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Sökning: WFRF:(Andersson Gabriella)

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1.
  • Andersson Chronholm, Jannika, 1972-, et al. (författare)
  • Förstaårsstudenters och lärares förhållningssätt till laborationer i fysik
  • 2014
  • Konferensbidrag (refereegranskat)abstract
    • Laborationer används som ett närmast självklart inslag på naturvetenskapliga utbildningar. Mål och syften med laborationer kan skifta mellan olika kurser och är inte alltid uppenbara för studenterna (Hart et al., 2000; Russell & Weaver, 2008). Ofta förväntas de lära sig hantering av utrustning, tolkning av data och rapportskrivning, samtidigt som de ska få bättre förståelse för teorin genom att seJohan Larsson undersökte 2012 hur hans studenter på tekniskt-naturvetenskapligt basår (högskoleförberedande) värderade olika undervisningsformer. Laborationer fick då sämst betyg. För att undersöka möjliga orsaker till detta tog vi initiativ till en fenomenografisk studie (Marton, 1981) av attityder till fysiklaborationer. Skriftliga enkätsvar samlades in från 38 förstaårsstudenter på kandidatprogrammet i fysik vid Uppsala universitet. Den öppna enkätfrågan inspirerades av en amerikansk studiebesvarades även av 18 anonyma lärare på Institutionen för fysik och astronomi. Både lärare och studenter har skrivit långa svar som vi kategoriserat fenomenografiskt, det vill säga vi har kartlagt förekomsten av attityder.Det finns tydliga nivåer av progression; från ett distanserat, ointresserat förhållningssätt till en nivå där man har en uppfattning om framtida behov. Studien visar inte på några större skillnader mellan lärarnas och studenternas syn. Laborationer förväntas koppla teori till praktik samt ge tillfälle att träna på instrumenthantering och vetenskapligt arbetssätt. Några nämner också att laborationer ökar deras förståelse och lärande, ger social träning och förbereder dem för ett kommande arbetsliv.Vår avsikt är att använda resultaten för att öka laborationernas upplevda värde, genom att uppmärksamma kollegor på de förekommande förhållningssätten och tillsammans förbereda oss för att bemöta dem. Frågor som vi vill diskutera är t.ex.: Vill vi att studenterna ska tycka så här?Hur speglar våra laborationsinstruktioner det vi vill att studenterna ska lära sig? Hur kommunicerar vi mål och syften med varje laboration på bästa sätt?Hart C., Mulhall, P., Berry, A., Loughran, J., & Gunstone, R. (2000). What is the purpose of this experiment? Or can students learn something from doing experiments? Journal of Research in Science Teaching, 37(7), 655-675. Marton, F. (1981). Phenomenography Describing conceptions of the world around us. Instructional Science, 10, 177-200.Russell, C. B., & Weaver, G. C. (2008). Student Perceptions of the Purpose and Function of the Laboratory in Science: A Grounded Theory Study. International Journal for the Scholarship of Teaching and Learning, 2(2), 1-14.
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2.
  • Andersson Chronholm, Jannika, 1972-, et al. (författare)
  • Förstaårsstudenters och lärares syn på laborationer i fysik
  • 2013
  • Konferensbidrag (refereegranskat)abstract
    • BakgrundDå institutionen för fysik och astronomi under 2013 identifierat laborationerna som ett problemområde har vi gjort en fenomenografisk studie som undersökte studenters och lärares syn på laborationer. Datainsamling och analysVi har samlat in skriftliga enkätsvar från 18 lärare och 38 förstaårsstudenter på kandidatprogrammet i fysik.Den öppna enkätfrågan var : - Varför har vissa kurser laborationer?Svaren visar på många olika uppfattningar och vi har kategoriserat dessa fenomenografiskt. ResultatVi ser tydliga nivåer av progression i svaren; från ett distanserat och ointresserat förhållningssätt, till en uppfattning om lärande och framtida yrkesliv.Studien visar att lärare och studenterna har mycket lika syn på laborationer.Uppfattningar som fördes fram var att kurser har laborationer för att : l   det är obligatorisktl   koppla teori till praktikl   öva instrumenthanteringl   träna vetenskapligt arbetssättl   öka förståelsen och lärandetl   ge social träningl   utgöra förberedelse för arbetsliv  ReferenserMarton, F. (1981) Phenomenography – Describing conceptions of the world around us. Instructional Science, 10, 177-200.Russell, C. B. and Weaver, G. C. (2008) Student Perceptions of the Purpose and Function of the Laboratory in Science: A Grounded Theory Study. International Journal for the Scholarship of Teaching and Learning 2(2).             
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  • Andersson, Gabriella, et al. (författare)
  • Aktiverande problemlösningsövningar i grupp.
  • 2010
  • Ingår i: Att undervisa med vetenskaplig förankring – i praktiken!. - Uppsala : Universitetstryckeriet. ; , s. 103-113
  • Bokkapitel (övrigt vetenskapligt/konstnärligt)
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  • Andersson, Lisa, et al. (författare)
  • Mutations in DMRT3 affect locomotion in horses and spinal circuit function in mice
  • 2012
  • Ingår i: Nature. - : Springer Science and Business Media LLC. - 0028-0836 .- 1476-4687. ; 488:7413, s. 642-646
  • Tidskriftsartikel (refereegranskat)abstract
    • Locomotion in mammals relies on a central pattern-generating circuitry of spinal interneurons established during development that coordinates limb movement(1). These networks produce left-right alternation of limbs as well as coordinated activation of flexor and extensor muscles(2). Here we show that a premature stop codon in the DMRT3 gene has a major effect on the pattern of locomotion in horses. The mutation is permissive for the ability to perform alternate gaits and has a favourable effect on harness racing performance. Examination of wild-type and Dmrt3-null mice demonstrates that Dmrt3 is expressed in the dI6 subdivision of spinal cord neurons, takes part in neuronal specification within this subdivision, and is critical for the normal development of a coordinated locomotor network controlling limb movements. Our discovery positions Dmrt3 in a pivotal role for configuring the spinal circuits controlling stride in vertebrates. The DMRT3 mutation has had a major effect on the diversification of the domestic horse, as the altered gait characteristics of a number of breeds apparently require this mutation.
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  • Fegraeus, K. Jaderkvist, et al. (författare)
  • Different DMRT3 Genotypes Are Best Adapted for Harness Racing and Riding in Finnhorses
  • 2015
  • Ingår i: Journal of Heredity. - : Oxford University Press (OUP). - 0022-1503 .- 1465-7333. ; 106:6, s. 734-740
  • Tidskriftsartikel (refereegranskat)abstract
    • Previous studies showed a positive effect of the DMRT3 "gait keeper" mutation on harness racing performance in Standardbreds, French-, and Nordic trotters. The mutation has also been shown to influence riding traits in multiple breeds. This study investigated the effect of the DMRT3 mutation on harness racing performance and riding traits in Finnhorses. Finnhorses used for harness racing (n = 180) and for riding (n = 59) were genotyped for the DMRT3 mutation. For the trotters the genotypes were evaluated for association with racing performance (number of starts, victories, placings, earnings, and race times). At 3-6 years of age the AA genotype was superior compared with the CA and CC genotypes. The AA horses had a significantly higher proportion of victories (P = 1.4 x 10(-6)) and placings (P = 4.1 x 10(-7)), better race times (P = 0.01), and earned more money (P = 0.009) compared with C-horses. For the Finnhorses used for riding the owners answered a questionnaire to score how well the horse performed the gaits walk, trot, and canter on a scale from 1 to 6. These scores were tested for association with the DMRT3 genotypes. Although AA horses were more successful as racehorses, the CC and CA horses appear more adapted for classical riding disciplines. The AA horses received significantly lower gait scores compared with C-horses for the majority of gaits. Except for rhythm in extended canter (P = 0.05), there were no significant differences between CA and CC horses. This study shows that there are different optimal genotypes for different disciplines and the DMRT3 mutation clearly influences gaits and performance in Finnhorses.
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  • Jäderkvist Fegraeus, Kim, et al. (författare)
  • Lack of significant associations with early career performance suggest no link between the DMRT3 "Gait Keeper" mutation and precocity in Coldblooded trotters
  • 2017
  • Ingår i: PLOS ONE. - : PUBLIC LIBRARY SCIENCE. - 1932-6203. ; 12:5
  • Tidskriftsartikel (refereegranskat)abstract
    • The Swedish-Norwegian Coldblooded trotter (CBT) is a local breed in Sweden and Norway mainly used for harness racing. Previous studies have shown that a mutation from cytosine (C) to adenine (A) in the doublesex and mab-3 related transcription factor 3 (DMRT3) gene has a major impact on harness racing performance of different breeds. An association of the DMRT3 mutation with early career performance has also been suggested. The aim of the current study was to investigate this proposed association in a randomly selected group of CBTs. 769 CBTs (485 raced, 284 unraced) were genotyped for the DMRT3 mutation. The association with racing performance was investigated for 13 performance traits and three different age intervals: 3 years, 3 to 6 years, and 7 to 10 years of age, using the statistical software R. Each performance trait was analyzed for association with DMRT3 using linear models. The results suggest no association of the DMRT3 mutation with precocity (i.e. performance at 3 years of age). Only two traits (race time and number of disqualifications) were significantly different between the genotypes, with AA horses having the fastest times and CC horses having the highest number of disqualifications at 3 years of age. The frequency of the AA genotype was significantly lower in the raced CBT sample compared with the unraced sample and less than 50% of the AA horses participated in a race. For the age intervals 3 to 6 and 7 to 10 years the AA horses also failed to demonstrate significantly better performance than the other genotypes. Although suggested as the most favorable genotype for racing performance in Standardbreds and Finnhorses across all ages, the AA genotype does not appear to be associated with superior performance, early or late, in the racing career of CBTs.
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  • Jäderkvist Fegraeus, Kim, et al. (författare)
  • The DMRT3 “Gait keeper” mutation affects harness racing performance and riding traits in Finnhorses
  • 2015
  • Ingår i: Journal of Equine Veterinary Science. - : Elsevier BV. - 0737-0806 .- 1542-7412. ; 35, s. 399-399
  • Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
    • The DMRT3 "Gait keeper" mutation is well known for its effects on gaits and locomotion patterns in horses. Previous studies have shown the mutation to have a strong favorable effect on harness racing performance in Standardbreds, French and Nordic trotters. The mutation also affects riding traits in Icelandic horses and in Standardbreds. The aim of this study was to investigate the effect of the DMRT3 mutation on harness racing performance and riding traits in Finnhorses. We genotyped for the DMRT3 mutation 180 Finnhorses of trotting type and 59 Finnhorses used for riding. For the trotters the genotypes were evaluated for association with racing performance traits (number of starts, victories, placings, earnings and race times) at different ages. For the Finnhorses used for riding the owners answered a 12 question survey about their horse and had to score how well the horse performed the gaits walk, trot and canter on a scale from 1 to 6. T€olt and pace ability was also reported. These scores were then tested for an association with the DMRT3 genotypes. Racing performance analyses were performed usingWald tests in PLINK. Fisher's exact tests in R were used for analyses on t€olt and pace ability, while pairwise t-tests were used for gait score analyses. The results showed that the DMRT3 mutation strongly influenced racing performance in Finnhorses. Between 3 and 6 years of age AA horses had a significantly higher proportion of victories (P ¼ 1.4 106) and placings (P ¼ 4.1 107) compared with C- horses. Additionally, they also had better race times (P ¼ 0.01) and earned more money (P ¼ 0.009). Despite CA horses not performing as well as AA horses, they still performed better than CC horses. Thus supporting an additive genetic effect of the DMRT3 mutation on racing performance. Similar results were found when comparing performance at different ages (4, 5, 6 and 10 years), except for 3 years of age where no significant differences were present. Although AA horses were more successful as racehorses, the C- horses appear more adapted for classical riding disciplines. This is supported by significantly lower gait scores for AA horses compared with C- horses for the majority of gaits. With the exception of rhythm in extended canter (P ¼ 0.05), no significant differences were present between CA and CC horses for gait scores. A significant association (P ¼ 0.006) between DMRT3 genotype and the ability to show t€olt was present; however, no significant association was present for pace (P ¼ 0.21). This study shows that different genotypes are optimal for different disciplines and the DMRT3 mutation clearly influences the pattern of locomotion in Finnhorses.
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  • Jäderkvist Fegraeus, Kim, et al. (författare)
  • The DMRT3 'Gait keeper' mutation affects performance of Nordic and Standardbred trotters
  • 2014
  • Ingår i: Journal of Animal Science. - : Oxford University Press (OUP). - 0021-8812 .- 1525-3163. ; 92:10, s. 4279-4286
  • Tidskriftsartikel (refereegranskat)abstract
    • In a previous study it was shown that a nonsense mutation in the DMRT3 gene alters the pattern of locomotion in horses and that this mutation has a strong positive impact on trotting performance of Standardbreds. One aim of this study was to test if racing performance and trotting technique in the Nordic (Coldblood) trotters are also influenced by the DMRT3 genotype. Another aim was to further investigate the effect of the mutation on performance in Standardbreds, by using a within-family analysis and genotype-phenotype correlations in a larger horse material than in the previous study. We genotyped 427 Nordic trotters and 621 Standardbreds for the DMRT3 nonsense mutation and a SNP in strong linkage disequilibrium with it. In Nordic trotters, we show that horses homozygous for the DMRT3 mutation (A) had significantly higher EBV for trotting performance traits than heterozygous (CA) or homozygous wild-type (CC) horses (P = 0.001). Furthermore, AA homozygotes had a higher proportion of victories and top 3 placings than horses heterozygous or homozygous wild-type, when analyzing performance data for the period 3 to 6 yr of age (P = 0.06 and P = 0.05, respectively). Another finding in the Nordic trotters was that the DMRT3 mutation influenced trotting technique (P = 2.1 x 10(-8)). Standardbred horses homozygous AA had significantly higher EBV for all traits than horses with at least 1 wild-type allele (CA and CC; P = 1.6 x 10(-16)). In a within-family analysis of Standardbreds, we found significant differences in several traits (e. g., earnings, P = 0.002; number of entered races, P = 0.004; and fraction of offspring that entered races, P = 0.002) among paternal half-sibs with genotype AA or CA sired by a CA stallion. For most traits, we found significant differences at young ages. For Nordic trotters, most of the results were significant at 3 yr of age but not for the older ages, and for the Standardbreds most of the results for the ages 3 to 5 were significant. For Nordic trotters, the proportion of victories and placings were the only traits that were significant for other ages than 3 yr.
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20.
  • Jäderkvist Fegraeus, Kim, et al. (författare)
  • The importance of the DMRT3 'Gait keeper' mutation on riding traits and gaits in Standardbred and Icelandic horses
  • 2015
  • Ingår i: Livestock Science. - : Elsevier BV. - 1871-1413 .- 1878-0490. ; 176, s. 33-39
  • Tidskriftsartikel (refereegranskat)abstract
    • Previous studies have shown that a single base-pair mutation, a change from cytosine (C) to adenine (A), in the DMRT3 gene affects both the ability to show ambling and lateral gaits in a wide range of horse breeds, as well as racing performance and trotting technique in Standardbred and Nordic trotters. The variant allele is present in gaited breeds but is absent, or found at a very low frequency, in breeds used for Western-European style riding and flat racing, like the Swedish Warmblood and Thoroughbreds as well as in draught horses. This indicates that the variant allele might have a negative effect on certain riding performance traits in horses. Therefore, one aim of this study was to investigate whether the DMRT3 variant affects canter in Standardbred trotters, and to test if heterozygous horses (CA) were better suited for Western-European style riding than homozygous horses (M). Riding traits were studied in 115 Standardbred horses, and a similar study was also performed with data from 55 Nordic trotters. The results showed that CA Standardbreds had significantly better balance in canter, both collected and extended canter, than M horses. The CA horses also got significantly higher scores for transitions in collected canter. For the rhythm we found no significant differences between the genotypes. In the Nordic trotters we were unable to establish any significant difference for canter ability. Another aim of this study was to investigate the effect of the variant allele on riding abilities and gaits in the Icelandic horse (n=446). Practically all horse breeds considered to be three-gaited have a CC genotype, in contrast Icelandic CC horses can show tolt We therefore tested whether the variant influenced how difficult it was to initiate tolt training for these horses. It was also investigated whether the variant affects which gaits Icelandic horses choose, both at liberty and during initial training. Icelandic CC horses were significantly more difficult to train to tolt compared to CA and AA horses. The M Icelandic horses showed the lateral gaits tolt and pace significantly more frequent, both at liberty and during initial training, than CA or CC horses. The majority of the Icelandic CC and CA horses chose trot at liberty and during initial training.
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  • Lindgren, Gabriella, et al. (författare)
  • Travtalang ligger i hästens gener
  • 2013
  • Ingår i: Travtränaren. ; , s. 1-6
  • Tidskriftsartikel (populärvet., debatt m.m.)abstract
    • I denna artikel, som är nummer ett i en serie om två, fokuserar vi på resultaten från varm- och kallblodstravare. Vi resonerar kring när och för vem ett DNA-test är till mest nytta samt beskriver hur man praktiskt går tillväga. I artikel nummer två kommer vi berätta om hur forskningen gick till, vad genen gör i hästens kropp och resultatet från andra raser. Vi kommer även gå djupare in på vad DNA är och vad vi troligen kan förvänta oss av DNA-teknik i framtiden.
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26.
  • Nilsson, Gabriella, et al. (författare)
  • Narrating the moral geography of rape in Swedish newspapers
  • 2019
  • Ingår i: Rape Narratives in Motion. - Cham : Springer International Publishing. - 9783030138516 - 9783030138523 ; , s. 119-146
  • Bokkapitel (refereegranskat)abstract
    • In the master narrative of rape some women’s testimonies of sexual violence become particularly tainted with doubt and disbelief. Conversely, only some men’s sexually violent acts are unconditionally marked by guilt and blame. The chapter stresses the spatial dimension of this master narrative of rape. With an analysis of two hyper-medialised Swedish gang rape cases, it is highlighted how a moral geography is evoked in news narratives of rape. More specifically, it is argued that location, and narratives of women and men crossing boundaries, walking in line, being in place or invading space are used as proxy for the socio-spatial dimensions of power and morality.
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  • Promerová, Marta, et al. (författare)
  • Worldwide frequency distribution of the 'Gait keeper' mutation in the DMRT3 gene
  • 2014
  • Ingår i: Animal Genetics. - : Wiley. - 0268-9146 .- 1365-2052. ; 45:2, s. 274-282
  • Tidskriftsartikel (refereegranskat)abstract
    • For centuries, domestic horses have represented an important means of transport and served as working and companion animals. Although their role in transportation is less important today, many horse breeds are still subject to intense selection based on their pattern of locomotion. A striking example of such a selected trait is the ability of a horse to perform additional gaits other than the common walk, trot and gallop. Those could be four-beat ambling gaits, which are particularly smooth and comfortable for the rider, or pace, used mainly in racing. Gaited horse breeds occur around the globe, suggesting that gaitedness is an old trait, selected for in many breeds. A recent study discovered that a nonsense mutation in DMRT3 has a major impact on gaitedness in horses and is present at a high frequency in gaited breeds and in horses bred for harness racing. Here, we report a study of the worldwide distribution of this mutation. We genotyped 4396 horses representing 141 horse breeds for the DMRT3 stop mutation. More than half (2749) of these horses also were genotyped for a SNP situated 32kb upstream of the DMRT3 nonsense mutation because these two SNPs are in very strong linkage disequilibrium. We show that the DMRT3 mutation is present in 68 of the 141 genotyped horse breeds at a frequency ranging from 1% to 100%. We also show that the mutation is not limited to a geographical area, but is found worldwide. The breeds with a high frequency of the stop mutation (>50%) are either classified as gaited or bred for harness racing.
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  • Rafati, Nima, et al. (författare)
  • Large Deletions at the SHOX Locus in the Pseudoautosomal Region Are Associated with Skeletal Atavism in Shetland Ponies
  • 2016
  • Ingår i: G3. - : Oxford University Press (OUP). - 2160-1836. ; 6:7, s. 2213-2223
  • Tidskriftsartikel (refereegranskat)abstract
    • Skeletal atavism in Shetland ponies is a heritable disorder characterized by abnormal growth of the ulna and fibula that extend the carpal and tarsal joints, respectively. This causes abnormal skeletal structure and impaired movements, and affected foals are usually killed. In order to identify the causal mutation we subjected six confirmed Swedish cases and a DNA pool consisting of 21 control individuals to whole genome resequencing. We screened for polymorphisms where the cases and the control pool were fixed for opposite alleles and observed this signature for only 25 SNPs, most of which were scattered on genome assembly unassigned scaffolds. Read depth analysis at these loci revealed homozygosity or compound heterozygosity for two partially overlapping large deletions in the pseudoautosomal region (PAR) of chromosome X/Y in cases but not in the control pool. One of these deletions removes the entire coding region of the SHOX gene and both deletions remove parts of the CRLF2 gene located downstream of SHOX. The horse reference assembly of the PAR is highly fragmented, and in order to characterize this region we sequenced bacterial artificial chromosome (BAC) clones by single-molecule real-time (SMRT) sequencing technology. This considerably improved the assembly and enabled size estimations of the two deletions to 1602180 kb and 60280 kb, respectively. Complete association between the presence of these deletions and disease status was verified in eight other affected horses. The result of the present study is consistent with previous studies in humans showing crucial importance of SHOX for normal skeletal development.
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  • Velie, Brandon, et al. (författare)
  • Horses: an underutilized animal model
  • 2015
  • Konferensbidrag (refereegranskat)abstract
    • Horses provide an opportunity to study unique phenotypes that can lead to fundamental biological insights as well as help to decipher mechanisms underlying biological and disease processes. At present, we have three horse projects with preliminary results that may serve as models for investigating gene functions in mammals.A GWAS of equine insect bite hypersensitivity (IBH), an allergic recurrent seasonal dermatitis classed as a type I and type IV hypersensitive reaction, suggests the importance of two genomic regions on Chromosome 8 (ECA8). An increased knowledge of the genes involved in the manifestation of IBH is expected to not only improve prevention, diagnosis, and treatment of equine IBH, but may also broaden our understanding of the biology underlying type I and type IV hypersensitive reactions across species.Observed in a wide range of species including humans, a second project concerns polydactyly, a genetic defect that presents as an increased number of digits. Preliminary analyses of a family of ponies suggest a recessive mode of inheritance in horses. Through whole-genome re-sequencing of this family (n=5) we aimed to confirm this mode of inheritance and identify the causative locus.Additionally, Delta F STanalyses of harness racing breeds have identified specific candidate regions that harbor genes selected for athletic performance. These regions contain genes known to be involved in energy metabolism and cell growth. Genes that regulate energy metabolism and other biological processes that impact racing performance have the potential to improve our understanding of metabolic defects and diseases in horses as well as in other species.At the meeting we will present results from the three aforementioned studies and comment on the fact that in some circumstances the horse may provide unique knowledge of biological pathways that may not otherwise be fully understood.
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  • Ahlberg, Martina, 1980- (författare)
  • Critical Phenomena and Exchange Coupling in Magnetic Heterostructures
  • 2012
  • Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
    • The continuous phase transition in thin magnetic films and superlattices has been studied using the magneto-optical Kerr effect (MOKE) and polarized neutron scattering (PNR).  It has been shown that the critical behavior of amorphous thin films belonging to the 2D XY universality class can be described within the same theory as crystalline sample. This means that quenched disorder only serves as a marginal perturbation in systems with this symmetry. The connection between interlayer exchange coupling and the observed critical behavior in Fe/V superlattices was explored. The results prove that the origin of unusually high values of the exponent β can be traced to a position dependence of the magnetization at elevated temperatures. The magnetization of the outermost layers within the superlattice shows a more pronounced decrease at lower temperatures, compared to the inner layers, which in turn have a more abrupt decrease in the vicinity of the critical temperature. This translates to a high exponent, especially when the layers are probed by a technique where more weight is given to the layers close to the surface, e.g.MOKE.  The interlayer exchange coupling as a function of spacer thickness and temperature was also studied in its own right. The data was compared to the literature, and a dependence on the thickness of the magnetic layers was concluded. The phase transition in amorphous FeZr/CoZr multilayers, where the magnetization emanates from ferromagnetic proximity effects, was investigated. Even though the determined exponents of the zero-field magnetization, the susceptibility and the critical isotherm did not correspond to any universality class, scaling plots displayed an excellent data collapse. Samples consisting of Fe δ-layers (0.3-1.4 monolayers) embedded in Pd were studied using element-specific resonant x-ray magnetic scattering. The magnetization of the two constituents showed distinctly different temperature dependences.
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  • Ahlberg, Martina, et al. (författare)
  • Effect of ferromagnetic proximity on critical behavior
  • 2012
  • Ingår i: Physical Review B Condensed Matter. - 0163-1829 .- 1095-3795. ; 85:22, s. 224425-1-224425-6
  • Tidskriftsartikel (refereegranskat)abstract
    • We have investigated the magnetic phase transition in amorphous Fe93Zr7(x angstrom)/Co95Zr5(1 angstrom) multilayers, where x = 25, 50, and 75. The extremely thin CoZr layer induces magnetic order at temperatures well above the inherent ordering temperature of Fe93Zr7. The changes in the critical exponent beta, associated with the temperature dependence of the magnetization, imply a crossover from two-to three-dimensional behavior as the FeZr thickness is reduced, consistent with a substantial magnetic induction in the FeZr layers. In addition we determined the exponents delta and gamma, of the critical isotherm and the susceptibility, respectively, and their values confirm the nonuniversal character of the phase transition. Scaling of the results yields an excellent data collapse and is found to hold in the crossover regime where the universality hypothesis is not applicable. 
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  • Ahlberg, Martina, et al. (författare)
  • Influence of boundaries on magnetic ordering in Fe/V superlattices
  • 2010
  • Ingår i: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121 .- 1550-235X. ; 81:21, s. 214429-
  • Tidskriftsartikel (refereegranskat)abstract
    • We study the role of surface boundaries on the magnetic properties of [Fe/V](n) superlattice structures, with n=2-10. Using the magneto-optical Kerr effect and polarized neutron reflectivity measurements, we examine the evolution of both the total and the layer-resolved magnetizations as a function of temperature. By varying n, we observe a large shift in the transition temperatures T-c and a substantial change in the total magnetization critical exponent beta. In particular, the thicker samples exhibit nonuniversal exponent values. By resolving the magnetization as a function of position within the superlattice, we show that this behavior arises from contributions of the surfaces. Furthermore, we attribute the large shift in T-c to long-ranged interactions present in the superlattice.
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  • Ahlberg, Martina, et al. (författare)
  • Two-dimensional XY-like amorphous Co68Fe24Zr8/Al70Zr30 multilayers
  • 2011
  • Ingår i: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121 .- 1550-235X. ; 83:22, s. 224404-
  • Tidskriftsartikel (refereegranskat)abstract
    • We present an experimental realization of a magnetic two-dimensional XY system using amorphous materials. The classification of the dimensionality is based on the critical behavior of amorphous Co68Fe24Zr8(d)/Al70O30 (20 angstrom) multilayers, where d = 11 - 16 angstrom. Analysis of the remanent magnetization, the magnetic isotherms, the initial susceptibility, and the magnetic correlation length shows that the magnetic phase transition can be described by the 2D XY model. The samples are not paramagnetic above the critical temperature but are characterized by local magnetic order manifested in the field and temperature dependence of the magnetization. Furthermore, an average spin-spin interaction length of 8.1 angstrom was estimated using the thickness dependence of the Curie temperature.
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34.
  • Akansel, Serkan, et al. (författare)
  • Effect of seed layers on dynamic and static magnetic properties of Fe65Co35 thin films
  • 2018
  • Ingår i: Journal of Physics D. - : IOP Publishing. - 0022-3727 .- 1361-6463. ; 51:30
  • Tidskriftsartikel (refereegranskat)abstract
    • Fe65Co35 thin films have been deposited on SiO2 substrates using sputtering technique with different choices of seed layer; Ru, Ni82.5Fe17.5, Rh, Y and Zr. Best soft magnetic properties were observed with seed layers of Ru, Ni82.5Fe17.5 and Rh. Adding these seed layers, the coercivity of the Fe65Co35 films decreased to values of around 1.5 mT, which can be compared to the value of 12.5 mT obtained for films deposited without seed layer. Further investigations were performed on samples with these three seed layers in terms of dynamic magnetic properties, both on as prepared and annealed samples, using constant frequency cavity and broadband ferromagnetic resonance measurements. Damping parameters of around 8.0X10-3 and 4.5X10-3 were obtained from in-plane and out-of-plane measurements, respectively, for as prepared samples, values that were reduced to 6.5X10-3 and 4.0X10-3 for annealed samples.
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35.
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36.
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37.
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38.
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39.
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40.
  • Andersson, Gabriella, et al. (författare)
  • Anisotropy Tuning in Tetragonal FeCo Alloys
  • 2010
  • Ingår i: Journal of Nanoscience and Nanotechnology. - : American Scientific Publishers. - 1533-4880 .- 1533-4899. ; 10:9, s. 6186-6189
  • Tidskriftsartikel (refereegranskat)abstract
    • We review our previous work on magnetocrystalline anisotropy tuning of superlattices based on tetragonally distorted FeCo-alloys. In addition we present new experimental results on the effect of changing the composition of the FeCo alloy. The discussion is based on the separation of the magnetocrystalline anisotropy into contributions from the interfaces and strain, as well as from the composition.
  •  
41.
  • Andersson, Gabriella, et al. (författare)
  • Effects of strain on magnetic anisotropy in Fe and Co based heterostructures
  • 2008
  • Ingår i: Phase Transitions. - : Informa UK Limited. - 0141-1594 .- 1029-0338. ; 81:7 & 8, s. 679-701
  • Tidskriftsartikel (refereegranskat)abstract
    • The magnetic ordering in transition metals is strongly affected by any strain in the lattice, due to the close connection between strain and anisotropy. This article reviews recent developments, both experimental and theoretical, in the field of strain-induced magnetic anisotropies, with focus on films and multilayers based on Fe and Co. It is demonstrated that the reorientation of preferred magnetization directions can be controlled through both the growth direction and the strain state, which is caused by interleaving with suitable spacers, as well as by tuning the chemical composition if the magnetic material is an alloy. Both in-plane and out-of-plane easy directions can be forced upon the films and superlattices in this manner. Some methods for local structural manipulation are also reviewed.
  •  
42.
  • Andersson, Gabriella (författare)
  • Hydrogen in ultrathin vanadium layers
  • 1999
  • Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
    • The influence of elastic boundary conditions on the thermodynamics of hydrogen in vanadium were investigated using resistometry, x-ray diffraction and nuclear reaction analysis. To provide varying lattice strain states Mo/V (110) and Fe/V (001) superlattices with thickness L of individual layers in the range 3-16 monolayers (ML) were used. In addition the thickness ratio LFe/LV in the latter samples was varied. The results were compared with earlier work on Mo/V (001) superlattices.In the Mo/V (110) superlattices the H-H interaction was found to be repulsive in contrast to the (001) oriented samples and bulk V. This was also the case for Fe/V (001). For the thickness ratios LFe/LV = 3/10 and 3/16 it was found that the hydrogen-depleted interface region in V was populated at lower average concentration than in the symmetric samples (LFeLV = 1). This was related to the decreased Fe thickness.For Fe(3ML)/V(12-15 ML) samples the effects of hydrogenation on the magnetic exchange coupling between the Fe layers were investigated using neutron reflectometry. For 12 and 14 ML of V the coupling was switched continuously from antiferromagnetic (AFM) to ferromagnetic (FM) upon introduction of small amounts of hydrogen, whereas the initially FM-coupled 15-ML sampleexhibited an antiferromagnetic "resonance" at H/V ≈ 0.02. This was found to be due to changes in the vanadium Fermi surface. An intermediate state of noncollinear coupling was also observed in the 14-ML sample.
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43.
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44.
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45.
  • Andersson, Gabriella, et al. (författare)
  • Influence of compressive biaxial strain on the hydrogen uptake of ultra-thin, single crystal vanadium layers
  • 1997
  • Ingår i: Physical Review B. - 0163-1829. ; 55:3, s. 1774-1781
  • Tidskriftsartikel (refereegranskat)abstract
    • We have investigated the influence of biaxial compressive strain on the thermodynamic propertied of hydrogen in thin, single-crystal vanadium layers (0.9, 1.6, and 2.0 nm). At H/V<0.1 (atomic ratio), the host-mediated H-H interaction was found to be attractive. For H/V>0.1, the interaction was found to be extremely weak in the 0.9-nm-thick layer and repulsive in the 1.6- and 2.0-nm-thick V layers. The repulsive interaction was found to increase with increasing layer thicknesses. These results are unexpected as the interaction is attractive in both bulk V and in thin vanadium layers under biaxial tensile strain for HV<0.5. Both the strained and unstrained vanadium lattices are found to have roughly the same hydrogen affinity at H/V=0.1 (0.3 eV/H). No ordered bulklike beta phase was observed at any concentration (0
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46.
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47.
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48.
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49.
  • Andersson, Gabriella, et al. (författare)
  • Kvinnor i fysik
  • 2004
  • Ingår i: KOSMOS.
  • Tidskriftsartikel (populärvet., debatt m.m.)
  •  
50.
  • Andersson, Gabriella, et al. (författare)
  • Perpendicular magnetocrystalline anisotropy in tetragonally distorted Fe-Co alloys
  • 2006
  • Ingår i: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 96:3
  • Tidskriftsartikel (refereegranskat)abstract
    • We report on the experimental realization of tetragonal Fe-Co alloys as a constituent of Fe(0.36)Co(0.64)/Pt superlattices with huge perpendicular magnetocrystalline anisotropy energy, reaching 210 mu eV/atom, and a saturation magnetization of 2.5 mu(B)/atom at 40 K, in qualitative agreement with theoretical predictions. At room temperature the corresponding values 150 mu eV/atom and 2.2 mu(B)/atom are achieved. This suggests that Fe-Co alloys with carefully chosen combinations of composition and distortion are good candidates for high-density perpendicular storage materials.
  •  
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