| 1. |
- Ferrari, Piero, et al.
(författare)
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The effect of radiative cooling on the size-dependent stability of small boron clusters
- 2018
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Ingår i: Physical Review A. Atomic, Molecular, and Optical Physics. - 1050-2947. ; 98
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Tidskriftsartikel (refereegranskat)abstract
- The mass spectrum of cationic boron clusters, BN+ (N = 5 − 20), after photoexcitation demonstrates that radiative cooling is an important, though often neglected, process in determining the relative stability of small and isolated particles. The observed intensities inmass spectra suggest that B5+, B11+, B13+, and B15+ are particularly stable clusters, consistent with density-functional theory calculations. Quantitative agreement, however, is only obtained if radiative cooling is included in the analysis.All clusters are found to radiate onmicrosecond timescales, suggesting recurrent fluorescence as the dominant photon emission process.
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| 2. |
- Mathijssen, Simon G. J., et al.
(författare)
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Manipulating the local light emission in organic light-emitting diodes by using patterned self-assembled monolayers
- 2008
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Ingår i: Advanced Materials. - : Wiley-VCH Verlag. - 0935-9648 .- 1521-4095. ; 20:14, s. 2703-
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Tidskriftsartikel (refereegranskat)abstract
- Patterned organic light-emitting diodes are fabricated by using microcontactDrinted self-assembled monolayers on a gold anode (see background figure). Molecules with dipole moments in opposite directions result in an increase or a decrease of the local work function (foreground picture), providing a direct handle on charge injection and enabling local modification of the light emission
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| 3. |
- de Andrade Schwerz, Claudia, 1992, et al.
(författare)
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Mechanical properties of Hastelloy X produced by laser powder bed fusion and affected by spatter redeposition
- 2024
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Ingår i: Journal of Materials Research and Technology. - : ELSEVIER. - 2238-7854. ; 29, s. 4200-4215
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Tidskriftsartikel (refereegranskat)abstract
- Defects in materials manufactured via laser powder bed fusion challenge this manufacturing process' dependability and may prevent it from being comprehensively used for structural components, particularly those intended to operate under dynamic loading conditions. This study aims to investigate the effect of spatter-driven lack of fusion on the mechanical properties of Hastelloy X, with a particular focus on fatigue performance. Mechanical test specimens were manufactured in two builds with different build rates and monitored through in-situ optical tomography. The images acquired in situ were analyzed to detect spatter redeposits to predict the defect content in the gauge section. Selected specimens were measured ex-situ using X-ray computed tomography to map the defect populations. Afterward, the specimens were tensile and fatigue tested, and their performance was analyzed based on the measured and expected defect populations. It was confirmed that a higher build rate is associated with more extensive detection of spatter redeposits in optical tomography images and lack of fusion defects. The fatigue lives of specimens manufactured at higher build rates presented higher scatter but significantly higher average, despite the more critical defect population. Surprisingly, the confirmed presence of lack of fusion defects in the gauge section of test specimens did not necessarily result in a poorer fatigue performance. It was concluded that the grain refinement obtained through the increase in nominal layer thickness has a life-prolonging effect that overrides the effects of spatter-induced lack of fusion defects.
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| 4. |
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| 5. |
- Mathijssen, Simon G. J., et al.
(författare)
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Charge trapping at the dielectric of organic transistors visualized in real time and space
- 2008
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Ingår i: Advanced Materials. - : Wiley-VCH Verlag. - 0935-9648 .- 1521-4095. ; 20:5, s. 975-
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Tidskriftsartikel (refereegranskat)abstract
- Scanning Kelvin probe microscopy demonstrates that water-induced charge trapping at the SiO2 dielectric visualized in real time and space - is responsible for the commonly observed gate-bias-induced threshold-voltage shift in organic field-effect transistors. When a bias is applied to the electrodes, charges are injected onto the SiO2 (see background of the figure). When the contacts are grounded, the charges are released again (foreground picture).
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| 6. |
- Mathillas, Johan, 1980-
(författare)
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Dementia, depression and delirium in the very old : prevalences and associated factors
- 2013
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Emotional suffering in old age is largely caused by a variety of psychiatric disorders which are often, however, undertreated and underrecognized. This leads to reduced quality of life and functional status and increased morbidity and mortality. Dementia, delirium and depression are common disorders in the very old, and are similar in several ways. All have multiple causes and are diagnosed by means of symptomatic criteria, are challenging to diagnose and difficult to differentiate from each other in the very old. They often coexist in the same individual, and may have common risk factors.The overall aim of this thesis was to add to our knowledge about threats to successful aging, by investigating the prevalences of dementia, depression and delirium, and factors associated with these three disorders. Further aims were to measure change over time in the prevalence of dementia and depression, respectively, and to investigate the risk factors for incident depression. This thesis uses the population-based Umeå85+/GErontological Regional DAtabase (GERDA) material.In 2000-2002, every other 85-year-old, all 90-year-olds and all people ≥95 years living in six municipalities in Västerbotten, Sweden were invited to participate, and in 2005-2007 the process was repeated, with the additional inclusion of the corresponding populations of two municipalities in Österbotten, Finland. A third data collection was carried out in 2010-2012. Trained assessors carried out assessments in the form of structured interviews during one or more home visits, recorded current medication and reviewed medical records obtained from general practitioners and hospitals. In 2000-2002 the prevalence of dementia was 17% among 85-year-olds, 24% among 90-year-olds and 46% among those aged ≥95 years. In 2005-2007 dementia prevalence reached 28% among 85-year-olds, 40% among 90-yearolds and 45% among those aged ≥95 years. The prevalence of dementia in the total sample was 27% in 2000-2002 and 37% in 2005-2007 (p=0.001). In 2000-2002 the prevalence of depressive disorders was 24% among 85-yearolds, 34% among 90-year-olds and 31% among those aged ≥95 years. In 2005-2007 the prevalence of depressive disorders was 33% among 85-year-olds, 39% among 90-year-olds and 38% among those aged ≥95 years. The prevalence of depressive disorders in the total sample was 29% in 2000-2002 and 37% in 2005-2007 (p=0.025). Among participants not depressed at baseline, 26% had developed depression after five years. Factors independently associated with new cases of depression at follow-up were hypertension, a history of stroke and a higher score on the 15-item Geriatric Depression Scale at baseline. The thirtyday prevalence of delirium in 2005-2007 was 17% among 85-year-olds, 21% among 90-year-olds and 39% among participants aged ≥95 years. Delirium prevalence among individuals with dementia was higher than among those without dementia (52% vs. 5%, p<.001). Factors independently associated with delirium superimposed on dementia in a multivariate logistic regression model were depression, heart failure, living in an institution and prescribed antipsychotics.There was a high prevalence of dementia, depression and delirium in the papers comprising this thesis, and 55% had at least one of the three disorders. The prevalence of dementia and depression also increased between 2000-2002 and 2005-2007, after controlling for age and sex. Dementia and depression were important associated factors for delirium and half of those with dementia were depressed. The increasing age-specific prevalence of depression seems to be associated with the increasing age-specific prevalence of dementia. The papers presented are among the first to report a significantly increasing age-specific prevalence of dementia and depression among very old people. More knowledge about associated factors and risk factors concerning these disorders may be helpful for carers and decision-makers, as well as providing reference values for studies in other regions. Further efforts are needed in both care and research to better prevent, screen for, diagnose and treat dementia, depression and delirium, especially considering the growing number of very old people.
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| 9. |
- You, Li, et al.
(författare)
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Hybrid Analog/Digital Precoding for Downlink Massive MIMO LEO Satellite Communications
- 2022
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Ingår i: IEEE Transactions on Wireless Communications. - : Institute of Electrical and Electronics Engineers (IEEE). - 1536-1276 .- 1558-2248. ; , s. 1-1
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Tidskriftsartikel (refereegranskat)abstract
- Massive multiple-input multiple-output (MIMO) is promising for low earth orbit (LEO) satellite communications due to the potential in enhancing the spectral efficiency. However, the conventional fully digital precoding architectures might lead to high implementation complexity and energy consumption. In this paper, hybrid analog/digital precoding solutions are developed for the downlink operation in LEO massive MIMO satellite communications, by exploiting the slow-varying statistical channel state information (CSI) at the transmitter. First, we formulate the hybrid precoder design as an energy efficiency (EE) maximization problem by considering both the continuous and discrete phase shift networks for implementing the analog precoder. The cases of both the fully and the partially connected architectures are considered. Since the EE optimization problem is nonconvex, it is in general difficult to solve. To make the EE maximization problem tractable, we apply a closed-form tight upper bound to approximate the ergodic rate. Then, we develop an efficient algorithm to obtain the fully digital precoders. Based on which, we further develop two different efficient algorithmic solutions to compute the hybrid precoders for the fully and the partially connected architectures, respectively. Simulation results show that the proposed approaches achieve significant EE performance gains over the existing baselines, especially when the discrete phase shift network is employed for analog precoding.
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