Photo- and Electro-Chemistry Methods for Waterborne Pathogen Treatment and Detection in Environmental Water

Waterborne disease is a global burden, which is mainly caused by waterborne pathogens disseminated through unsafe water, inadequate sanitation, and hygiene. Antibiotic resistance, which can also spread in water, has become an increasingly serious global health threat as it can prevent the effective treatment of infectious diseases. Improvements on water treatment and detection are the two critical strategies to control the surveillance of waterborne pathogens as well as antibiotic resistance bacteria and genes. The advancement in photo- and electro-chemical methods may provide more opportunities on decentralized water treatment and on-site pathogen monitoring under source-limited conditions. This thesis is dedicated to exploring the possible solutions to automatic, rapid, and easy-to-use in situ pathogen analysis for environmental water by adopting photo- or electro-chemical method, and to enhanced removal of antibiotic resistance bacteria (ARB) and antibiotic resistance genes (ARGs) from wastewater by combining photo- and electro-chemical techniques. These include removal of ARB and ARGs by UV-assisted electrochemical treatment, electrochemical cell lysis (ECL) for DNA extraction from bacteria, and sunlight-activated propidium monoazide (PMA) pretreatment for live/dead bacteria differentiation by quantitative real-time polymerase chain reaction (qPCR) detection. Both experimental approaches and computational modelling were used to evaluate the performance of the techniques and to bring more insights into the mechanism. Each study presents a demonstration on real environmental or wastewater to access the potential of their applications under complex environmental parameters. UV-assisted electrochemical treatment for ARB and ARGs was conducted using a blue TiO₂ nanotube array (BNTA) anode. The inactivation of tetracycline- and SMX-resistant E. coli and the corresponding plasmid coded genes (tetA and sul1) damage was measured by plate counting on selective agar and qPCR, respectively. As a comparison of UV treatment alone, the enhanced reduction of both ARB and ARGs was achieved by UV-assisted electrochemical oxidation (UV-EO) without Cl⁻ and was further facilitated with the presence of Cl⁻, which is attributed to the in-situ generated oxidants by electrochemical process. Significantly slower removal of ARG than ARB was observed for both UV irradiation alone and UV-EO treatment, wherein intracellular ARG generally reduced slower than extracellular ones, and short amplicons reduced significantly slower than long ones. The predominant nucleotide damage by UV irradiation and conformational change by UV-EO treatment was visualized by DNA gel electrophoresis for treated extracellular ARGs. The mechanism on ARB and ARGs damage was further understood by computational chemical modeling. The slower reduction was found for the native bacteria and genes, tetA and sul1, in the latrine wastewater than that in laboratory-prepared buffered samples. The result emphasizes that all the UV-based techniques may only apply after other treatments to avoid the impairment by the transmittance, color, and particulate material in environmental or wastewater. A comprehensive investigation was conducted for ECL in terms of its performance on DNA extraction from gram-negative bacteria (Escherichia coli and Salmonella Typhi) and gram-positive bacteria (Enterococcus durans and Bacillus subtilis). A milliliter-output ECL device was developed based on the disruption of the cell membrane by OH⁻ that can be generated locally at the cathode and accumulated improvingly through a cation exchange membrane. Both gram-negative and gram-positive bacteria were successfully lysed within 1 min at a low voltage of ~5 V. To better understand the pH effects on cell lysis, the pH profile at the cathode surface and in bulk cathodic effluent was simulated via hydroxide transport in the cathodic chamber. The demonstration of ECL on various environmental water sample types (including pond water, treated wastewater, and untreated wastewater) showed its potential as a prelude to nucleic-acid based analyses of waterborne bacteria in the field. Propidium monoazide (PMA), a nucleic acid-binding dye, has been used to distinguish live from dead cells prior to PCR-based detection. To explore the off-the-grid application of PMA, sunlight was investigated for PMA activation as an alternative light source to a typical halogen lamp. PMA was successfully activated by a solar simulator, and the pretreatment conditions were optimized with respect to the PMA concentration as 80 µM and the exposure time as 10 min. The optimal PMA pretreatment was tested on four different bacteria species (two gram-positive and two gram-negative), and the effects of sunlight intensity and multi-sequential treatment were studied. Sunlight-activated PMA pretreatment was eventually demonstrated on latrine wastewater samples with natural sunlight on both sunny and cloudy days. The results showed the potential of sunlight-activated PMA pretreatment to be integrated into a lab-on-a-chip (LOAC) PCR device for off-the-grid microbial detection and quantification.</p

A review of the application of digital identity in the Metaverse

The development of the internet has immensely expanded people’s social scope, which has necessitated the utilization of digital identity. In regard to social networks, the utilization of anonymity or pseudonyms increases the attractiveness of the network. Nevertheless, because online payments, online transactions, and online assets are becoming prevalent features, virtualization is gradually exhibiting highly negative impacts. With respect to the Metaverse, digital identity is potentially a key factor, which can influence the balance that affects the association between anonymity and pseudonyms. To enhance the contemporary scenario and to facilitate the potential utilization of digital identity, this study considers the application of digital identity in the Metaverse, and it utilizes the “Enterprise IA” miniature model (Morey et al.). With regard to the current debate on digital identity, we analyzed the most prominent topic; thus, we explored the application rules pertaining to digital identity. We propose that the Metaverse is primarily characterized by its ability to digitalize the physical world. Furthermore, with respect to digital identity, the power of ownership still represents the fundamental issue. Using technologies such as blockchain and privacy filters, we can not only alter the governance logic and methods, but we can also balance the correlation between private rights and public interests. Thus, to solve the burgeoning identity trust crisis, individual competition for identity authorization rights, and privacy problems that characterize the Metaverse, we explore novel governance approaches

Metacommunity Structure of Stream Insects across Three Hierarchical Spatial scales

A major challenge in community ecology is to understand the underlying factors driving metacommunity (i.e., a set of local communities connected through species dispersal) dynamics. However, little is known about the effects of varying spatial scale on the relative importance of environmental and spatial (i.e., dispersal related) factors in shaping metacommunities and on the relevance of different dispersal pathways. Using a hierarchy of insect metacommunities at three spatial scales (a small, within-stream scale, intermediate, among-stream scale, and large, among-sub-basin scale), we assessed whether the relative importance of environmental and spatial factors shaping metacommunity structure varies predictably across spatial scales, and tested how the importance of different dispersal routes vary across spatial scales. We also studied if different dispersal ability groups differ in the balance between environmental and spatial control. Variation partitioning showed that environmental factors relative to spatial factors were more important for community composition at the within-stream scale. In contrast, spatial factors (i.e., eigenvectors from Moran's eigenvector maps) relative to environmental factors were more important at the among-sub-basin scale. These results indicate that environmental filtering is likely to be more important at the smallest scale with highest connectivity, while dispersal limitation seems to be more important at the largest scale with lowest connectivity. Community variation at the among-stream and among-sub-basin scales were strongly explained by geographical and topographical distances, indicating that overland pathways might be the main dispersal route at the larger scales among more isolated sites. The relative effect of environmental and spatial factors on insect communities varied between low and high dispersal ability groups; this variation was inconsistent among three hierarchical scales. In sum, our study indicates that spatial scale, connectivity, and dispersal ability jointly shape stream metacommunities.Peer reviewe

Environmental Factors Override Dispersal-Related Factors in Shaping Diatom and Macroinvertebrate Communities Within Stream Networks in China

Metacommunity theory provides a useful framework to describe the underlying factors (e.g., environmental and dispersal-related factors) influencing community structure. The strength of these factors may vary depending on the properties of the region studied (e.g., environmental heterogeneity and spatial location) and considered biological groups. Here, we examined environmental and dispersal-related controls of stream macroinvertebrates and diatoms in three regions in China using the distance-decay relationship analysis. We performed analyses for the whole stream network and separately for two stream network locations (headwater and downstream sites) to test the network position hypothesis (NPH), which states that the strength of environmental and dispersal-related controls varies between headwater and downstream communities. Community dissimilarities were significantly related to environmental distances, but not geographical distances. These results suggest that communities are structured strongly by environmental filtering, but weakly by dispersal-related factors such as dispersal limitation. More importantly, we found that, at the whole network scale, environmental control was the highest in the regions with highest environmental heterogeneity. Results further showed that the influence of environmental control was strong in both headwaters and downstream sites, whereas spatial control was generally weak in all sites. This suggests a lack of consistent support for the NPH in our studied stream networks. Moreover, we found that local-scale variables relative to basin-scale variables better explained community dissimilarities for diatoms than for macroinvertebrates. This indicates that diatoms and macroinvertebrates responded to environment at different scales. Collectively, these results suggest that the importance of drivers behind the metacommunity assembly varied among regions with different level of environmental heterogeneity and between organism groups, potentially indicating context dependency among stream systems and taxa.Peer reviewe

Novel MARG-Sensor Orientation Estimation Algorithm Using Fast Kalman Filter

Orientation estimation from magnetic, angular rate, and gravity (MARG) sensor array is a key problem in mechatronic-related applications. This paper proposes a new method in which a quaternion-based Kalman filter scheme is designed. The quaternion kinematic equation is employed as the process model. With our previous contributions, we establish the measurement model of attitude quaternion from accelerometer and magnetometer, which is later proved to be the fastest (computationally) one among representative attitude determination algorithms of such sensor combination. Variance analysis is later given enabling the optimal updating of the proposed filter. The algorithm is implemented on real-world hardware where experiments are carried out to reveal the advantages of the proposed method with respect to conventional ones. The proposed approach is also validated on an unmanned aerial vehicle during a real flight. Results show that the proposed one is faster than any other Kalman-based ones and even faster than some complementary ones while the attitude estimation accuracy is maintained