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Search: WFRF:(Helmersson Erik)

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1.
  • Axell, Erik, et al. (author)
  • Coexistence of Speech and Best Effort Services in Enhanced Uplink WCDMA
  • 2005
  • In: in Proc. of Radiovetenskap och Kommunikation (RVK).
  • Conference paper (peer-reviewed)abstract
    • An evaluation of the performance of coexistent voice and best effort data users in Enhanced Uplink WCDMA is studied in this paper. The main focus is on deriving the capacity regions and compare with previous WCDMA releases. It is shown that the Enhanced Uplink yields a large capacity gain in many aspects for all fractions of voice users compared to previous WCDMA releases. It is also shown, by the cumulative distribution functions of noise rise at the capacity limits, that the best effort data users experience bad quality at lower noise rise than voice users. This means that the capacity is in fact limited by the best effort users.
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2.
  • Alami, Jones, et al. (author)
  • Phase tailoring of Ta thin films by highly ionized pulsed magnetron sputtering
  • 2007
  • In: Thin Solid Films. - : Elsevier. - 0040-6090 .- 1879-2731. ; 515:7-8, s. 3434-3438
  • Journal article (peer-reviewed)abstract
    • Ta thin films were grown on Si substrates at different inclination angles with respect to the sputter source using high power impulse magnetron sputtering (HIPIMS), an ionized physical vapor deposition technique. The ionization allowed for better control of the energy and directionality of the sputtered species, and consequently for improved properties of the deposited films. Depositions were made on Si substrates with the native oxide intact. The structure of the as deposited films was investigated using X-ray diffraction, while a four-point probe setup was used to measure the resistivity. A substrate bias process-window for growth of bcc-Ta was observed. However, the process-window position changed with changing inclination angles of the substrate. The formation of this low-resistivity bcc-phase could be understood in light of the high ion flux from the HIPIMS discharge.
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3.
  • Andersson, Jon M., et al. (author)
  • Ab initio calculations on the effects of additives on alumina phase stability
  • 2005
  • In: Physical review. B, Condensed matter and materials physics. - 1098-0121 .- 1550-235X. ; 71:014101, s. 014101-
  • Journal article (peer-reviewed)abstract
    • The effects of substitutional additives on the properties and phase stability of - and -alumina (Al2O3), are investigated by density functional theory total energy calculations. The dopants explored are 5 at. % of Cr, Mo, Co, and As substituting for Al, respectively, N and S substituting for O, in the and lattices. Overall, the results show that it is possible to shift, and even reverse, the relative stability between - and -alumina by substitutional additives. The alumina bulk moduli are, in general, only slightly affected by the dopants but density of states profiles reveal additional peaks in the alumina band gaps. We also show that phase separations into pure oxides are energetically favored over doped alumina formation, and we present results on a number of previously unstudied binary oxides.
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4.
  • Andersson, Jon M., et al. (author)
  • Energy distributions of positive and negative ions during magnetron sputtering of an Al target in Ar/O2 mixtures
  • 2006
  • In: Journal of Applied Physics. - College Park, MD, United States : American Institute of Physics (AIP). - 0021-8979 .- 1089-7550. ; 100:3, s. Art. No. 033305 AUG 1 2006-
  • Journal article (peer-reviewed)abstract
    • The ion flux obtained during reactive magnetron sputtering of an Al target in Ar/O2 gas mixtures was studied by energy-resolved mass spectrometry, as a function of the total and O2 partial pressures. The positive ions of film-forming species exhibited bimodal energy distributions, both for direct current and radio frequency discharges, with the higher energy ions most likely originating from sputtered neutrals. For the negative oxygen ions a high-energy peak was observed, corresponding to ions formed at the target surface and accelerated towards the substrate over the sheath potential. As the total pressure was increased the high-energy peaks diminished due to gas-phase scattering. Based on these results, the role of energetic bombardment for the phase constituent of alumina thin films are discussed.
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5.
  • Andersson, Jon M., et al. (author)
  • Molecular content of the deposition flux during reactive Ar/O2 magnetron sputtering of Al
  • 2006
  • In: Applied Physics Letters. - : Institutionen för fysik, kemi och biologi. - 0003-6951 .- 1077-3118. ; 88:05, s. Art. No. 054101 JAN 30 2006-
  • Journal article (peer-reviewed)abstract
    • The deposition flux obtained during reactive radio frequency magnetron sputtering of an Al target in Ar/O2 gas mixtures was studied by mass spectrometry. The results show significant amounts of molecular AlO+ (up to 10% of the Al+ flux) in the ionic flux incident onto the substrate. In the presence of ~10–4 Pa H2O additional OH+ and AlOH+ were detected, amounting to up to about 100% and 30% of the Al+ flux, respectively. Since the ions represent a small fraction of the total deposition flux, an estimation of the neutral content was also made. These calculations show that, due to the higher ionization probability of Al, the amount of neutral AlO in the deposition flux is of the order of, or even higher than, the amount of Al. These findings might be of great aid when explaining the alumina thin film growth process.
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6.
  • Andersson, Jon Martin, et al. (author)
  • Phase control of Al2O3 thin films grown at low temperatures
  • 2006
  • In: Thin Solid Films. - : Elsevier. - 0040-6090 .- 1879-2731. ; 513:1-2, s. 57-59
  • Journal article (peer-reviewed)abstract
    • Low-temperature growth (500 °C) of α-Al2O3 thin films by reactive magnetron sputtering was achieved for the first time. The films were grown onto Cr2O3 nucleation layers and the effects of the total and O2 partial pressures were investigated. At 0.33 Pa total pressure and ≥ 16 mPa O2 partial pressure α-Al2O3 films formed, while at lower O2 pressure or higher total pressure (0.67 Pa), only γ phase was detected in the films (which were all stoichiometric). Based on these results we suggest that α phase formation was promoted by a high energetic bombardment of the growth surface. This implies that the phase content of Al2O3 films can be controlled by controlling the energy of the depositing species. The effect of residual H2O (10− 4 Pa) on the films was also studied, showing no change in phase content and no incorporated H (< 0.1%). Overall, these results are of fundamental importance in the further development of low-temperature Al2O3 growth processes.
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7.
  • Carlsson, Axel C, et al. (author)
  • Urinary kidney injury molecule 1 and incidence of heart failure in elderly men
  • 2013
  • In: European Journal of Heart Failure. - : Oxford University Press. - 1388-9842 .- 1879-0844. ; 15:4, s. 447-446
  • Journal article (peer-reviewed)abstract
    • AIMS: There is growing recognition of the clinical importance of cardiorenal syndrome-the bidirectional interplay between kidney and cardiac dysfunction. Yet, the role of kidney tubular damage in the development of heart failure is less studied. The objective of this study was to investigate whether urinary kidney injury molecule (KIM)-1, a specific marker of tubular damage, predisposes to an increased heart failure risk.METHODS AND RESULTS: This was a community-based cohort study [Uppsala Longitudinal study of Adult Men (ULSAM)] of 565, 77-year-old men free from heart failure at baseline. Heart failure hospitalizations were used as outcome. During follow-up (median 8.0 years), 73 participants were hospitalized for heart failure. In models adjusted for cardiovascular risk factors (age, systolic blood pressure, diabetes, smoking, body mass index, LDL/HDL ratio, antihypertensive treatment, lipid-lowering treatment, aspirin treatment, LV hypertrophy, and prevalent cardiovascular disease) and markers of kidney dysfunction and damage [cystatin C-based glomerular filtration rate (GFR) and urinary albumin/creatinine ratio], a higher urinary KIM-1/creatinine ratio was associated with higher risk for heart failure (hazard ratio upper vs. lower tertile, 1.81; 95% confidence interval 1.01-3.29; P < 0.05). Participants with a combination of low GFR (<60 mL/min/1.72 m(2)) and high KIM-1/creatinine (>128 ng/mmol) had a 3-fold increase in heart failure risk compared with participants with normal GFR and KIM-1 (P < 0.001).CONCLUSION: Our findings suggest that kidney tubular damage predisposes to an increased risk for heart failure in the community. Further studies are needed to clarify the causal role of KIM-1 in the development of heart failure, and to evaluate the clinical utility of urinary KIM-1 measurements.
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8.
  • Carlsson, Axel C, et al. (author)
  • Urinary kidney injury molecule-1 and the risk of cardiovascular mortality in elderly men
  • 2014
  • In: American Society of Nephrology. Clinical Journal. - 1555-9041 .- 1555-905X. ; 9:8, s. 1393-1401
  • Journal article (peer-reviewed)abstract
    • BACKGROUND AND OBJECTIVES: Kidney injury molecule-1 (KIM-1) has been suggested as a clinically relevant highly specific biomarker of acute kidney tubular damage. However, community-based data on the association between urinary levels of KIM-1 and the risk for cardiovascular mortality are lacking. This study aimed to investigate the association between urinary KIM-1 and cardiovascular mortality.DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS: This was a prospective study, using the community-based Uppsala Longitudinal Study of Adult Men (N=590; mean age 77 years; baseline period, 1997-2001; median follow-up 8.1 years; end of follow-up, 2008).RESULTS: During follow-up, 89 participants died of cardiovascular causes (incidence rate, 2.07 per 100 person-years at risk). Models were adjusted for cardiovascular risk factors (age, systolic BP, diabetes, smoking, body mass index, total cholesterol, HDL cholesterol, antihypertensive treatment, lipid-lowering treatment, aspirin treatment, and history of cardiovascular disease) and for markers of kidney dysfunction and damage (cystatin C-based eGFR and urinary albumin/creatinine ratio). Higher urinary KIM-1/creatinine (from 24-hour urine collections) was associated with a higher risk for cardiovascular mortality (hazard ratio per SD increase, 1.27; 95% confidence interval [95% CI], 1.05 to 1.54; P=0.01). Participants with a combination of high KIM-1/creatinine (upper quintile, ≥175 ng/mmol), low eGFR (≤60 ml/min per 1.73 m(2)), and microalbuminuria/macroalbuminuria (albumin/creatinine ratio≥3 g/mol) had a >8-fold increased risk compared with participants with low KIM-1/creatinine (<175 ng/mmol), normal eGFR (>60 ml/min per 1.73 m(2)), and normoalbuminuria (albumin/creatinine ratio<3 g/mol) (hazard ratio, 8.56; 95% CI, 4.17 to 17.56; P<0.001).CONCLUSIONS: These findings suggest that higher urinary KIM-1 may predispose to a higher risk of cardiovascular mortality independently of established cardiovascular risk factors, eGFR, and albuminuria. Additional studies are needed to further assess the utility of measuring KIM-1 in the clinical setting.
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9.
  • Gevorgian, Spartak, 1948, et al. (author)
  • HTS/ferroelectric devices for microwave applications
  • 1997
  • In: IEEE Transactions on Applied Superconductivity. - : Institute of Electrical and Electronics Engineers (IEEE). - 1558-2515 .- 1051-8223. ; 7:2, s. 2458 - 2461
  • Journal article (peer-reviewed)abstract
    • High Temperature Superconducting (HTS, e.g. YBCO) microwave devices based on bulk or thin film ferroelectrics (e.g. Strontium Titanate-STO) are studied theoretically and experimentally. YBCO/STO/YBCO parallel-plate resonators and based on bulk single crystal STO are for electrically tunable high power filters, phase shifters and other devices in the frequency band 0.5-2.0 GHz of advanced microwave communication systems. Thin film YBCO/STO Inter-digital Capacitors (IDC), Coplanar Waveguides (CPW) phase shifters/delay lines are also designed and studied experimentally for low microwave power applications. Modelling problems of these devices and microwave losses in ferroelectrics are also discussed
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10.
  • Gevorgian, Spartak, 1948, et al. (author)
  • Modelling of thin-film HTS/ferroelectric interdigital capacitors
  • 1996
  • In: IEE Proceedings: Microwaves, Antennas and Propagation. - : Institution of Engineering and Technology (IET). - 1350-2417 .- 1359-706X. ; 143:5, s. 397 - 401
  • Journal article (peer-reviewed)abstract
    • The model of the interdigital capacitor (IDC) has been used for monitoring and analysing the dielectric properties of thin ferroelectric films. The dielectric properties of the film are correlated to its crystalline structure using a simple model of STO. The results of the analysis may be used for optimisation of growth and annealing processes of the films and reducing the effects of the electrode ferroelectric interface. The model can be used to optimise the design of IDCs in the sense of minimum losses and maximum controllability by selecting finger width and gapwidth of the IDC. Further improvement of the model suggests a comprehensive study of all possible mechanisms affecting the dielectric constant and the losses of STO films
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  • Result 1-10 of 43
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journal article (28)
conference paper (11)
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Type of content
peer-reviewed (30)
other academic/artistic (12)
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Author/Editor
Helmersson, Ulf (22)
Wallin, Erik (10)
Larsson, Anders (10)
Ingelsson, Erik (9)
Sundström, Johan (9)
Ärnlöv, Johan (8)
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Helmersson, Ulf, 195 ... (7)
Lind, Lars (6)
Risérus, Ulf (6)
Andersson, Jon M. (5)
Basu, Samar (5)
Chirita, Valeriu (4)
Lattemann, Martina (4)
Münger, Peter (3)
Carlsson, Axel C. (3)
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