Pulse broadening factor as a criterion to assess nonlinear penalty of 40-Gbit/s RZ-DQPSK signals in dynamic transparent optical networks

The real-time scheduling and routing in dynamic transparent optical networks requires fast and accurate evaluation of transmission penalty caused by nonlinear kerr effects with different dispersion maps. However, the conventional method using nonlinear phase shift can only be applied to assess the nonlinear penalty with optimized dispersion maps. In this paper, we introduce pulse broadening factor into the approach and propose a novel method to accurately evaluate nonlinear penalty and numerically investigate the feasibility of our novel method in 40-Gb/s Return-to-Zero Differential Quadrature Phase-Shift Keying (RZ-DQPSK) systems. Simulation results show that our approach can achieve good evaluation performance even with non-optimized dispersion maps.     

全正色散非线性放大环形镜保偏掺镱光纤激光器

基于非线性放大环形镜,设计了一种全正色散掺镱光纤锁模激光器。在抽运功率为80 mW的情况下,该掺镱光纤锁模激光器可以实现平均功率为7.8 mW的稳定输出。输出激光脉冲的重复频率为9.9 MHz,中心波长为1064 nm,脉冲宽度约为18 ps,相应的光谱宽度为0.18 nm。该激光器具有结构简单、自启动、稳定性高的优点。     

A study on tunable spectral frequency shift method with low phase noise

Based on the theory of dispersion characteristics of double-ring photoelectric oscillator and chirped grating, a broadband ultra-low phase noise spectral frequency shift system is constructed. Firstly, the mathematical model is discussed. Secondly, according to the frequency response of the photonic filter formed by the chirped grating interfering with the optoelectronic oscillation circuit, the simulation of the effect of grating dispersion on oscillation frequency is performed. The simulation results show that the oscillation frequency decreases with the increase of grating dispersion value. In the range of 350—4 000 ps/nm, the oscillation frequency varies from 5 GHz to 16.9 GHz, and the phase noise can reach ?140.5 dBc/Hz at 10 kHz, which realizes the generation of ultra-low phase noise spectral shift with broadband tuning.     

Hollow Multishelled Structure of Heterogeneous Co3O4–CeO2−x Nanocomposite for CO Catalytic Oxidation

Herein, hollow multishelled structure (HoMS) of Co₃O₄–CeO_2?x nanocomposites with controllable molar ratio of Co and Ce elements is synthesized by a general strategy sequential templating approach (STA) with a facile and efficient electrostatic spray process. As a catalyst of carbon monoxide (CO) catalytic oxidation, Co₃O₄–CeO_2?x (Co/Ce = 4/1) HoMS achieves good catalytic activity (complete conversion temperature is 166.9 °C) and stability (100 h). This performance is attributed to synergistic effects between the two components. The combination of Co₃O₄ and CeO₂ not only generates more interfaces of Co₃O₄–CeO_2?x, which is more favorable for the activation of oxygen, but also improves the oxidizability of Co₃O₄ as well as the capacity of oxygen storage of CeO₂. In addition, the relatively larger effective specific surface area of the HoMS can provide more active sites, while the unique structure of HoMS can facilitate gas diffusion and maintain structural stability.     

Ångstrom‐Scale Silver Particles as a Promising Agent for Low‐Toxicity Broad‐Spectrum Potent Anticancer Therapy

Cancer incidence is rising, and the efficacy of current available anticancer agents is limited by severe dose‐limiting toxicities and drug resistance problems. Nanoparticles are heralded as the next frontier in cancer treatment. Here, a pure physical method is used to efficiently fabricate very small silver particles even approaching the Ångstrom (Ång) dimension. Fructose is used as a dispersant and stabilizer to coat the Ång‐scale silver particles (AgÅPs). Functional and mechanistic studies demonstrate that fructose‐coated AgÅPs (F‐AgÅPs) can enter and accumulate in multiple cultured cancer cell lines to induce apoptotic death, whereas most normal cells are resistant to the efficacious dose of F‐AgÅPs; in vivo, intravenous administration of F‐AgÅPs potently inhibits the growth of pancreatic and lung cancer xenografts in nude mice, without inducing notable toxic effects on the healthy tissues. The results suggest the promising potential of F‐AgÅPs as a potent, safe, and broad‐spectrum agent for the cancer treatment.     

A Marine‐Inspired Hybrid Sponge for Highly Efficient Uranium Extraction from Seawater

Marine sponges are used as biomonitors of heavy metals contamination in coastal environment as they process large amounts of water and have a high capacity for accumulating heavy metals. Here, inspired by the unique physical and physiological features of marine sponges, a surface engineered synthetic sponge for the highly efficient harvesting of uranium from natural seawater is developed. An ultrathin poly(imide dioxime) (PIDO)/alginate (Alg) interpenetrating polymer network hydrogel layer is uniformly wrapped around the skeleton of a melamine sponge (MS) substrate through a simple dipping–drying–crosslinking process, providing the hybrid MS@PIDO/Alg sponge with excellent uranium adsorption performance and sufficient mechanical strength to withstand the harsh conditions of practical applications. The maximum adsorption capacity reaches 910.98 mg‐U g‐gel^‐1 for the PIDO/Alg hydrogel layer and 291.51 mg‐U g‐sponge^‐1 for the whole hybrid MS@PIDO/Alg sponge in uranium‐spiked natural seawater. The adsorption capacity measured after 56 d of exposure in 5 tons of natural seawater is evaluated to be 5.84 mg‐U g‐gel^‐1 (1.87 mg‐U g‐sponge^‐1). This novel approach shows great promise for the mass production of high‐performance sponge adsorbent for uranium recovery from natural seawater and nuclear waste.     

Engineering Fe–Fe3C@Fe–N–C Active Sites and Hybrid Structures from Dual Metal–Organic Frameworks for Oxygen Reduction Reaction in H2–O2 Fuel Cell and Li–O2 Battery

Dual metal–organic frameworks (MOFs, i.e., MIL‐100(Fe) and ZIF‐8) are thermally converted into Fe–Fe₃C‐embedded Fe–N‐codoped carbon as platinum group metal (PGM)‐free oxygen reduction reaction (ORR) electrocatalysts. Pyrolysis enables imidazolate in ZIF‐8 rearranged into highly N‐doped carbon, while Fe from MIL‐100(Fe) into N‐ligated atomic sites concurrently with a few Fe–Fe₃C nanoparticles. Upon precise control of MOF compositions, the optimal catalyst is highly active for the ORR in half‐cells (0.88 V in base and 0.79 V versus RHE in acid in half‐wave potential), a proton exchange membrane fuel cell (0.76 W cm^?2 in peak power density) and an aprotic Li–O₂ battery (8749 mAh g^?1 in discharge capacity), representing a state‐of‐the‐art PGM‐free ORR catalyst. In the material, amorphous carbon with partial graphitization ensures high active site exposure and fast charge transfer simultaneously. Macropores facilitate mass transport to the catalyst surface, followed by oxygen penetration in micropores to reach the infiltrated active sites. Further modeling simulations shed light on the true Fe–Fe₃C contribution to the catalyst performance, suggesting Fe₃C enhances oxygen affinity, while metallic Fe promotes *OH desorption as the rate‐determining step at the nearby Fe–N–C sites. These findings demonstrate MOFs as model system for rational design of electrocatalyst for energy‐based functional applications.     

In Situ Observation of Crystallization Dynamics and Grain Orientation in Sequential Deposition of Metal Halide Perovskites

Metal halide perovskites have revolutionized the development of highly efficient, solution‐processable solar cells. Further advancements rely on improving perovskite film qualities through a better understanding of the underlying growth mechanism. Here, a systematic in situ grazing‐incidence X‐ray diffraction investigation is performed, facilitated by other techniques, on the sequential deposition of formamidinium lead iodide (FAPbI₃)‐based perovskite films. The active chemical reaction, composition distribution, phase transition, and crystal grain orientation are all visualized following the entire perovskite formation process. Furthermore, the influences of additive ions on the crystallization speed, grain orientation, and morphology of FAPbI₃‐based films, along with their photovoltaic performances, are fully evaluated and optimized, which leads to highly reproducible and efficient perovskite solar cells. The findings provide key insights into the perovskite growth mechanism and suggest the fabrication of high‐quality perovskite films for widespread optoelectronic applications.