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.     

Size-Exclusion Chromatography: A Twenty-First Century Perspective

Now in its sixth decade, size-exclusion chromatography (SEC) remains the premier method by which to determine the molar mass averages and distributions of natural and synthetic macromolecules. Aided by its coupling to a variety and multiplicity of detectors, it has also shown its ability to characterize a host of other physicochemical properties, such as branching, chemical, and sequence length heterogeneity size distribution; chain rigidity; fractal dimension and its change as a function of molar mass; etc. SEC is also an integral part of most macromolecular two-dimensional separations, providing a second-dimension size-based technique for determining the molar mass of the components separated in the first dimension according to chemical composition, thus yielding the combined chemical composition and molar mass distributions of a sample. While the potential of SEC remains strong, our awareness of the pitfalls and challenges inherent to it and to its practice must also be ever-present. This Perspective aims to highlight some of the advantages and applications of SEC, to bring to the fore these caveats with regard to its practice, and to provide an outlook as to potential areas for expansion and growth.

     

中国科学院检验检测机构资质认定概况

中国科学院检验检测机构的使命与定位是为国家科技战略发展提供技术支撑和高水平服务,为中国科学院系统各单位的科研和工程及社会需求提供高科技含量的检验检测服务,满足社会的高新技术、新兴产业检验检测的需求,为高新技术、新兴产业的产品质量检验检测提供有效的技术保障.中国科学院系统现有检验检测机构67个,分布在21个省、市、地区,...     

Cell-based electrochemical biosensors for water quality assessment

During recent decades, extensive industrialisation and farming associated with improper waste management policies have led to the release of a wide range of toxic compounds into aquatic ecosystems, causing a rapid decrease of world freshwater resources and thus requiring urgent implementation of suitable legislation to define water remediation and protection strategies. In Europe, the Water Framework Directive aims to restore good qualitative and quantitative status to all water bodies by 2015. To achieve that, extensive monitoring programmes will be required, calling for rapid, reliable and cost-effective analytical methods for monitoring and toxicological impact assessment of water pollutants. In this context, whole cell biosensors appear as excellent alternatives to or techniques complementary to conventional chemical methods. Cells are easy to cultivate and manipulate, host many enzymes able to catalyse a wide range of biological reactions and can be coupled to various types of transducers. In addition, they are able to provide information about the bioavailability and the toxicity of the pollutants towards eukaryotic or prokaryotic cells. In this article, we present an overview of the use of whole cells, mainly bacteria, yeasts and algae, as sensing elements in electrochemical biosensors with respect to their practical applications in water quality monitoring, with particular emphasis on new trends and future perspectives. In contrast to optical detection, electrochemical transduction is not sensitive to light, can be used for analysis of turbid samples and does not require labelling. In some cases, it is also possible to achieve higher selectivities, even without cell modification, by operating at specific potentials where interferences are limited.     

Exploring supramolecular interactions and architectures by scanning force microscopies

The development of new methodologies based on scanning force microscopy (SFM) has made it possible to map topographies, chemical functionalities, and numerous other physicochemical properties of complex assemblies, to unravel dynamic processes, to measure forces generated along a reaction coordinate, to nanopattern surfaces and to nanomanipulate objects. This tutorial review highlights the most recent applications of these SFM-based capabilities, on and beyond imaging, to the exploration of supramolecular interactions and architectures, to the fabrication of smart materials and to the optimization of (nano)devices.     

Synthesis of heteroarylated ketones via bismuth(III) triflate-promoted regioselective 1,4- and 1,6-additions of electron-rich heteroarenes to cyclic enones and dienones

The development and optimization of bismuth(III) triflate-promoted regioselective 1,4- and 1,6-additions of electron-rich heteroarenes to cyclic, β,β-disubstituted enones and dienones is described. Additions of a range of heteroarenes, including furan, thiophene, pyrrole, and indole nucleophiles, to cyclic, β,β-disubstituted enones occur to form all-carbon quaternary centers in up to 88% yield. In addition, regioselective 1,6-additions of electron-rich heteroarenes to 3-vinyl-2-cyclohexenone occur to produce a variety of δ-heteroarylated, β,β-disubstituted enones in up to 93% yield. The high 1,6-selectivity for these reactions is attributed to the increased steric bulk at the β-position relative to the δ-position, and no competing 1,4-conjugate addition is observed.     

Water's polyamorphic transitions and amorphization of ice under pressure

Transformations of water's high density amorph (HDA) to low density amorph (LDA) and of LDA's to cubic ice (Ic) have been studied by in situ thermal conductivity kappa measurements at high pressures. The HDA to LDA transformation is unobservable at p of 0.07 GPa, indicating that, for a fixed heating rate, an increase in pressure increases the temperature of HDA to LDA transformation and decreases that of LDA to ice Ic, causing thereby the two transformations to merge, and HDA appears to convert directly to ice Ic. Thus either LDA forms but converts extremely rapidly to ice Ic, or LDA does not form. At a fixed p and T, in the range of pressure amorphization of hexagonal ice, kappa continues to decrease with time. Therefore, the amorphization of ice Ih is kinetically controlled. When HDA at 1 GPa was heated from 130 to 157 K and densified to very HDA, its kappa increased by 3%. Our findings and a scrutiny of earlier reports show that a reversible transition between HDA and LDA does not occur at approximately 135 K and approximately 0.2 GPa. Since there is no unique HDA, it is difficult to justify the conjecture for a second critical point for water.     

Molecular polarizability of organic compounds and their complexes: LVI. Molar volume and structure in a solution of the compounds with several axes of intramolecular rotation

Molar volumes in solutions of compounds like orthoformic esters, trialkyl phosphates, trialkylphosphites, substituted aziridines, cyclopropanes, cyclohexanes, boroxines, N-aryl-4-pyridones, decalines, and cyclooctane were determined and discussed. Conformations of alkyl substituents in the esters were found to be similar to the conformations of the corresponding alkanes. Molar volumes of aziridines and cyclopropanes were found to be additive with respect to the molar volumes of bond and group increments. The nature of solvation of the molecules of these compounds was found to be similar to that in the model systems which served for the calculations of the increments. Molar volumes of cyclohexane, decaline, and cyclooctane also were found to be additive with respect to the contributions of the molar volumes of increments of the corresponding bonds and groups. The solvation and the steric structure of substituted boroxines were found to be similar to those of the structurally analogous substituted benzenes. Conformations of N-aryl-4-pyridone and its substituted derivatives in solutions were found to be similar to the conformations of biphenyl and its derivatives. A possibility of simplification of the methods for determining the dipole moments and Kerr constants of compounds from their additive molar volumes was demonstrated.     

Structure and stability of xenon insertion compounds of hypohalous acids, HXeOX [X=F, Cl, and Br]: an ab initio investigation

The structure and stability of xenon-inserted hypohalous acids HXeOX (X=F, Cl, and Br) have been investigated theoretically using ab initio molecular orbital calculations. All these molecules are found to consist of a nearly linear HXeO moiety and a bend XeOX fragment. Geometrical parameters of HXeOX are comparable with that of experimentally observed HXeOH species. The dissociation energies corresponding to the lowest-energy fragmentation products, HOX+Xe have been computed to be -398.1, -385.5, and -386.7 kJmol for HXeOF, HXeOCl, and HXeOBr, respectively, at the MP2 level of theory. The respective barrier heights corresponding to the bent transition states (H-Xe-O bending mode) have been calculated to be 138.1, 138.4, and 138.2 kJmol with respect to HXeOX minimum. These species are found to be metastable in their respective potential-energy surface, and the dissociation energies corresponding to the H+Xe+OX products are found to be 56.8, 66.0, and 80.8 kJmol for HXeOF, HXeOCl, and HXeOBr, respectively. The energies corresponding to the H+Xe+O+X dissociation channel have been computed to be 272.0, 309.3, and 299.7 kJmol for HXeOF, HXeOCl, and HXeOBr, respectively, at the same level of theory. Energetics as well as geometrical considerations suggests that it may be possible to prepare these species experimentally similar to that of HXeOH species at low-temperature laser photolysis experiments.     

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。     

Affinity and enzyme-based biosensors: recent advances and emerging applications in cell analysis and point-of-care testing

The applications of biosensors range from environmental testing and biowarfare agent detection to clinical testing and cell analysis. In recent years, biosensors have become increasingly prevalent in clinical testing and point-of-care testing. This is driven in part by the desire to decrease the cost of health care, to shift some of the analytical tests from centralized facilities to "frontline" physicians and nurses, and to obtain more precise information more quickly about the health status of a patient. This article gives an overview of recent advances in the field of biosensors, focusing on biosensors based on enzymes, aptamers, antibodies, and phages. In addition, this article attempts to describe efforts to apply these biosensors to clinical testing and cell analysis.     

Functional molecules in electronic circuits

Molecular electronics is a fascinating field of research contributing to both fundamental science and future technological achievements. A promising starting point for molecular devices is to mimic existing electronic functions to investigate the potential of molecules to enrich and complement existing electronic strategies. Molecules designed and synthesized to be integrated into electronic circuits and to perform an electronic function are presented in this article. The focus is set in particular on rectification and switching based on molecular devices, since the control over these two parameters enables the assembly of memory units, likely the most interesting and economic application of molecular based electronics. Both historical and contemporary solutions to molecular rectification are discussed, although not exhaustively. Several examples of integrated molecular switches that respond to light are presented. Molecular switches responding to an electrochemical signal are also discussed. Finally, supramolecular and molecular systems with intuitive application potential as memory units due to their hysteretic switching are highlighted. Although a particularly attractive feature of molecular electronics is its close cooperation with neighbouring disciplines, this article is written from the point of view of a chemist. Although the focus here is largely on molecular considerations, innovative contributions from physics, electro engineering, nanotechnology and other scientific disciplines are equally important. However, the ability of the chemist to correlate function with structure, to design and to provide tailor-made functional molecules is central to molecular electronics.     

Editorial 2006

Dear Authors and Readers, The year 2005 was a specially remarkable year filled with much excitement, success, joy and sadness. The new format of the Journal proved to meet everybody's satisfaction. It is much easier to read, and the figures and tables are better positioned as there is more space to accommodate them. Not only did we change the appearance, but we have restructured the leading body of the Journal reorganizing the former Editorial Board and assigning Associate Editors according to main subject areas. With this solution proved to be a much more operational and practical one, and contributed to the increase of the scientific level of the Journal. It is a commonplace, that we live in a more and more specialised world. This trend is palpable in thermal analysis and we can experience it as we receive submissions dealing with very specialised topics. In order to strengthen our peer-review system, we hoped that the decision to divide the Associate Editors into main subject areas, will assist them in their work to establish and build a network of support reviewers from that particular field. After a year we can already see the result of this effort and we are very happy to look at the longer-than-ever list of reviewers we acknowledge for their scientific support (find the list of names on the next pages). Here I need to complement you all, as I am convinced that your enthusiastic and conscientious work is the foundation of our success, as it is reflected in the Impact Factor 2004 reaching the unprecedented height of 1.478 compared to 1.094 for 2003. Last but not least the novelty of 2005 was the introduction of the 'Online First' section on the electronic site of JTAC. We have fought for the opportunity to provide better service to our authors in terms of through-over-time for long and this solution finally offered the possibility to achieve it. It was a jubilation when we could publish the first papers in the 'Online First' section at the first time, and we felt that the most appropriate way to share our happiness is to publish the papers of the already finalized 'Celebration Issue' that was a surprise gift to us celebrating the 36th anniversary of the Journal with not less than 36 outstanding communications from the most prestigious scientists. I owe a special thanks to my long time friend and colleague Prof. Shmuel Yariv organising this Issue - this very moving gift - and for the excellence how he executed the collection and preparation of the papers. Last, but not least I need to express my sincere gratitude to all of those contributed with their high standard work to this December issue. We would like to acknowledge all those who had been working with us in the past years, and now giving space to new members in the line of Regional and Associate Editors. Special thanks to Prof. Gavrichev, Prof. Ray and Prof. Walter, Regional Editors, furthermore to Dr. Emmerich, Prof. Jones and Prof. Beezer, Associate Editors for their valuable work, and support. At the same time we have the pleasure to welcome the new Regional Editors: Prof. T. Usacheva for Russia, Prof. P. Thomas and Prof. D. Bessiéres for English and French speaking teritorries respectively. Our new Associate Editors are: Prof. G. Pokol, Prof. S. C. Mojumdar, Prof. E. Boldyreva and Prof. P. Budrugeac. I would like to provide a forum for new ideas and here I would like to call on to all Editors to contribute to this initiation. I am planning to write a mid-year editorial where we would share these new ideas, i.e. the issue of 'Short Communications' and similar topics of wide interest. This year was just as tragic as it was sucessful in losing many of our colleagues.We could hardly recover from the news of the sudden death of Prof. M. Richardson, Prof. Maria Kurzawa and our close friend and Associate Editor Prof. Lisardo Nuñez Reguiera when we had to say our final good bye to our beloved teacher, a world wide acknowledged scientist and inventor Prof. F. Paulik. Finally, I would like to wish a prosperous new year, health and success in every aspect of your life to all of you.     

Stress-induced increase in the amounts of maysin and maysin derivatives in world premium natural compounds from centipedegrass

The red leaves of centipedegrass are known to produce compounds with stronger antibiotic effects than those produced by green leaves. Therefore, the aim of this study was to identify if stress methods (e.g., gamma irradiation, UV-B irradiation, and wounding) could effectively convert green leaves to red leaves, and thereby increase the production of maysin and maysin derivatives that have been known for antibiotic properties. Our results showed differential concentration changes for different compounds using these stress methods. The concentrations of luteolin increased from 0.014% to 0.019%, 0.022%, and 0.028% following gamma irradiation, UV-B irradiation, and wounding, respectively. The concentration of isoorientin increased from 0.898% to 1.938% and 2.538%, while the concentration of mixed rhamnosylisoorientin and orientin increased from 0.303% to 0.474% and 0.690%, following UV-B irradiation and wounding, respectively. Gamma irradiation produced concentrations of isoorientin, rhamnosylisoorientin, and orientin similar to those found in red leaves. The concentrations of derhamnosylmaysin increased from 0.004% to 0.009%, 0.015%, and 0.024% by gamma irradiation, UV-B irradiation, and wounding, respectively. The concentration of maysin increased from 0.515% to 0.714%, 0.583%, and 0.777% by gamma irradiation, UV-B irradiation, and wounding, respectively, while the concentration of luteolin-6-C-boivinopyranoside increased from 0.324% to 0.834%, 0.979%, and 1.493% by gamma irradiation, UV-B irradiation, and wounding, respectively. According to these results, wounding and gamma irradiation are promising methods for increasing the concentrations of maysin and maysin derivatives.     

Sensitivity of metal nanoparticle surface plasmon resonance to the dielectric environment

Electrodynamic simulations of gold nanoparticle spectra were used to investigate the sensitivity of localized surface plasmon band position to the refractive index, n, of the medium for nanoparticles of various shapes and nanoshells of various structures. Among single-component nanoparticles less than 130 nm in size, sensitivities of dipole resonance positions to bulk refractive index are found to depend only upon the wavelength of the resonance and the dielectric properties of the metal and the medium. Among particle plasmons that peak in the frequency range where the real part of the metal dielectric function varies linearly with wavelength and the imaginary part is small and slowly varying, the sensitivity of the peak wavelength, lambda, to refractive index, n, is found to be a linearly increasing function of lambda, regardless of the structural features of the particle that determine lambda. Quasistatic theory is used to derive an analytical expression for the refractive index sensitivity of small particle plasmon peaks. Through this analysis, the dependence of sensitivity on band position is found to be determined by the wavelength dependence of the real part, epsilon', of the particle dielectric function, and the sensitivity results are found to extend to all particles with resonance conditions of the form, epsilon' = -2chin(2), where chi is a function of geometric parameters and other constants. The sensitivity results observed using accurate computational methods for dipolar plasmon bands of gold nanodisks, nanorods, and hollow nanoshells extend, therefore, to particles of other shapes (such as hexagonal and chopped tetrahedral), composed of other metals, and to higher-order modes. The bulk refractive index sensitivity yielded by the theory serves as an upper bound to sensitivities of nanoparticles on dielectric substrates and sensitivities of nanoparticles to local refractive index changes, such as those associated with biomolecule sensing.     

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.     

The Contribution of Carl (Speed) Marvel to Polymer Science

It is an exceptional honor and privilege for me to contribute to this special symposium “Polymer Synthesis-The 1980's”, and lam very much obliged to Eli Pearce for giving me the opportunity to present to you a short report on the life and on the extraordinary accomplishments of our new Honorary Doctor of Sciences. When, about a year ago a group of us thought that our Polymer Research Institute should recognize Professor Marvel's outstanding contribution to polymer science in an unusual manner, it was felt that a special symposium should be organized in his honor and that he should receive an Honorary Degree of Science at this occasion. The conferment of such a degree is, of course, a matter of the faculty, but our Provost, Professor Donaruma, succeeded to overcome all difficulties and we were able to issue the invitation for this symposium which, to our great satisfaction, is being attended by such a large group of friends and admirers of our honoree. A few who would have liked to be here were unable to come but sent letters with the expression of their sincere regrets to be absent and of their congratulations. I am giving these letters to Professor Marvel; they are signed by Ed Jefferson, Dick Heckert, Paul Flory, and Frank Press. But now to the topic of my address.     

Multivalent ions and biomolecules: Attempting a comprehensive perspective

Ions are ubiquitous in nature. They play a key role for many biological processes on the molecular scale, from molecular interactions, to mechanical properties, to folding, to self-organisation and assembly, to reaction equilibria, to signalling, to energy and material transport, to recognition etc. Going beyond monovalent ions to multivalent ions, the effects of the ions are frequently not only stronger (due to the obviously higher charge), but qualitatively different. A typical example is the process of binding of multivalent ions, such as Ca²⁺, to a macromolecule and the consequences of this ion binding such as compaction, collapse, potential charge inversion and precipitation of the macromolecule. Here we review these effects and phenomena induced by multivalent ions for biological (macro)molecules, from the “atomistic/molecular” local picture of (potentially specific) interactions to the more global picture of phase behaviour including, e. g., crystallisation, phase separation, oligomerisation etc. Rather than attempting an encyclopedic list of systems, we rather aim for an embracing discussion using typical case studies. We try to cover predominantly three main classes: proteins, nucleic acids, and amphiphilic molecules including interface effects. We do not cover in detail, but make some comparisons to, ion channels, colloidal systems, and synthetic polymers. While there are obvious differences in the behaviour of, and the relevance of multivalent ions for, the three main classes of systems, we also point out analogies. Our attempt of a comprehensive discussion is guided by the idea that there are not only important differences and specific phenomena with regard to the effects of multivalent ions on the main systems, but also important similarities. We hope to bridge physico-chemical mechanisms, concepts of soft matter, and biological observations and connect the different communities further.     

Syntheses of linear ethoxysiloxanes by the oxidative condensation of triethoxysilane

Linear ethoxysiloxanes were synthesized by the oxidative condensation of hydrosilane. Triethoxysilane was subjected to oxidation to form triethoxysilanol, and pentaethoxydisiloxane was formed by the condensation reaction of triethoxysilane with triethoxysilanol. Pentaethoxydisiloxane was also subjected to oxidative condensation to form a mixture of nona- and decaethoxytetrasiloxanes. In contrast, pentaethoxydisiloxane, heptaethoxytrisiloxane, and nonaethoxytetrasiloxanes were subjected to the reaction with ethanol in the presence of zinc to isolate hexaethoxydisiloxane, octaethoxytrisiloxane, and decaethoxytetrasiloxane, respectively.     

Patents and literature

Protein engineering and site-directed mutagenesis is becoming immensely important in both fundamental studies and commercial applications involving proteins and enzymes in biocatalysis. Protein engineering has become a powerful tool to help biochemists and molecular enzymologists elucidate structure-function relationships in enzymic active sites, to understand the intricacies of protein folding and denaturation, and to alter the selectivity of enzymatic catalysis. Commercial applications of engineered enzymes are being developed to increase protein stability, widen or narrow substrate specificity, and to develop novel approaches for use of enzymes in organic synthesis, drug design, and clinical applications. In addition to protein engineering, novel expression systems have been designed to prepare large quantities of genetically engineered proteins. Recent US patents and scientific literature on protein engineering, site-directed mutagenesis, and protein expression systems related to protein engineering are surveyed. Patent abstracts are summarized individually and a list of literature references are given.