Influence of Magnetic and Electric Fields on Universal Conductance Fluctuations in Thin Films of the Dirac Semimetal Cd3As2.

Time-reversal invariance (TRS) and inversion symmetry (IS) are responsible for the topological band structure in Dirac semimetals (DSMs). These symmetries can be broken by applying an external magnetic or electric field, resulting in fundamental changes to the ground state Hamiltonian and a topological phase transition. We probe these changes using universal conductance fluctuations (UCF) in the prototypical DSM, Cd3As2. With increasing magnetic field, the magnitude of the UCF decreases by a factor of 2, in agreement with numerical calculations of the effect of broken TRS. In contrast, the magnitude of the UCF increases monotonically when the chemical potential is gated away from the charge neutrality point. We attribute this to Fermi surface anisotropy rather than broken IS. The concurrence between experimental data and theory provides unequivocal evidence that UCF are the dominant source of fluctuations and offers a general methodology for probing broken-symmetry effects in topological quantum materials.

Chemistry of Quantum Spin Liquids.

Quantum spin liquids are an exciting playground for exotic physical phenomena and emergent many-body quantum states. The realization and discovery of quantum spin liquid candidate materials and associated phenomena lie at the intersection of solid-state chemistry, condensed matter physics, and materials science and engineering. In this review, we provide the current status of the crystal chemistry, synthetic techniques, physical properties, and research methods in the field of quantum spin liquids. We highlight a number of specific quantum spin liquid candidate materials and their structure-property relationships, elucidating their fascinating behavior and connecting it to the intricacies of their structures. Furthermore, we share our thoughts on defects and their inevitable presence in materials, of which quantum spin liquids are no exception, which can complicate the interpretation of characterization of these materials, and urge the community to extend their attention to materials preparation and data analysis, cognizant of the impact of defects. This review was written with the intention of providing guidance on improving the materials design and growth of quantum spin liquids, and to paint a picture of the beauty of the underlying chemistry of this exciting class of materials.

Vacancy-Driven Disorder and Elevated Dielectric Response in the Pyrochlore Pb1.5Nb2O6.5.

Lone pair-driven distortions are a hallmark of many technologically important lead (Pb)-based materials. The role of Pb2+ in polar perovskites is well understood and easily manipulated for applications in piezo- and ferroelectricity, but the control of ordered lone pair behavior in Pb-based pyrochlores is less clear. Crystallographically and geometrically more complex than the perovskite structure, the pyrochlore structure is prone to geometric frustration of local dipoles due to a triangular arrangement of cations on a diamond lattice. The role of vacancies on the O' site of the pyrochlore network has been implicated as an important driver for the expression and correlation of stereochemically active lone pairs in pyrochlores such as Pb2Ru2O6.5 and Pb2Sn2O6. In this work we report on the structural, dielectric, and heat capacity behavior of the cation- and anion-deficient pyrochlore Pb1.5Nb2O6.5 upon cooling. We find that local distortions are present at all temperatures that can be described by cristobalite-type cation ordering, and this ordering persists to longer length scales upon cooling. From a crystallographic perspective, the material remains disordered and does not undergo an observable phase transition. In combination with density function calculations, we propose that the stereochemical activity of the Pb2+ lone pairs is driven by proximity to O' vacancies, and the crystallographic site disorder of the O' vacancies prohibits long range correlation of lone pair-driven distortions. This in turn prevents a low-temperature phase transition and results in an elevated dielectric permittivity across a broad temperature range.

Dynamical Bonding Driving Mixed Valency in a Metal Boride.

Samarium hexaboride is an anomaly, having many exotic and seemingly mutually incompatible properties. It was proposed to be a mixed-valent semiconductor, and later a topological Kondo insulator, and yet has a Fermi surface despite being an insulator. We propose a new and unified understanding of SmB6 centered on the hitherto unrecognized dynamical bonding effect: the coexistence of two Sm-B bonding modes within SmB6 , corresponding to different oxidation states of the Sm. The mixed valency arises in SmB6 from thermal population of these distinct minima enabled by motion of B. Our model simultaneously explains the thermal valence fluctuations, appearance of magnetic Fermi surface, excess entropy at low temperatures, pressure-induced phase transitions, and related features in Raman spectra and their unexpected dependence on temperature and boron isotope.

Progress toward Solid State Synthesis by Design.

Ages of history are defined by the underlying materials that promoted human development: stone, bronze, and iron ages. Since the middle of the last century, humanity has lived in a silicon age, where the development of the transistor ushered in new technologies previously thought inconceivable. But as technology has advanced, so have the requirements for new materials to sustain increasing physical demands. The field of solid state chemistry is dedicated to the discovery of new materials and phenomena, and though most materials discoveries in history have been through serendipity rather than careful reaction design, the last few decades have seen an increase in the number of materials discovered through a consideration of chemical reaction kinetics and thermodynamics. Materials by design have changed the way solid state chemists approach the synthesis of possible materials with interesting and useful properties. Unlike other chemistry subfields such as organic chemistry and biochemistry, solid state chemistry does not currently benefit from a toolbox of reactions that can allow for the synthesis of any arbitrary material. The diversity and complexity of the solid state phase space likely inhibits chemists from ever having such a toolbox. However, a thorough understanding of the various synthetic techniques involved in the synthesis of stable and metastable solids may be realized through an understanding of the reaction kinetics and thermodynamics. In the Account, we review the common synthesis techniques involved in the formation of metastable materials and break down their underlying chemistry to the simplest reaction mechanisms involved. The synthesis reactions of most metastable materials can be understood through these three reaction driving parameters, which include the exploitation of Le Chatelier's principle, thermo-kinetic reaction coupling, and lowering the activation energy of formation of the metastable product, and we identify several materials whose syntheses are described either by one or a combination of these driving parameters. We identify what exists at the frontier of materials discovery by design, including novel applications of supercritical fluids for tuning between "gas" and "solvent"-like environments. While conventional solvation requires changes in either the temperature or composition of the system, supercritical fluid solvation requires only changes in the fluid density, which opens up the possibilities for the synthesis of new materials. Most importantly, however, we look toward the future of materials synthesis by design and see that it must be a collaborative one. At present, chemists design materials using knowledge about chemical structure and reactivity but often target specific materials with very specific properties. In contrast, computational chemists perform calculations on millions of different elemental combinations and find many candidates of possible materials with interesting properties, though most of these are not realizable synthetically due to limitations in reactivity, kinetics, or thermodynamics. Synthetic harmony can be achieved through active collaboration and communication between these two subfields of chemistry, such that new calculations can incorporate complete knowledge about reaction kinetics and thermodynamics, and new syntheses target computationally predicted materials derived from an understanding of mapped reaction landscapes.

(Cs X)Cu5O2(PO4)2 ( X = Cl, Br, I): A Family of Cu2+ S = 1/2 Compounds with Capped-Kagomé Networks Composed of OCu4 Units.

Three new salt inclusion compounds (Cs X)Cu5O2(PO4)2 ( X = Cl, Br, I), phosphate analogues of the kagomé mineral averievite, are reported. Their crystal structures are composed of trigonal networks of corner-sharing OCu4 anion-centered tetrahedra, forming capped-kagomé planes, which can also be regarded as two-dimensional slices along the [111] direction of a pyrochlore lattice. Magnetization and heat capacity measurements reveal strong geometric frustration of this network and complex magnetic behavior. X-ray and neutron diffraction studies show that all three compounds undergo a trigonal-to-monoclinic phase transition upon cooling, with a first-order phase transition seen in CsBr and CsI analogues. Along with the previously reported (CsCl)Cu5O2(VO4)2, these three new compounds belong to a large family of OCu4-based networks, which are a playground for studying frustrated quantum magnetism.

Universal Single-Ion Physics in Spin-Orbit-Coupled d5 and d4 Ions.

We have identified six new 4d4 and 4d5 compounds with isolated RuCl6 octahedra, with formulas (HMA)4RuCl6·Cl (1; MA = methylamine), (HGly)4RuCl6·Cl (2; gly = glycine), (HGly)3RuCl6·2H2O (3), (NH4)2RuCl6 (4), (HPy)2RuCl6 (5; py = pyridine), and H2(4,4'-bpy)RuCl6 (6; 4,4'-bpy = 4,4'-bipyridine). We find that the temperature-dependent magnetization is well described by single-ion physics in the presence of spin-orbit coupling and negligible superexchange interactions. Further, we find that many compounds in the literature are also well described by single-ion physics, and our results demonstrate the importance of considering single-ion physics when evaluating candidate geometric frustrated magnets in the presence of spin-orbit coupling.

Superconductivity-Electron Count Relationship in Heusler Phases-the Case of LiPd2Si.

We report superconductivity in the full Heusler compound LiPd2Si (space group Fm3̅m, No. 225) at a critical temperature of Tc = 1.3 K and a normalized heat capacity jump at Tc, ΔC/γTc = 1.1. The low-temperature isothermal magnetization curves imply type-I superconductivity, as previously observed in LiPd2Ge. We show, based on density functional theory calculations and using the molecular orbital theory approach, that while LiPd2Si and LiPd2Ge share the Pd cubic cage motif that is found in most of the reported Heusler superconductors, they show distinctive features in the electronic structure. This is due to the fact that Li occupies the site which, in other compounds, is filled with an early transition metal or a rare-earth metal. Thus, while a simple valence electron count-property relationship is useful in predicting and tuning Heusler materials, inclusion of the symmetry of interacting frontier orbitals is also necessary for the best understanding.

Eficacia y costo-utilidad de primer reemplazo total de cadera y rodilla en pacientes con osteoartritis / Efficacy and cost-utility of first total hip and knee replacement in patients with osteoarthritis

Objetivo: Determinar la eficacia, costos y razón incremental de costo-utilidad (RICu) de la cirugía de primer reemplazo total de rodilla y cadera en pacientes con osteoartritis. Material y métodos: Se diseñó un ensayo no controlado de tipo antes-después, incluyendo pacientes con osteoartritis primaria de cadera o rodilla en plan de primera cirugía de reemplazo articular total. El seguimiento incluyó los primeros 12 meses postcirugía, registrándose capacidad funcional [versión corta del Knee Injury and Osteoarthritis Outcome Score (KOOS-PS) y Hip Disability and Osteoarthritis Outcome (HOOS-PS)], y calidad de vida (EuROQOL­5D). El análisis de costo se realizó desde la perspectiva de la sociedad, calculándose la eficacia, años de vida ajustados por calidad (AvAC), y RICu del procedimiento. Se definió un valor dep de 0,05 como estadísticamente significativo. Resultados: Se incluyeron un total de 23 pacientes [coxartrosis (52%), gonartrosis (48%)]. Los pacientes sometidos a reemplazo articular presentaron una mejoría estadísticamente significativa en la funcionalidad y calidad de vida de los pacientes [diferencia de medias: Eu-ROQOL=0,69, HOOS-PS=-49, KOOS-PS=-31]. Al año de seguimiento se registró una ganancia de 0,43 AvACs. El costo de la cirugía y seguimiento postquirúrgico fue de 141.343 pesos por paciente, siendo el costo adicional de someterse al reemplazo de 3140 pesos por paciente. LaRICu resultante fue de 7302 pesos por AvAC ganado. Conclusiones: El reemplazo articular total resultó ser un procedimiento "muy costo-efectivo", mejorando la funcionalidad y calidad de vida de los pacientes con osteoartritis de caderay rodilla

Socio-economic cost and health-related quality of life of burn victims in Spain.

OBJECTIVES: The aim of the study was to determine the economic burden (direct and indirect costs) of burn victims and the impact of burn on health-related quality of life in Spain. METHODS: In 2003, a cross-sectional study was carried out with 898 burned people. Data regarding demographic features, health resource use, informal care, indirect costs and quality of life were prospectively collected through hospital admission databases and questionnaires filled out by burn victims and caregivers. RESULTS: The mean annual cost (direct and indirect) per burn patient was US$ 99,773. The most important categories of costs were those of in-patient care and temporary and permanent disability. Direct healthcare costs of burn patients represented 19.6% of the total. Total annual cost for burn patients in Spain was US$ 313 million. The mean health-related quality of life measured by European Quality of Life 5-Dimension score was 0.84 and the mean visual analogue score was 67. CONCLUSIONS: The costs of burn are higher than those of many other conditions, and a cost-effectiveness assessment of the different interventions for burn should become a priority in health policy.

Erbium:YAG laser as a method of deepithelization in corrective and reductive breast surgery.

Deepithelization of the breast in breast ptosis surgery is important, being associated with risks which could affect the clinical outcome. The role of Er:YAG laser deepithelization was investigated. A total of 12 bilateral mammoplasties were performed, randomly assigned to 2 groups, one of experienced and one of less-experienced surgeons. Results were compared between the 2 groups of surgeons for scalpel deepithelization on one breast and the Er:YAG laser on the contralateral breast. No complications; less edema, pain, and erythema; and quicker wound healing were observed in the laser-deepithelized breasts, with a shorter operation time even for the less-experienced surgeons. The authors do not suggest that the Er:YAG laser should replace the scalpel in the hands of the expert surgeon for breast deepithelization in breast ptosis surgery, but the results of the study suggest that Er:YAG laser ablation is a safe, precise, effective and complication-free method.

Proteinosis alveolar pulmonar asociada a lupus eritematoso sistémico / Alveolar proteinosis associated with systemic lupus erythematosus

Estamos presentando el caso de una paciente de 47 años, sin antecedentes importantes, que empezó un cuadro clínico de manifestaciones respiratorias inespecíficas, curso por varios años por distintos servicios de salud sin un diagnóstico específico, y que pocos meses después de ser diagnosticada con Proteinosis Alveolar Pulmonar PAP mediante biopsia pulmonar, presenta anticuerpos positivos para lupus eritematoso sistémico. (Nota: el enlace a Internet opera para todo el fasciculo 2/2008).