| 1. |
- Dreiser, Jan, et al.
(författare)
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Direct observation of a ferri-to-ferromagnetic transition in a fluoride-bridged 3d-4f molecular cluster
- 2012
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Ingår i: Chemical Science. - : Royal Society of Chemistry (RSC). - 2041-6520. ; 3:4, s. 1024-1032
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Tidskriftsartikel (refereegranskat)abstract
- We report on the synthesis, crystal structure and magnetic characterisation of the trinuclear, fluoride-bridged, molecular nanomagnet [Dy(hfac)(3)(H2O)-CrF2(py)(4)-Dy(hfac)(3)(NO3)] (1) (hfacH = 1,1,1,5,5,5-hexafluoroacetylacetone, py = pyridine) and a closely related dinuclear species [Dy(hfac)(4)-CrF2( py)(4)]center dot 1/2 CHCl3 (2). Element-specific magnetisation curves obtained on 1 by X-ray magnetic circular dichroism (XMCD) allow us to directly observe the field-induced transition from a ferrimagnetic to a ferromagnetic arrangement of the Dy and Cr magnetic moments. By fitting a spin-Hamiltonian model to the XMCD data we extract a weak antiferromagnetic exchange coupling of j -0.18 cm(-1) between the Dy-III and Cr-III ions. The value found from XMCD is consistent with SQUID magnetometry and inelastic neutron scattering measurements. Furthermore, alternating current susceptibility and muon-spin relaxation measurements reveal that 1 shows thermally activated relaxation of magnetisation with a small effective barrier for magnetisation reversal of Delta(eff) 3 cm(-1). Density-functional theory calculations show that the Dy-Cr couplings originate from superexchange via the fluoride bridges.
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| 2. |
- Dreiser, Jan, et al.
(författare)
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Exchange Interaction of Strongly Anisotropic Tripodal Erbium Single-Ion Magnets with Metallic Surfaces
- 2014
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Ingår i: ACS Nano. - : American Chemical Society (ACS). - 1936-0851 .- 1936-086X. ; 8:5, s. 4662-4671
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Tidskriftsartikel (refereegranskat)abstract
- We present a comprehensive study of Er(trensal) single-ion magnets deposited in ultrahigh vacuum onto metallic surfaces. X-ray photoelectron spectroscopy reveals that the molecular structure is preserved after sublimation, and that the molecules are physisorbed on Au(111) while they are chemisorbed on a Ni thin film on 0(100) single-crystalline surfaces. X-ray magnetic circular dichroism (XMCD) measurements performed on Au(111) samples covered with molecular monolayers held at temperatures down to 4 K suggest that the easy axes of the strongly anisotropic molecules are randomly oriented. Furthermore XMCD indicates a weak antiferromagnetic exchange coupling between the single-ion magnets and the ferromagnetic Ni/Cu(100) substrate. For the latter case, spin-Hamiltonian fits to the XMCD M(H) suggest a significant structural distortion of the molecules. Scanning tunneling microscopy reveals that the molecules are mobile on Au(111) at room temperature, whereas they are more strongly attached on Ni/Cu(100). X-ray photoelectron spectroscopy results provide evidence for the chemical bonding between Er(trensal) molecules and the Ni substrate. Density functional theory calculations support these findings and, in addition, reveal the most stable adsorption configuration on Ni/Cu(100) as well as the Ni-Er exchange path. Our study suggests that the magnetic moment of Er(trensal) can be stabilized via suppression of quantum tunneling of magnetization by exchange coupling to the Ni surface atoms. Moreover, it opens up pathways toward optical addressing of surface-deposited single-ion magnets.
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| 3. |
- Svensson, Jannet, et al.
(författare)
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Few differences in cytokines between patients newly diagnosed with type 1 diabetes and their healthy siblings
- 2012
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Ingår i: Human Immunology. - : Elsevier BV. - 0198-8859. ; 73:11, s. 1116-1126
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Tidskriftsartikel (refereegranskat)abstract
- The cause of the worldwide increase in type 1 diabetes (T1D) is largely unknown. T cells are thought to play a role in disease progression. In contemporary research over the last decade, age- and gender-specific serum levels as well as changes of Th1 and Th2-related cytokines are not well described. From a population-based register of children diagnosed from 1997 to 2005 this study explores eight different cytokines at time of diagnosis. Only TGF-beta and IL-18 showed higher levels in patients compared to siblings in an adjusted model (p < 0.01): whereas the other seven cytokines were not significantly different. IL-1 beta, IL-18, IL-12, IL-10 and IL-4 were significantly higher among the youngest children and males had significantly lower levels of IL-10 and IL-12 but higher levels of TNF-alpha. During the nine-year study all of the cytokines increased except TGF-beta, which showed a slight decrease over time. The cytokine levels tended to be highest during summer and were most pronounced for IL-1 beta and TNF-alpha. In conclusion, serum levels of known beta-cell cytotoxic cytokines were indifferent in patients and siblings, while gender, age and season appear to exert some influence on the serum level and need to be explored further. The influence of time on systemic levels cannot be ignored and may reflect decay or environmental impact on the immune system. (C) 2012 American Society for Histocompatibility and Immunogenetics. Published by Elsevier Inc. All rights reserved.
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| 4. |
- Svensson, Jannet, et al.
(författare)
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High levels of immunoglobulin E and a continuous increase in immunoglobulin G and immunoglobulin M by age in children with newly diagnosed type 1 diabetes
- 2012
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Ingår i: Human Immunology. - : Elsevier BV. - 0198-8859. ; 73:1, s. 17-25
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Tidskriftsartikel (refereegranskat)abstract
- The incidence of type 1 diabetes (T1D) is increasing, either because of environmental factors accelerating onset of the disease or because of inducement of autoimmune diabetes in children who previously were at lower risk. High levels of immunoglobulin (Ig), specifically, IgM and IgA, and a low level of IgG were reported in adult patients; however no studies have analyzed the increasing incidence in relation to Ig levels. Our aim was to describe Ig in children newly diagnosed with diabetes and in their healthy siblings. Children with T1D expressed significantly lower IgG (p < 0.01) and higher IgA levels (p = 0.045), whereas no differences in IgE or IgM (p > 0.5) levels were found. Age-specific levels were unchanged over a 9-year period. In patients and siblings IgG. IgA and IgE increased by age (p < 0.001); which was in contrast to IgM (p > 0.05). The continued increase in IgG levels by age indicates that adult levels are reached later than in previously studied cohorts, thereby indicating a slower maturation of the immune system. (C) 2012 American Society for Histocompatibility and Immunogenetics. Published by Elsevier Inc. All rights reserved.
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