Liquid Chromatographic/Mass Spectrometric Study on the Role of Beech (Fagus sylvatica L.) Wood Polyphenols in Red Heartwood Formation

The present research focused on the analysis of European beech (Fagus sylvatica L.) wood polyphenols in respect to red heartwood formation, which is a significant color and technological defect of the species. For the first time, high-performance liquid chromatography/tandem mass spectrometry and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF) were applied for the investigation of the structure and the radial distribution of polyphenols. Altogether 125 compounds were characterized by their MSn spectra, of which 71 were tentatively identified, including procyanidins (dimers to pentamers), flavonoids (taxifolin, naringenin, isorhamnetin, (epi)afzelechin), (+)-catechin, (–)-epicatechin) and their glycoside conjugates, phenolic acids (gallic acid, vanillic acid, syringic acid) and their glycosides as well as gallic acid derivatives, many of which were identified for the first time in beech wood. It was found that the concentration of many compounds increased at the color boundary. In situ polyphenol synthesis and metabolism were clearly evidenced at the color boundary. Red heartwood contained only free aglycones (syringic acid, taxifolin, naringenin, isorhamnetin, naringenin, syringic acid). Contrary to earlier assumptions, the MALDI-TOF analysis did not indicate the presence of oxidized high-molecular-weight polymeric polyphenols in the red heartwood tissues. The role of individual compounds in the formation of the red heartwood chromophores are discussed.

ANALYSIS OF THE BMA K2400 VERTICAL CENTRIFUGE TURBINE IN TERMS OF BALANCING AND VIBRATION DIAGNOSTICS

Physical damage to a material is a diffuse defect in the form of vacancies, microcracks, micro-voids or damaged micro-volumes, which reduce the effective or load-bearing part of the material. Surface fatigue defects, such as deformation and cracks, occur in the bearing during the load transfer. Imbalance is a practical problem in the operation of many rotating machines, causing not only increased vibration of the machine, but also leading to accelerated wear of the rotor bearings. The subject of this work is the analysis of the dynamics of the BMA K2400 centrifuge in terms of the possibility of correcting the balance in the given dynamic state. The paper describes the individual stages of solving the problem of excessive machine vibrations, assuming that its bearings were replaced before the diagnostic test. As a result of the lack of effects after replacing the motor bearings and after analyzing the vibration measurement results presented in article, a decision was made to inspect the centrifuge bearings. The diagnostics was performed again, but it concerned only the bearing node No. 1 with the disassembled basket. The measurements were performed using the DIAMOND 401 AX device, equipped with Wilcoxon 780B acceleration sensors with a sensitivity of 100mV/g. The appearance of a technological defect on the outer ring of the bearing, which is a friction pair with a housing, is not a typical damage for this type of machines and was an interesting problem. The consequence of the occurrence of bearing defects may be an increase in statistical values of the vibration signal and the appearance of new amplitudes in the FFT spectra. A vicious circle is created here, where bearings in poor dynamic condition increase the transmission of vibrations through the machine, and high vibrations accelerate the degradation of the bearings. The poor condition of rolling bearings may also prevent dynamic balancing of the rotor, and thus – lead to further propagation of bearing damage caused by an increased level of the machine’s own vibrations.