Detection of Geopolymer Structure by Spectroscopic and ­Molybdate Measurements

Geopolymer binder obtained from metakaolin and potassium water glass has been accepted to substitute classic cement in concretes and is consider as promising component in fibre composites, materials for toxic‐waste storage, or flame proofing agents. The mixture represents likewise a model system for estimation of characterization techniques. Compared to spectroscopic methods like IR or ²⁹Si MAS NMR spectroscopy, the molybdate method allows a deeper insight into the aging mechanism of geopolymer batches.     

Nitride layers on uranium surfaces

Uranium as an important energy material plays a significant role within the field of material sciences and nuclear industrial applications. However, metallic uranium is chemically active in ambient environment and is easily oxidized and corroded, leading to not only deterioration of its properties and failure of performance as working components but also nuclear pollution of the environment. Therefore, the development of corrosion protection systems for metallic uranium is an issue of prime importance. In view of the nitridation technology in Ti and Fe-based alloys, the successful application to improve the surface wear hardness and corrosion resistance, several nitridation methods have been developed for the surface modification of metallic uranium. Many studies have shown that the surface nitridation of metallic uranium can efficiently improve its corrosion resistance. The surface oxidation layer thickness is as thin as several nanometers even if placed 4?years in the atmosphere. At the present, nitridation of uranium surface is considered as the most promising surface modification way to protect uranium from corrosion. To design and fabricate nitride layers on uranium surface with reliable long-term protective effects, however, one needs deep understanding on the relationships among the physical and chemical properties of the nitride layers, the composition and structure of the layers, and the dependence on the techniques and the processing parameters. One also needs deep understanding on the corrosion behavior of the prepared nitride layers in the environment, and the related corrosion mechanism.In this review, we bring to the readers the achievements and recent advances on the uranium nitridation in the world, including the processing techniques and the related studies on the formation mechanism of the nitride layers, and the understanding on the property-processing-corrosion performance relationship of the layers, aiming at the development of high-performance resistance layers for metallic uranium by the surface nitridation technique. In the review (1) the surface nitridation techniques developed recently, the relationship between the preparation parameters and the composition as well as the structure of the surface layer are summarized; (2) the fundamental physical properties of the uranium nitrides are summarized, depicted and discussed; (3) the influence of the nitrides structure and composition and of the environment on resistance to corrosion as well as the formation mechanism of corroded products in oxidizing environments are depicted and discussed; (4) the potential application of uranium nitrides in other application field such as the application of thermal-electrical conversion is also discussed. Finally, the prospective on the investigations of nitride layers is suggested.     

Ene-reaction between a dienolic compound and 2-methyl-2-nitrosopropane: an EPR-MS study

The combination of electron paramagnetic resonance (EPR) and mass spectrometry (MS) was used as an efficient tool to elucidate the mechanism of an ene-reaction between a dienol compound and 2-methyl-2-nitrosopropane.     

Fluorides of some s-, p-, d-, and f-metals as prospective materials for interference optics: Present status and development

Materials with low refractive indices based on fluorides of some s-, p-, d- and f-metals for interference optics were examined. Issues concerned with the enhancement of both optical and operational properties of the thin-film coatings based on fluorides were discussed. A doping mechanism for REF₃ (RE - Sc, La-Lu) dopants in the widely used material - magnesium fluoride - was proposed. Interaction in the metal fluoride systems was established. The influence of the initial material composition on the structure and properties of coatings was determined.     

Layer-Resolved Magneto-Optical Kerr Effect In Semi-Infinite Inhomogeneous Layered Systems

The contour integration technique applied to calculate the optical conductivity tensor at finite temperatures in the case of inhomogeneous surface layered systems within the framework of the spin-polarized relativistic screened Korringa-Kohn-Rostoker band structure method is extended to arbitrary polarizations of the electric field. It is shown that besides the inter-band contribution, the contour integration technique also accounts for the intra-band contribution. Introducing a layer-resolved complex Kerr angle, the importance of the first, non-magnetic buffer layer below the ferromagnetic surface on the magneto-optical Kerr effect in the Co | Pt m multilayer system is shown. Increasing the thickness of the buffer Pt, the layer-resolved complex Kerr angles follow a linear dependence with respect to m only after nine Pt mono-layers.     

To the Knowledge of Interpseudohalogens: A Contribution to Cyanogen Isocyanate (NC–NCO)

Cyanogen isocyanate (NC–NCO) has been prepared and studied using a combined experimental and theoretical approach. A crystalline film of the interpseudohalogen species was stabilized by vapor deposition on a cold substrate (T = –100 °C). From IR spectroscopy on the “free” molecule, trapped in a matrix of solid argon, the connectivity and geometry of this unstable interpseudohalogen was deduced and substantiated by theoretical calculations. With this information, the crystal structure of NCNCO in the solid state could be analysed using powder X‐ray diffraction [Pbca (No. 61), a = 7.63(1) Å, b = 6.50(2) Å, c = 6.03(6) Å; V = 299.5(1) ų]. The compound transforms into amorphous polymeric C₂N₂O at T > –68 °C. The results obtained were compared with recent findings and further discussed in the general context of C–N–(O) chemistry.     

Surmounting the Multiple-Minima Problem in Protein Folding

Protein folding is a very difficult global optimization problem. Furthermore it is coupled with the difficult task of designing a reliable force field with which one has to search for the global minimum. A summary of a series of optimization methods developed and applied to various problems involving polypeptide chains is described in this paper. With recent developments, a computational treatment of the folding of globular proteins of up to 140 residues is shown to be tractable.     

Correlations and multi-affinity in high frequency financial datasets

In this paper we perform a quantitative check of long term correlations and multi-affinity in Deutsche Mark/US Dollar exchange rates using high frequency data. We show that the use of business time, i.e., the ranking of the quotes in the sequences, eliminates most of the seasonality in financial-time series, allowing a precise estimation of some return anomalies.     

Building confidence in models for multiple audiences: The modelling cascade

This paper reports on a model building process developed to enable multiple audiences, particularly non-experts, to appreciate the validity of the models being built and their outcomes. The process is a four stage reversible cascade. This cascade provides a structured, auditable/transparent, formalized process from “real world” interviews generating a rich qualitative model through two intermediate steps before arriving at a quantitative simulation model. There are a number of advantages of the cascade process including; achieving comprehensiveness, developing organizational learning, testing the veracity of multiple perspectives, modeling transparency, achieving common understanding across many audiences and promoting confidence building in the models. The paper, based on extensive work with organizations, discusses both the cascade process and its inherent benefits.