Entity

Time filter

Source Type

Iaşi, Romania

Popescu C.-M.,Romanian Academy P Poni | Tibirna C.M.,Laval University | Vasile C.,Romanian Academy P Poni
Photochemistry and Photobiology | Year: 2011

A series of experiments were carried out to investigate the photodegradation of lime wood (Tilia cordata Mill.) coated with acrylic copolymer during artificial UV/Vis light irradiation for 600 h. Photodegradation of the Paraloid B72 films and Paraloid B72 treated lime wood samples was evaluated by thermogravimetry throughout the irradiation period of 100 h. The results obtained indicate a shifting of the DTG maxima to lower temperatures, which may be related to a decrease in the stability of the copolymer and wood during photodegradation. The decrease of weight loss with increasing time of exposure was observed, while the global kinetic parameters for the main peak increases when increasing exposure time of wood to the UV light. Even when the surface of the wood was covered with a thin layer of acrylic resin, some photodegradation reactions of the wood surface occurred. The modifications in the wood structure may be influenced by the newly formed structures from acrylic resin photodegradation. Photodegradation of the Paraloid B72 films and Paraloid B72 treated lime wood (Tilia cordata Mill.) samples was evaluated by thermogravimetry throughout the irradiation period up to 600 h. The shifting of the DTG maxima to lower temperatures and the decrease of weight loss indicates a decrease in the stability of copolymer during photodegradation. Even the surface of wood was covered with a thin layer of acrylic resin, some photodegradation reactions of the wood surface occurred. The modifications in wood structure may be influenced by the newly formed structures from acrylic resin photodegradation. © 2011 The American Society of Photobiology. Source


Popescu C.-M.,Romanian Academy P Poni | Larsson P.T.,Innventia Ab | Tibirna C.M.,Laval University | Vasile C.,Romanian Academy P Poni
Applied Spectroscopy | Year: 2010

X-ray diffraction, scanning electron microscopy (SEM), and solid-state cross-polarization magic-angle-spinning (CP/MAS) 13C-NMR spectroscopy were applied to determine changes over time in the morphology and crystallinity of lime wood (Tilia cordata Miller) generated by the soft-rot fungi. Wood samples were inoculated with Trichoderma viride Pers for various durations up to 84 days. Structural and morphological modifications were assessed by comparing the structural features of decayed lime wood samples with references. Significant morphology changes such as defibration or small cavities were clearly observed on the SEM micrographs of lime wood samples exposed to fungi. Following the deconvolution process of the diffraction patterns, the degree of crystallinity, apparent lateral crystallite size, the proportion of crystallite interior chains, and the cellulose fraction have been determined. It was found that all crystallographic data vary with the duration of exposure to fungi. The degree of crystallinity and cellulose fraction tend to decrease, whereas the apparent lateral crystallite size and the proportion of crystallite interior chains increase with prolonged biodegradation processes. The most relevant signals in CP/MAS 13C-NMR spectra were assigned according to literature data. The differences observed were discussed in terms of lignin and cellulose composition: by fixing the lignin reference signal intensity, the cellulose and hemicelluloses moieties showed a relative decrease compared to the lignin signals in decayed wood. © 2010 Society for Applied Spectroscopy. Source


Popescu C.-M.,Romanian Academy P Poni | Spiridon I.,Romanian Academy P Poni | Tibirna C.M.,Laval University | Vasile C.,Romanian Academy P Poni
Journal of Photochemistry and Photobiology A: Chemistry | Year: 2011

A series of experiments were carried out to investigate photodegradation of lime wood (Tilia cordata Mill.) during artificial UV/Vis light irradiation for 600 h. Photodegradation of the wood samples was evaluated by thermogravimetry throughout the irradiation period at an interval of 100 h. The alteration of wood was observed by means of the peak temperatures of DTG variation and by the mass losses observed during heating, evaluated on the basis of the measured thermal data. The results obtained indicate a shifting of the DTG maxima to lower temperatures which may be related to the decreasing in the stability components during photodegradation. The values of the overall activation energies corresponding of the decomposition process progressively decreases. The decreased temperatures decomposition processes, weight losses and integral area of the peaks assigned to lignin, the increased integral area of the peaks assigned to hemicelluloses could be explained by new formed structures, mainly due to formation of reactive species. © 2010 Elsevier B.V. Source


Oprea A.-M.,Romanian Academy P Poni | Profire L.,Grigore T. Popa University of Medicine and Pharmacy | Lupusoru C.E.,Grigore T. Popa University of Medicine and Pharmacy | Ghiciuc C.M.,Grigore T. Popa University of Medicine and Pharmacy | And 2 more authors.
Carbohydrate Polymers | Year: 2012

Mixed hydrogels based on natural, biodegradable and biocompatible polysaccharides, such as cellulose (C) and chondroitin sulphate (CS) in various mixing ratios were prepared by a crosslinking technique and characterized by swelling behaviour, FTIR spectroscopy, scanning electron microscopy, toxicity and biocompatibility tests. The mixed cellulose/chondroitin sulphate hydrogels have been loaded with 7-[2-nitroxiacetyl-oxy-3-(4-acetyl-amino-phenoxy)-propyl]- 8-morpholino-1,3-dimethyl-xanthine, a novel nitric oxide donor compound with a lower toxicity and a higher anti-inflammatory activity than its parent molecules, paracetamol and theophylline. Swelling and release kinetics have been also studied. It has been established that an increase of CS content in hydrogels composition leads to a higher swelling ratio for all formulations and to a decreased released amount of nitric oxide donor compound. It has been found that the swelling occurs by an anomalous swelling mechanism, while the release of nitric oxide donor compound follows a diffusion controlled mechanism. © 2011 Elsevier Ltd. All Rights Reserved. Source


Popescu C.-M.,Romanian Academy P Poni | Larsson P.T.,Innventia Ab | Vasile C.,Romanian Academy P Poni
Carbohydrate Polymers | Year: 2011

The degradation of the plant cell wall by microorganisms has been studied by X-ray diffraction, and solid state CP/MAS 13C NMR spectroscopy. Lime wood (Tilia cordata Miller) samples were inoculated with Chaetomium globosum for various durations up to 133 days. Structural modifications were assessed by comparing decayed lime wood samples with reference. These methods proved to be able to give insights into the modifications at a molecular level of the cell wall components by Ascomycetes fungi attack. Significant changes in relative crystallinity and apparent lateral crystallite size, as measured by XRD, were detectable relatively early in the decay process. The content of hemicelluloses and cellulose in the wood samples decreased after biodegradation with Chaetomium globosum. The main chemical changes in wood during decay are the loss of hemicelluloses and cellulose simultaneously with lesser changes in lignin structure, which mainly consist in partial loss of methoxyl groups and Cα-Cβ bond cleavage and loss of β-O-4 linkages. © 2010 Elsevier Ltd. All rights reserved. Source

Discover hidden collaborations