Click‐Assembled,Oxygen‐Sensing Nanoconjugates for Depth‐Resolved,Near‐Infrared Imaging in a 3 D Cancer Model

Hypoxia is an important contributing factor to the development of drug‐resistant cancer, yet few nonperturbative tools exist for studying oxygenation in tissues. While progress has been made in the development of chemical probes for optical oxygen mapping, penetration of such molecules into poorly perfused or avascular tumor regions remains problematic. A click‐assembled oxygen‐sensing (CAOS) nanoconjugate is reported and its properties demonstrated in an in vitro 3D spheroid cancer model. The synthesis relies on the sequential click‐based ligation of poly(amidoamine)‐like subunits for rapid assembly. Near‐infrared confocal phosphorescence microscopy was used to demonstrate the ability of the CAOS nanoconjugates to penetrate hundreds of micrometers into spheroids within hours and to show their sensitivity to oxygen changes throughout the nodule. This proof‐of‐concept study demonstrates a modular approach that is readily extensible to a wide variety of oxygen and cellular sensors for depth‐resolved imaging in tissue and tissue models.     

Determination of pKa values of organic bases in aqueous acetonitrile solutions using capillary electrophoresis

Capillary electrophoresis (CE) was used for the determination of ionisation constants (pKa) of a variety of organic bases in aqueous acetonitrile solutions over the range 0-60% (v/v) acetonitrile. These bases are used as test compounds in HPLC column evaluation, thus knowledge of their pKa in hydro-organic solutions is useful. The base pKa decreased with acetonitrile concentration and significant shifts from the aqueous pKa (up to -0.8) were found using 60% acetonitrile. The CE application was confirmed to be very suitable for fast and accurate pKa measurement in aqueous organic solutions.     

Click‐Assembled,Oxygen‐Sensing Nanoconjugates for Depth‐Resolved,Near‐Infrared Imaging in a 3 D Cancer Model

Hypoxia is an important contributing factor to the development of drug‐resistant cancer, yet few nonperturbative tools exist for studying oxygenation in tissues. While progress has been made in the development of chemical probes for optical oxygen mapping, penetration of such molecules into poorly perfused or avascular tumor regions remains problematic. A click‐assembled oxygen‐sensing (CAOS) nanoconjugate is reported and its properties demonstrated in an in vitro 3D spheroid cancer model. The synthesis relies on the sequential click‐based ligation of poly(amidoamine)‐like subunits for rapid assembly. Near‐infrared confocal phosphorescence microscopy was used to demonstrate the ability of the CAOS nanoconjugates to penetrate hundreds of micrometers into spheroids within hours and to show their sensitivity to oxygen changes throughout the nodule. This proof‐of‐concept study demonstrates a modular approach that is readily extensible to a wide variety of oxygen and cellular sensors for depth‐resolved imaging in tissue and tissue models.     

高分子材料分析与测试课程设计与教学改革

介绍黎明职业大学高分子材料加工技术专业的核心课程《高分子材料分析与测试》的课程设计和教学改革的做法。课程以实现学生向"准员工"的转变为教学目标。通过对行业企业进行调研,确定该课程的对接岗位为质量检验岗位,工作内容为化验、质检和品管,基于岗位工作内容进行课程设计。采用项目化方式,三个工作内容分别对应以典型方法、典型产品和典型常识为项目进行模块设计。以模块任务为中心,将教师的"讲"与学生的"练"有机结合起来,综合应用提倡学生互教的交互培训法、引导学生自主学习的主题探究法、锻炼学生专业素质的四阶段技能训练法等教学方法。     

A new method for the calculation of atomic and local hardness

The relationships between atomic hardness, atomic electronegativity, and electronic energy are considered and emphasized. A new method for calculating atomic hardness is described. The concept of local hardness is quantified through the calculation of a new variable named alfahardness. Atomic hardness and alfahardness are used for the calculation of both the mean molecular and local properties. The results obtained are discussed and a comparison made with the analogous quantities presented by Pearson. An algorithm has been realized and transformed into a computer routine for use within a CAOS program.     

A review of the radiation stability of ion exchange materials

A comprehensive literature survey on the radiation stability of ion exchangers resulted in the publication of an extensive data compilation on the effects of ionizing radiation on synthetic organic ion exchangers in this journal (Vol. 97, No. 1). This paper is a brief review of the majorfindings of this literature survey along with similar information on synthetic inorganic ion exchangers. The primary goal of this literature survey is to review present knowledge on the effects of ionizing radiations on synthetic ion exchange materials used in radiochemical processing. Although there are gaps in our knowledge of the mechanisms of radiolytic changes in ion exchangers, the information available in the literature shows some general trends and similarities in observed qualitative effects by different types of organic and inorganic ion exchange materials. These trends and observations have been formulated into a set of qualitative and semi-quantitative statements that can be useful to potential users of ion exchange materials in nuclear material processing and radioactive waste management. Present knowledge, of the behavior of ion exchangers under the influence of ionizing radiations is too limited to justify quantitative predictive modeling.     

The methodology of knowledge acquisition from the collection of IR and UV spectra

An expert system for identification of parts of chemical molecules from IR and UV spectra is described. To develop the system, the intelligent knowledge engineering program environment SCANKEE¹ (elaborated at the Department of Computer Chemistry) was applied. The expert systems for identification of a chemical compound described in the literature use hand-crafted knowledge bases. To eliminate the time-consuming writing of the rules, a module for the automatic creation of rule knowledge bases was developed. The knowledge derives from the collection of molecular spectra of organic compounds and their structural formulae. The algorithm for the automatic generation of the production rules (in the rule knowledge base) is realized in two steps: (i) the creation of the correlation tables and (ii) the generation of the production rules base.     

The methodology of knowledge acquisition from the collection of IR and UV spectra

An expert system for identification of parts of chemical molecules from IR and UV spectra is described. To develop the system, the intelligent knowledge engineering program environment SCANKEE¹ (elaborated at the Department of Computer Chemistry) was applied. The expert systems for identification of a chemical compound described in the literature use hand-crafted knowledge bases. To eliminate the time-consuming writing of the rules, a module for the automatic creation of rule knowledge bases was developed. The knowledge derives from the collection of molecular spectra of organic compounds and their structural formulae. The algorithm for the automatic generation of the production rules (in the rule knowledge base) is realized in two steps: (i) the creation of the correlation tables and (ii) the generation of the production rules base. Received: 1 July 1997 / Revised: 3 November 1997 / Accepted: 7 November 1997     

Mechanistic considerations on catalytic H/D exchange mediated by organometallic transition metal complexes

The purpose of this review is to analyze the different reaction mechanisms of the H/D exchange on organic substrates catalyzed by transition metal complexes in homogeneous phase. The metal-catalyzed H/D exchange is a multifaceted reaction whose mechanism depends strongly on the reaction conditions and on the metal complex used as a catalyst. It is possible to group the different mechanisms into three main families depending on the “role” and behavior of the catalyst: (i) Lewis acid–base catalysis; (ii) CH activation (iii) insertion/β-elimination. For each macro-group, several representative examples are discussed and critically evaluated in order to provide the reader with keys to the understanding of how the different catalytic systems act and how their modification may affect their performance in terms of activity and selectivity. This knowledge is fundamental for designing improved organometallic H/D catalysts for labeling organic products in greener conditions with more cost-effective processes.     

Recent advances in anticancer ruthenium Schiff base complexes

Nowadays in cancer treatment, both metal complexes and organic molecules are being widely used. Current years have seen a surge of interest in the application of organometallic compounds to treat cancer and other diseases. Undeniably, the unique properties of organometallic compounds, intermediate between those of classical inorganic and organic materials, provide new opportunities in the field of medicinal chemistry. Since the discovery of cisplatin, many transition metal complexes have been synthesized and assayed for anticancer activity. In recent years, ruthenium-based Schiff base complexes have emerged as promising antitumor and antimetastatic agents with potential uses in treatment of platinum-resistant tumors or as alternatives to platinum-based chemotherapy. Advantages of utilizing ruthenium complexes in drug development include reliable methods of synthesizing stable complexes; the ability to tune ligand affinities, electron transfer and substitution rates, and reduction potentials; and an increasing knowledge of the biological effects of such complexes. This great expansion of ruthenium-based Schiff base complexes is mainly due to the unique ability of the ruthenium core to permit multiple oxidation states, hence versatile electron-transfer pathways, and because of the ease of preparation with versatile and variable-denticity Schiff base ligands. This review aims to bring the reader up to date with the more recent Ru(II)/(III)-based Schiff base complexes that have been synthesized and investigated for their cytotoxicity.     

Characterization of Radioactive Hazardous Waste

The characterization of radioactive hazardous waste, also known as transuranic "mixed waste" has to be completed before it can be classified for proper treatment (incinerator, mechanical compaction or thermal treatment), packing, and transport. The characterization of the TRU mixed waste is not only complex process but rather an expensive undertaking. The process knowledge is the basic foundation of characterization. It is the documented knowledge of processes and materials that generated the waste. The transuranic waste Quality Assurance Program Plan (QAPP) defines the Data Quality Objectives (DQO's) and provides the scope of analytical parameters and methods required to accurately characterize the radioactive mixed waste. Based on the historical data and process knowledge a sampling and analysis plan can be developed to characterize the radioactive hazardous waste. Based on the characterization, an assessment of the regulatory status can be made before the waste could be accepted for disposal at the WIPP facility. The Waste Acceptance Criteria (WAC) developed by WIPP defines the parameters for receiving and final disposal of the TRU waste. The sets of criteria, such as: heat generated, fissile gram equivalent (FGE), plutonium-equivalent (PE) curies, and specifications of a dose rate have to be met before the waste is accepted for deep geological disposal. The characterization of radioactive waste becomes even more complex due to the presence of iron base metals/alloys, aluminum base metals/alloys, organic, chelating agents that are mixed with plastic, rubber, cellulose, soils and cement. Some of the modern characterization technologies that are under development and currently used for TRU mixed wastes are: nondestructive examination, nondestructive assay, headspace gas analysis, and drum coring for Resources Conservation Recovery Act (RCRA) sampling.     

Solution Structure of Turbo‐Hauser Base TMPMgCl⋅LiCl in [D8]THF

Turbo‐Hauser bases are very useful and highly reactive organometallic reagents in synthesis. Especially TMPMgCl ? LiCl 1 (TMP=2,2,6,6‐tetramethylpiperidide) is an excellent base for converting a wide range of (hetero)aromatic substrates into highly functionalized compounds with a broad application in organic synthesis. The knowledge of its structure in solution is of essential importance to understand the extraordinary reactivity and selectivity. However, very little is known about the aggregation of this prominent reagent in solution. Herein, we present the THF‐solution structure of 1 by employing our newly elaborated DOSY NMR method based on external calibration curves (ECC) with normalized diffusion coefficients.     

Mannich-Type Reaction for Synthesis of 3-Methyl-4-nitroimino-tetrahydro-1,3,5-oxadiazine

The reaction of N-methyl-N′-nitroguanidine with 3-methyl-4-nitroimino-tetrahydro-1,3,5-oxadiazine is a Mannich-type reaction. The reaction was catalyzed by several organic and inorganic bases at different reaction times and temperatures. Three inorganic base catalysts [potassium carbonate (K₂CO₃), sodium hydrogen carbonate (NaHCO₃), and sodium hydroxide (NaOH)] and several organic bases (methylamine, ethamine, iso-propylamine, and n-butylamine) have been studied. The results showed that both the inorganic and organic base catalysts can be used as catalysts, with the organic bases performing better. N-Methyl-N′-nitroguanidine reacts to give the title compound 2 and is catalyzed by both acids and bases. The intensity of inorganic base catalysts, reaction temperature, and reaction time had significant effects on the products.     

N‐Heterocyclic Carbene Mediated Activation of Tetravalent Silicon Compounds: A Critical Evaluation

An overview of the recent bibliography concerning the N‐heterocyclic carbene (NHC)‐mediated activation of tetravalent silicon compounds is presented. Diverse reactions are discussed, such as the NHC‐mediated addition of silyl pronucleophiles to a variety of electrophiles, NHC‐promoted organic and inorganic polymerisation and the reduction of CO₂ by hydrosilanes as facilitated by NHCs. The review concludes with a discussion of the current knowledge regarding the role of Lewis acid–base NHC–Si interactions in the mechanistic course of these reactions.     

The Displacement of Sr from Organic Chelates by Hydroxide, Carbonate, and Calcium in Concentrated Electrolytes

The effects of calcium, hydroxide, and carbonate on the displacement of Sr from four organic chelates: ethylenedinitrilotetraacetic acid (EDTA), N-(2-hydroxyethyl)ethylenedinitrilotriacetic acid (HEDTA) nitrilotriacetic acid (NTA), and iminidiacetic acid (IDA) was studied in solutions with high base and carbonate concentration. Comparison of solutions with and without added chelators allowed the speciation changes in solution to be directly determined. Increases in both carbonate and calcium concentration were effective in displacing Sr from the chelators even under high carbonate concentration. Increases in hydroxide were ineffective in removal of Sr from the chelators, even at base concentrations as high as 6M. Under certain specific conditions, most notably when both CaCO₃(s) and SrCO₃(s) are present in solution, chemical equilibrium constraints result in cancelation of activity coefficient changes for aqueous Sr and Ca organic chelate complexes. Under such conditions the predicted ratios of chelated Ca and Sr become independent of the ionic media and predictive relations using known equilibrium constants give very good representations of the experimental data. These results indicate that manipulation of metal ion displacement reactions during chemical processing of Sr–chelate solutions can result in the displacement of Sr from organic chelators. The implications of such strategies in processing high level waste supernatants stored at Department of Energy (DOE) sites is discussed.     

Drug-like index: a new approach to measure drug-like compounds and their diversity

Combinatorial organic synthesis (combinatorial chemistry or CC) and ultrahigh-throughput screening (UHTS) are speeding up drug discovery by increasing capacity for making and screening large numbers of compounds. However, a key problem is to select the smaller set of "representative" compounds from a virtual library to make or screen. Our approach is to select drug-like as well as structurally diverse compounds. The compounds, which are not very drug-like, are less taken into account or excluded even if they contribute to the diversity of the collection. Hence, the first step in the compound selection is to rank compounds in drug-like "degree". To quantify the drug-like "degree", drug-like index (DLI) is introduced in this paper. A compound's DLI is calculated based upon the knowledge derived from known drugs selected from Comprehensive Medicinal Chemistry (CMC) database. The paper describes the way of this knowledge base is formed and the procedure for selecting drug-like compounds.     

Spectroscopic study of bituminous oxidative stress

Bitumen, as each organic substance, is a product which alters over time. Indeed, roads deteriorate under the effect of several phenomena. A number of studies have been undertaken to increase the quality of road's coating, mostly by adding polymer to bitumen. This work was based on the study, by electron paramagnetic resonance (EPR), FTIR and Synchronous UV fluorescence, of different base and modified bitumens after different treatments used to simulate the ageing (gamma irradiation, thermal treatment). Our purpose was to compare and correlate the results obtained by different techniques to improve the knowledge of bitumen's reactivity and evolution submitted to ageing phenomena.     

Stability of vinylidene chloride copolymers containing 4-vinylpyridine units

Vinylidene chloride copolymers are prominent in the barrier plastic packaging industry. These materials display excellent barrier to the transport of oxygen (and other small molecules) as well as flavor and aroma molecules. However, they suffer from a propensity to undergo degradative dehydrochlorination at process temperatures. To scavenge hydrogen chloride formed and prevent its interaction with the metallic components of process equipment, a passive base is usually included as an additive prior to processing. The base is most often an inorganic oxide or salt. These may negatively impact the properties of the polymer, particularly as a film. An organic base that could be covalently incorporated into the copolymer might display better behavior. Accordingly, a series of copolymers containing low levels of 4-vinylpyridine (0.05–3 mole%) have been prepared, characterized, and examined by thermogravimetry to assess thermal stability. In all cases, polymers containing 4-vinylpyridine units are less stable than the polymer containing none of this comonomer. Clearly, the pyridine moiety is a sufficiently strong base to promote E2 elimination of hydrogen chloride to generate dichlormethylene units in the mainchain from which thermal degradation may be initiated.     

Retention properties of a cyanopropylsiloxane-bonded silica-based sorbent for solid-phase extraction

The characteristic kinetic and retention properties of a silica-based cyanopropylsiloxane-bonded sorbent for solid-phase extraction are described. Abraham′s solvation parameter model is used to characterize the contribution of individual intermolecular interactions to retention under liquid chromatographic and sample processing conditions with aqueous methanol mixtures as the mobile phase. The main features governing retention by the sorbent are the solute's size and hydrogen-bond basicity; interactions of a dipole type are not significant when aqueous methanol solutions are employed as the mobile phase. Compared to typical silica-based octadecylsioxane-bonded sorbents the greater difficulty of forming a cavity in the solvated cyanopropylsiloxane-bonded sorbent more than offsets the more favorable dipole-type and solute hydrogenbond base interactions of the cyanopropylsiloxane-bonded sorbent. It is shown that there are no practical circumstances for which a cyanopropylsiloxane-bonded sorbent would be more useful than a typical ODS sorbent for the isolation of organic non-electrolytes from water by solid-phase extraction.