses the Darwinian processes involved, particularly at the level of genetic evolution. A logically separate and potentially complementary argument is to consider the application of Darwinian principles not only to genes but also to social entities and processes. This idea of extending Darwinian principles was suggested by Darwin himself. Attempts to do this appeared as early as the 1870s and proliferated until the early twentieth century. But such ideas remained dormant in the social sciences from the 1920s until after the Second World War. Some lessons can be learned from this earlier period, particularly concerning the problem of specifying the social units of selection or replication
Centrality, Rapidity and Transverse-Momentum Dependence of Cold Nuclear Matter Effects on J/Psi Production in d+Au, Cu+Cu and Au+Au Collisions at sqrt(s_NN)=200 GeV
We have carried out a wide study of Cold Nuclear Matter (CNM) effects on
J/Psi production in d+Au, Cu+Cu and Au+Au collisions at sqrt(s_NN)=200 GeV. We
have studied the effects of three different gluon-shadowing parametrisations,
using the usual simplified kinematics for which the momentum of the gluon
recoiling against the J/Psi is neglected as well as an exact kinematics for a 2
-> 2 process, namely g+g -> J/psi+g as expected from LO pQCD. We have shown
that the rapidity distribution of the nuclear modification factor R_dAu, and
particularly its anti-shadowing peak, is systematically shifted toward larger
rapidities in the 2 -> 2 kinematics, irrespective of which shadowing
parametrisation is used. In turn, we have noted differences in the effective
final-state nuclear absorption necessary to fit the PHENIX d+Au data. Taking
advantage of our implementation of a 2 -> 2 kinematics, we have also computed
the transverse momentum dependence of the latter nuclear modification factor,
which cannot be predicted with the usual simplified kinematics. All the
corresponding observables have been computed for Cu+Cu and Au+Au collisions and
compared to the PHENIX and STAR data. Finally, we have extracted the effective
nuclear absorption from the recent measurements of R_CP in d+Au by the PHENIX
collaboration.Comment: 12 pages, 14 figures, LaTeX. Version to appear in Phys. Rev. C: a few
typos corrected and one comment about the EPS08 nPDF parametrisation adde
Nanostructural Engineering of Steel
The concept of microstructural engineering of steels is well established and is the basis for a wide range of processes and products. Recently, though, there has been increasing emphasis in developing microstructures that have submicron length scales and also in understanding in far greater detail the structures and solute effects that are occurring at the nanoscale. In this review it is proposed that we are heading towards the situation where we are applying nanostructural engineering concepts in the development of new steels. A range of examples are given as well as a discussion of the potential impact of new processing routes. Clearly the future advances will be driven through improved characterization methods, such as atom probe tomography, in combination with advanced modeling
A Comparative Study of the Magnetization Process of Two-Dimensional Antiferromagnets
Plateaux in the magnetization curves of the square, triangular and hexagonal
lattice spin-1/2 XXZ antiferromagnet are investigated. One finds a zero
magnetization plateau (corresponding to a spin-gap) on the square and hexagonal
lattice with Ising-like anisotropies, and a plateau with one third of the
saturation magnetization on the triangular lattice which survives a small
amount of easy-plane anisotropy. Here we start with transfer matrix
computations for the Ising limit and continue with series in the XXZ-anisotropy
for plateau-boundaries using the groundstates of the Ising limit. The main
focus is then a numerical computation of the magnetization curves with
anisotropies in the vicinity of the isotropic situation. Finally, we discuss
the universality class associated to the asymptotic behaviour of the
magnetization curve close to saturation, as observed numerically in two and
higher dimensions.Comment: 21 pages plain TeX (with macro package included), 7 PostScript
figures included using psfig.st
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