Revisiting the Early History of Synthetic Polymers: Critiques and New Insights

This essay seeks to clarify existing confusion in terminology regarding the history of polymers, plastics, and macromolecules, and explores various factors that complicate the early history of macromolecules. It also suggests reasons why materials such as polyaniline, an early fully synthetic polymer that found widespread commercial application in dyes, have not previously been treated in accounts of polymer history.     

Colour Me Blue: The History and the Biotechnological Potential of Pyocyanin

Pyocyanin was the first natural phenazine described. The molecule is synthesized by about 95% of the strains of Pseudomonas aeruginosa. From discovery up to now, pyocyanin has been characterised by a very rich and avant-garde history, which includes its use in antimicrobial therapy, even before the discovery of penicillin opened the era of antibiotic therapy, as well as its use in electric current generation. Exhibiting an exuberant blue colour and being easy to obtain, this pigment is the subject of the present review, aiming to narrate its history as well as to unveil its mechanisms and suggest new horizons for applications in different areas of engineering, biology and biotechnology.     

A Brief History of Colour,the Environmental Impact of Synthetic Dyes and Removal by Using Laccases

The history of colour is fascinating from a social and artistic viewpoint because it shows the way; use; and importance acquired. The use of colours date back to the Stone Age (the first news of cave paintings); colour has contributed to the social and symbolic development of civilizations. Colour has been associated with hierarchy; power and leadership in some of them. The advent of synthetic dyes has revolutionized the colour industry; and due to their low cost; their use has spread to different industrial sectors. Although the percentage of coloured wastewater discharged by the textile; food; pharmaceutical; cosmetic; and paper industries; among other productive areas; are unknown; the toxic effect and ecological implications of this discharged into water bodies are harmful. This review briefly shows the social and artistic history surrounding the discovery and use of natural and synthetic dyes. We summarise the environmental impact caused by the discharge of untreated or poorly treated coloured wastewater to water bodies; which has led to physical; chemical and biological treatments to reduce the colour units so as important physicochemical parameters. We also focus on laccase utility (EC 1.10.3.2), for discolouration enzymatic treatment of coloured wastewater, before its discharge into water bodies. Laccases (p-diphenol: oxidoreductase dioxide) are multicopper oxidoreductase enzymes widely distributed in plants, insects, bacteria, and fungi. Fungal laccases have employed for wastewater colour removal due to their high redox potential. This review includes an analysis of the stability of laccases, the factors that influence production at high scales to achieve discolouration of high volumes of contaminated wastewater, the biotechnological impact of laccases, and the degradation routes that some dyes may follow when using the laccase for colour removal     

彩色照像中的化学

用彩色负片拍摄、在相纸上印像的彩色照像系统已成为当今的主流,这一系统的成像主要经过形成潜影、显影、漂白、定影等化学过程,而具有快速成像特点的彩色一步摄影成像系统,其成像的化学过程则有差别。本文对这两种体系的成像作了阐述,并对彩色照片的修饰以及彩色照片的褪色原因和保存方法作了介绍。     

卤素颜色成因浅析

从分子结构的角度分析卤素颜色产生的原因。电子跃迁时振动能级的改变对氯、溴和碘的颜色影响较大,而电子跃迁时转动能级变化产生的影响较小。     

Revisiting ceramics for medical applications

The most significant demand for biomaterials has emerged as a consequence of the need to provide clinical treatment to a large number of patients. The search for potential solutions produces a large demand for materials suitable for bone repair or replacement. Calcium phosphates, bio-glasses, bio-glass ceramics and ordered silica mesoporous materials, among other types of materials, will be reviewed and studied from the point of view of their potential applications as replacement materials in bone repair and regeneration, as potential substrates in tissue engineering, and also as drug delivery systems. An overview on the present achievements, but also on the "missing links" will be presented.     

Revisiting the stability of hexacenes

The Strating-Zwanenberg photodecarbonylation was used to prepare hexacene (1). Compound 1 was found to be extremely unstable in solution, undergoing dimerization and oxidation. However, when generated in a polymer matrix, 1 survived for more than 12 h under ambient conditions. Hexacenes substituted at the 6 and 15 positions with the phenyl, p-tert-butylphenyl, and mesityl groups were synthesized using the quinone reduction method, but these compounds were also shown to be unstable in solution.     

溶液表面吸附实验的再讨论

In the solution adsorption experiment, different adsorption mode has been observed for aqueous ethanol and aqueous n-butanol, respectively. However, it is difficult to make an adjustment by the profiles of σ-c relationship. Choosing the experimental conditions improperly will give wrong results. Since there is no consistency between the Gibbs adsorption isotherm and Langmuir adsorption isotherm, the experimental data should not be fitted by using any algebraic equations or physical models. The data fitting for this experiment should be carried out according to the following steps:fitting the σ-lnc curve manually, making it monotonic and smooth; retrieving more data from this fitting curve, and re-plotting the σ-lnc curve; calculating the first derivatives at these data points (i.e., (∂σ/∂lnc)_T); calculating surface adsorptions by Gibbs adsorption isotherm, Γ=-(∂σ/∂lnc)_T/RT. As for the calculation of the cross-section area for the solute molecule, the effect of concentration of bulk solution (i.e., c) on the surface molecular density should be taken into account.     

Revisiting Bohr's semiclassical quantum theory

Bohr's atomic theory is widely viewed as remarkable, both for its accuracy in predicting the observed optical transitions of one-electron atoms and for its failure to fully correspond with current electronic structure theory. What is not generally appreciated is that Bohr's original semiclassical conception differed significantly from the Bohr-Sommerfeld theory and offers an alternative semiclassical approximation scheme with remarkable attributes. More specifically, Bohr's original method did not impose action quantization constraints but rather obtained these as predictions by simply matching photon and classical orbital frequencies. In other words, the hydrogen atom was treated entirely classically and orbital quantized emerged directly from the Planck-Einstein photon quantization condition, E = h nu. Here, we revisit this early history of quantum theory and demonstrate the application of Bohr's original strategy to the three quintessential quantum systems: an electron in a box, an electron in a ring, and a dipolar harmonic oscillator. The usual energy-level spectra, and optical selection rules, emerge by solving an algebraic (quadratic) equation, rather than a Bohr-Sommerfeld integral (or Schroedinger) equation. However, the new predictions include a frozen (zero-kinetic-energy) state which in some (but not all) cases lies below the usual zero-point energy. In addition to raising provocative questions concerning the origin of quantum-chemical phenomena, the results may prove to be of pedagogical value in introducing students to quantum mechanics.     

Revisiting ether-derivatized imidazolium-based ionic liquids

A series of ether-derivatized imidazolium halides have been prepared and characterized. Contrary to literature reports, they are all crystalline solids and have melting points well above room temperature (50-100 degrees C). Single crystals of the imidazolium salts, obtained in situ by slow cooling from their molten state to room temperature, were analyzed by X-ray crystallography, revealing various anion-cation interactions in the solid state. Exchange of the halides with [Tf(2)N]- yielded room temperature ionic liquids with viscosities that are comparable to related 1-alkyl-3-methylimidazolium ionic liquids. Density functional theory combined with IR spectroscopy has been used to analyze the role of functionalization of the imidazolium side chain on the formation of the molecular and supramolecular structure of the compounds and its possible impact on their physical properties.     

Revisiting the Perfluorinated Trityl Cation

Although ultimately not isolable for X-ray structural characterization, the free perfluorinated trityl cation was shown to be observable in neat triflic acid, which represents milder conditions than previous reports of this cation in “magic acid” or oleum. A triflate-bound species could be generated in organic solvents using stoichiometric amounts of triflic acid and was shown to be synthetically viable for hydride abstraction from Et₃SiH. It was demonstrated that the para-position on the -C₆F₅ rings is the primary point of attack for decomposition of the cation.     

碘溶液的颜色

单质碘是紫黑色有金属光泽的鳞片状晶体,熔点113℃,沸点184℃,它的液态温度区间很小,熔点时蒸气压很大,易升华为紫色碘蒸气。碘是非极性分子,难溶于水,但极易溶于有机溶剂、碘化钾溶液及淀粉溶液中,而且形成的溶液都有美丽的颜色。     

Colour switching with photochromic vinylidene-naphthofurans

A series of novel photochromic vinylidene-naphthofurans with extended conjugation, and a free hydroxyl function, were easily prepared using the Suzuki reaction. After silanization, these dyes were embedded in ormosil matrices affording solid and transparent materials that acquire different colourations (violet, green, bluish), reversibly, when exposed to the UV (Sun) light, for 2?min, at room temperature. The presence of an extra phenyl ring in some positions affects both the λ_max of absorption of the photochromic compounds in the uncoloured closed and open coloured form. After removal of the light source the materials lose progressively their colouration returning to the initial uncoloured state in less than 15?min?at room temperature.     

关于过氧化钠的颜色

在中学教材里,过氧化钠的颜色是这样叙述的:过氧化钠是淡黄色的固体。对这一叙述,笔者认为有改进的必要: 一、过氧化钠的颜色是一个没有统一看法的问题。不同的书中,有不同的叙述。从我国已出版的书中,大体就能见以下几种: 1.纯的过氧化钠是淡黄色的固体（或粉末）[2].[3].[4].[5]. 2.纯的过氧化钠是无色粉末,工业制备的过氧化钠因含有超氧化钠（NaO2）杂质而呈黄色[6].[7].[8].[9]。     

Revisiting some phenomena in polyelectrolyte solutions

This review deals with the counterion distribution around rod‐shaped polyions, the reaction kinetics in polyelectrolyte solutions, the anomalous behavior of poly(methacrylic acid), and the formation of pearl‐necklace‐like structures of polyelectrolytes in poor solvent media. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 1080–1086, 2002     

Revisiting lithium-storage mechanisms of molybdenum disulfide

Molybdenum disulfide（MoS₂）,a typical two-dimensional transition metallic layered material,attracts tremendous attentions in the electrochemical energy storage due to its excellent physicochemical properties.However,with the deepening of the research and exploration of the lithium storage mechanism of these advanced MoS₂-based anode materials,the complex reaction process influenced by internal and external factors hinders the exhaustive understanding of the lithium storage p...     

Revisiting small clusters of water molecules

The geometries and relative energies of small clusters of water molecules, (H₂O)_n with 4 ⩽ n ⩽ 8, are reported. For each value of n we have considered the conformations corresponding to the lowest-energy minimum and those in nearby relative minima. Thus we report on six tetramers, four pentamers, six hexanlers, four heptamers, and eigth octamers. The geometrical conformations have been obtained using the Metropolis Monte Carlo method as a minimization technique, where the interaction energy is computed with the MCY potential plus three- and four-body corrections previously discussed. All the reported structures for a given cluster size are found to be close in energy. For the lowest conformation the geometry was optimized with ab initio SCF computations using energy gradients. Our results are compared with previous theoretical studies. We discuss the convergence of the interaction potential for liquid water when expressed in terms of a many-body series expansion.     

再论第三种自由概念

无论是基于伯林的概念框架,还是超出伯林的概念框架,对第三种自由概念的可能性及其成立依据的探究已经成为当代政治哲学的一个重要生长点。就自由平等主义而言,我们可以把关于消极自由的定义以及自由的价值问题的争辩,从理论上落实为罗尔斯的基本自由权理论对于自由问题上内外两种路径的整合;就公民共和主义而言,价值多元论仍然是提出第三种自由概念时必须正视的挑战和重建其自由理论的平台,而自由的原子层次和分子层次的区分又为调和自由平等主义和公民共和主义提供了一种有效的概念手段;就哈贝马斯与罗尔斯之争而言,围绕私人自主和公共自主以及所谓更高阶的政治自主性所展开的争论和回应,所指向的乃是政治哲学对于透明性理想的追求。