Nucleic Acid Catalysis under Potential Prebiotic Conditions

Catalysis by nucleic acids is indispensable for extant cellular life, and it is widely accepted that nucleic acid enzymes were crucial for the emergence of primitive life 3.5‐4 billion years ago. However, geochemical conditions on early Earth must have differed greatly from the constant internal milieus of today's cells. In order to explore plausible scenarios for early molecular evolution, it is therefore essential to understand how different physicochemical parameters, such as temperature, pH, and ionic composition, influence nucleic acid catalysis and to explore to what extent nucleic acid enzymes can adapt to non‐physiological conditions. In this article, we give an overview of the research on catalysis of nucleic acids, in particular catalytic RNAs (ribozymes) and DNAs (deoxyribozymes), under extreme and/or unusual conditions that may relate to prebiotic environments.     

A Universal Geochemical Scenario for Formamide Condensation and Prebiotic Chemistry

The condensation of formamide has been shown to be a robust chemical pathway affording molecules necessary for the origin of life. It has been experimentally demonstrated that condensation reactions of formamide are catalyzed by a number of minerals, including silicates, phosphates, sulfides, zirconia, and borates, and by cosmic dusts and meteorites. However, a critical discussion of the catalytic power of the tested minerals, and the geochemical conditions under which the condensation would occur, is still missing. We show here that mineral self-assembled structures forming under alkaline silica-rich solutions are excellent catalysts for the condensation of formamide with respect to other minerals. We also propose that these structures were likely forming as early as 4.4 billion years ago when the whole earth surface was a reactor, a global scale factory, releasing large amounts of organic compounds. Our experimental results suggest that the conditions required for the synthesis of the molecular bricks from which life self-assembles, rather than being local and bizarre, appears to be universal and geologically rather conventional.     

基于科学风险认知的九年级“营养与化学”复习课设计

基于科学风险认知角度创新设计“营养与化学”的中考复习课，尝试以食品营养相关的社会性科学议题和网络传播的伪科学信息为载体，引领学生运用基础知识加以分析、评价和批判，达到综合应用知识体系和培养科学风险决策能力的目的。     

Parameters influencing fatigue life prediction of dielectric elastomer generators

For energy scavenging applications, estimating fatigue life of dielectric elastomer is as crucial as computing the amount of scavenged energy. Crack growth approach, well known in rubber industry, is a fast methodology to estimate fatigue life. We adapt this methodology to dielectric silicone elastomers (Elastosil 2030) and we focus in particular on the factors influencing this estimation such as sample geometry, tearing energy, power law. We underline that the variation in tearing energy estimation induces a small dispersion on the fatigue life estimation whereas power law identification is the crucial and critical parameter. Finally, we define an index of performance based on fatigue life and scavenged energy density, and we compare two materials (acrylic 3MVHB4910 and silicone Elastosil 2030).     

The opposite effect of K+ and Na+ on the hydrolysis of linear and cyclic dipeptides

Potassium and sodium are generally considered inert ‘spectator’ ions for organic reactions. Here, we report rate constants for the acid-promoted hydrolysis of the seven dipeptides of glycine (G) and alanine (A) and an unexpected pattern in how these rates differ in the presence of K⁺ and Na⁺. The linear dipeptides hydrolyze 12–18% percent slower in the presence of KCl versus an equal concentration of NaCl, while the cyclic dipeptides hydrolyze 5–13% faster in the presence of KCl (all P-values?<?0.025). We believe this is the first report of a general organic reaction—here, amide hydrolysis—for which some substrates react faster in the presence of K⁺ and others in Na⁺. The results offer a potential reason for life’s mysterious universal selection of intracellular potassium over sodium.     

Investigation on Parylene-C based neural electrodes by accelerated life test and reliability improvement using polyimide flexible cable

Since the encapsulation layer of the neural electrode plays an important role in determining the reliability of the device, more studies on the long-term reliability of Parylene-C are required. In this paper, we described the long-term reliability of Parylene-C based neural electrodes through an accelerated lift test and proposed a method to improve the reliability using polyimide flexible cable (PFC) attached to the Parylene-C device. The accelerated lifetime test was performed in phosphate-buffered saline at 50 °C. The electrochemical characteristics were acquired and analyzed to evaluate the reliability of the Parylene-C coated neural electrode for up to 56 days, which is equivalent to 115 days as an accelerated time. The proposed PFC method showed improved long-term stability of the device, demonstrating an increased lifetime, showing that testing conditions and device setup affect overall results. This study will help make reliable Parylene-C based neural electrode systems with improved moisture protection.     

Ultrahigh Rate Capability and Lifespan MnCo2O4/Ni-MOF Electrode for High Performance Battery-Type Supercapacitor

MnCo₂O₄ is derived from a Co/Mn bimetallic metal-organic framework (MOF). Then Ni-MOF is directly grown on the surface of the obtained MnCo₂O₄ to form a nano-flower structure with small balls. A large surface area, abundant active sites of MnCo₂O₄ and porosity of Ni-MOF allow the prepared MnCo₂O₄/Ni-MOF composite material to deliver an excellent electrochemical performance. At the same time, an appropriate thermal treatment temperature of the MnCo₂O₄ precursor is also very important for controlling the morphology of the obtained MnCo₂O₄ and electrochemical performances of the resulted composite material including electric conductivity, specific capacitance and rate performance. The prepared MnCo₂O₄-600/Ni-MOF shows an ultrahigh rate performance (when the current density increases from 1 to 10 A g⁻¹, the capacitance retention rate is as high as 93.41 %) and good cycle stability (the assembled asymmetric supercapacitor advice delivers a capacitance retention rate of 94.74 % after 20 000 charge and discharge cycles) as well as a relatively high specific capacitance. These excellent electrochemical properties indicate that MnCo₂O₄/Ni-MOF has a good application prospect in the market.     

Analysis of mandipropamid residual levels through systematic method optimization against the matrix complexity of sesame leaves using HPLC/UVD

An analytical method was developed to detect mandipropamid residues in sesame leaves using high‐performance liquid chromatography–ultraviolet detection. Samples were extracted with acetonitrile and were prepurified using a solid‐phase extraction (SPE) cartridge with an additional dispersive‐SPE (d‐SPE) sorbent application. The method was validated using an external calibration curve prepared using pure solvent. The linearity was excellent with determination coefficient = 1. The limits of detection and quantification were 0.003 and 0.01 mg/kg, respectively. Recoveries at three spiking levels – 0.1, 0.5, and 1.0 mg/kg – were in the range 80.3–90.7% with relative standard deviations <2%. This method was applied to field‐treated samples collected from two different areas, Gwangju and Muan, in the Republic of Korea and the half‐lives were similar, 5.10 and 5.41 days, respectively. The pre‐harvest residue limit was also predicted for both sites. The proposed method is sensitive and able to quantify trace amounts of mandipropamid in leafy vegetables. The combination of SPE and d‐SPE effectively removed the matrix components in sesame leaves. Copyright © 2015 John Wiley & Sons, Ltd.     

Cyanoacetaldehyde as a building block for prebiotic formation of pyrimidines

The present study uses density functional theory to investigate the possible free radical pathways for cytosine and uracil formation from cyanoacetaldehyde in the presence of urea and ammonia. Our proposed mechanisms are characterized by a smaller number of precursors and relatively lower barriers compared to previously reported reactions with other prebiotic precursors. Thus, the proposed mechanisms are more plausible in environments like prebiotic earth and present-day Titan. Overall, this study suggests a kinetically accessible route to pyrimidine formation and will hopefully contribute toward understanding the relevance of these precursors in prebiotic reactions.     

Liquid Chromatography—Its Development and Key Role in Life Science Applications

Liquid chromatographic methods cover the broadest range of applications imaginable today. Nowhere is this more evident and relevant than in the life sciences, where identification of target substances relevant in disease mechanisms is performed down to the femtomole level. On the other hand, purification of therapeutic drugs on a multi‐ton scale is performed by process LC. The complexity and abundance range of biological systems in combination with the extreme purity requirements for drug manufacturing are the challenges that can be mastered today by chromatography, after more than a century of research and development. However, significant improvement is still required for a better understanding of the scientific fundamentals of the underlying phenomena and exploiting those for an enhanced quality of live.