The isotopic composition and fluence of solar-wind nitrogen in a genesis B/C array collector

We have measured the isotopic composition and fluence of solar-wind nitrogen in a diamond-like-carbon collector from the Genesis B/C array. The B and C collector arrays on the Genesis spacecraft passively collected bulk solar wind for the entire collection period, and there is no need to correct data for instrumental fractionation during collection, unlike data from the Genesis “Concentrator.” This work validates isotopic measurements from the concentrator by Marty et al. (2010, 2011); nitrogen in the solar wind is depleted in ^(15)N relative to nitrogen in the Earth’s atmosphere. Specifically, our array data yield values for ^(15)N/^(14)N of (2.17 ± 0.37) × 10^(−3) and (2.12 ± 0.34) × 10^(−3), depending on data-reduction technique. This result contradicts preliminary results reported for previous measurements on B/C array materials by Pepin et al. (2009), so the discrepancy between Marty et al. (2010, 2011) and Pepin et al. (2009) was not due to fractionation of solar wind by the concentrator. Our measured value of ^(15)N/^(14)N in the solar wind shows that the Sun, and by extension the solar nebula, lie at the low-^(15)N/^(14)N end of the range of nitrogen isotopic compositions observed in the solar system. A global process (or combination of processes) must have operated in interstellar space and/or during the earliest stages of solar system formation to increase the ^(15)N/^(14)N ratio of the solar system solids. We also report a preliminary Genesis solar-wind nitrogen fluence of (2.57 ± 0.42) × 10^(12) cm^(−2). This value is higher than that derived by backside profiling of a Genesis silicon collector (Heber et al. 2011a)

Universal criterion for the breakup of invariant tori in dissipative systems

The transition from quasiperiodicity to chaos is studied in a two-dimensional dissipative map with the inverse golden mean rotation number. On the basis of a decimation scheme, it is argued that the (minimal) slope of the critical iterated circle map is proportional to the effective Jacobian determinant. Approaching the zero-Jacobian-determinant limit, the factor of proportion becomes a universal constant. Numerical investigation on the dissipative standard map suggests that this universal number could become observable in experiments. The decimation technique introduced in this paper is readily applicable also to the discrete quasiperiodic Schrodinger equation.Comment: 13 page

Depth profiling analysis of solar wind helium collected in diamond-like carbon film from Genesis

The distribution of solar-wind ions in Genesis mission collectors, as determined by depth profiling analysis, constrains the physics of ion-solid interactions involving the solar wind. Thus, they provide an experimental basis for revealing ancient solar activities represented by solar-wind implants in natural samples. We measured the first depth profile of ^4He in a Genesis collector; the shallow implantation (peaking at <20 nm) required us to use sputtered neutral mass spectrometry with post-photoionization by a strong field. The solar wind He fluence calculated using depth profiling is ~8.5 × 10^(14) cm^(–2). The shape of the solar wind 4He depth profile is consistent with TRIM simulations using the observed ^4He velocity distribution during the Genesis mission. It is therefore likely that all solar-wind elements heavier than H are completely intact in this Genesis collector and, consequently, the solar particle energy distributions for each element can be calculated from their depth profiles. Ancient solar activities and space weathering of solar system objects could be quantitatively reproduced by solar particle implantation profiles

The serine protease hepsin mediates urinary secretion and polymerisation of Zona Pellucida domain protein uromodulin.

Uromodulin is the most abundant protein in the urine. It is exclusively produced by renal epithelial cells and it plays key roles in kidney function and disease. Uromodulin mainly exerts its function as an extracellular matrix whose assembly depends on a conserved, specific proteolytic cleavage leading to conformational activation of a Zona Pellucida (ZP) polymerisation domain. Through a comprehensive approach, including extensive characterisation of uromodulin processing in cellular models and in specific knock-out mice, we demonstrate that the membrane-bound serine protease hepsin is the enzyme responsible for the physiological cleavage of uromodulin. Our findings define a key aspect of uromodulin biology and identify the first in vivo substrate of hepsin. The identification of hepsin as the first protease involved in the release of a ZP domain protein is likely relevant for other members of this protein family, including several extracellular proteins, as egg coat proteins and inner ear tectorins

“She’s Definitely the Artist One”: How Learner Identities Mediate Multimodal Composing

Multimodal composing can activate literacy practices and identities not typically privileged in verbocentric English classrooms, and students’ identities as particular kinds of learners (e.g., “visual artist”) may propel—or limit—their engagement in classroom work, including in multimodal composing. Although researchers have studied the ways multimodal projects can evidence literacy learning and have argued that identity is negotiated, improvisational, and hybrid, they have offered few sustained analyses of the processes by which identities evolve during and across multimodal composing tasks. By examining how students position themselves and one another as particular kinds of learners over time, researchers can better understand the ways in which multimodal tasks help students explore new skills and roles or reify old ones. Drawing on an approach to discourse analysis from the linguistic anthropology of education, we trace the pathways of three 12th graders’ learner identities across two events as they worked in a group to compose visual responses to literary texts for their English class. We examine how one student’s robust identity as an artist emerged in tandem with the devaluing of other participants’ artist identities. Seven weeks later, these positionings led her to act as the painting’s primary author and other students to act in increasingly perfunctory ways. We call for teachers and researchers to consider how students’ identities—interacting with factors such as the teacher’s expectations for group work and the affordances of particular media and materials for collaboration—drive students’ participation in and ownership of multimodal compositions

“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

Changes to TSR control set due to changes in mission and lessons learned

Previous Technical Safety Requirements (TSRs) established to support plutonium production activities at the Rocky Flats Environmental Technology Site (RFETS) were heavily focused on engineered safety features that would mitigate potential accidents. With the change in mission in 1992 to Site closure, and considering antiquated equipment nearing the end of their useful life, a change in philosophy was adopted to emphasize preventive controls that are mostly administrative. The new Administrative Controls (ACs) developed in the last few years include discrete attributes of safety management programs (SMPs) that are specifically credited to prevent or mitigate an accident, and include requirements on handling individual deviations, programmatic deficiencies, and TSR AC violations. The primary benefit of these changes is fewer requirements on equipment that allow the contractor more flexibility to maintain the defense-in-depth safety systems in a more cost-effective manner. A disadvantage of these new ACs is that implementation has become cumbersome and difficult to manage, e.g., resulted in an increased burden of demonstrating compliance and required an additional infrastructure to track deviations and deficiencies. In order to improve the efficiency of the authorization basis (AB) process to support accelerated Site closure according to the 2006 Plan, the Site has recently modified the ABs to better focus on the programmatic elements that were credited in the accident analyses, and to rely on the Integrated Safety Management System to implement SMPs via one general TSR AC requirement. At the request of DOE/RFFO, a self-assessment of the Rocky Flats AB program was performed in November 1998 by Victor Stello, DOE Headquarters, along with representatives from other DOE sites and Defense Programs. Results of this self-assessment confirmed that the proposed AC changes would be beneficial and provided specific recommendations