A coupled hydrological and hydrodynamic model for flood simulation

This paper presents a new flood modelling tool developed by coupling a full 2D hydrodynamic model with hydrological models. The coupled model overcomes the main limitations of the individual modelling approaches, i.e. high computational costs associated with the hydrodynamic models and less detailed representation of the underlying physical processes related to the hydrological models. When conducting a simulation using the coupled model, the computational domain (e.g. a catchment) is first divided into hydraulic and hydrological zones. In the hydrological zones that have high ground elevations and relatively homogeneous land cover or topographic features, a conceptual lumped model is applied to obtain runoff/net rainfall, which is then routed by a group of pre-acquired ‘unit hydrographs’ to the zone borders. These translated hydrographs will then be used to drive the full 2D hydrodynamic model to predict flood dynamics at high resolution in the hydraulic zones that are featured with complex topographic settings, including roads, buildings, etc. The new coupled flood model is applied to reproduce a major flood event that occurred in Morpeth, northeast England in September 2008. While producing similar results, the new coupled model is shown to be computationally much more efficient than the full hydrodynamic model

Freeze–Thaw-Induced Gelation of Hyaluronan: Physical Cryostructuration Correlated with Intermolecular Associations and Molecular Conformation

Physically cross-linked hydrogels from hyaluronan (hyaluronic acid, HA) were prepared by a freeze–thaw technique at low pH. The effect of the freezing–thawing of HA solutions on the formation of physical cryogels is typical for the processes of noncovalent cryostructuration that takes the advantages of mild fabrication conditions and the absence of organic solvents and toxically cross-linking agents. The effects of processing steps (freezing time and number of freeze–thaw cycles), HA molecular weight (<i>M</i>_w), and the addition of typical polycarboxylic and polyhydric small molecules such as dicarboxylic acids and polyols on the formation of HA cryotropic hydrogels were investigated. Results verified that long freezing time and repeated freeze–thaw cycles benefited the alignment of polymer chains in the unfrozen liquid microphase, thereby promoting the formation of intermolecular aggregations and dense fibrillar network structures. High <i>M</i>_w of HA endowed the cryogel with strong mechanical strength. The influences of various small molecules on the cryogelation of HA revealed the different intermolecular association patterns in the gel network. Both succinic and glutaric acids participated in HA cryogelation, whereas oxalic, malic, and tartaric acids as well as some polyols (glycol, butanediol, and glycerol) inhibited the cryostructuration of HA. Hydrogen bonding and intermolecular interactions in acidic cryogels and in neutral cryogels obtained by <i>in situ</i> neutralizing the acidic cryogel were discussed at the molecular level in correlation with intermolecular associations and molecular conformation. A gelation mechanism for HA cryogel was proposed. In addition, experimental findings showed that the neutral HA cryogels possessed enhanced thermostability, resistance to acid decomposition, and enzyme degradation which are essentially important properties for biomaterials

Arylations of Substituted Enamides by Aryl Iodides: Regio- and Stereoselective Synthesis of (<i>Z</i>)‑β-Amido-β-Arylacrylates

Arylations of substituted enamides by aryl iodides were achieved for the first time via an unusual PdCl₂(COD)/Ag₃PO₄ catalytic system. A broad range of (<i>Z</i>)-β-amido-β-arylacrylates were prepared regio- and stereoselectively in a highly efficient manner

Seeding Bundlelike MFI Zeolite Mesocrystals: A Dynamic, Nonclassical Crystallization via Epitaxially Anisotropic Growth

Direct synthesis by assembly of precursor nanoparticles is a promising strategy for preparing distinct mesoscopic-structured crystals, especially when high controllability is realized. However, uncertain properties of amorphous precursors and inner complicacy of crystallization mechanisms hamper controllable synthesis of zeolite mesocrystals. Here, we develop a salt-aided seed-induced organic-free method to facilely synthesize anisotropic MFI-type nanorod-bundle zeolite mesocrystals. An epitaxial, anisotropic assembly and crystallization of precursor particles on seed crystals is successfully achieved via a distinctively dynamic, nonclassical process, from relatively disordered to ordered attachment (OA), triggering an enhanced one-dimensional (1D) growth, thus constructing a unique core–shell–shell structure. This work sheds new light on the insights of both zeolite mesocrystal properties and a nonclassical crystallization mechanism. With an understanding of the mechanism, this nonclassical process can be exploited to systematically tune mesocrystal properties and create zeolite materials with novel or enhanced physical and chemical performance

Synthesis of the Putative Structure of (±)-Amarbellisine

The title compound was synthesized mainly by palladium catalytic coupling, cyclopropyl ring-opening rearrangement, epoxidation, Swern oxidation, demethanol reactions, and selective reduction. This synthesis was achieved in 16 steps with 9.7% overall yield. Unfortunately, the published spectroscopic data do not match with those of our synthetic compound

High-Responsivity, High-Detectivity, Ultrafast Topological Insulator Bi₂Se₃/Silicon Heterostructure Broadband Photodetectors

As an exotic state of quantum matter, topological insulators have promising applications in new-generation electronic and optoelectronic devices. The realization of these applications relies critically on the preparation and properties understanding of high-quality topological insulators, which however are mainly fabricated by high-cost methods like molecular beam epitaxy. We here report the successful preparation of high-quality topological insulator Bi₂Se₃/Si heterostructure having an atomically abrupt interface by van der Waals epitaxy growth of Bi₂Se₃ films on Si wafer. A simple, low-cost physical vapor deposition (PVD) method was employed to achieve the growth of the Bi₂Se₃ films. The Bi₂Se₃/Si heterostructure exhibited excellent diode characteristics with a pronounced photoresponse under light illumination. The built-in potential at the Bi₂Se₃/Si interface greatly facilitated the separation and transport of photogenerated carriers, enabling the photodetector to have a high light responsivity of 24.28 A W^–1, a high detectivity of 4.39 × 10¹² Jones (Jones = cm Hz^1/2 W^–1), and a fast response speed of aproximately microseconds. These device parameters represent the highest values for topological insulator-based photodetectors. Additionally, the photodetector possessed broadband detection ranging from ultraviolet to optical telecommunication wavelengths. Given the simple device architecture and compatibility with silicon technology, the topological insulator Bi₂Se₃/Si heterostructure holds great promise for high-performance electronic and optoelectronic applications

Total Synthesis of (+)-Chimonanthine, (+)-Folicanthine, and (−)-Calycanthine

Facile, straightforward, and asymmetric total syntheses of (+)-chimonanthine (<b>1</b>), (+)-folicanthine (<b>2</b>), and (−)-calycanthine (<b>3</b>) were accomplished in four to five steps from commercially available tryptamine. The synthesis features copper-mediated asymmetric cyclodimerization of chiral tryptamine derivative, which established a new entry into constructing the sterically hindered vicinal quaternary stereogenic carbon centers of dimeric hexahydropyrroloindole alkaloids in one procedure. An unprecedented base-induced isomerization from the chimonanthine skeleton to the calycanthine skeleton was observed and facilitated the synthesis of (−)-calycanthine (<b>3</b>)

Copper-Catalyzed Arylation of <i>o</i>-Bromoanilides: Highly Flexible Synthesis of Hexahydropyrroloindole Alkaloids

In the presence of catalytic amount of copper iodide, a remote amide-assisted intramolecular arylation followed by alkylation leads to a general and flexible synthetic method toward the synthesis of medicinally interesting hexahydropyrroloindole alkaloids

Epitaxial Growth of Two-Dimensional MWW Zeolite

Two-dimensional (2D) zeolite, with a high aspect ratio, has more open skeletons and accessible active sites than its three-dimensional (3D) counterpart. However, traditional methods of obtaining 2D zeolites often cause structural damage and widespread skeleton defects, hindering efficient selectivity in molecular separation. In this study, we present, for the first time, a direct epitaxial synthesis of 2D zeolite (Epi-MWW) guided by hexagonal boron nitride (h-BN) with a coincidence matching of site lattices to MWW zeolite. The as-grown Epi-MWW zeolite possesses a high crystallinity and intact hexagonal 2D morphology, with an average thickness of 10 nm and an aspect ratio of over 50. Thanks to its excellent molecular accessibility, the diffusion time constants of o-xylene (OX) and p-xylene (PX) are as 12 and 133 times higher than those of conventional MCM-22, respectively; the PX/OX selectivity of Epi-MWW is 7.4 times better than MCM-22 as calculated by the ideal adsorbed solution theory

Fabrication of Robust Hydrogel Coatings on Polydimethylsiloxane Substrates Using Micropillar Anchor Structures with Chemical Surface Modification

A durable hydrophilic and protein-resistant surface of polydimethylsiloxane (PDMS) based devices is desirable in many biomedical applications such as implantable and microfluidic devices. This paper describes a stable antifouling hydrogel coating on PDMS surfaces. The coating method combines chemical modification and surface microstructure fabrication of PDMS substrates. Three-(trimethoxysilyl)­propyl methacrylates containing CC groups were used to modify PDMS surfaces with micropillar array structures fabricated by a replica molding method. The micropillar structures increase the surface area of PDMS surfaces, which facilitates secure bonding with a hydrogel coating compared to flat PMDS surfaces. The adhesion properties of the hydrogel coating on PDMS substrates were characterized using bending, stretching and water immersion tests. Long-term hydrophilic stability (maintaining a contact angle of 55° for a month) and a low protein adsorption property (35 ng/cm² of adsorbed BSA-FITC) of the hydrogel coated PDMS were demonstrated. This coating method is suitable for PDMS modification with most crosslinkable polymers containing CC groups, which can be useful for improving the anti-biofouling performance of PDMS-based biomedical microdevices