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In this work, three isoreticular covalent-organic frameworks (COFs) were successfully synthesized at room temperature, namely C1, C2, and C3, respectively. Due to their wide absorption ranges and sufficient photoredox potentials, the constructed COFs exhibited good photocatalytic performance for reducing Cr(VI). Among them, C2 displayed the best photocatalytic performance, which may be attributed to the unique donor-acceptor structure, good light absorption, and excellent photoinduced carriers' separation and migration efficiency. When the COFs were modified with gold nanoparticles (labeled as Au@C1, Au@C2, and Au@C3), their photocatalytic performance can be further improved. For Au@C2, 98.2% of Cr(VI) can be reduced within 120 min, and its photocatalytic activity can be maintained over five reaction cycles. The structure-activity correlation was studied via both experimental and DFT calculation methods. It is shown that although C3 displayed wider absorption range and smaller energy band gap, its photocatalytic activity was much lower than C2. This may be due to the rapid nonradiative electron-hole recombination in C3, leading to low light utilization. These results indicate that to construct excellent COF photocatalysts, it not only needs to pursue wider absorption range and smaller energy band gap, but also improve the utilization of light energy and photogenerated charge carriers. In addition, the active species and photocatalytic mechanism were also studied. Three isoreticular Schiff-based covalent-organic frameworks (COFs) were facial prepared at room temperature and modified by gold nanoparticles. The Au@COFs were developed as efficient photocatalysts for reducing Cr(VI) in water. [Display omitted] • Three Schiff-based Au@COF composites were facile prepared at room temperature. • Tiny regulation of D-A units can obviously promote COFs' photocatalytic activity. • The structure-activity correlation was studied via both experimental and DFT calculation methods. • 98.2% of Cr(VI) can be reduced by Au@C2 within 120 min. [ABSTRACT FROM AUTHOR]

As the conventional energy resources are limited and environmental problems are becoming increasingly prominent, new energy resources, being environmental friendly and renewable, are paid more and more attention by all the countries. At present, the development and utilization of new energy resources in China has made progress. However, due to the factors such as the international energy competition situation, China׳s productivity level and its development phase, and the lagging of related system and mechanism reforms, China׳s new energy has been faced with constraints in the aspects of the system, efficiency, supply, region and technology. If related reforms were not implemented, the development of new energy in China would be severely hindered for a long period of time in the future. In view of this, this paper reviewed the development status of China׳s new energy industry, and analyzed five aspects of constraints. Moreover, a discussion was carried out from four aspects of the system, consumption, production, technology reforms in order to break the corresponding constraints. Finally the future development planning of new energy was presented. All in all, the deep investigation into China׳s new energy development status, constraints, reforms and planning in this paper is aimed at promoting the reform of new energy resources production and utilization modes, improving the policy system continuously, addressing the deep-rooted institutional contradictions of the new energy industry, and providing the reference and advice for the transformation of China׳s energy structure. [ABSTRACT FROM AUTHOR]

Abstract: To study the content characteristics of Ca, Mg and Zn in bryophytes from different geological settings using atomic absorption spectrometry (AAS), the bryophytes and their growth substrates from Three Gorges karst and Huangzhou non-karst regions of Hubei province were chosen for comparative analysis. The results indicate: (1) the contents of Ca and Mg in the bryophytes and their growth substrates from Three Gorges karst region are significantly higher than those from Huangzhou non-karst region, and there are no clear differences among Zn contents in the bryophytes and their growth substrates from both regions; (2) there are no obvious correlations among Ca, Mg and Zn in bryophytes from both regions; (3) metal element uptakes by bryophytes from different geological background or by different bryophyte species are different, and the absorption of different metals by the same bryophytes is also distinct. [ABSTRACT FROM AUTHOR]

A newly pyrene functionalized zinc(II)-MOF was solvothermal synthesized and developed for fluorescence sensing of nitroaromatic compounds due to its good photoluminescence properties. [Display omitted] In this work, a zinc(II)-based metal–organic framework, namely [Zn 2 (TBAPy)(H 2 O)(DMF)]·4DMF·2H 2 O (JOU-34) (TBAPy = 1,3,6,8-tetrakis (p-benzoic acid) pyrene; DMF = N,N'-Dimethylformamide), has been solvothermally synthesized and characterized. Single-crystal X-ray diffraction shows that JOU-34 displays three-dimensional microporous framework with rare topology. Due to the introduction of pyrene groups, JOU-34 shows strong fluorescent emission cantered at about 470 nm. Furthermore, it shows a good fluorescence sensing performance toward nitroaromatic compounds, especially nitrobenzene (NB). Although the NB concentration was only 8.33 × 10−4 M, the quenching efficiency can reach 89 %. Further studies show that the quenching effect of JOU-34 in the presence of nitroaromatics may be attributed to the fluorescence resonant energy transfer and electron transfer between nitroaromatics and JOU-34. These results indicate that JOU-34 can be applied as a functional material for nitroaromatics detection. [ABSTRACT FROM AUTHOR]

In this work, a crystalline electroactive triphenylamine-based covalent-organic framework (TPA-COF) was composited with carbon black (CB) using a facile one-pot solvothermal method. It is shown that the loaded amount of CB significantly affects the electrochemical performance of the composites. On one hand, CB dispersed in the COF matrix can improve the conductivity of the composite. On the other hand, the π - π interactions between COF layers and carbon particles may affect the accumulation of COF layers, resulting in the increasement of the surface area and the exposure of active sites. These structural advantages promote the performance of the composite toward dopamine (DA) detection. When 30 wt% CB was loaded, the composite modified electrode demonstrates best activity with a wide linear range of 20 μ M–1000 μ M and a low detection limit of 0.17 μ M (S/N = 3). Moreover, due to its high selectivity, satisfying stability, and good repeatability, the constructed electrochemical sensor was successfully used to detect the DA concentration in real medical injection with satisfactory recovery results, that is in the range of 98.7–111.0%. Further studies show that the good performance of the constructed sensor is attributed to its good conductivity, high specific surface area and effective host guest interaction between DA molecules and COF framework. This work provides a simple method to utilize COFs for quantitative detection of DA, as well as a new way to extend the applications of COFs in sensing. A serial of composites composed of crystalline two-dimensional COF and carbon black was synthesized by using one pot method. Owing to its improved conductivity and highly porous structure, TPA-COF/CB 0.3 was developed as an electrochemical sensor for dopamine determination. [Display omitted] • A series of porous carbon-loaded TPA-COF composites were facile prepared by one-pot solvothermal method. • The loaded carbon black effectively promotes the conductivity and the specific surface area of the composites. • TPA-COF/CB 0.3 @GCE reveals good electrochemical performance toward dopamine detection. • TPA-COF/CB 0.3 @GCE was successfully used to detect the dopamine concentration in real medical injection. [ABSTRACT FROM AUTHOR]

The objective of this study was to evaluate the effect of dietary chloride (Cl) levels on performance, eggshell mechanical quality, and ultrastructure in layers based on the substitution of sodium chloride (NaCl) by sodium sulfate (Na2SO4). Three hundred sixty Jing Brown laying hens aged 43 wk were randomly divided into 5 groups and fed with corn–soybean meal diets containing 0.06, 0.10, 0.15, 0.20, and 0.25% total Cl inclusion. Every group had 8 replicates of 9 birds each. The feeding trial lasted for 12 wk. The results showed dietary 0.06% Cl due to complete substitution of NaCl by Na2SO4, depressed performance (P < 0.05) from 45 to 54 wk of age, increased serum creatinine level (P < 0.05), and caused visible renal tubular atrophy. Dietary Cl levels quadratically affected breaking strength, thickness, and weight of eggshell (P < 0.05). Better eggshell quality could be obtained when NaCl was partly replaced by Na2SO4 in laying hen diets maintaining Cl level at 0.10 or 0.15%. Moreover, the eggshell ash content was affected by Cl levels in a quadratic (P < 0.001) manner, with higher values observed in the 0.10 and 0.15% Cl groups (P < 0.05). Besides, the eggshell ultrastructural data showed that the total thickness and effective thickness significantly increased (P < 0.05) and mammillary thickness decreased (P < 0.05) in the group of dietary 0.15% Cl compared with the groups of 0.06 and 0.25% Cl. In conclusion, the complete substitution of dietary NaCl by Na2SO4 may induce Cl deficiency and depress laying performance and eggshell quality. Na2SO4 could partly replace NaCl in diets for laying hens (43–54 wk of age) without adverse effects on performance at the dietary Cl level from 0.10 to 0.25%. Better eggshell quality could be obtained when NaCl was partly replaced by Na2SO4 in laying hen diets maintaining Cl level at ∼0.15%. [ABSTRACT FROM AUTHOR]

This study was conducted to determine the standardized ileal digestible amino acids (SID AA) and nitrogen-corrected apparent metabolizable energy (AMEn) contents of 6 wheats from different origins in China and incidentally to investigate the effects of exogenous xylanase addition on SID AA and AMEn determination in broiler chicks. A total of 480 chicks were divided into 48 cages of 10 birds each balanced for body weight and fed 8 types of diets in a completely randomized design (6 replicated cages per diet) from 21 to 26 d of age. The individual wheat constituted the only source of crude protein in a semi-purified experimental diet. A nitrogen-free diet was designed to estimate basal endogenous AA loss and determine the SID AA. Titanium oxide (0.3%) was used as an indigestibility marker, and nutrient digestibility and retention were determined by the substitution method. From day 24 to 26, excreta samples were collected for AMEn determination. On day 26, the birds were euthanized, and ileum contents were obtained for AA digestibility determination. Wheat from Gansu had greater (P < 0.05) SID AA contents except Lys, Thr, Phe, and Cys, with a higher (P < 0.001) AMEn (11.83 MJ/kg) than the other wheats. The SID content of mean indispensable amino acids and dispensable amino acids were 87.35% and 88.17%, respectively, and the average AMEn value of 6 wheats was 11.14 MJ/kg. Compared with the diet without xylanase, the added xylanase resulted in higher (P < 0.05) SID contents of Met, Lys, Trp, Arg, Ile, Leu, Val, Gly, Asp, Glu, Pro, and Ala; the SID AA values were raised by 1.96% (mean of all AA); and the AMEn content was significantly increased (+0.87 MJ/kg) (P < 0.05). In conclusion, origins of wheats have significant effects on SID AA and AMEn values which were positively correlated with crude protein content of wheat; exogenous xylanase addition to a wheat-based poultry diet could significantly improve SID AA and AMEn contents for broilers. [ABSTRACT FROM AUTHOR]

This study was conducted to investigate the comparative effects of dietary supplementation with microalgae oil or fish oil on fatty acid composition, sensory quality, and overall acceptability of table eggs. A total of six hundred thirty, 30-week-old, Hy-Line Brown laying hens were allocated to 7 dietary treatments. Layers were fed with a control diet or the control diet supplemented with graded levels of docosahexaenoic acid (DHA; 1.25, 2.50, and 5.00 mg/g feed) derived from microalgae oil or fish oil. The feeding trial lasted 10 wk. Enrichment of eggs with DHA by dietary supplementation with microalgae oil or fish oil enhanced yolk DHA and total n-3 polyunsaturated fatty acid (PUFA) enrichment and reduced n-6-to-n-3 ratio in a doseresponse manner, whereas the efficiency decreased (P < 0.05). The overall efficiency of DHA incorporation into eggs was similar for the 2 sources (P < 0.05). In comparison with fish oil, dietary microalgae oil supplementation resulted in higher scores for egg flavor and overall acceptability, both of which declined linearly in response to DHA supplementation (P < 0.05). Among the aroma and flavor characteristics, fishy aroma and flavor scores increased linearly and quadratically (P < 0.05) in response to dietary DHA supplementation, and egg aroma and flavor and milky flavor scores decreased linearly (P < 0.05). The results from partial least squares analysis showed that fishy flavor and aroma were closely associated with DHA, a-linolenic acid, and total n-3 PUFA, and oleic acid, arachidonic acid, and dihomo-gamma-linolenic acid were more related to egg aroma and flavor. The results suggested that microalgae oil would be more promising for egg DHA enrichment owing to better sensory quality of the resultant eggs. [ABSTRACT FROM AUTHOR]

Clean energy dominant and electricity centric is the inevitable trend of the future energy development. Electric power industry has entered into an increasingly competitive era in recent years due to the deregulation of power systems. However, power market should not be fully competitive and need to be regulated strictly to satisfy the safe and reliable operation of power systems. Base on the market equilibrium principle in microeconomics, a novel power market clearing model with limited competition was put forward, in which the limited competition power satisfies the power flow adjustment and the network losses distribution. Further, the free transaction ratio which can be regarded as the measurement of the degree of power market deregulation was analyzed according to the formulated market clearing model. Finally, three case studies were made on the IEEE-30 test system to verify the practicality and efficiency of the method. The results show that different transaction ratio has significant influence on the operation of power systems and the optimal transaction ratio can be determined. [ABSTRACT FROM AUTHOR]

Large-scale blackouts have occurred frequently throughout the world. The blackouts that have occurred in recent years not only seriously affect the lives of local residents, but they also cause substantial economic losses. In particular, as modern society increasingly depends on electricity, power outages occurring at any time may result in devastating consequences. Accordingly, identifying the reasons for blackouts and implementing proper restoration measures are of particular importance. This paper analyses the sphere of influence, the scale of the effects, the restoration measures and the causes of previous worldwide blackouts. Based on the findings, suggestions for the development of China׳s power industry are then offered. [ABSTRACT FROM AUTHOR]

Enzyme stability is an important issue for protein engineers. Understanding how rigidity in the active site affects protein kinetic stability will provide new insight into enzyme stabilization. In this study, we demonstrated enhanced kinetic stability of Candida antarctica lipase B (CalB) by mutating the structurally flexible residues within the active site. Six residues within 10 Å of the catalytic Ser105 residue with a high B factor were selected for iterative saturation mutagenesis. After screening 2200 colonies, we obtained the D223G/L278M mutant, which exhibited a 13-fold increase in half-life at 48 °C and a 12 °C higher T5015, the temperature at which enzyme activity is reduced to 50% after a 15-min heat treatment. Further characterization showed that global unfolding resistance against both thermal and chemical denaturation also improved. Analysis of the crystal structures of wild-type CalB and the D223G/L278M mutant revealed that the latter formed an extra main chain hydrogen bond network with seven structurally coupled residues within the flexible α10 helix that are primarily involved in forming the active site. Further investigation of the relative B factor profile and molecular dynamics simulation confirmed that the enhanced rigidity decreased fluctuation of the active site residues at high temperature. These results indicate that enhancing the rigidity of the flexible segment within the active site may provide an efficient method for improving enzyme kinetic stability. [ABSTRACT FROM AUTHOR]