Degradation in phosphoric acid doped polymer fuel cells: A 6000 h parametric investigation

This paper reports an experimental study of the degradation of single PBI-based high temperature MEAs doped with phosphoric acid. The study is carried out by operating the single MEAs for long periods in steady state, the degradation is quantified considering the voltage decay rate. Besides the most common operating condition suggested by the MEAs producer (T = 160 °C, i = 0.2 A cm⁻², λH₂=1.2${\lambda }_{{\text{H}}_2}=1.2$, λ_air = 2), the study also investigates higher operating temperature (T = 180 °C), higher current density (i = 0.4 A cm⁻²) and double air flow rate (λ_air = 4). A temperature of 180 °C accelerates the degradation of the MEA which increases from around 8 μV h⁻¹ up to around 19 μV h⁻¹. On the opposite side, operating the MEA at i = 0.4 A cm⁻² reduces the voltage degradation rate down to 4 μV h⁻¹ and increases the power output making this condition particularly interesting. EIS, CV and LSV are used to clarify the causes of degradation. A consistent increase in the charge transfer resistance is observed and is related to the loss of catalyst active area due to catalyst agglomeration, carbon corrosion and possible acid leaching. Concerning the electrolyte membrane, a slight decrease in the proton conductivity is measured, a major effect on degradation is played by the increasing gas crossover rate and by the short circuit current.     

跳动的心脏

从一开始,商业空间。例如购物中心,百货商店和小规模的主营店,就是重要且有趣的课题之一。自查尔斯·W·摩尔（Chartes W.Moore）的意大利广场（Piazza Itatia）在新奥尔良的第一个工程以来,研究人员以及后来的著名建筑师们一直在对该主题进行讨论。主要问题是,从经济角度来看,商业空间首先必须是成功的,因此,开发商不得不经常听从零售咨询师的指点,而不是设计师的意见。     

水天千色

去年夏天，佛罗伦萨最热门的焦点无疑是Baglietto所建造的这艘名为RC的游艇了，意大利设计师的创作，采用了各种别具一格的设计形式，同时选用变化丰富的棉织物来做装饰，以及对游艇内部各个细节的关注使得整艘游艇最终呈现给世人的时候，不仅吸引了众人的眼光，更显示了作品的与众不同。     

Omicron Genetic and Clinical Peculiarities That May Overturn SARS-CoV-2 Pandemic: A Literature Review

The Coronavirus disease 2019 (COVID-19) pandemic poses a great threat to global public health. The original wild-type strain of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has genetically evolved, and several variants of concern (VOC) have emerged. On 26 November 2021, a new variant named Omicron (B.1.1.529) was designated as the fifth VOC, revealing that SARS-CoV-2 has the potential to go beyond the available therapies. The high number of mutations harboured on the spike protein make Omicron highly transmissible, less responsive to several of the currently used drugs, as well as potentially able to escape immune protection elicited by both vaccines and previous infection. We reviewed the latest publication and the most recent available literature on the Omicron variant, enlightening both reasons for concern and high hopes for new therapeutic strategies.     

Improved Synthesis of Pyrroles and Indoles via Lewis Acid‐Catalyzed Mukaiyama–Michael‐Type Addition/Heterocyclization of Enolsilyl Derivatives on 1,2‐Diaza‐1,3‐Butadienes. Role of the Catalyst in the Reaction Mechanism

The Mukaiyama–Michael‐type addition of various silyl ketene acetals or silyl enol ethers on some 1,2‐diaza‐1,3‐butadienes proceeds at room temperature in the presence of catalytic amounts of Lewis acid affording by heterocyclization 1‐aminopyrrol‐2‐ones and 1‐aminopyrroles, respectively. 1‐Aminoindoles have been also obtained by the same addition of 2‐(trimethylsilyloxy)‐1,3‐cyclohexadiene on some 1,2‐diaza‐1,3‐butadienes and subsequent aromatization. Mechanistic investigations indicate the coordination by Lewis acid of the enolsilyl derivative and its 1,4‐addition on the azo‐ene system of 1,2‐diaza‐1,3‐butadienes. The migration of the silyl group from a hydrazonic to an amidic nitrogen, its acidic cleavage and the final internal heterocyclization give the final products. Based on NMR studies and ab initio calculations, a plausible explanation for the migration of the silyl protecting group is presented.     

Calibration-Free and High-Sensitivity Microwave Detectors Based on InAs/InP Nanowire Double Quantum Dots

At the cutting-edge of microwave detection technology, novel approaches which exploit the interaction between microwaves and quantum devices are rising. In this study, microwaves are efficiently detected exploiting the unique transport features of InAs/InP nanowire double quantum dot-based devices, suitably configured to allow the precise and calibration-free measurement of the local field. Prototypical nanoscale detectors are operated both at zero and finite source-drain bias, addressing and rationalizing the microwave impact on the charge stability diagram. The detector performance is addressed by measuring its responsivity, quantum efficiency and noise equivalent power that, upon impedance matching optimization, are estimated to reach values up to ≈2000 A W⁻¹, 0.04 and ≈${10}^{-16}\mathrm{W}/\sqrt{Hz}$, respectively. The interaction mechanism between the microwave field and the quantum confined energy levels of the double quantum dots is unveiled and it is shown that these semiconductor nanostructures allow the direct assessment of the local intensity of the microwave field without the need for any calibration tool. Thus, the reported nanoscale devices based on III-V nanowire heterostructures represent a novel class of calibration-free and highly sensitive probes of microwave radiation, with nanometer-scale spatial resolution, that may foster the development of novel high-performance microwave circuitries.