The relation between writing in formal schooling and writing in other social practices is a central problem in writing research (e.g., critical pedagogy, writing in nonacademic settings, cognition in variable social contexts). How do macro-level social and political structures (forces) affect micro-level literate actions in classrooms and vice versa? To address these questions, the author synthesizes Yrjö Engeström's systems version of Vygotskian cultural-historical activity theory with Charles Bazerman's theory of genre systems. The author suggests that this synthesis extends Bakhtinian dialogic theory by providing a broader unit of analysis than text-as-discourse, wider levels of analysis than the dyad, and an expanded theory of dialectic. By tracing the intertextual relations among disciplinary and educational genre systems, through the boundary of classroom genre systems, one can construct a model of ways classroom writing is linked to writing in wider social practices and rethink such issues as agency, task representation, and assessment.

The shear velocity and [Formula: see text] structure for the upper 1 km in different tectonic regions of the Arabian shield have been investigated using high‐frequency vertical component records of Rayleigh waves (1–20 Hz), which were recorded at source‐to‐receiver separations 55–80 km during a deep seismic refraction survey. Group and phase velocities of the fundamental and first higher modes were inverted for the shear‐wave velocity structure; Rayleigh‐wave attenuation coefficients were determined from the decay of the amplitude spectrum of the fundamental mode and used to invert for the [Formula: see text] structure. Models derived from the data were tested by calculating synthetic seismograms for the fundamental and the first higher modes from surface‐wave theory with a center of compression used to represent the source; both band‐pass filtered step and Dirac delta source time functions were tested. Modeling indicates that the shear‐wave velocity of the shield increases from 2.6 km/s to 3.4 km/s in the upper 400 m of the crust. [Formula: see text] increases from 30 in the upper 50 m to 150 at 500 m depth. The underlying material has a [Formula: see text] of 400–500 for the out‐cropping igneous rocks such as granite and may reach values higher than 700 for the metamorphic green schist rock. A band‐pass filtered Dirac delta source time function produces the synthetic that is the best fit with observations.

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A new dual temporal resolution-based, high spatial resolution, pharmacokinetic parametric mapping method is describedimproved coverage and spatial resolution using dual injection dynamic contrast-enhanced (ICE-DICE) MRI. In a dualbolus dynamic contrast-enhanced-MRI acquisition protocol, a high temporal resolution prebolus is followed by a high spatial resolution main bolus to allow high spatial resolution parametric mapping for cerebral tumors. The measured plasma concentration curves from the dual-bolus data were used to reconstruct a high temporal resolution arterial input function. The new method reduces errors resulting from uncertainty in the temporal alignment of the arterial input function, tissue response function, and sampling grid. The technique provides high spatial resolution 3D pharmacokinetic maps (voxel size 1.0 3 1.0 3 2.0 mm 3 ) with whole brain coverage and greater parameter accuracy than that was possible with the conventional single temporal resolution methods. High spatial resolution imaging of brain lesions is highly desirable for small lesions and to support investigation of heterogeneity within pathological tissue and peripheral invasion at the interface between diseased and normal brain. The new method has the potential to be used to improve dynamic contrast-enhanced-MRI techniques in general. Magn Reson Med 68:452-462, 2012. V C 2012 Wiley Periodicals, Inc.