Effect of masonry mortar shrinkage on the linings impermeability

The results of physical and mechanical studies of andesite mastic modified with divinylstyrene latex are given. The introduction of latex into masonry mortar is shown to increase crack resistance and other operating abilities of anticorrosion linings, thus improving their impermeability.     

Phase transitions in O/W lauryl acrylate emulsions during phase inversion,studied by light microscopy and cryo-TEM

Phase changes during the preparation of nano-emulsions containing polymerizable monomer as the oil phase, by the phase inversion temperature technique (PIT), were investigated using light microscopy, cryo-TEM and viscosity measurements. The nano-emulsions were prepared using a poly(oxyethylene) nonionic surfactant and a polymerizable acrylic monomer (lauryl acrylate) as the oil phase. Inversion of the emulsion, followed by rapid cooling, resulted in emulsions having an average droplet size as low as 25 nm. Cryo-TEM was used to observe the structures that are present above and below the phase transition temperature, and gave, for the first time, visual indication of the presence of a microemulsion and a locally ordered structure in the process. At high surfactant concentrations, the inversion–cooling process yields emulsions with unique structures, in which the oil phase is present as worm-like structures.     

Marriage of exact enumeration and 1/d expansion methods: Lattice model of dilute polymers

We consider the properties of a self-avoiding polymer chain with nearestneighbor contact energy on ad-dimensional hypercubic lattice. General theoretical arguments enable us to prescribe the exact analytic form of then-segment chain partition functionC _n ,and unknown coefficients for chains of up to 11 segments are determined using exact enumeration data ind=2–6. This exact form provides the main ingredient to produce a large-n expansion ind ^–1of the chain free energy through fifth order with the full dependence on the contact energy retained. The -dependent chain connectivity constant and free energy amplitude are evaluated within thed ^–1expansion toO(d ^–5). Our general formulation includes for the first time self-avoiding walks, neighboravoiding walks, theta, and collapsed chains as particular limiting cases.     

Competitive C-I versus C-CN reductive elimination from a Rh(III) complex. Selectivity is controlled by the solvent

The RhIII complex [(PNP)Rh(CN)(CH3)][I] 5, obtained by oxidative addition of methyl iodide to [(PNP)Rh(CN)] 2, reacts selectively in two pathways: In aprotic solvents C-I reductive elimination of methyl iodide followed by its electrophilic attack on the cyano ligand takes place, giving the methyl isonitrile RhI complex [(PNP)Rh(CNCH3)][I] 3, while in protic solvents C-C reductive elimination of acetonitrile takes place forming an iodo RhI complex [(PNP)RhI] 9. Reaction of 2 with ethyl iodide in aprotic solvents gave the corresponding isonitrile complex, while in protic solvents no reactivity was observed. The selectivity of this reaction is likely due to a hydrogen bond between the cyano ligand and the protic solvent, as observed by X-ray diffraction, which retards electrophilic attack on this ligand.     

Generic approach for dispersing single-walled carbon nanotubes: the strength of a weak interaction

A generic noncovalent approach for dispersing high concentrations of individual single-walled carbon nanotubes (SWNT) in organic as well as aqueous solutions of synthetic block copolymers is presented. It is suggested that a weak, long-ranged entropic repulsion among polymer-decorated tubes acts as a barrier that prevents the tubes from approaching the attractive part of the intertube potential. The method opens a new route for utilization of block copolymers as compatibilizers for SWNT, improving the incorporation of de-agglomerated SWNT into target polymeric matrixes.     

Assessing the mechanical,phase inversion,and rheological properties of poly-[(R)-3-hydroxybutyrate-co-(R)-3-hydroxyvalerate] (PHBV) blended with poly-(l-lactic acid) (PLA)

Poly-(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) and poly-(l-lactic acid) (PLA) have attracted much interest in recent years since they are biodegradable, thus can replace synthetic non-degradable materials. In this study, improvements of PHBV, mechanical, phase inversions, and rheological properties were investigated after blending with PLA in varying ratio’s. Three different blends of commercially available PLAs with 92–98% l-lactide units and one grade of PHB with 5% valerate content were blended using a micro-compounder at 175 °C. The composition of PHBV in blends ranged from 50% to 80%. With the addition of PLA, increases in the flexural strength and elastic modulus were observed for several blends, while minor to no changes were detected in the elongation at break and tensile strength as compared to pure PHBV material. Like many conventional plastics, the complex viscosity decreased with increasing rotational frequency due to decreasing entanglements and molecular weight. The complex viscosity with respect to time was very stable for the blends, but no improvements in the PHBV viscosity were observed with the addition of PLA at 170 °C. Three phase inversion models were used to predict the continuity of the blends, and the results showed both dual- and PLA-continuity phase for the blends. In summary, the mechanical results showed improvements in the tensile and flexural properties, while the rheological observation showed minor improvements in the complex viscosity for numerous concentrations.     

Mono-, and dibenzacridine imines. Synthesis of 1a,11b- dihydrobenz[c]azirino[α]acridine, 4b,5a-dihydrodibenz[c,h]- azirino[α]acridine and 1a,13b-dihydrodibenz[c,j]azirino[α]acridine

The syntheses of the K-imine derivatives of benz[c]acridine, dibenz[c,h]acridine and dibenz[a,h]acridine are described. The parent hydrocarbons 1, 6 and 11 were oxidized with sodium hypochlorite under phase transfer conditions to the corresponding K-oxides 4,9 and 14 , which in turn were reacted with sodium azide. The resulting azido alcohols were then cyclized with tributylphosphine to the title compounds 5,10 and 15.     

Enzymes in a golden cage

We describe a general method for the entrapment of enzymes within bulk metallic gold. This is a new approach for the immobilization of enzymes on metals, which is commonly carried out by 2D adsorption or covalent biding, that is, the enzyme is in contact with the metal at a specific contact zone of the enzyme, while most of the rest of it remains exposed to the environment. The 3D metallic encaging of the enzymes is quite different: the enzyme is in contact with the metallic cage walls all around it and is well protected inside. The porous nature of the metallic matrix enables substrate molecules to diffuse inside, reach the active site, and let product molecules diffuse out. The generality of the approach was proven by the successful entrapment of five enzymes representing different classes and different bio- and medical applications: l-asparaginase (Asp), collagenase, horseradish peroxidase (HRP), laccase and glucose oxidase (GOx). GOx–gold conjugates have been of particular interest in the literature. The main challenge we had to solve was how to keep the enzyme active in the process of gold-synthesis from its cation – this required careful tailoring of reaction conditions, which are detailed in the paper. The gold entrapped enzymes gain thermal stability and protectability against harsh conditions. For instance, we could keep Asp alive at the extreme pH of 13, which normally kills the enzyme instantly. The entrapped enzymes obey the Michaelis–Menten kinetics, and activation energies were determined. Good recyclability for eight cycles was found. Multi-enzymatic reactions by combinations of the off-the-shelf bioactive enzyme@gold powders are possible, as demonstrated for the classical detection of GOx activity with HRP. Detailed material characterization and proposed mechanisms for the 3D protectability of the enzymes are provided. The new enzyme immobilization method is of wide potential uses in medicine, biotechnology, bio-fuel cells and enzymatic (electro)sensing applications.

We describe a general method for the entrapment of enzymes within bulk metallic gold.     

Dynamical bending of rigid-plastic annular plates

Dynamical bending of circular rigid-plastic annular plates, fixed along the exterior boundary and free on the interior boundary, when subjected to instantaneously applied transverse uniformly distributed blast-type load[1], is investigated in this paper.It is shown that annular plates are preferable to plates without holes, since their load capacity increases while residual deflections decrease. A so-called boundary parameter is introduced to estimate the effect of boundary conditions on the radial bending moment.A procedure for determining the residual deflections at every point of a plate is developed for use on an electronic computer. Numerical examples are given. In the end of the paper, the particularities of solution of our problem for annular plates, corresponding to the setting of Wang[2], Wang and Hopkins[3] for plates without holes are discussed.