Growth and Thermophysical Properties of the Nonlinear Optical Crystal LuAl₃(BO₃)₄

Single crystals of LuAl₃(BO₃)₄ (LuAB) have been grown with the top-seeded solution growth method from a new tungstate based flux Li₂WO₄–B₂O₃. The crystallization region of LuAB is revealed in a quasi-ternary system of LuAB–Li₂WO₄–B₂O₃. Correlation between the crystallization region of LuAB and an excess of Al₂O₃ in the flux system has been identified for the first time. Compared with the commonly used K₂Mo₃O₁₀–B₂O₃ flux at 1100 °C, the Li₂WO₄–B₂O₃ flux has lower volatility with lower incorporation of tungstate into the crystals. Thermophysical properties of the crystal have been investigated for the first time, where the thermal expansion coefficients along two crystallographic directions in the temperature range of 30–800 °C were determined to be α₁ = 3.38 × 10^–6 K^–1 and α₃ = 10.4 × 10^–6 K^–1. The specific heat was about 0.65 J/(g·K) at room temperature. The thermal conductivities at room temperature were 12.47 W/(m·K) and 10.443 W/(m·K) along the <i>a</i> and <i>c</i> axes, respectively, and the Vickers hardness values were measured at 1449 (HV) for (100) and 1595 (HV) for (001) faces

Three New Alkaline Beryllium Borates LiBeBO₃, Li₆Be₃B₄O₁₂, and Li₈Be₅B₆O₁₈ in the Ternary Phase Diagrams Li₂O–BeO–B₂O₃

The phase diagram in the Li₂O–BeO–B₂O₃ system has been systematically investigated by the methods of visual polythermal analysis, spontaneous crystallization, and X-ray diffraction. Three new alkaline beryllium borates, namely, LiBeBO₃, Li₆Be₃B₄O₁₂, and Li₈Be₅B₆O₁₈, were synthesized with molten fluxes based on Li₂O–B₂O₃ solvent in this system. All of the materials are centrosymmetric. The similarity of the fundamental building block of the title compounds has been compared. Thermal analysis and powder XRD studies were applied to determine phase relation and their incongruent melting behavior. The UV–vis diffuse reflectance spectroscopy demonstrated that the UV cutoff edges of the aforementioned materials are all below 200 nm

Enhancement of anaerobic digestive efficiency by the use of exchange resin to remove cations in sewage sludge

<p>Hydrolysis is considered as the rate-limiting stage of anaerobic digestion which is one of the most applied stabilization processes in the disposition of sludge. It is urgent to accelerate the hydrolysis of the sludge particles and improve its biodegradability. This study utilized cation-exchange resin (CER) to adsorb divalent cations in the supernatant of activated sludge with the purpose of making the sludge floc disintegrated. The results showed that the biopolymers incorporated in the tightly bound extracellular polymeric substances can be released to the bulk using CER to remove cations. However, the lack of essential elements led to a much lower methane yield of treated sludge than that of activated sludge. The treated sludge got a higher methane production rate constants after added Fe²⁺. It is necessary to add Fe²⁺ or regenerated liquid of resin-containing essential elements in order to maintain the activities of microbial life.</p

Alkaline-Alkaline Earth Fluoride Carbonate Crystals ABCO₃F (A = K, Rb, Cs; B = Ca, Sr, Ba) as Nonlinear Optical Materials

A new series of alkaline–alkaline earth fluoride carbonates (KSrCO₃F, RbSrCO₃F, KCaCO₃F, RbCaCO₃F, CsCaCO₃F, and Cs₃Ba₄(CO₃)₃F₅) were synthesized by spontaneous crystallization with molten fluxes. Their crystal structures, except for Cs₃Ba₄(CO₃)₃F₅, exhibit the stacking of [AF]_∞ (A = K, Rb, Cs) and [B(CO₃)]_∞ (B = Ca, Sr) layers, and the coplanar alignment of [CO₃] triangles. The results from the UV–vis diffuse reflectance spectroscopy study of the powder samples indicated that the short-wavelength absorption edges were all below 200 nm, except for Cs₃Ba₄(CO₃)₃F₅, which is about 210 nm. Second-harmonic generation (SHG) on polycrystalline samples was measured using the Kurtz and Perry technique, which indicated that these carbonates are all phase-matchable materials in both visible and the UV region, and their measured SHG coefficients were about 3.33, 3.33, 3.61, 1.11, 1.11, and 1.20 times as large as that of <i>d</i>₃₆ (KDP), respectively

Origin–destination (OD) of the interprovincial floating population of China

<p>China’s large floating population catalyzes economic development, redistributes the population, and promotes social changes to the social structure, lifestyle patterns, and cultural values. The floating population is a unique group faced with numerous problems stemming from cultural and lifestyle differences. Understanding and visualizing the distributional characteristics and patterns of the floating population is crucial for developing effective social policies. In this study, the origin–destination (OD) map and its adjustment destination–origin (DO) map are used to represent the interprovincial floating population. The OD or DO map can be regarded as a two-level spatial treemap representing the floating population recorded by pairs of locations. In accordance with the different hierarchy of the two-level spatial treemap, the OD and DO are distinguished. The migration volume of the floating population data is represented by the OD and DO maps to find the population’s direction of movement, magnitude, and hot-spots. The migration indicators including migration effectiveness, migration preference indexes, and sex ratios are represented by the OD and DO maps, which assist in to reviewing and studying the deep patterns of floating population.</p

Sulfur Vacancy-Engineered Co₃S₄/MoS₂‑Interfaced Nanosheet Array for Enhanced Alkaline Overall Water Splitting

Electrochemical water splitting, a crucial reaction for renewable energy storage, demands highly efficient and stable catalysts. Defect and interface engineering has been widely acknowledged to play a pivotal role in improving electrocatalytic performance. Herein, we demonstrate a facile strategy to construct sulfur vacancy (Sv)-engineered Co3S4/MoS2-interfaced nanosheet arrays to modulate the interface electronic structure in situ reduction with NaBH4. The abundant sulfur vacancies and well-arranged nanosheet arrays in Sv-Co3S4/MoS2 lead to pronounced electrocatalytic properties for hydrogen and oxygen evolution reactions (HER/OER) in an alkaline medium, with observed overpotentials of 156 and 209 mV at 10 mA cm–2, respectively. Additionally, as a bifunctional electrocatalyst, Sv-Co3S4/MoS2 requires a cell voltage of 1.67 V at 10 mA cm–2 for overall water splitting and exhibits long-term stability with activity sustained for more than 20 h. This study provides a novel approach to producing transition metal compound-interfaced electrocatalysts with rich vacancies under mild conditions, showcasing their potential for efficient water splitting applications

Structural Modulation of Nitrate Group with Cations to Affect SHG Responses in RE(OH)₂NO₃ (RE = La, Y, and Gd): New Polar Materials with Large NLO Effect after Adjusting pH Values of Reaction Systems

A series of rare-earth hydroxide nitrate crystals (La­(OH)₂NO₃, Y­(OH)₂NO₃, and Gd­(OH)₂NO₃) have been synthesized through adjusting pH values of reaction systems under the subcritical hydrothermal condition. All the titled compounds were isostructural with the noncentrosymmetric space group P2₁ (No. 4) with layer structure, containing [REO₉] (RE = La,Y, and Gd) polyhedra in each layer. The polyhedra were stacked on top of each other and further connected with zigzag strings of edge sharing to form infinite corrugated sheets that parallel to the a–c plane. The [NO₃] groups that presented two different orientation (A and B) project into the space between the layers. In this study, the angle θ between two different orientation [NO₃] groups was defined. With the decrease of ionic radii from La³⁺, Gd³⁺ to Y³⁺, the θ was increased, which led to different second harmonic generation (SHG) effects on lanthanide hydroxide nitrates. The powder SHG measurements revealed that La­(OH)₂NO₃, Gd­(OH)₂NO₃, and Y­(OH)₂NO₃ were phase-matchable in the visible and UV region and feature large SHG responsed that are approximately 5, 5.5, and 5.6 times that of KH₂PO₄ (KDP), respectively. Additionally, these title compounds had wide transparent regions from UV to near IR and larger birefringence, suggesting that these crystals were promising UV NLO materials. And their electronic structures and optical properties were calculated based on DFT methods

A Map-Based Service Supporting Different Types of Geographic Knowledge for the Public

<div><p>The internet enables the rapid and easy creation, storage, and transfer of knowledge; however, services that transfer geographic knowledge and facilitate the public understanding of geographic knowledge are still underdeveloped to date. Existing online maps (or atlases) can support limited types of geographic knowledge. In this study, we propose a framework for map-based services to represent and transfer different types of geographic knowledge to the public. A map-based service provides tools to ensure the effective transfer of geographic knowledge. We discuss the types of geographic knowledge that should be represented and transferred to the public, and we propose guidelines and a method to represent various types of knowledge through a map-based service. To facilitate the effective transfer of geographic knowledge, tools such as auxiliary background knowledge and auxiliary map-reading tools are provided through interactions with maps. An experiment conducted to illustrate our idea and to evaluate the usefulness of the map-based service is described; the results demonstrate that the map-based service is useful for transferring different types of geographic knowledge.</p></div

Structural Modulation of Nitrate Group with Cations to Affect SHG Responses in RE(OH)₂NO₃ (RE = La, Y, and Gd): New Polar Materials with Large NLO Effect after Adjusting pH Values of Reaction Systems

A series of rare-earth hydroxide nitrate crystals (La­(OH)₂NO₃, Y­(OH)₂NO₃, and Gd­(OH)₂NO₃) have been synthesized through adjusting pH values of reaction systems under the subcritical hydrothermal condition. All the titled compounds were isostructural with the noncentrosymmetric space group P2₁ (No. 4) with layer structure, containing [REO₉] (RE = La,Y, and Gd) polyhedra in each layer. The polyhedra were stacked on top of each other and further connected with zigzag strings of edge sharing to form infinite corrugated sheets that parallel to the a–c plane. The [NO₃] groups that presented two different orientation (A and B) project into the space between the layers. In this study, the angle θ between two different orientation [NO₃] groups was defined. With the decrease of ionic radii from La³⁺, Gd³⁺ to Y³⁺, the θ was increased, which led to different second harmonic generation (SHG) effects on lanthanide hydroxide nitrates. The powder SHG measurements revealed that La­(OH)₂NO₃, Gd­(OH)₂NO₃, and Y­(OH)₂NO₃ were phase-matchable in the visible and UV region and feature large SHG responsed that are approximately 5, 5.5, and 5.6 times that of KH₂PO₄ (KDP), respectively. Additionally, these title compounds had wide transparent regions from UV to near IR and larger birefringence, suggesting that these crystals were promising UV NLO materials. And their electronic structures and optical properties were calculated based on DFT methods

AZn₂BO₃X₂(A = K, Rb, NH₄; X = Cl, Br): New Members of KBBF Family Exhibiting Large SHG Response and the Enhancement of Layer Interaction by Modified Structures

A new category of five KBBF-analogy nonlinear optical (NLO) materials, AZn₂BO₃X₂ (A = K, Rb, NH₄; X = Cl, Br), are developed by the tetrahedron substitution of BeO₃F for ZnO₃X from KBe₂BO₃F₂ (KBBF). They preserve the structural merits of KBBF, consisting of the infinite planar [Zn₂BO₃X₂]_∞ layers. Optical measurements on this series of NLO crystals reveal that they are phase-matchable in the visible and UV region with powder second-harmonic generation (SHG) responses being more than twice that of isostructural KBBF. First-principles calculations and atom-cutting analysis were carried out to demonstrate that enhanced SHG response originates from the cooperative effect of coparallel [BO₃] triangles and distorted ZnO₃Cl/Br tetrahedra. The theoretical calculations and experimental results show that AZn₂BO₃X₂ exhibits a less-developed layer habit compared with KBBF. Especially, because of the existence of relatively strong hydrogen bond between NH₄⁺ groups and [Zn₂BO₃Cl₂]_∞ layers, NH₄Zn₂BO₃Cl₂ crystal exhibits the best growth behavior along the <i>c</i> axis. These results show that they may have prospects as a kind of UV nonlinear optical material