| 1. |
- Candinas, R, et al.
(författare)
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Impact of fusion avoidance on performance of the automatic threshold tracking feature in dual chamber pacemakers: A multicenter prospective randomized study
- 2002
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Ingår i: PACE. - : Wiley. - 1540-8159. ; 25:11, s. 1540-1545
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Tidskriftsartikel (refereegranskat)abstract
- The Autocapture algorithm enables automatic capture verification on a beat-by-beat basis by recognizing the evoked response signal following each pacemaker stimulus. The algorithm intends to increase patient safety while decreasing energy consumption. However, the occurrence of fusion beats, particularly during dual chamber pacing, may limit the energy saving effect of Autocapture. The aim of this multicenter, prospective, randomized study was to evaluate the impact of the Fusion Avoidance (FA) algorithm on the incidence of fusion beats. Thirty-eight patients (mean age 69 +/- 13 years) with intrinsic AV conduction who were implanted with an Affinity DR were studied. After programming a PV/AV delay of 120/190 ms, patients were randomized to FA On or Off. Each group was further randomized with respect to activation of the AutoIntrinsic Conduction Search (AICS) algorithm. The total number of beats, ventricular paced beats, fusion beats, backup pulses, and threshold searches were analyzed from 24-hour Holter recordings. The number of total beats was comparable in both FA groups. The number of total ventricular paced beats, fusion beats, backup pulses, and threshold searches were significantly reduced in the FA On group (% reduction: 68% P < 0.001, 75% P < 0.01, 95% P < 0.01, and 94% P < 0.05, respectively). The number of ventricular paced beats with full capture was significantly reduced when AICS was activated (P < 0.05). In conclusion, the FA algorithm substantially reduces the amount of ventricular paced beats, fusion beats, unnecessary backup pulses and threshold searches, and therefore, provides added benefits in energy saving obtained by Autocapture.
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| 2. |
- Wittborn, J., et al.
(författare)
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Magnetic domain and domain-wall imaging of submicron Co dots by probing the magnetostrictive response using atomic force microscopy
- 2000
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Ingår i: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 76:20, s. 2931-2933
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Tidskriftsartikel (refereegranskat)abstract
- An approach to image the domains and domain walls of small ferromagnetic entities using atomic force microscopy (AFM), with a nonmagnetic AFM probe, has been developed. Exciting the sample in an external ac magnetic field, the distribution of magnetostrictive response at the surface is detected. By this technique, the domains and domain walls of submicron Co dots have been imaged with a 1 nm lateral resolution. In elliptical Co dots with a 350-nm-long axis on a triangular lattice array with 400 nm periodicity, we find evidence for two domains with opposite magnetization orientation across a wall. The domain-wall width in these dots is found to be about 35 nm. Furthermore, we observe a ferromagnetic alignment of the domains in the neighboring dots, which suggests a magnetostatic interaction among the dots.
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| 3. |
- Batlle, X., et al.
(författare)
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Quantitative x-ray photoelectron spectroscopy study of Al/AlOx bilayers
- 2002
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Ingår i: Journal of Applied Physics. - : AIP Publishing. - 0021-8979 .- 1089-7550. ; 91:12, s. 10163-10168
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Tidskriftsartikel (refereegranskat)abstract
- An x-ray photoelectron spectroscopy (XPS) analysis of Nb/Al wedge bilayers, oxidized by both plasma and natural oxidation, is reported. The main goal is to show that the oxidation state-i.e., O:(oxidize)Al ratio-, structure and thickness of the surface oxide layer, as well as the thickness of the metallic Al leftover, as functions of the oxidation procedure, can be quantitatively evaluated from the XPS spectra. This is relevant to the detailed characterization of the insulating barriers in (magnetic) tunnel junctions.
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| 4. |
- Batlle, X., et al.
(författare)
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The oxidation state at tunnel junction interfaces
- 2003
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Ingår i: Journal of Magnetism and Magnetic Materials. - 0304-8853 .- 1873-4766. ; 260:02-jan, s. 78-83
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Tidskriftsartikel (refereegranskat)abstract
- The oxidation state at the interfaces of Nb/Al-AlOx/Pb junctions is discussed. Conductance-voltage curves below and above the superconducting temperature suggest tunneling conduction, while X-ray photoelectron spectroscopy shows the existence of a thin AlOx layer at the Nb/Al interface. We demonstrate that at the usual 10(-7) Torr range of base pressures in the sputtering chamber, this is due to the time elapsed between the deposition of the Nb and Al bottom layers, in both Nb/Al-AlOx/Pb tunnel junctions and Nb/Al bilayers. We also give some direct evidence of the oxidation of the top Pb electrode on the Nb electrode surface. Such oxidation probably occurs at the pinholes of the intermediate Al-AlOx layer of the tunnel junctions, as a consequence of the oxidation state at the Nb/Al interface, which helps to avoid barrier shorts and enhances the quality of the tunnel barrier. We therefore suggest that there is oxide formation in other places besides where there is an actual oxide deposited. This is relevant for the performance of magnetic tunnel junctions since in most tunneling studies it is assumed that once the oxide is deposited, that is the only place where there is an oxide. This is also a very general statement applicable to thin film systems.
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| 5. |
- Stensson, Annika, et al.
(författare)
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Industry demands on vehicle development - methods and tools
- 2000
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Ingår i: Vehicle System Dynamics. - : Taylor & Francis Ltd.. - 0042-3114 .- 1744-5159. ; 33:Suppl, s. 202-213
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Tidskriftsartikel (refereegranskat)abstract
- A very important goal of mechatronics in system development is the integration of mechanical, electronic and software subsystems in order to increase functionality, minimize weight, and reduce production costs. In this work, industry demands on methods and tools for mechatronic vehicle development are addressed from the current product development in industry. The development of a mechatronic car door concept and dynamic stability control are used as examples to identify strong and weak parts of the current processes. Railway vehicle development aspects are also discussed. It is shown that a very important aspect for a successful mechatronic design is co-operation in an interdisciplinary design team. In terms of design methodology, the systematic identification of mechatronic potential based on function analysis is a main issue. Computer tools and technology for concept simulation, co-simulation, managing of models with different complexity as well as model exchange are identified as important demands for future effective development of mechatronic vehicles.
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| 6. |
- Stoll, O. M., et al.
(författare)
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Hysteresis and fractional matching in thin Nb films with rectangular arrays of nanoscaled magnetic dots
- 2002
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Ingår i: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121 .- 1550-235X. ; 65:10
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Tidskriftsartikel (refereegranskat)abstract
- We have investigated the periodic pinning of magnetic flux quanta in thin Nb films with rectangular arrays of magnetic dots. In this type of pinning geometry, a change in the periodicity and shape of the minima in the magnetoresistance occurs for magnetic fields exceeding a certain threshold value. This was explained recently in terms of a reconfiguration transition of the vortex lattice due to an increasing vortex-vortex interaction with increasing magnetic field. In this picture the dominating elastic energy at high fields forces the vortex lattice to form a square symmetry, rather than being commensurate with the rectangular geometry of the pinning array. In this paper we present a comparative study of rectangular arrays with Ni dots, Co dots, and holes. In the magnetic dot arrays we found a strong fractional matching effect up to the second-order matching field. In contrast, no clear fractional matching is seen after the reconfiguration. Additionally, we discover the existence of hysteresis in the magnetoresistance in the crossover between the low- and high-field regimes. We find evidence that this effect is correlated with the reconfiguration phenomenon rather than to the magnetic state of the dots. The temperature and angular dependences of the effect are measured, and possible models are discussed to explain this behavior.
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| 7. |
- Åkerman, Johan, et al.
(författare)
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Criteria for ferromagnetic-insulator-ferromagnetic tunneling
- 2002
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Ingår i: Journal of Magnetism and Magnetic Materials. - 0304-8853 .- 1873-4766. ; 240:03-jan, s. 86-91
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Tidskriftsartikel (refereegranskat)abstract
- The Rowell criteria, commonly used to identify tunneling in magnetic tunnel junctions (MTJ), are scrutinized. While neither the exponential-thickness dependence of the conductivity nor fits of non-linear transport data are found to be reliable tunneling criteria, the temperature-dependent conductivity does remain a solid criterion. Based on experimental studies of the bias and temperature-dependent resistance and magnetoresistance of MTJs, with and without shorted barriers, a new set of criteria is formulated.
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| 8. |
- Åkerman, Johan, et al.
(författare)
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Origin of temperature dependence in tunneling magnetoresistance
- 2003
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Ingår i: Europhysics letters. - : IOP Publishing. - 0295-5075 .- 1286-4854. ; 63:1, s. 104-110
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Tidskriftsartikel (refereegranskat)abstract
- We present detailed measurements of the differential resistance (dV/dI) of state-of-the-art FM/AlOx/FM magnetic tunnel junctions (MTJ) as a function of applied bias and temperature. Temperature effects are particularly significant in physical quantities involving narrow features such as those at low-voltage bias. We show that the temperature evolution of the tunneling characteristics and, in particular, the pronounced rounding of the dV/dI curves with increasing temperature can be well explained by thermal smearing of the tunneling electron energy distribution.
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| 9. |
- Åkerman, Johan, et al.
(författare)
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Tunneling criteria for magnetic-insulator-magnetic structures
- 2001
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Ingår i: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 79:19, s. 3104-3106
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Tidskriftsartikel (refereegranskat)abstract
- The bias and temperature dependent resistance and magnetoresistance of magnetic tunnel junctions with and without intentional shorts through the insulating barrier were studied. Based on the experimental results, a set of quality criteria was formulated that enables the identification of barrier shorts. While the temperature and bias dependencies of the junction resistance and of the fitted barrier parameters are very sensitive to the presence of such shorts, the same dependencies of the magnetoresistance are surprisingly insensitive. Finally, junctions with a shorted barrier exhibit a dramatic increase in noise level and junction instability.
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