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We combine geomorphological and sediment core evidence to investigate phases of ice margin stability and instability during retreat of the Boothia Lancaster Ice Stream (BLIS) of the NE Laurentide Ice Sheet (LIS) since the Last Glacial Maximum (LGM). Sediment cores 2008029-059 PC and TWC (59CC) and 2013029-064 PC (64 PC) from Lancaster Sound and Baffin Bay, respectively, represent LGM through Holocene environments, including three Baffin Bay Detrital Carbonate (BBDC) events that have been thought to manifest calving events within Lancaster Sound. Previous mapping of glacigenic landforms shows that 64 PC lies within the LGM limit of the convergent BLIS and Tasiujaq Ice Stream (TIS) on the northeastern Baffin Island shelf, while 59CC terminates within subglacial/ice marginal sediments termed the Baffin Shelf Drift (BSD), capturing the history of BLIS retreat from 15.3 cal ka BP onward. In 64 PC, a basal sediment gravity flow deposit is overlain by dolomite-rich BBDC 2, which is re-interpreted here as a subglacial/ice marginal deposit and renamed GZ-BBDC. Both gravity flows are interpreted to have formed during retreat of the confluent TIS and BLIS from the LGM maximum extent. Overlying GZ-BBDC, in 64 PC, is a finely laminated lithofacies interpreted as an ice-shelf facies formed beneath the ice shelf fronting the confluent TIS and BLIS when it occupied a large LGM grounding zone wedge (GZW) in northern Baffin Bay. The ice-shelf facies indicates temporary stabilization of the conjoined TIS and BLIS. The overlying thin black glaciomarine diamicton records disintegration of the ice shelf and retreat of the TIS. Ice retreat over Cretaceous and younger bedrock into Lancaster Sound is recorded by dark brown diamicton and glaciomarine sediments in 59CC. The overlying tan, detrital carbonate-rich glaciomarine diamicton, BBDC 1 in 59 PC, manifests calving retreat of the BLIS onto the Paleozoic carbonate bedrock within Lancaster Sound by 15 cal ka BP. A slightly later onset of BBDC 1 in 64 PC, of ca.14.5 cal ka BP, points to the influence of local conditions such as sea ice and local iceberg calving on the distribution of IRD off of Pond Inlet. The pause in ice rafting and detrital carbonate deposition between BBDC 1 and BBDC 0 within the Younger Dryas chron likely results from BLIS readvance to Devon Island and its stabilization there until 11.6 cal ka BP. BLIS retreat into Prince Regent Inlet marks the onset of BBDC 0. These new results indicate multiple periods of instability of the BLIS, which are responsible for BBDC events identified throughout Baffin Bay. 

Abstract How seizures begin at the level of microscopic neural circuits remains unknown. High-density CMOS microelectrode arrays provide a new avenue for investigating neuronal network activity, with unprecedented spatial and temporal resolution. We use high-density CMOS-based microelectrode arrays to probe the network activity of human hippocampal brain slices from six patients with mesial temporal lobe epilepsy in the presence of hyperactivity promoting media. Two slices from the dentate gyrus exhibited epileptiform activity in the presence of low magnesium media with kainic acid. Both slices displayed an electrophysiological phenotype consistent with a reciprocally connected circuit, suggesting a recurrent feedback loop is a key driver of epileptiform onset. Larger prospective studies are needed, but these findings have the potential to elucidate the network signals underlying the initiation of seizure behavior. 

SUMMARY Electrophysiology offers a high-resolution method for real-time measurement of neural activity. Longitudinal recordings from high-density microelectrode arrays (HD-MEAs) can be of considerable size for local storage and of substantial complexity for extracting neural features and network dynamics. Analysis is often demanding due to the need for multiple software tools with different runtime dependencies. To address these challenges, we developed an open-source cloud-based pipeline to store, analyze, and visualize neuronal electrophysiology recordings from HD-MEAs. This pipeline is dependency agnostic by utilizing cloud storage, cloud computing resources, and an Internet of Things messaging protocol. We containerized the services and algorithms to serve as scalable and flexible building blocks within the pipeline. In this paper, we applied this pipeline on two types of cultures, cortical organoids andex vivobrain slice recordings to show that this pipeline simplifies the data analysis process and facilitates understanding neuronal activity. 

ABSTRACT Glacial marine sediment deposition varies both spatially and temporally, but nearly all studies evaluate down-core (∼ time) variations in sediment variables with little consideration for across core variability, or even the consistency of a data set over distance scales of 1 to 1000 m. Grain size and quantitative X-ray diffraction (qXRD) methods require only ≤ 1 g of sediment and thus analyses assume that the identification of coarse sand (i.e., ice-rafted debris) and sediment mineral composition are representative of the depth intervals. This assumption was tested for grain size and mineral weight % on core MD99-2317, off East Greenland. Samples were taken from two sections of the core that had contrasting coarse-sand content. A total of fourteen samples were taken consisting of seven (vertical) and two (horizontal) samples, with five replicates per sample for qXRD analyses and ∼ 10 to 20 replicates for grain size. They had an average dry weight of 10.5 ± 0.5 g and are compared with two previous sets of sediment samples that averaged 54.1 ± 18.9 g and 20.77 ± 5.8 g dry weight. The results indicated some significant differences between the pairs of samples for grain-size parameters (mean sortable silt, and median grain size) but little difference in the estimates of mineral weight percentages. Out of 84 paired mineral and grain-size comparisons only 17 were significantly different at p = < 0.05 in the post-hoc Scheffe test, all of which were linked to grain-size attributes. 

Abstract. Most extant ice caps mantling low-relief Arctic Canada landscapes remained cold based throughout the late Holocene, preserving in situ bryophytes killed as ice expanded across vegetated landscapes. After reaching peak late Holocene dimensions ∼1900 CE, ice caps receded as Arctic summers warmed, exposing entombed vegetation. The calibrated radiocarbon ages of entombed moss collected near ice cap margins (kill dates) define when ice advanced across the site, killing the moss, and remained over the site until the year of their collection. In an earlier study, we reported 94 last millennium radiocarbon dates on in situ dead moss collected at ice cap margins across Baffin Island, Arctic Canada. Tight clustering of those ages indicated an abrupt onset of the Little Ice Age at ∼1240 CE and further expansion at ∼1480 CE coincident with episodes of major explosive volcanism. Here we test the confidence in kill dates as reliable predictors of expanding ice caps by resampling two previously densely sampled ice complexes ∼15 years later after ∼250 m of ice recession. The probability density functions (PDFs) of the more recent series of ages match PDFs of the earlier series but with a larger fraction of early Common Era ages. Post 2005 CE ice recession has exposed relict ice caps that grew during earlier Common Era advances and were preserved beneath later ice cap growth. We compare the 106 kill dates from the two ice complexes with 80 kill dates from 62 other ice caps within 250 km of the two densely sampled ice complexes. The PDFs of kill dates from the 62 other ice caps cluster in the same time windows as those from the two ice complexes alone, with the PDF of all 186 kill dates documenting episodes of widespread ice expansion restricted almost exclusively to 250–450 CE, 850–1000 CE, and a dense early Little Ice Age cluster with peaks at ∼1240 and ∼1480 CE. Ice continued to expand after 1480 CE, reaching maximum dimensions at ∼1880 CE that are still visible as zones of sparse vegetation cover in remotely sensed imagery. Intervals of widespread ice cap expansion coincide with persistent decreases in mean summer surface air temperature for the region in a Community Earth System Model (CESM) fully coupled Common Era simulation, suggesting the primary forcings of the observed snowline lowering were both modest declines in summer insolation and cooling resulting from explosive volcanism, most likely intensified by positive feedbacks from increased snow cover and sea ice and reduced northward heat transport by the oceans. The clusters of ice cap expansion defined by moss kill dates are mirrored in an annually resolved Common Era record of ice cap dimensions in Iceland, suggesting this is a circum-North-Atlantic–Arctic climate signal for the Common Era. During the coldest century of the Common Era, 1780–1880 CE, ice caps mantled >11 000 km2 of north-central Baffin Island, whereas <100 km2 is glaciated at present. The peak Little Ice Age state approached conditions expected during the inception phase of an ice age and was only reversed after 1880 CE by anthropogenic alterations of the planetary energy balance.