196746 research outputs found
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Response of methanogenic metabolism to polystyrene microplastics at varying concentrations:the trade-off between inhibitory and protective effects in anaerobic digestion
No full textPolystyrene (PS) is an important raw material of food packages, and its induced microplastics (MPs) inevitably enter into the food waste (FW) with mechanical or hydrothermal pretreatment, which may affect the FW anaerobic digestion (AD). However, the different microbial responses to PS MPs in AD system have rarely been reported at varying PS MPs levels. In this study, the trade-off between positive and negative effects of PS MPs on syntrophic methanogenesis in AD for FW treatment was investigated when the dosage varied from 10 to 200 mg/L. The results showed that methane (CH4) yield was upgraded by 4.72% at a lower PS MPs concentration (25 mg/L) compared with the control reactor without PS MPs dosing. In contrast, it would be inhibited by 10.13% when PS MPs concentration increased to 100 mg/L. More secretion of extracellular polymeric substances was the main reason for methanogenic metabolism enhancement at lower dosages of PS MPs due to its characteristics of cell-protection and electron transfer facilitation. Furthermore, the higher abundance of genes regarding superoxide dismutase and catalase in the reactor with PS MPs of 25 mg/L could impede reactive oxygen species formation and alleviate its toxicity. The findings of the study provide a comprehensive understanding of the promotion and inhibition mechamisms of syntrophic metabolism in the AD process by PS MPs and their released substances at varying concentrations
Review of microplastics and chemical risk posed by plastic packaging on the marine environment to inform the Global Plastic Treaty
No full textPlastic overproduction and the resulting increase in consumption has made plastic pollution ubiquitous in all ecosystems. Recognizing this, the United Nations (UN) has started negotiations to establish a global treaty to end plastic pollution, especially in the marine environment. The basis of the treaty has been formulated in terms of turning off the tap, signaling the will to prevent plastic pollution at its source. Based on the distribution of plastic production by sector, the plastic packaging sector consumes the most plastic. The volume and variety of chemicals used in plastic packaging, most of which is single-use, is a major concern. Single-use plastics including packaging is one of the most dominant sources of plastic pollution. Plastic waste causes pollution in water, air and soil by releasing harmful chemicals into the environment and can also lead to exposure through contamination of food with micro- and nano-plastic particles and chemicals through packaging. Marine life and humans alike face risks from plastic uptake through bioaccumulation and biomagnification. While the contribution of plastics ingested to chemical pollution is relatively minor in comparison to other pathways of exposure, the effect of plastic waste on marine life and human consumption of seafood is beyond question. To reduce the long-term impact of plastic, it is crucial to establish a global legally binding instrument to ensure the implementation of upstream rather than downstream solutions. This will help to mitigate the impact of both chemicals and microplastics, including from packaging, on the environment.
Biogas upgrading by biotrickling filter:Effects of temperature and packing materials
No full textBiological hydrogen-methane conversion technology can combine Power-to-Gas technology with biogas engineering and showed great potential in breaking through the limitations of both hydrogen storage and CO2 removal for biogas upgrading. However, the low gas–liquid mass transfer rate of hydrogen greatly limited its conversion efficiency and actual application. This study used a biotrickling filter (BTF) to address this limiting factor, and the effects of temperature and packing materials on hydrogen-methane conversion were investigated. Results showed that higher temperature was beneficial for hydrogen-methane conversion, and the highest conversion efficiency of 8.3 L/Lw·d was obtained at 55 °C with the archaeal community dominated by Methanothermobacter (99.97 %). The reactor using activated carbon as packing material showed the best hydrogen-methane conversion efficiency of 91.9 %, with the most methanogens fixed on the surface. Due to the electronic conductor property of activated carbon, the microbial communities of the biofilm were also different from the other two packing materials. Finally, the H2/CO2 ratio of the gas inflow was optimized, and the most suitable result was 2.5:1 (H2/CO2, v/v), which was far below the previously reported results and indicated higher efficiency in carbon dioxide removal. This study provided a promising way for biogas upgrading
Identifying driving factors in cascaded packed bed latent thermal energy storage:An experimental validation
No full textThe cascaded packed bed latent thermal energy storage (PBLTES) system, an innovative and efficient technique, remains unexplored experimentally in terms of driving factors and cyclic stability. To address this gap, this study designed a cascaded PBLTES system, employing three phase-change-materials with varied phase transition temperatures. Parametric experiments were conducted to measure phase transition in capsules and temperature changes in heat transfer fluid. Pearson's correlation coefficients were used to establish relationships between driving factors and thermal performance metrics. This study developed multiple linear regression models based on experimental correlations to evaluate and predict thermal performance under various conditions. These results indicated that the employed multiple regression models are capable of making reliable quantitative predictions regarding the thermal behavior of cascaded PBLTES systems. The models showed a good fit to the experiment data (lowest R2 value at 0.776). The results also showed that the flow rate significantly affected total and phase transition times of the cascaded PBLTES for charging/discharging, with substantial Standardized Linear Regression Coefficients of −0.79/-0.8 and −0.74/-0.72, respectively. In contrast, inlet temperature, with coefficients of −0.18/0.15 and −0.34/0.21, has about a quarter of the flow rate's impact. These findings provide compelling experimental substantiation for the design of cascaded PBLTES.</p
Design of convertible patient care unit for both non-pandemic and pandemic times:Prototype, building spatial layout, and ventilation design
No full textConvertible patient care units can accommodate non-respiratory infectious disease patients in non-pandemic times and provide isolated treatment for respiratory infectious disease patients during pandemic times. A prototype convertible patient care unit covering a floor area of 1518 m2, featuring 16 wards, and accommodating 40 beds was developed to examine the impact of building spatial layout and ventilation design on the inter-zonal airborne transmission and energy use intensity (EUI) during both non-pandemic and pandemic times. Building spatial layout referred to the presence of patient corridors and anterooms, while ventilation design referred to the location of air terminals and the calculation method of residual air volume (namely, difference between supply and exhaust airflow rates). Adding anterooms provided an 18% reduction in pressure gradient fluctuations during door-opening events. The absence of exhaust in the medical corridor, anterooms, and wards increased contamination leakages to the patient corridors. Using the differential pressure method to calculate residual air volume was more effective in controlling the inter-zonal pressure gradient than the fixed residual air volume method. Various conversion methods resulted in an 84%-134% increase of EUI compared to non-pandemic times, without, however, corresponding reduction in inter-zonal airborne transmission risk. The condition of adding both patient corridors and anterooms, exhaust-only patient corridors, anterooms with balanced supply-exhaust airflow rates, and differential pressure method to calculate residual air volume were effective conversion strategies to simultaneously address both the inter-zonal airborne transmission and EUI. These findings provide fundamental information for designing convertible patient care units and revising related guidelines in China
A novel temporal–spatial graph neural network for wind power forecasting considering blockage effects
No full textWind Power Forecasting is crucial for the operational security, stability, and economic efficiency of the power grid, yet it faces significant accuracy challenges due to the variable nature of wind energy and complex interactions within wind farms. This study introduces a novel neural network model specifically designed for Wind Power Forecasting, incorporating both a gated dilated inception network and a graph neural network. This innovative approach enables the concurrent analysis of temporal and spatial features of wind energy, significantly enhancing the forecasting accuracy. A pivotal feature of this model is its unique mechanism to compute the mutual influence between wind turbines, with a particular focus on the blockage effect, a key factor in turbine interactions. The model's efficacy is validated using a real-world dataset, targeting a 48-hour prediction horizon. The experimental outcomes demonstrate that this model achieves superior performance compared to state-of-the-art methods, with a notable improvement of 6.87% in Root Mean Square Error and 8.77% in Mean Absolute Error. This study not only highlights the model's enhanced forecasting capabilities but also emphasizes the importance of integrating spatial and temporal dynamics in wind farms for improving Wind Power Forecasting accuracy.</p
Slicing Through Bias: Explaining Performance Gaps in Medical Image Analysis using Slice Discovery Methods
No full textMachine learning models have achieved high overall accuracy in medical image analysis. However, performance disparities on specific patient groups pose challenges to their clinical utility, safety, and fairness. This can affect known patient groups - such as those based on sex, age, or disease subtype - as well as previously unknown and unlabeled groups. Furthermore, the root cause of such observed performance disparities is often challenging to uncover, hindering mitigation efforts. In this paper, to address these issues, we leverage Slice Discovery Methods (SDMs) to identify interpretable underperforming subsets of data and formulate hypotheses regarding the cause of observed performance disparities. We introduce a novel SDM and apply it in a case study on the classification of pneumothorax and atelectasis from chest x-rays. Our study demonstrates the effectiveness of SDMs in hypothesis formulation and yields an explanation of previously observed but unexplained performance disparities between male and female patients in widely used chest X-ray datasets and models. Our findings indicate shortcut learning in both classification tasks, through the presence of chest drains and ECG wires, respectively. Sex-based differences in the prevalence of these shortcut features appear to cause the observed classification performance gap, representing a previously underappreciated interaction between shortcut learning and model fairness analyses
Balancing sustainability and safety for recirculating showers
No full textWater stress is both predicted and real in many areas in Europe, majorly affecting Mediterranean countries and large cities. Household water represents the largest share of the public water supply, accounting for precisely 60%. Showering accounts for 30-45% of the household water consumption. Recirculating showers are decentralized water reuse technologies which may prove a good solution for reliable water conservation at a household level. With savings up to 80% and 70% of water and energy respectively, household water with the intended use for personal hygiene shall also ensure minimal health risk.The aim of this thesis was to generate new insights in the area of microbial water quality and underline areas for improvement.As indicator microorganisms to monitor water quality in recirculating showers we proposed faecal indicator bacteria, Legionella pneumophila (L. pneumophila), Pseudomonas aeruginosa (P. aeruginosa) and heterotrophic bacteria. Future studies may be supplemented with Staphylococcus spp., Mycobacterium spp. model organisms for virus, protozoa and fungi. These could be included in future stress tests to further validate treatment technology.A monitoring campaign overviewed the technological development of the system through the proposed microbial indicators and across different recirculating shower designs. The studies revealed low carryover of faecal bacteria from a bather to the next measured after approximately a 24 h stagnation period. The heterotrophic bacteria did not show significant variations across different recirculating shower designs and were consistently higher at the initial flow coming out of the shower head. P. aeruginosa and L. pneumophila were also evaluated as model pathogenic bacteria. For the first one, 49% of the data was above the upper Limit of Quantification (LOQ) of 10,000 CFU/100 mL. For the second one, 70% of the data were below the lower Limit of Quantification (LOQ) of 10 CFU/100mL, although some high concentrations at low frequencies were also detected. Nevertheless, without clear standards regulating recirculating showers, the concentrations alone do not provide a full picture of the potential risk.A Quantitative Microbial Risk Assessment (QMRA) was used to evaluate the risk associated to the inhalation of the pathogenic bacteria P. aeruginosa and L. pneumophila. An infection target of 1 infection per 10,000 was used as benchmark. The median annual risk of infection through inhalation was below this benchmark, in the case of P. aeruginosa, or at slightly above the benchmark in the case of L. pneumophila. Few high concentrations at low frequencies underline the importance for proactive management towards microbial water quality to maintain recirculating showers safe.Recirculating showers remain a promising solution to conserve water resources at a household level while the result from this Ph.D. motivates to continue with further development of technology. As future perspectives, development of risk control strategies which are effectively communicated, i.e. periodic sampling or regular checks, along with in depth understanding of biofilm-water interactions for optimal design of maintenance protocols will be beneficial in future research
Associations between bedroom environment and sleep quality when sleeping less or more than 6h:A cross sectional study during summer
No full textA cross-sectional study was conducted in 50 bedrooms in Shanghai, each for one week during summer, to investigate the effects of the bedroom environment on sleep quality. Sleep quality was recorded with a wrist-worn sleep tracker and assessed with a questionnaire. The measurements from 168 person-nights were analysed after excluding unreliable data. The overnight means of bedroom temperature, relative humidity, CO2 and PM2.5 concentrations, which were continuously measured were between 21 to 30 °C, 43 to 86 %, 375 to 2756 ppm, and <1 to 43 μg/m3, respectively. Sleep duration in 36.3 % of the nights was less than 6 h, which is too short according to the recommendation of the American Sleep Foundation. The nights were then classified into two categories, with sleep duration above or below 6 h. The results show that the sleep quality in the short-sleep category was more sensitive to the bedroom environment. In the longer-sleep duration category, light sleep decreased with higher humidity and increased with higher PM2.5 concentration. In the short-sleep duration category, all the main sleep quality parameters including sleep efficiency and the duration and percentage of deep and rapid eye movement sleep stage decreased, and time spent awake increased with increased bedroom temperature, humidity, CO2 and PM2.5 concentration. The occupants who used air conditioning had a lower indoor temperature and humidity at night; opening windows decreased the indoor CO2 concentration but increased the PM2.5 concentration. These results suggest the need for alternative solutions to natural ventilation during summer in dwellings in Shanghai
Understanding the multifunctional anticorrosion protective mechanism of epoxy-based coatings modified with hydrogel and benzotriazole conveying nanotubes for Q235 steel protection in 3.5 % NaCl
No full textCoatings with multiple protective properties are highly desired for anti-corrosion purposes as they overcome the limitations of conventional coatings that have limited functionality in field applications. Thus, this study describes the protective mechanisms of a new class of composite coatings fabricated by embedding benzotriazole (BTA) laden nanotubes prior-functionalized with interfacial wrappings of chitosan hydrogel (CTSH) entrapping excess crosslinking agents (glutaraldehyde (GTRA) or epichlorohydrin (EPIH)) in epoxy (E44) matrix cured with polyamide. The modification led to an improvement in the barrier and physical properties of the composite coatings and introduced shape-memory self-repairing capabilities. Long-term impedance spectroscopy (EIS) complemented with the physical property tests was employed to interrogate the improved barrier properties. The coatings' microstructure and composition analyzed with SEM and EDS reveal the shape-memory self-repairing effect which was further characterized with overtime optical snapshots of samples exposed in a salt-spray chamber. The antibacterial functionality of the composite coatings against some marine bacteria (Marinobacter aquaeolei and Marinobacter salsuginis) was characterized using combined SEM and confocal laser scanning microscopy (CLSM). UV–visible spectrophotometry data reveal the pH-responsive release of the entrapped functional materials from the composite coatings. The experimental findings show that the new composite coatings exhibited intriguing triple-action protective functionalities and were more effective in protecting Q235 carbon steel exposed to 3.5 % NaCl compared to the conventional epoxy coating. This suggests that comparatively, the composite coatings have promising applications in structures that are exposed to sea environments