Hydrogenation of poly(myrcene) and poly(farnesene) using diimide reduction at ambient pressure

Ambient pressure chemical hydrogenation using p-toluene sulfonyl hydrazide (TSH) via thermal diimide formation (N₂H₂) permitted reduction of double bonds of poly(myrcene) (poly[Myr]) and poly(farnesene) (poly[Far]). Both pendent and backbone double bonds in poly(Myr) (M_n = 56 kg/mol) and poly(Far) (M_n = 62 kg/mol) synthesized by conventional free radical polymerization were hydrogenated to almost completion. Furthermore, TSH semi-batch addition efficiently hydrogenated double bonds, while avoiding undesired autohydrogenation of diimides that occurred in batch mode. Thermal stability improved for hydrogenated poly(Myr) and poly(Far), where temperature at 10% weight loss (T_10%) increased from 188 to 404°C for poly(Myr) and from 310 to 379°C for poly(Far). T_gs of poly(Myr) and poly(Far) also increased by about 10–25°C, indicating increased stiffness after hydrogenation. Finally, viscosities of poly(Myr) and poly(Far) were also increased after hydrogenation, and a greater increase was observed for poly(Myr) (by two orders of magnitude from 10² to 10⁴ Pa s) due to its M_n being much higher than its entanglement molecular weight. Poly(Far) viscosity only increased by 1.5 times after hydrogenation (~10⁴ Pa s), comparable to the poly(Myr) after hydrogenation, suggesting unsaturated poly(Far) was more entangled than unsaturated poly(Myr) because of its longer side chains.     

Dicyanamide complexes of copper(II), nickel(II) and cobalt(II) with benzimidazole and its 2-alkyl-derivatives

Summary Dicyanamide complexes of Cu^II, Ni^II and Co^II of the type M[N(CN)₂]₂L₂, where L = benzimidazole, 2-methyl- or 2-ethylbenzimidazole, have been prepared and studied by spectroscopy and magnetochemistry. The complexes, except for Co[N(CN)₂]₂ (benzimidazole)₂, are six-coordinate, involving bidentate bridging dicyanamide groups. While the Ni^II complexes have practically octahedral structures, the Cu^II complexes are pseudooctahedral with similar tetragonal distortion. The ligand field strength in these complexes depends mainly on the steric effect of the benzimidazole ligands. The Co^II complex of benzimidazole is monomeric tetrahedral, but that of 2-ethylbenzimidazole is tetragonal octahedral. The oridging function of dicyanamide in the six-coordinate complexes is realized either through both cyanide or through amide and cyanide nitrogens. The complex Cu[N(CN)₂]₂ (2-methylbenzimidazole)₂ is a weak antiferromagnet (J = -0.1 cm^–1), exhibiting under ca. 15 K a long-range antiferromagnetic ordering.     

Microbial screening methods for detection of antibiotic residues in slaughter animals

Monitoring of food products from animal origin for the presence of antimicrobial residues is preferably done using microbial screening methods because of their high cost-effectiveness. Traditionally applied methods fail to detect the maximum residue limits which were established when EU Council Regulation 2377/90 came into effect. Consequently, during the last decade this has led to the development of improved microbial screening methods. This review provides an overview of the efforts expended to bring antibiotic screening methods into compliance with EU legislation. It can be concluded that the current situation is still far from satisfactory.     

Braided Logic: The Simplest Models

The only pair of binary classical essential connectives for which the Artin braid relation holds is a distributive lattice, i.e. the Boolean disjunction and conjunction of     

Direct determination of benzylnitriles using the cyanide ion selective electrode

The response characteristics of the solid state cyanide ion selective electrode towards some benzylnitriles are investigated. In 10M KOH solution, the electrode exhibits nearly Nernstian response over the concentration range of 10^–2 to 10^–4 M of various substituted benzylnitriles with an anionic slope of 53–59 mV/concentration decade. The response time varies from 10 to 20 min depending on both the nature of the substituent group and the concentration of the nitrile compound. Direct potentiometric measurement of some nitrile compounds at the concentration level of 0.01 to 1 mg/ml shows an average recovery of 98.2% and a mean standard deviation of 2.3%. Many nitrogen functional groups do not interfere.     

Rapid solidification processing in molten salts chemistry: X-ray analysis of deeply undercooled cryolite-alumina melts

Rapid solidification processing (cooling rate from the interval 10⁵–10⁶ K s⁻¹) was used to prepare deeply undercooled cryolite-alumina melts. Such prepared samples were analyzed by the XRD method. Besides cryolite, XRD patterns belonging to ι-Al₂O₃ were recorded. The influence of annealing on the XRD patterns of deeply undercooled melts was also investigated.     

About the Importance of Nanometer-Thick Intergranular Penetration in the Analysis of Liquid Metal Embrittlement

Liquid metal embrittlement (LME) of copper by liquid bismuth is investigated at 300°C. It is shown that a very rapid damage is due to the synergy between the external stress and the phenomenon of intergranular penetration (IGP). Tests of IGP, i.e. without external stress, were done at 300°C and at 600°C and have resulted in strong intergranular embrittlement due to the formation of nanometer-thick intergranular films, as measured and quantified by Auger electron spectroscopy (AES). The formation of these films is discussed with respect to apparently non-zero dihedral angles at 600°C. A general procedure based on mechanical testing and AES measurements, to check whether IGP has occurred or not, is outlined. This procedure can be seen as an alternative way to determine the wetting transition temperature. The presence of nanometer-thick films due to IGP is discussed with respect to the LME mechanisms.     

Nanotubes Made from Deeply Undercooled Cryolite/Alumina Melts

The rapid‐solidification processing (by a cooling rate of 10⁵–10⁶ K/s) was used for the preparation of deeply undercooled cryolite/alumina (Na₃AlF₆/Al₂O₃) melts. We found a mass of nanotubes on the surface of these undercooled melts. The nanotubes were preferentially located on the defect places of the surface with the following approximate dimensions: base≈100×100 nm, length≈1000 nm. The solidified samples with the nanotubes on the surface were analyzed by scanning electron microscopy (SEM), energy‐dispersive X‐ray spectroscopy (EDX), X‐ray diffraction (XRD), and infrared spectroscopy (IR).     

Determination of the Robin coefficient in a nonlinear boundary condition for a steady‐state problem

In this paper, a constant heat transfer coefficient present in a nonlinear Robin‐type boundary condition associated with an elliptic equation is reconstructed uniquely from a single boundary energy measurement. Two types of such boundary energy measurement are considered, and solvability theorems for the solution of the resulting nonlinear inverse problems are provided. Further, one‐dimensional numerical results are presented and discussed. Copyright © 2008 John Wiley & Sons, Ltd.