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n-type Mg3Sb2-based materials have become a top candidate for efficient thermoelectric applications within 300–700 K, due to its high band degeneracy, inherently high carrier mobility and low lattice thermal conductivity, as well as its advantages of less toxicity and abundance. Existing works showed that Mg3Bi2-alloying largely help ensure the exceptional performance, leaving a key issue to be uncovered on the primary mechanisms favoring or limiting the thermoelectric performance of Mg3Sb2-xBix alloys. Here we focus on the alloy composition dependent transport properties at various temperatures, with a large volume of experimental data. It is revealed that, with increasing x, the reduction in both inertial mass and lattice thermal conductivity is significantly beneficial, but the closure in band gap leads to a strong compensation due to the bipolar effect. Such a compromise between band structure and phonon scattering results in optimal Mg3Bi2-alloying concentrations to be about 50%–75% at 300 K, 50%–60% at 450 K and 50% at 600 K, which successfully guiding this work to realize extraordinary thermoelectric figure of merit at these temperatures.

Over the past years, thermoelectric Mg3Sb2 alloys particularly in n-type conduction, have attracted increasing attentions for thermoelectric applications, due to the multivalley conduction band, abundance of constituents, and less toxicity. However, the high vapor pressure, causticity of Mg, and the high melting point of Mg3Sb2 tend to cause the inclusion in the materials of boundary phases and defects that affect the transport properties. In this work, a utilization of tantalum-sealing for melting enables n-type Mg3Sb2 alloys to show a substantially higher mobility than ever reported, which can be attributed to the purification of phases and to the coarse grains. Importantly, the inherently high mobility successfully enables the thermoelectric figure of merit in optimal compositions to be highly competitive to that of commercially available n-type Bi2Te3 alloys and to be higher than that of other known n-type thermoelectrics at 300-500 K. This work reveals Mg3Sb2 alloys as a top candidate for near-room-temperature thermoelectric applications.

High-symmetry thermoelectric materials usually have the advantage of very high band degeneracy, while low-symmetry thermoelectrics have the advantage of very low lattice thermal conductivity. If the symmetry breaking of band degeneracy is small, both effects may be realized simultaneously. Here we demonstrate this principle in rhombohedral GeTe alloys, having a slightly reduced symmetry from its cubic structure, to realize a record figure of merit (zT ∼ 2.4) at 600 K. This is enabled by the control of rhombohedral distortion in crystal structure for engineering the split low-symmetry bands to be converged and the resultant compositional complexity for simultaneously reducing the lattice thermal conductivity. Device ZT as high as 1.3 in the rhombohedral phase and 1.5 over the entire working temperature range of GeTe alloys make this material the most efficient thermoelectric to date. This work paves the way for exploring low-symmetry materials as efficient thermoelectrics. Thermoelectric materials enable a heat flow to be directly converted to a flow of charge carriers for generating electricity. The crystal structure symmetry is one of the most fundamental parameters determining the properties of a crystalline material including thermoelectrics. The common belief currently held is that high-symmetry materials are usually good for thermoelectrics, leading to great efforts having historically been focused on GeTe alloys in a high-symmetry cubic structure. Here we show a slight reduction of crystal structure symmetry of GeTe alloys from cubic to rhombohedral, enabling a rearrangement in electronic bands for more transporting channels of charge carriers and many imperfections for more blocking centers of heat-energy carriers (phonons). This leads to the discovery of rhombohedral GeTe alloys as the most efficient thermoelectric materials to date, opening new possibilities for low-symmetry thermoelectric materials. Cubic GeTe thermoelectrics have been historically focused on, while this work utilizes a slight symmetry-breaking strategy to converge the split valence bands, to reduce the lattice thermal conductivity and therefore realize a record thermoelectric performance, all enabled in GeTe in a rhombohedral structure. This not only promotes GeTe alloys as excellent materials for thermoelectric power generation below 800 K, but also expands low-symmetry materials as efficient thermoelectrics.

SnSe as a lead-free IV–VI semiconductor, has attracted intensive attention for its potential thermoelectric applications, since it is less toxic and much cheaper than conventional PbTe and PbSe thermoelectrics. Here we focus on its sister layered compound SnSe2 in n-type showing a thermoelectric performance to be similarly promising as SnSe in the polycrystalline form. This is enabled by its favorable electronic structure according to first principle calculations, its capability to be effectively doped by bromine on selenium site to optimize the carrier concentration, as well as its intrinsic lattice thermal conductivity as low as 0.4 W/m-K due to the weak van der Waals force between layers. The broad carrier concentration ranging from 0.5 to 6 × 1019 cm−3 realized in this work, further leads to a fundamental understanding on the material parameters determining the thermoelectric transport properties, based on a single parabolic band (SPB) model with acoustic scattering. The layered crystal structure leads to a texture in hot-pressed polycrystalline materials and therefore anisotropic transport properties, which can be well understood by the SPB model. This work not only demonstrates SnSe2 as a promising thermoelectric material but also guides the further improvements particularly by band engineering and texturing approaches.

To date, scholars have increasingly focused on the reduction in crop yields caused by cultivated land fragmentation, yet its effects on the ecological efficiency of cultivated land use are often overlooked. This oversight leads to land resource waste and environmental pollution. It is essential to explore this problem to achieve moderate-scale farming operations and promote the green transformation of agricultural land. This study theoretically analyzed the mechanisms by which cultivated land fragmentation and management scales influence the ecological efficiency of cultivated land use. Based on 2023 household data from Changde and Shaoyang, China, empirical tests were conducted using the stochastic frontier analysis method, Tobit model, and structural equation model. The research results indicate that: (1) The mean ecological efficiency of cultivated land use among the total sample households was 0.822, and the eco-efficiency in the plains was slightly lower than that in the hilly areas. (2) The scale of cultivated land management played a moderating role in the impact of cultivated land fragmentation on ecological efficiency, with differences observed between topographical types. The scale of management can offset part of the negative impact of cultivated land fragmentation on the ecological efficiency of cultivated land use. (3) Regarding the impact of cultivated land fragmentation on the ecological efficiency of cultivated land use, cultivated land management scale changes play a complete mediating role. These findings help provide policy implications to improve the ecological efficiency of cultivated land use. Policy support should be strengthened by promoting moderate-scale cultivated land operations, enhancing the comprehensive remediation of cultivated land fragmentation, and developing skilled farmers for long-term environmental sustainability. [ABSTRACT FROM AUTHOR]

Tuberculosis (TB), an infectious disease caused by Mycobacterium tuberculosis (Mtb) infection, remains a deadly global public health burden. The use of recommended drug combinations in clinic has seen an increasing prevalence of drug-resistant TB, adding to the impediments to global control of TB. Therefore, control of TB and drug-resistant TB has become one of the most pressing issues in global public health, which urges the exploration of potential therapeutic targets in TB and drug-resistant TB. Pyroptosis, a form of programmed cell death characterized by cell swelling and rupture, release of cellular contents and inflammatory responses, has been found to promote pathogen clearance and adopt crucial roles in the control of bacterial infections. It has been demonstrated that Mtb can cause host cell pyroptosis, and these host cells, which are infected by Mtb, can kill Mtb accompanied by pyroptosis, while, at the same time, pyroptosis can also release intracellular Mtb, which may potentially worsen the infection by exacerbating the inflammation. Here, we describe the main pathways of pyroptosis during Mtb infection and summarize the identified effectors of Mtb that regulate pyroptosis to achieve immune evasion. Moreover, we also discuss the potentials of pyroptosis to serve as an anti-TB therapeutic target, with the aim of providing new ideas for the development of TB treatments. [ABSTRACT FROM AUTHOR]