Publications by authors named "Mark Dean"

Material functionality can be strongly determined by structure extending only over nanoscale distances. The pair distribution function presents an opportunity for structural studies beyond idealized crystal models and to investigate structure over varying length scales. Applying this method with ultrafast time resolution has the potential to similarly disrupt the study of structural dynamics and phase transitions.

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A prominent characteristic of 2D magnetic systems is the enhanced spin fluctuations, which reduce the ordering temperature. We report that a magnetic field of only 1000th of the Heisenberg superexchange interaction can induce a crossover, which for practical purposes is the effective ordering transition, at temperatures about 6 times the Néel transition in a site-diluted two-dimensional anisotropic quantum antiferromagnet. Such a strong magnetic response is enabled because the system directly enters the antiferromagnetically ordered state from the isotropic disordered state, skipping the intermediate anisotropic stage.

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Understanding the driving mechanisms behind metal-insulator transitions (MITs) is a critical step toward controlling material's properties. Since the proposal of charge order-induced MIT in magnetite FeO in 1939 by Verwey, the nature of the charge order and its role in the transition have remained elusive. Recently, a trimeron order was found in the low-temperature structure of FeO; however, the expected transition entropy change in forming trimeron is greater than the observed value, which arises a reexamination of the ground state in the high-temperature phase.

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Magnetic domains play a fundamental role in physics of magnetism and its technological applications. Dynamics of antiferromagnetic domains is poorly understood, although antiferromagnets are expected to be extensively used in future electronic devices wherein it determines the stability and operational speed. Dynamics of antiferromagnets also features prominently in the studies of topological quantum matter.

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Article Synopsis
  • Understanding the formation of charge and spin-ordered states in materials like La_{2-x}Sr_{x}NiO_{4+δ} is key to unraveling high-temperature superconductivity qualities.
  • Recent studies using x-ray photon correlation spectroscopy show that the spin order stripes in LSNO have slow dynamics and reveal that these domains are spatially anisotropic.
  • The fluctuations observed in the amplitude signal of the spin order stripes are linked to thermal fluctuations at the domain boundaries, suggesting a complex relationship between the dimensions and dynamics of the SO domains.
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Although ultrafast manipulation of magnetism holds great promise for new physical phenomena and applications, targeting specific states is held back by our limited understanding of how magnetic correlations evolve on ultrafast timescales. Using ultrafast resonant inelastic X-ray scattering we demonstrate that femtosecond laser pulses can excite transient magnons at large wavevectors in gapped antiferromagnets and that they persist for several picoseconds, which is opposite to what is observed in nearly gapless magnets. Our work suggests that materials with isotropic magnetic interactions are preferred to achieve rapid manipulation of magnetism.

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Background: The appropriateness of the use of blood transfusion in patients with acute coronary syndromes (ACS) remains contested. In general, studies addressing this issue were based on data from clinical trials, registries, or electronic medical records, and were conducted across different settings. Our study aimed to use a linked patient blood management data system from existing hospital databases to examine the association between blood transfusion and in-hospital mortality, length of stay (LOS) and readmission rates among patients with ACS, and to investigate this relationship at different haemoglobin (Hb) concentrations.

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We report on the epitaxial strain-driven electronic and antiferromagnetic modulations of a pseudospin-half square-lattice realized in superlattices of (SrIrO_{3})_{1}/(SrTiO_{3})_{1}. With increasing compressive strain, we find the low-temperature insulating behavior to be strongly suppressed with a corresponding systematic reduction of both the Néel temperature and the staggered moment. However, despite such a suppression, the system remains weakly insulating above the Néel transition.

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Through a combination of experimental measurements and theoretical modeling, we describe a strongly orbital-polarized insulating ground state in an (LaTiO_{3})_{2}/(LaCoO_{3})_{2} oxide heterostructure. X-ray absorption spectra and ab initio calculations show that an electron is transferred from the titanate to the cobaltate layers. The charge transfer, accompanied by a large octahedral distortion, induces a substantial orbital polarization in the cobaltate layer of a size unattainable via epitaxial strain alone.

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Interface-induced modifications of the electronic, magnetic, and lattice degrees of freedom drive an array of novel physical properties in oxide heterostructures. Here, large changes in metal-oxygen band hybridization, as measured in the oxygen ligand hole density, are induced as a result of interfacing two isovalent correlated oxides. Using resonant X-ray reflectivity, a superlattice of SrFeO and CaFeO is shown to exhibit an electronic character that spatially evolves from strongly O-like in SrFeO to strongly Fe-like in CaFeO .

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We study the joint distribution of 11 behavioral phenomena in a group of 190 laboratory subjects and compare it to the predictions of existing models as a step in the development of a parsimonious, general model of economic choice. We find strong correlations between most measures of risk and time preference, between compound lottery and ambiguity aversion, and between loss aversion and the endowment effect. Our results support some, but not all attempts to unify behavioral economic phenomena.

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Background: In the phase 3 METEOR trial, cabozantinib improved progression-free survival (PFS), objective response rate (ORR), and overall survival (OS) versus everolimus in patients with advanced renal cell carcinoma (RCC), after prior antiangiogenic therapy.

Methods: Outcomes were evaluated for subgroups defined by prior therapy with sunitinib or pazopanib as the only prior VEGFR inhibitor, or prior anti-PD-1/PD-L1 therapy.

Results: For the prior sunitinib subgroup (N = 267), median PFS for cabozantinib versus everolimus was 9.

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The neurotransmitter dopamine is central to the emerging discipline of neuroeconomics; it is hypothesized to encode the difference between expected and realized rewards and thereby to mediate belief formation and choice. We develop the first formal test of this theory of dopaminergic function, based on a recent axiomatization by Caplin and Dean [2008A]. These tests are satisfied by neural activity in the nucleus accumbens, an area rich in dopamine receptors.

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Neuroimaging studies typically identify neural activity correlated with the predictions of highly parameterized models, like the many reward prediction error (RPE) models used to study reinforcement learning. Identified brain areas might encode RPEs or, alternatively, only have activity correlated with RPE model predictions. Here, we use an alternate axiomatic approach rooted in economic theory to formally test the entire class of RPE models on neural data.

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An otherwise fit and well 56-year-old man presented with extensive ecchymosis and soft-tissue haematomas affecting his legs. Coagulation studies were normal. Further questioning revealed a severely restricted diet.

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The phasic firing rate of midbrain dopamine neurons has been shown to respond both to the receipt of rewarding stimuli, and the degree to which such stimuli are anticipated by the recipient. This has led to the hypothesis that these neurons encode reward prediction error (RPE)-the difference between how rewarding an event is, and how rewarding it was expected to be. However, the RPE model is one of a number of competing explanations for dopamine activity that have proved hard to disentangle, mainly because they are couched in terms of latent, or unobservable, variables.

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Many studies have shown that humans face a trade-off between the speed and accuracy with which they can make movements. In this article, we asked whether humans choose movement time to maximize expected gain by taking into account their own speed-accuracy trade-off (SAT). We studied this question within the context of a rapid pointing task in which subjects received a reward for hitting a target on a monitor.

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Percutaneous vertebroplasty and sacroplasty are becoming common modalities of treatment for vertebral body compression fractures and sacral insufficiency fractures, respectively. The present report describes a case of a coccygeal fracture treated with injection of polymethylmethacrylate cement, which resulted in immediate relief of symptoms. It is suggested that this procedure be called coccygeoplasty.

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Evolutionary trace (ET) and entropy are two related methods for analyzing a multiple sequence alignment to determine functionally important residues in proteins. In this article, these methods have been enhanced with a view to reinvestigate the issue ofGPCR dimerization and oligomerization. In particular, cluster analysis has replaced the subjective visual analysis element of the original ET method.

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Acquired deficiencies of, or inhibitors to, factor V are considered rare events. We report a series of 14 acquired factor V deficiencies, 10 of which were confirmed to have inhibitors to factor V, as identified within Australia in the past 5 years following a multi-laboratory investigation. The initial index case seen by one laboratory was followed within 4 months by a separate similar case.

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Treating patients with multidirectional instability who have had multiple failed stabilization procedures is a challenging problem. These patients have disability from instability and pain. Final treatment may be glenohumeral narthrodesis.

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Methylglyoxal is a potent glycating agent under physiological conditions. Human serum albumin is modified by methylglyoxal in vivo. The glycation adducts formed and structural and functional changes induced by methylglyoxal modification have not been fully disclosed.

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Objectives: To estimate the appropriateness of transfusions of platelets, fresh frozen plasma (FFP) and cryoprecipitate using National Health and Medical Research Council and Australasian Society for Blood Transfusion guidelines (NHMRC/ASBT 2002).

Design And Setting: Three separate retrospective surveys of medical records from 1 January to 31 August 2000 (1147 transfused patients) from 14 hospitals selected randomly from all public hospitals that use these blood products in New South Wales: five tertiary referral, five major metropolitan, and four major rural (base) hospitals.

Main Outcome Measures: Proportion of potentially inappropriate transfusions.

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