Sarcopenia index as a predictor of clinical outcomes among older adult patients with acute exacerbation of chronic obstructive pulmonary disease: a cross-sectional study.

BACKGROUND: Sarcopenia is a geriatric syndrome with progressive loss of skeletal muscle mass and function and has a negative impact on clinical outcomes associated with chronic obstructive pulmonary disease (COPD). Recently, the sarcopenia index (SI) was developed as a surrogate marker of sarcopenia based upon the serum creatinine to cystatin C ratio. We aimed to assess the value of SI for predicting clinically important outcomes among elderly patients with acute exacerbation of COPD (AECOPD). METHODS: This cross-sectional study included elderly patients with AECOPD in China from 2017 to 2021. Clinical data were collected from medical records, and serum creatinine and cystatin C were measured. Outcomes included respiratory failure, heart failure, severe pneumonia, invasive mechanical ventilation, and mortality. Binary logistic regression was used to analyze the association between SI and clinical outcomes. RESULTS: A total of 306 patients (260 men, 46 women, age range 60-88 years) were enrolled in this study. Among the total patients, the incidence of respiratory failure and severe pneumonia was negatively associated with SI values. After adjusting for potential confounding factors, binary logistic regression analyses showed that a higher SI was still independently associated with a lower risk of respiratory failure (odds ratio [OR]: 0.27, 95% confidence interval [CI]: 0.13-0.56, P < 0.05). In subgroup analysis, the incidence of respiratory failure was negatively associated with SI values in groups with both frequent exacerbation and non-frequent exacerbation. After adjustment for potential confounders, binary logistic regression analyses showed that a higher SI was also independently associated with a lower risk of respiratory failure in both groups (OR: 0.19, 95% CI: 0.06-0.64 and OR: 0.31, 95% CI: 0.11-0.85). However, there were no significant differences in the correlations between SI and the risk of heart failure, invasive mechanical ventilation, and mortality in all groups. CONCLUSION: The SI based on serum creatinine and cystatin C can predict respiratory failure in patients with AECOPD and either frequent or infrequent exacerbations. This indicator provides a convenient tool for clinicians when managing patients with AECOPD in daily clinical practice.

Spin-liquid polymorphism in a correlated electron system on the threshold of superconductivity.

We report neutron scattering measurements which reveal spin-liquid polymorphism in an "11" iron chalcogenide superconductor. It occurs when a poorly metallic magnetic state of FeTe is tuned toward superconductivity by substitution of a small amount of tellurium with isoelectronic sulfur. We observe a liquid-like magnetic response, which is described by the coexistence of two disordered magnetic phases with different local structures whose relative abundance depends on temperature. One is the ferromagnetic (FM) plaquette phase observed in undoped, nonsuperconducting FeTe, which preserves the C4 symmetry of the underlying square lattice and is favored at high temperatures, whereas the other is the antiferromagnetic plaquette phase with broken C4 symmetry, which emerges with doping and is predominant at low temperatures. These findings suggest the coexistence of and competition between two distinct liquid states, and a liquid-liquid phase transformation between these states, in the electronic spin system of FeTe(1-x)(S,Se)(x). We have thus discovered the remarkable physics of competing spin-liquid polymorphs in a correlated electron system approaching superconductivity. Our results facilitate an understanding of large swaths of recent experimental data in unconventional superconductors. In particular, the phase with lower C2 local symmetry, whose emergence precedes superconductivity, naturally accounts for a propensity for forming electronic nematic states which have been observed experimentally, in cuprate and iron-based superconductors alike.

Asymmetric Splitting of an Antiferromagnetic Resonance via Quartic Exchange Interactions in Multiferroic Hexagonal HoMnO_{3}.

The symmetric splitting of two spin-wave branches in an antiferromagnetic resonance (AFR) experiment has been an essential measurement of antiferromagnets for over half a century. In this work, circularly polarized time-domain THz spectroscopy experiments performed on the low symmetry multiferroic hexagonal HoMnO_{3} reveal an AFR of the Mn sublattice to split asymmetrically in an applied magnetic field, with an ≈50% difference in g factors between the high and low energy branches of this excitation. The temperature dependence of the g factors, including a drastic renormalization at the Ho spin ordering temperature, reveals this asymmetry to unambiguously stem from Ho-Mn interactions. Theoretical calculations demonstrate that the AFR asymmetry is not explained by conventional Ho-Mn exchange mechanisms alone and is only reproduced if quartic spin interactions are also included in the spin Hamiltonian. Our results provide a paradigm for the optical study of such novel interactions in hexagonal manganites and low symmetry antiferromagnets in general.

Nodal to nodeless superconducting energy-gap structure change concomitant with fermi-surface reconstruction in the heavy-fermion compound CeCoIn(5).

The London penetration depth λ(T) was measured in single crystals of Ce_{1-x}R_{x}CoIn_{5}, R=La, Nd, and Yb down to T_{min}≈50 mK (T_{c}/T_{min}∼50) using a tunnel-diode resonator. In the cleanest samples Δλ(T) is best described by the power law Δλ(T)∝T^{n}, with n∼1, consistent with the existence of line nodes in the superconducting gap. Substitutions of Ce with La, Nd, and Yb lead to similar monotonic suppressions of T_{c}; however, the effects on Δλ(T) differ. While La and Nd substitution leads to an increase in the exponent n and saturation at n∼2, as expected for a dirty nodal superconductor, Yb substitution leads to n>3, suggesting a change from nodal to nodeless superconductivity. This superconducting gap structure change happens in the same doping range where changes of the Fermi-surface topology were reported, implying that the nodal structure and Fermi-surface topology are closely linked.

Vegetation resilience assessment and its climatic driving factors: Evidence from surface coal mines in northern China.

Vegetation resilience is a key concept for understanding ecosystem responses to disturbances and is essential for maintaining ecosystem sustainability. However, assessing vegetation resilience remains challenging, especially for areas with significant disturbances and ecological restoration, such as surface coal mine ecosystems. Vegetation resilience assessment requires a combination of disturbance magnitude, recovery magnitude, and recovery time. In this study, we propose a vegetation resilience assessment method by integrating disturbance magnitude, recovery magnitude and recovery time. Forty-six surface coal mines in northern China were analysed as the study areas. A geographical detector model was used to explore the influence of climatic factors on vegetation resilience. The results indicated that the vegetation resilience curves included three shapes, inverted U-shaped, S-shaped, and monotonically decreasing, and the different disturbance-recovery relationships of the curves indicated that natural and social factors jointly changed the ecological restoration process. The vegetation resilience of the 46 surface coal mines varies widely, ranging from 0.87 to 7.22, showing a spatial decreasing trend from east to west. The explanatory power of different climatic factors on vegetation resilience by indirectly affecting hydrothermal conditions varies, with the effect of atmospheric pressure being the most significant and the superposition of the two climatic factors enhancing the effect on vegetation resilience. This study enriches the understanding of vegetation resilience assessment and provides important information to guide the differentiation of ecological restoration and resource development of surface coal mines in different regions.

Electronic Griffiths phase in the Te-doped semiconductor FeSb2.

We report on the emergence of an electronic Griffiths phase in the doped semiconductor FeSb(2), predicted for disordered insulators with random localized moments in the vicinity of a metal-insulator transition. Magnetic, transport, and thermodynamic measurements of Fe(Sb(1-x)Te(x))(2) single crystals show signatures of disorder-induced non-Fermi liquid behavior and a Wilson ratio expected for strong electronic correlations. The electronic Griffiths phase states are found on the metallic boundary between the insulating state (x = 0) and a long-range albeit weak magnetic order (x ≥ 0.075).

Iron chalcogenide superconductors at high magnetic fields.

Iron chalcogenide superconductors have become one of the most investigated superconducting materials in recent years due to high upper critical fields, competing interactions and complex electronic and magnetic phase diagrams. The structural complexity, defects and atomic site occupancies significantly affect the normal and superconducting states in these compounds. In this work we review the vortex behavior, critical current density and high magnetic field pair-breaking mechanism in iron chalcogenide superconductors. We also point to relevant structural features and normal-state properties.

Beyond triplet: Unconventional superconductivity in a spin-3/2 topological semimetal.

In all known fermionic superfluids, Cooper pairs are composed of spin-1/2 quasi-particles that pair to form either spin-singlet or spin-triplet bound states. The "spin" of a Bloch electron, however, is fixed by the symmetries of the crystal and the atomic orbitals from which it is derived and, in some cases, can behave as if it were a spin-3/2 particle. The superconducting state of such a system allows pairing beyond spin-triplet, with higher spin quasi-particles combining to form quintet or septet pairs. We report evidence of unconventional superconductivity emerging from a spin-3/2 quasi-particle electronic structure in the half-Heusler semimetal YPtBi, a low-carrier density noncentrosymmetric cubic material with a high symmetry that preserves the p-like j = 3/2 manifold in the Bi-based Γ8 band in the presence of strong spin-orbit coupling. With a striking linear temperature dependence of the London penetration depth, the existence of line nodes in the superconducting order parameter Δ is directly explained by a mixed-parity Cooper pairing model with high total angular momentum, consistent with a high-spin fermionic superfluid state. We propose a k ⋅ p model of the j = 3/2 fermions to explain how a dominant J = 3 septet pairing state is the simplest solution that naturally produces nodes in the mixed even-odd parity gap. Together with the underlying topologically nontrivial band structure, the unconventional pairing in this system represents a truly novel form of superfluidity that has strong potential for leading the development of a new series of topological superconductors.

Low-energy structural dynamics of ferroelectric domain walls in hexagonal rare-earth manganites.

Domain walls (DWs) in ferroic materials, across which the order parameter abruptly changes its orientation, can host emergent properties that are absent in the bulk domains. Using a broadband (106 to 1010 Hz) scanning impedance microscope, we show that the electrical response of the interlocked antiphase boundaries and ferroelectric DWs in hexagonal rare-earth manganites (h-RMnO3) is dominated by the bound-charge oscillation rather than free-carrier conduction at the DWs. As a measure of the rate of energy dissipation, the effective conductivity of DWs on the (001) surfaces of h-RMnO3 at gigahertz frequencies is drastically higher than that at dc, whereas the effect is absent on surfaces with in-plane polarized domains. First-principles and model calculations indicate that the frequency range and selection rules are consistent with the periodic sliding of the DW around its equilibrium position. This acoustic wave-like mode, which is associated with the synchronized oscillation of local polarization and apical oxygen atoms, is localized perpendicular to the DW but free to propagate along the DW plane. Our results break the ground to understand structural DW dynamics and exploit new interfacial phenomena for novel devices.

Topological RPdBi half-Heusler semimetals: A new family of noncentrosymmetric magnetic superconductors.

We report superconductivity and magnetism in a new family of topological semimetals, the ternary half-Heusler compound RPdBi (R: rare earth). In this series, tuning of the rare earth f-electron component allows for simultaneous control of both lattice density via lanthanide contraction and the strength of magnetic interaction via de Gennes scaling, allowing for a unique tuning of the normal-state band inversion strength, superconducting pairing, and magnetically ordered ground states. Antiferromagnetism with ordering vector (½,½,½) occurs below a Néel temperature that scales with de Gennes factor dG, whereas a superconducting transition is simultaneously supressed with increasing dG. With superconductivity appearing in a system with noncentrosymmetric crystallographic symmetry, the possibility of spin-triplet Cooper pairing with nontrivial topology analogous to that predicted for the normal-state electronic structure provides a unique and rich opportunity to realize both predicted and new exotic excitations in topological materials.

Phonon properties of CoSb2 single crystals.

The phonon properties of CoSb(2) have been investigated by Raman scattering spectroscopy and lattice dynamics calculations. Sixteen out of eighteen Raman active modes predicted by factor-group analysis are experimentally observed and assigned. The calculated and measured phonon energies at the Γ point are in very good agreement. The temperature dependence of the A(g) symmetry modes is well represented by phonon-phonon interactions without contribution from any other phonon or electron related interactions.

Lattice dynamics of FeSb2.

The lattice dynamics of FeSb(2) is investigated by first-principles density functional theory calculations and Raman spectroscopy. All Raman- and infrared-active phonon modes are properly assigned. The calculated and measured phonon energies are in good agreement. We have observed strong mixing of the A(g) symmetry modes, with the intensity exchange in the temperature range 210 and 260 K. The A(g) mode repulsion increases by doping FeSb(2) with Co, with no signatures of the electron-phonon interaction for these modes.

Thermal destruction of spin-polaron bands in the narrow-gap correlated semiconductors FeGa3 and FeSb2.

We report muon spin rotation spectra in the narrow-gap semiconductors FeGa(3) and FeSb(2) consistent with a narrow band of small spin polarons (SPs). The characteristic sizes obtained for these SPs are R(FeGa(3)) ≈ 0.3-0.6 nm and R(FeSb (2)) ≈ 0.3 nm, respectively. Such SP states are expected to originate from the exchange correlations between localized and itinerant electrons. Our data suggest that SP bands are formed at low temperature, but are destroyed by thermal fluctuations above 10 K in FeGa(3) and above 7 K in FeSb(2). Formation of such SP band states can explain many of the low-temperature properties of these materials.