A narrative review of COVID-19-related acute respiratory distress syndrome (CARDS): "typical" or "atypical" ARDS?

Background and Objective: The coronavirus disease of 2019 (COVID-19) is highly infectious and mainly involves the respiratory system, with some patients rapidly progress to acute respiratory distress syndrome (ARDS), which is the leading cause of death in COVID-19 patients. Hence, fully understanding the features of COVID-19-related ARDS (CARDS) and early management of this disease would improve the prognosis and reduce the mortality of severe COVID-19. With the development of recent studies which have focused on CARDS, whether CARDS is "typical" or "atypical" ARDS has become a hotly debated topic. Methods: We searched for relevant literature from 1999 to 2021 published in PubMed by using the following keywords and their combinations: "COVID-19", "CARDS", "ARDS", "pathophysiological mechanism", "clinical manifestations", "prognosis", and "clinical trials". Then, we analyzed, compared and highlighted the differences between classic ARDS and CARDS from all of the aspects above. Key Content and Findings: Classical ARDS commonly occurs within 1 week after a predisposing cause, yet the median time from symptoms onset to CARDS is longer than that of classical ARDS, manifesting within a period of 9.0-12.0 days. Although the lung mechanics exhibited in CARDS grossly match those of classical ARDS, there are some atypical manifestations of CARDS: the severity of hypoxemia seemed not to be proportional to injury of lung mechanics and an increase of thrombogenic processes. Meanwhile, some patients' symptoms do not correspond with the extent of the organic injury: a chest computed tomography (CT) will reveal the severe and diffuse lung injuries, yet the clinical presentations of patients can be mild. Conclusions: Despite the differences between the CARDS and ARDS, in addition to the treatment of antivirals, clinicians should continue to follow the accepted evidence-based framework for managing all ARDS cases, including CARDS.

Enhancing Thermoelectrics for Small-Bandwidth n-Type PbTe-MnTe Alloys via Balancing Compromise.

Small-bandwidth n-type PbTe-MnTe alloys effectively modify the valley shape, while it also inevitably aggravates the deterioration of carrier mobility as nonpolar phonons dominate the scattering. It is found that a trace amount of Cu doping can alleviate the compromises among thermoelectric parameters, thereby significantly optimizing the electrical-transport performance near room temperature of n-type PbTe-MnTe alloys. The single-Kane model reveals that the physical origin of performance improvement lies in the carrier mobility enhancement and self-optimization of carrier concentration. The Debye-Callaway model further quantifies the contribution of copper defect scattering to the lattice thermal conductivity. Notably, the high thermoelectric quality factor obtained in this work rationalizes their superior properties and reveals immense potential for achieving higher zT. Herein, an extremely high zT of ∼0.52 at room temperature and a maximum zTmax of ∼1.2 at 823 K are achieved in 0.3% Cu-intercalated n-type PbTe-MnTe. The mechanism in balancing compromise elaborated in principle contributes to an improvement of thermoelectric properties of the n-type PbTe alloys in a broad temperature range.

High Quality Factor Enabled by Multiscale Phonon Scattering for Enhancing Thermoelectrics in Low-Solubility n-Type PbTe-Cu2Te Alloys.

The fundamental challenge for enhancing the thermoelectric performance of n-type PbTe to match p-type counterparts is to eliminate the Pb vacancy and reduce the lattice thermal conductivity. The Cu atom has shown the ability to fill the cationic vacancy, triggering improved mobility. However, the relatively higher solubility of Cu2Te limits the interface density in the n-type PbTe matrix, leading to a higher lattice thermal conductivity. In particular, a quantitative relationship between the precipitate scattering and the reduction of lattice thermal conductivity in the n-type PbTe with low solubility of Cu2Te alloys still remains unclear. In this work, trivalent Sb atoms are introduced, aiming at decreasing the solubility of Cu in PbTe for improving the precipitate volumetric density and ensuring n-type degenerate conduction. Benefiting from the multiscale hierarchical microstructures by Sb and Cu codoping, the lattice thermal conductivity is considerably decreased to 0.38 W m-1 K-1. The Debye-Callaway model quantifies the contribution from point defects and nano/microscale precipitates. Moreover, the mobility increases from 228 to 948 cm2 V-1 s-1 because of the elimination of cationic vacancies. Consequently, a high quality factor is obtained, enabling a superior peak figure of merit ZT of ∼1.32 in n-type Pb0.975Sb0.025Te by alloying with only ∼1.2% Cu2Te. The present finding demonstrates the significant role of low-solubility Cu2Te in advancing thermoelectrics in n-type PbTe.

Optimized Strategies for Advancing n-Type PbTe Thermoelectrics: A Review.

p-Type and n-type thermoelectric semiconductor materials with compatible performance are key components for thermoelectric devices. Great improvement in thermoelectric performance has been achieved in p-type PbTe, whereas the n-type counterpart still shows much inferior thermoelectric performance compared to that of the p-type PbTe. This inspires many strategies focused on advancing n-type PbTe thermoelectrics. Herein, not only effective mass engineering, resonance states, point defects, and nanostructures but also newly developed concepts including dynamic doping for stabilizing the optimal carrier concentration and introducing dislocations for reducing lattice thermal conductivity are summarized. In addition, the synergistic effects for further enhancing the thermoelectric performance are outlined, together with a discussion and outlook for boosting the advancement in n-type PbTe thermoelectric materials. Strategies discussed here are expected to be applicable to other thermoelectric materials.

Superconductivity related to the suppression of exciton formation in 1T-TiSe2.

In strongly correlated electron system, the impact of elementary substitution or intercalation plays a crucial role in determining electronic ground state among various macroscopic quantum phases such as charge order and superconductivity. Here, we report that simultaneous Cu intercalation and Ta substitution at Ti site in 1T-Cu x Ti0.8Ta0.2Se2 induce an intrinsic electronic phase diagram, characterized by an inherent superconducting transition in the x region of 0 ⩽ x ⩽ 0.12, with a maximum superconducting transition temperature T c of 2.5 K for x = 0.04, in contrast to the non-superconducting sample 1T-Cu0.04TiSe2. The increased density of free charge carriers screen the Coulomb interaction between electron-hole pairs effectively, promoting the occurrence of superconductivity favourably. Present results suggest that the Cu intercalation and the Ta substitution-induced suppression of the exciton condensation boost the superconductivity, shedding new light on the fundamental physics of the interplay between superconductivity, charge order, and electron correlation.

Reducing Effective Mass for Advancing Thermoelectrics in Sb/Bi-Doped AgCrSe2 Compounds.

Liquid-like materials have attracted increasing attention, owing to their phonon-liquid electron-crystal feature. As a typical representative, the superionic conductor AgCrSe2 is regarded as a promising thermoelectric for its intrinsic ultralow lattice thermal conductivity. The primary challenge for achieving high thermoelectric performance is to enhance the inferior electronic performance in AgCrSe2 compounds. Thus, it is very significant to manipulate band effective mass to achieve a higher power factor. In this work, the Sb/Bi elements are doped at Cr sites in Ag0.97CrSe2, i.e., Ag0.97Cr1-x(Sb/Bi)xSe2, aiming at producing a better overlap of electron orbits between different atoms for sharpening the valence band and decreasing the effective mass. In comparison to pristine AgCrSe2, a considerable improvement (>50%) in the power factor (∼387 µW m-1 K-2 at 750 K) is realized upon 3% Sb doping. The single parabolic band model clarifies that the decreased effective mass and optimized carrier concentration contribute to the enhanced electronic property. Furthermore, an ultralow lattice thermal conductivity (∼0.2 W m-1 K-1) is well-maintained for the sample with 3% Sb doping as a result of the nearly unchanged superionic conduction. Eventually, a high peak figure of merit zT (∼0.7 at 750 K) is obtained in Ag0.97Cr0.97Sb0.03Se2. The current finding provides an excellent avenue for advancing thermoelectrics in AgCrSe2 materials.

Texturization-Induced In-Plane High-Performance Thermoelectrics and Inapplicability of the Debye Model to Out-of-Plane Lattice Thermal Conductivity in Misfit-Layered Chalcogenides.

Texturization tuning is of crucial significance for designing and developing high-performance thermoelectric materials and devices. Here, we report for the first time that a strong texturization effect induces an in-plane high-performance thermoelectric and an out-of-plane low lattice thermal conductivity in Sb-substituted misfit-layered (SnS)1.2(TiS2)2 alloys. In the in-plane direction, the oriented texture promotes a high carrier mobility, contributing to the maximization of the power factor (∼0.90 mW K-2 m-1). Moreover, the in-plane lattice thermal conductivity dramatically reduces deriving from the point defects due to the Sb substitution and weakened transverse sound velocity owing to the softening of bonding, ultimately leading to one of the highest thermoelectric performances ever reported among misfit-layered chalcogenides. In particular, in the out-of-plane direction, the texturization triggers the lowest lattice thermal conductivity (∼0.39 W K-1 m-1), exceeding the theoretical limit of the Debye-Cahill model, which provides a precious opportunity to investigate this real Sb-substituted (SnS)1.2(TiS2)2 material. The present finding in misfit-layered chalcogenides provides a novel strategy for manipulating thermoelectrics via texturization engineering.