Andrea Nasswettrová

Release of Terpenes from Fir Wood during Its Long-Term Use and in Thermal Treatment

Building structures made from fir wood are often attacked by wood-destroying insects for which the terpenes it contains serve as attractants. One of the possibilities for extending the lifetime of structures is to use older wood with a lower content of terpenes and/or thermally modified wood. The study evaluated the levels of terpenes in naturally aged fir wood (108, 146, 279, 287 and 390 years) and their decrease by thermal treatment (the temperature of 60 °C and 120 °C, treatment duration of 10 h). Terpenes were extracted from wood samples by hexane and analyzed by gas-chromatography mass-spectrometry (GC-MS). The results indicate that recent fir wood contained approximately 60 times more terpenes than the oldest wood (186:3.1 mg/kg). The thermal wood treatment speeded up the release of terpenes. The temperature of 60 °C caused a loss in terpenes in the recent fir wood by 62%, the temperature of 120 °C even by >99%. After the treatment at the temperature of 60 °C the recent fir wood had approximately the same quantity of terpenes as non-thermally treated 108 year old wood, i.e., approximately 60–70 mg/kg. After the thermal treatment at the temperature of 120 °C the quantity of terpenes dropped in the recent as well as the old fir wood to minimum quantities (0.7–1.1 mg/kg). The thermal treatment can thus be used as a suitable method for the protection of fir wood from wood-destroying insects.

Chemical alterations of pine wood saccharides during heat sterilisation

Alterations in saccharides during heat sterilisation of pine wood (Pinus sylvestris L.) were investigated. The mass loss, extractives, lignin, cellulose, holocellulose and hemicelluloses were determined. Changes in saccharides were evaluated by the determination of monosaccharides in wood, size exclusion chromatography (SEC) as well as Fourier transform infrared (FTIR) spectroscopy. During heat sterilisation of pine wood the slight mass loss, an increase in extractives and a decrease in lignin and polysaccharides were observed. Hemicelluloses are degraded approximately twice as fast as cellulose. The degree of polymerisation of cellulose decreases approximately by 10% and it increases in holocellulose (by approx. 8%) as a result of a faster degradation of shorter hemicellulose chains. FTIR spectroscopy shows that sterilisation results in the deacetylation of cellulose and the formation of new carbonyl groups, an increase in the total crystallinity index (TCI) and a decrease in the lateral order index (LOI) and the hydrogen-bond intensity (HBI).

Numerical model a graphene component for the sensing of weak electromagnetic signals

The paper discusses a numerical model and provides an analysis of a graphene coaxial line suitable for sub-micron sensors of magnetic fields. In relation to the presented concept, the target areas and disciplines include biology, medicine, prosthetics, and microscopic solutions for modern actuators or SMART elements. The proposed numerical model is based on an analysis of a periodic structure with high repeatability, and it exploits a graphene polymer having a basic dimension in nanometers. The model simulates the actual random motion in the structure as the source of spurious signals and considers the pulse propagation along the structure; furthermore, the model also examines whether and how the pulse will be distorted at the beginning of the line, given the various ending versions. The results of the analysis are necessary for further use of the designed sensing devices based on graphene structures.

Noise spectroscopy of nano- and microscopic periodic material structures

The authors discuss the application of a broadband noise signal in the research of periodic structures and present the basic testing related to the described problem. Generally, noise spectroscopy tests are carried out to verify the behaviour of the response of periodic structures, and the related objective consists in recording the properties of microscopic structures in natural and artificial materials. The aim is to find a metrological method to investigate structures and materials in the frequency range between 100 MHz and 10 GHz; this paper therefore characterizes the design of a suitable measuring technique based on noise spectroscopy and introduces the first tests conducted on a periodic structure. In this context, the applied instrumentation is also shown to complement the underlying theoretical analysis.

Effect of metal ions on autofluorescence of the dry rot fungus Serpula lacrymans grown on spruce wood

This work describes autofluorescence of the mycelium of the dry rot fungus Serpula lacrymans grown on spruce wood blocks impregnated with various metals. Live mycelium, as opposed to dead mycelium, exhibited yellow autofluorescence upon blue excitation, blue fluorescence with ultraviolet (UV) excitation, orange-red and light-blue fluorescence with violet excitation, and red fluorescence with green excitation. Distinctive autofluorescence was observed in the fungal cell wall and in granula localized in the cytoplasm. In dead mycelium, the intensity of autofluorescence decreased and the signal was diffused throughout the cytoplasm. Metal treatment affected both the color and intensity of autofluorescence and also the morphology of the mycelium. The strongest yellow signal was observed with blue excitation in Cd-treated samples, in conjunction with increased branching and the formation of mycelial loops and protrusions. For the first time, we describe pink autofluorescence that was observed in Mn-, Zn-, and Cu-treated samples with UV, violet or. blue excitation. The lowest signals were obtained in Cu- and Fe-treated samples. Chitin, an important part of the fungal cell wall exhibited intensive primary fluorescence with UV, violet, blue, and green excitation.

Measurement of the microwave emitter's inhomogeneity using optical fiber DTS

Researcher’s teams were dealing with the microwave emitter’s inhomogeneity problem since the microwaves were used. One possible way, how to measure electromagnetic field is the measurement on inhomogeneous temperature distribution on the irradiated sample, which can cause problems as in other material processing, so in the undesirable change of properties and even security. Inhomogeneity of electromagnetic field is specific by creating spots with higher or lower temperature called “hot spots”. This inhomogeneity strongly affects the temperature distribution in the cross section of the material and its resultant heating. Given the impossibility of using classical electronic devices with metal temperature sensors were various indirect methods used in the past. This paper deals with experimental measurement of the microwave emitter’s inhomogeneity (2.45 GHz) using the optical fiber DTS. The greatest advantage of this sensor system is just in using of the optical fiber (electromagnetic resistance, small size, safety using in inflammable and explosive area, easy installation). Due to these properties of the optical fiber sensor it’s possible to measure the temperature of the sample in real time. These sensor are able to measure the temperature along the fiber, in some cases they use nonlinear effect in optical fiber (Raman nonlinear effect). The verification of non-homogeneity consists in experimental measuring of the temperature distribution within the wooden sample. The method is based on heat exchange in an isolated system where wooden sample serves as an absorber of the irradiated energy. To identify locations with different power density was used DTS system, based on nonlinear phenomena in optical fibers.

Usage of Distributed Fiber Optical Temperature Sensors during Building Redevelopment

This contribution describes the novel unique technology with the usage of fiber optical sensors with temperature resolution up to 0.01°C and spatial resolution 1m. This technology is supplemented with fiber optical strain sensor with pressure resolution 1Pa. Fiber optical sensors are based on nonlinear effects within the optical fibers, they behave as distributed sensors making possible to measure temperature and strain with one fiber in many points contemporarily during building redevelopments. For temperature measurements Raman scattering within multimode optical fiber is used. Results from real redevelopments are presented.

Non-Destructive Methods for the Localization of Woodworms via Acoustic Analysis

The problem of finding a suitable diagnostic procedure for the examination of structural elements has been closely analyzed in recent years. In this connection, the main material of interest is wood as a type of heterogeneous matter, and the diagnostic procedure is directed towards enabling prospective industrial application. A new diagnostic method based on X-ray imaging and acoustic electromagnetic waves has been proposed and tested. The X-ray technique utilizes the reduction of the imaging information into 2D planar projection; it allows us to represent clearly the rate of material damage through displaying the weighted damage rate.