| 1. |
- Berglund, Jan, 1950-, et al.
(författare)
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Long-term results of above knee femoro-popliteal bypass depend on indication for surgery and graft-material
- 2005
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Ingår i: European Journal of Vascular and Endovascular Surgery. - : Elsevier BV. - 1078-5884 .- 1532-2165. ; 29:4, s. 412-418
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Tidskriftsartikel (refereegranskat)abstract
- Objective. To determine the long-term results of above-knee femoro-popliteal bypass with autologous saphenous vein (SV) or expanded polytetrafluoroethylene (ePTFE) in routine surgical practice. Methods. Data from the Swedish vascular registry, Swedvasc was reviewed retrospectively. Patients with bypass surgery in 1996 and 1997 were assessed 5-7 years later. Data were gathered from the case-records and from clinical follow-up. The composite endpoint of graft failure included death within 30 days, occlusion, major amputation, extension of the graft to below-knee position and removal of an infected graft. Kaplan-Meier curves and Cox' proportional hazard ratios were calculated. Results. Four hundred and ninety-nine patients undergoing bypass for critical limb ischemia (CLI) (56%) or claudication (44%), SV (28%) or ePTFE (72%), were included. There were no significant differences in patient characteristics between patients with SV or ePTFE. CLI and ePTFE were risk factors for graft failure. For patients with both claudication and CLI SV grafts yielded better long-term results than ePTFE grafts (p<0.03) and (p<0.003), respectively. Symptom aggravation after graft occlusion was almost exclusively restricted to ePTFE grafts. Conclusions. Femoro-popliteal bypass above-knee with SV gives good long-term results, especially for claudication. ePTFE grafts cannot be recommended in claudicants, since occlusion occurs often and frequently leads to CLI. © 2005 Elsevier Ltd. All rights reserved.
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| 2. |
- Elfström, Niklas, et al.
(författare)
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Avalanche breakdown in surface modified silicon nanowires
- 2007
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Ingår i: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 91:10, s. 103502-1-103502-3
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Tidskriftsartikel (refereegranskat)abstract
- The electrical conductance of semiconductor nanowires can be changed by charges present on the nanowire surface. At high surface charge density, however, the nanowire channel may be quenched leading to a large shift in the I-DS-V-DS characteristics. In this letter, the authors demonstrate that this shift in V-DS is related to an avalanche effect in the nanowire. Silicon nanowires were fabricated in a top-down approach and the nanowire surface charge density was modified through buffer solutions of different pH values. Computer simulations using representative surface charge and interface charge densities clearly reproduce the data and unambiguously demonstrate the avalanche effect.
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| 3. |
- Elfström, Niklas, et al.
(författare)
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Biomolecule detection using a silicon nanoribbon : Accumulation mode versus inversion mode
- 2008
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Ingår i: Nanotechnology. - : IOP Publishing. - 0957-4484 .- 1361-6528. ; 19:23, s. 235201-
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Tidskriftsartikel (refereegranskat)abstract
- Silicon nanoribbons were fabricated using standard optical lithography from silicon on insulator material with top silicon layer thicknesses of 100, 60 and 45 nm. Electrically these work as Schottky-barrier field-effect transistors and, depending on the substrate voltage, electron or hole injection is possible. The current through the nanoribbon is extremely sensitive to charge changes at the oxidized top surface and can be used for biomolecule detection in a liquid. We show that for detection of streptavidin molecules the response is larger in the accumulation mode than in the inversion mode, although not leading to higher detection sensitivity due to increased noise. The effect is attributed to the location in depth of the conducting channel, which for holes is closer to the screened surface charges of the biomolecules. Furthermore, the response increases for decreasing silicon thickness in both the accumulation mode and the inversion mode. The results are verified qualitatively and quantitatively through a two-dimensional simulation model on a cross section along the nanoribbon device.
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| 4. |
- Elfström, Niklas, et al.
(författare)
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Sensitivity of silicon nanowires in biosensor applications
- 2008
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Ingår i: Journal of Physics, Conference Series. - : IOP Publishing. - 1742-6588 .- 1742-6596. ; 100:PART 5
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Tidskriftsartikel (refereegranskat)abstract
- A 2-dimensional simulation tool was designed to investigate the threshold voltage behaviour for a silicon nanowire constructed in a top down approach on silicon on insulator (SOI) material. The simulation shows, assuming a positive charge of +1.10(11) cm(-2) between the silicon/silicon dioxide interface and negatively charged surface states on top of the nanowire that the threshold voltage increases with decreasing height of the nanowire.
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| 5. |
- Elfström, Niklas, et al.
(författare)
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Silicon Nanoribbons for Electrical Detection of Biomolecules
- 2008
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Ingår i: Nano letters (Print). - : American Chemical Society (ACS). - 1530-6984 .- 1530-6992. ; 8:3, s. 945-949
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Tidskriftsartikel (refereegranskat)abstract
- Direct electrical detection of biomolecules at high sensitivity hat recently been demonstrated using semiconductor nanowires. Here we demonstrate that semiconductor nanoribbons, in this case, a thin sheet of silicon on an oxidized silicon substrate, can approach the same sensitivity extending below the picomolar concentration regime in the biotin/streptavidin case. This corresponds to less than similar to 20 analyte molecules bound to receptors on the nanoribbon surface. The micrometer-size lateral dimensions of the nanoribbon enable optical lithography to be used, resulting in a simple and high-yield fabrication process. Electrical characterization of the nanoribbons is complemented by computer simulations showing enhanced sensitivity for thin ribbons. Finally, we demonstrate that the device can be operated both in inversion as well as in accumulation mode and the measured differences in detection sensitivity are explained in terms of the distance between the channel and the receptor coated surface with respect to the Debye screening length. The nanoribbon approach opens up for large scale CMOS fabrication of highly sensitive biomolecule sensor chips for potential use in medicine and biotechnology.
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| 6. |
- Elfström, Niklas, 1979-
(författare)
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Silicon Nanowires for Biomolecule Detection
- 2008
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Starting from silicon on insulator (SOI) material, with a top silicon layer thickness of 100 nm, silicon nanowires were fabricated in a top down approach using electron beam (e-beam) lithography and subsequent eactive ion etching (RIE) and oxidation. Nanowires as narrow as 30 nm could be achieved. Further size reduction was done using electrochemical etching and/or oxidation. The nanowires were contacted creating drain, source and back gate contacts and characterized showing similar behavior as Schottky Barrier Metal Oxide Semiconductor Field Effect Transistors (SB-MOSFETs). As an alternative, by thinning the top silicon layer down nanoribbons, ~ 1 μm wide, with a thickness down to 45 nm could be produced using standard optical lithography showing similar behavior as the nanowires. The conduction mechanism for these devices is through electrons in an inversion current layer for positive back gate voltages and through holes in accumulation mode for negative back gate voltages. When the threshold voltage is extrapolated for the nanowires and the nanoribbons it scales with inverse width and thickness respectively, attributed to charged surface and/or interface states affecting more narrow/thinner devices essentially due to increased surface to volume ratio. Nanowires were functionalized with 3-aminopropyl triethoxysilane (APTES) molecules creating amino groups on the surface reactive to pH buffer solutions. By exposing the nanowires to buffer solutions of different pH value the conduction mechanism changed due to the surface becoming more or less negative. Threshold voltage shifts from pH = 3 to pH = 9 were seen to scale with inverse width again attributed to the larger surface to volume ratio for more narrow devices. Simulations confirm this behavior and further show that a charge change of a few elementary charges on the nanowire surface can alter the conductance significantly. Upon addition of the buffer solutions the channel is seen to be quenched for small drain bias attributed to negative surface charges screening the electron current. However, as the drain bias is increased the channel is restored. Computer simulations confirmed this behavior and further showed that the restoration of the channel was due to an avalanche process. A biomolecule detection experiment was set up using the specific binding of biotin to streptavidin. By functionalizing the nanoribbon with biotin molecules the current can be logged and as streptavidin molecules are added the current decreases (increases) if the nanoribbon is run in inversion (accumulation) mode due to the negative charge of the streptavidin molecule, delivered upon binding to biotin. A sensitivity significantly below the picomolar range was observed, corresponding to less than 20 streptavidin molecules attaching to the nanoribbon surface, assuming a homogeneous binding to the biotinylated surface. By decreasing the nanoribbon thickness the response was increased, a behavior attributed to the larger surface to volume ratio of these devices. The response was seen to be larger in the accumulation mode whereas close to the lower oxide in inversion mode. Computer simulations showed that this was due to the hole current running closer to the functionalized surface in accumulation mode and opposite in inversion mode. This was further investigated for different nanoribbon thicknesses and the response was shown to increase with inverse nanoribbon thickness again attributed to the larger surface to volume ratio. The nanoribbon has the advantage of simpler fabrication using standard optical lithography in comparison with e-beam lithography and it may provide a useful scheme for a practical biomolecule sensor.
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| 7. |
- Elfström, Niklas, et al.
(författare)
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Surface Charge Sensitivity of Silicon Nanowires : Size Dependence
- 2007
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Ingår i: Nano letters (Print). - : American Chemical Society (ACS). - 1530-6984 .- 1530-6992. ; 7:9, s. 2608-2612
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Tidskriftsartikel (refereegranskat)abstract
- Silicon nanowires of different widths were fabricated in silicon on insulator (SOI) material using conventional process technology combined with electron-beam lithography. The aim was to analyze the size dependence of the sensitivity of such nanowires for biomolecule detection and for other sensor applications. Results from electrical characterization of the nanowires show a threshold voltage increasing with decreasing width. When immersed in an acidic buffer solution, smaller nanowires exhibit large conductance changes while larger wires remain unaffected. This behavior is also reflected in detected threshold shifts between buffer solutions of different pH, and we find that nanowires of width > 150 nm are virtually insensitive to the buffer pH. The increased sensitivity for smaller sizes is ascribed to the larger surface/volume ratio for smaller wires exposing the channel to a more effective control by the local environment, similar to a surrounded gate transistor structure. Computer simulations confirm this behavior and show that sensing can be extended even down to the single charge level.
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| 8. |
- Juhasz, Robert, et al.
(författare)
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Controlled Fabrication of Silicon Nanowires by Electron Beam Lithography and Electrochemical Size Reduction
- 2005
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Ingår i: Nano letters (Print). - : American Chemical Society (ACS). - 1530-6984 .- 1530-6992. ; 5:2, s. 275-280
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Tidskriftsartikel (refereegranskat)abstract
- We demonstrate that electrochemical size reduction can be used for precisely controlled fabrication of silicon nanowires of widths approaching the 10 nm regime. The scheme can, in principle, be applied to wires defined by optical lithography but is here demonstrated for wires of similar to100-200 nm width, defined by electron beam lithography. As for electrochemical etching of bulk silicon, the etching can be tuned both to the pore formation regime as well as to electropolishing. By in-situ optical and electrical characterization, the process can be halted at a certain nanowire width. Further electrical characterization shows a conductance decreasing faster than dimensional scaling would predict. As an explanation, we propose that charged surface states play a more pronounced role as the nanowire cross-sectional dimensions decrease.
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| 9. |
- Nahlen Bose, Catarina
(författare)
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Coping and emotional well-being in patients with chronic heart failure
- 2015
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Background: Chronic heart failure (CHF) is a serious illness, with a profound impact on the patient. Poor health-related quality of life (HRQoL) as well as anxiety and depression are prevalent in CHF and predict mortality and rehospitalization, yet, psychosocial factors are infrequently treated and cared for.Aim: To gather scientific evidence on illness perception and coping strategies to predict emotional well-being in patients with CHF and to establish a measurement model of coping strategies. Furthermore, to evaluate a nurse-led psychoeducational intervention, Coping Effectiveness Training (CET) adapted for patients with CHF.Methods: Studies I-III were cross sectional. Study IV was a randomized controlled trial aimed to improve emotional well-being (one-year follow-up). All studies used patient reported outcome measures and clinical data via medical journals.Results: Younger age and male gender were associated with higher levels of alcohol usage and/or drugs to cope, p < 0.01. Poor sense of coherence was associated with maladaptive coping (I). A four factorial model of Brief COPE displayed the best psychometric properties (II). Avoidant coping influenced negative affect (NA) (I), worse HRQoL (II) and greater anxiety and depression (III). CET (IV) improved personal control in the intervention group (IG) compared to the control group (CG), p = 0.036. Improved scores for the IG were detected in emotional well-being and HRQoL, p = ns. The IG demonstrated reduced NA, p = 0.022, excluding cases with clinical anxiety and depression. Time to cardiovascular readmission or death was non-significantly lower in the IG vs the CG (Hazard ratio 0.58 [0.29-1.18]) adjusted p = 0.135.Conclusions: Personal resources seemed to influence the coping strategies used by patients with CHF. Avoidant coping had an adverse influence on emotional wellbeing and illness perception in CHF. The perceived sense of control and illness burden were of importance for emotional well-being. A CET intervention for patients with CHF increased sense of control over the illness. CET also reduced NA in patients with no or mild symptoms of anxiety and depression.
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| 10. |
- Nicklasson, Mercedes, 1958, et al.
(författare)
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The impact of individual quality of life assessment on psychosocial attention in patients with chest malignancies: A randomized study
- 2013
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Ingår i: Supportive Care in Cancer. - : Springer Science and Business Media LLC. - 0941-4355 .- 1433-7339. ; 21:1, s. 87-95
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Tidskriftsartikel (refereegranskat)abstract
- PurposeThe aims of this study were to investigate the impact of individual health-related quality of life (HRQL) evaluation on the attention towards symptom control and psychosocial function in advanced cancer patients.MethodsPatients with advanced lung cancer or mesothelioma who attended a pulmonary oncology outpatient clinic were randomized to either of two strategies for HRQL assessment. The experimental group (EG) answered the EORTC QLQ-C30 + LC13 questionnaire using a digital table interface, with outprint of aggregated scale scores presented to the consulting physician as a support for evaluation. The control group (CG) answered a paper version of the same questionnaire, which was stored for later analysis. Consultations were audio-recorded. Outcome measures were a quantitative content analysis of audio-recorded consultations and medical and psychosocial interventions abstracted from clinical records.ResultsOne hundred seventy-one patients were randomized and participated in the study. Issues regarding emotional function were more frequently discussed during consultations in the EG (p < 0.05). Similarly, interventions directed to emotional and social concerns were more frequent in the EG (p = 0.013 and p = 0.0036, respectively). HRQL measures over time were similar across the groups.ConclusionIndividual HRQL assessment increased the attention to psychosocial functioning in patients with chest malignancies.
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