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关键词： 工程认证   课程建设   金课   物理化学  

摘要： 工程认证是我国新工科建设的重要一环。本文基于工程认证对"物理化学"课程的要求,结合金课课程建设的标准,充分考虑工科"物理化学"课程目前存在的问题,围绕课程目标、课程内容、教学模式和课程评价等方面就工程认证背景下工科"物理化学"金课课程建设方式方法进行探索,为课程改革提供一定的经验借鉴,为工程应用人才的培养提供支撑。

关键词： 物理化学方法   羟基磷灰石晶体   牙釉质   平均宽度   合成类   数据差异   过饱和   矿物质  

摘要： 一、牙釉质结构及其性能分析牙釉质具有复杂的结构,主要由约1~2mm厚的羟基磷灰石晶体组成[1]。在过饱和离子环境下,蛋白质之间和蛋白质与矿物质之间相互作用产生了优先沿C轴生长的高度有序的羟基磷灰石晶体束[2],约30nm厚,60nm宽[3](由于成像局限性,文献间数据差异大:如,另有文献说横截面大致为矩形[4],平均宽度为68nm,平均厚度为26nm[5]。)。这些微晶的大小取决于其矿化的阶段:在分泌阶段晶体主要增加长度,在成熟阶段继续增加宽度和厚度。

关键词： Chitosan   Response surface methodology   High hydrostatic pressure   Antioxidant activities   Physicochemical properties  

摘要： Squid pen sample was treated by high hydrostatic pressure (HHP) prior to the extraction of chitosan. The physicochemical and antioxidant activities of the chitosan obtained with HHP (HHP-CS) were compared with chitosan of untreated squid pen sample (Ur-CS). The chitosan extraction yield was optimized using response suiface methodology, and the optimum condition was achieved at pressure of 500 MPa, extraction time of 10 min, and 1% (w/w) acetate concentration. The maximum yield of chitosan sample from the chitin of squid pens treated by HHP reached 81.9%. Among the process variables, the combined effects of pressure and acetate concentration significantly enhanced the extraction of chitosan from squid pens. The HHP-CS was found to be significantly effective in enhancing the fat binding capacity, water binding capacity, and water solubility index. SEM image analysis suggested that the HHP-CS had a rough surface with high porosity, while UT-CS exhibited a smooth surface. In vitro antioxidant assay suggested that HHP-CS had significantly higher DPPH radical scavenging activity, greater reducing power, and a stronger ferrous ion chelating effect than did UT-CS. Therefore, HHP can be an excellent alternative method for improving the physicochemical properties and antioxidant activities of chitosan from squid pens. (C) 2020 Elsevier B.V. All rights reserved.

关键词： 电力电网   变压器   瞬变现象  

摘要： 电力电网的安全,在国家政治、经济、文化各领域尤为突出重要。一个安全、高效、稳定的电力电网,是政治、经济、文化生活各领域的必须保障。电力电网是一个庞大复杂的系统,它是由发电、变电、输电、配电和用电环节组成的电能生产与消耗的能量转换系统。变配电环节中的电力变压器是电力电网设备中的重要设备之一,它运行状态的好坏直接影响到电网运行的安全与稳定。本文介绍的就是笔者在10kV中压变压器运行终端亲历的一次“瞬变”现象。

关键词： Viscosity  

摘要： Inulin and hydroxypropyl methylcellulose (HPMC) at 0.2 and 8% were evaluated as fat replacements in low-fat muffins. The viscosity of the muffin dough decreased from 903 cP in full-fat muffins (C1) to 377 cP in low-fat muffins (C2). The viscosity increased with 8% inulin (L2, 740 cP) or 0.2% HPMC (H1, 1332 cP). With increasing amounts of inulin, hardness decreased, whereas the opposite effect was found with HPMC. The hardness of L2 (8.66 N) and H1 (9.74 N) was not significantly different from C1 (8.25 N). Substitution with inulin or HPMC decreased the rate of retrogradation (n: 1.56-3.16) compared to C2 (3.22), except for 8% HPMC (5.28). In oiliness evaluated by the sensory panel, L2 (3.66) and H1 (3.62) had a better mouthfeel than C2 (2.82), which was next to C1 (5.13). Inulin and HPMC seemed to work as a fat replacers in low-fat muffins. However, different fat replacers need to be adjusted for the optimal amount. The addition of inulin at 8% or HPMC at 0.2% to low-fat muffins was found to produce acceptable qualities that were similar to those of full-fat muffins. Practical applications A muffin is a type of bread containing 50% fat to provide a smooth and soft texture. Two different carbohydrate-based fat replacements (inulin and HPMC) were evaluated in low-fat muffins. As the fat was reduced from 23% to 7%, the viscosity of the muffin batter decreased and the hardness of the muffin increased. Inulin or HPMC improved the viscosity of the batter and the hardness of the muffins as well as the sensory qualities. However, it is important to determine and use the optimal amount of different fat substitutes. Adding a large amount (8%) of inulin or a small amount (0.2%) of HPMC to low-fat muffin was found to be acceptable and can be widely applied.

关键词： postharvest   aroma   SPME  

摘要： The jabuticaba is a native Brazilian fruit that has aroused worldwide interest in terms of its nutritional composition and biological activity. However, research on the profile of volatile compounds (VOCs) emitted by these fruits is rare. This study presents the first identification of VOCs from four jabuticaba species. The aim of the study was to characterize the aromatic profile of the following species: 'Sabara' (Plinia jaboticaba), 'Escarlate' (Plinia phitrantha x Plinia cauliflora), 'Otto Andersen' (Plinia cauliflora), and 'Esalq' (Plinia phitrantha). The analysis was performed by headspace solid-phase microextraction combined with gas chromatography/mass spectrometry (SPME-GC-MS). Multivariate analysis techniques applying the partial least squares-discriminant analysis (PLS-DA) and heatmap were used to compare the results. Fruit quality parameters were determined in terms of fresh mass (g), skin color, soluble solids, and titratable acidity. A total of 117 VOCs was identified including terpenoids, esters, alcohols, aldehydes, alkanes, ketones, and carboxylic acids, with 36 VOCs common to all four species. Terpenes were the majority for all jabuticabas with smaller contributions from other volatile classes, especially beta-cubebene, beta-elemene, and D-limonene for the 'Otto Andersen' jabuticaba.

关键词： Goat milk   Heat treatment   Stabilizing salts   Ultra-high temperature instantaneous sterilization (UHT)   Turbiscan technique  

摘要： This study investigated the effects of heat treatment and stabilizing salts on the physicochemical properties, protein structure and salt balance of goat milk. Heat treatment altered the quantity of sediment (peak width) and particle concentration (delta backscattering) of goat milk observed in Turbiscan spectrograms. A higher Turbiscan Stability Index, and greater sediment thickness and velocity were observed in UHT goat milk than in UHT cow milk, indicating poorer heat stability of goat milk than cow milk. The poor heat stability of goat milk might be caused by the heat-induced conversion from stretching structure (beta-sheet and beta-turn) to globurizing structure (random coil and alpha-helix) of protein, and changes in distributions of proteins (beta-CN, alpha(s1)-CN, alpha(s2)-CN, kappa-CN, beta-LG and alpha-LA), calcium and phosphorus between supernatant and sediment. Compared with UHT goat milk without stabilizing salts, the addition of stabilizing salts increased the amounts of calcium and phosphorus in the supernatant and decreased the amounts of sediment, protein particle size, and globular protein structure in UHT goat milk. This demonstrates that stabilizing salts can be used to improve the heat stability of goat milk.

关键词： Browning reaction   Cysteine   Ultrasonication   Lotus root slices  

摘要： The effects of ultrasound (US) power of 200 w at a constant frequency of 40 kHz for 2 min, 0.01 % cysteine (Cys) and combinative application of US and Cys (US + Cys) on browning prevention and quality of lotus root slices were compared during storage at 4 degrees C for 12 d. The visual appearance, colour attributes including L*, b*, hue, chroma, whiteness index (WI), browning index (BI) and colour difference (Delta E*), browning enzymes activities such as polyphenol oxidase (PPO) and peroxidase (POD), total phenols concentration, texture, total sugars concentration and antioxidant activities were evaluated. US + Cys retarded browning incidence being greater than Cys, US and control treatments, respectively. The browning retardation was concomitant with the retention of high L* and WI values and low b*, chroma, BI and Delta E* value. Cys and US + Cys controlled the increased PPO activity rather than US. All treatments delayed the increased total phenols concentration compared to control. All treatments maintained hardness of lotus root slices, especially US, and did not affect total sugars con-centration. Both sonication treatment enhanced ferric reducing antioxidant potential (FRAP) whilst free radical scavenging activity was enhanced by Cys. In conclusion, both of the Cys and US could prevent browning and maintain physicochemical quality of lotus root slices and the simultaneous US and Cys treatment exhibited synergistic antibrowning effect.

关键词： Dipropylene glycol dimethyl ether   Methyl acetoacetate   Ethyl acetoacetate   Density   Speed of sound   FTIR  

摘要： Density rho, and speed of sound u, measurements have been carried out for the binary mixtures of dipropylene glycol dimethyl ether with methyl acetoacetate and ethyl acetoacetate at intervals 5 K, from temperatures T = (288.15 to 308.15) K and experimental pressure of p = 0.1 MPa. The entire ranges of composition have been measured using Anton-Paar DSA 5000 M densimeter i.e. density and speed of sound analyzer. Using experimental density data the excess molar volume, V-m(E) has been determined. Isentropic compressibility along with excess molar compressibility have been determined from the experimental speed of sound. Deviations in intermolecular free length and deviations in acoustic impedance along thermal expansion coefficient have also been calculated. The variation of these parameters with composition and temperature have discussed in terms of molecular interaction in these mixtures. FT-IR studies of these mixtures have been also reported and obtained results have been used to analyze the mixing behaviour of the components. (C) 2020 Elsevier Ltd.

关键词： Niosomal gel   Methylene blue   Box-Behnken design   Full-thickness wound model   Wound healing   Malondialdehyde   Superoxide dismutase  

摘要： Following skin injury, the overproduction of reactive oxygen species (ROS) during the inflammatory phase can cause tissue damage and delay in wound healing. Methylene blue (MB) decreases mitochondrial ROS production and has antioxidant effects. The authors aimed to prepare MB-loaded niosomes using the ultra-sonication technique as a green formulation method. A Box-Behnken design was selected to optimize formulation variables. The emulsifier to cholesterol ratio, HLB of mixed surfactants (Span 60 and Tween 60), and sonication time were selected as independent variables. Vesicle size, zeta potential (ZP), and drug entrapment capacity percentage were studied as dependent variables. The optimized formulation of niosomes showed spherical shape with optimum vesicle size of 147.8 nm, ZP of - 18.0 and entrapment efficiency of 63.27%. FTIR study showed no observable interaction between MB and other ingredients. In vivo efficacy of optimized formulation was evaluated using an excision wound model in male Wistar rat. Superoxide dismutase (SOD, an endogenous antioxidant) and malondialdehyde (MDA, an end product of lipid peroxidation) levels in skin tissue samples were evaluated. After 3 days, MDA was significantly decreased in niosomal gel-treated group, whereas SOD level was increased. Histological results indicate rats that received niosomal MB were treated effectively faster than other ones.