| 1. |
- Eklund, Anders, et al.
(author)
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Evaluation of applanation resonator sensors for intra-ocular pressure measurement : results from clinical and in vitro studies.
- 2003
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In: Medical and Biological Engineering and Computing. - 0140-0118 .- 1741-0444. ; 41:2, s. 190-197
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Journal article (peer-reviewed)abstract
- Glaucoma is an eye disease that, in its most common form, is characterised by high intra-ocular pressure (IOP), reduced visual field and optic nerve damage. For diagnostic purposes and for follow-up after treatment, it is important to have simple and reliable methods for measuring IOP. Recently, an applanation resonator sensor (ARS) for measuring IOP was introduced and evaluated using an in vitro pig-eye model. In the present study, the first clinical evaluation of the same probe has been carried out, with experiments in vivo on human eyes. There was a low but significant correlation between IOP(ARS) and the IOP measured with a Goldmann applanation tonometer (r = 0.40, p = 0.001, n = 72). However, off-centre positioning of the sensor against the cornea caused a non-negligible source of error. The sensor probe was redesigned to have a spherical, instead of flat, contact surface against the eye and was evaluated in the in vitro model. The new probe showed reduced sensitivity to off-centre positioning, with a decrease in relative deviation from 89% to 11% (1 mm radius). For normalised data, linear regression between IOP(ARS) and direct IOP measurement in the vitreous chamber showed a correlation of r = 0.97 (p < 0.001, n = 108) and a standard deviation for the residuals of SD < or = 2.18 mm Hg (n = 108). It was concluded that a spherical contact surface should be preferred and that further development towards a clinical instrument should focus on probe design and signal analysis.
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| 2. |
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| 3. |
- Jalkanen, Ville, 1978-, et al.
(author)
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Explanatory models for a tactile resonance sensor system-elastic and density-related variations of prostate tissue in vitro
- 2008
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In: Physiological Measurement. - Bristol : IOP Publ. Ltd. - 0967-3334 .- 1361-6579. ; 29:7, s. 729-745
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Journal article (peer-reviewed)abstract
- Tactile sensors based on piezoelectric resonance have been adopted for medical applications. The sensor consists of an oscillating piezoelectric sensor–circuit system, and a change in resonance frequency is observed when the sensor tip contacts a measured object such as tissue. The frequency change at a constant applied force or mass load is used as a stiffness-sensitive parameter in many applications. Differential relations between force and frequency have also been used for monitoring intraocular pressure and stiffness variations in prostate tissue in vitro. The aim of this study was to relate the frequency change (Δf), measured force (F) and the material properties, density and elasticity to an explanatory model for the resonance sensor measurement principle and thereby to give explanatory models for the stiffness parameters used previously. Simulations of theoretical equations were performed to investigate the relation between frequency change and contact impedance. Measurements with a resonance sensor system on prostate tissue in vitro were used for experimental validation of the theory. Tissue content was quantified with a microscopic-based morphometrical method. Simulation results showed that the frequency change was dependent upon density (ρ) and contact area (S) according to Δf ∝ ρS3/2. The experiments followed the simulated theory at small impression depths. The measured contact force followed a theoretical model with the dependence of the elastic modulus (E) and contact area, F ∝ ES3/2. Measured density variations related to histological variations were statistically weak or non-significant. Elastic variations were statistically significant with contributions from stroma and cancer relative to normal glandular tissue. The theoretical models of frequency change and force were related through the contact area, and a material-dependent explanatory model was found as Δf ∝ ρE−1F. It explains the measurement principle and the previously established stiffness parameters from the material properties point of view.
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| 4. |
- Jalkanen, Ville, 1978-, et al.
(author)
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Prostate tissue stiffness as measured with a resonance sensor system : a study on silicone and human prostate tissue in vitro.
- 2006
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In: Medical and Biological Engineering and Computing. - : Springer Science and Business Media LLC. - 0140-0118 .- 1741-0444. ; 44:7, s. 593-603
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Journal article (peer-reviewed)abstract
- Prostate cancer is the most common form of cancer in men in Europe and in the USA. Some prostate tumours are stiffer than the surrounding normal tissue, and it could therefore be of interest to measure prostate tissue stiffness. Resonance sensor technology based on piezoelectric resonance detects variations in tissue stiffness due to a change in the resonance frequency. An impression-controlled resonance sensor system was used to detect stiffness in silicone rubber and in human prostate tissue in vitro using two parameters, both combinations of frequency change and force. Variations in silicone rubber stiffness due to the mixing ratio of the two components could be detected (p<0.05) using both parameters. Measurements on prostate tissue showed that there existed a statistically significant (MANOVA test, p<0.001) reproducible difference between tumour tissue (n=13) and normal healthy tissue (n=98) when studying a multivariate parameter set. Both the tumour tissue and normal tissue groups had variations within them, which were assumed to be related to differences in tissue composition. Other sources of error could be uneven surfaces and different levels of dehydration for the prostates. Our results indicated that the resonance sensor could be used to detect stiffness variations in silicone and in human prostate tissue in vitro. This is promising for the development of a future diagnostic tool for prostate cancer.
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| 5. |
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| 6. |
- Jalkanen, Ville, 1978-, et al.
(author)
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Resonance sensor measurements of stiffness variations in prostate tissue in vitro : a weighted tissue proportion model
- 2006
-
In: Physiological Measurement. - : IOP Publishing. - 0967-3334 .- 1361-6579. ; 27:12, s. 1373-86
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Journal article (peer-reviewed)abstract
- Prostate cancer is the most common type of cancer in men in Europe and the US. The methods to detect prostate cancer are still precarious and new techniques are needed. A piezoelectric transducer element in a feedback system is set to vibrate with its resonance frequency. When the sensor element contacts an object a change in the resonance frequency is observed, and this feature has been utilized in sensor systems to describe physical properties of different objects. For medical applications it has been used to measure stiffness variations due to various patho-physiological conditions. In this study the sensor's ability to measure the stiffness of prostate tissue, from two excised prostatectomy specimens in vitro, was analysed. The specimens were also subjected to morphometric measurements, and the sensor parameter was compared with the morphology of the tissue with linear regression. In the probe impression interval 0.5-1.7 mm, the maximum R(2) > or = 0.60 (p < 0.05, n = 75). An increase in the proportion of prostate stones (corpora amylacea), stroma, or cancer in relation to healthy glandular tissue increased the measured stiffness. Cancer and stroma had the greatest effect on the measured stiffness. The deeper the sensor was pressed, the greater, i.e., deeper, volume it sensed. Tissue sections deeper in the tissue were assigned a lower mathematical weighting than sections closer to the sensor probe. It is concluded that cancer increases the measured stiffness as compared with healthy glandular tissue, but areas with predominantly stroma or many stones could be more difficult to differ from cancer.
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| 7. |
- Jalkanen, Ville, 1978-, et al.
(author)
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Spatial variations in prostate tissue histology as measured by a tactile resonance sensor
- 2007
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In: Physiological Measurement. - : IOP Publishing. - 0967-3334 .- 1361-6579. ; 28:10, s. 1267-81
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Journal article (peer-reviewed)abstract
- In recent years, tactile sensors based on piezoelectric resonance sensor technology have been used for medical diagnosis where the sensor's stiffness-measuring properties can reflect tissue pathology. The change in the frequency of the resonating system and the change in force when contact is made with tissue are used as a stiffness parameter. Earlier stiffness measurements of prostate tissue in vitro demonstrate variations related to tissue composition. In this study, measured stiffness from two human prostate specimens was compared to histological composition of prostate tissue below and around the measurement points. Tissue stiffness was measured with the resonance sensor system. Tissue composition was measured at four different depths in the tissue specimen using a microscopic-image-based morphometrical method. With this method, the proportion of tissue types was determined at the points of intersections in a circular grid on the images representing each measurement point. Numerical values were used for weighting the tissue proportions at different depths in the tissue specimen. For an impression depth of 1.0 mm, the sensing depth in this study was estimated to be 3.5-5.5 mm. Stiffness variations due to horizontal tissue variations were investigated by studying the dependence of the size of the circular grid area relative to the contact area of the sensor tip. The sensing area (grid radius) was estimated to be larger than the contact area (contact radius) between the sensor tip and the tissue. Thus, the sensor tip registers spatial variations in prostate tissue histology, both directly below and lateral to the tip itself. These findings indicate that tumours around the sensor tip could be detected, which in turn supports the idea of a future resonance-sensor-based clinical device for detecting tumours and for guiding biopsies.
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| 8. |
- Jonsson, Ulf G, et al.
(author)
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Modeling the high-frequency complex modulus of a silicone rubber using standing lamb waves and an inverse finite element method
- 2014
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In: IEEE Transactions on Ultrasonics, Ferroelectrics and Frequency Control. - : IEEE Press. - 0885-3010 .- 1525-8955. ; 61:12, s. 2106-2120
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Journal article (peer-reviewed)abstract
- To gain an understanding of the high-frequency elastic properties of silicone rubber, a finite element model of a cylindrical piezoelectric element, in contact with a silicone rubber disk, was constructed. The frequency dependent elastic modulus of the silicone rubber was modeled by a four parameter fractional derivative viscoelastic model in the 100 kHz to 250 kHz frequency range. The calculations were carried out in the range of the first radial resonance frequency of the sensor. At the resonance, the hyperelastic effect of the silicone rubber was modeled by a hyperelastic compensating function. The calculated response was matched to the measured response by using the transitional peaks in the impedance spectrum that originates from the switching of standing Lamb wave modes in the silicone rubber. To validate the results, the impedance responses of three 5 mm thick silicone rubber disks, with different radial lengths, were measured. The calculated and measured transitional frequencies have been compared in detail. The comparison showed very good agreement, with average relative differences of 0.7 %, 0.6 %, and 0.7 % for the silicone rubber samples with radial lengths of 38.0 mm, 21.4 mm, and 11.0 mm, respectively. The average, complex, elastic modulus of the samples were: (0.97 + 0.009i) GPa at 100 kHz and (0.97 + 0.005i) GPa at 250 kHz.
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| 9. |
- Jonsson, Ulf G., et al.
(author)
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Using a look-up table technique and finite element calculations for quick detection of stiff inclusions in silicone rubber
- 2020
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In: Engineering computations. - : Emerald Group Publishing Limited. - 0264-4401 .- 1758-7077. ; 37:6, s. 2137-2153
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Journal article (peer-reviewed)abstract
- Purpose: The aim of the study was to show that a new method, using a look-up table technique, can be used to detect the presence and position of an inclusion embedded in a tissue-like material. Due to the time-consuming nature of the finite element (FE) method or FEM, real-time applications involving FEM as part of a control loop, are traditionally limited to slowly varying systems. By using a simplified two-dimensional FE model and a look-up table, we show by simulations and experiments that it is possible to achieve reasonable computational times in a tactile resonance sensor application.Design/methodology/approach: A piezoelectric disk was placed in the center of a silicone rubber disk (SRD) with viscoelastic properties, where it acted as both sensor and actuator and dissipated radial acoustic waves into the silicone. The look-up table was constructed by calculating the radial Lamb wave transition frequencies in the impedance frequency response of the sensor while varying the position of an inclusion. A position-matching algorithm was developed that matched measured and calculated Lamb wave transitions and thereby identified the presence and position of an inclusion.Findings: In an experiment, the position of a hard inclusion was determined by measuring the Lamb transition frequencies of the first radial resonance in two SRDs. The result of the matching algorithm for Disk 1 was that the matched position was less than 3% from the expected value. For Disk 2, the matching algorithm erroneously reported two false positions before reporting a position that was less than 5% from the expected value. An explanation for this discrepancy is presented. In a verifying experiment, the algorithm identified the condition with no inclusion present.Originality/value: The approach outlined in this work, adds to the prospect of developing time-sensitive diagnostic instruments. This approach has the potential to provide a powerful technique to quickly present spatial information on detected tumors.
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| 10. |
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| 11. |
- Kumar Wagri, Naresh, 1988-
(author)
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Assessment of bio-based fuel ash effects on magnesia refractory materials in quicklime production kilns
- 2023
-
Doctoral thesis (other academic/artistic)abstract
- Limestone is calcined into quicklime in lime kilns at temperatures above 1000°C. Heat is supplied through combustion inside the kilns, which are insulated with a lining of refractory bricks to mitigate heat loss and to protect the kiln from the hot, chemically aggressive, and mechanically abrasive environment. While magnesia bricks have proven to be effective lining materials, they are still susceptible to extensive wear in lime kilns, especially in the burn zone. Refractory corrosion, in particular, can occur when melted fuel ash infiltrates the refractory materials through pores and small cracks. This resultant wear can lead to high maintenance and operational costs, often due to unplanned kiln shutdowns.To reduce the release of fossil-based carbon dioxide into the atmosphere from lime production kilns, there is a growing interest in introducing bio-based fuels with only relatively minor modifications to the process. Biomass fuels can be sourced from bio-based waste streams from industries or be specifically cultivated for combustion. However, the ash content and properties of bio-based fuels tend to be problematic from an ash chemistry perspective. Therefore, before introducing a new fuel source, it is essential to investigate its potential effects on the kiln lining material. In this thesis work, the interactions between melted olive pomace ash and coal ash with commercially available magnesia refractory materials, primarily composed of periclase (MgO) with minor amounts of spinel (MgAl2O4), were studied. A procedure for quantifying the intrusion depths was described. Refractory samples were exposed to the fuel ashes under a simulated lime kiln atmosphere with high CO2 levels at 1200 and 1400°C for 15 and 60 minutes. Cold crushing strength tests were conducted on refractory samples exposed to coal and olive pomace ash, along with CaO powder, at 1400°C for 96 hours. Additionally, postmortem analyses of spent MgO-based refractory bricks were carried out to investigate their chemical characterization and resistance to slag attack after serving as part of the lining in a quick lime rotary kiln for six months.The morphology and elemental compositions of the exposed samples were examined using scanning electron microscopy and energy-dispersive X-ray spectroscopy. Crystalline phases were investigated with powder X-ray diffraction. Thermodynamic equilibrium calculations were performed to further investigate the ash’s melting behavior in contact with the refractories.The results indicated that the potassium-rich olive pomace ash exhibited a greater tendency to infiltrate compared to the silicon-rich coal ash, while the latter formed a glassy melt layer on top of the refractory samples. The ash slags primarily infiltrated through the porous matrix and grain boundaries of the refractory materials. Also, refractory phases were observed in both types of ashes, indicating migration of refractory constituents. K2MgSiO4 phase was found in the olive pomace ash residues on top of the samples, both for the 1200°C and 1400°C exposures. Similarly, Al6Si2O13 phase was dominant in the residual coal ash, in both the 1200°C and 1400°C exposed samples. None of these phases were present in the original ashes.The results of the postmortem analysis revealed that there was no potassium (K) from the fuel ash present on the hot side of the refractory bricks. However, some K was detected in the middle and back parts of the bricks. On the other hand, some phases, possibly connected to degradation, could be found on the hot side of the bricks, where most of the wear was observed.The crushing strengths increased after exposure for all samples, except for those exposed exclusively to coal ash. One possible explanation for this is that the refractory materials exhibited a sintered structure, as a result of their interaction with the ashes and CaO. However, in the samples exposed to coal ash, forsterite (Mg2SiO4) was identified, which can be considered a corrosion product.
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| 12. |
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| 13. |
- Kumar Wagri, Naresh, et al.
(author)
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High temperature interactions between coal ash and MgO-based refractories in lime kiln conditions
- 2023
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In: Fuel. - : Elsevier. - 0016-2361 .- 1873-7153. ; 342
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Journal article (peer-reviewed)abstract
- Magnesium oxide (MgO)-based refractories are commonly used in quicklime and cement rotary kilns. At the high temperatures in the kiln burn zone, the infiltration of molten fuel ash into the refractory can occur. Subsequent chemical interactions can cause refractory wear that inflicts high maintenance costs and loss of production. To improve refractory reliability, it is necessary to increase the understanding of the interactions between fuel ash slag and refractory liner materials. Three commercially available MgO-based refractory materials were exposed to coal ash at 1200 °C and 1400 °C for between 15 and 60 min under a CO2-rich gaseous environment. Hot slag from the coal ash infiltrated the refractories and the infiltration depths were estimated with scanning electron microscope with energy dispersive X-ray spectroscopy. Based on detailed elemental and microstructure analyses, the interactions between ash and refractory were examined. Molten silicates infiltrated the refractory through grain boundaries and pores into depths of up to 2.8 mm. Powder X-ray diffraction of the exposed refractory samples indicated that MgO grains reacted with SiO2-containing phases to form Mg2SiO4. This was identified as a corrosion product whose formation was supported by thermochemical equilibrium calculations. Elevated Mg content was found in the ash residue on top of the samples, indicating the dissolution or dislocation of refractory components. In addition, phases such as MgO were identified in the ash residue.
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| 14. |
- Kumar Wagri, Naresh, et al.
(author)
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High temperature interactions between K-rich biomass ash and MgO-based refractories
- 2023
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In: Journal of the European Ceramic Society. - : Elsevier. - 0955-2219 .- 1873-619X. ; 43:8, s. 3770-3777
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Journal article (peer-reviewed)abstract
- MgO-based refractories are used in lime kilns to withstand the high temperature and chemical environment. Efforts to reduce CO2 emissions have led to an increased interest to use bio-based fuels as alternatives to traditional fossil sources. The potential for refractory corrosion from a potassium-rich biomass ash was investigated by studying the infiltration of olive pomace ash into magnesia/spinel refractories. Refractory samples were exposed to the ash at up to 1400 °C for 15–60 min in a CO2–rich atmosphere. Molten ash infiltrated the refractories through pores and grain boundaries to a depth of up to 9.6 mm, which was quantified with a new systematic procedure. The phase KAlO2 was identified inside the refractories after exposure, indicating an attack of spinel components by potassium. Phases found in the ash residues also indicated the migration of refractory constituents. Thermochemical equilibrium calculations were also used to investigate the ash/refractory chemistry.
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| 15. |
- Kumar Wagri, Naresh, et al.
(author)
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Interaction of olive pomace ash and coal ash with magnesium oxide based refractories
- 2022
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In: Proceedings of the 28th International Conference on the Impact of Fuel Quality on Power Production and the Environment. - : Department of Applied Physics and Electronics, Umeå University.
-
Conference paper (other academic/artistic)abstract
- In quicklime production, limestone is calcined at temperatures above 1000°C, depending on the desired product quality. Heat is supplied to the process from combustion inside the kilns that are insulated to reduce heat loss. The kilns are lined with insulating refractory bricks to withstand the hot, chemically aggressive, and mechanically abrasive environment. Magnesia bricks have emerged as well-performinglining materials, but they are still prone to extensive wear in kilns that are operated at higher temperatures. In particular, refractory corrosion can be caused by fuel ash infiltration that results inmaterial wear, which can incur high maintenance and operational costs through unplanned shutdowns of the kilns. At the same time, to reduce the release of fossil-based carbon to the atmosphere, it is of interest to introduce bio-based fuels into the kilns with only relatively small modifications to the process. Biobased waste streams from existing industries are preferable rather than biomass grown with the sole purpose of combustion. The ash content and properties of these types of waste residues do, however, tend to be problematic from a fuel ash chemistry point of view. Therefore, before introducing a new fuel, their potential effects on kiln lining material should be investigated. In this study, the infiltration of olivepomace ash and coal ash into commercially available refractory materials composed of mainly periclase(MgO) with minor amounts of spinel (MgAl2O4) were compared. They were exposed to the fuel ashes under a simulated lime kiln high CO2 atmosphere at 1200 and 1400°C for 15 and 60 minutes. The morphology and elemental composition of the exposed samples were investigated with scanning electron microscopy equipped with energy-dispersive X-ray spectroscopy. Ash-forming elements infiltrated the porous parts of the materials. The analytical results are complemented with thermodynamic equilibrium calculations to investigate the ash melting behavior. Crystalline phases in the residual ashes were investigated with X-ray diffraction. Refractory phases could be found in both ashes, indicating migration of refractory constituents. Olive pomace ash formed new crystalline compounds together with the refractory components whereas this was not observed for the coal ash, indicating that the former is more of a risk for material failure.
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| 16. |
- Lindahl, Olof A, et al.
(author)
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Biomedical engineering research improves the health care industry
- 2014
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In: XIII Mediterranean Conference on Medical and Biological Engineering and Computing 2013. - Cham : Springer. - 9783319008455 - 9783319008462 ; , s. 1124-1126
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Conference paper (peer-reviewed)abstract
- The health care industry is dependent on new innovations for its survival and expansion. Health care innovations are also important for improving patient care. Through activities at the centre for biomedical engineering and physics (CMTF) we have generated growth both in academia at the universities and in the industry in northern Sweden. Fruitful cooperation was generated between 26 research projects and about 15 established companies in the field of biomedical engineering. The established researcher-owned company for business development of the research results from the CMTF, CMTF Business Development Co Ltd, has so far launched three spin-off companies and has 10 new business leads to develop. The activities have also increased the interest for commercialization and entrepreneurship among the scientists in the centre. So far a total of nine spin-off companies have resulted from the CMTF-research since the year 2000 that has improved the health care market in northern Sweden. © Springer International Publishing Switzerland 2014.
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| 17. |
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| 18. |
- Lindberg, Peter L, et al.
(author)
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An image analysis method for prostate tissue classification : preliminary validation with resonance sensor data
- 2009
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In: Journal of Medical Engineering & Technology. - : Informa healthcare. - 0309-1902 .- 1464-522X. ; 33:1, s. 18-24
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Journal article (peer-reviewed)abstract
- Resonance sensor systems have been shown to be able to distinguish between cancerous and normal prostate tissue, in vitro. The aim of this study was to improve the accuracy of the tissue determination, to simplify the tissue classification process with computerized morphometrical analysis, to decrease the risk of human errors, and to reduce the processing time. In this article we present our newly developed computerized classification method based on image analysis. In relation to earlier resonance sensor studies we increased the number of normal prostate tissue classes into stroma, epithelial tissue, lumen and stones. The linearity between the impression depth and tissue classes was calculated using multiple linear regression (R(2) = 0.68, n = 109, p < 0.001) and partial least squares (R(2) = 0.55, n = 109, p < 0.001). Thus it can be concluded that there existed a linear relationship between the impression depth and the tissue classes. The new image analysis method was easy to handle and decreased the classification time by 80%.
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| 19. |
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| 20. |
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| 21. |
- Mejtoft, Thomas, Universitetslektor, 1976-, et al.
(author)
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Medtech innovation guide : an empiric model to support medical technology innovation
- 2022
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In: Health and Technology. - : Springer. - 2190-7188 .- 2190-7196. ; 12:5, s. 911-922
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Journal article (peer-reviewed)abstract
- Innovation has become increasingly important for most industries to cope with rapid technological changes as well as changing societal needs. Even though there are many sectors with specific needs when it comes to supporting innovation, the medical technology sector is facing several unique challenges that both increases the lead-time from idea to finished product and decreases the number of innovations that are developed. This paper presents a proposed innovation guide that has been developed and evaluated as a support for the innovation process within medical technology research. The guide takes the unique characteristics of the medical technology sector into account and serves as a usable guide for the innovator. The complete guide contains both a structure for the process and a usable web application to support the journey from idea to finished products and services. The paper also includes a new readiness level, Sect. 4.2 to provide support both when developing and determining the readiness for clinical implementation of a medical technology innovation.
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| 22. |
- Ramstedt, Madeleine, et al.
(author)
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Surface Properties of Hydrous Manganite (γ-MnOOH) : A Potentiometric, Electroacoustic, and X-ray Photoelectron Spectroscopy Study
- 2004
-
In: Langmuir. - : American Chemical Society (ACS). - 0743-7463 .- 1520-5827. ; 20:19, s. 8224-8229
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Journal article (peer-reviewed)abstract
- The acid-base characteristics of the manganite (-MnOOH) surface have been studied at pH above 6, where dissolution is negligible. Synthetic microcrystalline particles of manganite were used in the experiments. From potentiometric titrations, electrophoretic mobility measurements, and X-ray photoelectron spectroscopy (XPS), a one pKa model was constructed that describes the observed behavior. The data show no ionic strength effect at pH < 8.2, which is the pH at the isoelectric point (pHiep), but ionic strength effects were visible above this pH. To explain these observations, Na+ ions were suggested to form a surface complex. The following equilibria were established: =MnOH2+1/2 =MnOH-1/2 + H+, log 0 (intr.) = -8.20; =MnOH2+1/2 + Na+ =MnOHNa+1/2 + H+, log 0 (intr.) = -9.64. The excess of Na+ at the surface was supported by XPS measurements of manganite suspensions containing 10 mM NaCl. The dielectric constant of synthetic manganite powder was also determined in this study.
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| 23. |
- Shirdel, Mariam, et al.
(author)
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A pilot study : the UNC passive aerosol sampler in a working environment
- 2017
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In: Annals of Work Exposures and Health. - : Oxford University Press. - 2398-7308 .- 2398-7316. ; 61:8, s. 1029-1034
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Journal article (peer-reviewed)abstract
- Objectives: Dust is generally sampled on a filter using air pumps, but passive sampling could be a cost-effective alternative. One promising passive sampler is the University of North Carolina passive aerosol sampler (UNC sampler). The aim of this study is to characterize and compare the UNC sampler’s performance with PM10 and PM2.5 impactors in a working environment.Methods: Area sampling was carried out at different mining locations using UNC samplers in parallel with PM2.5 and PM10 impactors. Two different collection surfaces, polycarbonate (PC) and carbon tabs (CT), were employed for the UNC sampling. Sampling was carried out for 4–25 hours.Results: The UNC samplers underestimated the concentrations compared to PM10 and PM2.5 impactor data. At the location with the highest aerosol concentration, the time-averaged mean of PC showed 24% and CT 35% of the impactor result for PM2.5. For PM10, it was 39% with PC and 58% with CT. Sample blank values differed between PC and CT. For PM2.5, PC blank values were ~7 times higher than those of CT, but only 1.8 times higher for PM10. The blank variations were larger for PC than for CT.Conclusions: Particle mass concentrations appear to be underestimated by the UNC sampler compared to impactors, more so for PM2.5 than for PM10. CT may be preferred as a collection surface because the blank values were lower and less variable than for PC. Future validations in the working environment should include respirable dust sampling.
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| 24. |
- Shirdel, Mariam, et al.
(author)
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Choosing the number of images and image position when analysing the UNC Passive Aerosol Sampler for occupational exposure assessment
- 2018
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In: Journal of Occupational and Environmental Hygiene. - : Taylor & Francis. - 1545-9624 .- 1545-9632. ; 15:11, s. 767-772
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Journal article (peer-reviewed)abstract
- The University of North Carolina passive aerosol sampler (UNC sampler) could be an alternative when measuring occupational dust exposure, but the time required for microscopic imaging of the sampler needs to be reduced to make it more attractive. The aims of this study were to 1) characterise the effect on precision when reducing imaging, in order to shorten analysis time and 2) assess if the position of the images makes a difference. Eighty-eight samplers were deployed in different locations of an open pit mine. Sixty images were captured for each UNC sampler, covering 51% of its collection surface, using scanning electron microscopy. Bootstrapped samples were generated with different image combinations, to assess the within-sampler coefficient of variation (CVws) for different numbers of images. In addition, the particle concentration relative to the distance from the centre of the sampler was studied. Reducing the number of images collected from the UNC sampler led to up to 8.3% CVws for ten images when calculating respirable fraction. As the overall CV has previously been assessed to 36%, the additional contribution becomes minimal, increasing the overall CV to 37%. The mean concentrations of the images were modestly related to distance from the centre of the sampler. The CVws changed from 8.26% to 8.13% for ten images when applying rules for the image collection based on distance. Thus, the benefit of these rules on the precision is small and the images can therefore be chosen at random. In conclusion, reducing the number of images analysed from 60 to 10, corresponding to a reduction of the imaged sampling area from 51% to 8.5%, results in a negligible loss in precision for respirable fraction dust measurements in occupational environments.
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| 25. |
- Shirdel, Mariam, et al.
(author)
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Passive personal air sampling of dust in a working environment : A pilot study
- 2019
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In: Journal of Occupational and Environmental Hygiene. - : Taylor & Francis Group. - 1545-9624 .- 1545-9632. ; 16:10, s. 675-684
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Journal article (peer-reviewed)abstract
- The aim of this study was to make a preliminary evaluation of the University of North Carolina passive aerosol sampler (UNC sampler) for personal air sampling of particles. Nine personal air samplings of respirable fraction were conducted in an open-pit mine, with pairwise UNC samplers and a respirable cyclone mounted on the chest of workers. UNC samples were analyzed with scanning electron microscopy (SEM) and to some extent energy dispersive X-ray spectroscopy (EDS). Respirable cyclone filter samples were weighed. Correlations and particle elemental compositions were described. Microscopic imaging of the collection surface showed that the particles were heterogeneously deposited across the surface of the UNC sampler. Collected particles were shaped as gravel particles and the resulting particle size distribution in air showed a peak at ca. 3 µm aerodynamic diameter, similarly to what has previously been reported from the same mine. The elemental composition indicated mineral origin. All correlations between the airborne mass concentrations from UNC samplers and respirable cyclones (Pearson = 0.54 and Spearman = 0.43) and between pairs of parallel UNC samplers (Pearson = 0.55 and Spearman = 0.67) were weak. The UNC sampler mass concentrations were approximately 30 times higher than those measured with the respirable cyclone. In conclusion, the UNC sampler, when used for personal sampling in a mine, provides a reasonable particle size distribution and the deposited particles appeared to be of mineral origin and not from textile or skin but the approximately 30-fold overestimation of mass concentrations when comparing with respirable cyclone sampling indicates that further improvements are necessary. Positioning of the sampler may be critical and moving the UNC sampler from the chest to e.g. the top of a helmet might be an improvement. Grounding of the sampler in order to avoid static electricity might also be useful. The UNC sampler should continue to be researched for personal sampling, as passive sampling might become a useful alternative to more laborious sampling techniques.
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