The desorption of condensed noble gases and gas mixtures from cryogenic surfaces

In accelerators, operating at liquid-helium temperature, cold surfaces are exposed to intense synchrotron radiation and bombardment by energetic electrons and ions. Molecular desorption yield and secondary electron yield can strongly influence the performance of the accelerator. In order to predict the gas density during the operation, the knowledge of electron-induced desorption yields of condensed gases and of its variation with the gas coverage is necessary. Desorption yields under electron impact of various noble gases and gas mixtures condensed on a copper surface cooled at 4.2 K have been measured.     

Nanosize radon short-lived decay products in the air of the Postojna Cave

At two points in the Postojna Cave, short-term monitoring in summer and in winter of air concentrations of radon and radon decay products, equilibrium factor, unattached fraction of radon decay products (f_un), barometric pressure, relative air humidity in the cave and air temperature in the cave and outdoor has been carried out, with the emphasis on f_un. Dose conversion factors, calculated on the basis of f_un values obtained (ranging from 0.09 to 0.65) exceed 5 mSv WLM^− 1, by a factor of 11.5-14.0 in summer and of 3.0-4.0 in winter for mouth breathing, and 3.1-3.5 in summer and 1.5-1.7 in winter for nasal breathing.     

Engineered invasive plant cellulose fibers as resources for papermaking

Seven fast-growing invasive plant species were harvested in Slovenia and tested for their valorisation potential in the pulp and paper industry with the aim of sustainable substitution of commercial cellulose fibres. Cellulose fiber materials were isolated by filtration after solubilizing extractives, lignin and hemicellulose in a kraft pulping process. The chemical structure was thoroughly studied, as well as the optical, morphological and mechanical properties. All examined species (Ailanthus altissima, Fallopia bohemica, Fallopia japonica, Rhus typhina, Robinia pseudoacacia, Rudbeckia laciniata and Solidago canadensis) contain relatively high amount of C6 polysaccharides (>?35%), have notable hemicellulose content (30–40%), low ash content (<?2%) and can be easily delignified, while manufactured natural fibers exhibit convenient morphology (fiber length 0.47–0.88 mm; width 14.4–20.9 μm), optical (ISO whiteness 19.0–36.0%) and mechanical characteristics (tensile index 18.0–58.0 Nm/g; tear index 0.8–4.1 mN m²/g; and burst index 0.5–2.4 kPa m²/g indices), which makes them applicable to sustainable paper production. The pulp yields varied between 34–44%, where both darker herbaceous and brighter woody fibers were morphologically comparable to typical hardwoods. According to the observed properties Robinia pseudoacacia and Rudbeckia laciniata seem to be superior raw material for commercial papermaking products. The ubiquitous invasive plants pose a huge potential for the circular economy, especially in terms of their cascade valorisation of biorefinery by the isolation and valorization of hemicellulose, sugars, and lignins into added-value aromatic and aliphatic building blocks. However, promising yield of cellulose fibers of decent morphology and mechanical properties are reported in this study.

     

Extractable antioxidants and non-extractable phenolics in the total antioxidant activity of selected plum cultivars (Prunus domestica L.): Evolution during on-tree ripening

The purpose of this study was to evaluate the contribution of extractable antioxidants and non-extractable phenolics to the total antioxidant activity (TAA) of plums. Therefore, the antioxidant activity was determined (ABTS assay) in aqueous–organic extracts, as well as in the extraction residues which were a subject of two different acidic treatments to release hydrolysable tannins and non-extractable proanthocyanidins (NEPA). In addition, the changes in TAA during the last week of ripening were investigated. Extractable antioxidants contributed less than 18% to the TAA, considerably higher values of antioxidant activity were associated with hydrolysable tannins and NEPA, suggesting that the antioxidant activity of plums may be underestimated in the literature. The ripening resulted in an increase of TAA up to 38% in excess of the value determined on the first sampling date. TAA showed a similar pattern over the ripening period for all cultivars studied.     

Molecular Weight Distribution Study of Delignification of Spruce Wood Meal With Chloroacetic Acids

The amount of lignin removed from spruce wood meal at 50°C to 110°C with mono-, di-, and trichloroacetic acid, as well as its molecular weight (MW) distribution was studied. Trichloroacetic acid gives rise to the lowest M_n (2,000–4,000), the lowest M_w (4,500–8,000), the lowest upper MW limit (～40,000), and the lowest polydispersity (1.5–3.0) of lignin. The removed lignin is split by the tested acids to different extents.