Search

The accurate control of negative sequence (NS) current distribution among multiple grid-forming (GFM) sources can lower the requirement on NS current capability of the sources. Existing control approaches mainly focus on microgrids (MGs) with fixed points of common couplings and on only the NS current distribution among inverter-based resources (IBRs). As MG configuration has been rapidly evolving to be more complicated, it is critical to take into consideration the impact of MG topologies on the NS current sharing. Moreover, synchronous generators (SGs) are still commonly applied as sources in MGs. The NS current distribution among IBRs and SGs also needs to be considered. In this paper, a novel NS impedance design and regulation approach is proposed to achieve accurate and flexible NS current sharing among different GFM sources (IBRs and SGs). The approach accounts for MG topology impacts by including MG's NS admittance matrix in the impedance design. The effectiveness of the proposed approach is evaluated through simulations and compared to existing solutions in a MG with four different source locations. Results show improved flexibility and accuracy in NS current sharing when MG topology impacts are considered. The proposed approach is also validated through experimental testing on a converter-based hardware testbed.

A microgrid (MG) may lose its grounding provided by the main distribution grid in islanded mode, which could cause equipment insulation damage, hazards to personnel, and protection malfunction. Existing MG grounding schemes include the grounding transformer-based scheme and distributed energy resource (DER) transformer-based scheme. However, the grounding transformer-based scheme will increase MG’s cost, and the DER transformer approach will affect the main grid in the grid-connected mode. Moreover, future MGs may have multiple source locations. In each source location, the source and critical load can potentially operate as a sub-MG, requiring a grounding when it stands alone. In this scenario, the drawbacks of existing grounding schemes will be further magnified. In this paper, a novel controllable DER transformer-based grounding scheme is proposed, where a controllable switch is added to the neutral wire of the transformer. The proposed scheme can disable grounding capability in the grid-connected mode and enable it in the islanded mode by changing the transformer connection. The proposed approach can avoid impacts on the main distribution grid and eliminate the need for additional transformers. The design methodology of the proposed grounding scheme is provided. Simulation verification is conducted on a realistic MG model and experimental verification is conducted.

This article presents a desat protection scheme with the ultrafast response for high-voltage (>3.3 kV) SiC MOSFETs. Its working principle is the same as the conventional desat protection designed for high-voltage SiC MOSFETs, yet its blanking time is implemented by fully considering the influence of high negative dvds/dt during the fast turn-on transient. With the same circuitry as the conventional desat protection, the proposed protection scheme can significantly shorten the response time of the desat protection when it is used to protect high-voltage SiC MOSFETs. In addition, the proposed protection scheme with ultrafast response features strong noise immunity, low-cost, and simple implementation. By taking advantage of the high dv/dt during the normal turn-on transients, the proposed protection scheme can be even faster when the MOSFET has a faster switching speed. Design details and the response speed analysis under various short circuit faults are presented in detail. A half bridge phase leg based on discrete 10 kV/20 A SiC MOSFETs is built to demonstrate the proposed protection scheme. Experimental results at 6.5 kV validate the ultrafast response (115 ns response time under a hard switching fault, 155 ns response time under a fault under load), and strong noise immunity of the proposed desat protection scheme.

Abstract Background Mangrove tannins can participate in wetland biogeochemical cycling. However, their fate and dynamics during leaf litter leaching have yet to be elucidated in coastal aquatic environments. Methods By using a simulated microcosm experiment, changes in leaf litter mass and tannin compounds, including total phenolics (TP), extractable condensed tannins (ECT), and bound condensed tannins (BCT), were examined in the litters and leachates of four common mangrove species: Kandelia obovata (Ko), Aegiceras corniculatum (Ac), Sonneratia apetala (Sa), and Avicennia marina (Am). Results Leaching caused a notable decline in litter mass, TP, and ECT in the leaf litter of Ko, Ac, Sa, and Am, while BCT increased significantly in Ko and Ac. Loss in foliar TP was higher than in leaf litter mass, and loss in foliar ECT was higher than in TP of Ko and Ac, but Sa showed the opposite result. The temporal changes of TP and ECT concentrations in leachates followed a similar trend, with an initial increase followed by a decrease. ECT dynamics in Ko and Ac leachates correlated with their TP concentrations, while in Sa leachate, the peak ECT occurred 72 h later than its TP peak. The leachate ECT concentrations were highest in Ac, followed by Ko, and significantly lower in Sa. The peak TP and ECT proportions in leachates accounted for 9.2–23.9% and 7.7–9.4% of the total decreases in foliar TP and ECT, respectively. Conclusion During the leaching process, tannins’ fate was species-specific, while the dynamics were almost similar.

Mangroves are important coastal wetlands along tropical and subtropical regions. Pneumatophore, a kind of aerial root, is among the prominent components of a mangrove ecosystem, which provides microhabitats for a range of prokaryotic (bacteria and cyanobacteria) microbial assemblages, whose role in the maintenance of mangrove ecology often remains neglected. Very few studies are available on pneumatophore-associated prokaryotic microorganisms (PAPMs). The majority of them are related to the microscopic identification of cyanobacteria, with very limited research on the bacterial population, even though they demand more attention. Also, very scarce information is available on biotic and abiotic factors shaping the PAPMs. The objective of this review is to highlight the structural and functional importance of prokaryotic organisms associated with pneumatophores. This review begins with a brief introduction of what mangrove pneumatophores are, then focuses on the PAPMs, accentuating the breadth and depth of information gained from previous research. We further discuss how a combination of a traditional cultivable approach and a newly developed omics approach can be efficaciously employed to untangle PAPMs. This review provides updated information on PAPMs, which will intensify the visibility and necessity of pneumatophore-associated microbial community research.

The current trend in distributed electric aircraft propulsion systems is to utilize the DC bus system at higher voltage levels than conventional aircraft systems. With Boeing and Airbus utilizing the +/−270 V bipolar DC bus system, the research on high-voltage systems is increasing gradually, with voltage levels ranging from 1 to 10 kV systems or +/−0.5 to +/−5 kV DC bus systems. These voltage levels present considerable challenges to the distributed electric aircraft propulsion systems. In addition to partial discharge effects, there are other challenges, particularly the challenge associated with effectively limiting short-circuit fault currents due to the low cable impedance of the distribution system. The cable impedance is a significant factor that determines the fault current during fault conditions. Due to the low impedance, there is a sharp increase in fault current, necessitating an enhanced protection strategy, which ensures that the system is adequately protected. This paper introduces a coordinated protection strategy specifically designed for distributed electric aircraft propulsion systems to mitigate or prevent short-circuit faults. The proposed algorithm utilizes an I2t-based strategy and the current-limiting-based strategy to protect the system from short-circuit faults and overload conditions. Redundant backup protection is also included in the algorithm in case the circuit breaker fails to operate.

Power electronics converters can be applied as emulators to mimic different grid components used for system behavior analyses and control validation. Synchronous generators (SGs) are the major sources of electric grids. Converter-based SG emulators have been developed for system stability analysis, fault analysis, and frequency support. However, existing SG emulators have not considered the impacts of load unbalance, which is a common phenomenon in distribution grids and will lead to system-level issues. In this article, a SG emulator considering an actual SG's negative sequence (NS) performance is developed for system analyses under unbalanced load conditions. With different simplifications, a SG can have different orders of electrical models. By deriving the NS performances of different SG electrical models, an appropriate SG electrical model in unbalanced load conditions is selected. Then a novel control diagram is proposed to ensure that the NS performances of the selected model can be fully realized. The derived NS models and the proposed control diagram are verified through simulation first and then validated with a converter-based hardware testbed.

Mangrove wetlands are vulnerable coastal ecosystems that provide critical habitats for aquatic life. Tai O is a popular tourist village on Lantau Island, Hong Kong, which is surrounded by mangrove wetlands with rich biodiversity; and this village is also famous for its traditional stilt houses. However, the untreated municipal sewage from some stilt houses is directly discharged into nearby tidal channels, potentially threatening health of the adjacent mangrove wetlands. In order to evaluate the anthropogenic impact on these wetlands and identify the potential sources of their pollution, this study aimed to evaluate spatial (at the sampling points) and temporal (during weekdays and weekends) differences in the quality of their tidal water, and examine relationships between the water quality and the density of the stilt houses. The results indicated that the water quality was worse during weekends. The ammonia concentrations in most samples exceeded the limits of the Hong Kong Water Quality Objectives, China’s Sea Water Quality Standards, and even the U.S. EPA criterion for fish reproduction. This high ammonia input could potentially adversely affect the mangrove ecosystem, underscoring the need for further comprehensive studies. Moreover, some of the weekend water samples had lower dissolved oxygen levels and were polluted by phosphate. Our Principal Component Analysis revealed that water quality was correlated with stilt house density, suggesting that anthropogenic inputs of untreated sewage was the major source of pollution. These findings highlight that nutrients released from human activities, particularly ammonia and phosphate, must be controlled for a better protection of mangrove wetland ecosystems.

Abstract In this paper, an H‐type electric/hybrid electric aircraft propulsion architecture is proposed to address the issues associated with the radial electric propulsion architecture. In a radial architecture, a fault on the main bus or failure of the generator leads to shut down of all the propulsion motors in that channel, thus increasing the burden on the remaining motors to maintain the power required by the aeroplane. As a result, it is necessary to oversize the motors for the purpose of compensating for the loss of other motors. To mitigate these issues, a new H‐type architecture is introduced to isolate the particular faulty section while still maintaining power flow to the remaining healthy motors. The proposed architecture minimises the oversizing of various components in the system as compared to radial propulsion architecture. The sizing of components and the amount of overall mass reduction is discussed by using the proposed architecture. Typhoon Hardware in the Loop platform is used to validate the performance of both the architectures for faults at different locations, and the results are presented.

The impedance-based stability criteria are widely adopted for small-signal stability analysis of power systems. Among them, the determinant-based multi-input multi-output (MIMO) Nyquist criterion is particularly attractive since it simplifies the stability determination process without calculating the eigenvalues of MIMO systems. However, it is found in this letter that the determinant-based Nyquist criterion can potentially result in incorrect stability analysis results with pure inductance models in the MIMO models of the power network. This letter illustrates the issue and its root cause through mathematical derivation and numerical analysis. Then, the issue is demonstrated through an example system, and the corresponding solutions are provided as well.

This paper comprehensively analyzes desaturation (desat) protection for high voltage (>3.3 kV) silicon carbide (SiC) MOSFETs and especially how to build in noise immunity under high dv/dt. This study establishes a solid foundation for understanding the trade-offs between noise immunity and response speed of desat protection. Two implementations of the desat protection for high voltage SiC MOSFETs are examined, including desat protection based on discrete components and desat protection realized with a gate driver integrated circuit (IC). Both positive dv/dt and negative dv/dt are investigated. Analysis results show that the high dv/dt with long duration caused by high voltage SiC MOSFETs’ switching results in strong noise interference in the desat protection circuitry. The impact of numerous influencing factors is investigated analytically, such as parasitic capacitances, parasitic inductance, damping resistance, and clamping impedance. Under high positive dv/dt, extremely small parasitic capacitances (dv/dt is also derived quantitatively to guide the noise immunity improvement. The noise immunity analysis results and noise immunity improvement methods are validated with simulation and experimental results obtained from a phase leg based on 10 kV/20 A SiC MOSFETs.

With the increasing penetration of inverter-based resources (IBRs) and the standing down of synchronous generator-based resources (SGBRs), some IBRs, at least, need to provide grid support functions commonly provided by SGBRs. IBRs usually have a much smaller overcurrent capability than SGBRs, which can result in weak grid strength and corresponding issues on grid transient voltage support, system protection, and black start. This paper aims at addressing the low overcurrent capability issue of IBRs from the source side by combining an IBR with a co-located synchronous condenser (SC). Dubbed grid strengthening IBR (GSI), the proposed setup in grid forming mode uses the SC to regulate the terminal voltage and the IBR to regulate the frequency. The proposed GSI is evaluated through its comparison with an SGBR in the single-unit operation considering different grid faults, multi-unit operation, and transient stability performance. It is verified that the GSI can provide an overcurrent and maintain the terminal voltage comparable to or even slightly better than the SGBR during grid faults. The GSI does not have any transient stability issues; even after a long fault period, it can reestablish the system synchronism. The GSI can help the penetration of the IBRs in the system, as the system operation and the system loads will be largely unaffected, even during transients.

The dynamic boundary concept enables more flexible and efficient operation of microgrids with distributed energy resources (DER) that are intermittent in nature. As the integration of renewables continues to accelerate, an adaptive power management module that enables dynamic boundary operations in microgrids with an increasing number of source locations is essential for the fast and low-cost deployment of microgrid controllers. The power management module introduced in this paper is capable of handling the increased complexity in topological variations and transitions stemming from dynamic boundaries and multiple source locations. This includes real-time operation of multiple islands with dynamic boundaries, initiation of topological transitions (merging and separation of islands), and automatic source coordination for power sharing and frequency regulation. All functions in the power management module are designed to be automatically adaptable to arbitrary microgrids with non-meshed topologies so that the deployment of the controller at new microgrid sites can be expedited with a reduced cost. The module has been implemented on NI’s CompactRIO system as an essential part of an MG controller and tested on a converter-based hardware testbed (HTB). Testing results validated the effectiveness of the algorithms under various operating conditions.

A new species, Belbolla mangrove sp. nov., isolated from the mangrove wetlands of Fujian and Zhejiang Provinces in China, is described and illustrated. Belbolla mangrove sp. nov. is characterized by a pharynx with four bulbs, a small gubernaculum with a short dorsocaudal apophysis, four weakly developed precloacal supplements, a conico-cylindrical tail with a terminal spinneret, and the absence of terminal setae. This new species differs from B. vietnamica by the absence of ocelli and the blunt and rounded proximal ends of the spicules. The 18S rDNA GenBank accession numbers of B. mangrove sp. nov. are provided.

Kandelia obovata (S., L.) Yong and Sonneratia caseolaris (L.) Engl. are two dominant mangrove species in the subtropical coastlines of the Pearl River Estuary, China. The main aim of this study was to investigate the specific causes of K. obovata mortality versus S. caseolaris vitality on the west coast of Bao’an, Shenzhen, China and to propose sustainable management strategies for mangrove protection and future ecological planting restoration. Results showed that although both mangroves possessed simple and unstable community structures, S. caseolaris had a more tenacious vitality than the native species K. obovata, indicating that the former possesses stronger adaptability under adversity conditions. Moreover, the salinity of the seawater collection point 5 from the K. obovata plot was found to be lower than that of seawater collection point 1–3 from the S. caseolaris sample plots, indicating that no hydrologic connectivity existed in the K. obovata plots. In addition, the location of the drain outlet (seawater collection point 8) might be another potential risk factor for the dead of near K. obovata forests, implying that they were badly affected by poor oxygen and serious inorganic pollution, such as ammonium nitrogen, total phosphorus, and other inorganic substances. Depending on local circumstances, we should consider strengthening infrastructure construction to activate hydrological connectivity, reinforcing the stability of man-made mangrove communities, and controlling the pollution sources for sustainable mangrove protection and management on the western coast of Bao’an, Shenzhen, China.

A variable speed drive (VSD) based induction motor power emulator is presented in this paper, which is intended to be used in a real-time multi-converter-based hardware testbed (HTB) system. The presented HTB load emulator can accurately reflect the dynamic performance of a VSD-based load with multiple control algorithms without requiring significant computational resources and simulation time. Therefore, the developed VSD load emulator can not only mimic VSD-driven motor load performance, but also can be flexibly integrated into electric power grid emulators or simulators, which enable more detailed power grid analyses by providing a more accurate model for this particular type of load. This paper discusses the specification of the developed VSD-based load emulator, including multiple control schemes, and the physical realization in a power grid emulator. Finally, the accuracy of the VSD load emulator is demonstrated with experimental results.

Industrial motor systems make up a quarter of all electric sales in the United States. Variable speed drives (VSDs) can provide energy efficiency savings to the customer by regulating motor speed based on specific and varying needs. In addition to the benefits provided to the customer, VSDs can provide support to the grid through ancillary services. The Center for Ultra-Wide-Area Resilient Electric Energy Transmission Networks (CURENT) developed a power electronics converter-based grid emulator to allow testing of various power system architectures and demonstration of key technologies in monitoring, control, actuation, and visualization. This paper proposes using an active front-end VSD's connected motor load to provide frequency regulation to a large scale power grid. Each part of the emulator is described including motor and power electronics model and control. The proposed frequency regulation is implemented in VSDs and modeled in both a transmission system in EMTDC/PSCAD and verified on CURENT's hardware testbed.

Planned islanding is one of the fundamental functions of microgrid (MG) controllers. However, existing planned islanding functions cannot be directly utilized in MGs that have the capability to have both dynamic boundary and multiple sub-MGs. To optimize the smart switch operation and distributed energy resource (DER) output power, a planned islanding algorithm is designed to minimize the battery energy storage systems’ power difference before and after a planned islanding. To verify the performance of the proposed algorithm, a hardware-in-the-loop (HIL) test has been conducted by implementing the algorithm in a general purpose MG controller system. The results demonstrate that the difference in active power before and after the planned islanding decreases significantly with the proposed algorithm.

Abstract Academic research on dinoflagellate, the primary causative agent of harmful algal blooms (HABs), is often hindered by the coexistence with bacteria in laboratory cultures. The development of axenic dinoflagellate cultures is challenging and no universally accepted method suit for different algal species. In this study, we demonstrated a promising approach combined density gradient centrifugation, antibiotic treatment, and serial dilution to generate axenic cultures of Karenia mikimotoi (KMHK). Density gradient centrifugation and antibiotic treatments reduced the bacterial population from 5.79 ± 0.22 log10 CFU/mL to 1.13 ± 0.07 log10 CFU/mL. The treated KMHK cells were rendered axenic through serial dilution, and algal cells in different dilutions with the absence of unculturable bacteria were isolated. Axenicity was verified through bacterial (16S) and fungal internal transcribed spacer (ITS) sequencing and DAPI epifluorescence microscopy. Axenic KMHK culture regrew from 1000 to 9408 cells/mL in 7 days, comparable with a normal culture. The established methodology was validated with other dinoflagellate, Alexandrium tamarense (AT6) and successfully obtained the axenic culture. The axenic status of both cultures was maintained more than 30 generations without antibiotics. This efficient, straightforward and inexpensive approach suits for both armored and unarmored dinoflagellate species.

In contrast with conventional microgrids (MGs) with fixed boundaries, a smart and flexible MG with dynamic boundary is introduced in this paper. Such a MG can dynamically change its boundary by picking up or shedding load sections of a distribution feeder depending on its available power, leading to more flexible operation, better utilization of renewables, smaller size of energy storage system, higher reliability, and lower cost. To achieve a flexible MG, the main challenges in MG design are addressed, including recloser placement, MG asset sizing considering resilience, system grounding design, and protection system design. Meanwhile, a hierarchical structure is employed to design and implement the MG controller. On top of the functions defined in IEEE 2030.7-2018, a few new functions, e.g., online topology identification and PQ balance, are added, while the planned/unplanned islanding and reconnection functions are enhanced. The controller is implemented on a CompactRIO, a general-purpose hardware platform provided by National Instruments (NI), and tested on a controller hardware-in-the-loop setup based on an OPAL-RT real-time simulator and a reconfigurable power electronic converter-based hardware testbed. The test results have validated the performance of the developed controllers. Such a flexible MG and its controller have been deployed at a municipal utility, and part of the controller’s functions have been tested on-site.

Abstract Background Marine medaka is among the most popular models of fish species for ecotoxicology and environmental research and proteomic studies are useful tools for understanding the molecular responses of medaka upon exposure to different environmental stressors. The preparation of high-quality protein samples is the key to producing high-quality two-dimensional gel electrophoresis (2-DE) results for proteomic analysis. In recent years, Trizol-based protein extraction has been gaining popularity because of its promising performance in producing high-quality 2-DE as well as the convenience of the method. Methods Three Trizol-based approaches (Trizol method, Aliquot Trizol method and Trizol method with a commercial clean-up kit) were used to extract proteins from a marine medaka sample and 2-DE profiles were produced. Quality of the 2-DE profiles and effectiveness of the extraction methods were evaluated. For comparison, two common protein extraction methods (lysis buffer method and trichloroacetic acid (TCA)/acetone precipitation extraction) were also applied in parallel to Trizol-based approaches. Results Any of the three Trizol-based approaches produced a high-quality 2-DE profile of marine medaka compared with both lysis buffer method and TCA/acetone precipitation extraction. In addition, Trizol method with a commercial clean-up kit produced the best 2-DE profile in terms of background clarity, number of spots and resolution of proteins. Conclusions Trizol-based approaches offered better choices than traditional protein extraction methods for 2-DE analysis of marine medaka. The modified version of Trizol method with a commercial clean-up kit was shown to produce the best 2-DE profile.

Novel power system control and new utility devices need to be tested before their actual deployment to the power grid. To assist with such a testing need, real-time digital emulators such as RTDS and Opal-RT can be used to connect to the physical world and form a hardware in the loop (HIL) emulation. However, due to the limitations of today’s computational resources, the accuracy and fidelity suffer from different levels of model reductions in purely digital simulations. CURENT has developed a reconfigurable electric grid hardware testbed (HTB) to overcome the limitations of digital emulators. The HTB has been used to develop measurement, control, modeling, and actuation techniques for a national grid with a high penetration of renewables. The power electronic-based system includes emulators for synchronous generators; photovoltaics with grid-interfacing inverter; wind turbines; induction motor loads, ZIP loads, power electronic loads; batteries; ac and dc transmission lines; short circuit faults and grid relay protection; and a multiterminal HVDC overlay including power electronics interfaces. The system contains real elements of power flow, measurement, communication, protection, and control that mimic what would be seen in an actual electric grid. This paper presents an overview of the HTB and several scenarios that have been run to determine control and actions needed for the future power grid.

Some strains of the dinoflagellate species Prorocentrum hoffmannianum show contrasting ability to produce diarrhetic shellfish poisoning (DSP) toxins. We previously compared the okadaic acid (OA) production level between a highly toxic strain (CCMP2804) and a non-toxic strain (CCMP683) of P. hoffmannianum and revealed that the cellular concentration of OA in CCMP2804 would increase significantly under the depletion of phosphate. To understand the molecular mechanisms, here, we compared and analyzed the proteome changes of both strains growing under normal condition and at phosphate depletion using two-dimensional gel electrophoresis (2-DE). There were 41 and 33 differential protein spots observed under normal condition and phosphate depletion, respectively, of which most were upregulated in CCMP2804 and 22 were common to both conditions. Due to the lack of matched peptide mass fingerprints in the database, de novo peptide sequencing was applied to identify the differentially expressed proteins. Of those upregulated spots in CCMP2804, nearly 60% were identified as peridinin-chlorophyll a-binding protein (PCP), an important light-harvesting protein for photosynthesis in dinoflagellates. We postulated that the high expression of PCP encourages the production of DSP toxins by enhancing the yields of raw materials such as acetate, glycolate and glycine. Other possible mechanisms of toxicity related to PCP might be through triggering the transcription of non-ribosomal peptide synthetase/polyketide synthase genes and the transportation of dinophysistoxin-4 from chloroplast to vacuoles.

Karenia mikimotoi is one of the most damaging ichthyotoxic dinoflagellate species commonly found in China. However, its growth and ichthyotoxicity responses to salinity changes are still largely unknown. In this study, the growth and ichthyotoxicity of three K. mikimotoi strains, Hong Kong strain KMHK, Japanese strain NIES2411 and New Zealand strain CAWD133, under different salinities (25 to 35 ppt), initial algal densities (5 to 40 thousand cells) and growth phases were investigated. Results indicated that the optimum salinity for all three strains was 30 ppt. The Japanese strain achieved the highest maximum cell densities (cells mL−1) and the New Zealand strain achieved the highest specific growth rate. The Hong Kong and New Zealand strains could not tolerate the low salinity at 25 ppt and the algal cells burst after 3 days of exposure. The average cell widths of all three algal strains in 35 ppt salinity were significantly larger than that in 30 ppt. The acute toxicity test performed on Oncorhynchus mykiss gill cell line RTgill-W1 revealed that the median lethal times for KMHK and NIES2411 were 66.9 and 31.3 min, respectively, and their ichthyotoxicity was significantly affected by algal cell density and growth phase. Nevertheless, CAWD133 did not pose any ichthyotoxicity. The gill cell viability levels at 30 min were reduced from 96 to 61% and 95 to 39% for KMHK and NIES2411, respectively, when the algal cell density increased from 5 × 103 to 4 × 104 algal cells mL−1. Both KMHK and NIES2411 at stationary phase also had higher toxicity than at log phase, with a 27% reduction of gill cell viability, and exerted higher toxicity to the gill cells under extremely low (28 ppt) or high (35 ppt) salinity. These findings demonstrated that the growth–ichthyotoxicity response of Karenia mikimotoi to salinity was not only strain-specific but also depended on its density and growth phase. Study on the effects of salinity on the growth and toxicity of K. mikimotoi is greatly limited. Results from the present study provide valuable insight on the growth and toxicity of different K. mikimotoi strains, which is important in understanding their occurrence of algal bloom and fish-killing action.

Biosorption is an effective method for removing heavy metal ions from wastewater. In the current study, the biosorption capacity of a microalgae Prorocentrum triestinum strain AD1 was investigated for cadmium removal. The efficient biomass concentration was found to be 5 g/L. Based on the Langmuir adsorption model, the maximum adsorption capacity (qmax) value of cadmium removal was found to be 0.0196 mmol/g. The investigation results of the AD1 biosorption kinetics showed that the effective contact time on biosorption was 3 h, and the adsorption kinetics fitted well with the pseudo-second-order model. The optimum pH of biosorption was found to be 5. On the other hand, HCl could act as an efficient desorbent for cadmium recovery from AD1, with an optimum concentration of 0.01 M. These results suggest that the biomass of P. triestinum has great potential for the removal of cadmium from wastewater as an efficient biosorbent.

Nowadays, citizen science has become increasingly popular, especially in Western countries. In Hong Kong, citizen science projects are mostly used for public education, while utilizing citizen scientists in published scientific research is very rare. On the other hand, with the increasing threats to global water security, Hong Kong requires new adaptation and strategy in facing the impairment of local freshwater systems. However, unfortunately, the number of full-scale urban river research appears to be declining. In this regard, citizen science can offer an alternative option as one of the new integrated water management strategies in Hong Kong. In this study, the water quality of seven rivers and streams in Hong Kong was studied monthly for two years by a group of citizen scientists. The main goal is to examine the reliability of data collected by citizen scientists by comparing it with the official data from the Environmental Protection Department of Hong Kong (EPD). Results show that the water temperature and conductivity data acquired by the citizen scientists were highly comparable to the official data. Also, moderate to strong correlations in water pH, turbidity, and dissolved oxygen levels were found between citizen scientists and official data. Since the citizen science data remained as high as 70% of relevance to the official data, we believe that this may serve as a supplement to the lacking official or professional water quality monitoring data in Hong Kong. Even though the use of volunteer data in water quality monitoring unavoidably exists with errors and bias, this study demonstrates a successful outcome of utilizing citizen science programme in urban river monitoring in Hong Kong.

Karenia mikimotoi is a well-known harmful algal bloom species. Blooms of this dinoflagellate have become a serious threat to marine life, including fish, shellfish, and zooplanktons and are usually associated with massive fish death. Despite the discovery of several toxins such as gymnocins and gymnodimines in K. mikimotoi, the mechanisms underlying the ichthyotoxicity of this species remain unclear, and molecular studies on this topic have never been reported. The present study investigates the fish-killing mechanisms of K. mikimotoi through comparative proteomic analysis. Marine medaka, a model fish organism, was exposed to K. mikimotoi for a three-part time period (LT25, LT50 and LT90). Proteins extracted from the whole fish were separated by using two-dimensional gel electrophoresis, and differentially expressed proteins were identified with reference to an untreated control. The change in fish proteomes over the time-course of exposure were analyzed. A total of 35 differential protein spots covering 19 different proteins were identified, of which most began to show significant change in expression levels at the earliest stage of intoxication. Among the 19 identified proteins, some are closely related to the oxidative stress responses, energy metabolism, and muscle contraction. We propose that oxidative stress-mediated muscle damage might explain the symptoms developed during the ichthyotoxicity test, such as gasping for breath, loss of balance, and body twitching. Our findings lay the foundations for more in-depth studies of the mechanisms of K. mikimotoi’s ichthyotoxicity.

Paralytic shellfish toxins (PSTs) contamination of seafood has become a growing global problem. However, the molecular response of bivalves, some of the most popular seafoods, to PSP toxins has seldom been reported and the underlying molecular mechanisms of the interactions between Meretrix meretrix bivalves and PSTs-producing dinoflagellates are scarcely known. This study compared the protein expression profiles between PSP toxin-contaminated and non-PSP toxin contaminated M. meretrix, determined proteome responses and identified potential biomarkers based on feeding experiments. Results showed that the content of total PSP toxins in contaminated bivalves was 40.63 ± 4.08 μg saxitoxin (STX) equivalents per gram, with 95.3% in hepatopancreas, followed by gill (1.82%) and foot (1.79%). According to two-dimensional gel electrophoresis (2-DE), 15 differentially expressed proteins (at least 2-fold difference) between the hepatopancreas of bivalves with and without PSP toxins were detected. Eight of them were successfully identified by MALDI-TOF MS. These were catalase, protein ultraspiracle homolog, G2 and S phase-expression protein, paramyosin, Mn-superoxide dismutase, response regulator receiver domain-containing protein, sarcoplasmic calcium-binding protein and major facilitator superfamily transporters. The differences in the expression levels of the last three proteins involving in cell signaling, structure and membrane transport were 4.2, 5.3 and 4.9-fold, respectively. These proteins could be further developed as potential biomarkers. The other two up-regulated proteins, Mn-superoxide dismutase and catalase, were involved in cell defence mechanisms against oxidative stress, suggesting PSP toxin acts as xenobiotics and poses oxidative stress in bivalves. This study gives insights into the response of bivalves to PSP toxin-producing dinoflagellate at the proteomic level and the potential of using 2-DE to develop specific protein markers in bivalves.

Research on high voltage (HV) silicon carbide (SiC) power semiconductor devices has attracted much attention in recent years. This paper overviews the development and status of HV SiC devices. Meanwhile, benefits of HV SiC devices are presented. The technologies and challenges for HV SiC device application in converter design are discussed. The state-of-the-art applications of HV SiC devices are also reviewed.

The design, implementation, and testing of a control system for a flexible microgrid (MG) is presented in this study. The MG controllers can be implemented in a real-world MG with multiple smart switches, photovoltaic panel system, and battery energy storage systems (BESSs). With the benefits from smart switches, the MG has unique characteristics such as dynamic boundary and flexible point of interconnection (POI) concepts. To control such a unique MG and realise the dynamic boundary, an MG central controller and two types of local controllers are implemented. Compared to the MG with fixed boundary, the MG with dynamic boundary can have smaller BESS capacity, better utilisation of renewable energy, and multiple POI options. Also, compared with IEEE Std 2030.7–2017, the topology identification and active and reactive power balance functions are newly designed to realise the dynamic boundary concept. The planned islanding and reconnection functions are modified to realise the flexible POI concept. These functions are introduced including the software architecture, cooperation, and interaction among them. Finally, a hardware-in-the-loop testing platform based on the Opal-RT real-time simulator is set up to verify the performance, realisation of the dynamic boundary, and flexible POI concepts with four comprehensive test scenarios.

Hydroponic produce is gaining popularity due to its suitability for urban agriculture. The general public also considers that hydroponic produce is free from microbiological contamination. In this study, we compared the frequency and abundance of tetracycline-resistant and sulphadiazine-resistant bacteria and the minimal inhibitory concentration (MIC) of these isolates in conventional, organic, and hydroponic lettuce sold in retail. We also determined the frequency of samples carrying tetB, tetX, sul1, sul2, and int1 genes by PCR and further quantified the copy number of tetX, sul1, and int1 genes in samples positive for these genes using qPCR. As expected, the number of resistant bacteria and the MICs of these isolates were lowest in hydroponic lettuce and highest in organic lettuce. All tested resistant genes, except int1, were detected in samples of all three production methods, but no significant difference was observed between the three groups in the frequency of samples carrying the resistance genes examined or in their copy number. To the best of our knowledge, it is the first study directly reporting the existence of antibiotic-resistant bacteria and resistance genes in hydroponic vegetables sold in retail. The result highlights that the risk of antibiotic-resistant bacteria contamination in hydroponic produce should be further investigated.

To investigate the mechanism for the production of paralytic shellfish toxins (PST) in toxic dinoflagellates, with a 2D-gel based approach, we had made two sets of proteomic comparisons: (a) between a toxic Alexandrium catenella (AC-T) and a phylogenetically closely related non-toxic strain (AC-N), (b) between toxic AC-T grown in a medium with 10% normal amount of phosphate (AC-T-10%P) known to induce higher toxicity and AC-T grown in normal medium. We found that photosynthesis and energy production related proteins were up-regulated in AC-T when compared to AC-N. However, the same group of proteins was down-regulated in AC-T-10%P when compared to normal AC-T. Examining the relationship of photosynthesis and toxin content of AC-T upon continuous photoperiod experiment revealed that while growth and associated toxin content increased after 8 days of continuous light, toxin content maintained constant when cells were shifted from continuous light to continuous dark for 3 days. This emphasized the cruciality of light availability on toxin biosynthesis in AC-T, while another light-independent mechanism may be responsible for higher toxicity in AC-T-10%P compared to normal AC-T. Taken all together, it is believed that the interplay between “illumination”, “photosynthesis”, “phosphate availability”, and “toxin production” is much more complicated than what we had previously anticipated.

Microalgae-based biodiesel is increasingly recognized as an alternative to crop-based biodiesel. In this study, 10 local strains of dinoflagellates collected from Hong Kong waters, including a monoculture and field sample of Scrippsiella sp. isolated from an algal bloom, were evaluated against the performance of green alga Tetraselmis suecica. The specific growth rate, biomass production, lipid productivity, and fatty acid profile were investigated. The total lipid content of isolated strains ranged from 16.2% to 32.2% of the total dry biomass, whereas palmitic acid (C16:0) and docosahexaenoic acid (DHA, C22:6n3) were dominant in the fatty acid profile. Scrippsiella sp. has a high lipid productivity (47.3 mg/L/day) and fatty acid methyl esters (FAME) content (55.2–73 mg/g dry weight (dw)), which were comparable to that in green alga T. suecica. Further, monoculture and field sampled blooming Scrippsiella sp. showed no significant difference in most parameters, suggesting the possibility of harvesting a natural algal bloom population as a mitigation strategy to harmful algal bloom and to use as biodiesel feedstock. Overall, dinoflagellate species showed a slower growth rate (0.04–0.57 day−1) than most compared species (0.07–1.34 day−1), likely due to a large genome size and low chlorophyll to carbon ratio. Notably, most investigated dinoflagellates were not ideal for mass biodiesel production due to the low growth rate and lipid productivity. However, a high level of polyunsaturated fatty acids (PUFA) in dinoflagellates are prospective for further studies in other biotechnological applications. Though effectively harvesting algal blooming biomass can be complex, it can be further explored as a strategy for algal bloom mitigation and potentially creating values at the advantage of natural bloom when applying harvested biomass for biodiesel and bioactive compounds extraction.

Two-dimensional gel electrophoresis (2-DE) is a major element of conventional gel-based proteomics, which resolves complex protein mixtures. Protein extraction with the removal of interfering substances from the sample remains the key to producing high-quality 2-DE profiles. Marine dinoflagellates contain large endogenous amounts of salts, nucleic acids, polysaccharides, phenolic compounds, pigments, and other interfering compounds. These substances are detrimental to the quality of gel images. Protein preparation using TRIzol reagent is a promising method for producing high-quality 2-DE profiles for dinoflagellate samples. In addition to its remarkable performance, the TRIzol method’s several advantages have made it a popular and widely used method in the field of 2-DE sample preparation. Nonetheless, the quality of 2-DE of samples from certain dinoflagellate species is not as high as previously reported when the same TRIzol protocol is applied. Therefore, modifications to the original TRIzol method are required to remove interfering substances from those challenging dinoflagellate samples. In this study, the original TRIzol method and four modified methods, namely the aliquot TRIzol method, re-TRIzol method, TRIzol method with a commercial clean-up kit, and TRIzol method with trichloroacetic acid/acetone precipitation, were compared. Performance of these five methods in terms of protein yield, background signal, and resolution and number of protein spots was investigated on samples from two benthic Prorocentrum species: P. lima and P. hoffmannianum. Our results demonstrated that high-quality 2-DE could be achieved from P. lima samples prepared using both the original TRIzol method and the TRIzol method with a commercial clean-up kit. However, the original TRIzol method failed to produce high-quality 2-DE profiles for P. hoffmannianum samples. Among the four modified TRIzol methods, only the TRIzol method with a commercial clean-up kit could yield substantially improved high-quality 2-DE profiles for P. hoffmannianum samples. This combination of the conventional TRIzol method with a commercial clean-up kit potentially represents a promising protein extraction methodology for obtaining high-quality 2-DE profiles for difficult dinoflagellate samples.

Given that Chinese materia medica (CMM) is expensive and rare, people take tremendous risk to adulterate and falsify Cordyceps sinensis with counterfeit species with similar morphological features. It is thus essential to develop new methods to identify the authenticity of Cordyceps sinensis. It is hypothesized in this study that Cordyceps sinensis possesses certain protein biomarkers distinct from its counterfeits, which can be identified by proteomic technologies for authentication purposes. This is the first study that aims to optimize the conditions for extracting proteins from Cordyceps sinensis, a hybrid of fungal-animal CMM, and to compare the two-dimensional gel electrophoresis (2-DE) profiles between different Cordyceps species. Two different protein extraction buffer systems, namely, phenol/sodium dodecyl sulfate (SDS) buffer or lysis buffer, were evaluated, where the preparation using lysis buffer yielded better protein content. The results also showed that extraction with lysis buffer without pre- or post-washing of samples was the most effective protocol, with over 220% of protein yield and 819 protein spots detected on a 2-DE gel. Moreover, the results demonstrated that Cordyceps sinensis possesses protein biomarkers distinct from its counterfeits, and these biomarkers are not source- or origin-dependent, strongly supporting the feasibility of using identified biomarkers as indicators for authentication of Cordyceps species. The findings of this study warrant further investigations on the structural identification of protein biomarkers of Cordyceps species.

Epstein-Barr virus (EBV) and related lymphocryptoviruses (LCV) from non-human primates infect B cells, transform their growth to facilitate life-long viral persistence in the host, and contribute to B cell oncogenesis. Co-evolution of LCV with their primate hosts has led to species-specificity so that LCVs preferentially immortalize B cells from their natural host in vitro. We investigated whether the master regulator of transcription, EBV nuclear antigen 2 (EBNA2), is involved in LCV species-specificity. Using recombinant EBVs, we show that EBNA2 orthologues of LCV isolated from chimpanzees, baboons, cynomolgus or rhesus macaques cannot replace EBV EBNA2 for the immortalization of human B cells. Thus, LCV species-specificity is functionally linked to viral proteins expressed during latent, growth-transforming infection. In addition, we identified three independent domains within EBNA2 that act through species-specific mechanisms. Importantly, the EBNA2 orthologues and species-specific EBNA2 domains separate unique roles for EBNA2 in the initiation of B cell immortalization from those responsible for maintaining the immortalized state. Investigating LCV species-specificity provides a novel approach to identify critical steps underlying EBV-induced B cell growth transformation, persistent infection, and oncogenesis.

Puffer fish, Takifugu niphobles, collected from the Hong Kong coastal waters were screened for tetrodotoxin-producing bacteria. A Gram-negative, non-acid-fast, non-sporing and rod shaped bacterial strain (designated as gutB01) was isolated from the intestine of the puffer fish and was shown to produce tetrodotoxin (TTX). Based on the Microbial Identification (MIDI) and 16S-23S rDNA internal transcribed spacer (ITS) phylogenetic analysis, the strain was identified as Raoultella terrigena. The TTX production ability of the strain was confirmed by mouse bioassay, ELISA and mass spectrometry (MALDI-TOF). Our results reiterate that the TTX found in puffer fish was likely produced by the associated bacteria and TTX are widely produced amongst a diversity of bacterial species.

Although the emergence of gel-free approaches has greatly enhanced proteomic studies, two-dimensional gel electrophoresis (2-DE) remains one of the most widely used proteomic techniques for its high resolving power, relatively low cost, robustness, and high resolution. Preparation of high-quality protein samples remains the key in high-quality 2-DE for proteomic analysis. Samples with high endogenous levels of interfering molecules, such as salts, nucleic acids, lipids, and polysaccharides, would yield a low-quality 2-DE gel and hinder the analysis. Recently, a TRIzol-based protein extraction method has gained prominence and has attracted attention due to its promising performance in high-quality 2-DE. The authors evaluate the use of this approach for four valuable dried food products, namely two dried seafood products (abalone slices and whelk slices) and two traditional Chinese tonic foods (ganoderma and caterpillar fungus). The results indicate that 2-DE gels obtained through the TRIzol-based method are of high-quality and are comparable to those obtained through the trichloroacetic acid–acetone method in terms of spot number, spot intensity, and resolution. The TRIzol-based method is generally applicable to dried food samples and is simple and fast, which greatly streamlines the protein extraction procedure. Additionally, it enables the concurrent extraction and analysis of RNA, DNA, and protein from the same sample.

Acute Epstein-Barr virus (EBV) infection is the most common cause of Infectious Mononucleosis. Nearly all adult humans harbor life-long, persistent EBV infection which can lead to development of cancers including Hodgkin Lymphoma, Burkitt Lymphoma, nasopharyngeal carcinoma, gastric carcinoma, and lymphomas in immunosuppressed patients. BARF1 is an EBV replication-associated, secreted protein that blocks Colony Stimulating Factor 1 (CSF-1) signaling, an innate immunity pathway not targeted by any other virus species. To evaluate effects of BARF1 in acute and persistent infection, we mutated the BARF1 homologue in the EBV-related herpesvirus, or lymphocryptovirus (LCV), naturally infecting rhesus macaques to create a recombinant rhLCV incapable of blocking CSF-1 (ΔrhBARF1). Rhesus macaques orally challenged with ΔrhBARF1 had decreased viral load indicating that CSF-1 is important for acute virus infection. Surprisingly, ΔrhBARF1 was also associated with dramatically lower virus setpoints during persistent infection. Normal acute viral load and normal viral setpoints during persistent rhLCV infection could be restored by Simian/Human Immunodeficiency Virus-induced immunosuppression prior to oral inoculation with ΔrhBARF1 or infection of immunocompetent animals with a recombinant rhLCV where the rhBARF1 was repaired. These results indicate that BARF1 blockade of CSF-1 signaling is an important immune evasion strategy for efficient acute EBV infection and a significant determinant for virus setpoint during persistent EBV infection.

Diarrhetic shellfish poisoning (DSP) is a gastrointestinal disorder caused by the consumption of seafood contaminated with okadaic acid (OA) and dinophysistoxins (DTXs). OA and DTXs are potent inhibitors of protein phosphatases 2A, 1B, and 2B, which may promote cancer in the human digestive system. Their expression in dinoflagellates is strongly affected by nutritional and environmental factors. Studies have indicated that the level of these biotoxins is inversely associated with the growth of dinoflagellates at low concentrations of nitrogen or phosphorus, or at extreme temperature. However, the presence of leucine or glycerophosphate enhances both growth and cellular toxin level. Moreover, the presence of ammonia and incubation in continuous darkness do not favor the toxin production. Currently, studies on the mechanism of this biotoxin production are scant. Full genome sequencing of dinoflagellates is challenging because of the massive genomic size; however, current advanced molecular and omics technologies may provide valuable insight into the biotoxin production mechanism and novel research perspectives on microalgae. This review presents a comprehensive analysis on the effects of various nutritional and physical factors on the OA and DTX production in the DSP toxin-producing Prorocentrum spp. Moreover, the applications of the current molecular technologies in the study on the mechanism of DSP toxin production are discussed.

Viruses that naturally infect cells expressing both MHC I and MHC II molecules render themselves potentially visible to both CD8+ and CD4+ T cells through the de novo expression of viral antigens. Here we use one such pathogen, the B-lymphotropic Epstein-Barr virus (EBV), to examine the kinetics of these processes in the virally-infected cell, comparing newly synthesised polypeptides versus the mature protein pool as viral antigen sources for MHC I- and MHC II-restricted presentation. EBV-transformed B cell lines were established in which the expression of two cognate EBV antigens, EBNA1 and EBNA3B, could be induced and then completely suppressed by doxycycline-regulation. These cells were used as targets for CD8+ and CD4+ T cell clones to a range of EBNA1 and EBNA3B epitopes. For both antigens, when synthesis was induced, CD8 epitope display rose quickly to near maximum within 24 h, well before steady state levels of mature protein had been reached, whereas CD4 epitope presentation was delayed by 36-48 h and rose only slowly thereafter. When antigen expression was suppressed, despite the persistence of mature protein, CD8 epitope display fell rapidly at rates similar to that seen for the MHC I/epitope half-life in peptide pulse-chase experiments. By contrast, CD4 epitope display persisted for many days and, following peptide stripping, recovered well on cells in the absence of new antigen synthesis. We infer that, in virally-infected MHC I/II-positive cells, newly-synthesised polypeptides are the dominant source of antigen feeding the MHC I pathway, whereas the MHC II pathway is fed by the mature protein pool. Hence, newly-infected cells are rapidly visible only to the CD8 response; by contrast, latent infections, in which viral gene expression has been extinguished yet viral proteins persist, will remain visible to CD4+ T cells.

Harmful algal blooms (HABs) are a global environmental concern, causing significant economic losses in fisheries and posing risks to human health. Algicidal bacteria have been suggested as a potential solution to control HABs, but their algicidal efficacy is influenced by various factors. This study aimed to characterize a novel algicidal bacterium, Maribacter dokdonensis (P4), isolated from a Karenia mikimotoi (Hong Kong strain, KMHK) HAB and assess the impact of P4 and KMHK's doses, growth phase, and algicidal mode and the axenicity of KMHK on P4's algicidal effect. Our results demonstrated that the algicidal effect of P4 was dose‐dependent, with the highest efficacy at a dose of 25% v/v. The study also determined that P4's algicidal effect was indirect, with the P4 culture and the supernatant, but not the bacterial cells, showing significant effects. The algicidal efficacy was higher when both P4 and KMHK were in the stationary phase. Furthermore, the P4 culture at the log phase could effectively kill KMHK cells at the stationary phase, with higher algicidal efficacy in the bacterial culture than that of the supernatant alone. Interestingly, P4's algicidal efficacy was significantly higher when co‐culturing with xenic KMHK (~90% efficacy at day 1) than that with the axenic KMHK (~50% efficacy at day 1), suggesting the presence of other bacteria could regulate P4's algicidal effect. The bacterial strain P4 also exhibited remarkable algicidal efficacy on four other dinoflagellate species, particularly the armored species. These results provide valuable insights into the algicidal effect of M. dokdonensis on K. mikimotoi and on their interactions. [ABSTRACT FROM AUTHOR]