Use of molecular symmetry in two-electron integral transformation An MP2 program compatible with HONDO 5

A computer program is described which evaluates the second-order Møller-Plesset energy using the integral list formed by HONDO 5. In this program use may be made of full molecular symmetry for most common point groups, even if they contain two-dimensional representations. The algorithm for the integral transformation may also be applied to other methods beyond Hartree-Fock. Some numerical results and timings are presented.     

Pressure dependence of the demixing behaviour in polymer blends: I. Experimental procedure

The most common way to influence the liquid-liquid phase behaviour in partially miscible (co-)polymer blends is changing the blending temperature. Since most extruders can handle pressures, up to 300 bar, pressure may also be used to influence the miscibility of polymers during blending. We have developed equipment and an experimental procedure to study the pressure dependence of the liquid-liquid demixing behaviour of high-viscous polymer blends under equilibrium conditions. Small amounts (1–4 grams) of specially made polymers are blended in the ‘DSM MINI EXTRUDER’. After a chosen mixing time, a small portion of the blend is injected into a small capillary tube and kept at the blending temperature. The phase behaviour of the blends as a function of temperature and pressure is studied via laser light scattering (at a scattering angle of 90°) in a specially made 400 bar/250°C window autoclave, where the capillary cell is placed in a high temperature grade silicon oil.     

Defining the electroanalytically measured species in a natural water sample

The possible definition, using electroanalytical techniques, of the chemical species disolved in natural waters is discussed. Emphasis is place on the formulation of concepts rather than completely rigorous mathematical solutions. The time of measurement is identified as the critical parameter for determining which species in solution will be measured when using transient techniques. When measurements are made in stirred solutions, as is the case in anodic stripping voltammetry and conventional polarography the effective diffusion layer thickness becomes the critical parameter. It may be regarded as being analogous to the time of mesurement and for most experimental systems it is simple to measure. It is recommended that whenever polarographic or voltammetric measurements are made on complex natural systems either the effective diffusion layer thickness or the time of measurement should be reported. Evidence in the literature suggests that a better appreciation of exactly what species are measured would greatly increase our understanding of natural systems.     

Macrocycles in the construction of acyclic stereochemistry

The conformations of macrocyclic intermediates provide a useful medium through which distant chiral centers may control chemical reactions. In this paper, we show that macrocycles made by cyclization of simple acyclic starting materials with an auxiliary spacer may be used to prepare stereochemically complex acyclic products.     

Recent progress in copper catalyzed asymmetric Henry reaction

Henry reaction is one of the most classical reactions to construct synthetically useful product nitro alcohol, which as a privileged skeleton is widely distributed in various pharmaceuticals. This review summarizes the recent progress of copper-catalyzed asymmetric Henry reaction from 2011 to 2016. The significant progress that has been made in this area will be highlighted and some of challenges that the author believes may be hindering further progress will be revealed.     

The role of statistics in quality assurance

Summary The quality of data, which is to say its accuracy, must be known whenever it is to be used for purposes of decision. This is only possible as it is produced by a valid analytical system operating in a state of statistical control. A quality assurance program should be established, consisting of quality control of the analytical system and quality assessment of the data that are produced. Data quality objectives should be established for every measurement situation and the accuracy attained must be within these limits. Ideally, the attained accuracy should exceed the required accuracy by a factor of three, at a minimum. The estimation of attained accuracy is best made using reliable reference materials. When they are not available, spikes may be used with lesser confidence. No matter what estimation techniques are used, decisions must be made on the basis of statistical tests of significance. The evaluation of accuracy is a continuing operation and facilitated by the use of appropriate control charts. The paper discusses the above described concepts and summarizes the techniques most useful for evaluating the accuracy of analytical data.

---

Die Rolle der Statistik in der Qualitätssicherung

     

AB initio studies of chemical equilibria. Application of many-body rayleigh-schrödinger perturbation theory up to third order to the proton affinity of water

Many-body Rayleigh-Schrödinger perturbation theory (MBRSPT) up to third order has been applied to the proton affinity of water. Comparison was made with the most extensive MO calculations and latest experiments reported in the literature. The basis set effect on the MBRSPT results was investigated. A basis set has been recommended for which the MBRSPT approach may be expected to give reliable proton affinities at a relatively low cost.     

Catalogue of 45 reference Raman spectra of minerals concerning research in art history or archaeology,especially on corroded metals and coloured glass

Small catalogues of reference Raman spectra of interest for analysing geomaterials or biomaterials of relevance to art history or archaeology are gradually being published by different research groups. However, except for some older catalogues, they are all concerned primarily with pigments, whether inorganic or organic. Here we present for the first time a catalogue of Raman spectra of minerals that may be found in corroded metal artworks or artefacts. At the same time we include some inorganic pigments that may be found in or on stained glass. Most of the minerals analysed came from the Gallery of Mineralogy at the Muséum National d'Histoire Naturelle and most were verified by X-ray diffraction in order to augment the confidence in the mineral identity (which is not the case with many other catalogues). A number of problems encountered with mineral terminology are discussed. Comments are made on the spectra where appropriate.     

Living Polymers in Ionic and Radical Polymerizations: Recent Developments

The discovery of living polymers, that is, assemblies of polymer molecules formed by anionic polymerization which may grow without chain-breaking reaction and may react subsequently with other monomers and various reagents through their end-groups, has led to great progress in the knowledge of the mechanism of anionic polymerization and to the synthesis of a large variety of well-defined block copolymers, graft co-polymers, and polymers with functionalized end-groups. Since only a limited number of the current monomers are polymerizable by an anionic mechanism, many attempts have been made to obtain similar results by polymerizing other monomers by cationic, radical, and Ziegler polymerization. Systems making it possible to work at temperatures higher than those used for many anionic and most cationic polymerizations would be particularly interesting.     

X-ray crystallography and chirality: understanding the limitations

Advances in hardware and software have made X-ray crystallography even more attractive as the first-option method for structure analysis. For most organic materials containing up to 100 non-hydrogen atoms, getting from the initial visual examination of the sample to producing publication-ready tables and pictures should usually be achievable in a single morning. Improvements in hardware have also increased reliability of the determination of absolute configuration. A recently published new algorithm may extend the range of applicability of the method.     

On the Future Design of Bio‐Inspired Polyetheretherketone Dental Implants

Polyetheretherketone (PEEK) is a promising implant material because of its excellent mechanical characteristics. Although this polymer is a standard material in spinal applications, PEEK is not in use in the manufacturing of dental implants, where titanium is still the most‐used material. This may be caused by its relative bio‐inertness. By the use of various surface modification techniques, efforts have been made to enhance its osseointegrative characteristics to enable the polymer to be used in dentistry. In this feature paper, the state‐of‐the‐art for dental implants is given and different surface modification techniques of PEEK are discussed. The focus will lie on a covalently attached surface layer mimicking natural bone. The usage of such covalently anchored biomimetic composite materials combines many advantageous properties: A biocompatible organic matrix and a mineral component provide the cells with a surrounding close to natural bone. Bone‐related cells may not recognize the implant as a foreign body and therefore, may heal and integrate faster and more firmly. Because neither metal‐based nor ceramics are ideal material candidates for a dental implant, the combination of PEEK and a covalently anchored mineralized biopolymer layer may be the start of the desired evolution in dental surgery.     

Study on the melt entry flow characteristics in axisymmetric dies with abrupt contraction by a visualization technique

The die entry characteristics of low density polyethylenes (LDPE) were studied using a 45 mm diameter single-screw extruder. The extruder incorporated a “transparent” die to enable direct visualization to be performed. With the addition of a small percent of red colour masterbatch into the main polymer bulk, melt circulation near the die entry at the wall was clearly observed. The dynamic behaviour of the polymer melt was recorded by a digital video recorder. Upon replaying the films, detailed qualitative and quantitative analysis of the flow characteristics was made. The die entry performance was defined by the dimensionless vortex size which was found to be most susceptible to the contraction ratio of a die. It was found that temperature and length to diameter ratio had little or no effects on the dimensionless vortex size which, in turn, may be estimated by either of the two correlations (one based on theory whereas the other was obtained from curve-fitting) developed.     

Current technological challenges in capillary supercritical fluid chromatography

In cases where high efficiency is required to resolve complex mixtures of either thermally labile or nonvolatile organic compounds, capillary supercritical fluid chromatography may be the most desirable analytical method. While great strides in this new technology have been made over the last few years, several problem areas are requiring increased attention. These include sample introduction systems, pressure reduction at the end of the column, column stability in various supercritical mobile phases, and migration of polar solute molecules. This paper describes the state-of-the-art in capillary SFC with emphasis on the progress made and future needs in the solutions to these specific problems.     

Deliquescence and Efflorescence Processes of Aerosol Particles Studied by in situ FTIR and Raman Spectroscopy

Deliquescence and efflorescence are the two most important physicochemical processes of aerosol particles. In deliquescence and efflorescence cycles of aerosol particles, many fundamental problems need to be investigated in detail on the molecular level, including ion and molecule interactions in supersaturated aerosols, metastable solid phases that may be formed, and microscopic structures and deliquescence mechanisms of aerosol particles. This paper presents a summary of the progress made in recent investigations of deliquescence and e2orescence processes of aerosol particles by four common spectral techniques, which are known as Raman/electrodynamic balance, Fourier transform infrared/aerosol flow tube, Fourier transforminfrared/attenuated total reflection, and confocal Raman on a quartz substrate.     

Cycle time and carrier life in immobilized-glucoamylase reactors

The activity of immobilized enzymes decays with time, and the capacity of a carrier will decrease with repeated regeneration. Relations between production cost and these factors are shown, and demonstrated with data on glucoamylase immobilized on porous glass. Optimum design calls for very low temperature and for cycle times several years long. A practical design may be made by limiting cycle time to an upper limit and calculating the temperature for which this time is optimum. In this case, reagents and carrier are the most important costs, even with an expensive enzyme.     

Study of retention behaviour and mass spectrometry compatibility in zwitterionic hydrophilic interaction chromatography for the separation of modified nucleosides and nucleobases

A study has been made of the chromatographic behaviour of modified nucleosides and nucleobases using different stationary phases with functional groups of polar nature, all of them compatible with aquoorganic mobile phases. The stationary phases assayed were a pentafluorophenylpropyl (PFP) column for reverse phase separation, and another two for hydrophilic interaction chromatography (HILIC) separation. Six modified nucleosides and nucleobases (hydroxylated and methylated derivatives) were chosen as the target analytes. In the study, chromatographic resolution as well as the sensitivity in detection by mass spectrometry were taken into account. The results obtained showed that the zwitterionic (ZIC-HILIC) column was the most suitable one for the separation of these analytes. From the study of the different parameters affecting separation it may be concluded that in the ZIC-HILIC column separation is based on a mechanism of partition and interaction through weak electrostatic forces.     

Application and evaluation of a new cold-stable kinetic Jaffé reagent to the Hitachi 747 for the determination of serum creatinine

One of the most commonly requested tests of the clinical laboratory is that of serum creatinine. Since the late 19th century the most commonly used reagents have been those based upon the work of Jaffé [1], which are composed of alkali and picric acid. Upon addition of creatinine to this reagent a red color, referred to as a Janovsky complex [2 and 3] is rapidly formed. Almost all of the currently available approaches to the automated determination of creatinine are based upon this reaction. Furthermore, the rate of the reaction may be controlled so that either equilibrium [4] or kinetic [5] measurements can be made. Although various enzymic approaches have been proposed [6, 7, 8, 9 and 10] they, as yet, have not gained the same popular support of the modified Jaffé reagents.     

Model studies in heterogeneous catalysis at the microscopic level: from the structure and composition of surfaces to reaction kinetics

Heterogeneous catalysis is one of the fields of modern technology, in which a characterization of structural and chemical properties of solid surfaces at the microscopic level is of enormous importance. For a long time, such insights have been precluded by the complexity of most catalytically active materials. Recently, substantial progress has been made, however, toward a microscopic-level understanding of complex catalyst surfaces. We discuss the driving factors for these advancements, which are based on the development of new well-defined model systems as well as on advances in experimental technology and theory. Scrutinizing the example of planar model catalysts, we identify the process of linking structural and chemical information to microscopic reaction kinetics as a particular challenging aspect of today’s work. We review the kinetic effects which may have an influence on the reaction kinetics on complex surfaces. As an example how structural and kinetic information can be correlated at the microscopic level we discuss the case of surface oxidation and oxygen induced restructuring of Pd nanoparticles as studied by molecular beam methods.     

Mechanisms of spin transmission: Isotropic hyperfine interactions

The contributions of spin polarization and spin delocalization mechanisms to the proton hyperfine coupling constant is investigated. It is shown that these non-observables are not uniquely defined in most calculations. Arguments are presented which suggest that these non-observables may be profitably defined if both unrestricted Hartree-Fock and restricted Hartree-Fock calculations are made.     

Neutron activation analysis for provenance studies of archaeological artifacts

Differences in composition of archaeological artifacts may only in distinct cases be interpreted in terms of provenance differences. This point is discussed with examples: the large number of elements analyzed with precision and the relative lack of sensitivity of many of them to the presence of crystalline inclusions, made of NAA the method most commonly used for provenance studies of ceramics.