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关键词： Caffeine   Cement   Hydration   Compressive strength   Microstructure   Thermal properties  

摘要： Caffeine is a nontoxic and eco-friendly natural molecule used in the food industry as well as a corrosion inhibitor in various corrosive media. However, its behavior and performance as an additive in the construction industry has not been explored. This paper investigates the effect of caffeine as an additive on strength, water demands, setting time and hydration mechanism of cement. In the first instance, the water demand, volume expansion and setting time of cement pastes, incorporating 0, 25, 50 and 75 ppm of caffeine were determined. In the second section, the rate of hydration and cement pastes' products were conducted by means of X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), thermal analysis and scanning electron microscope (SEM) at 28 days. Finally, the cement mortars' compressive strengths were determined at 2, 7 and 28 days intervals. Consequently, mortars containing 75 ppm caffeine registered higher strength than the pure cement mortars due to high quantities of primary C-S-H gel, chemically bound water, compact structure at 28 days. Furthermore, by result of analysis and experiments, it was determined that caffeine had no negative effect on cement. (C) 2020 Elsevier Ltd. All rights reserved.

关键词： Agricultural waste   Lignocellulose   Valorisation   Plastic film   UV protection   Eco-friendly  

摘要： Cotton gin trash (CGT), a potential lignocellulose resource was combined with poly(vinyl alcohol) (PVA) to produce the biodegradable composite plastic film. A 50:50 CGT/PVA ratio was maintained using coarse and fine CGT powder particles and the effect of particle size on the morphology, crystallinity, tensile strength, optical transmittance, thermal stability and biodegradability was investigated. Scanning electron microscope (SEM) image showed uniform distribution of CGT in PVA matrix particularly of the fine powders (similar to 5.7 mu m). The incorporation of CGT in PVA enhanced the tensile strength, biodegradability, thermal stability and induced complete UV protection. Overall, while the flexibility of the composite film decreased, the tensile strength increased 10% and 20%, respectively by the coarse and fine CGT powders when compared to the pure PVA film. Considering the fabrication cost as estimated in the study, the results point towards the immense potential of CGT as a low-cost reinforcement material for PVA to be successfully used in the production of biodegradable plastic material. (C) 2020 Elsevier B.V. All rights reserved.

关键词： Andesite processing wastewater   ANN   Coagulation   Flocculation   Modeling   Turbidity  

摘要： A holistic approach has been introduced on the treatment of andesite marble processing wastewater. The treatment was implemented by using coagulants, flocculants, and minerals. Dosage, mixing time, settling time (ST), mixing speed (MS), and pH were optimized. Up to 99% turbidity removal was achieved by using Alum, FeCl3, PACl, and 40% cationic flocculant under optimized conditions of each. Among the minerals, pumice resulted in 81% turbidity removal efficiency in a much shorter duration as compared with the natural settling conditions. The obtained experimental data was used in the model established with Artificial Neural Network (ANN)-MLP for the prediction of treatment performance (final NTU). Feature selection was performed by using statistical correlations between each experimental parameter and final NTU. ST and MS were determined as the non-correlated parameters with final NTU. The model was integrated into feature selection approach upon establishing three scenarios with datasets: NFS was the whole experimental data consisting of all variables;FS1 was the dataset without ST and dataset FS2 was built up by removing both ST and MS. It was indicated that, when using chemical coagulants, there is no need to study the effects of ST to improve treatment performance, whereas, when using flocculants, both ST and MS has no influence on the treatment performance, so there is no need to perform extra experiments for these variables. Duration of training processes of modeling for all datasets was changing in range of 45-60 s. ANN configuration with two hidden layers was the best model structure, and ST was the parameter which had minimum influence on the treatment performance. The treatment and modeling approaches suggested in this study will be useful to give practical answers to the facility.

关键词： 物理化学实验   应用能力   创新能力   教学模式  

摘要： 物理化学是当前高校化学专业主修的重要基础课,是对化学运动普遍规律进行研究的一门学科。这门课程是在物理和化学两大学科基础上发展起来的,以实验为基础,综合运用了物理、数学等基础科学的理论成就与实验技术。因为物理化学的理论知识较抽象,所以需要充分利用好相对应的物理化学实验课程,在实践中探索出应用性更强的教学模式。特别是从“知识型”人才培养转变为“创造型”人才培养的今天,在进行教学过程中,教师怎样才能有效发挥其教学的主导作用,如何改善教学方法来提高教学效率及质量,是值得深入探讨的问题。

关键词： Plasmons   Quantum mechanics   Cavities   Polaritons   Molecules  

关键词： Potato cubes   drying kinetics   physicochemical properties   artificial neural network (ANN)   hot air drying based on temperature and humidity control (TH-HAD)  

摘要： In current work, air impingement drying (AID), infrared-assisted hot air-drying (IR-HAD), and hot air drying based on temperature and humidity control (TH-HAD) drying technologies were employed to drying potato cubes and their effects on drying kinetics, color, ascorbic acid content, rehydration ratio, microstructure, and specific energy consumption (SEC) were explored. Besides, artificial neural network (ANN) was used to predict changes in moisture ratio during the drying process. Results indicated that TH-HAD had the shortest drying time, followed by IR-HAD and AID. The effective moisture diffusivity (D-eff) of potato under TH-HAD, IR-HAD and AID were 1.35 x 10(-9), 1.18 x 10(-9), and 0.90 x 10(-9)m(2)/s, respectively. TH-HAD contributed to excellent physicochemical properties of dried potato when compared to samples dried by IR-HAD and AID. Overall, TH-HAD provided higher ascorbic acid content, better rehydration ability, brighter color, and had lower specific energy consumption (SEC). The microstructure well explained the difference of rehydration ratio and drying kinetics under different drying methods. The ANN models with the optimal topology could predict the moisture ratio under different drying methods with satisfactory accuracy. The current findings indicate that TH-HAD is a promising drying technology for potato cubes and has the potential to be applied in commercial scale.

关键词： Zirconia ceramics   resin cements   physicochemical properties   mu TBS  

摘要： The aim of this study was to investigate the physicochemical properties of five resin cements and their effects on bonding to zirconia ceramics. The degree of conversion (DC) and water contact angle of five resin cements were measured. Fifty zirconia blocks were randomly divided into five groups according to resin cements (RelyX Ultimate [RUL];Panavia F [PF];Clearfil SA Luing [CSA];Multilink Speed [MS];RelyX Unicem [RUN]) and bonded to the prepared dentin. After storage for 24 h and 5000 thermal cycles, the micro-tensile bond strength (mu TBS) was tested, the failure modes and bond interface morphology were observed. The results were subjected to statistical analysis. The DC of CSA and the contact angle of RUL was the largest. At 24 h, the mu TBS was MS > RUL > CSA approximate to PF > RUN (p < 0.05). After 5000 cycles, the mu TBS was MS > CSA > RUL > PF approximate to RUN (p < 0.05). The failure modes were determined to mixed and interface failures. The resin tags of RUL were thicker, longer, more uniform and numerous. In conclusion, the bond strength of resin cement is affected by many factors, such as DC and wettability. The Clearfil SA showed the lower reduction on bonding effect after 5000 cycles, while Multilink Speed presented the highest mu TBS before and after 5000 cycles.

关键词： aromaticity   nitrogen   phosphole   porphyrinoid   pyrrole  

摘要： Porphyrins with a fused five-membered ring, such as 7,8-dehydropurpurins, have appeared as an emerging class of unique porphyrinoids. Their altered absorption spectra, relatively short lifetimes of excited states, and small HOMO-LUMO gaps arise from the harmony of the antiaromatic 20 pi-circuit and the aromatic 18 pi-circuit. In this regard, the electronic properties of 7,8-dehydropurpurins are expected to be controlled by modulating the contribution of the antiaromatic pi-circuit to the whole aromaticity. Here the comparison of pyrrole- and phosphole-fused 7,8-dehydropurpurins is reported in terms of their aromaticity and physicochemical properties. The spectroscopic investigation revealed the larger contribution of the antiaromatic 24 pi-circuit in pyrrole-fused 7,8-dehyrdopurpurins than in phosphole-fused 7,8-dehydropurpurins. The DFT calculations also supported the feasibility of tuning the aromaticity of 7,8-dehydropurpurins by heterole-fused structures. Thus, the introduction of heterole-fused structures into porphyrinoids is a universal strategy to get new insight into aromaticity and their intrinsic properties in cyclic pi-conjugated molecules.

关键词： Chitin nano-objects   Mushroom   Waste by-products   Dispersion stability  

摘要： Chitin production from fungal sources has gained increased attention in recent years in terms of continuous supply and safety. In this study, we produced chitin from Shiitake stipes through deproteinization, depigmentation, demineralization and removal of glucans, and then prepared chitin nanocrystal (ChNC) and chitin nanofibers (ChNF) by acid hydrolysis or high-pressure homogenizers. Such obtained ChNFs have higher length than the ChNCs with a length of 142.4 +/- 40.4 nm, with the similar diameter (9 nm). In addition, the purity of ChNC and ChNF were over 98 % measured by HPAEC. The zeta potential analysis showed that ChNC is stable in acid form, while ChNF is in the opposite. Finally, we evaluated the rheology properties of samples to find the impact of salt concentrations on nanoparticles interactions. Overall, the fungi-derived chitin nanomaterials with diversity of characters exhibit immense potential for applications in nutraceutical and food industry.

关键词： Plant invasion   Species richness and composition   Managed forests   Soil nutrients   Phenolic compounds  

摘要： This study assessed the effects of invasive Quercus rubra on soil physicochemical properties and understory vegetation in native plant communities. Chemical properties of senesced tree leaves were also analysed. The study was performed at paired invaded-native plots in managed forests in southern Poland. Freshly fallen senesced leaves were characterized in terms of C, Ca, K, Mg, N, P, total phenolics and condensed tannins concentrations. Soil physicochemical parameters, namely bulk soil density, moisture, water holding capacity (WHC), pH, organic C, total Ca, K, Mg, N, P, exchangeable Ca, K, Mg, N-NH4, N-NO3, P-PO4, and total phenolics were analysed in organic and mineral soil horizons, and condensed tannins were analysed in organic soil horizon. The diversity, cover and composition of understory vegetation were assessed. Although, senesced leaves of Q. rubra and native trees, Quercus robur, Fagus sylvatica, Carpinus betulus and Acer pseudoplatanus among others, differed only in total K, N and C/N ratio, we observed considerable differences in soil physicochemical parameters between the plot types. Soil beneath Q. rubra was characterised by significantly lower WHC, organic C, total Mg, N, P, exchangeable Ca, Mg, N-NH4, N-NO3, total phenolics and higher moisture in organic and mineral soil horizons as well as lower content of P-PO4 and condensed tannins in organic soil horizon relative to native plant communities. Q. rubra negatively influenced species richness and cover of understory vegetation. The changes in soil physicochemical parameters and understory vegetation under Q. rubra may be associated with low quality (low N, high C/N) litter that decomposes slowly and generates a physical barrier, limiting seed germination and seedling growth. The changes in soil properties and vegetation under invasive Q. rubra indicate that this species may alter the structure and function of forest ecosystems and should be avoided in forest management practices.