Paraffin oil solutions of the mixture of sorbitan monolaurate-ethoxylated sorbitan monolaurate as lubricants

Paraffin mixtures of sorbitan monolaurate (SML)-ethoxylated sorbitan monolaurate (ESML) were applied as lubricant additives. The esters tested can be obtained from natural resources. They are environment-friendly. Tests under steady load conditions were performed to assess their tribological properties. The friction coefficient and wear scar diameter were measured. On the basis of the results obtained one can conclude that the mixtures tested significantly reduce motion resistance and wear. As compared to paraffin oil, wear scar diameter was reduced four times, while friction coefficient—even six times. The influence of total concentration and SML:ESML ratio on tribological properties was analyzed. The synergistic effect, attaining its optimum for comparable mole fraction of both esters, was observed. The results can be interpreted in terms of creation of micellar solutions and interaction of these structures with friction surface.     

The complete mitochondrial genome of Alligator mississippiensis and the separation between recent archosauria (birds and crocodiles)

The complete mitochondrial genome of the alligator, Alligator mississippiensis, was sequenced. The size of the molecule is 16,642 nucleotides. Previously reported rearrangements of tRNAs in crocodile mitochondrial genomes were confirmed and, relative to mammals, no other deviations of gene order were observed. The analysis of protein-coding genes of the alligator showed an evolutionary rate that is roughly the same as in mammals. Thus, the evolutionary rate in the alligator is faster than that in birds as well as that in cold-blooded vertebrates. This contradicts hypotheses of constant body temperatures or high metabolic rate being correlated with elevated molecular evolutionary rates. It is commonly acknowledged that birds are the closest living relatives to crocodiles. Birds and crocodiles represent the only archosaurian survivors of the mass extinction at the Cretaceous/Tertiary boundary. On the basis of mitochondrial protein-coding genes, the Haemothermia hypothesis, which defines birds and mammals as sister groups and thus challenges the traditional view, could be rejected. Maximum-likelihood branch length data of amino acid sequences suggest that the divergence between the avian and crocodilian lineages took place at approximately equal to 254 MYA.     

Reactive polytetrafluoroethylene/polyamide 6 compounds. II. Study of the reactivity with respect to the functionality of the polytetrafluoroethylene component and analysis of the notched impact strength of the polytetrafluoroethylene/polyamide 6 compounds

The formation of block copolymers as a result of an in situ chemical reaction during the reactive extrusion of electron‐beam‐irradiated polytetrafluoroethylene (PTFE) and polyamide 6 (PA) was detected indirectly with differential scanning calorimetry and Fourier transform infrared. As expected, the content of the block copolymers in the compound increased as the irradiation dose was increased. The notched impact strength showed an increase in the PTFE/PA compounds produced with highly irradiated PTFE. This behavior is discussed in the context of the degree of dispersion of the PTFE phase (as reported in part I of this series) and the adhesion changed by the in situ reaction. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 1317–1324, 2005     

Experimental Studies of the Alkali Behaviour in Blast Furnace Type Slags

In a preceding paper, existing data on the chemical behaviour of alkali compounds and their influence on physical properties of BF slags as well as on materials circulation in the BF operations were critically reviewed. In the present work, new investigations based on fundamental experiments and thermochemical modelling are introduced. They have been focused on the determination of both chemical activity of Na₂O and kinetics of Na₂O and K₂O evaporation from BF‐type slags. The results for the activities a_Na2O agree fairly well with data obtained from calculation based on the slag model of H. Gaye which seems generally suitable to predict chemical activities in molten slags. Kinetics of alkali evaporation from BF‐type slags follow a first‐order reaction. The rate constants for K₂O are remarkably higher than those for Na₂O. Alkali evaporation is enhanced with decreased %(CaO)/%(SiO₂) ratio and lower Al₂O₃ content and is increased with temperature. It is further favoured under reducing conditions in the absence of iron oxide in the slag.     

Crosslinkable coupling agents: Synthesis and use for modification of interfaces in polymer blends

A novel coupling agent containing 2-oxazoline and 2-oxazinone as well as hydrosilane moieties has been prepared by hydrosilylation of the corresponding allyl ether containing precursor with a methylhydrosiloxane-dimethylsiloxane copolymer. This hydrosiloxane containing coupling agent, termed as SCA, was characterized by ¹H NMR and its crosslinkability was proven by DSC. SCA was used for the modification of the interfaces in heterogeneous polymer blends. In a model blend system based on mono-carboxylic acid terminated polystyrene (PS-COOH) and mono-amino terminated poly(methyl methacrylate) (PMMA-NH₂) the 2-oxazoline and 2-oxazinone units of SCA can selectively react with the carboxylic groups or amino groups, respectively. The remaining hydrosilane units partially crosslink under the used mixing conditions.The morphology of the three-component blends prepared by melt mixing was evaluated. SCA is immiscible with the polymers and forms its own phase. The expected location of the SCA at the interface between the polymers was proven only in an annealed, strongly phase separated blend. Overall the effect of the compatibilizer on the morphology is very small. Neither the domain size nor the composition for phase inversion are significantly affected in this blend system by the presence of SCA.     

A note on varying lattice isotropy

We note how certain topological features of finite regular triangular lattice (hexagonal tiling) can be used to model most effectively various degrees of the lattice isotropy. This is illustrated with the example of simulating the process of two-dimensional unconditional spreading from a single cluster of the lattice sites.     

Developing and implementing interprofessional learning in a Faculty of Health Professions

Although medial displacement calcaneal osteotomy has been advocated for treatment of acquired pes planus, no studies have determined the biomechanical consequences at the ankle of such a procedure. The present investigation examined the alteration in ankle motion that resulted from a medial sliding calcaneal osteotomy. In dorsiflexion, the ankle specimens were found to have altered internal rotation and varus alignment. At maximal dorsiflexion, there was a 76% increase in internal rotation (4.4 degrees +/- 2.5 degrees versus 2.5 degrees +/- 1.7 degrees for intact ankles, P < 0.0004) and an increase of 425% in varus (0.42 degrees +/- 0.56 degrees versus 0.08 degrees +/- 0.34 degrees for intact ankles, P < 0.003). There were no significant differences seen in plantar flexion. Based on these results, caution is advised in the indiscriminate use of medial sliding osteotomies, because this procedure may predispose the patient to premature ankle arthritis as a consequence of the altered ankle motions.     

Massively parallelized replica-exchange simulations of polymers on GPUs

We discuss the advantages of parallelization by multithreading on graphics processing units (GPUs) for parallel tempering Monte Carlo computer simulations of an exemplified bead-spring model for homopolymers. Since the sampling of a large ensemble of conformations is a prerequisite for the precise estimation of statistical quantities such as typical indicators for conformational transitions like the peak structure of the specific heat, the advantage of a strong increase in performance of Monte Carlo simulations cannot be overestimated. Employing multithreading and utilizing the massive power of the large number of cores on GPUs, being available in modern but standard graphics cards, we find a rapid increase in efficiency when porting parts of the code from the central processing unit (CPU) to the GPU.     

Θ-polymers in crowded media under stretching force

We study the peculiarities of stretching of globular polymer macromolecules in a disordered (crowded) environment, using the model of self-attracting self-avoiding walks on site-diluted percolative lattices in space dimensions d=3. Applying the pruned–enriched Rosenbluth chain-growth method (PERM), we construct the phase diagram of collapsed–extended state coexistence when varying temperature and stretching force. The change in shape characteristics of globular polymers under stretching is analyzed as well.