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Hydrogel Microfluidics to Control Stem Cell Fate
No full textBiomolecular signaling is of utmost importance in governing many biological processes such as morphogenesis during tissue development where biomolecules regulate key cell-fate decisions. In vivo, these factors are presented in a spatiotemporally tightly controlled fashion and in the context of a soft and hydrated microenvironment. Although state-of-the-art microfluidic technologies allow precise biomolecule delivery in time and space, long-term (stem) cell culture at the micro- scale is far from ideal due to issues related to medium evaporation, limited space for cell growth, shear stress and a lack of cell-instructive microenvironments that might adversely impact cell-fate. As a result, microfluidic cell culture systems are not yet suitable to unravel complex multicellular phenomena. This may explain why they are not yet widely used in biology laboratories. Consequently, the overall goal of this thesis was to overcome this technology gap by developing next generation microfluidics through a combination of microfabrication and smart biomaterials. A special emphasis was placed on decoupling biomolecule presentation at micro-scale from macro-scale cell culture in order to enable long-term stem cell culture within user-friendly multiwell plate formats. First, a novel microfluidic concept was invented to rapidly immobilize linear protein gradients on the surface of poly(ethylene glycol) (PEG)-based hydrogels whose biophysical properties are reminiscent of natural extracellular matrices. This method allows efficient capture of steady-state gradients of tagged proteins (e.g. using Fc or biotin tags) in just a few minutes on engineered hydrogels that display the corresponding auxiliary proteins (e.g. ProteinA or NeutrAvidin). The selectivity and orthogonality of the chosen binding schemes enables the formation of parallel and orthogonal overlapping gradients of multiple proteins, which is impossible using existing platforms. After patterning, the microfluidic chip can be readily removed from the gel for cell culture applications. Using quantitative single-cell time-lapse microscopy, this platform was validated here by probing the effect of fibronectin concentration on the directionality and speed of cell migration. Next, the resolution, flexibility and throughput of the protein patterning on hydrogels was substantially enhanced by the introduction of hydrodynamic flow focusing, that is, the generation of user-defined patterns by spatially controlled step- wise deposition of biomolecules. To this end, a microfluidic device was conceived that enabled the generation of arrays of parallel and crossed overlapping gradients. Application of the platform to generate gradients of immobilized leukemia inhibitory factor (LIF) showed an influence of the LIF concentration on ESC self-renewal. This platform should be useful to systematically probe the effect of biomolecule dose, singly or in combinations, on stem cell behavior in vitro; however, it lacks the ability to dynamically vary the presentation of biomolecules that might be crucial to control stem cell fate towards establishing functional in vitro tissue models. To address this limitation, in the last part of the thesis work a hydrogel-based microfluidic chip was developed that decouples macro-scale cell culture on the gel surface from the precise spatiotemporal biomolecule delivery at the micro-scale, i.e. through the gel layer. The hydrogel chip, used here as a simple insert that is compatible with conventional multiwell plate formats, was optimized to support long- term ESC maintenance in both adherent format and as uniformly sized ESC aggregates termed embryoid bodies. The platform was successfully used for the spatially controlled neuronal commitment of ESC via delivery of gradients of the morphogen retinoic acid. Taken together, in this thesis several innovative microengineered cell culture platforms are presented which enable, perhaps for the first time, the long-term culture and manipulation of stem cell fate at the micro-scale. These systems should be useful to systematically probe in vitro the effect of biomolecule dose and delivery dynamics on stem cell behavior, ultimately facilitating the development of complex in vitro tissue models.UPLU
Bacterial Resource Management for Nutrient Removal in Aerobic Granular Sludge Wastewater Treatment Systems
No full textThe approach of wastewater treatment has shifted towards a holistic view in order to achieve sustainability in addition to environmental protection. The aerobic granular sludge (AGS) technology, which relies on the use of fast-settling granular biofilms called granules, is progressively becoming a new standard for high-rate biological nutrient removal (BNR) and secondary clarification in single sequencing batch reactors (SBR). The AGS intensive process has been related with definite savings in land area, construction, and operation costs. In an economical analysis, theoretical savings of CHF 0.45 per m3 (1 Swiss franc CHF ≈ 0.83 €) were computed for a Swiss wastewater treatment plant (WWTP) of 200’000 capita removing all nutrients biologically. Besides scale-up, fundamental research was required to understand and tailor the structure of underlying bacterial communities that form granules and remove nutrients. Mechanisms of bacterial selection were investigated in a systems approach to propose strategic axes for optimal management of the bacterial resource for efficient process performances. This research led to the following advances.
After having designed a flexible reactor infrastructure for AGS research, a mathematical modeling methodology was developed to understand the hydraulic and biological processes involved during plug-flow transport of wastewater across the settled AGS bed during the feeding phase. BNR relies on the preferential selection of polyphosphate-accumulating organisms (PAO) by proper uncoupled supply of electron donors and electron acceptors. A bed height to diameter ratio of 6 was deduced to be optimal for full bed loading and efficient anaerobic acetate uptake under reference simulation conditions (20°C, pH 7.0).
A bioinformatics methodology called PyroTRF-ID was developed for the identification of bacterial relatives involved in BNR processes by combination of terminal-restriction fragment length polymorphism (T-RFLP) and pyrosequencing data. This procedure provided high resolution of bacterial community structures and dynamics of AGS systems.
Electrical conductivity and polyphosphatase assays were proposed for rapid and low-cost assessment of the fractions of active PAO and of the dephosphatating potential of activated sludge and granular sludge. Positive linear correlations were obtained between the fraction of PAO, the biomass specific rate of conductivity evolution measured in anaerobic metabolic batch tests, and the polyphosphate-hydrolyzing enzymatic activity of cell extracts.
Wash-out conditions used to stimulate granule formation were shown to exert a selection pressure not only on physical properties of early-stage granules, but also on the underlying bacterial community composition. Operation with constant volumetric organic loading rates (OLR) during wash-out resulted in the formation of slow-settling fluffy granules dominated by filamentous Burkholderiales affiliates formed under low aeration (< 2 cm s-1) and high mesophilic temperature (30°C), and of fast-settling dense granules dominated by Zoogloea spp. under high aeration (4 cm s-1) and with an inoculum originating from a BNR-WWTP. These exopolysaccharide producers were considered as model organisms for granulation. However, their proliferation over PAO and nitrifiers correlated with poor BNR. PAO estab-lished at mature stage as soon as sufficient AGS was present to fully remove volatile fatty acids (VFA) during the anaerobic feeding phase. Without purge of excess sludge, glycogen-accumulating organisms (GAO) competed with PAO at a later stage of reactor operation.
Granulation was shown to occur in stirred-tank SBRs operated under steady-state condi¬tions to cultivate PAO and GAO enrichments. The Accumulibacter- and Competibacter-dominated communities displayed granulation potential without involvement of Zoogloea spp. Fast-settling nuclei formed despite initial operation with a settling time as high as 60 min, and evolved towards granules after decrease of settling time to 10 min. Dynamic control of the OLR, anaerobic contact time, and sludge retention time (SRT) selected for active PAO in early-stage granules. Confocal laser scanning microscopy (CLSM) revealed that granula¬tion mechanisms depend on the predominant organisms involved. Fast-growing Zoogloea spp. formed smooth biofilm continuum matrices. The slower-growing PAO and GAO formed het¬erogeneous granular structures by proliferation in compact colonies around flocs.
Fluctuations in operation variables were shown by multivariate statistics to impact on process performance and bacterial community structures in anaerobic-aerobic AGS-SBRs. The size of granules impacted on nitrification and dephosphatation by affecting oxygen mass transfer. Efficient BNR was obtained with at least 500 mgCOD L-1of acetate, 30 gCOD gP-1, and 10 gCOD gN-1. Although clades of PAO can denitrify, nitrogen removal was thus not restricted only to PAO. A broad denitrifying community was identified. The bacterial community continuum comprised two major opponent clusters, composed of members of the core microbiome of full-scale BNR-WWTPs. The first mainly comprised Accumulibacter, Nitrospira, Xanthomonadaceae, and Aminobacter affiliates selected by conditions of efficient BNR. The second mainly comprised Competibacter, Sphingobacteriales, Cytophaga, and Tetrasphaera affiliates correlating with periods of low BNR.
Bacterial selection in AGS systems was mainly impacted by pH, according to multifactorial experiments. Accumulibacter and BNR were favored with alkaline pH, low mesophilic temperatures, and in the presence of propionate. Competibacter proliferated with acidic pH, temperature close to 30°C, and only acetate. Tetrasphaera spp., potential major PAO of certain full-scale plants, withstood Competibacter-selective conditions. Enhanced BNR was obtained under non-limiting conditions with food-to-microorganism ratios above 25 mgCODs gCODx-1. With fixed 2-h starvation, dephosphatation was only complete with full aeration. Since alternating aerobic-anoxic starvation conditions led to partial conversions, the length of starvation phases should be controlled in function of the redox conditions applied.
Overall, optimal bacterial resource management in AGS systems requires full control of system behavior by taking advantage of the flexibility of the SBR technology. A methodology is proposed to this end, comprising milestones for wastewater characterization, SBR design, “anaerobic selector” design, control of the starvation phase length, shaving of fluctuations in operation variables, purge of excess sludge, proper selection for a stable, active and cooperative bacterial community, as well as efficient BNR. As key research perspective, investigations with real wastewater should validate the knowledge gained on bacterial behaviors under low-complexity conditions. Significant differences in predominant bacterial relatives were detected between lab-scale and full-scale BNR sludge. Metagenomics will provide a broader view on key organisms and functions of BNR and AGS microbiomes.LBETitre traduit: Gestion des ressources bactériennes pour le traitement des nutriments des eaux usées par la technologie des boues granulaires aérobie
Standard Model Higgs Boson Searches in the Weak Boson Decay Channels with the ATLAS Detector
No full textThe search of the Standard Model Higgs boson decaying into a pair of weak bosons with the subsequent leptonic decay of the W or Z bosons is presented. The contributions achieved by this work range from the réévaluation of Higgs boson normalisation cross-sections, to the development of the analysis strategies using detailed Monte Carlo simulations and the search results for the H -► ZZ -► l+l-ννbar decay mode based on 4.7 fb-1 of proton-proton collision data at sqrt(s) = 7 TeV taken during 2011 by the ATLAS detector. The computation of cross-sections values for Higgs boson production at centre-of-mass energies varying from 6 to 14 TeV, for the main production mechanisms at the LHC were documented for posterior usage among the Collaboration. Preliminary detector resolution studies on Z -► μμ events using early data collected by ATLAS are also described. Simulation studies for the H -► ZZ(*) -► l+l-l+l- and H — W+W- — l+νl-ν channels included feasibility checks used to quantify the expected sensitivity of the analyses for various scenarios with different centre-of-mass energy, luminosity and detector calibration conditions. These results were part of the input that the Collaboration used to feed the schedule and plans of the LHC. On the H -► ZZ -► l+l-ννbar channel, upper limits on the Higgs boson production cross-section in a mass range between 200 and 900 GeV are set. With this channel by itself, the Standard Model Higgs boson particle is excluded at 95% confidence level in the mass range between 319 and 558 GeV To complete the current picture of the Higgs boson searches in the ATLAS detector, a compilation of the different Higgs boson analyses performed by the ATLAS Collaboration are introduced. The Higgs boson existence is constrained to be in a narrow window between 122.5 GeV and 129 GeV with 95% confidence level; where an excess of 2.6 a local significance is observed.LPH
Improved Methodology for Rock Fall Hazard Zoning at the Local Scale
No full textRock falls represent a serious threat to communities living in mountainous areas in several European countries, and their potential hazard must be taken into account for an appropriate land use planning and for establishing risk mitigation measures. Rock fall hazard assessment and zoning at the local (and site specific) scale(s) require detailed information on rock fall frequency of departure and trajectories, which have to be determined quantitatively. The research work performed in this Thesis deals with procedures for rock fall hazard zoning for urban planning at the local scale, particularly focusing on methodologies based on rock fall trajectory modelling. This objective was pursued in the first part of the work by comparing current methodologies used in Europe, based on 2D rock fall modelling, for achieving a clearer understanding of differences, weak points and limits characterising each procedure. The results of the several performed sensitivity analyses show that rock fall hazard assessment and zoning are highly conditioned by both national guidelines and mapping methodologies. These results underline as well that, as a consequence of diversities in guidelines and due to assumptions/uncertainties in zoning techniques, land use planning measures at a given site do change considerably, depending on which methodology and respective guidelines are applied. In particular, significant differences arise both in terms of extent of the hazard zones, and in terms of type of land use planning. Measures for urban planning correspond indeed to definitions of hazard degrees changing from one country to another, according to the adopted risk management strategies, which condition the regulations for the areas in danger and therefore the choice of threshold values for energy and frequency. The purpose of the second part of the work was to propose improvements to quantitative rock fall hazard zoning at the local scale, based on the Cadanav methodology developed at the Rock Mechanics Laboratory of EPFL. In particular, the new methodology attempts at reducing assumptions and uncertainties affecting the use of trajectory modelling results and the techniques for combining energy and rock fall frequency according to an intensity-frequency diagram. The new Cadanav methodology evaluates the hazard degree by means of "hazard curves". The curves are described at each point of the slope by energy-return period couples, to be superposed to an intensity frequency diagram in order to determine which hazardous condition prevails at that point of the slope. The new methodology allows for hazard zoning obtained starting from either 2D or 3D trajectory modelling. For 2D modelling-based zoning, it was checked by means of comparisons with the original version of the Cadanav methodology, performing sensitivity analyses for several sites, block sizes and return period conditions. For 3D modelling-based zoning, the methodology was validated by studying benchmark problems for an infinite linear cliff topography, and tested as well on a more realistic complex topography. For these two configurations, the analyses were performed for several return period values and types of scenario, i.e. single rock fall hazard instabilities, either localised or diffused, and combined instabilities, characterised by different frequencies of failure, but same block size. In addition, further elements to be accounted for in rock fall hazard zoning were discussed, such as the influence of the block size on hazard zoning and the combination of several rock fall hazards affecting the same site, but characterised by different block sizes and failure frequencies. In terms of results, the new methodology performs well in all the tested conditions and provides a more objective and detailed hazard evaluation. Its implementation is general and flexible, as it can be used based both on 2D and on 3D trajectory modelling as well as according to different intensity-frequency diagrams (e.g. Switzerland, Principality of Andorra), and it allows for evaluating the rock fall hazard for complex scenarios involving several sources and event return periods.LM
Models of Political Communication between District Parliament and Local Government: A Case Study of the Regional Autonomy in Sumedang, West Java, Indonesia
Get PDFThe research is aimed to create model of political communication between DPRD (Dewan Perwakilan Rakyat Daerah or House of Representatives at Regional Level) and PEMDA (Pemerintah Daerah or Local Government) for local government board’s performance improvement in order to the effectivity of the regional autonomy implementation at Sumedang Regency, West Java Province, Indonesia. The influence of political communication between DPRD and PEMDA for local government board’s performance improvement in order to the effectivity of the regional autonomy implementation at Sumedang Regency is small, but it is significant. This is resulted by barrier of political communication between DPRD and PEMDA, especially difference of interest, ideology and paradigm from stakeholders, and shareholders of Sumedang Regency. Meanwhile, the influence of local government board’s performance to the effectivity of the regional autonomy implementation at Sumedang Regency is large enough and significant. This is interrelated with job description local government board which is interconected with functions of management as critical factor in process of work
 
Ecological Controls of Aerobic and Anaerobic Microbial Activities and Potential Impacts on Greenhouse Gases in Regenerating Peatlands
No full textPeatlands represent massive global carbon (C) pools and sinks. Carbon accumulation depends on the ratio between net primary production and decomposition of organic matter, both of which can change under projected increases of atmospheric carbon dioxide (CO2) and N deposition or after peat cutting. Significant areas of peatlands have been damaged by drainage and peat harvesting worldwide. After abandoning exploitations and spontaneous regeneration, these secondary peatlands can become major C-sinks but also important methane (CH4) sources. As the atmospheric concentration of methane, a greenhouse gas (GHG) of major importance, has more than doubled during the past 200 years, identifying factors regulating the flux of CH4 and CO2 into the atmosphere is crucial. This research focuses on the microbiological and ecological aspects of biodegradation (decay) occurring in abandoned cutover peatlands. This work is based on complementary fields such as plant eco-physiology, soil biology and biochemistry, microbial and molecular ecology and biogeochemistry. Initially, we described the gas exchange occurring between these ecosystems and the atmosphere and concluded that peatlands could sequester carbon during their regeneration, although not without emitting important quantities of methane. This brought us to consider the aerobic decomposition of plant litter. Decomposition was not only influenced by changes in produced plant litter quality but also more directly through micro-environmental conditions. Aerobic biodegradation creates the substrate for methanogenic microorganisms responsible for methane production. On the whole, these used acetate as a substrate for methanogenesis and were numerous in early peatland regeneration stages. In pioneering stages of regeneration, acetate production could be maintained by important contribution of homoacetogenic bacteria. Methane diffuses through the waterlogged peat and is turned into CO2 by methane oxidising bacteria in the upper layers. These bacteria, with various oxidation efficiencies, were shown to have contrasting ecologies in relation to vegetation type. Their abundance and distribution is also strongly linked to the emission of greenhouse gases. The common denominator of all these processes is the nature of the organic matter itself which plays a dominating role in the carbon transfer, energy transduction, and control of its own biodegradation.ECO
New Analytical Methods for Size Fractionated, Quantitative, and Element Specific Analysis of Metallic Engineered Nanoparticles in Aerosols and Dispersions
No full textThe application of engineered nanoparticles (ENP) increased almost exponentially during the last decade. Next to carbon based ENP, metal based ENP are the next most commonly employed. Utilization of such particles for medical applications, remediation of toxic substances, consumer products, new materials, and numerous other fields has been reported already. Despite their extraordinary success and implementation, concerns have been raised about possible negative effects in humans and the environment. Once released, ENP are easily distributed via the atmosphere and the aquatic environment where an exposure to organisms can occur. To understand ENP release, life cycle (fate), and exposure as well as to evaluate their toxicological mechanisms, appropriate, media-specific (aerosols and dispersions) analytical methods are required. First, the development of a new set-up to determine ENP in aerosols is presented. For this purpose online (SMPS) and offline (electrostatic sampling on TEM grids) aerosol particle measurement techniques were combined. The aim was to study the release and fate of metallic ENP from commercial available spray products. Method development and verification was performed employing a well characterized aqueous Ag-NP spray product. The investigations have shown that the method offers the possibility to determine size, and element -specific nanoparticle release. Furthermore information about particle morphology and quantity could be obtained. It was revealed, that the release of nanoparticles strongly depends on the type of spray. Pump sprays did not show to produce airborne ENP in the aerosol, whereas propellant gas sprays released nanoparticles in substantial quantities. The release of nanoparticles was correlated with the droplet size distributions generated from the different spray types. Following method development, the setup was applied to determine ENP release of commercial available sprays, indicated to contain ENP. The obtained data was useful to model the consumer exposure of ENP from such products. Second, a set-up to determine ENP in dispersions was developed. For this purpose an asymmetric flow field flow fractionation (A4F) apparatus was coupled to an UV/Vis, light scattering- and inductively coupled plasma mass spectrometric (ICPMS) detector, simultaneously. In the beginning, method development and systematic investigations of prospects and limitations was performed employing well-characterized Au nanoparticles (Au-NP). The investigation revealed that A4F is a versatile separation technique for metallic ENP. In contrast, size determination with the A4F system, derived from the retention times of nanoparticles in the chromatogram, was erroneous. Unspecific interaction of ENP with the A4F channel membrane led to retention time shifts resulting in biased size information. For this reason, online dynamic light scattering (DLS) was employed and it offered a reliable determination of nanoparticle dimensions. Determination of nanoparticle concentration also proved to be to be problematic. Unspecific loss of nanoparticles in the A4F separation channel led to insufficient recovery prevented direct quantification of nanoparticles. To overcome this problem an alternative method was employed. With ICPMS after ultracentrifugation, quantification of the ionic and particulate -fraction of metallic ENP dispersions was possible. Validation of the set-up was performed with certified Au-NP reference materials obtained from NIST and results showed excellent agreement. Combining both of these new methods provided a comprehensive understanding of the metallic ENP systems. After method development with well defined nanoparticle systems, the set-up was tested for its applicability to "real world" samples. First, the characterization of commercial available, polydisperse, commercial Ag nanoparticle (Ag-NP) products was performed. The new developed set-up allowed obtaining an element specific, mass, and number size distribution. Furthermore, Ag-NP concentrations as well as the toxicological relevant ionic Ag concentration could be determined. Figures of merit compared to transmission electron microscopy (TEM) and batch-DLS results were in good agreement and the new method was advantageous in terms of analysis time and reliability. Furthermore the possibility to characterize SiO2 coated Au nanoparticles (Au@SiO2) was investigated. These particles are employed for Shell-Isolated Nanoparticle Enhanced Raman Spectroscopy (SHINERS). It was shown that in terms of particle size characterization, the method provided excellent data. However, determination of Si concentrations to calculate the shell thickness of such particles was impeded by the poor A4F peak shape as well as the high Si background in ICPMS. In conclusion, both setups show great potential for the characterization of metallic ENP either in aerosols or dispersions, respectively.GR-LU
Monitoring of Steel Lined Pressure Shafts Considering Water-Hammer Wave Signals and Fluid-Structure Interaction
No full textIn the past, the safety margin for dynamic water pressure loads in steel-lined pressure tunnels and shafts was considered as acceptable by using conventional design safety factors. Due to high peak energy demands, existing plants are operating nowadays under rough conditions to regulate the discharge and power with relatively fast and repeated opening and closing of turbines and pumps. The economic and social costs due to production losses, when these water conveying structures are emptied for investigations and repairs, are considerable. Furthermore, the failure of pressure tunnels and shafts may produce catastrophic landslides and debris flows. An extensive literature review showed that the existing design methods have been based on the idea of keeping the allowable stress in steel liner below yielding threshold. These methods use also some rules for construction details and tolerances which minimize the risk of formation of high local concentrated stresses. Since the beginning of use of very high-strength steel liners in new hydro plants, the actual design methods and safety assessment have become inappropriate. This type of steel has a high risk of brittle failure and fatigue. Therefore, an enhancement of the existing theoretical design model for steel-lined pressure tunnels and shafts is necessary. Generally applicable approaches for estimating the quasi-static, which means without FluidˆStructure Interaction (FSI) and frequency-dependent water-hammer, wave speed in steel-lined pressure tunnels have been analyzed. The external constraints and assumptions of these approaches are discussed in detail and the reformulated formulas are then compared to commonly used expressions. For thin steel liners and weak rock mass modulus, Jaeger's and Parmakian's relationships overestimate the water-hammer velocity by approximately 3 – 4.5 %, while in Halliwell's formula this overestimation reaches 7.5 %. The quasi-static wave speed is significantly influenced by the state of the backfill concrete and the near-field rock zone (cracked or uncracked). In the case when these two layers are cracked, the quasi-static wave speed is overestimated in between 1% and 8% compared to uncracked concrete and near-field rock layers. Depending on the stiffness of steel liner and penstock, the FSI leads to significant difference in wave speeds values. As a first step, a fluid-structure interaction model is proposed as a basis for the development of new design criteria which consider fracture mechanics to access the response of high-strength steel liners. The effect of the backfill concrete and the surrounding rock mass has been mechanically modeled by a spring, a dashpot, and a lumped additional mass. The quadratic dispersion equation which results from FSI model, has been solved in the frequency domain through a numerical example. In this example and compared to the quasi-static case, the FSI approach results up to 13% higher wave speed values in the high-frequency range (higher than 600 Hz) and up to 150% lower values for frequencies between 150 and 300 Hz. In the intermediate frequency range (between 80 and 800 Hz), the precursor mode has a cut-off frequency which depends on the longitudinal distribution of the stiffness of the liner. The first acoustic mode begins to propagate at a frequency near 525 Hz. This cut-off frequency depends on the radial stiffness of the steel liner. For practical applications, the aforementioned wave speed differences in the quasi-static and FSI cases can be tolerated because of the uncertainty in the estimation of the rock mass characteristics and the presence of air in the water. The dynamic pressures obtained from classical water-hammer theory are not overly affected by such differences in wave speed while the FSI may lead to higher extreme dynamic pressures with higher frequencies. The influence of local drop of wall stiffness of pressurized waterways on the pressure wave speed and wave dissipation during transients was investigated experimentally. The weak reaches are resulting from local deterioration of the backfill concrete and the rock mass surrounding the steel liner. The change of wave speed generated by the weakening of the radial liner supports creates reflection boundaries for the incident pressure waves. A new signal processing procedure to identify the presence of these weak reaches has been proposed and validated by physical experiment tests. During water-hammer events, pressure and vibration records have been acquired at the both ends of a multi-reach steel test pipe. The weak reaches are simulated by replacing the steel reaches with Aluminum and PVC materials. The acquired data have been assessed using, amongst others, the Fourier Transform, wavelet decomposition, and cross-correlation techniques. The developed new monitoring method shows that wave speed and wave dissipation ratio are good indicators of the presence of local and large changes in stiffness. This method is also able to locate the weakness of stiffness along the test pipe when one PVC reach is used. When steep front wave have been generated inside the test pipe, it was possible to locate the position of the weak reach boundaries with a maximum relative mean error of 5.9 %. The severity of the local stiffness change has been also estimated with a maximum relative mean error of 20.6 %. In-situ measurements from a pressure shaft have been carried out to validate the new signal processing procedure. The prototype measurements use dynamic pressure and geophone sensors placed at both ends of the pressure shaft of the Grimsel II pumped-storage plant, in the Canton of Bern, in Switzerland. The data are acquired continuously and accessed on-line via internet. Different approaches to estimate the wave speed and wave dissipation generated inside the pressure shaft during start-up and shut-down of pumps and turbines have been applied. The relatively small water-hammer pressure fluctuations combined with the homogeneous quality of the rock mass surrounding the pressure shaft made it difficult to apply the entire localization procedure. Nevertheless, monitoring charts have been established based on the statistical quality control of the two indicators namely the water-hammer wave speed and the wave dissipation coefficient. The wave speed was assessed from the Fourier transformation spectrums (F) while the dissipation coefficient was determined by computing the root mean square (RMS) of the signal followed by an exponential regression fitting. Three control limits representing the actual state of the shaft wall have been set on these charts from the acquired and processed pressure data. These limits and the overall behaviour of the pattern of future measured points will be used for on-line monitoring of the shaft. The control limits of the monitoring charts for the water-hammer wave speed should be revised after acquiring a longer series of in-situ measurements. The control limits of the exponential dissipation coefficient computed during the pump and turbine start-up modes can be used for on-line monitoring. During the pump and turbine shut-down modes, the dissipation coefficient has encountered a shift of about 55 %. Additional measurements are needed to understand its global pattern behaviour.PL-LC
Biosensor microprobe arrays for in vivo monitoring of neurotransmitters
No full textReal-time monitoring of neurotransmitters is of utmost importance for understanding the functioning of the brain. Especially L-glutamate and choline play a major role in chemical signalling and are highly involved in cognitive functions such as learning, memory and behaviour. In this thesis, silicon microprobe arrays were realised comprising several microelectrodes with a size of 50×150 µm2. The microtechnological fabrication process allows an application-tailored design to position the electrodes at defined target regions in the brain. Microprobes with a length up to 8 mm and a cross-section of 40×100 µm2 have been fabricated allowing minimally invasive implantation at low tissue damage to be achieved. L-glutamate and choline are detected by the amperometric detection of peroxide using the microelectrodes coated with an enzymatic membrane. An array-compatible method for spatially controlled and parallel membrane deposition by electrochemically aided adsorption and chemical co-cross-linking with glutaraldehyde was developed. The enzymatic membrane deposition is followed by electropolymerisation of m-phenylenediamine to deposit a semi-permeable membrane rejecting electroactive interferents such as ascorbic acid and dopamine that are endogenously present in the extracellular fluid. The resulting biosensors show adequate characteristics in sensitivity, detection limit as well as functional and storage lifetimes for acute monitoring of the neuro-transmitters in brain tissue. The results of an extensive in vitro assessment and in vivo functional tests are presented. In array configuration, the biosensors allow simultaneous multi-site recordings of one analyte from different brain regions or multi-analyte recordings within defined spatial brain areas. Additionally, microchannels were integrated with the biosensor arrays to perform chemical stimulation by the local delivery of neuroactive substances: SU-8 microinjector arrays comprising several microfluidic channels or the direct integration of microchannels into the silicon shaft were realised. Both allow a precise positioning of the fluidic outlet relative to the biosensors and low-volume injections. The biosensors integrated with the delivery channels enable the bilateral interaction with neuronal tissue on the neurochemical level at required temporal and spatial resolution. This thesis is a part of the European integrated project NeuroProbes aiming at realising three-dimensional arrays of multi-functional microprobes, assembled in a modular way to perform in vivo electrophysiological and biological measurements. The biosensor is one of the functionalities to be integrated in this platform. The result is a new device for neuroscientists that will allow most complete 3D mapping of neuronal circuitry and relate these complex signalling mechanisms to observable behaviour.SAMLA
Iterative geometric design for architecture
No full textThis work investigates on computer aided integrated architectural design and production. The aim is to provide integral solutions for the design and the production of geometrically complex free-form architecture. Investigations on computer aided geometric design and integrated manufacturing are carried out with equal importance. This research is considering an integral and interdisciplinary approach, including computer science, mathematics and architecture. Inspired by fractal geometry, the IFS formalism is studied with regards to discrete architectural geometric design. The geometric design method studied provides new shape control possibilities unifying two separate design paradigms of rough and smooth objects. Capable to design fractal geometric figures, the method also covers the generation of classical objects such as conics and NURBS-curves. Close attention has been paid to the design of iterative free-form surfaces, which are composed entirely out of planar elements. A surface method based on projected vector sums is proposed. The resulting geometric figures are expressed in a discrete form and can be easily translated into a coherent set of constructional elements. The studies for translation of the geometrical elements into constructional elements consider integrated manufacturing. Addressing and numbering of the elements by iterative geometric design are investigated and compared to lexicographically ordered addressing systems, in order to provide an adequate data structure for the design, production and assembly of the constructional elements. For the generation of the data describing constructional elements, problems related to thickening and offset meshes are discussed. Once the global geometry of the constructional part has been computed, parameters are defined for generic automated detailing. Hereby the entire description of the constructional elements is completed. These elements are mapped and packed with regards to the coordinate system of a CNC-machine and the properties and the dimensions of the raw material, providing the complete set of workshop plans needed for integrated manufacturing. For automated generation of machine instructions (G-code), machining strategies – depending on the type of machine used, tool and material properties – are elaborated. Finally, the integrated digital design methods studied within the scope of this thesis are tested and verified by the realization of different reduced scale prototypes. The studied applications range from bearing vault structures to fractal and smooth timber panel shell structures. The developed methods have shown to be efficient for the design and the realization of geometrically complex architectural objects. The required planning effort to handle and manipulate the design and the production data has been greatly reduced. Some of the proposed methods have proved to be robust and general enough to be applied on real world applications. Iterative geometric design provides high degree of design possibilities offering an efficient tool for the creation of smooth and rough free form objects. The possibility to incorporate successive folds in free-form objects allows structural applications.IBOI