ZSM-5／Silicalite-1核壳分子筛含氟水热体系的合成及表征

以圆柱形ZSM-5为核,用柠檬酸对其外表面进行预处理后,在含氟壳层晶化体系中二次生长合成核壳分子筛.通过X射线衍射、扫描电镜、透射电镜、N2吸附及氨程序升温脱附对分子筛进行了表征,并以甲苯歧化和1,3,5-三甲苯裂化为探针反应对分子筛性能进行了考察.结果显示,产物是以ZSM-5为核、silicalite-1纳米晶为壳的两相复合微孔分子筛材料;在含氟体系中ZSM-5外延生长出了致密壳层;全硅壳层的覆盖度约达到97%,核壳分子筛的外表面酸位随之减少,但基本保持孔道内的酸性。     

Oriented Nickel Nanonetworks and Their Submicron Fibres as a Basis for a Transparent Electrically Conductive Coating

The paper demonstrates a technique for applying an oriented nickel network to a glass surface. The method is based on the chemical reduction of nickel salt. The shaping and orientation of the resulting system are carried out using a micellar template of a surfactant and a magnetic field. Submicron nickel fibres are used to impart unity to the plurality of individual-oriented nickel nanonetworks. The result is a single conductive coating on the surface of the glass, which has a transparency in the optical range. Investigations of the structure, chemical composition, morphology and electrical conductivity of the coating were performed.     

Thermotropic rigid chain copolymers I. crystallization kinetics and thermodynamic properties

The kinetics of structure formation and the thermal properties of the ordered phase were analyzed calorimetrically for a rigid polymer, characterized by an irregular chemical structure. The transition from the nematic melt to a partially ordered state was found to involve two different processes, a fast and a slow one. The fast one corresponds apparently to a thermally activated nucleation and growth mechanism, whereas the slow one is strongly self delaying. Its transition rate is only weakly dependent on the temperature. The thermal properties of the ordered phase, resulting from this process, vary strongly with the annealing temperature and annealing time. The enthalpy and entropy of fusion, characteristic for the pure ordered phase, are lower by a factor of about 10 in comparison to the corresponding values of flexible chain molecules.     

SPECIAL PP'S FOR A DEVELOPING AND FUTURE MARKET

The present article starts with a short overview of the international development of the polyolefin production in the last 10 years and with a forecast for the next 3 to 5 years. The reason for these developments, as the cost/properties relationships will be discussed. The extended properties of the polypropylenes, their molecular and supermolecular structures, and the correlations to the properties play a central role in the paper. The reinforcing and compounding maximized the properties and reduced the weaknesses of the mechanical and thermal properties. The narrower molecular weight distribution and the possible new copolymers with better randomness and new comonomers explain the importance of the metallocene catalysts. Examples demonstrate the future developments of new PP's by orientation on a second generation of single site catalysts.

The super soft PIP's as a new interesting elastomer class, are described. The new developments from the post reactor modification to a new HMS-PP technology are described in detail. The new graft copolymers with styrene and methylmethacrylate are pointed.     

Characterisation of optical detectors using high-accuracy instruments

The facilities of the Metrology Research Institute at the Helsinki University of Technology, and methods for characterisation of optical detectors for spectral radiant intensity and irradiance responsivity, are described. The instrumentation for such characterisations includes a reference spectrometer with a number of auxiliary set-ups, and equipment for the spectral irradiance measurements with a filter radiometer based on a trap detector. The methods of realising the spectral responsivity scales based on an absolute cryogenic radiometer in house are addressed. The procedures and results of characterisation of a multipoint measuring system of photosynthetically active radiation, by employing the available facilities, are briefly described. The absolute irradiance responsivity of the device is determined by using a photometric lamp, whose spectral irradiance has been measured with the filter radiometer. The combined standard uncertainty of this set of calibrations is 3.6% at the 1σ level. The uncertainty is caused almost completely by the multipoint measuring system.     

Kinetic modeling of industrial steam cracker

A comprehensive mathematical model is a very useful tool for the selection of feedstock, optimized cracker product mix, downstream production planning, and optimized plant performance. As a part of achieving this prime objective, a mathematical model has been developed for the simulation of the radiation section of a steam cracker unit. The model involves solving differential component, energy, and momentum balance equations numerically to generate temperature, concentration, and pressure profiles along the length of the reactor tube. The model has been developed in FORTRAN using the lSODE solver. The model considers 19 free radicals and 35 molecules connected over 433 reactions. The model was used to simulate the performance of propane and ethane cracking. The model predicted propane conversion is 95.55 against the plant data of 95% at a coil outlet temperature of 845 ​°C and the corresponding predicted ethylene and propylene yield is 34.49 and 11.53% respectively. The model has been validated for ethane cracking performance. The model predicted ethylene yield is in good agreement with that of plant values for ethane cracking. The model provides a basis for the optimization of process parameters for the given geometry. The model is useful to answer what-if questions and to investigate operational strategies.     

Zur Reaktion von Dihydroxybiphenylen mit Phosphorpentachlorid ‐ Phosphepine mit Phosphonium‐ und Phosphoranstruktur

The 2, 2'‐dihydroxybiphenyl derivatives 1d‐f react with phosphorus pentachloride to give the dioxaphosphepinium hexachlorophosphates 3a, 3b , and 17 . The trichloro‐dioxaphosphepins 8a, 8b , and 21 were discussed as intermediates, which were obtained by chlorination of the 6‐chloro‐dioxaphosphepins 7a, 7b , and 20 . The hydrolysis of the dioxaphosphepins leads to the stable, cyclic phosphates 4a, 4b, 9a, 9b, 11a, 11b, 19a, and 19b . The crystal struc‐ture of 4a was determined; two different molecules was observed in the asymmetric unit.     

聚苯胺在电化学电容器中的应用

The performance of a newly designed, polyaniline activated carbon, hybrid electrochemical capacitor was evaluated. The polyaniline was prepared by the chemical oxidation/polymerization process. The capacitor was assembled by using polyaniline as a positive electrode and an activated carbon as a negative electrode respectively. From a cyclic voltammograms test, a specific capacitance of 420 F/g was obtained for polyaniline electrode. The cycle life of the cell is proved to be more than 1000 times by the Galvanostatic charge and discharge test. Values for the specific energy and real specific power of 15.5 Wh/kg and 2.8 W/g, respectively, are demonstrated for a cell voltage between 0.0 and 1.4 V. The max specific power for the hybrid capacitor amounts to 20.4 W/g.     

Development of Enzyme Conductometric Biosensor for Dopamine Determination in Aqueous Samples

Dopamine is a biologically active chemical that performs a number of vital functions as a hormone and neurotransmitter. Therefore, the determination of dopamine concentration in the human body is important for biomedical research. The content of dopamine in the blood varies depending on the age of a healthy person and can serve as a prognostic marker of many diseases. The aim of this work was to develop a new enzyme conductometric biosensor for the determination of dopamine in aqueous samples and to study the biosensor's analytical characteristics. The conductometric method of analysis with differential measurement mode was used in the work. Two pairs of gold interdigitated electrodes deposited on a sitall substrate were used as a conductometric transducer. The biorecognition element of the biosensor was based on laccase immobilized by glutaraldehyde cross-linking. The optimal conditions of laccase immobilization were selected. The influence of solution parameters (ionic strength, pH, buffer capacity) on the biosensor work was investigated. The biosensors demonstrated high sensitivity to dopamine (minimum limit of detection −7.8 μM) with the linear range up to 1 mM. The biosensor was highly selective and reusable. The proposed biosensor was tested regarding the possibility of its long-term storage under different conditions. The developed conductometric biosensor was proven to be suitable for measuring dopamine concentration in biological and pharmaceutical samples.     

Stereocontrolled Total Synthesis of Polygalolide A

The total synthesis of polygalolide A, a secondary metabolite that was isolated from a Chinese medicinal plant, is reported. A key issue in this synthesis was construction of an oxabicyclo[3.2.1] skeleton, which was solved by the development of an intramolecular Ferrier‐type C‐glycosylation of a glucal with siloxyfuran as an internal nucleophile. The substrate was prepared from D ‐glucal by the introduction of trimethylsilylacetylene and siloxyfuran groups. Although C‐glycosylation did not occur under the conditions found from model experiments, further examination revealed that the combination of trimethylsilyl trifluoromethanesulfonate (TMSOTf) and 2,4,6‐collidine successfully afforded the desired product as a single diastereomer. The siloxy group at the C3 position played a crucial role in the stereocontrol of this reaction. The product was further transformed into a tetracyclic compound as follows: The vinyl ether and acetylenic moieties were reduced and the siloxy group was removed with a Barton–McCombie reaction. The construction of the six‐membered ether and the γ‐lactone provided the tetracyclic compound. Finally, a phenolic moiety was introduced by using a Mukaiyama aldol reaction to furnish polygalolide A.     

A designed well-folded monomeric four-helix bundle protein prepared by Fmoc solid-phase peptide synthesis and native chemical ligation

The design and total chemical synthesis of a monomeric native-like four-helix bundle protein is presented. The designed protein, GTD-Lig, consists of 90 amino acids and is based on the dimeric structure of the de novo designed helix-loop-helix GTD-43. GTD-Lig was prepared by the native chemical ligation strategy and the fragments (45 residues long) were synthesized by applying standard fluorenylmethoxycarbonyl (Fmoc) chemistry. The required peptide-thioester fragment was prepared by anchoring the free gamma-carboxy group of Fmoc-Glu-allyl to the solid phase. After chain elongation the allyl moiety was orthogonally removed and the resulting carboxy group was functionalized with a glycine-thioester followed by standard trifluoroacetic acid (TFA) cleavage to produce the unprotected peptide-thioester. The structure of the synthetic protein was examined by far- and near-UV circular dichroism (CD), sedimentation equilibrium ultracentrifugation, and NMR and fluorescence spectroscopy. The spectroscopic methods show a highly helical and native-like monomeric protein consistent with the design. Heat-induced unfolding was studied by tryptophan absorbance and far-UV CD. The thermal unfolding of GTD-Lig occurs in two steps; a cooperative transition from the native state to an intermediate state and thereafter by noncooperative melting to the unfolded state. The intermediate exhibits the properties of a molten globule such as a retained native secondary structure and a compact hydrophobic core. The thermodynamics of GuHCl-induced unfolding were evaluated by far-UV CD monitoring and the unfolding exhibited a cooperative transition that is well-fitted by a two-state mechanism from the native to the unfolded state. GTD-Lig clearly shows the characteristics of a native protein with a well-defined structure and typical unfolding transitions. The design and synthesis presented herein is of general applicability for the construction of large monomeric proteins.     

Analysis of nucleosides and monophosphate nucleotides from mushrooms with reversed‐phase HPLC

The retention characteristics of five stationary phases were tested by using a selection of 5′‐mononucleotides and nucleosides with the aim to develop a simple, rapid and sensitive reversed‐phase liquid chromatography method without ion‐pair reagent usage. The method was optimized by changes in temperature, pH and ionic strength on a column showing a superior performance. The mobile phase consisted of a mixture of 0.05 M phosphate buffer and methanol, delivered at a flow rate of 0.4 mL/min and based on a gradient program. UV detection was used at a 254 nm wavelength. The method was validated for a quantitative analysis of 5′‐mononucleotides and nucleosides in wild edible mushrooms. For all nucleosides and nucleotides, the LOD and LOQ were less than 0.02 and 0.07 μg/mL, respectively. Validation parameters yielded recovery rates between 68.6 and 98.2%, with a precision expressed as a relative standard deviation of 7.6–15.3%. The content of 5′‐mononucleotides and nucleosides was determined for 10 samples of wild edible mushrooms found in Croatia and, accordingly, the equivalent umami concentrations were calculated.     

Adsorption studies of dimethyl and methyl-ethyl ester molecules on silicene nanoring: Application of DFT study

The electronic and adsorption properties of dimethyl and methyl-ethyl ester molecules on a silicene nanoring (SiNR) are studied using first-principles calculations. The adsorption properties of dimethyl and methyl-ethyl ester molecules on the surface of a silicene nanoring is investigated in terms of density of states spectrum, adsorption energy, average energy gap variation, Mulliken charge and Bader charge transfer. The structural stability of the SiNR is ensured using formation energy. The variation in the electron density and energy gap is noticed upon adsorption of dimethyl and methyl-ethyl ester molecules in the SiNR base material compared with its isolated counterpart. The highlights of the present work are silicene nanoring is used as a base material for ester molecule adsorption. The adsorption behavior of ester molecules is studied using energy band structure. The DOS spectrum confirms the transfer of electrons between the SiNR and ester molecules. The findings suggest that a SiNR can be used as a base material for the detection of dimethyl and methyl-ethyl ester molecules.     

Electrospray ionization from an adjustable gap between two silicon chips

In this paper, a silicon chip-based electrospray emitter with a variable orifice size is presented. The device consists of two chips, with a thin beam elevating from the center of each of the chips. The chips are individually mounted to form an open gap of a narrow, uniform width between the top areas of the beams. The electrospray is generated at the endpoint of the gap, where the spray point is formed by the very sharp intersection between the crystal planes of the <100> silicon chips. Sample solution is applied to the rear end of the gap from a capillary via a liquid bridge, and capillary forces ensure a spontaneous imbibition of the gap. The sample solution is confined to the gap by means of a hydrophobic treatment of the surfaces surrounding the gap, as well as the geometrical boundaries formed by the edges of the gap walls. The gap width could be adjusted between 1 and 25 microm during electrospray experiments without suffering from any interruption of the electrospray process. Using a peptide sample solution, a shift toward higher charge states and increased signal-to-noise ratios was observed when the gap width was decreased. The limit of detection for the peptide insulin (chain B, oxidized) was approximately 4 nM. We also show a successful interfacing of the electrospray setup with capillary electrophoresis.     

Titanium Anodes with Active Coatings Based on Iridium Oxides: A Sublayer between the Active Coating and Titanium

An optimum composition and a technique for applying a protecting sublayer on titanium are substantiated experimentally. The sublayer prevents the oxidation of titanium during the production and application of highly porous metal oxide anodes. The formation of such a sublayer involves several stages: (a) coating chemically polished and etched in 5-% hydrofluoric acid titanium with hexachloroiridic acid, (b) drying hexachloroiridic acid, (c) a two-step treatment of anodes in argon with a low concentration of oxygen at 350°C, and (d) a brief annealing of the anodes in air at 400°C. The application of such a sublayer makes sense especially in the case of an anode with a thin highly porous active coating. The remarkable protecting properties of the sublayer are due to the formation of a dense coating on titanium. The coating consists of metallic iridium, titanium, and an amount of oxides of these metals. The titanium substrate itself undergoes minimum oxidation.     

Synthesis of 7-deoxypancratistatin from carbohydrates by the use of olefin metathesis

The stereocontrolled synthesis of (+)-7-deoxypancratistatin is described. The convergent synthesis has been achieved by two different strategies, both of which commence from a pentose and piperonal. The latter is converted into allylic bromide 7, which is then coupled with a protected methyl 5-deoxy-5-iodo-D-ribofuranoside in the presence of zinc metal. The first strategy involves a total of only 13 steps from D-ribose and piperonal, but suffers from a low yield in the zinc-mediated reaction between ribofuranoside 9, benzylamine, and bromide 7. The second strategy involves a total of 18 steps from D-xylose and piperonal. The former is converted into ribofuranoside 28, which is coupled with bromide 7 in the presence of zinc, and this is followed by ring-closing olefin metathesis. Subsequent Overman rearrangement, dihydroxylation, and deprotection then affords the natural product.     

An easy access to bioactive 13-hydroxylated and 11,13-dihydroxylated sesquiterpene lactones (SLs) through Michael addition of a nucleophilic hydroxyl group

The addition of a hydroxyl group to α,β-unsaturated carbonyl systems provides a new and easy access to bioactive difunctionalized sesquiterpene lactones (SLs) through a Michael addition to the α-methylene-γ-lactone system. The use of HMPA to enhance the nucleophilic properties of the hydroxyl groups and to stabilize the enolate is discussed. Also, we present a proposal for the mechanism based on the experimental data obtained. The scope and usefulness of the reaction are explored with other substrates and is limited by the need for a certain level of steric hindrance to avoid chain polycondensations. Nevertheless, the reaction works with esters, ketones and aldehydes. The absolute stereochemistry of some products has been elucidated by X-ray diffraction analysis. The synthesis of a natural SL using this methodology and the correction of the structure of another illustrate the usefulness of this reaction.     

The molecular anvil model of an enzyme taking into consideration the flexibility of enzyme molecules

The concept of a molecular anvil model of an enzyme, assuming a rigid enzyme molecule, is introduced. Two distinct features of enzymes, high catalytic power and high specificity, are reasonably and consistently explained. The dynamic nature of molecular anvil action is stressed. The origin of the high catalytic power is the spontaneous creation of a high energy state at the anvil site. The origin of the high specificity is a high sensitivity of the maximum accessible potential energy to the relatively extruded distance of the molecular anvil. The flexible model is developed by assuming a flexible enzyme molecule. It is deduced from this flexible model that enzyme activity shows a maximum with a wide range of monotonous change of the configuration of the enzyme molecule. This is the origin of the general property of enzymes that enzyme activity shows a maximum with monotonous variation of environmental parameters such as pH, temperature, pressure or some times concentration of chemical substances. The induced fit theory of Koshland is reasonably explained. The relation and differences between individual theories of enzymes are discussed. The enzymological basis of the complex regulation of biological organisms is discussed. The inversion of the sign of control of effectors is predicted when environmental parameters are varied. This concept may be useful in designing artificial enzymes or high specificity catalysts.Presented at the Fourth International Symposium on Inclusion Phenomena and the Third International Symposium on Cyclodextrins, Lancaster, U.K., 20–25 July 1986.     

Implementation of a quality system in a clinical laboratory – Evaluation of quality indicators

 The aim of this study was to evaluate the primary experience of implementing a quality system in a clinical laboratory. The second interrelated aim was to evaluate the quality and financial indicators needed for continuous measurement of quality, decision making in the laboratory management and everyday process control in analytical work. The quality process itself should be evaluated because the building up of a quality system requires a considerable amount of resources. The most effective and practical ways of using a quality system as a management tool should be found and the need for financial appraisal when the quality system is implemented is stressed. According to our study, when the effects of the quality system were evaluated, the managers of the laboratory had not considered the appropriate financial indicators. The quality indicators considered to be the best were internal quality control, external quality assessment and customer satisfaction surveys. The first benefits of the quality system evaluated by the personnel were other than the purely financial benefits, they include a more systematic and empowering approach to laboratory management, better working instructions, better knowledge of the methods and equipment, and fewer errors. The financial evaluation of a quality process in a public-owned clinical laboratory is complicated due to the fact that financial indicators are not as far developed and diverse as in industrial organisations. When starting to implement a quality system, it is important to pay attention to all measures that motivate the staff and help them benefit from the practical effects of the system. Received: 10 November 1999 / Accepted: 12 January 2000     

Directed assembly of copolymer materials on patterned substrates: Balance of simple symmetries in complex structures

The self-assembly of a lamella-forming blend of a diblock copolymer and its respective homopolymers on periodically patterned substrates is investigated by a concerted experimental and theoretical approach. The substrate pattern consists of square arrays of spots that preferentially attract one component of the blend. The mismatch between the lamellar equilibrium morphology of the copolymer material and the substrate pattern results in the formation of a bicontinuous morphology. At the substrate, a quadratically perforated lamella (QPL) assembles in perfect registry with the substrate pattern. From this, QPL necks emanate and reach the top surface of the film. The detailed structure of these cylindrical nanochannels is analyzed using Voronoi tessellation, orientation correlation functions, and the structure factor of the neck positions on the top surface. The surface morphology is dictated by the antagonism of the square symmetry of the substrate pattern and the tendency of the necks to locally pack in a hexagonal arrangement. The analogy and differences to a system of adsorbed monolayer on corrugated substrates is explored by comparing the arrangement of the necks on the film's top surface with the structure of a soft disk model on a quadratically corrugated substrate. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 2589–2604, 2006