| 1. |
- Ahlinder, Astrid, et al.
(författare)
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Nondegradative additive manufacturing of medical grade copolyesters of high molecular weight and with varied elastic response
- 2020
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Ingår i: Journal of Applied Polymer Science. - : WILEY. - 0021-8995 .- 1097-4628. ; 137:15
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Tidskriftsartikel (refereegranskat)abstract
- Although additive manufacturing through melt extrusion has become increasingly popular as a route to design scaffolds with complex geometries the technique if often limited by the reduction in molecular weight and the viscoelastic response when degradable aliphatic polyesters of high molecular weight are used. Here we use a melt extruder and fused filament fabrication printer to produce a reliable nondegradative route for scaffold fabrication of medical grade copolymers of L-lactide, poly(epsilon-caprolactone-co-L-lactide), and poly(L-lactide-co-trimethylene carbonate). We show that degradation is avoided using filament extrusion and fused filament fabrication if the process parameters are deliberately chosen based upon the rheological behavior, mechanical properties, and polymer composition. Structural, mechanical, and thermal properties were assessed throughout the process to obtain comprehension of the relationship between the rheological properties and the behavior of the medical grade copolymers in the extruder and printer. Scaffolds with a controlled architecture were achieved using high-molecular-weight polyesters exhibiting a large range in the elastic response causing negligible degradation of the polymers.
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| 2. |
- Almbladh, Carl-Olof, et al.
(författare)
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IMPORTANCE OF SURFACE EFFECTS AND DYNAMICAL CORE-HOLE EFFECTS IN AUGER SPECTRA OF METALS AND SEMICONDUCTORS
- 1987
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Ingår i: Journal de Physique. Colloques. ; 48:c-9, s. 879-890
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Tidskriftsartikel (refereegranskat)abstract
- Auger CVV spectra of sp-bonded materials are generally believed to be well described by one-electron theory in the bulk. We here perform detailed calculations on several simple metals and on silicon and obtain results which differ markedly from experiments. To explain these discrepancies we investigate effects of the surface and dynamical effects of the sudden disappearance of the core hole in the final state. To study core-hole effects we solve Mahan-Nozières-DeDominicis (MND) model numerically over the entire band. The core-hole potential and other parameters in the MND model are determined by self-consistent calculations on systems with a core-hole impurity. To study surface and mean free path effects we perform slab calculations in the case of silicon, whereas we for the metals use a simpler infinite barrier model in which the valence states near the surface are constructed from Bloch states in a simple way. In all cases investigated either the effects of the surface or the effects of the core hole give important modifications and a much improved agreement with experiments.
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| 3. |
- Almbladh, Carl-Olof, et al.
(författare)
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Many-Body Theory of Auger Processes in Metals and Semiconductors
- 1988
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Ingår i: Recent Progress in Many-Body Theories. - 9781461309734 ; 1, s. 317-328
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Bokkapitel (refereegranskat)abstract
- Auger spectra of solids arise from radiationless decay of innershell vacancies created by x-ray or electron bombardment. In a corevalence-valence (CVV) Auger process, for instance, one valence electron is filling the core hole while another valence electron is ejected and carries away the excess energy. The core hole is essentially dispersionless, and thus the spectrum of emitted electrons would, in the simplest one-electron picture, reflect the self-folded valence-electron state density. Such a simple model is, of course, grossly oversimplified, and the importance of matrix element effects has been demonstrated by several authors.1 However, no detailed investigation of many-body effects has been presented thus far for sp-bonded materials, and the current view is that one electron theory and bulk wavefunctions suffice to explain the experimental results.
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| 4. |
- Almbladh, Carl-Olof, et al.
(författare)
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Phonon effects in deep-level spectra of metals: Beyond the linear-screening and linear-coupling models
- 1983
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Ingår i: Physical Review B. - 1550-235X. ; 28:12, s. 7362-7365
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Tidskriftsartikel (refereegranskat)abstract
- A priori calculations of phonon broadening of core levels in metals are presented. The effects of nonlinear screening and higher-order couplings are taken into account for the first time. The nonlinear screening effects are very important for Li and must be accounted for in order to obtain agreement with experiment.
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| 5. |
- Almbladh, Carl-Olof, et al.
(författare)
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Phonon effects on deep-level excitations in metals: Beyond the linear-screening and linear-coupling models
- 1985
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Ingår i: Journal of Physics F: Metal Physics. - 0305-4608. ; 15:4, s. 991-1012
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Tidskriftsartikel (refereegranskat)abstract
- New theoretical developments in impurity lattice dynamics are presented, with the emphasis on phonon broadening of core levels in metals. Detailed calculations have been made for Li and Na. The effects of non-linear screening are evaluated for the first time and are shown to increase the phonon broadening by about 70% for Li compared with the linear-screening value. The present a priori estimate of the phonon broadening of the Li 1s level is the first which agrees with experiment. The effects of core-hole-lattice couplings of second order in ion displacements are also evaluated and shown to be unimportant for Li and Na. The usual linear-screening theory for lattice dynamics and for impurity-lattice couplings is analysed critically with regard to its sensitivity to the approximations for the pseudopotential and for the screening function. Both optimised model potentials and norm-conserving a priori potentials are considered. Finally, an indirect phonon broadening mechanism proposed previously is analysed and shown to give a negligible effect.
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| 6. |
- Almbladh, Carl-Olof, et al.
(författare)
-
Theory of Auger core-valence-valence processes in simple metals. I. Total yields and core-level lifetime widths
- 1989
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Ingår i: Physical Review B. - 1550-235X. ; 39:6, s. 3489-3502
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Tidskriftsartikel (refereegranskat)abstract
- There is a considerable disagreement in the literature on the description of lifetime effects arising from core-valence transitions in solids. We calculate here Auger and radiative widths of shallow core levels in Li, Be, Na, Mg, and Al with use of principles consistent with dynamical theories of secondary-emission processes developed earlier. The lifetime has no simple relation to the usual self-energy but is instead directly related to emission yields. The problem of choosing reliable approximations for Auger rates and matrix elements is analyzed theoretically and computationally. We also comment on some earlier approaches. Much of our discussion pertains also to calculations of Auger line shapes from first principles. For long hole lifetimes the total and partial level widths obey an initial-state rule and follow from wave functions perturbed by a static core hole. To obtain these impurity wave functions we perform self-consistent supercell calculations. The core-hole screening increases the Auger rates by factors of the order 2–4 compared with results from ground-state orbitals but has never been properly included before. The width of the 1s level in Li is rather accurately known because it monitors large effects of incomplete lattice relaxation. For Li we obtain here a width 17 meV in excellent agreement with the value 16 meV deduced earlier from measurements by Callcott et al.
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| 7. |
- Almbladh, Carl-Olof, et al.
(författare)
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Theory of Auger core-valence-valence processes in simple metals. II. Dynamical and surface effects on Auger line shapes
- 1989
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Ingår i: Physical Review B. - 1550-235X. ; 39:6, s. 3503-3516
-
Tidskriftsartikel (refereegranskat)abstract
- Auger CVV spectra of simple metals are generally believed to be well described by one-electron-like theories in the bulk which account for matrix elements and, in some cases, also static core-hole screening effects. We present here detailed calculations on Li, Be, Na, Mg, and Al using self-consistent bulk wave functions and proper matrix elements. The resulting spectra differ markedly from experiment and peak at too low energies. To explain this discrepancy we investigate effects of the surface and dynamical effects of the sudden disappearance of the core hole in the final state. To study core-hole effects we solve Mahan-Nozières-De Dominicis (MND) model numerically over the entire band. The core-hole potential and other parameters in the MND model are determined by self-consistent calculations of the core-hole impurity. The results are compared with simpler approximations based on the final-state rule due to von Barth and Grossmann. To study surface and mean-free-path effects we perform slab calculations for Al but use a simpler infinite-barrier model in the remaining cases. The model reproduces the slab spectra for Al with very good accuracy. In all cases investigated either the effects of the surface or the effects of the core hole give important modifications and a much improved agreement with experiment.
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| 8. |
- Barack, Leor, et al.
(författare)
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Black holes, gravitational waves and fundamental physics : a roadmap
- 2019
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Ingår i: Classical and quantum gravity. - : IOP Publishing. - 0264-9381 .- 1361-6382. ; 36:14
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Forskningsöversikt (refereegranskat)abstract
- The grand challenges of contemporary fundamental physics dark matter, dark energy, vacuum energy, inflation and early universe cosmology, singularities and the hierarchy problem all involve gravity as a key component. And of all gravitational phenomena, black holes stand out in their elegant simplicity, while harbouring some of the most remarkable predictions of General Relativity: event horizons, singularities and ergoregions. The hitherto invisible landscape of the gravitational Universe is being unveiled before our eyes: the historical direct detection of gravitational waves by the LIGO-Virgo collaboration marks the dawn of a new era of scientific exploration. Gravitational-wave astronomy will allow us to test models of black hole formation, growth and evolution, as well as models of gravitational-wave generation and propagation. It will provide evidence for event horizons and ergoregions, test the theory of General Relativity itself, and may reveal the existence of new fundamental fields. The synthesis of these results has the potential to radically reshape our understanding of the cosmos and of the laws of Nature. The purpose of this work is to present a concise, yet comprehensive overview of the state of the art in the relevant fields of research, summarize important open problems, and lay out a roadmap for future progress. This write-up is an initiative taken within the framework of the European Action on 'Black holes, Gravitational waves and Fundamental Physics'.
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| 9. |
- Benitez, Almudena, et al.
(författare)
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Recent advances in lithium-sulfur batteries using biomass-derived carbons as sulfur host
- 2022
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Ingår i: Renewable & sustainable energy reviews. - : Elsevier. - 1364-0321 .- 1879-0690. ; 154
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Tidskriftsartikel (refereegranskat)abstract
- While biomass waste is generated in abundance, these materials and their production processes are generally environmentally friendly, low cost, non-hazardous and easily scalable. These advantages position biomass materials as excellent candidates to solve problems of environmental pollution, primarily by substitution of less sustainable counterparts. This also applies to energy storage systems such as batteries, where several components have large environmental impacts. Lithium-Sulfur batteries have, in this context, been extensively researched to cope with the growing energy needs, and are expected to foresee a growing commercialization. Specifically, advances in the use of renewable cathode materials for Li-S batteries is a field that has been widely addressed in recent years, with carbonaceous materials (C) and/or activated carbons (AC), obtained from biomass, being intensively studied. We here reviewed this field through a classification and discussion of carbonaceous materials from natural waste according to the type of biomass: (1) woody, (2) herbaceous and agricultural, (3) aquatic, (4) animal and human, and (5) contaminated and industrial biomass waste materials. In addition, all porous carbons or activated carbons used as sulfur hosts have been exhaustively evaluated in terms of origin, synthesis parameters, physical properties, and electrochemical performance in Li-S batteries. The purpose is to provide a general description of the progress in the preparation of carbons from biomass resources, examine the textural and electrochemical properties of these materials focusing on the last decade, and also to present an outlook for future research in this developing area.
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| 10. |
- Calle Cordón, Álvaro, et al.
(författare)
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Combined RAMS and LCC analysis in railway and road transport infrastructures
- 2018
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Ingår i: Proceedings of 7th Transport Research Arena TRA. - Vienna, Austria.
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Konferensbidrag (refereegranskat)abstract
- Life-cycle cost (LCC) analysis is an assessment technique used to evaluate costs incurred during the life-cycle of a system to help in long term decision making. In railway and road transport infrastructures, costs are subject to numerous uncertainties associated to the operation and maintenance phase. By integrating in the LCC the stochastic nature of failure using Reliability, Maintainability, Availability and Safety (RAMS) analyses, maintenance costs can be more reliably estimated. This paper presents an innovative approach for a combined RAMS&LCC methodology for linear transport infrastructures which has been developed under the H2020 project INFRALERT. Results of the application of such methodology in two real use cases are shown, one for rail and another one for road. The use cases show how the approach is implemented in practice.
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