| 1. |
- Toijer, Elin, et al.
(författare)
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Ab initio investigation of effects of solute segregation onintergranular fracture in nickel: Importance of fracture path andstructural modification
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- In the present work, the impact of chromium and silicon impurities on thegrain boundary strength of nickel has been investigated by means of densityfunctional theory (DFT) modelling. The excess-energy approach has beenused to model the impact of the solutes, and a quantitative comparison of their corresponding impact in combination with the impact of phosphorus, self-interstitial Ni is here presented. The results of main importance are inreference to the Cr: It is shown that the common assumption that interstitial Cr segregates to the center of a GB gives decisively erroneous resultsregarding the impact of the solute in this context. The solute will instead remain at the GB surface, and consequently self interstitial Ni will migrateto the GB center. This configuration will give an important weakening tothe structure, in clear contrast to previous studies were Cr has been shown to promote strengthening of the same structure. However, the results in the current work further show that this weakening is in fact not due to the presence of Cr, but to the enrichment of self-interstitial atoms in the GB center.
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| 2. |
- Toijer, Elin, et al.
(författare)
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Ab initio modelling of intergranular fracture of nickel containing phosphorus : Interfacial excess properties
- 2021
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Ingår i: Nuclear Materials and Energy. - : Elsevier BV. - 2352-1791. ; 28
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Tidskriftsartikel (refereegranskat)abstract
- In the present work, the impact of phosphorus impurities on the grain boundary strength of nickel has been investigated by means of density functional theory (DFT) modelling. Owing to different outcomes and trends previously reported in the literature, it is unclear whether P is strengthening or weakening the Ni grain boundary. To address this issue, we utilize three different DFT based methods: the excess-energy approach, rigid grain separation, and Rice-Wang's thermodynamic approach. The results show that the commonly used rigid model predicts P to have an increasing effect on the peak stress of Ni of up to 14%, as opposed to a reduction, which is indicated by the excess-energy approach. Employment of the Rice-Wang approach, on the other hand, displays a slight reduction in work of separation. The results show that the discrepancies between previous works can be attributed not so much to the physics of the system, but to the applied model, the partition scheme and the interpretation of the outcomes. This underlines the importance of a proper description of the fracture process, and shows that common simplifications can have a decisive impact on the observed trends.
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| 3. |
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| 4. |
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| 5. |
- Rydén, Lisa, et al.
(författare)
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Reproducibility of human epidermal growth factor receptor 2 analysis in primary breast cancer: a national survey performed at pathology departments in Sweden.
- 2009
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Ingår i: Acta oncologica (Stockholm, Sweden). - : Informa UK Limited. - 1651-226X .- 0284-186X. ; 48:6, s. 860-6
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Tidskriftsartikel (refereegranskat)abstract
- HER2 is a treatment predictive factor for the effect of trastuzumab and associated with poor prognosis in breast cancer. The analysis of HER2 must be performed with good quality, with regard to both the immunohistochemical (IHC) and in situ hybridization (ISH) analysis.A tissue microarray (TMA) including 11 breast cancer samples was sent twice (once in 2005 and again in 2006) to 24 pathology departments in Sweden. A questionnaire was also sent to the departments in 2006.With IHC, all departments reported the same results (0/1+ vs. 2+ vs. 3 + ) for three (2005) and six samples (2006). The mean kappa-value increased from 0.67 to 0.77, indicating a good reproducibility at both occasions. With fluorescence-ISH (FISH), the 11 departments using this technique reported the same results (amplified vs. normal) for nine (2005) and ten samples (2006). The mean kappa-value showed very good reproducibility both 2005 and 2006 (0.92 and 0.96, respectively). Based on the answers from the participating departments, the questionnaire revealed that 31% of primary breast cancer diagnosed in 2006 (n = 5 043) were 2 + /3+. FISH analysis of 2+ confirmed 12% of the samples to be amplified. The corresponding figure for 3 + was 90%. In total, 14.3% of the samples were HER2 positive (2+ and amplified, or 3 + ).The results obtained in this study indicate that the reproducibility for HER2 analysis is good (IHC) and very good (FISH) between the pathology departments in Sweden using TMA-based tumor samples. In 2006, 14.3% of invasive breast cancers were HER2 positive.
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| 6. |
- Söderquist, Pär, et al.
(författare)
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Evaluation of Nutritional Quality and Sensory Parameters of Meat from Mallard and Four Species of Wild Goose
- 2022
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Ingår i: Foods. - : MDPI Multidisciplinary Digital Publishing Institute. - 2304-8158. ; 11:16, s. 1-13
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Tidskriftsartikel (refereegranskat)abstract
- Future challenges concerning protein supply for food and feed include the management of all currently available resources. In Sweden, wildfowl are hunted for several reasons, one of which is to protect growing crops. In this study, meat from wild geese and mallard was evaluated with respect to its quality and sensory parameters. The most pronounced sensory differences were between meat from the barnacle goose and the Canada goose and between meat from mallards that were farmed and born wild. This study also provides measurements of values for the nutritional and heavy metal contents of the meat from these wildfowl species in order to elucidate their possible use as modern foods.
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| 7. |
- Abdalla, Maie, et al.
(författare)
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Anorectal Function After Ileo-Rectal Anastomosis Is Better than Pelvic Pouch in Selected Ulcerative Colitis Patients
- 2020
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Ingår i: Digestive Diseases and Sciences. - : Springer-Verlag New York. - 0163-2116 .- 1573-2568. ; , s. 250-259
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: With a lifelong perspective, 12% of ulcerative colitis patients will need a colectomy. Further reconstruction via ileo-rectal anastomosis or pouch can be affected by patients' perspective of their quality of life after surgery.AIM: To assess the function and quality of life after restorative procedures with either ileo-rectal anastomosis or ileal pouch-anal anastomosis in relation to the inflammatory activity on endoscopy and in biopsies.METHOD: A total of 143 UC patients operated with subtotal colectomy and ileo-rectal anastomosis or pouches between 1992 and 2006 at Linköping University Hospital were invited to participate. Those who completed the validated questionnaires (Öresland score, SF-36, Short Health Scale) were offered an endoscopic evaluation including multiple biopsies. Associations between anorectal function and quality of life with type of restorative procedure and severity of endoscopic and histopathologic grading of inflammation were evaluated.RESULTS: Some 77 (53.9%) eligible patients completed questionnaires, of these 68 (88.3%) underwent endoscopic evaluation after a median follow-up of 12.5 (range 3.5-19.4) years after restorative procedure. Patients with ileo-rectal anastomosis reported better overall Öresland score: median = 3 (IQR 2-5) for ileo-rectal anastomosis (n = 38) and 10 (IQR 5-15) for pouch patients (n = 39) (p < 0.001). Anorectal function (Öresland score) and endoscopic findings (Baron-Ginsberg score) were positively correlated in pouch patients (tau: 0.28, p = 0.006).CONCLUSION: Patients operated with ileo-rectal anastomosis reported better continence compared to pouches. Minor differences were noted regarding the quality of life. Ileo-rectal anastomosis is a valid option for properly selected ulcerative colitis patients if strict postoperative endoscopic surveillance is carried out.
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| 8. |
- Abrikosov, I. A., et al.
(författare)
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Correlation between electronic structure, magnetism and physical properties of Fe-Cr alloys : Ab initio modeling
- 2008
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Ingår i: MATERIALS ISSUES FOR GENERATION IV SYSTEMS. - Dordrecht : Springer Netherlands. ; , s. 153-168
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Konferensbidrag (refereegranskat)abstract
- We review recent developments in the field of ab initio electronic structure theory and its application for studies of phase stability of alloy systems. Basic ideas behind state-of-the-art techniques for first-principles theoretical simulations of the phase stabilities and properties of intermetallic compounds and alloys based on the density functional theory are outlined. We concentrate on methods that allow for an efficient treatment of disorder effects, and illustrate their predictive power for the case of Fe-Cr system. We show that in the ferromagnetic alloys there are peculiarities of the mixing enthalpy in the low-Cr region in the bee phase. Thus the stability of the Cr containing steels stems from the negative mixing enthalpy at low concentrations of chromium. We explain the effect by the strong concentration dependence of the interatomic interactions in Fe-Cr system.
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| 9. |
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| 10. |
- Adelmann, Kenneth, et al.
(författare)
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Språkutveckling, medier och demokrati
- 2014
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Ingår i: Medie- och informationskunnighet i Norden. - Göteborg : Nordicom. - 9789186523886 ; , s. 117-129
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Bokkapitel (övrigt vetenskapligt/konstnärligt)
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| 11. |
- Adelmann, Kent, et al.
(författare)
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Språkutveckling, medier och demokrati
- 2014
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Ingår i: Medie- och informationskunnighet i Norden. - : Nordicom. - 9789186523886 ; , s. 117-121
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Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract
- Vi som har skrivit denna artikel är alla verksamma inom forskningsmiljön Svenska med didaktisk inriktning (SMDI) vid Malmö högskola. Frågor om språkutveckling i bred bemärkelse står här i centrum. För närvarande är vi engagerade i projektet ”SMDI och lärande i medielandskapet 2.0”. Vår teoretiska plattform kan beskrivas som medieekologisk, vilket kortfattat uttryckt innebär att vi är intresserade av de mångfaldiga och komplexa relationerna mellan medier och kommunikativa kompetenser (Elmfeldt & Erixon 2007; Erixon 2012; Hayles 2002). Dessa relationer förstås därför inte, som så ofta annars i skolsammanhang, i termer av enkelriktad påverkan eller effekter (exempelvis datorns och internets negativa inverkan på skriftspråket). Vår huvudpoäng i denna artikel är att medie- och informationskunnighet, MIK, handlar om, borde handla om, framför allt två saker: språkutveckling och demokrati.
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| 12. |
- Adloff, C, et al.
(författare)
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A measurement of the t dependence of the helicity structure of diffractive rho meson electroproduction at HERA
- 2002
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Ingår i: Physics Letters. Section B: Nuclear, Elementary Particle and High-Energy Physics. - 0370-2693. ; 539:1-2, s. 25-39
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Tidskriftsartikel (refereegranskat)abstract
- The helicity structure of the diffractive electroproduction of rho mesons, e + p --> e + rho + Y, is studied in a previously unexplored region of large four-momentum transfer squared at the proton vertex, t: 0 < t' < 3 GeV2, where t' = - min. The data used are collected with the HI detector at HERA in the kinematic domain 2.5 < Q(2) < 60 GeV2, 40 < W < 120 GeV No t dependence of the r(00)(04) spin density matrix element is found. A significant t dependent helicity non-conservation from the virtual photon to the rho meson is observed for the spin density matrix element combinations r(00)(5) + 2r(11)(5) and r(00)(1) + 2r(11)(1). These t dependences are consistently described by a perturbative QCD model based on the exchange of two gluons.
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| 13. |
- Adloff, C, et al.
(författare)
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Diffractive photoproduction of psi(2S) mesons at HERA
- 2002
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Ingår i: Physics Letters. Section B: Nuclear, Elementary Particle and High-Energy Physics. - 0370-2693. ; 541:3-4, s. 251-264
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Tidskriftsartikel (refereegranskat)abstract
- Results on diffractive photoproduction of psi(2S) mesons are presented using data collected between 1996 and 2000 with the H1 detector at the HERA ep collider. The data correspond to an integrated luminosity of 77 pb(-1). The energy dependence of the diffractive psi(2S) cross section is found to be similar to or possibly somewhat steeper than that for J/psi mesons. The dependences of the elastic and proton dissociative psi(2S) photoproduction cross sections on the squared momentum transfer t at the proton vertex are measured. The t-dependence of the elastic channel, parametrised as e(bt), yields b(el)(psi(2S)) = (4.31 +/- 0.57 +/- 0.46) GeV-2, compatible with that of the J/psi. For the proton dissociative channel the result b(pd)(psi(2S)) = (0.59 +/- 0.13 +/- 0.12) GeV-2 is 2.3 standard deviations smaller than that measured for the J/psi. With proper account of the individual wavefunctions theoretical predictions based on perturbative QCD are found to describe the measurements well. (C) 2002 Elsevier Science B.V. All rights reserved.
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| 14. |
- Adloff, C, et al.
(författare)
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Energy flow and rapidity gaps between jets in photoproduction at HERA
- 2002
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Ingår i: European Physical Journal C. Particles and Fields. - : Springer Science and Business Media LLC. - 1434-6044. ; 24:4, s. 517-527
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Tidskriftsartikel (refereegranskat)abstract
- Dijet events in photon-proton collisions in which there is a large pseudorapidity separation, Deltaeta > 2.5 between the two highest E-T jets are studied with the H1 detector at HERA. The inclusive dijet cross sections are measured as functions of the longitudinal momentum fractions of the proton and photon which participate in the production of the jets, x(p)(jets) and x(gamma)(jets) respectively, Deltaeta, the pseudorapidity P separation between the two highest E-T jets, and E-T(gap), the total summed transverse energy between the jets. Rapidity gap events are defined as events in which E-T(gap) is less than E-T(cut), for E-T(cut) varied between jets 0.5 and 2.0 GeV. The fraction of dijet events with a rapidity gap is measured differentially in Deltaeta, x(p)(jets) and x(gamma)(jets). An excess of events with rapidity gaps at low values of E-T(cut) is observed above the expectation from standard photoproduction processes. This excess can be explained by the exchange of a strongly interacting colour singlet object between the jets.
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| 15. |
- Adloff, C, et al.
(författare)
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Inelastic leptoproduction of J/psi mesons at HERA
- 2002
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Ingår i: European Physical Journal C. Particles and Fields. - : Springer Science and Business Media LLC. - 1434-6044. ; 25:1, s. 41-53
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Tidskriftsartikel (refereegranskat)abstract
- The leptoproduction of J/psi mesons is studied in inelastic reactions for four momentorri transfers 2 < Q(2) < 100GeV(2). The data were taken with the H1 detector at the electron proton collider HERA and correspond to an integrated luminosity of 77 pb(-1). Single differential and double differential cross sections are measured with increased precision compared with previous analyses. New leading order calculations within the non-relativistic QCD factorisation approach including colour octet and colour singlet contributions are compared with the data and are found to give a reasonable description of most distributions. An exception is the shape of the distribution in the J/psi fractional energy. z, which deviates significantly from that of the data. Comparisons with photoproduction are made and the polarisation of the produced J/psi meson is analysed.
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| 16. |
- Adloff, C, et al.
(författare)
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Inelastic photoproduction of J/psi mesons at HERA
- 2002
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Ingår i: European Physical Journal C. Particles and Fields. - : Springer Science and Business Media LLC. - 1434-6044. ; 25:1, s. 25-39
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Tidskriftsartikel (refereegranskat)abstract
- An analysis of inelastic photoproduction of J/psi mesons is presented using data collected at the ep collider HERA corresponding to an integrated luminosity of above 80 pb(-1), Differential and double I < P-t/psi(2) < differential cross sections are measured in a wide kinematic region: 60 < W-gammap < 260 GeV, 1 p(t,psi)(2) < 60 GeV2 and 0.05 < z < 0.9. where z is the fraction of the energy of the exchanged photon transferred to the J/psi meson in the rest frame of the target proton. Cross sections at z less than or similar to 0.3 are presented for the first time. Theoretical calculations within the Colour Singlet Model at NLO for direct photon processes are shown to give a good description of the data in the medium z region (0.3 < z < 0.9) up to the highest p(t,psi)(2) values. A calculation using a k(t) factorisation approach in LO in the Colour Singlet Model is also able to describe these data. The data in the full z range are also compared to LO calculations within a non-relativistic QCD framework including colour octet and colour singlet contributions for direct and resolved photons. It seems possible to reconcile data and theory with modest contributions from colour octet processes. The polarisation of the J/psi meson is measured as a function of z and p(t,psi) and is reasonably described by the theoretical predictions.
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| 17. |
- Adloff, C, et al.
(författare)
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Measurement of D*(+/-) meson production and F-2(c) in deep-inelastic scattering at HERA
- 2002
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Ingår i: Physics Letters. Section B: Nuclear, Elementary Particle and High-Energy Physics. - 0370-2693. ; 528:3-4, s. 199-214
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Tidskriftsartikel (refereegranskat)abstract
- The inclusive production of D*+/-(2010) mesons in deep-inelastic scattering is studied with the HI detector at HERA. In the kinematic region 1 < Q(2) < 100 GeV2 and 0.05 < y < 0.7 an e(+) p cross section for inclusive D*+/- meson production of 8.50 +/- 0.42(stat.)(-100)(+1.21)(syst.) nb is measured in the visible range p(tD*) > 1.5 GeV and eta(D*) < 1.5. Single and double differential inclusive D*+/- meson cross sections are compared to perturbative QCD calculations in two different evolution schemes, The charm contribution to the proton structure, F-c(2)(x, Q(2)), is determined by extrapolating the visible charm cross section to the full phase space. This contribution is found to rise from about 10% at Q(2) = 1.5 GeV2 to more than 25% at Q(2) = 60 GeV2 corresponding to x values ranging from 5 x 10(-5) to 3 x 10(-3). (C) 2002 Elsevier Science B.V. All rights reserved.
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| 18. |
- Adloff, C, et al.
(författare)
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Measurement of dijet cross sections in photoproduction at HERA
- 2002
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Ingår i: European Physical Journal C. Particles and Fields. - : Springer Science and Business Media LLC. - 1434-6044. ; 25:1, s. 13-23
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Tidskriftsartikel (refereegranskat)abstract
- Dijet cross sections as functions of several jet observables are measured in photoproduction using the HI detector at HERA. The data sample comprises e(+)p data with an integrated luminosity of 319 pb(-1). Jets are selected using the inclusive k(perpendicular to) algorithm with a minimum transverse energy of 25 GeV for the leading jet. The phase space covers longitudinal proton momentum fraction x(p) and photon longitudinal momentum fraction x(gamma) in the ranges 0.05 < x(p) < 0.6 and 0.1 < x(gamma) < 1. The predict ions of next-to-leading order perturbative QCD, including recent photon and proton parton densities, are found to be compatible with the data in a wide kinematical range.
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| 19. |
- Adloff, C, et al.
(författare)
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Measurement of dijet electroproduction at small jet separation
- 2002
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Ingår i: European Physical Journal C. Particles and Fields. - : Springer Science and Business Media LLC. - 1434-6044. ; 24:1, s. 33-41
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Tidskriftsartikel (refereegranskat)abstract
- Deep-inelastic scattering data in the range 150 < Q(2) < 35000 GeV2 are used to investigate the minimum jet separation necessary to allow accurate description of the rate of dijet production using next-to-leading order perturbative QCD calculations. The required jet separation is found to be small, allowing about 1/3 of DIS data to be classified as dijet, as opposed to approximately 1/10 with more typical jet analyses. A number of precision measurements made using this dijet sample are well described by the calculations. The data are also described by the combination of leading order matrix elements and parton showers, as implemented in the QCD based Monte Carlo model RAPGAP.
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| 20. |
- Adloff, C, et al.
(författare)
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Measurement of inclusive jet cross-sections in deep-inelastic ep scattering at HERA
- 2002
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Ingår i: Physics Letters. Section B: Nuclear, Elementary Particle and High-Energy Physics. - 0370-2693. ; 542:3-4, s. 193-206
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Tidskriftsartikel (refereegranskat)abstract
- A measurement of inclusive jet cross-sections in deep-inelastic ep scattering at HERA is presented based on data with an integrated luminosity of 21.1 pb(-1). The measurement is performed for photon virtualities Q(2) between 5 and 100 GeV2, differentially in Q(2), in the jet transverse energy E-T, in E-T(2)/Q(2) and in the pseudorapidity eta(lab). With the renormalization scale mu(R) = E-T, perturbative QCD calculations in next-to-leading order (NLO) give a good description of the data in most of the phase space. Significant discrepancies are observed only for jets in the proton beam direction with ET below 20 GeV and Q2 below 20 GeV2. This corresponds to the region in which NLO corrections are largest and further improvement of the calculations is thus of particular interest.
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| 21. |
- Adloff, C, et al.
(författare)
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Search for excited electrons at HERA
- 2002
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Ingår i: Physics Letters. Section B: Nuclear, Elementary Particle and High-Energy Physics. - 0370-2693. ; 548:1-2, s. 35-44
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Tidskriftsartikel (refereegranskat)abstract
- A search for excited electron (e*) production is described in which the electroweak decays e* --> egamma, e* --> eZ and e* ---> nuW are considered. The data used correspond to an integrated luminosity of 120 pb(-1) taken in e(+/-)p collisions from 1994 to 2000 with the H1 detector at HERA at centre-of-mass energies of 300 and 318 GeV. No evidence for a signal is found. Mass dependent exclusion limits are derived for the ratio of the couplings to the compositeness scale, f/A. These limits extend the excluded region to higher masses than has been possible in previous direct searches for excited electrons. (C) 2002 Published by Elsevier Science B.V.
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| 22. |
- Adloff, C, et al.
(författare)
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Search for excited neutrinos at HERA
- 2002
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Ingår i: Physics Letters. Section B: Nuclear, Elementary Particle and High-Energy Physics. - 0370-2693. ; 525:1-2, s. 9-16
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Tidskriftsartikel (refereegranskat)abstract
- We present a search for excited neutrinos using e(-) p data taken by the H1 experiment at HERA at a center-of-mass energy of 318 GeV with an integrated luminosity of 15 pb(-1). No evidence for excited neutrino production is found. Mass dependent exclusion limits are determined for the ratio of the coupling to the compositeness scale, f/Lambda, independently of the relative couplings to the SU(2) and U(1) gauge bosons. These limits extend the excluded region to higher masses than has been possible in previous searches at other colliders.
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| 23. |
- Adloff, C, et al.
(författare)
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Search for odderon-induced contributions to exclusive pi(0) photoproduction at HERA
- 2002
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Ingår i: Physics Letters. Section B: Nuclear, Elementary Particle and High-Energy Physics. - 0370-2693. ; 544:1-2, s. 35-43
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Tidskriftsartikel (refereegranskat)abstract
- A search for contributions to the reaction ep --> epi(0)N* from photon-odderon fusion in the photoproduction regime at HERA is reported, at an average photon-proton centre-of-mass energy = 215 GeV. The measurement proceeds via detection of the pi(0) decay photons, a leading neutron from the N* decay, and the scattered electron. No pi(0) signal is observed and an upper limit on the cross section for the photon-odderon fusion process of sigma(gammap --> pi(0)N*) < 49 nb at the 95% confidence level is derived, integrated over the experimentally accessible range of the squared four-momentum transfer at the nucleon vertex 0.02 < < 0.3 GeV2. This excludes a recent prediction from a calculation based on a non-perturbative QCD model of a photon-odderon fusion cross section above 200 nb. (C) 2002 Elsevier Science B.V. All rights reserved.
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| 24. |
- Adloff, C, et al.
(författare)
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Search for QCD instanton-induced processes in deep-inelastic scattering at HERA
- 2002
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Ingår i: European Physical Journal C. Particles and Fields. - : Springer Science and Business Media LLC. - 1434-6044. ; 25:4, s. 495-509
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Tidskriftsartikel (refereegranskat)abstract
- Signals of QCD instanton-induced processes are searched for in deep-inelastic scattering (DIS) at the electron-proton collider HERA in a kinematic region defined by the Bjorken-scaling variables x > 10(-3), 0.1 < y < 0.6 and photon virtualities 10 less than or similar to Q(2) < 100 GeV2. Several observables characterising hadronic final state properties of QCD instanton-induced events are exploited to identify a potentially instanton-enriched domain. While an excess of events with instanton-like topology is observed it cannot be claimed significant given the uncertainty of the standard DIS background simulation. Upper limits on the cross-section for instanton-induced processes of between 60 pb and 1000 pb are set dependent on the kinematic domain considered. The data do not exclude the cross-section predicted by instanton perturbation theory for small instanton sizes. At large instanton sizes a naive extrapolation of instanton perturbation theory yields a cross-section in the range of sensitivity of this study. Such a cross-section is not observed, in agreement with non-perturbative lattice simulations of the QCD vacuum.
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| 25. |
- Baison, John, et al.
(författare)
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Genome-Wide Association Study (GWAS) identified novel candidate loci affecting wood formation in Norway spruce
- 2019
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Ingår i: The Plant Journal. - : Wiley. - 0960-7412 .- 1365-313X. ; 100:1, s. 83-100
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Tidskriftsartikel (refereegranskat)abstract
- Norway spruce is a boreal forest tree species of significant ecological and economic importance. Hence there is a strong imperative to dissect the genetics underlying important wood quality traits in the species. We performed a functional Genome-Wide Association Study (GWAS) of 17 wood traits in Norway spruce using 178101 single-nucleotide polymorphisms (SNPs) generated from exome genotyping of 517 mother trees. The wood traits were defined using functional modelling of wood properties across annual growth rings.We applied a LASSO based association mapping method using a functional multi-locus mapping approach that utilizes latent traits, with a stability selection probability method as the hypothesis testing approach to determine significant Quantitative Trait Loci (QTLs). The analysis provided 52 significant SNPs from 39 candidate genes, including genes previously implicated in wood formation and tree growth in spruce and other species. Our study represents a multi-locus GWAS for complex wood traits in Norway spruce. The results advance our understanding of the genetics influencing wood traits and identifies candidate genes for future functional studies.
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| 26. |
- Baison, John, et al.
(författare)
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Genome-wide association study identified novel candidate loci affecting wood formation in Norway spruce
- 2019
-
Ingår i: The Plant Journal. - : John Wiley & Sons. - 0960-7412 .- 1365-313X. ; 100:1, s. 83-100
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Tidskriftsartikel (refereegranskat)abstract
- Norway spruce is a boreal forest tree species of significant ecological and economic importance. Hence there is a strong imperative to dissect the genetics underlying important wood quality traits in the species. We performed a functional genome-wide association study (GWAS) of 17 wood traits in Norway spruce using 178 101 single nucleotide polymorphisms (SNPs) generated from exome genotyping of 517 mother trees. The wood traits were defined using functional modelling of wood properties across annual growth rings. We applied a Least Absolute Shrinkage and Selection Operator (LASSO-based) association mapping method using a functional multilocus mapping approach that utilizes latent traits, with a stability selection probability method as the hypothesis testing approach to determine a significant quantitative trait locus. The analysis provided 52 significant SNPs from 39 candidate genes, including genes previously implicated in wood formation and tree growth in spruce and other species. Our study represents a multilocus GWAS for complex wood traits in Norway spruce. The results advance our understanding of the genetics influencing wood traits and identifies candidate genes for future functional studies.
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| 27. |
- Bakaev, A., et al.
(författare)
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Effect of isotropic stress on dislocation bias factor in bcc iron : an atomistic study
- 2018
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Ingår i: Philosophical Magazine. - : Taylor and Francis Ltd.. - 1478-6435 .- 1478-6443. ; 98:1, s. 54-74
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Tidskriftsartikel (refereegranskat)abstract
- The effect of externally applied stress on the dislocation bias factor (BF) in bcc iron has been studied using a combination of atomistic static calculations and finite element integration. Three kinds of dislocations were considered, namely, a0/2〈1 1 1〉{1 1 0} screw, a0/2〈1 1 1〉{1 1 0} edge and a0〈1 0 0〉{0 0 1} edge dislocations. The computations reveal that the isotropic crystal expansion leads to an increasing or constant dislocation bias, depending on the Burgers vector and type of dislocation. On the other hand, compressive stress reduces the dislocation bias for all the dislocations studied. Variation of the dislocation BF depending on dislocation type and Burgers vector is discussed by analysing the modification of the interaction energy landscape and the capture efficiency values for the vacancy and self-interstitial atom.
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| 28. |
- Bathellier, Didier, et al.
(författare)
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A new heat capacity law for UO2, PuO2 and (U,Pu)O-2 derived from molecular dynamics simulations and useable in fuel performance codes
- 2021
-
Ingår i: Journal of Nuclear Materials. - : Elsevier BV. - 0022-3115 .- 1873-4820. ; 549
-
Tidskriftsartikel (refereegranskat)abstract
- In this work, a computationally efficient law of a nuclear fuel property obtained from molecular dy-namics calculations is implemented in a fuel performance code, bridging the gap between atomic and pellet scales. The Cooper-Rushton-Grimes potential is employed through molecular dynamics simulations to compute the heat capacity of stoichiometric mixed-oxide fuels U1-yPuyO2 from 10 0 0 K to the melting temperature, and over the whole range of plutonium content from pure UO2 (y = 0) to pure PuO2 (y = 1). The heat capacity is found to exhibit a peak at the temperature TB = 0.84 Tm, with Tm the melting tem-perature, for all the compounds with a significant effect of the plutonium content solely at high temper-atures (T > 1800 K), i.e. around the peak. This peak is related to the so-called Bredig transition known to occur around 0.8 Tm. An analytical law of heat capacity Cp(T,y) has been established from our molecular dynamics data, and is valid from 700 K to the melting temperature and for the entire range of plutonium content. Concerning UO2, a good agreement is found between our calculations and the most recent ex-perimental measurements. The law we propose in the present study has been implemented in GERMINAL V2, the fuel performance code developed by CEA to predict the in-pile behavior of mixed-oxide fuel in sodium-cooled fast reactors, and tested through the simulations of transient power test operated in the CABRI reactor. The results show that our law yields a lower margin to melting in the case of Reactivity-Initiated Accident, but throughout power ramp transient tests, the results obtained with our new law are very consistent with the reference heat capacity law currently used in GERMINAL.
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| 29. |
- Bathellier, Didier, et al.
(författare)
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Effect of cationic chemical disorder on defect formation energies in uranium-plutonium mixed oxides
- 2022
-
Ingår i: Journal of Applied Physics. - : AIP Publishing. - 0021-8979 .- 1089-7550. ; 132:17, s. 175103-
-
Tidskriftsartikel (refereegranskat)abstract
- At the atomic scale, uranium-plutonium mixed oxides (U,Pu)O-2 are characterized by cationic chemical disorder, which entails that U and Pu cations are randomly distributed on the cation sublattice. In the present work, we study the impact of disorder on point defect formation energies in (U,Pu)O-2 using interatomic-potential and density functional theory (DFT + U) calculations. We focus on bound Schottky defects (BSD) that are among the most stable defects in these oxides. As a first step, we estimate the distance R-D around the BSD up to which the local chemical environment significantly affects their formation energy. To this end, we propose an original procedure in which the formation energy is computed for several supercells at varying levels of disorder. We conclude that the first three cation shells around the BSD have a non-negligible influence on their formation energy (R-D similar or equal to 7.0 angstrom). We apply then a systematic approach to compute the BSD formation energies for all the possible cation configurations on the first and second nearest neighbor shells around the BSD. We show that the formation energy can range in an interval of 0.97eV, depending on the relative amount of U and Pu neighboring cations. Based on these results, we propose an interaction model that describes the effect of nominal and local composition on the BSD formation energy. Finally, the DFT + U benchmark calculations show a satisfactory agreement for configurations characterized by a U-rich local environment and a larger mismatch in the case of a Pu-rich one. In summary, this work provides valuable insights on the properties of BSD defects in (U,Pu)O-2 and can represent a valid strategy to study point defect properties in disordered compounds.
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| 30. |
- Becquart, C. S., et al.
(författare)
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A DFT study of the stability of SIAs and small SIA clusters in the vicinity of solute atoms in Fe
- 2018
-
Ingår i: Journal of Nuclear Materials. - : Elsevier B.V.. - 0022-3115 .- 1873-4820. ; 500, s. 92-109
-
Tidskriftsartikel (refereegranskat)abstract
- The energetics, defect volume and magnetic properties of single SIAs and small SIA clusters up to size 6 have been calculated by DFT for different configurations like the parallel 〈110〉 dumbbell, the non parallel 〈110〉 dumbbell and the C15 structure. The most stable configurations of each type have been further analyzed to determine the influence on their stability of various solute atoms (Ti, V, Cr, Mn, Co, Ni, Cu, Mo, W, Pd, Al, Si, P), relevant for steels used under irradiation. The results show that the presence of solute atoms does not change the relative stability order among SIA clusters. The small SIA clusters investigated can bind to both undersized and oversized solutes. Several descriptors have been considered to derive interesting trends from results. It appears that the local atomic volume available for the solute is the main physical quantity governing the binding energy evolution, whatever the solute type (undersized or oversized) and the cluster configuration (size and type).
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| 31. |
- Becquart, Charlotte S., et al.
(författare)
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Modelling the primary damage in Fe and W : Influence of the short range interactions on the cascade properties: Part 1-Energy transfer
- 2021
-
Ingår i: Journal of Nuclear Materials. - : Elsevier. - 0022-3115 .- 1873-4820. ; 547
-
Tidskriftsartikel (refereegranskat)abstract
- The primary damage in metallic alloys, i.e. the point defect distribution resulting from the interaction between an energetic particle and a metallic matrix has been investigated for more than 60 years using atomistic simulations. The defect distribution produced in cascades is sensitive to the equilibrium part of the potential as well as its hardened part. An analysis based on large statistics of molecular dynamics simulations and comparison with different embedded atom method potentials in Fe and W allows to rationalize the potential behavior. Correlations between static non-equilibrium properties (quasi static drag (QSD)), threshold displacement energies (TDE), replacement collision sequences (RCS) along the < 110 > direction have been revealed. Along this direction, the lower the TDE, the lower the QSD and the more energy is transmitted along the < 110 > direction during the RCS, i.e. the softest potentials are the ones for which the most energy is transmitted from the PKA to the first head-on atom in the direction of the RCS sequence.
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| 32. |
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| 33. |
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| 34. |
- Berglund, Kim, et al.
(författare)
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Evaluating lifetime performance of limited slip differentials
- 2014
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Ingår i: Lubrication Science. - : Wiley. - 0954-0075 .- 1557-6833. ; 26:3, s. 189-201
-
Tidskriftsartikel (refereegranskat)abstract
- Extensive research has been performed regarding wet clutch function and performance. Although wet clutches are used in both automatic transmissions and limited slip differentials in cars, most research has been performed for wet clutches incorporated in automatic transmissions. The operating conditions of wet clutches in automatic transmissions differ from the operating conditions of the wet clutches used in limited slip differentials. Therefore, a method and a test bench to use in the investigation of the degradation of limited slip differentials were developed in this work. The typical operating conditions of the limited slip differential and the differences compared with wet clutches incorporated in automatic transmissions were also addressed. Tests performed showed that the developed test bench and method can be used to address differences in frictional response over time for different types of operating condition
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| 35. |
- Berglund, Kim, et al.
(författare)
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Predicting boundary friction of aging limited slip differentials
- 2014
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Ingår i: Journal of tribology. - : ASME International. - 0742-4787 .- 1528-8897. ; 137:1
-
Tidskriftsartikel (refereegranskat)abstract
- The prediction of friction is a challenge for scientists and engineers in a wide variety of applications in industry today. One such an application is the limited slip differential. The friction characteristics of the wet clutch are central to the performance of the limited slip differential system. Frictional changes with aging of the limited slip differential affect both the torque transfer accuracy and the tendencies to vibrations and noise generation due to stick-slip or shudder. Therefore, the objective of this work is to establish a method to predict the frictional changes of aging limited slip differential systems. In this study, a number of experiments were performed to establish a method to predict the changes in boundary friction with time due to aging. Accelerated aging was performed for different sets of operating conditions. Results from the tests were used to establish and verify a model to predict friction increase in limited slip differentials. The method assumes that frictional changes with aging are caused by decreased concentrations of friction modifying additives. The decrease in concentration was assumed to depend on the lubricant bulk temperature according to the Arrhenius equation. The model agreed well with tests performed at operating conditions close to the real operating conditions of the limited slip differential. The developed method can be implemented in a vehicle where it can be used to compensate for frictional changes and to indicate when service should be made.
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| 36. |
- Berglund, Kim, et al.
(författare)
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Wet clutch degradation monitored by lubricant analysis
- 2010
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Ingår i: SAE technical paper series. - 400 Commonwealth Drive, Warrendale, PA, United States : SAE International. - 0148-7191. ; :2010-01-2232
-
Tidskriftsartikel (refereegranskat)abstract
- In the competitive market of the car industry today, companies need to continuously strive to optimize the performance, price and environmental properties of their products in order to survive. Wet clutches, as parts of transmission components of passenger cars are no exception. An understanding of how the wet clutch system functions and fails is necessary to optimize price and service life. The friction characteristics of the wet clutch system are determined by lubricant-surface interactions in the contact between the friction discs. Wet clutch failure can often be associated with the deterioration of friction characteristics which eventually leads to stick-slip or shudder. Consequently, knowledge of why and of how friction characteristics change over time is of the outermost significance to enable the understanding and prediction of wet clutch performance. As the lubricant is an essential component of the wet clutch system, lubricant ageing is a factor of importance. Oxidation, thermal degradation, shearing, additive degradation and water contamination could all be considered to influence lubricant ageing. The aim of this work was therefore to find suitable ways of measuring the remaining useful life of wet clutch lubricants and to correlate changes in friction characteristics with changes in lubricant properties. Both field trials and measurements in a wet clutch test rig were performed. Viscosity, acid number, additive degradation, water contamination, particle content and metal content were measured for the lubricant as it degraded. Particle content results showed a rapid increase early in the ageing process. However, as ageing progressed particle levels actually decreased and this was probably a result of particles slowly grinded between contacting surfaces. On the other hand, metal content increased as ageing progressed, which could indicate slowly progressing wear. Water levels were found to be higher in field trials than in lubricants used in wet clutch test rigs. It is concluded that this was due to the severe and accelerated operating conditions of the wet clutch test rig.
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| 37. |
- Björkas, C., et al.
(författare)
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Simulation of displacement cascades in Fe90Cr10 using a two band model potential
- 2008
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Ingår i: Journal of Nuclear Materials. - : Elsevier BV. - 0022-3115 .- 1873-4820. ; 372:2-3, s. 312-317
-
Tidskriftsartikel (refereegranskat)abstract
- Molecular dynamics (MD) simulations of displacement cascades, with recoil energies up to 50 keV, have been performed in Fe90Cr10 and Fe using a recently developed two band embedded atomic model (2BM) potential that correctly describes the mixing enthalpy and the binding energy of the mixed dumbbell configurations. Comparisons between results obtained with the 2BM potential fitted to different data sets, a one band model (1BM), and another existing FeCr-potential previously used for similar calculations were done, showing differences in the vacancy clustered fraction and the Cr content in interstitials predicted by the potentials. The 2BM potential resulted in roughly the same concentration of Cr in interstitial positions as in the matrix, and the 1BM, which incorrectly predicts a positive heat of mixing, predicted even smaller concentrations. The calculated short range order parameter is around zero for the 2BM, and takes positive values within the 1BM, as expected from the mixing enthalpies.
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| 38. |
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| 39. |
- Bogatic, Wirginia, 1969-
(författare)
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Stanna eller återvända : Flyktingskap, återvändande och kvarstannande bland polska kvinnliga överlevande från koncentrationslägret Ravensbrück 1945-1946
- 2006
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Avhandlingen handlar om beslutsprocessen i fråga om återvändande till sitt hemland eller kvarstannande i flyktingskap, hos de överlevande polska kvinnliga koncentrationslägerfångar som räddades till Sverige 1945 med räddningsaktionen De vita bussarna. Räddningsaktionens namn till trots, lämnade kvinnorna koncentrationslägret Ravensbrück ombord på ett tåg. Den bygger på tretton djupintervjuer med de överlevande kvinnorna med målsättning att få ett svar på frågan varför vissa av dem efter krigets slut stannade kvar i Sverige, medan andra återvände till Polen. Intervjuerna genomfördes både med dem som stannade kvar och dem som återvände. Analysen utgår ifrån Svante Lundbergs analytiska modell kring flyktingskap med begreppen Bakgrund, Ram och Mening samt från det teoretiska begreppet sociologisk generation vid analysen av kvinnornas beslutsprocess. Innehållet i begreppet Bakgrund kan förenklat beskrivas som det ”bagage” som flyktingarna har med sig från sitt hemland, som de känner väl och längtar efter. På samma sätt kan innehållet i begreppet Ram definieras som allt nytt och okänt flyktingarna möter vid ankomsten till det nya landet. I båda begreppen ingår även flyktingarnas position i den rådande klasstrukturen samt möjligheter och erbjudanden om hur deras liv kan gestaltas i framtiden. Det har konstaterats att upplevelsen av traumatiserande, våldsamma och känslosamma händelser (significant historical experiences) såsom krig eller ockupation leder ofta till att en sociologisk generation uppstår. Vid analysen av både de kvarstannande och återvändande kvinnornas, som står i centrum för den här avhandlingen, uppväxt- och levnadsförhållanden framgår det att de har genomlevt ett antal signifikanta historiska erfarenheter: andra världskriget, ockupationen, förlusten av nära och kära, Warszawaupproret, fängelser, misshandel och koncentrationsläger, vilka sammanlagt (markerar förändringar i deras liv och som) även resulterade i att kvinnorna blev en del av en sociologisk generation. Världen som de kände den upphörde att existera. Därefter följde migration, flyktingskap och frågan om återvändandet till Polen eller kvarstannandet i Sverige. I kapitlet ”Bakgrund” har visats att den dominerade historieskrivningen i Polen under mellankrigstiden, som var en del av det polska kollektiva minnet, var den idealiserade och romantiskt-patriotiska synen med vilken resultat av förfädernas handlingar betraktades. Under sin tidiga uppväxt formades kvinnorna av föräldrarnas och mor- och farföräldrars berättelser om tiden då Polen som självständig stat inte fanns, om motståndet mot delningsmakterna, när fäder blev inkallade till den ryska eller preussiska armén och fick slåss mot sina ”bröder”, och om tiden då polska legioner bildades och därefter den polska staten. Utanför familjen utsattes de för den andra republikens medvetet nationalistiska politik som syftade till att skapa en stark polsk identitet. De var även åskådare till det polska samhällets radikalisering och nationalismens uppgång, samtidigt som de matades med den dominerande, romantiserade bilden av den återuppståndna polska staten, vilken förmedlades till dem genom familjen, skolan och det omgivande samhället med målsättning att skapa en gemensam identitet. Den förändrings- och utvecklingsprocess de genomgick som enskilda individer, delade de med andra som befann sig i samma situation, och processen resulterade i en känsla av grupptillhörighet, gemensamma värderingar, tolkningar och ideal, vilka låg som bakgrund för deras reaktioner på senare traumatiska erfarenheter. Sex av tretton av de intervjuade kvinnorna fattade ett medvetet beslut om att delta i motståndskampen mot ockupanten, tre gav sitt passiva stöd till kämparna i Warszawaupproret och betalade senare för det med att bli fångar i koncentrationsläger. I kapitlet ”Ram” har det visats på ett samband mellan transporterna för återvändande som startade på hösten 1945 och de svenska myndigheters önskan om handelsavtal med Polen samt Warszawaregeringens starka vil-ja att bli erkänd som den enda legitima polska regeringen. Samtidigt har det framkommit att kvinnorna kände en osäkerhet i fråga om återvändan-de både pga. de förändringar som höll på att inträffa i Polen i fråga om gränser och politisk orientering, och kvinnornas möjligheter till en okänd och kanske trygg och lugn framtid i Sverige. På flyktingförläggningarna började kvinnorna fundera huruvida de kunde stanna och vad det skulle innebära i fråga om arbete och boende. De erbjöds främst anställningar som hembiträden, lantarbetare eller inom industrin - inte alltid de yrken som kvinnorna hade drömt om före kriget eller önskat arbeta inom. För flertalet av dem innebar det ”abandonment of expectations”, då yrken/utbildningar som de hade med sig från hemlandet inte var möjliga att utöva/få användning för i mottagarlandet. Kvinnorna upptäckte också skillnader mellan det svenska och polska samhället, men de blev även uppmärksammade på förändringar som skedde i det polska samhället medan de hade varit borta. Olika grupper försökte påverka dem till att antingen stanna (som en möjlig protest mot det sovjetiska inflytandet i Polen och bevis på den polska Londonregeringens inflytande) eller återvända (för att Landet behövde dem). Den svenska regeringen underrättades om den polska Warszawaregeringens missnöje med Storbritanniens beslut att inte sända tillbaka de polska trupperna till Polen. De uppmärksammades även på att Warszawaregeringen inte accepterade omröstningen som genomfördes bland polska soldater i fråga om huruvida de ville återvända till Polen eller stanna i exil. Men de svenska myndigheterna insåg också den potential som fanns inom gruppen som en möjlig arbetskraft för att fylla den stora efterfrågan på arbeterskor som fanns vid den tiden. Därmed beslutade de också att inte skicka någon mot sin vilja och därmed öppnade sig en möjlighet för kvinnorna att stanna. Istället fick kvinnorna presentera sina individuella skäl till varför de ville stanna kvar i Sverige i ett brev till Svenska Utlänninsgkommissionen (SUK), som utredde frågan och efteråt meddelade beslutet. Inför brevskrivningen kände många repatriandi osäkerhet om uppgifterna i breven skulle föras vidare till den polska legationen, som representerade Warszawaregeringen och i förlängningen leda till problem för familjen/släkten i Polen. Ett flertal trotsade rädslan och uttalade oro för att återvända pga. den nya regeringen och faran för förföljelser. När de fick tillstånd att stanna kvar förvandlades repatriandi på en formell, politiskt–strukturell nivå från flyktingar i exil till nya medborgare/arbetstagare i Sverige och myndigheterna förväntade sig inte längre att de skulle återvända. Svante Lundberg definierar begreppet Mening som flyktingarnas avsikt att återvända till sitt hemland som medvetna subjekt. Under tiden flyktingarna väntar på att återvända till sitt hemland strävar de efter att förvärva kunskaper som kan vara till nytta för dem och hemlandet. De lever i diaspora och ägnar sin tid åt att försöka påverka hemlandets makthavare och politik på avstånd genom att anordna demonstrationer, studiecirklar m.m. för att uppmärksamma mottagarlandet på förhållanden i hemlandet och få dem att agera. Undersökningsperioden för den här avhandlingen omfattar nio måna-der under vilka de polska överlevande kvinnliga fångar från koncentra-tionslägret Ravensbrück fick fatta beslut om huruvida de skulle återvända till hemlandet Polen eller stanna kvar i mottagarlandet Sverige. Fokus ligger på kvinnornas egna berättelser och förklaringar. Kvarstannarna framhäver delvis innehållet i begreppet Ram som en kontext i vilken beslutet fattades, nämligen möjligheten att få anställning och möjligheten att få ett bättre liv i Sverige. De pekar också på bristerna i det som kvalificeras som Bakgrund, nämligen att ingen familj fanns kvar i hemlandet eller familjens uppmuntran att stanna i exil, samt den nya Polens förändringar. Det nya landet verkade inte så skrämmande. Kvinnorna lärde sig svenska genom sitt arbete, hade få kontakter med myndigheter, bildade familj och/eller engagerade sig i kulturell/idrottslig verksamhet. Återvändarna inser att kvarstannande i exil erbjöd dem möjligheter till ett tryggt liv (Ram), men de uppger i första hand att anledningen till deras återvändande var deras längtan till Landet som behövde dem. Först senare konstaterar de att även familjens brev hade inflytande på deras beslut (Bakgrund). De följde utvecklingen i Polen och i Europa men trots den osäkerhet som fanns ville de återvända. Kvinnorna vittnar om att de inte visste hur situationen i Polen skulle utvecklas och det dröjde innan de förstod vad som hände samt antyder om vilka konsekvenserna var av deras beslut. I sina levnadsberättelser placerar kvinnorna, i synnerhet återvändarna, sig själva i ett större sammanhang, i den polska nationens strävande för en fri polsk stat. De uppvisar likheter som kan hänföras till innebörden i generationsbegreppet och ger uttryck för ett generationsmedvetande. Dessa är mer framträdande i gruppen återvändarna som fortsatte den romantiskt-patriotiska traditionen efter kriget i större utsträckning än gruppen kvarstannarna. Kvinnorna pekar på att de i barndomen uppfostrades i patriotisk anda, både inom familjen och i skolan samt samhället i övrigt. Den polska mellankrigsstatens projekt och konnotationer av en stark moralisk förpliktelse gentemot familj och faderslandet uppvisas i kvinnornas egna liv. Andra världskrigets utbrott utgör en markering (significant historical experiences) då deras världsbild förändrades. Kriget och ockupation fick
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| 40. |
- Bonny, G., et al.
(författare)
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Density functional theory-based cluster expansion to simulate thermal annealing in FeCrW alloys
- 2017
-
Ingår i: Philosophical Magazine. - : Taylor & Francis. - 1478-6435 .- 1478-6443. ; 97:5, s. 299-317
-
Tidskriftsartikel (refereegranskat)abstract
- In this work, we develop a rigid lattice cluster expansion as an ultimate goal to track the micro-structural evolution of Eurofer steel under neutron irradiation. The fact that all (defect) structures are mapped upon a rigid lattice allows a simplified computation and fitting procedure, thus enabling alloys of large chemical complexity to be modelled. As a first step towards the chemical complexity of Eurofer steels, we develop a cluster expansion (CE) for the FeCrW-vacancy system based on density functional theory (DFT) calculations in the dilute alloy limit. The DFT calculations suggest that only CrW clusters containing vacancies are stabilised. The cluster expansion was used to simulate thermal annealing in Fe–20Cr–xW alloys at 773 K. It is found that the addition of W to the alloy results in a non-linear decrease in the precipitation kinetics. The CE was found suitable to describe the energetics of the FeCrW-vacancy system in the Fe-rich limit.
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| 41. |
- Bonny, G., et al.
(författare)
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Interatomic potential to study the formation of NiCr clusters in high Cr ferritic steels
- 2017
-
Ingår i: Journal of Nuclear Materials. - : Elsevier. - 0022-3115 .- 1873-4820. ; 484, s. 42-50
-
Tidskriftsartikel (refereegranskat)abstract
- Under irradiation NiSiPCr clusters are formed in high-Cr ferritic martensitic steels as well as in FeCr model alloys. In the literature little is known about the origin and contribution to the hardening of these clusters. In this work we performed density functional theory (DFT) calculations to study the stability of small substitutional NiCr-vacancy clusters and interstitial configurations in bcc Fe. Based on DFT data and experimental considerations a ternary potential for the ferritic FeNiCr system was developed. The potential was applied to study the thermodynamic stability of NiCr clusters by means of Metropolis Monte Carlo (MMC) simulations. The results of our simulations show that Cr and Ni precipitate as separate fractions and suggest only a limited synergetic effect between Ni and Cr. Therefore our results suggest that the NiCrSiP clusters observed in experiments must be the result of other mechanisms than the synergy of Cr and Ni at thermal equilibrium.
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| 42. |
- Bonny, G., et al.
(författare)
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Numerical prediction of thermodynamic properties of iron-chromium alloys using semi-empirical cohesive models : The state of the art
- 2009
-
Ingår i: Journal of Nuclear Materials. - : Elsevier BV. - 0022-3115 .- 1873-4820. ; 385:2, s. 268-277
-
Tidskriftsartikel (refereegranskat)abstract
- In this work the capability of existing cohesive models to predict the thermodynamicproperties of Fe-Cr alloys are critically evaluated and compared. The two-band model and the concentration-dependent model, which are independently developed extensions of the embedded-atom method, are demonstrated to be equivalent and equally capable of reproducing the thermodynamic properties of Fe-Cr alloys. The existing potentials fitted with these formalisms are discussed and compared with an existing cluster expansionmodel. The phase diagram corresponding to these models is evaluated using different but complementary methods. The influence of mixing enthalpy, low-energy states and vibrational entropy on the phase diagram is examined for the different cohesive models.
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| 43. |
- Bonny, G., et al.
(författare)
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The impact of alloying elements on the precipitation stability and kinetics in iron based alloys : An atomistic study
- 2019
-
Ingår i: Computational materials science. - : Elsevier. - 0927-0256 .- 1879-0801. ; 161, s. 309-320
-
Tidskriftsartikel (refereegranskat)abstract
- Iron based industrial steels typically contain a large number of alloying elements, even so-called low alloyed steels. Under irradiation, these alloying elements form clusters that have a detrimental impact of the mechanical properties of the steel. The stability and formation mechanisms of such clusters are presently not fully understood. Therefore, in this work, we study the thermal stability and formation kinetics of small solute clusters in the bcc Fe matrix. We use density functional theory (DFT) to characterize the binding energy of vacancy/solute clusters containing Cr, Mn, Ni, Cu, Si and P, thereby exploring >700 different configurations. The constructed DFT data base is used to fit a cluster expansion (CE) for the vacancy-FeCrMnNiCuSiP system. In turn, the obtained CE is applied in atomistic kinetic Monte Carlo simulations to study the effect of Mn, Ni, Cr, Si and P on the precipitation formation in the FeCu alloy. We conclude that the addition of Mn and Ni delay the precipitation kinetics by an order of magnitude. The additional alloying with traces of P/Si further delays the kinetics by an additional order of magnitude. We found that Si plays an essential role in the formation of spatially mixed MnNiCuSi cluster
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| 44. |
- Byström, Pär, et al.
(författare)
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Declining coastal piscivore populations in the Baltic Sea : where and when do sticklebacks matter?
- 2015
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Ingår i: Ambio. - : Springer Science and Business Media LLC. - 0044-7447 .- 1654-7209. ; 44:Suppl 3, s. S462-S471
-
Tidskriftsartikel (refereegranskat)abstract
- Intraguild predation interactions make fish communities prone to exhibit alternative stable states with either piscivore or prey fish dominance. In the Baltic Sea, local declines of coastal piscivores like perch (Perca fluviatilis) have been observed to coincide with high densities of sticklebacks (Gasterosteus aculeatus). Mechanisms behind this shift between piscivore and stickleback dominance were studied both experimentally and in field. Results showed that predation by sticklebacks has a strong negative effect on perch larvae survival, but this effect rapidly decreases with increasing perch size, likely due to gape limitations and digestion constraints in sticklebacks. Large spatial and temporal variations in patterns of stickleback migration into perch spawning sites were observed. Whether or not high density of sticklebacks will cause declines in coastal piscivore populations is suggested to depend on the availability of spawning sites in which sticklebacks do not migrate into or arrive late in the reproduction season of coastal piscivores.
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| 45. |
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| 46. |
- Castin, N., et al.
(författare)
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Advanced atomistic models for radiation damage in Fe-based alloys : Contributions and future perspectives from artificial neural networks
- 2018
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Ingår i: Computational materials science. - : Elsevier. - 0927-0256 .- 1879-0801. ; 148, s. 116-130
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Tidskriftsartikel (refereegranskat)abstract
- Machine learning, and more specifically artificial neural networks (ANN), are powerful and flexible numerical tools that can lead to significant improvements in many materials modelling techniques. This paper provides a review of the efforts made so far to describe the effects of irradiation in Fe-based and W-based alloys, in a multiscale modelling framework. ANN were successfully used as innovative parametrization tools in these models, thereby greatly enhancing their physical accuracy and capability to accomplish increasingly challenging goals. In the provided examples, the main goal of ANN is to predict how the chemical complexity of local atomic configurations, and/or specific strain fields, influence the activation energy of selected thermally-activated events. This is most often a more efficient approach with respect to previous computationally heavy methods. In a future perspective, similar schemes can be potentially used to calculate other quantities than activation energies. They can thus transfer atomic-scale properties to higher-scale simulations, providing a proper bridging across scales, and hence contributing to the achievement of accurate and reliable multiscale models.
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| 47. |
- Castin, N., et al.
(författare)
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Improved atomistic Monte Carlo models based on ab-initio -trained neural networks : Application to FeCu and FeCr alloys
- 2017
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Ingår i: Physical Review B. - : American Physical Society. - 2469-9950 .- 2469-9969. ; 95:21
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Tidskriftsartikel (refereegranskat)abstract
- We significantly improve the physical models underlying atomistic Monte Carlo (MC) simulations, through the use of ab initio fitted high-dimensional neural network potentials (NNPs). In this way, we can incorporate energetics derived from density functional theory (DFT) in MC, and avoid using empirical potentials that are very challenging to design for complex alloys. We take significant steps forward from a recent work where artificial neural networks (ANNs), exclusively trained on DFT vacancy migration energies, were used to perform kinetic MC simulations of Cu precipitation in Fe. Here, a more extensive transfer of knowledge from DFT to our cohesive model is achieved via the fitting of NNPs, aimed at accurately mimicking the most important aspects of the ab initio predictions. Rigid-lattice potentials are designed to monitor the evolution during the simulation of the system energy, thus taking care of the thermodynamic aspects of the model. In addition, other ANNs are designed to evaluate the activation energies associated with the MC events (migration towards first-nearest-neighbor positions of single point defects), thereby providing an accurate kinetic modeling. Because our methodology inherently requires the calculation of a substantial amount of reference data, we design as well lattice-free potentials, aimed at replacing the very costly DFT method with an approximate, yet accurate and considerably more computationally efficient, potential. The binary FeCu and FeCr alloys are taken as sample applications considering the extensive literature covering these systems.
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| 48. |
- Chang, Zhongwen, 1985-, et al.
(författare)
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Anomalous bias factors of dislocations in bcc iron
- 2015
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Ingår i: Journal of Nuclear Materials. - : Elsevier. - 0022-3115 .- 1873-4820. ; 461, s. 221-229
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Tidskriftsartikel (refereegranskat)abstract
- Dislocation bias factors in bcc Fe have been calculated based on atomistic interaction energy maps on three kinds of dislocations, namely the a0/2〈1 1 1〉{1 1 0} screw, a0/2〈1 1 1〉{1 1 0} and a0〈1 0 0〉{0 0 1} edge dislocations. The results show that the dislocation bias is higher for the a0/2〈1 1 1〉 edge dislocation than for the a0〈1 0 0〉 edge dislocation, even though the latter possesses a larger Burgers vector. This indicates the importance of the dislocation core contribution. For the a0/2〈1 1 1〉{1 1 0} screw dislocation, a negative dislocation bias has been obtained, which implies a more efficient absorption of vacancies than of SIAs. The effect of coexistence of both edge- and screw dislocations are assessed by a total bias. A possible complementary mechanism for explaining the long swelling incubation time in bcc metals is suggested and discussed.
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| 49. |
- Chang, Zhongwen, et al.
(författare)
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Assessment of the dislocation bias in fcc metals and extrapolation to austenitic steels
- 2015
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Ingår i: Journal of Nuclear Materials. - : Elsevier BV. - 0022-3115 .- 1873-4820. ; 465
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Tidskriftsartikel (refereegranskat)abstract
- A systematic study of dislocation bias has been performed using a method that combines atomistic and elastic dislocation-point defect interaction models with a numerical solution of the diffusion equation with a drift term. Copper, nickel and aluminium model lattices are used in this study, covering a wide range of shear moduli and stacking fault energies. It is found that the dominant parameter for the dislocation bias in fcc metals is the width of the stacking fault ribbon. The variation in elastic constants does not strongly impact the dislocation bias value. As a result of this analysis and its extrapolation, the dislocation bias of the widely applied austenitic stainless steels of 316 type is predicted to be about 0.1 at temperature close to the swelling peak (815 K) and typical dislocation density of 1014 m-2. This is in line with the bias calculated using the elastic interaction model, which implies that the prediction method can be used readily in other fcc systems even without EAM potentials. By comparing the bias values obtained using atomistic- and elastic interaction energies, about 20% discrepancy is found, therefore a more realistic bias value for the 316 type alloy is 0.08 in these conditions.
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| 50. |
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