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1.
Optimal process mode selection for clone screening
Jure Strnad, Vatroslav Spudić, Matjaž Brinc, Jerica Rozman Pungerčar, Zdravko Kravanja, 2011, izvirni znanstveni članek

Opis: A significant amount of data is generated during clone screening procedures because several cultivation systems are used such as well-plates, shake-flasks, laboratory-scale bioreactors among others. The amount of data can often be staggering and thus requires the use of statistical and data mining procedures in order to extract hidden information. In regard to a biosimilar monoclonal antibody project, data from the shake-flask scale was observed when comparing batch and fed-batch processes for several individual clones derived from two different cell lines. The aim of the research presented in this paper was to determine if clone selection based on batch data during the initial screening phase was equivalent to the results from fed-batch selection. It was determined that fed-batch processes should be implemented early during the screening procedure, if a choice is made that the final manufacturing process should also be operated in a fedbatch mode, as clone selection based on both batch and fed-batch analytical data was divergent.
Ključne besede: monoclonal antibody, batch, fed-batch, clone screening, glycosylation, charge variants
Objavljeno: 01.06.2012; Ogledov: 1224; Prenosov: 40
.pdf Celotno besedilo (654,73 KB)
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2.
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: 1066; Prenosov: 68
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3.
Influence of transient response of platinum electrode on neural signals during stimulation of isolated swinish left vagus nerve
Polona Pečlin, Franci Vode, Andraž Mehle, Igor Grešovnik, Janez Rozman, 2012, izvirni znanstveni članek

Opis: The main aim of the work was to measure transient response characteristics of interface between platinum stimulating electrodes and isolated swinish left cervical vagus nerve (segment), when electrical stimulating pulses are appliedto preselected locations along the segment and elicited neural signals,also described as compound action potentials (CAPs), are recorded fromparticular compartments of the nerve. The stimulating system was manufactured as a silicone self-coiling spiral cuff (cuff) with embedded matrix of ninety-nine rectangular electrodes (0.5 mm in width and 2mm in length), made of 45 microm thick annealed platinum ribbon (99.99 % purity), and a geometric surface of 1 mm2. For electrical stimulation, a current quasitrapezoidal, asymmetric and biphasic pulses with frequency of 1 Hz, were used. To test an influence of stimulating pulses having different parameters and waveforms on elicited CAPs, various degree of imbalance between an electric charge (charge) injected in cathodic phase as well as charge injectedin anodic phase of a biphasic stimulating pulse, were deployed and compared. To identify the differences in elicited CAPs however, an integral ofthe CAP cathodic phase as well as integral of the CAP anodic phase of stimulating pulse, were calculated and compared. Results showed a strong component superimposed in the CAPs, considered as an ensemble artefact which greatly obscured the components of the CAPs, and various components did overlap. Results also showed that stimulating pulses, having preset certain degree of imbalance between charge injected in cathodic and charge injected inanodic phase, elicited a slight change in a positive waveform deflection of CAP manifested under a cathodic phase as well as slight change in a negative waveform deflection of CAP manifested under an anodic phase. (Abstract truncated at 2000 characters)
Ključne besede: electrical stimulation, platinum electrodes, left vagus nerve, electrochemistry, electrical charge
Objavljeno: 16.03.2017; Ogledov: 432; Prenosov: 54
.pdf Celotno besedilo (179,34 KB)
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4.
Effective topological charge cancelation mechanism
Luka Mesarec, Wojciech Góźdź, Aleš Iglič, Samo Kralj, 2016, izvirni znanstveni članek

Opis: Topological defects (TDs) appear almost unavoidably in continuous symmetry breaking phase transitions. The topological origin makes their key features independent of systems’ microscopic details; therefore TDs display many universalities. Because of their strong impact on numerous material properties and their significant role in several technological applications it is of strong interest to find simple and robust mechanisms controlling the positioning and local number of TDs. We present a numerical study of TDs within effectively two dimensional closed soft films exhibiting in-plane orientational ordering. Popular examples of such class of systems are liquid crystalline shells and various biological membranes. We introduce the Effective Topological Charge Cancellation mechanism controlling localised positional assembling tendency of TDs and the formation of pairs {defect, antidefect} on curved surfaces and/or presence of relevant “impurities” (e.g. nanoparticles). For this purpose, we define an effective topological charge Δmeff consisting of real, virtual and smeared curvature topological charges within a surface patch Δς identified by the typical spatially averaged local Gaussian curvature K. We demonstrate a strong tendency enforcing Δmeff → 0 on surfaces composed of Δς exhibiting significantly different values of spatially averaged K. For Δmeff ≠ 0 we estimate a critical depinning threshold to form pairs {defect, antidefect} using the electrostatic analogy.
Ključne besede: topological defects, topological charge, numerical studies, orientational ordering, nematic liquid crystals, liquid crystalline shells, biological membranes, nanoparticles, Gaussian curvature, electrostatic analogy, annihilation, topology
Objavljeno: 23.06.2017; Ogledov: 269; Prenosov: 169
.pdf Celotno besedilo (2,15 MB)
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5.
Impact of curvature on nematic topological defects
Luka Mesarec, 2018, doktorska disertacija

Opis: Topological defects (TDs) appear almost unavoidably in continuous symmetry breaking phase transitions. The topological origin makes their key features independent of systems' microscopic details; therefore TDs display many universalities. Because of their strong impact on numerous material properties and their significant role in several technological applications it is of strong interest to find simple and robust mechanisms controlling the positioning and local number of TDs. There are strong evidences that in physics the fields are fundamental entities of nature and not particles. If this is the case then topological defects (TDs) might play the role of fundamental particles. An adequate testing ground to study and gain fundamental understanding of TDs are nematic liquid crystals. We present a numerical study of TDs within effectively two dimensional closed soft films exhibiting in-plane orientational ordering. Popular examples of such class of systems are liquid crystalline shells and various biological membranes. We analyze the impact of extrinsic and intrinsic curvature on positions of topological defects (TDs) in two-dimensional (2D) nematic films. We demonstrate that both these curvature contributions are commonly present and are expected to be weighted by comparable elastic constants. A simple Landau-de Gennes approach in terms of tensor nematic order parameter is used to numerically demonstrate impact of the curvatures on position of TDs on 2D ellipsoidal nematic shells. We introduce the Effective Topological Charge Cancellation mechanism controlling localised positional assembling tendency of TDs and the formation of pairs (defect,antidefect) on curved surfaces. Furthermore, we estimate a critical depinning threshold to form pairs (defect,antidefect) using the electrostatic analogy. Finally, we show how one could efficiently switch among qualitatively different structures by using a relative volume of ordered shells, which represents a relatively simple naturally accessible control parameter. In doctoral thesis, we developed theoretical model of erythrocyte membrane by using a hybrid Helfrich-Landau type mesoscopic approach, taking into account in-plane membrane ordering. We demonstrate that the derived extrinsic membrane energy term, which strongly depends on the local orientations of the molecules, is essential for the predicted broadening of the range of the relative volumes corresponding to the stable discocyte shapes, which is otherwise very narrow if only intrinsic curvature energy term dominates.
Ključne besede: Topological defects, Continuum fields, Nematic liquid crystals, Biological membranes, Nematic shells, Landau-de Gennes formalism, Topological charge, Nanoparticles, Gaussian curvature, Electrostatic analogy, Intrinsic curvature, Extrinsic curvature, Crystal growth nucleation, Relative volume
Objavljeno: 09.03.2018; Ogledov: 721; Prenosov: 72
.pdf Celotno besedilo (23,66 MB)

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