| 1. |
- Anna Karin, Hedström, et al.
(författare)
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The impact of bariatric surgery on disease activity and progression of multiple sclerosis : A nationwide matched cohort study
- 2022
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Ingår i: Multiple Sclerosis Journal. - : Sage Publications. - 1352-4585 .- 1477-0970. ; 28:13, s. 2099-2105
-
Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: Surgical outcomes in patients with multiple sclerosis (MS) following metabolic surgery appear to be similar compared to those of the general bariatric population.OBJECTIVE: To study the impact of metabolic surgery on the clinical course of MS.METHODS: Using data from the Scandinavian Obesity Surgery Registry and the Swedish Multiple Sclerosis register, we compared disease outcomes in 122 cases of MS who had undergone metabolic surgery with those of 122 cases of MS without surgery, matched by a two-staged Propensity score match, including age at disease onset, sex, MS phenotype, body mass index, and preoperative severity of MS as measured by the Expanded Disability Status Scale.RESULTS: The time to 6-month confirmed disability progression during the first five years postbaseline was shorter among the surgical patients (hazard ratio (HR) = 2.31, 95% confidence interval (CI) = 1.09-4.90; p = 0.03). No differences were observed regarding postoperative annual relapse rate (p = 0.24) or time to first postoperative relapse (p = 0.52).CONCLUSION: Although metabolic surgery appears to be a safe and efficient treatment of obesity in patients with MS, the clinical course of the disease might be negatively affected. Long-term nutritional follow-up after surgery and supplementation maintenance are crucial, particularly among those with preoperative deficits.
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| 2. |
- Lundskog, Anders
(författare)
-
Controlled growth of hexagonal GaN pyramids and InGaN QDs
- 2012
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Gallium-nitride (GaN) and its related alloys are direct band gap semiconductors, with a wide variety of applications. The white light emitting diode (LED) is of particular importance as it is expected to replace energy inefficient light bulb and hazardous incandescent lamps used today. However, today’s planar hetero epitaxial grown LEDs structures contain an unavoidable number of dislocations, which serves as non-radiative recombination centers. The dislocations harm the luminous efficiency of the LEDs and generate additional heat. Pseudomorphically grown quantum dots (QDs) are expected to be dislocation free thus the injected carriers captured by the QDs essentially recombine radiatively since the dislocations remain outside the QD. Furthermore the continuous character of the density of states in bulk materials is redistributed when the size of the dot is reduced within the Bohr radius of the material. Fully discret energy levels are eventually reached, which offers additional control of the optical properties. The Coulomb interaction between the confined carriers also has influence on the emission energy of the recombining carriers, which opens up the possibility of manufacturing novel light sources such as the single photon emitter. Single photon emitters are essential building blocks for quantum cryptography and teleportation applications.The main contribution of the present work is the investigation of growth and characterization of sitecontrolled indium-gallium-nitride QDs embedded in GaN matrixes. The goal has been to demonstrate the ability to grow site-controlled InGaN QDs at the apex of hexagonal GaN pyramids in a controlled way using hot-wall metal organic chemical vapor deposition (MOCVD). Strong emphasis was set on the controlled growth of InGaN QDs. For example the growth of a single InGaN QD located at the apex of hexagonal GaN pyramids with tunable emission energy, the QD emission energy impact on the mask design, and a novel approach for the growth of InGaN QDs with polarization deterministic photon vectors were reported. The thesis is mainly based on experimental investigations by secondary electron microscope (SEM), micro photo-luminescence (μPL), and scanning transition electron microscopy ((S)TEM) characterization techniques.In Paper 1 and 2, we present the growth of symmetric GaN hexagonal pyramids which served as template for the InGaN QDs grown. In paper 1, it was concluded that the selective area growth (SAG) of hexagonal GaN pyramids by MOCVD through symmetric openings in a SIN mask roughly can be divided in two regimes where either the pyramid expands laterally or not. When the pyramid expanded laterally the resulting pyramid apex became (0001) truncated even after prolonged growth times. Lateral expansion also had major impact on the pyramid-to-pyramid uniformity. In paper 2, the MOCVD process parameter impact on the pyramid morphology was investigated. By tuning the growth temperature, the ammonia, and TMGa-flows a self limited pyramid structure with only {1101} facets visible was achieved. The presence of the {1101}, {1102}, and {1100} facets were discussed from surface stabilities under various growth conditions.Paper 3 and 4 concern the growth of InGaN QDs located at the apex of hexagonal GaN pyramids. In paper 3, we showed that it is possible to grow single QDs at the apex of hexagonal pyramids with emission line widths in the Ångström range. The QD emission energy was demonstrated to be tunable by the growth temperature. Basic spectroscopy data is also presented on a single QD in paper 3. In paper 4, the growth mechanisms of the QDs presented in paper 3 are presented. We concluded that (0001) truncated GaN pyramid base initiated the growth of InGaN QDs which gave rise to narrow luminescence peaks in the μPL spectra.In paper 5, the QD emission energy impact of the mask design was investigated. To our big surprise the QD emission energy increased with increasing pyramid pitch while the emission energy of the InGaN quantum wells located on the {1101} facets of the pyramids energetically shifted towards lower energies. The energy shift at the apex was found to be associated with the (0001) truncation diameter of the underlying GaN pyramid since no energy shift was observed for (0001) truncated pyramids with truncation diameters larger than 100 nm.In paper 6, the symmetry of the GaN pyramids were intentionally broken through the introduction of elongated openings in the SiN mask (symmetric openings was used in the previous five papers). The emission polarization vectors of the subsequently grown InGaN QDs were deterministically linked to the in-plane orientation of the pyramid it was nucleated upon, implying that the QDs inhibit an inplane anisotropy directly inherited from the pyramid template.Finally, paper 7 describes a hot-wall MOCVD reactor improvement by inserting insulating pyrolytic boron-nitride (PBN) stripes in the growth chamber. By doing this, we have completely eliminated the arcing problem between different susceptor parts. As a consequence, the reactor gained run-to-run reproducibility. Growth of state of the art advanced aluminum-gallium-nitride high electron mobility transistor structures on a 100 mm wafer with electron mobility above 2000 Vs/cm2 was demonstrated by the improved process.
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| 3. |
- Moberg, Christina, et al.
(författare)
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De unga gör helt rätt när de stämmer staten
- 2022
-
Ingår i: Aftonbladet. - 1103-9000.
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Tidskriftsartikel (populärvet., debatt m.m.)abstract
- 1 620 forskare och lärare i forskarvärlden: Vi ställer oss bakom Auroras klimatkrav
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| 4. |
- Stenberg, Erik, 1979-, et al.
(författare)
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Bariatric and metabolic surgery in patients with morbid obesity and multiple sclerosis : a nationwide, matched cohort study
- 2021
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Ingår i: Surgery for Obesity and Related Diseases. - : Elsevier. - 1550-7289 .- 1878-7533. ; 17:6, s. 1108-1114
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: Despite an association between obesity and multiple sclerosis (MS), very little is known regarding the safety and efficacy outcomes for patients with MS and severe obesity undergoing metabolic surgery.OBJECTIVES: The aim of the present study was to evaluate early complications and efficacy outcomes of metabolic surgery in patients with severe obesity and MS.SETTING: Nationwide, Sweden.METHODS: In this, matched cohort study, 196 patients with an MS diagnosis in the Swedish MS register who were undergoing metabolic surgery (gastric bypass or sleeve gastrectomy) with a registration in the Scandinavian Obesity Surgery Registry (SOReg) were matched 1:10 with a control group without MS diagnosis from the SOReg. A 2-stage matching procedure was used (exact match by surgical method, followed by propensity Score matching, including age, sex, preoperative BMI, surgical center, surgical access, year of surgery, hypertension, diabetes, sleep apnea, and dyslipidemia).RESULTS: Weight loss at 2 years after surgery was similar for patients with MS and controls (total weight loss 31.6 ± 9.1 versus 31.8 ± 9.2, P = .735). No significant differences were seen in either the overall postoperative complication rate (7.9% versus 7.2%, P = .778), or serious postoperative complications (3.7% versus 2.8%, P = .430). All aspects of health-related quality of life (HRQoL) improved in both groups but less so for the physical aspects of HRQoL in patients with MS.CONCLUSION: Metabolic surgery is a safe and efficient treatment for severe obesity in patients with MS, and it leads to subsequent improvements in HRQoL. Further studies addressing the effects of metabolic surgery on MS-related symptoms are needed.
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| 5. |
- Stomrud, Erik, et al.
(författare)
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CSF biomarkers correlate with cerebral blood flow on SPECT in healthy elderly.
- 2012
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Ingår i: Dementia and geriatric cognitive disorders. - : S. Karger AG. - 1421-9824 .- 1420-8008. ; 33:2-3, s. 156-63
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Tidskriftsartikel (refereegranskat)abstract
- The preclinical patterns of biological markers for Alzheimer's disease (AD) in vivo need further exploration. The aim of this study was therefore to investigate CSF biomarkers, regional cerebral blood flow (rCBF) and cognitive performance in cognitively healthy older individuals.
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| 6. |
- Uhlén, Mathias, et al.
(författare)
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A human protein atlas for normal and cancer tissues based on antibody proteomics
- 2005
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Ingår i: Molecular & Cellular Proteomics. - 1535-9476 .- 1535-9484. ; 4:12, s. 1920-1932
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Tidskriftsartikel (refereegranskat)abstract
- Antibody-based proteomics provides a powerful approach for the functional study of the human proteome involving the systematic generation of protein-specific affinity reagents. We used this strategy to construct a comprehensive, antibody-based protein atlas for expression and localization profiles in 48 normal human tissues and 20 different cancers. Here we report a new publicly available database containing, in the first version, similar to 400,000 high resolution images corresponding to more than 700 antibodies toward human proteins. Each image has been annotated by a certified pathologist to provide a knowledge base for functional studies and to allow queries about protein profiles in normal and disease tissues. Our results suggest it should be possible to extend this analysis to the majority of all human proteins thus providing a valuable tool for medical and biological research.
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| 7. |
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| 8. |
- Adiels, Emil, et al.
(författare)
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The structural behaviour of masonry bridges designed ashydrostatic shells
- 2024
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Konferensbidrag (refereegranskat)abstract
- Masonry bridges are among the most sustainable structures ever to have been built. The long service time, the resilience to carry larger loads than originally intended, and significantly lower life cycle cost compared to other bridge types suggest that we should consider the design and construction of new masonry bridges, even if their initial cost is greater than that of steel or concrete bridges The aim of this work is to understand the structural behaviour and study the collapse of a single-span masonry hydrostatic shell, that is a shell designed specifically to carry a hydrostatic load. Due to the complexity of the masonry shell interacting with fill, it is necessary to use a combination of computational methods and load tests on physical models in their structural assessment. We perform a load test to failure on a physical model spanning 770 mm made from 3D printed blocks and analyse the model using the Discrete Element Method (DEM) in Dassault Systemes Abaqus. ` The physical model behaved well and predicts that the bridge could be used at full scale. The preliminary results from a computational DEM model are found to be qualitatively good, but greatly overestimate the collapse load of the bridge.
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| 9. |
- Andersson, Camilla, et al.
(författare)
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Achievements and experiences from science–policy interaction in the field of air pollution : Synthesising 20 years of research and outreach,thinking about future needs
- 2021
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- For 20 years, the Swedish Environmental Protection Agency together with the MISTRA research foundation have funded five air pollution research programmes with focus on producing knowledge that supports policy and emission control in national and international arenas. The research has been multidisciplinary and has included research on emissions, atmospheric transport and transformation processes, human health effects, ecosystem effects, and emission control strategies. Research has also been conducted on the interaction between air pollution and climate change.Over these years, the link between the research programmes and the development of emission control strategies and policies in Sweden, the EU, and the UNECE Air Convention has been of high importance. This report presents how the research programmes have created societal benefits through support for the development of air pollution policies and emission control measures. The report also identifies future research needs to ensure continued progress towards even better air quality for future generations.
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| 10. |
- Andersson, Henrik, et al.
(författare)
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Evaluation of coatings applied to flexible substrates to enhance quality of ink jet printed silver nano-particle structures
- 2012
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Ingår i: IEEE Transactions on Components, Packaging, and Manufacturing Technology, Part C. - 1083-4400 .- 1558-1241. ; 2:2, s. 342-348
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Tidskriftsartikel (refereegranskat)abstract
- Different types of the commercial surface treatment InkAid have been evaluated as a surface treatment to enhance print quality of silver nano-particle ink structures printed on polyimide and polyethene substrate. Originally these coatings have been specified to be applied on substrates for graphical ink jet printing. On the coated polyimide and polyethene substrates lines of different widths have been printed using a Dimatix materials printer together with silver nano-particle ink manufactured by Advanced Nano Products. The prints have then been evaluated in terms of print quality and resistivity before and after sintering. The results show that the application of these coatings can improve the print quality considerably, making it possible to print lines with a good definition, which is not otherwise possible with this type of ink on this substrate types. It has been found that the coating Semi Gloss provides the best results, both in terms of print quality as well as the lowest resistivity. The resistivity on polyethene is 3.5*10-7Ωm at best when sintered at 150°C and for polyimide 8.9*10-8Ωm sintered at 200°C. This corresponds to a conductivity of about 4.5% and 18%of bulk silver, respectively. It can be concluded that applying such PVP based coatings to polyethene and polyimide will increase the print quality quite substantially, making it possible to print patterns with requirements of smaller line widths and more details than what is possible without coating.
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| 11. |
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| 12. |
- Andersson, Henrik, et al.
(författare)
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Inkjet printed silver nanoparticle humidity sensor with memory effect on paper
- 2012
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Ingår i: IEEE Sensors Journal. - 1530-437X .- 1558-1748. ; 12:6, s. 1901-1905
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- In this paper, the design and the manufacture of an inkjet printed resistive type humidity sensor on paper are reported. After having been exposed to humidity above a given threshold level, the resistance of the sensor decreases substantially and remains at that level even when thehumidity is reduced. It is possible to deduce the humidity level by monitoring the resistance. The main benefit of the printed sensor presented in this case is in relation to its very low production costs. It has also been shown that both the ink type and this paper combination used prove to be crucial in order to obtain the desired sensor effect. More research is required in order to fully understand the humidity sintering effect on the nano particle ink and the role of the substrate. However, the observed effect can be put to use in printed humidity sensors which possess a memoryfunction. The sensor can be used in various applications for environmental monitoring, for example, in situations where a large number of inexpensive and disposable humidity sensors are required which are able to detect whether they have been subjected to high humidity. This could be the checking of transportation conditions of goods or monitoring humidity within buildings. © 2001-2012 IEEE.
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| 13. |
- Andersson, Henrik, et al.
(författare)
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Investigation of Humidity Sensor Effect in Silver Nanoparticle Ink Sensors Printed on Paper
- 2014
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Ingår i: IEEE Sensors Journal. - 1530-437X .- 1558-1748. ; 14:3, s. Art. no. 6615915-
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Tidskriftsartikel (refereegranskat)abstract
- Thin inkjet-printed tracks of silver nanoparticles have previously been observed to show a non-reversible decrease in resistance when exposed to a high degree of relative humidity and thus providing sensor functionality with a memory effect. This paper provides a more in-depth explanation of the observed humidity sensor effect that originates from inkjet-printed silver nanoparticle sensors on a paper substrate. It is shown that the geometry of the sensor has a large effect on the sensor's initial resistance, and therefore also on the sensor's resistive dynamic range. The importance of the sensor geometry is believed to be due to the amount of solvent from the ink interacting with the coating of the paper substrate, which in turn enables the diffusion of salts from the paper coating into the ink and thus affecting the silver ink.
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| 14. |
- Andersson, Henrik, et al.
(författare)
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The influence of paper coating content on room temperature sintering of silver nanoparticle ink
- 2013
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Ingår i: Nanotechnology. - : IOP Publishing. - 0957-4484 .- 1361-6528. ; 24:45, s. Art. no. 455203-
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Tidskriftsartikel (refereegranskat)abstract
- The resistance of inkjet printed lines using a silver nanoparticle based ink can be very dependent on the substrate. A very large difference in resistivity was observed for tracks printed on paper substrates with aluminum oxide based coatings compared to silica based coatings. Silica based coatings are often cationized with polymers using chloride as a counter ion. It is suggested that the precipitation of silver salts is the cause of the high resistivity, since papers pretreated with salt solutions containing ions that precipitate silver salts gave a high resistance. Silver nitrate has a high solubility and paper pretreated with nitrate ions gave a low resistivity without sintering. The results obtained show that, by choosing the correct type of paper substrate, it is possible to manufacture printed structures, such as interconnects on paper, without the need for, or at least to reduce the need for, post-print sintering. This phenomenon is, of course, ink specific. Inks without or with a low silver ion content are not expected to behave in this manner. In some sensor applications, a high resistivity is desired and, by using the correct combination of ink and paper, these types of sensors can be facilitated.
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| 15. |
- Armakavicius, Nerijus, et al.
(författare)
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Properties of two-dimensional electron gas in AlGaN/GaN HEMT structures determined by cavity-enhanced THz optical Hall effect
- 2016
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Ingår i: Physica Status Solidi C-Current Topics in Solid State Physics, Vol 13 No 5-6. - : Wiley-VCH Verlagsgesellschaft. ; , s. 369-373
-
Konferensbidrag (refereegranskat)abstract
- In this work we employ terahertz (THz) ellipsometry to determine two-dimensional electron gas (2DEG) density, mobility and effective mass in AlGaN/GaN high electron mobility transistor structures grown on 4H-SiC substrates. The effect of the GaN interface exposure to low-flow-rate trimethylaluminum (TMA) on the 2DEG properties is studied. The 2DEG effective mass and sheet density are determined tobe in the range of 0.30-0.32m0 and 4.3-5.5×1012 cm–2, respectively. The 2DEG effective mass parameters are found to be higher than the bulk effective mass of GaN, which is discussed in view of 2DEG confinement. It is shown that exposure to TMA flow improves the 2DEG mobility from 2000 cm2/Vs to values above 2200 cm2/Vs. A record mobility of 2332±61 cm2/Vs is determined for the sample with GaN interface exposed to TMA for 30 s. This improvement in mobility is suggested to be due to AlGaN/GaN interface sharpening causing the reduction of interface roughness scattering of electrons in the 2DEG.
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| 16. |
- Armstrong, Andrew J, et al.
(författare)
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Assessment of the bone scan index in a randomized placebo-controlled trial of tasquinimod in men with metastatic castration-resistant prostate cancer (mCRPC).
- 2014
-
Ingår i: Urologic oncology. - : Elsevier BV. - 1873-2496. ; 32:8, s. 1308-1316
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Tidskriftsartikel (refereegranskat)abstract
- Drug development and clinical decision making for patients with metastatic prostate cancer (PC) have been hindered by a lack of quantitative methods of assessing changes in bony disease burden that are associated with overall survival (OS). Bone scan index (BSI), a quantitative imaging biomarker of bone tumor burden, is prognostic in men with metastatic PC. We evaluated an automated method for BSI calculation for the association between BSI over time with clinical outcomes in a randomized double-blind trial of tasquinimod (TASQ) in men with metastatic castration-resistant PC (mCRPC).
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| 17. |
- Aziz, Emad F., et al.
(författare)
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Photoinduced formation of N-2 molecules in ammonium compounds
- 2007
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Ingår i: Journal of Physical Chemistry A. - : American Chemical Society (ACS). - 1089-5639 .- 1520-5215. ; 111:39, s. 9662-9669
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Tidskriftsartikel (refereegranskat)abstract
- Via fluorescence yield (FY) and resonant inelastic scattering spectroscopy in the soft X-ray range we find that soft X-rays induce formation of N-2 molecules in solid NH4Cl and in related compounds. The nitrogen molecules form weak bonds in NH4Cl, so that a substantial fraction of the molecules remains in the sample. From measurements of the FY as a function of exposure and temperature, the rates for the photochemical processes are estimated. At elevated temperatures (363 K), several nitrogen atoms are removed from the sample per incoming photon. At lower temperatures (233 K), the rate is reduced to around 0.02 nitrogen atoms for each incoming photon. Virtually all these atoms form N-2 molecules which are bound in the sample. The generality and implications of these results are briefly discussed.
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| 18. |
- Behzadi, Arvin, et al.
(författare)
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Neurofilaments can differentiate ALS subgroups and ALS from common diagnostic mimics.
- 2021
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Ingår i: Scientific reports. - : Springer Science and Business Media LLC. - 2045-2322. ; 11:1
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Tidskriftsartikel (refereegranskat)abstract
- Delayed diagnosis and misdiagnosis are frequent in people with amyotrophic lateral sclerosis (ALS), the most common form of motor neuron disease (MND). Neurofilament light chain (NFL) and phosphorylated neurofilament heavy chain (pNFH) are elevated in ALS patients. We retrospectively quantified cerebrospinal fluid (CSF) NFL, CSF pNFH and plasma NFL in stored samples that were collected at the diagnostic work-up of ALS patients (n=234), ALS mimics (n=44) and controls (n=9). We assessed the diagnostic performance, prognostication value and relationship to the site of onset and genotype. CSF NFL, CSF pNFH and plasma NFL levels were significantly increased in ALS patients compared to patients with neuropathies & myelopathies, patients with myopathies and controls. Furthermore, CSF pNFH and plasma NFL levels were significantly higher in ALS patients than in patients with other MNDs. Bulbar onset ALS patients had significantly higher plasma NFL levels than spinal onset ALS patients. ALS patients with C9orf72HREmutations had significantly higher plasma NFL levels than patients withSOD1mutations. Survival was negatively correlated with all three biomarkers. Receiver operating characteristics showed the highest area under the curve for CSF pNFH for differentiating ALS from ALS mimics and for plasma NFL for estimating ALS short and long survival. Allthree biomarkers have diagnostic value in differentiating ALS from clinically relevant ALS mimics. Plasma NFL levels can be used to differentiate between clinical and genetic ALS subgroups.
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| 19. |
- Benckert, Lars, et al.
(författare)
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Fresnel diffraction of a Gaussian laser beam by polished metal cylinders
- 1990
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Ingår i: Applied Optics. - 1559-128X .- 2155-3165. ; 29:3, s. 416-421
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Tidskriftsartikel (refereegranskat)abstract
- A laser beam touching the periphery of a polished cylinder is subjected to both diffraction and reflection. Inthe area where diffracted light and reflected light interact the resulting intensity distribution differs from thepattern predicted by diffraction theory for a sharp edge. The difference increases with cylinder radius. Inthis paper it is shown that a good description of the resulting intensity pattern is obtained by adding thereflected light amplitude to the diffracted amplitude as predicted by the Fresnel-Kirchhoff theory for a sharpedge.
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| 20. |
- Bergsten, Johan, et al.
(författare)
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AlGaN/GaN high electron mobility transistors with intentionally doped GaN buffer using propane as carbon precursor
- 2016
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Ingår i: Japanese Journal of Applied Physics. - : Institute of Physics Publishing (IOPP). - 0021-4922 .- 1347-4065. ; 55, s. 05FK02-1-05FK02-4
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Tidskriftsartikel (refereegranskat)abstract
- AlGaN/GaN high electron mobility transistors (HEMTs) fabricated on a heterostructure grown by metalorganic chemical vapor deposition using analternative method of carbon (C) doping the buffer are characterized. C-doping is achieved by using propane as precursor, as compared to tuningthe growth process parameters to control C-incorporation from the gallium precursor. This approach allows for optimization of the GaN growthconditions without compromising material quality to achieve semi-insulating properties. The HEMTs are evaluated in terms of isolation anddispersion. Good isolation with OFF-state currents of 2 ' 10%6A/mm, breakdown fields of 70V/μm, and low drain induced barrier lowering of0.13mV/V are found. Dispersive effects are examined using pulsed current–voltage measurements. Current collapse and knee walkout effectslimit the maximum output power to 1.3W/mm. With further optimization of the C-doping profile and GaN material quality this method should offer aversatile approach to decrease dispersive effects in GaN HEMTs.
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| 21. |
- Bergsten, Johan, et al.
(författare)
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Impact of AlGaN/GaN interface sharpness on HEMT performance
-
Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- The impact of the design and sharpness of the AlGaN/GaN interface in GaN-based HEMTs is investigated. Three structures with different AlGaN/GaN interface properties were grown with hot-wall MOCVD. One structure has a 2-nmthick AlN exclusion layer in between the AlGaN and the GaN, while the other two differ in their sharpness of the Al transition at the AlGaN/GaN interface. The structures with AlN exclusion layer and optimized sharpness of the interface show similar electron mobilities (1760 and 1740 cm2/Vs). HEMTs were processed and evaluated. Gated Hall-measurements indicate that the sharper interface maintains a higher mobility when the electrons are close to the interface compared both to the AlNexclusion layer and the non-optimized structure. The higher mobility manifests as lower parasitic resistance yielding better DC and high frequency performance. Pulsed IV measurements indicate that the sharper interface provide less dispersive effects compared both to the AlN exclusion layer and the optimized interface.
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| 22. |
- Bergsten, Johan, et al.
(författare)
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Performance Enhancement of Microwave GaN HEMTs Without an AlN-Exclusion Layer Using an Optimized AlGaN/GaN Interface Growth Process
- 2016
-
Ingår i: IEEE Transactions on Electron Devices. - : IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC. - 0018-9383 .- 1557-9646. ; 63:1, s. 333-338
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Tidskriftsartikel (refereegranskat)abstract
- The impact of the sharpness of the AlGaN/GaN interface in high-electron mobility transistors (HEMTs) is investigated. Two structures, one with an optimized AlGaN/GaN interface and another with an unoptimized, were grown using hot-wall metal-organic chemical vapor deposition. The structure with optimized sharpness of the interface shows electron mobility of 1760 cm(2)/V . s as compared with 1660 cm(2)/V . s for the nonoptimized interface. Gated Hall measurements indicate that the sharper interface maintains higher mobility when the electrons are close to the interface compared with the nonoptimized structure, indicating less scattering due to alloy disorder and interface roughness. HEMTs were processed and evaluated. The higher mobility manifests as lower parasitic resistance yielding a better dc and high-frequency performance. A small-signal equivalent model is extracted. The results indicate a lower electron penetration into the buffer in the optimized sample. Pulsed-IV measurements imply that the sharper interface provides less dispersive effects at large drain biases. We speculate that the mobility enhancement seen AlGaN/AlN/GaN structures compared with the AlGaN/GaN case is not only related to the larger conduction band offset but also due to a more welldefined interface minimizing scattering due to alloy disorder and interface roughness.
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| 23. |
- Besharati, Farshid, et al.
(författare)
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The EVI Distributed Shared Memory System
- 2015
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- With the data handled by companies and research institutes getting larger and larger every day, there is a clear need for faster computing. At the same time, we have reached the limit of power consumption and more power efficient computing is also called for, both in the datacenter and in the supercomputer room. For that, there is a great push, both in industry and academia, towards increasing the amount of computing power per watt consumed. With this shift towards a different computing paradigm, many older ideas are looked upon in a new light. One of these is the distributed shared memory (DSM) systems. It is becoming harder and harder to achieve higher performance and better power efficiency at the same form factor as we have always had. Furthermore, while we have seen a stop in the constant increase of processor speeds, there is a constant increase in network communication speeds. Software implemented DSM is again a viable solution for high performance computing, without the need for sacrificing ease of programming for performance gains. The goal of this course was to develop such a system, and learn in the process. We chose to work with the Adapteva Parallella boards and design a DSM system there. Over one semester we designed and developed that system.
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| 24. |
- Bjarnegård, Elin, 1976-, et al.
(författare)
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Gender, peace and armed conflict
- 2015
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Ingår i: SIPRI Yearbook 2015. - Oxford : Oxford University Press. - 9780198737810 ; , s. 101-109
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Bokkapitel (refereegranskat)
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| 25. |
- Bjerg, Anders, et al.
(författare)
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Increased Prevalence of Symptoms of Rhinitis but Not of Asthma between 1990 and 2008 in Swedish Adults : Comparisons of the ECRHS and GA(2)LEN Surveys
- 2011
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Ingår i: PLoS ONE. - : Public Library of Science (PLoS). - 1932-6203. ; 6:2, s. e16082-
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Tidskriftsartikel (refereegranskat)abstract
- Background: The increase in asthma prevalence until 1990 has been well described. Thereafter, time trends are poorly known, due to the low number of high quality studies. The preferred method for studying time trends in prevalence is repeated surveys of similar populations. This study aimed to compare the prevalence of asthma symptoms and their major determinants, rhinitis and smoking, in Swedish young adults in 1990 and 2008. Methods: In 1990 the European Community Respiratory Health Survey (ECRHS) studied respiratory symptoms, asthma, rhinitis and smoking in a population-based sample (86% participation) in Sweden. In 2008 the same symptom questions were included in the Global Allergy and Asthma European Network (GA(2)LEN) survey (60% participation). Smoking questions were however differently worded. The regions (Gothenburg, Uppsala, Umea) and age interval (20-44 years) surveyed both in 1990 (n = 8,982) and 2008 (n = 9,156) were analysed. Results: The prevalence of any wheeze last 12 months decreased from 20% to 16% (p<0.001), and the prevalence of "asthma-related symptoms" was unchanged at 7%. However, either having asthma attacks or using asthma medications increased from 6% to 8% (p<0.001), and their major risk factor, rhinitis, increased from 22% to 31%. Past and present smoking decreased. Conclusion: From 1990 to 2008 the prevalence of obstructive airway symptoms common in asthma did not increase in Swedish young adults. This supports the few available international findings suggesting the previous upward trend in asthma has recently reached a plateau. The fact that wheeze did not increase despite the significant increment in rhinitis, may at least in part be due to the decrease in smoking.
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