| 1. |
- Alpfält, Tina, et al.
(författare)
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Scope of export varieties and innovation milieu of local economies
- 2012
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Konferensbidrag (refereegranskat)abstract
- Innovation by firms and industries requires that the individual firm can combine internal and external knowledge resources. This paper studies product innovations as they are reflected by product varieties and destination markets, combined into observations of firms’ destination-specific varieties(variety pairs). The number of varieties (identified in this way) measuresthe extensive margin of exportflows from industries in local economies, reflecting past product and market (destination) innovations made by industries in each local economy. The empirical analysis identifies for each industry and local economy (i) the intra-industry knowledge resources, (ii) the local access to the supply knowledge-intensive producer services, and (iii) the access to the supply of knowledge-intensive producer servicesoutside the local economy. Thepapercontributes to existing knowledgein several ways. First, it introduces a knowledge-supply accessibility measure to model the local innovation milieu. Second, it shows the joint contribution to product innovation from internal and external knowledge sources. The estimation results supports the hypothesis that innovations are generated in the conjunction of internal and external knowledge.
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| 2. |
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| 3. |
- Dzansi, James
(författare)
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Essays on Financing and Returns on Investment
- 2011
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This dissertation consists of an introductory chapter and three independent essays on financing investment and their returns. The first essay studies the impact of remittances on domestic investment. The analysis is carried out with a focus on the moderating roles of domestic financial development and institutional quality. The empirical results suggest that remittance inflows are associated with increased domestic investment spending, particularly under conditions of inadequate financial intermediation and poor institutional quality. The second essay evaluates whether remittance inflows into the developing world impedes or spurs manufacturing growth. This study uses manufacturing data on a sample of 40 remittance dependent economies over the period from 1991 to 2004. The results suggest that remittance inflows accelerate manufacturing growth. This evidence is robust to industry- and year-specific effects, a range of country level control variables, and a number of estimators. The final essay examines the monitoring role of large shareholders and returns on investment. Specifically, the paper investigates the relevance of intrinsic motives of the large shareholder to monitor management in order to induce optimal return on investment. The findings suggest that large shareholders are actuated by both intrinsic and extrinsic motives to minimize managerial opportunism and inefficiency.
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| 4. |
- Johansson, Börje, et al.
(författare)
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Internal and External Knowledge – Innovation of Export Varieties
- 2013
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Firms in local industries maintain their capability to generate innovations by simultaneously exploiting internal and external knowledge resources. The paper introduces the notion variety triplet to distinguish individual export varieties, where a triplet is a unique combination of a firm, a product code and a destination country. For each date the set of variety triplets in each local industry records all remaining past product innovations. In view of this the paper examines how internal and external knowledge of local industries influence the industry’s scope and value of export varieties. The paper contributes to existing knowledge firstly by introducing variables that measure a local industry’s access to external supply of knowledge, divided into local and extra-local supply. Secondly, the paper sheds light on how internal and external knowledge influence the scope of product innovations in local industries, with firm-level data from Sweden. Thirdly, the paper compares the influence of knowledge on the entire set of variety triplets and on a separate set of recently introduced varieties.
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| 5. |
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| 6. |
- Johansson, Börje M., et al.
(författare)
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Internal and external knowledge and introduction of export varieties
- 2015
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Ingår i: The World Economy. - : Wiley. - 0378-5920 .- 1467-9701. ; 38:4, s. 629-654
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Tidskriftsartikel (refereegranskat)abstract
- Firms in local industries maintain their capability to generate new export varieties by simultaneously exploiting internal and external knowledge resources. The paper introduces the notion 'variety triplet' to distinguish individual export varieties, where a triplet is a unique combination of a firm, a product code and a destination country. For each date, the set of variety triplets in each local industry records all remaining export varieties introduced in the past. In view of this, the paper examines how internal and external knowledge of local industries influence the industry's scope and value of export varieties. First, the paper contributes by considering a local industry's internal and external knowledge, as well as the conjunction of its internal and external knowledge sources. Second, the knowledge sources are shown to influence both the stock and the dynamics of a local industry's variety triplets, using firm-level data from Sweden.
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| 7. |
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| 8. |
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| 9. |
- Johansson, Sara, 1975-
(författare)
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Knowledge, Product Differentiation and Trade
- 2010
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The purpose of this thesis is to analyze the influence of knowledge on the export performance of firms in different regions. More specifically, this study focuses on the impact of knowledge on the structure of regional export flows, in terms of horizontal and vertical product differentiation, as well as the geographical distribution of export flows. The thesis consists of four separate papers, which contribute to the overall analysis of knowledge, product differentiation and international trade in different ways. The second chapter presents a study of the effects of regional accessibility to R&D on the diversity of export flows with regard to goods, firms and destination markets. Chapter 3 provides an empirical analysis of vertical product differentiation, i.e. differentiation in terms of product quality, and examines the impact of educated labor and R&D on regional comparative advantages in goods of relatively high product quality. Chapter 4 contains a study of how the regional endowment of highly educated workers affects the structure of export flows, i.e. how the endowment of educated workers impacts on the number of product varieties exported, the average price per variety and the average quantity shipped out. The final chapter presents a micro-level analysis of firms’ propensity to participate in international markets and their propensity to expand export activities by introducing new export products or establishing export links with new destination countries. In summary, the empirical results of this thesis convey the message that regional accessibility to knowledge, embodied in highly educated labor and/or developed through R&D activities, plays a fundamental role in shaping the content and structure of regional export flows. More specifically, the present empirical observations suggest that the regional endowment of knowledge stimulates the size of the export base in terms of exporting firms and number of product varieties. The recurring significance of the accessibility variables in explaining spatial export patterns show that the knowledge endowment of a region must be defined in such ways that it captures sources of potential knowledge spillovers from inside as well as outside its own regional boundaries. This outcome shows that regional variations in knowledge endowments originate both in the actual spatial distribution of a nation’s knowledge labor across regions, and in regional differences in the geographical accessibility to internal and external knowledge labor.
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| 10. |
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| 11. |
- Lagerkvist, Anna-Lena, 1956, et al.
(författare)
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Obstetric brachial plexus palsy: a prospective, population-based study of incidence, recovery, and residual impairment at 18 months of age.
- 2010
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Ingår i: Dev Med Child Neurol. - : Wiley. - 1469-8749 .- 0012-1622. ; 52:6, s. 529-34
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Tidskriftsartikel (refereegranskat)abstract
- Aim The aim of this investigation was to study the incidence of obstetric brachial plexus palsy (OBPP), to prospectively follow the recovery process, to assess the functional outcome at 18 months of age, and to find early prognostic indicators. Method Of the 38 749 children born between 1999 and 2001 in western Sweden, 114 (70 males, 44 females) had an OBPP. Ninety-eight children were examined on six occasions at up to 18 months of age. Muscle strength, range of motion, hand preference, and functional abilities were noted, and the severity of the OBPP was classified. Results The incidence of OBPP was 2.9 per 1000 live births, and the incidence of persisting OBPP was 0.46 per 1000. At 3 months of age, the predictive value of regained elbow flexion for complete recovery was 100%, 99% of shoulder external rotation, and 96% of forearm supination. Most of the 18 children with persisting OBPP could perform functional activities but asymmetries were noted. Five children had a mild, 11 had a moderate, and two had a severe impairment. Three had undergone nerve surgery, one with a mild and two with a severe persisting impairment. Interpretation Most children with an OBPP recover completely. Muscle strength at 3 months of age can be used to predict outcome.
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| 12. |
- Mollberg, Margareta, 1953, et al.
(författare)
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Comparison in obstetric management on infants with transient and persistent obstetric brachial plexus palsy.
- 2008
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Ingår i: Journal of child neurology. - : SAGE Publications. - 1708-8283 .- 0883-0738. ; 23:12, s. 1424-32
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Tidskriftsartikel (refereegranskat)abstract
- The outcome of obstetric brachial plexus palsy depends on the severity of the lesion of the nerve fibers. The aim of the prospective study is to evaluate if differences in force used in downward traction on the fetal head correlate to the number of nerve roots affected. At final neurological examination at 18 months of age, complete neurological recovery occurred in 80 of 98 children (82%). Downward traction of the fetal head was applied more often and with greater force in the group with persistent damage. There was a significant correlation between the force used to the number of nerve roots affected. The risk of persistent obstetric brachial plexus palsy at age 18 months depended on obstetric management and increased significantly with increasing force used in downward traction of the fetal head.
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| 13. |
- Nyberg, Jan, 1960-, et al.
(författare)
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Single-dose irradiation followed by implant insertion in rat bone : An investigative study to find a critical level for osseointegration
- 2010
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Ingår i: Journal of Osseointegration. - Carimate, Italy : Ariesdue. - 2036-4121. ; 2:2, s. 52-60
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Tidskriftsartikel (refereegranskat)abstract
- Aim: No general consensus exists regarding the ideal time to insert implants in bone after irradiation or how the various irradiation doses influence implant success. This study aims at investigating integration of implants in pre-irradiated rat bone and find a critical level doses that cause disturbed osseointegration.Materials and methods: Single irradiation doses of 2, 5, 10, 20 and 30 Gy were given to one leg of adult rats 3 days prior to insertion of screw-shaped implants whereas the other leg served as a non-irradiated control. The follow up was 5 weeks. Bone implant contact (BIC) and bone area (BA) were measured on undecalcified cut and ground sections in the light microscope. The tissue quality was also examined in the light microscope.Results: Doses of 5 and 10 Gy resulted in 25% higher contact values for the irradiated samples compared to non-irradiated controls. The most impaired integration occurred when doses of 20 Gy were given, revealing a 50% difference between the irradiated (25%) and the non irradiated samples (50%). The bone area demonstrated no major quantitative differences albeit the qualitative observations differed substantially being most pronounced in the 20 and 30 Gy irradiated samples.Conclusions: The osseointegration was substantially impaired after radiation doses of 20 and 30 Gy. Quantitative data alone are insufficient to describe implant integration in situation like this. Qualitative observations are of utmost importance and require great attention. The importance of judging and describing various grades of tissue damage is complicated but necessary. Based on the results obtained in this study, full scale experiments are now ongoing.
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| 14. |
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| 15. |
- Soldati, P., et al.
(författare)
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Distributed cross-layer coordination of congestion control and resource allocation in S-TDMA wireless networks
- 2008
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Ingår i: Wireless networks. - : Springer Science and Business Media LLC. - 1022-0038 .- 1572-8196. ; 14:6, s. 949-965
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Tidskriftsartikel (refereegranskat)abstract
- We consider the problem of joint congestion control and resource allocation in spatial-TDMA wireless networks. The design problem is posed as a utility maximization problem subject to link rate constraints which involve both transmission scheduling and power allocation. Starting from the performance limitations of a centralized optimization based on global network information, we proceed systematically in our development of two distributed and transparent protocols that rely on local information only. In the process, we introduce a novel decomposition method for convex optimization, establish its convergence for the utility maximization problem, and demonstrate how it suggests a distributed solution based on TCP/AQM and incremental updates of the transmission schedule. We develop a two-step procedure for finding the schedule updates and suggest two schemes for distributed link scheduling and power control under realistic interference models. Although the final protocols are suboptimal, we isolate and quantify the performance losses incurred by each simplification and demonstrate strong performance in examples.
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| 16. |
- Vitos, Levente, et al.
(författare)
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Stainless steel alloys from first-principles theory
- 2011
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Ingår i: 7th European Stainless Steel Conference. - : Associazione Italiana di Metallurgia. - 9788885298842
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Konferensbidrag (refereegranskat)abstract
- Gaining an accurate description of materials obviously requires the most advanced atomic-scale techniques from both experimental and theoretical areas. In spite of the vast number of available techniques, however, the experimental study of the atomic-scale properties and phenomena even in simple solids is rather difficult. In steels the challenges become more complex due to the interplay between the structural, chemical and magnetic effects. On the other hand, advanced computational methods based on density functional theory ensure a proper platform for studying the fundamental properties of steel materials from first-principles. Our group at the Royal Institute of Technology in Stockholm has an international position in developing and applying computational codes for such applications. Using our ab initio tools, we have presented an insight to the electronic and magnetic structure, and micromechanical properties of austenitic stainless steel alloys. In the present contribution, we review the most important developments within the ab initio quantum-mechanics-aided steel design with special emphasis on the role of magnetism on the fundamental properties of alloy steels.
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| 17. |
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| 18. |
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| 19. |
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| 20. |
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Agglomeration, clusters and entrepreneurship : Studies in regional economic development
- 2014
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Samlingsverk (redaktörskap) (övrigt vetenskapligt/konstnärligt)abstract
- Regional economic development has experienced considerable dynamism over recent years. Perhaps the most notable cases were the rise of China and India to emergent country status by the turn of the millennium. With time now for hindsight, this book identifies some of the key forces behind these development successes, namely agglomeration, clusters and entrepreneurship.
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| 21. |
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| 22. |
- Ahuja, Rajeev, et al.
(författare)
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Electronic and optical properties of gamma-Al2O3 from ab initio theory
- 2004
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Ingår i: Journal of Physics. - : IOP Publishing. - 0953-8984 .- 1361-648X. ; 16:16, s. 2891-2900
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Tidskriftsartikel (refereegranskat)abstract
- We report on a density functional theory calculation of the electronic structure and optical properties of gamma-Al2O3. We have made a comparison between the optical and electronic properties of the alpha and gamma phases of alumina. The calculated bulk modulus of the gamma phase is slightly lower than that of the a phase. The calculated static dielectric function and the optical constant of the gamma phase are very close to those of the alpha phase.
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| 23. |
- Ahuja, Rajeev, et al.
(författare)
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Electronic and optical properties of lead iodide
- 2002
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Ingår i: Journal of Applied Physics. - : AIP Publishing. - 0021-8979 .- 1089-7550. ; 92:12, s. 7219-7224
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Tidskriftsartikel (refereegranskat)abstract
- The electronic properties and the optical absorption of lead iodide (PbI2) have been investigated experimentally by means of optical absorption and spectroscopic ellipsometry, and theoretically by a full-potential linear muffin-tin-orbital method. PbI2 has been recognized as a very promising detector material with a large technological applicability. Its band-gap energy as a function of temperature has also been measured by optical absorption. The temperature dependence has been fitted by two different relations, and a discussion of these fittings is given.
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| 24. |
- Ahuja, R., et al.
(författare)
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Electronic structure of Ti3SiC2
- 2000
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Ingår i: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 76:16, s. 2226-2228
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Tidskriftsartikel (refereegranskat)
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| 25. |
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| 26. |
- Ahuja, Rajeev, et al.
(författare)
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High-pressure structural transitions in Cm and Am0.5Cm0.5 binary alloy
- 2006
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Ingår i: High Pressure Research. - : Informa UK Limited. - 0895-7959 .- 1477-2299. ; 26:4, s. 377-381
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Tidskriftsartikel (refereegranskat)abstract
- The high-pressure behaviour of Cm and Am0.5Cm0.5 binary alloy is investigated theoretically using ab initio electronic structure methods. Our calculations reproduce the structural phase transitions, which are observed in recent experiment performed by Heathman et al. [S. Heathman, R.G. Haire, I Le Bihan et al., Science 309 110 (2005)] and Lindbaum et al. [A. Lindbaum, S. Heathman, T. Le Bihan et al., J. Phys: Condens. Matter 15 S2297 (2003)]. Calculated transition pressures are in reasonable agreement with the experimental values. Calculations performed for an antiferromagnetic state are essential to reproduce the stability of Cm-III phase.
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| 27. |
- Ahuja, Rajeev, et al.
(författare)
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High pressure structural transitions in Cm metal
- 2006
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Ingår i: Mater Res Soc Symp Proc. - 1558998470 - 9781558998476 ; , s. 247-254
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Konferensbidrag (refereegranskat)abstract
- The high pressure behaviour of Cm metal is investigated theoretically using ab initio electronic structure methods. Our calculations reproduce the structural phase transitions which are obsereved in recent experiment performed by Heatman et al. [Science 309, 110 (2005)]. Calculated transition pressures are in reasonable agreement with the experimental values. Calculations performed for an antiferromagnetic state is essential to reproduce the stability of Cm-III phase. Thus, the stability of the Cm-III phase is related to the spin polarization of its 5f electrons.
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| 28. |
- Ahuja, Rajeev, et al.
(författare)
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Optical properties of 4H-SiC
- 2002
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Ingår i: Journal of Applied Physics. - : AIP Publishing. - 0021-8979 .- 1089-7550. ; 91:4, s. 2099-2103
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Tidskriftsartikel (refereegranskat)abstract
- The optical band gap energy and the dielectric functions of n-type 4H-SiC have been investigated experimentally by transmission spectroscopy and spectroscopic ellipsometry and theoretically by an ab initio full-potential linear muffin-tin-orbital method. We present the real and imaginary parts of the dielectric functions, resolved into the transverse and longitudinal photon moment a, and we show that the anisotropy is small in 4H-SiC. The measurements and the calculations fall closely together in a wide range of energies.
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| 29. |
- Ahuja, Rajeev, et al.
(författare)
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Optical properties of SiGe alloys
- 2003
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Ingår i: Journal of Applied Physics. - : AIP Publishing. - 0021-8979 .- 1089-7550. ; 93:7, s. 3832-3836
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Tidskriftsartikel (refereegranskat)abstract
- The optical properties of Si1-xGex have been investigated theoretically using a full-potential linear muffin-tin-orbital method. We present the density-of-states as well as the real and imaginary parts of the dielectric function. The calculated dielectric function was found to be in good agreement with the spectroscopic ellipsometry measurements by J. Bahng , J. Phys.: Condens. Matter 13, 777 (2001), and we obtained a static dielectric constant of epsilon(0)=12.19+2.45x in the Si rich regime (xless than or equal to0.5).
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| 30. |
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| 31. |
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| 32. |
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| 33. |
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| 34. |
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| 35. |
- Airiskallio, E., et al.
(författare)
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High temperature oxidation of Fe-Al and Fe-Cr-Al alloys : The role of Cr as a chemically active element
- 2010
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Ingår i: Corrosion Science. - : Elsevier BV. - 0010-938X .- 1879-0496. ; 52:10, s. 3394-3404
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Tidskriftsartikel (refereegranskat)abstract
- Good high-temperature corrosion resistance of Fe-Al alloys in oxidizing environments is due to the alpha-Al2O3 film which is formed on the surface provided temperature is above 900 degrees C and the Al-content of the alloy exceeds the critical value. Ab initio calculations combined with experiments on Fe-13Al, Fe-18Al, Fe-23Al and Fe-10Cr-10Al alloys show that the beneficial effect of Cr on the oxidation resistance is significantly related to bulk effects. The comparison of experimental and calculated results indicates a clear correlation between the Fe-Cr chemical potential difference and the formation of the protective oxide scales. (C) 2010 Elsevier Ltd. All rights reserved.
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| 36. |
- Airiskallio, E., et al.
(författare)
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Magnetic origin of the chemical balance in alloyed Fe-Cr stainless steels : First-principles and Ising model study
- 2014
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Ingår i: Computational materials science. - : Elsevier BV. - 0927-0256 .- 1879-0801. ; 92, s. 135-140
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Tidskriftsartikel (refereegranskat)abstract
- Iron-chromium is the base material for most of the stainless steel grades. Recently, new insights into the origins of fundamental physical and chemical characteristics of Fe-Cr based alloys have been achieved. Some of the new results are quite unexpected and call for further investigations. The present study focuses on the magnetic contribution in the atomic driving forces related to the chemical composition in Fe-Cr when alloyed with Al, Ti, V, Mn, Co, Ni, and Mo. Using the ab initio exact muffin-tin orbitals method combined with an Ising-type spin model, we demonstrate that the magnetic moment of the solute atoms with the induced changes in the magnetic moments of the host atoms form the main factor in determining the mixing energy and chemical potentials of low-Cr Fe-Cr based alloys. The results obtained in the present work are related to the designing and tuning of the microstructure and corrosion protection of low-Cr steels.
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| 37. |
- Airiskallio, E., et al.
(författare)
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Third element effect in the surface zone of Fe-Cr-Al alloys
- 2010
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Ingår i: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121 .- 1550-235X. ; 81:3
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Tidskriftsartikel (refereegranskat)abstract
- The third element effect to improve the high temperature corrosion resistance of the low-Al Fe-Cr-Al alloys is suggested to involve a mechanism that boosts the recovering of the Al concentration to the required level in the Al-depleted zone beneath the oxide layer. We propose that the key factor in this mechanism is the coexistent Cr depletion that helps to maintain a sufficient Al content in the depleted zone. Several previous experiments related to our study support that conditions for such a mechanism to be functional prevail in real oxidation processes of Fe-Cr-Al alloys.
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| 38. |
- Airiskallio, E., et al.
(författare)
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Tuning the surface chemistry of Fe-Cr by V doping
- 2009
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Ingår i: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121 .- 1550-235X. ; 80:15
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Tidskriftsartikel (refereegranskat)abstract
- The reversal of the magnitudes of the bulk and surface chemical-potential differences induces the outburst of Cr on the otherwise pure Fe surface of Fe-Cr alloys. This threshold value for the Cr content is about 10 at. %. It is found that vanadium addition to Fe-Cr shifts the Cr threshold to a substantially lower value suggesting V having a positive effect on the corrosion resistance of low Cr steels. The obtained shift in the Cr threshold is shown to be connected to the change in volume of the alloy.
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| 39. |
- Al-Zoubi, N., et al.
(författare)
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Assessing the Exact Muffin-Tin Orbitals method for the Bain path of metals
- 2017
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Ingår i: Philosophical Magazine. - : Taylor & Francis. - 1478-6435 .- 1478-6443. ; 97:15, s. 1243-1264
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Tidskriftsartikel (refereegranskat)abstract
- We scrutinise the muffin-tin approximation and the screening within the framework of the Exact Muffin-Tin Orbitals method in the case of cubic and tetragonal crystal symmetries. Systematic total energy calculations are carried out for the Bain path including the body-centred cubic and face-centred cubic structures for a set of simple and transition metals. The present converged results in terms of potential sphere radius (S) and hard sphere radius (b) are in good agreement with previous theoretical calculations. We demonstrate that for all structures considered here, potential sphere radii around and slightly larger than the average Wigner–Seitz radius (w) yield accurate total energy results whereas S values smaller than w give large errors. It is shown that for converged total energies hard spheres with radii b = 0.7–0.8w should be used for an efficient screening within real space clusters consisting typically of 70–90 lattice sites. The less efficient convergence of the total energy in the case of small hard spheres is ascribed to the delocalisation of the screened spherical waves, which leads to inaccurate interstitial overlap matrix. The above conclusions are not significantly affected by the volume of the system.
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| 40. |
- Al-Zoubi, Noura, et al.
(författare)
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Completeness of the exact muffin-tin orbitals : application to hydrogenated alloys
- 2010
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Ingår i: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121 .- 1550-235X. ; 81:4
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Tidskriftsartikel (refereegranskat)abstract
- We investigate the basis set convergence of the exact muffin-tin orbitals by monitoring the equation of state for Al, Cu, and Rh calculated in the conventional face-centered-cubic lattice (str-I) and in a face-centered-cubic lattice with one atomic and three empty sites per primitive cell (str-II). We demonstrate that three (spd) muffin-tin orbitals are sufficient to describe Al in both structures, but for str-II Cu and Rh at least five (spdfg) orbitals are needed to get converged equilibrium Wigner-Seitz radius (within <= 0.8%) and bulk modulus (<= 3.3%). We ascribe this slow convergence to the nearly spherical densities localized around the Cu and Rh atoms, which create strongly asymmetric charge distributions within the nearest cells around the empty sites. The potential sphere radius dependence of the theoretical results for structure str-II is discussed. It is shown that a properly optimized overlapping muffin-tin potential in combination with the spdfg basis yields acceptable errors in the equilibrium bulk properties. The basis set convergence is also shown on hydrogenated Sc and Sc-based alloys.
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| 41. |
- Al-Zoubi, Noura, et al.
(författare)
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Elastic properties of 4d transition metal alloys : Values and trends
- 2019
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Ingår i: Computational materials science. - : ELSEVIER SCIENCE BV. - 0927-0256 .- 1879-0801. ; 159, s. 273-280
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Tidskriftsartikel (refereegranskat)abstract
- Using the Exact Muffin-Tin Orbitals method within the Perdew-Burke-Ernzerhof exchange-correlation approximation for solids and solid surfaces (PBEso1), we study the single crystal elastic constants of 4d transition metals (atomic number Z between 39 and 47) and their binary alloys in the body centered cubic (bcc) and face centered cubic (fcc) structures. Alloys between the first neighbors Z(Z + 1) and between the second neighbors Z(Z + 2) are considered. The lattice constants, bulk moduli and elastic constants are found in good agreement with the available experimental and theoretical data. It is shown that the correlation between the relative tetragonal shear elastic constant C-fcc'-2C(bcc)' and the structural energy difference between the fcc and bcc lattices Delta E is superior to the previously considered models. For a given crystal structure, the equiatomic Z(Z + 2) alloys turn out to have similar structural and elastic properties as the pure elements with atomic number (Z + 1). Furthermore, alloys with composition Z(1-x)(Z + 2)(x) possess similar properties as Z(1-2x)(Z + 1)(2x). The present theoretical data on the structural and the elastic properties of 4d transition metal alloys provides consistent input for coarse scale modeling of material properties.
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| 42. |
- Al-Zoubi, Noura, et al.
(författare)
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Influence of Magnesium on hydrogenated ScAl1-xMgx alloys : a theoretical study
- 2011
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Ingår i: Computational materials science. - : Elsevier BV. - 0927-0256 .- 1879-0801. ; 50:10, s. 2848-2853
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Tidskriftsartikel (refereegranskat)abstract
- Ab initio total energy calculations, based on the projector augmented wave method and the exact mu±n-tin orbitals method in combination with the coherent-potential approximation, are used to examine the effect of magnesium on hydrogen absorption/desorption temperature and phase stability of hydrogenated ScAl1-xMgx (0 ≤ x ≤ 0:3) alloys. According to the experiments, ScAl1-xMgx adopts the CsCl structure, and upon hydrogen absorption it decomposes into ScH2 with CaF2 structure and Al-Mg with face centered cubic structure. Here we demonstrate that the stability field of the hydrogenated alloys depends sensitively on Mg content and on the microstructure of the decomposed system. For a given microstructure, the critical temperature for hydrogen absorption/desorption increases with Mg concentration.
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| 43. |
- Al-Zoubi, Noura, et al.
(författare)
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Influence of manganese on the bulk properties of Fe-Cr-Mn alloys : a first-principles study
- 2014
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Ingår i: Physica Scripta. - : IOP Publishing. - 0031-8949 .- 1402-4896. ; 89:12, s. 125702-
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Tidskriftsartikel (refereegranskat)abstract
- We investigate the effect of manganese on lattice stability and magnetic moments of paramagnetic Fe-Cr-Mn steel alloys along the Bain path connecting the body-centered cubic (bcc) and face-centered cubic (fcc) structures. The calculations are carried out using the ab initio exact muffin-tin orbital method, in combination with the coherent potential approximation, and the paramagnetic phase is modeled by the disordered local magnetic moment scheme. For all Fe-Cr-Mn alloys considered here, the local magnetic moments on Fe atoms have the minimum values for the fcc structure and the maximum values for the bcc structure, whereas the local magnetic moments on Mn have almost the same value along the constant-volume Bain path. Our results show that Mn addition to paramagnetic Fe-Cr solid solution stabilizes the bcc structure. However, when considering the paramagnetic fcc phase relative to the ferromagnetic bcc ground state, then Mn turns out to be a clear fcc stabilizer, in line with observations.
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| 44. |
- Al-Zoubi, Noura, et al.
(författare)
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Tetragonality of carbon-doped ferromagnetic iron alloys : A first-principles study
- 2012
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Ingår i: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121 .- 1550-235X. ; 85:1, s. 014112-
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Tidskriftsartikel (refereegranskat)abstract
- Using density-functional theory in combination with the exact muffin-tin orbital (EMTO) method and coherent potential approximation, we investigate the alloying effect on the tetragonality of Fe-C solid solution forming the basis of steels. In order to assess the accuracy of our approach, first we perform a detailed study of the performance of the EMTO method for the Fe(16)C(1) binary system by comparing the EMTO results to those obtained using the projector augmented wave method. In the second step, we introduce different substitutional alloying elements (Al, Cr, Co, Ni) into the Fe matrix and study their impact on the structural parameters. We demonstrate that a small amount of Al, Co, and Ni enhances the tetragonal lattice ratio of Fe(16)C(1) whereas Cr leaves the ratio almost unchanged. The obtained trends are correlated with the single-crystal elastic parameters calculated for carbon-free alloys.
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| 45. |
- Al-Zoubi, Noura, et al.
(författare)
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The bain path of paramagnetic Fe-Cr based alloys
- 2011
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Ingår i: Journal of Applied Physics. - : AIP Publishing. - 0021-8979 .- 1089-7550. ; 110:1, s. 013708-
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Tidskriftsartikel (refereegranskat)abstract
- Employing the first-principles exact muffin-tin orbital method in combination with the coherent potential approximation, we calculated the total energy and local magnetic moments of paramagnetic Fe-Cr-M (M = Cr, Mn, Fe, Co, Ni) alloys along the tetragonal distortion (Bain) path connecting the body centered cubic (bcc) and the face centered cubic (fcc) structures. The paramagnetic phase is modeled by the disordered local magnetic moment scheme. For all alloys, the local magnetic moments on Fe atoms decrease from the maximum value corresponding to the bcc phase toward the minimum value realized for the fcc phase. Cobalt atoms have non-vanishing local magnetic moments only for tetragonal lattices with c/a < 1.30, whereas the local magnetic moments of Mn show weak crystal structure dependence. We find that Cr stabilizes the bcc lattice and increases the energy barrier as going from the bcc toward the fcc phase. Both Co and Ni favor the fcc lattice and decrease the energy barrier relative to the bcc phase. On the other hand, the tetragonal distortion around the fcc phase is facilitated by Cr and to a somewhat lesser extent also by Ni, but strongly impeded by Co. Manganese has negligible effect on the structural energy difference as well as on the energy barrier along the Bain path. Our findings on the alloying induced softening or hardening of Fe-Cr based alloys against tetragonal distortions are important for understanding the interstitial driven martensitic transformations in alloy steels.
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| 46. |
- Albrekt, Ann-Sofie, et al.
(författare)
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Skin sensitizers differentially regulate signaling pathways in MUTZ-3 cells in relation to their individual potency
- 2014
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Ingår i: Bmc Pharmacology & Toxicology. - : Springer Science and Business Media LLC. - 1471-2210 .- 2050-6511. ; 15
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Tidskriftsartikel (refereegranskat)abstract
- Background: Due to the recent European legislations posing a ban of animal tests for safety assessment within the cosmetic industry, development of in vitro alternatives for assessment of skin sensitization is highly prioritized. To date, proposed in vitro assays are mainly based on single biomarkers, which so far have not been able to classify and stratify chemicals into subgroups, related to risk or potency. Methods: Recently, we presented the Genomic Allergen Rapid Detection (GARD) assay for assessment of chemical sensitizers. In this paper, we show how the genome wide readout of GARD can be expanded and used to identify differentially regulated pathways relating to individual chemical sensitizers. In this study, we investigated the mechanisms of action of a range of skin sensitizers through pathway identification, pathway classification and transcription factor analysis and related this to the reactive mechanisms and potency of the sensitizing agents. Results: By transcriptional profiling of chemically stimulated MUTZ-3 cells, 33 canonical pathways intimately involved in sensitization to chemical substances were identified. The results showed that metabolic processes, cell cycling and oxidative stress responses are the key events activated during skin sensitization, and that these functions are engaged differently depending on the reactivity mechanisms of the sensitizing agent. Furthermore, the results indicate that the chemical reactivity groups seem to gradually engage more pathways and more molecules in each pathway with increasing sensitizing potency of the chemical used for stimulation. Also, a switch in gene regulation from up to down regulation, with increasing potency, was seen both in genes involved in metabolic functions and cell cycling. These observed pathway patterns were clearly reflected in the regulatory elements identified to drive these processes, where 33 regulatory elements have been proposed for further analysis. Conclusions: This study demonstrates that functional analysis of biomarkers identified from our genomics study of human MUTZ-3 cells can be used to assess sensitizing potency of chemicals in vitro, by the identification of key cellular events, such as metabolic and cell cycling pathways.
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| 47. |
- Alcala, Karine, et al.
(författare)
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The relationship between blood pressure and risk of renal cell carcinoma
- 2022
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Ingår i: International Journal of Epidemiology. - : Oxford University Press (OUP). - 1464-3685 .- 0300-5771. ; 51:4, s. 1317-1327
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: The relation between blood pressure and kidney cancer risk is well established but complex and different study designs have reported discrepant findings on the relative importance of diastolic blood pressure (DBP) and systolic blood pressure (SBP). In this study, we sought to describe the temporal relation between diastolic and SBP with renal cell carcinoma (RCC) risk in detail.METHODS: Our study involved two prospective cohorts: the European Prospective Investigation into Cancer and Nutrition study and UK Biobank, including >700 000 participants and 1692 incident RCC cases. Risk analyses were conducted using flexible parametric survival models for DBP and SBP both separately as well as with mutuality adjustment and then adjustment for extended risk factors. We also carried out univariable and multivariable Mendelian randomization (MR) analyses (DBP: ninstruments = 251, SBP: ninstruments = 213) to complement the analyses of measured DBP and SBP.RESULTS: In the univariable analysis, we observed clear positive associations with RCC risk for both diastolic and SBP when measured ≥5 years before diagnosis and suggestive evidence for a stronger risk association in the year leading up to diagnosis. In mutually adjusted analysis, the long-term risk association of DBP remained, with a hazard ratio (HR) per standard deviation increment 10 years before diagnosis (HR10y) of 1.20 (95% CI: 1.10-1.30), whereas the association of SBP was attenuated (HR10y: 1.00, 95% CI: 0.91-1.10). In the complementary multivariable MR analysis, we observed an odds ratio for a 1-SD increment (ORsd) of 1.34 (95% CI: 1.08-1.67) for genetically predicted DBP and 0.70 (95% CI: 0.56-0.88) for genetically predicted SBP.CONCLUSION: The results of this observational and MR study are consistent with an important role of DBP in RCC aetiology. The relation between SBP and RCC risk was less clear but does not appear to be independent of DBP.
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| 48. |
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| 49. |
- Ambrosch-Draxl, C., et al.
(författare)
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First-principles study of oxygen ordering in YBa2Cu3O7-x
- 2000
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Ingår i: Physica. C, Superconductivity. - 0921-4534 .- 1873-2143. ; 341, s. 1997-1998
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Tidskriftsartikel (refereegranskat)abstract
- We have performed first-principles calculations considering different patterns of oxygen/vacancy ordering in the Cu-O chains of YBa2Cu3O7-x. From the total-energy values we determine the effective interactions of the oxygen atoms within the basal plane by using the cluster expansion technique. Furthermore, we discuss the effect of ordering to the density of states at the Fermi level.
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| 50. |
- Amft, Martin, et al.
(författare)
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Influence of the cluster dimensionality on the binding behavior of CO and O(2) on Au(13)
- 2012
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Ingår i: Journal of Chemical Physics. - : AIP Publishing. - 0021-9606 .- 1089-7690. ; 136:2, s. 024312-
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Tidskriftsartikel (refereegranskat)abstract
- We present an ab initio density functional theory study of the binding behavior of CO and O(2) molecules to two-and three-dimensional isomers of Au(13) in order to investigate the potential catalytic activity of this cluster towards low-temperature CO oxidation. First, we scanned the potential energy surface of Au(13) and studied the effect of spin-orbit coupling on the relative stabilities of the 21 isomers we identified. While spin-orbit coupling increases the stability of the three-dimensional more than the two-dimensional isomers, the ground state structure at 0 K remains planar. Second, we systematically studied the binding of CO and O(2) molecules onto the planar and three-dimensional structures lowest in energy. We find that the isomer dimensionality has little effect on the binding of CO to Au(13). O(2), on the other hand, binds significantly to the three-dimensional isomer only. The simultaneous binding of multiple CO molecules decreases the binding energy per molecule. Still, the CO binding remains stronger than the O(2) binding. We did not find a synergetic effect due to the co-adsorption of both molecular species. On the three-dimensional isomer, we find O(2) dissociation to be exothermic with an dissociation barrier of 1.44 eV.
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