Bidirectional Transfer Research Articles

Live tracking metabolic networks and physiological responses within microbial assemblages at single-cell level.

Microbial interactions impact the functioning of both natural and engineered systems, yet our ability to directly monitor these highly dynamic and spatially resolved interactions in living cells is very limited. Here, we developed a synergistic approach coupling single-cell Raman microspectroscopy with 15N2 and 13CO2 stable isotope probing in a microfluidic culture system (RMCS-SIP) for live tracking of the occurrence, rate, and physiological shift of metabolic interactions in active microbial assemblages. Quantitative and robust Raman biomarkers specific for N2 and CO2 fixation in both model and bloom-forming diazotrophic cyanobacteria were established and cross-validated. By designing a prototype microfluidic chip allowing simultaneous microbial cultivation and single-cell Raman acquisition, we achieved temporal tracking of both intercellular (between heterocyst and vegetative cells of cyanobacteria) and interspecies N and C metabolite exchange (from diazotroph to heterotroph). Moreover, single-cell N and C fixation and bidirectional transfer rate in living cells were quantified via SIP-induced characteristic Raman shifts. Remarkably, RMCS captured physiological responses of metabolically active cells to nutrient stimuli through comprehensive metabolic profiling, providing multimodal information on the evolution of microbial interactions and functions under fluctuating conditions. This noninvasive RMCS-SIP is an advantageous approach for live-cell imaging and represents an important advancement in the single-cell microbiology field. This platform can be extended for real-time tracking of a wide range of microbial interactions with single-cell resolution and advances the understanding and manipulation of microbial interactions for societal benefit.

Reciprocal facilitation between mental and visuomotor rotations

Humans exhibit remarkably complex cognitive abilities and adaptive behavior in daily life. Cognitive operation in the "mental workspace," such as mentally rotating a piece of luggage to fit into fixed trunk space, helps us maintain and manipulate information on a moment-to-moment basis. Skill acquisition in the "sensorimotor workspace," such as learning a new mapping between the magnitude of new vehicle movement and wheel turn, allows us to adjust our behavior to changing environmental or internal demands to maintain appropriate motor performance. While this cognitive and sensorimotor synergy is at the root of adaptive behavior in the real world, their interplay has been understudied due to a divide-and-conquer approach. We evaluated whether a separate domain-specific or common domain-general operation drives mental and sensorimotor rotational transformations. We observed that participants improved the efficiency of mental rotation speed after the visuomotor rotation training, and their learning rate for visuomotor adaptation also improved after their mental rotation training. Such bidirectional transfer between two widely different tasks highlights the remarkable reciprocal plasticity and demonstrates a common transformation mechanism between two intertwined workspaces. Our findings urge the necessity of an explicitly integrated approach to enhance our understanding of the dynamic interdependence between cognitive and sensorimotor mechanisms.

Ultrafast Charge Separation Driven by Torsional Motion in Orthogonal Boron Dipyrromethene Dimer

In this work, the photoinduced charge separation (CS) via symmetry breaking in an orthogonal meso-β-linked boron dipyrromethene (BODIPY) dimer was investigated by polarized transient absorption spectroscopy. The time constant about 0.76 ps of the CS reaction determined in dimethyl sulfoxide is much faster than the solvation dynamics. The observed transient anisotropy of the BODIPY anion band implies that both hole and electron transfers occur with similar probabilities. The bidirectional charge transfer processes suggest that the locally excited state is weakly coupled to the polar solvent, and the solvation coupled excited-state structural relaxation within the BODIPY monomeric unit is rather limited. In combination with the electronic excitation analysis based on time-dependent density-functional theory calculations, we deduced that the CS in the orthogonal BODIPY dimer is enabled via the torsional motion associated with covalently connected BODIPY units, promoting the electronic coupling, and irrelevant to the dynamic solvent relaxation.

Incorporation of Blockchain Technology for Different Smart Grid Applications: Architecture, Prospects, and Challenges

Smart grid integrates computer, communication, and sensing technologies into existing power grid networks to achieve significant informatization-related advantages. It will provide communication between neighbors, localized management, bidirectional power transfer, and effective demand response. Smart grids (SG) replace conventional grids by integrating various operational measures, including smart automation appliances, smart meters, and renewable energy sources. Regarding energy management and resolving energy issues, SG is one of the most cutting-edge and potentially game-changing innovations. Even still, its complexity suggests that decentralization may provide significant gains. Because of its increasing digitization and interconnectedness, it is also vulnerable to cyber threats. Blockchain, in this sense, is a potential SG paradigm solution that provides several great benefits. Even though blockchains have been widely discussed to decentralize and strengthen smart grid cybersecurity, they have not yet been researched in depth from an application and architectural standpoint. Blockchain-enabled SG applications are the subject of an in-depth research investigation. Electric vehicles (EVs), home automation, energy management systems, etc., are only a few of the many examples that have prompted the proposal of blockchain designs for their respective use cases. Information communication network security is of paramount importance. However, this evolving system raises cybersecurity issues. This paper aims to guide researchers in the right manner so they may build blockchain-based, secure, distributed SG applications in the future. This article also summarizes cybersecurity threats pertaining to smart grids. It starts with a description of a blockchain followed by the blockchain infrastructure, challenges, and solutions for different smart grid applications. A look back at the tried-and-true methods of securing a power grid is offered, and then it discusses the newer and more complex cybersecurity threats to the smart grid. In addition, models of common cyberattacks are presented, and the methods of defense against them are examined.

Characterizing Current THD’s Dependency on Solar Irradiance and Supraharmonics Profiling for a Grid-Tied Photovoltaic Power Plant

The rapidly increasing distributed energy resources (DERs) in power systems are now getting interconnected to set community grid structures, where power quality will be a major concern. The grid-to-grid (G2G) bidirectional power transfer among the distribution microgrid will not be considered commercially feasible unless the upstream harmonics are under the limits. The aggregation of such harmonics, measured as total harmonic distortion (THD), is feared to be beyond tolerable limits with the progression of rooftop grid-tied PV-like installations. Hence, this THD needs to be characterized with DER generation end variables. In this work, the photovoltaic (PV) DERs’ dependency on environment variables such as irradiance was profiled in the context of generating and injecting harmonics into the grid. A mathematical model of a grid-tied three-phase PV DER was developed as part of this correlation characterization, matching the fundamental unit structure of a 1.4 MW solar canopy located on the Florida International University (FIU) Miami campus. To determine the qualitative association with produced THD patterns, the model was evaluated with various irradiance settings. A real-time digital simulation (RTDS) platform was used to verify it. Following this confirmation, sets of data from power quality meters at the point of common coupling and FIU field sensors were utilized to validate further the correlation model. The results showed that the grid current’s THD exhibited a high correlation with the irradiance profile and its variation over time. The early morning and late afternoon periods of the day, associated with a low irradiance, constantly had higher harmonics generated from the PV DER. The midday THD was rather rational with partial shadings, hence a geolocation-dependent factor. These findings were verified by an RTDS and validated by real field data. In quantifying the THD injected by a single DER at a high-frequency (2–150 kHz) supraharmonics (SH) level, a 3% peak increment in magnitude was observed from the high-fixed to the low-fixed irradiance profile. The correlation characteristics depicted that the hybrid microgrid suffered from a daytime-dependent harmonic insertion from the grid-tied DER. This is a global problem unless specific measures are taken to mitigate the harmonics. The electrically notorious higher-frequency SH was found to increase proportionally. The G2G power transfer can be limited because of the higher THD in the early morning and late afternoon, which will also worsen because the numbers of grid-tied PV DERs (i.e., rooftop solar and industrial solar) are likely to increase rapidly soon. The community grid structure can thus have a controlled harmonics filtration setup purposefully designed to address the findings of this work, which also fall within the scope of our future research.

Control Strategy for a Bidirectional Wireless Power Transfer System With Vehicle to Home Functionality

Control Strategy for a Bidirectional Wireless Power Transfer System With Vehicle to Home Functionality

Mechanism and applications of bidirectional extracellular electron transfer of Shewanella.

Electrochemically active microorganisms (EAMs) play an important role in the fields of environment and energy. Shewanella is the most common EAM. Research into Shewanella contributes to a deeper comprehension of EAMs and expands practical applications. In this review, the outward and inward extracellular electron transfer (EET) mechanisms of Shewanella are summarized and the roles of riboflavin in outward and inward EET are compared. Then, four methods for the enhancement of EET performance are discussed, focusing on riboflavin, intracellular reducing force, biofilm formation and substrate spectrum, respectively. Finally, the applications of Shewanella in the environment are classified, and the restrictions are discussed. Potential solutions and promising prospects for Shewanella are also provided.

Gd–Er interaction promotes NaGdF4:Yb, Er as a new candidate for high-power density applications

Efficient Gd–Er bidirectional energy transfer in NaGdF4:Yb, Er nanoparticles makes this upconversion system relevant for high-power density applications.

Red upconversion emission of Er<sup>3+</sup> enhanced by building NaErF<sub>4</sub>@ NaYbF<sub>4</sub>:2%Er<sup>3+</sup> core-shell structure

Building core-shell structures are widely used to enhance and regulate the luminescence properties of rare-earth-doped micro/nano materials. In this work, a variety of different NaErF<sub>4</sub> core-shell and core-shell-shell nanocrystals are successfully constructed based on high temperature co-precipitation method by epitaxial growth technology. The upconversion red emission intensities of Er<sup>3+</sup> ions in different core-shell structures are effectively enhanced by regulating their structures and doping ions. The experimental structures show that the constructed core-shell nanocrystals each have a hexagonal phase structure, and core-shell structure of about 40 nm. In the near infrared 980 nm laser excitation, the NaErF<sub>4</sub> core-shell nanocrystal shows a strong single-band red emission. And the single-band red emission intensity of Er<sup>3+</sup> ions is enhanced through constructing the NaErF<sub>4</sub>@NaYbF<sub>4</sub>:2%Er<sup>3+</sup> core-shell structure. The experimental results show that red emission intensity of Er<sup>3+</sup> ions is about 1.4 times higher than that of the NaErF<sub>4</sub>@NaYbF<sub>4</sub> core-shell structure by constructing the NaErF<sub>4</sub>@NaYbF<sub>4</sub>:2%Er<sup>3+</sup> core-shell structures under 980 nm excitation, and its red/green emission intensity ratio increases from 5.4 to 6.5. Meanwhile, when NaErF<sub>4</sub>@NaYbF<sub>4</sub>:2%Er<sup>3+</sup> core-shell structure recoats the NaYF<sub>4</sub> inert shell and is added with a small quantity of Tm<sup>3+</sup> ions, their red emission intensities of Er<sup>3+</sup> ions are 23.2 times and 40.3 times that of NaErF<sub>4</sub>@NaYbF<sub>4</sub> core-shell structures, and their red/green emission intensity ratios reach 7.5 and 10.2, respectively. The red emission enhancement of Er<sup>3+</sup> ions is mainly caused by bidirectional energy transfer process of high excitation energy of Yb<sup>3+</sup> ions and energy trapping center of Tm<sup>3+</sup> ions which effectively change the density of population of luminescent energy levels of Er<sup>3+</sup> ions. Furthermore, the coated NaYF<sub>4</sub> inert shell also effectively weakens the surface quenching effect of nanocrystals. The mechanisms of red enhancement in different core-shell structures are discussed based on the spectral properties, the process of interion energy transfer, and luminescence kinetics. The constructed NaErF<sub>4</sub>@NaYbF<sub>4</sub>:2%Er<sup>3+</sup>@NaYF<sub>4</sub> core-shell structures with high-efficiency red emission in this work have great potential applications in the fields of colorful anti-counterfeiting, display and biological imaging.

A systemic approach to the transformation of swiss railway stations: Mind the gap between the local, short-term and national, long-term worldviews

The continuing growth in passenger transport and the associated increase in CO2 emissions remain major challenges for our society. Shifting passenger transport to more sustainable modes of transportation contributes to addressing this challenge. Multimodal transportation hubs (MMTHs) coordinate and integrate different modes of transportation by improving transfers between them. In addition, MMTHs offer a high quality of stay with a wide range of services, as well as a compact, mixed-use urban development with a high density of uses around them. The transformation of railway stations and their environments into MMTHs is addressed in discussions of transit-oriented development (TOD) and the concept of “node and place.” However, there is a lack of a systemic approach that structures the problem involving the different worldviews of the actors. In addition, the necessary changes and measures are largely unknown. Based on the soft systems methodology (SSM), we conducted 20 SSM interviews and two SSM workshops (n = 10 each). Our results show that the problem can be structured into the three layers of “national long-term integrated optimization of the passenger transport sector and spatial development,” “local short-to medium-term planning and implementation,” and a “regional, bidirectional transfer by policy-making and planning.” The transfer layer between the national, long-term and local, short-term worldviews is key and must be strengthened. Furthermore, we present systemically desirable and culturally feasible measures for each layer to improve the current situation of the transformation—a national MMTH program, creating an overarching vision, a caretaker for local implementation to coordinate the interests of actors, and collaborative development of regional master plans and an explorative approach to ensure bidirectional exchanges between the national and local layers. Although the structuring of the problem and the measures were developed from a Swiss viewpoint, we expect that the results will also be useful for other decentralized states.

Coupling multifunctional catalytic active sites into metal carbide catalysts to promote the multipath bidirectional conversion of Li-S redox

Li-S batteries are hampered by sluggish liquidsolid redox and shuttle effects. Herein, a strategy of coupling multifunctional catalytic sites is proposed to fabricate bidirectional catalysts to promote multipath bidirectional Li-S redox conversion. By engineering Co or Zr dopants into Ni3C/C, the obtained Co0.30Ni2.70C/C and Zr0.30Ni2.70C/C electrocatalysts play different roles in polysulfide adsorption and multipath bidirectional conversion. During the discharging/charging process, due to limited electron transfer between the Co3+/Co2+ pair and polysulfides, Co sites themselves are catalytically inactive for the conversion of polysulfides and only act as promoters to improve the catalytic activity of Ni sites. In contrast, in addition to being promoters, Zr sites serve as electron acceptors and donors to catalyze bidirectional Li-S redox due to the flexible electron transfer between the Zr4+/Zr2+ pair and polysulfides. Such bidirectional electron transfer is accompanied by thiosulfate-mediated redox. Therefore, Zr doping not only accelerates the inherent solid (S8)-liquid (polysulfide)-solid (Li2S) conversion pathway but also propels the reversible thiosulfate-mediated conversion pathway. As a result, when the Zr0.30Ni2.70C/C nanosheets were used to modify the commercial PP separator, the Li-S batteries exhibit improved electrochemical performance (a decay of 0.0756 % over 200 cycles with a sulfur loading of 5.0 mgs cm−2).

Water transport through the inward combined carbon nanotube

The structure of the carbon nanotube affects water transport greatly. However, there is little understanding of water transport through the inward combined carbon nanotube. Molecular dynamics simulations are adopted to investigate the properties of water molecules through the inward combined carbon nanotube in this article. We find that water unidirectional transport efficiency increases in the inward combined carbon nanotube unless water molecules cannot pass through the inward combined carbon nanotube. The occupancy of water molecules, the bidirectional water transfer rate, the unidirectional water transfer rate, the velocity, and the order parameter of water molecules in the inward carbon nanotube are dependent on the structure of the inward combined carbon nanotube. Our results pave the way for understanding the inward combined structure effect on the transport of water molecules.

Modular Multilevel Matrix Converter as Solid State Transformer for Medium and High Voltage AC Substations

The use of power converters as solid state transformers is an attractive solution to modernize the power network, but this solution has not been fully addressed for MV and HV substations. This paper presents a customized and simple control for the Modular Multilevel Matrix Converter (M3C), specially conceived for its operation on synchronous ports, which is the case of AC substations. The control allows bidirectional power transfer, generation/absorption of reactive power and provisions of ancillary services. The converter is compared to the back-to-back Modular Multilevel Converter (B2B-MMC) where the key performance indicators to carry out the comparison are power efficiency, number of semiconductor devices, passive components required, footprint, voltage cell balance, fault blocking capability and stress of components. The simulation results show the features, performance and attractiveness of the M3C topology in a 33/11 kV, 16 MW substation under different operating conditions, including grid faults and dynamic operation. The M3C presents similar efficiency and performance than the B2B-MMC, but it uses fewer semiconductor devices, passive components and total cell capacitor energy than the B2B-MMC, reducing cost and footprint. The experimental results show the performance of the M3C under less ideal conditions including a substation transformer saturation and power step response.

Assisted Power Transfer for Voltage Balance of Bipolar DC MicroGrids Using Inactive Motor Drives

A voltage balancer remains a good solution of power transfer for bipolar dc grids, which, however, would increase the costs due to its requirement for additional hardware support. In this article, an auxiliary power transfer strategy is proposed by using the inactive motor drives affiliated with the bipolar dc grid. During idle periods of the motor drive, one inverter bridge arm is connected with the bipolar dc grid at their neutral points, allowing bidirectional power transfer between the upper and lower dc-bus sources. The proposed strategy share part of the voltage balancer's power transfer burden without requiring additional hardware and affecting the normal operations of the motor drive. In addition, its effectiveness is verified by experimental results on an interior permanent magnet synchronous motor drive, showing that the power flows among the upper and lower dc-bus power supplies are controlled effectively. Also, the active control of the dc-bus voltages could be achieved by modulation of the phase currents.

Application of Blockchain for Secure Data Transmission in Distributed State Estimation

The application of renewable energy sources in the power grid increases the necessity of tracking the system state, especially in smart grids, where there is a bidirectional transfer of data and power. The complexity of coupling between communication and the electrical infrastructure in a smart grid increases the risk of security breaches. Increasing the state estimation accuracy helps the smart grid operator efficiently manage the system. This article proposes an integration of distributed state estimation with a blockchain-designed communication platform. Additionally, the asynchronous data transmission, which is more likely to happen in the real world, is considered as the second task of this research. Finally, a detailed analysis of the blockchain-based application in distributed state estimation is provided. The numerical analysis shows that the proposed method meets real-world performance requirements and brings high security and reliability to the distributed state estimation process.

Kinetics of DNA strand transfer between polymerase and proofreading exonuclease active sites regulates error correction during high-fidelity replication

We show that T7 DNA polymerase (pol) and exonuclease (exo) domains contribute to selective error correction during DNA replication by regulating bidirectional strand transfer between the two active sites. To explore the kinetic basis for selective removal of mismatches, we used a fluorescent cytosine analog (1,3-diaza-2-oxophenoxazine) to monitor the kinetics of DNA transfer between the exo and pol sites. We globally fit stopped-flow fluorescence and base excision kinetic data and compared results obtained with ssDNA versus duplex DNA to resolve how DNA transfer governs exo specificity. We performed parallel studies using hydrolysis-resistant phosphorothioate oligonucleotides to monitor DNA transfer to the exo site without hydrolysis. ssDNA binds to the exo site at the diffusion limit (109M-1 s-1, Kd = 40 nM) followed by fast hydrolysis of the 3'-terminal nucleotide (>5000s-1). Analysis using duplex DNA with a 3'-terminal mismatch or a buried mismatch exposed a unique intermediate state between pol and exo active sites and revealed that transfer via the intermediate to the exo site is stimulated by free nucleoside triphosphates. Transfer from the exo site back to the pol site after cleavage is fast and efficient. We propose a model to explain why buried mismatches are removed faster than single 3'-terminal mismatches and thereby provide an additional opportunity for error correction. Our data provide the first comprehensive model to explain how DNA transfer from pol to exo active sites and back again after base excision allow efficient selective mismatch removal during DNA replication to improve fidelity by more than 1000-fold.

Dynamic wireless power transfer for real-time coordination of electrical vehicles between distributed energy resources and power grid

Electrical vehicle (EV), as an active participator in urban energy Internet (UEI), plays an indispensable role in the grid-EVs-distributed energy resource (DER) coordination. While the traditional wired charging mode cannot meet the need of flexible real-time interaction between grid and DERs, a mode featuring charging while moving which is realized by dynamic wireless power transfer (WPT) technology is proposed. A symmetrical WPT system with transmitter and receiver both constructed by identical bipolar pad (BPP) is proposed to realize a bidirectional power transfer, and a hybrid resonant tank is adopted to stabilize power transfer as well as provide reactive power compensation. The performance of the proposed WPT system is validated by simulation and experiment on a 6kW VNA prototype, where the DER is equivalent to a DC source. Power can be transferred from DER to the battery with an average power of 5.82kW and system efficiency higher than 86.3%. The proposed concept can be adopted in the construction of UEI to improve absorption rate of power generated by DERs, support power system operation and bring economic benefits to both power grid and EV owners.

Structure evolution and performance of poly (vinyl alcohol) fibers with controllable cross-section fabricated using a combination of melt-spinning and stretching

Profiled fibers are gained potential applications in the fields of both functional textiles and cements reinforcements. While the commercial Poly (vinyl alcohol) (PVA) fibers are generally produced by solution spinning, which is difficult to prepare profiled PVA fiber with controllable cross-section because of bidirectional mass transfer in coagulation bath. In this work, based on intermolecular complexation and plasticization, water was adopted to improve the thermal-processing of PVA, the special-shaped PVA fibers such as triangular, trilobal, cruciform and wavy cross-sections were prepared by melt-spinning. The crystallinity of profiled as-spun PVA fibers was lower than 32%, and their elongation at break was higher than 400%, resulting in good stretch-ability for hot-drawing. During the hot-drawing of profiled PVA fibers, the circular trend of the characteristic sections can be controlled, and the reduction in profile degree was lower than 9.4%. Hot-drawing improved the crystalline structure of PVA, and increased the crystallinity, orientation, tensile strength, and melting point of profiled fibers. When the draw ratio was 9, the tensile strength of triangular, cruciform, trilobal and wavy fibers were 585 MPa, 559 MPa, 481 MPa and 585 MPa, respectively, which proposed a new processing technology of special-shaped PVA fiber and enriched the kinds of special-shaped fibers.

Steering bi-directional charge transfer via non-conjugated insulating polymer

Exquisite tuning of spatial charge transfer and separation has been an enduringly core issue in heterogeneous photocatalysis. Nevertheless, precise modulation of directional charge transfer to the ideal catalytically active sites remains challenging owing to rapid recombination rate of photoinduced charge carriers and sluggish charge transfer kinetics. Herein, bi-directional spatially separated electron and hole transport channels were simultaneously constructed over transition metal chalcogenides (TMCs)-based heterostructures via an efficient and facile electrostatic self-assembly strategy. Tailor-made positively charged non-conjugated polymer of branched polyethyleneimine (BPEI) and negatively charged metal nanocrystals (NCs) building blocks were controllably anchored on the TMCs substrate. We found that electrons photoexcited over TMCs substrate can migrate spontaneously, smoothly and unidirectionally to the tightly integrated neighboring metal NCs, wherein metal NCs function as Schottky-type electron-trapping reservoirs and the ultra-thin intermediate BPEI layer serves as a directional hole transport mediator, thus synergistically contributing to the significantly enhanced charge separation and prolonged charge lifetime. Benefiting from these merits, such self-assembled TMC@BPEI/metal heterostructure exhibits the markedly enhanced photoreduction catalysis toward photocatalytic hydrogen generation and anaerobic selective reduction of nitroaromatics to amino derivatives under visible light irradiation. Our work would provide inspiring idea for fine modulation of charge separation and transfer toward solar-to-chemical energy conversion.

Lateral dynamics of a monopile partially embedded in layered saturated soil with radial disturbance

A bidirectional transfer matrix method is presented to investigate the impedances of a laterally loaded monopile partially embedded in layered saturated soil with radial disturbance. To characterize the radial variation of soil properties induced by construction excitations or cyclic lateral excitations, the radial transfer matrix of the saturated soil is developed to determine the horizontal resistance of soil to the pile shaft based on Biot's theory. Lateral, rocking and lateral-rocking coupled impedances at the head of the monopile are obtained by solving the differential equations for transverse vibration of the pile shaft based on the Timoshenko beam theory, combined with an axial transfer matrix to treat the layered property of soil along the partially embedded monopile. The proposed model is validated by comparing it with some existing results. The theoretical rigour and broad engineering applicability of the present model are highlighted by a series of parametric analyses for the influences of soil and pile properties on the impedances of the laterally loaded monopile.