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关键词： 物理化学实验   民族院校   知识模块   理论实验结合  

摘要： 长期以来,西南民族大学本科阶段《物理化学》及实验课程教学存在学业优秀率低的问题。本文根据笔者的实际教学和调查总结,剖析西南民族大学《物理化学实验》教学内容和教学安排中长期存在的问题,提出了较合理的改进建议。

关键词： 物理化学   HMX   静电喷雾   超细化   包覆   降感  

摘要： 为了降低工业级HMX的感度,提高其安全性能,采用静电喷雾法分别制备了亚微米HMX、HMX和F2603的共混样品、HMX与F2603的同轴样品;用扫描电子显微镜(SEM)对其形貌和粒度大小进行了观察;用X射线光电子能谱仪(XPS)对样品的包覆效果进行了分析;用X射线衍射(XRD)和傅里叶变换红外光谱(FT-IR)对其晶型进行了判定;用差示扫描量热仪(DSC)研究了其热力学性能;并测试了原料HMX及制备样品的撞击感度。结果表明,制备的HMX颗粒形貌良好,粒度为亚微米级别,表面光滑无棱角;包覆的样品粒径在2μm左右,形貌规则、粒径分布均匀;XRD和FT-IR的结果表明,样品的晶型都已转化为γ-HMX;样品的活化能较原料HMX下降,求得的热分解峰温和自发火温度表明样品的热安定性升高,且同轴样品的热安定性优于共混样品;与原料HMX相比,样品的撞击感度分别下降了7.8%、27.1%和37.0%,降感效果明显。

关键词： Sago starch   Structural properties   Pasting   Thermal properties   Rheology  

摘要： A comprehensive study was conducted to elucidate physicochemical and structural properties of sago starches. Two sago starch granules were oval in shape with an average diameter of 34.41 mu m and had C-type polymorph with a crystallinity of about 28.13%. The amylose and resistant starch (RS) contents of two sago starches were higher than those of corn and potato starches. The two sago starches had a large amount of A and B1 chains (DP 6-24) which could form double helix structures. FTIR exhibited that the structure of two sago starches had a lower degree of order. The peak viscosity and breakdown of sago starch 2 were lower than corn starch, and the setback was higher than potato starch. Additionally, sago starches had lower gelatinization enthalpy and higher regeneration tendency. According to rheological results, sago starches showed lower shear thinning degree and thixotropy compared to corn and potato starches. Sago starch 1 gels represented the highest hardness, adhesiveness, springiness and cohesiveness, which could be used as potential food stabilizer. This study revealed the characteristics of two sago starches compared with other starches. The results indicated that the amylose content and amylopectin structures had significant influence on the physicochemical properties of sago starch. (C) 2020 Elsevier B.V. All rights reserved.

关键词： Pig slurry   Organic fertilization   Physicochemical soil parameters   Soil quality  

摘要： Soil amendment with manures from intensive livestock breeding is, currently, a usual practice which could produce positive and/or negative effect on several soil properties. In this work, the effect of consecutive additions of pig slurry (PS), during 1 and 15 years, in two different farms in the Province of Cordoba (Argentina), was analyzed. Also, a control soil (without amendment), and an untilled soil were studied for comparison for each farm. This is the first research to be conducted in this part of the country. In this research we study the effect of PS applications in large commercial pig farms. For all soils and PS samples collected the following parameters: pH, electrical conductivity (EC), total N (TN), available phosphorus (P), Na, K, Ca and Mg, were analyzed. PS presents an alkaline pH, high EC, high phosphorus and nitrogen content. The statistical analysis, shown that PS application for 15 years could significantly modify the soil physicochemical properties, but one PS application before harvest, is similar to soil control. The soil amended with PS through 15 years shown: higher pH (7.57), and EC (3.09 dSm(-1)) values, and high P content (264 ppm), probably due to the low P mobility. Values of TN (2.15 g L-1) increased with the PS application, making this. The PS application, as a soil amendment, an advantage treatment for TN conservation and to avoid the commercial fertilizer use. PS application has to be planned in order to increase the soil nutrient recovery. The PS doses (m(3) ha(-1)) must be carefully calculated to prevent soil nutrient unbalance and possible soil and/or groundwater contamination. These results could be an important contribution on the proper PS application, as soil amendment, in the province of C ' ordoba and in other Argentinian regions.

关键词： Sonication  

摘要： This study aims to investigate the effect of the application of an ultrasound pretreatment on physicochemical, surface, thermal, and functional properties of two extracts from male date palm flowers. The obtained extracts were compared based on their structural and functional properties. It was proved that the application of sonication pretreatment has modified significantly (p < .05) the extract's characteristics. The protein yield, the essential amino acid content and the protein solubility were improved (29.61%, 29.22 g/100 g protein, and 91.1% for native sample against 35.26%, 41.04 g/100 g protein, and 100% for treated sample, respectively), while the protein content and the surfactant behavior at 1% were decreased due to the liberation of other compounds than protein. Moreover, the sonication has engendered some structural modifications such as the dissociation of some intermolecular bonds (FTIR) and the increase of crystalline region (X-ray), which influenced the protein unfolding and have led to the decrease of enthalpy (DSC) (272.2 against 228.6 J/g) and the decrease of water-holding capacity (11.62 against 9.51 g water/g of dry sample). Practical applications The male date palm flowers (MDPF) present a rich matrix composed mainly of dietary fiber, protein, and minerals. The protein fraction of MDPF was considered as an excellent source of amino acids supplying the human requirements. The dietary fiber fraction was composed essentially of insoluble dietary fibers which contribute to a balanced diet by creating satiety feeling and facilitating the intestinal transit. The fibro-proteic extract (FPE) of MDPF could be a potential functional ingredient for food applications. The physicochemical and functional properties of the FPE was changed by ultrasound pretreatment, which was beneficial to improve the protein yield, the amino acid profile, and the protein solubility. Nevertheless, both treated and non-treated samples showed promising nutritional and function

关键词： Milk   Calcium fortification   Rheology   Physicochemical changes   Heat stability  

摘要： The objective of this work was to analyze the changes in the physicochemical and rheological characteristics of milk fortified with different calcium salts. Reconstituted milk samples using skim milk powder with different concentrations of calcium chloride and calcium lactate (0, 5 and 30 mmol kg(-1)) were obtained. Several physicochemical and rheometric techniques were used to analyze the effect of milk fortification. According to the results, all the applied techniques indicated that some of the added calcium migrates into the casein micelle forming colloidal calcium phosphate, and that the calcium added as lactate enters the micelles to a greater extent. A part of whey proteins would also be integrated into the micellar structure. An addition of 5 mmol kg(-1) of calcium chloride and calcium lactate would be practically feasible, due to the mineral balance and the thermal stability that were not significantly affected at that concentration level. In conclusion, the results obtained with physicochemical techniques commonly used in literature are in agreement with those obtained in this study by rheometry, demonstrating that this simple and rapid technique allows inferring about the changes in mineral balance and effects on thermal stability when different salts are used for milk fortification.

关键词： Carbon dots   Pathogen   E. coli   Blood compatibility   Thrombolytic activity   Turn-off sensor  

摘要： The reliable means for the quick recognition of pathogenic bacteria for disease prevention has acquired a considerable significance among researchers for human wellbeing. The purpose of current study is to fabricate highly photo-luminescent and biocompatible carbon dots (CQDs) from single used plastic waste such as poly bags, cups and bottles for selective sensing of E. coli. The formed small sized spherical CQDs have possessed high water solubility with excellent photo stable nature. The detailed fluorescence emission studies of CQDs have illustrated the overview of different types of surface defects and emissive states in formed particles. In addition, the specific role of prepared CQDs with bio-compatible nature has been thoroughly checked on hemolysis of red blood cells by employing in-vitro blood compatibility assay. A combination of anticoagulant and thrombolytic activity of CQDs with anti-oxidative activities from reactive oxygen species (ROS) generation were found to be responsible for the biocompatibility of formed CQDs. The effective in vitro stability toward histidine, cysteine, bovine serum albumin (BSA), human serum albumin (HSA) and saline supported the biocompatibility of formed particles as a function of different concentrations of CQDs. The optimized fluorescence properties with high surface to volume ratio of CQDs have provided a better alternative for "turn-off" fluorescence detection of E. coil in aqueous media with limit of detection down to 10(8) CFU/mL estimated by using standard colony-counting method. The as prepared nanosensor provided easy fabrication with fast response, high sensitivity and selectivity in real water samples which might be necessary for detecting pathogenic agents. In addition, the current work has provided the large overview in blood compatibility and anti-oxidative potential of prepared CQDs and giving useful information for preparing blood-compatible nanoparticles with enhanced bacterial discrimination ability.

关键词： apple polyphenol   corn starch   rice starch   ultrahigh-pressure treatment  

摘要： BACKGROUND Ultrahigh-pressure (UHP) treatment, a non-thermal processing technology, exerts a bactericidal effect and affects food texture. How UHP treatments influence starch-polyphenol complexes has not yet been reported. Here, we studied the effects of UHP treatment on the structure of common rice starch (CRS)-apple polyphenol (AP) and common corn starch (CCS)-AP mixtures. RESULTS Overall, UHP treatment decreased the particle size of the CRS-AP and CCS-AP composites. Furthermore, the Delta Hvalues of the CRS-AP and CCS-AP mixtures decreased, and the heating stability was improved after UHP treatment. X-ray diffraction indicated that the relative crystallinity of the mixtures was unaffected by UHP treatment. Fourier-transform infrared spectroscopy proved that no new absorption peaks were observed in the infrared spectra, and the order of starch-AP was decreased after UHP treatment. These results indicated that UHP treatment inhibited the retrogradation of the starch-AP mixture. Our analyses of the microstructures of CRS-AP and CCS-AP mixtures showed increased folding and more pronounced network structures under high-pressure. CONCLUSIONS These results provide a theoretical basis for further exploring the properties of starch-AP mixtures following UHP treatment and provide insights regarding the use of UHP treatments for food production. (c) 2020 Society of Chemical Industry

关键词： Pasteurized pineapple juice   Color   K2O:N ratio   Quantitative descriptive analysis   Consumers  

摘要： High quality products can be produced only from high quality raw materials. The best agricultural practices that lead to pineapple fruits of desirable quality were investigated in the present study, focusing on the quality of the derived pasteurized juices. Physicochemical characteristics and sensory quality of the juices were determined in relation to planting density and fertilizer formulation, namely the K2O:N ratio. Three planting densities (D1: 54 400 plants/ha, D2: 66 600 plants/ha and D3: 74 000 plants/ha) and three K2O:N ratios (E1: 0.37, E2: 1.0 and E3: 2.0) were applied in nine treatments. Fruits were harvested and processed into juice following a standardized process. Pasteurization was applied after bottling, at 85 degrees C for 15 min. Juices' pH, total soluble solids, color and density were determined. Sensory profiles were established by 14 trained panelists using the Quantitative Descriptive Analysis (QDA) method and their acceptability was evaluated. Results showed that the lower the planting density, the less yellow the pasteurized juice. The K2O:N ratio increased the juices' degrees Brix from 13.1 to 14.4 and the yellow color. Pineapple fruits produced at a density of 54 400 plants/ha with a K2O:N ratio of 1.0 (D1E2) yielded the most sweet, least acid and pasteurized juice most liked by consumers, supported by high values of degree Brix and pH. Juices with the closest similar sensory appreciation were those obtained from treatments D3E2 and D3E1. Pineapple farmers that furnish their products to juice processors should adopt one of the best combinations stated in this study.

关键词： ultrafine grinding   ginger stem   powder properties   FTIR   X-ray diffraction  

摘要： BACKGROUND Ginger stem (GS) is a by-product of ginger processing. It is not directly edible as a feed or food, which leads to it being discarded as waste or burned. Accordingly, it is very important to develop new functional products in the food or feed industry as a result of high nutritional and medicinal values. In the present study, the structures and physicochemical properties of GS powders of different sizes were evaluated after ultrafine grinding by a vibrating mill. RESULTS The ultrafine powders exhibited a smaller particle size and uniform distribution. Higher values in bulk density (from 1.07 +/- 0.06 to 1.62 +/- 0.08 g mL(-1)), oil holding capacity (from 3.427 +/- 0.04 to 4.83 +/- 0.03 g mL(-1)), and repose and slide angles (from 42.33 +/- 1.52 to 54.36 +/- 1.15 degrees and 33.62 +/- 0.75 to 47.27 +/- 1.34 degrees, respectively) of ultrafine GS powders were exhibited compared to coarse powders. With a reduced particle size, the solubility of ultrafine powders increased significantly (P < 0.05), whereas the water holding and swelling capacities decreased with a reduced particle size and then increased. Fourier transform infrared spectroscopy analysis showed that ultrafine grinding did not damage the main cellular structure of GS powder. The reduction of fiber length and particle size in GS was observed by light microscopy and scanning electron microscopy. The X-ray diffraction patterns demonstrated the crystallinity and the intensity of the peak in superfine GS powders. CONCLUSION The present study suggests that ultrafine grinding treatments influence the structures and physicochemical properties of GS powders, and such changes would improve the effective utilization of GS in the food or feed industry. (c) 2020 Society of Chemical Industry