Prominent Boundary Research Articles

Gas-surface interaction in rarefied gas flows through long capillaries via the linearized Boltzmann equation with various boundary conditions

Reliable gas–surface interaction modeling is of major importance in consistent simulation of rarefied gas flows with applications in vacuum technology and micro-electromechanical systems. The effectiveness of the most prominent kinetic boundary conditions, namely the ones by Maxwell, Cercignani-Lampis and Epstein, is elaborated by numerically solving the classical plane Poiseuille and thermal creep flows via the linearized Boltzmann equation, subject to these boundary conditions. The flow rates are provided in a wide range of the gas rarefaction for many values of the accommodation coefficients of each scattering kernel, identifying in parallel, the sensitivity of the flow rates in small variations of the free parameters. A comparison with available experimental data is performed to deduce that the Cercignani-Lampis and Epstein scattering kernels, compared to the Maxwell one, are more suitable to characterize coupled momentum and energy accommodation modes. With these boundary conditions, the accommodation coefficients may be extracted by fitting computations with measurements, in the Poiseuille flow in a wide range of gas rarefaction, but in the thermal creep flow, experimental data under rarefied conditions, as high as possible, are recommended. The present work may be useful in determining the measurement conditions and uncertainties, allowing accurate extraction of the accommodation coefficients.

Taxonomic re-appraisal for toothfish (Dissostichus: Notothenioidea) across the Antarctic Polar Front using genomic and morphological studies.

The Patagonian toothfish, Dissostichus eleginoides, is one of the largest predatory fishes inhabiting Southern Ocean waters spanning the Antarctic Polar Front (APF), a prominent biogeographic boundary restricting gene flow and driving species divergence between Antarctic and sub-Antarctic waters. In the light of emerging threats to toothfish conservation and sustainability, this study investigated genetic [mtDNA sequences and genome wide nuclear single nucleotide polymorphisms (SNPs)] and morphological data to critically evaluate the taxonomic status of toothfish north (Chile and Patagonian shelf) and south (South Georgia and South Sandwich Islands) of the APF. mtDNA revealed reciprocally monophyletic lineages on either side of the APF with coalescent analysis indicating these diverged during the Pleistocene. Integration with data from other sources suggests the Chilean/Patagonian lineage is endemic. SNP analysis confirmed restricted nuclear gene flow between both groups and revealed a consensus suite of positive outlier SNPs compatible with adaptive divergence between these groups. Finally, several morphological features permit unequivocal assignment of individuals to either of the clades. Based on the genetic, phenotypic and ecological divergence, the authors propose that toothfish on either side of the APF be recognised as distinct species, with the name D. eleginoides used for toothfish occurring in South American waters north of the APF and toothfish south of the APF being classified using the new name D. australis reflecting their southern distribution.

Overcoming the liability of origin: cross-listing in developed economies as a signal

PurposeThe purpose of this paper is to investigate the role of cross-listing in overcoming liability of origin (LOO) facing emerging economy corporations (EECs).Design/methodology/approachThis paper takes Chinese firms' cross-listing in Hong Kong and the firms' establishment of international joint ventures (IJVs) with foreign partners as the research setting. This is an empirical study using Heckman's self-selection model as the primary econometric technique and two-stage least square (2SLS) regressions as the supplementary estimation procedure.FindingsCross-listing in developed economies can serve as a signal for EECs to overcome the LOO. In addition, the regional institutional voids of emerging economies (EEs) and state ownership are prominent boundary conditions shaping this effect.Research limitations/implicationsOnly Chinese firms and the firms' cross-listing in Hong Kong are considered for the empirical context as a result of data availability.Practical implicationsThis paper provides a practical solution for EECs whose internationalisation tends to be hindered by the LOO.Originality/valueThis study is of high importance in that it centres on a distinctive and challenging problem faced with EECs—the LOO. Besides, it ascribes this liability to a matter of information asymmetries and explores how cross-listing can serve as a signal to cope with this challenge.

Interplay between CTCF boundaries and a super enhancer controls cohesin extrusion trajectories and gene expression

To understand how chromatin domains coordinate gene expression, we dissected select genetic elements organizing topology and transcription around the Prdm14 super enhancer in mouse embryonic stem cells. Taking advantage of allelic polymorphisms, we developed methods to sensitively analyze changes in chromatin topology, gene expression, and protein recruitment. We show that enhancer insulation does not rely strictly on loop formation between its flanking boundaries, that the enhancer activates the Slco5a1 gene beyond its prominent domain boundary, and that it recruits cohesin for loop extrusion. Upon boundary inversion, we find that oppositely oriented CTCF terminates extrusion trajectories but does not stall cohesin, while deleted or mutated CTCF sites allow cohesin to extend its trajectory. Enhancer-mediated gene activation occurs independent of paused loop extrusion near the gene promoter. We expand upon the loop extrusion model to propose that cohesin loading and extrusion trajectories originating at an enhancer contribute to gene activation.

An efficient brain tumor image classifier by combining multi-pathway cascaded deep neural network and handcrafted features in MR images.

Accurate segmentation and delineation of the sub-tumor regions are very challenging tasks due to the nature of the tumor. Traditionally, convolutional neural networks (CNNs) have succeeded in achieving most promising performance for the segmentation of brain tumor; however, handcrafted features remain very important in identification of tumor's boundary regions accurately. The present work proposes a robust deep learning-based model with three different CNN architectures along with pre-defined handcrafted features for brain tumor segmentation, mainly to find out more prominent boundaries of the core and enhanced tumor regions. Generally, automatic CNN architecture does not use the pre-defined handcrafted features because it extracts the features automatically. In this present work, several pre-defined handcrafted features are computed from four MRI modalities (T2, FLAIR, T1c, and T1) with the help of additional handcrafted masks according to user interest and fed to the convolutional features (automatic features) to improve the overall performance of the proposed CNN model for tumor segmentation. Multi-pathway CNN is explored in this present work along with single-pathway CNN, which extracts simultaneously both local and global features to identify the accurate sub-regions of the tumor with the help of handcrafted features. The present work uses a cascaded CNN architecture, where the outcome of a CNN is considered as an additional input information to next subsequent CNNs. To extract the handcrafted features, convolutional operation was applied on the four MRI modalities with the help of several pre-defined masks to produce a predefined set of handcrafted features. The present work also investigates the usefulness of intensity normalization and data augmentation in pre-processing stage in order to handle the difficulties related to the imbalance of tumor labels. The proposed method is experimented on the BraST 2018 datasets and achieved promising results than the existing (currently published) methods with respect to different metrics such as specificity, sensitivity, and dice similarity coefficient (DSC) for complete, core, and enhanced tumor regions. Quantitatively, a notable gain is achieved around the boundaries of the sub-tumor regions using the proposed two-pathway CNN along with the handcrafted features. Graphical Abstract This data is mandatory. Please provide.

A Plio-Pleistocene (c. 0–4 Ma) cyclostratigraphy for IODP Site U1478 (Mozambique Channel, SW Indian Ocean): Exploring an offshore record of paleoclimate and ecosystem variability in SE Africa

The paleoclimate and ecosystem variability in Africa during the Plio/Pleistocene has received considerable attention due to its potential links to hominid evolution. However, the reconstruction of this variability hinges critically upon highly temporally resolved proxy data from continuous, well-dated sediment archives. In light of these requirements we use a new XRF core-scanning record from International Ocean Discovery Program (IODP) Site U1478 off the Limpopo River mouth (Mozambique Channel, SW Indian Ocean) spanning the past c. 4 Ma to identify the climate variability in SE Africa. Our results show that the elemental distribution in the Site U1478 cores is mainly controlled by the rate of terrigenous input and – to a lesser extent – by bottom-current transport and post-depositional processes such as propagation of paleoredox boundaries and diagenesis across some intervals. The log(Ti/Ca) ratio, which is used as a tracer of terrigenous sediment input, shows quasi-cyclical variability across the entire record that closely matches the periods of orbital parameters. However, the cyclical behaviour of the log(Ti/Ca) signal varies through time, with the uppermost 106 m of the sequence (0–1.07 Ma) displaying a mix of precession and obliquity signals, the intervals 106–223 m (1.07–2.80 Ma) and 240–257 m (3.68–4.05 Ma) being dominated by precession, and the interval 223–240 m (2.80–3.68 Ma) being controlled by eccentricity. To refine the available chronology for Site U1478, which is based on shipboard biostratigraphic and paleomagnetic data, we have tuned the log(Ti/Ca) record to the LR04 benthic oxygen isotope record, summer insolation at 25° S, and orbital eccentricity depending on the dominant cyclicities in the XRF dataset across individual time intervals. The resulting chronology enables us to evaluate the XRF data as well as the previously available shipboard sedimentological and geochemical datasets within a regional and global climatic context. This allows the connection of a c. 7-m-thick contourite deposit and a prominent paleoredox boundary to hydroclimate and ocean-circulation changes during the early Pleistocene and across the Mid-Pleistocene Transition, respectively. Moreover, a decoupling of the log(Ti/Ca) and the log(Ti/K) records, with the latter indicating the degree of sediment weathering, from 3.2 to 2.8 Ma points to an increased delivery of highly weathered sediments to Site U1478. We attribute this to temporarily wetter and warmer conditions in the catchment of the Limpopo River and/or a change in the sediment source, perhaps associated with the tectonically driven enlargement of the Zambezi River catchment during the late Pliocene/early Pleistocene.

Recovery and recrystallisation during creep exposure of cold worked Ti-modified 14Cr–15Ni austenitic stainless steel

ABSTRACT Creep behaviour of Ti-modified 14Cr–15Ni austenitic stainless steel in solution annealed, 20%, 30%, and 40% cold-worked conditions, was studied at 973 K and 175 MPa stress level in the current investigation. Increase in cold-work level resulted in denser dislocation network resulting in prominent low-angle grain boundaries. Low-angle boundary fraction increased as the amount of cold working increased from 20% to 40% prior to creep loading. The variation in the fraction of low-angle boundaries impacted the creep rupture strength of the steel. During creep exposure of the cold-worked steels, softening occurred due to both recovery and recrystallisation. The extent to which recrystallisation and recovery occurred during creep was dependent on the level of cold work. Subgrain formation and recrystallisation resulted in enhanced recovery and decreased the creep strength of 40% cold-worked steel. The creep rupture life was highest for 30% cold-worked steel.

Competing modes of assembly restrict amyloid formation by a neurodegenerative protein, TDP43

The accumulation of aberrant deposits of specific protein(s) in the brain is a hallmark of many neurodegenerative diseases including amyotrophic lateral sclerosis (TDP43) and frontotemporal lobar degeneration (FUS and/or TDP43). These proteins exhibit “prion‐like” low complexity domains (LCDs), with the defining property of templating their own assembly into highly ordered aggregates known as amyloid. Structural biology investigations from other labs have revealed a multitude of TDP‐43 self‐assembly modes in vitro, ranging from cooperatively folding alpha‐helices to amyloid‐like beta‐sheets of varying stability. However, the extent to which these assembly modes occur in the intracellular environment, and their full relationship to physiological and/or pathological self‐assembly, have not yet been feasible to study.To interrogate mechanistic features of amyloid nucleation by the TDP43 LCD in the cellular milieu, I employed a recently developed FRET‐based flow cytometry approach along with rational mutagenesis informed by existing structural models. I observed that the LCD transitions from monomers to small condensates with a prominent phase boundary. I further found that these condensates were qualitatively distinct from amyloid, and that amyloid occurred probabilistically and only in cells harboring pre‐existing amyloids of other pathogenic proteins.Mutations designed to enhance or disrupt alpha‐helicity exhibited corresponding effects on non‐amyloid condensation, confirming the role of this assembly mode in non‐pathogenic aggregation. Remarkably, amyloid formation exhibited the opposite dependence, with strong alpha‐helix‐promoting mutations eliminating amyloid formation altogether. Mutations designed to probe the role of cooperative beta‐sheet formation revealed that amyloid‐like interactions either promote or inhibit amyloid formation depending on their stability. Importantly, I verified that the full‐length protein follows the same aggregation pathway, but does so at lower concentrations due to additional homotypic interactions mediated by non‐LCD domains. In summary, my data suggested the tendency of TDP43 toward amyloid is balanced by competing alternative modes of self‐assembly.Support or Funding InformationNIH Director’s Early Independence Award DP5‐OD009152 (to RH), the University of Kansas Alzheimer’s Disease CenterStowers Institute for Medical Research

Spatiotemporal Evolution of the Microphysical and Thermodynamic Characteristics of the 20 June 2015 PECAN MCS

Abstract This study examines microphysical and thermodynamic characteristics of the 20 June 2015 mesoscale convective system (MCS) observed during the Plains Elevated Convection At Night (PECAN) experiment, specifically within the transition zone (TZ), enhanced stratiform rain region (ESR), anvil region, melting layer (ML), and the rear inflow jet (RIJ). Analyses are developed from airborne optical array probe data and multiple-Doppler wind and reflectivity syntheses using data from the airborne NOAA Tail Doppler Radar (TDR) and ground-based Weather Surveillance Radar-1988 Doppler (WSR-88D) radars. Seven spiral ascents/descents of the NOAA P-3 aircraft were executed within various regions of the 20 June MCS. Aggregation modified by sublimation was observed in each MCS region, regardless of whether the sampling was within the RIJ. Sustained sublimation and evaporation of precipitation in subsaturated layers led to a trend of downward moistening across the ESR spirals, with greater degrees of subsaturation maintained when in the vicinity of the descending RIJ. In all cases where melting was observed, the ML acted as a prominent thermodynamic boundary, with differing rates of change in temperature and relative humidity above and below the ML. Two spiral profiles coincident with the rear inflow notch provided unique observations within the TZ and were interpreted in the context of similar observations from the 29 June 2003 Bow Echo and Mesoscale Convective Vortex Experiment MCS. There, sublimation cooling and enhanced descent within the RIJ allowed ice particles to survive to temperatures as warm as +6.8°C before completely sublimating/evaporating.

Llywarch Hen’s Dyke: Place and Narrative in Early Medieval Wales

Dykes must have been important features within the early medieval landscape, but scarcely attract more than cursory discussion in archaeological literature focused on Wales and western Britain. Analysis of a dyke recorded in a boundary clause attached to an eighth century charter in the Book of Llandaff demonstrates how a multidisciplinary approach can garner new insights into the function and significance of dykes in the early medieval landscape. Llywarch Hen’s Dyke defined a large part of the bounds of Llan-gors, a royal estate in the kingdom of Brycheiniog. On the ground the dyke is represent by a prominent agricultural land boundary, but the monument also operated as a ‘mnemonic peg’ through which oral traditions associated with power and place were narrated.

From Product to Dust: Looking at the Ways to Regenerate Value in Product Life Cycle

AbstractThe shift from linear to circular patterns is on the way and rise many questions. In the last ten years, reuse and upcycling are gaining more attention. Since reduce and reuse were describe as a priority by the European Union, some leading projects are unveiled in different countries. Scale and quality of those projects push the reuse issue out of the shadow, far from original prejudices who associate waste and reuse to « poverty » and « Do It Yourself ». Although Reuse emerge as a prominent question, the idea and boundaries of « what is reuse » appears to be blur and not clearly understood. This situation lead to general incomprehension, even for professionals. Reuse, repurpose, upcycling and recycling are usually considered to wear the same meaning despite a huge difference on what it implies.In this paper we will examine these different notions through a pedagogical case study. We will draw the different ways to regenerate value at all steps of product life cycle in a precise manner. This allows to better insight the meaning of those issues in the case of student design education. In the same time, it aims to be a tool for teaching sustainable design and waste management.

Low temperature synthesis and characterization of nano‐crystalline Mg(Zr0.05Ti0.95)O3 ceramics

AbstractMg(Zr0.05Ti0.95)O3 (MZrT) ceramics nanoparticles have been synthesized by polyol method for the first time. The phase evaluation of the MZrT nanoparticles was confirmed using thermo gravimetric analysis and the phase purity of the samples were analyzed using X‐ray diffraction and Raman spectroscopy. The transmission electron microscopy (TEM) images revealed the average particle size between 30 and 40 nm. The optical bandgap is in the range of 3.66‐3.82 eV and is attributed to the quantum confinement effect. Interestingly, the nanopowders sintered at 950°C for 3 hours exhibit the maximum density of 97.52% of the theoretical density which is attributed to the higher sintering velocity of the smaller particles. The obtained microstructure of the ceramics reveals porous free uniform microstructure with prominent grain boundaries. A best combination of microwave dielectric properties (εr ~18.04, Q × fo ~175 THz at 9.5 GHz) are obtained for MZrT ceramics sintered at 950°C for 3 hours. The non‐Debye‐like relaxation process is found to exist inside the sample confirmed by impedance spectroscopy. The AC conduction mechanism is explained on the basis of Correlated Barrier Hopping model. Thermal conductivity of the MZrT ceramics is found to be 10 W/mK. The obtained properties of MZrT ceramics are suitable for resonator, microwave integrated circuit and LTCC applications.

New insights into Cenomanian paleoceanography and climate evolution from the Tarfaya Basin, southern Morocco

A 325 m long continuous succession of uppermost Albian to lower Turonian pelagic (outer shelf) deposits was recovered from a new drill site in the central part of the Tarfaya Basin (southern Morocco). Natural gamma ray wireline logging, carbonate and organic carbon content, bulk carbonate and organic carbon stable isotopes and X-ray fluorescence (XRF)-scanner derived elemental distribution data in combination with planktonic foraminiferal biostratigraphy indicate complete recovery of the Cenomanian Stage. This exceptional sediment archive allows to identify orbitally driven cyclic sedimentation patterns and to evaluate the pacing of climatic events and regional environmental change across the Albian-Cenomanian boundary (ACB), the mid-Cenomanian Event (MCE) and Oceanic Anoxic Event 2 (OAE2) in the latest Cenomanian. The deposition of organic-rich sediments in the Tarfaya Basin, likely driven by upwelling of nutrient-rich water masses, started during the latest Albian and intensified in two major steps following the MCE and the onset of OAE2. The duration and structure of the MCE and OAE2 carbon isotope excursions exhibit striking similarities, suggesting common driving mechanisms and climate-carbon cycle feedbacks. Both events were also associated with eustatic sea level falls, expressed as prominent sequence boundaries in the Tarfaya Basin. Based on the 405 kyr signal imprinted on the Natural Gamma Ray (NGR) and XRF-scanner derived Log(Zr/Rb) records, we estimate the duration of the Cenomanian Stage to be 4.8 ± 0.2 Myr.

Analysis of the stress field and strain rate in Zagros-Makran transition zone

Transition boundary between Zagros continental collision and Makran oceanic-continental subduction can be specified by two wide limits: (a) Oman Line is the seismicity boundary with a sizeable reduction in seismicity rate from Zagros in the west to Makran in the east; and (b) the Zendan-Minab-Palami (ZMP) fault system is believed to be a prominent tectonic boundary. The purpose of this paper is to analyze the stress field in the Zagros-Makran transition zone by the iterative joint inversion method developed by Vavrycuk (Geophysical Journal International 199:69-77, 2014). The results suggest a rather uniform pattern of the stress field around these two boundaries. We compare the results with the strain rates obtained from the Global Positioning System (GPS) network stations. In most cases, the velocity vectors show a relatively good agreement with the stress field except for the Bandar Abbas (BABS) station which displays a relatively large deviation between the stress field and the strain vector. This deviation probably reflects a specific location of the BABS station being in the transition zone between Zagros continental collision and Makran subduction zones.

Integrating traditional field methods with emerging digital techniques for enhanced outcrop analysis of deep water channel-fill deposits

The development of emerging digital technologies that allow the collection and analysis of field data represents a significant innovation in field-based geological studies. The integration of these digital techniques with traditional sedimentological field methods facilitates considerable improvements in outcrop characterization. An example of this integrated modern approach for geological data collection is employed for the detailed characterization of a turbidite channel-lobe system of the Gorgoglione Flysch Formation in Southern Italy. The study area, exposed above the village of Castelmezzano, has been measured and described in detailed stratigraphic sections, providing data for both sedimentological analysis and correlation of the stratigraphy. In order to gain a complete perspective on the exposure and stratigraphic elements, analysis of physical outcrop data was enhanced by the use of high-resolution Gigapixel imagery and 3D photogrammetric outcrop reconstructions. The Santa Maria section has been assessed in terms of vertical and lateral facies stacking arrangements and subdivided into two component facies associations separated by a prominent concave-up erosional boundary. The lower facies association, interpreted as a frontal lobe complex, consists of tabular, thick-bedded coarse sandstones interbedded with persistent heterolithic packages of thin-bedded sandstones and mudstones, and minor soft-sediment deformed strata. The upper facies association represents the infill of a channel-form and consists of a basal conglomerate, passing gradually upwards into massive amalgamated sandstones overlain by large-scale cross-laminated sandstones. The excellent exposure of the Santa Maria section records the complete evolution of a channel-lobe system, transitioning from frontal lobe deposition through channel incision and bypass, to progressive backfilling. This study shows how facies characterization, stratigraphic correlations and reconstruction of the depositional architectures have been substantially enhanced by the use of emerging digital techniques for geological data collection.

Application and Implementation of Incorporating Local Boundary Conditions into Nonlocal Problems

ABSTRACTWe study nonlocal equations from the area of peridynamics, an instance of nonlocal wave equation, and nonlocal diffusion on bounded domains whose governing equations contain a convolution operator based on integrals. We generalize the notion of convolution to accommodate local boundary conditions. On a bounded domain, the classical operator with local boundary conditions has a purely discrete spectrum, and hence, provides a Hilbert basis. We define an abstract convolution operator using this Hilbert basis, thereby automatically satisfying local boundary conditions. The main goal in this paper is twofold: apply the concept of abstract convolution operator to nonlocal problems and carry out a numerical study of the resulting operators. We study the corresponding initial value problems with prominent boundary conditions such as periodic, antiperiodic, Neumann, and Dirichlet. To connect to the standard convolution, we give an integral representation of the abstract convolution operator. For discretization, we use a weak formulation based on a Galerkin projection and use piecewise polynomials on each element which allows discontinuities of the approximate solution at the element borders. We study convergence order of solutions with respect to polynomial order and observe optimal convergence. We depict the solutions for each boundary condition.

Orogen transplant: Taconic–Caledonian arc magmatism in the central Brooks Range of Alaska

The Doonerak fenster of the central Brooks Range, Alaska, exposes a unique package of Cambrian−Devonian(?) volcanic and sedimentary basement rocks (Apoon assemblage) within the Mesozoic−Cenozoic Brookian fold-and-thrust belt. Recognition of a major pre-Mississippian unconformity within the fenster led to previous correlations between the Apoon assemblage and age-equivalent strata in the North Slope subterrane of the composite Arctic Alaska−Chukotka microplate. Previous age constraints on the Apoon assemblage are limited to a handful of Cambrian−Devonian paleontological collections and hornblende K-Ar and 40 Ar/ 39 Ar ages from mafic dikes ranging from ca. 520 to 380 Ma. We conducted U-Pb and Hf isotopic analyses on igneous and sedimentary units in the Apoon assemblage to test links with the North Slope subterrane and assess the tectonic and paleogeographic setting of this early Paleozoic arc complex. Igneous zircon from a leucogabbro in the Apoon assemblage analyzed using a sensitive high-resolution ion microprobe with reverse geometry (SHRIMP-RG) provided a 207 Pb-corrected 206 Pb/ 238 U age of 462 ± 8 Ma (2σ). Detrital zircon analyzed using laser ablation−inductively coupled plasma−mass spectrometry (LA-ICP-MS) from volcaniclastic and tuffaceous strata of the Apoon assemblage yielded a spectrum of unimodal and polymodal age populations, including prominent age groups at ca. 490−420, 540−520 Ma, 1250−960, 1500−1380, 1945−1750, and 2830−2650 Ma. Lu-Hf isotopic data from the ca. 490−420 Ma age population, including the Middle Ordovician leucogabbro, are highly juvenile (e Hf ∼+7−10), implying a distinct lack of crustal assimilation during Ordovician−Silurian arc magmatism. In context, these data suggest that a juvenile arc complex, herein referred to as the Doonerak arc, marks a prominent tectonic boundary between pre-Mississippian crustal fragments of Laurentian- and non-Laurentian affinity in the Arctic Alaska−Chukotka microplate. The U-Pb geochronologic and Hf isotopic data also provide a connection to Taconic−Caledonian arc magmatism along the edge of the Iapetus Ocean and linkages between the Apoon assemblage and the Descon Formation and plutonic equivalents of the Alexander terrane (Prince of Wales Island, Alaska).

Zircon U-Pb ages and Hf isotopic systematics of charnockite gneisses from the Ediacaran–Cambrian high-grade metamorphic terranes, southern India: Constraints on crust formation, recycling, and Gondwana correlations

The Southern Granulite terrane, southern India, comprises a vast exposure of deep crust and forms a key region in the reconstruction of the Gondwana supercontinent. An E-W−trending crustal-scale shear zone, the Palghat-Cauvery suture zone system, which formed during the late Neoproterozoic−Cambrian (0.75−0.50 Ga), marks a prominent terrane boundary separating terranes with a predominantly late Neoarchean (ca. 2.5 Ga) regional granulite metamorphism to the north from those with an Ediacaran−Cambrian (0.63−0.50 Ga) regional granulite metamorphism to the south. Focusing on the younger granulite metamorphic domains, we present here new zircon U-Pb ages and Hf isotopic compositions for 11 charnockite orthogneisses from the Madurai, Trivandrum, and Nagercoil blocks and contribute to the resolution of the age of their magmatic protoliths. This study shows that the charnockite orthogneisses south of the Palghat-Cauvery suture zone relate to a minimum of four distinct episodes of felsic magmatism centered at: ca. 2.62−2.46 Ga, ca. 2.05−1.84 Ga, ca. 1.0−0.9 Ga, and ca. 0.80−0.76 Ga, pertaining to the Siderian, Orosirian, and Tonian Periods. Hafnium isotope analyses of zircon grains from the charnockite gneisses suggest that the protoliths of the ca. 2.05−1.98 Ga gneisses from the Trivandrum and Nagercoil blocks and the ca. 1.0−0.9 Ga gneisses along the southeastern Madurai block involved a significant juvenile magma component, while the protoliths of charnockite gneisses elsewhere in the Madurai block formed mainly through recycling of older crust up to ca. 3.2 Ga. A regional granulite-facies metamorphic imprint during the Ediacaran−Cambrian marked an advanced stage in the amalgamation of the Madurai, Trivandrum, and Nagercoil blocks into the East African orogen and its collision with the Dharwar craton.

Prosody and the Acquisition of Hierarchical Structure in Toddlers and Adults

Though language manifests linearly, one word at a time, children must learn that words are embedded in constituents, which are in turn embedded in larger constituents. That is, they must learn that syntax is hierarchically structured. Prosody—speech melody and rhythm—is likewise hierarchically organized, with smaller prosodic constituents embedded in larger ones. This paper presents results showing that 20-month-olds (N = 40) can use modifier + clause prosody to learn constituents at multiple levels in a hierarchically structured artificial grammar, but that they fail to learn from clause + modifier prosody. We consider several explanations for this asymmetry, and suggest that it may be due to the frequency of the two constructions in the input. Two parallel experiments with adults suggest that older learners may not be able to learn the prosodically marked constituents. Instead, adult responses are likely based on perceptually prominent boundary words.

Fault segmentation: New concepts from the Wasatch Fault Zone, Utah, USA

AbstractThe question of whether structural segment boundaries along multisegment normal faults such as the Wasatch fault zone (WFZ) act as persistent barriers to rupture is critical to seismic hazard analyses. We synthesized late Holocene paleoseismic data from 20 trench sites along the central WFZ to evaluate earthquake rupture length and fault segmentation. For the youngest (<3 ka) and best‐constrained earthquakes, differences in earthquake timing across prominent primary segment boundaries, especially for the most recent earthquakes on the north‐central WFZ, are consistent with segment‐controlled ruptures. However, broadly constrained earthquake times, dissimilar event times along the segments, the presence of smaller‐scale (subsegment) boundaries, and areas of complex faulting permit partial‐segment and multisegment (e.g., spillover) ruptures that are shorter (~20–40 km) or longer (~60–100 km) than the primary segment lengths (35–59 km). We report a segmented WFZ model that includes 24 earthquakes since ~7 ka and yields mean estimates of recurrence (1.1–1.3 kyr) and vertical slip rate (1.3–2.0 mm/yr) for the segments. However, additional rupture scenarios that include segment boundary spatial uncertainties, floating earthquakes, and multisegment ruptures are necessary to fully address epistemic uncertainties in rupture length. We compare the central WFZ to paleoseismic and historical surface ruptures in the Basin and Range Province and central Italian Apennines and conclude that displacement profiles have limited value for assessing the persistence of segment boundaries but can aid in interpreting prehistoric spillover ruptures. Our comparison also suggests that the probabilities of shorter and longer ruptures on the WFZ need to be investigated.