Efficiency of acetic acid and formic acid as a catalyst in catalytical and mechanocatalytical pretreatment of barley straw

In this study, the potential of organic acids (formic acid, acetic acid) in a catalytical and mechanocatalytic conversion of lignocellulosic barley straw to valuable sugars is explored using sulfuric acid as a reference. Acid-catalyzed hydrolysis has been carried out with acid-impregnated samples as well as unmodified barley straw. In the mechanocatalytical approach, pretreatment consists of impregnation with the acid catalyst and mechanical treatment by ball milling following chemical hydrolysis. Straw samples and residues were analyzed by Fourier transform infrared spectrometry (FT-IR) whereas hydrolysate analysis was based on total reducing sugar (TRS) determination following the DNS method and capillary electrophoresis (CE) analysis. The results indicated that acetic acid and formic acid are rather mild acids yielding low TRS levels compared to the reference acid. Mechanocatalytical pretreatment slightly increased TRS yields, but not significantly. Strikingly, sulfuric acid showed an efficient conversion efficiency yielding almost 45% of TRS. Furthermore, this study provided evidence for the acetylation of straw components when acetic acid was used as catalyst. Alkali hydrolysis induced the de-esterification, but revealed no significant increase of TRS yields.     

Stability of viscoelastic liquid curtain

Thin liquid sheets occur in several practical applications. In curtain coating, a thin liquid sheet is formed and falls freely over a considerable height before it impinges onto a moving substrate. Precision curtain coating was developed for multi layer photographic films but its use has expanded to many different applications. One of the important limits of this process is the stability of the liquid curtain, which may define the minimal thickness that can be coated at a given web speed.The condition at which a low viscosity Newtonian liquid curtain breaks was first derived based on a simple balance between inertial and capillary forces. There is a critical flow rate below which the curtain becomes unstable. For viscoelastic liquids, the normal stress related to the stretching of polymer molecules as the liquid accelerates down the curtain changes the force balance. Here, the critical condition at which a viscoelastic liquid curtain breaks was determined as a function of the rheological properties of the liquid. The results show that high extensional viscosity liquids create more stable curtains. Liquid additives could be used to push the limits of curtain flow rates to smaller values and consequently to widen the operability window of the process.     

How does the new-type urbanisation affect CO2 emissions in China? An empirical analysis from the perspective of technological progress

The development of traditional urbanisation has generated environmental problems, so the Chinese Government has proposed a new-type of urbanisation path with uniquely Chinese characteristics. How does this new-type of urbanisation affect CO₂ emissions? Based on panel data from 29 provinces in China (2005 to 2016), we apply an exploratory spatial data analysis model, a spatial econometric model, and a threshold model to analyse the spatial autocorrelation of CO₂ emissions, the direct and indirect effects of new-type urbanisation on CO₂ emissions, and the threshold characteristics produced by technological progress, respectively. The key results are: (1) CO₂ emissions show significant positive autocorrelation in China, and the spatial distribution of CO₂ emissions is HH (High-High) or LL (Low-Low) clustered in most provinces; (2) new-type urbanisation has a paradoxical effect on CO₂ emissions. Energy-saving technology has a rebound effect on CO₂ emissions, but environmental technology inhibits CO₂ emissions; (3) by eliminating the rebound effect of energy-saving technology on CO₂ emissions and promoting environmental technology, new-type urbanisation indirectly inhibits CO₂ emissions; (4) new-type urbanisation exhibits a threshold effect on CO₂ emissions due to the different levels of energy-saving technology and environmental technology. Finally, policy recommendations for CO₂ emissions reduction are proposed from the perspective of new-type urbanisation, energy-saving technology, and environmental technology.     

Oxy-fuel combustion of heavy oil based on OH - PLIF technique

Oxy-fuel combustion of heavy oil can be applied to oil field steam injection boilers, allowing the utilization of both heavy oil and CO₂ resources. This paper studied the local distribution characteristics of OH on oxy-fuel combustion of heavy oil during the ignition and stable combustion processes. During the ignition process, we observed the generation and evolution of fire kernel, and got the flame propagation velocity. During the stable combustion process, the results showed that the OH distribution and its relative signal intensity were influenced by the oxygen concentration, excess air coefficient, gas flow, reaction atmosphere, oil mist scattering, incident laser energy and laser sheet position. In the same reaction atmosphere, the ranges of OH dense distribution and the high temperature area increased as O₂ concentration increased. In the same O₂ concentration, both the ranges of OH dense distribution and the high temperature area in O₂/N₂ were larger than that in O₂/CO₂. In 29% O₂/71% CO₂, the flame shape was similar to combust in air, while the OH relative signal intensity and its volatility were much larger than that in air. In the same combustion condition, the location of high concentration of OH relative concentration field lagged behind the high temperature area. The results further reveal the differences between the conventional and oxy-fuel combustion.     

Effect of Mn inclusion in superconducting YBCO-based composites

The doping effect of Mn in polycrystalline YBa₂Cu₃O_{7 − δ} material (YBCO) is carefully analyzed considering the transport properties of composites formed by small inclusion particles of Mn embedded whether in a YBCO matrix or in superconducting Fe-YBCO composites. In both cases, the improvement of their respective electrical resistivity was evidenced. The use of double element doping clearly shows that an a priori degradation of the YBCO electrical properties by Fe atoms can be greatly restored by appropriate Mn doping. This character can be very useful for technological applications. This improvement is mainly due to the reduction of the secondary and/or insulating phases formed at the grain boundaries, limiting the current transport. The involved mechanism is the probable existence of free charged Mn-based species which are responsible for an optimal oxygenation in the material contributing to the electrical response improvement. These species can be located in the composite, whether entering the CuO chains of the YBCO lattice or complexing and reducing the secondary phases formed during the sintering process, especially Fe₂O₃ and Y₂BaCuO₅ in the case of Fe-YBCO composites.     

国内外旅游食品安全保障体系建设研究进展

随着旅游食品安全受到的关注越来越多,相关的理论研究也将会不断地深入,结合当前我国旅游食品安全保障体系建设的现状可以发现,其在相关理论的推动下,我国旅游食品安全保障体系的建设正在不断完善。为了系统认知国内外旅游食品安全保障体系建设研究进展,本文对国内外关于食品安全保障方面取得的研究成果进行归纳总结,明确旅游食品安全保障体系建设的规律以及影响旅游食品安全保障体系建设的因素,并在此基础上,结合目前国内旅游食品安全保障体系建设的现状,提出我国旅游食品安全体系的建设应结合我国旅游业发展的实际状况、对我国现有的食品安全相关制度进行补充和借鉴、扩大食品安全宣传,提升旅游行业食品经营者对食品安全的重视程度等建议,为推动我国旅游业的可持续发展提供参考。     

Diborane–tetraborane conversion in C60 vesicles—a theoretical study

Diborane–tetraborane conversion in a C₆₀ cage is theoretically considered by using AM1-RHF type semiempirical quantum chemical approach. Molecular orbital characteristics of some endohedrally boron hydride doped C₆₀ composite systems are investigated and the likeliness of diborane–tetraborane conversion in a C₆₀ vesicle for the purpose of hydrogen storage is discussed.     

Surface dissolution and amorphization of electrocatalysts during oxygen evolution reaction: Atomistic features and viewpoints

Electrochemical electrolysis with an aqueous electrolyte is a key method to obtain green hydrogen energy, convert carbon dioxide into high value-added carbon-based chemicals, and produce ammonia by nitrogen reduction at ambient conditions. For better efficiency of these electrolysis processes, lowering the comparatively large activation barrier of the sluggish oxygen evolution reaction (OER) at the anode side is necessary. Therefore, suitable electrocatalysts should be adopted to facilitate the OER. As a highly oxidizing environment along with high overpotential is unavoidable at the anode during electrolysis, degradation of both the activity and durability of OER catalysts inevitably takes place. In this Review, we classify four significant origins directly affecting the stability of oxide-based OER catalysts: (1) Alkali and alkaline-earth metal dissolution; (2) transition-metal leaching; (3) lattice oxygen evolution; and (4) rapid dissolution of phosphorus and chalcogens. In particular, because these origins usually induce amorphization or reconstruction at the surface, we systematically summarize atomic-level evidence largely based on transmission electron microscopy in each section. Providing integrated viewpoints for a better understanding of catalyst degradation, we believe that this Review offers valuable insight toward designing new OER catalysts with enhanced durability and activity.     

Synthesis and antimicrobial activities of acrylamide polymers containing quaternary ammonium salts on bacteria and phytopathogenic fungi

Three series of acrylamide monomers/polymers containing quaternary ammonium salts (QASs), i.e., acrylamide QAS monomers (QDs), homopolymers of QDs (PQDs) and copolymers of QDs with acrylate monomer (PQDCs), were synthesized and employed in antimicrobial tests against both bacteria (Escherichia coli (E. coli) and Staphylococcus albus (S. albus)) and phytopathogenic fungi (Rhizoctonia solani (R. solani) and Fusarium oxysporum f. sp. cubense race 4 (Foc4)). The antibacterial activity of the QASs was evaluated by determining the minimum inhibitory concentration (MIC) against E. coli and S. albus by the TTC coloration method, and the antifungal activity was measured by mycelia growth inhibition as well as MIC and the minimum fungicidal concentration (MFC) values. The results indicated that PQD homopolymers and PQDC copolymers showed far better antimicrobial activities than QD monomers. PQDC copolymers by incorporating hydrophobic acrylate units into the main chain of polyacrylamide backbone displayed even better antimicrobial activities, depending on QAS structure and hydrophobic content. Moreover, polymers with benzyl group attached to nitrogen atom showed better inhibitory effect on bacteria and phytopathogenic fungi. The results could assist understanding and development of future design of antimicrobial polymers as potential fungicide agents to control plant disease.