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关键词： 物理化学   电化学   迁移数   希托夫法   计算策略  

摘要： 希托夫法计算离子迁移数是大学物理化学教学中的重点和难点知识,也是实际教学过程中学生提问较多的内容之一。一些经典物理化学教材中只给出一两个相关例题,却并未介绍希托夫法计算离子迁移数的步骤和思路,导致学生难以深刻理解和掌握希托夫法计算离子迁移数的教学内容。提出采用希托夫法计算离子迁移数的新策略,并用实例进行详细阐述。通过提出的新策略,用希托夫法计算离子迁移数将更加方便、快捷且不易出错,有利于学生对离子迁移数知识的掌握及增加学习物理化学知识的兴趣。

关键词： 交互式   物理化学   创新  

摘要： 物理化学课程逻辑性强、理论性强、公式繁多。教师难教、学生难学的现象时有发生。采用"交互式"教学,以学生为中心,因材施教,重视基础,强调综合应用能力,培养学生的创新意识,实现了物理化学课程从晦涩难懂、枯燥无趣、内容抽象到清晰易懂、生动有趣、理论实际结合紧密的转变。

关键词： 化学史   物理化学教学   学习兴趣   核心素养  

摘要： 本文简述在物理化学课程中融入化学史教学的重要性,并以实例论证化学史可以激发大学生的学习兴趣,培养科学素养和进行爱国主义教育。

关键词： 墨层厚度   覆膜工艺   操作工艺   印刷品   油墨性能   粘合性能   物理化学   印刷图文  

摘要： 覆膜效果,不仅同覆膜原材料、覆膜操作工艺方法有关,更重要的,还同被粘印刷品的墨层状况有关。印刷品的墨层状况主要由纸张的性质、油墨性能、墨层厚度、图文面积以及印刷图文积分密度等决定,这些因素影响粘合机械结合力、物理化学结合力等形成条件,从从而引起印刷品表面粘合性能的改变。今天在这里详细介绍一下相关内容。

关键词： chalcohalide glasses   physico-chemical properties   glass-transition temperature   band gap   NIR applications  

摘要： The dependence of band gap energy (E-g) and glass-transition temperature (T-g) on physico-chemical properties for the (GeS2)(10)(Sb2S3)(90-x)(AgI)(x) (10 <= x <= 50 at%) chalcohalide glasses were theoretically investigated. Chalcohalide glasses have wide technological applications owing to the aptitude of tuning their optical band gap through composition change. Therefore, E-g of the studied chalcohalide glasses was estimated using different methods, and it was turned out that it decreased as the AgI amount increases. This decrease was elucidated in terms of physico-chemical properties. In addition, we determined the positions of conduction band (E-CB) and valence band (E-VB) by using the computed values of E-g. The density and molar volume increased while the packing density decreased by adding AgI. The overall coordination number (CN), crosslinking density (CD), constraints number (N-s), cohesive energy (CE), heat of atomization (H-s) and overall mean bonds energy (E);computed via the chemical bond approach (CBA);decreased with the increment of AgI amount. In contrary, the floppy (F) and mean bonds energy (E-s) increased. Finally, two estimations of T-g were presented based on E and CN. The two estimations showed a decreasing trend when adding AgI content.

关键词： unripe green banana   Cavendish spp   wheat flour substitution   bread   gluten-free   functional properties  

摘要： This study aimed to utilize unripe green bananas obtained from those that were graded as unacceptable for export. Bread was selected as the product model for the application of banana flour. As carbohydrates and other functional active compounds make up the main composition of green bananas, unripe banana flour (UBF) was prepared and characterized. The chemical composition, physico-chemical properties, and functional properties of UBF, as well as its application in bread for wheat flour (WF) substitution at different levels, were investigated. Quality attributes of the bread were determined. High carbohydrate (89%), total dietary fiber (7%), ash (2%), potassium content and radical scavenging activity were found in UBF bread, while protein (15%) and fat contents (0.9%) were higher in WF bread (p < 0.05). Starch granules of different sizes and shapes (round, long and oblong) were observed in the starch from UBF bread. Solubility, swelling power, and the water absorption capacity of WF bread were greater than UBF bread (p < 0.05). The gelatinization enthalpy (Delta H) was 0.69 and 5.00 J/g for WF and UBF, respectively. The rapid viscoanalyzer (RVA) pasting profile showed that UBF bread had a higher pasting temperature, peak viscosity, breakdown, and final viscosity than WF bread (p < 0.05). Increasing the level of UBF caused an increase in bread hardness and a decrease in loaf volume (p < 0.05). We show that UBF can be considered a value-added product with health-promoting properties. The utilization of UBF as a functional food ingredient will benefit the consumer.

关键词： Protic ionic liquid   Water effect   Dynamic viscosity   Electric conductivity   Ionicity  

摘要： The effects of water content on physicochemical properties such as density, dynamic viscosity, and electrical conductivity of HHexen(Tf2N), composed of monoprotic N-hexylethylenediaminium as cation and bis(trifluoromethylsulfonyl) imide as anion, were studied in the temperature range T = 303.15-353.15 K. HHexen(Tf2N) was dissolved a small amount of water (up to 6.53 wt%, corresponding to w(0) = [H2O]/[PIL] = 1.65) as it is a hydrophobic protic ionic liquid (PIL). The physicochemical properties of HHexen(Tf2N) were significantly influenced by its water content. The temperature dependence of the physicochemical properties at different water contents (0.50 wt%, 0.95%, 1.93%, 3.02%, 4.03%, 5.14% and 5.95%, corresponding to w(0) = 0.12, 0.23, 0.47, 0.74, 1.0, 1.28 and 1.50, respectively) were studied. With an increase in the water content, the density and dynamic viscosity decreases while the electric conductivity increases in a given temperature range. The Walden lines of HHexen(Tf2N) show a good ionic character as the curves are all located in the range of Delta W = 0.5 +/- 0.2 (Delta W = log(10)1/eta -log(10)?) at different water contents. The ionicity shows an increasing trend with an increase of water content;this is evident when the water content rises to approximately 4.0% (w(0) = 1.0). Additionally, HHexen(Tf2N) was used to extract Co(II) ions from an aqueous solution. Inductive coupled plasma emission spectrometry results showed that more than 99.5 wt% of Co(II) ions moved from the 100 mmol center dot kg(-1) aqueous layer to the HHexen(Tf2N) layer (of equal volume). After extraction of the Co(II) ions, the PIL layer contained 7.90% of water (w(0) = 2.0).

关键词： Controlled release   hydrogel   pathogens   periodontitis   spirulina  

摘要： Context: Periodontitis is primarily an inflammatory condition caused by an array of microorganisms present in dental plaque. Elimination or adequate suppression of periodontal pathogens in the subgingival microflora is essential for adequate periodontal healing to take place. The development of subgingivally placed controlled delivery systems has provided the possibility of effective intrapocket concentration levels of antibacterial agents for an extended period of time, resulting in an altered subgingival flora and enhanced healing of the attachment apparatus. Although a number of synthetic antimicrobial agents are being used as local drug delivery, currently, pharmaceutical technology development has focused on the ingredients derived from nature. Natural phytochemicals have proven to be worthy substitutes of their synthetic and chemical-laden counterparts owing to their extensive natural activity, advanced safety margins, and inferior costs so that they can be of huge benefits, especially to the lower socioeconomic population around the world and spirulina platensis (SP) is one such emerging remedy. Aims: The aim of the study was to develop three controlled release drug delivery systems containing different concentrations of SP to be used inside the periodontal pockets. The study also aimed to determine the antimicrobial activity of all the three concentrations of SP drug delivery system against major periodontopathic microorganisms and to test the physicochemical properties of the delivery system that exhibited maximum antimicrobial efficacy so that the suitability of its use inside the periodontal pocket could be determined. Settings and Design: The study was an in vitro experimental design. Subjects and Methods: Three different controlled release SP hydrogels (4%, 6%, and 12%) to be used inside the periodontal pockets were developed and antibacterial properties against periodontal pathogens were assessed. The hydrogel exhibiting maximum antimicrobial efficacy

摘要： Edible films containing natural antimicrobials, like natamycin and nisin, constitute an emerging technology that provides an additional stress factor for food preservation. However, it has been observed that edible films based only on tapioca starch present several failures, such as poor mechanical properties and low hydrophobicity. Pumpkin and oat bran are ingredients that provide multiple health benefits. In this work, it was intended to improve mechanical properties and hydrophobicity of tapioca starch edible films, containing natamycin and nisin, by the addition of pumpkin peel, pumpkin mesocarp or oat bran fillers. In turn, the effect of fillers on the films was evaluated through the evaluation of their color, water vapor permeability, morphological characteristics, and microbiological behavior. Results showed that pumpkin fillers improved mechanical properties, reducing the strain at break and increasing the stress at break of tapioca starch edible films. Particularly, pumpkin peel filler increased 36 times the firmness of tapioca starch films, reaching a value of 87.64 MPa. Also, this filler increased 300% the hydrophobicity of the films with a contact angle of 48.29 degrees. The incorporation of all studied fillers allowed the normal diffusion of natamycin. However, the different fillers retained the nisin in different degrees and, particularly, oat bran filler was the one with the highest affinity for it. After evaluating all the studied properties, it can be concluded that the composite film filled with pumpkin peel, is an improved version to the one without it, for food packaging.

关键词： Branched silicone methacrylate   Anti-adhesion   Dual-species biofilm   Shear bond strength   Cell cytotoxicity  

摘要： Dental resin composites (DRCs) with 15 wt% (EC-15%) and 20 wt% (EC-20%) synthesized branched silicone methacrylate (BSM) in resin matrix have showed anti-adhesion effect against Streptococcus mutans. With the aim to evaluate the BSM containing DRCs further, water sorption (WS), solubility (SL), mechanical properties before and after water immersion, anti-adhesion effect against dual-species, bonding strength to adhesive treated dentin, and cytotoxicity of BSM containing DRCs were investigated. DRC without BSM was used as control. The WS and SL were obtained until the mass variation of composite in distilled water kept stable. Three-point bending test was used to evaluate flexural strength (FS) and modulus (FM) of composite before and after water immersion. Mixture of Streptococcus mutans and Lactobacillus acidophilus was used to study the anti-adhesion effect against dual-species. Bonding strength of composite to adhesive treated dentin was measured through macro-shear test. Extract of composite was used to evaluate its cytotoxicity effect on L-929 mouse fibroblasts, and cell viability was obtained by MTT assay. The results showed that EC-15% and EC-20% had similar WS and SL as control (p < 0.05);After water immersion, FS and FM of all composites decreased (p < 0.05), but there was no significant difference in value of FS and FM between different groups (p > 0.05);More bacteria were recovered from the surface of control than those from the surface of EC-15% and EC-20% (p < 0.05);Extract of EC-15% was less cytotoxic (higher cell viability) than those EC-20% and control (p < 0.05). All of results revealed that incorporation of 15 wt% or 20 wt% BSM in resin matrix could endow DRC with inhibition effect on dual-species biofilm formation without impairing physiochemical properties, bonding strength to adhesive treated dentin, and cytotoxicity of DRC.