Research Articles

Modes of antibacterial action of the extract from edible brown algae Ascophyllum nodosum against food spoilage bacteria Pseudomonas fluorescens and Shewanella putrefaciens were investigated. The colony forming units in P. fluorescens and S. putrefaciens were 0.70 and 1.03 log cfu/mL less than the negative control in the time-kill assay, indicating the inhibitory effect of the extract on the two bacteria at high cell density. The extract also inhibited the extracellular protease activity of the two bacteria, where the exopolysaccharide (EPS) content was reduced by 44.8% in P. fluorescens and 64.7% in S. putrefaciens after treating them with the extract of the minimum inhibition concentration (MIC). Reduction in live bacteria cells in the biofilm formed by the two bacteria strains exposed to 1×MIC and 2×MIC levels was also observed. Significant increase in 260-nm absorbing material, protein content, and electrical conductivity of the culture media was observed after 6-h incubation with the extract in both bacteria strains, suggesting a leakage of nucleic material, protein, and other intracellular constitutes. It was concluded that the extract of A. nodosum could exert antibacterial activity against P. fluorescens and S. putrefaciens by reducing their extracellular enzymatic activity, inhibiting EPS production and biofilm formation, and increasing cell permeability.

The objective of this study was to shorten the drying time of wood material using microwave and infrared + microwave drying methods, compare the energy assumption, analyze their improvement in water absorption, and compare the compression strength perpendicular and parallel to fibers. Red pine (Pinus brutia) and Eastern spruce (Picea orientalis) woods were prepared in three groups. The first group was oven dried, the second group was dried by microwave, and the third group was dried by infrared + microwave methods. The analysis results for energy consumption, moisture content, and compression strength perpendicular and parallel to the fibers were performed. Compression strengths were determined with a universal testing device. According to the results obtained, with 15 min microwave drying, 4% moisture content was reached in the wood samples and both time and energy were saved. It was observed that oven drying consumed 93% more energy than 15 min microwave drying. Samples dried with infrared 30 s + microwave 5 min had higher compression strength in the direction perpendicular to the fibers and samples dried with microwave for 5 min had higher compression strength in the direction parallel to the fibers.

The thermal conductivity was measured for Al₂O₃ nanofluid using a newly developed polymeric base fluid. The novel base fluid of cross-linked polyacrylic acid (PAA) solutions was synthesized via radical polymerization using a distinct deep eutectic solvent (DES). Five weight concentrations of Al₂O₃ nanoparticles, 0.05, 0.10, 0.15, 0.20, and 0.25 wt%, were dispersed in the polymeric fluid via two dispersing techniques. In the first step, the nanoparticles were stirred using magnetic stirring for 1 h, followed by the sonication technique for another hour to ensure the nanoparticles were well suspended in the base fluid. A KD2 Pro thermal analyzer measured the thermal conductivity of each concentration for the temperature from 30 to 70 °C. The experimental data demonstrated a correlation between thermal conductivity and nanoparticle weight fraction. The results showed that the thermal conductivity increased with the increment of Al₂O₃ concentration for all set temperatures. The study revealed that the polymeric base fluid could replace the conventional base fluid since the thermal conductivity results were comparable with those reported in the literature.

This study aimed to assess the chemical composition, specifically metal content, phenolics, and fatty acids, of two bryophyte species, Polytrichum formosum and Polytrichum commune, which belong to the Polytrichaceae family. The bioactivities of these species were also evaluated. Microwave plasma atomic emission spectroscopy was used to analyze 13 elements, revealing the presence of 10 elements at varying concentrations in both species. Iron (Fe) was the most prominent element in P. formosum, with a concentration of 7610 mg/kg, whereas calcium (Ca) was the most prominent element in P. commune, at a concentration of 8430 mg/kg. The high-performance liquid chromatography mass spectrometry analysis revealed the presence of 53 phenolic compounds, with quinic acid, protocatechuic acid, and fisetin being the most prominent with concentrations of 4.45, 2.26, and 1.46 mg analyte/g extract, respectively. When evaluated for total phenolic content, P. commune had a higher concentration of phenolic compounds than P. formosum. The fatty acid profile obtained via gas chromatography-mass spectrometry analysis revealed higher concentrations of oleic acid (36.6% for P. formosum and 38.0% for P. commune) and palmitic acid (35.5% for P. formosum and 33.8% for P. commune). Three independent assays assessed the antioxidant capacities of both plants, which revealed significant antioxidant potential in both species.

Prefabricated construction has rapidly developed due to its efficiency and environmental benefits. With the widespread application of the EPC (Engineering, Procurement, and Construction) model, achieving fair and reasonable distribution of profits in prefabricated construction projects under this model has become an urgent issue that needs to be addressed. In response to the limitations of the traditional Shapley value method, this paper introduces input factors, technological factors, and management factors to develop an improved profit distribution model based on entropy-weighted TOPSIS and the Shapley value. A case study is presented to validate the model, aiming to achieve fair and equitable profit distribution.

Thermal, morphological, and mechanical properties were studied for 3D-printed biocomposites prepared from polylactic acid (PLA) and hemp fibers. For this purpose, the neat PLA, PLA/Hemp fiber (3 wt%), PLA/Hemp fiber/Maleic anhydride (3 wt% and 0.6 wt%), and PLA/Hemp fiber/Maleic anhydride/Glycerol (3 wt% and 0.6 wt% + Glycerol added in 10% of PLA) biocomposites were extruded to obtain filaments for fused filament fabrication (FFF). Thermogravimetric analysis (TGA) provided temperatures corresponding to 5%, 10%, and 90% mass losses for materials before and after 3D printing. During 3D printing, filaments were extruded with a nozzle temperature of 220 ºC; consequently, their thermal properties worsened after 3D printing. In thermal analysis, T_g increased by adding hemp fiber and maleic anhydride but was decreased with glycerol addition. The tensile and flexural strengths of neat PLA and biocomposites were not statically different, but flexural strength was slightly increased by adding ingredients one by one. Regarding modulus of elasticity (MOE) of materials, the sample group of the PLA/hemp fiber/maleic anhydride had the highest value. However, glycerol addition decreased MOE by 17%. These results showed that material performance of the PLA could be improved or remain statistically identical by adding hemp fiber, maleic anhydride, and glycerol.

This study highlights the sound analyses in a studio settings for a KadazanDusun bamboo musical instrument from Sabah Malaysia called the tongkungon. The tongkungon is a type of chordophone built from betung bamboo trees, which are found growing close to rivers and also known as ‘poring’ in Sabah, Malayisa. It is also a plucked idiochordal  bamboo tube zither. To adjust the pitches of the strings, the wedges can be shifted to shorten or lengthen them.The tongkungon sound radiator is made up of six strings with unique and innovative sound reproduction capabilities. Fast Fourier Transform (FFT) analysis was used to evaluate the frequency spectrum via a PicoScope oscilloscope. Adobe Audition was used to produce the time frequency analysis (TFA) spectrograms. The results showed the notes of the tongkungon strings 1, 2, 3 ,4, 5, and 6 to be C, E, B, A, F, and A, respectively. The tongkungon was tuned in the pentatonic scale F, A, B, C, and E. The 1^st, 2^nd, 3^rd, 4^th, 5^th, and 6^th strings were C4(261.63Hz), E4(329.63Hz), B3(246.94Hz), A3(220.00Hz), F3(174.61Hz), and A3(220.00Hz), respectively, i.e., with both 4^th and 6^th strings in A3. The frequency spectrum showed distinct fundamental and overtones frequencies. The first octave behaved as a multiple integer of the fundamental frequency for all strings. The number of partials in each string was inconsistent due to non-uniform thickness of the raised fibres from the bamboo tube.

This study focuses on the effectiveness of a new substance in stabilizing paper information carriers – hydrotalcite applied to the paper in a partially polar environment. The effect of modification on the stabilization of paper during accelerated aging was investigated by measuring chemical (surface pH, rate of glycosidic bond cleavage), mechanical (coefficient of the relative increase of the lifetime for folding endurance), optical (colorimetry – CIE L*a*b*), and spectral (FTIR) properties. Three types of hydrotalcites differing in composition, particle size, and preparation conditions, were tested and compared. After the modification, all the properties of acidic test papers improved. The most promising type of hydrotalcite was prepared under the nucleation action of citric acid. The atomic ratio of Mg²⁺ to Al³⁺ of this hydrotalcite was equal to 5. Modification by this hydrotalcite led to an increase in surface pH by 1.3 to 2.7 units.

This work was designed to evaluate the bioactivity of four monoterpenes, namely carvacrol, p-cymene, eugenol, and iso-eugenol, applied to wood blocks from Pinus sylvestris sapwood using the vapor method against Aspergillus flavus, Aspergillus niger, and Fusarium culmorum. These monoterpenes were prepared at 20, 40, 60, 80, and 100 µL/mL. The highest fungal inhibition percentage (FIP, 24.4%) against the growth of A. flavus was observed for p-cymene when applied to a wood sample at 100 µL/mL. The highest FIPs observed against the growth of A. niger were 21.5% and 16.3%, by p-cymene and iso-eugenol, respectively, at 100 µL/mL. The highest FIPs observed against the growth of F. culmorum were 41.5 and 27.0% by the application of carvacrol at 100 µL/mL and 80 µL/mL, respectively. This study showed the importance of monoterpenes for antifungal activity and may contribute to the most rational use of these compounds as antimicrobial agents for wood protection.

The structural performance was tested for two plywood products distributed in South Korea: Plywood for roof (RP) and plywood for concrete form (CP), in accordance with ASTM standards. The evaluation included tests for tensile-shear strength under wet conditions, bending performance, compressive strength, and rolling shear strength. Results indicated that the CP specimens exhibited a compressive strength of 37 MPa, surpassing that of structural cross-laminated timber (CLT) with comparable specific gravity. The bending performance of CP plywood was also notable, with a modulus of rupture of 56.8 MPa and a modulus of elasticity of 12 GPa. The rolling shear strength was measured at 2.4 MPa, which is favorable compared to the rolling shear strengths of European structural wood species. Notably, the failure pattern was ideal. Furthermore, the CP specimens demonstrated excellent adhesive strength in the tensile-shear test after cyclic boiling, both meeting and exceeding the Korean standards for structural plywood in all evaluated aspects. In contrast, the RP specimens did not fully meet some of the Korean standards, indicating areas for improvement in structural applications.