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Unlike conventional magnets where the magnetic moments are partially or completely static in the ground state, in a quantum spin liquid they remain in collective motion down to the lowest temperatures. The importance of this state is that it is coherent and highly entangled without breaking local symmetries. In the case of magnets with isotropic interactions, spin-liquid behaviour is sought in simple lattices with antiferromagnetic interactions that favour antiparallel alignments of the magnetic moments and are incompatible with the lattice geometries. Despite an extensive search, experimental realizations remain very few. Here we investigate the novel, unexplored magnet Ca 10 Cr 7 O 28 , which has a complex Hamiltonian consisting of several different isotropic interactions and where the ferromagnetic couplings are stronger than the antiferromagnetic ones. We show both experimentally and theoretically that it displays all the features expected of a quantum spin liquid. Thus spin-liquid behaviour in isotropic magnets is not restricted to the simple idealized models currently investigated, but can be compatible with complex structures and ferromagnetic interactions. A detailed and systematic study of Ca 10 Cr 7 O 28 reveals all the hallmarks of spin-liquid behaviour, in spite of the compound’s unusually complex structure.

A spin liquid is a new state of matter with topological order where the spin moments continue to fluctuate coherently down to the lowest temperatures rather than develop static long-range magnetic order as found in conventional magnets. For spin liquid behavior to arise in a material the magnetic Hamiltonian must be \"frustrated\" where the combination of lattice geometry, interactions and anisotropies gives rise to competing spin arrangements in the ground state. Theoretical Hamiltonians which produce spin liquids are spin ice, the Kitaev honeycomb model and the Heisenberg kagome antiferromagnet. Spin liquid behavior however in real materials is rare because they can only approximate these Hamiltonians and often have weak higher order terms that destroy the spin liquid state. Ca10Cr7O28 is a new quantum spin liquid with magnetic Cr5+ ions that possess quantum spin number S=1/2. The spins are entirely dynamic in the ground state and the excitation spectrum is broad and diffuse as is typical of spinons which are the excitations of a spin liquid. In this paper we determine the Hamiltonian of Ca10Cr7O28 using inelastic neutron scattering under high magnetic field to induce a ferromagnetic ground state and spin-wave excitations that can be fitted to extract the interactions. We further explore the phase diagram by using inelastic neutron scattering and heat capacity measurements and establish the boundaries of the spin liquid phase as a function of magnetic field and temperature. Our results show that Ca10Cr7O28 consists of distorted kagome bilayers with several isotropic ferromagnetic and antiferromagnetic interactions where unexpectedly the ferromagnetic interactions are stronger than the antiferromagnetic ones. This complex Hamiltonian does not correspond to any known spin liquid model and points to new directions in the search for quantum spin liquid behavior.

Unlike conventional magnets where the magnetic moments are partially or completely static in the ground state, in a quantum spin liquid they remain in collective motion down to the lowest temperatures. The importance of this state is that it is coherent and highly entangled without breaking local symmetries. Such phenomena is usually sought in simple lattices where antiferromagnetic interactions and/or anisotropies that favor specific alignments of the magnetic moments are \"frustrated\" by lattice geometries incompatible with such order e.g. triangular structures. Despite an extensive search among such compounds, experimental realizations remain very few. Here we describe the investigation of a novel, unexplored magnetic system consisting of strong ferromagnetic and weaker antiferromagnetic isotropic interactions as realized by the compound Ca\\(_{10}\\)Cr\\(_7\\)O\\(_{28}\\). Despite its exotic structure we show both experimentally and theoretically that it displays all the features expected of a quantum spin liquid including coherent spin dynamics in the ground state and the complete absence of static magnetism.

Ultrasound velocity measurements of the orbital-degenerate frustrated spinel MgV\\(_2\\)O\\(_4\\) are performed in the high-purity single crystal which exhibits successive structural and antiferromagnetic phase transitions, and in the disorder-introduced single crystal which exhibits spin-glass-like behavior. The measurements reveal that two-types of unusual temperature dependence of the elastic moduli coexist in the cubic paramagnetic phase, which are resolved by magnetic-field and disorder sensitivities: huge Curie-type softening with decreasing temperature, and concave temperature dependence with a characteristic minimum. These elastic anomalies suggest the coupling of lattice to coexisting orbital fluctuations and orbital-spin-coupled excitations.

We present a unique study of the frustrated spinel MgV2O4 which possesses highly coupled spin, lattice and orbital degrees of freedom. Using large single-crystal and powder samples, we find a distortion from spinel at room temperature (space group F-43m) which allows for a greater trigonal distortion of the VO6 octahedra and a low temperature space group (I-4m2) that maintains the mirror plane symmetry. The magnetic structure that develops below 42 K consists of antiferromagnetic chains with a strongly reduced moment while inelastic neutron scattering reveals one-dimensional behavior and a single band of excitations. The implications of these results are discussed in terms of various orbital ordering scenarios. We conclude that although spin-orbit coupling must be significant to maintain the mirror plane symmetry, the trigonal distortion is large enough to mix the 3d levels leading to a wave function of mixed real and complex orbitals.

Sr\\(_{3}\\)Cr\\(_{2}\\)O\\(_{8}\\) consist of a lattice of spin-1/2 Cr\\(^{5+}\\) ions, which form hexagonal bilayers and which are paired into dimers by the dominant antiferromagnetic intrabilayer coupling. The dimers are coupled three-dimensionally by frustrated interdimer interactions. A structural distortion from hexagonal to monoclinic leads to orbital order and lifts the frustration giving rise to spatially anisotropic exchange interactions. We have grown large single crystals of Sr\\(_{3}\\)Cr\\(_{2}\\)O\\(_{8}\\) and have performed DC susceptibility, high field magnetisation and inelastic neutron scattering measurements. The neutron scattering experiments reveal three gapped and dispersive singlet to triplet modes arising from the three twinned domains that form below the transition thus confirming the picture of orbital ordering. The exchange interactions are extracted by comparing the data to a Random Phase Approximation model and the dimer coupling is found to be \\(J_{0}=5.55\\) meV, while the ratio of interdimer to intradimer exchange constants is \\(J'/J_{0}=0.64\\). The results are compared to those for other gapped magnets.

Materials with switchable absorption properties have been widely used for smart window applications to reduce energy consumption and enhance occupant comfort in buildings. In this work, we combine the benefits of smart windows with energy conversion by producing a photovoltaic device with a switchable absorber layer that dynamically responds to sunlight. Upon illumination, photothermal heating switches the absorber layer—composed of a metal halide perovskite-methylamine complex—from a transparent state (68% visible transmittance) to an absorbing, photovoltaic colored state (less than 3% visible transmittance) due to dissociation of methylamine. After cooling, the methylamine complex is re-formed, returning the absorber layer to the transparent state in which the device acts as a window to visible light. The thermodynamics of switching and performance of the device are described. This work validates a photovoltaic window technology that circumvents the fundamental tradeoff between efficient solar conversion and high visible light transmittance that limits conventional semitransparent PV window designs. Conventional smart windows with tunable transparency are based on electrochromic systems that consumes energy. Here Wheeler et al. demonstrate a halide perovskite based photo-switchable window that dynamically responds to sunlight and change colors via reversible phase transitions.

ObjectiveIn multiple sclerosis (MS), MRI measures at the whole brain or regional level are only modestly associated with disability, while network-based measures are emerging as promising prognostic markers. We sought to demonstrate whether data-driven patterns of covarying regional grey matter (GM) volumes predict future disability in secondary progressive MS (SPMS).MethodsWe used cross-sectional structural MRI, and baseline and longitudinal data of Expanded Disability Status Scale, Nine-Hole Peg Test (9HPT) and Symbol Digit Modalities Test (SDMT), from a clinical trial in 988 people with SPMS. We processed T1-weighted scans to obtain GM probability maps and applied spatial independent component analysis (ICA). We repeated ICA on 400 healthy controls. We used survival models to determine whether baseline patterns of covarying GM volume measures predict cognitive and motor worsening.ResultsWe identified 15 patterns of regionally covarying GM features. Compared with whole brain GM, deep GM and lesion volumes, some ICA components correlated more closely with clinical outcomes. A mainly basal ganglia component had the highest correlations at baseline with the SDMT and was associated with cognitive worsening (HR=1.29, 95% CI 1.09 to 1.52, p<0.005). Two ICA components were associated with 9HPT worsening (HR=1.30, 95% CI 1.06 to 1.60, p<0.01 and HR=1.21, 95% CI 1.01 to 1.45, p<0.05). ICA measures could better predict SDMT and 9HPT worsening (C-index=0.69–0.71) compared with models including only whole and regional MRI measures (C-index=0.65–0.69, p value for all comparison <0.05).ConclusionsThe disability progression was better predicted by some of the covarying GM regions patterns, than by single regional or whole-brain measures. ICA, which may represent structural brain networks, can be applied to clinical trials and may play a role in stratifying participants who have the most potential to show a treatment effect.

B rtCGM can be effectively used to lower HbA1c levels, reach target HbA1c level, reduce glucose variability (for insulin pumps, closed-loop systems, and multiple daily injections [MDI]), increase TIR, reduce mild to moderate hypoglycemia and shorten time spent in hypoglycemia in the pediatric population with T1D. TABLE 1 Comparison of ISO 15197:2013 and FDA BG meter accuracy standards Setting ISO 15197:20135 FDA6,7 Home use 95% within 15% for BG ≥100 mg/dl 95% within 15 mg/dl for BG <100 mg/dl 99% in A or B region of consensus error grida 95% within 15% for all BG in the usable BG rangeb 99% within 20% for all BG in the usable BG rangeb Hospital use 95% within 12% for BG ≥75 mg/dl 95% within 12 mg/dl for BG <75 mg/dl 98% within 15% for BG ≥75 mg/dl 98% within 15 mg/dl for BG <75 mg/dl The specified accuracy standard achieved during controlled conditions might vary significantly from actual SMBG meter performance in real-world settings.4 Detailed information on the actual performance of SMBG devices is provided by The Diabetes Technology Society Blood Glucose Monitoring System Surveillance Program (). For persons using intensive insulin regimens (multiple daily injections of insulin pump therapy), SMBG testing should be performed: during the day, prior to meals and snacks, at other times (e.g., 2–3 h after food intake) to determine appropriate meal insulin doses and show levels of BG in response to the action profiles of insulin (at anticipated peaks and troughs of insulin action) to confirm hypoglycemia and after treating low BG to monitor recovery at bedtime, as needed overnight and on awakening to detect and prevent nocturnal hypoglycemia and hyperglycemia prior to and while performing potentially hazardous tasks (e.g., driving) In association with vigorous exercise (before, during, and several hours after physical activity) during intercurrent illness to prevent hyperglycemic crisis. Successful intensive insulin management requires at least 6 to 10 checks per day, appropriate response to the observed values, and regular, frequent review of the results to identify patterns requiring adjustment to the diabetes treatment plan.15 This includes review by the person with diabetes and their caregivers/family in addition to consultation with the diabetes care team.

Insulin Storage and Glucose Homeostasis in Mice Null for the Granule Zinc Transporter ZnT8 and Studies of the Type 2 Diabetes–Associated Variants Tamara J. Nicolson 1 , Elisa A. Bellomo 1 , Nadeeja Wijesekara 2 , Merewyn K. Loder 1 , Jocelyn M. Baldwin 3 , Armen V. Gyulkhandanyan 2 , Vasilij Koshkin 2 , Andrei I. Tarasov 1 , Raffaella Carzaniga 4 , Katrin Kronenberger 4 , Tarvinder K. Taneja 1 , Gabriela da Silva Xavier 1 , Sarah Libert 5 , Philippe Froguel 6 , 7 , Raphael Scharfmann 8 , Volodymir Stetsyuk 8 , Philippe Ravassard 9 , Helen Parker 10 , Fiona M. Gribble 10 , Frank Reimann 10 , Robert Sladek 11 , Stephen J. Hughes 12 , Paul R.V. Johnson 12 , Myriam Masseboeuf 13 , Remy Burcelin 13 , Stephen A. Baldwin 3 , Ming Liu 14 , Roberto Lara-Lemus 14 , Peter Arvan 14 , Frans C. Schuit 15 , Michael B. Wheeler 3 , Fabrice Chimienti 6 and Guy A. Rutter 1 1 Section of Cell Biology, Division of Medicine, Imperial College London, London, U.K.; 2 Department of Physiology, University of Toronto, Toronto, Canada; 3 Institute of Membrane and Systems Biology, University of Leeds, Leeds, U.K.; 4 Electron Microscopy Centre, Imperial College London, London, U.K.; 5 Mellitech, Grenoble, France; 6 Section of Genomic Medicine, Division of Medicine, Imperial College London, London, U.K.; 7 Centre National de la Recherche Scientifique Unite Mixte de Recherche 8090, Institute of Biology, Lille, France; 8 INSERM U845, University Paris Descartes, Paris, France; 9 Centre National de la Recherche Scientifique and Université Pierre et Marie Curie, Paris, France; 10 Cambridge Institute for Medical Research, University of Cambridge, Cambridge, U.K.; 11 Department of Human Genetics, McGill University, Montreal, Canada; 12 Nuffield Department of Surgery, University of Oxford, Oxfordshire, U.K.; 13 Institut de Medecine Moleculaire de Rangueil, INSERM U858, IFR31, Toulouse III University, CHU Rangueil, Toulouse Cedex, Toulouse, France; 14 Division of Metabolism, Endocrinology & Diabetes, University of Michigan Medical School, Ann Arbor, Michigan; 15 Gene Expression Unit, Department of Molecular Cell Biology, Katholieke Universiteit Leuven, Leuven, Belgium. Corresponding author: Guy A. Rutter, g.rutter{at}imperial.ac.uk . T.J.N., E.A.B., N.W., M.K.L., and J.M.B. contributed equally to this study. Abstract OBJECTIVE Zinc ions are essential for the formation of hexameric insulin and hormone crystallization. A nonsynonymous single nucleotide polymorphism rs13266634 in the SLC30A8 gene, encoding the secretory granule zinc transporter ZnT8, is associated with type 2 diabetes. We describe the effects of deleting the ZnT8 gene in mice and explore the action of the at-risk allele. RESEARCH DESIGN AND METHODS Slc30a8 null mice were generated and backcrossed at least twice onto a C57BL/6J background. Glucose and insulin tolerance were measured by intraperitoneal injection or euglycemic clamp, respectively. Insulin secretion, electrophysiology, imaging, and the generation of adenoviruses encoding the low- (W325) or elevated- (R325) risk ZnT8 alleles were undertaken using standard protocols. RESULTS ZnT8 −/− mice displayed age-, sex-, and diet-dependent abnormalities in glucose tolerance, insulin secretion, and body weight. Islets isolated from null mice had reduced granule zinc content and showed age-dependent changes in granule morphology, with markedly fewer dense cores but more rod-like crystals. Glucose-stimulated insulin secretion, granule fusion, and insulin crystal dissolution, assessed by total internal reflection fluorescence microscopy, were unchanged or enhanced in ZnT8 −/− islets. Insulin processing was normal. Molecular modeling revealed that residue-325 was located at the interface between ZnT8 monomers. Correspondingly, the R325 variant displayed lower apparent Zn 2+ transport activity than W325 ZnT8 by fluorescence-based assay. CONCLUSIONS ZnT8 is required for normal insulin crystallization and insulin release in vivo but not, remarkably, in vitro. Defects in the former processes in carriers of the R allele may increase type 2 diabetes risks. Footnotes The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked “advertisement” in accordance with 18 U.S.C. Section 1734 solely to indicate this fact. Received April 15, 2009. Accepted June 2, 2009. © 2009 by the American Diabetes Association.