Synchronous Events Research Articles

Energy Transduction in Nitrogenase.

Nitrogenase is a complicated two-component enzyme system that uses ATP binding and hydrolysis energy to achieve one of the most difficult chemical reactions in nature, the reduction of N2 to NH3. One component of the Mo-based nitrogenase system, Fe protein, delivers electrons one at a time to the second component, the catalytic MoFe protein. This process occurs through a series of synchronized events collectively called the "Fe protein cycle". Elucidating details of the events associated with this cycle has constituted an important challenge in understanding the nitrogenase mechanism. Electron delivery is a multistep process involving three metal clusters with intra- and interprotein events. It is proposed that the first electron transfer event is a gated intraprotein transfer of one electron from the MoFe protein P-cluster to the FeMo cofactor. Measurement of the effect of osmotic pressure on the rate of this electron transfer process revealed that it is gated by protein conformational changes. This first electron transfer is activated by binding of the Fe protein containing two bound ATP molecules. The mechanism of how this protein-protein association triggers electron transfer remains unknown. The second electron transfer event is proposed to be a rapid interprotein "backfill" with transfer of one electron from the reduced Fe protein 4Fe-4S cluster to the oxidized P-cluster. In this way, electron delivery can be viewed as a case of "deficit spending". Such a deficit-spending electron transfer process can be envisioned as a way to achieve one-direction electron flow, limiting the potential for back electron flow. Hydrolysis of two ATP molecules associated with the Fe protein occurs after the electron transfer and therefore is not used to directly drive the electron transfer. Rather, ATP hydrolysis is proposed to contribute to relaxation of the "activated" conformational state associated with the ATP form of the complex, with the free energy from ATP hydrolysis being used to pay back energy associated with component protein association and electron transfer. Release of inorganic phosphate (Pi) and protein-protein dissociation follow electron transfer and ATP hydrolysis. The rate-limiting step for the Fe protein cycle is not dissociation of the two proteins, as previously believed, but rather is release of Pi after ATP hydrolysis, which is then followed by rapid protein-protein complex dissociation. Nitrogenase is composed of two catalytic halves that do not function independently but rather exhibit anticooperative nuclear motion in which electron transfer in one-half of the complex partially inhibits electron transfer and ATP hydrolysis in the other half. Calculations indicated the existence of anticooperative interactions across the entire nitrogenase complex, suggesting a mechanism for the control of events on opposite ends of this large complex. The mechanistic necessity for this anticooperative process remains unknown. This Account presents a working model for how all of these processes work together in the nitrogenase "machine" to transduce the energy from ATP binding and hydrolysis to drive N2 reduction.

Pre-emergence growth and development in the arctic midge Trichotanypus alaskensis Brundin

Developing at low mean temperatures, arctic chironomids often have prolonged larval growth yet adult emergence is typically a brief and highly synchronous event. How does a midge population achieve synchronous emergence? Under the Absolute Spring Species Hypothesis (AbSS), adult eclosion by early-emerging species may be synchronized by overwintering as fully mature larvae. Such prepupal larvae would neither feed nor grow after spring thaw, only pupate and emerge. The podonomine Trichotanypus alaskensis Brundin is an abundant midge in tundra ponds on Alaska’s Arctic Coastal Plain, and one of the earliest-emerging species in this chironomid-dominated insect community. T. alaskensis is univoltine in these arctic ponds, with most emergence from any one pond occurring within less than a one-week span during late June, typically about three weeks after pond thaw. We evaluated T. alaskensis for conformity to the AbSS model by documenting the overwintering state of this species in a tundra pond near Barrow, Alaska, then monitoring larval growth and development of the population from spring thaw to pupation. Most T. alaskensis were immature instar IV larvae when collected in late September of both 2010 and 2011, with 10-30% still in late instar III. Immediately after pond thaw in 2011, all collected larvae had imaginal disc primordia showing early stages of instar IV development. Within the first two weeks following pond thaw, most larvae had doubled their dry mass and developed into mature (prepupal) final-instar larvae. Highly synchronized emergence by T. alaskensis is not a consequence of a population overwintering as fully-mature larvae, as per the Absolute Spring Species Hypothesis. Rather, larvae in a given tundra pond appear to develop synchronously throughout the life cycle, including a period of substantial growth and rapid prepupal development between spring thaw and early-summer emergence.

Measuring and Comparing Extinction Events: Reconsidering Diversity Crises and Concepts.

To understand our present diversity crisis, it is natural to look to past crises for parallels and indicators. This is difficult because the present crisis is unlike the "Big Five" of the past: it is mostly terrestrial (with an increasing marine component), involves widespread habitat destruction and alteration of climate, and is largely anthropogenic, with confounding effects of differences in loss of diversity among continents and the difficulty of separating anthropogenic extinctions from natural Pleistocene and post-Pleistocene extinctions. In contrast, the "Big Five" crises of the geologic record are mainly marine (in the first two, no land vertebrates existed), and because marine taxa outnumber terrestrial taxa by a margin of about 25:1, global analyses of diversity crises have tended to lump together all phyla and environments. As a result, terrestrial evidence has been "swamped" statistically by the marine data. Both synchroneity and causality of terrestrial and marine events have usually been assumed, but without decisive data. Terrestrial vertebrate faunas do not seem to have been suddenly and catastrophically affected at the ends of the Permian, the Triassic, and the Cretaceous; rather, the pattern generally seems to be of steady turnover and replacement of groups and sometimes of slow decline. Here I suggest a revision of the concept of "mass extinction," which has no definitional limits on the application of the term with respect to duration, geography, ecology, or taxa affected. Unusual drops in taxonomic diversity have traditionally focused on increases in extinction rates, with scarce consideration of origination rates and their interplay with extinction rates. Analyses of hypothesized diversity crises should be operationally and situationally defined and statistically normalized through the histories of taxa and biotas, and should explicitly include both origination and extinction rates. The term "mass extinctions" would be usefully replaced by "diversity crises." These parameters require not absolute numerical (or percentage) limits but situational ones.

Simulating the effects of colony density and intercolonial distance on fertilisation success in broadcast spawning scleractinian corals

Coral reefs are predicted to be vulnerable to the Allee effect due to the density dependence of broadcast spawning fertilisation success. Verifying such effects in corals, however, is hindered by their annual or biannual nocturnal multispecific synchronous spawning events, the lack of colony spatial distribution data, and the difficulty of manipulating coral colony density in the field. These obstacles were overcome by simulating scleractinian coral spawning events at various distances between colonies. While controlling for density, and including the influence of colony size and current flow speed, we investigated the distance at which reproductive contact became unlikely (critical intercolonial distance). The relationship between fertilisation success and colony density was also examined by simulating broadcast spawning events at different densities, with the aim of investigating whether Allee effects can occur at population densities observed in the literature. Fertilisation events rarely occurred between simulated coral colonies that were more than 30–40 m apart in the conditions tested due to sperm dilution and insufficient mixing between gametes from different colonies. Higher flow speeds improved mixing for distant colonies but generally resulted in low fertilisation success; larger colonies reduced the impact of dilution due to increased reproductive output. Fertilisation success exhibited a logarithmic relationship as colony density increased (e.g. 99.0% at 3.36 × 10−2 colonies m−2 for colonies with 1 m2 surface area), with low fertilisation success (21.0% at 2.70 × 10−3 colonies m−2 for 1 m2 colonies) at densities comparable to post-disturbance populations. These findings suggest the potential for strong component Allee effects due to broadcast spawning. Our critical intercolonial distance results support existing evidence that coral populations within a reef may consist of multiple breeding groups instead of a single homogeneous one. The inclusion of spatial data when surveying for coral colony density should be considered when attempting to predict density dependent effects.

Complex networks for tracking extreme rainfall during typhoons.

Reconciling the paths of extreme rainfall with those of typhoons remains difficult despite advanced forecasting techniques. We use complex networks defined by a nonlinear synchronization measure termed event synchronization to track extreme rainfall over the Japanese islands. Directed networks objectively record patterns of heavy rain brought by frontal storms and typhoons but mask out contributions of local convective storms. We propose a radial rank method to show that paths of extreme rainfall in the typhoon season (August-November, ASON) follow the overall southwest-northeast motion of typhoons and mean rainfall gradient of Japan. The associated eye-of-the-typhoon tracks deviate notably and may thus distort estimates of heavy typhoon rainfall. We mainly found that the lower spread of rainfall tracks in ASON may enable better hindcasting than for westerly-fed frontal storms in June and July.

A novel pyramidal cell type promotes sharp-wave synchronization in the hippocampus.

To support cognitive function, the CA3 region of the hippocampus performs computations involving attractor dynamics. Understanding how cellular and ensemble activities of CA3 neurons enable computation is critical for elucidating the neural correlates of cognition. Here we show that CA3 comprises not only classically described pyramid cells with thorny excrescences, but also includes previously unidentified 'athorny' pyramid cells that lack mossy-fiber input. Moreover, the two neuron types have distinct morphological and physiological phenotypes and are differentially modulated by acetylcholine. To understand the contribution of these athorny pyramid neurons to circuit function, we measured cell-type-specific firing patterns during sharp-wave synchronization events in vivo and recapitulated these dynamics with an attractor network model comprising two principal cell types. Our data and simulations reveal a key role for athorny cell bursting in the initiation of sharp waves: transient network attractor states that signify the execution of pattern completion computations vital to cognitive function.

Estimates of fish and coral larvae as nutrient subsidies to coral reef ecosystems

AbstractNutrient subsidies are essential for the functioning of many ecosystems. A long‐standing conundrum in coral reef ecology is how these systems can be among the most productive globally, but persist in nutrient‐poor conditions. Here, we investigate the importance of the larvae of fishes and corals and gametes of corals as nutrient subsidies for coral reefs. We provide evidence that fish larvae may be an ecologically important source of exogenous nutrients. We found that at the high end of mean estimates of fish larval supply rates, larvae can replace the nutrients in the entire fish community (estimated from Caribbean coral reefs) in 28 and 434 d for nitrogen (N) and phosphorus, respectively. Coral larvae, on the other hand, appear to represent only a fraction of the nutrients supplied by the larval fish community. In contrast, coral gametes provide substantial pulses of recycled nutrients during synchronous spawning events. Within a single night, gametes from coral spawning events can produce nutrient fluxes that represent 13 and 64 times the amount of N and carbon, respectively, stored in coral reef fish communities. Our analysis suggests that larvae and/or gametes of fishes and corals may represent an important, but previously underappreciated, source of nutrients to coral reefs that warrant inclusion into models of nutrient dynamics and ecosystem function.

Writing Artifacts as Narratives of Emotion

This manuscript will examine the role of emotion in writing through a comparative analysis of home-based written artifacts from children between the ages of 5 and 7 from seven families. We investigate how writing reflects the emotional context of the family that can function as a tool for the construction of narratives. The examination of writing through this perspective illustrates how the process of composing written artifacts reflects the synchronization and coordination of social and historical events imbued with emotions as told by the children’s written artifacts.

Silurian magmatism on the eastern margin of the Erguna Block, NE China: Evolution of the northern Great Xing'an Range

There are few Early Paleozoic volcanics and mafic rocks in the Xing'an-Mongolia Orogenic Belt in spite of the extensive occurrence of granites caused by a synchronous orogenic event. Despite the fact that this was a major orogen, the properties of the lithosphere and its associated orogenic processes are poorly known. In this paper, a comprehensive study of U-Pb zircon ages, Lu-Hf isotopes, and whole-rock elemental analyses was carried out on three intermediate-mafic intrusions, which were recently identified in the northern Great Xing'an Range. Representative samples of the Yikete, Yalu, and Xinglong intrusions yielded the weighted mean 206Pb/238U ages of 435 ± 1 Ma, 430 ± 8 Ma, and 447 ± 4 Ma, respectively. This indicates the presence of Silurian intermediate-mafic rocks in the region. The dioritic rocks exhibit a Na-rich, a calc-alkaline affinity and enrichment in LILEs (Rb, Ba, K, and Sr) and depletion in HSFEs (Ta, Ti, Zr, and Hf), indicating that the Yikete dioritic rocks were a mantle wedge that had previously been subjected to metasomatism by fluids and melts related to a subducted oceanic slab and its overlying sediments. The gabbroic rocks are tholeiitic in composition with variable MgO (3.14–8.31%), and low K2O (0.16–1.0%) and TiO2 (0.25–2.12%) contents. They are characterized by enrichment of LILEs, depletion of HFSEs, and highly positive zircon εHf(t) (+5.8 to +13.3) values. In addition, they possess geochemical features of MORB with subordinate OIB. The geochemical features indicate that the gabbroic rocks were derived from an upwelling of asthenospheric mantle that had been into the supra-subduction wedge facilitated by subduction rollback before their generation. Combined with the coeval arc-type magmatic rocks widely exposed on the eastern margin of the Erguna Block, we link the generation of the dioritic rocks to the northwestern subduction of the Nenjiang oceanic plate during the Early Paleozoic. The generation of the gabbroic rocks might result from rifting of the back-arc basin. Consequently, an arc-back-arc model is proposed to explain the subduction evolution of the Nenjiang Ocean during the Early Paleozoic.

Laugh with us, not at us

In keeping with its theme, this paper has a light touch and a serious point. It arose from a concern that networked learning may not be recognisable enough to be parodied. Parody is a pervasive and ubiquitous cultural practice that entails imitation and laughter – features which could perhaps contribute to making networked learning knowable to a wider community. Despite parody’s potential for serious damage, its broadest use supports the recognition, consolidation, development and renewal of a genre or movement. Drawing on Bakhtinian notions of the dialogic and carnival, as well as the light thrown on contemporary discourse through Bakhtin’s literary insights, the paper explores the extent to which networked learning artefacts and practices engage in parody and have been parodied. A thought experiment to parody a networked learning conference paper led to the current paper’s structure. This attempt to parody highlights the difficulties of departing from conventional academic genres even in a field of study that challenges those genres. The study identifies how themes of genre, intertextuality and multimodality combine in papers and events about networked learning to produce texts and practices that are open to renewal, hacking and augmentation, but without the need for the laughter that comes with parody that might have the same results. In papers and book chapters, although there are lively forms of writing, heavy use of citation is the main source of intertextuality. Evidence of parody was found in a symposium, including (self) parody of networked learning conference practices, suggesting that we are more likely to find parody during synchronous events than in peer reviewed academic texts. An almost accidental result of the parodied structure of the paper suggests that networked learning could be developing in a way that parallels Bakhtin’s understanding of the novel, yet without the cultural work that parody has contributed to the novel. This line of reasoning brings into sharper focus one of the key features of this author’s own initial parody of networked learning: its emphasis on boundaries and boundary crossing. It seems that networked learning, like the novel, cannot be parodied as a ‘complete’ form: like the novel it is constantly changing to reflect its contemporary world.

Time-varying synchronous cell ensembles during consummatory periods correlate with variable numbers of place cell spikes.

Spike rates of a hippocampal place cell are not constant and vary even when an animal visits an identical place field with nearly identical behavior. As one potential neurophysiological source underlying place cell spiking variability, we focused on the temporally fluctuating activity states of neuronal ensembles. Spike patterns of hippocampal neurons were recorded from rats performing a linear track task. Within a single consummatory period, similar sets of neurons were more frequently recruited in synchronous firing events, whereas different synchronized firing patterns of neuronal populations tended to be identified in different consummatory periods. A linear regression analysis indicated that the time-varying activation patterns of neuronal populations during consummatory periods are correlated with the spike rates of a place cell within its place field during running. These findings suggest that place cell in-field spiking is not only triggered by static inputs that represent external environments but also strongly depends on the time-varying internal states of neuronal populations.

Astrocyte as a Detector of Synchronous Events of a Neural Network

The principles and mechanisms of information processing in the brain are among key fundamental problems of modern science. Neurons being the main signal cells of the brain provide the transmission and transformation of sequences of electrical pulses in a neural network. Signal networks include not only neurons but also glial cells called astrocytes executing regulatory functions, as is accepted in neurobiology. In this work, a morphofunctional (compartment) model of an astrocyte has been proposed. It has been shown that the astrocyte can serve as a detector of synchronous events of different points of the neural network, generating a calcium response signal. In turn, this signal induces the synchronous ejection of neuroactive substances to the corresponding points of the network, which can enhance the spatial synchronization of neurons or the synchronous modulation of different neural paths.

SynchroTrace

Trace-driven simulation of chip multiprocessor (CMP) systems offers many advantages over execution-driven simulation, such as reducing simulation time and complexity, allowing portability, and scalability. However, trace-based simulation approaches have difficulty capturing and accurately replaying multithreaded traces due to the inherent nondeterminism in the execution of multithreaded programs. In this work, we present SynchroTrace, a scalable, flexible, and accurate trace-based multithreaded simulation methodology. By recording synchronization events relevant to modern threading libraries (e.g., Pthreads and OpenMP) and dependencies in the traces, independent of the host architecture, the methodology is able to accurately model the nondeterminism of multithreaded programs for different hardware platforms and threading paradigms. Through capturing high-level instruction categories, the SynchroTrace average CPI trace Replay timing model offers fast and accurate simulation of many-core in-order CMPs. We perform two case studies to validate the SynchroTrace simulation flow against the gem5 full-system simulator: (1) a constraint-based design space exploration with traditional CMP benchmarks and (2) a thread-scalability study with HPC-representative applications. The results from these case studies show that (1) our trace-based approach with trace filtering has a peak speedup of up to 18.7× over simulation in gem5 full-system with an average of 9.6× speedup, (2) SynchroTrace maintains the thread-scaling accuracy of gem5 and can efficiently scale up to 64 threads, and (3) SynchroTrace can trace in one platform and model any platform in early stages of design.

Locate, Combine, Contradict, Iterate: Serial Strategies for PostInternet Art

Locate, Combine, Contradict, Iterate: Serial Strategies for PostInternet Art

Synchronic historical patterns of species diversification in seasonal aplocheiloid killifishes of the semi-arid Brazilian Caatinga.

The Caatinga is the largest nucleus of seasonally dry tropical forests in South America, but little is known about the evolutionary history and biogeography of endemic organisms. Evolutionary diversification and distribution of terrestrial vertebrates endemic to the Caatinga have been explained by palaeogeographical Neogene episodes, mostly related to changes in the course of the São Francisco River, the largest river in the region. Our objective is to estimate the timing of divergence of two endemic groups of short-lived seasonal killifishes inhabiting all ecoregions of the Caatinga, testing the occurrence of synchronic events of spatial diversification in light of available data on regional palaeogeography. We performed independent time-calibrated phylogenetic molecular analyses for two clades of sympatric and geographically widespread seasonal killifishes endemic to the Caatinga, the Hypsolebias antenori group and the Cynolebias alpha-clade. Our results consistently indicate that species diversification took place synchronically in both groups, as well as it is contemporary to diversification of other organisms adapted to life in the semi-arid Caatinga, including lizards and small mammals. Both groups originated during the Miocene, but species diversification started between the Late Miocene and Early Pliocene, when global cooling probably favoured the expansion of semi-arid areas. Synchronic diversification patterns found are chronologically related to Tertiary palaeogeographical reorganizations associated to continental drift and to Quaternary climatic changes, corroborating the recent proposal that South American biodiversity has been continuously shaped between the Late Paleogene and Pleistocene.

Past growth suppressions as proxies of fire incidence in relict Mediterranean black pine forests

Abstract Global warming and land use changes, contributing to landscape level fuel increments, could threaten Mediterranean pine forest resilience to wildfire disturbances. Reconstructions of historical fire regimes allow for the disentanglement of these two drivers by comparing the influence of climatic and anthropogenic variables on fire. Here we combine three sources of historical data: charcoal accumulation rates from a peat bog, detailed historical records of fire incidence and tree-ring width data from five relict black pine (Pinus nigra) forests with fire-scarred trees located in Sierra de Gredos (central Spain). We found growth suppression in 1893 and 1894 in all the sites which coincided with a peak of fire incidence in historical records and an increase in charcoal accumulation rates. The occurrence of these three synchronous events suggests increased wildfire incidence in the area which shaped the current stand structure of relict black pine forests. These late 19th century developments, we argue, can be mainly attributed to anthropogenic factors and contributing climatic drivers. We argue that the dissolution of the “Mesta”, the biggest transhumance livestock organization in Europe lasting from the 13th to the 19th centuries, led to more extensive grazing and uncontrolled use of forests and grasslands which likely contributed to increased wildfire incidence. Additionally, 1893 was characterized by anomalously warm spring temperatures which may have facilitated vegetation flammability. Our approach couples human and climate systems as drivers of historical fire incidence in Mediterranean pine forests.

Envelope analysis links oscillatory and arrhythmic EEG activities to two types of neuronal synchronization

Traditionally, EEG is understood as originating from the synchronous activation of neuronal populations that generate rhythmic oscillations in specific frequency bands. Recently, new neuronal dynamics regimes have been identified (e.g. neuronal avalanches) characterized by irregular or arrhythmic activity. In addition, it is starting to be acknowledged that broadband properties of EEG spectrum (following a 1/f law) are tightly linked to brain function. Nevertheless, there is still no theoretical framework accommodating the coexistence of these two EEG phenomenologies: rhythmic/narrowband and arrhythmic/broadband. To address this problem, we present a new framework for EEG analysis based on the relation between the Gaussianity and the envelope of a given signal. EEG Gaussianity is a relevant assessment because if EEG emerges from the superposition of uncorrelated sources, it should exhibit properties of a Gaussian process, otherwise, as in the case of neural synchronization, deviations from Gaussianity should be observed. We use analytical results demonstrating that the coefficient of variation of the envelope (CVE) of Gaussian noise (or any of its filtered sub-bands) is the constant 4π−1≈0.523, thus enabling CVE to be a useful metric to assess EEG Gaussianity. Furthermore, a new and highly informative analysis space (envelope characterization space) is generated by combining the CVE and the envelope average amplitude. We use this space to analyze rat EEG recordings during sleep-wake cycles. Our results show that delta, theta and sigma bands approach Gaussianity at the lowest EEG amplitudes while exhibiting significant deviations at high EEG amplitudes. Deviations to low-CVE appeared prominently during REM sleep, associated with theta rhythm, a regime consistent with the dynamics shown by the synchronization of weakly coupled oscillators. On the other hand, deviations to high-CVE, appearing mostly during NREM sleep associated with EEG phasic activity and high-amplitude Gaussian waves, can be interpreted as the arrhythmic superposition of transient neural synchronization events. These two different manifestations of neural synchrony (low-CVE/high-CVE) explain the well-known spectral differences between REM and NREM sleep, while also illuminating the origin of the EEG 1/f spectrum.

Aeolian stratigraphy describes ice-age paleoenvironments in unglaciated Arctic Alaska

Terrestrial paleoenvironmental records with high dating resolution extending into the last ice age are rare from the western Arctic. Such records can test the synchronicity and extent of ice-age climatic events and define how Arctic landscapes respond to rapid climate changes. Here we describe the stratigraphy and sedimentology of a yedoma deposit in Arctic Alaska (the Carter Section) dating to between 37,000 and 9000 calibrated radiocarbon years BP (37–9 ka) and containing detailed records of loess and sand-sheet sedimentation, soil development, carbon storage, and permafrost dynamics. Alternation between sand-sheet and loess deposition provides a proxy for the extent and activity of the Ikpikpuk Sand Sea (ISS), a large dune field located immediately upwind. Warm, moist interstadial times (ca. 37, 36.3–32.5, and 15–13 ka) triggered floodplain aggradation, permafrost thaw, reduced loess deposition, increased vegetation cover, and rapid soil development accompanied by enhanced carbon storage. During the Last Glacial Maximum (LGM, ca. 28–18 ka), rapid loess deposition took place on a landscape where vegetation was sparse and non-woody. The most intense aeolian activity occurred after the LGM between ca. 18 and 15 ka when sand sheets fringing the ISS expanded over the site, possibly in response to increasingly droughty conditions as summers warmed and active layers deepened. With the exception of this lagged LGM response, the record of aeolian activity at the Carter Section correlates with other paleoenvironmental records from unglaciated Siberia and Alaska. Overall, rapid shifts in geomorphology, soils, vegetation, and permafrost portray an ice-age landscape where, in contrast to the Holocene, environmental change was chronic and dominated by aeolian processes.

Subcortical evidence for a contribution of arousal to fMRI studies of brain activity

Cortical activity during periods of rest is punctuated by widespread, synchronous events in both electrophysiological and hemodynamic signals, but their behavioral relevance remains unclear. Here we report that these events correspond to momentary drops in cortical arousal and are associated with activity changes in the basal forebrain and thalamus. Combining fMRI and electrophysiology in macaques, we first establish that fMRI transients co-occur with spectral shifts in local field potentials (LFPs) toward low frequencies. Applying this knowledge to fMRI data from the human connectome project, we find that the fMRI transients are strongest in sensory cortices. Surprisingly, the positive cortical transients occur together with negative transients in focal subcortical areas known to be involved with arousal regulation, most notably the basal forebrain. This subcortical involvement, combined with the prototypical pattern of LFP spectral shifts, suggests that commonly observed widespread variations in fMRI cortical activity are associated with momentary drops in arousal.

Quaternary radiolarian biostratigraphy in the subarctic northeastern Pacific (IODP Expedition 341 Site U1417) and synchroneity of bioevents across the North Pacific

Abstract. Expedition 341 of the Integrated Ocean Drilling Program (IODP) retrieved sediment cores spanning the time interval between the Pleistocene and Miocene from the southern Gulf of Alaska. Onboard Pleistocene radiolarian biostratigraphy is hereby refined by increasing the sampling resolution. The 178 core samples from the upper 190 m CCSF-B (Composite Core Depth Scale F-B) of Site U1417 contained faunal elements similar to the northwestern Pacific; for example, the three biozones in the northwestern Pacific (i.e., Eucyrtidium matuyamai, Stylatractus universus and Botryostrobus aquilonaris) were also recognized in the Gulf of Alaska, spanning 1.80–1.13 Ma, 1.13–0.45 Ma, and the last 0.45 Myr, respectively. Based on the age model that we used in this study and the shipboard paleomagnetic reversal events, the first occurrences (FOs) of Amphimelissa setosa and Schizodiscus japonicus in the northeastern Pacific were preliminarily determined to be 1.48 and 1.30 Ma, respectively. The last occurrence (LO) of Eucyrtidium matuyamai and the FO of Lychnocanoma sakaii, both well-established bioevents in the northwestern Pacific, were dated at 0.80 and 1.13 Ma, respectively. The LO of E. matuyamai is a synchronous event at 1.05 ± 0.1 Ma in the North Pacific, while the FOs of A. setosa and S. japonicus at 1.48 and 1.30 Ma, respectively, are significantly older than what has been found elsewhere.