A Multi-Agent Deep Reinforcement Learning-Based Popular Content Distribution Scheme in Vehicular Networks.

The Internet of Vehicles (IoV) enables vehicular data services and applications through vehicle-to-everything (V2X) communications. One of the key services provided by IoV is popular content distribution (PCD), which aims to quickly deliver popular content that most vehicles request. However, it is challenging for vehicles to receive the complete popular content from roadside units (RSUs) due to their mobility and the RSUs' constrained coverage. The collaboration of vehicles via vehicle-to-vehicle (V2V) communications is an effective solution to assist more vehicles to obtain the entire popular content at a lower time cost. To this end, we propose a multi-agent deep reinforcement learning (MADRL)-based popular content distribution scheme in vehicular networks, where each vehicle deploys an MADRL agent that learns to choose the appropriate data transmission policy. To reduce the complexity of the MADRL-based algorithm, a vehicle clustering algorithm based on spectral clustering is provided to divide all vehicles in the V2V phase into groups, so that only vehicles within the same group exchange data. Then the multi-agent proximal policy optimization (MAPPO) algorithm is used to train the agent. We introduce the self-attention mechanism when constructing the neural network for the MADRL to help the agent accurately represent the environment and make decisions. Furthermore, the invalid action masking technique is utilized to prevent the agent from taking invalid actions, accelerating the training process of the agent. Finally, experimental results are shown and a comprehensive comparison is provided, which demonstrates that our MADRL-PCD scheme outperforms both the coalition game-based scheme and the greedy strategy-based scheme, achieving a higher PCD efficiency and a lower transmission delay.

CuS NP-based nanocomposite with photothermal and augmented-photodynamic activity for magnetic resonance imaging-guided tumor synergistic therapy.

Although many treatments have been developed for oncotherapy, the lack of effective imaging guidance in the therapeutic process is still an urgent problem to be solved. In this study, magnetic resonance contrast agent (Gd) chelated on CuS nanoparticles and glucose oxidase (GOx) were coloaded into mesoporous silica nanoparticles (MSNs) to form GOx-Gd-CuS@MSNs, in which the Gd provided magnetic resonance imaging (MRI) for therapeutic process monitor while GOx could catalyze the generation of H2O2 to enhance the photodynamic therapy (PDT). The in vitro results show that under near-infrared (NIR) laser irradiation (2 W·cm-2, 5 min), temperature rapidly increased by approximately 30 °C for the accumulation of heat. At the same time, GOx on GOx-Gd-CuS@MSNs effectively consumed glucose to produce a large amount of H2O2, which was used to augment PDT through producing highly toxic hydroxyl radicals (·OH) and singlet oxygen (1O2). The photothermal and augmented-photodynamic could induce apoptosis and death of tumor cells. More importantly, the study found that GOx-Gd-CuS@MSNs had MRI performance, which provided imaging guidance during the treatment process, and it can monitor the diffusion of water molecules in the tumor tissue during the treatment and microcirculation perfusion of capillary network. These results indicate that the nanomaterial produced significant synergistic therapeutic effects through photothermal and photodynamic forces, meanwhile showed excellent spatial resolution and deep tissue penetration in imaging.

Construction of oxygen vacancy mediated direct Z scheme Bi2WO6/SrTiO3 hybrid on cellulose fibers for high-performance and recyclable photocatalytic paper.

The O-vacancy Bi2WO6/SrTiO3 heterojunction photocatalyst with Z scheme photogenerated electron transfer mechanism was loaded on cellulose fibers to construct a visible light-responsive photocatalytic composite paper for efficient and recyclable degradation of organic dyes in water. The introduction of O vacancies in Bi2WO6 by alkali etching increased the utilization rate of Bi2WO6 for visible light and achieved effective regulation of the energy band structure and Fermi level, which transformed Bi2WO6/SrTiO3 type-II heterojunction into Z scheme heterojunction. The light-excited electrons in the conduction band of O-vacancy Bi2WO6 directly migrated to the valence band of SrTiO3, which improved the separation efficiency of photogenerated carriers and maximized the redox capability of semiconductors. Compared with other control papers, O-vacancy Bi2WO6/SrTiO3 paper exhibited the best photocatalytic performance, and its degradation rate for rhodamine B could reach 71.1% under 100 min of Xe lamp irradiation. The O-vacancy Bi2WO6/SrTiO3 paper also showed good photocatalytic cycle stability. Loading heterojunction on the cellulose fibers solved the problem of poor reusability and difficult in recovery for powder semiconductor photocatalyst in practical applications. This study provides a novel strategy for constructing Z scheme heterogeneity on cellulose fibers to prepare composite paper with high photocatalytic activity and good reusability.

Surface Functionalization of Graphene Oxide with Hyperbranched Polyamide-Amine and Microcrystalline Cellulose for Efficient Adsorption of Heavy Metal Ions.

Graphene oxide (GO)-based adsorbents have received attention in the removal of heavy metal ions in wastewater due to its large specific surface area and oxygen-containing functional groups, which can enhance the interaction between GO and heavy metal ions. Many researchers are seeking economical and effective strategies to further improve the adsorption capacity of GO. In this study, hyperbranched polymers and cellulose were used to surface functionalize GO for the efficient adsorption of heavy metal ions. First, hyperbranched polyamide-amine (HPAMAM) functionalized GO was fabricated by the formation of an amide bond between the carboxyl group of GO and the amino group of HPAMAM, increasing the active groups on the GO surface and enhancing the affinity with heavy metal ions. Then, dialdehyde cellulose (DAC) obtained through the oxidation of microcrystalline cellulose was grafted onto GO/HPAMAM by forming a Schiff-based structure between the amino group of HPAMAM and aldehyde group of DAC. Interestingly, DAC formed micro/nano bumps on GO, which was beneficial to increase the hydroxyl number and contact area with heavy metal ions. The Fourier-transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), thermogravimetric analysis (TGA), and scanning electron microscopy (SEM) results confirmed the successful synthesis of GO/HPAMAM/DAC. The obtained GO/HPAMAM/DAC adsorbent exhibited strong adsorption capacity and good cycle stability for heavy metal ions. The maximum adsorption capacities of Pb(II), Cd(II), and Cu(II) were 680.3, 418.4, and 280.1 mg/g at 298 K, which were better than those of most adsorbents reported. A pseudo-second-order kinetic model could well-describe the Pb(II), Cd(II), and Cu(II) adsorption onto GO/HPAMAM/DAC, and the equilibrium data fitted well with the Langmuir isotherm model. The adsorption of Pb(II), Cd(II), and Cu(II) was mainly attributed to the chelation or complexation of nitrogen- and oxygen-containing groups on the GO/HAPAMAM/DAC adsorbent. This study may provide a novel strategy for improving the adsorption performance of GO with hyperbranched polymers and cellulose.

Application of Multiparametric Magnetic Resonance Imaging to Monitor the Early Antitumor Effect of CuS@GOD Nanoparticles in a 4 T1 Breast Cancer Xenograft Model.

BACKGROUND: We have developed hybrid nanoparticles (NPs) by co-loading copper sulfide (CuS) NPs and glucose oxidase (GOD) (CuS@GOD NPs) to explore their antitumor properties. PURPOSE: To investigate the feasibility of using multiparametric magnetic resonance imaging (MRI) including intravoxel incoherent motion diffusion-weighted imaging (IVIM-DWI) and R2 * mapping to quantitatively assess the early antitumor effect of CuS@GOD NPs. STUDY TYPE: Prospective. ANIMAL MODEL: The orthotopic BALB/c mice 4 T1 breast cancer model. The 4 T1 xenografts in group 1 mice received normal saline, group 2 received CuS@GOD NPs, group 3 received CuS NPs plus laser, and group 4 received CuS@GOD NPs plus laser (n = 28 for each group). FIELD STRENGTH/SEQUENCE: A 3.0 T/IVIM-DWI MRI single-shot echo-planar imaging, R2 * mapping spoiled gradient recalled echo (SPGR) sequence, T2-weighted images (T2WI) and T1-weighted images (T1WI) fast spin echo (FSE) sequence. ASSESSMENT: The IVIM-DWI and R2 * mapping were performed before and after treatment at 0 hour, 0.5 hour, 1 hour, 2 hours, 4 hours, and 24 hours in four groups and the MRI parameters were obtained. Correlation analysis between the MRI parameters and histological analyses was conducted. STATISTICAL TESTS: One-way ANOVA, Pearson's correlation analysis, two independent samples t test, intraclass correlation coefficient. P < 0.05 was considered to be statistically significant. RESULTS: In group 4, the tumoral D value was significantly higher than that of group 2 at 24 hours (0.541 ± 0.065 vs. 0.492 ± 0.051). The f value of group 4 was significantly lower than that of groups 1 and 2 at 2 hours (10.83 ± 2.16 vs. 14.28 ± 1.86, 16.67 ± 3.53, respectively). The R2 * value was significantly increased at 0 hour in group 4 compared to that of groups 1 and 2 (64.552 ± 4.663 vs. 42.441 ± 1.516, 43.165 ± 1.709, respectively). D, f, and R2 * were correlated with the histological staining results (r = 0.695-0.970). DATA CONCLUSION: The IVIM-DWI-derived D and f and R2 * mapping-derived R2 * could monitor early response to CuS@GOD NPs treatment in vivo. EVIDENCE LEVEL: 2 TECHNICAL EFFICACY: Stage 2.

Anti-hypertensive and cardioprotective activities of traditional Chinese medicine-derived polysaccharides: A review.

Cardiovascular diseases (CVDs), a leading cause of death in modern society, have become a major public health issue globally. Although numerous approaches have been proposed to reduce morbidity and mortality, the pursuit of pharmaceuticals with more preventive and/or therapeutic value remains a focus of attention. Being a vast treasure trove of natural drug molecules, Traditional Chinese Medicine (TCM) has a long history of clinical use in the prophylaxis and remedy of CVDs. Increasing lines of preclinical evidence have demonstrated the effectiveness of TCM-derived polysaccharides on hindering the progression of CVDs, e.g. hypertension, myocardial infarction. However, to the best of our knowledge, there are few reviews on the application of TCM-derived polysaccharides in combating CVDs. Hence, we provide an overview of primary literature on the anti-hypertensive and cardioprotective activities of herbal polysaccharides. Additionally, we also discuss the current limitations and propose a new hypothesis about how polysaccharides exert cardiovascular effects based on the metabolism of polysaccharides.

Regenerated Cellulose Films with Amino-Terminated Hyperbranched Polyamic Anchored Nanosilver for Active Food Packaging.

The nanosilver-based antibacterial composite film used as food packaging has a potential hazard of silver leakage into the human body. In this study, hyperbranched polyamide-amine (HPAMAM) was used as a template, reducing agent, and stabilizer to synthesize Ag nanoparticles (Ag NPs) in situ, and then HPAMAM anchored Ag NPs onto oxidized cellulose to construct a regenerated cellulose film with a low silver leakage for antibacterial food packaging. Alkali hydroxide/urea solution was used to dissolve cotton fibers, and the hydroxyl groups at C-2 and C-3 of the glucose residues were oxidized to two aldehyde groups by NaIO4. Then, HPAMAM/Ag NPs composites (Ag@HPAMAM NPs) were grafted on the oxidized cellulose by the reaction between aldehyde groups and amino groups. The Ag@HPAMAM NPs-embedded cellulose films were achieved by regenerating the dissolved cellulose with ethanol and drying naturally. With a low silver leakage (<10%), Ag@HPAMAM NPs-embedded cellulose films exhibited a strong antibacterial effect on Escherichia coli and Staphylococcus aureus and effectively extended the storage life of cherry tomatoes as food packaging. In addition, the physical properties of Ag@HPAMAM NPs-embedded cellulose films were improved due to the anchor of Ag NPs onto oxidized cellulose by HPAMAM. This study provides a strategy for synthesizing Ag@HPAMAM NPs-embedded cellulose film, which has the potential to be used as a biodegradable, renewable, and safe antibacterial food package material.

Quaternized chitosan-stabilized copper sulfide nanoparticles for cancer therapy.

In this study, we report a smart and green strategy to synthesize copper sulfide nanoparticles (CuS-NPs) for clinically translatable cancer treatment. For the first time, the preparation of CuS-NPs was developed by taking advantage of the copper-amine complex as the copper source and sodium sulfide as the sulfide source, in which the quaternized chitosan (QCS) was used as a biotemplate and stabilizing agent. The obtained QCS/CuS-NPs composites (CuS@QCS-NPs) were spherical and stable with an average diameter of 5.6 nm, and showed strong NIR absorbance for photothermal conversion. Moreover, in vitro and in vivo cancer theranostic capability of CuS@QCS-NPs without any biomodification was evaluated. The result reveals that after intratumoral (i.t.) injection of CuS@QCS-NPs with NIR laser irradiation (808 nm, 1.5 W/cm2, 5 min), the 4T1 mammary tumor growth could be effectively suppressed comparing with the other control groups, and there was no obvious lethal toxicity to liver function, kidney function, and vital organs. Such QCS-stabilized CuS-NPs may provide an alternative for clinical application of CuS-based photothermal therapy.

Novel chitosan films with laponite immobilized Ag nanoparticles for active food packaging.

Silver nanoparticles (AgNPs) are a kind of excellent antimicrobial agent, but the application is limited in food field due to easy leakage. In this work, for the first time, laponite immobilized silver nanoparticles (LAP@AgNPs) were synthesized with quaternized chitosan as green reductant, in which AgNPs were embedded in the interlayer of laponite due to confinement effect. Subsequently, chitosan-based films with LAP@AgNPs were prepared for keeping litchis fresh. The results show that only about 5.6% of AgNPs were released from the films with laponite, which were much lower than those films without laponite (about 29.1%), and physicochemical properties of the films were improved due to the suitable addition of laponite. Furthermore, although the films showed very low toxicity to cells, they exhibited good antimicrobial activity and effectively extended the storage life of litchi as a packaging. Hence, the research provides the potential application for silver nanoparticles in food field.

Biopolymer as Stabilizer and Adhesive To in Situ Precipitate CuS Nanocrystals on Cellulose Nanofibers for Preparing Multifunctional Composite Papers.

In order to solve the uneven distribution of copper sulfide nanocrystals (CuS-NCs) on cellulose nanofibers (CNFs), this work reports a feasible method to in situ precipitate CuS-NCs on CNF by utilizing biopolymers (lignin, xylan, or starch) as stabilizer and adhesive for fabricating the multifunctional composite papers. In the presence of biopolymers, CuS-NCs deposited in situ on CNF could be capped and stabilized by the biopolymers molecular chains for uniform distribution. Subsequently, biopolymers could anchor CuS-NCs on CNF by the hydrogen bonding. Compared to the composite paper with lignin or xylan as stabilizer and adhesive, CuS-NCs/starch/CNF paper showed the highest content and most uniform and continuous distribution of CuS-NCs, which not only enhanced the conductivity of composite paper to 10.12 S/cm but also increased the reaction rate constant on photocatalytic degradation of rhodamine B to 0.317 min-1. The reaction rate constant is higher than most of the other reported CuS photocatalysts to date. It indicates that our method has a potential to be a novel strategy to precipitate nanocrystals uniformly on cellulose fibers for fabricating the multifunctional composite paper.

A Probabilistic Analysis of Sparse Coded Feature Pooling and Its Application for Image Retrieval.

Feature coding and pooling as a key component of image retrieval have been widely studied over the past several years. Recently sparse coding with max-pooling is regarded as the state-of-the-art for image classification. However there is no comprehensive study concerning the application of sparse coding for image retrieval. In this paper, we first analyze the effects of different sampling strategies for image retrieval, then we discuss feature pooling strategies on image retrieval performance with a probabilistic explanation in the context of sparse coding framework, and propose a modified sum pooling procedure which can improve the retrieval accuracy significantly. Further we apply sparse coding method to aggregate multiple types of features for large-scale image retrieval. Extensive experiments on commonly-used evaluation datasets demonstrate that our final compact image representation improves the retrieval accuracy significantly.

Starch/rosin complexes for improving the interaction of mineral filler particles with cellulosic fibers.

On the basis of inclusion complex formation of starch with small guest molecules, the concept of filler modification for papermaking by calcium-ion-induced deposition of starch/rosin complexes in the presence of filer particles was demonstrated. The rosin amount of 3% (on the basis of the dry weight of starch) induced effective starch deposition. Due to the cellulose-bondable nature of starch/rosin complexes, filler modification resulted in improved interaction of precipitated calcium carbonate particles with cellulosic fibers, leading to reduced negative impact of filler addition on paper strength. The efficiency of alkyl ketene dimer emulsion as an internal sizing agent for cellulosic paper was also improved as a result of filler modification. The concept demonstrated in this study may provide a useful alternative to the improvement of the use of mineral fillers in the paper industry.

Filler modification for papermaking with starch/oleic acid complexes with the aid of calcium ions.

To mitigate the negative effect of filler addition on paper strength and improve filler retention, filler modification with hydrogen bonding polymers (e.g., starch) or their composites is an interesting research topic. Differing from previous reports, the concept related to the deposition of starch/oleic acid complexes on precipitated calcium carbonate (PCC) with the aid of calcium ions was demonstrated. The introduction of calcium ions resulted in effective starch deposition. As a result of filler modification, filler retention and the tensile strength of the filled paper were simultaneously improved essentially due to the aggregation of PCC particles in filler modification process as well as improved filler bondability. The concept demonstrated in this brief study may provide an alternative approach to filler bondability enhancement for improved papermaking performances.