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Tyrosinase catalysed coupling of functional molecules onto protein fibres
Suzana Jus, Vanja Kokol, Georg M. Gübitz, 2008, izvirni znanstveni članek

Opis: Grafting, using oxidative enzymes shows a high potential for wool fibres funktionalisation. In this work we attempt to graft on wool fibres with phenolic antioxidants order to introduce and improve the properties of the fibre. The approach of tyrosinase to oxidize tyrosine residues in wool proteins to quinones, which can further react with free sulfhydryl (thiol), amino or phenolic groups of different substrates was exploited to couple different phenolic antioxidants (caffeic acid and chlorogenic acid) onto the wool fibre proteins. Tyrosinase catalysed reactions were followed by different analytical methods like oxygen consumption, FT-NIR Raman and UV/VIS spectroscopy. It was proved that phenolic compounds used are strongly cross-linked on the wool fibre resulting to an improved antioxidant activity.
Ključne besede: textile fibres, wool fibers, tyrosinase, caffeic acid, chlorogenic acid, grafting, chemical modification of fibres
Objavljeno: 31.05.2012; Ogledov: 895; Prenosov: 53
URL Povezava na celotno besedilo

Intelligent FEA-based design improvement
Marina Novak, Bojan Dolšak, 2008, izvirni znanstveni članek

Opis: Structural analysis using the finite element method is an integrate part of the design process for many components. Finite element analysis is the most extensively used numerical analysis in mechanical engineering practice and is incorporated into many computer-aided design systems. The existing commercial software is very helpful when supporting realisation of the analysis process but still fails to provide adequate support during the post-processing phase. The results of analysis should be studied and decisions made regarding the designćs suitability with respect to its engineering specifications. In general, design changes are indispensable and designers need help to design them properly. The prototype of an intelligent rule-based consultative system is being developed by the authors to provide such advice when considering a description of the design structurećs critical area. This system is encoded in Prolog. It can deal with the results of prior strain-stress or thermal analysis. It presents a short list of proposed design changes that should be taken into account when improving the design.
Ključne besede: structural analysis, finite elment analysis, design modification, decision support, Prolog, knowledge-base systems
Objavljeno: 31.05.2012; Ogledov: 1070; Prenosov: 41
URL Povezava na celotno besedilo

Grafting of cotton with [beta]-cyclodextrin via poly(carboxylic acid)
Bojana Vončina, Alenka Majcen Le Marechal, 2005, izvirni znanstveni članek

Opis: Cyclodextrins are cyclic oligosaccharides. Cyclodextrin molecules can form inclusion complexes with a large number of organic molecules. The properties of cyclodextrins enable them to be used in a variety of different textile applications. Cyclodextrins can act as auxiliaries in washing and dyeing processes, and they can also be fixed onto different fiber surfaces. Because of the complexing abilities of cyclodextrins, textiles with new functional properties can be prepared. Poly(carboxylic acid)s such as 1,2,3,4-butane tetracarboxylic acid (BTCA) are well-known non-formaldehyde crosslinking reagents. BTCA has four carboxylic acid groups, which can react with hydroxyl groups of cellulose and form stable ester bonds. We crosslinked -cyclodextrin molecules on hydroxyl groups of cellulose via BTCA.
Ključne besede: textile fibres, chemical modification, beta cyclodextrines, butane tetracarboxylic acid, BTCA, FTIR, host-guest systems, formaldehyde-free crosslinking reagents
Objavljeno: 01.06.2012; Ogledov: 1240; Prenosov: 33
URL Povezava na celotno besedilo

Grafting of ethylcellulose microcapsules onto cotton fibres
Roxana Badulescu, Vera Vivod, Darja Jaušovec, Bojana Vončina, 2008, izvirni znanstveni članek

Opis: In this paper a treatment of cotton with ethylcellulose (EC) microcapsules wasinvestigated. EC microcapsules containing Rosemary oil were obtained by phase separation method. The surface and morphology of microcapsules were characterized by scanning electron microscopy (SEM). Microcapsules with a regular spherical shape in the 10-90 m size range were prepared and grafted onto cotton using the crosslinking reagent 1,2,3,4-butanetetracarboxylic acid (BTCA) in the presence of catalysts. The influence of the two catalysts, cyanamide (CA) and N,N'-dicyclohexylcarbodiimide (DCC) on curing efficiency (grafting) was investigated. SEM and Fourier transform infrared spectroscopy (FT-IR) were used to study the formation of ester bonds between BTCA and hydroxyl groups of cotton and/or hydroxyl groups of EC. When DCC was used as acatalyst, the esterification took place slowly at room temperature. In the case of CA, the cotton was cured at 110 °C for several minutes. After 2 min curing, the microcapsules, which kept their original shape, were bonded to thecotton fibers. Increasing the curing time altered the microcapsule shell. Grafting and crosslinking reactions of the thermofixed EC microcapsules onto cotton were proposed.
Ključne besede: textiles, chemical modification, cotton fibres, ethylcellulose, microcapsules, BTCA, SEM, FT-IR, grafting
Objavljeno: 01.06.2012; Ogledov: 1094; Prenosov: 24
URL Povezava na celotno besedilo

Topochemical modification of cotton fibres with carboxymethyl cellulose
Lidija Fras Zemljič, Peer Stenius, Janne Laine, Karin Stana-Kleinschek, 2008, izvirni znanstveni članek

Opis: The research reported in this paper demonstrates that the capacity of cotton fibres to adsorb cationic surfactants as well as the rate of the adsorption process can be increased by adsorbing carboxymethyl cellulose (CMC) onto the fibre surfaces; in addition, the adsorption can be restricted to the fibre surface. CMC was deposited by means of adsorption from an aqueous solution. The adsorption of N-cetylpyridinium chloride (CPC) from an aqueous solution onto the CMC-modified fibres was measured using UVspectrometric determination of the surfactant concentration in the solution. Adsorption onto the cotton fibres was studied in a weakly basic environment (pH 8.5) where cotton fibres are negatively charged and the CPC ion is positively charged. Modification of the fibres by adsorption of CMC introduces new carboxyl groups onto the fibre surfaces, thereby increasing the adsorption capacity of the fibres for CPC. The initial rate of adsorption of CPC increased proportionally with the amountof charge; however, this rate slowed down at high degrees of coverage onfibres with a high charge. The adsorption of cationic surfactant to the anionic surface groups was stoichiometric, with no indication of multilayer oradmicelle formation. It was evident that the acidic group content of the fibres was the primary factor determining cationic surfactant adsorption to these fibres.
Ključne besede: textile fibres, cotton fibres, modification, carboxymethyl cellulose, acid groups, charge increase, conductiometric titration, phenol-sulphuric acid test, practical applications
Objavljeno: 01.06.2012; Ogledov: 1026; Prenosov: 58
URL Povezava na celotno besedilo

A novel metalloprotease from Bacillus cereus for protein fibre processing
Fernanda de Sousa, Suzana Jus, Anita Erbel, Vanja Kokol, Artur Cavaco-Paulo, Georg M. Gübitz, 2007, izvirni znanstveni članek

Opis: A novel protease produced by Bacillus cereus grown on wool as carbon and nitrogen source was purified. B. cereus protease is a neutral metalloprotease with a molecular mass of 45.6 kDa. The optimum activity was at 45 °C and pH 7.0. The substrate specificity was assessed using oxidized insulin B-chain and synthetic peptide substrates. The cleavage of the insulin B-chain was determined to be Asn3, Leu6, His10-Leu11, Ala14, Glu21, after 12 h incubation. Among the peptide substrates, the enzyme did not exhibit activity towards ester substrates; with p-nitroanilide, the kinetic data indicate that aliphatic and aromatic amino acids were the preferred residues at the P1 position. For furylacryloyl peptides substrates, which are typical substrates for thermolysin, the enzyme exhibited high hydrolytic activity with a Km values of 0.858 and 2.363 mM for N-(3-[2-Furyl]acryloyl)-Ala-Phe amide and N-(3-[2-Furyl]acryloyl)-Gly-Leu amide, respectively. The purified protease hydrolysed proteins substrates such as azocasein, azocoll, keratin azure and wool.
Ključne besede: textile finishing, enzymatic modification, wool fibre, enzymes, Bacilus cereus, specificity, kinetics, metalloprotease
Objavljeno: 01.06.2012; Ogledov: 964; Prenosov: 58
URL Povezava na celotno besedilo

The influence of enzymatic treatment on wool fibre properties using PEG-modified proteases
Suzana Jus, Marc Schroeder, Georg M. Gübitz, Elisabeth Heine, Vanja Kokol, 2007, izvirni znanstveni članek

Opis: The main contribution of the presented work was to introduce the use of proteases modified with the soluble polymer polyethylene glycol (PEG) in the bio-finishing process of wool fibres, to target enzyme action to the outerparts of wool fibres, i.e. to avoid the diffusion and consequent destroying of the inner parts of the wool fibre structure, in the case of native proteases using. Different proteolytic enzymes from Bacillus lentus and Bacillus subtilis in native and PEG-modified forms were investigated and their influence on the modification of wool fibres morphology surface, chemical structure, as well as the hydrolysis of wool proteins, the physico-mechanical properties, and the sorption properties of 1:2 metal complex dye during dyeing were studied. SEM images of wool fibres confirmed smoother and cleaner fibre surfaces without fibre damages using PEG-modified proteases. Modified enzyme products have a benefit effect on the wool fibres felting behaviours (14%) in the case when PEG-modified B. lentus is used, without markedly fibre damage expressed by tensile strength and weight loss ofthe fibre. Meanwhile the dye exhaustion showed slower but comparable level of dye uptake at the end of the dyeing.
Ključne besede: volnena vlakna, proteolitski encimi, encimske modifikacije, sorpcija barve, morfologija vlaken, wool fibres, proteolytic enzymes, enzyme modification, felting, dye sorption, protein hydrolysis, XPS-analysis, fibre morphology
Objavljeno: 01.06.2012; Ogledov: 1616; Prenosov: 56
URL Povezava na celotno besedilo

The influence of structural properties on the dye diffusion and dyeability of PA 6 fibres
Simona Strnad, Slava Jeler, Karin Stana-Kleinschek, Tatjana Kreže, 2003, izvirni znanstveni članek

Opis: The relationships were investigated between the structural and dyeing properties of different structurally modified PA 6 fibers. PA 6 monofilament yarn samples were applied having different crystalline degrees and different content of alpha, respectively gamma crystalline modification. The diffusion coefficients of two different acid dyes were determined together with the content of dyestuff absorbed (under specific conditions) by fiber samples. In order to estimate colorimetry method from the viewpoint of polymer structural change detection, the colors of the dyed PA 6 samples were determined (L*, a*,b*, C*, h coordinates) and the color differences (L*, a*, b*, C*, H*, E*) were calculated between untreated standard and structurally modified samples. The dyeability of PA 6 fibers depended mainly on the way in which crystallinity had been achieved, i.e. on the materialćs history. Different crystalline modifications caused different sorption properties and fiber dyeability. Smaller increases (app 20%) of crystallinity degree caused a decrease in diffusion coefficients. Contrary to expectations, the significant increase of crystallinity degree (app 50%) had an influence on the increase ofdyeability, presumably owing to the formation of larger empty spaces in the structure. The results achieved by colorimetry were in good correlation with dye absorption measurements. The colorimetry of dyed fiber samples was sensitive enough to detect even small differences in the quantities of absorbed dyestuff.
Ključne besede: textiles, PA 6 fibres, dyeing, dyeability, fibre structure, crystallinity, chemical modification
Objavljeno: 01.06.2012; Ogledov: 1398; Prenosov: 10
URL Povezava na celotno besedilo

Aspects of titanium-implant surface modification at the micro and nano levels
Iva Milinković, Rebeka Rudolf, Karlo Raić, Zoran Aleksić, Vojkan Lazić, Aleksandar Todorović, Dragoslav Stamenković, 2012, izvirni znanstveni članek

Opis: The shape and chemical composition, as well as the macro- and microtopography, of an implant surface have been studied widely as the major factors that positively influence implant osseointegration. Titanium and titanium alloys have been used extensively over the past 20 years as biomedical materials in orthopedic and dental surgery because of their good mechanical properties, corrosion resistance, no cell toxicity, and very poor inflammatory response in peri-implant tissue, which confirms their high biocompatibility. Their favorable biological performance is attributed to a thin native oxide film that forms spontaneously on the titanium surface. It is well established that surface roughness plays an important role in implant fixation. Accordingly, some authors have indicated the existence of an optimal range of surface roughness. The titanium surface can be either chemically or physically modified, or both, in order to improve biomaterial-tissue integration. Different treatments are used to modify the titanium surface. Hydroxyapatite coatings, preceded or not by acid etching, are used to create a rough, potentially bioactive surface. Oxide blasting treatments, either with or without chemical etching, are used to develop roughsurfaces. Thick oxide films obtained by anodic or thermal oxidation have been used to accelerate the osseointegration process. The ideal microtopography of the surface is still unknown, however, because it is very difficult to associate surface properties with clinical results. As more accurate knowledge is required, several Ti surfaces have been analyzed and the endosseous implant surface modified on the micro level has been thoroughly studied. Additionally, the production of gold (Au) nanoparticles to be added to the micron-scale modified surface has been performed. In this respect, an appropriate overview of our results is given.
Ključne besede: Ti implant, Au nanoparticles titan alloys, surface modification, microstructure
Objavljeno: 10.07.2015; Ogledov: 662; Prenosov: 42
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