Kinetics of thermal decomposition of aseptic packages

Kinetics of thermal decomposition of aseptic packages (e.g. Tetrapak cartons) and pyrolysis of this waste in a laboratory flow reactor was studied. Three different models for the calculation of the reaction rate and the determination of apparent kinetic parameters of thermal decomposition were used. The first method assumes a two stage thermal decomposition and the kinetic parameters were determined by fitting a derivative thermogravimetric (DTG) curve to experimentally determined thermogravimetric data of whole aseptic cartons. The second method uses kinetic parameters determined by fitting DTG curves to thermogravimetric data of individual components of aseptic packages. The last method was a multi-curve isoconversion method assuming a change of kinetic parameters with the increasing conversion. All types of the determined kinetic parameters were used in a mathematical model for thermal decomposition of mini briquettes made from aseptic packages at the temperature of 650°C. The model calculated also the heat conduction in the particles and it was verified by an independent set of experiments conducted in a laboratory screw type flow reactor.     

Controlled synthesis of photoluminescent Bi<Subscript>4</Subscript>Ti<Subscript>3</Subscript>O<Subscript>12</Subscript> nanoparticles from metal-organic polymeric precursor

Bi₄Ti₃O₁₂ (BIT) nanoparticles with a narrow average particle size distribution in the range of 11–46 nm was synthesized via a metal-organic polymeric precursor process. The crystallite size and lattice parameter of BIT were determined by XRD analysis. At annealing temperatures >550 °C, the orthorhombic BIT compound with lattice parameters a = 5.4489 Å, b = 5.4147 Å, and c = 32.8362 Å was formed while at lower annealing temperatures orthorhombicity was absent. Reaction proceeded via the formation of an intermediate phase at 500 °C with a stoichiometry close to Bi₂Ti₂O₇. The particle size and the agglomerates of the primary particles have been confirmed by FESEM and TEM. The decomposition of the polymeric gel was ascertained in order to evaluate the crystallization process from TG-DSC analysis. Raman spectroscopy was used to investigate the lattice dynamics in BIT nanoparticles. In addition, investigation of the dependence of the visible emission band around the blue–green color emission on annealing temperatures and grain sizes showed that the effect of grain size plays important roles, and that oxygen vacancies may act as the radiative centers responsible for the observed visible emission band.     

EPR study of crystalline and glassy ethanol

Pulsed X-band electron paramagnetic resonance (EPR) spectroscopy was applied in studying molecular dynamics in two different solid ethanol matrices. Nitroxyl radicals as paramagnetic reporter groups were embedded in crystalline and glassy ethanol and the phase memory time, T_m, was investigated at 5–80 K. Temperature variation revealed a maximum in 1/T_m centered around 50 K and a small linear decrease with temperature, below ca. 25 K. Faster phase memory time relaxation in crystalline ethanol than in ethanol glass was observed throughout the temperature range studied. This can be attributed to differences in spectral diffusion due to distinct molecular packing densities.     

Halving transversal designs

A factor H of a transversal design TD(k,n) = (V,𝒢, ℬ︁), where V is the set of points, 𝒢 the set of groups of size n and ℬ︁ the set of blocks of size k, is a triple (V,𝒢, 𝒟) such that 𝒟 is a subset of ℬ︁. A halving of a TD (k, n) is a pair of factors H_i = (V, 𝒢, 𝒟_i), i = 1,2 such that 𝒟₁ ∪ 𝒟₂ = ℬ︁, 𝒟₁ ∩ 𝒟₂ = ∅︁ and H₁ is isomorphic to H₂. A path of length q is a sequence x₀, x₁,…,x_q of points such that for each i = 1, 2,…, q the points x_i‐1 and x_i belong to a block B_i and no point appears more than once. The distance between points x and y in a factor H is the length of the shortest path from x to y. The diameter of a connected factor H is the maximum of the set of distances among all pairs of points of H. We prove that a TD (3, n) is halvable into isomorphic factors of diameter d only if d = 2,3,4, or ∞ and we completely determine for which values of n there exists such a halvable TD (3, n). We also show that if any group divisible design with block size at least 3 is decomposed into two factors with the same finite diameter d, then d≤ 4. © 2000 John Wiley & Sons, Inc. J Combin Designs 8: 83–99, 2000     

Skin Cleansing without or with Compromise: Soaps and Syndets

Products designed to cleanse the skin commonly do so through surfactant action, which leads to the lowering of the surface tension of the skin to facilitate the removal of dirt from its surface. Skin cleansers generally come in one of two types: soap-based and synthetic detergents, or syndets. While the latter can effectively maintain the native skin structure, function and integrity, the former tends to negatively affect the skin by causing barrier disruption, lipid dissolution and pH alteration. Despite this, soap is still often preferred, possibly due to the negative connotations around anything that is not perceived as ‘natural’. It is, therefore, important that the science behind cleansers, especially those designed for the maintenance of healthy skin and the management of common skin conditions such as eczema, be understood by both formulators and end-users. Here, we carefully weigh the advantages and disadvantages of the different types of surfactant—the key ingredient(s) in skin cleansers—and provide insight into surfactants’ physicochemical properties, biological activity and potential effects. Fine-tuning of the complex characteristics of surfactants can successfully lead to an ‘optimal’ skin cleanser that can simultaneously be milder in nature, highly effective and beneficial, and offer minimal skin interference and environmental impact.