31 research outputs found

    The Analysis of the Guidance and Psychological Counselling Needs of Older People in Terms of Several Variables

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    AbstractThis study examines the guidance and psychological needs of older people in terms of two variables: current employment status of older people and the place where they have spent most of their lives. The sample group of the study consists of 667 randomly selected independent older people who resided in the city centres of Amasya, Samsun and Sanlıurfa between 2009 and 2010. The study shows that there is a significant difference between current employment status of older people, the type of place where they have spent most of their lives, and the guidance and psychological counselling needs of them

    Disorder, critical currents, and vortex pinning energies in isovalently substituted BaFe2_{2}(As1−x_{1-x}Px_{x})2_{2}

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    We present a comprehensive overview of vortex pinning in single crystals of the isovalently substituted iron-based superconductor BaFe2_{2}(As1−x_{1-x}Px_{x})2_{2}, a material that qualifies as an archetypical clean superconductor, containing only sparse strong point-like pins [in the sense of C.J. van der Beek {\em et al.}, Phys. Rev. B {\bf 66}, 024523 (2002)]. Widely varying critical current values for nominally similar compositions show that flux pinning is of extrinsic origin. Vortex configurations, imaged using the Bitter decoration method, show less density fluctuations than those previously observed in charge-doped Ba(Fe1−x_{1-x}Cox_{x})2_{2}As2_{2} single crystals. Analysis reveals that the pinning force and -energy distributions depend on the P-content xx. However, they are always much narrower than in Ba(Fe1−x_{1-x}Cox_{x})2_{2}As2_{2}, a result that is attributed to the weaker temperature dependence of the superfluid density on approaching TcT_{c} in BaFe2_{2}(As1−x_{1-x}Px_{x})2_{2}. Critical current density measurements and pinning force distributions independently yield a mean distance between effective pinning centers Lˉ∼90\bar{\mathcal L} \sim 90 nm, increasing with increasing P-content xx. This evolution can be understood as being the consequence of the P-dependence of the London penetration depth. Further salient features are a wide vortex free "Meissner belt", observed at the edge of overdoped crystals, and characteristic chain-like vortex arrangements, observed at all levels of P-substitution.Comment: 11 page

    Strong pinning and vortex energy distributions in single-crystalline Ba(Fe1−xCox)2As2

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    International audienceThe interrelation between heterogeneity and flux pinning is studied in Ba(Fe1−xCox)2As2 single crystals with widely varying Co content x. Magnetic Bitter decoration of the superconducting vortex ensemble in crystals with x=0.075 and x=0.1 reveals highly disordered vortex structures. The width of the Meissner belt observed at the edges of the crystals, and above the surface steps formed by cleaving, as well as the width of the intervortex distance distribution, indicate that the observed vortex ensemble is established at a temperature just below the critical temperature Tc. The vortex interaction energy and pinning force distributions extracted from the images strongly suggest that the vortex lattice disorder is attributable to strong pinning due to spatial fluctuations of Tc and of the superfluid density. Correlating the results with the critical current density yields a typical length scale of the relevant disorder of 40-60 nm

    Phase diagram of Eu magnetic ordering in Sn-flux-grown Eu(Fe1−x_{1-x}Cox_{x})2_{2}As2_{2} single crystals

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    The magnetic ground state of the Eu2+^{2+} moments in a series of Eu(Fe1−x_{1-x}Cox_{x})2_{2}As2_{2} single crystals grown from the Sn flux has been investigated in detail by neutron diffraction measurements. Combined with the results from the macroscopic properties (resistivity, magnetic susceptibility and specific heat) measurements, a phase diagram describing how the Eu magnetic order evolves with Co doping in Eu(Fe1−x_{1-x}Cox_{x})2_{2}As2_{2} is established. The ground-state magnetic structure of the Eu2+^{2+} spins is found to develop from the A-type antiferromagnetic (AFM) order in the parent compound, via the A-type canted AFM structure with some net ferromagnetic (FM) moment component along the crystallographic c\mathit{c} direction at intermediate Co doping levels, finally to the pure FM order at relatively high Co doping levels. The ordering temperature of Eu declines linearly at first, reaches the minimum value of 16.5(2) K around x\mathit{x} = 0.100(4), and then reverses upwards with further Co doping. The doping-induced modification of the indirect Ruderman-Kittel-Kasuya-Yosida (RKKY) interaction between the Eu2+^{2+} moments, which is mediated by the conduction d\mathit{d} electrons on the (Fe,Co)As layers, as well as the change of the strength of the direct interaction between the Eu2+^{2+} and Fe2+^{2+} moments, might be responsible for the change of the magnetic ground state and the ordering temperature of the Eu sublattice. In addition, for Eu(Fe1−x_{1-x}Cox_{x})2_{2}As2_{2} single crystals with 0.10 ⩽\leqslant x\mathit{x} ⩽\leqslant 0.18, strong ferromagnetism from the Eu sublattice is well developed in the superconducting state, where a spontaneous vortex state is expected to account for the compromise between the two competing phenomena.Comment: 10 pages, 9 figure

    Vortex pinning : a probe for nanoscale disorder in iron-based superconductors

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    4 pagesInternational audienceThe pinning of quantized flux lines, or vortices, in the mixed state is used to quantify the effect of impurities in iron-based superconductors (IBS). Disorder at two length scales is relevant in these materials. Strong flux pinning resulting from nm-scale heterogeneity of the superconducting properties leads to the very disordered vortex ensembles observed in the IBS, and to the pronounced maximum in the critical current density jc at low magnetic fields. Disorder at the atomic scale, most likely induced by the dopant atoms, leads to "weak collective pinning" and a magnetic field-independent contribution jcoll. The latter allows one to estimate quasi-particle scattering rates

    Electron irradiation of Co, Ni, and P-doped BaFe2As2 - type iron-based superconductors

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    17 pages, soumis pour publications dans les actes de M2S-2012International audienceHigh energy electron irradiation is used to controllably introduce atomic-scale point defects into single crystalline Ba(Fe_1-xCo_x)_2As_2, Ba(Fe_1-xNi_x)_2As_2, and BaFe_2(As_1-xP_x)_2. The appearance of the collective pinning contribution to the critical current density in BaFe_2(As_1-xP_x)_2, and the magnitude of its enhancement in Ba(Fe_1-xCo_x)_2As_2, conform with the hypothesis of quasi-particle scattering by Fe vacancies created by the irradiation. Whereas the insignificant modification of the temperature dependence of the superfluid density in Ba(Fe_1-xCo_x)_2As_2 and Ba(Fe_1-xNi_x)_2As_2 points to important native disorder present before the irradiation, the critical temperatures of these materials undergo a suppression equivalent to that observed in the much cleaner BaFe_2(As_1-xP_x)_2. This lends credence to the hypothesis of line nodes of the order parameter (at finite k_{z}) in the former two materials

    Attitudes of Mathematics Teachers in Turkish Lower Secondary Schools Towards the Inclusion of Children with Special Educational Needs in Those Schools

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    Inclusive education is an educational practice based on the premise of equality that advocates for equal access to educational opportunities for all children, regardless of their special educational needs and disabilities. Teachers have a major responsibility in terms of inclusive education practices, and their attitudes and knowledge are key factors in the successful practice of inclusive education. The current study investigated the attitudes of mathematics teachers in Turkish lower secondary schools towards the inclusion of children with special educational needs in those schools. A mixed-methods approach was adopted in the current study. Eighteen interviews and 262 questionnaires were conducted with mathematics teachers working in Turkish lower secondary schools. The findings of the current study showed that mathematics teachers have a negative attitudes towards inclusion of students with special educational needs. To provide a deeper investigation of this negative attitude, factors affecting teacher attitudes were also investigated. Training and experience, age, years of teaching experience, educational environment-related and child-related factors all had an effect on mathematics teachers’ attitudes towards inclusion, while gender and having a friend with SEN had no influence on their attitudes. For example, younger mathematics teachers had more positive attitudes towards inclusion of children with special educational needs than older and more experienced teachers. Teachers working in rural areas showed more positive attitudes than other teachers in semi-urban and rural areas. Moreover, any type of training has a positive effect on mathematics teachers' attitudes towards inclusion of children with special educational needs. It was also revealed that most mathematics teachers did not make and implement individualised education programmes for each student with SEN. Finally, recommendations were offered, including fostering a more positive attitude towards inclusion among mathematics teachers, and enhancing pre-service and in-service training and assistance

    Effets du désordre dans les supraconducteurs à base de fer

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    The pinning of vortices is used as a probe for the identification of disorder and its effect on superconductivity in 122-type iron-based superconductors. Using a new analysis method taking into account the interaction of individual vortices with their neighbors, pinning energies and pinning forces in Ba(Fe1-xCox)2As2 are extracted from the vortex distributions in the regime of small fields. The correlation of measurements of the critical current density Jc with the spatial distribution of vortices shows that pinning in this particular regime is due to the heterogeneity of superconducting properties, on the scale of 20-100 nm. Application of the same analysis procedure on the vortex structure in BaFe2(As1-xPx)2 with less density fluctuations, shows that the pinning forces and energies depend on the doping level x. Both Jc measurements and pinning force distributions independently yield a mean distance between pinning centers of about 90 nm, increasing with increasing P-content x. Combination of the above results and critical current density measurements lead to the conclusion that the low field plateau observed in Jc curves, followed by a power-law decrease, emerges from strong pinning due to nm scale heterogeneity of superconducting properties. Attention is also paid to the weak collective pinning contribution that manifests itself at higher fields > 1 T. Notably, this contribution is consistently analyzed in terms of quasiparticle scattering and mean free path fluctuations. In order to test this premise irradiation of Co, Ni and P-doped 122-type iron-based compounds with high-energy 2.5 MeV electrons is performed for several doping levels of the materials and to different doses. Such irradiation introduces atomic sized point-like defects. Following irradiation it appears that the critical temperature Tc shows a similar depression for all studied materials. The weak collective contribution to Jc in Co-doped is found to clearly increase. Moreover this contribution appears after irradiation of the P-doped compound in which it was previously absent. This allows one to confirm the role of atomic point-like pins as scatterers in Ni and Co-doped compounds, as well as the hypothesis that these defects are at the origin of the weak collective pinning contribution to Jc at larger fields.L'ancrage des vortex est utilisé comme une sonde pour l'identification du type de désordre et son effet sur la supraconductivité dans la famille 122 des supraconducteurs à base de fer. Une nouvelle technique d'analyse obtenue d'images de décoration de Bitter prenant en compte l'interaction de chaque vortex avec ses voisins, a permis d'obtenir l'énergie et la force de piégeage dans Ba(Fe1-xCox)2As2, dans le régime de bas champ magnétique. La corrélation avec des mesures de courant critique Jc a montré que le piégeage des vortex dans ce composé est due à l'hétérogénéité des propriétés supraconductrices sur une échelle de 20-100 nm. Application de la même méthode d'analyse pour les vortex dans le BaFe2(As1-xPx)2 a montré que l'énergie et la force d'ancrage dépendent du dopage x. Les mesures de Jc et de la distribution des forces de piégeage ont montré que la distance moyenne entre différents centres de piégeage est de l'ordre de 90 nm et que cette distance augmente quand on augmente le conteneur en P. La combinaison de ces résultats avec les mesures de Jc mène à la conclusion que l'ancrage fort des lignes de flux due à l'hétérogénéité des propriétés supraconductrice à l'échelle de nm est à l'origine de la constante observé à des champ faibles dans les courbes de Jc ainsi que la diminution en loi de puissance qui suit. On traite également la contribution d'ancrage faible collectif à Jc, qui se manifeste à des champs magnétiques plus importants, de l'ordre de 1 T. Cette contribution a été analysée en terme de la diffusion des quasiparticules et de la fluctuation spatiale du libre parcours moyen. Afin de tester l'hypothèse avancé ci-dessus, l'irradiation aux électrons d'énergie 2.5 MeV, sur les composés dopé au Co, Ni et P de la famille 122 a été réalisé à des différentes doses pour plusieurs dopage de ces matériaux. Ce type d'irradiation introduit des défauts ponctuels de taille atomique dans le matériau. La température critique Tc de tous les matériaux étudiés diminue après irradiation de façon similaire. Une claire augmentation de la contribution d'ancrage faible collectif à Jc dans le composé dopé au Co a été observée. De plus, cette contribution qui, avant irradiation, était absente dans tous les dopages du composé au P, apparait après irradiation. Les défauts ponctuels de taille atomique, diffuseur des quasiparticules, dans les supraconducteurs à base de fer sont donc à l'origine de la contribution d'ancrage faible collectif à Jc

    Hashtag publics, networked framing and the July 2016 'coup' in Turkey

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    On 15 July 2016, Turkey faced a military coup attempt against the government. Most Turkish citizens learned about the coup attempt from President Recep Tayyip Erdoğan, who contacted a television channel using FaceTime and urged citizens to go into the streets to resist it. Social media platforms, such as Twitter, were used heavily by Turkish citizens, with hashtags such as #TurkeyCoupAttempt, #darbeyehayir, #NoCoupInTurkey and #TurkeyCoup all trending during this period. This paper focuses on one of the most important anti-coup hashtags, #darbeyehayir (NoCoup), to examine how it was used during the anti-coup protests. By applying a mixed methods approach for Twitter content under the hashtag, the aim of the study is to unveil motivational frames used to call for action and provide a rationale for those participating in anti-coup protests. Results demonstrate that the framing dynamics emerging in the hashtags publics in which pro-Erdoğan supporters were dominant and used this process to provide support to the government during the ‘coup’. The hashtag was mainly used as a tool for government propaganda rather than encouraging civic discussions and participation, and ultimately democratic acts in authoritarian countries
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