| 1. |
- Andersson, Mike, et al.
(författare)
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On the CO response mechanism of SiC based field effect gas sensors
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- The response characteristics of Metal Insulator Silicon Carbide (MISiC) field effect sensor devices, with platinum (Pt) as the metal contact, towards carbon monoxide (CO) at varying oxygen (O2) concentrations and over a wide range of temperatures have been investigated in detail at atmospheric pressure. The influence of hydrogen (H2) on the CO response was also studied. Sensor devices with thin, porous as well as dense, homogeneous Pt films on top of both silicon dioxide (SiO2) and magnesium oxide (MgO) as insulator materials were investigated in this study. The reaction products generated on the sensor surfaces were also monitored with a mass spectrometer connected to the gas flow just downstream of the sensor location and the results compared to CO oxidation characteristics over Pt/SiO2 and to some extent Pt/MgO catalysts as reported in literature. By correlating the response characteristics of these devices with CO2 formation and hydrogen consumption on the sensor surfaces, strong indications for a CO response mechanism involving a CO induced increased sensitivity to background hydrogen have been obtained, this mechanism being hypothesized to be the only one behind the CO sensitivity of devices with dense Pt metal contacts. The results also give further support to the idea that also other processes than an increased sensitivity to background hydrogen contribute to the CO response of sensor devices with a porous platinum film as the metal contact, one candidate being the removal of oxygen anions from the surface of exposed oxide areas through the oxidation reaction with CO.
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| 2. |
- Andersson, Mike, et al.
(författare)
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On the response mechanism of SiC based field effect gas sensors towards non-hydrogen containing species and specifically NO
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- The response characteristics of Metal Insulator Silicon Carbide (MISiC) field effect sensor devices, with platinum (Pt) as the metal contact, towards nitrogen oxide (NO) for both low as well as relatively high background oxygen (O2) concentrations and different temperatures have been investigated at atmospheric pressure. Devices with both porous and dense Pt metal gate contacts have been investigated and the results seem to confirm the theories and results from earlier measurements regarding the requirement of porous metal films for the existence of a response to NO for this kind of sensor device. The results also suggest that no NO induced increased sensitivity to background hydrogen exists, at least it does not play any role in the observed NO sensitivity, as opposed to what has been suggested in the case of CO. The obtained results are also discussed in relation to some of the proposed sensing mechanisms for non-hydrogen containing substances and in comparison to NO reduction characteristics on Pt/SiO2 catalysts, as reported in literature. The results further give some indications about also some other process/ processes being important for the response of SiC based field effect sensors towards NO than just adsorption/desorption.
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| 3. |
- Bonn, Stephanie Erika, et al.
(författare)
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App Technology to Support Physical Activity and Intake of Vitamins and Minerals After Bariatric Surgery (the PromMera Study): Protocol of a Randomized Controlled Clinical Trial
- 2020
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Ingår i: JMIR Research Protocols. - : JMIR PUBLICATIONS, INC. - 1929-0748. ; 9:8
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Tidskriftsartikel (refereegranskat)abstract
- Background: To optimize postoperative outcomes after bariatric surgery, lifestyle changes including increased physical activity are needed. Micronutrient deficiency after surgery is also common and daily supplementation is recommended. Objective: The aim of the PromMera study is to evaluate the effects of a 12-week smartphone app intervention on promotion of physical activity (primary outcome) and adherence to postsurgery vitamin and mineral supplementation, as well as on other lifestyle factors and overall health in patients undergoing bariatric surgery. Methods: The PromMera study is a two-arm, randomized controlled trial comprising patients undergoing bariatric surgery. Participants are randomized postsurgery 1:1 to either the intervention group (ie, use of the PromMera app for 12 weeks) or the control group receiving only standard care. Clinical and lifestyle variables are assessed pre- and postsurgery after 18 weeks (postintervention assessment), 6 months, 1 year, and 2 years. Assessments include body composition using Tanita or BOD POD analyzers, muscle function using handgrip, biomarkers in blood, and an extensive questionnaire on lifestyle factors. Physical activity is objectively measured using the ActiGraph wGT3X-BT triaxial accelerometer. Results: A total of 154 participants have been enrolled in the study. The last study participant was recruited in May 2019. Data collection will be complete in May 2021. Conclusions: Implementing lifestyle changes are crucial after bariatric surgery and new ways to reach patients and support such changes are needed. An app-based intervention is easily delivered at any time and can be a key factor in the adoption of healthier behavioral patterns in this rapidly growing group of patients.
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| 4. |
- Bonn, Stephanieb E. E., et al.
(författare)
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Effect of a Smartphone Application on Physical Activity and Weight Loss After Bariatric Surgery-Results from a Randomized Controlled Trial
- 2023
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Ingår i: Obesity Surgery. - : SPRINGER. - 0960-8923 .- 1708-0428. ; 33:9, s. 2841-2850
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Tidskriftsartikel (refereegranskat)abstract
- Purpose Ways to motivate and support patients in being physically active after bariatric surgery are needed. This trial was aimed at evaluating the effect of using a smartphone application targeting physical activity during 12 weeks on moderate-to-vigorous physical activity (MVPA, primary outcome) and secondary outcomes of inactivity, light physical activity (LPA), body mass index (BMI), and percent total weight loss (%TWL) after bariatric surgery.Materials and Methods Data from a randomized controlled trial comprising 146 patients (79.5% women) undergoing bariatric surgery was analyzed. Mean age and BMI pre-surgery were 40.9 years and 40.5 kg/m(2), respectively. Participants were randomized 1:1 to an intervention or a control group. Physical activity and body weight were objectively measured at baseline pre-surgery and post-surgery follow-ups after 6 weeks (weight only), 18 weeks, 6 months, and 1 year. Linear mixed models were fitted to assess longitudinal differences in outcomes between the groups.Results A significant effect of the intervention (group-by-time interaction 16.2, 95% CI 3.5 to 28.9) was seen for MVPA at 18 weeks; the intervention group had increased their MVPA since baseline, while the control group had decreased their MVPA. The control group had lowered their BMI approximately 1 kg/m(2) more than the intervention group at follow-up after 18 weeks and 12 months, yet, mean BMI did not differ between the groups. No intervention effect was seen on inactivity, LPA, or %TWL.ConclusionOur results indicate that use of a smartphone application targeting physical activity may have the potential to promote short-term MVPA post bariatric surgery.
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| 5. |
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| 6. |
- Buchholt, Kristina, 1978-, et al.
(författare)
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Electrochemically Synthesised Pd- and Au-nanoparticles as sensing layers in NOx-sensitive field effect devices
- 2008
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Ingår i: Smart Sensors and Sensing Technology. - Berlin, Heidelberg : Springer. - 9783540795896 - 9783540795902 ; , s. 63-75
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- An environmental pollutant of great concern is NOx (nitrogen monoxide and nitrogen dioxide). Here we report the utilisation of electrochemically synthesised gold and palladium nanoparticles as catalytically active gate material on gas sensitive field effect sensor devices. The synthesised nanoparticles have been characterised by TEM and XPS, and the morphology of the thermally treated nanostructured sensing layers has been investigated using SEM and XPS. Measurements on the gas response of the palladium as well as the gold nanoparticle sensors towards a number of analytes found in automotive gas exhausts were performed and their response patterns were compared. The initial gas response measurements show interesting sensing properties for both the gold and the palladium nanoparticle sensors towards NOx detection.
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| 7. |
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| 8. |
- Buchholt, Kristina, et al.
(författare)
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Growth and characterization of epitaxial Ti3GeC2 thin films on 4H-SiC(0001)
- 2012
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Ingår i: Journal of Crystal Growth. - : Elsevier. - 0022-0248 .- 1873-5002. ; 343:1, s. 133-137
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Tidskriftsartikel (refereegranskat)abstract
- Epitaxial Ti3GeC2 thin films were deposited on 4 degrees off-cut 4H-SiC(0001) using magnetron sputtering from high purity Ti, C, and Ge targets. Scanning electron microscopy and helium ion microscopy show that the Ti3GeC2 films grow by lateral step-flow with {11 (2) over bar0} faceting on the SiC surface. Using elastic recoil detection analysis, atomic force microscopy, and X-Ray diffraction the films were found to be substoichiometric in Ge with the presence of small Ge particles at the surface of the film.
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| 9. |
- Buchholt, Kristina, 1978-
(författare)
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Nanostructured materials for gas sensing applications
- 2011
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- In this Thesis I have investigated the use of nanostructured films as sensing and contact layers for field effect gas sensors in order to achieve high sensitivity, selectivity, and long term stability of the devices in corrosive environments at elevated temperatures. Electrochemically synthesized Pd and Au nanoparticles deposited as sensing layers on capacitive field effect devices were found to give a significant response to NOx with small, or no responses to H2, NH3, and C3H6. Pt nanoparticles incorporated in a TiC matrix are catalytically active, but the agglomeration and migration of the Pt particles towards the substrate surface reduces the activity of the sensing layer. Magnetron sputtered epitaxial films from the Ti-Si-C and the Ti-Ge-C systems were grown on 4H-SiC substrates in order to explore their potential as high temperature stable ohmic contact materials to SiC based field effect gas sensors. Ti3SiC2 thin films deposited on 4H-SiC substrates were found to yield ohmic contacts to n-type SiC after a high temperature rapid thermal anneal at 950 ºC. Investigations on the growth mode of Ti3SiC2 thin films with varying Si content on 4H-SiC substrates showed the growth to be lateral step-flow with the propagation of steps with a height as small as half a unit cell. The amount of Si present during deposition leads to differences in surface faceting of the films and Si-supersaturation conditions gives growth of Ti3SiC2 films with the presence of TiSi2 crystallites. Current-voltage measurements of the as-deposited Ti3GeC2 films indicate that this material is also a promising candidate for achieving long term stable contact layers to 4H-SiC for operation at elevated temperatures in corrosive environments. Further investigations into the Ti-Ge-C system showed that the previously unreported solid solutions of (Ti,V)2GeC, (Ti,V)3GeC2 and (Ti,V)4GeC3 can be synthesized, and it was found that the growth of these films is affected by the nature of the substrate.
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| 10. |
- Buchholt, Kristina, et al.
(författare)
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Ohmic contact properties of magnetron sputtered Ti3SiC2 on n- and p-type 4H-silicon carbide
- 2011
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Ingår i: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 98:4, s. 042108-
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Tidskriftsartikel (refereegranskat)abstract
- Epitaxial Ti3SiC2 (0001) thin film contacts were grown on doped 4H-SiC (0001) using magnetron sputtering in an ultra high vacuum system. The specific contact resistance was investigated using linear transmission line measurements. Rapid thermal annealing at 950 degrees C for 1 min of as-deposited films yielded ohmic contacts to n-type SiC with contact resistances in the order of 10(-4) Omega cm(2). Transmission electron microscopy shows that the interface between Ti3SiC2 and n-type SiC is atomically sharp with evidence of interfacial ordering after annealing. (c) 2011 American Institute of Physics.
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