| 1. |
- FOLKE, MIA, 0967-
(author)
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Measurements of Respiratory Carbon Dioxide
- 2005
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Doctoral thesis (other academic/artistic)abstract
- Koldioxid är en central parameter för metabolismen i alla levande varelser. Hos människan regleras koldioxidhalten främst genom andningen. Därför är det viktigt att kunna mäta och övervaka koldioxidhalten i fysiologiska applikationer så väl inom sportmedicin som inom vården, till exempel på intensivvårdsavdelningar. Dessa mätningar kräver adekvat mätutrustning.Syftet med denna avhandling är att kritiskt granska föreslagna metoder för övervakning av andningsaktiviteten, att föreslå och utveckla förbättringar, samt att föreslå och utveckla nya applikationer för mätning av koldioxidhalten i utandningsluften med hjälp av en elektroakustisk sensor.Mätning av koldioxid i utandningsluften har den fördelen över andra föreslagna metoder för andningsövervakning att den även ger information om förhållandet i arteriellt blod då partialtrycket för koldioxid i slutet av ett andetag är lika stort som i artärblod hos lungfriska personer.Den föreslagna tekniken bygger på en elektroakustisk sensor som kan registrera och mäta koldioxidhalten i utandningsluften om fukt- och temperaturvariationer utjämnas med hjälp av filter. Den elektroakustiska sensorn består av en ultraljudssändare och en reflektor placerade i varsin ände av ett perforerat rör. Den elektriska impedansen i sensorn representerar molekylvikten inne i sensorkaviteten. Molekylmassan har ett linjärt förhållande till koldioxidhalten så länge övriga gaser hålls konstanta.Det faktum att partialtrycket av koldioxid i slutet av ett andetag kan mätas med den elektroakustiska sensorn gör den användbar i flera kliniska situationer om andra gaser inte kan påverka mätningarna.Partialtrycket av koldioxid i slutet av ett andetag har visat sig vara användbar som en indikator för mjölksyratröskeln då personens individuella mjölksyratröskel infaller då partialtrycket av koldioxid i slutet av ett andetag börjar minska. Det ger en ny applikation inom sportmedicin. På det sättet är det möjligt för en idrottare att mäta variationerna i sin mjölksyratröskel, i sin egen sport på daglig basis, vilket kan användas för att optimera arbetsintensiteten under träning och tävling. Trots att det elektroakustiska sensorsystemet inte är selektivt för koldioxid och därför påverkas även av förändringar i syre i utandningsluften har det visat sig fungera i denna applikation.
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| 2. |
- Åstrand, Anders P, 1961-
(author)
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A Tactile Resonance Sensor System for Detection of Prostate Cancer ex vivo : Design and Evaluation on Tissue Models and Human Prostate
- 2014
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Doctoral thesis (other academic/artistic)abstract
- Background The most common form of cancer among males in Europe and the USA is prostate cancer, PCa. Surgical removal of the prostate is the most common form of curative treatment. PCa can be suspected by a blood test for a specific prostate antigen, a PSA-test, and a digital rectal examination, DRE where the physician palpates the prostate through the rectum. Stiff nodules that can be detected during the DRE, and elevated levels of PSA are indications for PCa, and a reason for further examination. Biopsies are taken from the prostate by guidance of a transrectal ultrasound. Superficial cancer tumours can indicate that the cancer has spread to other parts of the body. Tactile resonance sensors can be used to detect areas of different stiffness in soft tissue. Healthy prostate tissue is usually of different stiffness compared to tissue with PCa.AimThe general aim of this doctoral thesis was to design and evaluate a flexible tactile resonance sensor system (TRSS) for detection of cancer in soft human tissue, specifically prostate cancer. The ability to detect cancer tumours located under the surface was evaluated through measurements on tissue phantoms such as silicone and biological tissues. Finally measurements on resected whole prostate glands were made for the detection of cancer tumours.Methods The sensor principle was based on an oscillating piezoelectric element that was indented into the soft tissue. The measured parameters were the change in resonance frequency, Δf, and the contact force F during indentation. From these, a specific stiffness parameter was obtained. The overall accuracy of the TRSS was obtained and the performance of the TRSS was also evaluated on tissue models made of silicone, biological tissue and resected whole human prostates in order to detect presence of PCa. Prostate glands are generally spherical and a special rotatable sample holder was included in the TRSS. Spherically shaped objects and uneven surfaces call for special attention to the contact angle between the sensor-tip and the measured surface, which has been evaluated. The indentation velocity and the depth sensitivity of the sensor were evaluated as well as the effect on the measurements caused by the force with which spherical samples were held in place in the sample holder. Measurements were made on silicone models and biological tissue of chicken and pork muscles, with embedded stiff silicone nodules, both on flat and spherical shaped samples. Finally, measurements were made on two excised whole human prostates.ResultsA contact angle deviating ≤ 10° from the perpendicular of the surface of the measured object was acceptable for reliable measurements of the stiffness parameter. The sensor could detect stiff nodules ≤ 4 mm under the surface with a small indentation depth of 0.4 to 0.8 mm.Measurements on the surface of resected human prostate glands showed that the TRSS could detect stiff areas (p < 0.05), which were confirmed by histopathological evaluation to be cancer tumours on, and under the surface.Conclusions A flexible resonance sensor system was designed and evaluated on soft tissue models as well as resected whole prostate glands. Evaluations on the tissue models showed that the TRSS can detect stiffer volumes hidden below the surface on both flat and spherical samples. The measurements on resected human prostate glands showed that PCa could be detected both on and under the surface of the gland. Thus the TRSS provides a promising instrument aimed for stiffness measurements of soft human tissue that could contribute to a future quantitative palpation method with the purpose of diagnosing cancer.
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| 3. |
- Andersson, Roger, 1967-
(author)
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Monitoring principles for haemodialysis
- 2002
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Doctoral thesis (other academic/artistic)abstract
- This thesis deals with non-invasive monitoring techniques for haemodialysis. Three applications in particular have been investigated: Blood pressure measurements in the extra corporal circuit, the relationship between UV measurements and dialysate urea concentration and photoplethysmography (PPG) in haemodialysis patients.A non-invasive pressure sensor as an integrated part of the extracorporeal tube circuit was developed using modified cross-section tube geometry. The expansions of the modified tubes with different cross-sectional geometries were studied upon application of pressure, both experimentally and numerically, using the finite element method. Factorial design was used to study the relationship between pressure in the tube and force needed to restore the expanding tube to its original dimension. This investigation was performed for different tube cross-sectional geometries. A pressure sensor was designed, based on the previously obtained findings. The evaluation of the pressure sensor showed that the output corresponded well to applied pressure (R2=0.99).An UV-method for studying waste products in the dialysate has recently been developed by our research group. In the present study, it was investigated how the relationship between UV-absorption and dialysate urea concentration was affected by the treatment settings, patient anamnesis and prescribed pharmaceuticals. A mathematical model was proposed which includes these effects. Multiregression analysis indicated the possibility of performing individual estimates of urea concentration from UV-absorption.During haemodialysis, the patient's cardiovascular system is affected when excess fluid is extracted, which may result in blood pressure fluctuations. In the present study, a novel PPG method for monitoring haemodynamic changes during dialysis was investigated. The performed study indicates that PPG measurements relate to haemodynamic changes and may thus be useful in the patient monitoring. However, the relationship is complex and needs further studies.
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| 4. |
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| 5. |
- Baraldi, Enrico, Professor, 1970-, et al.
(author)
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Managing interorganizational interactions for social impact : A study of two antibiotics R&D networks
- 2022
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In: Journal of Business Research. - : Elsevier. - 0148-2963 .- 1873-7978. ; 141, s. 264-278
-
Journal article (peer-reviewed)abstract
- This paper relies on a comparative case study of two antibiotics R&D networks, ENABLE and CARB-X, to understand how interorganizational interactions can be managed to achieve social impact. In particular, we investigate (1) how particular management mechanisms and interorganizational interactions relate to the network's intended social impact, and (2) how these management mechanisms influence interorganizational interactions. We find that (1) the intended social impact influences the choice of management mechanisms from the very start of a partnership and orients the kind of interactions occurring within the network, and (2) that management mechanisms can shape the interactions unfolding in the network, but that the structural elements of these interactions also make these mechanisms more or less applicable to the network. We contribute to the Industrial Marketing & Purchasing (IMP) view with a model of managing networks building on the three concepts of: intended social impact, management mechanisms, and interorganizational interactions.
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| 6. |
- Candefjord, Stefan, et al.
(author)
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Combining scanning haptic microscopy and fibre optic Raman spectroscopy for tissue characterization
- 2012
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In: Journal of Medical Engineering & Technology. - : Taylor & Francis. - 0309-1902 .- 1464-522X. ; 36:6, s. 319-327
-
Journal article (peer-reviewed)abstract
- The tactile resonance method (TRM) and Raman spectroscopy (RS) are promising for tissue characterization in vivo. Our goal is to combine these techniques into one instrument, to use TRM for swift scanning, and RS for increasing the diagnostic power. The aim of this study was to determine the classification accuracy, using support vector machines, for measurements on porcine tissue and also produce preliminary data on human prostate tissue. This was done by developing a new experimental set-up combining micro-scale TRMscanning haptic microscopy (SHM)for assessing stiffness on a micro-scale, with fibre optic RS measurements for assessing biochemical content. We compared the accuracy using SHM alone versus SHM combined with RS, for different degrees of tissue homogeneity. The cross-validation classification accuracy for healthy porcine tissue types using SHM alone was 6581%, and when RS was added it increased to 8187%. The accuracy for healthy and cancerous human tissue was 6770% when only SHM was used, and increased to 7277% for the combined measurements. This shows that the potential for swift and accurate classification of healthy and cancerous prostate tissue is high. This is promising for developing a tool for probing the surgical margins during prostate cancer surgery.
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| 7. |
- Ciabuschi, Francesco, 1973-, et al.
(author)
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Joining Forces to Prevent the Antibiotic Resistance Doomsday Scenario : The Rise of International Multisectoral Partnerships as a New Governance Model
- 2020
-
In: Academy of Management Perspectives. - : Academy of Management. - 1558-9080 .- 1943-4529. ; 34:4, s. 458-479
-
Journal article (peer-reviewed)abstract
- Humanity is facing a global threat caused by growing antibiotic resistance. If the current lack of innovation in antibiotics persists, we will face a doomsday scenario with drastic implications for society, health, and business worldwide. In this study, we examine international multisectoral partnerships (IMSPs), one of the policy interventions introduced to incentivize the antibiotic innovation necessary to avoid such a scenario. Based on insights from three recently launched antibiotics IMSPs, we present their key features and argue that such partnerships represent a novel type of organizational form and governance, different from others discussed in previous research. Specifically, antibiotics IMSPs are interorganizational structures showing great governance complexity, strong centralized control, strict boundaries, and formalization of roles and rules. We discuss how antibiotics IMSPs differ from other partnerships dealing, for instance, with the environmental global challenge, and their usefulness in other contexts where similar uncertain, risky, urgent, and complex tasks need to be faced. We conclude with implications for theory as well as for policy and managerial practice, along with avenues for future research.
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| 8. |
- Ciabuschi, Francesco, 1973-, et al.
(author)
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Supporting innovation against the threat of antibiotic resistance : Exploring the impact of public incentives on firm performance and entrepreneurial orientation
- 2020
-
In: Journal of Business Research. - : Elsevier BV. - 0148-2963 .- 1873-7978. ; 112, s. 271-280
-
Journal article (peer-reviewed)abstract
- Although there is an urgent need to find new antibiotics to fight growing antibiotic resistance, the development of antibiotics is at its lowest level ever. This innovation drought in the antibiotics industry is a challenge for managers, policy makers, and public health authorities. Currently, several strategies to incentivize antibiotic innovation are being considered, but their effects are unknown. Using the theoretical lens of the entrepreneurial orientation framework and Monte Carlo-based simulations on state-of-the-art pharmaceutical industry data, this study found that several incentives can increase the innovativeness of firms in this industry. However, the results show that these effects vary between incentives, between large and small firms, and across different research and development stages. This study analyzed these findings in the light of the entrepreneurial orientation framework and presents implications for theory, policy makers, and managers.
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| 9. |
- Hallberg, Per, 1965-
(author)
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Applanation Resonance Tonometry for Intraocular Pressure Measurement
- 2006
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Doctoral thesis (other academic/artistic)abstract
- Elevated intraocular pressure (IOP) is one of the major risk factors for glaucoma. Since glaucoma is a leading cause of blindness, reliable methods for measuring the IOP are important. This doctoral dissertation presents a new method, applanation resonance tonometry (ART), for measurement of IOP. The method is based on resonance sensor technology combined with the novel multipoint analysis of continuously sampled data of both contact force and contact area. The ART was evaluated in in vitro porcine-eye studies as well as in clinic on both healthy volunteers and patients. A new symmetric probe with a larger sensor tip and improved aligning light was developed and evaluated in vitro. It showed that the error from off-centring was highly reduced. The new ART probe, used as a biomicroscope device (ARTBiom) and as a handheld device (ARTHand), was further evaluated in a clinical study designed in accordance with the International Standard Organisation’s (ISO) requirement. Both the ARTBiom and the ARTHand met the precision set by the requirements. Laser surgery is a common way to correct vision. The biomechanical effect of photorefractive keratectomy (PRK) on IOP measurements was evaluated using Goldmann applanation tonometry (GAT) and ART in an in vitro study. Both methods were affected, but to a different extent. The flat contact probe of GAT, as compared with the convex tip of ART, and single point vs. multipoint approach, provide explanation to the ART advantage regarding measurement error of IOP after PRK. In conclusion, resonance sensor technology has made it possible to introduce a new multipoint method for measuring IOP, and the method is relevant for measuring IOP in humans. It may be possible to reduce errors in the clinical measurement of IOP with this new method, especially after corneal surgery. The ART has the potential to become a useful clinical instrument for IOP measurement.
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| 10. |
- Jalkanen, Ville, 1978-
(author)
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Tactile sensing of prostate cancer : a resonance sensor method evaluated using human prostate tissue in vitro
- 2007
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Doctoral thesis (other academic/artistic)abstract
- Prostate cancer is the most frequent type of cancer in men in Europe and the USA. The methods presently used to detect and diagnose prostate cancer are inexact, and new techniques are needed. Prostate tumours can be regarded as harder than the surrounding normal healthy glandular tissue, and therefore it is of interest to be able to reliably measure prostate tissue stiffness. In this dissertation the approach was to evaluate tactile resonance sensor technology and its ability to measure mechanical properties and to detect cancer in human prostate tissue. The tactile resonance sensor is based on a piezoelectric transducer element vibrating at its resonance frequency through a feedback circuit. A change in the resonance frequency is observed when the sensor contacts an object. This feature has been utilized to measure tissue stiffness variations due to various pathophysiological conditions. An impression-controlled tactile resonance sensor system was first used to quantify stiffness and evaluate performance on silicone. Then the sensor system was used on fresh human prostate tissue in vitro to measure stiffness using a combination of frequency change and force measurements. Significant differences in measured stiffness between malignant and healthy normal tissue were found, but there were large variations within the groups. Some of the variability was explained by prostate tissue histology using a tissue stiffness model. The tissue content was quantified at four depths in the tissue specimens with a microscope-image-based morphometrical method involving a circular grid. Numerical weights were assigned to the tissue data from the four depths, and the weighted tissue proportions were related to the measured stiffness through a linear model which was solved with a least-squares method. An increase in the proportion of prostate stones, stroma, or cancer in relation to healthy glandular tissue increased the measured stiffness. Stroma and cancer had the greatest effect and accounted for 90 % of the measured stiffness (45% and 45%, respectively). The deeper the sensor was pressed, the greater, i.e., deeper, volume it sensed. A sensing depth was extrapolated from the numerical weights for the measurements performed at different impression depths. Horizontal surface tissue variations were studied by altering the circular grid size relative to the contact area between the sensor tip and the tissue. The results indicated that the sensing area was greater than the contact area. The sensor registered spatial tissue variations. Tissue density-related variations, as measured by the frequency change, were weakly significant or non-significant. The measured force registered elastic-related tissue variations, to which stroma and cancer were the most important variables. A theoretical material-dependent linear relation was found between frequency change and force from theoretical models of frequency change and force. Tactile resonance sensor measurements on prostate tissue verified this at small impression depths. From this model, a physical interpretation was given to the parameters used to describe stiffness. These results indicate that tactile resonance sensor technology is promising for assessing soft tissue mechanical properties and especially for prostate tissue stiffness measurement with the goal of detecting prostate cancer. However, further studies and development of the sensor design must be performed to determine the full potential of the method and its diagnostic power. Preferably, measurements of tissue mechanical properties should be used in combination with other methods, such as optical methods, to increase the diagnostic power.
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| 11. |
- Jonsson, Ulf G, 1950-
(author)
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Detecting Inclusions in a Silicone Rubber Phantom Using Standing Lamb Waves and Multiple Frequency Footprints
- 2014
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Doctoral thesis (other academic/artistic)abstract
- The thesis deals with one major question: is it possible, using one piezoelectric sensor/vibrator, to detect a hard inclusion in a silicone rubber phantom? The question was approached with an open mind and the task was subdivided into three clearly identifiable parts: characterization of the piezoelectric sensor/vibrator (paper I), creating a model of the visco-elastic properties of a tissue-like material (phantom) in contact with the sensor/vibrator (paper II), and to detect the presence of a hard inclusion in the phantom (paper III). All vibrations of the sensor/vibrator and phantom was modeled using a finite element method (FEM). To minimize the computational time and to maximize the FEM model's ability to correctly reproduce the vibrations, a two-dimensional model system consisting of a cylindrical piezoelectric sensor/vibrator, emitting radial elastic waves in to a cylindrical disk-shaped phantom, was chosen. The piezoelectric sensor/vibrator was characterized using a parameter tuning procedure using harmonic overtones. The procedure enables tuning of the electro-elastic parameters of the sensor/vibrator so that the measured and calculated impedance frequency responses match. Silicone rubber was chosen as a phantom to mimic soft tissue. The properties of the phantom was modeled using a fractional derivative visco-elastic model. The hyperelastic effect at the first radial resonance of the sensor vibrator was corrected for by a compensating function. The high frequency complex visco-elastic modulus of the silicone rubber was determined using the transitions of standing Lamb waves in the phantom. The presence of a ring-shaped inclusion in the phantom, of polyamide, was detected using the change of the transitional Lamb wave patterns in the phantom. The tuning of the PZT5A1 sensor/vibrator parameters yielded a match between the calculated and the measured impedance spectra better than 0.54%. The average, complex, elastic modulus of three silicone rubber, Silgel 612, samples were: (0.97 + 0.009i) GPa at 100 kHz and (0.97 + 0.005i) GPa at 250 kHz. The presence of a polyamide inclusion, PA6GPE, was detected in the phantom using multiple frequency footprints.
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| 12. |
- Karbalaie, Abdolamir
(author)
-
Novel Analysis Toolkit for Capillaroscopic Images: Development and Clinical Evaluation
- 2018
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Doctoral thesis (other academic/artistic)abstract
- Nailfold capillaroscopy (NC) is an invasive imaging technique that is used to assess the blood capillary network in the nailfold area. NC is routinely used for patients with microcirculation problems, such as systemic sclerosis and other connective tissue diseases. NC is repeatable and appears to be simple and harmless. However, there is a lack of established guidelines [QCE1] and instructions for both the acquisition and interpretation of the images obtained, which may lead to various ambiguities.The general aim of this thesis was to reduce the inherent ambiguities in human judgment and diagnosis by introducing novel techniques for assessing the nailfold capillary density, which is an important parameter in NC. To achieve this goal, a toolkit was developed that includes a method to measure the capillary density, an image enhancement technique and a graphical user interface (GUI).In the first study, a summary of the nailfold videocapillaroscopy procedure was presented, and the common techniques used to evaluate capillaroscopic parameters were reviewed. In the second study, common methods for calculating the capillary density were reviewed, and a survey of the relationship between the number of capillaries as well as the existence of digital ulcers, pulmonary arterial hypertension, autoantibodies, scleroderma patterns and the different scoring systems was performed. In the third study, a novel method was proposed to determine the nailfold capillary density, and this method is referred to as the elliptic broken line (EBL) method. In the fourth study, the EBL method for measuring capillary density was evaluated. In the fifth study, a new image enhancement technique was introduced and evaluated both subjectively and objectively. Finally, clinical applications of the EBL method and enhancement techniques were demonstrated in the sixth study. The result verifies the potential of the proposed EBL method to improve the reliability and repeatability of assessments. Additionally, improving the image quality, i.e., using the proposed enhancement method, can reveal more capillary details for an observer compared to the raw original image, and the results motivate the future development of automatic tools for the EBL method, e.g., automatic segmentation and capillary detection and characterization.Please note that the font changes here. Please consider using a consistent font type and size throughout the manuscript.
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| 13. |
- Lindahl, Berit
(author)
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Möten mellan människor och teknologi : berättelser från intensivvårdssjuksköterskor och personer som ventilatorbehandlas i hemmet
- 2005
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Doctoral thesis (other academic/artistic)abstract
- The overall aim of this thesis is to illuminate meanings of the relation between human beings, technology and care, as narrated by critical care nurses and people in need of home mechanical ventilation (HMV). The data are based on narrative research interviews with six intensive care nurses (I), 13 people who were about to start HMV (II), these 13 people were interviewed for a second time six to eight months after HMV had started (III), and nine persons with more than two years HMV experience (IV). The text was analysed using a phenomenological-hermeneutic research method as described by Lindseth and Norberg. The method is developed from the writings of the French philosopher Paul Ricoeur. The findings illuminate meanings of nursing care in an intensive care unit (I) as undertaking the role of advocacy as a caring response to another human being. The basic condition for this caring response depends on the nurses' openness and sensitivity to the needs of patients or patients' next of kin. The nurses were aware of the influence of technology and tried to modify its negative effects. Meanings of becoming dependent on HMV (II) are interpreted and metaphorically expressed as "to get one's breath" and "to hold one's breath" respectively. On the one hand, breathing ensures the cellular oxidation process within the body, but on the other hand there can be "shortness of breath" in "spiritual breathing", and starting HMV will influence patients' whole life situation, body and spirit. After using a ventilator six to eight months, meanings of a life dependent on a ventilator was interpretd as either a closure or an opening of the lived body to oneself, other people and the world. This interpretation is illustrated by two images. A life on a ventilator at home is not to be seen as static being. On the contrary, it is a being which moves and changes over time. Being dependent on a ventilator and living at home, as narrated by adults with more than two years of HMV experience (IV), was interpreted as being able to rise above yourself and your personal boundaries in order to live a good life. These meanings are bound up with experiencing a vital force and interdependency, and despite fragility being able to reach others and the outside world. Design and function of technology had an impact on the lived body. The comprehensive understanding of the four articles (I-IV) unfolded meanings of the relation between human beings, technology and care, as an interchange and a creation of physical and spiritual energy among humans and between human and technology. It could be an experience of the lived body being filled with as well as emptied of energy. This interpretation points at a call for the caring personnel to be attentive and to listen to the voices of the lived body in health and illness, and to bear witness to those who suffer. Technology acts between the person and the world and in order to be embodied, technology must be "transparent", i.e. beautiful and fit to its use.
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| 14. |
- Lindahl, Karl-Olof
(author)
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On the linearization of non-Archimedean holomorphic functions near an indifferent fixed point
- 2007
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Doctoral thesis (other academic/artistic)abstract
- We consider the problem of local linearization of power series defined over complete valued fields. The complex field case has been studied since the end of the nineteenth century, and renders a delicate number theoretical problem of small divisors related to diophantine approximation. Since a work of Herman and Yoccoz in 1981, there has been an increasing interest in generalizations to other valued fields like p-adic fields and various function fields. We present some new results in this domain of research. In particular, for fields of prime characteristic, the problem leads to a combinatorial problem of seemingly great complexity, albeit of another nature than in the complex field case. In cases for which linearization is possible, we estimate the size of linearization discs and prove existence of periodic points on the boundary. We also prove that transitivity and ergodicity is preserved under the linearization. In particular, transitivity and ergodicity on a sphere inside a non-Archimedean linearization disc is possible only for fields of p-adic numbers.
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| 15. |
- Lindahl, Olof A, et al.
(author)
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A tactile resonance sensor for prostate cancer detection – evaluation on human prostate tissue
- 2021
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In: Biomedical Engineering & Physics Express. - : Institute of Physics (IOP). - 2057-1976. ; 7:2
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Journal article (peer-reviewed)abstract
- Prostate cancer surgery risks erectile problems and incontinence for the patient. An instrument for guiding surgeons to avoid nerve bundle damage and ensure complete cancer removal is desirable. We present a tactile resonance sensor made of PZT ceramics, mounted in a 3D motorized translation stage for scanning and measuring tissue stiffness for detecting cancer in human prostate. The sensor may be used during surgery for guidance, scanning the prostate surface for the presence of cancer, indicating migration of cancer cells into surrounding tissue. Ten fresh prostates, obtained from patients undergoing prostate cancer surgery, were cut into 0.5 cm thick slices. Each slice was measured for tissue stiffness at about 25 different sites and compared to histology for validation cancer prediction by stiffness. The statistical analysis was based on a total of 148 sites with non-cancer and 40 sites with cancer. Using a generalized linear mixed model (GLMM), the stiffness data predicted cancer with an area under the curve of 0.74, after correcting for overfitting using bootstrap validation. Mean prostate stiffness on the logarithmic scale (p = 0.015) and standardized Z-scores (p = 0.025) were both significant predictors of cancer. This study concludes that stiffness measured by the tactile resonance sensor is a significant predictor of prostate cancer with potential for future development towards a clinical instrument for surgical guidance.
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| 16. |
- Lindenberg, Björn, Doktorand, 1978-
(author)
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Reinforcement Learning and Dynamical Systems
- 2023
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Doctoral thesis (other academic/artistic)abstract
- This thesis concerns reinforcement learning and dynamical systems in finite discrete problem domains. Artificial intelligence studies through reinforcement learning involves developing models and algorithms for scenarios when there is an agent that is interacting with an environment. By taking actions the agent may induce changes in the observed environment, where a modeled reward system reinforces correct behavior through learning algorithms. Reinforcement learning can be used in a wide variety of different domains, such as finance, robotics, games, routing and health care. However as the subject matures there is an increasing need to more heavily rely on advanced concepts in mathematics and deep learning to further our understanding of existing problems and find new algorithmic insights. Discrete dynamical systems arise in virtually any setting as soon as there is a set of elements subjected to iteration by a defining function. The function may be seen to represent the passing of time or to define the rules for state transitions. If the set of elements is finite but very large then we may find applications in several different fields such as operations research, cryptography and biology, where understanding properties of the structure and long-term behavior without explicit enumeration is key. In Paper I we extend the model of categorical reinforcement learning with a group-aided training procedure involving multiple agents. By having the agents learn through shared distributional information but act independently we argue for an accelerated learning process. We empirically show that the procedure may lead to much more robust learning, stronger individual agent performance and good ensemble efficiency.In Paper II we continue to build upon distributional reinforcement learning for finite Markov processes. A common approach amongalgorithms is to apply transformations on agent returns for stability and flexibility over a variety of different tasks. We show that one of the most successful methods may not work for a stochastic process. As a solution we introduce a new distributional operator that handles a large class of transformations with guaranteed theoretical convergence. We also propose an approximating single-actor algorithm based on these novel insights, which when tested achieves state-of-the-art performance compared to similar algorithms.In Paper III we focus on the issue of efficient exploration in reinforcement learning by studying the regret that a learning algorithm might have versus an optimal policy. Specifically, in the paper we derive a Bayesian regret bound for Thompson sampling on linear multi-armed bandits with Gaussian reward models when we have environment uncertainty described by a set of multivariate normal-gamma distributions.In Paper IV we derive sharp bounds on the number of iterations needed for any linear finite dynamical system to stabilize on an inner set of cycles. These bounds may be used in cycle analysis and criterion tests to understand the long-term behavior of extremely large systems.
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| 17. |
- Ljungblad, Jonas, 1984-
(author)
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High performance breath alcohol analysis
- 2017
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Doctoral thesis (other academic/artistic)abstract
- Alcohol breath testing on a larger scale will save lives. Alcohol intake affects the human body by significantly longer response time to external stimuli. In demanding situations where the senses need to be on alert a prolonged reaction time can be the difference between life and death, both for the intoxicated subject and for surrounding individuals.The aims of this thesis include investigations of a new type of breath alcohol sensor, designed for operation without a mouthpiece, both with regards to sensor performance as well as usability in relation to various breath alcohol screening applications.In many situations where breath alcohol screening is suitable, there is a need for quick and easy use. The instrument should interfere as little as possible with the regular routines and procedures. One such task is driving. To accommodate for these needs in an in-vehicle application, the breath alcohol sensing system must be seamlessly installed in the vehicle and not interfere with the normal behavior of the sober driver. Driving is also a task requiring high level of concentration over a prolonged period of time. In the U.S. alone thousands of lives are annually lost in accidents where the driver was under the influence of alcohol. Similar numbers have been recorded for Europe. The potential for a system handling the needs for ease-of-use is huge and may result in successful products.The results presented within this thesis provide experimental evidence of sufficient sensor performance for screening applications with an instrument operating without a mouthpiece. Smarter calculation methods were also shown to be a feasible path to improved measurement reliability. Important steps towards an even more passive solution for in-vehicle screening is also presented. Experiments showed that given enough time and sensor resolution, passive alcohol detection systems are feasible.
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| 18. |
- Nordqvist, Jonas
(author)
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Residue fixed point index and wildly ramified power series
- 2020
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Doctoral thesis (other academic/artistic)abstract
- This thesis concerns discrete dynamical systems. These are systems where the dynamics is modeled by iterated functions. There are several applications of discrete dynamical system e.g. in biology, pseudo random number generation and statistical mechanics. In this thesis we are interested in discrete dynamical systems described by iterations of a power series f fixing the origin, where it is tangent to the identity. In particular, the coefficients of f are given in a field of positive characteristic p. We are interested in the so-called lower ramification numbers of such series. The lower ramification numbers encodes the multiplicity of the origin as a fixed point of f under p-power iterates. In particular this thesis contains four papers all related to the topic of lower ramification numbers of such power series.In Paper I we consider so-called 2-ramified power series and give a characterization of such in terms of its first significant terms. This is further extended in Paper II, where we geometrically locate the periodic points of 2-ramified power series in the open unit disk. In doing, so we provide a self-contained proof of the main result of the first paper.In Paper III, we consider power series with a fixed point at the origin of small multiplicity, i.e. the multiplicity of the fixed point is less than that of the characteristic of the ground field. We provide a characterization of all such power series having the smallest possible lower ramification numbers, in terms of its first significant terms, and in terms of the nonvanishing of the so-called iterative residue. In doing so, we also provide a formula for the residue fixed point index for the case of a multiple fixed point. We further extend the results of Paper II by locating geometrically the periodic points in the open unit disk of convergent power series with small multiplicity.In Paper IV we consider power series of large multiplicity, and introduce an invariant in positive characteristic closely related to the residue fixed point index. We provide a characterization of these power series having the smallest possible lower ramification numbers in terms of the nonvanishing of this invariant. As a by-product we obtain results about the dimension of the moduli space of formal classification of wildly ramified power series.
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- Åstrand, Anders P.
(author)
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A flexible resonance sensor system for detection of cancer tissue : evaluation on silicon
- 2012
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Licentiate thesis (other academic/artistic)abstract
- The most common form of cancer among men in Europe and the US is prostate cancer. When a radical prostatectomy has been found necessary, it is of interest to examine the prostate, as tumour tissue on the capsule might indicate that the cancer has metastased. This is commonly done by a microscope-based morphometric investigation. Tumour tissue is normally stiffer than healthy tissue. Sensors based on piezoelectric resonance technology have been introduced into the medical field during the last decade. By studying the change in resonance frequency when a sensor comes into contact with a material, conclusions can be drawn about the material.A new and flexible measurement system using a piezoelectric resonance sensor has been evaluated. Three translation stages, two for horizontal movements and one for vertical movement, with stepper motors are controlled from a PC. A piezoelectric resonance element and a force sensor are integrated into a sensor head that is mounted on the vertical translation stage. The piezoelectric element is connected to a feed-back circuit and resonating at its resonance frequency until it comes into contact with a material, when a frequency shift can be observed. The force sensor is used to measure the applied force between the sensor and the material. These two parameters are combined into a third, called the stiffness parameter, which is important for stiffness evaluation. For measurements on objects with different geometries, the vertical translation stage can be aimed at a platform for flat objects or a fixture for spherical objects. The vertical translation stage is mounted on a manual rotational stage with which the contact angle between the sensor and the measured surface can be adjusted. The contact angles covered are between 0° and 35° from a line perpendicular to the surface of the measured object. The measured objects used were made from silicones of different stiffness and in the shape of flat discs and spheres. The indentation velocity of the sensor can be set at 1 mm/s to 5 mm/s. In the three papers that are the base for this licentiate thesis, we have investigated the dependence of the frequency shift, the applied force and the stiffness parameter on the contact angle, and the indentation velocity at different impression depths. The maximum error for the measurement system has also been determined.The results of the measurements indicate that great care must be taken when aiming the sensor against the surface of the point where the measurements are to be performed. Deviations in contact angle of more than iv±10° from a line perpendicular to the surface will result in an underestimation of the frequency shift, meaning that the tissue will be regarded as stiffer than it really is. This result is important as the flat silicone models have a very even surface, which makes a controlled contact angle possible. Biological tissue can have a rough and uneven surface, which can lead to unintentional deviations in the contact angle. The magnitude of the stiffness parameter is favoured by a high indentation velocity compared to a low.The evaluation of this measurement system has shown that it is possible to distinguish between soft and stiff silicone models, which have been used in this initial phase of the study. A new feature in this measurement system is the fixture that makes measurements on spherical objects possible and the possibility to vary the angle of contact. This is promising for future studies and measurements on whole prostate in vitro. A future application for this measurement system is to aid surgeons performing radical prostatectomy in the search for tumour tissue on the capsule of the prostate, as the presence of tumour tissue can indicate that the cancer has spread to the surrounding tissue.
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