Production Rate Research Articles

THE EFFECT OF NF-ΚB ON THE INTENSITY OF OXIDATIVE STRESS IN THE CEREBRAL CORTEX OF RATS UNDER THE COMBINED INFLUENCE OF THE LIGHT-DARK CYCLE, SYSTEMIC INFLAMMATORY RESPONSE, AND SODIUM GLUTAMATE ADMINISTRATION

To date, scientists have confirmed the link between the development of oxidative stress and disruptions in the light regime, as well as the systemic inflammatory response. The impact of monosodium glutamate on increasing oxidative damage to rat brain tissue has also been identified. The aim of this study was to investigate the role of the transcription factor NF-κB by examining the effect of its inhibitor, ammonium pyrrolidinedithiocarbamate, on the development of oxidative stress in the cerebral hemispheres of rats, in combination with acute desynchronosis, systemic inflammatory response, and monosodium glutamate administration. The study was conducted on 45 white Wistar rats weighing 150-200 g, divided into three groups: control (n=15), a group subjected to a combination of acute desynchronosis, systemic inflammatory response, and sodium glutamate administration (n=15), and a group exposed to the combination of acute desynchronosis, systemic inflammatory response, and received sodium glutamate and pyrrolidinedithiocarbamate (n=15). To induce acute desynchronosis, the rats were initially kept under a regular light-dark cycle (12 hours of light, 12 hours of darkness) for 3 weeks, followed by a shift in the light-dark phases by 6 hours back over the next 3 days. The systemic inflammatory response was modeled through intraperitoneal administration of Salmonella typhi lipopolysaccharide. During the first week, lipopolysaccharide was administered three times at a dose of 0.4 μg per 1 kg of body weight, and during the following seven weeks, it was given once a week. Sodium glutamate, at a dose of 30 mg/kg, dissolved in 0.5 ml of distilled water, was administered intragastrically for 20 days. The NF-kB activation inhibitor ammonium pyrrolidinedithiocarbamate (Sigma-Aldrich, Inc., USA) was administered at a dose of 76 mg/kg three times a week for 20 days. In a 10% homogenate of the cerebral hemispheres, the following were measured: the rate of superoxide anion radical production, the content of thiobarbituric acid-reactive substances (TBARS), the increase in these parameters, as well as the activity of catalase and superoxide dismutase. Administration of pyrrolidinedithiocarbamate in combination with acute desynchronosis, systemic inflammatory response, and sodium glutamate reduced the rate of basic superoxide anion radical production by 10%, NADPH-induced production by 17.6%, NADH-induced production by 13%, reduced the concentration and growth of TBC-active products by 6.6% and 14.6%, respectively, increased the activity of superoxide dismutase by 35.2%, catalase by 10.5% compared to the group exposed to the combination of acute desynchronosis, systemic inflammatory response, and sodium glutamate administration. Conclusion. The administration of pyrrolidinedithiocarbamate in combination with a systemic inflammatory response, acute desynchronosis and the action of sodium glutamate reduces the production of the superoxide anion radical, the concentration and increase in TBC-active products, enhances antioxidant protection that indicates the possible influence of the nuclear factor NF-κB on the development of oxidative processes in the cerebral hemispheres of rats.

Organic matter processing by heterotrophic bacterioplankton in a large tropical river: Relating elemental composition and potential carbon mineralization

River hydrology shapes the sources, concentration, and stoichiometry of organic matter within drainage basins. However, our understanding of how the microbes process dissolved organic matter (DOM) and recycle nutrients in tropical rivers needs to be improved. This study explores the relationships between elemental DOM composition (carbon/nitrogen/phosphorus: C/N/P), C and N uptake, and C mineralization by autochthonous bacterioplankton in the Usumacinta River, one of the most important fluvial systems in Mexico. Our study investigated changes in the composition and concentration of DOM and evaluated carbon dioxide (CO2)production rates (C–CO2) through laboratory experiments. We compared three sites representing the middle and lower river basins, including their transitional zones, during the rainy and dry seasons. After incubation (120 h at 25°C), the DOM decreased between 25% and 89% of C content. Notably, the initial high proportion of C in DOM in samples from the middle–forested zone and the transition led to elevated C–CO2 rates (>10 mg l−1 day−1), in contrast to the lower initial C proportion and subsequent C–CO2 rates (<7 mg l−1 day−1) in the lower river basin. We also found that dissolved organic carbon uptake and NO3− and NH4+ production were higher during the dry season than in the rainy season. The low water flow in the river during the dry season accentuated the differences in elemental composition and microbial processing of DOM among the sites, while the high water flow of the rainy season homogenized these factors. Our findings indicate that microbial metabolism operates with reduced efficiency in C-rich environments like forests, particularly when faced with high C/N and C/P ratios in DOM. This study highlights the influence of the tropical hydrological regime (rainy and dry seasons) and the longitudinal changes in the river basin (middle and lower) topography and land cover on microbial metabolism by constraining DOM characteristics, emphasizing the crucial role of elemental ratios in river DOM processing.

Aerobic and anaerobic poise of white swimming muscles of the deep-diving scalloped hammerhead shark: comparison to sympatric coastal and deep-water species

Scalloped hammerhead sharks (Sphyrna lewini) routinely perform rapid dives to forage on mesopelagic prey. These deep dives consist of intensive swimming followed by recovery periods in the surface mixed layer. Swimming muscle temperature profiles suggest that S. lewini suppresses gill function as a means to reduce convective heat loss during dives into cool water. Such intensive swimming behavior coupled with reduced respiration prompted us to test whether the aerobic and anaerobic metabolic capacities of the white swimming muscle tissue of this species are greater than those of other shark species from the same region. The activities of key enzymes used in aerobic and anaerobic metabolism provide an indirect indicator of the metabolic potential (“poise”) of a tissue. Here we measured the maximal activities [international units (µmol substrate converted to product per min, U) per gram of wet tissue mass at 10°C] of the citric acid cycle enzymes citrate synthase (CS) and malate dehydrogenase (MDH) and glycolytic enzymes pyruvate kinase (PK) and lactate dehydrogenase (LDH) from white swimming muscle of S. lewini. Enzyme activities, and ratios of these enzyme activities that indicate relative indexes of aerobic to anaerobic capacity, were compared to those measured in three sympatric coastal carcharhinid sharks and two deep-dwelling species, Echinorhinus cookei and Hexanchus griseus. This is the first report of swimming-muscle enzyme activity for these deep-dwelling species. In comparison to the other species, S. lewini had significantly higher activities of both LDH and MDH in the white muscle, and a higher MDH/CS ratio. The high LDH activities suggest that the white muscle of S. lewini relies on relatively high rates of anaerobic ATP production, with would result in build up of high lactate levels, during deep foraging dives. High MDH activity in S. lewini white muscle suggests the potential for lactate levels to be rapidly reduced when aerobic conditions are restored while in the surface mixed layer between dives. These biochemical characteristics may enable S. lewini to swim rapidly while suppressing gill function during deep dives and thereby exploit a very different ecological niche from sympatric shark species (e.g., coastal carcharhinids) and hunt more rapidly via faster swimming for deep-water prey compared to species that permanently inhabit deep depths.

Reinforcing Photogenerated Carrier Extraction of Environment‐Friendly InP/ZnSeS Quantum Dots for High‐Performing Photoelectrochemical Photodetection and Solar Energy Conversion

AbstractColloidal InP/ZnSeS‐based quantum dots (QDs) are considered promising building blocks for light‐emitting devices due to their environmental friendliness, high quantum yield (QY), and narrow emission. However, the intrinsic type‐I band structure severely hinders potential photoelectrochemical (PEC) applications requiring efficient photoexcited carrier separation and transfer. In this study, the optoelectronic properties of InP/ZnSeS QDs are tailored by introducing Al dopants in the ZnSeS layer, which concurrently passivate the surface defects and act as shallow donor states for suppressed non‐radiative recombination and improved charge extraction efficiency. Consequently, as‐fabricated InP/ZnSeS:Al QDs‐based PEC‐type photodetector exhibited a high detectivity up to 1011 Jones and a remarkable responsivity of 0.66 A W−1 at 600 nm even under self‐powered condition (0V bias). In addition, as‐prepared InP/ZnSeS:Al QDs‐based photoanode can be alternatively used for PEC hydrogen generation, showing an H2 production rate of 73.7 µmol cm−2 h−1 under 1 sun illumination (AM 1.5G, 100 mW cm−2). The results offer a prospective strategy for optimizing eco‐friendly QDs for high‐performance multifunctional light detection/conversion devices.

Chance vs. Chants

This study was designed to determine if there is a difference between English Language Learner (ELL) production of /s/ in words such as prince and prints, as it appeared that ELLs were pronouncing “prince” for the former, but “print” for the latter. Study subjects completed a dictation task using a paragraph with many words ending in /s/. The results were that final /s/ in words such as prince was produced in 94.1% of the required contexts, while /s/ in words like prints was produced in 64.9% of the required contexts. The structural difference between pairs such as prince and prints is that prince has no internal morphological structure, while prints consists of print + s. The different production rates for final /s/ suggest that ELLs are processing the words differently, and are apparently unconsciously aware of the morphological difference between pairs such prince and prints. Contrary to expectations, this morphological awareness leads to incorrect responses. The discussion shows that issues such as salience, sonority, and L1 transfer cannot account for the data obtained in the study. In the paper suggestions are presented for raising morphological awareness to a more conscious level, thereby potentially aiding acquisition.

A 3D Macroporous Carbon NiCu Single‐Atom Catalyst for High Current Density CO2 Electroreduction

AbstractTransition metal and nitrogen co‐decorated carbon materials are promising platforms for CO2 electroreduction. A hard‐template 2‐step pyrolysis method is proposed for the fabrication of highly dispersed Ni and Cu atomic active sites on a 3D macroporous carbon matrix. The pyrrolic N‐type Ni−Nx sites serve as dominant active sites toward selective CO2 electroreduction to CO. The incorporation of Cu alters the distribution of N species and simultaneously optimizes the electronic state and geometric structure of the Ni−Nx moiety, thereby improving its adsorption and activation capacity for CO2. Moreover, the isolated Cu atomic sites enhance the resistance of corresponding gas‐diffusion electrodes against electrolyte flooding. The optimal catalyst 3D NiCu‐69 achieves nearly exclusive production of CO with a Faraday efficiency (FECO) of 98% at a current density of −700 mA cm−2 in a CO2‐gas‐fed flow‐through electrolyzer and delivers a CO production rate of 1363 mol(m2s)−1, which is exceeding most reported electrocatalysts. The FECO remained as high as 94% after electrolyzing at a current density of −100 mA cm−2 for 22 h. 3D NiCu‐69 exhibits a favorable performance in both acidic and neutral conditions, with a high FECO of ≈90.2% within the current density range of −100 to −500 mA cm−2.

Heterostructuring Uniform 2D CdS on Ru/Ti3C2‐TiO2 via In situ Oxidized Ru‐Loaded MXene for Boosting Photocatalytic H2 Production

AbstractBuilding heterojunctions and exposing more catalytic active sites are effective strategies to enhance the photocatalytic hydrogen evolution activity. Herein, TiO2 nanosheets are oxidized in situ on Ru‐loaded MXene as carriers and subsequently loaded with uniform 2D CdS via hydrothermal method to obtain 2D Ru/Ti3C2‐TiO2/CdS composite photocatalysts that integrate heterojunctions and cocatalysts. The formation of heterojunction between CdS and TiO2 is conducive to promoting the separation and transfer of photogenerated charges, simultaneously, Ru/Ti3C2 with the fully exposed Ru and Ti3C2 can act as effective active sites of photocatalytic hydrogen production reaction. The composite photocatalyst exhibits an improved hydrogen production rate with 5479 µmol g−1 h−1, which is 5, 3, and four times more than that of pristine CdS, CdS loaded Ti3C2‐TiO2 and CdS loaded Ru‐TiO2 respectively. The results reveal that the notable enhancement in performance can primarily be ascribed to the introduction of the TiO2/CdS heterojunction and the efficient cocatalysts of Ru/Ti3C2. Moreover, the 2D Ti3C2 with high conductivity as carriers can increase charge transfer, and its 2D structure can serve as a template for growing 2D photocatalysts with higher activity. The interface engineering with multiple interfaces can offer novel insights for the advancement of efficient hydrogen evolution reaction catalysts.

Evaluation of Performance Improvement Rate of Plastic Production System Using ARENA: A Case Study of Phoenix Plastic Services

Production improvement has become essential to all industrial activity because of the fierce competition among today's production systems and organizations and the unquenchable customer demand. The shorter product life cycle has significantly increased the demand for prompt reactions to increase the productivity and efficiency of these industrial systems. This study examined the evaluation of performance improvement rate of plastic production system using ARENA. The report provided by the plastics industry was used in the study to analyze and assess the rate of performance improvement of the plastic manufacturing system. The location of the bottleneck was determined by the research following a thorough analysis of the plastic company's data, which included information on all manufacturing lines and procedures. The research employed Arena to assess and compute the rate of improvement in system performance while accounting for the material transporting process throughout the production line. The conveyor velocity maintains a lock at 75m/min, despite the company's report stating that the transports run at 30m/min. The optimized and unoptimized processes when obtained from a finished recycling process running for 1000 working hours, indicate that the conveyor process had 1045 and 1027 entity input and output, respectively, and the transporter process had 953 and 929 entities input and output respectively. The remaining number left when considering the number that enters the system with the number that leaves the system went to waste, resulting from the sorting and demagnetization process. The introduction of the conveyor brings 10.549% in the production rate and 50% decrease on expenses spent in labor. Through the conveyor system's speed control factor, which is an automated procedure, the system's percentage increment may be further raised. By raising the conveyor system's speed, more items will be produced. Conveyor system installation free up more space for additional production-related equipment, increasing products formed and the company's profit. The cost of purchasing and installing the conveyor will be covered by the excess profit.

A comparative analysis of supply chain factors impacting COVID-19 vaccine security in high-income countries (HICs) and low-income and middle-income countries (LMICs)

IntroductionThe COVID-19 pandemic focused attention on the importance of vaccine security to national security. Demand for vaccines far exceeded supply when the first COVID-19 vaccines were released. Growing data suggest...

The Warburg Effect is the result of faster ATP production by glycolysis than respiration

Many prokaryotic and eukaryotic cells metabolize glucose to organism-specific by-products instead of fully oxidizing it to carbon dioxide and water—a phenomenon referred to as the Warburg Effect. The benefit to a cell is not fully understood, given that partial metabolism of glucose yields an order of magnitude less adenosine triphosphate (ATP) per molecule of glucose than complete oxidation. Here, we test a previously formulated hypothesis that the benefit of the Warburg Effect is to increase ATP production rate by switching from high-yielding respiration to faster glycolysis when excess glucose is available and respiration rate becomes limited by proteome occupancy. We show that glycolysis produces ATP faster per gram of pathway protein than respiration in Escherichia coli , Saccharomyces cerevisiae , and mammalian cells. We then develop a simple mathematical model of energy metabolism that uses five experimentally estimated parameters and show that this model can accurately predict absolute rates of glycolysis and respiration in all three organisms under diverse conditions, providing strong support for the validity of the ATP production rate maximization hypothesis. In addition, our measurements show that mammalian respiration produces ATP up to 10-fold slower than respiration in E. coli or S. cerevisiae , suggesting that the ATP production rate per gram of pathway protein is a highly evolvable trait that is heavily optimized in microbes. We also find that E. coli respiration is faster than fermentation, explaining the observation that E. coli , unlike S. cerevisiae or mammalian cells, never switch to pure fermentation in the presence of oxygen.

Distribution characteristics and photochemical effects of isoprene in a coastal city of southeast China

As forest coverage and urban greening increase in China, the impact of biogenic volatile organic compounds (BVOCs) on urban atmospheric environment cannot be neglected. As one of the most abundant and reactive BVOCs globally, isoprene plays a crucial role in atmospheric radical chemistry. However, the reports on quantifying the impact of isoprene on atmospheric photochemistry remain scarce. This study selected Xiamen, a typical coastal city in Fujian Province, as the research area. By employing field observation and Photochemical Box Model (PBM), the study investigated the distribution characteristics, pollution mechanisms, and impact on O3 of the atmospheric photochemical active species isoprene in coastal urban area. The study found that the average concentration of isoprene in summer was 4.7 times higher than that in autumn. Isoprene degradation primarily occurred through oxidation by OH· radicals, reaching 88 % and 86 % in summer and autumn, respectively. Based on scenario simulations using the PBM model, it was observed that isoprene photochemistry led to increased daytime concentrations of ROx radicals (summer: 24 %, autumn: 23 %), peroxyacetyl nitrate (PAN, 49 %, 44 %), and formaldehyde (HCHO, 37 %, 38 %). Additionally, isoprene photochemistry enhanced reaction rates of HO₂· + NO (summer: 21 %, autumn: 16 %) and RO₂· + NO (50 %, 52 %), ultimately resulting in a 19 % and 15 % increase in net O3 production rates in summer and autumn, respectively. This study provides scientific evidence for exploring the photochemical mechanisms and pollution control strategies of O3 in coastal atmospheric environments.

Physicochemical perturbation increases nitrous oxide production from denitrification in soils and sediments

Abstract. Atmospheric concentrations of nitrous oxide (N2O), a potent greenhouse gas that is also responsible for significant stratospheric ozone depletion, have increased in response to the intensified use of agricultural fertilizers and other human activities that have accelerated nitrogen cycling processes. Microbial denitrification in soils and sediments is a major source of N2O, produced as an intermediate during the reduction of oxidized forms of nitrogen to dinitrogen gas (N2). Substrate availability (nitrate and organic matter) and environmental factors such as oxygen levels, temperature, moisture, and pH influence rates of denitrification and N2O production. Here we describe the role of physicochemical perturbation (defined here as a change from the ambient environmental conditions) in influencing rates of denitrification and N2O production. Changes in salinity, temperature, moisture, pH, and zinc in agricultural soils induced a short-term perturbation response characterized by lower rates of total denitrification and higher rates of net N2O production. The ratio of N2O to total denitrification (N2O : DNF) increased strongly with physicochemical perturbation. A salinity press experiment on tidal freshwater marsh soils revealed that increased N2O production was likely driven by transcriptional inhibition of the nitrous oxide reductase (nos) gene and that the microbial community adapted to altered salinity over a relatively short time frame (within 1 month). Perturbation appeared to confer resilience to subsequent disturbance, and denitrifiers from an environment without salinity fluctuations (tidal freshwater estuarine sediments) demonstrated a stronger N2O perturbation response than denitrifiers from environments with more variable salinity (oligohaline and mesohaline estuarine sediments), suggesting that the denitrifying community from physicochemically stable environments may have a stronger perturbation response. These findings provide a framework for improving our understanding of the dynamic nature of N2O production in soils and sediments, in which changes in physical and/or chemical conditions initiate a short-term perturbation response that promotes N2O production that moderates over time and with subsequent physicochemical perturbation.

Identification of Agricultural Socioeconomic Factor and Its Relationship with Exports of Palm and Palm Kernel Oils in Indonesia

The research aim was to study the influence of area size consisting of Government Estate (Government Estate), Private Estate (PBS), Smallholder (PR), price and exchange rate on production, and the influence of production, price and Exchange rate on palm oil exports which consists of Crude Palm Oil (CPO) and Palm Kernel Oil (PKO) using panel data for 2000-2022. Whether viewed from CPO or PKO, the results of the analysis show that the Government State has a real negative influence on production where the elasticity of the Government Estate for CPO towards production is lower than for PKO. The increase in production was significantly caused by the increase in PR for both CPO and PKO, where the elasticity of the increase in PR for CPO was higher than the increase in PKO. PBS provides a positive influence on production which is significant for PKO but not significant for CPO, while prices and exchange rates do not have an influence on CPO production, nor on PKO production. CPO and PKO exports are significantly influenced by prices, where CPO's price elasticity is higher than that of PKO. Furthermore, production and exchange rates have no influence on exports of either CPO or PKO, while the increase in CPO exports is determined significantly by PR, where the elasticity of CPO is higher than PKO.

Vertically Expanded Covalent Organic Frameworks for Photocatalytic Water Oxidation into Oxygen

Covalent organic frameworks with unique π architectures and pores could be developed as photocatalysts for transformations. However, they usually form π‐stacking layers, so that only surface layers function in photocatalysis. Here we report a strategy for developing vertically expanded frameworks to expose originally inaccessible active sites hidden in layers to catalysis. We designed covalently linked two‐dimensional cobalt(II) porphyrin layers and explored coordination bonds to connect the cobalt(II) porphyrin layers with bidentate ligands via a three‐component one‐pot polymerization. The frameworks expand the interlayer space greatly, where both the up and down faces of each cobalt(II) porphyrin layer are exposed to reactants. Unexpectedly, the vertically expanded frameworks increase skeleton oxidation potentials, decrease exciton dissociation energy, improve pore hydrophilicity and affinity to water, and facilitate water delivery. Remarkably, these positive effects work collectively in the photocatalysis of water oxidation into oxygen, with an oxygen production rate of 1155 µmol g−1 h−1, a quantum efficiency of 1.24% at 450 nm, and a turnover frequency of 1.39 h−1, which is even 5.1‐fold as high as that of the π‐stacked frameworks and ranks them the most effective photocatalysts. This strategy offers a new platform for designing layer frameworks to build various catalytic systems for chemical transformations.

Vertically Expanded Covalent Organic Frameworks for Photocatalytic Water Oxidation into Oxygen.

Covalent organic frameworks with unique π architectures and pores could be developed as photocatalysts for transformations. However, they usually form π-stacking layers, so that only surface layers function in photocatalysis. Here we report a strategy for developing vertically expanded frameworks to expose originally inaccessible active sites hidden in layers to catalysis. We designed covalently linked two-dimensional cobalt(II) porphyrin layers and explored coordination bonds to connect the cobalt(II) porphyrin layers with bidentate ligands via a three-component one-pot polymerization. The frameworks expand the interlayer space greatly, where both the up and down faces of each cobalt(II) porphyrin layer are exposed to reactants. Unexpectedly, the vertically expanded frameworks increase skeleton oxidation potentials, decrease exciton dissociation energy, improve pore hydrophilicity and affinity to water, and facilitate water delivery. Remarkably, these positive effects work collectively in the photocatalysis of water oxidation into oxygen, with an oxygen production rate of 1155 µmol g-1 h-1, a quantum efficiency of 1.24% at 450 nm, and a turnover frequency of 1.39 h-1, which is even 5.1-fold as high as that of the π-stacked frameworks and ranks them the most effective photocatalysts. This strategy offers a new platform for designing layer frameworks to build various catalytic systems for chemical transformations.

Pyrene‐4,5,9,10‐Tetraone‐Based Porous Aromatic Frameworks for Photocatalytic Production of Hydrogen Peroxide

AbstractThree pyrene‐4,5,9,10‐tetraone‐based porous aromatic frameworks (PT‐PAFs) are synthesized and their photocatalytic properties for H2O2 production are studied. It is found that the combination of pyrene‐4,5,9,10‐tetraone with anthraquinone affords an efficient PT‐PAF photocatalyst (PAF‐371) for H2O2 production, which achieves production rates of 3791 µmol g−1 h−1 (with sacrificial reagent) and 923 µmol g−1 h−1 (without sacrificial reagent) from water and oxygen under visible light irradiation. This work demonstrates that pyrene‐4,5,9,10‐tetraone molecule could be introduced into PAF materials to construct efficient organic semiconductor photocatalysts for H2O2 production.

Structurally Asymmetric Ni‐O‐Mn Node in Metal‐Organic Layers on Carbon Nitride Support for CO2 Photoreduction

The Jahn‐Teller (J‐T) effect‐induced lattice distortion presents an advantageous approach to tailor the electronic structure and CO2 adsorption properties of catalytic centers, consequently conferring desirable photocatalytic CO2 reduction activity and selectivity. Nevertheless, achieving precise J‐T distortion control over catalytic sites to enhance CO2 adsorption/activation and target‐product desorption remains a formidable challenge. In this work, we successfully induced J‐T lattice distortion in neighboring Ni sites by exchanging high‐spin Mn2+ into Ni‐O‐Ni nodes. EXAFS results and DFT simulations revealed that the highly asymmetric Ni‐O‐Mn nodes induced structural contraction (shortened Ni‐O bonds) in the adjacent Ni‐O lattice. The magnetic hysteresis loop (M‐H) confirmed that the introduction of Mn2+ increased the number of spin electrons, thereby increasing the magnetization intensity. The spin mismatch between photogenerated electrons and holes suppressed charge recombination. Significantly, the d orbitals of the Ni sites in the Ni‐O‐Mn nodes exhibited strong orbital hybridization with the p orbitals of CO2, as evidenced by the enhanced d‐p orbital overlap, facilitating rapid CO2 adsorption and activation. Consequently, the sample featuring lattice‐mismatched Ni‐O‐Mn nodes exhibited an 8.79‐fold enhancement in CO production rate compared to the Ni‐O‐Ni nodes, in the absence of cocatalysts and sacrificial reagents.

Enhancing photocatalytic performance of covalent organic frameworks via ionic polarization

Covalent organic frameworks have emerged as a thriving family in the realm of photocatalysis recently, yet with concerns about their high exciton dissociation energy and sluggish charge transfer. Herein, a strategy to enhance the built-in electric field of series β-keto-enamine-based covalent organic frameworks by ionic polarization method is proposed. The ionic polarization is achieved through a distinctive post-synthetic quaternization reaction which can endow the covalent organic frameworks with separated charge centers comprising cationic skeleton and iodide counter-anions. The stronger built-in electric field generated between their cationic framework and iodide anions promotes charge transfer and exciton dissociation efficiency. Moreover, the introduced iodide anions not only serve as reaction centers with lowered H* formation energy barrier, but also act as electron extractant suppressing the recombination of electron-hole pairs. Therefore, the photocatalytic performance of the covalent organic frameworks shows notable improvement, among which the CH3I-TpPa-1 can deliver an high H2 production rate up to 9.21 mmol g−1 h−1 without any co-catalysts, representing a 42-fold increase compared to TpPa-1, being comparable to or possibly exceeding the current covalent organic framework photocatalysts with the addition of Pt co-catalysts.

Structurally Asymmetric Ni-O-Mn Node in Metal-Organic Layers on Carbon Nitride Support for CO2 Photoreduction.

The Jahn-Teller (J-T) effect-induced lattice distortion presents an advantageous approach to tailor the electronic structure and CO2 adsorption properties of catalytic centers, consequently conferring desirable photocatalytic CO2 reduction activity and selectivity. Nevertheless, achieving precise J-T distortion control over catalytic sites to enhance CO2 adsorption/activation and target-product desorption remains a formidable challenge. In this work, we successfully induced J-T lattice distortion in neighboring Ni sites by exchanging high-spin Mn2+ into Ni-O-Ni nodes. EXAFS results and DFT simulations revealed that the highly asymmetric Ni-O-Mn nodes induced structural contraction (shortened Ni-O bonds) in the adjacent Ni-O lattice. The magnetic hysteresis loop (M-H) confirmed that the introduction of Mn2+ increased the number of spin electrons, thereby increasing the magnetization intensity. The spin mismatch between photogenerated electrons and holes suppressed charge recombination. Significantly, the d orbitals of the Ni sites in the Ni-O-Mn nodes exhibited strong orbital hybridization with the p orbitals of CO2, as evidenced by the enhanced d-p orbital overlap, facilitating rapid CO2 adsorption and activation. Consequently, the sample featuring lattice-mismatched Ni-O-Mn nodes exhibited an 8.79-fold enhancement in CO production rate compared to the Ni-O-Ni nodes, in the absence of cocatalysts and sacrificial reagents.

Spectral bounds on the entropy flow rate and Lyapunov exponents in differentiable dynamical systems

Abstract Some microscopic dynamics are also macroscopically irreversible, dissipating energy and producing entropy. For many-particle systems interacting with deterministic thermostats, the rate of thermodynamic entropy dissipated to the environment is the average rate at which phase space contracts. Here, we use this identity and the properties of a classical density matrix to derive upper and lower bounds on the entropy flow rate with the spectral properties of the local stability matrix. These bounds are an extension of more fundamental bounds on the Lyapunov exponents and phase space contraction rate of continuous-time dynamical systems. They are maximal and minimal rates of entropy production, heat transfer, and transport coefficients set by the underlying dynamics of the system and deterministic thermostat. Because these limits on the macroscopic dissipation derive from the density matrix and the local stability matrix, they are numerically computable from the molecular dynamics. As an illustration, we show that these bounds are on the electrical conductivity for a system of charged particles subject to an electric field.