How mobile NMR can help with the conservation of paintings

The conservation of paintings is fundamental to ensure that future generations will have access to the ideas of the grand masters who created these art pieces. Many factors, such as humidity, temperature, light, and pollutants, pose a risk to the conservation of paintings. To help with painting conservation, it is essential to be able to noninvasively study how these factors affect paintings and to develop methods to investigate their effects on painting degradation. Hence, the use of mobile nuclear magnetic resonance (NMR) as a method of investigation of paintings is gaining increased attention in the world of Heritage Science. In this mini-review, we discuss how this method was used to better understand the stratigraphy of paintings and the effect different factors have on the painting integrity, to analyze the different cleaning techniques suitable for painting conservation, and to show how mobile NMR can be used to identify forgeries. It is also important to keep in mind its limitations and build upon this information to optimize it to extend its applicability to the study of paintings and other precious objects of cultural heritage.     

The electrochemistry of electrode edges and its relevance to partially blocked voltammetric electrodes

Analytical mathematics and digital simulation are used to predict the response, to a potential jump, of the junction between insulating and conducting regions of an electrode. The simulation is carried out differentially and employs other novel features. Concentrations in the vicinity of edges of positive and negative curvatures, as well as straight edges, are analyzed by the model and thereby the faradaic current densities and currents are predicted. It is shown that, in addition to the well-understood cottrellian current arising from the surface of the conducting electrode, currents are generated that are proportional to the length of the edge and to its curvature. These results are then applied to inlaid disks and to partially blocked electrodes. The possibility is explored of using the response to a potential step to gain information on the geometry of a partially blocked electrode.     

杨石先对农药化学学科的重要贡献及其学术思想

杨石先先生一生献身于我国的教育事业与化学学科的发展,在62年中为我国培养了无数高质量的科教人才。他除了长期担任南开大学校长之外, 还创建了我国大学第一个专职研究所,即元素有机化学研究所。他率先开展了我国元素有机化学与农药化学的科学研究,领导了元素有机化学国家重点实验室的建立,是我国元素有机化学和农药化学的奠基人和开拓者。他倡导用有机化学的专业知识,科学和系统地开展农药化学研究,组建队伍获得20项科研成果,发表上百篇科学与论述性论文,为我国开展自主创新农药研究事业作出重要贡献。在农药化学学科的学术思想中,他强调要弄清该学科的交叉性、系统性和内在规律性,倡导要学习国际先进经验,要结合国情自主创新,要为国家经济服务,要对世界农药科技做出贡献。他毕生对人才培养给予了特别的重视,为我国科技事业持续发展作出了重大贡献。     

高校无机化学实验室资源合理配置的探索与实践

高校实验室是“立德树人”的重要阵地,实验技术队伍是实现“三全育人”的重要保障。高校快速发展过程中,对实验技术队伍赋予了建设和管理的多重任务,而自身缺乏明确的发展方向和目标,实验技术队伍职业化研究成为高校发展的现实需求。构建适应高等学校发展的实验技术队伍专业化管理体系,明确实验队伍职业化发展路径选择的具体措施,促进实验技术队伍稳定性,强化实验技术队伍在高等学校治理结构和提升内涵建设的有效作用,为提升高校实验室育人功能奠定基础,为高等学校快速发展提供有力支撑。     

和医学相关有机化合物绿色鉴别实验的设计*

为了将医用化学实验中“有机化合物的鉴别”实验更加密切地与医学相关专业结合,并提高实验操作的安全性,降低化学试剂的毒性与刺激性,甄选出一系列与医学密切相关的有机化合物作为待鉴别试剂,同时设计绿色环保、安全低毒、现象明显、操作简便、成本低廉的鉴别方法,为学生实验方案的设计提供指导。以期提高医学生学习的积极性与主动性,促进学生灵活运用知识分析问题、解决问题,为相关教学工作的改进提供借鉴意义。     

Polylactic acid/polypropylene polyblend fibers for better resistance to degradation

Polyblend fibers were produced from five ratios of polylactic acid/polypropylene (PLA/PP) in an effort to improve the resistance to hydrolysis and biodegradation, and to improve the dyeability of PLA. The inherent limitations of PLA such as its relatively poor resistance to hydrolysis have restricted the use of PLA. When made into polyblend fibers, the two polymers, PLA and PP, show partial compatibility and the mechanical properties of the blends are inferior compared to the pure PLA or PP fibers. However, PLA in the blends had substantially better resistance to biodegradation and hydrolysis, and dyeability with disperse dyes, resulting in a polyblend fiber with much better resistance to hydrolysis and similar dyeability to PLA. Blending PP with PLA could be a simple and effective method to create a new fiber with better resistance to hydrolysis and lower price than PLA, and better dyeability, sustainability and faster degradability than PP.     

Total error and uncertainty: Friends or foes?

Guidelines ISO 17025 and ISO 15189 aim to improve the quality-assurance scheme of laboratories. Reliable analytical results are of central importance due to the critical decisions that are taken with them. ISO 17025 and ISO 15189 therefore require that analytical methods be validated and that laboratories can routinely provide the measurement uncertainty of the results of measurements. To evaluate the fitness of purpose of analytical methods, total error is increasingly applied to assess the reliability of results generated by analytical methods. However, the ISO requirement to estimate measurement uncertainty seems opposed to the concept of total error, leading to delays in laboratories implementing ISO 17025 and ISO 15189 and confusion for the analysts. This article therefore aims to clarify the divergences between total error and measurement uncertainty, but also to discuss their main similarities and emphasize their implementation.     

Metrology in laboratory medicine – A necessity

 In a recent Letter to the Editor, Dr. B. Neidhart questioned the need to make clinical chemical measurement results traceable to international standards and to incorporate the principles of analytical quality assurance into clinical chemistry. An analysis of the arguments presented shows that modern laboratory medicine has to deliver accurate results, which are comparable over space and time, in order to improve the accuracy of diagnostic tools and minimize cost. The means to achieve accuracy and comparability are metrological traceability and quality assurance as supported by many national and international initiatives.     

Electrochemical approaches for the detection of amyloid-β, tau,and α-synuclein

According to the World Health Organization, there are 47 million people worldwide who are afflicted with dementia today, and this is expected to rise to 132 million by 2050. Therefore, it is pertinent to develop efficient analytical methods such as electrochemical biosensors to study these disorders and diagnose them early. This review highlights some of the recent key developments in the use of electrochemical biosensors to study the biomarkers related to neurodegenerative diseases such as Alzheimer's disease and Parkinson's disease. Especially, we focus on the applications of electrochemistry to analyze amyloid-β and tau related to Alzheimer's disease and α-synuclein related to Parkinson's disease.     

从氨的合成认识氮分子化学键的稳定性和活化

先从氮分子的化学键讨论其稳定性,再从最早工业化的合成氨出发,讨论氮分子化学键活化的相关研究,意欲探索一种元素化学新的教学方法。目的在于引导学生灵活学习并运用知识去认识自然世界,提高分析问题和解决问题的能力。     

NMR spectroscopic study of the Murex trunculus dyeing process

It is widely accepted that indigo dyes derived from Murex trunculus were used to produce the biblical dyes tekhelet and argaman. We describe a method of following the debromination of natural leucoindigos and their binding to wool using NMR spectroscopy. Debromination is observed prior to reaction with the wool and prior to oxidation. Binding to the wool is shown to occur prior to oxidation. NMR allows the dyeing process to be followed. This, in principle, could be used to correct problems during dyeing that would increase the reliability of the process.     

Fluorocarbons in the global environment: a review of the important interactions with atmospheric chemistry and physics

Fluorocarbon impact on ozone depletion is reviewed together with the efficacy of the Montreal Protocol in acting to correct the imbalance between stratospheric ozone production and destruction. The Protocol is also helping to reduce global warming: CFCs are shown to be currently the largest fluorocarbon contributors to climate change. Relative contributions to climate change from CFCs and their HFC substitutes are discussed, together with the consequences of control of minor greenhouse gases on an environmental impact which is dominated by carbon dioxide emissions. Both the potencies of the materials for environmental change and their concentrations in the atmosphere are important and are considered here.Trifluoroacetic acid, a minor product of atmospheric decomposition of some HCFCs and HFCs and of the pyrolysis of fluoropolymers, has been shown to be uniformly distributed in seawater to a depth of over 4000 m and so is natural, although the actual source has yet to be identified.The Montreal Protocol is only one example of action to reduce undesirable impact from fluorocarbons. Other, less universal, actions include abatement of fluoroform greenhouse gas emissions from HCFC manufacturing, process changes to eliminate trifluoromethylsulfur pentafluoride emissions from electrochemical fluorination and ceasing manufacture of perfluorooctanyl sulfonate compounds due to their persistence in human tissue.     

Interpretation of analysis of variance models using principal component analysis to assess the effect of a maternal anticancer treatment on the mineralization of rat bones

The aim of this paper is to show how it is possible to extract analytical information from images acquired with a flatbed scanner and make use of this information for real time control of a nickel plating process. Digital images of plated steel sheets in a nickel bath are used to follow the process under degradation of specific additives. Dedicated software has been developed for making the obtained results accessible to process operators. This includes obtaining the RGB image, to select the red channel data exclusively, to calculate the histogram of the red channel data and to calculate the mean colour value (MCV) and the standard deviation of the red channel data. MCV is then used by the software to determine the concentration of the additives Supreme Plus Brightner (SPB) and SA-1 (for confidentiality reasons, the chemical contents cannot be further detailed) present in the bath (these two additives degrade and their concentration changes during the process). Finally, the software informs the operator when the bath is generating unsuitable quality plating and suggests the amount of SPB and SA-1 to be added in order to recover the original plating quality.     

Tyrosine derivatives assembled on gold

Two different tyrosine derivatives, one with the OH group free and one with the OH group phosphorylated, linked to 3-mercaptopropionic acid through an amide bond are adsorbed to gold surfaces. The adsorbates are studied by means of X-ray photoelectron spectroscopy (XPS) and infrared reflection-absorption spectroscopy (IRAS). The techniques are used to investigate the coordination to the surface and the molecular orientation of adsorbates relative to the surface. Molecular surface interactions, causing chemical shifts in the core level XPS spectra of the adsorbates on gold, are investigated using multilayer films as references. Angle-dependent XPS, XPS(theta), and IRAS are used to estimate molecular orientation relative to the surface. The tyrosine derivatives adsorb chemically to the surface through the sulfur atoms and highly organized monolayers are formed with the OH and the PO(2-)(3) exposed to the air/vacuum interface.     

Measurement of <Emphasis Type="Italic">T</Emphasis><Subscript>g</Subscript> in lyophilized protein and protein excipient mixtures by dynamic mechanical analysis

The glass transition of lyophilized materials is normally measured by conventional or temperature modulated differential scanning calorimetry (TMDSC). However, because of the weakness of these transitions when protein concentrations are high, these techniques are often unable to detect the glass transition (T _g). High ramp rate DSC, where heating rates of 100 K per min and higher are used, has been shown to be able to detect weak transitions in a wide range of materials and has been applied to these materials in previous work. Dynamic mechanical analysis (DMA) is also known to be much more sensitive to the presence of relaxations in materials than other commonly used thermal techniques. The development of a method to handle powders in the DMA makes it now possible to apply this technique to protein and protein-excipient mixtures. HRR DSC, TMA and DMA were used to characterize the glass transition of lyophilized materials and the results correlated. DMA is shown to be a viable alternative to HRR DSC and TMA for lyophilized materials.     

Spectroscopy of Fluid Phases—The Study of Chemical Reactions and Equilibria up to High Pressures

The properties of fluid phases can be altered considerably by the external conditions. Phase equilibria and chemical equilibria can be greatly affected, and it is possible to carry out chemical reactions by exploiting the special properties of compressed fluid phases. The use of high pressure in chemical reactions is of considerable diagnostic and preparative value. Applied research is directed towards elucidating the details of existing technical high pressure processes and to the development of novel fluid phase reactions where the application of high pressure is able to induce selectivity. In order to pursue these lines of research, and to study structure and dynamics throughout the entire range from gaseous to liquidlike states, it is important to have spectroscopic methods for characterizing systems at high pressures and temperatures. This article is concerned with quantitative absorption spectroscopy in the infrared to the ultraviolet spectral region at pressures up to about 7 kbar and temperatures up to 900 K.     

Regulation of π‐Stacked Anthracene Arrangement for Fluorescence Modulation of Organic Solid from Monomer to Excited Oligomer Emission

The construction and precise control of the face‐to‐face π‐stacked arrangements of anthracene fluorophores in the crystalline state led to a remarkable red shift in the fluorescence spectrum due to unprecedented excited oligomer formation. The arrangements were regulated by using organic salts including anthracene‐1,5‐disulfonic acid (1,5‐ADS) and a variety of aliphatic amines. Because of the smaller number of hydrogen atoms at the edge positions and the steric effect of the sulfonate groups, 1,5‐ADS should prefer face‐to‐face π‐stacked arrangements over the usual edge‐to‐face herringbone arrangement. Indeed, as the alkyl substituents were lengthened, the organic salts altered their anthracene arrangement to give two‐dimensional (2D) edge‐to‐face and end‐to‐face herringbone arrangements, one‐dimensional (1D) face‐to‐face zigzag and slipped stacking arrangements, a lateral 1D face‐to‐face arrangement like part of a brick wall, and a discrete monomer arrangement. The monomer arrangement behaved as a dilute solution even in the close‐packed solid state to emit deep blue light. The 1D face‐to‐face zigzag and slipped stacking of the anthracene fluorophores caused a red shift of 30–40 nm in the fluorescence emission with respect to the discrete arrangement, probably owing to ground‐state associations. On the other hand, the 2D end‐to‐face stacking induced a larger red shift of 60 nm, which is attributed to the excimer fluorescence. Surprisingly, the brick‐like lateral face‐to‐face arrangement afforded a remarkable red shift of 150 nm to give yellow fluorescence. This anomalous red shift is probably due to excited oligomer formation in such a lateral 1D arrangement according to the long fluorescence lifetime and little shift in the excitation spectrum. The regulation of the π‐stacked arrangement of anthracene fluorophores enabled the wide modulation of the fluorescence and a detailed investigation of the relationships between the photophysical properties and the arrangements.     

Advancing the Drug Discovery and Development Process

The current state of affairs in the drug discovery and development process is briefly summarized and then ways to take advantage of the ever‐increasing fundamental knowledge and technical knowhow in chemistry and biology and related disciplines are discussed. The primary motivation of this Essay is to celebrate the great achievements of chemistry, biology, and medicine and to inform and inspire students and academics to enter the field of drug discovery and development while, at the same time, continue to advance the fundamentals of their disciplines. It is also meant to encourage and catalyze multidisciplinary partnerships between academia and industry as scientists attempt to merge their often complementary interests and expertise to achieve new improvements and breakthroughs in their respective fields, and the common goal of applying them to the discovery and invention of new and better medicines, especially in areas of unmet needs.     

How to approach membership of IAF/ILAC Arrangements: the peer evaluation system of IAF and ILAC for single accreditation bodies

Peer evaluation is used by the international accreditation organisations IAF and ILAC as a tool to harmonise the results of accreditation of conformity assessment bodies and as a control mechanism to ensure constantly competent services according to harmonized standards. Upon positive evaluation outcome, the accreditation body may join an Arrangement (MLA/MRA) between accreditation bodies, confirming systematic reliability and competence to the market. The objective of these Arrangements is that they will cover all accreditation bodies in all countries in the world, thus eliminating the need for suppliers of products or services to be certified in each country where they sell their products or services. This article is to aid single accreditation bodies wishing to sign these Arrangements in the future, and, furthermore, to communicate the procedure and the relevance of evaluation to the public in order to build up confidence in such Arrangements.     

加深对现代分析仪器的认识提高使用与维修水平

熟悉了解仪器的总体结构性能,剖析零部件的功能,注重基础研究,弄清仪器的安全联锁保护是提高仪器使用与维修水平的关键;重视仪器的故障分析与判断、准确及地维修、合理地使用保养是保持仪器良好运行状态的唯一手段;建立仪器档案,定期进行性能测试是了解仪器,把握仪器运行脉搏、充分利用仪器的前提。