Production Ratio Research Articles

Direct Hydrogen Production Promoted by Laser-Induced Water Plasma.

Hydrogen, as a clean energy carrier, plays an important role in addressing the current energy and environmental crisis. However, conventional hydrogen production technologies require extreme reaction conditions, such as high temperature, high pressure, and catalysts. Herein, we study the microscopic mechanism of laser-induced water plasma and subsequent H2 production with real-time time-dependent density functional theory simulations and ab initio molecular dynamics simulations. The results demonstrate that intense laser excites liquid water to generate nonequilibrium plasma in a warm-dense state, which constitutes a superior reaction environment. Subsequent annealing leads to the recombination of energetic reactive particles to generate H2, O2, and H2O2 molecules. Annealing rate and laser wavelength are shown to modulate the product ratio, and the energy conversion efficiency can reach ∼9.2% with an annealing rate of 1.0 K/fs. This work reveals the nonequilibrium atomistic mechanisms of hydrogen production from laser-induced water plasma and shows far-reaching implications for the design of optically controllable hydrogen technology.

Independent isomeric yield ratios of fission products in the epi-cadmium neutron induced fission of 235U

In the epi-cadmium neutron induced fission of 235U, independent isomeric yield ratios (IR) of fission products 130,132Sb, 131,133Te, 134,136I, 135Xe and 138Cs have been measured by using an off-line gamma-ray spectrometric technique. The average neutron energy of the epi-cadmium reactor neutron spectrum is 1.9 MeV. From the IR values, the root mean square fragment angular momenta (JRMS) were deduced by using spin dependent statistical model analysis. The IR and JRMS values of considered fission products in the epi-cadmium neutron induced fission of 235U were compared with the literature data in the thermal neutron induced fission of 235U to examine the influence of excitation energy on nuclear structure effect.

Molecular-chemical characterization of soil organic matter in wetlands by pyrolysis-gas chromatography/mass spectrometry

The carbon cycle in ecosystems is fundamentally controlled by the composition and transformation of organic molecules. Alpine wetland soils have enormous carbon storage, but they are sensitive to climate change, and can easily shift from carbon sink to carbon source. However, we currently lack understanding in molecular-chemical composition of soil organic matter (SOM) in alpine wetlands. In this study, we tried to decipher molecular-chemical features of SOM in typical alpine wetlands using the pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS). Results indicated that nitrogen-containing compounds were the most abundant moieties among pyrolytic products of SOM. More than 83 % of pyrolytic moieties had a molecular weight of no more than 200 Daltons and a H/C ratio of no more than 2.0. O/C ratio of most pyrolytic products were less than 0.5. A van Krevelen diagram potentially indicated that SOM in wetlands might consist of massive heterogeneous molecules where aromatic compounds and their derivatives served as the core, with aliphatic hydrocarbon molecules of varying carbon chain lengths attached externally. About 72.25 % of variances in SOM were explained by 50 pyrolytic products, of which toluene was the most important. A significantly negative relation was observed between molecular weight (MW) and abundance of pyrolytic products, while positive relations were found between H/C, O/C, and abundance of pyrolytic products. Our work implied that SOM in wetlands was mainly composed of molecules with low MW and aromatic function groups.

The effect of pre-dehydrated magnesium-silicate-hydrate on the properties of the castables bonded with hydrable magnesium carboxylate

This study investigates the effect of pre-dehydrated magnesium-silicate-hydrate (PMSH) on the properties of HMC-bonded castables (HMCC), aiming to enhance the medium-temperature mechanical performance of HMCC through the structural memory characteristics of PMSH. The results indicate that adding M-S-H-300 (PMSH treated at 300 °C) improves the mid-temperature mechanical properties of HMCC. Specifically, the cold modulus of rupture (CMOR) for the samples 300MSH increases by 605.9% at 500 °C and 582.6% at 800 °C compared to control samples due to the excellent thermal stability of M-S-H-300 and a 38.3% improvement in castable sintering performance. Additionally, M-S-H-300 improves the thermal shock resistance and setting properties of HMCC, extending the castable's setting time by 19%. The conductivity test results indicate that the addition of M-S-H-300 inhibits the ionization of HMC, thereby delaying its hydration process. Castables with M-S-H-300 demonstrate higher CMOR and residual strength ratio before and after thermal shock. Further testing reveals that adding M-S-H-300 increased the castable's elastic modulus by 482.6% and fracture toughness by 35.6% after sintering at 1500 °C, enhancing resistance to microcrack propagation during thermal shock. Furthermore, adding M-S-H-300 reduces the aspect ratio of HMC hydration products, optimizing microstructure and reducing porosity. However, this modification slightly decreases the mechanical properties of the green body.

Assessing the mass-culture system and proximate content of Arthrospira maxima local for biogas and biohydrogen productions

Arthrospira maxima is a type of local cyanobacteria that has shown success in being grown massively in Indonesia. This research is aimed at looking at the resilience and ability to grow in outdoor conditions using cheap media and following environmental patterns in terms of temperature, sunlight and aeration. In specific purpose is utilization of the obtained biomass for biogas or biohydrogen production. Also, media optimization research from chemical pour grade analyzes into commercial types has been carried out at laboratory scale and field scale. The results show that at the scaling up process from laboratorial to outdoor condition the amount of biomass ratio has decreased by 2–10%, whereas proximate of protein has decreased from 46% to 38%, in contrast starch tends to increase from 10% to 23% and lipid was increase from around 9%–12%. Freshwater and marine water basic media also showing difference in ratio of biomass production and main proximate. The total calory and protein seems higher if A. maxima cultivate using marine water. Cultivation time outdoors turns out to be faster growth when compared to controlled conditions indoors. Biomass analysis results show that the largest content is protein, followed by carbohydrates and lipid. Considering the composition of the proximate, the cyanobacteria biomass tends to be used for biogas conversion rather than alcohol, due to the high protein with less carbohydrate content. Moreover, Arthrospira is cyanobacteria which is capable for producing heterocyst cells that can be excite gas. It was found the cyanobacteria release hydrogen gas around 54 μL/g wet biomasses/day mature culture. However, it should be remembered that this strain is still original or wild type, and can still be developed using both environmental and molecular manipulation approaches. Survival rate from laboratory scale to field scale shows that the microalgae is strong and worthy of consideration for industrial applications. Apart from that, high pH culture conditions are very good for removing contaminants. Also changing the media from pour analyses grade chemicals to commercial chemicals grade only reduces the biomass composition by 2–5% so it is worth considering for commercial applications. Testing various reactors to make biomass as needed with high productivity will be a challenge in the future.

Optimizing Soil Moisture, Mulching, and Spacing for Yield and Water Productivity in Irrigated Elephant Foot Yam (Amorphophallus paeoniifolius)

Aims: To standardize crop spacing and irrigation requirements under different mulching situation for better yield and water productivity. Study Design: The experiment was designed in RBD with two replications. Place and Duration of Study: The experiment was conducted at Agronomic Research Station, Kerala Agriculture University (KAU), Chalakudy for three consecutive years from 2016 -17, 2017 – 18 and 2018 – 2019. Methodology: Study conducted with 18 treatments, includes three levels of irrigation, three types of mulching and with two different crop spacing. Observations on weed count and weed dry matter production were also taken to study the effect of different mulches on weed growth. Biometric observations of crop growth and yield were recorded. Results: Observations on biometric characters revealed that both the height and diameter of the crop canopy were significantly influenced by mulching and found to be highest in the plot where leaf was used as the mulching material and the yield of Amorphophallus during 2016 - 2017 showed that corm weight was greatly influenced by irrigation levels, mulching and spacing. Corm yield was lowest in the plot where irrigation frequency was once in three days (21.02 t/ha). Yield in leaf mulched plot was 38.11 t/ha while in plastic mulched and no mulched plots were 23.50 and 19.50 t/ha. Effect of treatments on water productivity and BC ratio showed that leaf mulching of the crop has significant effect. In leaf mulched plot, water productivity in 2016-17 was 2.03 while it was only 1.854 and 0.886 in 2017-18 and 2018-19. Similarly, BC ratio was highest for leaf mulched plot followed by no mulch and plastic mulch plot. Conclusion: The experimental results from 2016 -17, 2017 – 18 and 2018 – 2019, showed that Amorphophallus planted at a spacing of 90 cm x 90 cm, irrigated at a frequency of once in three days along with leaf mulching can increase the yield and water productivity along with effective control of weed population.

Preparation and Interfacial Behavior of Mg-based Nanosheets

Abstract Two-dimensional nanosheets have attracted considerable attention as oil displacement agent due to their unique interfacial properties. But the high cost limits the application of traditional nanosheets. In this study, a hydrophilic magnesium-based nanosheet (HMN) was synthesized and modified to obtain the amphiphilic magnesium-based nanosheets(AMN). The influences of reaction time, reaction temperature, stirring rate and raw materials ratio of product were studied and the optical reaction condition were summed up as follows: reaction time was 27 h, reaction temperature was 50 °C, stirring rate was 100 rpm, magnesium source: synthetic agent was 0.5:1. Though AFM, SEM and TEM, it was confirmed that nanosheets were two-dimensional sheet-like with 100-300 nm of plane size and 4-20 nm of thickness size. FTIR confirmed the successful modification of AMN from HMN. AMN had good interfacial properties, 0.05wt% AMN could reduce the oil-water interfacial tension from 34.67 mN/m to 1.08 mN/m, and make the oil wet glass into a neutral wetting. Furthermore, emulsion could be formed by AMN with an ultralow concentration (10 mg/L), while a stable interfacial film could be formed at higher concentrations(500mg/L). The low cost and simple synthesis of AMN make it a unique oil displacement agent with great interfacial properties and promise when compared to traditional nanosheets.

Direct-drive photovoltaic electrodialysis via flow-commanded current control

Renewable powered, brackish groundwater desalination is an underutilized resource in the developing world, where there are unreliable energy sources and reliance on increasingly saline groundwater. Traditional renewable desalination technologies require sizable energy storage for sufficient water production, leading to increased cost, maintenance and complexity. We theorize and demonstrate a simple control strategy—flow-commanded current control—using photovoltaic electrodialysis (PV-ED) to enable direct-drive (little to no energy storage), optimally controlled desalination at high production rates. This control scheme was implemented on a fully autonomous, community-scale (2–5 m3 d−1) PV-ED prototype system and operated for 6 months in New Mexico on real brackish groundwater. The prototype fully harnessed 94% of the extracted PV energy despite featuring an energy storage to water productivity ratio of over 99% less than the median PV desalination systems in literature. Flow-commanded current control PV-ED provides a simple strategy to desalinate water for resource-constrained communities and has implications for decarbonizing larger, energy-intensive desalination industries.

Study on plugging mechanism and acidizing plugging removal technology of shale reservoir

Abstract Ordos Basin is rich in unconventional oil and gas resources. Shale resources are developed in source rock series. With the continuous development, many oil wells have different degrees of blockage in the production process. It has different levels of complex performance in wellhead, wellbore and formation, which seriously restricts reservoir production. The formation fluid, reservoir rock samples and plugging materials were analyzed from multiple angles by means of nuclear magnetic electron microscopy, X-ray and acid dissolution to determine the source and formation mechanism of plugging materials. The analysis results show that the main component of the formation mineral is quartz, and the formation crude oil is mainly alkane. The scale sample is a mixture of formation minerals, scaling and corrosion products, and the content varies greatly. It is considered that the particle migration in the reservoir is an important cause of inorganic damage, and the organic matter damage cooperates with the inorganic damage to make the damage more serious. On this basis, this paper puts forward the organic cleaning of wellhead and wellbore, and then inorganic plugging removal of formation plugging, and constructs the deep acidification system of 12 % HCL + 10 % HBF4 and 10 % GT-α. The experiment shows that the effective production ratio can reach 3.6, and the effect of acidizing and plugging removal is remarkable. This study has formed an effective plugging treatment technology for shale reservoir, which can provide technical support for similar reservoir acidification.

Study on the Effect of Nitrogen Bubble Foam Flooding in Deep Heavy Oil Reservoirs with Edge And Bottom Water

Abstract The oil recovery rate is low, the degree of recovery is low and the water content rises fast after water flooding in deep edge and bottom water heavy oil reservoir in Lukeqin oilfield. In order to explore the method to improve the production effect, the integrated foam system of high temperature and high pressure resistant viscosity reduction and oil displacement is optimized. On the basis of clarifying the mechanism of improving the production effect of nitrogen foam flooding for deep heavy oil, taking the west area of Lukeqin oilfield as the research object, the parameter optimization design of nitrogen foam flooding for deep edge and bottom water heavy oil is carried out, such as injection section plug, gas-liquid ratio and injection-recovery ratio. The optimization results are as follows: the injected nitrogen foam slug is 0.2pv, the gas-liquid ratio is 1-1.2, and the injection production ratio is 1:1. The pilot test of 4 well groups was carried out on the site. After foam flooding, the injection pressure was increased by 5.2mpa, the daily oil production of the oil well was increased by 43T / D, the water cut was decreased by 45%, the accumulated oil production was increased by 32000 tons, and the oil recovery was expected to be increased by more than 10%. The purpose of improving the development efficiency of this type of oil reservoir was achieved. Using this optimization technology for scheme design and field implementation, the oil enhancement effect is remarkable and improves the benefit of deep thick oil development, which can provide technical support for the development of similar domestic reservoirs.

Experimental Study on Factors Influencing the Efficiency of Hot Water Injection in Offshore Heavy Oil Reservoirs

Abstract In response to the problem of low final recovery rate in conventional water flooding development of offshore heavy oil, the Bohai LD5 heavy oil field was taken as the target area. Through one-dimensional oil displacement efficiency experiments, the influence of crucial injection and production parameters on oil displacement efficiency, such as temperature, injection rate, injection production ratio, timing of hot water flooding, and injection medium, was studied. The key injection and production parameters were optimized, and the main controlling factors affecting the efficiency of hot water flooding after water flooding were identified through data analysis. Propose an optimization approach for thermal injection media and quantitatively evaluate the oil recovery efficiency under different injection and production parameters. Research has shown that for the Bohai LD5 heavy oil field, the optimal combination of injection and production parameters is: an injection rate of 2mL/min, injection temperature of 110°C, and timing of conversion to flooding at a recovery rate of 20% to 30% (water content of 55% to 70%). The hot water composite flue gas has the best oil recovery effect, considering both oil recovery efficiency and on-site construction conditions. The degree of influence of various factors on the efficiency of hot water flooding is as follows: temperature>timing of hot water flooding (recovery degree)>injection rate. Under low temperature (within 110 °C) conditions, temperature is the main factor affecting the efficiency of hot water flooding. The overall recovery rate of different injection media shows a trend of hot water composite>hot water>cold recovery.

Influence of axial distance between impeller and diffuser on the hydraulic performance and flow loss characteristics of bulb tubular pump

Abstract Bulb tubular pumps used in regional water transfer projects consume substantial power. Optimizing the geometric parameters of tubular pumps is crucial for enhancing efficiency and minimizing hydraulic losses. ANSYS CFX is used to investigate the axial distance between the impeller and the diffuser on the hydraulic performance and flow loss characteristics of the rear-bulb tubular pump, and the numerical simulation results are compared with the experimental data. Then, the entropy production theory is introduced to analyze flow losses. As the axial distance increases, the diffuser’s rectification effect on the flow at the impeller outlet deteriorates, leading to increased flow losses and decreased head and efficiency of the device. Flow losses in the bulb tubular pump are ranked from largest to smallest as follows: impeller, outflow channel, diffuser, inlet channel. The impeller exhibits the highest entropy production ratio, reaching 61.05% at an axial distance of 25 mm. By elucidating the energy loss distribution of each component under varying axial distances, this paper offers insights for the hydraulic optimization design of bulb tubular pumps.

소비자 안전보건을 위한 ESG 공시기준에의 제품안전 지표설정 연구

ESG management has now become a new management paradigm both domestically and internationally. ESG is a non-financial performance indicator to achieve corporate sustainability, and encompasses responsibilities and obligations to stakeholders. Recently, as the safety issue of overseas products imported from online shopping malls in China has emerged, the need to ensure consumer safety and health from hazardous products is increasing. Accordingly, the establishment of product safety disclosure standards for consumer protection is required in the ESG information disclosure process. In this paper, in order to establish product safety indicators for sustainability disclosure standards for ESG management, the disclosure standards of major domestic and foreign initiatives were reviewed and analyzed to examine the introduction of product safety-related indicators, and product safety indicators that can be set for consumer safety and health were developed and presented. As product safety indicators, this paper first presented the occurrence of illegal and defective products, occurrence of product accidents, block hazardous products, number of recall orders and recommendations, and recall recovery rate as indicators that can be introduced throughout the entire product life cycle. In addition, the product risk level, the number and ratio of products for which risk assessment was performed, and the methods and standards used for risk assessment were presented as indicators related to product risk that indicate the level of impact of the product on consumer safety and health. In addition, the consumer safety index was presented as an indicator related to product safety accidents that occur during the consumer product use phase. The consumer safety index is an index that allows consumers to directly feel the level of product safety due to product accidents that occur when consumers use the product. It can be said to be a product safety index from the consumer's perspective that can protect consumer safety.

Testing the ability of water hyacinth for wastewater treatment and methane biogas production

This study aims to assess the potential of water hyacinth (WH) in treating wastewater and its viability for co-digestion with municipal solid waste to achieve zero waste treatment by generating methane biogas. A batch flow reactor treated wastewater, evaluating nine parameters (NO3, PO4, BOD5, Turbidity, Chromium, Cadmium, Lead, Calcium, and Magnesium). The highest removal efficiencies were observed for NO3 (94.13%), PO4 (75.85%), BOD5 (100%), Turbidity (93.86%), Chromium (94.3%), Cadmium (94.93%), Lead (91.33%), Calcium (41.42%), and Magnesium (43.13%). The pH ranged from 7.82 to 7.44. Methane biogas production was examined using anaerobic digesters with varying ratios of carbon-based waste and WH, along with pH, temperature, and total solid content variations. The optimal methane biogas production ratio was found to be 1:3 for WH and solid waste at 35°C, 10% total solids, and a pH of 7.5, resulting in the highest cumulative methane generation of 1039.80 mL/gm vs. The Gompertz model accurately described methane biogas generation with a yield of 1083.088 mL/gm vs., supported by a coefficient of determination (R2) of 0.999. The kinetics of the biodegradation process were evaluated using a first-order kinetic model. The negative value of k (-0.2364) suggests a rapid solid waste biodegradation, with a high correlation coefficient (R2) of 0.9971. Numerous correlations were employed to enhance the production of methane, yielding a correlation coefficient of 91.36%.

Spatiotemporal dynamics of irrigated cropland water use efficiency and driving factors in northwest China’s Hexi Corridor

BackgroundAgricultural irrigation is an important practice to safeguard crops against drought and enhance grain yield in arid regions. The Hexi Corridor, known as a classic arid region, faces significant pressure on agricultural production and food security due to the scarcity of water resources. There is an urgent need to investigate agricultural water use of the irrigated regions. Water use efficiency (WUE), defined as the ratio of gross primary productivity (GPP) to actual evapotranspiration (ET), serves as a valuable indicator linking carbon assimilation and water loss. It enables the quantification of areas where water can be utilized more effectively. However, the long-term spatiotemporal dynamics of WUE and driving mechanism in the irrigated areas of the Hexi Corridor remain unclear.ResultsThis study used GPP calculated by a light use efficiency model (EF-LUE), ET estimated by an ETMonitor model and irrigated cropland maps across China (IrriMap_CN) to examine the spatiotemporal dynamics of irrigated cropland WUE and its controlling factors in the Hexi Corridor from 2001 to 2018. The results are as following: (1) The average annual WUE was approximately 1.34 ± 0.38 g C kg−1 H2O yr−1, with an increasing trend of 0.012 g C kg−1 H2O yr−1, and faster growth observed during 2011–2018 compared to 2001–2010. (2) The contribution of GPP to WUE trends and WUE interannual variability (IAV) was greater than that of ET. (3) The dominant climatic factors of WUE IAV in the Hexi Corridor were SPEI, precipitation, and soil moisture. (4) The standardized Structural Equation Model (SEM), incorporating the relationship between WUE and factors such as water, energy, NDVI, and water-saving irrigation, explained 81% of the variation in irrigated cropland WUE. Here, biological factors (GPP and NDVI) were the primary factors influencing WUE variability, and water-saving irrigation had a stronger indirect effect than climate factors (water and energy) on variation in WUE.ConclusionsOur findings offer valuable theoretical insights into the mechanisms governing the interaction between the carbon and water of irrigated cropland, guiding the management of water resources and land in agricultural practices within the Hexi Corridor.

Inter- and intra-annual variability and climatic responses of ecosystem water use efficiency in a cool-temperate freshwater wetland

Wetland ecosystems play a pivotal role in terrestrial carbon and water cycles, thereby possessing great potential to regulate terrestrial water use efficiency (WUE), which is calculated as the ratio of gross primary productivity (GPP) to evapotranspiration (ET). However, it remains unclear the possible changes in wetland WUE under present and future climate conditions. In this research, WUE variations in a Phragmites australis-dominated freshwater wetland were determined by the eddy covariance method during 2020–2023. Further, we projected future GPP, ET, and WUE under four Representative Concentration Pathway (RCP) scenarios based on five Earth System Models. The 3-year average field observation suggested that the P. australis marsh exhibited high GPP (1149 g C m−2), but consumed large amounts of water through ET (611 mm H2O), resulting in relatively low WUE (1.89 g C mm−1 H2O). During wet years, the studied marsh consumed much more water through evaporation than through transpiration, thus exhibiting lower WUE. Contrarily, large amounts of water were utilized to maintain high primary productivity through transpiration in 2021–2022 dry year, leading to higher WUE. In future scenarios, GPP in the P. australis marsh shows consistently faster uptrends compared to ET from 2020 to 2100, consequently yielding persistent growths of WUE. Future growths of WUE indicate that P. australis marsh tends consume more water for maintaining productivity levels rather than loss via evaporation under future climate conditions, thereby intensifying the carbon–water interaction. Driven by the most rapid growth of environmental drivers, the RCP8.5 scenario shows the fastest increasing trends in GPP, ET, and WUE among four RCP scenarios, whereas the reverse ocurres under RCP2.6 scenario. Overall, our study advocates for more comprehensive research encompassing field observation and model simulation to address the current knowledge gap regarding the response of wetland WUE to contemporary and future climate change.

Species‐specific stoichiometric effects of leaf litter on algal growth, production, and cell quotas

AbstractDissolved organic matter and nutrients released from leaf litter are important cross‐ecosystem resources supporting freshwater food webs. Dissolved organic matter supports heterotrophic organisms in freshwater communities. However, the role of nutrients released from leaf litter in the autochthonous production in aquatic ecosystems is not well understood. Therefore, we investigated how dissolved nutrients released from leaf litter affect algal growth, biomass production, and cellular elemental ratios. Specifically, we experimentally examined the response of green algae to nitrogen (N) and phosphorus (P) released from leaf litter of 11 temperate tree species and the degree of deficiency of nutrient elements other than N and P relative to algal demand in these litter leachates by supplementing these elements. We found that algal growth did not significantly increase with dissolved N or P in the leaf leachates. In contrast, algal biomass production increased with dissolved N concentration, regardless of amendment. Algal growth and production limitation by deficiency of elements other than N and P was found only in the leachate of Japanese hemlock, indicating that the concentrations or release efficiencies of these elements in this leaf litter were lower than those of N and P relative to algal requirements. More importantly, leaf litter leachates from different tree species altered algal cell quotas and C:N:P ratios, which would affect secondary production. These results suggest that variations in leaf litter leachate stoichiometry caused by vegetation change would affect the abundance and chemical composition of phytoplankton, and thus the trophic transfer efficiency between phytoplankton and herbivorous zooplankton.

Investigating Competing Inner- and Outer-Sphere Electron-Transfer Pathways in Copper Photoredox-Catalyzed Atom-Transfer Radical Additions: Closing the Cycle.

This integrated computational and experimental study comprehensively examines the viability of competing inner-sphere electron transfer (ISET) and outer-sphere electron transfer (OSET) processes in [Cu(dap)2]+-mediated atom-transfer radical additions (ATRA) of olefins and CF3SO2Cl that can deliver both R-SO2Cl and R-Cl products. Five sterically- and electronically-varied representative alkenes were selected from which to explore and reconcile the range of experimentally observed outcomes. Findings are consistent with photoexcited [Cu(dap)2]+ initiating photoelectron transfer via ISETand the subsequent regeneration of the oxidized catalyst via single-electron transfer in the ground state via ISETto close the catalytic cycle and liberate products. R-SO2Cl/R-Cl product ratios appear to be primarily governed by the relative rates of direct catalyst regeneration {i.e., [Cu(dap)2SO2Cl]•+ + R•} and ligand exchange {i.e., [Cu(dap)2SO2Cl]•+ + Cl- }. Through this work, a more consistent and more complete conceptual framework has been developed to better understand this chemistry and how catalyst regeneration occurs. It is this important ground state process, which closes the catalytic cycle, and ultimately controls the enantioselectivity of ATRA reactions employing chiral copper photocatalysts.

Investigating Competing Inner‐ and Outer‐Sphere Electron‐Transfer Pathways in Copper Photoredox‐Catalyzed Atom‐Transfer Radical Additions: Closing the Cycle

This integrated computational and experimental study comprehensively examines the viability of competing inner‐sphere electron transfer (ISET) and outer‐sphere electron transfer (OSET) processes in [Cu(dap)2]+‐mediated atom‐transfer radical additions (ATRA) of olefins and CF3SO2Cl that can deliver both R–SO2Cl and R–Cl products. Five sterically‐ and electronically‐varied representative alkenes were selected from which to explore and reconcile the range of experimentally observed outcomes. Findings are consistent with photoexcited [Cu(dap)2]+ initiating photoelectron transfer via ISET and the subsequent regeneration of the oxidized catalyst via single‐electron transfer in the ground state via ISET to close the catalytic cycle and liberate products. R–SO2Cl/R–Cl product ratios appear to be primarily governed by the relative rates of direct catalyst regeneration {i.e., [Cu(dap)2SO2Cl]•+ + R•} and ligand exchange {i.e., [Cu(dap)2SO2Cl]•+ + Cl– }. Through this work, a more consistent and more complete conceptual framework has been developed to better understand this chemistry and how catalyst regeneration occurs. It is this important ground state process, which closes the catalytic cycle, and ultimately controls the enantioselectivity of ATRA reactions employing chiral copper photocatalysts

Government size and the effectiveness of fiscal policy: the bigger the better?

Abstract This study investigates the effect of government size, as measured by the tax revenue to gross domestic product (tax-GDP) ratio, on output responses to increases in government purchases. First, we show that in a standard static neoclassical model, the stimulus effect of fiscal expansion on output increases with the tax-GDP ratio. This finding is quantitatively confirmed using a dynamic neoclassical model with standard functional forms and parameter values. To empirically test the theoretical findings, we analyze the responses of macroeconomic variables to an unanticipated increase in government purchases for 12 Organisation for Economic Cooperation and Development (OECD) countries during 1985–2019 using a state-dependent local projection method. The estimation results reveal that while output responses to an unanticipated fiscal expansion are significantly positive when the tax-GDP ratio is high, they are statistically indistinguishable from zero when the ratio is low. Overall, our findings suggest that fiscal expansion can stimulate output more effectively at high tax rates, unlike the well-known predictions of the traditional Keynesian model.