前驱体法制备氮氧化硅纳米线及其光学性能研究

在Ni催化剂的存在下,通过SiCl4的水解氨解反应并在1300℃氨气气氛中进行热氮化处理制得了无定形氮氧化硅纳米线.产物经X射线衍射(XRD)、热重-差示扫描量热(TG-DSC)、扫描电镜(SEM)、透射电镜(TEM)、能量色散谱(EDS)和选区电子衍射(SAED)等表征手段进行分析,结果表明纳米线为无定形结构,直径为100～150nm.在波长为220nm的光激发下,产物的光致发光光谱(PL)在563nm和289nm处分别出现了一个强的绿光发光峰和一个弱的紫光发光峰.对纳米线的生长机理进行分析,表明纳米线的生长遵循气-液-固(VLS)机制控制模式.     

Cloning,Expression, Purification,and Characterization of β-Galactosidase from Bifidobacterium longum and Bifidobacterium pseudocatenulatum

Expression and purification of β-galactosidases derived from Bifidobacterium provide a new resource for efficient lactose hydrolysis and lactose intolerance alleviation. Here, we cloned and expressed two β-galactosidases derived from Bifidobacterium. The optimal pH for BLGLB1 was 5.5, and the optimal temperature was 45 °C, at which the enzyme activity of BLGLB1 was higher than that of commercial enzyme E (300 ± 3.6 U/mg) under its optimal conditions, reaching 2200 ± 15 U/mg. The optimal pH and temperature for BPGLB1 were 6.0 and 45 °C, respectively, and the enzyme activity (0.58 ± 0.03 U/mg) under optimum conditions was significantly lower than that of BLGLB1. The structures of the two β-galactosidase were similar, with all known key sites conserved. When o-nitrophenyl-β-D-galactoside (oNPG) was used as an enzyme reaction substrate, the maximum reaction velocity (V_max) for BLGLB1 and BPGLB1 was 3700 ± 100 U/mg and 1.1 ± 0.1 U/mg, respectively. The kinetic constant (K_m) of BLGLB1 and BPGLB1 was 1.9 ± 0.1 and 1.3 ± 0.3 mmol/L, respectively. The respective catalytic constant (k_cat) of BLGLB1 and BPGLB1 was 1700 ± 40 s⁻¹ and 0.5 ± 0.02 s⁻¹, respectively; the respective k_cat/K_m value of BLGLB1 and BPGLB1 was 870 L/(mmol∙s) and 0.36 L/(mmol∙s), respectively. The K_m, k_cat and V_max values of BLGLB1 were superior to those of earlier reported β-galactosidase derived from Bifidobacterium. Overall, BLGLB1 has potential application in the food industry.     

Preparation of Silica Aerogel/Resin Composites and Their Application in Dental Restorative Materials

As the most advanced aerogel material, silica aerogel has had transformative industrial impacts. However, the use of silica aerogel is currently limited to the field of thermal insulation materials, so it is urgent to expand its application into other fields. In this work, silica aerogel/resin composites were successfully prepared by combining silica aerogel with a resin matrix for dental restoration. The applications of this material in the field of dental restoration, as well as its performance, are discussed in depth. It was demonstrated that, when the ratio of the resin matrix Bis-GMA to TEGDMA was 1:1, and the content of silica aerogel with 50 μm particle size was 12.5%, the composite achieved excellent mechanical properties. The flexural strength of the silica aerogel/resin composite reached 62.9546 MPa, which was more than five times that of the pure resin. Due to the presence of the silica aerogel, the composite also demonstrated outstanding antibacterial capabilities, meeting the demand for antimicrobial properties in dental materials. This work successfully investigated the prospect of using commercially available silica aerogels in dental restorative materials; we provide an easy method for using silica aerogels as dental restorative materials, as well as a reference for their application in the field of biomedical materials.     

Chemical Characteristics of Ethanol and Water Extracts of Black Alder (Alnus glutinosa L.) Acorns and Their Antibacterial,Anti-Fungal and Antitumor Properties

The aim of this study was to identify polyphenolic compounds contained in ethanol and water extracts of black alder (Alnus glutinosa L.) acorns and evaluate their anti-cancer and antimicrobial effects. The significant anti-cancer potential on the human skin epidermoid carcinoma cell line A431 and the human epithelial cell line A549 derived from lung carcinoma tissue was observed. Aqueous and ethanolic extracts of alder acorns inhibited the growth of mainly Gram-positive microorganisms (Staphylococcus aureus, Bacillus subtilis, Streptococcus mutans) and yeast-like fungi (Candida albicans, Candida glabrata), as well as Gram-negative (Escherichia coli, Citrobacter freundii, Proteus mirabilis, Pseudomonas aeruginosa) strains. The identification of polyphenols was carried out using an ACQUITY UPLC-PDA-MS system. The extracts were composed of 29 compounds belonging to phenolic acids, flavonols, ellagitannins and ellagic acid derivatives. Ellagitannins were identified as the predominant phenolics in ethanol and aqueous extract (2171.90 and 1593.13 mg/100 g DM, respectively) The results may explain the use of A. glutinosa extracts in folk medicine.     

Effect of biaxial strain and hydrostatic pressure on the magnetic properties of bilayer CrI3

Two-dimensional van der Waals magnetic materials are intriguing for applications in the future spintronics devices, so it is crucial to explore strategy to control the magnetic properties. Here, we carried out first-principles calculations and Monte Carlo simulations to investigate the effect of biaxial strain and hydrostatic pressure on the magnetic properties of the bilayer CrI₃. We found that the magnetic anisotropy, intralayer and interlayer exchange interactions, and Curie temperature can be tuned by biaxial strain and hydrostatic pressure. Large compressive biaxial strain may induce a ferromagneticto-antiferromagnetic transition of both CrI₃ layers. The hydrostatic pressure could enhance the intralayer exchange interaction significantly and hence largely boost the Curie temperature. The effect of the biaxial strain and hydrostatic pressure revealed in the bilayer CrI₃ may be generalized to other two-dimensional magnetic materials.     

Optical properties of two-dimensional perovskites

The optical properties of two-dimensional (2D) perovskites recently receive numerous research focus thanks to the strong quantum and dielectric confinement effects. In addition to the strong excitonic effect at room temperature, 2D perovskites also have appealing features that their optical properties can be flexibly tuned by alternating organic or inorganic layers. Particularly, 2D chiral perovskites and 2D perovskites based heterostructures are emerging as new platforms to extend their functionalities. To optimize performance of 2D perovskites-based optoelectronic devices, it is critical to understand the fundamentals and explore the strategies to engineer their optical properties. This review begins with an introduction to the excitons and self-trapped excitons of 2D perovskites. Subsequently, inorganic/organic layer effects on optical properties and 2D perovskites based heterostructures are discussed. We also discussed the nonlinear optical properties of 2D perovskite. We are looking forward to that this review can stimulate more efforts to understand and optimize the optical properties of 2D perovskites.     

Multi-scale homogenization-based modeling of semi-crystalline polymers

This paper presents a finite-strain, multi-scale constitutive model for semi-crystalline polymers, accounting explicitly for the current state and evolution of the underlying crystallographic, lamellar and morphological texture. Specifically, a semi-crystalline polymer is modeled as a two-scale composite, assumed to be, at the larger length scale, an aggregate of randomly distributed grains that, at the smaller length scale, are made up of alternating layers of an amorphous and a crystalline phase. The model incorporates finite elasticity for the amorphous phase and crystallographic hardening for the crystalline phase. The instantaneous effective response of this composite is determined by means of multi-scale homogenization methods, consisting in the use of a “linear comparison composite” (LCC) with the same internal structure as the actual nonlinear composite, with local properties that are optimally chosen via suitably designed variational principles. The effective properties of the resulting two-scale LCC are obtained through a “sequential” homogenization procedure, involving the exact solution for the effective behavior of the lamellar grains and a self-consistent estimate for the aggregate. The latter results are also used to establish evolution laws for the appropriate internal variables in the material. The predictions of the model for the macroscopic response and texture evolution in high-density polyethylene are confronted with available experimental results and compared with those of earlier models.     

Spectroscopy of light nuclei with skyrme-type interactions

Deformed Hartree-Fock calculations are performed for some light nuclei in a large configuration space consisting of first four major shells. The interaction employed is the modified Skyrme interaction in which the deformed density is replaced by the band averaged scalar density that makes the Hamiltonian rotationally invariant rendering the spectroscopic calculations feasible. It is shown that the introduction of density dependence spreads out the energy spectra and that the Skyrme variant SIV which has a weak density dependence gives best overall agreement for energy spectra and the available data for the electromagnetic properties of the nuclei studied. It is found that the maximum contribution to the energy of any state in the low lying spectrum comes from thes-state attractive ands-state repulsive parts of the Skyrme interaction. It is also shown that when two-body density dependent version of Skyrme interaction is used, the Koopmans theorem no longer holds.     

DFT Investigations of Aun Nano-Clusters Supported on TiO2 Nanotubes: Structures and Electronic Properties

TiO₂ nanotubes (TiO₂NTs) are beneficial for photogenerated electron separation in photocatalysis. In order to improve the utilization rate of TiO₂NTs in the visible light region, an effective method is to use Au_n cluster deposition-modified TiO₂NTs. It is of great significance to investigate the mechanism of Au_n clusters supported on TiO₂NTs to strengthen its visible-light response. In this work, the structures, electronic properties, Mulliken atomic charge, density of states, band structure, and deformation density of Au_n (n = 1, 8, 13) clusters supported on TiO₂NTs were investigated by DMOL3. Based on published research results, the most stable adsorption configurations of Au_n (n = 1, 8, 13) clusters supported with TiO₂NTs were obtained. The adsorption energy increased as the number of Au adatoms increased linearly. The Au_n clusters supported on TiO₂NTs carry a negative charge. The band gaps of the three most stable structures of each adsorption system decreased compared to TiO₂NTs; the valence top and the conduction bottom of the Fermi level come mainly from the contribution of 5d and 6s-Au. The electronic properties of the 5d and 6s impurity orbitals cause valence widening and band gap narrowing.     

Albatrellus confluens (Alb. & Schwein.) Kotl. & Pouz.: Natural Fungal Compounds and Synthetic Derivatives with In Vitro Anthelmintic Activities and Antiproliferative Effects against Two Human Cancer Cell Lines

Neglected tropical diseases affect the world’s poorest populations with soil-transmitted helminthiasis and schistosomiasis being among the most prevalent ones. Mass drug administration is currently the most important control measure, but the use of the few available drugs is giving rise to increased resistance of the parasites to the drugs. Different approaches are needed to come up with new therapeutic agents against these helminths. Fungi are a source of secondary metabolites, but most fungi remain largely uninvestigated as anthelmintics. In this report, the anthelmintic activity of Albatrellus confluens against Caenorhabditis elegans was investigated using bio-assay guided isolation. Grifolin (1) and neogrifolin (2) were identified as responsible for the anthelmintic activity. Derivatives 4–6 were synthesized to investigate the effect of varying the prenyl chain length on anthelmintic activity. The isolated compounds 1 and 2 and synthetic derivatives 4–6, as well as their educts 7–10, were tested against Schistosoma mansoni (adult and newly transformed schistosomula), Strongyloides ratti, Heligmosomoides polygyrus, Necator americanus, and Ancylostoma ceylanicum. Prenyl-2-orcinol (4) and geranylgeranyl-2-orcinol (6) showed promising activity against newly transformed schistosomula. The compounds 1, 2, 4, 5, and 6 were also screened for antiproliferative or cytotoxic activity against two human cancer lines, viz. prostate adenocarcinoma cells (PC-3) and colorectal adenocarcinoma cells (HT-29). Compound 6 was determined to be the most effective against both cell lines with IC₅₀ values of 16.1 µM in PC-3 prostate cells and 33.7 µM in HT-29 colorectal cells.