Search Results (154)

The role of Enterococcus spp. in food is debated since this group of lactic acid bacteria contains opportunistic pathogenic strains, some of which exhibit a multidrug-resistant profile. In livestock farms, the use of antibiotics is the most common practice to deal with mastitis-causing bacteria. However, the heavy usage and/or misuse of antibiotics has led to the emergence of antibiotic resistance. This study aimed to genetically and phenotypically characterize Enterococcus strains isolated from raw sheep milk. Samples were collected over one year from the bulk tank of a dairy sheep farm and cultured on selective media. Isolates were purified and analyzed by whole-genome sequencing and antimicrobial susceptibility testing. The isolates were divided into clusters and the corresponding species were identified along with their genes related to virulence and antibiotic resistance. The pan-, core- and accessory-genomes of the strains were determined. Finally, the antibiotic-resistant profile of selected strains was examined and associated with their genomic characterization. These findings contribute to a better understanding of Enterococci epidemiology, providing comprehensive profiles of their virulence and resistance genes. The presence of antibiotic-resistant bacteria in raw sheep milk destined for the production of cheese should raise awareness. Full article

Staphylococcus aureus frequently causes intramammary infections in dairy cows (bovine mastitis), which impair animal welfare, milk yield, and food safety. This study determined the prevalence and genetic diversity of S. aureus in bulk tank milk (BTM) samples from community-based Alpine dairy pastures in Tyrol, a major milk-producing region in Austria. Throughout the 2023 Alpine season (May–September), 60.3% (94/156) of BTM samples tested positive for S. aureus at least once over the course of up to four samplings. A total of 140 isolates collected from the 94 S. aureus-positive community-based Alpine dairy pastures revealed 33 distinct spa types, with t2953 (n = 33), t529 (n = 12), t267 (n = 11), and t024 (n = 10) being the most common. Selected isolates representing the different spa types were characterised by DNA microarray-based genotyping, multi-locus sequence typing (MLST), and antimicrobial susceptibility testing. Isolates with spa types associated with bovine-adapted CC8 (CC8bov/GTB) were identified as the most common subtype, being detected in BTM samples from 35.3% (55/156) of the pastures. This emphasises the high prevalence of this subtype in dairy herds across European Alpine countries. Other common bovine-associated subtypes were also detected, including CC97, CC151, and CC479. While antimicrobial resistance was rare, enterotoxin-producing genes were detected in all CC8bov-associated spa types. Overall, these findings underscore the importance of rigorous hygiene practices in dairy farming, particularly in community-based Alpine dairy pastures, where the risk of transmission is particularly high. It also emphasises the need for continued surveillance and subtyping to improve animal health, ensure food safety, and promote sustainable milk production. Full article

Ships are designed to withstand various types of hull structure damage, including corrosion, fatigue, damage, crack, fouling, etc., throughout their projected life cycle of 25 years. In this study, we used a database of 25 different bulk carriers aged from five to twenty-five years, consisting of a total of 1920 thickness measurements of girder plate damage across 110 fuel tanks. Thickness measurements of longitudinal girder plate were conducted by certified technicians and approved company. Ultrasound thickness gauging equipment was used to collect data in accordance with the developed methodology and gauging scheme. Based on the classification societies’ rules, the values of the reduction in steel plate thickness due to corrosion over time fall into three categories: acceptable corrosion, substantial corrosion, and extensive corrosion. While classification societies prescribe permissible thickness reductions between 15 and 30%, in this study, the authors considered the excessive corrosion values to be above 20% reduction in initial thickness. Measurements indicating more than 20% reduction were classified as failures, necessitating the replacement of the corroded surfaces. After applying the multistate approach to the reliability analysis of longitudinal girder plates and improving reliability after reaching the critical state, the results show that usability dropped significantly between ten and fifteen years of service for upper girder plating and between twenty and twenty-five years of service for lower girder plates. These findings highlight the crucial impact of gauging location on reliability analysis. Full article

Electrocoagulation (EC) systems are regaining attention as a promising wastewater treatment technology due to their numerous advantages, including low system and operational costs and environmental friendliness. However, the widespread adoption and further development of EC systems have been hindered by a lack of fundamental understanding, necessitating systematic research to provide essential insights for system developers. In this study, a continuous EC system with a realistic setup is analyzed using an unsteady, two-dimensional physics-based model that incorporates multiphysics. The model captures key mechanisms, such as arsenic adsorption onto flocs, electrochemical reactions at the electrodes, chemical reactions in the bulk solution, and ionic species transport via diffusion and convection. Additionally, it accounts for bulk wastewater flow circulating between the EC cell and an external storage tank. This comprehensive modeling approach enables a fundamental analysis of how operating conditions influence arsenic removal efficiency, providing crucial insights for optimizing system utilization. Furthermore, the developed model is used to generate data under various operating conditions. Seven machine learning models are trained on this data after hyperparameter optimization. These high-accuracy models are then employed to develop processing maps that identify the conditions necessary to achieve acceptable removal efficiency. This study is the first to generate processing maps by synergistically integrating physics-based and data-driven models. These maps provide clear design and operational guidelines, helping researchers and engineers optimize EC systems. This research establishes a framework for combining physics-based and data-driven modeling approaches to generate processing maps that serve as essential guidelines for wastewater treatment applications. Full article

Nitrous oxide is a highly suitable oxidizer for hybrid rockets due to its self-pressurizing properties, moderate cost, and high accessibility. However, its vapor pressure and density are highly dependent on ambient temperature, requiring careful consideration of temperature variations in real applications. To mitigate this issue, an oxidizer called Nytrox was produced by adding a small fraction of oxygen to bulk nitrous oxide. This modification enables the hybrid rocket propulsion system to maintain a nearly constant average thrust and total impulse across a wide range of ambient temperatures. A series of 7 s hot-fire tests of a small Nytrox/polypropylene hybrid rocket engine operating at ~60 barA of running tank pressure demonstrated a consistent average thrust of 45.3 ± 0.7 kgf and a total impulse of 307.6 ± 3.9 kgf·s within a N₂O temperature range of 5.9–22.6 °C, compared to highly varying values of the N₂O/polypropylene one within a N₂O temperature range of 10.8–29.8 °C. Furthermore, the specific impulse of the Nytrox hybrid rocket engine increases mildly with decreasing temperature because of the increasing amount of added oxygen that benefits the combustion for generating the thrust. Full article

Automated feeding robots (AFR) are increasingly being used on North American dairy farms to reduce dependency on human labor for feeding. These systems mix, deliver, and push up feed to cows at any frequency or interval desired, allowing for more frequent feed delivery than conventional feeding systems (CFS). This observational study investigated differences in ration consistency, milk components, milk fatty acid profile, and cow behavior between herds using AFR and those using CFS. Sixteen commercial dairies with automated milking systems (AMS) in the upper Midwest United States were paired based on herd size and location into eight blocks each consisting of one CFS and one AFR herd. Feed bunk samples were collected at four equally spaced time points for 3 consecutive d and analyzed for coefficient of variation (CV) of nutrient composition and particle size distribution. Bulk tank milk samples were collected 1 ×/d for 3 d and analyzed for fat, protein, milk urea nitrogen (MUN), lactose, and milk fatty acid (FA) profile. Daily AMS visit intervals, milk yield and composition, and rumination time data were collected from AMS software. A linear mixed model tested fixed effects of feeding system, block, and the random effect of day nested within block. The CV of feed bunk DM, ADF, NDF, and lignin was lower in AFR. Bulk tank milk fat, protein, and MUN were not different between AFR or CFS. AFR had a greater proportion of de novo synthesized FA, but no difference in preformed or mixed FA. Herds with AFR had a shorter AMS visit interval with more AMS refusals per day than CFS. Results imply that AFR may be associated with lower daily variation in fiber concentration at the feed bunk, increased mammary de novo fatty acid synthesis, and increased frequency of cow visits to the AMS compared to conventional PMR feeding. Full article

Reinforced concrete (RC) tanks are essential for storing liquids and bulk materials across various industries. However, simplified analytical methods fall short in providing an accurate analysis, while traditional methods, such as finite element modeling, can be computationally intensive and time-consuming, especially when dealing with nonlinear material properties and complex geometries, like conical and cylindrical shapes. This highlights the need for a more efficient and simplified analysis approach. Accordingly, the present paper introduces a machine learning (ML) framework as an effective predictive tool for RC conical and cylindrical tanks under hydrostatic pressure. Data from 320 RC conical and cylindrical water tanks, previously analyzed using finite element modeling, were used to train and test various ML models, considering geometrical and material nonlinearities. Four machine learning models—decision trees, random forests, gradient boosting, and extreme gradient boosting—were utilized to predict critical internal forces, including the maximum ring tension force, maximum meridional moment, and maximum meridional axial force. The accuracy of each model was evaluated using different statistical measures. To improve model interpretability and identify key predictors, feature importance techniques were employed to rank the significance of each input variable to the predictions. Furthermore, Accumulated Local Effects (ALE) plots were utilized to visualize the relationships between model inputs and outputs, providing a clearer understanding of the inner workings of the ML models. The combined use of feature importance and ALE plots enhances model transparency by illustrating how specific features contribute to the predictions, thereby supporting the informed application of ML in the structural design and analysis of RC tanks. Ultimately, the framework presented in this study aims to promote the practical application of machine learning in structural engineering, contributing to simpler, more efficient, and accurate analysis and design processes for RC water tanks. Full article

Using a laboratory-scale system, consisting of a primary disinfection tank (PDT) and three intermittently mixed reactors (R1–R3) in series, bulk water and biofilm contributions to chlorine decay were quantified. The reactors (surface-to-volume ratio: 23.7 m⁻¹; retention time in each reactor: 42.6 ± 1.18 h) were fed with plant-filtered water (PFW). Secondary disinfection was carried out in R1. Free chlorine concentration decreased with travel time (R1: 1.2 mg/L; R2: 0.6 mg/L; and R3: 0.12 mg/L). The bacterial number (ATP) decreased from 67 pg/mL in PFW and remained at ~2–3 pg/mL in R1 and R2 but increased back to 68 pg/mL in R3. First-order chlorine decay rate coefficients decreased from R1 to R2, as expected, but increased by five-fold from R2 to R3. The increased bacterial number (ATP) in R3 and batch chlorine decay tests confirmed that bulk water (soluble compounds, microbes, and sediments) contributed approximately 40% of the decay, and the biofilm contributed 60% in R3. When ATP levels in the reactors were combined with literature data, the bacterial number increased significantly when free chlorine decreased below 0.2 mg/L, but data between 0.2 and 0.5 mg/L are limited. More investigation is needed in the future for chlorine < 0.5 mg/L regarding bacterial regrowth and its effect on bulk water chlorine decay. Full article

The production of farm bulk milk with low bacterial counts is a key quality index used by industry to help ensure the production of high-quality dairy products. The primary metrics used to determine the microbiological quality of bulk tank milk on a farm are the total bacteria count (TBC) and thermoduric bacteria count. To maintain TBCs and thermoduric counts at the lowest attainable levels, i.e., TBC ≤ 15,000 cfu/mL and thermoduric bacteria ≤ 200 cfu/mL, it is imperative that milk quality management is treated as a multi-faceted endeavor. Milking equipment cleaning, pre-milking teat preparation, milk filtration, cooling and storage, milking equipment maintenance and management of a cow’s environment and diet must each be managed with best practice in mind if farm bulk milk is to consistently attain low TBCs and thermoduric counts. This is especially important when using chlorine-free cleaning protocols, which are more complex than traditional chlorine-based cleaning methods and if not implemented correctly do not offer the confidence of achieving required hygiene standards. Full article

The objectives of this work were as follows: (i) the evaluation of the prevalence of detection of genetic material of Coxiella burnetii in the bulk tank milk of sheep and goat farms in Greece and (ii) the investigation of variables related to the management applied in farms as possible predictors for this. The presence of C. burnetii genetic material was studied in the bulk tank milk of 325 sheep and 119 goat farms throughout the country. For qualitative and quantitative identification of the genetic material of the pathogen, a commercially available real-time PCR was used. In total, 45 parameters were assessed for potential association with the detection of the pathogen: these referred to the management system, infrastructure, health management, animals, production characteristics, and human resources on the farms. Genetic material of the pathogen was detected in bulk tank milk samples from nine sheep (2.8%) and six goat (5.0%) farms. Genetic material was at significantly higher median concentrations in samples from goat farms than from sheep farms, 1,078,096 (min: 181,121, max: 2,331,386) versus 15,728 (min: 507, max: 505,852) GE mL⁻¹, respectively. For sheep farms, the intensive or semi-intensive management system applied in farms (p = 0.003), and for goat farms, the intensive or semi-intensive management system applied in farms (p = 0.0007) and the smaller number of annual veterinary visits to farms (p = 0.044) emerged as significant predictors. Among sheep farms managed under the intensive or semi-intensive system, the lack of accessory barns on farms (p = 0.024) emerged as a significant predictor; no significant predictor could be found among goat farms under such management systems. There was no significant difference in production outcomes between farms in which C. burnetii was or was not detected in the bulk tank milk; also, there was no association between the detection of C. burnetii and the annual incidence rate of cases of abortion on the farms. The results suggest that the risk of transfer of C. burnetii to dairy products from sheep and goat milk appears to be small, but not negligible, which indicates that the pasteurization of milk from small ruminants must be carried out consistently and correctly to ensure the safety of the product. Full article

Volatile corrosion inhibitors (VCIs) are increasingly used in closed systems affected by atmospheric corrosion. In order to achieve a satisfactory level of protection, an inhibitor must be present in a sufficient concentration that should be determined experimentally. Electrochemical measurements are indispensable in corrosion studies examining the protection efficiency of corrosion inhibitors. Volatile corrosion inhibitors are often examined by electrochemical measurements conducted in a bulk of electrolyte, although they protect metal surfaces from atmospheric corrosion where a thin film of electrolyte is present. The aim of this work is to study the protection of carbon steel by two VCIs on different types of electrodes that allow electrochemical tests in a thin electrolyte film and to compare the obtained results with those obtained in a larger volume in a classical electrochemical cell. For this purpose, disc and comb-like electrodes are used. The investigations are carried out in two corrosion media simulating either a marine or urban polluted atmosphere. Studies are performed on low-carbon S235JR steel, which is typically used for crude oil tank bottoms that often suffer from atmospheric corrosion and are increasingly protected by VCIs. Two benzoate-based VCIs recommended for such application are selected for this study. Full article

The mechanical properties of faecal sludge (FS) influence its moisture retention characteristics to a greater extent than other properties. A comprehensive fundamental characterisation of the mechanical properties is scarcely discussed in the literature. This research focused on bulk and true densities, porosity, particle size distribution and zeta-potential, extracellular polymeric substances, rheology and dilatancy, microstructure analysis, and compactibility in the context of using the FS as a substitute for soil in land reclamation and bioremediation processes. FSs from different on-site sanitation systems were collected from around Durban, South Africa. The porosity of the FSs varied between 42% and 63%, with the zeta-potential being negative, below 10 mV. Over 95% of the particles were <1000 µm. With its presence in the inner part of the solid particles, tightly bound extra-cellular polymeric substances (TB-EPSs) influenced the stability of the sludge by tightly attaching to the cell walls, with the highest being in the septic tank with the greywater sample. More proteins than carbohydrates also confirmed characterised the anaerobic nature of the sludge. The results of the textural properties using a penetrometer showed that the initial slope of the positive part of the penetration curve was related to the stiffness of the sludge sample and similar to that of sewage sludge. The dynamic oscillatory measurements exhibited a firm gel-like behaviour with a linear viscoelastic behaviour of the sludges due to the change in EPSs because of anaerobicity. The high-TS samples exhibited the role of moisture as a lubricating agent on the motion of solid particles, leading to dilatancy with reduced moisture, where the yield stress was no longer associated with the viscous forces but with the frictional contacts of solid–solid particle interactions. The filtration–compression cell test showed good compactibility, but the presence of unbound moisture even at a high pressure of 300 kPa meant that not all unbound moisture was easily removable. The moisture retention behaviour of FS was influenced by its mechanical properties, and any interventional changes to these properties can result in the release of the bound moisture of FS. Full article

Developing an exceptional reaction medium with high promotion efficiency, desirable biodegradability and good recyclability is necessary for hydrate-based methane storage. In this work, a kind of eco-friendly hydrogel, polyvinyl alcohol-co-acrylic acid (PVA-co-PAA), was utilized to absorb dilute sodium p-styrenesulfonate (SS) solution, for constructing a hybrid reaction medium for methane hydrate formation. Hydrogels or dilute SS solutions (1–4 mmol L⁻¹) had weak or even no promoting effects on hydrate formation kinetics, while the combination of them could synergistically promote methane hydrate formation. In hydrogel-SS hybrid media containing 1, 2, 3 and 4 mmol L⁻¹ of SS solutions, the storage capacity reached 121.2 ± 1.6, 121.5 ± 3.1, 122.6 ± 1.9 and 120.6 ± 1.6 v/v, respectively. In this binary reaction system, the large surface area of hydrogels provided hydrate formation with sufficient nucleation sites and an enlarged gas–liquid interface, and in the meantime, the dilute SS solution produced an adequate capillary effect, which together enhanced mass transfer and accelerated hydrate formation kinetics. Additionally, the hybrid medium could relieve wall-climbing hydrate growth and improve poor hydrate compactness resulting from the bulk SS promoter. Moreover, the hybrid medium exhibited a preferable recyclability and could be reused at least 10 times. Therefore, the hydrogel-SS hybrid medium can serve as an effective and eco-friendly packing medium for methane hydrate storage tanks, which holds great application potential in hydrate-based methane storage technology. Full article

Udder health consulting is an essential aspect of mastitis control and is based on herd-specific intervention often provided by the herd veterinarian, focusing on managing the bulk tank somatic cell count. Effective communication and alignment of expectations between dairy farmers and herd veterinarians are more critical than ever due to the substantial increase in herd sizes, which amplifies both potential gains and losses. To facilitate future cooperation between dairy farmers and herd veterinarians, it is important to understand the current level of agreement in communication, and therefore, we conducted a study to describe the agreement in the perception of their communication during udder health consulting. From August 2019 to February 2021, herds (n = 88) were selected to participate in the study, with the herd size ranging from 105 to 1291 milking cows. The dairy farmer and herd veterinarian were encouraged to answer a questionnaire to shed light on their perception of communication during udder health consulting. The agreement between the dairy farmer and herd veterinarian regarding their perception of communication during udder health consulting was initially analyzed using Cohen’s weighted kappa. The agreement between farmers and veterinarians ranged from −0.06 and 0.12, indicating that the herd veterinarians’ focus is inconsistent with the dairy farmers’ preferences. The frequency with which udder health is discussed and how potential problems are identified were associated with a significantly lower BTSCC estimate of 427 cells/mL. In contrast, general cooperation between the dairy farmer and herd veterinarian was associated with an estimated increase of 604 cells/mL in BTSCC. Full article

The Sri Lankan transport sector still depends predominantly on petroleum fuels, mainly diesel and gasoline. Gasoline holds the second highest market share, and with the increasing number of gasoline-fueled vehicles, its proportion in the transport fuel mix is continuously expanding. The main objective of this study is to assess the ecological burden associated with the gasoline supply chain in Sri Lanka by conducting a life cycle assessment from a ‘well-to-tank’ perspective. In the scenario analysis, the environmental impacts of four potential gasoline distribution scenarios were assessed and compared with the existing distribution model. According to the results, the refining process was predominant, contributing more than 50% to climate change, terrestrial acidification, marine and freshwater eutrophication, human toxicity, and terrestrial and marine ecotoxicities. Meanwhile, crude oil extraction dominates in its contribution to ozone depletion, photochemical oxidant formation, freshwater ecotoxicity, and fossil depletion. The results of the scenario analysis show a remarkable reduction in the environmental load when rail transport is solely used to transfer gasoline from bulk terminals to regional depots. The reduction is over 65% in most impact categories compared to the existing distribution method, which involves a combination of both road and rail transport. This study identifies the key areas that need to be further analyzed to lower the environmental impacts while also establishing a foundation for conducting comparative environmental assessments of alternative fuel options in the Sri Lankan context. Full article