教学课程资源库 更多>>

关键词： Dentin bonding agent   Magnetic field   Iron oxide nanoparticles   Inorganic chemicals   Iron compounds   Tensile strength   Nanoparticles  

摘要： The limited durability of dentin bonding harshly shortens the lifespan of resin composites restorations. The controlled, dynamic movement of materials through non-contacting forces provides exciting opportunities in adhesive dentistry. We, herein, describe comprehensive investigations of a new dental adhesive with superparamagnetic iron oxide nanoparticles (SPIONs) sensitive to magnetic fields for bonding optimization. This contribution outlines a roadmap of (1) designing and tuning of an adhesive formulation containing SPIONs to enhance penetrability into etched dentin guided by magnetic-field;(2) employing a clinically relevant model of simulated hydrostatic pulpal pressure on the microtensile bond to dentin;and (3) investigating a potential antibacterial effect of the formulated adhesives, and their biocompatibility. SPION-concentration-dependency chemical and mechanical behavior was shown via the degree of conversion, ultimate tensile strength, and micro shear bond strength to dentin. The effects of SPIONs carried on a dental adhesive on the bonding strength to dentin are studied in depth by combining experiments with in vitro simulated model. The results show that under the guided magnetic field, 0.07 wt.% of SPIONs-doped adhesive increased the bond strength that surpasses the reduction caused by hydrostatic pulpal pressure. Using a magnetic guide workflow during the bonding procedures, SPIONs-doped adhesives improved dentin's adhesion without changing adhesives' physicochemical properties. This outcome addresses the key challenge of poor resin infiltration of dentin's conventional total etching during the bonding procedure. The real-time magnetic motion of dental adhesives may open new paths to enhance resin-based restorations' longevity. Statement of significance In this study, dental adhesives containing superparamagnetic iron oxide nanoparticles (SPIONs) were developed to enhance penetrability into dentin guided by a magnetic field. The adhesives were scree

关键词： Lipids   Peptides and proteins   Micelles   Hydrophobicity   Pharmaceuticals  

摘要： Several drug-fatty acid (FA) prodrugs have been reported to exhibit desirable physicochemical and pharmacological profile;however, comparative beneficial effects rendered by different FAs have not been explored. In the present study, four different FAs (linoleic acid, oleic acid, palmitic acid, and a-lipoic acid) were selected based on their chain length and degree of unsaturation and conjugated to Lisofylline (LSF), an antidiabetic molecule to obtain different drug-FA prodrugs and characterized for molecular weight, hydrophobicity, purity, self-assembly, and efficacy in vitro and in vivo in type 1 diabetes model. Prodrugs demonstrated a 2- to 6-fold increase in the plasma half-life of LSF. Diabetic animals treated with prodrugs, once daily for 5 weeks, maintained a steady fasting blood glucose level with a significant increase in insulin level, considerable restoration of biochemical parameters, and preserved beta-cells integrity. Among the different LSF-FA prodrugs, LSF-OA and LSF-PA demonstrated the most favorable physicochemical, systemic pharmacokinetic, and pharmacodynamic profiles.

关键词： Aniline  

摘要： A series of new soluble N-substituted poly(beta-haloallylaniline)s, namely poly[N-(2-chloroprop-2-en-1-yl)aniline] (NPC), poly[N-(2-chloroprop-2-en-1-yl)-2-methylaniline] (NPT) and poly[N-(2-chloroprop-2-en-1-yl)-2-methoxyaniline] (NPA), were synthesized by oxidative polymerization in 1 M HCl medium using (NH4)(2)S2O8 as the oxidant. Based on these polymers and polyphosphoric acid, various functionalized polyindoles of a new type were obtained in high yields. All the polymers obtained were characterized by H-1 and C-13 NMR, IR and UV-spectroscopy, elemental analysis, scanning electron microscopy (SEM), and thermal gravimetric analysis (TGA). The optical properties were studied, and the indole polymers were found to exhibit photoconductivity. Comparative analysis of spectral data and physicochemical properties indicates that intramolecular cyclization of the polyaniline derivatives occurs successfully.

关键词： Peat   Straw   Nursery substrate   Lignocellulose   Soilless cultivation   Physical and chemical properties  

摘要： The extensive use of nonrenewable peat does not meet the strategic goals of sustainable development. This study explores the advantages and disadvantages of using lignocellulose-based agricultural and forestry wastes as peat substitute in substrates for soilless cultivation;further, it also investigates the key factors influencing the physical and chemical properties of the substrates. Accordingly, the physical and chemical properties of four gramineous crop straws and two woody forestry wastes were determined and compared with those of peat and coconut bran. In addition, cellulose, hemicellulose, and lignin were extracted from wheat straw and pine sawdust, and their basic characteristics and structures were compared and analyzed. The results showed that the influence of particle size on the physical properties of substrates was significantly higher (P < 0.01) than the influence of the substrate type, especially with respect to the water-holding and aeration porosities, which had effect sizes (Eta2) of 73.8% and 68.2%, respectively. The electrical conductivity values of the four straws (1.87-3.42 mS/cm) were higher than those of peat and coconut bran (0.50-0.96 mS/cm), which was mainly due to the high hemicellulose contents (28.52%-30.10%) and total nutrient contents (28.46-47.81 g/kg) of the straws. In contrast, the electrical conductivity values of the woody waste substrates were lower (0.28-0.33 mS/cm) than those of peat and coconut bran. Peat and coconut bran contained the lowest cellulose (17.84%-20.95%) and hemicellulose contents (5.14%- 7.19%) of all substrates, resulting in a low degradability and good stability. The crystallinity of coconut bran (23.06%) was significantly lower than that of all other substrates (30.36%-43.03%), which mainly contributed to the superior compressibility of coconut bran. The best pretreatment method for biomass waste used as a substrate should be selected according to the target properties of the corresponding components. (C) 2

关键词： ash   char   mineral transformation   physicochemical property   pressurized combustion   pressurized pyrolysis  

摘要： Physicochemical properties of coal char during pressurized pyrolysis and the mineral transformations of coal ash during pressurized O-2/N(2)and O-2/CO(2)combustion were investigated by a pressurized tube furnace with Fourier transform infrared spectroscopy and X-ray diffraction analysis. The results indicated that as the pyrolysis pressure increased, the decompositions of the aromatic ring structure and the hydroxyl hydrogen bonds of char were enhanced and the aromatic ring transformed to the low-substituted single ring. Meanwhile, the aliphatic chain and carboxyl group in the char shortened at elevated pressures. Furthermore, pressurized pyrolysis increased the degree of graphitization of the char, which further influenced the microcrystalline parameters of char. During the pyrolysis process, the decompositions of some low-temperature minerals in the char were inhibited by the elevated pressure. In addition, the effect of the furnace temperature on the mineral transformations of char was more significant than the effect of the furnace pressure. Compared to what observed at atmospheric pressure, the primary minerals in the coal ash remained the same at elevated pressure, but their relative contents changed to some extent. And, the influence of the furnace pressure on the transformations of minerals in the ash was mainly affected by the combustion temperatures of different ignition mechanisms at different pressures. Compared to the O-2/N(2)mixture, the decompositions of low-temperature minerals and the formations of high-temperature minerals were restrained due to the relatively low combustion temperature in the O-2/CO(2)mixture. And, the furnace temperature instead of the furnace pressure was the primary factor which influenced the mineral transformations of ash.

关键词： DBD plasma-catalysis   CO2 methanation   Doped ceria zirconia support   Energy efficiency   Dielectric constant  

摘要： Promoters covering alkaline earth metals, lanthanides, transition and some of the typical rare earth metals, were added to Ni/CeZrOx based catalysts and examined in non-thermal plasma (NTP)-assisted CO2 methanation. The influence of physicochemical properties was examined by X-Ray Diffraction, N-2 adsorption/desorption, H-2-TPR, CO2-TPD, TPD-MS and FTIR spectroscopy. Moreover, the measurement of the dielectric constant of each catalyst was also performed. The promotion of Ni/CeZrOx with 4 wt% Gd significantly increases the energy efficiency. Furthermore, NiCZ-Gd resulted in the highest activity with 85 % conversion of CO2 fully converted to methane at 7 W. The enhancement of energy efficiency was attributed to electrical and physicochemical properties in particular: a low dielectric constant, a high metal dispersion, a high percentage of medium basic sites and finally an adequate promoter's cation radii. This study allowed to set up a new methodology to select the most appropriate catalysts in terms of energy efficiency for plasma catalytic CO2 methanation.

关键词： organocation sorption   cation exchange   pyrogenic carbons   biochar   black carbon   char oxidation   char weathering   adsorption   solid-state C-13 NMR  

摘要： This study examined conditions that mimic oxidative processes of biomass chars during formation and weathering in the environment. A maple char prepared at the single heat treatment temperature of 500 degrees C for 2 h was exposed to different thermal oxidation conditions or accelerated oxidative aging conditions prior to sorption of naphthalene or the dication paraquat. Strong chemical oxidation (SCO) was included for comparison. Thermal oxidation caused micropore reaming, with ambient oxidation and SCO much less so. All oxidative treatments incorporated O, acidity, and cation exchange capacity (CEC). Thermal incorporation of O was a function of headspace O-2 concentration and reached a maximum at 350 degrees C due to the opposing process of burn-off. The CEC was linearly correlated with O/C, but the positive intercept together with nuclear magnetic resonance data signifies that, compared to O groups derived by anoxic pyrolysis, O acquired through oxidation by thermal or ambient routes contributes more to the CEC. Thermal oxidation increased the naphthalene sorption coefficient, the characteristic energy of sorption, and the uptake rate due to pore reaming. By contrast, ambient oxidation (and SCO) suppressed naphthalene sorption by creating a more hydrophilic surface. Paraquat sorption capacity was predicted by an equation that includes a CEC2 term due to bidentate interaction with pairs of charges, predominating over monodentate interaction, plus a term for the capacity of naphthalene as a reference representing nonspecific driving forces.

关键词： Uranium dioxide (UO2)   Nuclear fuel   Ceramic   Integral fuel burnable absorbers (IFBA)   Yttrium oxide (Y2O3)   SPS   Neutron adsorption  

摘要： The paper studies spark plasma sintering of UO2-based ceramics nuclear fuel obtained from a mixture of pristine urania with 2 and 8 wt% of Y2O3 (integral fuel burnable absorber) produced by liquid-phase ultrasonic homogenizing. Densification dynamics of UO2-Y2O3 system is investigated for the first time in the temperature range up to 1250 degrees C under spark plasma sintering (SPS) conditions followed by a comparative analysis with UO2-Gd2O3 and UO2-Eu2O3 analogs. Earlier unknown data on formation of (U,Y)O-2 solid solutions, isostructural to UO2, under SPS conditions is presented. Structural changes manifested in stable pore and defect occurrence within the ceramics bulk are shown to depend on Y2O3 amount proving the occurrence of the Kirkendall effect, which is commonly known phenomenon in the field of traditional methods of fuel manufacturing. Microhardness (HV), compressive strength (sigma(cs)) and density (rho) are found to degrade in the presence of Y2O3, however their values remain within acceptable limits. For the first time, neutron-activation analysis is implemented as a laboratory means to assess neutron absorption efficiency of the SPS fuels containing various IFBA additives (Gd2O3, Eu2O3, Y2O3). These novel results contribute to the fundamental knowledge on the range of possible applications available owing to nonconventional SPS technology, thus extending the methods palette of fuel fabrication as well as providing new characterization approaches to probe important fuel properties for nuclear power engineering field. (C) 2021 Elsevier B.V. All rights reserved.

关键词： Skin surface model   Physicochemical properties   Polyoxazoline   Lipid nanocapsule   Mixed micelles   Free surface energy   Contact angle  

摘要： The behavior of polyoxazolines based mixed micelles and lipid nanocapsules on skin surface was studied on nonbiological human skin surface model to assess the formulations potential for topical delivery. Two amphiphilic polyoxazolines, saturated (C16POx15) and unsaturated (C18:2POx15), were used to evaluate the polymer architecture impact on formulations interaction with skin surface. To do so, the formulations spontaneous spreading and their residual film left on surface after manual application was investigated using contact angle measurements and free surface energy determination. The Van Oss model was employed to identify the physicochemical interactions in order to understand how the formulations can change the skin surface properties. In brief, both formulations showed a good affinity with the surface but depending on the polyoxazoline used, the spontaneous formulation spreading was modulated. Overall, the residual film left on the model surface modified the skin model physicochemical properties leading to a better interaction with hydrophilic and polar compounds. Regarding in detail each excipient impact on the surface physicochemical properties further explained the resulting formulation behavior on the skin surface model and highlighted the crucial role of the main component.

关键词： 物理化学实验   试错法   实验教学   探索与实践  

摘要： 实验教学是本科教学的重要组成部分,充分利用和挖掘现有基础实验的潜力,对提高实践教学质量具有重要意义。为适应新工科的发展需要,结合物理化学实验的特点,探索与尝试了新的教学模式,以物理化学实验中的氨基甲酸铵分解平衡常数测定实验为例,采用"试错法"教学,启发学生思考,使学生在解决错误的过程中磨练,让学生成为实验教学的主体,培养学生分析问题解决问题的能力、自主学习能力和创新综合素质。