| 1. |
- Abtahi, Farhad, 1981-
(författare)
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Aspects of Electrical Bioimpedance Spectrum Estimation
- 2014
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Electrical bioimpedance spectroscopy (EBIS) has been used to assess the status or composition of various types of tissue, and examples of EBIS include body composition analysis (BCA) and tissue characterisation for skin cancer detection. EBIS is a non-invasive method that has the potential to provide a large amount of information for diagnosis or monitoring purposes, such as the monitoring of pulmonary oedema, i.e., fluid accumulation in the lungs. However, in many cases, systems based on EBIS have not become generally accepted in clinical practice. Possible reasons behind the low acceptance of EBIS could involve inaccurate models; artefacts, such as those from movements; measurement errors; and estimation errors. Previous thoracic EBIS measurements aimed at pulmonary oedema have shown some uncertainties in their results, making it difficult to produce trustworthy monitoring methods. The current research hypothesis was that these uncertainties mostly originate from estimation errors. In particular, time-varying behaviours of the thorax, e.g., respiratory and cardiac activity, can cause estimation errors, which make it tricky to detect the slowly varying behaviour of this system, i.e., pulmonary oedema.The aim of this thesis is to investigate potential sources of estimation error in transthoracic impedance spectroscopy (TIS) for pulmonary oedema detection and to propose methods to prevent or compensate for these errors. This work is mainly focused on two aspects of impedance spectrum estimation: first, the problems associated with the delay between estimations of spectrum samples in the frequency-sweep technique and second, the influence of undersampling (a result of impedance estimation times) when estimating an EBIS spectrum. The delay between frequency sweeps can produce huge errors when analysing EBIS spectra, but its effect decreases with averaging or low-pass filtering, which is a common and simple method for monitoring the time-invariant behaviour of a system. The results show the importance of the undersampling effect as the main estimation error that can cause uncertainty in TIS measurements. The best time for dealing with this error is during the design process, when the system can be designed to avoid this error or with the possibility to compensate for the error during analysis. A case study of monitoring pulmonary oedema is used to assess the effect of these two estimation errors. However, the results can be generalised to any case for identifying the slowly varying behaviour of physiological systems that also display higher frequency variations. Finally, some suggestions for designing an EBIS measurement system and analysis methods to avoid or compensate for these estimation errors are discussed.
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| 2. |
- Asplund, Maria, 1978-
(författare)
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Conjugated Polymers for Neural Interfaces : Prospects, possibilities and future challenges
- 2009
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Within the field of neuroprosthetics the possibility to use implanted electrodes for communication with the nervous system is explored. Much effort is put into the material aspects of the electrode implant to increase charge injection capacity, suppress foreign body response and build micro sized electrode arrays allowing close contact with neurons. Conducting polymers, in particular poly(3,4-ethylene dioxythiophene) (PEDOT), have been suggested as materials highly interesting for such neural communication electrodes. The possibility to tailor the material both mechanically and biochemically to suit specific applications, is a substantial benefit with polymers when compared to metals. PEDOT also have hybrid charge transfer properties, including both electronic and ionic conduction, which allow for highly efficient charge injection. Part of this thesis describes a method of tailoring PEDOT through exchanging the counter ion used in electropolymerisation process. Commonly used surfactants can thereby be excluded and instead, different biomolecules can be incorporated into the polymer. The electrochemical characteristics of the polymer film depend on the ion. PEDOT electropolymerised with heparin was here determined to have the most advantageous properties. In vitro methods were applied to confirm non-cytotoxicity of the formed PEDOT:biomolecular composites. In addition, biocompatibility was affirmed for PEDOT:heparin by evaluation of inflammatory response and neuron density when implanted in rodent cortex. One advantage with PEDOT often stated, is its high stability compared to other conducting polymers. A battery of tests simulating the biological environment was therefore applied to investigate this stability, and especially the influence of the incorporated heparin. These tests showed that there was a decline in the electroactivity of PEDOT over time. This also applied in phosphate buffered saline at body temperature and in the absence of other stressors. The time course of degradation also differed depending on whether the counter ion was the surfactant polystyrene sulphonate or heparin, with a slightly better stability for the former. One possibility with PEDOT, often overlooked for biological applications, is the use of its semi conducting properties in order to include logic functions in the implant. This thesis presents the concept of using PEDOT electrochemical transistors to construct textile electrode arrays with in-built multiplexing. Using the electrolyte mediated interaction between adjacent PEDOT coated fibres to switch the polymer coat between conducting and non conducting states, then transistor function can be included in the conducting textile. Analogue circuit simulations based on experimentally found transistor characteristics proved the feasibility of these textile arrays. Developments of better polymer coatings, electrolytes and encapsulation techniques for this technology, were also identified to be essential steps in order to make these devices truly useful. In summary, this work shows the potential of PEDOT to improve neural interfaces in several ways. Some weaknesses of the polymer and the polymer electronics are presented and this, together with the epidemiological data, should point in the direction for future studies within this field.
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| 3. |
- Ayas, Ebru, 1977-
(författare)
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Engineering Quality Feelings : Applications in products, service environments and work systems
- 2011
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Contemporary quality issues in product design are moving from materialistic to emotional user fulfillment; comprehensive research is needed to examine quality product feelings. This research is directed toward a deeper understanding of user and customer quality feelings for different product types, including services. The quality feelings concept includes dimensions of product quality, especially functionality, ergonomics and aesthetics. The first objective of this thesis is to identify, prioritize and synthesize quality feelings into product attributes in product development applications. The second objective is to explore, test and propose methodological approaches for designing quality feelings into products. Several methods from psychology, ergonomics, statistics and probabilistic methods and heuristics were applied to achieve the objectives. From a methodological viewpoint, Likert scales, free elicitation technique and Just About Right scales were applied for data collection. Multiple Regression, Factor Analysis, Correspondence Analysis, Genetic algorithms, Partial Least Squares (PLS) and Rough Sets (RS) were applied for data analyses. For ergonomic product evaluations, direct observations, 3D workload simulations, time and frequency analyses were conducted. Five product applications are included in this thesis: operator driver cabin design of reach trucks, steering wheel design trigger switch design in right-angled nutrunners, bed-making systemsproducts and waiting room environments. Heuristic methods were found effective when there is a high number of product attributes that interact to provide quality feelings. RS results are consistent with PLS attribute predictions. When the number of product attributes is large in comparison to the number of observations, PLS extracts informative results for quality feelings. The RS method is effective in identifying interactions among design attributes. Quality feelings are associated with both tangible (tactile characteristics) and intangible (quick and easy to use) product characteristics. Words such as safety, functionality, ergonomics, comfort, reliability, supportiveness, usability, feedback, pleasantness, attractiveness, durability and distinctiveness describe quality feelings from tangible products and services. Based on product type, the quality dimensions represented by these words possess different interactions and dependencies. In work environments, products act as prostheses between workers for social interaction, which need to be considered as important quality feelings dimensions.
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| 4. |
- Bengt, Halling, 1959-
(författare)
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Lean Implementation : the significance of people and dualism
- 2013
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Lean, with its origins at the Toyota Motor Company, is a concept that is known to increase effectiveness in manufacturing. The Lean concept is now argued to be relevant not only in manufacturing but in service and health-care delivery as well. The reported results of Lean implementation efforts are divided. There are reports that most of the Lean implementation efforts are not reaching the goal; on the other hand, there are reports of promising results. The divided results from Lean implementation efforts show how important it is to research and identify factors that are barriers to successful implementation of Lean. This thesis aims to contribute knowledge about barriers to Lean implementation by collecting empirical findings from manufacturing and health care and structuring the perceived barriers and difficulties to Lean implementation. My first study aimed to compare similarities and divergences in barriers to Lean described by key informants in manufacturing and health care. The data was collected via semi-structured interviews. Findings showed that the perceived difficulties and barriers are much the same in manufacturing and health care. The second study was a case study at a manufacturing firm, researching how the views on Lean of the managers implementing Lean influence its implementation. Data was collected via semi-structured interviews with 20 individuals and covered all hierarchical management levels in the company. Findings showed that managers' views on Lean influence the implementation but also that learning during the implementation process can alter managers' views of Lean. The third study aimed to research how management of Lean is described in the literature. This was done through a literature review. The findings showed that Lean management is a matter of dualism, consisting of two complementary systems of action, management and leadership, which are related to the two basic principles of Lean, continuous improvement and respect for the people.
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| 5. |
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| 6. |
- Berglund, Martina, 1963-
(författare)
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Using Tentacles in Planning and Scheduling Work : Activities, Roles and Contributions
- 2009
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Handling production scheduling is increasingly difficult for manyenterprises, and human involvement is necessary. The overall objective ofthis research was to gain further understanding of planners’ and schedulers’work within the manufacturing industry, to elucidate how their worksituation is formed, and to explain their significance to other employees’work and company activities. Scheduling work was studied in fourcompanies in the Swedish woodworking industry; a sawmill, a parquet floormanufacturer, a furniture manufacturer and a house manufacturer. Themethod used was activity analysis which is based on the analysis of workactivities in real work situations. Data collection included 20 days’observations and 65 interviews. Cross-case analysis with British cases onplanning work was also included.The findings revealed that the schedulers’ tasks lead to many activities. Twothirds of these are what can be expected. The remaining third constitutesactivities that depend on the schedulers’ individual attributes and the contextin which they work. The schedulers serve as problem solvers in a number ofdomains and constitute efficient information nodes, making them animportant service function. Furthermore, they have an alignment rolebetween different organizational groups. This role is specifically remarkablein dealing with production enquiries that must be aligned with productioncapability. Here, both planners and schedulers play an essential role inlinking the manufacturing and the commercial sides and their differentfunctional logics.Planners and schedulers in daily work exert strong influence on others. Theydo not hold legitimate power. Instead their influence emanates mainly fromaccess to and control of information and their ability to apply expertise tointerpret this information and examine the impact of decisions made acrossdifferent areas of the business. Personal power related to social skills is alsosignificant.Furthermore, they facilitate others’ work in continuous personalinteractions, serving the technical scheduling software system, and aligningdifferent organizational functions. In combination with expert knowledgeand developed social skills, they significantly contribute to quality operationsperformance. Finally, the schedulers influence the decision latitude of otheremployees and may indirectly promote job satisfaction, thus contributing todeveloping appropriate working conditions for others in the company.
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| 7. |
- Bjällmark, Anna, 1980-
(författare)
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New ultrasonographic approaches to monitoring cardiac and vascular function
- 2009
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Atherosclerotic cardiovascular disease is the leading cause of death worldwide. To decrease mortality and morbidity in cardiovascular disease, the development of accurate, non-invasive methods for early diagnosis of atherosclerotic cardiac and vascular engagement is of considerable clinical interest. Cardiovascular ultrasound imaging is today the cornerstone in the routine evaluation of cardiovascular function and recent development has resulted in two new techniques, tissue velocity imaging (TVI) and speckle tracking, which allow objective quantification of cardiovascular function. TVI and speckle tracking are the basis for three new approaches to cardiac and vascular monitoring presented in this thesis: wave intensity wall analysis (WIWA), two-dimensional strain imaging in the common carotid artery, and the state diagram of the heart. WIWA uses longitudinal and radial strain rate as input for calculations of wave intensity in the arterial wall. In this thesis, WIWA was validated against a commercially available wave intensity system, showing that speckle tracking-derived strain variables can be useful in wave intensity analysis. WIWA was further tested in patients with end stage renal disease and documented high mortality in cardiovascular disease. The latter study evaluated the effects of a single session of hemodialysis using WIWA and TVI variables and showed improved systolic function after hemodialysis. The results also indicated that preload-adjusted early systolic wave intensity obtained by the WIWA system may contribute in the assessment of left ventricular contractility in this patient category. Two-dimensional strain imaging in the common carotid artery is a new approach showing great potential to detect age-dependent differences in mechanical properties of the common carotid artery. Among the measured strain variables, global circumferential strain had the best discriminating performance and appeared to be superior to conventional measures of arterial stiffness such as elastic modulus and β stiffness index. The state diagram is a visualisation tool that provides a quantitative overview of the temporal interrelationship of mechanical events in the left and right ventricles. Case examples and a small clinical study showed that state diagrams clearly visualize cardiac function and can be useful in the detection of non ST-elevation myocardial infarction (NSTEMI). Even though WIWA, two-dimensional strain imaging in the common carotid artery and the state diagram show potential to be useful in the evaluation of cardiovascular function, there still remains a considerable amount of work to be done before they can be used in the daily clinical practice.
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| 8. |
- Buendía López, Rubén, 1982-
(författare)
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Model Based Enhancement of Bioimpedance Spectroscopy Analysis : Towards Textile Enabled Applications
- 2011
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Several signal processing approaches have been developed to overcome the effect of stray capacitances in Electrical Bioimpedance Spectroscopy (EBIS) measurements. EBIS measurements obtained with textile-enabled instrumentation are more vulnerable to stray capacitances. Currently, the most widespread approach for correcting the effect of stray capacitances in EBIS is the time delay ( Td) compensation method, which also has several drawbacks. In this study, the Td method is revisited and its limitations and its lack of a scientific basis are demonstrated. To determine better ways to overcome the effect of stray capacitances, a simplified measurement model is proposed that is based on previous models of artefacts in EBIS measurements described in the literature. The model consists of a current divider with a parasitic capacitance (Cpar) in parallel with the load. Cpar creates a pathway for the measurement current to leak away from the load, provoking a capacitive leakage effect. In this thesis, three approaches with different limitations are proposed to overcome the capacitive leakage effect. The first approach estimates Cpar and subtracts it from the measurements, thus finding the load. Cpar can be estimated because the susceptance of biological tissue is null at infinite frequency. Therefore, at high frequencies, the susceptance of the tissue can be neglected, and the slope of the susceptance of the measurement is Cpar. The accuracy of Cpar depends on the maximum frequency measured and the value of Cpar. Therefore, it may not be possible to accurately estimate small values of Cpar in the typical frequency ranges used in EBIS. The second and third approaches use the Cole fitting process to estimate the Cole parameters, which form the basis for most EBIS applications. Because the conductance of the measurement is free from the effect of Cpar, performing Cole fitting on the conductance avoids the effect of Cpar in the fitting process. With a poor skin-electrode contact, this approach may not be sufficiently accurate. The third approach would be to perform the Cole fitting on the modulus with a reduced upper frequency limit because the modulus and the low-medium frequencies are very robust against the effect of artefacts. In this approach, a slight capacitive leakage effect is unavoidable. Since it is common to find tainted measurements, especially among those obtained with textile-enabled instrumentation, it is important to find viable methods to avoid their effect. The three methods studied showed that they could reduce the effect of tainted measurements.
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| 9. |
- Buendia, Ruben, 1982-
(författare)
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Improvements in Bioimpedance SpectroscopyData Analysis : Artefact Correction, ColeParameters, and Body Fluid Estimation
- 2013
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The estimation of body fluids is a useful and common practice in the status assessment of diseasemechanisms and treatments. Electrical bioimpedance spectroscopy (EBIS) methods are non-invasive,inexpensive, and efficient alternatives for the estimation of body fluids. However, these methods areindirect, and their robustness and validity are unclear.Regarding the recording of measurements, a controversy developed regarding a spectrum deviationin the impedance plane, which is caused by capacitive leakage. This deviation is frequentlycompensated for by the extended Cole model, which lacks a theoretical basis; however, there is nomethod published to estimate the parameters. In this thesis, a simplified model to correct thedeviation was proposed and tested. The model consists of an equivalent capacitance in parallel withthe load.Subsequently, two other measurement artefacts were considered. Both artefacts were frequentlydisregarded with regard to total body and segmental EBIS measurements as their influence isinsignificant with suitable skin-electrode contact. However, this case is not always valid, particularlyfrom a textile-enabled measurement system perspective. In the estimation of body fluids, EBIS dataare fitted to a model to obtain resistances at low and high frequencies. These resistances can berelated to body fluid volumes. In order to minimise the influence of all three artefacts on theestimation of body fluids and improve the robustness and suitability of the model fitting the differentdomains of immittance were used and tested. The conductance in a reduced frequency spectrum wasproposed as the most robust domain against the artefacts considered.The robustness and accuracy of the method did not increase, even though resistances at low and highfrequencies can be robustly estimated against measurement artefacts. Thus, there is likely error in therelation between the resistances and volumes. Based on a theoretical analysis, state of the artmethods were reviewed and their limitations were identified. New methods were also proposed. Allmethods were tested using a clinical database of patients involved in growth hormone replacementtherapy. The results indicated EBIS are accurate methods to estimate body fluids, however they haverobustness limits. It is hypothesized that those limits in extra-cellular fluid are primarily due toanisotropy, in total body fluid they are primarily due to the uncertainty ρi, and errors in intra-cellularfluid are primarily due to the addition of errors in extracellular and total body fluid. Currently, theseerrors cannot be prevented or minimised. Thus, the limitations for robustness must be predicted priorto applying EBIS to estimate body fluids.
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| 10. |
- Cheng, Kimberley
(författare)
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Single-particle cryo-electron microscopy of macromolecular assemblies
- 2009
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- In this thesis, single-particle cryo-electron microscopy (cryo-EM) was used to study the structure of three macromolecular assemblies: the two hemocyanin isoforms from Rapana thomasiana, the Pyrococcus furiosus chaperonin, and the ribosome from Escherichia coli. Hemocyanins are large respiratory proteins in arthropods and molluscs. Most molluscan hemocyanins exist as two distinct isoforms composed of related polypeptides. In most species the two isoforms differ in terms of their oligomeric stability, and thus we set out to investigate the two Rapana thomasiana hemocyanins (RtH) in order to explain this behaviour. Our findings showed that the two RtHio forms are identical at the experimental resolution. Furthermore, three previously unreported connections that most likely contribute to the oligomeric stability were identified. Chaperonins are double-ring protein complexes that assist the folding process of nascent, non-native polypeptide chains. The chaperonin from the hyperthermophilic archaea Pyrococcus furiosus belongs to Group II chaperonins, and unlike most othergroup II chaperonins it appears to be homo-oligomeric. The 3D reconstruction of the Pyrococcus furiousus chaperonin revealed a di-octameric structure in a partially closed/open state, something in between the closed folding-active state and the open substrate-accepting state. The ribosome is the molecular machine where protein synthesis takes place. In bacteria there is a unique RNA molecule called transfer-messenger RNA (tmRNA) that together with its helper protein SmpB rescues ribosomes trapped on defective messenger RNAs (mRNAs) through a process called trans-translation. tmRNA is about 4 times the size of a normal tRNA, and it is composed of a tRNA-like domain (TLD) that is connected to the mRNA-like domain (MLD) by several pseudoknots (PKs) and RNA helices. During trans-translation, tmRNA utilize its TLD to receive the incomplete polypeptide from the peptidyl-tRNA in the ribosomal P site of the stalledribosome. Subsequently, its MLD is used to tag the incomplete polypeptide with adegradation signal. When tmRNA enters a stalled ribosome the MLD and pseudoknots form a highly structured arc that encircles the beak of the small ribosomal subunit. Byutilizing maximum-likelihood based methods for heterogeneity analysis we could observe the Escherichia coli ribosome in a number of different tmRNA·SmpB-boundstates. The cryo-EM map of the post-accommodated state revealed that the TLD·SmpBpart of the tmRNA·SmpB complex mimics native tRNAs in the A site of stalled ribosomes. The density map also showed that the tmRNA arc remains well structuredand that it is still attached to the beak of the small ribosomal subunit. Thereconstructions of the double-translocation tmRNA-bound ribosome complex showed that the pseudoknots of tmRNA still form an arc, and that they are located at positions similar to the ones assigned for the pseudoknots in the post-accommodated state. In addition, the tmRNA arc exists in two states; one stable and highly structured and another more flexible and disorganized.
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