Chemical composition determination of complex organic-aqueous mixtures of alcohols, acetone, acetonitrile, hydrocarbons and water by near-infrared spectroscopy

Near-infrared spectroscopy (NIRS) combined with chemometric techniques has provided fast and precise methods for quality control in the petrochemical industry. In the present work, NIRS multivariate models were used to predict the chemical composition of an organic-aqueous solvent used in an isoprene production plant. The models were developed to predict the mass percent concentration of the components present in the solvent, namely water, acetonitrile, acetone, n-propanol, i-propanol, t-butanol, allyl alcohol and 1,3-dicyclopentadiene (DCPD) plus codimers. Each component concentration was estimated from FT-NIR spectra within the 7300-3900 cm⁻¹ region, using the whole range or only selected regions. Principal component analysis (PCA) was used for exploratory data analysis and partial least-squares models were employed for calibration based on at least 70 samples. The models’ accuracy, in terms of deviation from the primary method (gas chromatography) results, was also confirmed using external validation sets and expressed by the standard error of prediction (SEP) which ranged from 0.18 to 1.27% (w/w). Therefore, the feasibility of performing the chemical composition analysis required for process control of the isoprene unit solvent has been demonstrated. The simple and fast procedure, based on a single NIR spectrum, was able to differentiate between spectroscopic features of water, hydrocarbons, alcohols, ketones and nitrile compounds present in a complex organic-aqueous sample.     

Influence of lead dioxide electrodes morphology on kinetics and current efficiency of oxygen-ozone evolution reactions

Influence of electrode morphology on electrochemical properties of lead dioxide electrodes (β-PbO₂) for oxygen-ozone evolution reactions in acid medium was investigated using scanning electronic microscopy (SEM), cyclic voltammetry (CV), polarization curves (PC), and determination of the current efficiency (Φ). Experimental findings revealed that application of high electrodeposition current densities furnishes more rough β-PbO₂ films. Surface characteristics were verified by SEM images and the analysis of interfacial pseudo-capacitances and morphology factor (φ). Kinetic study of the overall electrode process (O₂ + O₃) based on the analysis of the Tafel slope revealed that the electrode morphology and electrolyte composition considerably affect the electrode kinetics. In most cases, the existence of two Tafel slopes distributed in the low and high overpotential domains was observed. Abnormal Tafel slopes (b ≠ 120 mV) obtained for the primary water discharge step during water electrolysis were interpreted considering the apparent charge transfer coefficient (α _apa). Optimum conditions for the ozone production were obtained for the less rough β-PbO₂ electrode immersed in a sulfuric acid solution (1.0 mol dm⁻³) containing KPF₆ (30 × 10⁻³ mol dm⁻³), where the current efficiency of 15 mass % for the ozone production was obtained.     

Kinetics of the gas-phase thermal elimination of (β-chloro ethyl)-pyrazole

Flash vacuum pyrolysis of (β-chloro ethyl)-pyrazole was studied. Pyrazole elimination and vinyl chloride formation were found. Competitive reactions with (β-chloro ethyl)-pyrazole were carried out using N-ethyl-3,5-dimethyl pyrazole as internal standard to obtain the kinetic parameters (E_a). Δ(ΔH${}_{\text{?}}^{\text{°}}$ ) for this reaction was calculated.     

Photoacoustic Generation: Optical Fiber Ultrasonic Sources for Non-Destructive Evaluation and Clinical Diagnosis

An innovative photoacoustic source for ultrasonic non destructive evaluation (NDE) and clinical diagnosis is proposed. The working principle is based on thermal conversion of laser pulses into a metallic film evaporated directly onto the tip of an optical fiber. Attractive advantages of the proposed transducer are high frequency, large bandwidth and good efficiency.     

Simulation of Finline structures using the tlm method

A new model of absorbing boundary for the TLM Method, based on absorvence condition on the node, is presented. Numerical and experimental results are presented; and the convergence aspect is discussed.     

On the Velocity Distribution Function of Light Ions in Heavy Gases in an Electric Field

The special properties presented by the Boltzmann collision operator in the case of an induced-dipole interaction (Maxwellian interaction) between ions and neutrals are exploited to obtain in such case a proper solution of the Boltzmann equation for light ions in heavy gases in an electric field. Meanwhile it is proved that consideration of more than two terms of the spherical harmonic expansion of the ion velocity distribution requires to improve the usual accuracy of the terms deriving from the collision integral; vice versa, the improvement of the accuracy of the collision terms requires to retain more than two terms of the spherical harmonic expansion. The consistency of our procedure and results in the approximation neglecting the square of the ion-neutral mass ratio with respect to unity is discussed. Finally, the most significant velocity averages are calculated on the basis of the obtained ion distribution. In the limit of the above approximation they are shown to agree with Wannier's results.     

Stereoselective bioreduction of β-carboline imines through cell-free extracts from earthworms (Eisenia foetida)

Although remarkable advances have been made over the last decade in organic synthesis, catalysis, and biotechnology, there is still a need to introduce and develop new processes for chemical production to achieve sustainable and cleaner approaches to support the increasing global pharmaceutical/chemical industry. There is a growing need to produce optically active compounds in high yields to maintain and support areas such as pharmaceutical and natural product synthesis. Thus, chemists today are looking for alternative reactions carried out under green conditions. In this context, we describe β-carboline imine reductions employing cell-free extracts from red Californian earthworms (Eisenia foetida) in high yields and enantiomeric excesses. The enantiomeric excess values of the bioreduction showed no dependence on the imine 1a–g substituents to afford amines with an (R)-configuration. Based on these data, a model for the cell-free extract from the earthworm is proposed.     

Equiconvergence Theorems for Sturm Liouville Expansions and Sets of Divergence for Bochner Riesz Means in Sobolev Spaces

We state some equiconvergence results between Bochner Riesz means of expansions in eigenfunctions of suitable Sturm Liouville operators. Then we determine the Hausdorff dimension of the divergence set of Bochner Riesz means of radial functions in Sobolev classes on Euclidean and non Euclidean spaces.     

Archaeometric Analysis of Ancient Copper Artefacts by Laser-Induced Breakdown Spectroscopy Technique

Twelve archaeological copper objects from the burial site of “Fontino” cave, near Grosseto, (around 2500–2000 B.C.) were analysed using laser-induced breakdown spectroscopy. Qualitative results and a preliminary study of the samples’ composition are reported and used to make a quantitative estimate; based on these results, the samples were classified using principal components statistical analysis. The perspectives of using laser-induced breakdown spectroscopy for archaeometric analysis are also discussed.