Comparison of antioxidant capacities of different types of tea using the spectroscopy methods and semi-empirical mathematical model

The antioxidant properties of different types of tea—green, black and earl grey—were investigated using the EPR spectroscopy method based on a new semi-empirical mathematical model and on a single EPR spectroscopy measurement. The obtained values of the antioxidant capacity were correlated with the bioactive ingredient content identified through the NMR spectroscopy. Moreover, an attempt was made to determine what impact on the antioxidant properties of tea does adding sugar, milk, lemon and honey have. All studied teas exhibited antioxidant properties. The best DPPH free radical scavengers were green teas. Adding sugar, milk and lemon juice to tea did not significantly impact the antioxidant properties of the infusion; adding honey, however, caused an increase in the total antioxidant capacity of the infusion. The aromatic proton content correlates positively with the antioxidant capacity value

Thermodynamic and acoustic properties of mixtures of dibromomethane + heptane

Densities and speeds of ultrasound in binarymixtures of dibromomethane with heptane have been measured within the temperature range from 288.15K to 318.15 K. From the experimental data, the thermodynamic excess volume, molar isobaric expansion, molar isentropic compression, and ultrasonic speed were calculated. The excess volume and excess isentropic compression have opposite signs, whereas the excess isobaric expansion is an S-shaped function of the mole fraction. An explanation was suggested to account for the excesses in terms of intermolecular interactions. It involved energetic and steric factors. Moreover, itwas shown that the positive excess sound speed results almost entirely from the negative excess compression

Changes in the Distribution of Temperature in a Coal Deposit and the Composition of Gases Emitted during Its Heating and Cooling

This article presents the results of tests conducted on a measuring system for monitoring changes in the distribution of temperature in a coal deposit during the heating and cooling phases, and their correlation with the analysis of the concentration of gases. The tests were conducted on five samples of hard coal collected in deposits mined in Poland. Measurements of the changes in temperature and changes in gas concentration were conducted from the temperature of 35 to 300 C, for the heating phase, and from 300 to 35 C, for the cooling phase. The percentage share of coal of given temperatures was calculated. When comparing the percentage share for the same temperature in the hot spot, for the heating and cooling phase, significant differences in the distribution of the given percentages were observed. Changes in gas concentrations during heating and cooling were analyzed and the dynamics of changes in gas concentrations were determined for the coals tested. Changes in the values of fire hazard indices were analyzed. There were significant differences in the concentration of gases and the values of fire hazard indices between the heating and the coolin

Speed of Sound and Ultrasound Absorption in Ionic Liquids

International audienceA complete review of the literature data on the speed of sound and ultrasound absorption in pure ionic liquids (ILs) is presented. Apart of the analysis of data published to date, the significance of the speed of sound in ILs is regarded. An analysis of experimental methods described in the literature to determine the speed of sound in ILs as a function of temperature and pressure is reported, and the relevance of ultrasound absorption in acoustic investigations is discussed. Careful attention was paid to highlight possible artifacts, and side phenomena related to the absorption and relaxation present in such measurements. Then, an overview of existing data is depicted to describe the temperature and pressure dependences on the speed of sound in ILs, as well as the impact of impurities in ILs on this property. A relation between ions structure and speeds of sound is presented by highlighting existing correlation and evaluative methods described in the literature. Importantly, a critical analysis of speeds of sound in ILs vs those in classical molecular solvents is presented to compare these two classes of compounds. The last part presents the importance of acoustic investigations for chemical engineering design and possible industrial applications of ILs

Fabrication of superhydrophobic metallic porous surfaces <i>via </i>CO₂ and water processing

Superhydrophobic surfaces are of paramount importance for a great number of applications ranging from heat transfer to medicine. However, their mass production is challenging from environmental and scaling points of views. This work proposes a simple, scalable, production method for superhydrophobic surfaces and porous materials. In particular, highly hydrophobic CH2/CH3-grafted copper is achieved via exposure to a high-pressure supercritical CO2 +H2O environment. The hydrophobicity was further reinforced by using hierarchical macro- nanoporous copper prepared by a simple templating-annealing method reaching a water contact angle of ~ 150◦ . The grafting is found to be durable in terms of ageing, abrasion and water impact. The superhydrophobic porous material is successfully used to separate oil emulsions from water. Molecular dynamics simulations are employed to investigate the underlying superhydrophobicity mechanisms further. We hypothesise that the obtained grafting results from a CO2 hydrogenation reaction. The proposed approach may pave the way for the mass use of superhydrophobic surfaces and porous materials for anti-corrosion, anti-icing, separation, batteries, sensors, electronic materials, etc

The effect of surface entropy on the heat of non-wetting liquid intrusion into nanopores

On-demand access to renewable and environmentally friendly energy sources is critical to address current and future energy needs. To achieve this, the development of new mechanisms of efficient thermal energy storage (TES) is important to improve the overall energy storage capacity. Demonstrated here is the ideal concept that the thermal effect of developing a solid−liquid interface between a non-wetting liquid and hydrophobic nanoporous material can store heat to supplement current TES technologies. The fundamental macroscopic property of a liquid’s surface entropy and its relationship to its solid surface are one of the keys to predict the magnitude of the thermal effect by the development of the liquid−solid interface in a nanoscale nvironment driven through applied pressure. Demonstrated here is this correlation of these properties with the direct measurement of the thermal effect of non-wetting liquids intruding into hydrophobic nanoporous materials. It is shown that the model can resonably predict the heat of intrusion into rigid mesoporous silica and some microporous zeolite when the temperature dependence of the contact angle is applied. Conversely, intrusion into flexible microporous metal−organic frameworks requires further improvement. The reported results with further development have the potential to lead to the development of a new supplementary method and mechanim for TES