Dans la ceinture parautochtone de la Province de Grenville centrale (réservoir Manicouagan), la datation des structures révèle que l’orogène grenvillien a oblitéré les fabriques antérieures. Ainsi, ...les structures D1 et D2 indiquent un cisaillement inverse à vergence nord, avec respectivement des linéations SSE et SSO. Les structures D3 indiquent un cisaillement oblique-normal à vergence OSO. Une stratégie innovatrice combinant la géochronologie U–Pb sur zircon par ablation laser (LA-ICP-MS) et par abrasion chimique par dilution isotopique (CA-ID-TIMS) contraint l’âge de ces déformations. Les surcroissances internes et externes des grains de zircon d’un leucosome syn-D2, indiquant deux périodes de croissance, sont interprétées respectivement comme les âges de D1 et D2. Le groupe 1 donne un âge
206
Pb/
207
Pb de 1008 ± 18 Ma (LA-ICP-MS) et un âge concordia de 1002 ± 2 Ma (CA-ID-TIMS). Le groupe 2 donne un âge
206
Pb/
207
Pb de 995 ± 21 Ma (LA-ICP-MS) et un âge concordia de 986 ± 4 Ma (CA-ID-TIMS). Une pegmatite tardi-D2 donne un âge
206
Pb/
207
Pb de 961 ± 22 Ma (LA-ICP-MS). L’âge de D1 coïncide avec celui du groupe 1 du leucosome, soit 1002 Ma. En effet, le zircon ne peut croître avant l’anatexie, or ce groupe possède les caractéristiques d’une croissance en présence de fusion partielle et un rubanement migmatitique définit la S1. L’âge de D2 est contraint à 986-961 Ma par la cristallisation du leucosome syn-D2 coïncidant au groupe 2, et celle de la pegmatite tardi-D2. Ainsi, dans la Ceinture parautochtone centrale près de l’ « Allochthon Boundary Thrust » (ABT), la première déformation étant grenvillienne, aucune évidence d’évènement tectono-métamorphique pré-grenvillien n’est préservée.
Past studies of the end-Permian extinction (EPE), the largest biotic crisis of the Phanerozoic, have not resolved the timing of events in southern high-latitudes. Here we use palynology coupled with ...high-precision CA-ID-TIMS dating of euhedral zircons from continental sequences of the Sydney Basin, Australia, to show that the collapse of the austral Permian Glossopteris flora occurred prior to 252.3 Ma (~370 kyrs before the main marine extinction). Weathering proxies indicate that floristic changes occurred during a brief climate perturbation in a regional alluvial landscape that otherwise experienced insubstantial change in fluvial style, insignificant reorganization of the depositional surface, and no abrupt aridification. Palaeoclimate modelling suggests a moderate shift to warmer summer temperatures and amplified seasonality in temperature across the EPE, and warmer and wetter conditions for all seasons into the Early Triassic. The terrestrial EPE and a succeeding peak in Ni concentration in the Sydney Basin correlate, respectively, to the onset of the primary extrusive and intrusive phases of the Siberian Traps Large Igneous Province.
Transformers trained with self-supervision using selfdistillation loss (DINO) have been shown to produce attention maps that highlight salient foreground objects. In this paper, we show a graph-based ...method that uses the selfsupervised transformer features to discover an object from an image. Visual tokens are viewed as nodes in a weighted graph with edges representing a connectivity score based on the similarity of tokens. Foreground objects can then be segmented using a normalized graph-cut to group self-similar regions. We solve the graph-cut problem using spectral clustering with generalized eigen-decomposition and show that the second smallest eigenvector provides a cutting solution since its absolute value indicates the likelihood that a token belongs to a foreground object. Despite its simplicity, this approach significantly boosts the performance of unsupervised object discovery: we improve over the recent state-of-the-art LOST by a margin of 6.9%, 8.1%, and 8.1% respectively on the VOC07, VOC12, and COCO20K. The performance can be further improved by adding a second stage class-agnostic detector (CAD). Our proposed method can be easily extended to unsupervised saliency detection and weakly supervised object detection. For unsupervised saliency detection, we improve IoU for 4.9%, 5.2%, 12.9% on ECSSD, DUTS, DUT-OMRON respectively compared to state-of-the-art. For weakly supervised object detection, we achieve competitive performance on CUB and ImageNet. Our code is available at: https://www.m-psi.fr/Papers/TokenCut2022/
The authors present their "lived-with" experience with an end-user development (EUD) prototype deployed in their home and show how the results overlap and complement findings from more traditional ...approaches to the study of EUD for the home. This article is part of a special issue on domestic pervasive computing.
A strategy for the generation of heterotrimetallic double cavity (DC) cages PdnPtmL46+ (DC1: n=1, m=2; and DC2: n=2, m=1) is reported. The DC cages were generated by combining an inert platinum(II) ...tetrapyridylaldehyde complex with a suitably substituted pyridylamine and PdII ions. 1H and DOSY nuclear magnetic resonance spectroscopy (NMR) and electrospray ionization mass spectrometry (ESIMS) data were consistent with the formation of the DC architectures. DC1 and DC2 were shown to interact with several different guest molecules. The structure of DC1, which features two identical cavities, binding two 2,6‐diaminoanthraquinone (DAQ) guest molecules was determined by single‐crystal X‐ray crystallography. In addition, DC1 was shown to bind two molecules of 5‐fluorouracil (5‐FU) in a statistical (non‐cooperative) manner. In contrast, DC2, which features two different cage cavities, was found to interact with two different guests, 5‐FU and cisplatin, selectively.
A method for the synthesis of two heterotrimetallic double cavity cages, PdnPtmL46+, (where n=1 and m =2 or n=2 and m=1) is described. The cages are shown to interact with several different guest molecules. The cage with two identical cavities can bind two identical guest molecules in a non‐cooperative fashion, whereas the cage with two different cavities can bind two different guests in a segregated manner.
The pose of a rigid object is usually regarded as a rigid transformation, described by a translation and a rotation. However, equating the pose space with the space of rigid transformations is in ...general abusive, as it does not account for objects with proper symmetries—which are common among man-made objects. In this article, we define pose as a distinguishable static state of an object, and equate a pose to a set of rigid transformations. Based solely on geometric considerations, we propose a frame-invariant metric on the space of possible poses, valid for any physical rigid object, and requiring no arbitrary tuning. This distance can be evaluated efficiently using a representation of poses within a Euclidean space of at most 12 dimensions depending on the object’s symmetries. This makes it possible to efficiently perform neighborhood queries such as
radius searches
or
k-nearest neighbor searches
within a large set of poses using off-the-shelf methods. Pose averaging considering this metric can similarly be performed easily, using a projection function from the Euclidean space onto the pose space. The practical value of those theoretical developments is illustrated with an application of pose estimation of instances of a 3D rigid object given an input depth map, via a Mean Shift procedure.
U–Th–Pb zircon geochronology is an essential tool for quantifying the emplacement, differentiation and thermal evolution of crustal magmatic systems. However, the power of U–Pb zircon dates can be ...enhanced through complementary characterization of mineral texture and geochemistry, as this permits more detailed interpretations of geochronological datasets than conventionally achieved. Our approach to better relating zircon dates and geological processes consists of a multi-method analytical workflow, including cathodoluminescence imaging (CL), in situ LA-ICPMS/EPMA zircon geochemistry, U–Pb zircon ID-TIMS geochronology, and solution ICPMS zircon Trace Element Analysis (U–Pb TIMS-TEA). These methods are here applied to zircon from the Bergell Intrusion, a composite Alpine pluton preserving a ~10km mid-crustal transect. Hand samples of tonalite, granodiorite and hybridized granitoid each record 250–700kyr of autocrystic zircon growth. Bergell zircons are ubiquitously zoned with ca. 104–106yr growth histories, as evidenced by ID-TIMS analysis of microsampled fragments from single crystals. U–Pb TIMS-TEA data exhibit compositional trends on multiple spatiotemporal scales, including the handsample-scale, representing in situ differentiation at the emplacement level (e.g., Th/U); lithology-scale, defining trajectories corresponding to the production of tonalitic versus granodioritic magmas (Lu/Hf); and pluton-scale, indicating increasingly-evolved melts over ~1.6Myr of pluton assembly (Zr/Hf). These absolute TIMS-TEA temporal trends are corroborated by relative LA-ICPMS/EPMA core-to-rim geochemistry. We compare records of trace element evolution from TIMS-TEA, Bergell whole-rock geochemistry, and a global compilation of whole-rock geochemical data. These findings support zircon compositional evolution as a robust indicator of differentiation at local and crustal scales, and provide key empirical constraints on melt differentiation and cooling timescales in the middle crust.
•Introduction of zircon workflow, including LA-ICPMS transects, ID-TIMS geochronology, and solution ICPMS geochemistry.•Resolution of 104–106yr timescales of single zircon U–Pb age heterogeneity in mid-crustal plutonic rocks by ID-TIMS.•Temporal trends in zircon geochemistry are consistent with handsample-, lithology-, and pluton-scale differentiation.•Zircon growth histories permit determination of ~100–1000°C/Myr cooling rates in the middle to lower crust.
A strategy is presented that enables the quantitative assembly of a heterobimetallic PdPtL44+ cage. The presence of two different metal ions (PdII and PtII) with differing labilities enables the cage ...to be opened and closed selectively at one end upon treatment with suitable stimuli. Combining an inert PtII tetrapyridylaldehyde complex with a suitably substituted pyridylamine and PdII ions led to the assembly of the cage. 1H and DOSY NMR spectroscopy and ESI mass spectrometry data were consistent with the quantitative formation of the cage, and the heterobimetallic structure was confirmed using single‐crystal X‐ray crystallography. The structure of the host–guest adduct with a 2,6‐diaminoanthraquinone guest molecule was determined. Addition of N,N′‐dimethylaminopyridine (DMAP) resulted in the formation of the open‐cage PtL42+ compound and Pd(DMAP)42+ complex. This process could then be reversed, with the reformation of the cage, upon addition of p‐toluenesulfonic acid (TsOH).
Open, sesame! A method for the quantitative assembly of the heterobimetallic cage, PdPtL44+, is described. The cage interacts with quinone guest molecules in a 1:1 fashion. The cage can be selectively and reversibly opened and then re‐closed at the PdII end by the sequential addition of base then acid. Guest molecules can be reversibly released/bound during this process.
High‐precision ID‐TIMS U‐Pb zircon ages for 12 interstratified tuffs and tonsteins are used to radiometrically calibrate the detailed lithostratigraphic, cyclostratigraphic, and biostratigraphic ...framework of the Carboniferous Donets Basin of eastern Europe. Chemical abrasion of zircons, use of the internationally calibrated EARTHTIME mixed U‐Pb isotope dilution tracer, and improved mass spectrometry guided by detailed error analysis have resulted in an age resolution of <0.05%, or ∼100 ka, for these Carboniferous volcanics. This precision allows the resolution of time in the Milankovitch band and confirms the long‐standing hypothesis that individual high‐frequency Pennsylvanian cyclothems and bundles of cyclothems into fourth‐order sequences are the eustatic response to orbital eccentricity (∼100 and 400 ka) forcing. Tuning of the fourth‐order sequences in the Donets Basin to the long‐period eccentricity cycle results in a continuous age model for the Middle to Late Pennsylvanian (Moscovian‐Kasimovian‐Ghzelian) strata of the basin and their record of biological and climatic changes through the latter portion of the late Paleozoic Ice Age. Detailed fusulinid and conodont zonations allow the export of this age model to sections throughout Euramerica. Additional ages for Mississippian strata provide among the first robust radiometric calibration points within this subperiod and result in variable lowering of the base ages of its constituent stages compared to recent global time scale compilations.
Calibrating the End-Permian Mass Extinction Shen, Shu-zhong; Crowley, James L.; Wang, Yue ...
Science (American Association for the Advancement of Science),
12/2011, Volume:
334, Issue:
6061
Journal Article
Peer reviewed
The end-Permian mass extinction was the most severe biodiversity crisis in Earth history. To better constrain the timing, and ultimately the causes of this event, we collected a suite of ...geochronologic, isotopie, and biostratigraphic data on several well-preserved sedimentary sections in South China. High-precision U-Pb dating reveals that the extinction peak occurred just before 252.28 ± 0.08 million years ago, after a decline of 2 per mil (%◦) in ¹³ C over 90,000 years, and coincided with a δ¹³ C excursion of -5%◦ that is estimated to have lasted < 20,000 years. The extinction interval was less than 200,000 years and synchronous in marine and terrestrial realms; associated charcoal-rich and soot-bearing layers indicate widespread wildfires on land. A massive release of thermogenic carbon dioxide and/or methane may have caused the catastrophic extinction.
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