From High-Entropy Ceramics to Compositionally-Complex Ceramics: A Case Study of Fluorite Oxides

Using fluorite oxides as an example, this study broadens high-entropy ceramics (HECs) to compositionally-complex ceramics (CCCs) or multi-principal cation ceramics (MPCCs) to include medium-entropy and/or non-equimolar compositions. Nine compositions of compositionally-complex fluorite oxides (CCFOs) with the general formula of (Hf1/3Zr1/3Ce1/3)1-x(Y1/2X1/2)xO2-delta (X = Yb, Ca, and Gd; x = 0.4, 0.148, and 0.058) are fabricated. The phase stability, mechanical properties, and thermal conductivities are measured. Compared with yttria-stabilized zirconia, these CCFOs exhibit increased cubic phase stability and reduced thermal conductivity, while retaining high Young's modulus (~210 GPa) and nanohardness (~18 GPa). Moreover, the temperature-dependent thermal conductivity in the non-equimolar CCFOs shows an amorphous-like behavior. In comparison with their equimolar high-entropy counterparts, the medium-entropy non-equimolar CCFOs exhibit even lower thermal conductivity (k) while maintaining high modulus (E), thereby achieving higher E/k ratios. These results suggest a new direction to achieve thermally-insulative yet stiff CCCs (MPCCs) via exploring non-equimolar and/or medium-entropy compositions.Comment: 39 pages; 8 + 5 figures; Accepted for publications in Journal of the European Ceramic Society (1/7/2020

Comparison of staged-stent and stent-assisted coiling technique for ruptured saccular wide-necked intracranial aneurysms: Safety and efficacy based on a propensity score-matched cohort study

BackgroundApplication of stent-assisted coiling and FD in acute phase of ruptured wide-necked aneurysms is relatively contraindicated due to the potential risk of ischemic and hemorrhagic complications. Scheduled stenting after initial coiling has emerged as an alternative paradigm for ruptured wide-necked aneurysms. The objective of this study is to evaluate the safety and efficacy of a strategy of staged stent-assisted coiling in acutely ruptured saccular wide-necked intracranial aneurysms compared with conventional early stent-assisted coiling strategy via propensity score matching in a high-volume center.MethodsA retrospective review of patients with acutely ruptured saccular wide-necked intracranial aneurysms who underwent staged stent-assisted coiling or conventional stent-assisted coiling from November 2014 to November 2019 was performed. Perioperative procedure-related complications and clinical and angiographic follow-up outcomes were compared.ResultsA total of 69 patients with staged stent-assisted coiling and 138 patients with conventional stent-assisted coiling were enrolled after 1:2 propensity score matching. The median interval time between previous coiling and later stenting was 4.0 weeks (range 3.5–7.5 weeks). No rebleeding occurred during the intervals. The rate of immediate complete occlusion was lower with initial coiling before scheduled stenting than with conventional stent-assisted coiling (21.7 vs. 60.9%), whereas comparable results were observed at follow-up (82.5 vs. 72.9%; p = 0.357). The clinical follow-up outcomes, overall procedure-related complications and procedure-related mortality between the two groups demonstrated no significant differences (P = 0.232, P = 0.089, P = 0.537, respectively). Multivariate analysis showed that modified Fisher grades (OR = 2.120, P = 0.041) were independent predictors for overall procedure-related complications and no significant predictors for hemorrhagic and ischemic complications.ConclusionsStaged stent-assisted coiling is a safe and effective treatment strategy for acutely ruptured saccular wide-necked intracranial aneurysms, with comparable complete occlusion rates, recurrence rates at follow-up and overall procedure-related complication rates compared with conventional stent-assisted coiling strategy. Staged stent-assisted coiling could be an alternative treatment option for selected ruptured intracranial aneurysms in the future

OGLE-2019-BLG-1470LABc : another microlensing giant planet in a binary system?

We report the discovery and analysis of a candidate triple-lens single-source (3L1S) microlensing event, OGLE-2019-BLG-1470. This event was first classified as a normal binary-lens single-source (2L1S) event, but a careful 2L1S modelling showed that it needs an additional lens or source to fit the observed data. It is found that the 3L1S model provides the best fit, but the binary-lens binary-source (2L2S) model is only disfavoured by Δχ2 ≃ 18. All of the feasible models include a planet with planet-to-host mass-ratios 10−3 ≲ q ≲ 10−2. A Bayesian analysis based on a Galactic model indicates that the planet is super-Jovian, and the projected host-planet separation is about 3 au. Specifically, for the best-fitting 3L1S model, the two stars have masses of M1=0.57+0.43−0.32M⊙⁠, and M2=0.18+0.15−0.10M⊙ with projected separation of 1.3+0.5−0.5 au, and the planetary mass is M3=2.2+1.8−1.3MJupiter⁠. For the 2L2S model, the masses of the host star and the planet are 0.55+0.44−0.31M⊙ and 4.6+3.7−2.6MJupiter⁠, respectively. By investigating the properties of all known microlensing planets in binary systems, we find that all planets in binary systems published by the KMTNet survey are located inside the resonant caustics range with q ≳ 2 × 10−3, indicating the incompleteness of the KMTNet sample for planets in binary systems. Thus, planets in binary systems cannot be included in the current study of the KMTNet mass-ratio function, and a systematic search for planetary anomalies in KMTNet microlensing light curves of binary systems is needed

From High-Entropy Ceramics to Compositionally-Complex Ceramics: A Case Study of Fluorite Oxides

The article of record as published may be found at https://doi.org/10.1016/j.jeurceramsoc.2020.01.015Using fluorite oxides as an example, this study broadens high-entropy ceramics (HECs) to compositionally-complex ceramics (CCCs) or multi-principal cation ceramics (MPCCs) to include medium-entropy and/or non-equimolar compositions. Nine compositions of compositionally-complex fluorite oxides (CCFOs) with the general formula of (Hf1/3Zr1/3Ce1/3)1-x(Y1/2X1/2)xO2-δ (X = Yb, Ca, and Gd; x = 0.4, 0.148, and 0.058) are fabricated. The phase stability, mechanical properties, and thermal conductivities are measured. Compared with yttria-stabilized zirconia, these CCFOs exhibit increased cubic phase stability and reduced thermal conductivity, while retaining high Young’s modulus (∼210 GPa) and nanohardness (∼18 GPa). Moreover, the temperature-dependent thermal conductivity in the non-equimolar CCFOs shows an amorphous-like behavior. In comparison with their equimolar high-entropy counterparts, the medium-entropy non-equimolar CCFOs exhibit even lower thermal conductivity (k) while maintaining high modulus (E), thereby achieving higher E/k ratios. These results suggest a new direction to achieve thermally-insulative yet stiff CCCs (MPCCs) via exploring non-equimolar and/or medium-entropy compositions.This material is primarily based upon work supported by the U.S. Department of Energy’s Office of Energy Efficiency and Renewable Energy (EERE) under Solar 17 Energy Technologies Office (SETO) Agreement Number EE0008529 (for Feb 2019 to July 2020). J.L. and A.W. also acknowledge earlier (before Feb 2019) and partial support of a Vannevar Bush Faculty Fellowship (via ONR Grant No. N00014-16-1-2569) and an associated Laboratory-University Collaboration Initiative (LUCI) program to investigate interfaces in thermal and environmental barrier coatings, which subsequently led to this new direction of HEFOs and CCFOs.This material is primarily based upon work supported by the U.S. Department of Energy’s Office of Energy Efficiency and Renewable Energy (EERE) under Solar 17 Energy Technologies Office (SETO) Agreement Number EE0008529 (for Feb 2019 to July 2020). J.L. and A.W. also acknowledge earlier (before Feb 2019) and partial support of a Vannevar Bush Faculty Fellowship (via ONR Grant No. N00014-16-1-2569) and an associated Laboratory-University Collaboration Initiative (LUCI) program to investigate interfaces in thermal and environmental barrier coatings, which subsequently led to this new direction of HEFOs and CCFOs

Interfacial Electronic Effects in Co@N-Doped Carbon Shells Heterojunction Catalyst for Semi-Hydrogenation of Phenylacetylene

Metal-supported catalyst with high activity and relatively simple preparation method is given priority to industrial production. In this work, this study reported an easily accessible synthesis strategy to prepare Mott-Schottky-type N-doped carbon encapsulated metallic Co (Co@Np+gC) catalyst by high-temperature pyrolysis method in which carbon nitride (g-C3N4) and dopamine were used as support and nitrogen source. The prepared Co@Np+gC presented a Mott-Schottky effect; that is, a strong electronic interaction of metallic Co and N-doped carbon shell was constructed to lead to the generation of Mott-Schottky contact. The metallic Co, due to high work function as compared to that of N-doped carbon, transferred electrons to the N-doped outer shell, forming a new contact interface. In this interface area, the positive and negative charges were redistributed, and the catalytic hydrogenation mainly occurred in the area of active charges. The Co@Np+gC catalyst showed excellent catalytic activity in the hydrogenation of phenylacetylene to styrene, and the selectivity of styrene reached 82.4%, much higher than those of reference catalysts. The reason for the promoted semi-hydrogenation of phenylacetylene was attributed to the electron transfer of metallic Co, as it was caused by N doping on carbon

Fe-Based MOFs for Photocatalytic CO₂ Reduction: Role of Coordination Unsaturated Sites and Dual Excitation Pathways

The utilization of solar energy for the conversion of CO₂ into valuable organic products is one of the best solutions to solve the problems of global warming and energy shortage. The development of photocatalysts capable of reducing CO₂ under visible light, especially those containing earth-abundant metals, is significant. Herein we report that a series of earth-abundant Fe-containing MOFs (MIL-101­(Fe), MIL-53­(Fe), MIL-88B­(Fe)) show photocatalytic activity for CO₂ reduction to give formate under visible light irradiation. The direct excitation of the Fe–O clusters in these MOFs induces the electron transfer from O^2– to Fe³⁺ to form Fe²⁺, which is responsible for the photocatalytic CO₂ reduction. Among the three investigated Fe-based MOFs, MIL-101­(Fe) showed the best activity due to the existence of the coordination unsaturated Fe sites in its structure. All three amine-functionalized Fe-containing MOFs (NH₂-MIL-101­(Fe), NH₂-MIL-53­(Fe) and NH₂-MIL-88B­(Fe)) showed enhanced photocatalytic activity in comparison to the unfunctionalized MOF, due to the existence of dual excitation pathways: i.e., excitation of an NH₂ functionality followed by an electron transfer to the Fe center in addition to the direct excitation of Fe–O clusters

Begonia parvibracteata, a new species in Begonia sect. Platycentrum (Begoniaceae) from Guangxi of China, based on morphological and molecular evidence

The previously reported begonias in a limestone forest of Guangxi mainly belong to Begonia sect. Coelocentrum Irmscher. In this article, we described and illustrated a new species in sect. Platycentrum (Klotzsch) A.DC., Begonia parvibracteata X.X.Feng, R.K.Li & Z.X.Liu, which was discovered in a karst forest of south-western Guangxi. The begonia shows high morphological similarity to B. subhowii S.H. Huang and B. psilophylla Irmscher, but differs from the latter two in its narrower oblique-ovate asymmetric leaf blade, 4 (occasionally 6) tepals of pistillate flower and smaller membranous inflorescence bracts. Molecular phylogenetic analysis, based on ITS sequence data, supports the new species as monophyletic and distinct from B. subhowii and B. psilophylla. Considering its narrow distribution and the disturbance of human activities, the conservation status of new taxon is evaluated as “Vulnerable” (VU B1, B2 ab (i, iv, v), D2) according to the IUCN Red List Categories and Criteria

Exploring the Different Photocatalytic Performance for Dye Degradations over Hexagonal ZnIn₂S₄ Microspheres and Cubic ZnIn₂S₄ Nanoparticles

Different pathways for the degradation of rhodamine (RhB) as well as different activity order for the degradation of RhB and methyl orange (MO) were observed over hexagonal ZnIn₂S₄ microspheres and cubic ZnIn₂S₄ nanoparticles. A detailed study of the physicochemical and surface properties of these two ZnIn₂S₄ polymorphs has been carried out to elucidate these phenomena. The results reveal that hexagonal ZnIn₂S₄ microspheres are composed of nanolamella petals growing in the <i>ab</i> plane, i.e., the negative (0001) S plane. This negative (0001) S plane not only is favorable for the adsorption of the cationic dye RhB via N­(Et)₂ groups but also can accumulate the photogenerated holes. These make the hole-directed photocatalytic de-ethylation of RhB more expedient over hexagonal ZnIn₂S₄ microspheres. This negative (0001) S plane of hexagonal ZnIn₂S₄ microspheres also shows promoting effect for the degradation of cationic dye like MB, but not for the degradation of anionic dye like MO. Our result provides some new insights in how the surface facet can take effect on influencing the performance of a photocatalyst and why different polymorphs can exhibit different photocatalytic performance