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We demonstrate a pulsed Er-doped ZBLAN fiber laser operating at 3.75 μm based on the gain-switching scheme. A diffraction grating is introduced as a wavelength selection component to enable stable lasing in this long-wavelength region that deviates from the emission peak of 4F9/2→4I9/2 transition in Er3+. Different from the conventional gain-switching behavior where the pulse repetition frequency of the output laser is same as the that of the pump, the gain-switched laser demonstrated here shows a variable pulse repetition frequency, which accounts for 1/n (n = 4, 3, 2) of the pump pulse repetition frequency, in response to the 1950 nm pump power. The output pulse characteristics, including average output power, repetition frequency, pulse duration, and peak power, are investigated in detail. Over 200 mW average output power at 3.75 μm was obtained at 12 W of 1950 nm pump power. This work demonstrates that the Er-doped ZBLAN fiber laser, in combination with gain-switched scheme, is a feasible and promising approach to generate powerful pulsed emission > 3.7 μm. [ABSTRACT FROM AUTHOR]

With the deployment of the fifth generation (5G) in many countries, people start to think about what the next-generation of wireless communications will be. The current communication technologies are already approaching the Shannon physical capacity limit with advanced encoding (decoding) and modulation techniques. On the other hand, artificial intelligence (AI) plays an increasingly important role in the evolution from traditional communication technologies to the future. Semantic communication is one of the emerging communication paradigms, which works based on its innovative “semantic-meaning passing” concept. The core of semantic communication is to extract the “meanings” of sent information at a transmitter, and with the help of a matched knowledge base (KB) between a transmitter and a receiver, the semantic information can be “interpreted” successfully at a receiver. Therefore, semantic communication essentially is a communication scheme based largely on AI. In this article, an overview of the latest deep learning (DL) and end-to-end (E2E) communication based semantic communications will be given and open issues that need to be tackled will be discussed explicitly. [ABSTRACT FROM AUTHOR]

Growing computation requirements in emerging intelligently connected vehicle (ICV) networks has posed a big challenge for vehicles to process computation-intensive tasks on-board, and thus computation partition and offloading plays a critical role. Owing to broadcast nature of wireless channels, confidential messages without proper security protection in ICVs may be easily exposed to malicious users. In this paper, a mobile crowdsourcing (MCS) based mobile crowd computing framework for ICV networks is proposed, where multiple vehicles act as workers to provide computing services for end user (EU). In particular, artificial noise (AN) assisted physical (PHY) layer security approaches are used to enhance the security in offloading links. Ergodic secrecy rates in different offloading phases in time-varying channels are derived. In addition, an incentive-driven mechanism is introduced to encourage workers to share their idle computing resources, and an optimization problem is formulated to minimize the overall price paid for computing tasks, subject to energy consumption and delay constraints. Finally, Monte Carlo simulations verify the analysis on the ergodic secrecy rates. [ABSTRACT FROM AUTHOR]

Vehicle-to-vehicle (V2V) underlay cellular communication plays an important role in the fifth-generation (5G) and beyond communications and its security issues attract a lot of attention. Physical layer security, which explores channel characteristics to protect wireless communications, is very attractive due to its low latency. This paper focuses on secrecy capacity maximization in V2V underlay cellular communications, where the secrecy capacity of vehicular user equipments (VUEs) is optimized first, followed by sum proportional fairness function optimization for both VUEs and cellular user equipments (CUEs). The optimization problems can be solved in two sub-problems, e.g., power and subcarrier allocation problems. The power allocation can be done with the first strategy using a one-dimensional searching algorithm, whereas a genetic algorithm (GA) is used to solve the second optimization problem. In addition, as VUEs share uplink resources with CUEs, the co-channel interference exists and the subcarrier allocation sub-problem is a 3D search problem, which is solved by a two-step iterative Hungarian algorithm (IHA). Finally, simulations are performed to validate the performance of the proposed schemes. [ABSTRACT FROM AUTHOR]

This article aims to provide a comprehensive overview on PHY layer security assisted ICV networks. Beginning with a discussion from a general perspective of the ICV network architecture, this work summarizes the major security threats faced by ICV networks. To achieve confidential data transmission with a low latency and a high data rate, several physical layer security schemes are surveyed in this article, which include RRM, cooperative jamming, multi-antenna technologies, and PHY-layer key generation. In addition, the performances of the aforementioned schemes are compared in terms of different aspects, followed by a discussion on some major challenges that need to be tackled in the implementation of ICV networks. [ABSTRACT FROM AUTHOR]

Advanced oxidation processes based on persulfate activation can produce strong reactive oxygen species, which can effectively degrade a variety of organic pollutants. However, finding cost-effective activation methods and materials have become the key in the research process of this oxidation technology. With the discovery of the catalytic activity of biochar, the application of carbonaceous materials in persulfate activation has recently emerged. In this study, recyclable magnetic biochar was prepared from dewatered piggery sludge, and was used to activate peroxymonosulfate to degrade antibiotic tetracycline. Results showed that the catalytic activity of magnetic biochar was stronger than that of unmagnetized sludge biochar, and magnetic biochar showed better separation and sustainability in recovery and reuse. Neutral pH condition was also favorable for biochar and magnetic biochar to activate peroxymonosulfate. Peroxymonosulfate activation using magnetic biochar is an economical, efficient and environmentally friendly method for organic pollutants degradation. [Display omitted] • The catalyst with high efficiency and low cost was prepared by Fe 3 O 4 modification. • Magnetic biochar showed a high activity for the activation of peroxymonosulfate. • Reveal the mechanism of tetracycline degradation catalyzed by magnetic biochar. • Valuable utilization of agricultural waste piggery sludge was proposed. [ABSTRACT FROM AUTHOR]

Our previous study showed that emodin enema modulates gut microbiota and delays CKD progression. However, the poor solubility, limited colonic irrigation retention time, and inadequate colon adhesion of emodin hinder its clinical application. Based on the deficiencies of emodin, we prepared monomethoxy-poly (ethylene glycol)-poly (lactic acid)-chitosan-2-mercaptobenzimidazole nanoparticles with incorporated emodin (emodin-NP) and studied their efficacy in delaying CKD progression. 5/6 nephrectomized Male Sprague Dawley rats were administered via colonic irrigation with emodin-NP every two days for eight weeks. We found that treatment with emodin-NP improved the kidney function of the rats and limited the expansion of tubulointerstitial fibrosis. Treatment with emodin-NP once every two days is comparable to emodin treatment once a day. Furthermore, emodin-NP via colonic irrigation remarkably reduced IL-1β, IL-6, and LPS levels in serum, improved intestinal barrier functions, and downregulated the key proteins (TLR4, MyD88, and NF-κB) expression in intestinal TLR4 signaling pathway. 16S rDNA analyses showed that emodin-NP can regulate microbiota disturbance in CKD. Taken together, these results suggest that emodin-NP alleviates kidney dysfunction and tubulointerstitial fibrosis by mediation through the modification of gut microbiota disorders. Emodin-NP may be a new method to treat CKD. [ABSTRACT FROM AUTHOR]

Zeolite-Mg/Fe chloride dual enhanced coagulation is a cost-effective method for advanced treatment of swine wastewater, but the sludge generated after the enhanced coagulation remains to be a problem. In this study, the precipitate from a swine wastewater coagulation unit was regenerated by pyrolysis treatment in an O 2 -limited environment to develop a high efficient adsorbent (biochar-mineral composite, BMC) for the removal of Pb(II) from wastewater. SEM images indicate that complex Mg/Fe oxides and sludge biochar gathered around zeolite particles. Effects of different influencing factors such as Pb(II) initial concentration, pH, adsorption time and ion concentration on the adsorption performance were investigated. The results show that the Langmuir isotherm model can better express the adsorption of Pb(II) on BMC than Freundlich model and Temkin model. BMC pyrolyzed at 500 °C showed the maximum adsorption capacity of 450.58 mg/g under experimental condition of 25 °C, 100 mg/L Pb(II) initial concentration and the initial pH of 5.6. The adsorption mechanisms on BMC mainly include ion exchange, electrostatic interaction. Therefore, it is a cost-effective and environmental-friendly strategy to obtain biochar-mineral composite from recycled sludge, which can efficiently remove Pb(II) from wastewater. • Recycled BMC adsorbent derived from a swine wastewater enhanced coagulation unit. • Pb(II) removal via ion exchange, electrostatic interaction, & physical adsorption. • Pseudo-second-order kinetic adsorption model fit kinetic adsorption process of BMC. • Increased Na+ concentration weakened Pb(II) adsorption by BMC. [ABSTRACT FROM AUTHOR]

Aberrant expression of microRNAs (miRNAs) has been widely recognized to play critical roles in the pathogenic processes of colon cancer. However, the expression and functions of miR-3653 in colon cancer remain uncovered. This study revealed for the first time that miR-3653 expression was significantly decreased in colon cancer tissues and cell lines. MiR-3653 overexpression led to decreased migration and invasion of HCT116 cells while miR-3653 knockdown resulted in opposite influence of the metastatic behaviors of HT29 cells. qRT-PCR and western blot demonstrated that miR-3653 suppressed the epithelial-mesenchymal transition (EMT) of colon cancer cells using both gain- and loss- of function assay. Mechanically, miR-3653 was found to interact with the 3′-UTR of Zeb2 through the complementary sequences and inhibited the expression of Zeb2 in colon cancer cells. Rescue experiments demonstrated that the inhibitory effect of miR-3653 overexpression on cell metastasis and EMT was abrogated by forced expression of Zeb2. This study demonstrates that miR-3653 suppresses the metastasis and EMT of colon cells by targeting Zeb2, and serves as a promising biomarker and therapeutic target in colon cancer. [ABSTRACT FROM AUTHOR]

Nanoplastics (NPs) nano-scale effects and have strong mobility, posing potential risks to ecosystems and human health. Therefore, it is of great significance to study the interactions of minerals and NPs in water to understand the migration, transformation, and fate of NPs in the environment. This study investigated the flocculation of NPs on layered double hydroxides (LDHs) in water via heteroaggregation under various conditions such as different Mg/Al ratios of LDHs, calcination temperatures, coexisting ions, solution pH, and contact time. We found that the overall reaction achieved high efficiency that almost surpassed 70% and varied with solution pH. The highest flocculation performance (85.87%) was achieved at a Mg:Al ratio of 3:1, followed by 4:1 and 2:1. Moreover, the highest removal rate (80.85%) of NPs on cLDHs was achieved at calcination temperature of 300 °C. The heteroaggregation mechanism, bonding type, and interface reaction of the NPs–LDHs system were analyzed using the Derjaguin–Landau–Verwey–Overbeek (DLVO) theory, spectroscopy, and microscopy. At short separation distance within 5 nm, the total interaction energy was governed by electrostatic repulsion. However, at longer distance, the interparticle forces became dominated by van der Waals and electrostatic attractions, leading to attachment of two types of particles. The NPs could be removed by attachment onto the surface of LDHs without forming other functional groups. However, the calcined LDHs and those prepared by hydrothermal reactions showed different attachment morphologies under scanning electron microscopy, which revealed the mechanisms of surface attachment and encased precipitation. These results provided new insights and theoretical support for controlling NPs pollution in surface water, which could reduce the risks of NPs to ecosystems and human health. [Display omitted] • The settling efficiency of NPs with Mg/Al LDHs surpassed 80%. • NPs tended to attach to the surface of Mg/Al LDHs and settled down. • The maximum removal rate was achieved for 10 mg/L NPs on 0.5 g/L Mg/Al LDHs. • Electrostatic and van der Waals forces are the main interaction mechanisms. • This study provided a new insight for controlling NPs pollution in surface water. [ABSTRACT FROM AUTHOR]

Non-free radical photocatalysis with metal oxide catalysts is an important advanced oxidation process that enables the removal of various emerging environmental pollutants, such as tetracycline. Here, four hexagonal La 2 O 3 photocatalysts with different densities of oxygen vacancy and crystalline features are synthesized and then further treated by ball milling. Ball milling of these La 2 O 3 photocatalysts is found to increase the amount of oxygen vacancies on their surfaces and thereby the amount of 1 O 2 species produced by them. The photocatalytic degradation of TC by these La 2 O 3 photocatalysts depends on the oxygen vacancies present on them. Furthermore, the ones with a strong (101) diffraction peak remove tetracycline from water systems largely with 1 O 2 and • OH species, whereas those with a weak (101) diffraction peak do so mainly via 1 O 2 and direct electron transfer (DET) process. Their overall catalytic properties are also studied by density functional theory calculations. Moreover, the organic products produced from tetracycline by La 2 O 3 photocatalysts containing a strong (101) diffraction peak are found to be less toxic than those produced by La 2 O 3 photocatalysts containing a weak (101) diffraction peak. This study also provides convincing evidence that the structures of La 2 O 3 determine the species that is produced by it and that end up mediating photocatalytic reaction pathways (i.e., free radical versus non-free radical) to degrade an emerging environment pollutant.

We demonstrate a widely tunable single-frequency Er-doped ZBLAN fiber laser operating on a 4 F 9/2 → 4 I 9/2 transition band. An uncoated germanium (Ge) plate serves as a narrow-bandwidth etalon and is inserted in the cavity to achieve a single longitudinal mode selection. Wavelength tuning from 3373.8 nm to 3718.5 nm was demonstrated by using a blazed diffraction grating at 3.5 µm. At the emission peak of 3465.6 nm, the laser yields over 100 mW single-frequency output power, with a 3 dB linewidth <6.9 MHz, and a slope efficiency (with respect to the incident 1990 nm pump power) of 20.3%. Such a tunable mid-infrared single-frequency fiber laser may serve as a versatile laser source in spectroscopy and sensing applications.