A Bayesian approach to the evaluation of comparisons of individually value-assigned reference materials

Several recent international comparison studies used a relatively novel experimental design to evaluate the measurement capabilities of participating organizations. These studies compared the values assigned by each participant to one or more qualitatively similar materials with measurements made on all of the materials by one laboratory under repeatability conditions. A statistical model was then established relating the values to the repeatability measurements; the extent of agreement between the assigned value(s) and the consensus model reflected the participants’ measurement capabilities. Since each participant used their own supplies, equipment, and methods to produce and value-assign their material(s), the agreement between the assigned value(s) and the model was a fairer reflection of their intrinsic capabilities than provided by studies that directly compared time- and material-constrained measurements on unknown samples prepared elsewhere. A new statistical procedure is presented for the analysis of such data. The procedure incorporates several novel concepts, most importantly a leave-one-out strategy for the estimation of the consensus value of the measurand, model fitting via Bayesian posterior probabilities, and posterior coverage probability calculation for the assigned 95% uncertainty intervals. The benefits of the new procedure are illustrated using data from the CCQM-K54 comparison of eight cylinders of n-hexane in methane.     

New approach to the calculation of the refractive index of liquid and solid xenon

A model for the calculation of the refractive index based on a dispersion relation that incorporates the exciton transition energies is presented. The refractive indices of liquid and solid xenon for different wavelengths are evaluated using this model. Comparison between calculated and experimental values existing in the literature is presented.     

Novel method of detecting stress-strain state of materials

The technique of the novel method of detecting the stress-strain state of polymeric materials, which is based on the change in the color of the sensor depending on the rate of microcrack propagation, is discussed. The geometrical sizes of capsules containing a dyeing agent are calculated using the method of finite elements. The mechanism of stress redistribution at the structural level is considered.     

Nondestructive evaluation of polymer materials by solid state NMR imaging

Many polymer products are heterogeneous. Examples of heterogeneities are the chemical composition, distributions of mechanical stress, and variations in flexibility or molecular orientation. Applications of NMR imaging to polymers are summarized and investigations of the aging of rubber are reported as well as novel deuteron NMR techniques to image molecular order and mobility of polymers below the glass transition temperature.     

New catalytic methods for processing solid organic raw materials

New catalytic methods are described for production of metallurgical coke and electrode materials from coals, carbon reductants, improved solid fuels and sorbents from lignite and lignine, levulinic acid from wood wastes, and aromatic aldehydes from lignin-containing stock.     

New approach for chiral separation: from polysaccharide-based materials to chirality-responsive polymers

Chiral separation that is closely related to daily life is a meaningful research. Polysaccharide-(e.g., cellulose, amylose derivatives) based chiral packing materials afford powerful chiral stationary phases(CSPs) toward a broad range of racemic compounds. However, considering the explosive growth of specific chiral drugs, the separation efficiencies of these CSPs need further improvement, which calls for new approaches and strategies. Smart polymers can change their physical or chemical properties dynamically and reversibly according to the external stimuli(e.g., thermo-, pH, solvent, ion, light, critical parameters for chromatographic separation) exerted on them, subsequently resulting in tunable changes in the macroscopic properties of materials. In addition to their excellent controllability, the introduction of chiral characteristics into the backbones or side-chains of smart polymers provides a promising route to realize reversibly conformational transition in response to the chiral analytes. This dramatic transition may significantly improve the performance of materials in chiral separation through modulating the enantioselective interactions between materials and analytes. With the help of chirality-responsive polymers, intelligent and switchable CSPs could be developed and applied in column-liquid chromatography. In these systems, the elution order or enantioselectivity of chiral drugs can be precisely modulated, which will help to solve many challenging problems that involve complicated enantiomers. In this paper we introduce some typical examples of smart polymers that serve as the basis for a discussion of emerging developments of CPSs, and then briefly outline the recent CSPs based on natural and certain synthetic polymers.     

A second-quantization approach to the analytical evaluation of response properties for perturbation-dependent basis sets

A general theory for response properties is presented which is applicable to perturbations affecting the molecular basis set, notably nuclear derivatives. A perturbation-independent Fock space is introduced, and the necessary reorthonormalization of a truncated basis set after a perturbation is explicitly incorporated in the Hamiltonian. Explicit formulas for MCSCF first- and second-order properties are presented, and some computational aspects are briefly discussed. A brief comparison with previous results is given.     

The preparation and properties of chromium oxide nanolayers on semiconducting matrices

Ultrathin chromium oxide layers (nanostructures) were synthesized on the (100) and (110) silicon and gallium arsenide surfaces by molecular layering (atom layer deposition). Technological factors were shown to influence the main rules governing nanolayer formation, nanolayer composition, and some electric nanolayer characteristics.     

Chemometrics-based approach to enhancing the usefulness of time domain reflectometry in investigating properties of granular materials.

Sets of time domain reflectometry waveforms analyzed with appropriate chemometric methods, instead of typical single waveform analysis, enable one to detect and quantify differences between waveforms, even if they appear at the level of several orders of magnitude below the scale of the measurements. Typical applications of such an approach to samples of healthy and damaged grain showed that differences contributing five orders of magnitude below the scale are still detectable. Under more rigorous experimental conditions, the level of detectable differences can be expected to be even lower.     

New approach to characterise physicochemical properties of solid substrates by inverse gas chromatography at infinite dilution. I. Some new methods to determine the surface areas of some molecules adsorbed on solid surfaces

This study was divided into three different parts that tried to give a new contribution to determine and quantify more precisely the superficial properties of solid substrates (polymers and/or oxides) obtained by inverse gas chromatography (IGC) at infinite dilution. It criticised certain of the classical methods and relationships used to determine some physico-chemical properties of a solid and gave new methods and equations that can be more precise and more realistic. Part I developed some new methods to determine the surface areas of some molecules adsorbed on solids. A theoretical calculation of surface areas of molecules adsorbed on solid substrates was proposed by using some theoretical models. Two new methods to determine the surface areas of polar molecules were developed. The first one consists of the determination of surface areas by coupling two classical methods, the dynamic contact angle and IGC techniques. The second new and general method, using the IGC technique, assumes that the specific interactions between a polar molecule and a solid proposed by Papirer and Schultz are the same. A new equation was obtained to determine the surface areas of polar molecules.     

Evaluation of the stress-strain properties of surface layers in plasma-treated polymers

The surface treatment of poly(ethylene terephthalate) (PET) and poly(vinyl chloride) (PVC) films in cold plasma over 1–15 min was carried out. It was found that the subsequent deformation of the films is accompanied by a special type of surface structuring that has been previously observed for polymer films with a thin hard coating. It was shown that unlike metal coatings, the thickness of the modified surface layer slightly depends on the time of treatment in plasma. The previously developed approach to analysis of the emerging patterns makes it possible to evaluate the stress-strain properties of the coatings. It was first revealed that the tensile strength of the modified layer produced in PET by plasma treatment is ∼12.3 MPa and its elongation at break varies from 20 to 90%. The differences in the properties between the plasma-modified surface layers of the polymer and the metal coatings studied earlier are discussed.     

New approach to determine absolute partial pressures of ions in saturated vapors of inorganic materials

A new complex approach to determine absolute partial pressures of molecular and ionic components of vapor is advanced on the basis of a combination of mass-spectrometric and quantum-chemical methods using sodium bromide as an example. Thermodynamic parameters of molecules and ions and the electron work function are determined for crystalline NaBr.     

New approach to characterise physicochemical properties of solid substrates by inverse gas chromatography at infinite dilution. III. Determination of the acid-base properties of some solid substrates (polymers,oxides and carbon fibres): a new model

HPLC experiments to separate butyl-terminated polystyrene (B-PS) oligomers have been mimicked by equilibrium self-consistent-field calculations based upon the Scheutjens Fleer formalism for polymers at interfaces. The adsorption-desorption transition as a function of the fraction of good solvent in a non-solvent (water)-solvent (tetrahydrofuran) mixture has been analysed and correlated to corresponding experiments. Much attention is paid to keeping the modelling as realistic as possible; for example, the effects of the solvent mixture on the C18-alkyl tails that are grafted on the silica surface are retained in the calculations. It is shown that the butyl end groups affect the elution properties up to chains with approximately 30 styrene units. Excellent semi-quantitative comparison is found with experiments for a realistic set of interaction parameters. Molecular-level information is available for the adsorption layer as a function of the solvent quality. Going from poor to good solvent, it is typical to find that the B-PS is fully absorbed inside the alkyl brush, then adsorbed on top of it, and finally depleted from it. The depletion effect in good solvents increases with increasing molecular mass.     

固相反应中扩散动力学方程的新探讨

通过对г~NHCTJINHT方程中把э~c/э~r作为产物层增厚速率的基础作出分析,对由扩散控制的固相反应中扩散浓度与时间的关系作了进一步探讨, 提出产物层增厚速率应建立在Fick第二定律的基础上, 并导出了新的扩散动力学方程。     

The H-phosphonate approach to the synthesis of phosphopeptides on solid phase

[reaction: see text]. Ammonium tert-butyl H-phosphonate was used for the phosphorylation of Tyr- and Ser-containing peptides synthesized by an Fmoc strategy. This reaction, leading to a monoprotected peptide phosphate, was found to be highly efficient and generally applicable. Moreover, the method employed avoids undesired side reactions during chain elongation (pyrophosphate formation and beta-elimination catalyzed by piperidine).