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.     

Individual exponential stability for linear skew-products semiflows over a semiflow

Periodica Mathematica Hungarica - In this paper we consider individual stability for linear skew-product semiflows over semiflows by using the standard Perron’s method. To our knowledge, in...     

Metallophilic bonding and agostic interactions in gold(I) and silver(I) complexes bearing a thiotetrazole unit

Gold(I) and silver(I) complexes of 1-methyl-5-thio-tetrazole (1) have been prepared and the coordination chemistry of this ligand toward metal-phosphine frameworks has been explored. As indicated by IR and Raman data, ligand 1 is deprotonated and the resulted anion acts as a bidentate (S,N)-tetrazole-5-thiolato unit in the new gold(I) complexes, [Au(SCN(4)Me)(PPh(3))] (2), [{Au(SCN(4)Me)}(2)(μ-dppm)] (3), and [{Au(SCN(4)Me)}(2)(μ-dppe)] (4), while it is coordinated only through the sulfur atom as its neutral tetrazole-5-thione form in the silver(I) derivative, [Ag(HSCN(4)Me)(PPh(3))](2)(OTf)(2) (5). Further characterization of the new compounds was performed using multinuclear ((1)H, (13)C, (31)P, (19)F) NMR spectroscopy, mass spectrometry, and DSC measurements. Single-crystal X-ray diffraction studies revealed basically linear P-M-S arrangements in complexes 3-5. The bidentate (S,N) coordination pattern results in a T-shaped (S,N)PAu core in 3 and 4, whereas, in 5, a similar coordination geometry is achieved in the dimer association based on S-bridging ligand 1. Herein, weak (C)H···Au and (C)H···Ag agostic interactions were observed. An intramolecular Au···Au contact occurs in 3, while in 4 intermolecular aurophilic bonds lead to formation of a chain polymer. An intermolecular Ag···Ag contact is also present in the dimer unit of 5. Low-temperature (31)P NMR data for 5 evidenced the presence of monomer and dimer units in solution. Theoretical calculations on model of the complexes 2 and 4 are consistent with the geometries found by X-ray diffraction studies.     

<Emphasis Type="Italic">SO</Emphasis>(3,1)-Invariant Approach to Dipole Radiation

The aim of the present work is to revisit the theory of the dipole radiation, within an SO(3,1)-gauge invariant formulation, by solving the Maxwell equations. Thus, we obtain the two interconnected components, A _B , B=1,2, of the vector potential A, in terms of Hankel and Legendre polynomials. Finally, for the pure dipole-like radiation, the observables, regarded as phasors, the Umov–Poynting vector components and the well-known Larmor formula for the effective radiated power are explicitly derived.     

Spectral interferometry and reflectometry used to measure thin films

A new method for a precise measurement of the oscillatory part of phase change on reflection (interferometric phase) from a thin-film structure is presented. The method, which is based on phase retrieval from the spectral interferograms recorded at the output of a slightly dispersive Michelson interferometer, is combined with reflectometry. The interferometric phase of the thin-film structure is measured precisely using a reference sample of known phase change on reflection. The spectral reflectance of the thin-film structure is also measured in the interferometer. The feasibility of the method is confirmed in processing the experimental data for SiO₂ thin film on a silicon wafer of known optical constants. Four samples of the thin film are used and their thicknesses are determined. We confirm very good agreement between the thicknesses obtained from the interferometric phase and reflectance measurements. PACS  07.60.Ly; 68.55.Jk; 78.20.Bh     

Windowed Fourier transform applied in the wavelength domain to process the spectral interference signals

We report on processing the spectral interference signals by a new method based on a windowed Fourier transform applied in the wavelength domain. First, the numerical simulations are performed to demonstrate high precision of the phase retrieval from the spectral signal. Second, the feasibility of the method is confirmed in processing experimental data from a dispersive Michelson interferometer comprising a cube beamsplitter made of BK7 glass. From the retrieved spectral phase difference, the effective thickness of the beamsplitter is determined precisely.     

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.