875 research outputs found
Synergistic antibacterial effect of 405 nm blue light-emitting diodes (LEDs) and gelatin film for inactivation of Escherichia coli O157:H7 and Salmonella Typhimurium on stainless steel and fresh fruit peel
No full textA combined antibacterial effect of 405 nm blue LEDs (BL) and gelatin film (G) was investigated on stainless steel (SUS) and fresh fruit peel for the inactivation of Escherichia coli O157:H7 and Salmonella Typhimurium. On the SUS, the sum of the individual treatments of G for 20 min and BL at 20 J/cm2 was <1 log reduction (log CFU/ cm2). In comparison, combination treatment of G and BL (G + BL) at 20 J/cm2 exhibited 2.37 and 3.09 log reduction on E. coli O157:H7 and S. Typhimurium. The G + BL treatment only increased a propidium iodide (PI) uptake, indicating that cell membrane damage occurred. In the G + BL treatment, reactive oxygen species (ROS) scavenging assay confirmed that ROS involved in the bactericidal mechanism. On orange peel, the G + BL treatment at 40 J/cm2 resulted in a 3.05 and 3.17 log reduction on E. coli O157:H7 and S. Typhimurium. In contrast, the individual treatment of G for 40 min led to reductions of 0.63 log CFU/cm2 for E. coli O157:H7 and 0.50 log CFU/cm2 for S. Typhimurium, while the BL treatment at 40 J/cm2 achieved reductions of 0.78 and 0.69 log CFU/cm2, respectively. A synergistic bactericidal effect was similarly observed in the combined treatment groups for both apple and grapefruit peels. In a color and texture analysis, G did not affect hardness, toughness, and visual color of fruit.N
Ultimate strength characteristics of unstiffened cylindrical shell in axial compression
No full textCylindrical shell is a common structural design solution in many engineering fields, such as the foundation supporting structures and buoyant column of the offshore wind turbine in the maritime sector. Operating in an ocean environment, these cylindrical shell structures need to withstand a combination of axial compression, bending moment, torsion and external pressure. This study contributes a parametric investigation for unstiffened cylindrical shells subjected to axial compression. Emphasis is placed on the ultimate strength characteristics and their relation with the initial geometric imperfection. The nonlinear finite element method is adopted by considering geometric and material nonlinearities in conjunction with an arc-length incrementation to solve the governing equilibrium equation. The numerical prediction is compared with the prevailing code-based approach, i.e. DNV, ABS, API and Eurocode. This study shows that the ultimate strength of unstiffened cylindrical shells in axial compression is highly sensitive to initial geometric imperfection. The code-based formulae appear to be overly conservative for predicting the ultimate compressive strength of cylindrical shells
A comparison of numerical methods for damage index based residual ultimate limit state assessment of grounded ship hulls
No full textConsiderable efforts have been devoted to developing rapid methodologies for predicting the residual strength of ship hull girders for a given damage scenario (e.g., R–D diagram). This task is usually challenged by the difficulty of a proper definition of damaged scenarios, which is a function of the damage location and extent. The concept of damage index (DI) was proposed to resolve this issue, and its application has been demonstrated previously through the incorporation of the Intelligent Supersize Finite Element Method (ISFEM) and Modified Paik–Mansour (P–M) approach. Alternatively, a Smith-type progressive collapse can be adopted. In fact, this may enable a more comprehensive application of the DI concept, as the Smith-type approach is codified in the Common Structural Rule (CSR) for assessing the longitudinal strength of the hull girder. In light of this, the damage index based assessment tools (i.e., R–D diagram) incorporated with a Smith-type progressive collapse method is presented in this paper. This also facilitates a comparison with the R–D diagram previously developed by ISFEM and Modified P–M approach. Discussion is given regarding the discrepancy between different methods, and recommendations for future research are outlined
Impact of Hull Condition and Propeller Surface Maintenance on Fuel Efficiency of Ocean-Going Vessels
No full textThe fuel consumption of marine diesel engines holds paramount importance in contemporary maritime transportation and shapes energy efficiency strategies of ocean-going vessels. Nonetheless, a noticeable gap in knowledge prevails concerning the influence of ship hull conditions and propeller roughness on fuel consumption. This study bridges this gap by utilizing artificial intelligence techniques in Matlab, particularly convolutional neural networks (CNNs) to comprehensively investigate these factors. We propose a time-series prediction model that was built on numerical simulations and aimed at forecasting ship hull and propeller conditions. The model's accuracy was validated through a meticulous comparison of predictions with actual ship-hull and propeller conditions. Furthermore, we executed a comparative analysis juxtaposing predictive outcomes with navigational environmental factors encompassing wind speed, wave height, and ship loading conditions by the fuzzy clustering method. This research's significance lies in its pivotal role as a foundation for fostering a more intricate understanding of energy consumption within the realm of maritime transport
Synergistic antimicrobial effects of ammonium persulfate, ultrasound, and mild heat on<i> Staphylococcus</i><i> aureus</i> under varied conditions
No full textThis study elucidated the antimicrobial effect of ammonium persulfate (PS), ultrasound (US), and 40-60 degrees C mild heat on Staphylococcus aureus ATCC 27213 under various growth conditions, including non-adaptation, pH- adaptation, and aridity-adaptation, in buffered peptone water (BPW) and on orange peel surfaces. For non- adapted, pH-adapted, and aridity-adapted S. aureus, the combined treatment of PS, US, and mild heat showed a synergistic effect, with log reductions of 2.05, 6.44, and 1.11 log CFU/mL in BPW after 6 min, respectively. Mechanistic experiments showed that pH-adapted S. aureus had increased SOD activity due to oxidative stress from the acidic environment, but the introduction of PS further elevated this stress, leading to greater cell death primarily through membrane damage, as confirmed by TEM, with leakage of nucleic acids and proteins. This technique was applied to an orange peel washing system, effectively inactivating aridity-adapted S. aureus, resulting in 3.51 log CFU/cm2 and 3.20 log CFU/mL reductions on orange peel and in BPW washing water, respectively, after a 6-min treatment, without any quality changes, including color and texture attributes. The enhanced inactivation on orange peel may be attributed to the presence of compounds such as ascorbic acid and limonene, which further activate persulfate and exhibit antimicrobial properties, thereby contributing to the increased efficacy of the treatment. The combined PS, US, and mild heat treatment provides an effective strategy for controlling resilient bacterial strains in the food industry, enhancing food safety through oxidative stress and mild thermal effects.N
Synergistic antimicrobial action of chlorogenic acid and ultraviolet-A (365 nm) irradiation; mechanisms and effects on DNA integrity
No full textChlorogenic acid (CGA) is abundant in various plants and notably in coffee beans. This study investigated the bactericidal activity of CGA combined with ultraviolet-A light (UVA, 365 nm) (CGA + UVA) against Escherichia coli DH5α, with the aim of developing novel strategies for food preservation and healthcare. CGA + UVA treatment was superiorin reducing bacterial survival than either treatment alone. At 20 J/cm2 and pH 7, CGA (0.3%) + UVA treatment resulted in only about a 3-log reduction in bacterial survival, whereas at 15 J/cm2 and pH 3, no surviving bacteria could be detected, demostrating that the treatment was more effective at acidic pH. CGA + UVA treatment was also bactericidal in green plum juice, confirming that its low pH-dependent property could be effective in acidic food products. To elucidate the bactericidal mechanism of CGA + UVA treatment, its effects on reactive oxygen species (ROS) generation, membrane integrity, and enzyme activity were measured. ROS generated via the type-1 reaction, such as hydrogen peroxide (H2O2) and hydroxyl radicals (·OH), were mainly detected. CGA + UVA disrupted the bacterial cell membrane, causing the leakage of cellular components, particularly proteins. CGA + UVA treatment also led to deoxyribonucleic acid (DNA) degradation and reduced succinate-coenzyme Q reductase activity by approximately 72 %. Furthermore, CGA + UVA treatment decreased β-lactamase activity and plasmid transforming efficacy with maximal reductions of 68 % and 98 %, respectively, highlighting its potential for increasing antibiotic susceptibility and preventing the spread of antimicrobial resistance. The results demonstrate that CGA + UVA treatment could be used to effectively combat antibiotic-resistant bacteria and prevent the spoilage of preserved foods or food poisoning.N
Synergistic effect of naringenin and mild heat for inactivation of E. coli O157:H7, S. Typhimurium, L. monocytogenes, and S. aureus in peptone water and cold brew coffee
No full textThis study aimed to investigate the bactericidal effect of naringenin (NG), a plant-derived flavonoid, and its synergistic effect with mild heat (MH) treatment at 50 °C in peptone water (PW) and ready-to-drink cold brew coffee (RDC). Among various NG concentrations (1–20 mM), 10 mM NG resulted in the greatest inactivation for Escherichia coli O157:H7, Salmonella Typhimurium, Listeria monocytogenes, and Staphylococcus aureus. In RDC, NG + MH treatment resulted in a 5–8-log reduction in all pathogens after 10 min, except for S. aureus. In contrast, NG or MH treatment alone exhibited only marginal bactericidal effects. From inactivating mechanism analysis, lipid membrane destruction and intracellular enzyme inactivation were the key factors for pathogen inactivation. Cell membrane and enzyme dysfunctions were identified in propidium iodide (PI) uptake test, membrane potential assay, and membrane protein analysis. Furthermore, NG + MH exerted minimal influence on the quality attributes of RDC in pH, color, and total phenolic content. These results indicated that the NG + MH treatment system effectively ensured microbial safety in cold brew coffee while enhancing its nutritional value and preserving quality attributes.N
Bioconversion of cabbage juice: Enhanced S-Methylmethionine via non-thermal treatment and lactic acid bacteria fermentation
No full textBioconversion technology represents a promising strategy for enhancing the functional attributes of natural products, with significant implications for the food industry. This study focused on the application of bioconversion technology to cabbage juice, a cruciferous vegetable renowned for its nutritional value and health-promoting properties. To facilitate effective fermentation, non-thermal treatments, including ultrasound, UV-lamp, and aeration tank, were employed to control microorganisms present in raw cabbage prior to fermentation initiation. The non-thermal treatment protocol entailed a 20-min duration, resulting in the inactivation of 2.5–4.5 log CFU/g of microorganisms in the raw cabbage material. Fermentation by Leuconostoc mesenteroides was followed for 15 h at concentrations of 0.2%. As a result, fermented cabbage juice was observed improvements not only in the S-methylmethionine content but also in the amino acid composition. This work lays the foundation for advancing research in bioconversion and food science, aiming to contribute to the development of functional foods and healthier lifestyles.N
A novel formula for predicting the ultimate compressive strength of the cylindrically curved plates
No full text''The present study aims to develop an empirical formula to predict the ultimate compressive strength of unstiffened cylindrically curved plates. Drawing from an extensive analysis of 400 unique curved plate scenarios under longitudinal compression, we investigated critical parameters: the flank angle (denoted as θ), plate aspect ratio (denoted as a/b), and plate slenderness ratio (denoted as β). The ANSYS Nonlinear Finite Element Method (NLFEM) was employed to assess each scenario, considering the average level of initial imperfections (denoted as 0.1β2t) and configurations of one-bay and one-span. It is important to note that the models were designed without accounting for the effects of residual stresses. The simulation data generated from this analysis served as the foundation for developing our empirical formula. The proposed formula strongly agreed with the numerical simulations and experimental test results. This research provides structural engineers with a reliable predictive tool, aiding in more accurate predictions of the ultimate limit state (ULS) of curved plates during early design phases
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