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51. Microscopic theory of magnetism in the magnetocaloric material Fe2P1-xTx (T = B and Si)

Author

Delczeg-Czirjak, E. K., Bergqvist, L., Eriksson, Olle, Gercsi, Z., Nordblad, Per, Szunyogh, L., Johansson, Börje, Vitos, Levente, Delczeg-Czirjak, E. K., Bergqvist, L., Eriksson, Olle, Gercsi, Z., Nordblad, Per, Szunyogh, L., Johansson, Börje, and Vitos, Levente

Abstract

Landau phenomenological theory in combination with first-principles calculations was used to reveal the origin of the metamagnetic nature and the unusually strong dependence of the ordering temperature with doping of the Fe2P compound. We show that the magnetism of the two sublattices occupied by Fe atoms has an entwined codependency, which is strongly influenced by alloying. We furthermore demonstrate that a constrained disordered local moment approach combined with Monte Carlo simulations can only reproduce the experimental ordering temperatures in these technologically important prototype alloys for magnetocaloric refrigeration., Correction in: Physical Review B, 2013, vol. 88, issue 19, Article Number: 199904.DOI: 10.1103/PhysRevB.88.199904

Published
2012
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52. Theory of diluted magnetic semiconductors

Author

Eriksson, Olle, Iusan, M., Thunström, Patrik, Hellsvik, J., di Marco, Igor, Bergqvist, L., Dederichs, P., Sanyal, Biplab, Eriksson, Olle, Iusan, M., Thunström, Patrik, Hellsvik, J., di Marco, Igor, Bergqvist, L., Dederichs, P., and Sanyal, Biplab

Abstract

In order to understand and manipulate the properties of diluted magnetic semiconductors, a precise knowledge of interactions in these systems should be available. In this chapter, we review ab initio studies on DMS, in particular, calculations of ordering temperatures by Monte Carlo simulations. We argue why we do not expect large values of ordering temperatures from the point of view of dilute spin system, short ranged magnetic exchange interactions and magnetic percolation. Also, we show results of atomistic spin dynamics using Landau–Lifshitz–Gilbert equations for Mn-doped GaAs. The effects of strong electron correlation on the electronic and magnetic structure are demonstrated by dynamical mean field theory.

Published
2012
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57. Seeing through the blind! : ability of hospital staff to differentiate morphine from placebo, in neonates at a placebo controlled trial

Author

Bergqvist, L., Eriksson, Mats, Kronsberg, S.S., Schollin, Jens, Barton, B., Anand, K.J.S., Bergqvist, L., Eriksson, Mats, Kronsberg, S.S., Schollin, Jens, Barton, B., and Anand, K.J.S.

Abstract

AIM: To investigate whether professional training and/or clinical experience affect the ability of caregiver to assess clinical signs of pre-emptive morphine analgesia. METHODS: In the Neurological Outcomes & Pre-emptive Analgesia In Neonates trial preterm infants undergoing mechanical ventilation were randomized to receive continuous infusion, either of morphine or placebo blinded. Staff from centres in Sweden (Stockholm and Orebro) completed an assessment form. RESULTS: A total of 360 assessment forms were collected from 52 neonates. In 59% of the cases, caregivers correctly identified patients group. Comparable proportion of answers were correct between physicians, nurses and assistant nurses (63, 60 and 54%, respectively, p = 0.60). Staff with Neonatal intensive care unit experience <1 year identified 63%, as compared to 65% for working 1-5 year, and 55% that has been working >5 years (p = 0.28). Staff's ability to correctly identify group assignment was reduced by amount of additional morphine (p < 0.01) and severity of illness (p = 0.01). CONCLUSIONS: Clinical medical staffs, including neonatologists, have great difficulties in assessing the presence and severity of pain. Further studies should focus on the methods for assessment of prolonged pain in preterm neonates, define the effects of adequate analgesia, and investigate the clinical factors that may alter neonatal responses to acute and prolonged pain.

Published
2007
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58. Magnetic properties of selected Mn-based transition metal compounds with β-Mn structure: Experiments and theory

Author

Eriksson, Therese, Bergqvist, L, Andersson, Yvonne, Nordblad, P, Eriksson, O, Eriksson, Therese, Bergqvist, L, Andersson, Yvonne, Nordblad, P, and Eriksson, O

Abstract

Two compounds, Mn3CoSi and Mn3CoGe have been synthesized and found to crystallize in the AlAu4 type structure, an ordered form of the β-Mn structure. The magnetic structure and properties have been studied by magnetometry and neutron powder diffraction and the theoretical work is based on first principles total energy calculations. Comparison is made with the magnetic properties of the isostructural compounds Mn3IrGe and Mn3IrSi. The solid solutions Mn3Ir1–yCoySi (0y1) and Mn3CoSi1–xGex (0x1) are also studied. A noncollinear antiferromagnetic structure is experimentally observed for y=0.20 as well as for x=0.50 and 1.0, similar to that of Mn3IrSi and Mn3IrGe, with 120° angles between magnetic moments on a triangular network of Mn atoms, and this finding is corroborated by theoretical calculations. For y=0.80–1.0 a transformation to a new type of magnetic structure takes place. The magnetic transition temperature decreases on decreasing unit cell dimension, with good qualitative agreement with the decay of the calculated interatomic exchange energy. Both theory and experiments find the magnitude of the Mn magnetic moment to decrease on decreasing unit cell volume, the same trend is found in calculations for β-Mn.

Published
2005
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63. Abstract P6-10-03: Bilateral Prophylactic Mastectomy in Swedish Women at High Risk of Breast Cancer — A National Survey

Author

Isaksson, K, primary, Arver, B, additional, Atterhem, H, additional, Baan, A, additional, Bergqvist, L, additional, Brandberg, Y, additional, Ehrencrona, H, additional, Emanuelsson, M, additional, Hellborg, H, additional, Henriksson, K, additional, Karlsson, P, additional, Loman, N, additional, Lundberg, J, additional, Ringberg, A, additional, Stenmark Askmalm, M, additional, Wickman, M, additional, and Sandelin, K., additional

Published
2010
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65. Defect-induced magnetic structure in (Ga1-xMnx)As

Author

Korzhavyi, Pavel A., Abrikosov, I. A., Smirnova, E. A., Bergqvist, L., Mohn, P., Mathieu, R., Svedlindh, P., Sadowski, J., Isaev, E. I., Vekilov, Y. K., Eriksson, O., Korzhavyi, Pavel A., Abrikosov, I. A., Smirnova, E. A., Bergqvist, L., Mohn, P., Mathieu, R., Svedlindh, P., Sadowski, J., Isaev, E. I., Vekilov, Y. K., and Eriksson, O.

Abstract

We show that magnetic structures involving partial disorder of local magnetic moments on the Mn atoms in (Ga1-xMnx)As lower the total energy, compared to the case of perfect ferromagnetic ordering, when As defects on the Ga sublattice are present. Such magnetic structures are found to be stable for a range of concentrations of As antisites, and this result accounts for the observed magnetic moments and critical temperatures in (Ga1-xMnx)As . We propose an explanation for the stabilization of the partially disordered magnetic structures and conclude that the magnetization and critical temperatures should increase substantially by reducing the number of As antisite defects., QC 20100525 NR 20140804

Published
2002
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66. Defect-induced magnetic structure in (Ga1-xMnx)As - article no.187202

Author

Korzhavyi, PA, Abrikosov, IA, Smirnova, EA, Bergqvist, L, Mohn, P, Mathieu, R, Svedlindh, P, Sadowski, J, Isaev, EI, Vekilov, YK, Eriksson, O, Korzhavyi, PA, Abrikosov, IA, Smirnova, EA, Bergqvist, L, Mohn, P, Mathieu, R, Svedlindh, P, Sadowski, J, Isaev, EI, Vekilov, YK, and Eriksson, O

Published
2002

67. Defect-induced magnetic structure in (Ga/sub 1-x/Mn/sub x/)As

Author

Korzhavyi, P.A., Abrikosov, I.A., Smirnova, E.A., Bergqvist, L., Mohn, P., Mathieu, R., Svedlindh, P., Sadowski, Janusz, Isaev, E.I., Vekilov, Yu.Kh., Eriksson, O., Korzhavyi, P.A., Abrikosov, I.A., Smirnova, E.A., Bergqvist, L., Mohn, P., Mathieu, R., Svedlindh, P., Sadowski, Janusz, Isaev, E.I., Vekilov, Yu.Kh., and Eriksson, O.

Published
2002

69. P19-08. Immunisation with recombinant HLA class I and II, HIV-1gp140 and SIVp27 antigens elicits protection against SHIV-SF162P4 infection in rhesus macaques

Author

Mörner, A, primary, Schøller, J, additional, Bunnik, E, additional, Jansson, M, additional, Wehlin, L, additional, Bergqvist, L, additional, Pihlainen, E Hansson, additional, Shaw, O, additional, Seidl, T, additional, Wang, Y, additional, Bergmeier, LA, additional, Singh, M, additional, Vaughan, R, additional, Yang, G, additional, Shao, Y, additional, Wyatt, RT, additional, Schuitemaker, H, additional, Biberfeld, G, additional, Thorstensson, R, additional, and Lehner, T, additional

Published
2009
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90. Magnetic and electronic structure of(Ga1−xMnx)As

Author

Bergqvist, L., primary, Korzhavyi, P. A., additional, Sanyal, B., additional, Mirbt, S., additional, Abrikosov, I. A., additional, Nordström, L., additional, Smirnova, E. A., additional, Mohn, P., additional, Svedlindh, P., additional, and Eriksson, O., additional

Published
2003
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91. Magnetism of Fe/V and Fe/Co multilayers

Author

Eriksson, O, primary, Bergqvist, L, additional, Holmstr m, E, additional, Bergman, A, additional, LeBacq, O, additional, Frota-Pessoa, S, additional, Hj rvarsson, B, additional, and Nordstr m, L, additional

Published
2003
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92. Defect-Induced Magnetic Structure in(Ga1−xMnx)As

Author

Korzhavyi, P. A., primary, Abrikosov, I. A., additional, Smirnova, E. A., additional, Bergqvist, L., additional, Mohn, P., additional, Mathieu, R., additional, Svedlindh, P., additional, Sadowski, J., additional, Isaev, E. I., additional, Vekilov, Yu. Kh., additional, and Eriksson, O., additional

Published
2002
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95. Osteoderm histology of Late Pleistocene cingulates from the intertropical region of Brazil.

Author

Da Costa Pereira, P. V. L. G., Victer, G. D., Porpino, K. O., and Bergqvist, L. P.

Subjects
CLASSIFICATION of mammals, PLEISTOCENE Epoch, MAMMAL ecology, GLYPTODONTIDAE
Abstract

During the Late Pleistocene, several possibly endemic cingulate species, known mostly from isolated osteoderms, cara-pace fragments, and caudal tubes, coexisted in the Brazilian Intertropical Region. Here, we describe the osteoderm micro- structure of Pachyarmatherium brasiliense, as well as the glyptodonts Panochthus greslebini, Panochthus jaguaribensis and Glyptotherium sp., in order to provide additional species-diagnostic characters and shed light on their evolutionary relationships. Pachyarmatherium brasiliense lacks several derived features shared by glyptodonts and pampatheres, such as extensive bone remodeling, fibers arranged in large bundles, and relatively poorly developed layers of compact bone, thus supporting its exclusion from glyptodonts as suggested by a recent cladistic study. The osteoderm histology of P. greslebini resembles that of other species of Panochthus (e.g., Panochthus frenzelianus). By contrast, the presence of relatively thick layers of compact bone, the configuration and size of resorption areas, the absence of randomly oriented lateral fiber bundles, and the absence of an intermediary region between the compact and trabecular bone potentially support the exclusion of Panochthus jaguaribensis from the genus. Finally, osteoderms of the Brazilian specimens of Glyptodontinae share histological features with Glyptotherium floridanus, rather than Glyptodon, thus reinforcing their assignment to Glyptotherium. These results highlight the relevance of histological osteoderm characters in cingulate systematics, ands call for further and more comprehensive studies. [ABSTRACT FROM AUTHOR]

Published
2014
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96. Microscopic theory of magnetism in the magnetocaloric material Fe2P1-xTx (T = B and Si).

Author

Delczeg-Czirjak, E. K., Bergqvist, L., Eriksson, O., Gercsi, Z., Nordblad, P., Szunyogh, L., Johansson, B., and Vitos, L.

Subjects
*IRON alloys, *MAGNETISM, *MICROSCOPY, *LANDAU levels, *ORDER-disorder in alloys, *MONTE Carlo method, *PROTOTYPES
Abstract

Landau phenomenological theory in combination with first-principles calculations was used to reveal the origin of the metamagnetic nature and the unusually strong dependence of the ordering temperature with doping of the Fe2P compound. We show that the magnetism of the two sublattices occupied by Fe atoms has an entwined codependency, which is strongly influenced by alloying. We furthermore demonstrate that a constrained disordered local moment approach combined with Monte Carlo simulations can only reproduce the experimental ordering temperatures in these technologically important prototype alloys for magnetocaloric refrigeration. [ABSTRACT FROM AUTHOR]

Published
2012
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97. Computational materials design for high-Tc (Ga, Mn)As with Li codoping.

Author

Bergqvist, L., Sato, K., Katayama-Yoshida, H., and Dederichs, P. H.

Subjects
*MONTE Carlo method, *SEMICONDUCTOR doping, *DOPED semiconductor superlattices, *INTERPHOTORECEPTOR matrix, *SEMICONDUCTORS, *CURIE temperature
Abstract

Based on first-principles calculations and kinetic Monte Carlo simulations, we design a realistic and practical codoping technique for increasing the concentration of Mn atoms in GaAs and realizing high Curie temperatures in (Ga,Mn)As. We found that using codoping of Li interstitial atoms during the crystal growth has two great advantages. First, due to lower formation energy of Li interstitials compared to Mn interstitials, Li prevents formation of unwanted Mn interstitials. Second, Li interstitials can be removed by using post-growth annealing at low temperatures. This codoping method offers a general strategy to go far beyond the solubility limit and it should be applicable also to other diluted magnetic semiconductor systems. [ABSTRACT FROM AUTHOR]

Published
2011
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98. Structural and magnetic characterization of Mn3IrGe and Mn3Ir(Si1-xGex): experiments and theory

Author

Eriksson, T., Bergqvist, L., Nordblad, P., Eriksson, O., and Andersson, Y.

Subjects
*MANGANESE, *NEUTRON diffraction, *MAGNETIC properties, *SOLID solutions
Abstract

Abstract: The structural and magnetic properties of a new ternary Ir–Mn–Ge phase, Mn3IrGe, as well as the solid solution Mn3Ir(Si1-xGex), , have been investigated by means of X-ray and neutron powder diffraction, magnetization measurements and first principles calculations. The crystal structure is cubic, of the AlAu4-type (an ordered form of the β-Mn structure), , space group P213, and the unit-cell dimension varies linearly with the silicon content. For all compositions, antiferromagnetic ordering is found below a critical temperature of about 225K. The magnetic structure is noncollinear, as a result of frustrated magnetic interactions on a triangular network of Mn atoms, on which the moments rotate 120° around the triangle axes. The magnitude of the magnetic moment at 10K is 3.39(4)μB for Mn3IrGe. The theoretical calculations reproduce with very good accuracy the magnitudes as well as the directions of the experimentally observed magnetic moments. [Copyright &y& Elsevier]

Published
2004
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100. Isolated liver perfusion using percutaneous methods: an experimental study in the pig.

Author

Harnek, Jan, Cwikiel, Wojciech, Bergqvist, Lennart, Persson, Bo, Stridbeck, Hans, Harnek, J, Cwikiel, W, Bergqvist, L, Persson, B, and Stridbeck, H

Subjects
ANIMAL experimentation, ANIMALS, CATHETERIZATION, LIGATURE (Surgery), LIVER, PERFUSION, PORTAL vein, RADIOGRAPHY, SWINE, VENA cava inferior, HEPATIC veins
Abstract

Purpose: To develop a method for isolated perfusion of the liver using radiological methods.Methods: Twenty-one pigs, weighing about 20 kg, were divided into three groups. By transjugular and transfemoral approaches two occlusion balloons were placed in the inferior vena cava cranial and caudal, respectively, to the origin of the hepatic veins. One occlusion balloon was placed transfemorally in the common hepatic artery. Another occlusion balloon was inserted in the main branch of the portal vein via the transjugular-transhepatic approach in 11 pigs (groups 1 and 2), and in 10 pigs (group 3) by a percutaneous transhepatic route. After inflation of the balloons, patency of the isolated liver circulation was evaluated by recirculation of 99Tcm-labelled human albumin during 30 min. Blood tests were obtained after 1, 3, 5, 10, 15, and 30 min to evaluate leakage from the liver to the systemic circulation.Results: Increasing leakage to the systemic circulation from the isolated liver circulation was observed in groups 1 and 2. In the third group the leakage was less than 10%.Conclusion: In an experimental animal model, isolated perfusion of the liver with minor leakage to the systemic circulation may be achieved using radiological methods. [ABSTRACT FROM AUTHOR]

Published
1996
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