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Long-term nitrogen deposition enhances microbial capacities in soil carbon stabilization but reduces network complexity
Background: Anthropogenic activities have increased the inputs of atmospheric reactive nitrogen (N) into terrestrial ecosystems, affecting soil carbon stability and microbial communities. Previous studies have primarily examined the effects of nitrogen deposition on microbial taxonomy, enzymatic activities, and functional processes. Here, we examined various functional traits of soil microbial communities and how these traits are interrelated in a Mediterranean type grassland administrated with 14 years of 7 g m –2 year –1 of N amendment, based on estimated atmospheric N deposition in areas within California, USA, by the end of the twenty-first century. Results: Soil microbial communities were significantly altered by N deposition. Consistent with higher aboveground plant biomass and litter, fast-growing bacteria, assessed by abundance-weighted average rRNA operon copy number, were favored in N deposited soils. The relative abundances of genes associated with labile carbon (C) degradation (e.g., amyA and cda) were also increased. In contrast, the relative abundances of functional genes associated with the degradation of more recalcitrant C (e.g., mannanase and chitinase) were either unchanged or decreased. Compared with the ambient control, N deposition significantly reduced network complexity, such as average degree and connectedness. The network for N deposited samples contained only genes associated with C degradation, suggesting that C degradation genes became more intensely connected under N deposition. Conclusions: We propose a conceptual model to summarize the mechanisms of how changes in above- and belowground ecosystems by long-term N deposition collectively lead to more soil C accumulation.
Passive Stability on an Entry Vehicle to Enhance Crew Survival
The most desirable crew survival feature for an entry vehicle is probably a full coverage escape system. With full coverage escape, crew survival is maintained for a wide range of failures by the allowing the crew to escape from the failed vehicle and performing the entry to touchdown flight phase in an alternative system. However, there are considerable challenges in providing a separate entry capability, and for some programs, requiring full coverage escape could result in program cancellation. An alternative means of providing for crew survival if the flight control system fails is to design a return vehicle that can enter without active attitude control. A study was performed to assess the feasibility of performing a totally passive entry. Lift over drag has a major impact on performing a passive entry, so a parametric of three typical lift over drag concepts was performed. First an assessment of historical entry vehicles was completed. Second an assessment of end of mission entry trajectories and entry trajectories initiated from ascent abort profiles were made. Trajectories for a wide array of pitch, yaw, and roll rates were made. Third, six-degree-of freedom analyses of the entry were performed. FOP a truly passive return, the entry vehicle must trim in only the heat shield forward orientation. An assessment of the effect of center of gravity placement to achieve this orientation was made.
Surface Stabilization with Fluorine of Layered Ultrahigh-Nickel Oxide Cathodes for Lithium-Ion Batteries
High-nickel layered oxide cathodes are key to meet the demands of the electric vehicle industry because of their high specific capacity. However, commercialization of these materials is hindered by critical challenges, such as phase transitions, particle cracking, aggressive surface reactivity, and thermal instability. Cation doping along with surface coating has proven to be an effective way to circumvent some of these issues to a large extent. Herein, fluorine coating is employed on a high-nickel Li[Ni 0.95 Mn 0.015 Co 0.02 Al 0.01 Mg 0.005 ]O 2 (NMCAM) cathode via a solution route. Detailed structural and electrochemical analyses indicate fluorine largely decorates the surface at low enough calcination temperatures. The cathode with 1 mol % fluorine coating exhibits a capacity retention of 71% after 500 cycles as compared to 59% for the control sample when cycled to a high cutoff voltage of 4.3 V in a full cell configuration with graphite anode. Post-mortem analysis of cycled electrodes reveals that surface reactivity is a major contributor to capacity fade as compared to particle cracking. Fluorine coating reduces surface reactivity and the depth to which rock-salt phase is formed on the surface during cycling. The thermal stability is also enhanced after fluorine coating as the material shows less heat release at high states of charge. Furthermore, this work demonstrates an effective, economical, and scalable way to stabilize the surface with fluorine and enhance the electrochemical performance of high-nickel cathodes.
Pore Aperture Control Toward Size‐Exclusion‐Based Hydrocarbon Separations
Abstract Metal–organic frameworks (MOFs) have been proposed as a promising material for non‐thermal chemical separations owing to their high structural diversity and tunability. Here, we report the synthesis of a zinc‐based MOF containing a three‐dimensional (3D) linker, bicyclo[2.2.2]octane‐1,4‐dicarboxylic acid, with high thermal stability towards the separation of hexane isomers. The incorporation of the 3D linker enhances the structural stability and provides well‐defined pore apertures/channels with sub‐Ångstrom precision. This precision allowed for the separation of similarly sized hexane isomers based on subtle differences in their kinetic diameters. Multi‐component liquid phase batch experiments confirmed the separation of hexanes mixture into linear, monobranched, and dibranched isomers. This work represents a significant milestone in the construction of stable Zn‐based MOFs and the incorporation of 3D linkers as a potential solution to challenging separations.
Pore Aperture Control Toward Size‐Exclusion‐Based Hydrocarbon Separations
Metal–organic frameworks (MOFs) have been proposed as a promising material for non-thermal chemical separations owing to their high structural diversity and tunability. Here, we report the synthesis of a zinc-based MOF containing a three-dimensional (3D) linker, bicyclo[2.2.2]octane-1,4-dicarboxylic acid, with high thermal stability towards the separation of hexane isomers. The incorporation of the 3D linker enhances the structural stability and provides well-defined pore apertures/channels with sub-Ångstrom precision. This precision allowed for the separation of similarly sized hexane isomers based on subtle differences in their kinetic diameters. Multi-component liquid phase batch experiments confirmed the separation of hexanes mixture into linear, monobranched, and dibranched isomers. This work represents a significant milestone in the construction of stable Zn-based MOFs and the incorporation of 3D linkers as a potential solution to challenging separations.
Improving the Comprehensive Performance of Na 0.7 MnO 2 for Sodium Ion Batteries by ZrO 2 Atomic Layer Deposition
Sodium ion batteries with Na-Mn-O compounds as cathode have been widely studied as substitutes for lithium ion batteries due to their abundant resources. Still, the relatively poor cycling stability and low capacity of Na-Mn-O compounds significantly limit their applications. Different approaches, including element substitution and surface modification, have been applied to improve the electrochemical performance of those cathode materials. Herein, element doping and coating of ZrO 2 on Na 0.7 MnO 2 particles have been achieved by atomic layer deposition (ALD) followed by post-annealing. The rate capability and cycling stability of the modified material were significantly improved, and the mechanism of performance enhancement was revealed. The ZrO 2 coatings acted as a stable interfacial layer to enhance the cycling stability of Na 0.7 MnO 2 by suppressing side reactions between the electrode and electrolyte. The doping of transition metal ions reduced energy barriers for sodium ion insertion and deintercalation during cycling, further improving the charge and discharge capacity and rate performance of Na 0.7 MnO 2 .
Deep Reinforcement Learning-Based Control of Energy Storage for Interarea Oscillation Damping
With the increasing electricity consumption and lack of transmission investment, today's power systems are operated much closer to their limits, raising concerns of inter-area oscillations that deteriorate the system stability. Here, this article presents a novel energy storage placement and control approach for enhanced damping of interarea oscillations. Combining the residual analysis and dominant mode analysis, we are able to identify the advantageous locations for placing energy storage that achieve improved damping performance. To overcome the challenges, such as fixed control parameters and insufficient damping, we propose to use a deep reinforcement learning-based approach for energy storage control. A state-of-the-art guided surrogate-gradient-based evolutionary strategy is used to train a learning agent in a robust, efficient, and reproducible manner. Parallel computing is also adopted to speed up the training process. The proposed strategy has been tested on both medium and large-scale systems. The proposed methods have demonstrated their effectiveness in mitigating various interarea oscillations within a timeframe of 20 s, thereby averting system collapse and enhancing power grid stability effectively.
Comparison of Numerical Results and Multicavity Purge and Rim Seal Data with Extensions to Dynamics
The computation of flows within interconnected, multiple-disk cavities shows strong interaction between the cavities and the power stream. For this reason, simulations of single cavities in such cases are not realistic; the complete, linked configuration must be considered. Unsteady flow fields affect engine stability and can engender power-stream-driven secondary flows that produce local hot spotting or general cavity heating. Further, a concentric whirling rotor produces a circumferential pressure wave, but a statically eccentric whirling rotor produces a radial wave; both waves affect cavity ingestion and the stability of the entire engine. It is strongly suggested that seals be used to enhance turbojet engine stability. Simple devices, such as swirl brakes, honeycomb inserts, and new seal configurations, should be considered. The cost effectiveness of the NASA Lewis Research Center seals program can be expressed in terms of program goals (e.g., the Integrated High-pressure/Temperature Engine Technology (IHPTET) cannot be achieved without such a program), cost (savings to $250 million/1-percent decrease in specific fuel consumption), and indirect benefits (reduction of atmospheric NO(x) and CO2 and reduction of powerplant downtime).
Water/Ionic Liquid/Succinonitrile Hybrid Electrolytes for Aqueous Batteries
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Dynamic-Phasor Model of Transformer Inrush Simulation for Unbalanced Distribution System
Abstract— Power system stability is a critical concern, with respect to the increasing distributed energy resources, microgrids, and emphasis on enhancing resiliency. For stability analysis and evaluation, modeling and simulation capabilities are important. In this paper, the authors’ previous work on modeling transformer inrush dynamics is improved with a new formulation of the key equation that converts the dynamic-phasor into real-time value. Simulation results in an electromechanical time-scale are compared with PSCAD results in an electromagnetic time-scale to demonstrate the improvement. The impact of simulation step size is discussed. A bug in PSCAD transformer setting that leads to incorrect magnetizing flux and current under Delta winding type is identified and reported. In addition, explanations and analysis are provided on two modeling techniques utilized since the previous work. This work is being incorporated into the next release of GridLAB-D. The improved transformer inrush calculation enables more accurate predictions of current amplitudes for analyzing the dynamics of distribution operation and control.
Molecular Additive Engineering for Process-Humidity Robustness and Reproducible Fabrication of Perovskite Solar Cells and Modules
The commercialization of perovskite solar cells (PSCs) faces significant challenges due to their sensitivity to environmental humidity, which compromises film crystallization and device stability. Here, we introduce diphenylvinylphosphine (DPVP) as a Lewis base additive that enhances the performance and reproducibility of PSCs fabricated under ambient-air conditions. DPVP suppresses moisture-induced defect formation and stabilizes crystallization within realistic process-humidity ranges (20–40% relative humidity) commonly encountered in laboratory and pilot-scale manufacturing environments. It improves film uniformity, reduces trap densities, and yields highly reproducible device performance, enabling champion PCEs of 24.2% in small-area devices and 20.5% in blade-coated 12 cm 2 mini-modules. Furthermore, DPVP-assisted modules exhibit enhanced stability, retaining over 85% of their initial efficiency after 900 h of maximum power point tracking (MPPT) at 65 °C. This study demonstrates a humidity-resilient and scalable additive strategy for ambient-air perovskite photovoltaic manufacturing.
Development of a Telemanipulator for Dexterity Enhanced
The precision and stability of motion achievable with the human hand limits current microsurgical practice. Were it possible to overcome these natural limits, better procedures of the eye, ear, hand, brain, and spin would result. Such issues of dexterity enhancement lie not only with scaling down surgical skills of the most gifted, but also addressing widely variable skills of the entire surgical community.
Improved storage stability of conjugated polymer solutions with a versatile Non-halogenated solvent for organic solar cells
The utilization of TMB, featuring a large solvent polarity and molar volume, can generally enhance the solution stability of conjugated polymers for OSCs, which will benefit the preparation, storage, and processing of active layer solutions.
Exploring the Promise of Multifunctional “Zintl-Phase-Forming” Electrolytes for Si-Based Full Cells
Li-M-Si ternary Zintl phases have gained attention recently due to their high structural stability, which can improve the cycling stability compared to a bulk Si electrode. Adding multivalent cation salts (such as Mg 2+ and Ca 2+ ) in the electrolyte was proven to be a simple way to form Li-M-Si ternary phases in situ in Si-based Li-ion cells. To explore the promise of Zintl-phaseforming electrolytes, we systematically investigated their application in pouch cells via electrochemical and multiscale postmortem analysis. The introduction of multivalent cations, such as Mg 2+ , during charging can form Li x M y Si ternary phases. They can stabilize Si anions and reduce side reactions with electrolyte, improving the bulk stability. More importantly, Mg 2+ and Ca 2+ incorporate into interfacial side reactions and generate inorganic-rich solid- electrolyte interphase, thus enhancing the interfacial stability. Therefore, the full cells with Zintl-phase-forming electrolytes achieve higher capacity retentions at the C/3 rate after 100 cycles, compared to a baseline electrolyte. Additionally, strategies for mitigating the electrode-level fractures of Si were evaluated to make the best use of Zintl-phase-forming electrolytes. In conclusion, this work highlights the significance of synergistic impact of multifunctional additives to stabilize both bulk and interface chemistry in high-energy Si anode materials for Li-ion batteries.
Gamma Radiolysis of Phenyl-Substituted TODGAs: Part I
The radiolytic stabilities of three phenylated analogs of N,N,N’,N’-tetraoctyl diglycolamide (TODGA) were investigated: 2-(2-(di-n-octylamino)-2-oxoethoxy)-N,N-di-n-octyl-2-phenylacetamide (PhTODGA), which has a phenyl substituent bound to a central methylene, 2-(2-(di-n-octylamino)-2-oxo-1-phenylethoxy)-N,N-di-n-octylpropanamide (PhMeTODGA), which also contains a methyl substituent bound to the methylene on the other side of the ether moiety, and, 2-(2-N-n-hexyl-N-phenylamino)-2-oxoethoxy)-N-n-hexyl-N-phenylacetamide (DHDPDGA), which has phenyl substituents located on the amide groups instead of the central methylenes. The objective of Part I of this series of papers covers was to evaluate the contribution of the phenyl group to the radiolytic stability of these diglycolamides when irradiated in a) n-dodecane, and b) n-dodecane in the presence of a nitric acid-containing aqueous phase. The results indicate that the presence of the phenyl group decreases the overall radiolytic stability compared to unsubstituted TODGA. However, the results also indicate that the phenyl groups interact with nitric acid in a cooperative fashion that enhances the radiation stability of the phenylated diglycolamide (DGA) derivatives in the presence of a nitric acid-containing aqueous phase compared to irradiation in only n-dodecane. So, the results are consistent with the hypothesized formation of nitric acid-phenylated DGA complexes in the n-dodecane phase that are significantly more stable with respect to gamma irradiation, compared to the phenylated DGA molecules alone.
Two human antibodies to a meningococcal serogroup B vaccine antigen enhance binding of complement Factor H by stabilizing the Factor H binding site
Microbial pathogens bind host complement regulatory proteins to evade the immune system. The bacterial pathogen Neisseria meningitidis, or meningococcus, binds several complement regulators, including human Factor H (FH). FH binding protein (FHbp) is a component of two licensed meningococcal vaccines and in mice FHbp elicits antibodies that inhibit binding of FH to FHbp, which defeat the bacterial evasion mechanism. However, humans vaccinated with FHbp develop antibodies that enhance binding of FH to the bacteria, which could limit the effectiveness of the vaccines. In the present study, we show that two vaccine-elicited antibody fragments (Fabs) isolated from different human subjects increase binding of complement FH to meningococcal FHbp by ELISA. The two Fabs have different effects on the kinetics of FH binding to immobilized FHbp as measured by surface plasmon resonance. The 1.7- and 2.0-Å resolution X-ray crystal structures of the Fabs in complexes with FHbp illustrate that the two Fabs bind to similar epitopes on the amino-terminal domain of FHbp, adjacent to the FH binding site. Superposition models of ternary complexes of each Fab with FHbp and FH show that there is likely minimal contact between the Fabs and FH. Collectively, the structures reveal that the Fabs enhance binding of FH to FHbp by altering the conformations and mobilities of two loops adjacent to the FH binding site of FHbp. In addition, the 1.5 Å-resolution structure of one of the isolated Fabs defines the structural rearrangements associated with binding to FHbp. The FH-enhancing human Fabs, which are mirrored in the human polyclonal antibody responses, have important implications for tuning the effectiveness of FHbp-based vaccines.