Al_5+αSi_5+δN₁₂, a new Nitride compound

The family of III-Nitride semiconductors has been under intensive research for almost 30 years and has revolutionized lighting applications at the dawn of the 21st century. However, besides the developments and applications achieved, nitride alloys continue to fuel the quest for novel materials and applications. We report on the synthesis of a new nitride-based compound by using annealing of AlN heteroepitaxial layers under a Si-atmosphere at temperatures between 1350 °C and 1550 °C. The structure and stoichiometry of this compound are investigated by high resolution transmission electron microscopy (TEM) techniques and energy dispersive X-Ray (EDX) spectroscopy. Results are supported by density functional theory (DFT) calculations. The identified structure is a derivative of the parent wurtzite AlN crystal where the anion sublattice is fully occupied by N atoms and the cation sublattice is the stacking of 2 different planes along lt;0001gt;: The first one exhibits a ×3 periodicity along lt;11–20gt; with 1/3 of the sites being vacant. The rest of the sites in the cation sublattice are occupied by an equal number of Si and Al atoms. Assuming a semiconducting alloy, a range of stoichiometries is proposed, Al5+αSi5+δN12 with α being between −2/3 and 1/4 and δ between 0 and 3/4. © 2019, The Author(s)

The Importance of Major Mergers in the Build Up of Stellar Mass in Brightest Cluster Galaxies at \u3cem\u3ez\u3c/em\u3e = 1

Recent independent results from numerical simulations and observations have shown that brightest cluster galaxies (BCGs) have increased their stellar mass by a factor of almost 2 between z ∼ 0.9 and z ∼ 0.2. The numerical simulations further suggest that more than half this mass is accreted through major mergers. Using a sample of 18 distant galaxy clusters with over 600 spectroscopically confirmed cluster members between them, we search for observational evidence that major mergers do play a significant role. We find a major merger rate of 0.38 ± 0.14 mergers per Gyr at z ∼ 1. While the uncertainties, which stem from the small size of our sample, are relatively large, our rate is consistent with the results that are derived from numerical simulations. If we assume that this rate continues to the present day and that half of the mass of the companion is accreted on to the BCG during these mergers, then we find that this rate can explain the growth in the stellar mass of the BCGs that is observed and predicted by simulations. Major mergers therefore appear to be playing an important role, perhaps even the dominant one, in the build up of stellar mass in these extraordinary galaxies

The role of C and N dopants incorporation in phase change materials

Phase change memory (PCM) technology is considered to be among the most promising alternatives to conventional technologies in embedded memories [1]. To allow operation at relatively high temperatures in embedded applications, it is crucial to improve the stability of the amorphous phase. Carbon and nitrogen doping have been shown to significantly increase the crystallization temperature [1-3]. Moreover, the high RESET current requirement [2], which is a limit to the scalability of GeTe and GST, can be reduced by the incorporation of a dopant element [4]. In this presentation we focus on correlating experimental results and ab initio simulations to understand the effect of C and N incorporation in GeTe and GST PCM devices. Understanding the effect of dopants on the change of electronic properties and the mechanisms of the phase transformation requires analysis of the local order and structure of the amorphous to crystalline phases. In this context, we demonstrate that carbon and nitrogen deeply affects the structure and the dynamical properties of the amorphous phase of GeTe. In particular, the inclusion of N and C dopant elements in GeTe has a drastic effect on the vibrational modes of GeTe therefore improving the stability of the glass. This effect goes with an increased mechanical rigidity explaining why these doped GeTe compounds have a higher crystallization temperature than the undoped ones. Finally we will explore, mainly by FTIR and XRD measurements, the effect of C and N dopants during the annealing of amorphous PCMaterials towards their crystalline phases. These results will be discussed in order to understand the origin of the differences of the doped PCMaterials amorphous phase stability (data retention) observed between full sheet materials and the materials integrated in PCM devices. [1] A. Fantini et al., 2010 IEEE International Electron Devices Meeting (IEDM), 2010, pp. 29.21.21-29.21.24. [2] G. Betti Beneventi et al., Solid-State Electronics, 65-66 (2011) 197-204. [3] V. Sousa et al., EPCOS 2011. [4] Q. Hubert et al., IMW 2012.A.R.C. Themoter

Blueprint for a minimal photoautotrophic cell: conserved and variable genes in Synechococcus elongatus PCC 7942

Background: Simpler biological systems should be easier to understand and to engineer towards pre-defined goals. One way to achieve biological simplicity is through genome minimization. Here we looked for genomic islands in the fresh water cyanobacteria Synechococcus elongatus PCC 7942 (genome size 2.7 Mb) that could be used as targets for deletion. We also looked for conserved genes that might be essential for cell survival.Results: By using a combination of methods we identified 170 xenologs, 136 ORFans and 1401 core genes in the genome of S. elongatus PCC 7942. These represent 6.5%, 5.2% and 53.6% of the annotated genes respectively. We considered that genes in genomic islands could be found if they showed a combination of: a) unusual G+C content; b) unusual phylogenetic similarity; and/or c) a small number of the highly iterated palindrome 1 (HIP1) motif plus an unusual codon usage. The origin of the largest genomic island by horizontal gene transfer (HGT) could be corroborated by lack of coverage among metagenomic sequences from a fresh water microbialite. Evidence is also presented that xenologous genes tend to cluster in operons. Interestingly, most genes coding for proteins with a diguanylate cyclase domain are predicted to be xenologs, suggesting a role for horizontal gene transfer in the evolution of Synechococcus sensory systems.Conclusions: Our estimates of genomic islands in PCC 7942 are larger than those predicted by other published methods like SIGI-HMM. Our results set a guide to non-essential genes in S. elongatus PCC 7942 indicating a path towards the engineering of a model photoautotrophic bacterial cell.Financial support was provided by grants BFU2009-12895-C02-01/BMC (Ministerio de Ciencia e Innovación, Spain), the European Community’s Seventh Framework Programme (FP7/2007-2013) under grant agreement number 212894 and Prometeo/2009/092 (Conselleria d’Educació, Generalitat Valenciana, Spain) to A. Moya. Work in the FdlC laboratory was supported by grants BFU2008-00995/BMC (Spanish Ministry of Education), RD06/0008/1012 (RETICS research network, Instituto de Salud Carlos III, Spanish Ministry of Health) and LSHM-CT- 2005_019023 (European VI Framework Program). Dr. González-Domenech was supported by grant from the University of Granada. LD, thanks to financial support from Facultad de Ciencias, Universidad Nacional Autónoma de México

Evolutionary origins of Brassicaceae specific genes in Arabidopsis thaliana

<p>Abstract</p> <p>Background</p> <p>All sequenced genomes contain a proportion of lineage-specific genes, which exhibit no sequence similarity to any genes outside the lineage. Despite their prevalence, the origins and functions of most lineage-specific genes remain largely unknown. As more genomes are sequenced opportunities for understanding evolutionary origins and functions of lineage-specific genes are increasing.</p> <p>Results</p> <p>This study provides a comprehensive analysis of the origins of lineage-specific genes (LSGs) in <it>Arabidopsis thaliana </it>that are restricted to the Brassicaceae family. In this study, lineage-specific genes within the nuclear (1761 genes) and mitochondrial (28 genes) genomes are identified. The evolutionary origins of two thirds of the lineage-specific genes within the <it>Arabidopsis thaliana </it>genome are also identified. Almost a quarter of lineage-specific genes originate from non-lineage-specific paralogs, while the origins of ~10% of lineage-specific genes are partly derived from DNA exapted from transposable elements (twice the proportion observed for non-lineage-specific genes). Lineage-specific genes are also enriched in genes that have overlapping CDS, which is consistent with such novel genes arising from overprinting. Over half of the subset of the 958 lineage-specific genes found only in <it>Arabidopsis thaliana </it>have alignments to intergenic regions in <it>Arabidopsis lyrata</it>, consistent with either <it>de novo </it>origination or differential gene loss and retention, with both evolutionary scenarios explaining the lineage-specific status of these genes. A smaller number of lineage-specific genes with an incomplete open reading frame across different <it>Arabidopsis thaliana </it>accessions are further identified as accession-specific genes, most likely of recent origin in <it>Arabidopsis thaliana</it>. Putative <it>de novo </it>origination for two of the <it>Arabidopsis thaliana</it>-only genes is identified via additional sequencing across accessions of <it>Arabidopsis thaliana </it>and closely related sister species lineages. We demonstrate that lineage-specific genes have high tissue specificity and low expression levels across multiple tissues and developmental stages. Finally, stress responsiveness is identified as a distinct feature of Brassicaceae-specific genes; where these LSGs are enriched for genes responsive to a wide range of abiotic stresses.</p> <p>Conclusion</p> <p>Improving our understanding of the origins of lineage-specific genes is key to gaining insights regarding how novel genes can arise and acquire functionality in different lineages. This study comprehensively identifies all of the Brassicaceae-specific genes in <it>Arabidopsis thaliana </it>and identifies how the majority of such lineage-specific genes have arisen. The analysis allows the relative importance (and prevalence) of different evolutionary routes to the genesis of novel ORFs within lineages to be assessed. Insights regarding the functional roles of lineage-specific genes are further advanced through identification of enrichment for stress responsiveness in lineage-specific genes, highlighting their likely importance for environmental adaptation strategies.</p

Properties of Electrodeposited CuSCN 2D Layers and Nanowires Influenced by Their Mixed Domain Structure

International audienc

Eclipse in the Dark Years: Pick-up Flights, Routes of Resistance and the Free French

This article charts the importance of clandestine flights from Britain into occupied France during the Second World War as a route of resistance. These pick-up flights were coordinated from London and were an example of the inter-allied cooperation and Franco-British negotiation that took place between the BCRA, SIS, and SOE. The flights allowed General Charles de Gaulle to hold court with the leaders of resistance networks, smoothing problems on the route to a unified resistance council. Likewise, they allowed him to build bridges between vying factions in France and in London, drawing together the movements under his command and personalising the narrative of resistance. From busy London restaurants and family homes via secret flights to darkened fields in Occupied France, the route of these transfers shaped the character of resistance. This article draws out the personal interactions and connections that underpinned these networks and describes the enduring connections of this route of resistance, starting with the commemoration of Jean Moulin's crash landing at RAF Tangmere, the forward station for many of these flights

Descomposición de una enmienda orgánica bajo diferentes suelos, dosis y formas de aplicación

PósterEl compostaje, la estabilización y/o pirólisis permiten transformar residuos orgánicos industriales en enmiendas orgánicas de valor agronómico y reducir su huella ambiental. Cuando se aplican al suelo incrementan la biomasa, la respiración microbiana y la actividad enzimática, afectando los procesos biogeoquímicos del suelo.EEA PergaminoFil: Delorensi, V. Universidad Nacional del Noroeste de la Provincia de Buenos Aires; ArgentinaFil: Milesi Delaye, Luis. Instituto Nacional de Tecnología Agropecuaria (INTA). Estación Experimental Agropecuaria Pergamino. Departamento de Laboratorio de Suelo; ArgentinaFil: Irizar, Alicia. Instituto Nacional de Tecnología Agropecuaria (INTA). Estación Experimental Agropecuaria Pergamino. Departamento de Laboratorio de Suelo; Argentin