Effect of water content on thermal and dynamic mechanical properties of xanthan powder: A comparison between standard and novel techniques

In this work, the sorption isotherms of xanthan powder obtained under static and dynamic conditions and their fitting with mathematical models were discussed. The transitions within xanthan-water systems have been investigated using a standard material characterization technique - Differential Scanning Calorimetry (DSC) - and two novel techniques - Dynamic Mechanical Thermal Analysis (DMTA) material pocket and Phase Transition Analysis (PTA). It was found that within water-xanthan systems, the onset temperature for the melting of freezable water obtained from DSC method was in agreement with freezable water melting peaks obtained via DMTA material pocket at levels of hydration when the freezable water was present. Also, low-temperature transitions, related to polysaccharide-water interactions, were observed by both techniques within xanthan systems which contained no freezable water. However, the use of the PTA technique was limited to xanthan systems with low water content.     

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.     

Assessment of subcritical crack growth in hydrogen-containing environment by the parameters of acoustic emission signals

Estimation models (differential equations, initial and final conditions) for determining the crack propagation kinetics in hydrogen-containing environments using the acoustic emission (AE) signal parameters are proposed. The formulation of these models is based on the main ideals of the AE method, dependence between the crack increment area and a sum of AE-signals amplitude, main criteria of fracture mechanics and laws of thermodynamics.     

Potentiometric determination of ketoprofen and piroxicam at a new PVC electrode based on ion associates of Rhodamine 6G

The characteristics, performance and application of ion-selective electrodes for ketoprofen and piroxicam ions based on Rhodamine 6G as electrode-active substances are described. These electrodes respond with sensitivities of (58.0 ± 1.0) and (57.0 ± 2.0) mV/decade over the range 1.0 × 10^? 4–1.0 × 10^? 1 and 1.0 × 10^? 4–5.0 × 10^? 2 mol/l at pH 5–9 and 6–10 and a detection limit of 6.3 × 10^? 5 and 3.2 × 10^? 5 mol/l for ketoprofen and piroxicam, respectively. The electrodes are easily constructed at a relatively low cost, have a fast response time and can be used for a period of 5 months without any considerable divergence in potential. The proposed sensor displayed good selectivity for ketoprofen and piroxicam in the presence of several substances and inorganic anions. It was used for the direct assay of ketoprofen and piroxicam in commercial pharmaceutical preparations.     

Dielectric and thermal studies of segmental dynamics in silica/PDMS and silica/titania/PDMS nanocomposites

Effects of silica and silica/titania nanoparticles on glass transition and segmental dynamics of poly(dimethylsiloxane) (PDMS) were studied for composites of a core–shell type using differential scanning calorimetry, thermally stimulated depolarization current, and dielectric relaxation spectroscopy techniques. Strong interactions between the filler and the polymer suppress crystallinity (T_c, X_c) and affect significantly the evolution of the glass transition in the nanocomposites. The segmental relaxation associated with the glass transition consists of three contributions, arising, in the order of decreasing mobility, from the bulk (unaffected) amorphous polymer fraction (α relaxation), from polymer chains restricted between condensed crystal regions (α_c relaxation), and from the semi‐bound polymers in an interfacial layer with strongly reduced mobility due to interactions with surface hydroxyls of silica and silica/titania nanoparticles (α′ relaxation). The evolution of surface affected CH₃ groups, as well as the degree of interaction of PDMS molecules with surface hydroxyl groups as a function of treatment temperature, was assessed by Fourier transform infrared spectroscopy, thermogravimetry and differential thermal analysis. The effectiveness of silica/PDMS and silica/titania/PDMS nanocomposites as hydrophobic coatings was investigated by static contact angle measurements. It was shown that the presence of titania nanoparticles and adsorbed PDMS promotes the hydrophobic properties of the PDMS coating after treatment in the 80–650°C range. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 41154.     

Double-layer imprint lithography on wafers and foils from the submicrometer to the millimeter scale

In this paper, a thermal imprint technique, double-layer nanoimprint lithography (dlNIL), is introduced, allowing complete filling of features in the dimensional range of submicrometer to millimeter. The imprinting and filling quality of dlNIL was studied on Si substrates as a model system and compared to results obtained with regular NIL (NIL) and reverse NIL (rNIL). Wavy foils were imprinted with NIL, rNIL and dlNIL and the patterning results compared and discussed. With dlNIL, a new application possibility was introduced in which two different resists having, for example, a different etch resistance to a certain plasma were combined within one imprint step. dlNIL allows extension to many resist combinations for tailored nanostructure fabrication.     

Antioxidant properties of various solvent extracts of potato peel,sugar beet pulp and sesame cake

BACKGROUND: Growing interest in the replacement of synthetic food antioxidants by natural ones has fostered research on vegetable sources and screening of raw materials to identify new antioxidants. The food‐processing industry generates substantial quantities of phenolic‐rich by‐products that could be valuable natural sources of antioxidants. In this study the antioxidant properties and total phenolic, flavonoid and flavonol contents of three industrial by‐products, sugar beet pulp, sesame cake and potato peel, extracted with various solvents were examined. Since different antioxidant compounds have different mechanisms of action, several methods were used to assess the antioxidant efficacy of extracts. RESULTS: Among the six solvents tested, methanol gave the highest extract yield of potato peel and sugar beet pulp, while diethyl ether gave the highest extract yield of sesame cake. Methanol exhibited the highest extraction ability for phenolic compounds, with total phenolics amounting to 2.91, 1.79 and 0.81 mg gallic acid equivalent g^?1 dry weight in potato peel, sugar beet pulp and sesame cake extracts respectively, and also showed the strongest antioxidant capacity in the three assays used. All three methods proved that potato peel extract had the highest antioxidant activity owing to its high content of phenolic compounds and flavonoids. CONCLUSION: On the basis of the results obtained, potato peel, sugar beet pulp and sesame cake extracts could serve as natural antioxidants owing to their significant antioxidant activity. Therefore they could be used as preservative ingredients in the food and/or pharmaceutical industries. Copyright © 2009 Society of Chemical Industry     

Effect of Hydrogen Bonding on a Value of an Open Circuit Potential of Poly-(3,4-ethylenedioxythiophene) as a Beneficial Mode for Energy Storage Devices

Poly(3,4-ethylenedioxythiophene) is one of the semiconducting polymers that has attracted attention as electroactive materials for many different applications such as electrochromic devices, light-emitting diodes, biosensors, and supercapacitors. The fundamental understanding of the origin of its energy storage ability will lead to the proper design of such devices. Generally, the charge storage in supercapacitors is due to the formation of an electrical double layer and/or redox reactions. Recently, it is shown that the formation of cation radicals in PEDOT is induced by the hydrogen-bond formation between formic acid and polymer during electrochemical polymerization. The induced cation radicals play a major role in the charge storage ability of PEDOT, as studied in the current work. Furthermore, the presence of hydrogen bonds in PEDOT leads to the stable in time open circuit potential of 900 mV. This new knowledge leads to the designing of a symmetrical supercapacitor based on PEDOT as active material where hydrogen-bonds play a crucial role in the improved performance of the device.     

Mechanical properties with respect to water content of gelatin films in glassy state

Changes on the structural and molecular level of gelatin films induced by hydration below 25±3% water content (glass–rubbery transition at ambient temperature) were identified with DSC and FTIR spectroscopy. Three main stages of hydration were distinguished: (I) water bound by high-energy sorption centres; (II) structural water; (III) polymolecular layer water. The mechanical behaviour of gelatin films at each stage of hydration was characterized. Relaxation of the films during hydration was taken into account in the analysis of results. Hydrated gelatin films were characterized as brittle below the glass–rubbery transition at ambient temperature, however some improvement of mechanical properties related to a higher renaturation level was showed between 7 and 14% of water content in stage II (structural water).