| 1. |
- Eklund, Anders, 1965-, et al.
(author)
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A resonator sensor for measurement of intraocular pressure : evaluation in an in vitro pig-eye model
- 2000
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In: Physiological Measurement. - : IOP Publishing. - 0967-3334 .- 1361-6579. ; 21:3, s. 355-367
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Journal article (peer-reviewed)abstract
- Intraocular pressure (IOP) measurement is performed routinely at every eye clinic. High IOP, which can be a sign of glaucoma, can lead to degeneration of the retina and can cause blindness. In this study we developed a resonator sensor for IOP measurement based on an oscillator consisting of a piezoelectric element made of lead zirconate titanate, a flat contact piece of nylon and a feedback circuit. The aim of this study was to evaluate the new sensor's ability to determine lOP in an in vitro pig-eye model. Six eyes from four pigs were removed and fixed in agar. They were then pressurized by a saline column (10-35 cm H2O) through a cannula inserted into the vitreous chamber. The IOP was measured with the resonator sensor applied to cornea. An Alcon applanation pneumatonometer and a standard Viggo-Spectramed pressure sensor connected to the saline column were used as references. The IOP as measured with the resonator sensor correlated well with the pressure elicited by the saline column for individual eyes (r = 0.96-0.99, n = 60) and for all eyes (r = 0.92, n = 360). The correlation between the resonance sensor and the pneumatonometer was r = 0.92 (n = 360). The pneumatonometer also showed a good correlation with the saline column (r = 0.98, n = 360). We conclude that our in vitro pig-eye model made it possible to induce reproducible variation in IOP, and measurement of that pressure with the newly developed resonator sensor gave very promising results for development of a clinically applicable IOP tonometer with unique properties.
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| 2. |
- Öhman, Marcus, et al.
(author)
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Bed agglomeration characteristics during fluidized bed combustion of biomass fuels
- 2000
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In: Energy & Fuels. - : American Chemical Society (ACS). - 0887-0624 .- 1520-5029. ; 14:1, s. 169-178
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Journal article (peer-reviewed)abstract
- The in-bed behavior of ash-forming elements in fluidized bed combustion (FBC) of different biomass fuels was examined by SEM/EDS analysis of samples collected during controlled agglomeration test runs. Eight fuels were chosen for the test. To cover the variations in biomass characteristics and to represent as many combinations of ash-forming elements in biomass fuels as possible, the selection was based on a principal-component analysis of some 300 biomass fuels, with respect to ash-forming elements. The fuels were then combusted in a bench-scale fluidized bed reactor (5 kW), and their specific agglomeration temperatures were determined. Bed samples were collected throughout the tests, and coatings and necks formed were characterized by SEM/EDS analyses. On the basis of their compositions, the corresponding melting behaviors were determined, using data extracted from phase diagrams. The bench-scale reactor bed samples were finally compared with bed samples collected from biomass-fired full-scale fluidized bed boilers. In all the analyzed samples, the bed particles were coated with a relatively homogeneous ash layer. The compositions of these coatings were most commonly constricted to the ternary system K2O-CaO-SiO2. Sulfur and chlorine were further found not to `participate' in the agglomeration mechanism. The estimated melting behavior of the bed coating generally correlated well with the measured agglomeration temperature, determined in the 5 kW bench-scale fluidized bed reactor. Thus, the results indicate that partial melting of the coating of the bed particles would be directly responsible for the agglomeration.
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| 3. |
- Kadi, F., et al.
(author)
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The effects of different training programs on the trapezius muscle of women with work-related neck and shoulder myalgia
- 2000
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In: Acta Neuropathologica. - Berlin : Springer Berlin/Heidelberg. - 0001-6322 .- 1432-0533. ; 100:3, s. 253-258
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Journal article (peer-reviewed)abstract
- The aim of this study was to examine the effects of training on the structural characteristics of the trapezius muscle in women with work-related trapezius myalgia. Muscle biopsies were taken before and after 10 weeks of three different training programs (strength, endurance and coordination). Enzyme-immunohistochemical analysis was performed to assess muscle fibre types, fibre area, capillary supply and cytochrome c oxidase (COX) activity. There was an increase in the proportion of type LIA fibres in strength trained group (P < 0.05). Strength training elicited a preferential increase in the area of type II fibres (P < 0.05); both strength and endurance programs induced an increase in the number of capillaries around type I and IIA muscle fibres. Finally, all training programs induced a decrease in the proportion of COX-negative fibres. In conclusion, the trapezius muscle of women with neck and shoulder myalgia is characterised by a great potential of adaptation to physical exercise over a period of 10 weeks. The significant changes in the number of capillaries and the specific changes induced by training at the level of muscle fibres might well explain the improvement of muscle function.
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| 4. |
- Karlsson, Stefan, et al.
(author)
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Time-Frequency Analysis of Myoelectric Signals During Dynamic Contractions: A Comparative Study
- 2000
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In: IEEE Transactions on Biomedical Engineering. - : Institute of Electrical and Electronics Engineers (IEEE). - 0018-9294 .- 1558-2531. ; 47:2, s. 228-238
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Journal article (peer-reviewed)abstract
- In this paper, we introduce the nonstationary signal analysis methods to analyze the myoelectric (ME) signals during dynamic contractions by estimating the time-dependent spectral moments. The time-frequency analysis methods including the short-time Fourier transform, the Wigner–Ville distribution, the Choi–Williams distribution, and the continuous wavelet transform were compared for estimation accuracy and precision on synthesized and real ME signals. It is found that the estimates providedby the continuous wavelet transform have better accuracy and precision than those obtained with the other time-frequency analysis methods on simulated data sets. In addition, ME signals from four subjects during three different tests (maximum static voluntary contraction, ramp contraction, and repeated isokinetic contractions) were also examined.
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| 5. |
- McRae, Edward, et al.
(author)
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Raman light scattering and c-axis resistivity evidence for a pressure-induced stage transformation in PdAl2Cl8 intercalated graphite.
- 2000
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In: Physical Review B. Condensed Matter and Materials Physics. - : American Physical Society. - 1098-0121 .- 1550-235X. ; 62:20, s. 13757-13766
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Journal article (peer-reviewed)abstract
- We have examined several samples of first- to third-stage PdAl2Cl8-intercalated graphite under hydrostatic pressures up to 1 GPa. In stage-1 highly oriented pyrolytic graphite–(HOPG) and single-crystal-graphite-based materials, the c-axis resistivity decreases sharply above a few kilobars; pressure release induces a reversible return to the initial value only in the case of the latter sample. Raman spectra taken in situ under pressure on a HOPG-based material show similarly irreversible effects. Analysis of the spectra taken on higher-stage samples leads to the conclusion that hydrostatic pressure beyond a few kilobars increases the density of the intercalate within the graphitic galleries, transforming the initial sample to a higher-stage material. Since there is no loss of intercalate, the overall intercalate-to-host charge transfer remains constant so that the Raman frequency is approximately the same for both first- and second-stage products. This is an unusual situation in which there is thus an apparent lack of Raman signature in spite of the stage change.
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| 6. |
- Chernysova, Irina V., et al.
(author)
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Mechanism of adsorption of long-chain alkylamines on silicates. A spectroscopic study. 1. Quartz
- 2000
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In: Langmuir. - : American Chemical Society (ACS). - 0743-7463 .- 1520-5827. ; 16:21, s. 8071-8084
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Journal article (peer-reviewed)abstract
- The mechanism of adsorption of long-chain alkylamines at pH 6-7 onto quartz was studied using FTIR and XPS spectroscopy. The spectroscopic data were correlated with ζ potential and Hallimond flotation results. For the first time it was shown that (1) amine cation in the first monolayer is H-bonded with surface silanol group and this H-bond becomes stronger after the break in the adsorption characteristics (isotherm, ζ potential, floatability); (2) at the break the origin of the adsorbed amine species changes qualitatively, and along with alkylammonium ion attached to deprotonated silanol group, molecular amine appears at the surface and, as a result, monolayer thick patches of well-oriented and densely packed adsorbed amine species form rendering the surface highly hydrophobic; and (3) at higher amine concentration, bulk precipitation of molecular amine takes place. The counterion was found to influence both these steps. A model of successive two-dimensional and three-dimensional precipitation was suggested to explain amine adsorption on a silicate surface.
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| 7. |
- Larsson, Roland, et al.
(author)
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Lubricant thermal conductivity and heat capacity under high pressure
- 2000
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In: Proceedings of the Institution of mechanical engineers. Part J, journal of engineering tribology. - : SAGE Publications. - 1350-6501 .- 2041-305X. ; 214:4, s. 337-342
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Journal article (peer-reviewed)abstract
- The thermal conductivity and the heat capacity per unit volume, ρcp, have been measured for a number of common lubricating oils. The oils tested were paraffinic and naphthenic mineral oils and a 50/50 blend of these. Poly-alpha-olefin, polyglycol, Santotrac, ester and rapeseed oils have also been tested. The measurements, using the transient hot-wire method, were carried out under isothermal conditions over a pressure range from atmospheric to 1.1 GPa and at two temperatures, 295 and 380 K (22 and 107 degrees C respectively).The temperature had only a marginal effect on thermal conductivity; however, the thermal conductivity was doubled as the pressure was increased to 1 GPa. The heat capacity per unit volume was influenced by both the pressure and the temperature. Some of the lubricants solidified as the pressure increased and the transition from a fluid to a solid state could be detected in the measurements of ρcp.The relationship between the thermodynamic properties and the pressure and temperature are described by two empirical equations. These equations can be used in thermal elastohydrodynamic analyses.
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| 8. |
- Sandström, K. J. Mattias, et al.
(author)
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Amperometric biosensor for formic acid in air
- 2000
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In: Sensors and actuators. B, Chemical. - : Elsevier. - 0925-4005 .- 1873-3077. ; 70:1–3, s. 182-187
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Journal article (peer-reviewed)abstract
- The possibility of developing a simple, inexpensive and specific personal passive “real-time” air sampler incorporating a biosensor for formic acid was investigated. The sensor is based on the enzymatic reaction between formic acid and formate dehydrogenase (FDH) with nicotinamide adenine dinucleotide (NAD+) as a co-factor and Meldola's blue as mediator. An effective way to immobilise the enzyme, co-factor and Meldola's blue on screen-printed, disposable, electrodes was found to be in a mixture of glycerol and phosphate buffer covered with a gas-permeable membrane. Steady-state current was reached after 4–15 min and the limit of detection was calculated to be below 1 mg/m3. However, the response decreased by 50% after storage at −15°C for 1 day.
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| 9. |
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| 10. |
- Karlsson, Stefan, et al.
(author)
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Estimation of surface electromyogram spectral alteration using reduced-order autoregressive model
- 2000
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In: Medical and Biological Engineering and Computing. - 0140-0118 .- 1741-0444. ; 38, s. 520-527
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Journal article (peer-reviewed)abstract
- A new method is proposed, based on the pole phase angle (PPA) of a second-order autoregressive (AR) model, to track spectral alteration during localised muscle fatigue when analysing surface myo-electric (ME) signals. Both stationary and non-stationary, simulated and real ME signals are used to investigate different methods to track spectral changes. The real ME signals are obtained from three muscles (the right vastus lateralis, rectus femoris and vastus medialis) of six healthy male volunteers, and the simulated signals are generated by passing Gaussian white-noise sequences through digital filters with spectral properties that mimic the real ME signals. The PPA method is compared, not only with spectra-based methods, such as Fourier and AR, but also with zero crossings (ZCs) and the first AR coefficient that have been proposed in the literature as computer efficient methods. By comparing the deviation (dev), in percent, between the linear regression of the theoretical and estimated mean frequencies of the power spectra for simulated stationary (s) and non-stationary (ns) signals, in general, it is found that the PPA method (dev(s) = 4.29; dev(ns) = 1.94) gives a superior performance to ZCs (dv(s) = 8.25) and the first AR coefficient (4.18
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