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| 2. |
- Broomé, Michael, et al.
(författare)
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Pressure-independent cardiac effects of angiotensin II in pigs.
- 2004
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Ingår i: Acta Anaesthesiol Scand. - 0001-6772 .- 1365-201X. ; 182:2, s. 111-9
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: Angiotensin II (Ang II) is a potent vasoconstrictor with an important role in the development of cardiovascular disease. Earlier results have shown a positive acute inotropic effect of Ang II in anaesthetized pigs together with significant vasoconstriction. This investigation was designed to study cardiac effects of Ang II, when blood pressure was maintained constant by experimental means. METHODS: Ang II (200 microg h(-1)) was infused in anaesthetized pigs (n = 10) at two different arterial blood pressures, the first determined by the effects of Ang II alone, and the second maintained at baseline blood pressure with nitroprusside. Cardiac systolic and diastolic function was evaluated by analysis of left ventricular pressure-volume relationships. RESULTS: Heart rate, end-systolic elastance (Ees) and pre-load adjusted maximal power (PWRmax EDV(-2)) increased at both blood pressure levels, although less when blood pressure was kept constant with nitroprusside. The time constant for isovolumetric relaxation (tau(1/2)) was prolonged with Ang II alone and shortened with Ang II infused together with nitroprusside. CONCLUSION: Ang II infusion in the pig has inotropic and chronotropic properties independent of arterial blood pressure levels, although the effects seem to be blunted by pharmacological actions of the nitric oxide donor nitroprusside.
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| 4. |
- Heister, Karin, et al.
(författare)
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A detailed Analysis of the C 1s Photoemission of n-Alkanethiolate Films on Noble Metal Substrates
- 2003
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Ingår i: Surface Science, 529, 36 (2003).
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Tidskriftsartikel (refereegranskat)abstract
- High-resolution C 1s X-ray photoemission spectra for the series of n-alkanethiolate (AT) self-assembled monolayers (SAMs) with different lengths of the alkyl chain have been acquired and analyzed in terms of initial and final state effects and fine structure of the C 1s emission. Independent of the alkyl chain length, the binding energy position of this emission was found to be higher by ?0.35 eV for AT SAMs on Ag substrate as compared to Au, which was attributed to the differences in the final state screening mediated by the intermolecular charge transfer. It was assumed that the extent of this effect is a function of the detailed molecular arrangement in the alkyl matrix and demonstrated that the difference in the C 1s peak position disappears as soon as this arrangement is distorted by the incorporation of sulfone moiety in the alkyl chain. In addition, a change of the C 1s peak shape from a symmetric to asymmetric line with increasing alkyl chain length has been observed. This development could be described assuming the existence of a fine structure in the C 1s emission, with two low-intensity components at the higher and lower BE sides of the main emission peak. An assignment of these components has been considered
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| 5. |
- Schoenberg, Stefan O, et al.
(författare)
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Quantification of renal perfusion abnormalities using an intravascular contrast agent (part 2) : results in animals and humans with renal artery stenosis
- 2003
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Ingår i: Magnetic Resonance in Medicine. - : Wiley. - 0740-3194 .- 1522-2594. ; 49:2, s. 288-298
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Tidskriftsartikel (refereegranskat)abstract
- The interrelation between the morphologic degree of renal artery stenosis and changes in parenchymal perfusion is assessed using an intravascular contrast agent. In seven adult foxhounds, different degrees of renal artery stenosis were created with an inflatable clamp implanted around the renal artery. Dynamic susceptibility-weighted gradient-echo imaging was used to measure signal-time curves in the renal artery and the renal parenchyma during administration of 1.5 mg/kg BW of an intravascular ultrasmall particle iron oxide (USPIO) contrast agent. From the dynamic series, regional renal blood volume (rRBV), regional renal blood flow (rRBF), and mean transit time (MTT) were calculated. The morphologic degree of stenosis was measured in the steady state using a high-resolution 3D contrast-enhanced (CE) MR angiography (MRA) sequence (voxel size = 0.7 x 0.7 x 1 mm(3)). Five patients with renoparenchymal damage due to long-standing renal artery stenosis were evaluated. In the animal stenosis model, cortical perfusion remained unchanged for degrees of renal artery stenosis up to 80%. With degrees of stenoses > 80%, cortical perfusion dropped to 151 +/- 54 ml/100 g of tissue per minute as compared to a baseline of 513 +/- 76 ml/100 g/min. In the patients, a substantial difference in the cortical perfusion of more than 200 +/- 40 ml/100 g/min between the normal and the ischemic kidneys was found. The results show that quantitative renal perfusion measurements in combination with 3D-CE-MRA allow the functional significance of a renal artery stenosis to be determined in a single MR exam. Differentiation between renovascular and renoparenchymal disease thus becomes feasible.
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| 6. |
- Arapan, Sergiu, et al.
(författare)
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Conductance of a disordered double quantum wire in a magnetic field: Boundary roughness scattering
- 2003
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Ingår i: PHYSICAL REVIEW B. ; 67:11
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Tidskriftsartikel (refereegranskat)abstract
- Boundary roughness scattering in disordered tunnel-coupled quantum wires in the presence of a magneticfield is considered. The low-temperature conductance as a function of applied magnetic field is calculated fordifferent structure and disorder parameters using the method of the generalized S-matrix composition.We showthat despite the fact that lateral wire width fluctuations of the size of few atomic layers may significantly shiftthe partial energy gap, the effect of the conductance enhancement at energies in the partial energy gap doestake place in sufficiently strong magnetic fields and small correlation length of the disorder defined as theaverage distance between the neighboring discontinuities of the boundary profile. The last parameter is shownto be particularly important for the determination of the transport properties of the system. Remarkably, we findthat in a wide range of system parameters the conductance decreases with the correlation length despite thedecreasing number of boundary discontinuities.
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| 7. |
- Arapan, Sergiu, et al.
(författare)
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Effect of the boundary roughness on the conductance of double quantum wire in a magnetic field
- 2003
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Ingår i: EUROPHYSICS LETTERS. ; 64, s. 239-245
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Forskningsöversikt (populärvet., debatt m.m.)abstract
- We investigate the effect of the boundary roughness scattering on the conductance of a disordered tunnel-coupled quantum wire in the presence of a magnetic field. It is shown that the average distance between the neighboring discontinuities of the boundary profile plays an important role in the transport properties of the system and the manifestation of the localization-delocalization effect. Present studies point out a new effect consisting in thedecrease of the conductance with the increase of the disorder correlation length.
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| 8. |
- Bask, Michael, et al.
(författare)
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Model-based supervision of valves in a flotation process
- 2003
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Ingår i: 42nd IEEE International Conference on Decision and Control. - Piscataway, NJ : IEEE Communications Society. - 0780379241 ; , s. 744-749
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Konferensbidrag (refereegranskat)abstract
- An observer based approach for detecting clogging in valves in flotation processes is investigated. Integral action and linear feedback applied to a nonlinear process model constitutes the observer for which local stability is shown. The integral terms give estimates of the clogging in the valves of the process and this estimate is compared to a constant threshold. Experiments on real data from Boliden's flotation series at the Boliden Area Concentrator, Sweden, show no false alarm during any of the two working conditions, PI control and LQ control. It is also shown that cloggings, simulated by manipulating measurement data, are promptly detected. The observer based fault detection algorithm is compared to an algorithm based on parameter estimation and advantages of the two approaches are highlighted.
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| 9. |
- Bask, Michael, et al.
(författare)
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Robust time-varying thresholds for supervision of valves in a flotation process
- 2004
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Ingår i: 2004 43rd IEEE Conference on Decision and Control. - Piscataway, NJ : IEEE Communications Society. - 0780386825 ; , s. 4305-4310
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Konferensbidrag (refereegranskat)abstract
- Robust thresholds for observer-based residuals are developed for the purpose of detecting clogging in the valves of a flotation process. The observer in the residual generator is a linear model of the flotation process extended with integrators and corrected with a linear feedback term. The integral states in the observer constitute the residual. Contribution to the residual comes not only from the faults but also from uncertainties in measurements, estimates and working point To avoid false alarms generated by these uncertainties, robust time-varying thresholds depending on the uncertainties are derived. Experiments on a froth flotation process with four cascade coupled tanks are carried out successfully. The data was provided by Boliden Area Concentrator in Boliden, Sweden.
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| 10. |
- Blideanu, V., et al.
(författare)
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Nucleon-induced reactions at intermediate energies : New data at 96 MeV and theoretical status
- 2004
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Ingår i: Physical Review C. Nuclear Physics. - 0556-2813 .- 1089-490X. ; 70:1, s. 014607-
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Tidskriftsartikel (refereegranskat)abstract
- Double-differential cross sections for light charged particle production (up to A=4) were measured in 96 MeV neutron-induced reactions, at the TSL Laboratory Cyclotron in Uppsala (Sweden). Measurements for three targets, Fe, Pb, and U, were performed using two independent devices, SCANDAL and MEDLEY. The data were recorded with low-energy thresholds and for a wide angular range (20°–160°). The normalization procedure used to extract the cross sections is based on the np elastic scattering reaction that we measured and for which we present experimental results. A good control of the systematic uncertainties affecting the results is achieved. Calculations using the exciton model are reported. Two different theoretical approaches proposed to improve its predictive power regarding the complex particle emission are tested. The capabilities of each approach is illustrated by comparison with the 96 MeV data that we measured, and with other experimental results available in the literature.
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