Poroelastic response of mid-ocean ridge hydrothermal systems to ocean tidal loading : implications for shallow permeability structure

Author Posting. © American Geophysical Union, 2016. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Geophysical Research Letters 43 (2016): 1660–1668, doi:10.1002/2015GL066479.We use the time delay between tidal loading and exit-fluid temperature response for hydrothermal vents to model the poroelastic behavior and shallow upflow zone (SUZ) effective permeability structure of three mid-ocean ridge (MOR) sites with different spreading rates. Hydrothermal vents at Lucky Strike field exhibit relatively small phase lags corresponding to high SUZ effective permeabilities of ≥ ~10−10 m2, with variations that we interpret as resulting from differences in the extrusive layer thickness. By contrast, vents at East Pacific Rise site exhibit relatively large phase lags corresponding to low SUZ effective permeabilities of ≤ ~10−13 m2. Vents at Main Endeavour field exhibit both high and low phase lags, suggestive of a transitional behavior. Our results demonstrate that tidal forcing perturbs hydrothermal flow across the global MOR system, even in places where the tidal amplitude is very low, and that the flow response can be used to constrain variations in SUZ permeability structure beneath individual vent fields.This research was funded by Woods Hole Oceanographic Institution (USA). Thibaut Barreyre was supported by WHOI's Deep Ocean Exploration Institute (DOEI) postdoctoral scholarship.2016-08-2

LITERACY AND LEARNING ACROSS PHYSICAL AND DIGITAL SPACES: A CASE STUDY IN A BLENDED PRIMARY CLASSROOM

In light of technological innovations, schools are increasingly adopting digital tools and promoting online spaces for learning. Consequently, the shape of teaching and learning is shifting beyond the physical classroom. Drawing on sociocultural theory, distributed cognition and a networked learning framework, this case study explores how a blended approach shapes teachers’ practices and students’ learning and literacy processes. The study was situated in a Year Six classroom in an Australian technology-rich independent school. Data was collected during the 2013 school year and included: 1) observations; 2) 125 hours of classroom video-recordings; 3) a collection of digital artefacts designed by the students; 4) interviews with teachers and students; 5) a student survey regarding technology integration in the classroom; 6) entry logs posted by participants on the Edmodo social network site. Multiple approaches to data analysis were used in order to answer the study’s research questions, including: networked learning analysis, thematic analysis, situated discourse analysis, multimodal discourse analysis and a quantitative descriptive analysis. The findings suggest that blended learning spaces support teachers’ distributed orchestration of classroom activities across tools and resources while also leveraging students’ engagement in reciprocal teaching as well as self-driven and collaborative learning. Digital technologies open space for new ways of communication, interaction and learning in the classroom, yet such affordances are dependent upon teacher’s facilitation and expertise. In addition, an interactive pattern of literacy practices was evident in the classroom, where processes of authorship, readership, production, audience, and consumption were established between students. Finally, alignment between teachers’ beliefs and the perceived value of technology was a key factor for technology integration in the classroom

A transmission problem across a fractal self-similar interface

We consider a transmission problem in which the interior domain has infinitely ramified structures. Transmission between the interior and exterior domains occurs only at the fractal component of the interface between the interior and exterior domains. We also consider the sequence of the transmission problems in which the interior domain is obtained by stopping the self-similar construction after a finite number of steps; the transmission condition is then posed on a prefractal approximation of the fractal interface. We prove the convergence in the sense of Mosco of the energy forms associated with these problems to the energy form of the limit problem. In particular, this implies the convergence of the solutions of the approximated problems to the solution of the problem with fractal interface. The proof relies in particular on an extension property. Emphasis is put on the geometry of the ramified domain. The convergence result is obtained when the fractal interface has no self-contact, and in a particular geometry with self-contacts, for which an extension result is proved