Conspectus Polymer brushes are special macromolecular structures with polymer chains densely tethered to another polymer chain (one-dimensional, 1D) or the surface of a planar (two-dimensional, 2D), ...spherical or cylindrical (three-dimensional, 3D) solid via a stable covalent or noncovalent bond linkage. In comparison with the corresponding linear counterpart with similar molecular composition, one-dimension polymer brushes have some fascinating properties including wormlike conformation, compact molecular dimension, and notable chain end effects due to their compact and confined densely grafted structure. The introduction of polymer chains onto the surface of planar and spherical or cylindrical matrix will not only significantly change the surface-related properties of the matrix but also endows the obtained hybrid polymer brushes with new functionalities. Thus, polymer brushes are of great interest in the fields of polymer and material science due to their broad applications, such as catalysis, nanolithography, biomineralization, drug delivery, medical diagnosis, optoelectronics, and so on. Although a variety of 1D, 2D, and 3D polymer brushes have been prepared with the advent of living/controlled polymerization, the development of more efficient and facile synthetic protocols that permit access to polymer brushes with precisely controlled composition, structure, and functionality still represents a key contemporary challenge. In this Account, we summarize our recent efforts on the development of efficient methods to prepare 1D, 2D, and 3D polymer brushes and exploration of their potential applications in drug delivery, antifouling coating, catalysis, and lithium-ion batteries and also highlight related achievements by other groups. First, we briefly introduce the precedent examples of efficient synthesis of polymer brushes with different structures and functionalities by the combination of monomer design with living/controlled polymerization. Given the excellent tolerance and use of the same catalytic system without any mutual interference of ATRP and Cu-catalyzed alkyne–azide cyclization (CuAAC) click reaction, a versatile and efficient platform for precise synthesis of complex asymmetric (Janus-type) 1D polymer brushes was developed on the basis of the “trifunctional monomer” strategy without polymeric functionality transformation. Subsequently, a noncovalent strategy based on crystallization-driven self assembly to prepare well-defined polymer brushes with precise control over their composition and dimensions is described. Notably, the crystallization-driven self assembly can be treated as a living/controlled polymerization of “polymeric monomer” with a special building segment for crystallization, which allows for preparing linear polymer brushes with length as high as tens of micrometers. Moreover, the properties and related applications of polymer brushes as interesting building blocks for constructing hierarchical nanostructures, efficient drug deliver carriers, antifouling films, and lithium-ion batteries are addressed by some typical examples. These advancements in this field will provide a new avenue for obtaining fascinating polymer-brush-based functional materials.
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Acquiring sufficient ground-truth supervision to train deep visual models has been a bottleneck over the years due to the data-hungry nature of deep learning. This is exacerbated in some structured ...prediction tasks, such as semantic segmentation, which require pixel-level annotations. This work addresses weakly supervised semantic segmentation (WSSS), with the goal of bridging the gap between image-level annotations and pixel-level segmentation. To achieve this, we propose, for the first time, a novel group-wise learning framework for WSSS. The framework explicitly encodes semantic dependencies in a group of images to discover rich semantic context for estimating more reliable pseudo ground-truths, which are subsequently employed to train more effective segmentation models. In particular, we solve the group-wise learning within a graph neural network (GNN), wherein input images are represented as graph nodes, and the underlying relations between a pair of images are characterized by graph edges. We then formulate semantic mining as an iterative reasoning process which propagates the common semantics shared by a group of images to enrich node representations. Moreover, in order to prevent the model from paying excessive attention to common semantics, we further propose a graph dropout layer to encourage the graph model to capture more accurate and complete object responses. With the above efforts, our model lays the foundation for more sophisticated and flexible group-wise semantic mining. We conduct comprehensive experiments on the popular PASCAL VOC 2012 and COCO benchmarks, and our model yields state-of-the-art performance. In addition, our model shows promising performance in weakly supervised object localization (WSOL) on the CUB-200-2011 dataset, demonstrating strong generalizability. Our code is available at: https://github.com/Lixy1997/Group-WSSS .
The advancement of automation and Internet of Things technology has bolstered the automation process in the logistics sector. To address the challenge of localizing and generating grasping positions ...for intelligent robots in logistics sorting, this study developed an algorithm for item localization. The algorithm relies on enhanced YOLOv3 target detection and instance segmentation technologies to design a position generation algorithm for the robotic arm, which was further refined using sampling evaluation. The experimental results showed that the research-improved target detection model performed better on different datasets in terms of F1 value, accuracy and Area under the Curve (AUC) metrics, with the highest values of 95.77%, 94.05%, and 91.30%, respectively, which was effective in localizing document-like parcels. Meanwhile, the instance segmentation algorithm with fused features took significantly lower values than other target detection algorithms in terms of average absolute value error and root mean square error. The accuracy rate and all-class average precision value were higher than other target detection models, and the fluctuation of the value taken was smaller, which was suitable for logistics parcel localization. The position generation model, based on a sampling evaluation, yielded significantly different values compared to other algorithms. The relative position error and absolute trajectory error indexes were all below 0.4. The combined indexes of grasping accuracy and error indicate the superior performance of the research-designed algorithms. They can effectively enhance the sorting effects of real logistics scenarios. This research contributes to the improvement of the automated sorting system through the use of visual robotic arm technology. Additionally, it encourages the development of logistics automation and the establishment of intelligent logistics factories.
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Toward the aim of personalized treatment, three-dimensional (3D) printing technology has been widely used in bone tissue engineering owing to its advantage of a fast, precise, and ...controllable fabrication process. Conventional bioceramic scaffolds are mainly used for bone tissue engineering; however, there has been a significant change in the application of bioceramic scaffolds during the past several years. Therefore, this review focuses on 3D-printed bioceramic scaffolds with different compositions and hierarchical structures (macro, micro, and nano scales), and their effects on the mechanical, degradation, permeability, and biological properties. Further, this review highlights 3D-printed bioceramic scaffolds for applications extending from bone tissue regeneration to bone tumor therapy. This review emphasizes recent developments in functional 3D-printed bioceramic scaffolds with the ability to be used for both tumor therapy and bone tissue regeneration. Considering the challenges in bone tumor therapy, these functional bioceramic scaffolds have a great potential in repairing bone defects induced by surgery and kill the possibly residual tumor cells to achieve bone tumor therapy. Finally, a brief perspective regarding future directions in this field was also provided. The review not only gives a summary of the research developments in bioceramic science but also offers a new therapy strategy by extending multifunctions of traditional biomaterials toward a specific disease.
This review outlines the development tendency of 3D-printed bioceramic scaffolds for applications ranging from bone tissue regeneration to bone tumor therapy. Conventional bioceramic scaffolds are mainly used for bone tissue engineering; however, there has been a significant change in the application of bioceramic scaffolds during the past several years. Therefore, this review focuses on 3D-printed bioceramic scaffolds with different compositions and hierarchical structures (macro, micro, and nano scales), and their effects on the mechanical, degradation, permeability, and biological properties. Further, this review highlights 3D-printed bioceramic scaffolds for applications extending from bone tissue regeneration to bone tumor therapy. This review emphasizes recent developments in the functional 3D-printed bioceramic scaffolds with the ability to be used for both bone tumor therapy and bone tissue regeneration.
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Solar energy is considered the most promising energy source for the future. Nanocomposites of TiO2 and CdS (denoted as TiO2/CdS) compose a class of materials with potential application in the ...photocatalysis and photovoltaic industry due to simple compositions, easily controlled microstructures and high extinction coefficients. TiO2/CdS nanocomposites with different microstructures have been designed and prepared over the past 30 years, and their performance for photocatalytic hydrogen production through water splitting and quantum-dot-sensitized solar cells was studied. This paper reviewed recent advances in the TiO2/CdS nanocomposite. The preparation, microstructure and application of the TiO2/CdS nanocomposite powder, TiO2/CdS nanocomposite film, and TiO2/CdS-based multiple nanocomposite and the interfacial charge transfer between TiO2 and CdS were introduced and summarized. Future developments of the TiO2/CdS nanocomposite were also discussed.
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Pressure retarded osmosis (PRO) is a promising technology to produce clean and sustainable osmotic energy from salinity gradient. Fresh water is of scarcity in Singapore; however, alternative sources ...of feed solutions and draw solutions are well explored. For the first time, seawater brine from the TuaSpring desalination plant and wastewater retentate from the NEWater plant were used in a state-of-the-art TFC–PES hollow fiber membrane PRO process. The highest power densities obtained with 1 M NaCl solution and seawater brine were 27.0 W/m2 and 21.1 W/m2 at 20bar, respectively, when deionized (DI) water was used as the feed solution. However, the highest power density dropped to 4.6W/m2 when wastewater retentate was used as the feed solution. Fouling on the porous substrate induced by the wastewater retentate was identified as the main cause of the reduction in the power densities, while the negative effects of seawater brine on the PRO performances were negligible. Both ultrafiltration (UF) and nanofiltration (NF) pretreatment were employed to mitigate fouling from the wastewater retentate, and the power densities were boosted to 6.6W/m2 and 8.9W/m2, respectively, beyond the power density of 5W/m2 proposed by Statkraft for the PRO process to be economical.
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•A power density of 27.0W/m2 can be generated with 1M NaCl solution and DI water.•The power density drops to 4.6W/m2 using seawater brine and wastewater retentate.•Reduction in water flux is mainly caused by fouling from the wastewater retentate.•After UF pretreatment, the power densities is increased to 6.6W/m2.•After NF pretreatment, the power densities is increased to 8.9W/m2.
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•We work on a generalized (2+1)-dimensional dispersive long-wave system.•With the help of symbolic computation, we give rise to four sets of the similarity reductions, each of which leads to a known ...ordinary differential equation.•Our similarity reductions are in respect of the horizontal velocity and the wave elevation above the undisturbed water surface.•All of our results depend on the constant coefficients in the system.
Active researches on the oceanic water waves have been done. As for the nonlinear and dispersive long gravity waves in two horizontal directions on the shallow water of an open sea or a wide channel of finite depth, the paper commented i.e., Chaos Solitons Fract. 138, 109950 (2020) has investigated a generalized (2+1)-dimensional dispersive long-wave system. In respect of the horizontal velocity and the wave elevation above the undisturbed water surface, with the help of symbolic computation, we give rise to four sets of the similarity reductions, each of which leads to a known ordinary differential equation. All of our results depend on the constant coefficients in the original system.
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In this paper, we use a robust inversion algorithm, which we have tested in many regional studies, to obtain the first global model of Curie-point depth (GCDM) from magnetic anomaly inversion based ...on fractal magnetization. Statistically, the oceanic Curie depth mean is smaller than the continental one, but continental Curie depths are almost bimodal, showing shallow Curie points in some old cratons. Oceanic Curie depths show modifications by hydrothermal circulations in young oceanic lithosphere and thermal perturbations in old oceanic lithosphere. Oceanic Curie depths also show strong dependence on the spreading rate along active spreading centers. Curie depths and heat flow are correlated, following optimal theoretical curves of average thermal conductivities K = ~2.0 W(m°C)
for the ocean and K = ~2.5 W(m°C)
for the continent. The calculated heat flow from Curie depths and large-interval gridding of measured heat flow all indicate that the global heat flow average is about 70.0 mW/m
, leading to a global heat loss ranging from ~34.6 to 36.6 TW.
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Asymmetric molecular brushes emerge as a unique class of nanostructured polymers, while their versatile synthesis keeps a challenge for chemists. Here we show the synthesis of well-defined asymmetric ...molecular double-brushes comprising two different side chains linked to the same repeat unit along the backbone by one-pot concurrent atom transfer radical polymerization (ATRP) and Cu-catalyzed azide/alkyne cycloaddition (CuAAC) reaction. The double-brushes are based on a poly(Br-acrylate-alkyne) homopolymer possessing an alkynyl for CuAAC reaction and a 2-bromopropionate initiating group for ATRP in each repeat unit. The versatility of this one-shot approach is demonstrated by CuAAC reaction of alkynyl/poly(ethylene oxide)-N
and ATRP of various monomers. We also show the quantitative conversion of pentafluorophenyl ester groups to amide groups in side chains, allowing for the further fabrication of diverse building blocks. This work provides a versatile platform for facile synthesis of Janus-type double-brushes with structural and functional control, in a minimum number of reactions.Producing well-defined polymer compositions and structures facilitates their use in many different applications. Here the authors show the synthesis of well-defined asymmetric double-brushes by a one-pot concurrent atom transfer radical polymerization and Cu-catalyzed Click reaction.
Hybrid materials integrated with a variety of physical properties, such as spin crossover (SCO) and fluorescence, may show synergetic effects that find applications in many fields. Herein we ...demonstrate a promising post‐synthetic approach to achieve such materials by grafting fluorophores (1‐pyrenecarboxaldehyde and Rhodamine B) on one‐dimensional SCO FeII structures. The resulting hybrid materials display expected one‐step SCO behavior and fluorescent properties, in particular showing a coupling between the transition temperature of SCO and the temperature where the fluorescent intensity reverses. Consequently, synergetic effect between SCO and fluorescence is incorporated into materials despite different fluorophores. This study provides an effective strategy for the design and development of novel magnetic and optical materials.
Two hybrid materials assembled from a 1D spin‐crossover structure and the fluorophores 1‐pyrenecarboxaldehyde and Rhodamine B were prepared. A synergetic effect between spin crossover and fluorescence was proposed.
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