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Understanding plant response and resilience to drought under a high CO2 environment will be crucial to ensure crop production in the future. Sorghum bicolor is a C4 plant that resists drought better than other crops, which could make it a good alternative to be grown under future climatic conditions. Here, we analyse the physiological response of sorghum under 350 ppm CO2 (aCO2) or 700 ppm CO2 (eCO2) with drought (D) or without drought (WW) for 9, 13 and 16 days; as well as its resilience under long (R1: 9D + 7R) or short (R2: 13D + 3R) recovery treatments. Sorghum showed elevated rates of gs under aCO2 and WW, which resulted in a significant decrease in Ψw, gs, E, ΦPSII, Fv’/Fm′ when exposed to drought. Consequently, A was greatly decreased. When re-watered, both re-watering treatments prioritized A recovery by restoring photosynthetic machinery under aCO2, whereas under eCO2 plants required little recovery since plant were hardly affected by drought. However, sorghum growth rate for aboveground organs did not reach control values, indicating a slower long-term recovery. Overall, these results provide information about the resilience of sorghum and its utility as a suitable candidate for the drought episodes of the future. This research was financially supported by grant GRUPO Gobierno Vasco-IT022-16. X. S. Martínez-Goñi is the recipient of a grant from Departamento de Universidades e Investigación del Gobierno Vasco (Spain). A. Robredo was the recipient of a grant from Departamento de Educación, Universidades e Investigación del Gobierno Vasco (Spain).

Bioenergy grass species are a renewable energy source, but their productivity has not been fully realized. Improving photosynthetic efficiency has been proposed as a mechanism to increase the productivity of bioenergy grass species. Fluctuating light, experienced by all field grown crops, is known to reduce photosynthetic efficiency. This experiment aimed to evaluate the photosynthetic performance of both C3 and C4 bioenergy grass species under steady state and fluctuating light conditions by examining leaf gas exchange. The fluctuating light regime used here decreased carbon assimilation across all species when compared to expected steady state values. Overall, C4 species assimilated more carbon than C3 species during the fluctuating light regime, with both photosynthetic types assimilating about 16% less carbon than expected based on steady state measurements. Little diversity was observed in response to fluctuating light among C3 species, and photorespiration partially contributed to the rapid decreases in net photosynthetic rates during high to low light transitions. In C4 species, differences among the four NADP‐ME species were apparent. Diversity observed among C4 species in this experiment provides evidence that photosynthetic efficiency in response to fluctuating light may be targeted to increase C4 bioenergy grass productivity.

The response function identification method introduced in the first part of this study is applied here to investigate the land carbon cycle in the Max Planck Institute for Meteorology Earth System Model. We identify from standard C4MIP 1 % experiments the linear response functions that generalize the land carbon sensitivities β and γ. The identification of these generalized sensitivities is shown to be robust by demonstrating their predictive power when applied to experiments not used for their identification. The linear regime for which the generalized framework is valid is estimated, and approaches to improve the quality of the results are proposed. For the generalized γ sensitivity, the response is found to be linear for temperature perturbations until at least 6 K. When this sensitivity is identified from a 2×CO2 experiment instead of the 1 % experiment, its predictive power improves, indicating an enhancement in the quality of the identification. For the generalized β sensitivity, the linear regime is found to extend up to CO2 perturbations of 100 ppm. We find that nonlinearities in the β response arise mainly from the nonlinear relationship between net primary production and CO2. By taking as forcing the resulting net primary production instead of CO2, the response is approximately linear until CO2 perturbations of about 850 ppm. Taking net primary production as forcing also substantially improves the spectral resolution of the generalized β sensitivity. For the best recovery of this sensitivity, we find a spectrum of internal timescales with two peaks, at 4 and 100 years. Robustness of this result is demonstrated by two independent tests. We find that the two-peak spectrum can be explained by the different characteristic timescales of functionally different elements of the land carbon cycle. The peak at 4 years results from the collective response of carbon pools whose dynamics is governed by fast processes, namely pools representing living vegetation tissues (leaves, fine roots, sugars, and starches) and associated litter. The peak at 100 years results from the collective response of pools whose dynamics is determined by slow processes, namely the pools that represent the wood in stem and coarse roots, the associated litter, and the soil carbon (humus). Analysis of the response functions that characterize these two groups of pools shows that the pools with fast dynamics dominate the land carbon response only for times below 2 years. For times above 25 years the response is completely determined by the pools with slow dynamics. From 100 years onwards only the humus pool contributes to the land carbon response.

This paper focus on the influence of oxygen on the partial discharge (PD) and decomposition characteristics of C 4 F 7 N/CO 2 /O 2 gas mixture as eco-friendly gas insulating medium. The PD characteristic parameters and phase resolved partial discharge (PRPD) patterns of C 4 F 7 N/CO 2 /O 2 gas mixture are, respectively, extracted and constructed. The influences of oxygen content and applied voltage on the PD and decomposition characteristics of C 4 F 7 N/CO 2 /O 2 gas mixture are investigated based on gas chromatography-mass spectrometry (GC-MS). We find that the addition of 2-4% O 2 to C 4 F 7 N/CO 2 gas mixture can significantly inhibit the negative half-cycle PDs and the generation of most by-products (CF 4 , C 2 F 6 , C 3 F 6 , CO, C 2 F 6 O 3 , CF 3 CN, C 2 F 5 CN, C 2 N 2 ). With the oxygen content higher than 6%, the accumulation discharge magnitude and discharge repetition rates of C 4 F 7 N/CO 2 /O 2 gas mixture increase sharply, accompanying the intensification of decomposition and deterioration of insulation strength. There is a positive correlation between the mean discharge magnitude and gas mixture decomposition intensity. To avoid the serious impact of PD fault on gas insulated equipment (GIE), the optimal oxygen addition in C 4 F 7 N/CO 2 /O 2 gas mixture should not exceed 6%.

Eco-friendly C4F7N (Perfluoroisobutyronitrile)/N 2 gas mixture is now recognized as a potential alternative gas insulating medium to the most greenhouse gas SF 6 used in the power industry. In order to reduce the carbon generated during the discharge process, O 2 can be used as an additional gas of C 4 F7N-N2 gas mixture to improve its electrical endurance. This paper investigates the AC breakdown strength and the change rule of by-products content of C 4 F 7 N/O 2 /N 2 gas mixture used in high-voltage gas insulating equipment (HV-GIE) for the first time. We find that adding 4-10% oxygen into the C 4 F7N-N2 gas mixture at 0.6 MPa can significantly enhance the insulating self-recovery characteristic and reduce the breakdown voltage dispersity of the gas mixture. The insulation strength of C 4 F 7 N/O 2 /N 2 gas mixture with 6% oxygen can reach 60% of SF 6 at 0.6 MPa. The addition of 2-8% oxygen can inhibit the generation of characteristic by-products at high pressure. Considering the insulation performance and the impact of by-products on personnel safety, adding 6% oxygen into the C 4 F 7 N-N 2 gas mixture for HV equipment application is appropriate.

This study explores the effect of O 2 as the second-component buffer gas on the power frequency breakdown characteristics and decomposition products of C5-PFK/CO 2 gas mixture. It is found that the breakdown voltage of C5-PFK/CO 2 gas mixture containing 7.5% C5-PFK is about 1.4 times that of CO 2 gas and about 2/3 of SF 6 gas at the same pressure. Although the average breakdown voltage of C5-PFK/CO 2 /O 2 gas mixture is slightly lowered, the addition of O 2 reduces the standard deviation of the breakdown voltage, improving the insulation stability of the C5-PFK/CO 2 gas mixture. The decomposition by products of C5-PFK/CO 2 gas mixture include CO, CO 2 , CF 4 , COF 2 , C 2 F 4 , C 2 F 6 , C 3 F 6 , C 3 F 6 0, C 3 F 8/ , C 4 F 10 , CHF 3 , C3HF7 and other fluorocarbon compounds. C5-PFK/CO 2 /O 2 gas mixture with 4% O 2 produces much CF 4 , C 2 F 6 and less CO after breakdown. It is recommended to add 4 to 6% O 2 in C5-PFK/CO 2 gas mixture to improve the power frequency breakdown characteristics for engineering application.

Leaf hydraulic and mesophyll CO2 conductance are both influenced by leaf anatomical traits, however it is poorly understood how the temperature response of these conductances differs between C4 and C3 species with distinct leaf anatomy. This study investigated the temperature response of leaf hydraulic conductance (Kleaf ), stomatal (gs ) and mesophyll (gm ) conductance to CO2 , and leaf anatomical traits in phylogenetically related Panicum antidotale (C4 ) and P. bisulcatum (C3 ) grasses. The C4 species had lower hydraulic conductance outside xylem (Kox ) and Kleaf compared with the C3 species. However, the C4 species had higher gm compared with the C3 species. Traits associated with leaf water movement, Kleaf and Kox , increased with temperature more in the C3 than in the C4 species, whereas traits related to carbon uptake, Anet and gm , increased more with temperature in the C4 than the C3 species. Our findings demonstrate that, in addition to a CO2 concentrating mechanism, outside-xylem leaf anatomy in the C4 species P. antidotale favours lower water movement through the leaf and stomata that provides an additional advantage for greater leaf carbon uptake relative to water loss with increasing leaf temperature than in the C3 species P. bisulcatum.

C4 crops of agricultural importance all belong to the NADP-malic enzyme (ME) subtype, and this subtype has been the template for C4 introductions into C3 crops, like rice, to improve their productivity. However, the ATP cost for the C4 cycle in both NADP-ME and NAD-ME subtypes accounts for > 40% of the total ATP requirement for CO2 assimilation. These high ATP costs, and the associated need for intense cyclic electron transport and low intrinsic quantum yield Φ CO 2 , are major constraints in realizing strong improvements of canopy photosynthesis and crop productivity. Based on mathematical modelling, we propose a C4 ideotype that utilizes low chloroplastic ATP requirements present in the nondomesticated phosphoenolpyruvate carboxykinase (PEP-CK) subtype. The ideotype is a mixed form of NAD(P)-ME and PEP-CK types, requires no cyclic electron transport under low irradiances, and its theoretical Φ CO 2 is c. 25% higher than that of a C4 crop type. Its cell-type-specific ATP and NADPH requirements can be fulfilled by local energy production. The ideotype is projected to have c. 10% yield advantage over NADP-ME-type crops and > 50% advantage over C3 counterparts. The ideotype provides a unique (theoretical) case where Φ CO 2 could be improved, thereby paving a new avenue for improving photosynthesis in both C3 and C4 crops.

We give an upper bound on the diameter of a 3-edge-connected C4-free graph in terms of order. In particular we show that if G is a 3-edge-connected C4 free graph of order n, and diameter d, then the inequality $$d \le {{3n} \over 7} — {3 \over 7}$$ holds. Moreover, graphs are constructed to show that the bound is almost asymptotically sharp.

Recently, it has become highly desirable to develop low-cost, dopant-free, hole-transport materials with a high charge mobility for perovskite solar cells. Herein, by using an electron deficient be...

We give an upper bound on the radius of a $$C_{4}$$ -free graph in terms order and edge-connectivity. In particular we show that if G is a 3-edge-connected $$C_{4}$$ -free graph of order n and radius r, then the inequality $$\begin{aligned} r\le \frac{n}{4}+\frac{58}{4} \end{aligned}$$ holds. Moreover, graphs are constructed to show that the bounds are asymptotically sharp.

Based on the density functional theory (DFT) method, the behavioral mechanism of carbon addition to promote TiO2 chlorination is investigated based on the adsorption energy, charge transfer and density of states (DOS) in the coadsorption system of a C4 cluster and a Cl2 molecule on the TiO2 (110) surface. The investigated results indicate that C4 cluster bonding with an O atom on the TiO2 (110) surface could promote the Cl2 molecule to dissociate into two Cl atoms that bond with the Ti atom on the TiO2 (110) surface and a C atom of the C4 cluster. The newly formed C-O bond and Ti-Cl bond constitute the channel of electron transfer from C4 to the Cl atom and weaken the adjacent O-Ti bonding effect, which are conducive to the formation of new Ti-Cl and C-O bonds. Moreover, the tendency of C4OCl dissociation from the TiO2 (110) surface is obvious, forming oxygen vacancy defects for the next Cl atom adsorption.

In this paper, a calculation method is proposed to predict the dielectric strength (DS) of gases and the DS of some promising SF 6 alternative gases and their mixtures is further evaluated by DC breakdown tests. The calculation method is based on the density functional theory (DFT), so that the DS of the gases can be obtained by only calculating their molecular parameters, including the average static electronic polarizability and adiabatic ionization energy. The paper also presents the DC breakdown strength of the C 4 F 7 N, C 5 F 10 O, and HFO-type gases, and it is found that the experimental DS values are in good agreement with the calculated values. In addition, DC breakdown tests for gas mixtures are also conducted and their synergistic effect is discussed in detail. The results show that the DS of C 4 F 7 N mixed gases is equivalent to that of pure SF 6 gas even under high pressures, indicating their potential applications in HV electrical equipment. The DS of C 5 F 10 O mixed gas is slightly lower than that of C 4 F 7 N mixed gas. Compared with CO 2 , mixing with air brings stronger synergistic effect in C 5 F 10 O and C 4 F 7 N in our experiment. The DS of HFO mixture is substantially less than that of SF 6 because of the weak synergistic effect when mixed with CO 2 or N 2 . This paper presents an effective method to evaluate DS of SF 6 alternative gases and the results are useful for their future engineering applications.

In this paper, the insulation strength of C 4 F 7 N/CO 2 with temperature is obtained by AC breakdown tests and theoretical calculations. The experimental results with 9%C 4 F 7 N/91%CO 2 at 0.7 and 0.5 MPa pressures show that the breakdown voltage changes nonlinearly with temperature. Theoretical analysis shows that the nonlinear change is caused by liquefaction of C 4 F 7 N. The critical electric field of C 4 F 7 N/CO 2 is calculated based on the streamer discharge theory. A calculation model is established to calculate the usable pressure of C 4 F 7 N/CO 2 and the mole fraction of C 4 F 7 N at given minimum temperature, which can provide reference for its practical application.

This study explores the breakdown properties of three C 4 F 7 N binary gas mixtures under lightning impulse and the reduction of dielectric strength in the presence of insulation defects. The 50% breakdown voltage (U 50% ) of three C 4 F 7 N binary gas mixtures in a quasi-uniform electric field is observed to determine the basic dielectric strength, which has the ranking C 4 F 7 N/Air ≈ C 4 F 7 N/CO 2 > C 4 F 7 N/N 2 . A coefficient S E is introduced to quantitatively describe the sensitivity of dielectric strength to electric field inhomogeneity. The S E of different gas medium can be ranked as SF 6 4 F 7 N/CO 2 4 F 7 N/Air 4 F 7 N/N 2 , indicating that C 4 F 7 N mixed with nitrogen, carbon dioxide, or dry air is less capable of tolerating insulation defects than SF 6 , which merits consideration in insulation designs.

Fluorinated nitrile (C 4 F 7 N) gas mixture has been introduced as the most promising candidate to replace sulfur hexafluoride using in gas-insulated equipment. In this study, the authors explored the influence of oxygen on the dielectric and decomposition properties of C 4 F 7 N–CO 2 –O 2 gas mixture. The authors found that the dielectric strength of the C 4 F 7 N–CO 2 –O 2 gas mixture with 2, 4, 6, 8 and 10% O 2 was increased by 4.85%, 6.49%, 7.70%, 3.21% and 2.74% compared with C 4 F 7 N–CO 2 . The addition of 2–6% O 2 to the C 4 F 7 N–CO 2 gas mixture could effectively reduce the content of most of the decomposition by-products such as CF 4 , CO, C 2 F 6 , C 3 F 6 , C 3 F 8 , CF 3 CN, C 2 F 5 CN, (CN) 2 . While high content of oxygen (>6%) results in higher decomposition of C 4 F 7 N, which has a negative effect on the stability of C 4 F 7 N gas mixture. Generally, it is recommended to add 2–6% O 2 in the C 4 F 7 N–CO 2 gas mixture to improve its insulation properties as well as inhibit the decomposition of C 4 F 7 N in the discharge for medium-voltage engineering application.

An asymmetric total synthesis of [13 C4 ]-anatoxin-a ([13 C4 ]-1) has been developed from commercially available ethyl [13 C4 ]-acetoacetate ([13 C4 ]-15). The unique requirements associated with isotope incorporation inspired a new, robust, and highly scalable route, providing access to 0.110 g of this internal standard for use in the detection and precise quantification of anatoxin-a in freshwater. A highlight of the synthesis is a method that leverages a cyclic iminium ion racemization to achieve dynamic kinetic resolution in an enantioselective Morita-Baylis-Hillman (MBH) cyclization.

Plant responses to major environmental drivers like precipitation can influence important aspects of carbon (C) cycling like soil CO2 efflux ( urn:x-wiley:00220477:media:jec13382:jec13382-math-0001 ). These responses may be predicted by two independent classes of drivers: plant size—larger plants respire more and produce a larger quantity of labile C, and plant economics—plants possessing more acquisitive plant economics strategies (i.e. high metabolic rate and tissue nutrient content) produce higher‐quality tissue that respires rapidly and decomposes quickly. At two sites in central Texas, USA with similar climates and differing soil characteristics, we examined the response of eight Panicum virgatum genotypes to three annual precipitation levels defined by the driest, average and wettest years from each site's precipitation history. We evaluated the individual and joint influence of plant genotypes and precipitation on urn:x-wiley:00220477:media:jec13382:jec13382-math-0002 and traits related to plant economics and plant size. We then used confirmatory path analysis to evaluate whether effects of precipitation on urn:x-wiley:00220477:media:jec13382:jec13382-math-0003 were in part related to effects of precipitation on plant economics traits or size (‘mediated’ effects). These genotypes exhibited variation in plant economics traits and above‐ground net primary productivity (ANPP), an above‐ground measure of plant size. Increasing precipitation increased urn:x-wiley:00220477:media:jec13382:jec13382-math-0004 and ANPP more than plant economics traits. At both sites, ANPP was the best predictor of urn:x-wiley:00220477:media:jec13382:jec13382-math-0005 . Moreover, the sites differed in the ways that plant size and plant economics traits combined with precipitation to influence urn:x-wiley:00220477:media:jec13382:jec13382-math-0006 . At the Austin site, the positive effect of precipitation on urn:x-wiley:00220477:media:jec13382:jec13382-math-0007 was mediated primarily by ANPP, offset by a smaller effect of leaf nitrogen content; no direct precipitation effect was detected. At the Temple site, increasing precipitation had positive direct and ANPP‐mediated effects on urn:x-wiley:00220477:media:jec13382:jec13382-math-0008 . This suggests that greater water limitation at Austin may strengthen the links between plant size and urn:x-wiley:00220477:media:jec13382:jec13382-math-0009 . Synthesis. Estimates of C cycling can be improved by accounting for mediation of precipitation effects on urn:x-wiley:00220477:media:jec13382:jec13382-math-0010 by plant economics traits and plant size in resource‐limited environments.

The C 4 F 7 N/CO 2 gas mixture has attracted much attention due to its excellent insulation property and eco-friendly character. In order to evaluate the feasibility of its application in DC GIL, this paper focuses on the surface charging characteristics of spacers under DC stress in the C 4 F 7 N/CO 2 mixture. First, the DC insulation strength was tested under uniform field. The results show that the critical dielectric strength of pure C 4 F 7 N is more than twice that of SF 6 and the dielectric strength of 15%∼20% C 4 F 7 N/CO 2 mixture is equivalent to that of SF 6 . Next, the surface charge measurement of spacers was performed in C 4 F 7 N/CO 2 mixtures, which reveals that the surface charge density decreases slightly with the increase of C 4 F 7 N content. However, the surface charging level in 25% C 4 F 7 N/CO 2 mixture is still much higher than that in SF 6 . It is found that most of the surface charge stems from partial discharges (PDs) near the flange. The PD measurement shows that in SF 6 , there are more PDs with low magnitude, but much less PDs with high magnitude compared to that in the 15%∼25% C 4 F 7 N/CO 2 mixtures. It is the different PD behaviors between C 4 F 7 N/CO 2 mixtures and SF 6 that lead to their different surface charging characteristics.

Benzo[1,2- b :4,5- b′ ]dithiophene (BDT) has been widely used to construct donor-acceptor (D-A) copolymers in organic solar cells (OSCs). However, benzo[1,2- b :4,5- b′ ]difuran (BDF), an analogue of BDT, has received less attention than BDT. The photovoltaic performance of BDF copolymers has lagged behind that of BDT copolymers. Here, we designed and synthesized two BDF copolymers, PBF1-C and PBF1-C-2Cl. PBF1-C-2Cl, which is composed of BDF and benzo[1,2- c :4,5- c′ ]dithiophene-4,8-dione connected by a chlorinated thiophene π-bridge, displays a low-lying highest occupied molecular orbital energy level, which helps in yielding a high open-circuit voltage ( V oc) in OSCs. As a result, when blended with Y6, PBF1-C-2Cl-based devices showed a high V oc of 0.83 V and a power conversion efficiency (PCE) of 13.10%. To the best of our knowledge, the PCE of 13.10% is among the highest efficiency values for OSCs based on BDF copolymers.

C 4 F 7 N and mixtures have been intensively investigated around the world for the substitution of SF 6 in gas insulated transmission lines (GIL). In the present paper, the authors experimentally investigate the lightning impulse (LI) breakdown voltages of C 4 F 7 N/CO 2 in different electric field uniformities, temperatures and pressures. In a slightly nonuniform electric field, the insulation strength of 9%C 4 F 7 N/91%CO 2 can reach 80% strength of SF 6 at the same pressure. In a very un-uniform electric field, the pressure of 9%C 4 F 7 N/91%CO 2 must be increased to 0.7 MPa to keep 80% strength of the 0.4 MPa SF 6 . Also, the polarity effect occurred in different electric fields. The breakdown voltage of 9%C 4 F 7 N/91%CO 2 versus gas pressure shows an N-curve, which may be utilized for the design of GIL. At the pressure of 0.35∼0.7 MPa, 9%C 4 F 7 N/91%CO 2 gas mixtures in ultra-high voltage platform has passed the LI withstand voltage tests. Based on various temperature breakdown tests and the Antoine equation calculation, 9%C 4 F 7 N/91%CO 2 could work at −15 °C.

The authors explored the thermal decomposition characteristics of perfluoroisobutyronitrile–carbon dioxide (C 4 F 7 N–CO 2 ) gas mixture as eco-friendly dielectric medium. The main by-products and decomposition mechanism of C 4 F 7 N–CO 2 gas mixture under different temperature and gas pressure conditions were revealed and analysed. It was found that the thermal decomposition of 6%C 4 F 7 N–94%CO 2 gas mixture starts at about 350°C (0.15 MPa), producing C 3 F 6 and CO first. Some other characteristic by-products such as CF 4 , C 2 F 6 , CF 3 CN, COF 2 and (CN) 2 could also be detected at higher temperature. The yield of C 3 F 6 , (CN) 2 increased with the temperature (lower than 450°C) first and then decreased when it reached to 500°C. While the yield of CO, C 3 F 8 , COF 2 and CF 3 CN increased with temperature (350–550°C). The generation of CF 4 and C 2 F 6 begins at temperatures higher than 500°C, which can be used as the feature component of severe overheating fault. The thermal decomposition amount and by-products yield of C 4 F 7 N–CO 2 gas mixture slowed down with the increase of gas pressure, indicating that C 4 F 7 N–CO 2 gas mixture is quite suitable used at high-pressure equipment, especially high-voltage devices such as gas insulated switchgear.

Heptafluoroisobutyronitrile (C 3 F 7 CN) has received extensive attention for replacing SF 6 in high voltage electrical equipment. It is necessary to assess the suitability of traditional common adsorbent activated alumina (γ-Al 2 O3) used in C 3 F 7 CN based equipment as adsorbent. In this paper, C 4 F 7 N/N 2 hybrid gas discharge test was carried out on the gas insulation performance test platform, and the decomposition products mainly included CF 4 , C 2 F 6 , C 3 F 8 , CF 3 CN, C 2 F 4 , C 3 F 6 and C 2 F 5 CN. Secondly, gas samples were collected at different periods, and the gas before and after being adsorbed by γ-Al 2 O 3 was analyzed and compared by GC-MS. Finally, based on the density functional theory, the adsorption of gas molecular on the surface of γ-Al 2 O 3 was studied. The adsorption effect of γ-Al 2 O 3 to C 3 F 7 CN, C 2 F 5 CN and CF 3 CN is very strong, so it is difficult to be used as adsorbing material for C 3 F 7 CN type gas insulated equipment. However, due to the low cost of γ-Al 2 O3, it can be used in waste gas treatment for new environment-friendly insulating gas.

Steep-wavefront impulse overvoltages may be generated, including fast-front overvoltage (FFO) with wavefront time of 0.1~20 μs, during the operations of disconnector switch in gas insulated equipment (GIE), threatening its insulation. To study the breakdown characteristics of SF6 alternative C4F7N/CO2 mixtures under FFO, the influence of FFO wavefront time, pressures and polarities on the breakdown characteristics of C4F7N/CO2 in slightly non-uniform and extremely non-uniform electric field were investigated. The results show that the effects of FFO wavefront time, polarities and pressures on the insulation properties of C4F7N/CO2 and SF6 are similar. In the slightly non-uniform electric field, the insulation performance of 9%C4F7N/91% CO2 reaches 78% SF6 under the same conditions. The 50% breakdown voltage of gas under impulse voltage (U50%) of the C4F7N/CO2 decreases first then rise with the FFO wavefront time showing a U-curve. It is also found that the voltage polarity has little effect on the trend of the 50% breakdown voltage curve with wavefront time of impulse voltage (U50%-Tf) and the 50% breakdown voltage curve with gas pressure (U50%-P) in the slightly non-uniform electric field. In the extremely non-uniform electric field, the U50% of the C4F7N/CO2 tends to decrease first and then stabilize with the increase of wavefront time. With the increase of pressure, the U50% of C4F7N/CO2 increases linearly in the slightly non-uniform electric field. Under the positive FFO, in the extremely non-uniform electric field, the U50% of the C4F7N/CO2 changes with the rise in pressure showed a tendency to increases first, then decreases and rises again, resembling the N letter. Under the negative FFO, the U50% of C4F7N/CO2 rises with the increase of pressure and tends to be saturated.

Perfluoroisobutyronitrile (C4F7N)/CO2/O2 has been considered as a potential eco-friendly gas insulating medium to replace SF6 due to its unique dielectric properties. Nowadays, few studies on the thermal stability and decomposition properties of C4F7N/CO2/O2 gas mixture were reported, which needs to be evaluated comprehensively. Herein, for the first time, we explored the effect of oxygen and temperature on thermal decomposition characteristics of C4F7N/CO2/O2 gas mixture. It was found that CF4, C3F8, C3F6, CO, COF2, CF3CN, C2F5CN and C2N2 are the main by-products of C4F7N/CO2/O2 gas mixture upon decomposition. The addition of 2%-10% O2 in the C4F7N/CO2 gas mixture yielded decreased of C3F6 and C2N2 while the increase of other by-products. The yields and effective formation rates of C3F8 and COF2 accelerated when the content of O2 was higher than 8%. In terms of practical application, adding 4-6% O2 to C4F7N/CO2 gas mixture is appropriate and COF2, C2N2, C2F5CN can be used as the characteristic products to reflect the severity of partial overheating fault of C4F7N/CO2/O2 gas insulated equipment.

One of the important mechanisms in solvent-aided thermal recovery processes is viscosity reduction. Light n-alkane hydrocarbons are among the potential solvents for solvent-aided thermal recovery processes. In this study, the viscosity of C1- C4 n-alkanes in bitumen was investigated. Adaptive neuro-fuzzy interference system (ANFIS) was used for this aim. The result obtained by the ANFIS model analyzed with the statistical parameters (i.e., MSE, MEAE, MAAE, and R2) and graphical methods. Results show that the ANFIS has high capability to the prediction of solvent/bitumen mixture viscosity.

As one of the alternative insulation gases, C4F7N/CO2 gas mixtures have attracted much attention recently. In this study, the normalized Townsend first ionization coefficient α/N and the normalized attachment coefficient η/N were measured in C4F7N/CO2 gas mixtures by using the Steady-State Townsend (SST) method over a range of electric fields E/N from 100 to 550 Td. The concentrations of C4F7N studied were 4.99, 7.00, 9.00, 13.13 and 20.02%, and the gas pressure were 500 Pa at 20°C. The effective ionization coefficients and the critical electric field were obtained at 500, 1000 and 2000 Pa to investigate the effect of gas pressure on dielectric strength in 9.00%C4F7N/91.00%CO2 respectively. The results indicated that the (E/N)lim have not significant change on the SST experimental conditions. Meanwhile, a comparison with SF6 gas indicates that 20.02% C4F7N/79.98% CO2 has a similar insulation performance with (E/N)lim as 358.82 Td. However, when the liquefaction temperature is considered, the C4F7N/CO2 gas mixtures with 9.00% C4F7N could be considered as an appropriate substitute gas for SF6, because the critical electric field of this gas mixture is over 70% of SF6 gas and could be used under -15°C at 0.7 MPa.

© 2021 The Author(s)., Understanding future changes in global terrestrial near-surface wind speed (NSWS) in specific global warming level (GWL) is crucial for climate change adaption. Previous studies have projected the NSWS changes; however, the changes of NSWS with different GWLs have yet to be studied. In this paper, we employ the Max Planck Institute Earth System Model large ensembles to evaluate the contributions of different GWLs to the NSWS changes. The results show that the NSWS decreases over the Northern Hemisphere (NH) mid-to-high latitudes and increases over the Southern Hemisphere (SH) as the GWL increases by 1.5 °C–4.0 °C relative to the preindustrial period, and that these characteristics are more significant with the stronger GWL. The probability density of the NSWS shifts toward weak winds over NH and strong winds over SH between the current climate and the 4.0 °C GWL. Compared to 1.5 °C GWL, the NSWS decreases −0.066 m s−1 over NH and increases +0.065 m s−1 over SH with 4.0 °C GWL, especially for East Asia and South America, the decrease and increase are most significant, which reach −0.21 and +0.093 m s−1, respectively. Changes in the temperature gradient induced by global warming could be the primary factor causing the interhemispheric asymmetry of future NSWS changes. Intensified global warming induces the reduction in Hadley, Ferrell, and Polar cells over NH and the strengthening of the Hadley cell over SH could be another determinant of asymmetry changes in NSWS between two hemispheres., The work is supported by National Key Research and Development Program of China (2018YFA0606004), National Natural Science Foundation of China (42005023, 41875178, 41865001, 41775087), Nanjing Meteorological Bureau Scientific Project (NJ202103), the Program for Special Research Assistant Project of Chinese Academy of Sciences, the Program for Key Laboratory in University of Yunnan Province, and the C.A.M. was supported by Ramon y Cajal fellowship (RYC-2017-22830), the Leonardo grant 2021 from the BBVA Foundation, and the Grant Nos. VR-2017-03780 and RTI2018-095749-A-I00 (MCIU/AEI/FEDER, UE).

The AC insulation properties of C 4 F 7 N/CO 2 mixtures in non-uniform electric fields were investigated. The optimized interval time between AC breakdowns for C 4 F 7 N/CO 2 mixtures was determined for a range of electric field non-uniformity f. At high value of f, the test results demonstrated some interesting dielectric behavior. The breakdown electric field strength of C 4 F 7 N/CO 2 was inversely related to f until the critical non-uniformity f 0 . Once f reached beyond the f 0 , the breakdown electric field strength became constant. Also, the gas pressure was positively correlated with f 0 . In addition, the trend of AC breakdown test in C 4 F 7 N/CO 2 mixtures and SF 6 demonstrated different N-curve phenomenon. The N-curve phenomenon, which has potential to be utilized for the design of gaseous insulation in electrical systems, could be attributed to the influence of corona and to the mean free path of electrons, which competes with each other. The breakdown voltage of 5∼9%C 4 F 7 N/CO 2 mixtures is more sensitive to the change of non-uniformity than SF 6 . The AC insulation strength of the mixture 9%C 4 F 7 N/91%CO 2 is 80% that of SF 6 .

C4F7N/N2 gas mixtures are considered as new candidate insulation gases to replace SF6. In this study, the Townsend first ionization coefficient α and the attachment coefficient η were measured in C4F7N/N2 gas mixtures using the steady-state Townsend method over a range of electric fields E/N from 200 to 500 Td. The C4F7N concentrations studied were 5.07, 7.00, 13.10 and 19.09%. In addition, the effective ionization coefficients and the critical electric field were also obtained. A comparison of the experimental results with those for SF6 gas indicates that 19.09% C4F7N/80.91% N2 provides better insulation performance with a higher normalized critical electric field of 395 Td. However, when the liquefaction temperature is considered, the C4F7N/N2 gas mixtures with C4F7N content varying from 7.00 to 13.10% may be an appropriate substitute gas for SF6 in electrical industry applications.

The growth of Ruddlesden–Popper perovskite thin films of organic lead halides is complicated by the existence of multiple crystallization pathways available to precursors in solution. During thin-f...

C4F7N is one of the most promising candidate to replace SF6 as arc quenching medium. Some buffer gases (N2 and CO2) are usually mixed with C4F7N to reduce the operating temperature. In order to provide priori knowledge of the arc quenching performance for C4F7N mixtures, the plasma properties including equilibrium compositions, thermodynamic properties, transport coefficients, and net emission coefficients of C4F7N–N2 and C4F7N–CO2 arc plasmas are calculated and the effects of buffer gases are discussed. Taking these properties as input, a 1D arc decaying model is constructed to describe arc decaying characteristics. According to the evolution of axial temperature and arc conductance over time, the arc decaying process is divided into three stages, i.e. the thermal recovery stage, the pre-dielectric recovery stage, and the post-dielectric recovery stage. We focus on the first two stages and describe them by the thermal recovery time (or rate) and the pre-dielectric recovery time (or rate) respectively. According to the results of 1D arc decaying modelling, the descending order of the thermal recovery ability for the gases studied in this work is: SF6 > C4F7N > 75%C4F7N–25%N2 > 75%C4F7N–25%CO2 > 50%C4F7N–50%N2 > 25%C4F7N–75%N2 > 50%C4F7N–50%CO2 > CO2 > 25%C4F7N–75%CO2 > N2; and the pre-dielectric recovery ability is: N2 > SF6 > CO2 > 25%C4F7N–75%CO2 > 25%C4F7N–75%N2 > 50%C4F7N–50%CO2 > 75%C4F7N–25%CO2 > 50%C4F7N–50%N2 > 75%C4F7N–25%N2 > C4F7N.

Formation of hydrocarbons (HCs) by reactions of hydrogen-bearing fluids with carbon ( 13 C soot-like carbon, graphite, or diamond) has been simulated in experiments at pressures of 5.5–7.8 GPa and temperatures of 1100–1400 °C. Hydrogen fugacity ( f H 2 ) in tightly sealed Pt and Au capsules was controlled using the double capsule technique at the Mo + MoO 2 + H 2 O (MMO) or Fe + FeO + H 2 O (IW) equilibria. Synthesis of light alkanes (C 2 > C 1 > C 3 > C 4 ), with smaller amounts of unsaturated hydrocarbons and O-bearing species, occurred all over the experimental P-T- f H 2 ranges. For the first time, formation of hydrocarbons from inorganic compounds was directly proved by the reaction of 13 C carbon with hydrogen, which yielded isotopically pure 13 C light alkanes. In 6.3 GPa runs, the fluid-graphite reaction rate progressively grew, and the process became avalanche-like as the run duration exceeded 1 h. The greatest amounts of HCs (CH 4 /C 2 H 6 4 /C 3 H 8 , and CH 4 /C 4 H 10 ≤ 10) formed at 1400 °C in the 10-hr run. The amount of HC fluid synthesized at 1200 °C was twice smaller. An increase in the experiment duration to 40 h had no effect on amounts of HCs and the composition of species, which indicated that the system achieved equilibrium. The rate of HCs formation was slowest in runs with diamond. The fluid composition varied with pressure and temperature: it contained less methane and slightly more unsaturated hydrocarbons and O-bearing species as pressure and temperature were increased from 5.5 to 7.8 GPa and from 1150 to 1350 °C. An increase in the CO 2 concentration in the fluid led to a drastic decrease in the yield of hydrocarbons. The absence of C 17 O 2 in products of the reaction between graphite and fluid containing 17 O-labeled water indicated that water was not directly involved in HCs synthesis. The experiments have provided the first unambiguous evidence that volatile-rich and reduced mantles of terrestrial planets (at f O 2 near or below IW) provided favorable conditions for formation of a wide range of HCs, mainly light alkanes. Carbon for the HC synthesis may come from graphite, diamond, and soot-like carbon. It should be expected that the efficiency of HCs formation by carbon hydrogenation should be maximal for an increased heat flux (>40 mW/m 2 ) at mantle depths corresponding to the graphite stability region.

To reduce CPU time in compositional petroleum simulation models (e.g. compositional reservoir simulations), a minimum number of components should be used in the equation of state (EOS) to describe the fluid phase and volumetric behavior. A ″detailed” EOS model often contains from 20 to 40 components, with the first 10 components representing pure compounds and the remaining components represent a split of the heavier C 6 + material in single-carbon-number (SCN) fractions. A ″pseudoized” (or lumped) EOS model might contain only 6–9 lumped components. The selection of which components to lump together is difficult because of the huge number of possible combinations. This paper describes an automated method to find the best pseudoized EOS model based on an initial detailed SCN EOS model. The method is based on (1) a fitness function quantifying the quality of match between a pseudoized EOS model and the detailed SCN EOS model from which it is derived, (2) a genetic algorithm used to obtain a first initial solution and (3) a tabu search to refine this initial solution and find the optimal lumping scheme. The method allows for a set of constraints to be imposed on the lumping of components, such as (1) not lumping certain components (e.g. CO 2 ), (2) forcing lumping of some components (e.g. i − C 4 and n − C 4 ). The proposed procedure was successfully able to find the optimal lumped EOS from a detailed SCN EOS with 34 components for three scenarios with different number of components in the lumped EOS (15, 9 and 6). The runtime is ranging from 10 to 45 min.

Reported here are the low-temperature photoluminescence (PL), energy-transfer mechanism, and exciton dynamics of Mn2+-doped two-dimensional (2D) perovskites that show interesting differences from t...

Canopy structural and leaf photosynthesis parameterizations such as maximum carboxylation capacity (Vcmax), slope of the Ball–Berry stomatal conductance model (BBslope) and leaf area index (LAI) are crucial for modeling plant physiological processes and canopy radiative transfer. These parameters are large sources of uncertainty in predictions of carbon and water fluxes. In this study, we develop an optimal moving window nonlinear Bayesian inversion framework to use the Soil Canopy Observation Photochemistry and Energy fluxes (SCOPE) model for constraining Vcmax, BBslope and LAI with observations of coupled carbon and energy fluxes and spectral reflectance from satellites. We adapted SCOPE to follow the biochemical implementation of the Community Land Model and applied the inversion framework for parameter retrievals of plant species that have both the C3 and C4 photosynthetic pathways across three ecosystems. We present comparative analysis of parameter retrievals using observations of (i) gross primary productivity (GPP) and latent energy (LE) fluxes and (ii) improvement in results when using flux observations along with reflectance. Our results demonstrate the applicability of the approach in terms of capturing the seasonal variability and posterior error reduction (40 %–90 %) of key ecosystem parameters. The optimized parameters capture the diurnal and seasonal variability in the GPP and LE fluxes well when compared to flux tower observations (0.95>R2>0.79). This study thus demonstrates the feasibility of parameter inversions using SCOPE, which can be easily adapted to incorporate additional data sources such as spectrally resolved reflectance and fluorescence and thermal emissions.

As a new environmental-friendly gas insulating medium, perfluoroisobutyronitrile (C4F7N) has been widely concerned in recent years due to its relatively low global warming potential and excellent dielectric strength, which has the potential to replace the most greenhouse gas, sulfur hexafluoride(SF6). However, there are a few systematic studies on the influence of gas pressure and mixing ratio on the dielectric strength of C4F7N/CO2 gas mixture at present. In this paper, the power frequency breakdown characteristics of C4F7N/CO2 gas mixture under different pressure and mixing ratio conditions were tested using the gas insulation performance test platform. The optimal mixing ratio and pressure range of C4F7N/CO2 gas mixture for engineering application were also discussed. It is found that the breakdown voltages of C4F7N/CO2 gas mixture show a saturated growth trend with gas pressure and mixing ratio. The breakdown voltage of the gas mixture with 10% C4F7N can reach 80% of pure SF6 under the same condition. The insulation performance of the gas mixture with 20% C4F7N can reach more than 95% of pure SF6. Relevant results indicate that the gas mixture with 4%-12% C4F7N has the potential to be applied to high-voltage gas-insulated equipment.

There is growing interest in developing spatially resolved methane (CH4) isotopic source signatures to aid in geographic source attribution of CH4 emissions. CH4 hydrogen isotope measurements (δ2H–CH4) have the potential to be a powerful tool for geographic differentiation of CH4 emissions from freshwater environments, as well as other microbial sources. This is because microbial δ2H–CH4 values are partially dependent on the δ2H of environmental water (δ2H–H2O), which exhibits large and well-characterized spatial variability globally. We have refined the existing global relationship between δ2H–CH4 and δ2H–H2O by compiling a more extensive global dataset of δ2H–CH4 from freshwater environments, including wetlands, inland waters, and rice paddies, comprising a total of 129 different sites, and compared these with measurements and estimates of δ2H–H2O, as well as δ13C-CH4 and δ13C–CO2 measurements. We found that estimates of δ2H–H2O explain approximately 42 % of the observed variation in δ2H–CH4, with a flatter slope than observed in previous studies. The inferred global δ2H–CH4 vs. δ2H–H2O regression relationship is not sensitive to using either modelled precipitation δ2H or measured δ2H–H2O as the predictor variable. The slope of the global freshwater relationship between δ2H–CH4 and δ2H–H2O is similar to observations from incubation experiments but is different from pure culture experiments. This result is consistent with previous suggestions that variation in the δ2H of acetate, controlled by environmental δ2H–H2O, is important in determining variation in δ2H–CH4. The relationship between δ2H–CH4 and δ2H–H2O leads to significant differences in the distribution of freshwater δ2H–CH4 between the northern high latitudes (60–90∘ N), relative to other global regions. We estimate a flux-weighted global freshwater δ2H–CH4 of −310 ± 15 ‰, which is higher than most previous estimates. Comparison with δ13C measurements of both CH4 and CO2 implies that residual δ2H–CH4 variation is the result of complex interactions between CH4 oxidation, variation in the dominant pathway of methanogenesis, and potentially other biogeochemical variables. We observe a significantly greater distribution of δ2H–CH4 values, corrected for δ2H–H2O, in inland waters relative to wetlands, and suggest this difference is caused by more prevalent CH4 oxidation in inland waters. We used the expanded freshwater CH4 isotopic dataset to calculate a bottom-up estimate of global source δ2H–CH4 and δ13C-CH4 that includes spatially resolved isotopic signatures for freshwater CH4 sources. Our bottom-up global source δ2H–CH4 estimate (−278 ± 15 ‰) is higher than a previous estimate using a similar approach, as a result of the more enriched global freshwater δ2H–CH4 signature derived from our dataset. However, it is in agreement with top-down estimates of global source δ2H–CH4 based on atmospheric measurements and estimated atmospheric sink fractionations. In contrast our bottom-up global source δ13C-CH4 estimate is lower than top-down estimates, partly as a result of a lack of δ13C-CH4 data from C4-plant-dominated ecosystems. In general, we find there is a particular need for more data to constrain isotopic signatures for low-latitude microbial CH4 sources.

Charges deposited over the spacers surface will deteriorate the interface insulation level, which severely restrains the progress of DC GIL. Since SF 6 , has strong greenhouse effect, C 4 F 7 N mixtures, as potential substitutes, have been widely concerned by researchers. The current researches mainly focus on insulation characteristics of C 4 F 7 N mixtures, while surface charge needs further investigation. Thus, the surface charge characteristics of C 4 F 7 N/CO 2 and C 4 F 7 N/N 2 mixtures is deeply studied in this paper. Besides, surface charge characteristics of SFr, is also studied as a control study. The results show that two completely different portions of surface charge accumulation patterns are observed: 1) an approximate central ring-like symmetry homo-charges injected ring; 2) several amorphous hetero-charges spots or strips randomly existing on spacer surface. The total charges in C 4 F 7 N/CO 2 mixture is most, followed by C 4 F 7 N/N 2 mixture, and SFr, is the least. More hetero-charges are deposited on spacer surface in C 4 F 7 N/CO 2 and C 4 F 7 N/N 2 mixtures, which is because that the gas discharge in mixtures is more severe than that in SF«. The conclusions could provide appropriate suggestions for the practical engineering application of C 4 F 7 N mixtures in DC GIL.

We investigate pressure-induced structural changes to the Peierls-type distorted low-temperature phase of the low-dimensional ${\mathrm{Sc}}_{3}\mathrm{Co}{\mathrm{C}}_{4}$ as a possible origin of its pressure-enhanced superconductivity. By means of cryogenic high-pressure x-ray diffraction experiments we could reveal subtle, but significant structural differences between the low-temperature phase at ambient and elevated pressures. We could thus establish the structure of the superconducting phase of the title compound, which interestingly still shows the main features of the Peierls-type distorted low-temperature phase. This indicates that in contrast to other low-dimensional materials a suppression of periodic structural distortions is no prerequisite for superconductivity in the transition-metal carbide.