A Review of: “Polycyclic Aromatic Hydrocarbons: Chemistry and Carcinogenicity”

Abstract

Ronald G. Harvey, Cambridge University Press, Cambridge 1991. 396 pages. £80. ISBN 0 521 36458 2.     

Comment on “The effects of molecular weight and thermal decomposition on the sensitivity of a thermal desorption aerosol mass spectrometer”

Copyright © American Association for Aerosol Research     

A study of the effect of iron oxide nanoparticles on the optical and adhesive properties of thermal control coatings of the “solar reflector” and “true absorber” class

The ability to acquire thermal control coatings of the “solar reflector” and “true absorber” class modified with iron oxide nanoparticles has been studied. The optical and adhesive properties of thermal control coatings have also been established.     

Additive Manufacturing of ceramic components by Digital Light Processing: A comparison between the “bottom-up” and the “top-down” approaches

A systematic study of the additive manufacturing of complex ceramic objects was carried out using two different Digital Light Processing (DLP) approaches, the "bottom-up" and "top-down" ones, employing the same projector as light source and a photosensitive Al₂O₃-based ceramic slurry.Cylindrical periodic architectures having different macro-porosity, as well a bulk (dense) component in the form of a disk, were designed and additively manufactured with the two printers employing similar printing conditions.In the "bottom-up" approach, the periodic detachment of the part being manufactured from the bottom surface of the vat, to enable the insertion of a fresh layer of slurry, introduced stresses and deformations in the component, leading to several problems.In the "top-down" approach, the main issue is that the thickness of the printed slices is not precise and constant, due to the difficulty of the viscous slurry to uniformly wet and coat the already printed layers.     

A perspective on the contribution of surfactants and lipids toward “Green Chemistry”: Present states and future potential

“Green Chemistry” has become a subject of increasing interest in recent years. The goal of efforts in this area is to develop environmentally friendly methods and processes to replace traditional reactions that use organic solvents, consume much energy, and generate undesirable by-products and/or waste. Utilization of renewable resources is an important component of Green Chemistry. Fats and oils represent one such resource. They can give rise to many types of surfactants and lipids that can modify properties of boundary phases between different phases. Thus, phase-transfer catalysts (PTC) based on surfactants or lipids have been reported to be useful in reactions such as oxidation and hydration reactions and in glycidyl ether formation. Another approach to satisfying Green Chemistry requirements is the recovery and recycling of reactants and/or substrates used. In the preparation of alkyl glyceryl ethers, the intermediate 1,3-dioxolane compounds prepared by addition of acetone to alkyl glycidyl ethers can be hydrolyzed to regenerate reusable acetone. Other examples of methodologies based on surfactants or lipids are summarized, and their potential contribution to Green Chemistry is discussed.     

“TRU-SANEX”: A variation on the EURO-GANEX and i-SANEX processes for heterogeneous recycling of actinides Np-Cm

A novel separation process for recovering transuranic actinides has been tested in centrifugal contactors using a surrogate feed solution. This “TRU-SANEX” (transuranic element-selective actinide extraction) process uses solvent extraction between nitric acid and an organic phase containing 0.2 mol/L N,N,N′,N′-tetraoctyl diglycolamide with 0.5 mol/L N,N′-dimethyl-N,N′-dioctylhexylethoxy-malonamide to co-extract actinides and lanthanides followed by separate sections for plutonium–neptunium and americium–curium stripping. Overall, good performance was achieved with good recoveries of plutonium and americium in the products and only small amounts of cross-contamination between products. Decontamination factors for selected lanthanides in the americium–curium product ranged from ~40 to >1300.     

Experimental investigation of effects of the feed flow rate and “tail scoop-wall” clearance on the performance of a gas centrifuge by feeding a Freon mixture

Experimental study of the performance of a gas centrifuge can be appreciably simplified if instead of isotopic mixtures, a binary mixture of gases with large molecular weight difference is used. The current study undertook this approach by injecting a 53%–47% (w/w) mixture of “Freon12-Freon22” into a gas centrifuge. The two parameters, whose investigation was the objective of the current study were: the feed flow rate (F), and the clearance between tail scoop and the rotor wall (d). The results demonstrated that changing the scoop-wall clearance has the most significant effect on the cut (θ), so that by fixing “d”, “θ” becomes nearly invariant. The head separation factor (α) exhibited the same dependency, but it was more influenced by the “F” than the “d”. Apparently the following regression exists between the inspected parameters:

Decreasing “d” → Decreasing “θ” → Increasing “α”.

Variations of the tail separation factor (β) with “F” or “d” was quite slight, even though similar to “α”, it was lowered with increasing of the “F”. The separation capacity (δU) as the most significant parameter of a centrifuge was optimised at the highest value of “F = 40.5 g/h”, and lowest value of “d = 3 mm”. The study achieved a separation capacity and an overall separation factor equal to 195.53 kg Freon/y and 16.87, respectively. These values are several times larger than those of the isotopic mixtures, demonstrating that application of Freons is a useful mean for magnifying the features of a gas centrifuge.     

A discussion of the paper “Differential-scheme based dissolution diffusion model for calcium leaching in cement-based materials accounting for mix design and binder composition”

This paper presents a discussion on a recent article authored by Pichler et al. [Differential-scheme based dissolution diffusion model for calcium leaching in cement-based materials accounting for mix design and binder composition, Cem. Concr. Res. 42 (2012) 686–699].     

Adhere to the principle of “Science and technology is the No. 1 productive force”, strive for the realization of the strategic target of“Boosting chemical industry by science and technology”

In this pen conference, we have invited authorities and experts concerned to further elaborate the connotations and significance of the principle of "Science and technology is the No. 1 productive force" , discuss the problems encountered in implementing the principle in chemical industry and measures consequently taken against them and exchange experience gained in executing the policy of "Boosting chemical industry by science and technology" , The purpose is to accelerate the modernization process of China's chemical industry and realize the strategic target set by the government.     

A “Golden Age” for the discovery of new antileishmanial agents: Current status of leishmanicidal gold complexes and prospective targets beyond the trypanothione system

Leishmaniasis is one of the most neglected diseases worldwide and is considered a serious public health issue. The current therapeutic options have several disadvantages that make the search for new therapeutics urgent. Gold compounds are emerging as promising candidates based on encouraging in vitro and limited in vivo results for several Au^I and Au^III complexes. The antiparasitic mechanisms of these molecules remain only partially understood. However, a few studies have proposed the trypanothione redox system as a target, similar to the mammalian thioredoxin system, pointed out as the main target for several gold compounds with significant antitumor activity. In this review, we present the current status of the investigation and design of gold compounds directed at treating leishmaniasis. In addition, we explore potential targets in Leishmania parasites beyond the trypanothione system, taking into account previous studies and structure modulation performed for gold-based compounds.     

A “chopped fast flow” technique for transient surface reaction rate measurement: Carbon deposition and oxidation on hot PT

A novel “chopped fast flow” technique for surface reaction studies is described. It extends the molecular beam chopping approach to fast flow systems, exploits higher reactant and product fluxes, and permits transient rate measurements of fast surface reactions at much higher pressure. It employs an oscillating needle gas source to generate reactant square wave flows. The method was used to measure rates of carbon deposition following impact of hydrocarbon molecules on a hot Pt surface (T > 1000 °K). Square wave flows of hydrocarbon and oxygen, out of phase, produced period changes in carbon coverage, surface work function, and thermionic electron emission current. Carbon deposition rates were inferred from the variation of emission current with time. Deposition probabilities were low and very sensitive to hydrocarbon chain length. The results suggest that energy transfer during the short physisorption lifetime of the hydrocarbon molecule limits the deposition probability.