Experimental study of Fe–C–O based system below 1000 °C

The paper deals with the study of phase transformation temperatures of Fe (Fe–C–O) based metallic alloys. Six model alloys with graded carbon and oxygen content were used for experimental investigation. Low-temperature region (<1000 °C) was the investigated area. Phase transformation temperatures were obtained using Differential thermal analysis and Setaram Setsys 18_TM laboratory system. Controlled heating was conducted at the rates of 2, 4, 7, 10, 15, 20 °C min^?1. Region of eutectoid transformation (Fe_α(C) + Fe₃C → Fe_γ(C)), alpha–gamma (Fe_α(C) → Fe_γ(C)) and transformation Fe_α(O) + Fe_0.92O → Fe_γ(O) + Fe_0.92O was studied. New original data (phase transformation temperatures) were obtained in this study. The relationship between shift of phase transformation temperatures and chemical composition (mainly carbon and oxygen content) is investigated in this paper. To achieve good approximation to the equilibrium conditions, the extrapolation of the obtained phase transformation temperatures to the zero heating rate was performed. The influence of experimental conditions (heating rate) on temperatures of phase transformations was studied as well. Comparison of the obtained experimental data with the data presented in the accessible literature and IDS calculations (Solidification Analysis Package) was carried out. It follows from literature search that there is a lack of thermo-physical and thermo-dynamical data on Fe–C–O system.     

Rolling up a Graphene Sheet

Carbon Nanotubes, CNTs, have been described as rolled‐up graphene layers. Matching this concept to experiments has been a great experimental challenge for it requires a method to exfoliate graphite, generate ordered and stable dangling carbon bonds, and roll up the layer without affecting the unpaired electrons of the dangling bonds that finally have to zip up in an orderly fashion: A tall order for any synthetic strategy. The combined use of ultrasonication of graphite in dimethylformamide and addition of ferrocene aldehyde just does it!     

High-resolution monolithic columns—a new tool for effective and quick separation

This work describes a comparison of three types of commercial high-performance liquid chromatography silica monolithic columns with different inner diameters and generations of monolithic sorbent: a “classic” monolithic column, the first generation (Onyx? monolithic C₁₈, 100 mm?×?4.6 mm, Phenomenex); a “narrow” monolithic column for fast separation at lower flow rates (Chromolith® Performance RP-18e, 100 mm?×?3 mm, Merck); and a recently introduced “high-resolution” monolithic column, the next generation (Chromolith® HighResolution RP-18e, 100 mm?×?4.6 mm, Merck). Separation efficiency (number of theoretical plates, height equivalent to a theoretical plate and van Deemter curves), working pressure, the symmetry factor and resolution were critical aspects of the comparison in the case of the separation of ascorbic acid, paracetamol and caffeine. The separations were performed under isocratic conditions with a mobile phase consisting of 10:90 (v/v) acetonitrile–phosphoric acid (pH 2.80). Detailed comparison of the newest-generation monolithic column (Chromolith® HighResolution) with the previously introduced monolithic sorbents was performed and proved the advantages of the Chromolith® HighResolution column.

Critical investigation of the substituent distribution in the polymer chains of hydroxypropyl methylcelluloses by (LC-)ESI-MS

Three hydroxypropyl methylcellulose samples (HPMC1–3, DS_Me?=?1.45, 1.29, and 1.36; MS_HP?=?0.28, 0.46, and 0.84) were analyzed with respect to their methyl and hydroxypropyl substitution pattern in the polymer chains. Ionization yield of HPMC oligomers in electrospray ionization ion trap mass spectrometry (ESI-IT-MS) is strongly influenced by the hydroxypropyl pattern. Therefore, a sample derivatization procedure, as well as suitable measurement conditions that enable relative quantification were elaborated. Analysis was performed by negative ESI-IT-MS after per(deutero)methylation, partial depolymerization, and reductive amination with m-aminobenzoic acid. Measurement parameters like solvent, trap drive, and voltages of the ion transportation unit were studied with regard to the suitability for quantitative evaluation. Using direct infusion of the samples, strong influence of trap drive and octopole settings was observed. Optimized measurement conditions were used for the determination of the HP pattern of the permethylated samples by direct infusion. The methyl pattern was determined from the perdeuteromethylated samples by high-performance liquid chromatography–electrospray tandem mass spectrometry. For HPMC1, substituents were both found to fit the random distribution model. The other two samples showed pronounced heterogeneity which could be interpreted in more detail by extracting methyl subpatterns depending on the number of HP groups.

Optimization in multidimensional gas chromatography applying quantitative analysis via a stable isotope dilution assay

Trace level analyses in complex matrices benefit from heart-cut multidimensional gas chromatographic (MDGC) separations and quantification via a stable isotope dilution assay. Minimization of the potential transfer of co-eluting matrix compounds from the first dimension (¹D) separation into the second dimension separation requests narrow cut-windows. Knowledge about the nature of the isotope effect in the separation of labeled and unlabeled compounds allows choosing conditions resulting in at best a co-elution situation in the ¹D separation. Since the isotope effect strongly depends on the interactions of the analytes with the stationary phase, an appropriate separation column polarity is mandatory for an isotopic co-elution. With 3-alkyl-2-methoxypyrazines and an ionic liquid stationary phase as an example, optimization of the MDGC method is demonstrated and critical aspects of narrow cut-window definition are discussed.

Agency and structure: a social simulation of knowledge-intensive industries

Modern knowledge-intensive economies are complex social systems where intertwining factors are responsible for the shaping of emerging industries: the self-organising interaction patterns and strategies of the individual actors (an agency-oriented pattern) and the institutional frameworks of different innovation systems (a structure-oriented pattern). In this paper, we examine the relative primacy of the two patterns in the development of innovation networks, and find that both are important. In order to investigate the relative significance of strategic decision making by innovation network actors and the roles played by national institutional settings, we use an agent-based model of knowledge-intensive innovation networks, SKIN. We experiment with the simulation of different actor strategies and different access conditions to capital in order to study the resulting effects on innovation performance and size of the industry. Our analysis suggests that actors are able to compensate for structural limitations through strategic collaborations. The implications for public policy are outlined.     

Spin Transition of 1D, 2D and 3D Iron(II) Complex Polymers The Tug-of-War between Elastic Interaction and a Shock-Absorber Effect

Summary.  The structures of linear chain Fe(II) spin-crossover compounds of α,β- and α,ω-bis (tetrazol-1-yl)alkane type ligands are described in relation to their magnetic properties. The first threefold interlocked 3-D catenane Fe(II) spin-transition system, [μ-tris(1,4-bis(tetrazol-1-yl)butane-N1,N1′) iron(II)] bis(perchlorate), will be discussed. An analysis is made among the structures and the cooperativity of the spin-crossover behaviour of polynuclear Fe(II) spin-transition materials. Corresponding author. E-mail: koning@iacgu7.chemie.uni-mainz.de Received April 8, 2002; accepted April 18, 2002     

Derivatives of arylhydrazonic acids. Part 3: Stereochemical rearrangement of Z-oxanilo-N-dialkyl-N-arylamidrazones

Oxanilo-N¹-dialkyl-N²-arylamidrazones have been prepared by nucleophilic substitution of the chloride function of appropriate hydrazonoyl chlorides. Relative stabilities of Z- and E-isomers, calculated with the RHF/6-31G^∗ ab initio method, range between 0.7 and 2.1 kcal/mol. The Z-isomer is detected to be thermodynamically more stable for studied compounds. X-ray structure determination of 2-dimethylamino-N-phenyl-2-phenylhydrazonoacetamide revealed E- and Z-isomers (ratio 1:1) in the crystal. The different intra- and intermolecular hydrogen bond interactions, which are identified in solid state of compounds, are dissolved in polar solvents. All compounds were found to form E/Z-equilibrium in solution. In some cases E-isomers could be separated and fully characterized.     

Improvement of H/V technique by rotation of the coordinate system

In this work we investigate the application of the rotation of the coordinate system before applying denoising techniques aimed at improving the H/V spectral ratio for seismic site effects estimation. By this rotation, one can detect the direction of maximum and minimum matching between any couple of orthogonal H/V ratios. The direction of minimum matching should represent the direction of maximum anisotropy of the surface layer or a directional noise. To further improve the method, singular spectrum analysis and WASEE techniques are then applied.