Halide Double Perovskites Cs2PdBr6-xIx with Tunable Bandgaps for Solar Cells.

Inorganic lead-free vacancy-ordered double perovskites with the chemical formula A2BX6 are promising candidates to overcome Pb-based organic-inorganic perovskite's toxicity and instability issues. We designed the mixed-halide double perovskites Cs2PdBr6-xIx by halogen anions substitution. The structure, stability, and electronic and photoelectric properties were explored using density functional theory (DFT). The negative value of the formation energy indicated that the Cs2PdBr6-xIx perovskites are thermodynamically stable. These perovskites exhibit tunable bandgap values in the range of 0.77-1.73 eV, which are direct or quasi-direct bandgaps except for Cs2PdBr3I3. Their absorption spectrum shows that the absorption range of visible light expands significantly. The theoretical spectral limit maximum efficiency (SLME) of Cs2PdBr5I with 1.3 eV and Cs2PdBr4I2 with 1.04 eV reached 32 and 30.4%, respectively, which are becoming comparable to or slightly surpassing CH3NH3PbI3, indicating they could be candidates for single-junction solar cells. In addition, the Cs2PdBr3I3 and the Cs2PdBr4I2, with the bandgap of 1.12 and 1.04 eV, respectively, could be the bottom cell to form the homogeneous tandem solar cells with the Cs2PdBr6, which could be the top cell with the bandgap of 1.73 eV.

Effects of Noninvasive Brain Stimulation (NIBS) on Cognitive Impairment in Mild Cognitive Impairment and Alzheimer Disease: A Meta-analysis.

OBJECTIVE: The purpose of this meta-analysis was to evaluate the beneficial effects and optimal stimulation protocol of noninvasive brain stimulation (NIBS) including repetitive transcranial magnetic stimulation (rTMS) and transcranial direct current stimulation (tDCS) on patients with mild cognitive impairment and Alzheimer disease. MATERIALS AND METHODS: PubMed, Web of Science, Embase, and the Cochrane Library were searched until March 2020. The cognitive outcomes were extracted and the standardized mean difference with 95% confidence interval was calculated. RESULTS: Twenty-eight studies were included. The result of NIBS showed significant effect on global cognition (P<0.05). Low-frequency rTMS over right dorsolateral prefrontal cortex (DLPFC), high-frequency rTMS (HF-rTMS) over left DLPFC, and the tDCS over left DLPFC and temporal lobe can significantly improve the memory function (P<0.05). HF-rTMS over left, right, or bilateral DLPFC can significantly improve the language function (P<0.05). Both HF-rTMS and tDCS over left DLPFC can obviously improve the executive function (P<0.05). Multiple sessions of rTMS with 80% to 100% intensity and anode tDCS with 2 mA current density are more suitable for all these functions. CONCLUSIONS: NIBS has a beneficial effect on cognitive performance in both mild cognitive impairment and Alzheimer disease patients. Distinct optimal stimulation parameters were observed for different cognitive functions.

Predicted CsSi compound: a promising material for photovoltaic applications.

Exploration of photovoltaic materials has received enormous interest for a wide range of both fundamental and applied research. Therefore, in this work, we identify a CsSi compound with a Zintl phase as a promising candidate for photovoltaic material by using a global structure prediction method. Electronic structure calculations indicate that this phase possesses a quasi-direct band gap of 1.45 eV, suggesting that its optical properties could be superior to those of diamond-Si for capturing sunlight from the visible to the ultraviolet range. In addition, a novel silicon allotrope is obtained by removing Cs atoms from this CsSi compound. The superconducting critical temperature (Tc) of this phase was estimated to be of 9 K in terms of a substantial density of states at the Fermi level. Our findings represent a new promising CsSi material for photovoltaic applications, as well as a potential precursor of a superconducting silicon allotrope.

Repression of GRIM19 expression potentiates cisplatin chemoresistance in advanced bladder cancer cells via disrupting ubiquitination-mediated Bcl-xL degradation.

OBJECTIVE: The mainstay of treatment for advanced bladder cancer (BC) is cisplatin (CDDP)-based systematic chemotherapy. However, acquired chemoresistance induced by as yet unidentified mechanisms is encountered frequently and often results in treatment failure and disease progression. The present study was designed to elucidate the expression and potential role of the gene associated with retinoid-interferon-induced mortality-19 (GRIM19) in the pathogenesis of CDDP resistance in BC. METHODS: RT-qPCR and immunoblotting were employed to evaluate the expression profile of GRIM19 in clinical BC samples and in different BC cells. Using cell viability assay, apoptotic ELISA, xenografts mouse model, and Transwell assay, the effects of GRIM19 inhibition or GRIM19 overexpression on CDDP resistance were determined in different BC cells. Lastly, using co-immunoprecipitation, we provided the molecular evidence for the interaction between GRIM19 and Bcl-xL. RESULTS: Expression levels of GRIM19 were significantly down-regulated in recurrent BC specimens, and in experimentally induced CDDP-resistant BC cells. Functionally, overexpression of the exogenous GRIM19 potentiated CDDP sensitivity and suppressed the survival and invasion of BC cells in the presence of CDDP challenge. Mechanistically, the compromised CDDP chemosensitization induced by GRIM19 loss was at least partially attributed to the attenuation of Bcl-xL polyubiquitination and subsequent degradation, because (1) GRIM19 colocalized with Bcl-xL in the mitochondria of BC cells and (2) GRIM19 overexpression promoted the ubiquitination of Bcl-xL, and this event could be effectively reversed by pretreatment with inhibitors of p38-MAPK and JNK pathways, indicating that GRIM19 overexpression-induced Bcl-xL ubiquitination may achieve in a p38/JNK-dependent manner. Using the UMUC-3 cells stably depleted of endogenous GRIM19, we further show that inhibition of Bcl-xL rectified GRIM19 deficiency-caused CDDP resistance in BC cells. In addition, BCL2L1 mRNA levels were negatively correlated with GRIM19 mRNA levels in CDDP-associated clinical BC tissues. CONCLUSIONS: Disruption of GRIM19/Bcl-xL is a key mechanism of CDDP resistance in advanced BC. Therapeutically, enhancement of GRIM19 expression or employment of p38/JNK inhibitors may serve as resensitizing therapies for subgroups of CDDP-resistant or refractory BC patients.

Hardness of FeB4: density functional theory investigation.

A recent experimental study reported the successful synthesis of an orthorhombic FeB4 with a high hardness of 62(5) GPa [H. Gou et al., Phys. Rev. Lett. 111, 157002 (2013)], which has reignited extensive interests on whether transition-metal borides compounds will become superhard materials. However, it is contradicted with some theoretical studies suggesting transition-metal boron compounds are unlikely to become superhard materials. Here, we examined structural and electronic properties of FeB4 using density functional theory. The electronic calculations show the good metallicity and covalent Fe-B bonding. Meanwhile, we extensively investigated stress-strain relations of FeB4 under various tensile and shear loading directions. The calculated weakest tensile and shear stresses are 40 GPa and 25 GPa, respectively. Further simulations (e.g., electron localization function and bond length along the weakest loading direction) on FeB4 show the weak Fe-B bonding is responsible for this low hardness. Moreover, these results are consistent with the value of Vickers hardness (11.7-32.3 GPa) by employing different empirical hardness models and below the superhardness threshold of 40 GPa. Our current results suggest FeB4 is a hard material and unlikely to become superhard (>40 GPa).

Orthorhombic C32: a novel superhard sp3 carbon allotrope.

Using a recently developed 'Crystal structure AnaLYsis by Particle Swarm Optimization' (CALYPSO) algorithm on a structural search, we predicted a novel sp(3) carbon allotrope possessing an orthorhombic lattice with the space group Cmmm (oC32). The calculated elastic constants and the simulated hardness revealed that oC32 simultaneously possesses ultra-incompressible and superhard properties with a high bulk modulus of 457 GPa and a high Vickers hardness of 96.2 GPa. This oC32 phase is dynamically stable and energetically more preferable than the experientially observed cold-compressed carbon, thus oC32 is expected to be experimentally synthesizable under extreme conditions. These results further expand the list of meta-stable carbon allotropes and superhard materials under atmospheric and extreme conditions.