Controllable Sign Reversal of the Seebeck Coefficient and Thermoelectric Performance of the Janus MoSH Monolayer.

The Janus MoSH monolayer has attracted extensive attention from researchers; however, to our knowledge, there is no work yet to investigate the thermoelectric properties governed by electron-phonon (e-ph) interactions of the Janus MoSH monolayer in detail, either experimentally or theoretically. In this work, we carry out first-principles calculations on the thermoelectric performance of the MoSH monolayer in the presence of e-ph scattering by solving the Boltzmann transport equation iteratively. We find that by adjusting the Fermi level to the nearby band edge which corresponds to the van Hove singularity (VHS), the sign of the Seebeck coefficient of MoSH can be inverted and the ZT value (figure of merit) increases about 13 times (from 0.0011 to 0.0145). This sizable enhancement of ZT value requires not only the existence of the VHS at Fermi level, but also a constant Fermi surface. Such a case is expected to occur often in realistic materials, not limited only to the MoSH monolayer. In view of the nature of two-dimensional (2D) materials, the Fermi level of the Janus MoSH monolayer can be readily controlled by applying a gate voltage instead of chemical carrier doping. As such, our study proposes a feasible way to control the thermoelectric performance in a 2D structure.

Soluble starch-derived porous carbon microspheres with interconnected and hierarchical structure by a low dosage KOH activation for ultrahigh rate supercapacitors.

The developed porous structure and high density are essential to enhance the bulk performance of carbon-based supercapacitors. Nevertheless, it remains a significant challenge to optimize the balance between the porous structure and the density of carbon materials to realize superior gravimetric and areal electrochemical performance. The soluble starch-derived interconnected hierarchical porous carbon microspheres were prepared through a simple hydrothermal treatment succeeded by chemical activation with a low dosage of KOH. Due to the formation of interconnected spherical morphology, hierarchical porous structure, reasonable mesopore volume (0.33 cm3 g-1) and specific surface area (1162 m2 g-1), the prepared carbon microsphere has an ultrahigh capacitance of 394 F g-1 @ 1 A g-1 and a high capacitance retention of 62.7 % @ 80 A g-1. The assembled two-electrode device displays good cycle stability after 20,000 cycles and an ultra-high energy density of 11.6 Wh kg-1 @ 250 W kg-1. Moreover, the sample still exhibits a specific capacitance of 165 F g-1 @ 1 A g-1 at a high mass loading of 10 mg cm-2, resulting in a high areal capacitance of 1.65 F cm-2. The strategy proposed in this study, via a low-dose KOH activation process, provides the way for the synthesis of high-performance porous carbon materials.

Crystallization-induced formation of two-dimensional carbon nanosheets derived from sodium lignosulfonate for fast lithium storage.

Sodium lignosulfonate, an abundant natural resource, is regarded as an ideal precursor for the synthesis of hard carbon. The development of high-performance, low-cost and sustainable anode materials is a significant challenge facing lithium-ion batteries (LIBs). The modulation of morphology and defect structure during thermal transformation is crucial to improve Li+ storage behavior. Synthesized using sodium lignosulfonate as a precursor, two-dimensional carbon nanosheets with a high density of defects were produced. The synergistic influence of ice templates and KCl was leveraged, where the ice prevented clumping of potassium chloride during drying, and the latter served as a skeletal support during pyrolysis. This resulted in the formation of an interconnected two-dimensional nanosheet structure through the combined action of both templates. The optimized sample has a charging capacity of 712.4 mA h g-1 at 0.1 A g-1, which is contributed by the slope region. After 200 cycles at 0.2 A g-1, the specific charge capacity remains 514.4 mA h g-1, and a high specific charge capacity of 333.8 mA h g-1 after 800 cycles at 2 A g-1. The proposed investigation offers a promising approach for developing high-performance, low-cost carbon-based anode materials that could be used in advanced lithium-ion batteries.

First-principles calculations on the intrinsic resistivity of realistic metals: a case study of monolayer V2N.

The Ziman resistivity formula is extensively employed to calculate the intrinsic resistivity of realistic metals using recent works of first-principles calculations. Owing to the approximation, Allen's generalization, which relates the solution of the Boltzmann transport equation (BTE) for metals to the transport electron-phonon (e-ph) spectral function, the applicability of the Ziman resistivity formula still needs to be discussed. In this work, we perform first-principles calculations of the intrinsic resistivity of the V2N monolayer, a kind of MXene material, by employing the Ziman resistivity formula and the iterative solution of BTE. We find that in the wide temperature range of 50-1400 K, the intrinsic resistivity of the V2N monolayer obtained by means of the two approaches, has the same order of magnitude. However the Ziman resistivity formula fails to correctly describe the Fermi level dependence of the intrinsic resistivity of the V2N monolayer. The underlying reason is that the band edge of the V2N and hence Van Hove singularity (VHS), is near the shifted Fermi level. We suggest a modified Ziman resistivity formula which is valid even if there is a band edge at the Fermi level.

Anomalous Klein tunneling in two-dimensional black phosphorus heterojunctions.

We investigate the role of heterojunctions of few-layer black phosphorus (BP) with band gap inversion in governing the quantum transport behaviors. Numerical results show that in the armchair junction, electron tunneling probability occurs under approximately normal incidence with its magnitude T > 0.5. More interestingly, when different band gaps are taken into account on two sides of this junction, the maximum transmission appears away from the center of the valley, leading to the occurrence of anomalous Klein tunneling. Such a result tends to be independent of the width and height of the potential barrier. On the other hand, in the zigzag junction, electron transmission arises in a larger range of angles, and perfect electron transmission (T = 1.0) or reflection appears under specific band gap configurations. These findings provide a new understanding for the study of Klein tunneling and anomalous Klein tunneling based on tunable band gap BP or other two-dimensional Dirac semimetals.

Monolayer AsC5 as the Promising Hydrogen Storage Material for Clean Energy Applications.

One of the critical techniques for developing hydrogen storage applications is the advanced research to build novel two-dimensional materials with significant capacity and effective reversibility. In this work, we perform first-principles unbiased structure search simulations to find a novel AsC5 monolayer with a variety of functionally advantageous characteristics. Based on theoretical simulations, the proposed AsC5 has been found to be energetically, dynamically, and thermally stable, supporting the viability of experiment. Since the coupling between H2 molecules and the AsC5 monolayer is quite weak due to physisorption, it is crucial to be enhanced by thoughtful material design. Hydrogen storage capacity can be greatly enhanced by decorating the AsC5 monolayer with Li atoms. Each Li atom on the AsC5 substrate is shown to be capable of adsorbing up to four H2 molecules with an advantageous average adsorption energy (Ead) of 0.19 eV/H2. The gravimetric density for hydrogen storage adsorption with 16Li and 64 H2 of a Li-decorated AsC5 monolayer is about 9.7 wt%, which is helpful for the possible application in hydrogen storage. It is discovered that the desorption temperature (TD) is much greater than the hydrogen critical point. Therefore, such crucial characteristics make AsC5-Li be a promising candidate for the experimental setup of hydrogen storage.

Giant magnetoresistance in spin valves realized by substitutingY-site atoms in Heusler lattice.

'All-Heusler' spin-valve constructed by two half-metallic Heusler electrodes and a non-magnetic Heusler spacer contains two interfaces that have a crucial influence on the magnetoresistance. In order to reduce the disorder at the interface and protect the half metallicity of the electrode at the same region, we propose a scheme to construct a spin valve by replacing theY-site atoms in the half-metallic Heusler electrode to obtain the corresponding non-magnetic spacer based on the Slater-Pauling rule. In this way, the lattice and band match of the two materials can be ensured naturally. By using Co2FeAl as electrode and Co2ScAl as the spacer materials, we construct the Co2FeAl/Co2ScAl/Co2FeAl(001)-spin valve. Based on the first-principles calculation, the most stable FeAl/CoCo-interface is determined both from the phonon spectra and the formation energy when the spacer Co2ScAl grows on the FeAl-terminated (001) surface of electrode material Co2FeAl. By comparing the projected density of states of the interfacial atoms with the corresponding density of states of the bulk electrode material, only the value of spin-up state of Al changes from 0.17 states/atom/eV to 0.06 states/atom/eV before and after substitution, the half metallicity at the interface is maintained. As a result, the spin-dependent transport properties show significant theoretical magnetoresistance MRopwhich can reach up to 1010% and much larger than 106% reported before.

An integrated method for hybrid distribution with estimation of demand matching degree.

Timely and effective distribution of relief materials is one of the most important aspects when fighting with a natural or a man-made disaster. Due to the sudden and urgent nature of most disasters, it is hard to make the exact prediction on the demand information. Meanwhile, timely delivery is also a problem. In this paper, taking the COVID-19 epidemic as an example, we propose an integrated method to fulfill both the demand estimation and the relief material distribution. We assume the relief supply is directed by government, so it is possible to arrange experts to evaluate the situation from aspects and coordinate supplies of different sources. The first part of the integrated method is a fuzzy decision-making process. The demand degrees on relief materials are estimated by extending COPRAS under interval 2-tuple linguistic environment. The second part includes the demand degrees as one of the inputs, conducts a hybrid distribution model to decide the allocation and routing. The key point of hybrid distribution is that each demand point could be visited by different vehicles and each vehicle could visit different demand points. Our method can also be extended to include both relief materials and medical staffs. A real-life case study of Wuhan, China is provided to illustrate the presented method.

Public Health and Online MICE Technology During the COVID-19 Pandemic: The Role of Health Beliefs and Technology Innovation.

The traditional meetings, incentives, conferences, and exhibitions (MICE) industry has been hit hard by social distancing regulations introduced to combat the COVID-19 pandemic, with concerns about pandemic risks and personal hygiene increasing the demand for online MICE technology. With the introduction of innovative new technologies to the MICE industry, it is important to study the psychology of online MICE attendees, particularly the factors affecting their behavioral intention to adopt online MICE technology during the pandemic. This study investigates the attitudes toward attending online MICE since the start of the epidemic based on the health belief model (HBM) and innovation diffusion theory (IDT). A total of 439 valid questionnaires were collected in China and used for structural equation modeling. The results show that the perceived safety threat, the comparative advantage, trialability, and outcome expectations positively impact the attendees' attitudes. Moreover, this study finds that attitude completely mediates the impact of perceived safety threat, comparative advantages, trialability, and outcome expectation on behavioral intention to attend online MICE events. These findings theoretically enrich the understanding of online MICE technology, the HBM, and the IDT and offer managerial implications for MICE organizers and exhibitors.

Up-regulation of CIT promotes the growth of colon cancer cells.

Colon cancer is one of the major causes of cancer mortality worldwide. However, the underlying mechanism and therapeutic targets of colon cancer have not yet been fully elucidated. In the present study, we demonstrate that citron rho-interacting, serine/threonine kinase 21 (CIT) promotes the growth of human colon cancer cells. CIT is overexpressed in human colon cancer tissues and cell lines. High expression of CIT predicts poor survival for patients with colon cancer. In colon cancer cells, CIT knockdown represses cellular proliferation and colony formation. Our in vivo xenograft experiments showed that CIT knockdown reduces the growth rate of colon cancer cells and the final tumor weight. We found that CIT knockdown induces cell cycle arrest and apoptosis in colon cancer cells. Further microarray and bioinformatics analyses indicated that CIT regulates the p53 signaling pathway, which may account for the effects of CIT on colon cancer cells. Taken together, our findings provide evidence that CIT may promote the development of colon cancer, at least in part, through the p53 signaling pathway. Therefore, CIT may be a potential therapeutic target for colon cancer treatment.