Optimization of cultivation conditions for mammalian cell lines producing complex biosimilarsJure Strnad
, 2011, dissertation
Abstract: EXTENDED ABSTRACT
The possibility to replace standard single use 250 mL shake flasks with single use 50 mL spin tubes was investigated using the design of experiments methodology. Experimental throughput could be tripled to a maximum of 120 spin tubes per shaker-incubator unit if similar process performance could be proven in shake flasks and spin tubes. A D-optimal response surface design was used to model titer values in a seven day batch process producing recombinant erythropoietin. Shaking rate and working volume in spin tubes were adjusted to simulate titers that are produced in shake flasks at the reference setting. Research results indicated that equivalent titers as in shake flasks at the reference setting can be produced in spin tubes; moreover, even higher titers are possible. The maximal titers in spin tubes reached values as observed in 6 L bioreactors. Furthermore, a comparison of process performance and product quality attributes between two spin tube settings, the reference shake flask setting, a standard bioreactor run and a bioreactor run without pH control was made. Process performance and product quality attributes in spin tubes at the equality setting (shaking rate of 180 rpm and 30 mL working volume) were comparable to the ones derived from the reference shake flask setting. Results derived for both bioreactor runs were not fully comparable to the spin tube and shake flask systems. The statistical model for calculating titers on day seven of a batch process in spin tubes was successfully validated and can be used for titer prediction in the proposed design space.
The optimized spin tube settings were further used in a repetitive batch process where in the harvest phase of the process medium was daily exchanged to prevent component depletion or build-up of inhibitors. Spin tubes and shake flasks were used to simulate the industrial process of erythropoietin production. The effect of process mode change from seven-day batch to repetitive batch was investigated on process performance and product quality attributes, such as isoform distribution and glycan group distribution. Spin tube performance at the equality setting was comparable to the shake flask performance also in the repetitive batch process. Performance, especially titers at the maximal titer spin tube setting was, however, not fully comparable to the results obtained in previous optimization experiments.
The spin tube equality setting was also used for cultivating two cell lines producing different monoclonal antibodies. The goal was to investigate how different cell lines influence process performance and product quality attributes, such as monoclonal antibody charge variant distribution and glycan group distribution. Both cell lines were derived from a Chinese hamster ovary parental cell line, therefore, it was proposed that maybe the optimal spin tube setting derived for the erythropoietin producing cell line, which was also derived from the Chinese hamster ovary parental cell line, could also be used for these subtypes. Cell growth of the monoclonal antibody producing cell lines was extensively better as observed for the erythropoietin producing cell line, which meant that culture demands were more pronounced, such as oxygen transfer or mass transfer. It was observed that the erythropoietin derived equality spin tube setting did not produce similar process responses as shake flask at the reference setting for both monoclonal antibodies. The foremost difference was that the metabolite lactate was being consumed in shake flasks after it reached a maximum value but was not consumed in spin tubes for both monoclonal antibody producing cell lines. In these experiments also amino acid time profiles during a seven day batch process were monitored and subsequently compared. It was seen that several amino acids seemed to be in excess as most of them were only half way consumed. Product quality attributes also differed between the spin tube and the shake flask setting. The conclusion of the experimental work was that some fine tuning of th
Keywords: design of experiments, spin tube, shake flask, optimization, erythropoietin, monoclonal antibodies
Published: 22.12.2011; Views: 2468; Downloads: 127
Full text (6,72 MB)
MONTE CARLO MODEL FOR NEUTRON PRODUCTION BY THE INTERACTIONS OF LOW ENERGY DEUTERONS IN SOLID TARGETS Alberto Milocco
, 2012, dissertation
Abstract: The construction of the nuclear fusion plant 'ITER' has started in 2009 at Cadarache, France. The ITER machine represents a milestone in the civil use of the nuclear fusion energy. The physics of ITER is based on the fusion reaction between deuteron and triton nuclei (d-t). The deuteron-deuteron reaction (d-d) is also interesting and is foreseen for the next generation of fusion reactors. The experimental activities carried out in the context of the ITER neutronics involve intense fields of neutrons produced with a linear accelerator for deuterons, a target containing tritium or deuterium and auxiliary structures, such as the detector system, cooling system, room walls, etc. Experimental data have been obtained from the FNG (Frascati Neutron Generator, Italy), FNS (Fast Neutron Source, Japan), OKTAVIAN (Osaka University, Japan) and IRMM (Institute for Reference Materials and Measurements, EU). An independent method was developed at FNG for the simulation of the d-t neutron spectra at different angles. The FNG source routine models the Monte Carlo deuteron transport in solid tritiated targets as done in the well known SRIM code. The neutrons are generated according to the tabulated probability of the d-t reactions as for the DROSG2000 code. The FNG source routine is implemented into the MCNP distributions. The user is asked to define into the MCNP input file the deuteron energy (up to 10 MeV), the beam width and the target dimensions and composition. This source routine has been chosen as starter for the present thesis. Improvements and extensions were introduced.
- The methodology, originally developed for the d-t neutron source, has been extended to d-d neutron sources.
- Assuming the the SRIM code constitutes the reference calculation for the deuteron transport in matter, its implementation in the source routine has been cross-checked by extracting from the latter the same quantities as provided by the original code.
- In the present version of the source routines, the cross sections are internally generated from built in table based on modern evaluated nuclear data files instead of tables obtained from the DROSG200 code.
- Since the model may be used up to 10 MeV deuteron energy, the relativistic kinematics has been implemented to avoid unnecessary approximations.
- Simulations of the bare neutron source spectra and angular yields measurements have been carried out to validate the model.
- New editions of the d-t and d-d source routine have been released for the latest versions of the MCNP codes and tested on LINUX and WINDOWS machines. The validation activities with the FNG and IRMM experimental data suggested a possible application of the source routine for the characterisation of neutron spectrometers in the MeV energy region.
The source routine has been adopted to simulate integral benchmark experiments at FNG, FNS and OKTAVIAN. Brand new MCNP benchmark models have been developed for inclusion of all the available experimental information. It is shown that the d-t source routine is an accurate tool for the generation of the source eutrons. It also demonstrates to be useful for the evaluation of the neutron source term and associated uncertainties. The accuracy of the analyses is pursued to the point that the quality of the nuclear data employed in the simulation can be assessed. To this extent, the case of a new evaluation of the neutron interaction nuclear data for Manganese-55 is tested. A set of integral benchmark experiments has been used in the validation phase of the nuclear data. The computational models rely on the source routine, the object of the thesis. In conclusion, the source routine claims the inclusion of the major features responsible for the experimental resolution associated with the source term. The doctoral thesis explores its usage in the context of the experimental activities for ITER. The future exploitation of the source routine for the simulation of worldwide experiments might become an occasion to compare it with the source models available in the other laboratories
Keywords: deuteron-triton reactions, low-energy deuterons, neutron source model, Monte Carlo method, solid tritium target, solid deuterium target, fusion neutronics, benchmark experiments, diamond detectors.
Published: 07.03.2012; Views: 3033; Downloads: 93
Full text (8,50 MB)
Analysis of growth models for batch kefir grain biomass production in RC1 reaction systemMarko Tramšek
, Andreja Goršek
, 2008, original scientific article
Abstract: This work describes the statistical analysis of three mathematical models, modified for describing the kefir grain biomass growth curve. Experimental data of time-dependent kefir grain mass increase were used. The propagation was performed in RC1 batch reaction system under optimal bioprocess parameters (temperature, rotational frequency of stirrer, glucose mass concentration) using traditional cultivation in fresh, high-temperature, pasteurized whole fat cow's milk. We compared values of biological parameters obtained by applying the nonlinear regression of experimental data in logistic, Gompertz and Richards models. The most statistically appropriate model was determined using the seven statistical indicators. We established that the kefir grain biomass growth curve during batch propagation under optimal bioprocess conditions can be most successfully described using the Gompertz growth model.
Keywords: chemical processing, milk products, kefir grain growth, process parameters, design of experiments, modeling, mathematical models, Gompertz growth model, RC1
Published: 31.05.2012; Views: 1857; Downloads: 72
Link to full text
Quantitative examination of process parameters during kefir grain biomass productionAndreja Goršek
, Marko Tramšek
, 2007, short scientific article
Abstract: This article examines the propagation of kefir grains in fresh HTP whole fat cows' milk, with some additions (glucose and bakers yeast). The objective of our work was an experimental determination of the various process parameters relative influence on the propagation and daily kefir grain increase mass, using the Taguchi method for experimental design. The effects of medium temperature, glucose mass concentration, bakers yeast mass concentration and the rotational frequency of the stirrer at four levels were studied. Orthogonal array layout of L16 was selected for the proposed experimental design. All experiments were performed in an automated laboratory reaction calorimeter RC1 (Mettler-Toledo) with the same milk (3.5 % fat). The gravimetric method was used to determine daily kefir grain mass increases. Relative contributions of the proposed influencing process parameters on the daily kefir grains increase mass were estimated by analysis of the variance (ANOVA). The highest increase (51.5 %) was found at the rotational frequency of the stirrer 90 (1/min), at glucose mass concentration 20 g/L, and at mediumtemperature 24 °C. Within the observed range of yeast mass concentrationthis process parameter was found to be insignificant compared to others. The rotational frequency of the stirrer has the highest relative influence on the daily kefir grains increase mass (37.3 %) while glucose mass concentration and medium temperature have lower ones, 18.8 % and 9.9 %, respectively. The remaining fraction represents error influence. The main reason for its relatively high value (34.0 %) is that kefir grains are bulky and awkward to handle. This fact confirms the importance of optimal kefir grains production management.
Keywords: chemical processing, milk products, kefir, kefir grain growth, process parameters, design of experiments, Taguchi method, RC1
Published: 31.05.2012; Views: 1668; Downloads: 33
Link to full text
Optimization of extrusion process by genetic algorithms and conventional techniquesZoran Jurković
, Miran Brezočnik
, Branko Grizelj
, Vesna Mandić
, 2009, original scientific article
Abstract: The purpose of this research is the determination of the optimal cold forward extrusion parameters with the minimization of tool load as objective. This paper deals with different optimization approaches in order to determine optimal values of logarithmic strain, die angle and friction factor with the purpose to find minimal tool loading obtained by cold forward extrusion process. Two experimental plans based on factorial design of experiment and orthogonal array have been carried out. Classical optimization, according to the response model of extrusion forming force, and the Taguchi approach are presented. The obtained extrusion force model as the fitness function was used to carry out genetic algorithm optimization. Experimental verification of optimal forming parameters with their influences on the forming forces was also performed. The experimental results show an improvement in the minimization of tool loading. The results of optimal forming parameters obtained with different optimization approaches have been compared and based on that the characteristics analysis (features and limitations) of presented techniques.
Keywords: metal forming, forward extrusion force optimization, design of experiments, Taguchi approach, genetic algortihm
Published: 31.05.2012; Views: 1098; Downloads: 56
Full text (469,47 KB)
This document has many files! More...
Rapid control prototyping using MATLAB/Simulink and a DSP-based motor controllerDarko Hercog
, Karel Jezernik
, 2005, original scientific article
Abstract: A rapid control prototyping (RCP) system, based on commercially available software and custom in-house developed hardware is presented. An RCP system successfully combines the well-known simulation program MATLAB/Simulink and the custom DSP-based floating point motor controller. An RCP system provides smooth and fast transition from off-line simulation in Simulink to real-time operation on the embedded motor controller. On-the-fly parameter tuning and data visualization are provided in addition to rapid code generation. The presented solution represents a powerful, versatile and portable RCP system especially suitable for educational processes as well as motor control research. This article is supplemented by an example of cascade DC motor control.
Keywords: control education, control experiments, rapid control prototyping, DSP controller
Published: 01.06.2012; Views: 1278; Downloads: 33
Link to full text
Fatigue behaviour of 42CrMo4 steel under contact loadingPéter Göncz
, Rok Potočnik
, Srečko Glodež
, 2010, original scientific article
Abstract: The presented paper describes the experimental determination of fatigue crack growth parameters for high strength low-alloy steel 42CrMo4. The experiments were performed according to the ASTM E647 standard and the parameters of the Paris equation (C and m) were determined. Test specimens were subjected to impulsive cyclic tensile loading on a testing machine. During that the fatigue crack propagation was monitored as a function of elapsed fatigue cycles. Taking these experimental results into account the fatigue crack growth rates at different stress-intensity factor ranges was determined. To consider the variable material properties of the slewing bearing ring trough depth, specimens of different hardnesses were tested. Beside the experimental result a 2D contact fatigue crack propagation model is also presented. This model can be used for the simulation of surface initiated contact fatigue crack propagation on the roller slewing bearing's raceway. As a computational example the results of a finite element method contact fatigue crack propagation simulation are presented.
Keywords: crack propagation, slewing bearings, numerical modelling, experiments
Published: 07.06.2012; Views: 1190; Downloads: 51
Link to full text
MODERN INTERPRETATIONS OF THE MORAL AND ETHICAL ISSUES IN H. G. WELLS' THE ISLAND OF DOCTOR MOREAUTjaša Šuc
, 2014, master's thesis
Abstract: In the time of H.G. Wells, vivisection of animals and the human were common topics. Nowadays, the human still remains a common topic. Scientific research has developed further with cloning, in-vitro fertilization, organ transplantation, etc. Out of these various scientific developments and experiments, which are examined in the Island of Doctor Moreau, the question of ethics and morality arises, as well as the question how these concepts have changed from the time of Wells` Doctor Moreau and today.
The objective of my thesis, Modern Interpretations of the Moral and Ethical Issues in H. G. Wells` The Island of Doctor Moreau, is to analyze the moral and ethical issues in the work of H. G. Wells' The Island of Doctor Moreau and to show their relevance and topicality. Firstly, the genre of science-fiction novel is discussed, followed by an analysis and the structure of the work, and an analysis of the characters, which enables further analysis and relevance to the main theme: moral and ethical issues.
Keywords: H. G. Wells, Doctor Moreau, vivisection, ethics and morality, scientific experiments.
Published: 29.10.2014; Views: 1018; Downloads: 94
Full text (565,16 KB)
If cooperation is likely punish mildly: insights from economic experiments based on the snowdrift gameLuo-Luo Jiang
, Matjaž Perc
, Attila Szolnoki
, 2013, original scientific article
Abstract: Punishment may deter antisocial behavior. Yet to punish is costly, and the costs often do not offset the gains that are due to elevated levels of cooperation. However, the effectiveness of punishment depends not only on how costly it is, but also on the circumstances defining the social dilemma. Using the snowdrift game as the basis, we have conducted a series of economic experiments to determine whether severe punishment is more effective than mild punishment. We have observed that severe punishment is not necessarily more effective, even if the cost of punishment is identical in both cases. The benefits of severe punishment become evident only under extremely adverse conditions, when to cooperate is highly improbable in the absence of sanctions. If cooperation is likely, mild punishment is not less effective and leads to higher average payoffs, and is thus the much preferred alternative. Presented results suggest that the positive effects of punishment stem not only from imposed fines, but may also have a psychological background. Small fines can do wonders in motivating us to chose cooperation over defection, but without the paralyzing effect that may be brought about by large fines. The later should be utilized only when absolutely necessary.
Keywords: public goods, punishment, economic experiments, snowdrift game
Published: 19.06.2017; Views: 348; Downloads: 225
Full text (522,94 KB)
This document has many files! More...