| 1. |
- Shah, Furqan A., et al.
(författare)
-
3D printed Ti6Al4V implant surface promotes bone maturation and retains a higher density of less aged osteocytes at the bone-implant interface.
- 2016
-
Ingår i: Acta Biomaterialia. - : Elsevier BV. - 1878-7568 .- 1742-7061. ; 30, s. 357-367
-
Tidskriftsartikel (refereegranskat)abstract
- For load-bearing orthopaedic applications, metal implants having an interconnected pore structure exhibit the potential to facilitate bone ingrowth and the possibility for reducing the stiffness mismatch between the implant and bone, thus eliminating stress-shielding effects. 3D printed solid and macro-porous Ti6Al4V implants were evaluated after six-months healing in adult sheep femora. The ultrastructural composition of the bone-implant interface was investigated using Raman spectroscopy and electron microscopy, in a correlative manner. The mineral crystallinity and the mineral-to-matrix ratios of the interfacial tissue and the native bone were found to be similar. However, lower Ca/P ratios, lower carbonate content, but higher proline, phenylalanine and tyrosine levels indicated that the interfacial tissue remained less mature. Bone healing was more advanced at the porous implant surface (vs. the solid implant surface) based on the interfacial tissue ν1 CO3(2-)/ν2 PO4(3-) ratio, phenylalanine and tyrosine levels approaching those of the native bone. The mechanosensing infrastructure in bone, the osteocyte lacuno-canalicular network, retained ∼40% more canaliculi per osteocyte lacuna, i.e., a 'less aged' morphology at the interface. The osteocyte density per mineralised surface area was ∼36-71% higher at the interface after extended healing periods.
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| 2. |
- Shah, Furqan A., et al.
(författare)
-
Long-term osseointegration of 3D printed CoCr constructs with an interconnected open-pore architecture prepared by electron beam melting.
- 2016
-
Ingår i: Acta Biomaterialia. - : Elsevier BV. - 1878-7568 .- 1742-7061. ; 36:May, s. 296-309
-
Tidskriftsartikel (refereegranskat)abstract
- In orthopaedic surgery, cobalt chromium (CoCr) based alloys are used extensively for their high strength and wear properties, but with concerns over stress shielding and bone resorption due to the high stiffness of CoCr. The structural stiffness, principally related to the bulk and the elastic modulus of the material, may be lowered by appropriate design modifications, to reduce the stiffness mismatch between metal/alloy implants and the adjacent bone. Here, 3D printed CoCr and Ti6Al4V implants of similar macro-geometry and interconnected open-pore architecture prepared by electron beam melting (EBM) were evaluated following 26week implantation in adult sheep femora. Despite higher total bone-implant contact for Ti6Al4V (39±4%) than CoCr (27±4%), bone formation patterns were similar, e.g., densification around the implant, and gradual ingrowth into the porous network, with more bone in the outer half (periphery) than the inner half (centre). Raman spectroscopy revealed no major differences in mineral crystallinity, the apatite-to-collagen ratio, or the carbonate-to-phosphate ratio. Energy dispersive X-ray spectroscopy showed similar Ca/P ratio of the interfacial tissue adjacent to both materials. Osteocytes made direct contact with CoCr and Ti6Al4V. While osteocyte density and distribution in the new-formed bone were largely similar for the two alloys, higher osteocyte density was observed at the periphery of the porous network for CoCr, attributable to slower remodelling and a different biomechanical environment. The results demonstrate the possibility to achieve bone ingrowth into open-pore CoCr constructs, and attest to the potential for fabricating customised osseointegrated CoCr implants for load-bearing applications.
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| 3. |
- Andrews, L, et al.
(författare)
-
Infrared spectra of cis and trans-(NO)(2)(-) anions in solid argon
- 1998
-
Ingår i: Journal of Chemical Physics. - 1089-7690 .- 0021-9606. ; 109:1, s. 177-185
-
Tidskriftsartikel (refereegranskat)abstract
- Laser-ablation of over 20 different metal targets with concurrent 10 K codeposition of Ar/NO mixtures produces metal independent infrared bands at 1589.3 cm−1 due to (NO)2+, a new absorption at 1221.0 cm−1, and a band set at 1300.3, 1222.7, 884.4 cm−1. The latter bands decrease more on annealing than the 1221.0 cm−1 band. Isotopic substitution (14NO,15NO, 15N18O, and mixtures) shows that these new vibrations involve two equivalent N–O oscillators, which identifies two new (NO)2 species. The excellent agreement with frequencies, intensities, and isotopic frequency ratios from density functional theory calculations substantiates assignment of the 1221.0 cm−1 band to trans-(NO)2− and the three band set to cis-(NO)2−. The observation of a weak combination band at 2492.0 cm−1 further substantiates assignment of the two N–O stretching modes in cis-(NO)2−
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| 4. |
- Balachandramurthi, Arun Ramanathan, 1989-, et al.
(författare)
-
Microstructure tailoring in Electron Beam Powder Bed Fusion Additive Manufacturing and its potential consequences
- 2019
-
Ingår i: Results in Materials. - : Elsevier. - 2590-048X. ; 1
-
Tidskriftsartikel (refereegranskat)abstract
- Electron Beam Powder Bed Fusion process for Alloy 718 was investigated, in the sense of microstructural evolution with varying process conditions. The existence of a geometric relationship between the melt front and the processing parameters was observed. By understanding and capitalizing on this relationship, it was possible to obtain columnar, equiaxed or bimodal microstructure.
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| 5. |
- Bauschlicher, C.W., et al.
(författare)
-
A further study of the products of scandium and dioxygen reactions
- 1999
-
Ingår i: Journal of Physical Chemistry A. - 1089-5639 .- 1520-5215. ; 103:28, s. 5463-5467
-
Tidskriftsartikel (refereegranskat)abstract
- The products of the reaction of Sc and dioxygen have been reinvestigated. By adding the electron-trapping molecule CCl4 additional information about the IR spectra has been obtained, as well as the observation of new bands. New ab initio calculations are also performed on possible products of the Sc plus O-2 reaction. The previously observed band at 722.5 cm(-1) is assigned as the b(2) mode of ScO2-. Bands arising from ScO+, Sc(O-2)(+), and(O-2)ScO are also assigned. We are still unable to assign any bands to OScO. The problems associated with the computational study of ScO2 are discussed.
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| 6. |
- de Peppo, Giuseppe Maria, 1981, et al.
(författare)
-
Free-form-fabricated commercially-pure Ti and Ti6Al4V porous scaffolds support the growth of human embryonic stem cell-derived medsodermal progenitors
- 2012
-
Ingår i: The Scientific World Journal. - : Hindawi Limited. - 2356-6140 .- 1537-744X. ; 2012
-
Tidskriftsartikel (refereegranskat)abstract
- Commercially-pure titanium (cp-Ti) and the titanium-aluminum-vanadium alloy (Ti6Al4V) are widely used as reconstructive implants for skeletal engineering applications, due to their good mechanical properties, biocompatibility and ability to integrate with the surrounding bone. Electron beam melting technology (EBM) allows the fabrication of customized implants with tailored mechanical properties and high potential in the clinical practice. In order to augment the interaction with the biological tissue, stem cells have recently been combined with metallic scaffolds for skeletal engineering applications. We previously demonstrated that human embryonic stem cell-derived mesodermal progenitors (hES-MPs) hold a great potential to provide a homogeneous and unlimited supply of cells for bone engineering applications. This study demonstrates the effect of EBM-fabricated cp-Ti and Ti6Al4V porous scaffolds on hES-MPs behavior, in terms of cell attachment, growth and osteogenic differentiation. Displaying different chemical composition but similar surface properties, EBM-fabricated cp-Ti and Ti6Al4V scaffolds supported cell attachment and growth, and did not seem to alter the expression of genes involved in osteogenic differentiation and affect the alkaline phosphatase activity. In conclusion, interfacing hES-MPs to EBM-fabricated scaffolds may represent an interesting strategy for design of third-generation biomaterials, with the potential to promote implant integration in clinical conditions characterized by poor bone quality. Copyright 2012 G. M. de Peppo et al.
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| 7. |
- Forslund, Robert, 1990, et al.
(författare)
-
Analytical solution for heat conduction due to a moving Gaussian heat flux with piecewise constant parameters
- 2019
-
Ingår i: Applied Mathematical Modelling. - : Elsevier BV. - 0307-904X. ; 66, s. 227-240
-
Tidskriftsartikel (refereegranskat)abstract
- We provide an analytical solution of the heat equation in the half-space subject to a moving Gaussian heat flux with piecewise constant parameters. The solution is of interest in powder bed fusion applications where these parameters can be used to control the conduction of heat due to a scanning beam of concentrated energy. The analytical solution is written in a dimensionless form as a sum of integrals over (dimensionless) time. For the numerical computation of these integrals we suggest a quadrature scheme that utilizes pre-calculated look-up tables for the required quadrature orders. Such a scheme is efficient because the required quadrature orders are strongly dependent on the parameters in the heat flux. The possibilities of using the obtained computational technique for the control and optimization of powder bed fusion processes are discussed.
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| 8. |
- Karlsson, Joakim, et al.
(författare)
-
Characterization and comparison of materials produced by Electron Beam Melting (EBM) of two different Ti-6Al-4V powder fractions
- 2013
-
Ingår i: Journal of Materials Processing Technology. - : Elsevier BV. - 0924-0136 .- 1873-4774. ; 213:12, s. 2109-2118
-
Tidskriftsartikel (refereegranskat)abstract
- Electron Beam Melting (EBM) has been recognized as a revolutionary technique to produce mass-customized parts to near-net-shape from various metallic materials. The technique produces parts with unique geometries from a powder stock material and uses an electron beam to melt the powder layer-by-layer to fully solid structures. In this study we have investigated the use of two different Ti-6Al-4V powders of different size fractions in the EBM process; a larger 45-100 mu m powder, and a smaller 25-45 mu m powder. We have also investigated the effects of two build layer thicknesses, 70 mu m and 50 mu m. respectively. We hypothesize that the smaller powder has the potential to improve surface resolution of parts produced in the EBM process. The EBM as-built parts were investigated regarding surface and bulk chemistry, surface oxide thickness, macro- and microstructure, surface appearance and mechanical properties. We conclude from the results that both powders and both build layer thicknesses are feasible to use in the EBM process. The investigated material properties were not significantly affected by powder size or layer thickness within the studied range of process parameters. However, the surface appearance was found to be different for the samples made with the different powder sizes.
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| 9. |
- Karlsson, Joakim, 1984-, et al.
(författare)
-
Digital image correlation analysis of local strain fields on Ti6Al4V manufactured by electron beam melting
- 2014
-
Ingår i: Materials Science & Engineering. - : Elsevier BV. - 0921-5093 .- 1873-4936. ; 618, s. 456-461
-
Tidskriftsartikel (refereegranskat)abstract
- Additive manufacturing, or 3D-printing as it is often called, build parts in a layer-by-layer fashion. A common concern, regardless of the specific additive manufacturing technique used, is the risk of inadequate fusion between the adjacent layers which in turn may cause inferior mechanical properties. In this work, the local strain properties of titanium parts produced by Electron Beam Melting (EBM®) were studied in order to gain information about the quality of fusion of the stock powder material used in the process. By using Digital Image Correlation (DIC) the strain fields in the individual layers were analyzed, as well as the global strain behavior of the bulk material. The results show that fully solid titanium parts manufactured by EBM are homogenous and do not experience local deformation behavior, neither on local nor on a global level.
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| 10. |
- Karlsson, Joakim, 1984-, et al.
(författare)
-
Thickness dependency of mechanical properties for thin-walled titanium parts manufactured by Electron Beam Melting (EBM®)
- 2024
-
Ingår i: Additive Manufacturing. - : Elsevier. - 2214-8604 .- 2214-7810.
-
Tidskriftsartikel (refereegranskat)abstract
- Metal powder bed additive manufacturing technologies, such as the Electron Beam Melting process, facilitate a high degree of geometric flexibility and have been demonstrated as useful production techniques for metallic parts. However, the EBM process is typically associated with lower resolutions and higher surface roughness compared to similar laser-based powder bed metal processes. In part, this difference is related to the larger powder size distribution and thicker layers normally use As part of an effort to improve the resolution and surface roughness of EBM fabricated components, this study investigates the feasibility of fabricating components with a smaller powder size fraction and layer thickness (similar to laser based processes). The surface morphology, microstructure and tensile properties of the produced samples were evaluated. The findings indicate that microstructure is dependent on wall-thickness and that, for thin walled structures, tensile properties can become dominated by variations in surface roughness.
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| 11. |
- Karlsson, Joakim, 1984-, et al.
(författare)
-
Thickness dependency of surface properties for thin-walled titanium parts manufactured by Electron Beam Melting (EBM®)
-
Ingår i: Additive Manufacturing. - 2214-8604 .- 2214-7810.
-
Tidskriftsartikel (refereegranskat)abstract
- The surface morphology of components produced by powder bed metal additive manufacturing is of interest for multiple industry sectors including biomedical and aerospace. For some applications, improvements in surface finish can reduce or eliminate the requirement for secondary finishing processes. In this study, titanium alloy (Ti6Al4V) samples were manufactured using the Electron Beam Melting (EBM) process. The effect of variations in sample thickness, powder size distribution and layer thickness were measured with three different techniques, both for direct measurement and comparison of the techniques. Ra-values in the range of 15 µm – 37 µm were obtained and varied depending on measurement technique. However, independent of technique, Ra values were found to be dependent on powder size distribution, build layer thickness, and wall thickness. Analytical transmission electron microscopy of cross sections prepared by focused ion beam milling revealed that the outermost surfaces consisted of an oxide layer of 5 nm -6 nm thickness.
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| 12. |
- Lindahl, Carl, et al.
(författare)
-
Biomimetic calcium phosphate coating of additively manufactured porous CoCr implants
- 2015
-
Ingår i: Applied Surface Science. - : Elsevier BV. - 0169-4332 .- 1873-5584. ; 353, s. 40-47
-
Tidskriftsartikel (refereegranskat)abstract
- The aim of this work was to study the feasibility to use a biomimetic method to prepare biomimetic hydroxyapatite (HA) coatings on CoCr substrates with short soaking times and to characterize the properties of such coatings. A second objective was to investigate if the coatings could be applied to porous CoCr implants manufactured by electron beam melting (EBM). The coating was prepared by immersing the pretreated CoCr substrates and EBM implants into the phosphate-buffered solution with Ca2+ in sealed plastic bottles, kept at 60 degrees C for 3 days. The formed coating was partially crystalline, slightly calcium deficient and composed of plate-like crystallites forming roundish flowers in the size range of 300-500 nm. Cross-section imaging showed a thickness of 300-500 nm. In addition, dissolution tests in Tris-HCl up to 28 days showed that a substantial amount of the coating had dissolved, however, undergoing only minor morphological changes. A uniform coating was formed within the porous network of the additive manufactured implants having similar thickness and morphology as for the flat samples. In conclusion, the present coating procedure allows coatings to be formed on CoCr and could be used for complex shaped, porous implants made by additive manufacturing.
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| 13. |
- Lugez, C.L., et al.
(författare)
-
Infrared spectra of (NO)(2)(+), (NO)(2)(-), and (NO)(3)(-) trapped in solid neon
- 1999
-
Ingår i: Journal of Chemical Physics. - 1089-7690 .- 0021-9606. ; 110:21, s. 10345-10358
-
Tidskriftsartikel (refereegranskat)abstract
- New studies of the infrared spectra of the products which result on codeposition at approximately 5 K of a Ne:NO sample with Ne atoms that have been excited in a microwave discharge have led to new and revised assignments for several ionic species. The appearance of the ν1 absorption of ONNO+ for several new species with asymmetric isotopic substitution, but for no symmetrically substituted species, confirms the trans ground-state configuration for ONNO+. The behavior of a neon-matrix product absorption at 1227.5 cm−1 parallels that of an argon-matrix absorption at 1221.0 cm−1 which has recently been assigned to trans-ONNO−. The identity of the carrier of a product absorption at 1424.1 cm−1, contributed by a vibration of two symmetrically equivalent NO groups, has not been definitively established. This absorption exhibits complex photodestruction behavior. Three absorptions are assigned to cis,cis-(NO)3−, which has C2v symmetry, with the aid of density functional calculations of the isotopic substitution pattern for the vibrational fundamentals of this species. Similar calculations of the isotopic substitution patterns for other structures result in poor agreement with the experiments. Photodestruction of cis,cis-(NO)3− trapped in solid neon yields the N2O⋯NO2− complex.
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| 14. |
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| 15. |
- Palmquist, Anders, 1977, et al.
(författare)
-
Long-term biocompatibility and osseointegration of electron beam melted, free-form-fabricated solid and porous titanium alloy: Experimental studies in sheep.
- 2013
-
Ingår i: Journal of biomaterials applications. - : SAGE Publications. - 1530-8022 .- 0885-3282. ; 27:8, s. 1003-1016
-
Tidskriftsartikel (refereegranskat)abstract
- The purpose of the present study was to evaluate the long-term osseointegration and biocompatibility of electron beam melted (EBM) free-form-fabricated (FFF titanium grade 5 (Ti6Al4V) implants. Porous and solid machined cylindrical and disk-shaped implants were prepared by EBM and implanted bilaterally in the femur and subcutaneously in the dorsum of the sheep. After 26 weeks, the implants and surrounding tissue were retrieved. The tissue response was examined qualitatively and quantitatively using histology and light microscopic (LM) morphometry. Selected bone implants specimens were evaluated by scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), and micro-computed tomography (mCT). The results showed that both porous and solid implants were osseointegrated and high bone-implant contact was observed throughout the porous implant. In the soft tissue, the porous implants showed thinner fibrous encapsulation while no signs of intolerance were observed for either implant type. Taken together, the present experimental results show that FFF Ti6Al4V with and without porous structures demonstrate excellent long-term soft tissue biocompatibility and a high degree of osseointegration. The present findings extend earlier, short-term experimental observations in bone and suggest that EBM, FFF Ti6Al4V implants possess valuable properties in bone and soft tissue applications.
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| 16. |
- Panas, Itai, 1959, et al.
(författare)
-
Local signatures of high-T-c superconductivity - Possible origin of the pseudogap
- 1999
-
Ingår i: Journal of Low Temperature Physics. - 0022-2291 .- 1573-7357. ; 17:3-4, s. 419-423
-
Tidskriftsartikel (refereegranskat)abstract
- We have studied buffer ions induced holes clustering in the CuO2 plane by means of embedded cluster quantum chemistry calculations. This instability is suggested by Raman spectroscopy to be characteristic of the pseudo-gapped fermi surface at T
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| 17. |
- Panas, Itai, 1959, et al.
(författare)
-
Spectroscopic Properties of the High-Tc Materials by the Ab Initio Quantum Chemistry Paradigm
- 1998
-
Ingår i: International Journal of Modern Physics B. ; 12:29-31, s. 3317-3322
-
Tidskriftsartikel (refereegranskat)abstract
- The σ-π splitting for an embedded O- ion in a CuO2 plane is estimated and effects of crystal fields are evaluated. High fields favor σ-hole while the π-hole scenario is favored in low lattice fields. The results are discussed in the context of the tow-bands Raman continuum understanding put forward by Monien and Zawadowski2 and argued to support a recently proposed two-bands two-physics mechanism for superconductivity in the cuprates.
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| 18. |
- Panas, Itai, 1959, et al.
(författare)
-
Transition metal complexes with (NO)(3)(-) anions
- 1999
-
Ingår i: Chemical Physics Letters. - 0009-2614. ; 302:5-6, s. 431-436
-
Tidskriftsartikel (refereegranskat)abstract
- Density functional theory calculations are performed to determine structures, stabilities, and characteristic vibrational frequencies for metal complexes with nitric oxide trimer ligands. The study emphasizes the possible crucial importance of the 3.0 eV first ionization energy of the (NO)3− anion. Metal complexes with the composition M[(NO)3]2 are considered, where M is Mg, Ni, Cu, and Zn. Properties of the Cu(NO)3 complex are evaluated for reference. Possible technological importance to catalysis and drug delivery systems is implied.
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| 19. |
- Sandblad, Anders
(författare)
-
Yrkeskunnande Maskiner Människor
- 2021
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Denna avhandling handlar om yrkeskunnande och vad som händer när arbetsuppgifter läggs över på teknologi. Syftet är att bidra till förståelsen av yrkeskunnandet, dess roll och utveckling i ett allt mer digitaliserat arbetsliv. Intresset är riktat mot den erfarenhetsbaserade kunskapen.Avhandlingen omfattar tre delstudier: (i) en syntetiserande studie av resultat från ett urval av tidigare fallstudier om yrkeskunnande från 1970-talet och framåt; (ii) en ny fallstudie om yrkeskunnande i tillblivelse, där informanterna består av unga ingenjörer som är nya i yrkeslivet; samt (iii) en ny fallstudie om yrkeskunnande i karriären, där informanterna består av yrkesmänniskor med olika yrkesbakgrund och ett antal års praktisk erfarenhet. Den sistnämnda fallstudien är utvecklad inom masterprogrammet yrkeskunnande och professionsutveckling. De tre delstudierna förs samman för att forma en syntes som skapar insikter avseende långsiktiga kunskapsrelaterade konsekvenser av teknologins användning. Syntesen innebär en historieskrivning kring forskningen om yrkeskunnande och det paradigm som denna bygger på, där konsten som kunskapskälla utgör ett fundament.Resultaten visar att människor succesivt anpassar sitt sätt att tänka och uppfatta verkligheten efter den teknologi de använder. Teknologins utveckling har medfört att människan gradvis blir som maskinen hon använder. Det pågår en intellektuell inre mekanisering, vilken kan kontrasteras mot den yttre mekanisering av mänsklig muskelkraft som den industriella revolutionen innebar. Den digitala tidserans intellektuellt maskinella människa betraktar och beskriver verkligheten i teknologins termer och tappar gradvis förmågan att urskilja nyanser och göra kvalificerade bedömningar. Begreppen turingmänniskan respektive funktionell autism fångar dessa fenomen, vars långsiktiga konsekvens är att det professionella omdömet urholkas. Tacit engagement är ett begrepp som står för den tysta kunskap som bara kan komma till uttryck när människor delar fysisk plats.Skickligt yrkesutövande bygger på ansvarig handling. Det en skicklig yrkesmänniska kan har hon lärt genom reflekterad erfarenhet från de ansvariga handlingar hon utför. Ansvarigheten är situations- och kontextberoende och kan inte fångas av någon teknologi. Kärnan ligger i mötet med det oväntade. I ett samhälle och arbetsliv som alltmer domineras av teknologi och formalisering av arbete finns en risk att ansvaret riktas mot teknologin eller mot de formella processer, instruktioner och mätetal man använder. Konsekvensen är att såväl yrkeskunnandet som kvaliteten i arbetet urholkas långsiktigt.Det är inte maskiner med förmodat mänskliga förmågor och egenskaper vi behöver uppmärksamma, utan människor som succesivt blir som maskiner. Det som krävs för att värna den kunskap som är unik för människan i ett arbetsliv som blir allt mer digitaliserat är bildning. Inte minst den bildning avseende människan, livet och teknologins användning som konsten, den klassiska litteraturen och dramatiken är bärare av.
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| 20. |
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| 21. |
- Snis, Anders, et al.
(författare)
-
Abstraction of preadsorbed oxygen from CaO(100) by carbon monoxide
- 1994
-
Ingår i: Surf Sci Lett. - 0039-6028. ; 310:1-3
-
Tidskriftsartikel (refereegranskat)abstract
- The mechanism for abstraction of preadsorbed oxygen from CaO(100) by CO(g) to form CO2(g) is investigated by electronic structure calculations. The reaction mechanism is assumed to be the reverse of the one obtained for the decomposition of N2O(g) at CaO(100) [Surf. Sci 292 (1993) 317]. A 32 kcal/mol barrier for reaction is calculated. Adsorbed oxygen, Oads, to surface vibration frequencies in the range 840–930 cm−1 are calculated. These values are in qualitative agreement with experiment.
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| 22. |
- Snis, Anders, et al.
(författare)
-
Characterizations of (NO)(3)- and N3O2- molecular anions
- 1999
-
Ingår i: Chemical Physics Letters. - 0009-2614. ; 305:3-4, s. 285-292
-
Tidskriftsartikel (refereegranskat)abstract
- Isomers of (NO)3− are characterized by means of B3LYP density functional theory and the wavefunction-based CASPT2 method. Stabilities, vertical electron detachment energies (VDEs), vertical electron excitation energies (VEEs), and vibration frequencies are determined. Experimental isotope shifts in the IR spectrum of (NO)3− and theory were previously employed to determine the structure of an N–N–N connected anion. Further support for this assignment is obtained in the present study by comparing experimental and theoretical VDEs and VEEs. A parallel analysis of a w-shaped N3O2− molecular anion along the above lines is performed for reference, as a comprehensive understanding of the two systems is sought.
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| 23. |
- Snis, Anders, et al.
(författare)
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Effective dynamic correlation in multiconfigurational wave-function calculations on atoms and molecules
- 1997
-
Ingår i: Theoretical Chemistry Accounts. - 1432-881X .- 1432-2234. ; 97:1-4, s. 232-239
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Tidskriftsartikel (refereegranskat)abstract
- An intuitive understanding of dynamic correlation in terms of a regularized electron repulsion expression is outlined. Expressions for cusp kinetic energy corrected regularized electron repulsion integrals are deduced and implemented in a multiconfigurational wave-function framework. A regularized complete active space self-consistent field (reg-CASSCF) technique is suggested and tested on atomic total energies, molecular structures and binding energies.
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| 24. |
- Snis, Anders, et al.
(författare)
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MECHANISMS FOR MOLECULAR-OXYGEN DESORPTION FROM THE CAO(100) SURFACE
- 1995
-
Ingår i: Journal of Chemical Physics. - 1089-7690 .- 0021-9606. ; 103:17, s. 7626-7630
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Tidskriftsartikel (refereegranskat)abstract
- Electronic structure calculations have been employed to study the associative desorption of preadsorbed atomic oxygen from a calcium oxide (100) surface. Two reaction mechanisms were considered, corresponding to symmetric and asymmetric reaction paths. The energy barrier of the latter was found to be the lower of the two. The barrier for the asymmetric reaction was found to be sensitive both to the location of the nearest calcium ions and to the distance between the surface oxygen ions, and is argued to be strongly affected by surface temperature. The desorption mechanism is shown to be conceptually similar to the previously addressed N2O decomposition and CO2 formation reactions. Catalytical aspects are stressed as oxygen desorption from CaO(100) is compared to those of nickel and platinum.
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| 25. |
- Snis, Anders, et al.
(författare)
-
N2O adsorption and decomposition at a CaO (100) surface studied by means of theory
- 1993
-
Ingår i: Surf Sci. - 0039-6028. ; 292:3, s. 317-324
-
Tidskriftsartikel (refereegranskat)abstract
- The adsorption and decomposition of an N2O molecule at different sites on a CaO(s) surface are investigated by means of ab initio quantum chemistry. The calcium, Ca2+, and oxygen, Os2−, sites at a perfect (100) surface and at a corner position, Oc2−, are considered. Adsorption energies at different sites are calculated and the largest value, 6 kcal/mol, is obtained for a corner site. The barrier for dissociation is calculated to 26 and 27 kcal/mol at the Oc2− and Os2− sites, respectively. These values are some 10 kcal/mol lower than the experimental estimate, and the discrepancy is understood from methodological difficulties to describe the free N2O molecule. A mechanism for the dissociation over an O2− site is proposed, whereby the transfer of the O atom goes via a linear N-N … O … O2− transition state.
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| 26. |
- Snis, Anders, et al.
(författare)
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N2O2, N2O2- and N2O22-: structures, energetics and N-N bonding
- 1997
-
Ingår i: Chemical Physics. - 0301-0104. ; 221:1-2, s. 1-10
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Tidskriftsartikel (refereegranskat)abstract
- The density functional theory and the ab initio quantum chemistry methods, Becke3LYP and CASPT2, have been employed to determine structures and energetics of neutral and anionic N2O2 species. When going from a neutral NO dimer to an anionic species the N---N bond lengths decrease drastically and the corresponding N---N frequencies increase. The relative stabilities of the different N2O2− isomers suggest an ONNO structure in a Trans configuration to be the most stable mono valent anion. The formation energies of 1.4–1.7 eV relative to the NO + NO− asymptote are in agreement with experiments. Excitation energies are determined and specific formation channels for three N2O2− isomers are discussed. The hyponitrite ion, N2O22−, is also studied. Its total energy is 2.7–2.8 eV above the total energy of two NO−. In order to connect to an experimental study of NO adsorption on MgO the ability of two NO molecules to form a complex with Mg and Mg+ is investigated.
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| 27. |
- Snis, Anders, et al.
(författare)
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Structures and stabilities of some neutral and anionic (NO)(n)H-m based compounds (n=2-8, m=0-2)
- 1997
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Ingår i: Molecular Physics. - 1362-3028 .- 0026-8976. ; 91:5, s. 951-962
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Tidskriftsartikel (refereegranskat)abstract
- Structures and stabilities of various neutral and anionic (NO)nHm (n = 2-8, m =0-2) based molecules which display diaza bonds are determined. By taking the oxygen biradical resonance in ON=NO as the chemical building unit, some understanding of the bindings in these systems is obtained. The calculations employ the gradient corrected hybrid density functional theory approach Becke3LYP. For some of the species single point correlated ab initio electronic structure calculations were performed by means of the CASPT2 method. Connections are made to experimental findings at surfaces, where (NO)n clusters appear as either stable or metastable intermediates.
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| 28. |
- Snis, Anders, et al.
(författare)
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Surface complexes of nitric oxide: adsorption of anionic NO and N2O2 on CaO
- 1998
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Ingår i: Surface Science. - 0039-6028. ; 412-413, s. 477-488
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Tidskriftsartikel (refereegranskat)abstract
- Chemical reactions involving nitric oxide molecules and a calcium oxide surface are addressed by means of quantum chemistry. The regularised complete active space self-consistent field method (reg-CASSCF) is employed to determine structures and vibrational frequency bands of the monomeric and dimeric surface species. Stabilities are computed by the CASPT2 method. Reactivity trends for the adsorbates are estimated for various surface sites, including bonding to the Ca and O surface atoms, to an oxygen vacancy and to two different edge sites. Implications of excess surface electrons to heterogeneous NO reduction processes at oxide catalysts are discussed.
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| 29. |
- Suska, Felicia, 1974, et al.
(författare)
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Electron Beam Melting Manufacturing Technology for Individually Manufactured Jaw Prosthesis: A Case Report
- 2016
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Ingår i: Journal of Oral and Maxillofacial Surgery. - : Elsevier BV. - 0278-2391 .- 1531-5053. ; 74:8
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Tidskriftsartikel (refereegranskat)abstract
- In the field of maxillofacial reconstruction, additive manufacturing technologies, specifically electron beam melting (EBM), offer clinicians the potential for patient-customized design of jaw prostheses, which match both load-bearing and esthetic demands. The technique allows an innovative, functional design, combining integrated porous regions for bone ingrowth and secondary biological fixation with solid load-bearing regions ensuring the biomechanical performance. A patient-specific mandibular prosthesis manufactured using EBM was successfully used to reconstruct a patient's mandibular defect after en bloc resection. Over a 9-month follow-up period, the patient had no complications. A short operating time, good esthetic outcome, and high level of patient satisfaction as measured by quality-of-life questionnaires-the European Organisation for Research and Treatment of Cancer QLQ-C30 (30-item quality-of-life core questionnaire) and H&N35 (head and neck cancer module)-were reported for this case. Individually planned and designed EBM-produced prostheses may be suggested as a possible future alternative to fibular grafts or other reconstructive methods. However, the role of porosity, the role of geometry, and the optimal combination of solid and porous parts, as well as surface properties in relation to soft tissues, should be carefully evaluated in long-term clinical trials. (C) 2016 American Association of Oral and Maxillofacial Surgeons
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| 30. |
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| 31. |
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| 32. |
- Willermark, Sara, 1988-
(författare)
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Digital Didaktisk Design : Att utveckla undervisning i och för en digitaliserad skola
- 2018
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- I denna avhandling undersöks grundskollärares arbete med att utveckla sin undervisningspraktik med digital teknik. Mer precist undersöks hur en sådan utveckling kan identifieras, förstås och stödjas. Empirin härstammar primärt från ett treårigt aktionsorienterat skolutvecklingsprojekt i nordisk grundskola. Inom projektet samarbetade lärare från Sverige, Norge och Danmark för att utveckla nya undervisningsaktiviteter över nationsgränserna med stöd av digital teknik. Lärare organiserades inom olika ämnesspecifika designteam för att planera, implementera och utvärdera undervisningsaktiviteter, så kallad digital didaktisk design, vilket avser utformandet av en undervisningssekvens, som adresserar ett specifikt ämne inom ett visst ämnesområde. Det empiriska underlaget utgörs av dokumentation över den digitala didaktiska designen, deltagande observationer, intervjuer och innehållsanalyser samt en enkätundersökning. Två teoretiska ramverk används, TPACK (akronym för Technological Pedagogical And Content Knowledge) och verksamhetsteori. Resultaten påvisar en utveckling av lärares undervisningspraktik. Med stöd av digital teknik skapar lärare digital didaktisk design över nationsgränser, som ger upphov till nya aktiviteter, situationer och möten. Det krävdes dock både omfattande arbetsinsatser och ett praktiskt experimenterande under lång tid, för att lärarna skulle kunna utveckla digital didaktisk design som upplevdes meningsfull i den nya kontexten. Motsättningar och organisatoriska gränser mellan de samverkande lärarna identifierades som avgörande för utvecklingen, genom att ge upphov till förhandlingar, kompromisser och reflektion. Avhandlingen bidrar med ett verktyg för att identifiera och stödja lärares arbetemed att utveckla sin undervisningspraktik med digital teknik. Vidare föreslås en strategi för att identifiera och analysera lärares utveckling över tid. Avhandlingen bidrar också med kunskap om hur olika typer av spänningar och gränser vid samarbete kan stimulera till lärande för en digitaliserad undervisningspraktik, liksom rekommendationer för hur utbildningsinsatser för lärare kan utformas i syfte att stödja lärares utveckling av undervisningspraktiken.
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| 33. |
- Ålgårdh Karlsson, Joakim, et al.
(författare)
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Thickness dependency of mechanical properties for thin-walled titanium parts manufactured by Electron Beam Melting (EBM)®
- 2016
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Ingår i: Additive Manufacturing. - : Elsevier. - 2214-8604 .- 2214-7810. ; 12, s. 45-50
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Tidskriftsartikel (refereegranskat)abstract
- Metal powder bed additive manufacturing technologies, such as the Electron Beam Melting process, facilitate a high degree of geometric flexibility and have been demonstrated as useful production techniques for metallic parts.However, the EBM process is typically associated with lower resolutions and higher surface roughness compared to similar laser-based powder bed metal processes. In part, this difference is related to the larger powder size distribution and thicker layers normally used. As part of an effort to improve the resolution and surface roughness of EBM fabricated components, this study investigates the feasibility of fabricating components with a smaller powder size fraction and layer thickness (similar to laser based processes). The surface morphology, microstructure and tensile properties of the produced samples were evaluated. The findings indicate that microstructure is dependent on wall-thickness and that, for thin walled structures, tensile properties can become dominated by variations in surface roughness.
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