Finite mixture models are being used increasingly to model a wide variety of random phenomena for clustering, classification and density estimation.
is a powerful and popular package which allows ...modelling of data as a Gaussian finite mixture with different covariance structures and different numbers of mixture components, for a variety of purposes of analysis. Recently, version 5 of the package has been made available on CRAN. This updated version adds new covariance structures, dimension reduction capabilities for visualisation, model selection criteria, initialisation strategies for the EM algorithm, and bootstrap-based inference, making it a full-featured R package for data analysis via finite mixture modelling.
The appinite suite of rocks offers a unique opportunity to study the effect of water on the generation, emplacement and crystallization history of mafic to felsic magma. The suite consists of a group ...of coeval plutonic and/or hypabyssal rocks, ranging from ultramafic to felsic in composition in which hornblende is the dominant mafic mineral, and typically occurs both as large prismatic phenocrysts and in the finer grained matrix. The suite is also characterized by abundant evidence for mixing and mingling between diverse magma types and variable degrees of contamination by host rock.
Field observations corroborate experimental and theoretical studies that the hornblende stability field expands at the expense of olivine and pyroxene with increasing pH2O in the magma. Textures characteristic of appinites are consistent with rapid growth and with experimental evidence for the reduced viscosity of melts allowing efficient migration of ions to the sites of mineral growth.
The appinite suite was originally defined in the Paleozoic Caledonide orogen in Scotland, where it occurs as a number of small shallow crustal bodies that were emplaced after the cessation of subduction and in the immediate aftermath of terrane collision and closure of the Iapetus Ocean. The mafic component is thought to have been triggered by asthenospheric upwelling following stab break-off, and magmas produced have both juvenile and sub-continental lithospheric mantle components. Its compositions have affinities with shoshonites. The felsic components include large batholiths that were probably derived by fractional crystallization.
Other appinite suites share some, but not all of these characteristics. Appinite suites apparently range in age from Neo-Archean to Recent, and occur at all crustal levels, at depths of up to 40km. In addition to shoshonites, appinite suites share some similar geochemical features with high-Mg andesites, sanukitoids and adakites. Some common tectonic traits include a tendency to form soon after the cessation of subduction, and the important role of deep crustal faults as conduits for magmas of various compositions to rise towards the surface. These conduits provide the setting for magmas of diverse composition to mix and mingle. Neo-Archean appinites, and their genetic relationship with abundant coeval sanukitoids, have been interpreted as evidence for the existence of some form of plate tectonics at that time.
Melting may be triggered by asthenospheric upwelling caused either by slab breakoff (e.g. after terrane or continental collision) or by the generation of a slab window (e.g. where a ridge collides with a subduction zone). Mafic magma may contain a juvenile component, but Nd isotopic data suggest the additional involvement of a sub-continental lithospheric mantle that, in many instances, was previously metasomatized by fluids and magma and was underplated by mafic complexes during subduction. The composition of the mafic magma may vary from one suite to another. In several suites, the mafic magmas have more traditional calc alkalic or tholeiitic affinities and do not share the shoshonitic characteristics of the type area. In addition, in several appinite complexes, felsic magma was formed by crustal anatexis, rather than fractional crystallization.
We present a pre-orogenic, early Paleozoic, palinspastic reconstruction of the northern Gondwana margin that was subsequently involved in the Late Paleozoic Variscan orogeny in central and Western ...Europe. Our reconstruction is based on two pre-orogenic data sets, the age and distribution of Cambrian-Ordovician magmatism and the detrital zircon age signature of late Neoproterozoic-early Paleozoic clastic rocks. We obtain this reconstruction by unfolding the Ibero-Armorican arc and by restoring the movement of the large-scale dextral strike-slip faults that transect the different tectono-stratigraphic units. Our results favour an irregular shape for this part of the northern Gondwana margin with a N-S central segment linking two E-W oriented segments. The proposed reconstruction and the structural restoration of the main features of Variscan deformation is in accordance with some aspects of previously proposed structural models, such as the curved geometry of the Gondwanan margin required by the indentor model for continental collision, the role played by the large strike-slip faults in dispersing formerly juxtaposed units, and the regional-scale oroclinal folding of part of this margin during late Carboniferous-Early Permian times. The combined use of the pre-orogenic geological constraints and palinspastic restoration is a useful approach that may provide a foundation for continual refinement of reconstructions as more data become available.
•Pre-orogenic, early Palaeozoic, palinspastic reconstruction of the northern Gondwana margin.•Two pre-orogenic data sets: age and distribution of Cambrian-Ordovician magmatism and the detrital zircon age signature.•Reconstruction by unfolding the Ibero-Armorican arc and restoring the movement of the large-scale dextral strike-slip faults•Curved geometry of the Gondwanan margin.
In cerebral cortex, ongoing activity absent a stimulus can resemble stimulus-driven activity in size and structure. In particular, spontaneous activity in cat primary visual cortex (V1) has structure ...significantly correlated with evoked responses to oriented stimuli. This suggests that, from unstructured input, cortical circuits selectively amplify specific activity patterns. Current understanding of selective amplification involves elongation of a neural assembly's lifetime by mutual excitation among its neurons. We introduce a new mechanism for selective amplification without elongation of lifetime: “balanced amplification.” Strong balanced amplification arises when feedback inhibition stabilizes strong recurrent excitation, a pattern likely to be typical of cortex. Thus, balanced amplification should ubiquitously contribute to cortical activity. Balanced amplification depends on the fact that individual neurons project only excitatory or only inhibitory synapses. This leads to a hidden feedforward connectivity between activity patterns. We show in a detailed biophysical model that this can explain the cat V1 observations.
Cell engineering, soft robotics, and wearable electronics often desire soft materials that are easy to deform, self‐heal readily, and can relax stress rapidly. Hydrogels, a type of hydrophilic ...networks, are such kind of materials that can be made responsive to environmental stimuli. However, conventional hydrogels often suffer from poor stretchability and repairability. Here, hydrogels consisting of boronic ester dynamic covalent bonds in a double network of poly(vinyl alcohol)/boric acid and chitosan are synthesized, which demonstrate extreme stretchability (up to 310 times the original length), instant self‐healing (within 5 s), and reusability and inherent adhesion. Their instant stress relaxation stems from a low activation energy of the boronic ester bond exchange (≤20 kJ mol−1) and contributes to the extreme stretchability and self‐healing behaviors. Various water‐dispersible additives can be readily incorporated in the hydrogels via hand kneading for potential applications such as soft electronics, bio‐signal sensing, and soft artificial joints.
An extremely stretchable, malleable, adherable, reusable, and tear‐resistible (SMART) hydrogel is synthesized from a double network of poly(vinyl alcohol)/boric acid and chitosan. The instant bond exchange of boronic ester dynamic covalent bonds leads to extreme stretchability and rapid self‐healing and stress relaxation. Various water‐dispersible additives can be readily incorporated in the hydrogels via hand kneading.
Seven rhenium(I) complexes of the general formula fac-Re(CO)3(NN)(OH2)+ where NN = 2,2′-bipyridine (8), 4,4′-dimethyl-2,2′-bipyridine (9), 4,4′-dimethoxy-2,2′-bipyridine (10), dimethyl ...2,2′-bipyridine-4,4′-dicarboxylate (11), 1,10-phenanthroline (12), 2,9-dimethyl-1,10-phenanthroline (13), or 4,7-diphenyl-1,10-phenanthroline (14), were synthesized and characterized by 1H NMR spectroscopy, IR spectroscopy, mass spectrometry, and X-ray crystallography. With the exception of 11, all complexes exhibited 50% growth inhibitory concentration (IC50) values that were less than 20 μM in HeLa cells, indicating that these compounds represent a new potential class of anticancer agents. Complexes 9, 10, and 13 were as effective in cisplatin-resistant cells as wild-type cells, signifying that they circumvent cisplatin resistance. The mechanism of action of the most potent complex, 13, was explored further by leveraging its intrinsic luminescence properties to determine its intracellular localization. These studies indicated that 13 induces cytoplasmic vacuolization that is lysosomal in nature. Additional in vitro assays indicated that 13 induces cell death without causing an increase in intracellular reactive oxygen species or depolarization of the mitochondrial membrane potential. Further studies revealed that the mode of cell death does not fall into one of the canonical categories such as apoptosis, necrosis, paraptosis, and autophagy, suggesting that a novel mode of action may be operative for this class of rhenium compounds. The in vivo biodistribution and metabolism of complex 13 and its 99mTc analogue 13* were also evaluated in naı̈ve mice. Complexes 13 and 13* exhibited comparable biodistribution profiles with both hepatic and renal excretion. High-performance liquid chromatography inductively coupled plasma mass-spectrometry (HPLC-ICP-MS) analysis of mouse blood plasma and urine postadministration showed considerable metabolic stability of 13, rendering this potent complex suitable for in vivo applications. These studies have shown the biological properties of this class of compounds and demonstrated their potential as promising theranostic anticancer agents that can circumvent cisplatin resistance.
Progressive mantle melting during the Earth's earliest evolution led to the formation of a depleted mantle and a continental crust enriched in highly incompatible elements. Re-enrichment of Earth's ...mantle can occur when continental crustal materials begin to founder into the mantle by either subduction or, to a lesser degree, by delamination processes, profoundly affecting the mantle's trace element and volatile compositions. Deciphering when mantle re-enrichment/refertilization became a global-scale process would reveal the onset of efficient mass transfer of crust to the mantle and potentially when plate tectonic processes became operative on a global-scale. Here we document the onset of mantle re-enrichment/refertilization by comparing the abundances of petrogenetically significant isotopic values and key ratios of highly incompatible elements compared to lithophile elements in Archean to Early-Proterozoic mantle-derived melts (i.e., basalts and komatiites). Basalts and komatiites both record a rapid-change in mantle chemistry around 3.2 billion years ago (Ga) signifying a fundamental change in Earth geodynamics. This rapid-change is recorded in Nd isotopes and in key trace element ratios that reflect a fundamental shift in the balance between fluid-mobile and incompatible elements (i.e., Ba/La, Ba/Nb, U/Nb, Pb/Nd and Pb/Ce) in basaltic and komatiitic rocks. These geochemical proxies display a significant increase in magnitude and variability after ~3.2 Ga. We hypothesize that rapid increases in mantle heterogeneity indicate the recycling of supracrustal materials back into Earth's mantle via subduction. Our new observations thus point to a ≥ 3.2 Ga onset of global subduction processes via plate tectonics.
Motivated by the discovery of main group Lewis acids that could compete or possibly outperform the ubiquitous organoboranes, several groups, including ours, have engaged in the chemistry of Lewis ...acidic organoantimony compounds as new platforms for anion capture, sensing, and transport. Principal to this approach are the intrinsically elevated Lewis acidic properties of antimony, which greatly favor the addition of halide anions to this group 15 element. The introduction of organic substituents to the antimony center and its oxidation from the + III to the + V state provide for tunable Lewis acidity and a breadth of applications in supramolecular chemistry and catalysis. The performances of these antimony-based Lewis acids in the domain of anion sensing in aqueous media illustrate the favorable attributes of antimony as a central element. At the same time, recent advances in anion binding catalysis and anion transport across phospholipid membranes speak to the numerous opportunities that lie ahead in the chemistry of these unique main group compounds.
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