Gaps within a subducting plate can alter the surrounding mantle flow field and the overall subduction zone dynamics by allowing hot sub-slab mantle to flow through the gaps and into the mantle wedge. This through-slab flow can produce melting of the slab gap edges as well as significant upwelling that can lead to anomalous alkaline volcanism and/or dynamic uplift in the overriding plate, while the altered mantle flow patterns affect the trench evolution. Numerous geodynamic models have investigated the processes that form slab gaps, but few studies have examined the dynamics of slab gap-altered mantle flow, its effects on trench morphology and kinematics, or the controlling parameters on these processes. Here, laboratory subduction models with a pre-cut gap in a subducting silicone plate are used to explore how slab gap size, and slab gap depth influence the surrounding mantle flow field and trench dynamics. Results suggest that both the vertical extent and the depth of the top (trailing edge) of the slab gap are crucial parameters for modulating overall subduction dynamics. They show that a slab gap, which occurs near the surface and initially comprises 30% of the subducting plate width, can extend enough vertically in the slab to produce significant vertical flow through the gap. Changes to the trench geometry and kinematics are also evident in the models, such that double- and triple-arc geometries are formed during subduction of a shallow slab gap. All of these results are consistent with observations of slab gaps and their induced surface expressions, or the lack thereof, in Eastern Anatolia, East Java, Daly, and Argentina.

Climate warming is known to impact ecosystem composition and functioning. However, it remains largely unclear how soil microbial communities respond to long-term, moderate warming. In this study, we used Illumina sequencing and microarrays (GeoChip 5.0) to analyze taxonomic and functional gene compositions of the soil microbial community after 14 years of warming (at 0.8-1.0 degrees C for 10 years and then 1.5-2.0 degrees C for 4 years) in a Californian grassland. Long-term warming had no detectable effect on the taxonomic composition of soil bacterial community, nor on any plant or abiotic soil variables. In contrast, functional gene compositions differed between warming and control for bacterial, archaeal, and fungal communities. Functional genes associated with labile carbon (C) degradation increased in relative abundance in the warming treatment, whereas those associated with recalcitrant C degradation decreased. A number of functional genes associated with nitrogen (N) cycling (e.g., denitrifying genes encoding nitrate-, nitrite-, and nitrous oxidereductases) decreased, whereas nifH gene encoding nitrogenase increased in the warming treatment. These results suggest that microbial functional potentials are more sensitive to long-term moderate warming than the taxonomic composition of microbial community.

The prototype of accreting, pulsating white dwarfs (GW Lib) underwent a large amplitude dwarf nova outburst in 2007. We used ultraviolet data from Galaxy Evolution Explorer and ground-based optical photometry and spectroscopy to follow GW Lib for three years following this outburst. Several variations are apparent during this interval. The optical shows a superhump modulation in the months following outburst, while a 19 minute quasi-periodic modulation lasting for several months is apparent in the year after outburst. A long timescale (about 4 hr) modulation first appears in the UV a year after outburst and increases in amplitude in the following years. This variation also appears in the optical two years after outburst but is not in phase with the UV. The pre-outburst pulsations are not yet visible after three years, likely indicating the white dwarf has not returned to its quiescent state. The prototype