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Determination of the process parameters relative influence on k[sub]La value using Taguchi design methodology
Marko Tramšek, Andreja Goršek, 2007, izvirni znanstveni članek

Opis: This article describes experimental determination of the relative impact of significant process parameters that influence volumetric oxygen mass transfer coefficient (kLa) using Taguchi design methodology. For this purpose an automated RC1 reaction calorimeter (Mettler-Toledo), which was originally developed for chemical processes, was modified for the bioprocesses. Simple fermentation using Baker's yeast was studied to illustrate the design procedure. Orthogonal array L25 was selected for the proposed design and ANOVA method was used for recognizing the relative influence of the process parameters. Within the observed range of temperature (?), fermentation media volume (VFM), and yeast mass concentration (?Y), these process parameters were found to be unimportant compared to the volumetric air flow rate (qV,a) and rotational frequency of the stirrer (fm). The qV,a had a substantial effect on the kLa value (89.2 %) and the fm had just a small one (3.6 %), meanwhile the remain fraction to 100 % represents error. The results refer strictly to the selected case study. Anyhow, the proposed procedure shows that application of the Taguchi approach for analyzing the oxygen mass transfer based on the experimental data obtained from a highly-automated laboratory reactor appears to have potential usage in general biopharmaceutical process design.
Ključne besede: bioprocess parameters, mass transfer, volumetric oxygen mass transfer coefficient, process parameters, Taguchi method, analysis of variance
Objavljeno: 31.05.2012; Ogledov: 1484; Prenosov: 23
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Determination of oxygen by means of a biogas and gas - interference study using an optical tris (4,7-diphenyl-1,10-phenanthroline) ruthenium(II) dichloride complex sensor
Polonca Brglez, Andrej Holobar, Aleksandra Pivec, Nataša Belšak, Mitja Kolar, 2012, izvirni znanstveni članek

Opis: Biogas is a mixture of gases produced by anaerobic fermentation where biomass or animal waste is decomposed and methane and carbon dioxide are mainly released. Biogas also has a very high moisture content (up to 80%), temperatures of around 60 °C, high pressure, and can contain other gases ($N_2$, $H_2S$, $NH_3$ and $H_2$). We searched for an appropriate measuring system for the determining of oxygen in biogas, since the production process of biogas must be run under anaerobic conditions; as the presence of oxygen decreases the quality of the biogas. Ruthenium (II) complexes are by far the most widely-used oxygen dyes within optical oxygen sensors. In general, they have efficient luminescences, relatively long-life metal-ligand charge-transfer excited states, fast response times, strong visible absorptions, large Stokes shifts, and high-photochemical stability. The purpose of this work was to characterise and optimize an optical oxygen sensor using tris (4,7-diphenyl-1,10-phenanthroline) ruthenium(II) dichloride complex for measuring oxygen. Different sensor properties were additionally studied, focusing on the interference of external light, temperature, and various gases. A special gas-mixing chamber was developed for gas interference study, and online experiments are presented for oxygen determination within the pilot biogas reactor.
Ključne besede: tris(4, 7-diphenyl-1, 10-phenanthroline)ruthenium(II) dichloride complex, oxygen optical sensor, interferences, biogas
Objavljeno: 01.06.2012; Ogledov: 1294; Prenosov: 54
.pdf Celotno besedilo (315,15 KB)
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Tuning of poly(ethylene terephtalate)(PET)surface properties by oxygen plasma treatment
Aleš Doliška, Metod Kolar, 2011, izvirni znanstveni članek

Opis: Modification of surface properties of poly(ethyleneterephtalate) (PET) thin films by treatment with weakly ionized oxygen plasma was studied by contact angles of water and diiodomethane (DIM) drops. Samples were exposed to oxygen plasma with the ion density of 5 x 1015/m[sup]3 and the neutral oxygen atom density of 3 x 1021/m[sup]3. Just after the treatment they were characterized by contact angle measurements. Results showed a quick decrease of the water contact angle in the first few seconds of plasma treatment, while prolonged treatment did not cause any substantiated modification. The contact angles of DIM, on the other hand, remained rather constant for the first several secondsof plasma treatment, and increased after prolonged treatment. It was found that the dispersion component of the surface free energy decreased with increasing treatment time, while the polar component increased with treatment time. The results were explained by surface functionalization as well as by roughness effects.
Ključne besede: poly(ethylene terephtalante), PET, oxygen plasma, contact angle, hydrophilic, functionalization
Objavljeno: 01.06.2012; Ogledov: 1124; Prenosov: 22
.pdf Celotno besedilo (329,87 KB)
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Oxygen cylinder filling
Danilo Ritlop, Andrej Predin, Ignacijo Biluš, Gorazd Hren, 2012, izvirni znanstveni članek

Ključne besede: oxygen cylinder, dilling, flow conditions
Objavljeno: 10.07.2015; Ogledov: 291; Prenosov: 15
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Modification of non-woven cellulose for medical applications using non-equlibrium gassious plasma
Karin Stana-Kleinschek, Zdenka Peršin, Tina Maver, 2011, izvirni znanstveni članek

Opis: This paper presents the use of a non-equilibrium gaseous plasma technique for the activation of regenerated non-woven cellulose, as used in the preparation of wound-dressing materials. Plasma technology provides surface modification according to the required quality in terms of speed, homogeneity, process stability, and efficiency. In this study the non-woven cellulose was exposed to oxygen plasma (O2) in order to acquire the natural polymer's super-hydrophilicity which, among others, defines the materials' usability forwound-dressing. The influence of the plasma parameters on the material's hydrophilicity was studied; and the optimal plasma conditions defined. Combinations of different experimental techniques (contact angle, water retention value, and moisture content) were studied and correlated with the mechanical properties, as a function of plasma modification. The specific adsorption capacity of the non-woven cellulose using oxygen plasma treatment was achieved. In the next step, this material with increased hydrophilicity and improved mechanical properties will be used in the preparation of multilayered wound-dressing materials for specific functionalities (incorporation of drugs, specific functional properties).
Ključne besede: plasma, oxygen, regenerated non-woven cellulose, super-hydrophilicity, mechanical properties
Objavljeno: 10.07.2015; Ogledov: 444; Prenosov: 41
.pdf Celotno besedilo (101,91 KB)
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The effect of nitrogen-ion implantation on the corrosion resistance of titanium in comparison with oxygen- and argon-ion implantations
T. Sundararajan, Zdravko Praunseis, 2004, izvirni znanstveni članek

Opis: Commercially pure (CP) titanium was surface modified with nitrogen-, argon- and oxygen-ion implantations in order to investigate the material's corrosion resistance in a simulated body fluid. Five doses were chosen for the ions, ranging from 5.1015 cm-2 to 2.5-1017 cm-2. In-vitro open-cyclic potential-timemeasurements and cyclic polarization studies were carried out to evaluate the corrosion resistance of the modified surface in comparison to an unmodified surface. Specimens implanted at 4.1016 cm-2 and 7.1016 cm-2 showed the optimum corrosion resistance, higher doses showed a detrimental effect on the corrosion resistance. Argon- and oxygen-ion implantation at these doses did not show any improved corrosion resistance, indicating the beneficial role of nitrogen on the corrosion resistance of titanium in the simulated body-fluid environment. Grazing-incidence X-ray diffraction (GIXD) was employed on the implanted specimens to determine the phases formed with the increasing doses. X-ray photoelectron spectroscopy (XPS) studies on the passive film of the implanted samples and on the unimplanted samples were analyzed in order to understand the role of nitrogen in improving the corrosion resistance. The results of the present investigation indicated that nitrogen-ion implantation can be used as a viable method for improving the corrosion resistance of titanium. The nature of the surface and the reason for the variation and the improvement in the corrosion resistance are discussed in detail.
Ključne besede: metallurgy, ion implantation, orthopedic implants, corrosion, titanium, nitrogen, oxygen, argon
Objavljeno: 10.07.2015; Ogledov: 1296; Prenosov: 51
.pdf Celotno besedilo (3,38 MB)
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Protein adsorption on various plasma-treated polyethylene-terephthalate substrates
Nina Recek, Morana Jaganjac, Metod Kolar, Lidija Milković, Miran Mozetič, Karin Stana-Kleinschek, Alenka Vesel, 2013, izvirni znanstveni članek

Opis: Protein adhesion and cell response to plasma-treated polymer surfaces were studied. The polymer polyethylene terephthalate (PET) was treated in either an oxygen plasma to make the surface hydrophilic, or a tetrafluoromethane CF4 plasma to make the surface hydrophobic. The plasma source was radiofrequency (RF) discharge. The adsorption of albumin and other proteins from a cell-culture medium onto these surfaces was studied using a quartz crystal microbalance (QCM), X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM). The cellular response to plasma-treated surfaces was studied as well using an MTT assay and scanning electron microscopy (SEM). The fastest adsorption rate was found on the hydrophilic oxygen plasma-treated sample, and the lowest was found on the pristine untreated sample. Additionally, the amount of adsorbed proteins was higher for the oxygen-plasma-treated surface, and the adsorbed layer was more viscoelastic. In addition, cell adhesion studies support this finding because the best cell adhesion was observed on oxygen-plasma-treated substrates.
Ključne besede: oxygen and fluorine plasma treatment, polymer surface modification, protein adsorption, cell adhesion, quartz crystal microbalance, QCM
Objavljeno: 22.06.2017; Ogledov: 258; Prenosov: 190
.pdf Celotno besedilo (2,39 MB)
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Sol-gel/Ag coating and oxygen plasma treatment effect on synthetic wound fluid sorption by non-woven cellulose material
Zdenka Peršin, Tanja Pivec, Miran Mozetič, Karin Stana-Kleinschek, 2017, kratki znanstveni prispevek

Opis: Non-woven cellulose material was functionalized using two techniques, i.e. the coating with AgCl via sol-gel and oxygen plasma. The treatment effects were studied regarding the wound fluid adsorption potential using physiological saline, synthetic exudate and synthetic blood. Plasma treatment was most efficient since a significant improvement by absorbency rate and capacity was evident, less pronounced in case of synthetic blood. The combination of both treatments showed a similar trend, while the effects were less prominent, but still sufficient by managing fluid-associated as well as infected wounds.
Ključne besede: non-woven cellulose fabric, sol-gel, oxygen plasma, absorption, synthetic wound fluids
Objavljeno: 31.08.2017; Ogledov: 317; Prenosov: 189
.pdf Celotno besedilo (86,21 KB)
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Cardiorespiratory fitness in primary education pupils
Matea Gašparović, Vilko Petrić, Vesna Štemberger, Marija Rakovac, Iva Blažević, 2017, izvirni znanstveni članek

Opis: The goal of this research was to determine cardiorespiratory fitness (CRF) among primary school male and female pupils and its association with their anthropometric characteristics. The sample consisted of 112 boys and 136 girls, primary school pupils, aged 7 to 10. The Eurofit test battery was used to evaluate anthropometric characteristics (body height, body mass, body mass index (BMI)) and CRF (Beep test to estimate maximal oxygen uptake). The results indicate stagnation in the CRF with chronological age, in both sexes. A statistically significant association (p = 0.001) was shown for all CRF variables and anthropometric variables except for body height, which was not significantly associated with CRF. An increase in body mass and BMI was associated with a significant (p = 0.001) decrease in male and female pupils' CRF.
Ključne besede: health, primary school, maximal oxygen uptake, body height, body weight
Objavljeno: 23.04.2018; Ogledov: 288; Prenosov: 37
.pdf Celotno besedilo (264,35 KB)
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