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Gross primary productivity (GPP) is an important component of the terrestrial carbon cycle in climate change research. The global GPP product derived using Moderate Resolution Imaging Spectroradiometer (MODIS) data is perhaps the most widely used. Unfortunately, many studies have indicated evident error patterns in the MODIS GPP product. One of the main reasons for this is that the applied big‐leaf (BL) MOD17 model cannot properly handle the variable relative contribution of sunlit and shaded leaves to the total canopy‐level GPP. In this study, we developed a model for correcting the errors in the MODIS GPP product by bridging BL and two‐leaf (TL) light use efficiency (LUE) models (CTL‐MOD17). With the available MODIS GPP product, which considers environmental stress factors, the CTL‐MOD17 model only needs to reuse the two inputs of the leaf area index (LAI) and incoming radiation. The CTL‐MOD17 model was calibrated and validated at 153 global FLUXNET eddy covariance (EC) sites. The results indicate that the modeled GPP obtained with the correction model matches better with the EC GPP than the original MODIS GPP product at different time scales, with an improvement of 0.07 in R2 and a reduction in root‐mean‐square error (RMSE) of 117.08 g C m−2 year−1. The improvements are more significant in the green season when the contribution of shaded leaves is larger. In terms of the global spatial pattern, the obvious underestimation in the regions with high LAI and the overestimation in the low LAI regions of the MODIS GPP product is effectively corrected by the CTL‐MOD17 model. This paper not only bridges the BL and TL LUE models, but also provides a new and simple method to obtain accurate GPP through reusing two inputs used in producing the MODIS GPP product. Plain Language Summary: Gross primary productivity (GPP) is crucial for terrestrial carbon cycle study. The Moderate Resolution Imaging Spectroradiometer (MODIS) GPP data is perhaps the most widely used product, but many studies have indicated evident error patterns in it. These errors can be mainly explained by the applied big‐leaf (BL) MOD17 model cannot properly handle the variable relative contribution of sunlit and shaded leaves to the total canopy‐level GPP. As a result, this paper developed a novel and simple model (CTL‐MOD17) to obtain accurate GPP by reusing two inputs data from the MODIS GPP product, based on a two‐leaf (TL) theory. The CTL‐MOD17 model is evaluated at 153 global FLUXNET eddy covariance (EC) sites, and compared with other TL GPP products and models. The results indicate that CTL‐MOD17 can significantly improve the accuracy of MODIS GPP products at different time scales, to be similar to other TL models but with fewer data inputs. The obvious underestimation/overestimation of MODIS GPP in the high/low leaf area index (LAI) regions are all effectively corrected. This study proves the possibility of bridging the BL and TL models for the first time, which can be migrated to other BL products and models. Key Points: A novel product‐based model (CTL‐MOD17) corrects Moderate Resolution Imaging Spectroradiometer (MODIS) gross primary productivity (GPP) product bias, achieving results similar to two‐leaf models with fewer inputsIt is the first time to prove the possibility of bridging the big‐leaf and two‐leaf models, which can be migrated to other big‐leaf GPP products and modelsThe obvious underestimation/overestimation of MODIS GPP in high/low LAI regions are all effectively corrected by the CTL‐MOD17 model [ABSTRACT FROM AUTHOR]

Water availability is the dominant control of global terrestrial primary productivity with concurrent effects on evapotranspiration and ecosystem respiration, especially in water-limited ecosystems. Process-oriented ecosystem models are critical tools for understanding land-atmosphere exchanges and for up-scaling this information to regional and global scales. Thus, it is important to understand how ecosystem models simulate ecosystem fluxes under changing weather conditions. Here, we applied both time-series analysis and meta-analysis techniques to study how five ecosystem process-oriented models-simulated gross primary production (GPP), ecosystem respiration (Reco), and evapotranspiration (ET). Ecosystem fluxes were simulated for 3 years at a daily time step from four evergreen and three deciduous Mediterranean oak woodlands (21 site-year measurements; 105 site-year-simulations). Mediterranean ecosystems are important test-beds for studying the interannual dynamics of soil moisture on ecosystem mass and energy exchange as they experience cool, wet winters with hot, dry summers and are typically subject to drought. Results show data-model disagreements at multiple temporal scales for GPP, Reco, and ET at both plant functional types. Overall there was a systematic underestimation of the temporal variation of Reco at both plant functional types at temporal scales between weeks and months, and an overestimation at the yearly scale. Modeled Reco was systematically overestimated during drought for all sites, but daily GPP was systematically underestimated only for deciduous sites during drought. In contrast, daily estimates of ET showed good data-model agreement even during drought conditions. This meta-analysis brings attention to the importance of drought conditions for modeling purposes in representing forest dynamics in water-limited ecosystems. © 2013 Springer Science+Business Media New York.

Background: pH‐sensitive peptides are a relatively new strategy for conquering the poor endosomal release of cationic polymer‐mediated transfection. Modification of antimicrobial peptides by exchanging positively‐charged residues with negatively‐charged glutamic acid residues (Glu) greatly improves its lytic activity at the endosomal pH, which could improve cationic polymer‐mediated transfection. Methods: In the present study, we investigated the effect of the number of Glu substituted for positively‐charged residues on the endosomal escape activity of AR‐23 and the ability of mutated AR‐23 with respect to enhancing cationic polymer‐mediated transfection. Three analogs were synthesized by replacing the positively‐charged residues in the AR‐23 sequence with Glu one‐by‐one. Results: The pH‐sensitive lysis ability of the peptides, the effect of peptides on the physicochemical characteristics, the intracellular trafficking, the transfection efficiency and the cytotoxicity of the polyplexes were determined. Increased lytic activity of peptides was observed with the increased number of Glu replacement in the AR‐23 sequence at acidic pH. The number of Glu substituted for positively‐charged residues of AR‐23 dramatically affects its lysis ability at neutral pH. Triple‐Glu substitution in the AR‐23 sequence greatly improved poly(l‐lysine)‐mediated gene transfection efficiency at the same time as maintaining low cytotoxicity. Conclusions: The results indicate that replacement of positively‐charged residues with sufficient Glu residues may be considered as a method for designing pH‐sensitive peptides, which could be applied as potential enhancers for improving cationic polymer‐mediated transfection. [ABSTRACT FROM AUTHOR]

The chemical industry is one of the most important industry sectors in terms of energy consumption and CO2 emissions in China. However, few studies have undertaken accounting of the CO2 emissions in the chemical industry. In addition, there are some shortcomings in the traditional accounting method as a result of poor data availability, such as the incomplete consideration of emission sources and overestimation of actual emissions. Based on the traditional accounting method and the actual situation of the chemical industry, this study proposes a method called the Emission Accounting Model in the Chemical Industry, which covers fossil energy-related emission, indirect emission generated by electricity and heat, carbonate-related process emission and the reuse of CO2. In particular, fossil energy used as feedstock is included. By applying the Emission Accounting Model in the Chemical Industry in China, the calculated CO2 emissions would be 19–30% less than the result from the traditional method. In addition, it is found that the indirect CO2 emissions generated by electricity and heat account for 67% of the total amount, the fossil energy-related emissions account for approximately 37%, the process-related emissions accounted for 2%, and reuse of CO2 accounts for − 6% in 2016. The production of ammonia, ethylene and calcium carbide generated approximately half of the total CO2 emissions in 2016. In addition, in view of emission sources and carbon source flow, two other bottom-up accounting methods are proposed that can take effect when the chemical plant-level data are available. [ABSTRACT FROM AUTHOR]