Nicoleta Iftimie

NIR Study of Chemically Modified Cellulosic Biopolymers

ABSTRACT Near-infrared spectral analysis was useful to quantify the ester content of chemically modified cellulose and lignocellulosics. Two kinds of samples were studied, as long aliphatic-chain cellulose esters and wood sawdust chemically-modified either by anhydrides or by ethylene carbonate. It was possible to determine the degree of substitution (DS) of such samples through a correlation by partial least square (PLS) of second-order derivative of NIR spectra. This technique was efficient even when DS values were low, which is difficult to do by using FTIR. It was also possible to distinguish reagent molecules that were attached to the cellulosic substrate by hydrogen bonding from those linked by covalent bonding.

Characterization of Aluminophosphate Glasses Containing Pr3+, Er3+, Gd3+ and Yb3+ Ions

A wet non-conventional method for preparing aluminophosphate glasses is presented. Aluminophosphate glasses belonging to the oxide system Li2O-BaO-Al2O3-La2O3-P2O5, doped with rare-earth ions (Pr3+, Er3+, Gd3+, and Yb3+) were obtained. The influence of the doping ions on the optical properties of the phosphate glasses has been investigated in relation with micro-structural and local electronic phenomena The optical behavior of Li2O-BaO-Al2O3-La2O3-P2O5 glasses doped with 3% mol. rare-earth ions has been studied by ultra-violet-visible-near-infra-red (UV-VISNIR) spectroscopy. The transmission spectra revealed electronic transitions between 4f and 6s inner orbital of the rare-earth ions. Structural information via optical phonons was provided by infra-red (IR) absorption spectra in the range 400-4000 cm-1. IR optical phonons are characteristic for the vitreous phosphate network, showing out the glass network-forming role of P2O5. The absorption spectra present the main PO2 and P-O-P symmetrical stretch modes besides P-O-P bend mode, P-OH, P=O, PO3 2-, asymmetrical and symmetrical vibration modes. Fluorescence spectra of the rareearth- doped aluminophosphate glasses, in the visible range, were obtained by laser excitation at 514.5 nm. The fluorescence signals revealed specific electronic transitions, which provide visible and near-infra-red emission. Glasses containing rare-earth ions exhibit luminescence at the following wavelengths: Pr3+ ions at 820 nm and 880 nm, Er3+ ions at 520 nm, 550 nm and 560 nm, Gd3+ ions at 530 nm, 540 nm, 550 nm 820 and 880 nm, Yb3+ions at 530 nm, 540 nm, 550 nm and 980 nm.

Behaviour to Accelerate Ageing of Some Natural Biopolymer Constituents of Parchment

The aim of this study is testing different new types of parchment materials during thermo-oxidative ageing at 70°C temperature, as well as under UV radiation at 50°C. The changes have been monitored by the physical–chemical tests, UV–VIS and FT–IR spectra, color and thermal analysis.Based on these experiments the corresponding types of parchment have been selected in order to assure appropriate protection of patrimony materials.

Imaging Subsurface Water Pipe Using GPR and Evanescent Waves: Experimental and Simulations Data

In this paper there are presented a series of methods and algorithms for signal processing (A-scan) and image processing (B-scan) which allow an easier and more accurate interpretation of the inspection results. The methods and the algorithms were tested for detection of a buried pipe, made of glass fiber polyester composite with a diameter of 1.3m, first when the survey conditions allowed only the scanning along the pipe, the most disadvantageous situation, but it has imposed by the configuration of the examined zone. After a few days of construction works, the site was prepared for inspection, orthogonally on the first scan direction.

New Nanostructured Complex Systems with Antioxidant and Photoprotective Activity

ABSTRACT It has been demonstrated that the alarming increase in UV radiation on the ground and intensive or repeated sun expositions cause systemic effects that can be shown as alterations of the general defense mechanisms against free radicals, increase of red blood cells fragility or a systemic immunosuppression. This article is the first step in developing new cosmetics based on nanostructured complexes containing active principles extracted from animal (collagen) and vegetal (polyphenols) tissues, with sun protective and antioxidant activity. The antioxidant activity has been monitored by chemiluminescence, while the photoprotective capacity has been quantified by using diffuse reflectance spectroscopy (Sun Protection Factor).

Redox Properties of Some Aminoacids and Proteins

ABSTRACT In order to characterize redox properties of biomolecules, specific methods for evaluating the antioxidant capacity of some biological structures or their components (like aminoacids) are used, such as chemiluminescence (CL) and cyclic voltametry coupled with UV-VIS spectroscopy. The CL antioxidant capacity, the reduction potential (ϵ1/2), and the anodic current intensity (Ia) have been determined by controlling the behavior of the compounds under redox conditions. The value of the half-wave potential of the first peak was correlated with the reduction tendency on the electrode, and this behavior was analyzed in relation to the antioxidant capacity observed by CL.