A simple algorithm for the calculation of multiple site titration curves

A simple algorithm for the calculation of multiple site titrationcurves is proposed. It is based on a hybridization of two computationaltechniques: (i) a modified Tanford-Roxby iterative procedure[Tanford and Roxby (1972) Biochemistry, 11, 2193–2198]and (ii) the Boltzmann statistics. The sites characterized bystrong electrostatic coupling were selected for statisticalmechanical treatment, whereas all other sites were treated bymeans of the modified Tanford-Roxby procedure. The selectionof the two sets was made on the basis of a criterion relatedto the interaction energy between the titratable sites in theprotein molecule. The algorithm was tested for bovine pancreatictrypsin inhibitor and the pK values calculated were discussedin the light of experimental data and theoretical results obtainedby other authors. The algorithm can easily be coded and incorporatedinto any program package for the calculation of electrostaticinteractions in proteins.     

Metall-Matrix-Verbundwerkstoffe auf Eisenbasis

Metal-Matrix-Composites use a reinforcing phase to improve the mechanical properties of the matrix material or achieve a weight reduction. For example in iron and steel industrial applications typically carbides and borides are used to improve wear resistance. The intention of current investigations at the Chair of Metallurgy at the Montanuniversitaet Leoben is to produce a composite with reduced density and consistent or increased stiffness as steel. This paper reviews possible processing routes on steel composites with ceramic reinforcing phases based on a literature survey. A classification of the processing steps based on the origin of the ceramic phase is made and the advantages and disadvantages of these steps are summarized. Two tables are given to present the high amount of possible producing steps and the used investigation techniques for steel-based metal matrix composites.     

Numerical simulation of backdraft phenomena

This paper reports preliminary computational fluid dynamics (CFD) simulations of backdraft observed in an experimental rig at Lund University. The analysis was performed with the CFX software using the Detached Eddy Simulation (DES) turbulence model, a hybrid of Large Eddy Simulation (LES) and RANS, in combination with the EDM combustion model. The DES model uses a RANS formulation in wall proximity to avoid computationally expensive grid resolution that is necessary for realistic LES predictions in wall layers.     

Polymerization of chlorophenyl glycidyl ethers. VI

Summary Polymerization of p-chlorophenyl glycidyl ether initiated by potassium glycolates (ethylene, propylene and 2-methyl propylene glycolatea) in DMSO containing some 18-crown-6 ether or glycol was investigated. For the reaction system containing the propylene glycolate asymmetrically substituted with a methyl group, relatively high polymerization rates were obtained as compared with those found for the other systems studied, the resultant polymers also having higher molecular weights and comparatively low polydispersities. Aliphatic double bonds were found to be absent in the polymers synthesized, which would suggest that in the anionic polymerization process studied the growing chain is not transferred to the monomer.Dedicated to Prof. C.I. Simionescu on the occasion of the 60th anniversary of his birthday     

Rolling contact fatigue endurance of powder-extruded bearing steel

The mechanical and toughness properties and rolling contact fatigue endurance of powder-extruded bearing steel made from nitrogen atomized remelted turning powder in as-extruded and as-heat treated state are presented. The mechanical and toughness properties are comparable with those of wrought bearing steel. Rolling contact fatigue endurance was tested by the AXMAT method in as-extruded and as-spheroidizing annealed states depending on the austenitizing temperature, which ranged from 790 °C to 870 °C. Powder-extruded bearing steel in both states showed slightly higher hardness (63 HRC), higher contact fatigue resistance (L₁₀ = 80.7 and 55.2 million load cycles, respectively) in comparison with wrought steel (L₁₀ = 31.8 million load cycles). The results demonstrate the advantageous properties of powder-extruded bearing steel for high dynamic loading.     

Production of High Purity Magnesium Alloys by Melt Purification with Zr

The efficacy of Zr in removing Fe from molten Mg‐X binary alloys was studied experimentally and using calculated phase diagrams. Zr is effective in reducing the Fe content from the Mg melt for Mg‐X binary alloys, X = Y, Si, Sn, Ca, Sr, Ce, Gd, Nd, Li, La, Mn, and Zn. Purification occurs by the precipitation from the melt of Fe rich precipitates, and the settling of the precipitates to the bottom of the melt. Any desired Fe content down to 1 ppm can be achieved by appropriate melt treatment.     

pH-based one pot synthesis of biocompatible olive shaped inorganic particles

A novel, single-step, one-pot method for preparation of inorganic hollow particles is introduced. The concept is grounded on the classical theory of nucleation of growth and can be carried out entirely at room temperature. Starting from an appropriate solution, precipitation and selective dissolution of inorganic nanoparticles are triggered by continuous addition of a salt while carefully controlling the pH. The approach is demonstrated on the example of hollow calcium phosphate particles using calcium carbonate solid nanoparticles as a template. The proposed synthesis procedure is simple and cheap and can be extended to other biocompatible compounds. It also can be upgraded with an additional in situ step.     

Sphinganine‐Like Biogenesis of (E)‐1‐Nitropentadec‐1‐ene in Termite Soldiers of the Genus Prorhinotermes

In 1974, (E)‐1‐nitropentadec‐1‐ene, a strong lipophilic contact poison of soldiers of the termite genus Prorhinotermes, was the first‐described insect‐produced nitro compound. However, its biosynthesis remained unknown. In the present study, we tested the hypothesis that (E)‐1‐nitropentadec‐1‐ene biosynthesis originates with condensation of amino acids with tetradecanoic acid. By using in vivo experiments with radiolabeled and deuterium‐labeled putative precursors, we show that (E)‐1‐nitropentadec‐1‐ene is synthesized by the soldiers from glycine or L ‐serine and tetradecanoic acid. We propose and discuss three possible biosynthetic pathways.     

The Chemistry and Biology of 6‐Hydroxyceramide,the Youngest Member of the Human Sphingolipid Family

Sphingolipids are crucial for the life of the cell. In land‐dwelling mammals, they are equally important outside the cell—in the extracellular space of the skin barrier—because they prevent loss of water. Although a large body of research has elucidated many of the functions of sphingolipids, their extensive structural diversity remains intriguing. A new class of sphingolipids based on 6‐hydroxylated sphingosine has recently been identified in human skin. Abnormal levels of these 6‐hydroxylated ceramides have repeatedly been observed in atopic dermatitis; however, neither the biosynthesis nor the roles of these unique ceramide subclasses have been established in the human body. In this Minireview, we summarize the current knowledge of 6‐hydroxyceramides, including their discovery, structure, stereochemistry, occurrence in healthy and diseased human epidermis, and synthetic approaches to 6‐hydroxysphingosine and related ceramides.     

Kinetics of catalytic transfer hydrogenation of some vegetable oils

Catalytic transfer hydrogenation of corn, peanut, olive, soybean, and sunflower oils has been studied with aqueous sodium formate solution as hydrogen donor and palladium on carbon as catalyst. Kinetic constants and selectivity have been determined under intensive stirring in the presence of stabilizing agents. Hydrogenation reactions followed first-order kinetics with respect to fatty acids. Besides good selectivity and short reaction time, this method offers safe and easy handling. The presence of linolenic acid retards the migration of double bonds, which explains why soybean oil is the most appropriate for this hydrogenation process.