Energy Conservation Mechanism Research Articles

Trans-spectral transfer of spatio-temporal optical Ferris wheel with nonlinear wave mixing

The trans-spectral manipulation of spatio-temporal structured light, characterized by dynamic inhomogeneous trajectories and a unique nature in the space–time domain, opens myriad possibilities for high-dimensional optical communication in the ultraviolet band. Here, we experimentally demonstrate the high-performance transfer of the spatio-temporal optical Ferris wheel beam from near-infrared to blue–violet wavelengths. Owing to the energy conservation and momentum conservation mechanism, the 420 nm output signal beam accurately retains the spatio-temporal characteristics of the 776 nm input probe optical Ferris wheel beam, facilitated by the 780 nm Gaussian pump beam. The identical multi-petal intensity profiles confirm the successful transfer of spatial characteristics from the input probe to the output signal beams. The fully synchronized rotation velocities and directions of the probe and signal beams demonstrate the precise transfer of temporal characteristics, achieving approximately 98% conversion accuracy. This work enables efficient information transfer across different wavelength bands and offers a promising approach for achieving high-dimensional quantum communication.

Comparison of energy conservation strategies for 5G NR RedCap service in industrial environment

The recently standardized reduced capability (RedCap) type of user equipment (UE) for 5G New Radio (NR) systems offers a useful option for energy-constrained devices. By utilizing a combination of discontinuous reception (DRX), wake-up signal (WUS), and radio resource management (RRM) relaxation functions, RedCap UE may provide excellent power efficiency for a large set of applications. In this study, we investigate power efficiency and battery lifetime for RedCap UEs for different types of applications and various combinations of energy conservation mechanisms. We utilize extended virtual reality (X-VR) and web browsing as applications of interest. To this aim, we develop a versatile mathematical framework representing the sought metrics as a function of time, accounting for specifics of millimeter wave (mmWave) propagation, micro- and macro-mobility of UEs, human body blockage, and type of application. Numerically, we show that higher micro- and macro-mobility speeds lead to worse power efficiency and the loss can be quite substantial amounting up to 30%. Antenna arrays with worse directivity show better performance in the presence of micro- and macro-mobilities when RRM Relaxation is utilized, with a difference between 15×15 and 4×4 arrays reaching 1.5 bit/J/KHz, which is approximately 40%. The energy conservation mechanisms produce no noticeable impact on the power efficiency and battery lifetime for rate-greedy applications such as X-VR. Low-data-rate applications with long pauses between transmission cycles, such as web browsing, may benefit from utilizing WUS and RRM Relaxation in addition to conventional DRX. However, their impact is rather small at a scale of 5%–10%.

Ionised AGN outflows in the Goldfish galaxy: The illuminating and interacting red quasar eFEDSJ091157.4+014327 at z ∼ 0.6

Context. Evolutionary models suggest that the initial growth phases of active galactic nuclei (AGN) and their central supermassive black holes (SMBHs) are dust-enshrouded and characterised by jet or wind outflows that should gradually clear the interstellar medium (ISM) in the host by heating and/or expelling the surrounding gas. eFEDSJ091157.4+014327 (z ∼ 0.6) was selected from X-ray samples of eROSITA (extended ROentgen Survey with an Imaging Telescope Array) for its characteristics: red colours, X-ray obscuration (NH = 2.7 × 1022 cm−2) and luminous (LX = 6.5 × 1044 erg s−1), similar to those expected in quasars with outflows. It hosts an ionised outflow as revealed by a broad [O III]λ5007 Å emission line in the SDSS integrated spectrum. For a proper characterisation of the outflow properties and their effects, we need spatially resolved information. Aims. We aim to explore the environment around the red quasar, morphology of the [O III] gas and characterise the kinematics, mass outflow rates and energetics within the system. Methods. We used spatially resolved spectroscopic data from Multi Unit Spectroscopic Explorer (MUSE) with an average seeing of 0.6″ to construct flux, velocity and velocity dispersion maps. Thanks to the spatially resolved [O III]λ5007 Å emission detected, we provide insights into the morphology and kinematics of the ionised gas and better estimates of the outflow properties. Results. We find that the quasar is embedded in an interacting and merging system with three other galaxies ∼50 kpc from its nucleus. Spatially resolved kinematics reveal that the quasar has extended ionised outflows of up to 9.2−0.4+1.2 kpc with positive and negative velocities up to 1000 km s−1 and −1200 km s−1, respectively. The velocity dispersion (W80) ranges from 600–1800 km s−1. We associate the presence of high-velocity components with the outflow. The total mass outflow rate is estimated to be ∼10 M⊙ yr−1, a factor of ∼3–7 higher than the previous findings for the same target and kinetic power of 2 × 1042 erg s−1. Considering different AGN bolometric luminosities, the kinetic coupling efficiencies range from 0.01%–0.03% and the momentum boosts are ∼0.2. Conclusions. The kinetic coupling efficiency values are low, which indicates that the ionised outflow is not energetically relevant. These values don’t align with the theoretical predictions of both radiation-pressure-driven outflows and energy-conserving mechanisms. However, note that our results are based only on the ionised phase while theoretical predictions are multi-phase. Moreover, the mass loading factor of ∼5 is an indication that these outflows are more likely AGN-driven than star formation-driven.

Alpha-glucans from bacterial necromass indicate an intra-population loop within the marine carbon cycle

Phytoplankton blooms provoke bacterioplankton blooms, from which bacterial biomass (necromass) is released via increased zooplankton grazing and viral lysis. While bacterial consumption of algal biomass during blooms is well-studied, little is known about the concurrent recycling of these substantial amounts of bacterial necromass. We demonstrate that bacterial biomass, such as bacterial alpha-glucan storage polysaccharides, generated from the consumption of algal organic matter, is reused and thus itself a major bacterial carbon source in vitro and during a diatom-dominated bloom. We highlight conserved enzymes and binding proteins of dominant bloom-responder clades that are presumably involved in the recycling of bacterial alpha-glucan by members of the bacterial community. We furthermore demonstrate that the corresponding protein machineries can be specifically induced by extracted alpha-glucan-rich bacterial polysaccharide extracts. This recycling of bacterial necromass likely constitutes a large-scale intra-population energy conservation mechanism that keeps substantial amounts of carbon in a dedicated part of the microbial loop.

Theoretical Framework and Research Proposal for Energy Utilization, Conservation, Production, and Intelligent Systems in Tropical Island Zero-Carbon Building

This study aims to theoretically explore the technological systems of tropical island zero-carbon building (TIZCB) to scientifically understand the characteristics of these buildings in terms of energy utilization, energy conservation, energy production, and intelligent system mechanisms. The purpose is to address the inefficiencies and resource wastage caused by the traditional segmented approach to building energy consumption management. Thus, it seeks to achieve a comprehensive understanding and application of the zero-carbon building (ZCB) technology system. This article focuses on the demands for energy-efficient comfort and innovative industrialization in construction. Through an analysis of the characteristics of TIZCB and an explanation of their concepts, it establishes a theoretical framework for examining the system mechanisms of these buildings. Additionally, it delves into the energy utilization, energy conservation, energy production, and intelligent system from macro, meso, and micro perspectives. This approach results in the development of an implementation strategy for studying the mechanisms of energy usage, conservation, and intelligent production systems in TIZCB. The results show that: (1) this study delves into the theoretical underpinnings of TIZCB, emphasizing their evolution from a foundation of low-carbon and near-zero energy consumption. The primary goal is to achieve zero carbon emissions during building operation, with reliance on renewable energy sources. Design considerations prioritize adaptation to high-temperature and high-humidity conditions, integrating regional culture along with the utilization of new materials and technologies. (2) A comprehensive technical framework for TIZCB is proposed, encompassing energy utilization, conservation, production capacity, and intelligent systems. Drawing from systems theory, control theory, and synergy theory, the research employs a macro–meso–micro analytical framework, offering extensive theoretical support for the practical aspects of design and optimization. (3) The research implementation plan establishes parameterized models, unveiling the intricate relationships with building performance. It provides optimized intelligent system design parameters for economically viable zero-carbon operations. This study contributes theoretical and practical support for the sustainable development of TIZCB and aligns with the dual carbon strategy in China and the clean energy free trade zone construction in Hainan.

Genetic tools for the electrotroph Sporomusa ovata and autotrophic biosynthesis.

Sporomusa ovata is a Gram-negative acetogen of the Sporomusaceae family with a unique physiology. This anerobic bacterium is a core microbial catalyst for advanced CO2-based biotechnologies including gas fermentation, microbial electrosynthesis, and hybrid photosystem. Until now, no genetic tools exist for S. ovata, which is a critical obstacle to its optimization as an autotrophic chassis and the acquisition of knowledge about its metabolic capacities. Here, we developed an electroporation protocol for S. ovata. With this procedure, it became possible to introduce replicative plasmids such as pJIR751 and its derivatives into the acetogen. This system was then employed to demonstrate the feasibility of heterologous expression by introducing a functional β-glucuronidase enzyme under the promoters of different strengths in S. ovata. Next, a recombinant S. ovata strain producing the non-native product acetone both from an organic carbon substrate and from CO2 was constructed. Finally, a replicative plasmid capable of integrating itself on the chromosome of the acetogen was developed as a tool for genome editing, and gene deletion was demonstrated. These results indicate that S. ovata can be engineered and provides a first-generation genetic toolbox for the optimization of this biotechnological workhorse.IMPORTANCES. ovata harbors unique features that make it outperform most microbes for autotrophic biotechnologies such as a capacity to acquire electrons from different solid donors, a low H2 threshold, and efficient energy conservation mechanisms. The development of the first-generation genetic instruments described in this study is a key step toward understanding the molecular mechanisms involved in these outstanding metabolic and physiological characteristics. In addition, these tools enable the construction of recombinant S. ovata strains that can synthesize a wider range of products in an efficient manner.

Characterization of the Membrane-Associated Electron-Bifurcating Flavoenzyme EtfABCX from the Hyperthermophilic Bacterium Thermotoga maritima.

Electron bifurcation is an energy-conservation mechanism in which a single enzyme couples an exergonic reaction with an endergonic one. Heterotetrameric EtfABCX drives the reduction of low-potential ferredoxin (E°' ∼ -450 mV) by oxidation of the midpotential NADH (E°' = -320 mV) by simultaneously coupling the reaction to reduction of the high-potential menaquinone (E°' = -74 mV). Electron bifurcation occurs at the NADH-oxidizing bifurcating-flavin adenine dinucleotide (BF-FAD) in EtfA, which has extremely crossed half-potentials and passes the first, high-potential electron to an electron-transferring FAD and via two iron-sulfur clusters eventually to menaquinone. The low-potential electron on the BF-FAD semiquinone simultaneously reduces ferredoxin. We have expressed the genes encodingThermotoga maritimaEtfABCX in E. coli and purified the EtfABCX holoenzyme and the EtfAB subcomplex. The bifurcation activity of EtfABCX was demonstrated by using electron paramagnetic resonance (EPR) to follow accumulation of reduced ferredoxin. To elucidate structural factors that impart the bifurcating ability, EPR and NADH titrations monitored by visible spectroscopy and dye-linked enzyme assays have been employed to characterize four conserved residues, R38, P239, and V242 in EtfA and R140 in EtfB, in the immediate vicinity of the BF-FAD. The R38, P239, and V242 variants showed diminished but still significant bifurcation activity. Despite still being partially reduced by NADH, the R140 variant had no bifurcation activity, and electron transfer to its two [4Fe-4S] clusters was prevented. The role of R140 is discussed in terms of the bifurcation mechanism in EtfABCX and in the other three families of bifurcating enzymes.

Genomic insights into clostridia in bioenergy production: Comparison of metabolic capabilities and evolutionary relationships.

Bacteria from diverse genera, including Acetivibrio, Bacillus, Cellulosilyticum, Clostridium, Desulfotomaculum, Lachnoclostridium, Moorella, Ruminiclostridium, and Thermoanaerobacterium, have attracted significant attention due to their versatile metabolic capabilities encompassing acetogenic, cellulolytic, and C1-metabolic properties, and acetone-butanol-ethanol fermentation. Despite their biotechnological significance, a comprehensive understanding of clostridial physiology and evolution has remained elusive. This study reports an extensive comparative genomic analysis of 48 fully sequenced bacterial genomes from these genera. Our investigation, encompassing pan-genomic analysis, central carbon metabolism comparison, exploration of general genome features, and in-depth scrutiny of Cluster of Orthologous Groups genes, has established a holistic whole-genome-based phylogenetic framework. We have classified these strains into acetogenic, butanol-producing, cellulolytic, CO2-fixating, chemo(litho/organo)trophic, and heterotrophic categories, often exhibiting overlaps. Key outcomes include the identification of misclassified species and the revelation of insights into metabolic features, energy conservation, substrate utilization, stress responses, and regulatory mechanisms. These findings can provide guidance for the development of efficient microbial systems for sustainable bioenergy production. Furthermore, by addressing fundamental questions regarding genetic relationships, conserved genomic features, pivotal enzymes, and essential genes, this study has also contributed to our comprehension of clostridial biology, evolution, and their shared metabolic potential.

Phase change mechanism of periodic cavitation evolution in turbulent cavitation boundary layer

The instantaneous flow features of a partial cavity were investigated using a mass transfer cavitation model and large eddy simulations around a three-dimensional symmetric hydrofoil at Reynolds number Re=1×106, cavitation number σ = 0.43, and attack angle α = 0°. The phase change mechanism of periodic cavitation evolution, that is, energy conservation and transformation between turbulent fluctuation kinetic energy and water-vapor volume fraction ∝vapor, was identified in the turbulent cavitation boundary layer. The streamwise velocity Vx and pulsation Vx′,Vx′Vx′ play the dominant role in the cavitation evolution, whereas the spanwise and normal magnitudes and their pulsations are all less than 1–2 orders of magnitude. Because of the flow stratification phenomenon, the boundary layer is divided into the inner (below y+=40), transition (within a range of y+=50–80), and outer zones (beyond y+=90) in the normal y+ direction. Along all chordwise points, cavitation initiates entirely within the inner zone of y+=12–30, where Vx′Vx′ is strongest at the water saturation pressure. In the inner zone of y+=5–8 and the outer zone, cavitation initiation is delayed with a low ∝vapor. The expression between the instantaneous ∝vapor and Vx′Vx′ was improved by adding a correction term (γ*Sc) to validate the rationality of the phase change mechanism.

Dark Energy from Cosmological Energy Conservation

The value of the gravitational wave energy density is unknown. Current progress in gravitational wave detection suggests that the energy density of the stochastic gravitational wave background (SGWB) will be estimated in the next decades. A derivation of its value is presented under the assumption that energy lost due to cosmic redshift is fully responsible for the energy gained by the cosmological constant in the expanding universe. This unknown nonlocal mechanism of energy conservation on the cosmic scale could explain dark energy and hint at a property of a theory of quantum gravity.

Global distribution and diversity of antimicrobial genes across subsurface bacterial and archaeal metagenome assembled genomes

Microorganisms have the capability to produce antimicrobial compounds through secondary metabolism, which are not essential within their natural environments, but have been found to have many effects on the ecosystem. Antimicrobial production genes have been identified in a wide range of microorganisms; however, research into natural ecosystems has historically been limited to continental soil environments. Antimicrobial production research has been limited in the deep continental subsurface and marine environments, especially deeply buried marine sediments. We analyzed 466 high-quality metagenome assembled genomes (MAGs) collected from continental and marine subsurface environments through the Deep Carbon Observatory’s Census of Deep Life. A total of 383 MAGs contained biosynthetic gene clusters, namely Type I and Type III polyketide synthase genes, non-ribosomal peptide synthetase genes, and other unspecified ribosomally synthesized and post-translationally modified peptide products. All of these genes were found across continental mines, subglacial lakes, hotsprings, and serpentinizing environments. These environments have previously not been investigated via metagenomics for antimicrobial gene diversity, which may be produced for competition or communication purposes. All other biosynthetic genes identified in this study were less than 50% similar to reference biosynthesis genes indicating the novelty of secondary metabolism in subsurface microorganisms. The majority of predicted antimicrobial products were found to be produced exergonically, which could indicate microbial populations use energy-conserving mechanisms to produce compounds that could offer a competitive advantage.

Improving mesophilic anaerobic digestion of food waste by side-stream thermophilic reactor: Activation of methanogenic, key enzymes and metabolism.

Anaerobic digestion (AD) is a favorable way to convert organic pollutants, such as food waste (FW), into clean energy through microbial action. This work adopted a side-stream thermophilic anaerobic digestion (STA) strategy to improve a digestive system's efficiency and stability. Results showed that the STA strategy brought higher methane production as well as higher system stability. It quickly adapted to thermal stimulation and increased the specific methane production from 359mL CH4/g·VS to 439mL CH4/g·VS, which was also higher than 317mL CH4/g·VS from single-stage thermophilic anaerobic digestion. Further exploration of the mechanism of STA using metagenomic and metaproteomic analysis revealed enhanced activity of key enzymes. The main metabolic pathway was up-regulated, while the dominant bacteria were concentrated, and the multifunctional Methanosarcina was enriched. These results indicate that STA optimized organic metabolism patterns, comprehensively promoted methane production pathways, and formed various energy conservation mechanisms. Further, the system's limited heating avoided adverse effects from thermal stimulation, and activated enzyme activity and heat shock proteins through circulating slurries, which improved the metabolic process, showing great application potential.

Muscle architectural properties indicate a primary role in support for the pelvic limb of three-toed sloths (Bradypus variegatus).

Tree sloths evolved below-branch locomotion making them one of few mammalian taxa beyond primates for which suspension is nearly obligatory. Suspension requires strong limb flexor muscles that provide both propulsion and braking/support, and available locomotor kinetics data indicate that these roles differ between fore- and hindlimb pairs. Muscle structure in the pelvic limb is hypothesized to be a key anatomical correlate of function in braking/support during suspensory walking and propulsion and/or support during vertical climbing. This expectation was tested by quantifying architecture properties in the hindlimb limb musculature of brown-throated three-toed sloths (Bradypus variegatus: N = 7) to distinguish the roles of the flexor/extensor functional muscle groups at each joint. Measurements of muscle moment arm (rm ), mass, belly length, fascicle length, pennation angle, and physiological cross-sectional area (PCSA) were taken from n = 45 muscles. Overall, most muscles studied show properties for contractile excursion and fast joint rotational velocity. However, the flexor musculature is more massive (p = 0.048) and has larger PCSA (p = 0.003) than the extensors, especially at the knee joint and digits where well-developed and strong flexors are capable of applying large joint torque. Moreover, selected hip flexors/extensors and knee flexors have modified long rm that can amplify applied joint torque in muscles with otherwise long, parallel fascicles, and one muscle (m. iliopsoas) was capable of moderately high power in B. variegatus. The architectural properties observed in the hip flexors and extensors match well with roles in suspensory braking and vertical propulsion, respectively, whereas strong knee flexors and digital flexors appear to be the main muscles providing suspensory support in the pelvic limb. With aid in support by the forelimbs and the use of adaptive slow locomotion and slow muscle fiber recruitment patterns, structure-function in the tensile limb systems of sloths appears to collectively represent an additional mechanism for energy conservation.

Review on energy conservation and congestion mechanism in mobile WSN: taxonomy, software programs, challenges, and future trends

Review on energy conservation and congestion mechanism in mobile WSN: taxonomy, software programs, challenges, and future trends

Seasonal variation in thermoregulatory capacity of three closely related Afrotropical Estrildid finches introduced to Europe

A species' potential geographical range is largely determined by how the species responds physiologically to its changing environment. It is therefore crucial to study the physiological mechanisms that species use to maintain their homeothermy in order to address biodiversity conservation challenges, such as the success of invasions of introduced species. The common waxbill Estrilda astrild, the orange-cheeked waxbill E. melpoda, and the black-rumped waxbill E. troglodytes are small Afrotropical passerines that have established invasive populations in regions where the climate is colder than in their native ranges. As a result, they are highly suitable species for studying potential mechanisms for coping with a colder and more variable climate. Here, we investigated the magnitude and direction of seasonal variation in their thermoregulatory traits, such as basal (BMR), summit (Msum) metabolic rates and thermal conductance. We found that, from summer to autumn, their ability to resist colder temperatures increased. This was not related to larger body masses or higher BMR and Msum, but instead, species downregulated BMR and Msum toward the colder season, suggesting energy conservation mechanisms to increase winter survival. BMR and Msum were most strongly correlated with temperature variation in the week preceding the measurements. Common waxbill and black-rumped waxbill, whose native ranges encompass the highest degree of seasonality, showed the most flexibility in metabolic rates (i.e., stronger downregulation toward colder seasons). This ability to adjust thermoregulatory traits, combined with increased cold tolerance, may facilitate their establishment in areas characterized by colder winters and less predictable climates.

Performance analysis of biomass direct combustion heating and centralized biogas supply system for rural districts in China

With the rapid urbanization of China, many farmers are living in buildings and districts far from natural gas pipelines and heating pipe networks. Besides electricity, they urgently need a cheaper energy source for heating and cooking. In this paper, a novel mode of biomass direct combustion heating and centralized biogas supply system was put forward, and corresponding theritical model was developed and verified with a practical operation system in Nan'an community of Wuwei City, China. The energy conservation and loss mechanism, energy economy, thermodynamic performance, and environmental benefits of the system are analyzed and explored on the basis of the system's year-round operating conditions and the community’s dynamic load characteristics. The results show that it is possible to meet the users' heat and biogas demands economically with biomass; the dynamic investment payback period(DIPP)is 4.23 years;the average annual primary energy saving rate(PESR)is 21.82 %; and the annual treatment of agricultural and livestock waste is 8198.57 t.The results of the study demonstrate the value and significance of biomass direct combustion heating and centralized biogas supply systems for achieving China's “Double Carbon” goal.

Carnot battery system integrated with low-grade waste heat recovery: Toward high energy storage efficiency

The low-grade waste heat is widely distributed in various scenarios and lacks suitable technologies for recovery. Carnot battery is a large-scale electrical energy storage technology, and pumped thermal energy storage (PTES) is one of the branches in which the waste heat can be efficiently utilized. The integration of the PTES system and waste heat promotes energy storage efficiency and tackles the problem of low-grade waste heat utilization. Aiming to improve the energy storage efficiency of the system, several PTES systems have been put forward, where the system configurations were modified and the waste heat is employed in both the heat pump cycle and the organic Rankine cycle. The novel concept of the PTES systems was examined, and the energy-conservation mechanism was further explored. Moreover, the effect of the heat storage temperature pair on the PTES system was evaluated, and the results indicate that the highest efficiency can attain when the low heat storage temperature is around 100.0 °C. The implementation of different working fluids in the charging and discharging process leads to the promotion of power-to-power efficiency, and the efficiency increases from 65.56 % to 66.52 % when the high heat storage temperature is chosen as 130 °C. In terms of various waste heat parameters, the power-to-power efficiency of the advanced PTES system can attain 99.3 % as the inlet temperature of the waste heat rises to 90.0 °C.

A novel approach to improve network validity using various soft computing techniques

Mobile Adhoc Networks (MANET) in modern research have many optimal energy conservation mechanisms that can be deployed easily and in a faster manner. The routing approaches associated with energy consumption play a dominant role in routing the data packets between the mobile sensor nodes within the range of optimization. However, major challenges associated with energy consumption in MANETs include reduced lifetime of sensor nodes, poor coverage, and throughput. Most methods tend to reduce the interference of data while traversing between the sensor nodes and increase the capacity of the network. This results in delays while transmitting the packets across the network, and this may result in failure of packets being transmitted. To resolve this issue, in this paper, we propose an ant colony optimization combined with a flower pollination algorithm for minimal energy consumption and throughput maximisation in MANETs. This hybrid meta-heuristic model resolves the issues, including delays, poor coverage, and reduced network lifetime. This hybrid model uses the estimation of neighbourhood distance among the nodes for optimal placement of nodes for effective location. The estimation of location is found using a flower pollination algorithm with a levy flight mechanism. The estimation is carried out in a hyper sphere model that helps in finding the coverage area of the sensor nodes. Depending upon the estimation of neighbourhood distance among the sensor nodes, the consumption of energy among the sensor nodes in MANETs is reduced. The simulation was conducted between the proposed hybrid approach and conventional soft computing heuristics, where the results show that the proposed model achieves a higher rate of energy conservation and reduces delay than other methods.

Structural insight on the mechanism of an electron-bifurcating [FeFe] hydrogenase.

Electron bifurcation is a fundamental energy conservation mechanism in nature in which two electrons from an intermediate-potential electron donor are split so that one is sent along a high-potential pathway to a high-potential acceptor and the other is sent along a low-potential pathway to a low-potential acceptor. This process allows endergonic reactions to be driven by exergonic ones and is an alternative, less recognized, mechanism of energy coupling to the well-known chemiosmotic principle. The electron-bifurcating [FeFe] hydrogenase from Thermotoga maritima (HydABC) requires both NADH and ferredoxin to reduce protons generating hydrogen. The mechanism of electron bifurcation in HydABC remains enigmatic in spite of intense research efforts over the last few years. Structural information may provide the basis for a better understanding of spectroscopic and functional information. Here, we present a 2.3 Å electron cryo-microscopy structure of HydABC. The structure shows a heterododecamer composed of two independent 'halves' each made of two strongly interacting HydABC heterotrimers connected via a [4Fe-4S] cluster. A central electron transfer pathway connects the active sites for NADH oxidation and for proton reduction. We identified two conformations of a flexible iron-sulfur cluster domain: a 'closed bridge' and an 'open bridge' conformation, where a Zn2+ site may act as a 'hinge' allowing domain movement. Based on these structural revelations, we propose a possible mechanism of electron bifurcation in HydABC where the flavin mononucleotide serves a dual role as both the electron bifurcation center and as the NAD+ reduction/NADH oxidation site.

Research on energy conservation and carbon emission reduction effects and mechanism: Quasi-experimental evidence from China

This paper aims to identify three batches of low-carbon city pilot (LCCP) policy on energy conservation and carbon emission reduction. Specifically, we first innovatively develop a theoretical model incorporating energy conservation and emission reduction technologies, industrial structure adjustment, and government environmental regulation into the traditional pollution emission model. Furthermore, we provide quasi-experimental evidence using a city-panel dataset from China for 2003–2017. Specifically, we adopt the time-varying difference-in-difference model to examine the mechanism of how LCCP policy affects energy conservation and carbon emission reduction through various channels. The results show that the implementation of LCCP led to a significant decrease in energy intensity and carbon emission intensity of the pilot cities. This conclusion is tested by placebo and endogeneity, and it is robust under multiple scenarios. We find that LCCP policy had a heterogeneous impact on different resource types, including the proportion of the secondary industry, financial support, and the city administrative level. The mechanism shows that the city’s innovation, industrial structure, and regulatory effect are important influencing channels. Our findings also indicate that LCCP policy has a positive spatial spillover effect, promoting energy and carbon reduction in neighboring cities.