Plasma modification of viscose textile

A study on plasma treatment of a textile is presented. Samples of pure viscose textile were exposed to RF oxygen, nitrogen or hydrogen plasma for 5 s. The gas pressure was 75 Pa and the RF power was 250 W. In all cases plasma treatment induced chemical changes in the samples' surface, which were determined by using high-resolution XPS (X-ray photoelectron spectrometer). Treatments in oxygen and nitrogen plasma increased the concentration of existing as well as formation of oxygen functional groups, while hydrogen plasma caused a substantial decrease of these groups. SEM (Scanning electron microscopy) analysis of the surface of the textile fibres was performed as well. The results showed that the fibres' surface treated in nitrogen plasma was similar to the untreated surface, while after treatment in hydrogen or oxygen plasma, the surface became rougher.     

Selenium concentration in St. John’s wort (Hypericum perforatum L.) herb after foliar spraying of young plants under different UV-B radiation levels

St. John’s wort (Hypericum perforatum L.) was grown under different levels of UV-B radiation, with selenium (10 mg l⁻¹ Se applied by foliar spraying in the form of sodium selenate) or without foliar Se application. The different levels of UV-B radiation comprised an enhanced level simulating 17% ozone depletion, ambient level, and a reduced level of UV-B radiation. The concentration of Se in unsprayed plants was from 20 ng g⁻¹ to 120 ng g⁻¹. The concentration of Se in the organs of plants foliarly sprayed with Se ranged from 1000 ng g⁻¹ to 12,000 ng g⁻¹, the highest concentration being detected in plants grown under reduced levels of UV-B radiation. Foliar application of Se fertiliser is feasible and effective in St. John’s wort and results in Se-enriched nutritional supplements.     

Furcellaran Surface Deposition and Its Potential in Biomedical Applications

Surface coatings of materials by polysaccharide polymers are an acknowledged strategy to modulate interfacial biocompatibility. Polysaccharides from various algal species represent an attractive source of structurally diverse compounds that have found application in the biomedical field. Furcellaran obtained from the red algae Furcellaria lumbricalis is a potential candidate for biomedical applications due to its gelation properties and mechanical strength. In the present study, immobilization of furcellaran onto polyethylene terephthalate surfaces by a multistep approach was studied. In this approach, N-allylmethylamine was grafted onto a functionalized polyethylene terephthalate (PET) surface via air plasma treatment. Furcellaran, as a bioactive agent, was anchored on such substrates. Surface characteristics were measured by means of contact angle measurements, X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM). Subsequently, samples were subjected to selected cell interaction assays, such as antibacterial activity, anticoagulant activity, fibroblasts and stem cell cytocompatibility, to investigate the Furcellaran potential in biomedical applications. Based on these results, furcellaran-coated PET films showed significantly improved embryonic stem cell (ESC) proliferation compared to the initial untreated material.     

Exploring color attractiveness and its relevance to fashion

Many studies have been conducted on the phenomenon of color preference, with the aim of identifying the key color preferences. Most of the previous studies have been placing blue in the most preferred position and green-yellow in the least preferred position. This study was conducted online and aims to showcase new color preference trends in the digital age. The colors selected for this study were based on the colors most frequently mentioned in previous color studies. Here, we show an evaluation using 14 Pantone colors as stimuli on the sample of (N = 146) participants based on pairwise adjectives (attractive-unattractive). Principal component analysis and other multivariate statistics were used to examine participants' color attractiveness. In addition, gender and age were examined to determine if they had an impact on color attractiveness ratings. Results show that participants tend to prefer distinctive colors (black, pink, yellow), but there are slight differences in preferences that could be related to the influence of gender and age.     

Surface modification and ageing of PMMA polymer by oxygen plasma treatment

We present a study on ageing of polymethyl methacrylate (PMMA) polymer treated with oxygen plasma. Oxygen plasma was created with an RF generator operating at a frequency of 27.12 MHz and a power of 200 W. The oxygen pressure was 75 Pa. The samples were treated for different time from 5 s to 60 s. The chemical modifications of the surface after plasma treatment were monitored by XPS (X-ray photoelectron spectroscopy), while the wettability and ageing effects were studied by WCA (water contact angle measurements). The samples were aged in dry air or in water. In the case of dry air, the least pronounced ageing was observed for the sample treated for 60 s. For samples aged in water, however, the lowest ageing rate was observed for the sample treated for 5 s. The samples were ageing slightly faster in water than in air. We also investigated the temperature effect on ageing of plasma treated samples. A set of samples was stored in a refrigerator at 5 °C and the other set was placed into an oven at 50 °C. The ageing rate of the samples stored at 5 °C was significantly lower than for the samples stored at 50 °C, so cooling the samples help keeping the required surface properties.     

Influence of Al(OH)3 nanoparticles on the mechanical and fire resistance properties of poly(methyl methacrylate) nanocomposites

One of the drawbacks of poly(methyl methacrylate) (PMMA) is its flammability. This limits its use in many areas, particularly in constructions. Although there are several fire retardants commercially available, certain disadvantages remain. Introduction of fire retardants into PMMA can change the mechanical properties and transparency can be significantly reduced. Our attention in this study was focused on aluminium trihydroxide (ATH) nanoparticles as the filler for PMMA. To achieve better compatibility and avoid the agglomeration of nanoparticles, 2‐hydroxyethyl methacrylate was used as a co‐monomer for nanocomposite preparation. The characteristics of sheets made with ATH nanoparticles were compared to standard PMMA sheets prepared without additives. Better thermal properties and impact hardness were observed, the speed of burning was significantly lower, while complete transparency of the material was retained. POLYM. COMPOS., 37:1659–1666, 2016. © 2014 Society of Plastics Engineers     

Comparison of oxygen plasma and cutinase effect on polyethylene terephthalate surface

The aim of the study is to activate inert PET surface in order to introduce the carboxyl groups and to obtain its hydrophilic character. Two advanced and environmentally friendly techniques were used for these purposes: i) oxygen plasma activation; ii) enzymatic treatment by cutinase. Differently treated PET foils were studied in terms of carboxylic group content (non‐aqueous potentiometric titrations, XPS) and hydrophobic/hydrophilic character (goniometry). Moreover, the influence of both activation procedures onto chitosan adsorption was examined by XPS, zeta potential measurements and ATR‐FTIR spectroscopy. Obtained results show that plasma activation gives for around 19% higher amount of carboxylic groups than cutinase treatment and is during the storage less stable. Results clearly show that the use of both surfaces activation processes increases the ability of PET foils for chitosan adsorption. Due to the fact that chitosan is an antimicrobial agent, obtained materials may be applied as an active packaging system. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Inter-pulse interval between rectangular voltage pulses affects electroporation threshold of artificial lipid bilayers

Describes experiments that determine how the inter-pulse interval between rectangular pulses in a train of pulses alters the threshold of electroporation of 1-pamitoyl 2-oleoyl phosphatidycholine bilayer lipid membranes. The bilayers were exposed to a train of sixteen 100-/spl mu/s duration pulses. Threshold voltage and the sequence number of the pulse in the train, where onset of the electroporation occurred, were recorded for six inter-pulse intervals (/spl infin/, 1000 /spl mu/s, 100 /spl mu/s, 10 /spl mu/s, 1 /spl mu/s, 0 /spl mu/s). The threshold voltage of the pulse train decreased linearly with the logarithm of the inter-pulse interval. When the inter-pulse interval was 1 /spl mu/m, electroporation threshold dropped to that of a single pulse with duration 1600 /spl mu/s (equal to the sum of all pulse durations in the train). In this case, the occurrence of bilayer rupture was almost equally frequent for all pulses in the train. When the inter-pulse interval between the pulses exceeded 1 /spl mu/s, the influence of the previous pulse on the response to the following pulse declined. It became more likely that the bilayer ruptured during the first half of the train. These experimental observations suggest that a train of pulses applied with short inter-pulse interval (less than 1 ms) can lower the electroporation threshold of bilayer lipid membranes.     

Human errors versus stress

This paper discusses human errors in a man-machine system with the dependence on different stresses. A method is presented for defining ranges of normal stress values, based on the construction of the membership function from the fuzzy set theory. This method is applied to a stress analysis for a sample of station foremen in the railway traffic system of Slovenia. The results of this analysis are given.