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- Diaz-Mendez, Rogelio, et al.
(författare)
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Scaling of the magnetic permeability at the Berezinskii–Kosterlitz–Thouless transition from Coulomb gas simulations
- 2018
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Ingår i: Journal of Statistical Mechanics. - : IOP Publishing. - 1742-5468 .- 1742-5468. ; 2018:12
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Tidskriftsartikel (refereegranskat)abstract
- A new approach to the Berezinskii–Kosterlitz–Thouless transition in the two-dimensional Coulomb gas model is explored by Monte Carlo simulation and finite size scaling. The usual mapping of a neutral two-dimensional superconductor in zero magnetic field to a Coulomb gas leads to an unscreened logarithmic interaction between the vortices, and with periodic boundary conditions vortex configurations are always vorticity neutral with an equal number of plus and minus vortices. We demonstrate that relaxing the neutrality condition has certain advantages. It leads to non-neutral vortex configurations that can appear in real systems with open boundary conditions and permits calculation of the compressibility, which for thin film superconductors corresponds to the magnetic permeability. The vortex-number fluctuation has remarkable scaling properties at and below the Berezinskii–Kosterlitz–Thouless transition. The fugacity variable becomes dangerously irrelevant in the low-temperature phase and leads to a multiplicative scaling correction to the mean-square vortex-number fluctuation and to the magnetic permeability. This multiplicative correction strongly affects the scaling properties of the vorticity fluctuation at and below the transition. Consequences of these findings are demonstrated using Monte Carlo simulations. Inclusion of the next-higher order correction to scaling is found to play an important role in the analysis of numerical data for the vortex number fluctuation and permits accurate determination of the critical properties.
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- Fischer, Klara, et al.
(författare)
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Social Impacts of GM Crops in Agriculture : A Systematic Literature Review
- 2015
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Ingår i: Sustainability. - : MDPI AG. - 2071-1050. ; 7:7, s. 8598-8620
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Forskningsöversikt (refereegranskat)abstract
- It has recently been argued that the fragmented knowledge on the social impacts of genetically modified (GM) crops is contributing to the polarised debate on the matter. This paper addresses this issue by systematically reviewing 99 peer-reviewed journal articles published since 2004 on the social impacts of GM crops in agriculture; summarising current knowledge, and identifying research gaps. Economic impact studies currently dominate the literature and mainly report that GM crops provide economic benefits for farmers. Other social impacts are less well studied, but present a more complex picture. Studies on access to and benefits of GM crops show that these vary significantly depending on the political and regulatory setting. Substantial evidence indicates that intellectual property rights (IPR) and the private industry's dominance limit the access and utility of available GM crops to many farmers. Wellbeing is frequently discussed in the literature, but rarely investigated empirically. Existing evidence is contradictory and inconclusive. Impact studies from the Global North are virtually non-existent. Moreover, two-thirds of publications are based on previously published empirical evidence, indicating a need for new empirical investigations into the social impacts of GM crops in agriculture.
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- Fischer, Klara, et al.
(författare)
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Social Science Studies on European and African Agriculture Compared: Bringing Together Different Strands of Academic Debate on GM Crops
- 2016
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Ingår i: Sustainability. - : MDPI AG. - 2071-1050. ; 8
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Forskningsöversikt (refereegranskat)abstract
- This study explored the social science-orientated literature on genetically modified (GM) crops in Europe and compared it with the corresponding literature on GM crops in African contexts, in order to determine the nature and extent of north-south cross-fertilisation in the literature. A total of 1625 papers on GM crops and agriculture falling within the social science and humanities' subject area in the Scopus abstract and citation database of peer-reviewed literature were analysed for major trends relating to geographical areas. More detailed analysis was performed on papers discussing African (56 papers) and European (127 papers) contexts. The analysis revealed that studies on policy and politics were common in both strands of the literature, frequently focusing on effects of the relatively restrictive European Union regulations on GM crops. There were also clear differences, however. For example, papers focusing on Africa frequently examined farm-level impacts and production, while this theme was almost non-existent in the Europe literature. It focused instead on policy impacts on trade and consumer attitudes to GM products. The lack of farm-level studies and of empirical studies in general in the European literature indicates a need for empirical research on GM crops in European farming. Social science research on GM crop production in Europe could draw lessons from the African literature.
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| 6. |
- Harrison, G, et al.
(författare)
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Association between psychotic disorder and urban place of birth is not mediated by obstetric complications or childhood socio-economic position: a cohort study
- 2003
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Ingår i: Psychological medicine. - : Cambridge University Press (CUP). - 0033-2917 .- 1469-8978. ; 33:4, s. 723-731
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Tidskriftsartikel (refereegranskat)abstract
- Background. Although urban place of birth has been identified as a risk factor for schizophrenia, the extent to which this association is mediated by socially patterned risk factors such as obstetric complications and childhood socio-economic position is unclear. The diagnostic specificity of the association within the clinical psychotic syndromes is also unclear.Method. A population cohort of 696025 males and females, born in Sweden between 1973 and 1980 and with linked birth and socio-economic data was followed up from age 16 for up to 9·8 years. Hospitalized cases of schizophrenia and other non-affective psychosis were identified from the Swedish Inpatient Discharge Register. We examined associations of these disorders with a three-level measure of urbanicity of birthplace before and after controlling for measures of foetal nutrition, obstetric complications and level of maternal education.Results. Urban compared to rural birthplace was associated both with increased risk of adult onset schizophrenia (hazard ratio 1·34, CI 0·91–1·96) and other non-affective psychoses (hazard ratio 1·63, CI 1·18–2·26). None of these associations was greatly affected by adjustment for obstetric complications or maternal educational level. In the group of other non-affective psychoses urban–rural differences in disease risk were strongest among those born in the winter months.Conclusion. Urbanization of birthplace is associated with increased risk of non-affective psychosis but this is not confined to narrowly defined cases. The magnitude of the association in Sweden is lower than that reported in other studies. Causal factors underlying this association appear to operate independently of risks associated with obstetric complications and parental educational status.
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- Huldtgren, Therese, et al.
(författare)
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Subcellular structures in Ediacaran fossil cleavage embryos
- 2008
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Ingår i: The Palaeontological Association.
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Konferensbidrag (refereegranskat)abstract
- The Ediacaran Doushantuo phosphoritic deposits in southern China hold exquisitely preserved microfossils, and a large number of papers on this biota have been published. The controversial cleavage embryos, preserved as diagenetically phosphatized replacements and encrustations, have been proposed to belong to animals, but no co-occurring adult forms have yet been identified. Recent studies, in which fossil embryos were analysed with synchrotron-radiation X-ray tomographic microscopy (srXTM), have shown that with this technique it is possible not only to distinguish between taphonomic and diagenetic features, but also to depict cellular and subcellular details of the internal structures. In this study, we describe some of the diversity of internal morphological features found in early-stage cleavage embryos by use of srXTM. A few exceptionally preserved 4-cell stage specimens exhibit subcellular structures indicative of eukaryotic affinity, such as complex nucleus-like structures, which are centrally located in each cell. One of these displays a spiral structure on the surface of each blastomere, suggesting affinity with Spiralicellula Xue et al. 1995. Other specimens display spheroidal and ovoidal structures interpreted as lipid vesicles or yolk granules. In 2007, Bailey et al. (Nature 445) published an alternative interpretation, in which they propose that the alleged cleavage fossils represent giant sulphur-oxidizing bacteria. However, recent decay studies of modern animal embryos in combination with the likely eukaryotic subcellular features described here supports the interpretation that these Ediacaran fossils from the Doushantuo Formation are in fact of embryonic nature.
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- Rinaldi, S, et al.
(författare)
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Physical activity, sex steroid, and growth factor concentrations in pre- and post-menopausal women : a cross-sectional study within the EPIC cohort
- 2014
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Ingår i: Cancer Causes and Control. - : Springer Science and Business Media LLC. - 0957-5243 .- 1573-7225. ; 25:1, s. 111-124
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Tidskriftsartikel (refereegranskat)abstract
- Increased physical activity (PA) is associated with a reduced risk of several cancers. PA may reduce cancer risk by changing endogenous hormones levels, but relatively little research has focused on this topic. The purpose of this study was to elucidate the relation between PA and endogenous hormone concentrations. A cross-sectional analysis of 798 pre- and 1,360 post-menopausal women included as controls in case-control studies on endogenous hormones (steroids, progesterone, sex-hormone-binding globulin (SHBG), and growth factors) levels, and cancer risk nested within European Prospective Investigation into Cancer and Nutrition cohort was performed. Multivariate regression analyses were performed to compare geometric mean levels of hormones and SHBG by categories of PA. In pre-menopausal women, active women had 19 % significantly lower concentrations of androstenedione, 14 % lower testosterone, and 20 % lower free testosterone than inactive women, while no differences were observed for estrogens, progesterone, SHBG, and growth factors. In post-menopausal women, active women had 18 % significantly lower estradiol and 20 % lower free estradiol concentrations than inactive women, while no differences were observed for the other hormones and SHBG. More vigorous forms of physical activity were associated with higher insulin-like growth factor-I concentrations. Adjustment for body mass index did not alter the associations. Overall, the percentage of variance in hormone concentrations explained by PA levels was < 2 %. Our results support the hypothesis of an influence, although small in magnitude, of PA on sex hormone levels in blood, independent of body size.
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| 10. |
- Ropo, M., et al.
(författare)
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Segregation at the PdAg(111) surface : Electronic structure calculations
- 2005
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Ingår i: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121 .- 1550-235X. ; 71:4
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Tidskriftsartikel (refereegranskat)abstract
- An efficient procedure to calculate surface segregation profiles of substitutionally disordered binary alloys is presented. We show that a simple thermodynamic model with realistic atomic configurations at the surface region combined with the total energies obtained from exact muffin-tin orbitals calculations leads to accurate surface segregation profiles. We find that the calculated surface segregation energies in random alloys show significant dependence on the local environment of the atoms involved in the segregation process. Correspondingly, the alloy surface energy is significantly affected by the subsurface atomic layers. As an example the PdAg(111) surface is considered.
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