The Indirect Excitons Contribution to the Polarizability of a Dielectric Nanoparticle

Semiconductors - The optical properties of dielectric nanostructures strongly depend on dielectric nanoparticles (NP) polarizability which can take the high values even interacting with...     

Resource potential for wind-hydrogen power in Ukraine

The paper provides an assessment of the current wind energy potential in Ukraine, and discusses developmental prospects for wind-hydrogen power generation in the country. Hydrogen utilization is a highly promising option for Ukraine's energy system, environment, and business. In Ukraine, an optimal way towards clean zero-carbon energy production is through the development of the wind-hydrogen sector. In order to make it possible, the energy potential of industrial hydrogen production and use has to be studied thoroughly.Ukraine possesses huge resources for wind energy supply. At the beginning of 2020, the total installed capacity of Ukrainian wind farms was 1.17 GW. Wind power generation in Ukraine has significant advantages in comparison to the use of traditional sources such as thermal and nuclear energy.In this work, an assessment of the wind resource potential in Ukraine is made via the geographical approach suggested by the authors, and according to the «Methodical guidelines for the assessment of average annual power generation by a wind turbine based on the long-term wind speed observation data». The paper analyses the long-term dynamics of average annual wind speed at 40 Ukrainian weather stations that provide valid data. The parameter for the vertical wind profile model is calculated based on the data reanalysis for 10 m and 50 m altitudes. The capacity factor (CF) for modern wind turbine generators is determined. The CF spatial distribution for an average 3 MW wind turbine and the power generation potential for the wind power plants across the territory of Ukraine are mapped.Based on the wind energy potential assessment, the equivalent possible production of water electrolysis-derived green hydrogen is estimated. The potential average annual production of green hydrogen across the territory of Ukraine is mapped.It is concluded that Ukraine can potentially establish wind power plants with a total capacity of 688 GW on its territory. The average annual electricity production of this system is supposed to reach up to 2174 bln kWh. Thus, it can provide an average annual production of 483 billion Nm³ (43 million tons) of green hydrogen by electrolysis. The social efficiency of investments in wind-hydrogen electricity is presented.     

Influence of structural variation in room-temperature ionic liquids on the selectivity and efficiency of competitive alkali metal salt extraction by a crown ether

An improved method for the preparation of 1-alkyl-3-methylimidazolium hexafluorophosphates provides a series of room-temperature ionic liquids (RTILs) in which the 1-alkyl group is varied systematically from butyl to nonyl. For competitive solvent extraction of aqueous solutions of alkali metal chlorides with solutions of dicyclohexano-18-crown-6 (DC18C6) in these RTILs, the extraction efficiency generally diminished as the length of the 1-alkyl group was increased. Under the same conditions, extraction of alkali metal chlorides into solutions of DC18C6 in chloroform, nitrobenzene, and 1-octanol was undetectable. The extraction selectivity order for DC18C6 in the RTILs was K+ > Rb+ > Cs+ > Na+ > Li+. As the alkyl group in the RTIL was elongated, the K+/ Rb+ and K+/Cs+ selectivities exhibited general increases with the larger enhancement for the latter. For DC18C6 in 1-octyl-3-methylimidazolium hexafluorophosphate, the alkali metal cation extraction selectivity and efficiency were unaffected by variation of the aqueous-phase anion from chloride to nitrate to sulfate.     

Determinants and nature of dietary underreporting in a free-living population: the Fleurbaix Laventie Ville Santé (FLVS) Study

OBJECTIVE: To study the determinants and nature of dietary underreporting in a free-living population. DESIGN: Cross-sectional study of nutritional and behavioural characteristics. SUBJECTS: 1030 weight-stable subjects, 501 women and 529 men older than 15 y, included in the Fleurbaix Laventie Ville Santé study. MEASUREMENTS: Dietary intake was assessed using a 3 dy dietary record. Self assessed body weight and height were also recorded. Behavioural and socio-economic data were obtained from a questionnaire. Underreporters were defined as people with a reported ratio of energy intake to estimated basal metabolic rate lower than 1.05. RESULTS: Underreporting concerned 16% of the population and was significantly more frequent in obese than in non obese subjects (P < 0.001). Underreporting was significantly associated with a high socio-professional class (P < 0.05), having dieted at least once (P < 0.01) and to be in dietary restraint (P < 0.05). Furthermore, the contribution of protein to energy intake was significantly higher in underreporters than in non underreporters, independently of weight status. CONCLUSIONS: These data underline that underreporting may bias the assessment of energy and macronutrient intake, particularly in studies on obesity and dietary restraint. Questions about weight concern, dieting and dietary restraint may be useful to identify subjects who underestimate their food intake.     

A model of nonlinear optical transmittance for insulator nanocomposites

A theoretical model of the laser radiation transmittance of insulator nanocomposites containing low concentrations of nanoparticles is proposed. It is shown that the basic mechanisms of low-threshold effects of nonlinear absorption and scattering of laser radiation are, first, the induction of electric dipole moments of nanoparticles in the external field and, second, the orientation of nanoparticles along the polarization direction of this field. The behavior of the transmittance in the vicinity of the central region of a separate absorption band and the dependence of the depth of this band in the transmittance spectrum on the external radiation intensity are considered.