Hopp til hovedinnholdet

Publications

NIBIOs employees contribute to several hundred scientific articles and research reports every year. You can browse or search in our collection which contains references and links to these publications as well as other research and dissemination activities. The collection is continously updated with new and historical material.

2016

Abstract

In order to determine the relation between the structural properties and fungistatic activity of quinolizidine and bisquinolizidine alkaloids, the bioactive derivatives of cytisine, sparteine and lupanine were tested for the inhibitory activity against the microfungus causing mould growth phenomenon (Aspergillus niger van Tieghem ATCC 6275). The compounds tested were screened for antifungal properties using the bioautography-TLC. According to the results, the following cytisines showed an inhibiting effect on mould; spirocytisine, 3,5-dibromocytisine, bromo-N-boccytisine, N-Boccytisine, 3-bromobenzylocytisine, 4-bromo-benzylcytisine, 3-iodobenzylcytisine, 4-iodobenzylcytisine.

To document

Abstract

Untreated wooden surfaces degrade when exposed to natural weathering. In this study thin wood samples were studied for weather degradation effects utilising a hyperspectral camera in the near infrared wavelength range in transmission mode. Several sets of samples were exposed outdoors for time intervals from 0 days to 21 days, and one set of samples was exposed to ultraviolet (UV) radiation in a laboratory chamber. Spectra of earlywood and latewood were extracted from the hyperspectral image cubes using a principal component analysis-based masking algorithm. The degradation was modelled as a function of UV solar radiation with four regression techniques, partial least squares, principal component regression, Ridge regression and Tikhonov regression. It was found that all the techniques yielded robust prediction models on this dataset. The result from the study is a first step towards a weather dose model determined by temperature and moisture content on the wooden surface in addition to the solar radiation.

To document

Abstract

Use of uncoated wood in building façades has increased the last years, and therefore it is important to understand and control the aesthetical character and appearance of wood materials used outdoors. By predicting the aesthetical service life and the visual appearance of a wooden façade over time, we can accommodate some of the end-user expectations, perception, values and aesthetical preferences. The spatial variation of climate on a façade is large, and estimation of the weathering process and mould growth on outdoor exposed wood should be based on the actual surface climate rather than data from meteorological stations. A first version of a simulation model that aims to predict and visualize future aesthetical appearance of wooden façades has been developed. The model is based on existing mould growth models and on a new model for surface meteorological conditions that account for RH, temperature and UV. The on-set of mould growth on selected wood materials (pine, spruce, larch, oak, aspen, thermally treated pine) have been studied in 8 different controlled climate conditions, where two levels of surface condensation regimes have been mimicked to capture time-of-wetness. Wood samples in conditions with high RH (85%) and longest time-of-wetness had the earliest on-set of mould growth, and under these conditions temperature (25°C/10°C) had no significant impact. Generally aspen had the earliest on-set of mould growth and thermally treated pine the latest. Data on on-set of mould growth will be incorporated in the simulation model to enable a knowledge-based decision tool regarding design and material selection.

Abstract

Uncoated wood is increasingly used in building façades in Northern Europe. The benefits can be both low maintenance and low environmental impact. An even, grey color of the façade is often the intention, but in several cases, an uneven pattern of light, grey and dark/black areas is the result. The effect of weathering and the influencing factors have to be considered when designing and building uncoated and coated wooden façade to avoid unwanted weathering effects. Wood weathering is commonly described to be caused by: accumulation of extractives on the surface, photo-degradation of lignin, staining by dark colored mould fungi, checking, cracking and splitting due to moisture fluctuation and erosion. This paper reviews, analyzes and exemplifies weathering as a finishing system and design option for uncoated wood. Furthermore, it also discusses and exemplifies the main influencing factors and weathering effects on coated wood in facades.

To document

Abstract

Wooden elements may be subjected to mechanical, environmental or biological alterations during their service life. The most susceptible parts of wood structural members are the exposed surfaces since they are subjected to ageing, weathering and/or decay. Knowledge of the influence of weathering factors and polymer degradation mechanisms is essential for understanding the weathering process of wood. The goal of this study was to investigate the degradation of thin wooden samples exposed to short-term weathering. Tests were performed through the European summer (July), which according to previous research is considered as the most severe period for weathering of wood micro-sections. Fourier transform near infrared spectroscopy was used for evaluation of chemical changes of wood samples. Three approaches for data evaluation are presented in this paper: (1) direct spectral interpretation, (2) a concept for calculation of a weathering index Wind and (3) kinetics of lignin changes in relation to the exposure direction for selected wavelengths. Observation of the effects of weathering will allow better understanding of the degradation process. The southern exposure site was slightly more affected by weathering than other sites. Results of this research will be used for future determination of the weather-dose response model and could be essential for predicting the future performance of timber facade elements.

To document

Abstract

Two new species of Schistidium are described from Asian Russia. Their distinctness is supported by nrDNA ITS1-2 sequence data. S. austrosibiricum was not previously differentiated from S. sinensi- apocarpum, mainly due to their similarly long and sharply serrate hair-points in stem and perichaetial leaves and papillose dorsal side of costa. However, they differ in leaf size and shape, hair-points flatness and leaf lamina areolation. S. austrosibiricum is known from southernmost mountain areas of Asian Russia, while S. sinensiapocarpum is a widespread circumholarctic montane species. The sec- ond species, S. scabripilum is morphologically similar to S. echinatum, and some specimens were previously referred to it. The main differences between them concern hair-point length and structure, including length of protruding spinulae and their angle with the hair-point axis. However, they belong to different clades in the molecular phylogenetic tree and possess different distribution patterns. S. scabripilum is a northern Asian species, found in the Putorana Plateau, southern Taimyr, Yakutia and Chukotka, while S. echinatum is known from the Alps, Caucasus and Ural mountains, and in western North America. Description, illustrations, distribution and ecological data are provided for the new species, and comparison with similar species is given.