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Carmen-mihaela Popescu - One of the best experts on this subject based on the ideXlab platform.
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Evaluation of the thermal stability and set recovery of thermo-hydro-mechanically treated lime (Tilia cordata) wood
Wood Science and Technology, 2014Co-Authors: Maria-cristina Popescu, Julien Froidevaux, Parviz Navi, Gabriela Lisa, Carmen-mihaela PopescuAbstract:The effect of the thermo-hydro-mechanical (THM) densification in a closed system on the set recovery and thermal stability of lime ( Tilia cordata ) wood was evaluated. The THM densification process consists of four steps: plastification, densification, post-treatment and cooling. The THM-densified wood samples were subjected to three different post-treatment temperatures, and for each one, three different periods were used. Comparison between THM-densified wood sample without and with post-treatment at different temperatures and times was made. The set recovery tests showed that the post-treatment at higher temperatures and times improves the dimensional stability of the samples suggesting a permanent fixation of the transversal compression, but also reduces their thermal stability, by having lower temperatures corresponding to the maximum decomposition rate, lower values for the mass loss at the end of decomposition stage and lower values for the kinetic parameters. The samples with post-treatments at lower temperatures showed high set recovery values and exhibited higher values for the temperatures corresponding to the maximum decomposition rate, lower values for the mass loss at the end of the stage and higher activation energies and reaction orders.
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the water vapour adsorption desorption behaviour of naturally aged Tilia cordata mill wood
Polymer Degradation and Stability, 2013Co-Authors: Carmen-mihaela Popescu, Callum A. S. HillAbstract:Abstract The effect caused by the natural ageing of wood on the sorption properties during two consecutive sorption cycles of historical Tilia cordata Mill. wood has been investigated and compared with a reference sample. Differences were found in the sorption isotherm between the first and second sorption cycles for most of the samples and also between the reference and historical wood. All samples exhibited sorption hysteresis, but with important differences in behaviour observed with the historic wood samples. It was interesting to note that the oldest historic wood sample did not display any discernible difference between the first and second sorption cycle throughout much of the hygroscopic range and also exhibited absolute hysteresis values essentially identical with the reference sample. These results indicate that the sorption behaviour of wood is dependent upon the previous exposure of the wood to atmospheric relative humidity. The sorption kinetics was also analysed in terms of the parallel exponential kinetics (PEK) model, and excellent fits to the data were obtained. The PEK model describes the dynamic sorption behaviour in terms of a fast and slow kinetic process and important differences in behaviour for these two processes were found. It is thought that the fast process is associated with a physical diffusion phenomenon, while the slow kinetics process is considered to be associated with cell wall matrix polymer relaxation processes.
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The water vapour adsorption–desorption behaviour of naturally aged Tilia cordata Mill. wood
Polymer Degradation and Stability, 2013Co-Authors: Carmen-mihaela Popescu, Callum A. S. HillAbstract:Abstract The effect caused by the natural ageing of wood on the sorption properties during two consecutive sorption cycles of historical Tilia cordata Mill. wood has been investigated and compared with a reference sample. Differences were found in the sorption isotherm between the first and second sorption cycles for most of the samples and also between the reference and historical wood. All samples exhibited sorption hysteresis, but with important differences in behaviour observed with the historic wood samples. It was interesting to note that the oldest historic wood sample did not display any discernible difference between the first and second sorption cycle throughout much of the hygroscopic range and also exhibited absolute hysteresis values essentially identical with the reference sample. These results indicate that the sorption behaviour of wood is dependent upon the previous exposure of the wood to atmospheric relative humidity. The sorption kinetics was also analysed in terms of the parallel exponential kinetics (PEK) model, and excellent fits to the data were obtained. The PEK model describes the dynamic sorption behaviour in terms of a fast and slow kinetic process and important differences in behaviour for these two processes were found. It is thought that the fast process is associated with a physical diffusion phenomenon, while the slow kinetics process is considered to be associated with cell wall matrix polymer relaxation processes.
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Structural modifications of Tilia cordata wood during heat treatment investigated by FT-IR and 2D IR correlation spectroscopy
Journal of Molecular Structure, 2013Co-Authors: Maria-cristina Popescu, Julien Froidevaux, Parviz Navi, Carmen-mihaela PopescuAbstract:Abstract It is known that heat treatment of wood combined with a low percent of relative humidity causes transformations in the chemical composition of it. The modifications and/or degradation of wood components occur by hydrolysis, oxidation, and decarboxylation reactions. The aim of this study was to give better insights on wood chemical modifications during wood heat treatment under low temperature at about 140 °C and 10% percentage of relative humidity, by infrared, principal component analysis and two dimensional infrared correlation spectroscopy. For this purpose, hardwood samples of lime ( Tilia cordata ) were investigated and analysed. The infrared spectra of treated samples were compared with the reference ones, the most important differences being observed in the “fingerprint” region. Due to the complexity of this region, which have contributions from all the wood constituents the chemical changes during hydro-thermal treatment were examined in detail using principal component analysis and 2D IR correlation spectroscopy. By hydro-thermal treatment of wood results the formation of acetic acid, which catalyse the hydrolysis reactions of hemicelluloses and amorphous cellulose. The cleavage of the β-O-4 linkages and splitting of the aliphatic methoxyl chains from the aromatic lignin ring was also observed. For the first treatment interval, a higher extent of carbohydrates degradation was observed, then an increase of the extent of the lignin degradation also took place.
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A thermogravimetric study of structural changes of lime wood (Tilia cordata Mill.) induced by exposure to simulated accelerated UV/Vis-light
Journal of Photochemistry and Photobiology A: Chemistry, 2011Co-Authors: Carmen-mihaela Popescu, Iuliana Spiridon, Carmen Mihaela Tibirna, Cornelia VasileAbstract:Abstract 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.
Callum A. S. Hill - One of the best experts on this subject based on the ideXlab platform.
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the water vapour adsorption desorption behaviour of naturally aged Tilia cordata mill wood
Polymer Degradation and Stability, 2013Co-Authors: Carmen-mihaela Popescu, Callum A. S. HillAbstract:Abstract The effect caused by the natural ageing of wood on the sorption properties during two consecutive sorption cycles of historical Tilia cordata Mill. wood has been investigated and compared with a reference sample. Differences were found in the sorption isotherm between the first and second sorption cycles for most of the samples and also between the reference and historical wood. All samples exhibited sorption hysteresis, but with important differences in behaviour observed with the historic wood samples. It was interesting to note that the oldest historic wood sample did not display any discernible difference between the first and second sorption cycle throughout much of the hygroscopic range and also exhibited absolute hysteresis values essentially identical with the reference sample. These results indicate that the sorption behaviour of wood is dependent upon the previous exposure of the wood to atmospheric relative humidity. The sorption kinetics was also analysed in terms of the parallel exponential kinetics (PEK) model, and excellent fits to the data were obtained. The PEK model describes the dynamic sorption behaviour in terms of a fast and slow kinetic process and important differences in behaviour for these two processes were found. It is thought that the fast process is associated with a physical diffusion phenomenon, while the slow kinetics process is considered to be associated with cell wall matrix polymer relaxation processes.
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The water vapour adsorption–desorption behaviour of naturally aged Tilia cordata Mill. wood
Polymer Degradation and Stability, 2013Co-Authors: Carmen-mihaela Popescu, Callum A. S. HillAbstract:Abstract The effect caused by the natural ageing of wood on the sorption properties during two consecutive sorption cycles of historical Tilia cordata Mill. wood has been investigated and compared with a reference sample. Differences were found in the sorption isotherm between the first and second sorption cycles for most of the samples and also between the reference and historical wood. All samples exhibited sorption hysteresis, but with important differences in behaviour observed with the historic wood samples. It was interesting to note that the oldest historic wood sample did not display any discernible difference between the first and second sorption cycle throughout much of the hygroscopic range and also exhibited absolute hysteresis values essentially identical with the reference sample. These results indicate that the sorption behaviour of wood is dependent upon the previous exposure of the wood to atmospheric relative humidity. The sorption kinetics was also analysed in terms of the parallel exponential kinetics (PEK) model, and excellent fits to the data were obtained. The PEK model describes the dynamic sorption behaviour in terms of a fast and slow kinetic process and important differences in behaviour for these two processes were found. It is thought that the fast process is associated with a physical diffusion phenomenon, while the slow kinetics process is considered to be associated with cell wall matrix polymer relaxation processes.
Claudia Anesini - One of the best experts on this subject based on the ideXlab platform.
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Tilia cordata mill extracts and scopoletin isolated compound differential cell growth effects on lymphocytes
Phytotherapy Research, 2006Co-Authors: Maria Laura Barreiro Arcos, Graciela Cremaschi, Silvia Werner, J.d. Coussio, Graciela Ferraro, Claudia AnesiniAbstract:Aqueous extracts or infusions obtained from the flowers of Tilia species are widely used for the treatment of anxiety in folk medicine. In this work, the antiproliferative action of aqueous, dichloromethane and ethanol extracts obtained from Tilia cordata Mill. flowers on tumoral (BW 5147 lymphoma) and normal lymphocytes is described. Both extracts showed a selective action on tumoral cells, inducing apoptosis. In the case of normal T cells these extracts suppressed mitogen-induced proliferation without affecting viability, suggesting a suppressive but not cytotoxic effect. These effects were clearly concentration dependent. A coumarin (scopoletin), the main component in the dichloromethane extract presented antiproliferative action on BW 5147 cells, suggesting that it may be at least partly responsible for the activity displayed by this extract. Copyright © 2006 John Wiley & Sons, Ltd.
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Tilia cordata Mill. Extracts and scopoletin (isolated compound): differential cell growth effects on lymphocytes.
Phytotherapy research : PTR, 2006Co-Authors: Maria Laura Barreiro Arcos, Graciela Cremaschi, Silvia Werner, J.d. Coussio, Graciela Ferraro, Claudia AnesiniAbstract:Aqueous extracts or infusions obtained from the flowers of Tilia species are widely used for the treatment of anxiety in folk medicine. In this work, the antiproliferative action of aqueous, dichloromethane and ethanol extracts obtained from Tilia cordata Mill. flowers on tumoral (BW 5147 lymphoma) and normal lymphocytes is described. Both extracts showed a selective action on tumoral cells, inducing apoptosis. In the case of normal T cells these extracts suppressed mitogen-induced proliferation without affecting viability, suggesting a suppressive but not cytotoxic effect. These effects were clearly concentration dependent. A coumarin (scopoletin), the main component in the dichloromethane extract presented antiproliferative action on BW 5147 cells, suggesting that it may be at least partly responsible for the activity displayed by this extract.
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Effect of Tilia cordata flower on lymphocyte proliferation: participation of peripheral type benzodiazepine binding sites
Fitoterapia, 1999Co-Authors: Claudia Anesini, Silivia Werner, Enri BordaAbstract:The aqueous extract of Tilia cordata flowers showed in vitro stimulatory effects on lymphocyte proliferation (maximum stimulatory concentration: 20 μg/ml). This effect was mimicked by Ro 5-4864, an agonist of the peripheral benzodiazepine receptor, and by Pk 11195, an agonist/antagonist of the same receptor. These results suggest that Tilia extract could exert its stimulatory effect acting as an agonist of the peripheral benzodiazepine receptor.
Cornelia Vasile - One of the best experts on this subject based on the ideXlab platform.
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A thermogravimetric study of structural changes of lime wood (Tilia cordata Mill.) induced by exposure to simulated accelerated UV/Vis-light
Journal of Photochemistry and Photobiology A: Chemistry, 2011Co-Authors: Carmen-mihaela Popescu, Iuliana Spiridon, Carmen Mihaela Tibirna, Cornelia VasileAbstract:Abstract 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.
Thomas Rötzer - One of the best experts on this subject based on the ideXlab platform.
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How Do Tilia cordata Greenspire Trees Cope with Drought Stress Regarding Their Biomass Allocation and Ecosystem Services
Forests, 2019Co-Authors: Chi Zhang, Hans Pretzsch, Laura Myrtiá Faní Stratópoulos, Thomas RötzerAbstract:In the context of climate change, drought is likely to become more frequent and more severe in urban areas. Urban trees are considered to play an important role in fixing carbon, improving air quality, reducing noise and providing other ecosystem services. However, data on the response of urban trees to climate change, particularly to drought, as well as the relationship between their below- and above-ground processes in this context, are still limited, which prevents a comprehensive understanding of the role of urban trees in ameliorating some of the adverse effects of climate change and their ability to cope with it. To investigate whole-plant responses to water shortages, we studied the growth of Tilia cordata Greenspire, a commonly planted urban tree, including development of its roots and stem diameter, leaf parameters and the harvested biomass. Our results showed that this cultivar was susceptible to drought and had reduced biomass in all three compartments: branch (30.7%), stem (16.7%) and coarse roots (45.2%). The decrease in the root:shoot ratio under drought suggested that more carbon was invested in the above-ground biomass. The development of fine roots and the loss of coarse root biomass showed that T. cordata Greenspire prioritised the growth of fine roots within the root system. The CityTree model’s simulation showed that the ability of this cultivar to provide ecosystem services, including cooling and CO2 fixation, was severely reduced. For use in harsh and dry urban environments, we recommend that urban managers take into account the capacity of trees to adapt to drought stress and provide sufficient rooting space, especially vertically, to help trees cope with drought.
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Within canopy temperature differences and cooling ability of Tilia cordata trees grown in urban conditions
Building and Environment, 2017Co-Authors: Mohammad A. Rahman, Astrid Moser, Thomas Rötzer, Stephan PauleitAbstract:Abstract Urban trees regulate their thermal environment mostly through the canopies. With multilayered complex canopies trees prevent solar radiation (reaching the ground) thus reduce the heat storage underneath. More importantly the intercepted energy rather increases the latent heat flux, hence reduces the air temperature during the daytime. However, there is little information on within canopy temperature of urban trees and inter-relationships between latent heat flux exchanges to identify thermal impact of vegetation. The present study continuously measured sapflow and within the canopy air temperature of Tilia cordata trees along with meteorological variables at two different street canyons in Munich, Germany over the summer, 2015. Within the canopy radius of 4.5 m, daytime temperature reduced up to 3.5 °C with energy loss of 75 W m−2 during warm and dry August when the soil moisture potential was below 1.5 MPa and vapour pressure deficit was 4 kPa, but the nighttime temperature went up to 0.5 °C. Deeper underneath the tree canopy, 1.5 m above the ground the average temperature fell by up to 0.85 °C on hot sunny days. The regression equation showed better agreement of this air temperature reduction with the sap flow of trees (R2 = 0.61) rather than the differences between shaded and unshaded, paved and grass surface temperatures. Although the research is at an early stage, the results showed the potential of using canopy air temperature differences as a tool to better understand the transpiration response to within and below canopy temperature and also to be used in climate models.
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The Urban Environment Can Modify Drought Stress of Small-Leaved Lime (Tilia cordata Mill.) and Black Locust (Robinia pseudoacacia L.)
Forests, 2016Co-Authors: Astrid Moser, Thomas Rötzer, Stephan Pauleit, Hans PretzschAbstract:The urban environment characterized by various stresses poses challenges to trees. In particular, water deficits and high temperatures can cause immense drought stress to urban trees, resulting in reduced growth and die-off. Drought-tolerant species are expected to be resilient to these conditions and are therefore advantageous over other, more susceptible species. However, the drought tolerance of urban trees in relation to the specific growth conditions in urban areas remains poorly researched. This study aimed to analyze the annual growth and drought tolerance of two common urban tree species, namely small-leaved lime (Tilia cordata Mill. (T. cordata)) and black locust (Robinia pseudoacacia L. (R. pseudoacacia)), in two cities in southern Germany in relation to their urban growing conditions. Marked growth reductions during drought periods and subsequent fast recovery were found for R. pseudoacacia, whereas T. cordata exhibited continued reduced growth after a drought event, although these results were highly specific to the analyzed city. We further show that individual tree characteristics and environmental conditions significantly influence the growth of urban trees. Canopy openness and other aspects of the surrounding environment (water supply and open surface area of the tree pit), tree size, and tree species significantly affect urban tree growth and can modify the ability of trees to tolerate the drought stress in urban areas. Sustainable tree planting of well adapted tree species to their urban environment ensures healthy trees providing ecosystem services for a high quality of life in cities.
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Structure and ecosystem services of small-leaved lime (Tilia cordata Mill.) and black locust (Robinia pseudoacacia L.) in urban environments
Urban Forestry & Urban Greening, 2015Co-Authors: Astrid Moser, Thomas Rötzer, Stephan Pauleit, Hans PretzschAbstract:Abstract Knowledge of the structure and morphology of common urban trees is scarce, particularly of the full life cycle of a tree. The present and future structural dimensions of urban tree species are of an increasing interest because tree growth is associated with its ecosystem services. The purpose of this study was to characterize the dimensions of two urban tree species (small-leaved lime, Tilia cordata Mill. and black locust, Robinia pseudoacacia L.) and to predict future structural dimensions based on the diameter at breast height and tree age. Regression equations were developed for tree height, crown diameter, crown height, crown volume, crown projection area, and open surface area of the tree pit. The data revealed strong relationships ( r 2 > 0.7) between crown diameter, crown volume, crown projection area, crown height, tree pit for both species, and tree height of T. cordata . Based on tree dimensions and the leaf area index (LAI), three ecosystem services (carbon storage, shading, and cooling effects) were estimated for the analyzed trees. The results indicated that urban trees considerably improved the climate in cities, with carbon storage, shading, and cooling of single trees showing a direct relationship with LAI and age. The associations of tree growth patterns identified in this study can be used as guidelines for tree planting in cities and their ecosystem services; they may improve the management and planning of urban green areas.