The high-pressure phases and superconductivity of CaYH 12 have been explored by using a particle swarm optimization structure prediction methodology in combination with first-principles calculations. Our results show that CaYH 12 becomes stable with a cubic F d3m structure above 170 GPa, where metal atoms form body-centered-cubic (bcc) lattices and hydrogens occupy all the tetrahedral interstices of these bcc lattices, completing sodalitelike cages. The electron-phonon coupling calculations indicate that the F d3m structure is a potential high-temperature superconductor, with a calculated T c of 258 K at 200 GPa. Our current study provides a possibility for searching new high-T c superconductors in ternary hydrides.
Non-small-cell lung cancer (NSCLC) represents the most common deadly disease. Emerging evidences suggest that abnormal epigenetic modulation via mRNAs and microRNAs (miRNAs) might be involved in the tumorigenesis. To explore novel therapeutic target of NSCLC, a more detailed mRNAs and miRNA expression profiling study is needed. High-quality total RNA including miRNA was isolated from NSCLC tissue and para-carcinoma tissue and used for RNA and small RNA sequencing. Results were analyzed bioinformatically and validated using quantitative real-time (qRT)-PCR. A total of 3530 genes (1977 up-regulated and 1553 down-regulated) and 211 miRNAs (171 up-regulated and 30 down-regulated) were differentially expressed (DE) in NSCLC tissue versus adjacent normal tissues. Furthermore, 157 novel miRNAs were predicted in our samples. Of these, 918 significant miRNA-mRNA pairs were identified, consisting of 100 miRNAs and 443 mRNAs. Gene ontology analysis revealed that most of the target genes were enriched in the terms of plasma membrane, binding, and multiple biological-molecular signaling processes. Pathway analysis of these miRNA signatures highlights their critical roles in calcium signaling pathway. Using qRT-PCR, the expression of several DE genes (KRAS and RBM5) and miRNAs (miR-1-5p, let-7b-5p, miR-21-5p, miR-1290, miR-149-5p, chr8_28846, chrX_31594, and chr9_29897) were confirmed. The integrative analysis based on mRNA and miRNA profiling may provide more potential molecular for the tumorigenesis and development of NSCLC.
As the only semiconductor material exhibiting ultrahigh thermal conductivity under ambient conditions, cubic boron arsenide (BAs) is currently attracting great interest. Thanks to the development of high-quality BAs single crystal growth techniques, investigation of its basic physical properties has now become possible. Here, the mechanical properties of BAs single crystals are studied by experimental measurements combined with first-principles calculations. A Vickers hardness of 22 GPa suggests that BAs is a hard material, although not among the hardest. The bulk and Young's moduli are measured to be 142 and 388 GPa, respectively. These important mechanical performance parameters, in conjunction with the unusual high thermal conductivity, show great potential for BAs to serve in next-generation semiconductor applications.
The study of superconductivity in compressed hydrides is of great interest due to measurements of high critical temperatures (T c ) in the vicinity of room temperature, beginning with the observations of LaH 10 at 170-190 GPa. However, the pressures required for synthesis of these high-T c superconducting hydrides currently remain extremely high. Here we show the investigation of crystal structures and superconductivity in the La-B-H system under pressure with particle-swarm intelligence structure-searches methods in combination with first-principles calculations. Structures with seven stoichiometries, LaBH, LaBH 4 , LaBH 6 , LaBH 7 , LaBH 8 , La(BH) 3 , and La(BH 4 ) 3 were predicted to become stable under pressure. Remarkably, the hydrogen atoms in LaBH 8 were found to bond with B atoms in a manner that is similar to that in H 3 S. Lattice dynamics calculations indicate that LaBH 7 and LaBH 8 become dynamically stable at pressures as low as 109 and 48 GPa, respectively. Moreover, the two phases were predicted to be superconducting with a critical temperature T c of 93 K and 156 K at 110 GPa and 55 GPa, respectively (μ * = 0.1). The present results provide guidance for future experiments targeting hydride superconductors with both low synthesis pressures and high T c .
The crystal structures and properties of boron-silicon (B-Si) compounds under pressure have been systematically explored using particle swarm optimization structure prediction method in combination with first-principles calculations. Three new stoichiometries, B 2 Si, BSi, and BSi 2 , are predicted to be stable gradually under pressure, where increasing pressure favors the formation of silicon rich B-Si compounds. In the boron-rich compounds, the network of boron atoms changes from B 12 icosahedron in the ambient phases to the similar buckled graphenelike layers in the high-pressure phases, which crystalize in the same P3m1 symmetry but with different numbers of boron layers between adjacent silicon layers. Phonon calculations show that these structures might be retained to ambient conditions as metastable phases. Further electron-phonon coupling calculations indicate that the high-pressure phases of boron-rich compounds might superconduct at 1 atm, with the highest T c value of 21 K from the Allen-Dynes equation in P3m1 B 2 Si, which is much higher than the one observed in boron doped diamond-type silicon. Moreover, further fully anisotropic Migdal-Eliashberg calculations indicate that B 2 Si is a two-gap anisotropic superconductor and the estimated T c might reach up to 30 K at 1 atm. On the silicon-rich side, BSi 2 is predicted to be stable in the CuAl 2 -type structure. Our current results significantly enrich the phase diagram of the B-Si system and will stimulate further experimental study.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.