A cross‐faculty simulation model for authentic learning

This paper proposes a cross‐faculty simulation model for authentic learning that bridges the gap between short group‐based simulations within the classroom and longer individual placements in professional working contexts. Dissemination of the model is expected to widen the use of authentic learning approaches in higher education (HE). The model is based on a cross‐faculty project in which UK HE students acted as professional developers to produce prototype educational games for academic clients from other subject areas. Perceptions about the project were obtained from interviews with project participants. The stakeholders believed the cross‐faculty simulation to be a motivating learning experience, whilst identifying possible improvements. To evaluate whether the authenticity of the student–client relationship could be improved, the interview data were compared to four themes for authentic learning described by Rule in 2006. The data supported Rule’s themes, whilst highlighting the added value gained from meta‐awareness of the simulation as a learning opportunity

Nature of the spin dynamics and 1/3 magnetization plateau in azurite

We present a specific heat and inelastic neutron scattering study in magnetic fields up into the 1/3 magnetization plateau phase of the diamond chain compound azurite Cu$_3$(CO$_3$)$_2$(OH)$_2$. We establish that the magnetization plateau is a dimer-monomer state, {\it i.e.}, consisting of a chain of $S = 1/2$ monomers, which are separated by $S = 0$ dimers on the diamond chain backbone. The effective spin couplings $J_{mono}/k_B = 10.1(2)$ K and $J_{dimer}/k_B = 1.8(1)$ K are derived from the monomer and dimer dispersions. They are associated to microscopic couplings $J_1/k_B = 1(2)$ K, $J_2/k_B = 55(5)$ K and a ferromagnetic $J_3/k_B = -20(5)$ K, possibly as result of $d_{z^2}$ orbitals in the Cu-O bonds providing the superexchange pathways.Comment: 5 pages, 4 figure

Luttinger-Liquid Behavior in the Alternating Spin-Chain System Copper Nitrate

We determine the phase diagram of copper nitrate Cu(NO$_3$)$_2\cdot$2.5D$_2$O in the context of quantum phase transitions and novel states of matter. We establish this compound as an ideal candidate to study quasi-1D Luttinger liquids, 3D Bose-Einstein-Condensation of triplons, and the crossover between 1D and 3D physics. Magnetocaloric effect, magnetization, and neutron scattering data provide clear evidence for transitions into a Luttinger liquid regime and a 3D long-range ordered phase as function of field and temperature. Theoretical simulations of this model material allow us to fully establish the phase diagram and to discuss it in the context of dimerized spin systems.Comment: 5 pages, 4 figure

Quantum phase transitions and decoupling of magnetic sublattices in the quasi-two-dimensional Ising magnet Co3V2O8 in a transverse magnetic field

The application of a magnetic field transverse to the easy axis, Ising direction in the quasi-two-dimensional Kagome staircase magnet, Co3V2O8, induces three quantum phase transitions at low temperatures, ultimately producing a novel high field polarized state, with two distinct sublattices. New time-of-flight neutron scattering techniques, accompanied by large angular access, high magnetic field infrastructure allow the mapping of a sequence of ferromagnetic and incommensurate phases and their accompanying spin excitations. At least one of the transitions to incommensurate phases at \mu 0Hc1~6.25 T and \mu 0Hc2~7 T is discontinuous, while the final quantum critical point at \mu 0Hc3~13 T is continuous.Comment: 5 pages manuscript, 3 pages supplemental materia

Are foot and ankle characteristics associated with falls in people with rheumatoid arthritis? A prospective study.

OBJECTIVE: To determine whether foot and ankle characteristics are associated with falls in people with rheumatoid arthritis (RA). METHODS: Two hundred and one adults with RA were recruited from rheumatology outpatient clinics in Auckland, New Zealand. Clinical characteristics, common fall risk factors, and foot and ankle variables were measured. Participants were prospectively studied for 12 months, to record the occurrence of falls using falls diaries. Logistic regression analysis identified baseline variables which were independent predictors of falls over the 12 months. RESULTS: Eighty-four (42%) participants fell at least once and 39 (19%) experienced multiple (>1) falls over the 12-month follow-up period. In logistic regression analysis, including age and significant baseline variables in bivariate analysis but not baseline fall history, presence of foot or ankle tender joints (odds ratio (OR) 1.95, P=0.034) and psychotropic medication (OR 2.35, P=0.025) were independent predictors of prospective falls. However, when baseline fall history was included in the analysis, psychotropic medication (OR 2.34, P=0.025) and baseline fall history (over the preceding 12 months) (OR 2.27, P=0.008) were independent predictors of prospective falls. CONCLUSION: Foot and ankle characteristics are not associated with falls in people with RA, independent of prior falls. Enquiry about prior falls and psychotropic medications may assist in identifying patients with RA who are at high risk of future falls. This article is protected by copyright. All rights reserved

Structural Fluctuations in the Spin Liquid State of Tb2Ti2O7

High resolution X-ray scattering measurements on single crystal Tb2Ti2O7 reveal finite structural correlations at low temperatures. This geometrically frustrated pyrochlore is known to exhibit a spin liquid, or cooperative paramagnetic state, at temperatures below ~ 20 K. Parametric studies of structural Bragg peaks appropriate to the Fd$\bar{3}$m space group of Tb2Ti2O7 reveal substantial broadening and peak intensity reduction in the temperature regime 20 K to 300 mK. We also observe a small, anomalous lattice expansion on cooling below a density maximum at ~ 18 K. These measurements are consistent with the development of fluctuations above a cooperative Jahn-Teller, cubic-tetragonal phase transition at very low temperatures.Comment: 5 pages, 4 figures, submitted for publicatio

Magnetic soft modes in the locally distorted triangular antiferromagnet alpha-CaCr2O4

In this paper we explore the phase diagram and excitations of a distorted triangular lattice antiferromagnet. The unique two-dimensional distortion considered here is very different from the 'isosceles'-type distortion that has been extensively investigated. We show that it is able to stabilize a 120{\deg} spin structure for a large range of exchange interaction values, while new structures are found for extreme distortions. A physical realization of this model is \alpha-CaCr2O4 which has 120{\deg} structure but lies very close to the phase boundary. This is verified by inelastic neutron scattering which reveals unusual roton-like minima at reciprocal space points different from those corresponding to the magnetic order.Comment: 5 pages, 3 figures and lots of spin-wave

Critical X-ray Scattering Studies of Jahn-Teller Phase Transitions in TbV1−x_{1-x}Asx_{x}O4_{4}

The critical behaviour associated with cooperative Jahn-Teller phase transitions in TbV$_{1-x}$As$_{x}$O$_{4}$ (where \textit{x} = 0, 0.17, 1) single crystals have been studied using high resolution x-ray scattering. These materials undergo continuous tetragonal $\to$ orthorhombic structural phase transitions driven by Jahn-Teller physics at T$_C$ = 33.26(2) K, 30.32(2) K and 27.30(2) K for \textit{x} = 0, 0.17 and 1 respectively. The orthorhombic strain was measured close to the phase transition and is shown to display mean field behavior in all three samples. Pronounced fluctuation effects are manifest in the longitudinal width of the Bragg scattering, which diverges as a power law, with an exponent given by $x=0.45 \pm 0.04$, on approaching the transition from either above or below. All samples exhibited twinning; however the disordered x = 0.17 sample showed a broad distribution of twins which were stable to relatively low temperatures, well below T$_C$. This indicates that while the orthorhombic strain continues to develop in a conventional mean field manner in the presence of disorder, twin domains are easily pinned by the quenched impurities and their associated random strains.Comment: 8 pages, 6 figure

Evidence for an Extended Hydrogen Bond Network in the Binding Site of the Nicotinic Receptor: Role of the Vicinal Disulfide of the α1 Subunit

The defining feature of the α subunits of the family of nicotinic acetylcholine receptors is a vicinal disulfide between Cys-192 and Cys-193. Although this structure has played a pivotal role in a number of pioneering studies of nicotinic receptors, its functional role in native receptors remains uncertain. Using mutant cycle analysis and unnatural residue mutagenesis, including backbone mutagenesis of the peptide bond of the vicinal disulfide, we have established the presence of a network of hydrogen bonds that extends from that peptide NH, across a β turn to another backbone hydrogen bond, and then across the subunit interface to the side chain of a functionally important Asp residue in the non-α subunit. We propose that the role of the vicinal disulfide is to distort the β turn and thereby properly position a backbone NH for intersubunit hydrogen bonding to the key Asp

Asymmetric Thermal Lineshape Broadening in a Gapped 3-Dimensional Antiferromagnet - Evidence for Strong Correlations at Finite Temperature

It is widely believed that magnetic excitations become increasingly incoherent as temperature is raised due to random collisions which limit their lifetime. This picture is based on spin-wave calculations for gapless magnets in 2 and 3 dimensions and is observed experimentally as a symmetric Lorentzian broadening in energy. Here, we investigate a three-dimensional dimer antiferromagnet and find unexpectedly that the broadening is asymmetric - indicating that far from thermal decoherence, the excitations behave collectively like a strongly correlated gas. This result suggests that a temperature activated coherent state of quasi-particles is not confined to special cases like the highly dimerized spin-1/2 chain but is found generally in dimerized antiferromagnets of all dimensionalities and perhaps gapped magnets in general