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关键词： 《黄金时代》   王小波   文学期刊   文科生   音乐性   发明家   《青铜时代》   物理化学  

摘要： 《发明家》是我正式在文学期刊上发表的第一篇小说,主人公是奇怪的发明家三叔。我真的有个三叔,他没当过老师,更不是发明家。如果非要在三叔身上找一个原型的话,我想说那是我自己。我是文科生,物理化学一塌糊涂,唯一的爱好是写作。高中时看了王小波先生的《黄金时代》和《青铜时代》,体味到文字中蕴含的音乐性,便立志当一名作家。

关键词： Microalgae   Vacuum distillation   Methyl esters   Biodiesel  

摘要： To prepare quality biodiesel from microalgal lipids in pilot-scale reactors, methyl esters from microalgal cells were extracted with hexane after direct transesterification and then refined by vacuum distillation. The refined methyl esters were comprehensively characterized via gas chromatography-mass spectrometry, Fourier transform infrared spectroscopy, nuclear magnetic resonance, and thermogravimetric analysis. The methyl ester refined at 255 degrees C-259 degrees C was found to be the ideal fuel with a high fatty acid methyl ester content of 94.6%, a low combustion activation energy of 42.1 kJ/mol, and a proper carbon-chain length distributed in C14-C18. Impurities extracted with hexane, such as alkanes and short-chain esters, were separated at 105 degrees C-254 degrees C owing to their low polarity and molecular weight. Highly unsaturated methyl esters with a long carbon-chain were collected at 260 degrees C-280 degrees C owing to their high boiling point. Separation of alkanes, short-chain esters, and highly unsaturated methyl esters through vacuum distillation effectively improved the properties of the methyl esters extracted with hexane as a fuel and enhanced the economic feasibility of microalgal lipids.

关键词： 过渡态   化学动力学   物理化学  

摘要： 在物理化学教学中,过渡态理论是化学动力学学习的重点和难点。通过三种计算方法搜索反应过渡态,并展示了温度对吉布斯自由能、反应速率常数的影响,让学生对过渡态和反应过程有更加直观、清晰的认识,帮助学生更好地丰富和理解化学动力学理论。

关键词： Fish enzymes   Calcium activation   Substrate specificity   Serine proteases  

摘要： Specificity studies can contribute to the understanding of how substrate binding and catalysis change among similar enzymes. This study evaluated through the substrate specificity, physicochemical and kinetic properties of a trypsin from the pyloric caeca of pirarucu (Arapaima gigas). For such purposes, two series of FRET-peptides (Abz-RXFK-Eddnp and Abz-XRFK-Eddnp) were used. The mature trypsin molecular mass was 23.5 kDa and N-terminal sequence was IVGGYECPRNSVPYQVSLNVGYH. Moreover, higher trypsin catalytic efficiency was observed for the substrates containing Arg, Tyr and Ser at P1' and Lys and Val at P2. However, catalytic deficiency was found in the presence of Pro, Trp, Asp, Gly, Glu, Ala at P1' and Gly, Glu, Trp, Asn, Gln and Tyr at P2. Using z-FR-MCA as a substrate, the optimum pH (9.25) and temperature (45 degrees C) were determined by pseudo-first-order kinetics. The enzyme retained all of its initial activity after 180 min incubation at temperatures up to 45 degrees C. Kinetic assays in the presence of Ca2+ showed an increase of approximately 7-fold in enzyme catalytic efficiency (kcat/Km). On the other hand, Na+, K+ and Mg2+ were able to inhibit pirarucu trypsin. Therefore, the knowledge of kinetic and biochemical properties, as well as enzyme specificity, are important for the evaluation of biotechnological use of this enzyme and may contribute to the development of more efficient substrates for fish trypsin.

关键词： Chitosan   Film properties   Biodegradable films   Antioxidant activity   Active packaging   Shelf life  

摘要： This study investigated the application of active packaging from chitosan (CS) incorporated with graphene oxide (GO) to maintain the quality and extend the storage life of palm-oil based margarine. Composite films containing various concentrations of CS (1.5 and 2.0%w/v) and GO (0, 0.5, 1.0, and 2.0%w/w CS) were produced using the solution casting method and were characterized regarding their mechanical, barrier, and antioxidant properties. For both concentrations of CS, the composite films with 2.0% GO exhibited significantly (p < 0.05) lower water vapor permeability and oxygen permeability by -43 and -55%, respectively. The transmittance of UV light was virtually undetectable in CSGO composites. In addition, the radical scavenging activity increased (p < 0.05) with the increasing GO concentration, as demonstrated by the 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging assay. The changes in the peroxide value (PV) and thiobarbituric acid reactive substances (TBARS) of the margarine samples were monitored for 30 d at 4 ?C. The margarine sample that was wrapped with the CS1.5 GO2.0 film sample showed lower (p < 0.05) PV and TBARS values in comparison to the samples wrapped with CS1.5 and low-density polyethylene (LDPE) films. In conclusion, the CSGO composite film in this study shows great potential as an antioxidant food packaging material.

关键词： T. utriculosum residue   Biorefinery   Cellulose nanocrystals   Structural characterization  

摘要： Tribonema biomass is considered promising biorefinery feedstock for the co-production of biodiesel and valuable bioproducts;however, the extraction of these useful compounds produces large amounts of algal residues, which produce increased environmental concerns. Herein, cellulose was extracted from the waste residue of T. utriculosum via alkalization and bleaching, followed by the production of high-value-added cellulose nanocrystals (CNCs) via acid hydrolysis. The hydrolysis was performed with 60% (wt%) H2SO4 at a yield of 13.31%, resulting in the generation of rod-shaped nanoparticles averaging 39.5 nm in diameter and 239.2 nm in length. The structural characterization analysis revealed that the prepared CNCs had high crystallinity (73.0%) due to the removal of non-cellulose components and amorphous regions by chemical treatment, as well as possessing good aqueous suspension stability (zeta potential = - 40.1 mV). Although the CNCs showed lower thermal stability than extracted cellulose, they spanned a broader temperature range due to two-stage degradation behaviour, with higher residue weight (16.7%). This work represents the first report on the preparation of a high-value-added industrial product, CNCs, from the filamentous microalga T. utriculosum, aiming to maximize benefits from waste algal residue reutilization.

关键词： Blackberry juice   Preservatives   Physicochemical properties   Bioactive compounds   Storage  

摘要： This study was conducted to analyze the impact of sodium benzoate (SB), potassium sorbate (PS), and citric acid (CA) on the physicochemical properties, bioactive components, antioxidant activity, and color of Blackberry juice during storage at 4 degrees C. The total content of phenol (14 mg/100 g), anthocyanin (32.26 mu g/100 g), proanthocyanidin (203.01 mg/100 g), and antioxidant activity (723.62 mmol/100 g) of juice prepared with preservatives (SB + PS + CA) substantially increased on the first day than those of the juice made with preservatives (SB + PS) and without preservatives. On the other hand, total phenol content and color values (L* and a*) increased while the amount of anthocyanin, flavonoid, and antioxidant activity declined for all samples over the storage period. A strong correlation between anthocyanin and flavonoid, anthocyanin and DPPH, anthocyanin and total sugar, phenol and acidity were observed. Therefore, preservatives (sodium benzoate, potassium sorbate, and citric acid were used to manufacture Blackberry juice, a practical approach to maintain nutritional quality.

关键词： herbicide composition   disperse systems   physicochemical properties   fluorescence   N-(phosphonomethyl)glycine   Roundup   succinic acid   low concentrations   aquatic life   wheat roots  

摘要： Self-organization, physicochemical properties (specific electrical conductivity, surface tension), UV absorption, and fluorescence of aqueous herbicide compositions based on N-(phosphonomethyl)glycine and plant growth regulator succinic acid (SA) were studied in a range of herbicide concentrations of 1 center dot 10(-19)-1 center dot 10(-1) g L-1 at the constant concentrations of SA 1 center dot 10(-3) g L-1 (series 1) and 1 center dot 10(-13) g L-1 (series 2). Such compositions are used in agriculture for decreasing toxic effects on cultural plants and environment. A comparison of the nonmonotonic concentration dependences of the size and xi-potential of the disperse phase, properties, and bioeffects of systems 1 and 2 revealed significant distinctions in these compositions in the ability of self-organization and surfactant properties, which can cause, as a whole, their substantial difference in the degree of harmful influence on aquatic life and higher plants. The influence of the compositions of series 1 is accompanied by a decrease in the harmful effect on the chosen biological test objects compared to the herbicide, and that of series 2 results in an almost complete elimination of the harmful effect against multicellular organisms (cladocerans and wheat roots) and an insignificant effect on unicellular aquatic life (infusoria and algae). The influence of the compositions of series 2 on aquatic life is related to the formation of a negatively charged disperse phase accompanied by an increase in the fluorescence intensity in a range of 300-360 nm (lambda(exc) = 225 nm).

关键词： Thermodynamics   Energetics   Entropy   Enthalpy   Compensation  

摘要： Around two hundred years of thermodynamics' history have been re-analyzed. The priority of thermodynamics by Carnot for the modern scientific research has been stressed.