A detailed experimental study on single-pump Raman/EDFA hybrid amplifiers: static, dynamic, and system performance comparison

This paper presents an experimental study on the performance comparison of three different schemes of single-pump dispersion-compensating fiber (DCF)-based Raman/erbium-doped fiber amplifier (EDFA) hybrid amplifiers together with a DCF-based Raman-only amplifier in terms of static properties, dynamic properties, and system impact: Raman-only amplifier (Type I), Raman/EDFA hybrid amplifiers recycling residual Raman pump in a cascaded EDF located either after (Type II) or prior to (Type III) a DCF, and a Raman-assisted EDFA (Type IV), the concept of which was proposed by Kurosawa et al. With respect to the overall gain and system impact based on bit error rate (BER) measurements in a transmission system, the hybrid amplifier of Type II was found to have the best performance among the four types while the Raman-only amplifier shows the best tolerance to transient response.     

MOS characteristics of ultrathin CVD HfAlO gate dielectrics

Thermally stable, high-quality ultrathin (EOT=13 A) CVD HfAlO gate dielectrics with poly-Si gate electrode have been investigated for the first time. Results demonstrate that while in situ doping with Al significantly increases the crystallization temperature of HfO/sub 2/ up to 900/spl deg/C and improves its thermal stability, it also introduces negative fixed oxide charges due to Al accumulation at the HfAlO-Si interface, resulting in mobility degradation. The effects of Al concentration on crystallization temperature, fixed oxide charge density, and mobility degradation in HfAlO have been characterized and correlated.     

All-diode-laser cooling of single Ca+ ions

+ ions. The Ca⁺ ions are trapped in a miniature rf Paul trap and irradiated by light from a frequency-doubled diode laser at 397 nm and by light from a diode laser at 866 nm. We are able to cool a single ion and observe its fluorescence continuously with the laser diode locked to the external frequency-doubling cavity. Quantum jumps in the fluorescence light of a single ion and of a small cloud of five ions have been induced by driving the “clock” transition at 729 nm. We were able to resolve the influence of the micromotion on the excitation spectrum of the small ion cloud. Received: 10 July 1997/Revised version: 17 November 1997     

Fatigue crack initaition and propagation from hole defects

The aim of this study is to investigate the interaction of two hole defects affecting fatigue crack initiation life and propagation behavior. The location of two hole defects was characterized by an angle of alignment and the distance between the centers of two hole defects. The fatigue cracking behavior is studies under bending for AI 5086. When defects are located close to each other, the fatigue crack initiation lives are varied with their relative locations. In the experiments, the area of the local plastic stratin strongly played a role in the fatigue crack initiation lives. Therefore, the authors introduce a parameter which contains the plastic deformation are at stress concentrations and proposed a fatigue crack initiation life prediction curve. In addition, the directions and propagation rates of fatigue cracks initiated at two hole defects were studied experimentally.     

Anchored Mediator Enabling Shuttle‐Free Redox Mediation in Lithium‐Oxygen Batteries

Redox mediators (RMs) are considered an effective countermeasure to reduce the large polarization in lithium‐oxygen batteries. Nevertheless, achieving sufficient enhancement of the cyclability is limited by the trade‐offs of freely mobile RMs, which are beneficial for charge transport but also trigger the shuttling phenomenon. Here, we successfully decoupled the charge‐carrying redox property of RMs and shuttling phenomenon by anchoring the RMs in polymer form, where physical RM migration was replaced by charge transfer along polymer chains. Using PTMA (poly(2,2,6,6‐tetramethyl‐1‐piperidinyloxy‐4‐yl methacrylate)) as a polymer model system based on the well‐known RM tetramethylpiperidinyloxyl (TEMPO), it is demonstrated that PTMA can function as stationary RM, preserving the redox activity of TEMPO. The efficiency of RM‐mediated Li₂O₂ decomposition remains remarkably stable without the consumption of oxidized RMs or degradation of the lithium anode, resulting in an improved performance of the lithium‐oxygen cell.     

Phytochemicals from Echinacea and Hypericum: A Direct Synthesis of Isoligularone

Reaction of trienes with α,β‐unsaturated aldehydes produces bicyclic products via a tandem Diels–Alder/ene reaction. The adduct from tiglic aldehyde was converted into isoligularone by conversion to a furan followed by benzylic oxidation.     

The dimension of the determinantal scheme vs (t,t,2) of the catalecticant matrix

Let T be a Gorenstein sequence of a graded artinian Gorenstein ring k[x ₀,x ₁,x ₂]/I We develop a dimension formula for PGor(T) in terms of the alignment character. Based on our formula, we find a very large component of V_s (t,t,2) when s=r_t-1+1 and t is large enough. This answers Diesel’s conjecture negatively. Further we show that V_s (t,t,2) is irreducible of dimension 3s-1 for s ≤t+1,t ≥ 2 and dim V_s (t,t,2)= 3s-1 for small s. Finally an algorithm to calculate dim V_s (t,t,2) is constructed, and we find the values of dim V_s (t,t,2) for t ≤ 16.     

Operando Stability of Single-Atom Electrocatalysts

Single-atom catalysts (SACs) are appealing next-generation catalysts for various electrochemical technologies. Along with significant breakthroughs in their initial activity, SACs now face the next challenge for their viable applications, insufficient operational stability. In this Minireview, we summarize the current knowledge of SAC degradation mechanisms mainly based on Fe−N−C SACs, some of the most investigated SACs. Recent studies on isolated metal, ligand, and support degradations are introduced, and the underlying fundamentals of each degradation path are categorized into active site density (SD) and turnover frequency (TOF) losses. Finally, we discuss the challenges and prospects for the future outlook of stable SACs.