半夏淀粉的理化特性

研究了不同产地的4种半夏淀粉的理化特性,包括直链淀粉含量、膨胀度、溶解性、持水性、淀粉粒大小和形貌、结晶类型、热特性和糊化特性等。结果表明,这些半夏淀粉中直链淀粉含量为18.60%～23.91%;膨胀度21.53%～23.09%;溶解度11.5%～32.3%;持水性100.3%～119.0%。淀粉粒单粒球形,卵形或圆半球形,直径2～20μm,复粒由2～3个分粒组成,其结晶类型均为C型,结晶度15.0%～37.9%。用差示扫描量热仪测得的转变温度TO、TP和TC分别为71.58～77.75℃、83.03～83.84℃和89.41～90.99℃,热焓为4.316～5.809 J/g。用快速粘度分析仪测定了4种半夏淀粉的糊化特征值:峰值粘度、热糊粘度、冷糊粘度、稀懈值和回复值分别为149.5～226.2、97.7～127.2、141.8～194.3、50.4～99.0和44.2～67.2 RVU。糊化温度77.8～79.9℃,峰值时间8.3～8.7 min。     

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,...     

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。     

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.     

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.     

“The Fitness of Their Union”: Travel and Health in the Letters of Humphry and Jane Davy

The letters of Humphry Davy and his circle, to be published shortly, shed new light on his marriage to Jane Apreece. This paper examines the journeys undertaken by the couple, together and separately, with particular attention to the therapeutic benefits they sought from travel. I argue that their increasingly divergent itineraries reflected a growing understanding that Humphry and Jane had different humoral temperaments or constitutions, leading them to seek different climatic conditions to cure their ailments. While Jane’s temperament was classified as melancholic, requiring her to travel to warmer and sunnier climes during the English winter, Humphry’s was believed to be sanguine, meaning he had to avoid excessive heat along with stimulating food and drink. He relied on classical ideas about individuals’ different humoral constitutions, and the therapies appropriate to them, while measuring atmospheric variables to determine the best places to restore his health. The Davys’ letters reveal the beliefs about bodily differences and atmospheric conditions that shaped their therapeutic travels.     

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.

     

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.     

Designing for sustainability with biocatalytic and chemoenzymatic cascade processes

Cascade reactions have been widely recognized to cut costs, decrease solvent usage, and reduce cycle times in chemical processes. Recently, biocatalytic cascades have altered how we design synthetic routes to complex molecules to achieve sustainable commercial processes for pharmaceutical, agricultural, and fine chemical industries. With advancements in protein engineering and an increase in the number of enzyme classes available to chemists, industrial and academic groups alike have endeavored to expand the scope of biocatalysis from single reactions to multi-enzyme cascades to rapidly build complex molecular structures. Recent reports have drawn inspiration from biosynthetic pathways and have applied engineered enzymes to in vitro enzymatic cascades. Furthermore, combining transition-metal catalysis and enzymes in one-pot chemoenzymatic cascades likewise serves to broaden the scope of biocatalysis, enabling traditional chemical reactions to be performed under mild aqueous conditions. In this article, we review recent biocatalytic and chemoenzymatic cascades from 2019 to 2021.     

Distribution of uranium and thorium in fractionated sediment samples obtained from different locations across Thane Creek area (Mumbai,India)

Uranium concentration varies from 9.01 to 12.7, 8.03 to 11.5, 9.1 to 14.0 and 10.1 to 14.2 mg/kg in grab sediment, coarse sand fraction, fine sand fraction, silt and clay fraction respectively. Thorium concentration varies from 20.0 to 29.4, 17.3 to 28.6, 19.6 to 30.4 and 21.1 to 35.9 in grab sediment, coarse sand fraction, fine sand fraction, silt and clay fraction respectively. Uranium and thorium concentrations vary in different size fractionated sediment samples like silt and clay fraction > fine sand fraction > coarse sand fraction.     

A Festschrift in honor of Akira Imamura��s 77th birthday, his recent retirement, and his many contributions to theoretical chemistry

The Imamura Festschrift Issue of Theoretical Chemistry Accounts is a special multifocus international issue commemorating the 77th birthday of Professor Akira Imamura and his many contributions to the fields of theoretical chemistry, polymer science, molecular biophysics, chemical physics, and molecular biology. This issue has contributions in theoretical developments of methods applicable to larger polymeric systems, for example, the elongation method pioneered by Professor Imamura and his group, and more recently by the groups of Professor Yuriko Aoki at Kyushu University and Professor Feng Long Gu at South China Normal University, supported by several funds from the Japan Science and Technology Agency (JST). In addition, there are contributions from top experimental and theoretical groups in the areas of nanotechnology, bionanotechnology, quantum transport theory, molecular biophysics, molecular electronics, and even molecular medicine and medical diagnostics, where the marriage between theory and experiment is very important to be able to fully understand, interpret, and utilize the wealth of new and exciting experimental data. The development of new and refined methods, and the extension of older more conventional methods, will be required for these fields to continue to evolve/co-evolve and develop, as they have in the last 60?years. But to evolve in a guided fashion (guided evolution), that is, to meet the needs and functions of not only the individual scientists and research groups but also of society in general, will require a concerted effort from not only experimentalists and theoreticians in each individual subdiscipline but also for them to work together and share their accumulated knowledge and experience, as is now being done in various research networks around the world, including the one originally initiated/formed by Professor Imamura and Professor Janos Ladik at the Third International Congress of Quantum Chemistry (ICQC) in Kyoto, Japan. Through this network, Professor Imamura has been able to pass on a wealth of knowledge, expertise, and experience to the current and future generations of scientists in Germany, the United States, and China, as Professor Imamura is still doing with his lectures both in Japan at Kyushu University and in China at South China Normal University, and previously in Erlangen at the University of Erlangen, in Heidelberg at the German Cancer Research Center (DKFZ) in Germany, and in Ithaca, New York at Cornell University in the United States. He has been a real example of the modern protean research scientist and professor who has continued to be in research and teaching, active well beyond the formerly set retirement age of 63 or 65 set by society. The idea that researchers and professors cannot be active in their 60s, 70s, and 80s has now also been shown to be a misconception that needs to be corrected at the funding and institutional levels. Too many very active, knowledgeable, and experienced researchers and professors have been forced to stand on the sidelines, while those who have replaced them have very little practical knowledge, expertise, and more importantly, life experience. A whole generation of young academics are being hired who have never worked a day in industry, never visited an industrial laboratory and/or research group, and hence are unable, (don??t know) and in many cases, unwilling to train and educate their students with the skills they need to not only work in industry but also to create new and exciting new industries. The idea that the large chemical and pharmaceutical companies and government laboartories will hire all of the ever increasing numbers of undergraduate and graduate (MSc and PhD) students no longer applies. The university mission is no longer just to teach, give knowledge, and to do research, but also to innovate, that is, to train the students to take their acquired knowledge from their text books and apply it with the newly acquired knowledge in the research laboratories to start and develop new industries and companies. But this means that the students need to be trained in the fields of engineering economics, finance, and scientific and international law, so that they are able to undertake such projects, in addition to understanding and applying their scientific knowledge. It will also require a concerted effort by funding agencies, state, local, federal, and even international bodies that seek to create and sustain strong economies and infrastructure, which will support and be supported by the highly motivated, trained, and educated work forces. The third pillar is now being established, but it needs to now be totally and completely integrated with the other establishments and infrastructure.     

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.     

Optimization of mass spectrometry acquisition parameters for determination of polycarbonate additives,degradation products,and colorants migrating from food contact materials to chocolate

The interest towards “substances of emerging concerns” referred to objects intended to come into contact with food is recently growing. Such substances can be found in traces in simulants and in food products put in contact with plastic materials. In this context, it is important to set up analytical systems characterized by high sensitivity and to improve detection parameters to enhance signals. This work was aimed at optimizing a method based on UHPLC coupled to high resolution mass spectrometry to quantify the most common plastic additives, and able to detect the presence of polymers degradation products and coloring agents migrating from plastic re‐usable containers. The optimization of mass spectrometric parameter settings for quantitative analysis of additives has been achieved by a chemometric approach, using a full factorial and d‐optimal experimental designs, allowing to evaluate possible interactions between the investigated parameters. Results showed that the optimized method was characterized by improved features in terms of sensitivity respect to existing methods and was successfully applied to the analysis of a complex model food system such as chocolate put in contact with 14 polycarbonate tableware samples. A new procedure for sample pre‐treatment was carried out and validated, showing high reliability. Results reported, for the first time, the presence of several molecules migrating to chocolate, in particular belonging to plastic additives, such Cyasorb UV5411, Tinuvin 234, Uvitex OB, and oligomers, whose amount was found to be correlated to age and degree of damage of the containers.     

Effects of Variety and Growing Location on Physicochemical Properties of Starch from Sweet Potato Root Tuber

Three sweet potato varieties with purple-, yellow-, and white-fleshed root tubers were planted in four growing locations. Starches were isolated from their root tubers, their physicochemical properties (size, iodine absorption, amylose content, crystalline structure, ordered degree, lamellar thickness, swelling power, water solubility, and pasting, thermal and digestion properties) were determined to investigate the effects of variety and growing location on starch properties in sweet potato. The results showed that granule size (D[4,3]) ranged from 12.1 to 18.2 μm, the iodine absorption parameters varied from 0.260 to 0.361 for OD620, from 0.243 to 0.326 for OD680 and from 1.128 to 1.252 for OD620/550, and amylose content varied from 16.4% to 21.2% among starches from three varieties and four growing locations. Starches exhibited C-type X-ray diffraction patterns, and had ordered degrees from 0.634 to 0.726 and lamellar thicknesses from 9.72 to 10.21 nm. Starches had significantly different swelling powers, water solubilities, pasting viscosities, and thermal properties. Native starches had rapidly digestible starch (RDS) from 2.2% to 10.9% and resistant starch (RS) from 58.2% to 89.1%, and gelatinized starches had RDS from 70.5% to 81.4% and RS from 10.8% to 23.3%. Two-way ANOVA analysis showed that starch physicochemical properties were affected significantly by variety, growing location, and their interaction in sweet potato.     

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。     

防生物危害学:保障生物安全的新学科

生物安全作为我国12个安全领域之一,已经得到社会各界的重视,《中华人民共和国生物安全法》也于2020年10月颁布,为科学应对生物危害提供了法律基础。生物威胁来源及其危害对象(人、动物、植物和环境)都是多元的。目前,应对生物威胁仍是以"防生物危害医学"学科为基础,但在应对这种多元化生物安全问题上,显示出了该学科的局限性。该文在讨论生物安全概念演化和生物威胁类别的基础上,提出了防生物危害学新学科的发展及其涵盖范畴,以从学科发展角度为保障我国生物安全奠定基础。     

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.     

Resonant soft X-ray scattering in polymer science

Resonant soft X-ray scattering (RSoXS) is an emerging, powerful technique to probe the nano-to-mesoscale structure of polymers and other molecules. It joins together small-angle X-ray scattering (a statistical nanoprobe) with X-ray spectroscopy that brings with it unique chemical and bond-orientation sensitivity. Through over a decade of discovery and development, RSoXS is moving from a niche technique applied to organic electronic thin films to a mature tool applicable to a plethora of polymeric and molecular systems, encompassing new modalities, analyses, and simulation methods. This development promises to deliver increasingly quantitative answers to challenging questions in polymer science as well as expand its usefulness to complementary fields. This review presents a full synopsis of the technique, including background on the theoretical underpinnings, measurement best practices, and examples of recent RSoXS applications and discoveries provided here to accelerate the transition to a broader range of soft matter and polymeric fields.     

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.