Structural and Superconducting Properties of Tungsten Hydrides Under High Pressure

Unveiling the relation between crystal structure and superconductivity of hydrides becomes a fascinating research area in chemistry and condensed-mater physics. Although much efforts have been made to study chemical reaction between tungsten and hydrogen, the crystal structures, superconductivity, and phase diagram of tungsten hydrides under high pressure have not been fully explored and built thus far. In this work, we carried out extensive structural search on W-H binary compounds through first-principles swarm-intelligence structural search calculations. Besides reproducing the known W-H compounds, a new stoichiometry WH5 with P6mm symmetry becomes stable above 230.2 GPa. Intriguingly, P6mm WH5 shows a critical temperature (Tc) value of 60.8 K, which is much higher than 31.6 K in WH6. This finding is different from the knowledge of compounds with higher H content exhibiting higher Tc, which might be attributed to the appearance of unique H network and tetrahedron H units in WH5. Electronic property and superconductivity of the other tungsten hydrides are also investigated. The built pressure-composition phase diagram provides some useful information for experimental synthesis

Weighted Gene Co-expression Network Analysis for RNA-Sequencing Data of the Varicose Veins Transcriptome

ObjectiveVaricose veins are a common problem worldwide and can cause significant impairments in health-related quality of life, but the etiology and pathogenesis remain not well defined. This study aims to elucidate transcriptomic regulations of varicose veins by detecting differentially expressed genes, pathways and regulator genes.MethodsWe harvested great saphenous veins (GSV) from patients who underwent coronary artery bypass grafting (CABG) and varicose veins from conventional stripping surgery. RNA-Sequencing (RNA-Seq) technique was used to obtain the complete transcriptomic data of both GSVs from CABG patients and varicose veins. Weighted Gene Co-expression network analysis (WGCNA) and further analyses were then carried out with the aim to elucidate transcriptomic regulations of varicose veins by detecting differentially expressed genes, pathways and regulator genes.ResultsFrom January 2015 to December 2016, 7 GSVs from CABG patients and 13 varicose veins were obtained. WGCNA identified 4 modules. In the brown module, gene ontology (GO) analysis showed that the biological processes were focused on response to stimulus, immune response and inflammatory response, etc. Kyoto encyclopedia of genes and genomes (KEGG) pathway analysis showed that the biological processes were focused on cytokine-cytokine receptor interaction and TNF signaling pathway, etc. In the gray module, GO analysis showed that the biological processes were skeletal myofibril assembly related. The immunohistochemistry staining showed that the expression of ASC, Caspase-1 and NLRP3 were increased in GSVs from CABG patients compared with varicose veins. Histopathological analysis showed that in the varicose veins group, the thickness of vascular wall, tunica intima, tunica media and collagen/smooth muscle ratio were significantly increased, and that the elastic fiber/internal elastic lamina ratio was decreased.ConclusionThis study shows that there are clear differences in transcriptomic information between varicose veins and GSVs from CABG patients. Some inflammatory RNAs are down-regulated in varicose veins compared with GSVs from CABG patients. Skeletal myofibril assembly pathway may play a crucial role in the pathogenesis of varicose veins. Characterization of these RNAs may provide new targets for understanding varicose veins diagnosis, progression, and treatment

Single-cell RNA sequencing reveals cell subpopulations in the tumor microenvironment contributing to hepatocellular carcinoma

Background: Hepatocellular carcinoma (HCC) is among the deadliest cancers worldwide, and advanced HCC is difficult to treat. Identifying specific cell subpopulations in the tumor microenvironment and exploring interactions between the cells and their environment are crucial for understanding the development, prognosis, and treatment of tumors.Methods: In this study, we constructed a tumor ecological landscape of 14 patients with HCC from 43 tumor tissue samples and 14 adjacent control samples. We used bioinformatics analysis to reveal cell subpopulations with potentially specific functions in the tumor microenvironment and to explore the interactions between tumor cells and the tumor microenvironment.Results: Immune cell infiltration was evident in the tumor tissues, and BTG1+RGS1+ central memory T cells (Tcms) interact with tumor cells through CCL5-SDC4/1 axis. HSPA1B may be associated with remodeling of the tumor ecological niche in HCC. Cancer-associated fibroblasts (CAFs) and macrophages (TAMs) were closely associated with tumor cells. APOC1+SPP1+ TAM secretes SPP1, which binds to ITGF1 secreted by CAFs to remodel the tumor microenvironment. More interestingly, FAP+ CAF interacts with naïve T cells via the CXCL12–CXCR4 axis, which may lead to resistance to immune checkpoint inhibitor therapy.Conclusion: Our study suggests the presence of tumor cells with drug-resistant potential in the HCC microenvironment. Among non-tumor cells, high NDUFA4L2 expression in fibroblasts may promote tumor progression, while high HSPA1B expression in central memory T cells may exert anti-tumor effects. In addition, the CCL5–SDC4/1 interaction between BTG1+RGS1+ Tcms and tumor cells may promote tumor progression. Focusing on the roles of CAFs and TAMs, which are closely related to tumor cells, in tumors would be beneficial to the progress of systemic therapy research

Superconducting boron allotropes

The search for elemental allotropes is an active research field to get unusual structures with unique properties. The removal of metal atoms from pressure-induced stable binary compounds has become a useful method for obtaining elemental allotropes with interesting properties that otherwise would not be accessible at ambient pressure. Although three-dimensional boron allotropes have been studied extensively, none of those found so far are superconducting at ambient pressure. Here we propose that NaB4 and Na2B17 can be used as precursors to achieve superconducting boron allotropes at ambient pressure. First-principle swarm-intelligence structure search calculations identify several novel sodium borides (e.g., Na3B2,Na2B3,NaB4, and Na2B17) under high pressure. Interestingly, the B atoms in I4/mmmNaB4 and PmNa2B17 form three-dimensional frameworks with open channels, where Na atoms are located. After the removal of Na atoms, two hitherto unknown boron allotropes, named as I4/mmmB4 and PmB17, are stable at ambient pressure. They are metallic with superconducting critical temperatures of 19.8 and 15.4 K, respectively, becoming the highest ones among bulk boron allotropes. In addition, considering their predicted Vickers hardness of 27.3 and 26.8 GPa, they are also potential hard materials.The authors acknowledge the funding supports from the Natural Science Foundation of China under Grants No. 21573037, No. 21873017, No. 11704062, No. 11974208, and No. 51732003, the Postdoctoral Science Foundation of China under Grant No. 2013M541283, the Natural Science Foundation of Jilin Province (20190201231JC), the “111” Project (No. B13013), and the Fundamental Research Funds for the Central Universities (2412017QD006). A.B. acknowledges financial support from the Spanish Ministry of Economy and Competitiveness (FIS2016-76617-P).Peer reviewe

Exploring the Limits of Transition-Metal Fluorination at High Pressures

Fluorination is a proven method for challenging the limits of chemistry, both structurally and electronically. Here we explore computationally how pressures below 300 GPa affect the fluorination of several transition metals. A plethora of new structural phases are predicted along with the possibility for synthesizing four unobserved compounds: TcF7, CdF3, OsF8, and IrF8. The Ir and Os octaflourides are both predicted to be stable as quasi-molecular phases with an unusual cubic ligand coordination, and both compounds formally correspond to a high oxidation state of +8. Electronic-structure analysis reveals that otherwise unoccupied 6p levels are brought down in energy by the combined effects of pressure and a strong ligand field. The valence expansion of Os and Ir enables ligand-to-metal F 2p -> M 6p charge transfer that strengthens M-F bonds and decreases the overall bond polarity. The lower stability of IrF8, and the instability of PtF8 and several other compounds below 300 GPa, is explained by the occupation of M-F antibonding orbitals in octafluorides with a metal-valence-electron count exceeding 8

Evaluation of the Effect of a Health Education Campaign of HIV by Using an Analytical Hierarchy Process Method

This study was designed to understand the status of HIV/AIDS knowledge, attitude and practice (KAP) among different populations and to provide scientific evidences for further health education. Three rounds of questionnaires were administered among service industry workers who were selected through stratified cluster sampling. Study subjects included hotel attendants, employees of beauty parlors and service workers of transportation industry. Data were analyzed using the analytical hierarchy process. All demonstrated high KAP overall. Synthetic scoring indexes of the three surveys were above 75%. However, the correct response rate on questions whether mosquito bite can transmit HIV/AIDS and what is the relationship between STD with HIV was unsatisfactory (lower than expected); and their attitudes towards people living with HIV and AIDS need to be improved. Moreover, the effect of health education on these groups was unclear. In conclusion, analytical hierarchy process is a valid method in estimating overall effect of HIV/AIDS health education. Although the present status of HIV/AIDS KAP among the service industry workers was relatively good, greater efforts should be made to improve their HIV transmission knowledge, attitude and understanding of the relationship between STDs and HIV

Phase diagrams and electronic properties of B-S and H-B-S systems under high pressure

Pressure has become an effective way to obtain new materials with desirable properties. Considering the various stoichiometries, wide applications, and unique structures of binary H-S, H-B, and B-S compounds, especially at high pressures, it is worth expecting that they might form ternary compounds with interesting properties as well. Here, phase stabilities of H-B-S ternary compounds, in the pressure range from 0 to 200 GPa, are reliably determined through first-principles unbiased structural search calculations. A hitherto unknown orthorhombic HBS compound with Ama2 symmetry is identified to be stable above 25 GPa, in which B and S atoms alternate to form distorted chains and H atoms are covalently bonded with Bs. With pressure, Ama2 HBS undergoes a semiconductor-to-metal electronic transition and even becomes superconducting. The exploration of the binary B-S phase diagram indicates that B-S compounds tend to decompose into elemental solids above 208 GPa. However, two S-rich phases, B2S3 and BS2, are predicted at low pressures, exhibiting semiconducting and metallic properties, respectively. BS2 shows a calculated Tc value of 21.9 K at 200 GPa, becoming a superconductor among bulk binary B-S compounds.The authors acknowledge funding support from the Natural Science Foundation of China under Grants No. 21573037, No. 21873017, No. 11704062, and No. 51732003, the Postdoctoral Science Foundation of China under Grant No. 2013M541283, the Natural Science Foundation of Jilin Province (Grant No. 20190201231JC), the “111” Project (No. B13013), and the Fundamental Research Funds for the Central Universities (2412017QD006). The work was carried out at National Supercomputer Center in Tianjin, and the calculations were performed on TianHe-1 (A). A.B. acknowledges financial support from the Spanish Ministry of Economy and Competitiveness (FIS2016-76617-P) and the Department of Education, Universities and Research of the Basque Government and the University of the Basque Country (IT756-13)

Nonmetallic FeH6 under high pressure

High pressure induces unexpected chemical and physical properties in materials. For example, hydrogen-rich compounds under pressure have recently gained much attention as potential room-temperature superconductors, and iron hydrides have also gained significant interest as potential candidates for being the main constituents of the Earth’s core. It is well-known that pressure induces insulator-to-metal transitions, whereas pressure-induced metal-to-insulator transitions are rare, especially for transition metal hydrides. In this article, we have extensively explored the structural phase diagram of iron hydrides by using ab initio particle swarm optimization. We have found a new stable stoichiometry, FeH6, above 213.7 GPa with C2/c symmetry. Interestingly, C2/c FeH6 presents an unexpected nonmetallicity, and its band gap becomes larger with increasing pressure. This is in sharp contrast with P21/m FeH4. The nonmetallicity of C2/c FeH6 mainly originates from the pressure-induced hybridization between the Fe and H orbitals. This new compound shows a unique structure with a mixture of nonbonded hydrogen atoms in a helical iron framework. The strong Fe–Fe interaction and ionic Fe–H bonds are responsible for its structural stability. In addition, we have also found a more stable tetragonal FeH2 structure with the same I4/mmm symmetry as the previously proposed one, the X-ray diffraction pattern of which perfectly agrees with that of the experiment.This research was supported by Natural Science Foundation of China under nos. 21573037 and 11704062, the Postdoctoral Science Foundation of China under grant 2013M541283, the Natural Science Foundation of Jilin Province (20150101042JC), and the Fundamental Research Funds for the Central Universities (2412017QD006). A.B. acknowledges financial support from the Spanish Ministry of Economy and Competitiveness (FIS2016-76617-P) and the Department of Education, Universities and Research of the Basque Government and the University of the Basque Country (IT756-13).Peer reviewe