Bimodal pumice populations in the 13.5 Ma Harsány ignimbrite, Bükkalja Volcanic Field, Northern Hungary: Syn-eruptive mingling of distinct rhyolitic magma batches?

Abstract The 13.5 Ma Harsány ignimbrite, in the eastern part of the Bükkalja volcanic field, eastern-central Europe, provides a rare example of mingled rhyolite. It consists of two distinct pumice populations (‘A’- and ‘B’-type) that can be recognized only by detailed geochemical work. The pumice and the host ignimbrite have a similar mineral assemblage involving quartz, plagioclase, biotite and sporadic Kfeldspar. Zircon, allanite, apatite and ilmenite occur as accessory minerals. The distinct pumice types are recognized by their different trace element compositions and the different CaO contents of their groundmass glasses. Plagioclase has an overlapping composition; however, biotite shows bimodal composition. Based on trace element and major element modeling, a derivation of ‘A’-type rhyolite magma from the ‘B’-type magma by fractional crystallization is excluded. Thus, the two pumice types represent two isolated rhyolite magma batches, possibly residing in the same crystal mush. Coeval remobilization of the felsic magmas might be initiated by intrusion of hot basaltic magma into the silicic magma reservoir The rapid ascent of the foaming rhyolite magmas enabled only a short-lived interaction and thus, a syn-eruptive mingling between the two magma batches

Probing the mechanical properties of graphene using a corrugated elastic substrate

The exceptional mechanical properties of graphene have made it attractive for nano-mechanical devices and functional composite materials. Two key aspects of graphene's mechanical behavior are its elastic and adhesive properties. These are generally determined in separate experiments, and it is moreover typically difficult to extract parameters for adhesion. In addition, the mechanical interplay between graphene and other elastic materials has not been well studied. Here, we demonstrate a technique for studying both the elastic and adhesive properties of few-layer graphene (FLG) by placing it on deformable, micro-corrugated substrates. By measuring deformations of the composite graphene-substrate structures, and developing a related linear elasticity theory, we are able to extract information about graphene's bending rigidity, adhesion, critical stress for interlayer sliding, and sample-dependent tension. The results are relevant to graphene-based mechanical and electronic devices, and to the use of graphene in composite, flexible, and strain-engineered materials.Comment: 5 pages, 4 figure

Пейзаж как важнейший компонент раскрытия личности персонажей

Актуальным и необходимым для изучения и раскрытия особенностей личности является пейзаж. Описание пейзажа в повести “Саба ола, хайыр ола” играет особую роль, поскольку насыщает его аллегорическим и сакральным смыслом сакральный

Radius constraints from high-speed photometry of 20 low-mass white dwarf binaries

We carry out high-speed photometry on 20 of the shortest-period, detached white dwarf binaries known and discover systems with eclipses, ellipsoidal variations (due to tidal deformations of the visible white dwarf), and Doppler beaming. All of the binaries contain low-mass white dwarfs with orbital periods less than 4 hr. Our observations identify the first eight tidally distorted white dwarfs, four of which are reported for the first time here, which we use to put empirical constraints on the mass-radius relationship for extremely low-mass (<0.30 Msun) white dwarfs. We also detect Doppler beaming in several of these binaries, which confirms the high-amplitude radial-velocity variability. All of these systems are strong sources of gravitational radiation, and long-term monitoring of those that display ellipsoidal variations can be used to detect spin-up of the tidal bulge due to orbital decay.Comment: 14 pages, 5 figures, accepted for publication in The Astrophysical Journa

Measuring and Correcting Wind-Induced Pointing Errors of the Green Bank Telescope Using an Optical Quadrant Detector

Wind-induced pointing errors are a serious concern for large-aperture high-frequency radio telescopes. In this paper, we describe the implementation of an optical quadrant detector instrument that can detect and provide a correction signal for wind-induced pointing errors on the 100m diameter Green Bank Telescope (GBT). The instrument was calibrated using a combination of astronomical measurements and metrology. We find that the main wind-induced pointing errors on time scales of minutes are caused by the feedarm being blown along the direction of the wind vector. We also find that wind-induced structural excitation is virtually non-existent. We have implemented offline software to apply pointing corrections to the data from imaging instruments such as the MUSTANG 3.3 mm bolometer array, which can recover ~70% of sensitivity lost due to wind-induced pointing errors. We have also performed preliminary tests that show great promise for correcting these pointing errors in real-time using the telescope's subreflector servo system in combination with the quadrant detector signal.Comment: 17 pages, 11 figures; accepted for publication in PAS

Comprehensive Analysis of mRNA Methylation Reveals Enrichment in 3′ UTRs and near Stop Codons

SummaryMethylation of the N6 position of adenosine (m6A) is a posttranscriptional modification of RNA with poorly understood prevalence and physiological relevance. The recent discovery that FTO, an obesity risk gene, encodes an m6A demethylase implicates m6A as an important regulator of physiological processes. Here, we present a method for transcriptome-wide m6A localization, which combines m6A-specific methylated RNA immunoprecipitation with next-generation sequencing (MeRIP-Seq). We use this method to identify mRNAs of 7,676 mammalian genes that contain m6A, indicating that m6A is a common base modification of mRNA. The m6A modification exhibits tissue-specific regulation and is markedly increased throughout brain development. We find that m6A sites are enriched near stop codons and in 3′ UTRs, and we uncover an association between m6A residues and microRNA-binding sites within 3′ UTRs. These findings provide a resource for identifying transcripts that are substrates for adenosine methylation and reveal insights into the epigenetic regulation of the mammalian transcriptome

Precursors of Cytochrome Oxidase in Cytochrome-Oxidase-Deficient Cells of Neurospora crassa

Three different cell types of Neurospora crassa deficient in cytochrome oxidase were studied: the nuclear mutant cni-1, the cytoplasmic mutant mi-1 and copper-depleted wild-type cells. * 1. The enzyme-deficient cells have retained a functioning mitochondrial protein synthesis. It accounted for 12–16% of the total protein synthesis of the cell. However, the analysis of mitochondrial translation products by gel electrophoresis revealed that different amounts of individual membrane proteins were synthesized. Especially mutant cni-1 produced large amounts of a small molecular weight translation product, which is barely detectable in wild-type. * 2. Mitochondrial preparations of cytochrome-oxidase-deficient cells were examined for precursors of cytochrome oxidase. The presence of polypeptide components of cytochrome oxidase in the mitochondria was established with specific antibodies. On the other hand, no significant amounts of heme a could be extracted. * 3. Radioactively labelled components of cytochrome oxidase were isolated by immunoprecipitation and analysed by gel electrophoresis. All three cell types contained the enzyme components 4–7, which are translated on cytoplasmic ribosomes. The mitochondrially synthesized components 1–3 were present in mi-1 mutant and in copper-depleted wild-type cells. In contrast, components 2 and 3 were not detectable in the nuclear mutant cni-1. Both relative and absolute amounts of these polypeptides in the enzyme-deficient cells were quite different from those in wild-type cells. * 4. The components of cytochrome oxidase found in the enzyme-deficient cells were tightly associated with the mitochondrial membranes. * 5. Processes, which affect and may control the production of enzyme precursors or their assembly to a functional cytochrome oxidase are discussed

A clinopyroxene record of primitive melt diversity and mantle heterogeneity beneath Italy

The young potassium-rich volcanic rocks of peninsular Italy are the products of a complex post-collisional geodynamic setting. These volcanic rocks exhibit extreme compositional variability in space and time, resulting from large variations in the subducted material in their mantle sources. The genetic relationships between distinct Italian magmatic series—shoshonitic, potassic, ultrapotassic and lamproitic, among others—that are closely related in space and time, as well as the exact nature and provenance of the metasomatic agents, are subject to active debate. The earliest crystallised silicate phases from mafic lavas—olivine and clinopyroxene—carry valuable information on the nature of mantle sources and melt extraction processes. Because Mg-rich clinopyroxene incorporates significant amounts of incompatible elements and is a ubiquitous phase in mafic Italian lavas, it potentially represents a versatile instrument for delineating the compositional complexity and regional variability of subduction-modified mantle sources in this region. Here we present the results of an extensive study of Mg-rich clinopyroxene (Mg# = 88–93 mol%) from potassium-rich mafic rocks from a chain of volcanic centres in central-southern Italy, from Tuscany down to Campania. We compare major- and trace-element data from clinopyroxenes with those from bulk rocks and olivine-hosted melt inclusions, using new estimates of trace-element partitioning between clinopyroxene and potassium-rich magmas based on cogenetic clinopyroxene-olivine crystallisation. The Mg-rich clinopyroxenes show a marked compositional diversity that reflects the nature of the (near-)primary mantle-derived melts from which they crystallised, and allow us to characterise the metasomatic agents responsible for the formation of different compositional end-members. We demonstrate that clinopyroxenes provide a detailed archive of mantle heterogeneity beneath Italy, highlighting systematic variations both regionally and beneath individual volcanic complexes

Clinopyroxene diversity and magma plumbing system processes in an accreted Pacific ocean island, Panama

Characterising equilibrium and disequilibrium crystal-melt processes is critical in determining the extent of magma mixing and crystallization conditions in the roots of volcanoes. However, these processes remain poorly investigated in most Pacific intraplate ocean settings that are difficult to access and study. To help address this issue, we investigated crystallization conditions of clinopyroxene phenocrysts in an accreted Palaeogene oceanic island in Panama. Petrographic and geochemical observations, petrological modelling of major and trace elements, and liquid-mineral multicomponent equilibrium tests were carried out using basalts, picrites, and hawaiites of the transitional tholeiitic shield to alkaline post-shield volcanic stages of the island. Five types of clinopyroxene crystals were identified, including (1) microphenocrysts with micron-scale oscillatory zoning, (2) primitive, yet resorbed picrite-hosted phenocrysts, (3) chemically homogeneous, anhedral crystals found in the remaining basalts, (4) Ti–rich euhedral hawaiite-hosted phenocrysts, and (5) evolved sector-zoned phenocrysts. Liquid-clinopyroxene multicomponent equilibrium tests in combination with textural analysis show that ~ 74% of the studied clinopyroxenes are in possible major element equilibrium with one of the available whole rock magma compositions, of which only 21% are equilibrated with their carrier liquid. To deconvolute clinopyroxene-melt pairings and determine plumbing system conditions, we combine rhyolite-MELTS modelling, geothermobarometry, and major- and trace-element equilibrium evaluations, limiting crystallization conditions to crustal levels (< 23 km depth). No migration of magmatic reservoirs to deeper levels is observed during the shield- to post-shield transition. These results suggest the occurrence of an extensive crystal mush system during the late shield to post-shield volcanic stages of this intraplate volcanic system, with both primitive and evolved crystallization domains sampled during eruptions