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关键词： 知识权力   约瑟夫·劳斯   交叉学科   物理化学  

摘要： 本文以劳斯的知识权力观为理论基础,对物理化学学科的诞生及早期发展进行分析,探索交叉学科形成过程中科学知识与权力的关系。通过分析发现,在交叉学科诞生过程中,知识与权力相互交织;每个知识过程都发生在实践的权力网络中。这种权力网络虽然在一定程度上限制了交叉学科的诞生,却又与新的知识相互作用并使其自身得以发展。而对于交叉学科的发展而言,一方面需要尽可能多地与原来的知识网络建立联系,另一方面可能也需要相关研究进一步促进我们对交叉学科的理解。

关键词： 化学实验邀请赛   物理化学实验   试题解析  

摘要： 对第12届全国大学生化学实验邀请赛物理化学实验操作考试试题命题、考试情况进行了总结,并对实验竞赛过程中反映出的当前实验教学所存在的问题进行了分析。

关键词： Adductor muscle   high pressure processing   quality   scallop   storage  

摘要： Scallops are the third largest aquaculture mollusks product, while they are highly perishable during storage. The main purpose of the present study was to evaluate the effect of high pressure processing (HPP) on physicochemical and sensorial properties of scallop (Mizuhopecten yessoensis) during refrigeration storage. The scallop adductor muscle was treated with different pressures (200, 300, 400 and 500 MPa, 5 min) and iced storage for 28 days. Results showed that HPP delayed microbial growth as pressure increased. HPP (>= 400 MPa) resulted in myosin and actin denaturation, increased hardness, whiteness, pH and promoted water migration. However, preliminary sensory analysis showed no significant difference between pressure-treated and control adductor muscles in appearance, odour, texture and overall acceptability after cooking. In addition, pressure-treated adductor muscles (>= 300 MPa) remained edible after 28 days of storage. Overall, these results can provide basic knowledge for the storage of pressure-treated scallop meat.

关键词： Pyrolysis   Gasification   Filtration media   PAH and PCB release   Metal release   Drinking water plant  

摘要： Seven biochars (BCs) obtained from pyrolysis or gasification of different vegetal feedstocks were thoroughly characterized in comparison with three commercial activated carbons (ACs) routinely used in drinking water treatment plants. BCs and ACs characterization included the determinations of ash, iodine and methylene blue adsorption indexes, and the release of metals and polycyclic aromatic hydrocarbons, which were performed according to international standards applied for adsorption media to be used in drinking waters. Total specific surface area, micropore and mesopore specific surface area, pH of the point of zero charge, and the release of polychlorinated biphenyls were also determined in all chars. Principal component analysis and cluster analysis were performed in order to summarize the complex set of information deriving from the aforementioned characterizations, highlighting the BC most similar (BC6 from high temperature gasification of woody biomass) and most different (BC7 from low-temperature pyrolysis of corn cob) from ACs. These BCs were studied for their adsorption in ultrapure water towards diiodoacetic acid (an emergent disinfection by-product), benzene, and 1.2dichlorobenzene, in comparison with ACs, and results obtained were fitted by linearized Freundlich equation. Overall, BC6 showed higher sorption performances compared to BC7, even though both BCs were less performing sorbents than ACs. However, the sorption properties of BCs were maintained also in real water samples collected from drinking water treatment plants.

关键词： CaCl2   KCl   salted eggs   sodium salt  

摘要： KCl and CaCl2 were used as partial substitutes for NaCl during pickling salted eggs process in this study. The effects on the physicochemical properties, microstructure, textural properties and sensory quality of the salted eggs were evaluated, while comparing with the 18% NaCl group (Na group). The 3% replacement of NaCl by KCl reduced the Na content (p < 0.05), accelerated the water migration (p < 0.05) in salted eggs and increased the apparent oil yield and oil exudation of salted egg yolk (p < 0.05);but the rheological properties and microstructure of salted egg yolk were minimally affected. The 3% replacement of NaCl by CaCl2 reduced the Na content (p < 0.05), delayed the water migration rate (p < 0.05) in salted eggs and decreased the apparent oil yield and oil exudation of salted egg yolk (p < 0.05). Additionally, the process of egg white thinning and egg yolk hardening were delayed. The results indicate that the partial substitution of NaCl by KCl or CaCl2 during the pickling process of salted eggs could effectively inhibit the infiltration of Na+, and the presence of KCl could improve the quality of salted eggs. Still, the presence of CaCl2 delay the ripening of salted eggs. Practical Application KCl and CaCl2 as substitutes of sodium salt could play the role of reducing Na content but not affecting saline taste of salted eggs, which is conducive to the development of low-sodium salted eggs.

关键词： Anticancer activity   Antimicrobial activity   Aspergillus kambarensis   Green synthesis   in vitro cytotoxicity   Metallic nanoparticles  

摘要： In the present study, metal and metal oxide nanoparticles were successfully synthesized using Aspergillus kambarensis. UV-Vis spectroscopy showed maximum absorbance of 417 nm for silver (AgNPs), 542 nm for gold (AuNPs), 582 nm for copper (CuNPs) and 367 nm for zinc oxide (ZnONPs) nanoparticles. Fourier transform infrared spectroscopy indicated the presence of various mycochemicals with diverse functional groups in the fungal cell-free filtrate. Transmission electron microscopy revealed mono and poly dispersed particles with an estimate size of 50 nm and different shapes for synthesized manufacture metallic nanoparticles (MNPs. Dynamic light scattering confirmed that MNPs were dispersed in the size range less than 50 nm. Zeta potential analysis showed values of -41.32 mV (AgNPs), -41.26 mV (AuNPs), -34.74 mV (CuNPs) and 33.72 mV (ZnONPs). X-ray diffraction analysis demonstrated crystalline nature for MNPs. All the synthesized MNPs except AuNPs showed strong antifungal and antibacterial activity in disc diffusion assay with growth inhibition zones of 13.1-44.2 mm as well as anticancer activity against HepG-2 cancer cell line with IC50 in the range of 62.01-77.03 mu g/ml. Taken together, the results show that biologically active MNPs synthesized by A. kambarensis for the first time could be considered as promising antimicrobial and anticancer agents for biomedical applications.

关键词： V2R   AVP   Vasopressin antagonist   GPCR   QSAR   Docking   Molecular dynamics simulations  

摘要： We have developed two ligand- and receptor-based computational approaches to study the physicochemical properties relevant to the biological activity of vasopressin V2 receptor (V2R) antagonist and eventually to predict the expected binding mode to V2R. The obtained quantitative structure activity relationship (QSAR) model showed a correlation of the antagonist activity with the hydration energy (E-H2O), the polarizability (P), and the calculated partial charge on atom N7 (q6) of the common substructure. The first two descriptors showed a positive contribution to antagonist activity, while the third one had a negative contribution. V2R was modeled and further relaxed on a 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocoline (POPC) membrane by molecular dynamics simulations. The receptor antagonist complexes were guessed by molecular docking, and the stability of the most relevant structures was also evaluated by molecular dynamics simulations. As a result, amino acid residues Q96, W99, F105, K116, F178, A194, F307, and M311 were identified with the probably most relevant antagonist-receptor interactions on the studied complexes. The proposed QSAR model could explain the molecular properties relevant to the antagonist activity. The contributions to the antagonist-receptor interaction appeared also in agreement with the binding mode of the complexes obtained by molecular docking and molecular dynamics. These models will be used in further studies to look for new V2R potential antagonist molecules.

关键词： Artificial aging   Dental composites   Static and dynamic compression tests   Mechanical and physicochemical properties  

摘要： Objective The aim of the study was to evaluate the influence of filler content, degradation media and time on the mechanical properties of different dental composites after in vitro aging. Materials and Methods Specimens (1 mm(3)) of three commercially available composites (GrandioSO (R), Arabesk Top (R), Arabesk Flow (R)) with respect to their filler content were stored in artificial aging media: artificial saliva, ethanol (60%), lactic acid (pH 5) and citric acid (pH 5). Parameters (Vickers microhardness, compressive strength, elastic modulus, water sorption and solubility) were determined in their initial state (control group, n = 3 for microhardness, n = 5 for the other parameters) and after 14, 30, 90 and 180 days (n = 3 for microhardness, n = 5 for the other parameters for each composite group, time point and media). Specimens were also characterized with dynamic-mechanical-thermal analysis (compression tests, F = +/- 7 N;f = 0.5 Hz, 1 Hz and 3.3 Hz;t = 0-170 degrees C). Results Incorporation of fillers with more than 80 w% leads to significantly better mechanical properties under static and dynamic compression tests and a better water sorption behavior, even after chemical degradation. The influence of degradation media and time is of subordinate importance for chemical degradation. Conclusion Although the investigated composites have a similar matrix, they showed different degradation behavior. Since dentine and enamel occur only in small layer thickness, a test specimen geometry with very small dimensions is recommended for direct comparison. Moreover, the use of compression tests to determine the mechanical parameters for the development of structure-compatible and functionally adapted composites makes sense as an additional standard. Clinical relevance Preferential use of highly filled composites for occlusal fillings is recommended.

关键词： Conducting polymers   Polymer synthesis   Polymer chemistry   Thermal properties   Manufacturing  

摘要： Conducting polymers (CPs) possess unique electrical and electrochemical properties and hold great potential for different applications in the field of bioelectronics. However, the widespread implementation of CPs in this field has been critically hindered by their poor processibility. There are four key elements that determine the processibility of CPs, which are thermal tunability, chemical stability, solvent compatibility and mechanical robustness. Recent research effort s have focused on enhancing the processibility of these materials through pre-or post-synthesis chemical modifications, the fabrication of CP-based complexes and composites, and the adoption of additive manufacturing techniques. In this review, the physicochemical and structural properties that underlie the performance and processibility of CPs are examined. In addition, current research efforts to overcome technical limitations and broaden the potential applications of CPs in bioelectronics are *** of significanceThis review details the inherent properties of CPs that have hindered their use in additive manufacturing for the creation of 3D bioelectronics. A fundamental approach is presented with consideration of the chemical structure and how this contributes to their electrical, thermal and mechanical properties. The review then considers how manipulation of these properties has been addressed in the literature including areas where improvements can be made. Finally, the review details the use of CPs in additive manufacturing and the future scope for the use of CPs and their composites in the development of 3D bioelectronics. (c) 2021 The Author(s). Published by Elsevier Ltd on behalf of Acta Materialia Inc. This is an open access article under the CC BY-NC-ND license (http://***/licenses/by-nc-nd/4.0/)

关键词： Lysozyme   Mucin   Assembly mechanism   Fluorescence   Light scattering   Chromatography  

摘要： Mucin and lysozyme are the most important components of mucous membranes. The complexes of pig gastric mucin (PGM) and the bacteriolytic enzyme lysozyme (LZ) have been studied using a wide range of physico-chemical methods (turbidimetry, light scattering, fluorescence, electron microscopy, chromatography, and electrophoresis). The strongest binding of LZ to PGM was observed at pH 6-7 in a salt-free medium. Complexes between biomolecules were formed due to electrostatic interactions between the positively charged amino groups of LZ and the negatively charged carboxyl groups of the carbohydrate shell of PGM, van der Waals forces, and hydrogen bonds. Supramolecular LZ:PGM assemblies were polydisperse heterogeneous microaggregates with both LZ and PGM molecules located on their surface. The LZ activity in the presence of PGM changed through both the formation of complexes and the fact that PGM caused an increase in the viscosity of the medium and created diffusion restrictions for the enzyme's access to the cellular substrate. Based on the data obtained, strategies can be developed to regulate antimicrobial properties of lytic enzymes (and their complexes with mucins) for mucosal use.