The Solubility Parameters of Ionic Liquids

The Hildebrand’s solubility parameters have been calculated for 18 ionic liquids from the inverse gas chromatography measurements of the activity coefficients at infinite dilution. Retention data were used for the calculation. The solubility parameters are helpful for the prediction of the solubility in the binary solvent mixtures. From the solubility parameters, the standard enthalpies of vaporization of ionic liquids were estimated.     

Impedance study of protecting film formation on lithium and lithiated graphite induced by bis(fluorosulfonyl) imide anion

The process of Li⁺ reduction from room temperature ionic liquids consisting of N-methyl-N-propylpyrrolidinium cation (MPPyr⁺) and bis(fluorosulfonyl) imide (FSI⁻) or bis(trifluoromethanesulfonyl) imide (TFSI⁻) anions was studied with the use of impedance spectroscopy. Reduction was carried out on both metallic lithium (Li) and graphite (G) electrodes. It has been found that the FSI anion in high amounts is able to form a protective film on both graphite and metallic lithium. The Li⁺/Li couple should rather be represented by a Li⁺/SEI/Li system. The SEI structure depends on the manner of its formation (chemical or electrochemical) and is not stable with time. The rate constant for the Li⁺ + e⁻ → Li process at the Li/SEI/Li⁺ (in MPPyrFSI) interface is k_o = 4.2 × 10⁻⁵ cm/s. In the case of carbon electrodes (G/SEI/Li⁺ interface), lithium diffusion in solid graphite is the rate determining step, reducing current by ca. two orders of magnitude, from ca. 10⁻⁴ A/cm², characteristic of the Li/SEI/Li⁺ electrode, to ca. 10⁻⁶ A/cm².     

Electrochemical study of lithium insertion into carbon-rich polymer-derived silicon carbonitride ceramics

This paper presents the lithium insertion into carbon-rich polymer-derived silicon carbonitride (SiCN) ceramic synthesized by the thermal treatment of poly(diphenylsilylcarbodiimide) at three temperatures, namely 1100, 1300, and 1700 °C under 0.1 MPa Ar atmosphere. At lower synthesis temperatures, the material is X-ray amorphous, while at 1700 °C, the SiCN ceramic partially crystallizes. Anode materials prepared from these carbon-rich SiCN ceramics without any fillers and conducting additives were characterized using cyclic voltammetry and chronopotentiometric charging/discharging. We found that the studied silicon carbonitride ceramics demonstrate a promising electrochemical behavior during lithium insertion/extraction in terms of capacity and cycling stability. The sample synthesized at 1300 °C exhibits a reversible capacity of 392 mAh g⁻¹. Our study confirms that carbon-rich SiCN phases are electrochemically active materials in terms of Li inter- and deintercalation.     

Electronic-level interactions of tungsten oxide with unsupported Se/Ru electrocatalytic nanoparticles

Se/Ru nanoparticles - a potent non-platinum catalyst towards oxygen reduction reaction - were modified by hydrated WO₃ and investigated using the rotating disk/ring electrode methods and by synchrotron X-ray photoelectron spectroscopy. The modification resulted in an enhanced catalytic activity towards oxygen reduction reaction (ORR). Our data indicate that the oxygen reduction current starts ca. 70 mV more positive and formation of undesirable hydrogen peroxide has significantly decreased following the modification of Se/Ru with WO₃. X-ray photoelectron spectroscopy reveals that WO₃ interacts electronically with Se/Ru as the W 4f and Se 3d line-shapes change. We therefore conclude that the electronic interactions between Se/Ru and WO₃ are primarily responsible for the increase in activity and selectivity of the WO₃-modified Se/Ru towards ORR.     

Associations between Endogenous Dimethylarginines and Renal Function in Healthy Children and Adolescents

The structural isomer of asymmetric dimethylarginine (ADMA), symmetric dimethylarginine (SDMA), is eliminated almost entirely by urinary excretion and considered a sensitive index of glomerular filtration rate (GFR). However, reports on this relationship in healthy subjects younger than 18 years of age are rare. Therefore, our aim was to investigate relations between endogenous dimethylarginines and renal function indices in healthy children and adolescents. We studied 40 subjects aged 3–18 years free of coexistent diseases or subclinical carotid atherosclerosis. A serum creatinine-derived estimated GFR (eGFR) was calculated by the revised bedside Schwartz equation. L-arginine, ADMA and SDMA were measured by liquid chromatography-tandem mass spectrometry. Mean eGFR was 122 ± 22 (SD) mL/min per 1.73 m². Creatinine and eGFR exhibited closer correlations with the SDMA/ADMA ratio (r = 0.64, p < 0.0001; r = −0.63, p < 0.0001, respectively) than with SDMA (r = 0.31, p = 0.05; r = −0.35, p = 0.03). Neither creatinine nor eGFR correlated with ADMA or L-arginine. Adjustment for age or height only slightly attenuated the associations between the SDMA/ADMA ratio and eGFR or creatinine. Our findings suggest the superiority of the SDMA/ADMA ratio over SDMA as a renal function index in healthy children. Thus, further studies are warranted to verify our preliminary results in a larger group of subjects below 18 years of age.     

Experimental investigation of oil pockets effect on abrasive wear resistance

The experiments were carried out using a block-on-ring tester. The stationary blocks were modified by a burnishing technique in order to obtain surfaces with oil pockets of spherical shape. The area density of oil pockets varied in order to explore their effect on wear resistance and wear intensity. Specimen surfaces had dimples with depths 45-60 μm and diameters 1-1.2 mm. The area density of oil pockets S_p was in the range 4-20%. The block samples were made from bronze B101 (CuSn10P) of 138 HB hardness. The rotated rings were made from 42CrMo4 steel, hardness of 40 HRC obtained after heat treatment. The tested assembly was lubricated by mineral oil L-AN 46. The experiment was carried out under artificially increased dustiness conditions. The dust added to oil consists mainly of SiO₂ (74%) and Al₂O₃ (15%) particles. During the test friction force and temperature of block sample were registered. The tendencies of block surface topography changes during wear were analysed. It was found that sliding pairs with textured specimens were not superior to a system with a turned block with regard to abrasive wear resistance.     

Antimicrobial and Antioxidative Activity of Newly Synthesized Peptides Absorbed into Bacterial Cellulose Carrier against Acne vulgaris

The ongoing search for effective treatment of Acne vulgaris is concentrated, i.a., on natural peptides with antimicrobial properties. The aim of this work was the development of new amino acid derivatives with potential activity on dermal infections against selected microorganisms, including the facultative anaerobe C. acne. The peptides P1–P6 were synthesized via Fmoc solid phase peptide synthesis using Rink amide AM resin, analyzed by RP-HPLC-MS, FTIR, DPPH radical scavenging activity, and evaluated against C. acne and S. aureus, both deposited and non-deposited in BC. Peptides P1–P6 presented a lack of cytotoxicity, antimicrobial activity, or antioxidative properties correlated with selected structural properties. P2 and P4–P6 sorption in BC resulted in variable data, i.a., confirming the prospective topical application of these peptides in a BC carrier.     

Ozone Solubility in Liquids

A comprehensive and critical survey of the available data on ozone solubility in different liquids—in water and aqueous solutions, as well as in organic solvents has been made. Apart of comparing the data published by the various authors after 1981 for water and aqueous solutions, special attention has been paid to the effects of pH and the composition of the liquid phase (salt effect). The published data on ozone solubility in organic liquids have been compiled and the listing of such data given by Battino (1981) Battino, R. 1981. “Oxygen and Ozone”. In Solubility Data Series, 474492Oxford: Pergamon Press.  [Google Scholar] has been supplemented by the more recent ones. Special interest has been given to perfluorinated organic solvents, which exhibit high solubility for both oxygen and ozone. More formal thermodynamic approach has also been attempted. Special attention has then been paid to the predictive methods developed for oxygen solubility in non-polar and polar solvents.     

Polyoxymethylene composites with natural and cellulose fibres: Toughness and heat deflection temperature

Cellulose and abaca fibre reinforced polyoxymethylene (POM) composites were fabricated using an extrusion coating (double screw) compounding followed by injection moulding. The long cellulose or abaca fibres were dried online with an infrared dryer and impregnated fibre in matrix material by using a special extrusion die. The fibre loading in composites was 30 wt.%. The tensile properties, flexural properties, Charpy impact strength, falling weight impact strength, heat deflection temperature and dynamic mechanical properties were investigated for those composites. The fibre pull-outs, fibre matrix adhesion and cracks in composites were investigated by using scanning electron microscopy. It was observed that the tensile strength of composites was found to reduce by 18% for abaca fibre and increase by 90% for cellulose fibre in comparison to control POM. The flexural strength of composites was found to increase by 39% for abaca fibre and by 144% for cellulose fibre. Due to addition of abaca or cellulose fibre both modulus properties were found to increase 2-fold. The notched Charpy impact strength of cellulose fibre composites was 6-fold higher than that of control POM. The maximum impact resistance force was shorted out for cellulose fibre composites. The heat deflection temperature of abaca and cellulose fibre composites was observed to be 50 °C and 63 °C higher than for control POM respectively.