| 1. |
- Ahmad, Irma, et al.
(författare)
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High prevalence of persistent symptoms and reduced health-related quality of life 6 months after COVID-19
- 2023
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Ingår i: Frontiers In Public Health. - : Frontiers Media S.A.. - 2296-2565. ; 11
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: The long-term sequelae after COVID-19 constitute a challenge to public health and increased knowledge is needed. We investigated the prevalence of self-reported persistent symptoms and reduced health-related quality of life (HRQoL) in relation to functional exercise capacity, 6 months after infection, and explored risk factors for COVID-19 sequalae.METHODS: This was a prospective, multicenter, cohort study including 434 patients. At 6 months, physical exercise capacity was assessed by a 1-minute sit-to-stand test (1MSTST) and persistent symptoms were reported and HRQoL was evaluated through the EuroQol 5-level 5-dimension (EQ-5D-5L) questionnaire. Patients with both persistent symptoms and reduced HRQoL were classified into a new definition of post-acute COVID syndrome, PACS+. Risk factors for developing persistent symptoms, reduced HRQoL and PACS+ were identified by multivariable Poisson regression.RESULTS: Persistent symptoms were experienced by 79% of hospitalized, and 59% of non-hospitalized patients at 6 months. Hospitalized patients had a higher prevalence of self-assessed reduced overall health (28 vs. 12%) and PACS+ (31 vs. 11%). PACS+ was associated with reduced exercise capacity but not with abnormal pulse/desaturation during 1MSTST. Hospitalization was the most important independent risk factor for developing persistent symptoms, reduced overall health and PACS+.CONCLUSION: Persistent symptoms and reduced HRQoL are common among COVID-19 survivors, but abnormal pulse and peripheral saturation during exercise could not distinguish patients with PACS+. Patients with severe infection requiring hospitalization were more likely to develop PACS+, hence these patients should be prioritized for clinical follow-up after COVID-19.
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| 2. |
- Aboulfadl, Hisham, 1986, et al.
(författare)
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Alkali Dispersion in (Ag,Cu)(In,Ga)Se2 Thin Film Solar Cells - Insight from Theory and Experiment
- 2021
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Ingår i: ACS Applied Materials & Interfaces. - : American Chemical Society (ACS). - 1944-8252 .- 1944-8244. ; 13:6, s. 7188-7199
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Tidskriftsartikel (refereegranskat)abstract
- Silver alloying of Cu(In,Ga)Se2 absorbers for thin film photovoltaics offers improvements in open-circuit voltage, especially when combined with optimal alkali-treatments and certain Ga concentrations. The relationship between alkali distribution in the absorber and Ag alloying is investigated here, combining experimental and theoretical studies. Atom probe tomography analysis is implemented to quantify the local composition in grain interiors and at grain boundaries. The Na concentration in the bulk increases up to ∼60 ppm for [Ag]/([Ag] + [Cu]) = 0.2 compared to ∼20 ppm for films without Ag and up to ∼200 ppm for [Ag]/([Ag] + [Cu]) = 1.0. First-principles calculations were employed to evaluate the formation energies of alkali-on-group-I defects (where group-I refers to Ag and Cu) in (Ag,Cu)(In,Ga)Se2 as a function of the Ag and Ga contents. The computational results demonstrate strong agreement with the nanoscale analysis results, revealing a clear trend of increased alkali bulk solubility with the Ag concentration. The present study, therefore, provides a more nuanced understanding of the role of Ag in the enhanced performance of the respective photovoltaic devices.
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| 3. |
- Baldissera, Gustavo, 1983-
(författare)
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Optical and Electronic Properties of WO3 and Zn Chalcogenides Alloys: A Theoretical study
- 2020
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- I denna avhandling analyseras optiska och elektroniska egenskaper hos WO3 och Zn-relaterade legeringar med hjälp av täthetsfunktionalteori (DFT). Metoder som går utöver DFT, såsom GW-approximationen och hybridfunktionaler, används för att minimera det fel som genereras av det smala bandgapet som erhålls med konventionella DFT-funktionaler. WO3 har sex olika stabila termodynamiska faser i olika temperaturintervall. En triklinisk till monoklinisk fasövergång sker nära rumstemperatur, och därför innehåller experimentprover ofta båda faserna. Beräkningar av dessa två strukturer visar likheter i absorption och bandstruktur, med en liten skillnad på 0,1 eV vid påbörjan av absorption. Detta värde är relaterat till skillnaden i bandgap mellan de två faserna. Den monokliniska fasen vid låg temperatur uppvisar en annan banddispersion och ett bredare bandgap som påverkar huvudsakligen absorptionsstarten. Modellering av volframvakanser i superceller av WO3 uppvisar magnetiska moment i vissa kristallfaser, varvid effekten är starkare i strukturer med låg symmetri, nämligen de trikliniska och monokliniska. Det magnetiska momentet uppstår från de oparade elektronerna från syreatomer i anslutning till vakansen. Denna effekt är emellertid lokaliserad och genererar inte en hålmedierad ferromagnetisk fas i materialet. Studien av zinklegeringar utförs med superceller för att nå en önskad mix av grundämnen. För Zn(O,S)- och Zn(O,Se)-legeringar sker väsentliga minskningar av bandgapet med ∼1 eV vid koncentrationer nära 50%. För att beskriva beteendet hos bandgapet hos dessa legeringar föreslogs ett tillvägagångssätt som kombinerar två olika metodologier, där regionen nära binärerna beskrivs av bandets antikorsningsmodell, medan mellanregionen representerar legeringsbandets böjningsmodell. ZnO-GaN-legeringar visar också en bandgapsböjning och resultaten som erhållits genom beräkningarna är i god överensstämmelse med experimentella observationer. ZnTe uppvisar ett mellanband när det är dopat med en III-nitridförening, såsom GaN, AlN och InN. Denna effekt tros vara resultatet av resonansen mellan ZnTe-tillstånden och tillstånden härstammande från dopningselementen.
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| 4. |
- Bostrom, Mathias, et al.
(författare)
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Self-preserving ice layers on CO2 clathrate particles : Implications for Enceladus, Pluto, and similar ocean worlds
- 2021
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Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 650
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Tidskriftsartikel (refereegranskat)abstract
- Context. Gas hydrates can be stabilised outside their window of thermodynamic stability by the formation of an ice layer - a phenomenon termed self-preservation. This can lead to a positive buoyancy for clathrate particles containing CO2 that would otherwise sink in the oceans of Enceladus, Pluto, and similar oceanic worlds.Aims. Here we investigate the implications of Lifshitz forces and low occupancy surface regions on type I clathrate structures for their self-preservation through ice layer formation, presenting a plausible model based on multi-layer interactions through dispersion forces.Methods. We used optical data and theoretical models for the dielectric response for water, ice, and gas hydrates with a different occupancy. Taking this together with the thermodynamic Lifshitz free energy, we modelled the energy minima essential for the formation of ice layers at the interface between gas hydrate and liquid water.Results. We predict the growth of an ice layer between 0.01 and 0.2 mu m thick on CO, CH4, and CO2 hydrate surfaces, depending on the presence of surface regions depleted in gas molecules. Effective hydrate particle density is estimated, delimiting a range of particle size and compositions that would be buoyant in different oceans. Over geological time, the deposition of floating hydrate particles could result in the accumulation of kilometre-thick gas hydrate layers above liquid water reservoirs and below the water ice crusts of their respective ocean worlds. On Enceladus, the destabilisation of near-surface hydrate deposits could lead to increased gas pressures that both drive plumes and entrain stabilised hydrate particles. Furthermore, on ocean worlds, such as Enceladus and particularly Pluto, the accumulation of thick CO2 or mixed gas hydrate deposits could insulate its ocean against freezing. In preventing freezing of liquid water reservoirs in ocean worlds, the presence of CO2-containing hydrate layers could enhance the habitability of ocean worlds in our Solar System and on the exoplanets and exomoons beyond.
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| 5. |
- Boström, M., et al.
(författare)
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Tuning the Casimir-Lifshitz force with gapped metals
- 2023
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Ingår i: Physical Review B. - : American Physical Society (APS). - 2469-9950 .- 2469-9969. ; 108:16
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Tidskriftsartikel (refereegranskat)abstract
- The Casimir-Lifshitz interaction, a long-range force that arises between solids and molecules due to quantum fluctuations in electromagnetic fields, has been widely studied in solid-state physics. The degree of polarization in this interaction is influenced by the dielectric properties of the materials involved, which in turn are determined by factors such as band-to-band transitions, free carrier contributions, phonon contributions, and exciton contributions. Gapped metals, a new class of materials with unique electronic structures, offer the potential to manipulate dielectric properties and, consequently, the Casimir-Lifshitz interaction. In this study, we theoretically investigate the finite temperature Casimir-Lifshitz interaction in La3Te4-based gapped metal systems with varying off-stoichiometry levels. We demonstrate that off-stoichiometric effects in gapped metals can be used to control the magnitude and, in some cases, even the sign of Casimir-Lifshitz interactions. We predict measurable corrections due to stoichiometry on the predicted Casimir force between a La3Te4 surface and a gold sphere, attached to an atomic force microscopy tip.
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| 6. |
- Boström, M., et al.
(författare)
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Understanding ice and water film formation on soil particles by combining density functional theory and Casimir-Lifshitz forces
- 2023
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Ingår i: Physical Review B. - : American Physical Society (APS). - 2469-9950 .- 2469-9969. ; 108:12
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Tidskriftsartikel (refereegranskat)abstract
- Thin films of ice and water on soil particles play crucial roles in environmental and technological processes. Understanding the fundamental physical mechanisms underlying their formation is essential for advancing scientific knowledge and engineering practices. Herein, we focus on the role of the Casimir-Lifshitz force, also referred to as dispersion force, in the formation and behavior of thin films of ice and water on soil particles at 273.16 K, arising from quantum fluctuations of the electromagnetic field and depending on the dielectric properties of interacting materials. We employ the first-principles density functional theory (DFT) to compute the dielectric functions for two model materials, CaCO3 and Al2O3, essential constituents in various soils. These dielectric functions are used with the Kramers-Kronig relationship and different extrapolations to calculate the frequency-dependent quantities required for determining forces and free energies. Moreover, we assess the accuracy of the optical data based on the DFT to model dispersion forces effectively, such as those between soil particles. Our findings reveal that moisture can accumulate into almost micron-sized water layers on the surface of calcite (soil) particles, significantly impacting the average dielectric properties of soil particles. This research highlights the relevance of DFT-based data for understanding thin film formation in soil particles and offers valuable insights for environmental and engineering applications.
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| 7. |
- Damas, Giane B.
(författare)
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Atomic Scale Modelling in Photoelectrocatalysis : Towards the Development of Efficient Materials for Solar Fuel Production
- 2020
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Using sunlight to produce valuable chemicals has been pointed out as an interesting alternative to deal with the well-known environmental problem related to the use of fossil fuels for energy generation. Thus, it is crucial for this field the development of novel photocatalysts that could drive the uphill reactions with high efficiency while presenting low price and toxicity. In this context, conjugated polymers with a donor-acceptor architecture have shown good photoactivity for the hydrogen evolution reaction (HER) due to their advantageous properties, including a broad UV-Vis absorption spectrum and thermodynamic driving force to carry out the charge transfer processes. In this thesis, a series of fluorene- and benzothiadiazole-based polymers are evaluated by means of ab initio methods as potential candidates for photocatalytic HER. A set of small-molecules with well-defined molecular weight have also been considered for this application. In general, tailoring a chemical unit has enabled an improvement of the absorption capacity in benzo(triazole-thiadiazole)-based polymers and cyclopentadithiophene-based polymers, with a higher impact exhibited upon acceptor tailoring. On the other hand, all systems under investigation present favorable thermodynamics for proton reduction or hole removal by an appropriate sacrificial agent. In particular, it is demonstrated the active role played by nitrogen atoms from the acceptor units in the hydrogenation process, whose binding strength is significantly decreased in benzo(triazole-thiadiazole)-based polymers. Furthermore, the extension of the electron-hole separation has been assessed through the calculation of the exciton binding energies, which are diminished with an improvement in the donating ability on cyclopentadithiophene-based materials.In another approach to deal with the aforementioned problem, it has been considered the direct conversion of carbon dioxide into formic acid, an important chemical that finds applications in fuel cells, medicine and food industries. In this thesis, such electrocatalytic process has been investigated by using Sn-based electrodes and Ru-complexes. In the former case, a solid-state modelling approach based on slab geometries to model surface states has been employed to explore the reaction thermochemistry. The outcomes support the reaction mechanism where the carbon dioxide insertion into the Sn-OH bond is a thermodynamically favorable step prior to reduction, which has a redox potential in fair agreement with the measurements carried out by our collaborators. In a Ru-complex, the reaction mechanism is likely to follow the route with natural production of CO due to ligand release after the first reduction process, which is further protonated to originate the active species. In this case, the insertion occurs at the Ru-H bond to generate a carbon-bound species that is the intermediate in the formic acid production after the second protonation step. Finally, it has been studied the physical adsorption of carbon dioxide in metal-organic frameworks with a varying metallic center in a theoretical point of view.
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| 8. |
- Fiedler, Johannes, et al.
(författare)
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Full-Spectrum High-Resolution Modeling of the Dielectric Function of Water
- 2020
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Ingår i: Journal of Physical Chemistry B. - : American Chemical Society (ACS). - 1520-6106 .- 1520-5207. ; 124:15, s. 3103-3113
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Tidskriftsartikel (refereegranskat)abstract
- In view of the vital role of water, exact knowledge of its dielectric function over a large frequency range is important. We report on currently available measurements of the dielectric function of water at room temperature (25 degrees C) across the full spectrum: microwave, IR, UV, and X-ray (up to 100 eV). We parameterize the complex dielectric function of water with two Debye (microwave) oscillators and high resolution of IR and UV/X-ray oscillators. We also report dielectric parameters for ice-cold water with a microwave/IR spectrum measured at 0.4 degrees C, while taking the UV spectrum at 25 degrees C (assuming negligible temperature dependence in UV). We employ van der Waals dispersion interactions to contrast our model of ice-cold water with earlier models. Air bubbles in water and dissolved gas molecules show attraction toward interfaces rather than repulsion. The van der Waals interaction promotes complete freezing rather than supporting a thin layer of water on ice. We infer that premelting is driven by charge and ion adsorption. Density-based extrapolation from warm to cold water of the dielectric function is satisfactory in microwave but poor (40% error) at IR frequencies.
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| 9. |
- Fiedler, J., et al.
(författare)
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Perspectives on weak interactions in complex materials at different length scales
- 2023
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Ingår i: Physical Chemistry, Chemical Physics - PCCP. - : Royal Society of Chemistry (RSC). - 1463-9076 .- 1463-9084. ; 25:4, s. 2671-2705
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Forskningsöversikt (refereegranskat)abstract
- Nanocomposite materials consist of nanometer-sized quantum objects such as atoms, molecules, voids or nanoparticles embedded in a host material. These quantum objects can be exploited as a super-structure, which can be designed to create material properties targeted for specific applications. For electromagnetism, such targeted properties include field enhancements around the bandgap of a semiconductor used for solar cells, directional decay in topological insulators, high kinetic inductance in superconducting circuits, and many more. Despite very different application areas, all of these properties are united by the common aim of exploiting collective interaction effects between quantum objects. The literature on the topic spreads over very many different disciplines and scientific communities. In this review, we present a cross-disciplinary overview of different approaches for the creation, analysis and theoretical description of nanocomposites with applications related to electromagnetic properties.
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| 10. |
- Gao, Jiacheng, et al.
(författare)
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Irvsp : To obtain irreducible representations of electronic states in the VASP
- 2021
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Ingår i: Computer Physics Communications. - : ELSEVIER. - 0010-4655 .- 1879-2944. ; 261
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Tidskriftsartikel (refereegranskat)abstract
- We present an open-source program irvsp, to compute irreducible representations of electronic states for all 230 space groups with an interface to the Vienna ab-initio Simulation Package. This code is fed with plane-wave-based wavefunctions (e.g. WAVECAR) and space group operators (listed in OUTCAR), which are generated by the VASP package. This program computes the traces of matrix presentations and determines the corresponding irreducible representations for all energy bands and all the k-points in the three-dimensional Brillouin zone. It also works with spin-orbit coupling (SOC), i.e., for double groups. It is in particular useful to analyze energy bands, their connectivities, and band topology, after the establishment of the theory of topological quantum chemistry. Accordingly, the associated library -irrep_bcs.a - is developed, which can be easily linked to by other ab-initio packages. In addition, the program has been extended to orthogonal tight-binding (TB) Hamiltonians, e.g. electronic or phononic TB Hamiltonians. A sister program is presented as well. Program summary Program title: irvsp CPC Library link to program files: http://doi.org/10.1763/y9ds5nnm2f.1 Licensing provisions: GNU Lesser General Public License Programming language: Fortran 90/77 Nature of problem: Determining irreducible representations for all energy bands and all the k-points in 230 space groups. It is in particular useful to analyze energy bands, their connectivities, and band topology. Solution method: By computing the traces of matrix presentations of space group operators for the eigen-wavefunctions at a certain k-point in a given space group, one can determine irreducible representations for them.
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