Oxidation of organic pollutants in aqueous solutions by nanosized copper oxide catalysts

The catalytic activity of copper oxide nanoparticles was investigated for the removal of organic pollutants in aqueous solutions, using hydrogen peroxide as an oxidant. Complete degradation of both alachlor and phenanthrene was achieved after 20 min. The kinetics of the reaction was found to be pseudo-first-order with respect to the pollutant. The influence on the reaction kinetics of different catalyst samples, consisting of the same material but of different origin and different particle properties, was examined. The effects of several factors such as irradiation, oxidant concentration, ionic strength and pH on the reaction were also investigated. The catalysis is not photo-induced and can be performed without UV–vis irradiation. In particular, an optimal oxidant concentration was determined for the studied system. The presence of salts was found to inhibit the alachlor degradation rate. The addition of high concentrations of oxidant or salt results in pseudo-zero-order kinetics. However, NaCl at very high concentrations (>1 M) was found to cause a dramatic increase in reaction rate. The catalysis is efficient over a wide range of pH values.     

A new cohesive zone model for mixed mode interface fracture in bimaterials

A new two-dimensional cohesive zone model which is suitable for the prediction of mixed mode interface fracture in bimaterials is presented. The model accounts for the well known fact that the interfacial fracture toughness is not a constant, but a function of the mode mixity. Within the framework of this model, the cohesive energy and the cohesive strength are not chosen to be constant, but rather functions of the mode mixity. A polynomial cohesive zone model is derived in light of analytical and experimental observations of interface cracks. The validity of the new cohesive law is examined by analyzing double cantilever beam and Brazilian disk specimens. The methodology to determine the parameters of the model is outlined and a failure criterion for a pair of ceramic clays is suggested.     

Living in a bubble? Toward a unified bubble theory

We generalise the notion of a bubble beyond the financial domain, by showing how a single social mechanism, based on an information feedback-loop, explains both financial bubbles and other seemingly disparate social phenomena, such as the recognition of academic articles, website popularity, and the spread of rumours.

We discuss examples of phenomena explained by this bubble mechanism, as well as other phenomena that exhibit certain bubble characteristics, yet are not bubbles according to our model. Finally, we present mathematical mechanisms for two phenomena that conform with our model, and show by computer simulation how they exhibit bubble behaviour.     

Environmental effects on deformation,strength, and degradation of unidirectional glass-fiber reinforced plastics. II. Experimental study

Glass-fiber reinforced epoxy (GRP) and unfilled epoxy specimens were exposed to different environmental conditions consisting of hot- and cold-water absorption and subsequent drying. Effects of the environmental history on deformational and strength characteristics of the composite material were investigated. GRP specimens exposed to hot water undergo pronounced degradation, which sets in shortly after exposure and is associated with a significant irrecoverable weight loss. Degraded specimens are characterized by higher void content and lower strength compared with their cold-water and reference counterparts. The degradation process is attributed to penetration of water into the matrix-fiber interfaces and is followed by an attack, at high temperatures, on the glass-fibers surface and coupling agent. As a result, glass constituents are leached out and then removed from the system by diffusion. The degradation effect was also confirmed by micro-observation of the fractured surfaces and by infra-red spectroscopy. A simple and effective testing method is recommended, permitting detection of degradation onset and its progress by simultaneous measurement of weight and dimensional changes with time.     

One‐Pot Chemoenzymatic Cascade for Labeling of the Epigenetic Marker 5‐Hydroxymethylcytosine

The epigenetic DNA modification 5‐hydroxymethylcytosine (5‐hmC) is important for the regulation of gene expression during development and in tumorigenesis. 5‐hmC can be selectively glycosylated by T4 β‐glucosyltransferase (β‐GT); introduction of an azide on the attached sugar provides a chemical handle for isolation or fluorescent tagging of 5‐hmC residues by click chemistry. This approach has not been broadly adopted because of the challenging synthesis and limited commercial availability of the glycosylation substrate, 6‐deoxy‐6‐azido‐α‐D ‐glucopyranoside. We report the enzyme‐assisted synthesis of this precursor by the uridylyltransferase from Pasteurella multocida (PmGlmU). We were able to directly label 5‐hmC in genomic DNA by an enzymatic cascade involving successive action of PmGlmU and β‐GT. This is a facile and cost‐effective one‐pot chemoenzymatic methodology for 5‐hmC analysis.