The growth of ZnO crystals from the melt

The peculiar properties of zinc oxide (ZnO) make this material interesting for very different applications like light emitting diodes, lasers, and piezoelectric transducers. Most of these applications are based on epitaxial ZnO layers grown on suitable substrates, preferably bulk ZnO. Unfortunately the thermochemical properties of ZnO make the growth of single crystals difficult: the triple point 1975 deg C., 1.06 bar and the high oxygen fugacity at the melting point p_O2 = 0.35 bar lead to the prevailing opinion that ZnO crystals for technical applications can only be grown either by a hydrothermal method or from "cold crucibles" of solid ZnO. Both methods are known to have significant drawbacks. Our thermodynamic calculations and crystal growth experiments show, that in contrast to widely accepted assumptions, ZnO can be molten in metallic crucibles, if an atmosphere with "self adjusting" p_O2 is used. This new result is believed to offer new perspectives for ZnO crystal growth by established standard techniques like the Bridgman method.Comment: 6 pages, 6 figures, accepted for J. Crystal Growt

An integrated framework for solid modeling and structural analysis of layered composites with defects

Laminated fiber-reinforced polymer (FRP) composites are widely used in aerospace and automotive industries due to their combined properties of high strength and low weight. However, owing to their complex structure, it is difficult to assess the impact of manufacturing defects and service damage on their residual life. Non-destructive evaluation (NDE) of composites using ultrasonic testing (UT) can identify the presence of defects. However, manually incorporating the damage in a CAD model of a multi-layered composite structure and evaluating its structural integrity is a tedious process. We have developed an automated framework to create a layered 3D CAD model of a composite structure and automatically preprocess it for structural finite element (FE) analysis. In addition, we can incorporate flaws and known composite damage automatically into this CAD model. The framework generates a layer-by-layer 3D structural CAD model of the composite laminate, replicating its manufacturing process. The framework can create non-trivial composite structures such as those that include stiffeners. Outlines of structural defects, such as delaminations detected using UT of the laminate, are incorporated into the CAD model between the appropriate layers. The framework is also capable of incorporating fiber/matrix cracking, another common defect observed in fiber-reinforced composites. Finally, the framework can preprocess the resulting 3D CAD models with defects for direct structural analysis by automatically applying the appropriate boundary conditions. In this paper, we show a working proof-of-concept of the framework with capabilities of creating composite structures with stiffeners, incorporating delaminations between the composite layers, and automatically preprocessing the CAD model for finite element structural analysis. The framework will ultimately aid in accurately assessing the residual life of the composite and making informed decisions regarding repairs

The lichens of Bolshoy Tuters Island (Tytärsaari), Leningrad Region, Russia

The updated checklist of Tuters Island (Leningrad Region, Russia) is presented. Of 331 species of recognized biota, 314 species of lichens, 16 lichenicolous fungi and one non-lichenized saprobic fungus are reported from Tuters Island. Of them, 202 species are new to the study area. Aspicilia epiglypta, Fuscidea praeruptorum, Micarea byssacea and Sarcogyne hypophaeoides are reported for the first time for Russia, Roselliniella stereocaulorum – for European Russia, Aspicilia polychroma, Carbonea vorticosa, Cercidospora stereocaulorum, Cladonia ciliata f. flavicans, C. rangiformis, Parmelia ernstiae, Plectocarpon cf. encausticum and Roselliniella cladoniae – for North-Western European Russia; Bachmanniomyces uncialicola, Bacidina sulphurella, Micarea botryoides, Miriquidica griseoatra and Stereocaulon nanodes are new to the Leningrad Region.Peer reviewe

Strong near-infrared carbon in the Type Ia supernova iPTF13ebh

We present near-infrared (NIR) time-series spectroscopy, as well as complementary ultraviolet (UV), optical, and NIR data, of the Type Ia supernova (SN Ia) iPTF13ebh, which was discovered within two days from the estimated time of explosion. The first NIR spectrum was taken merely 2.3 days after explosion and may be the earliest NIR spectrum yet obtained of a SN Ia. The most striking features in the spectrum are several NIR C i lines, and the C iλ1.0693 μm line is the strongest ever observed in a SN Ia. Interestingly, no strong optical C ii counterparts were found, even though the optical spectroscopic time series began early and is densely cadenced. Except at the very early epochs, within a few days from the time of explosion, we show that the strong NIR C i compared to the weaker optical C ii appears to be general in SNe Ia. iPTF13ebh is a fast decliner with Δm15(B) = 1.79 ± 0.01, and its absolute magnitude obeys the linear part of the width-luminosity relation. It is therefore categorized as a "transitional" event, on the fast-declining end of normal SNe Ia as opposed to subluminous/91bg-like objects. iPTF13ebh shows NIR spectroscopic properties that are distinct from both the normal and subluminous/91bg-like classes, bridging the observed characteristics of the two classes. These NIR observations suggest that composition and density of the inner core are similar to that of 91bg-like events, and that it has a deep-reaching carbon burning layer that is not observed in more slowly declining SNe Ia. There is also a substantial difference between the explosion times inferred from the early-time light curve and the velocity evolution of the Si iiλ0.6355 μm line, implying a long dark phase of ∼4 days. © 2015 ESO

Expression of the ethylene biosynthetic machinery in maize roots is regulated in response to hypoxia

Ethylene regulates plant growth in response to many adverse environmental conditions, including the induction of aerenchyma, i.e. the formation of air spaces, in flooded roots in an effort to maintain oxygen levels. In this work, quantitative RT-PCR and in situ RNA hybridization were used to determine how the expression of the ethylene biosynthetic machinery in maize roots is spatially and temporally regulated following exposure to 4% oxygen (i.e. hypoxia) for up to 24 h, conditions that induced aerenchyma formation in the fully-expanded region of the root and reduced cytoplasmic density throughout the root. Expression of ACC oxidase, the ethylene forming enzyme, was observed in the root cap, protophloem sieve elements, and companion cells associated with metaphloem sieve elements. Exposure to 4% oxygen induced ACC oxidase expression in these cell types as well as in the root cortex. ACC synthase, which generates the ethylene precursor, was expressed in the root cap and the cortex and its expression was induced in cortical cells following low oxygen treatment. The induction of expression of the ethylene biosynthetic machinery was accompanied by an induction of ethylene evolution and a reduced rate of root growth. These results suggest that maize roots respond to conditions of hypoxia by inducing the spatially restricted expression of the ethylene biosynthetic machinery, resulting in increased ethylene production

Identification of Fluorescent Compounds with Non-Specific Binding Property via High Throughput Live Cell Microscopy

10.1371/journal.pone.0028802PLoS ONE71

Diversity in Expression of Phosphorus (P) Responsive Genes in Cucumis melo L

Phosphorus (P) is a major limiting nutrient for plant growth in many soils. Studies in model species have identified genes involved in plant adaptations to low soil P availability. However, little information is available on the genetic bases of these adaptations in vegetable crops. In this respect, sequence data for melon now makes it possible to identify melon orthologues of candidate P responsive genes, and the expression of these genes can be used to explain the diversity in the root system adaptation to low P availability, recently observed in this species

Oak root response to ectomycorrhizal symbiosis establishment: RNA-Seq derived transcript identification and expression profiling

Ectomycorrhizal symbiosis is essential for the life and health of trees in temperate and boreal forests where it plays a major role in nutrient cycling and in functioning of the forest ecosystem. Trees with ectomycorrhizal root tips are more tolerant to environmental stresses, such as drought, and biotic stresses such as root pathogens. Detailed information on these molecular processes is essential for the understanding of symbiotic tissue development in order to optimize the benefits of this natural phenomenon. Next generation sequencing tools allow the analysis of non model ectomycorrhizal plant-fungal interactions that can contribute to find the "symbiosis toolkits" and better define the role of each partner in the mutualistic interaction. By using 454 pyrosequencing we compared ectomycorrhizal cork oak roots with non-symbiotic roots. From the two cDNA libraries sequenced, over 2 million reads were obtained that generated 19,552 cork oak root unique transcripts. A total of 2238 transcripts were found to be differentially expressed when ECM roots were compared with non-symbiotic roots. Identification of up- and down-regulated gens in ectomycorrhizal roots lead to a number of insights into the molecular mechanisms governing this important symbiosis. In cork oak roots, ectomycorrhizal colonization resulted in extensive cell wall remodelling, activation of the secretory pathway, alterations in flavonoid biosynthesis, and expression of genes involved in the recognition of fungal effectors. In addition, we identified genes with putative roles in symbiotic processes such as nutrient exchange with the fungal partner, lateral root formation or root hair decay. These findings provide a global overview of the transcriptome of an ectomycorrhizal host root, and constitute a foundation for future studies on the molecular events controlling this important symbiosis.This work was funded by the Portuguese Foundation for Science and Technology (www.fct.pt) in the frame of the project Cork Oak EST Consortium SOBREIRO/0034/2009. Post-doc grant to MS was supported by the Portuguese Foundation for Science and Technology (SFRH/BPD/25661/2005). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript