Testing of explosive welding and welded joints. Wavy character of the process and joint quality

The basic defects occuring in explosive clad plates were properly systemized and the reasons of their formation were explained. Cases of cracks and delaminations in explosive clad plates were examined in this work. Various values of tensile stresses coming from loading and unloading waves were analysed, as they were the main reason of defects. The defects were connected with properties of welded materials in the joint area and beyond it. Some practical aspects of this process were shown as well.     

Effect of menadione (vitamin K3) addition on lipid oxidation and tocopherols content in plant oils

The effect of added menadione (vitamin K3) on stored corn and wheat germ oil on the dissolution and dimerization of natural tocopherols and autoxidation of triacylglycerols was investigated. Samples of corn and wheat germ oils pure and with added menadione were stored at +20 degrees C in brown and transparent glass bottles. During storage their peroxide value, changes of the content of fatty acids and dissolution of tocopherols were measured. Destruction of individual tocopherols in tested oils with menadione stored in both dark and transparent glass bottles was greater than in the oil samples without menadione. However, the degradation of individual tocopherols was different in each oil. Addition of menadione to the both oils resulted in accelerated the process of autoxidation of these oils. The corn oil stored in transparent bottles was oxidized faster than the one stored in brown bottles. The pro-oxidant activity of menadione was additionally activated by light. In contrast, in the case of germ oil, the process of autoxidation was very fast regardless of sort of container. Addition of menadione to the plant oils influenced the dissolution of natural tocopherols but did not influence the dimerization of tocopherols. As from the experiment, the addition of menadione to the oils decreased their nutritive value.     

Multi-layered graphenic structures as the effect of chemical modification of thermally treated anthracite

Graphenic materials have been produced from thermally treated highly metamorphosed carbon material – anthracite using two different methods: (1) the improved Hummers method followed by thermal reduction and (2) cycloaddition of azomethine ylide. Distinct differences were found between both anthracite-derived graphenic materials. The oxidation Hummers process resulted in a wide variety of oxygen functional groups incorporated into the carbon layers, while subsequent thermal reduction caused separation of graphene sheets but reduced the oxygen moieties. The cycloaddition of azometine ylide led to the formation of functionalized graphene sheets containing mostly 3,4-bonded N-methyl-2-(3,4-dihydroxyphenyl)pyrrolidine groups. The first attempts of application of anthracite-derived fillers to epoxy composites showed the improvement of their mechanical and viscoelastic properties, comparable to composites with graphene nanofillers.     

Testing of explosive welding and welded joints. The microstructure of explosive welded joints and their mechanical properties

The present essential models and some theories were applied to explain the wavy phenomenon, microstructure and mechanical properties of the characteristic joint area. Two phenomena occurring in the plate collision zone during welding were carefully tested. These phenomena were connected with forming the wavy joint surface and the interpass. The available data referring to forming the interpass were further developed.     

Hydrogel membranes based on genipin-cross-linked chitosan blends for corneal epithelium tissue engineering

Novel polymeric hydrogel scaffolds for corneal epithelium cell culturing based on blends of chitosan with some other biopolymers such as hydroxypropylcellulose, collagen and elastin crosslinked with genipin, a natural substance, were prepared. Physicochemical and biomechanical properties of these materials were determined. The in vitro cell culture experiments with corneal epithelium cells have indicated that a membrane prepared from chitosan-collagen blend (Ch-Col) provided the regular stratified growth of the epithelium cells, good surface covering and increased number of the cell layers. Ch-Col membranes are therefore the most promising material among those studied. The performance of Ch-Col membranes is comparable with that of the amniotic membrane which is currently recommended for clinical applications.     

Selenium bioaccumulation in eutrophic lake – Dąbie Małe Lake,Poland

While the world literature presents many studies on the occurrence of selenium in aquatic ecosystems, the risks associated with overexposure of hydrobionts to this element and the consequences of its magnification in the food chain (areas rich in Se), there are few studies on Se concentration in Poland's water bodies and watercourses (Se deficient area). The objective of the study was to assess the Se bioaccumulation in D?bie Ma?e Lake, based on Se concentration in the water, bottom sediments, and organs of Rutilus rutilus and Perca fluviatilis. The accumulation and biomagnification factor averaged 231 ± 69 and 1.2, respectively. Bioconcentration factor, calculated as Se in muscle divided by Se in water, ranged 35–104. Although Se concentrations in bottom sediments and fish were generally lower than the values reported in the literature, Se concentration in the water exceeded 2 µg/L, recommended value as a probable safe water concentration for wildlife.     

Electrospun polyacrylonitrile nanofibers modified by quaternary ammonium salts

Electrospinning from a capillary is one of the methods for the production of nanofibers. The specific properties of such fibers result first of all from their large specific surface and the high porosity of the fiber mat. This article presents a process for producing functional nanofibers with antimicrobiological properties by electrospinning from polyacrylonitrile/dimethyl sulphoxide solution containing a bioactive agent based on quaternary ammonium salts (N, N, n, n,‐didecyl‐N,N‐dimethylammonium chloride, Bis‐(3‐aminopropyl)‐dodecylamine) and 2‐propanol. The structure of the nanofibers obtained and their antimicrobial activity are investigated. A 5 wt % addition of bioactive preparation to the polymer solution (concentration of active substance in solution about 1.5 wt %) makes it possible to obtain fibers showing good bactericidal properties. After 6 h in contact with these fibers, Escherichia coli are eliminated to a level of 99.84% and Staphylococcus aureus to 99.99%. The IR spectrophotometric measurements do not indicate a residue of solvent in the bioactive nanofibers and show an increase in content of CH and CH₂ groups in relation to the pure nanofibers, which is connected with the presence of the biocide. Their degree of crystallinity determined by the X‐ray scattering method is 44.4%. The nanofibers obtained can be designed for medical and filtration applications. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Polymer Chain Relaxation Mechanisms in Siloxane-Carbosilane Systems

The effect of sterically hindered carbosilane moieties, situated as end groups in telechelic oligodimethylsiloxanes, was investigated with respect to the mobility of silicon atoms in the main chain. The relaxation phenomena in such crowded systems were studied by DSC and NMR methods. Spin–lattice relaxation times T ₁ (²⁹Si NMR) of silicon atoms in the oligomer chain were estimated and related to the distance between a given siloxane unit and the carbosilane moiety. It was found that the mobility of terminal siloxane units has been substantially affected. However, in the long range, the effect does not to seem to outweigh the intrinsic flexibility of the siloxane bonds.     

Convectional mass/heat transfer in a rotary regenerator rotor consisted of the corrugated sheets

The results of an electrolytic research of convectional mass/heat transfer in a rotational regenerator model are presented. A rotor model consisted of the five corrugated sheets of the two kinds, after assembly of which 300 ducts occurred. They were short and their cross-section was of varied shape and surface areas along the curved axes. The research was carried out both, with and without the baffles of two kinds. The central and side nickel sheets were used as the cathodes for proving the inequality of flow rate of electrolyte along the axis of the rotor. NaOH based electrolyte (1 mol) with equimolar quantities of K₃Fe(CN)₆ and K₄Fe(CN)₆ was used during the whole experiment. Schmidt number was 1590. Rotation number of: 0, 0.15, 0.20 and 0.25 for Reynolds number in the interval 150–1270, was adjusted. The rate of increase of the transfer coefficient as a result of rotation and the final correlations on the Chilton–Colburn coefficient were stated in power form j_M = j_M(Re) at parameter Ro and in the compact form j_M = j_M(Re, Ro). The influence of the shape of the baffle on the intensity of the transfer process was proved, which may help in design.