A hierarchy of models for superconducting thin films

A hierarchy of models for type-II superconducting thin films is presented. Through appropriate asymptotic limits this hierarchy passes from the mesoscopic Ginzburg--Landau model to the London model with isolated vortices as $\delta$-function singularities to vortex-density models and finally to macroscopic critical-state models. At each stage it is found that a key nondimensional parameter is $\Lambda = \lambda^2/d L$, where $\lambda$ is the penetration depth of the magnetic field, a material parameter, and d and L are a typical thickness and lateral dimension of the film,respectively. The models simplify greatly if this parameter is large or small

The motion of superconducting vortices in thin films of varying thickness

The interaction of superconducting vortices with superconductor/vacuum interfaces is considered. A vortex is first shown to intersect such an interface normally. Various thin-film models are then formulated, corresponding to different parameter regimes. A local analysis of a vortex is performed, and a law of motion for each vortex deduced. This law of motion implies that the vortex will move to the locally thinnest part of the film, and is consistent with the vortex moving under the curvature induced by being forced to intersect the boundaries of the film normall

Evidence for competition between the superconducting and the pseudogap state in (BiPb)_2(SrLa)_2CuO_{6+\delta} from muon-spin rotation experiments

The in-plane magnetic penetration depth \lambda_{ab} in optimally doped (BiPb)_2(SrLa)_2CuO_{6+\delta} (OP Bi2201) was studied by means of muon-spin rotation. The measurements of \lambda_{ab}^{-2}(T) are inconsistent with a simple model of a d-wave order parameter and a uniform quasiparticle weight around the Fermi surface. The data are well described assuming the angular gap symmetry obtained in ARPES experiments [Phys. Rev. Lett {\bf 98}, 267004 (2007)], where it was shown that the superconducting gap in OP Bi2201 exists only in segments of the Fermi surface near the nodes. We find that the remaining parts of the Fermi surface, which are strongly affected by the pseudogap state, do not contribute significantly to the superconducting condensate. Our data provide evidence that high temperature superconductivity and pseudogap behavior in cuprates are competing phenomena.Comment: 5 pages, 3 figure

“I Didn’t Want to Make Them Feel Wrong in Any Way”: Preservice Teachers Craft Digital Feedback on Sociopolitical Perspectives in Student Texts

This qualitative multicase analysis investigated the role of “educational niceness” and “neutrality” (e.g., Baptiste, 2008; Bissonnette, 2016) in preservice English teacher feedback on sociopolitical issues in student writing. As part of the field experiences for several ELA methods courses at two universities, one urban and one rural, the teacher-researchers used Google Docs and other technologies (e.g., screencasts and Google Community) to connect preservice teachers (PSTs) with high school writers at a geographical distance so that urban-situated PSTs could mentor rural-situated writers and vice versa. Five methods courses over two semesters served as cases, and 12 PSTs from those courses participated in focus groups. Data included audio recordings of nine focus groups and PSTs’ digital responses to student writing. Using thematic analysis, the authors explored how PSTs responded to sociopolitical perspectives in students’ writing — both engaging them and staying neutral. Although authentic opportunities for responding to student writers supported PSTs’ critical reflection on teaching writing, analysis of PSTs’ responses indicate that such authentic practice may not be sufficient for preparing PSTs to navigate sociopolitical issues and may, in fact, exacerbate PSTs’ impulse to enact educational niceness

“I Didn’t Want to Make Them Feel Wrong in Any Way”: Preservice Teachers Craft Digital Feedback on Sociopolitical Perspectives in Student Texts

This qualitative multicase analysis investigated the role of “educational niceness” and “neutrality” (e.g., Baptiste, 2008; Bissonnette, 2016) in preservice English teacher feedback on sociopolitical issues in student writing. As part of the field experiences for several ELA methods courses at two universities, one urban and one rural, the teacher-researchers used Google Docs and other technologies (e.g., screencasts and Google Community) to connect preservice teachers (PSTs) with high school writers at a geographical distance so that urban-situated PSTs could mentor rural-situated writers and vice versa. Five methods courses over two semesters served as cases, and 12 PSTs from those courses participated in focus groups. Data included audio recordings of nine focus groups and PSTs’ digital responses to student writing. Using thematic analysis, the authors explored how PSTs responded to sociopolitical perspectives in students’ writing — both engaging them and staying neutral. Although authentic opportunities for responding to student writers supported PSTs’ critical reflection on teaching writing, analysis of PSTs’ responses indicate that such authentic practice may not be sufficient for preparing PSTs to navigate sociopolitical issues and may, in fact, exacerbate PSTs’ impulse to enact educational niceness

“It Doesn’t Feel Like a Conversation”: Digital Field Experiences and Preservice Teachers’ Conceptions of Writing Response

Research shows that preservice English teachers (PSETs) lack opportunities to respond to student writing and that they may view student writing through a deficit lens. To address this need, the authors developed the Writing Mentors (WM) program, a digital field placement that gave PSETs experience providing feedback to high school writers. In this analysis, we examine how PSETs’ views of response were shaped by their digital interactions with high school writers. The challenges of interacting asynchronously created opportunities for PSETs to identify limitations in the mode of communication, propose approaches to providing feedback, and reflect on how teacher feedback can nurture or constrain relationships with students. These findings point to the promise of critical reflection on the disruptive potential of digital feedback for supporting PSTs’ response to student writing

Zero-field superfluid density in d-wave superconductor evaluated from the results of muon-spin-rotation experiments in the mixed state

We report on measurements of the in-plane magnetic penetration \lambda_{ab} in the optimally doped cuprate superconductor (BiPb)_2(SrLa)_2CuO_6+\delta (OP Bi2201) by means of muon-spin rotation (\muSR). We show that in unconventional $d-$wave superconductors (like OP Bi2201), \muSR experiments conducted in various magnetic fields allow to evaluate the zero-field magnetic penetration depth \lambda_0, which relates to the zero-field superfluid density in terms of \rho_s\propto\lambda_0^-2.Comment: 4 pages, 5 figure

Strain-dependent and distinctive T-cell responses to HIV antigens following immunisation of mice with differing chimpanzee adenovirus vaccine vectors

In vivo vaccination studies are conventionally conducted in a single mouse strain with results, only reflecting responses to a single immunogenetic background. We decided to examine the immune response to an HIV transgene (gag, pol and nef fusion protein) in 3 strains of mice (CBA, C57BL/6 and BALB/c) to determine the spectrum of responses and in addition to determine whether the serotype of the adenoviral vector used (ChAd3 and ChAd63) impacted the outcome of response. Our results demonstrated that all three strains of mice responded to the transgene and that the magnitude of responses were different between the strains. The C57BL/6 strain showed the lowest range of responses compared to the other strains and, very few responses were seen to the same peptide pool in all three strains of mice. In CBA and BALB/c mice there were significant differences in IFNγ production dependent on the adenoviral vector used. Our results suggest that employing a single strain of mouse may underestimate the efficacy and efficiency of vaccine products