Study aim: to compare the physical fitness of bus drivers and fare collectors (working hours per day in sitting position = 7h) with and without low back pain. The subjects consisted of sixty-six bus drivers and fare collectors working in a public transport company.
Material and methods: the prevalence of low back pain, age and working time was determined for bus drivers and fare collectors using a questionnaire. All subjects underwent anthropometric assessment (weight, height and waist circumference), an abdominal endurance test and a hip flexibility test.
Results: there was a significant difference between the low back pain group (n = 27) and the group without pain (n = 39) in body mass index (27.5 ± 3.9 kg · m–2 vs. 25.6 ± 4.0 kg · m–2), waist circumference (92.5 ± 10 cm vs. 85.9 ± 9 cm), the abdominal endurance test (28.9 ± 17.5 repetitions vs. 38.4 ± 19.2 repetitions) and the hip flexibility test (69.1 ± 14.4 degrees vs. 78.3 ± 16.9 degrees). There was no significant difference in age and working time.
Conclusion: anthropometric measures, abdominal endurance and hip flexibility are deficient in bus drivers and fare collectors with low back pain. We suggest that workers with prevalent low back pain increase their physical fitness.
Hot water extraction of pine wood was carried out after 10 days of exposure to brown-rot fungi (Gloeophyllum trabeum, Coniophora puteana and Poria placenta) and a white-rot fungus (Coriolus versicolor). The microstructure of the wood cell wall was analysed by the water vapour sorption method. The content and composition of monosaccharides in the extracts were determined by high performance liquid chromatography. Despite the absence of essential mass losses at the initial stage of the contact with the fungi, slight changes in the cell wall microstructure can be observed, namely, the hydrophobisation and the change in the character of porosity in the region of 1–10 nm pore sizes. After hot water treatment, the mass decreases considerably, i.e., to 25% for the control and brown-rot treated samples and more than 30% for the white-rot treated sample. The sorption-desorption isotherms for the washed control sample and brown-rot samples were not changed practically, but the isotherm was changed clearly in the case of the white-rot treated sample. The microstructure of the white-rot sample changed after hot water washing radically and was accompanied with the formation of wide mesopores in the range of 5–9 nm width.
Brown rotted Scots pine (Pinus sylvestris) sapwood was studied using scanning UV microspectrophotometry. Wood blocks were exposed to the fungus Coniophora puteana (Schum.: Fr.) Karst. (BAM Ebw.15) for 6, 8, 10, 30, and 50 days. No wood weight loss was detected in the initial decay periods. On the other hand, point analyses of lignin distribution in wood cells revealed higher absorbance after 6–10 days of decay, which we interpret as an increase in the absorption coefficient of lignin due to its oxidative modification by the fungus. Uneven wood degradation occurred in the later periods (30 and 50 days), with both significantly decayed and visually sound cells observed. The decayed cells showed a higher absorbance at 280 nm, although the apparently sound cells were also degraded to a lower extent. Degradation of lignin-rich compounds in middle lamellae and cell corners was not observed during fungal attack.
The chemical changes in birch wood occurring at thermo-hydro treatment (THT) was studied at temperatures (T) of 150, 160 and 170°C by analytical pyrolysis [Py-gas chromatography/mass spectrometry/flame ionisation detector (GC/MS/FID)], elemental analysis and traditional wet-chemical analysis. THT wood (THTW) was also extracted with acetone. Mass losses (ML) due to THT and acetone extraction of THTW were considered for material balance calculations. The holocellulose and hemicellulose (HC) contents decrease with increasing THT temperature (THTT), thus the apparent lignin content is elevated by ca. 20%. The HC degradation begins at 150°C, while that of α-cellulose modification at 170°C. Compared to unmodified birch, the THT170°C material contains ca. 10% less α-cellulose and up to 40% less HC. The Py-GC/MS also indicates decreasing amounts of volatile products from polymeric carbohydrates (CHs) and lignin origin as a function of increasing THTT. The identified CH-based Py products of THT170°C of non-extracted (ne) and extracted (e) materials resulted in 13 and 22% weight decrements, respectively, while the lignin-type Py products were reduced by 13 and 49%, respectively. With increasing THTT, the total content of CO2, water and methanol decreases, and the amount of unidentified compounds increases by 30%.
Thermal modification (TM) of wood has occupied a relatively narrow but stable niche as an alternative for chemical wood protection. There are different technological solutions for TM and not all details of their effects on wood tissue have been understood. The one-stage hydrothermal modification (HTM) at elevated vapour pressure essentially changes the wood’s composition and structure. In the present paper, the changes in three hardwood lignins (alder, aspen, and birch) were observed within the cell wall by means of cellular UV microspectrophotometry. The lignin absorbances in the compound middle lamella (CML) of unmodified wood are 1.7- to 2.0-fold higher than those in the fibre S2 layer. The woods were modified in the temperature range from 140 to 180°C, while in the lower temperature range (140°C/1 h), the UV absorbances are little affected. Essential changes occur in the range of 160–180°C and the UV data reflect these by absorbtion changes, while the absorbances at 278 nm rise with factors around 2 more in the S2 layer than in the CML. The absorbance increments are interpreted as polycondensation reactions with furfural and other degradation products of hemicelluloses with the lignin moiety of the cell wall.
The effect of the hydrothermal modification (HTM) of the deciduous woods birch and aspen on their sorption behavior has been investigated by the vapor sorption method. An analysis of the experimental results was carried out based on the concept of Hansen solubility parameters (HSP), which takes into account the contribution of different forces – dispersion forces, dipole action, and hydrogen bonding – to the total cohesion energy. Sorption isotherms were measured concerning the vapors of water, methanol, and ethanol with unmodified and HTM woods at 160°C and 170°C during 3 and 1 h, respectively. The choice of sorbates was based on the parts of the hydrogen bonding and dispersion force to cohesion energy, in decreasing order of the former and increasing order of the latter. As a criterion of sorption, the value of the monolayer capacity was used, which was derived from the Brunauer-Emmett-Teller equation. Vapor sorption with unmodified and modified wood increased with increasing dispersion force component of the HSP of the sorbate. However, more substantial increase occurred for HTM wood, that is, wood surface became more hydrophobic. The reason for this observation is the change in the decreasing ratio holocellulose/lignin upon HTM. However, the chemical structure of lignin is also changed by HTM.
Pinewood was modified by vacuum impregnation with various aqueous lignin solutions of low concentration (0.5– 1.0%) and its decay resistance was tested by the standard procedure EN 113. Five lignin types were tested against three brown rot and one white rot fungi. The bio-durability of wood was considerably increased by the treatment. The highest effect of modification was for alkali, kraft, hydrolysis lignins and industrial lignosulfonate, when mass losses of wood for brown-rot fungi were negligible. The effect of the modification with certified lignosulfonates was insignificant. Chemical analysis revealed that phenols, which are leached from lignin and are adsorbed by wood in the impregnation process, could act as a biocide. The hydrophilic properties of wood either did not change (certified lignins) or were enhanced because of some change in the pore structure (industrial lignins). Further tests are needed to verify the positive effects of this technologically simple and environmentally friendly treatment.
A newly developed thermo-hydro treatment (THT) for use in a one-stage heat treatment process was examined by focusing on the form stability-related properties of European aspen (Populus tremula), birch silver (Betula pendula), and gray alder (Alnus incana). In particular, wood specimens were subjected to THT in a saturated steam atmosphere in a pilot-scale autoclave heated between 140 and 180°C for 1–3 h. Several parameters of untreated and treated samples after several soaking and drying cycles were compared, namely, the changes in the volumetric swelling, swelling in the radial and tangential directions, cell wall total water capacity, and anti-swelling efficiency (ASE). Due to repeated wetting in the cyclic water submersion-drying test, the original ASE of 73% decreased to 65% (180°C for 1 h), and the original ASE of 33% decreased to 5% (140°C for 1 h). Wood modified at 170°C presented good results that were not significantly lower than wood treated at higher temperatures while consuming less energy to deliver ASE improvement and was selected as optimum. To increase the ASE by 1%, the amount of energy consumed was decreased by 41%, 39%, and 17% compared with the treatment regimes of 160°C for 1 h, 160°C for 3 h, and 180°C for 1 h, respectively. The new THT regime led to improved long-term dimensional stability due to the cross-linking of cell wall polymers, which resulted in increased cell wall rigidity.