Quantum electron liquid and its possible phase transition.

Purely quantum electron systems exhibit intriguing correlated electronic phases by virtue of quantum fluctuations in addition to electron-electron interactions. To realize such quantum electron systems, a key ingredient is dense electrons decoupled from other degrees of freedom. Here, we report the discovery of a pure quantum electron liquid that spreads up to ~3 Å in a vacuum on the surface of an electride crystal. Its extremely high electron density and weak hybridization with buried atomic orbitals show the quantum and pure nature of the electrons, which exhibit a polarized liquid phase, as demonstrated by our spin-dependent measurement. Furthermore, upon enhancing the electron correlation strength, the dynamics of the quantum electrons change to that of a non-Fermi liquid along with an anomalous band deformation, suggestive of a transition to a hexatic liquid crystal phase. Our findings develop the frontier of quantum electron systems and serve as a platform for exploring correlated electronic phases in a pure fashion.

On the Origin of the Negative Thermal Expansion Behavior of YCu.

Among the intermetallics and alloys, YCu is an unusual material because it displays negative thermal expansion without spin ordering. The mechanism behind this behavior that is caused by the structural phase transition of YCu has yet to be fully understood. To gain insight into this mechanism, we experimentally examined the crystal structure of the low-temperature phase of YCu and discuss the origin of the phase transition with the aid of thermodynamics calculations. The result shows that the high-temperature (cubic CsCl-type) to low-temperature (orthorhombic FeB-type) structural phase transition is driven by the rearrangement of three covalent bonds, namely, Y-Cu, Y-Y, and Cu-Cu, which compete for the bonding energy and phonon entropy. At low temperatures, the mixing of Y and Cu does not take place easily because of the weak attractive force between these atoms expected from the small negative mixing enthalpy. This causes all three interactions to take part in the bonding, and Y and Cu are segregated to form an FeB-type structure, which is stabilized by internal energy. At higher temperatures, Cu ions are bound loosely with Y ions due to the large Y-Cu distance (3.01 Å), which results in large vibration entropy and stabilizes a CsCl-type crystal structure. In addition, the CsCl-type structure is reinforced by the Y-Y interaction between next-nearest neighbors, resulting in a smaller unit cell volume. The crystal structure has the simple cubic framework of Y containing Cu ions bound loosely at the cavity sites. The calculated frequency of the Y-like phonon modes is much higher than that of the Cu-like modes, indicating the presence of Y-Y covalent interactions in the CsCl-type phase.

Hydrogen ordering and new polymorph of layered perovskite oxyhydrides: Sr2VO(4-x)H(x).

Compositionally tunable vanadium oxyhydrides Sr2VO(4-x)H(x) (0 ≤ x ≤ 1.01) without considerable anion vacancy were synthesized by high-pressure solid-state reaction. The crystal structures and their properties were characterized by powder neutron diffraction, synchrotron X-ray diffraction, thermal desorption spectroscopy, and first-principles density functional theory (DFT) calculations. The hydrogen anions selectively replaced equatorial oxygen sites in the VO6 layers via statistical substitution of hydrogen in the low x region (x < 0.2). A new orthorhombic phase (Immm) with an almost entirely hydrogen-ordered structure formed from the K2NiF4-type tetragonal phase with x > 0.7. Based on the DFT calculations, the degree of oxygen/hydrogen anion ordering is strongly correlated with the bonding interaction between vanadium and the ligands.

Prevalence and Burden of Carotid and Femoral Atherosclerosis in Subjects Without Known Cardiovascular Disease in a Large Community Hospital in South-America.

INTRODUCTION: Clinical guidelines recommend measurement of arterial (carotid and femoral) plaque burden by vascular ultrasound (VUS) as a risk modifier in individuals at low or moderate risk without known atherosclerotic cardiovascular disease (ASCVD). AIM: To evaluate the prevalence of carotid and femoral plaques by age and sex, the burden of subclinical atherosclerosis (SA), and its association with classic CVRF in subjects over 30 years of age without ASCVD. METHODS: We prospectively enrolled 5775 consecutive subjects referred for cardiovascular evaluation and determined the prevalence and burden of SA using 2D-VUS in carotid and femoral arteries. RESULTS: Sixty-one percent were men with a mean age of 51.3 (SD 10.6) years. Overall, plaque prevalence was 51% in carotid arteries, 39.3% in femoral arteries, 62.4% in carotid or femoral arteries, and 37.6% in neither. The prevalence of plaques and SA burden showed an increasing trend with age, being higher in men than in women and starting before the age of 40, both in the carotid and femoral sites. There was also an increasing prevalence of plaques according to the number of CVRF, and interestingly we found a high prevalence of plaques in subjects with 0 or 1 classic CVRF. CONCLUSIONS: We observed an increased prevalence and burden of carotid or femoral SA, higher in men, beginning before the fourth decade of life and increasing with age. Despite a significant association with classic CVRF, a significant number of subjects with low CVRF were diagnosed with SA.

Acceleration of NO2 gas sensitivity in two-dimensional SnSe2 by Br doping.

The authors report a Br doping effect on the NO2 gas sensing properties of a two-dimensional (2D) SnSe2 semiconductor. Single crystalline 2D SnSe2 samples with different Br contents are grown by a simple melt-solidification method. By analyzing the structural, vibrational as well as electrical properties, it can be confirmed that the Br impurity substitutes on the Se-site in SnSe2 serving as an efficient electron donor. When we measure the change of resistance under a 20 ppm NO2 gas flow condition at room temperature, both responsivity and response time are drastically improved by Br doping from 1.02% and 23 s to 3.38% and 15 s, respectively. From these results, it can be concluded that Br doping plays a key role for encouraging the charge transfer efficiency from the SnSe2 surface to the NO2 molecule by elaborating Fermi level in 2D SnSe2.

Characteristics of a-IGZO/ITO hybrid layer deposited by magnetron sputtering.

Transparent a-IGZO (In-Ga-Zn-O) films have been actively studied for use in the fabrication of high-quality TFTs. In this study, a-IGZO films and a-IGZO/ITO double layers were deposited by DC magnetron sputtering under various oxygen flow rates. The a-IGZO films showed an amorphous structure up to 500 degrees C. The deposition rate of these films decreased with an increase in the amount of oxygen gas. The amount of indium atoms in the film was confirmed to be 11.4% higher than the target. The resistivity of double layer follows the rules for parallel DC circuits The maximum Hall mobility of the a-IGZO/ITO double layers was found to be 37.42 cm2/V x N s. The electrical properties of the double layers were strongly dependent on their thickness ratio. The IGZO/ITO double layer was subjected to compressive stress, while the ITO/IGZO double layer was subjected to tensile stress. The bending tolerance was found to depend on the a-IGZO thickness.

Identifying the Correlation between Structural Parameters and Anisotropic Magnetic Properties in IMnV Semiconductors: A Possible Room-Temperature Magnetism.

Layer-structured materials are of central importance in a wide range of research fields owing to their unique properties originating from their two dimensionality and anisotropy. Herein, quasi-2D layer-structured IMnV (I: alkali metals and V: pnictogen elements) compounds are investigated, which are potential antiferromagnetic (AFM) semiconductors. Single crystals of IMnV compounds are successfully grown using the self-flux method and their electronic and magnetic properties are analyzed in correlation with structural parameters. Combined with theoretical calculations, the structural analysis indicates that the variation in the bonding angle between VMnV is responsible for the change in the orbital hybridization of Mn and V, predominantly affecting their anisotropic semiconducting properties. Anisotropy in the magnetic properties is also found, where AFM ordering is expected to occur in the in-plane direction, as supported by spin-structure calculations. Furthermore, a possible ferromagnetic (FM) transition is discussed in relation to the vacancy defects. This study provides a candidate material group for AFM and FM spintronics and a basis for exploring magnetic semiconductors in quasi-2D layer-structured systems.

Non-oxidized bare copper nanoparticles with surface excess electrons in air.

Copper (Cu) nanoparticles (NPs) have received extensive interest owing to their advantageous properties compared with their bulk counterparts. Although the natural oxidation of Cu NPs can be alleviated by passivating the surfaces with additional moieties, obtaining non-oxidized bare Cu NPs in air remains challenging. Here we report that bare Cu NPs with surface excess electrons retain their non-oxidized state over several months in ambient air. Cu NPs grown on an electride support with excellent electron transfer ability are encapsulated by the surface-accumulated excess electrons, exhibiting an ultralow work function of ~3.2 eV. Atomic-scale structural and chemical analyses confirm the absence of Cu oxide moiety at the outermost surface of air-exposed bare Cu NPs. Theoretical energetics clarify that the surface-accumulated excess electrons suppress the oxygen adsorption and consequently prohibit the infiltration of oxygen into the Cu lattice, provoking the endothermic reaction for oxidation process. Our results will further stimulate the practical use of metal NPs in versatile applications.

Stoner enhancement from interstitial electrons in Y2C toward a spontaneous ferromagnetic electride.

The evolutionary magnetism associated with the interlayer spacing in two-dimensional (2D) Y2C electrides has been investigated by first-principles total-energy calculations based on density functional theory. Several structures with different c-axis parameters around the optimized value were taken into our consideration. Mapping of the electron localization function shows that the interstitial electron is strongly localized at the body center position (denoted as the X-site) in the primitive rhombohedral unit cell, serving as an anion which is ionically bonded with the cationic framework of the Y2C layer. As the c-axis parameter decreases, the volume of the X-site is systematically reduced while both the charge and magnetization density for X are increased. It indicates that the compressed inter-layer space effectively increases the degree of localization of interstitial anionic electrons (IAEs) correlated with their enhanced local magnetic moments. We have found that the exchange splitting of the density of states for Y2C becomes more prominent with a decrease in the c-axis parameter as predicted from a pressurized alkali metal system. Accompanied by the calculated magnetization values, it can be concluded that the increased degree of localization for IAEs between cationic framework layers has greatly influenced the Stoner parameter leading to the increased magnetic moment based on the Stoner enhancement mechanism; hence, it plays a key role in the emergence of a spontaneous ferromagnetic electride.

Boosting Photoredox Catalysis Using a Two-Dimensional Electride as a Persistent Electron Donor.

Electrides, which have excess anionic electrons, are solid-state sources of solvated electrons that can be used as powerful reducing agents for organic syntheses. However, the abrupt decomposition of electrides in organic solvents makes controlling the transfer inefficient, thereby limiting the utilization of their superior electron-donating ability. Here, we demonstrate the efficient reductive transformation strategy which combines the stable two-dimensional [Gd2C]2+·2e- electride electron donor and cyclometalated Pt(II) complex photocatalysts. Strongly localized anionic electrons at the interlayer space in the [Gd2C]2+·2e- electride are released via moderate alcoholysis in 2,2,2-trifluoroethanol, enabling persistent electron donation. The Pt(II) complexes are adsorbed onto the surface of the [Gd2C]2+·2e- electride and rapidly capture the released electrons at a rate of 107 s-1 upon photoexcitation. The one-electron-reduced Pt complex is electrochemically stable enough to deliver the electron to substrates in the bulk, which completes the photoredox cycle. The key benefit of this system is the suppression of undesirable charge recombination because back electron transfer is prohibited due to the irreversible disruption of the electride after the electron transfer. These desirable properties collectively serve as the photoredox catalysis principle for the reductive generation of the benzyl radical from benzyl halide, which is the key intermediate for dehalogenated or homocoupled products.

Antiperovskite Gd3 SnC: Unusual Coexistence of Ferromagnetism and Heavy Fermions in Gd Lattice.

Inverted structures of common crystal lattices, referred to as antistructures, are rare in nature due to their thermodynamic constraints imposed by the switched cation and anion positions in reference to the original structure. However, a stable antistructure formed with mixed bonding characters of constituent elements in unusual valence states can provide unexpected material properties. Here, a heavy-fermion behavior of ferromagnetic gadolinium lattice in Gd3 SnC antiperovskite is reported, contradicting the common belief that ferromagnetic gadolinium cannot be a heavy-fermion system due to the deep energy level of localized 4f-electrons. The specific heat shows an unusually large Sommerfeld coefficient of ≈1114 mJ mol-1 K-2 with a logarithmic behavior of non-Fermi-liquid state. It is demonstrated that the heavy-fermion behavior in the non-Fermi-liquid state appears to arise from the hybridized electronic states of gadolinium 5d-electrons participating in metallic GdGd and covalent GdC bonds. These results accentuate the unusual chemical bonds in CGd6 octahedra with the dual characters of gadolinium 5d-electrons for the emergence of heavy fermions.

Water- and acid-stable self-passivated dihafnium sulfide electride and its persistent electrocatalytic reaction.

Electrides have emerged as promising materials with exotic properties, such as extraordinary electron-donating ability. However, the inevitable instability of electrides, which is caused by inherent excess electrons, has hampered their widespread applications. We report that a self-passivated dihafnium sulfide electride ([Hf2S]2+∙2e-) by double amorphous layers exhibits a strong oxidation resistance in water and acid solutions, enabling a persistent electrocatalytic hydrogen evolution reaction. The naturally formed amorphous Hf2S layer on the cleaved [Hf2S]2+∙2e- surface reacts with oxygen to form an outermost amorphous HfO2 layer with ~10-nm thickness, passivating the [Hf2S]2+∙2e- electride. The excess electrons in the [Hf2S]2+∙2e- electride are transferred through the thin HfO2 passivation layer to water molecules under applied electric fields, demonstrating the first electrocatalytic reaction with excellent long-term sustainability and no degradation in performance. This self-passivation mechanism in reactive conditions can advance the development of stable electrides for energy-efficient applications.

Author Correction: Ferromagnetic quasi-atomic electrons in two-dimensional electride.

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

Ferromagnetic quasi-atomic electrons in two-dimensional electride.

An electride, a generalized form of cavity-trapped interstitial anionic electrons (IAEs) in a positively charged lattice framework, shows exotic properties according to the size and geometry of the cavities. Here, we report that the IAEs in layer structured [Gd2C]2+·2e- electride behave as ferromagnetic elements in two-dimensional interlayer space and possess their own magnetic moments of ~0.52 µB per quasi-atomic IAE, which facilitate the exchange interactions between interlayer gadolinium atoms across IAEs, inducing the ferromagnetism in [Gd2C]2+·2e- electride. The substitution of paramagnetic chlorine atoms for IAEs proves the magnetic nature of quasi-atomic IAEs through a transition from ferromagnetic [Gd2C]2+·2e- to antiferromagnetic Gd2CCl caused by attenuating interatomic exchange interactions, consistent with theoretical calculations. These results confirm that quasi-atomic IAEs act as ferromagnetic elements and trigger ferromagnetic spin alignments within the antiferromagnetic [Gd2C]2+ lattice framework. These results present a broad opportunity to tailor intriguing ferromagnetism originating from quasi-atomic interstitial electrons in low-dimensional materials.

Strong Thermopower Enhancement and Tunable Power Factor via Semimetal to Semiconductor Transition in a Transition-Metal Dichalcogenide.

Electronic band engineering is a promising approach to enhance the thermopower of thermoelectric materials. In transition-metal dichalcogenides (TMDCs), this has so far only been achieved using their inherent semiconducting nature. Here, we report the thickness-modulated band engineering of nanosheets based on semimetallic platinum diselenide (PtSe2) resulting in a thermopower enhancement of more than 50 times than that of the bulk. We obtained this by introducing a semimetal to semiconductor (SMSC) transition resulting in the formation of a bandgap. This approach based on semimetallic TMDCs provides potential advantages such as a large variation of transport properties, a decrease of the ambipolar transport effect, and a high carrier density dependence of the transport properties. Our observations suggest that the SMSC transition in TMDCs is a promising and straightforward strategy for the development of two-dimensional nanostructured thermoelectric materials.

Role of fluorine in two-dimensional dichalcogenide of SnSe 2.

Authors report an effect of F substitution on layered SnSe2 through the successful synthesis of polycrystalline SnSe2-δF x (0.000 ≤ x ≤ 0.010) by solid-state reaction. Accompanied with density functional theory calculations, the blue shift of A1g peak in Raman spectra reveal that F- ions are substituted at Se vacancy sites as decreasing the reduced mass of vibrational mode associated with Sn-Se bonding. From the measurements of electrical parameters, conductivity as well as carrier concentration are governed by thermally activated behavior, while such behavior is suppressed in Hall mobility, which occurs as F ratio increases. Based on Arrhenius relation, it is found that the potential barrier height at the grain boundary is suppressed with increasing F amount, suggesting that the F- ion is a promising candidate for the grain boundary passivation in the two-dimensional dichalcogenide system.

Angioplastia coronaria en la República Argentina. Resultados intrahospitalarios y del seguimiento alejado. Registro CONAREC V / Percutaneous coronary angioplasty in Argentina. In-hospital and follow-up results. CONAREC V registry

La angioplastia transluminal coronaria se ha constituído en una técnica de revascularización segura en el tratamiento de pacientes con cardiopatía isquémica. En la República Argentina aún no disponemos de datos precisos que permitan conocer la evolución clínica alejada de los pacientes sometidos a angioplastia. Con la intención de determinar el éxito clínico y conocer los resultados en el seguimiento alejado de la angioplastia coronaria en nuestro país, se llevó adelante la experiencia del Registro CONAREC V. De esta manera, se incluyeron en forma prospectiva y consecutiva 1295 pacientes, provenientes de 41 centros con residencia en cardiología. Se efectuó el análisis en el seguimiento alejado en el 91,7 por ciento de los pacientes con éxito clínico. La angioplastia logró resultados intrahospitalarios y una tasa de eventos durante el seguimiento similares a los descriptos en la literatura

Análisis de los recursos utilizados en el manejo del dolor precordial / Analysis of resources used in the management of chest pain

El dolor precordial es motivo de una de las consultas cardiológicas más frecuentes y que plantea mayores problemas. dado que en Argentina no se conocen datos acerca de la evolución de estos pacientes, se realizó un registro prospectivo multicéntrico. Completaron el seguimiento a 30 días 1255 pacientes, en los que se analizó el diagnóstico de guardia y el criterio de internación en términos de sensibilidad, especificidad, valor predictivo positivo y error predictivo. Se analizaron los recursos empleados en el diagnóstico y tratamiento según se realizara o no el diagnóstico en guardia, según diagnóstico final y de acuerdo con el tipo de centro