196 research outputs found
Instabilities and Insulator-Metal transitions in Half-Doped Manganites induced by Magnetic-Field and Doping
We discuss the phase diagram of the two-orbital model of half-doped
manganites by calculating self-consistently the Jahn-Teller (JT) distortion
patterns, charge, orbital and magnetic order at zero temperature. We analyse
the instabilities of these phases caused by electron or hole doping away from
half-doping, or by the application of a magnetic-field. For the CE insulating
phase of half-doped manganites, in the intermediate JT coupling regime, we show
that there is a competition between canting of spins (which promotes mobile
carriers) and polaronic self-trapping of carriers by JT defects. This results
in a marked particle-hole asymmetry, with canting winning only on the electron
doped side of half-doping. We also show that the CE phase undergoes a
first-order transition to a ferromagnetic metallic phase when a magnetic-field
is applied, with abrupt changes in the lattice distortion patterns. We discuss
the factors that govern the intriguingly small scale of the transition fields.
We argue that the ferromagnetic metallic phases involved have two types of
charge carriers, localised and band-like, leading to an effective two-fluid
model.Comment: 22 pages, 28 figure
Doping and Field-Induced Insulator-Metal Transitions in Half-Doped Manganites
We argue that many properties of the half-doped manganites may be understood
in terms of a new two-(eg electron)-fluid description, which is energetically
favorable at intermediate Jahn-Teller (JT) coupling. This emerges from a
competition between canting of the core spins of Mn promoting mobile carriers
and polaronic trapping of carriers by JT defects, in the presence of CE,
orbital and charge order. We show that this explains several features of the
doping and magnetic field induced insulator-metal transitions, as the
particle-hole asymmetry and the smallness of the transition fields.Comment: 4 pages, 4 figure
The incarnation of the Nersesyan-Tsvelik model in (NO)[Cu(NO3)3]
The topology of the magnetic interactions of the copper spins in the
nitrosonium nitratocuprate (NO)[Cu(NO3)3] suggests that it could be a
realization of the Nersesyan-Tsvelik model, whose ground state was argued to be
either a resonating valence bond (RVB) state or a valence bond crystal (VBC).
The measurement of thermodynamic and resonant properties reveals a behavior
inherent to low dimensional spin S = 1/2 systems and provides indeed no
evidence for the formation of long-range magnetic order down to 1.8 K.Comment: 12 pages, 6 figure
In Vitro Evaluation of the Toxicological Profile and Oxidative Stress of Relevant Diet-Related Advanced Glycation End Products and Related 1,2-Dicarbonyls
During food processing and storage, and in tissues and fluids under physiological conditions, the Maillard reaction occurs. During this reaction, reactive 1,2-dicarbonyl compounds arise as intermediates that undergo further reactions to form advanced glycation end products (AGEs). Diet is the primary source of exogenous AGEs. Endogenously formed AGEs have been proposed as a risk factor in the pathogenesis of diet-related diseases such as diabetes, insulin resistance, cardiovascular diseases, or chronic disease. AGEs may differently contribute to the diet-related exacerbation of oxidative stress, inflammation, and protein modifications. Here, to understand the contribution of each compound, we tested individually, for the first time, the effect of five 1,2-dicarbonyl compounds 3-deoxyglucosone (3-DG), 3-deoxygalactosone (3-DGal), 3,4-dideoxyglucosone-3-ene (3,4-DGE), glyoxal (GO), and methylglyoxal (MGO) and four different glycated amino acids N-ε-(carboxyethyl)lysine (CEL), N-ε-(carboxymethyl)lysine (CML), methylglyoxal-derived hydroimidazolone-1 (MG-H1), and pyrraline (Pyrr) in a cell line of human keratinocytes (HaCaT). We found that most of the glycated amino acids, i.e., CEL, CML, and MG-H1, did not show any cytotoxicity. At the same time, 1,2-dicarbonyl compounds 3-DGal, 3,4-DGE, GO, and MGO increased the production of reactive oxygen species and induced cell death. MGO induced cell death by apoptosis, whereas 3-DGal and 3,4-DGE induced nuclear translocation of the proinflammatory NF-κB transcription pathway, and the activation of the pyroptosis-related NLRP3 inflammasome cascade. Overall, these results demonstrate the higher toxic impact of 1,2-dicarbonyl compounds on mucosal epithelial cells when compared to glycated amino acids and the selective activation of intracellular signaling pathways involved in the crosstalk mechanisms linking oxidative stress to excessive inflammation
Chlorosphaerolactylates A-D: Natural Lactylates of Chlorinated Fatty Acids Isolated from the Cyanobacterium Sphaerospermopsis sp. LEGE 00249
Topological variation in single-gene phylogenetic trees
A large-scale phylogenetic study of the human lineage dramatically points up the problems of using single genes to build phylogenetic trees
The Quest for Orthologs benchmark service and consensus calls in 2020.
The identification of orthologs-genes in different species which descended from the same gene in their last common ancestor-is a prerequisite for many analyses in comparative genomics and molecular evolution. Numerous algorithms and resources have been conceived to address this problem, but benchmarking and interpreting them is fraught with difficulties (need to compare them on a common input dataset, absence of ground truth, computational cost of calling orthologs). To address this, the Quest for Orthologs consortium maintains a reference set of proteomes and provides a web server for continuous orthology benchmarking (http://orthology.benchmarkservice.org). Furthermore, consensus ortholog calls derived from public benchmark submissions are provided on the Alliance of Genome Resources website, the joint portal of NIH-funded model organism databases
MultiMSOAR 2.0: An Accurate Tool to Identify Ortholog Groups among Multiple Genomes
The identification of orthologous genes shared by multiple genomes plays an important role in evolutionary studies and gene functional analyses. Based on a recently developed accurate tool, called MSOAR 2.0, for ortholog assignment between a pair of closely related genomes based on genome rearrangement, we present a new system MultiMSOAR 2.0, to identify ortholog groups among multiple genomes in this paper. In the system, we construct gene families for all the genomes using sequence similarity search and clustering, run MSOAR 2.0 for all pairs of genomes to obtain the pairwise orthology relationship, and partition each gene family into a set of disjoint sets of orthologous genes (called super ortholog groups or SOGs) such that each SOG contains at most one gene from each genome. For each such SOG, we label the leaves of the species tree using 1 or 0 to indicate if the SOG contains a gene from the corresponding species or not. The resulting tree is called a tree of ortholog groups (or TOGs). We then label the internal nodes of each TOG based on the parsimony principle and some biological constraints. Ortholog groups are finally identified from each fully labeled TOG. In comparison with a popular tool MultiParanoid on simulated data, MultiMSOAR 2.0 shows significantly higher prediction accuracy. It also outperforms MultiParanoid, the Roundup multi-ortholog repository and the Ensembl ortholog database in real data experiments using gene symbols as a validation tool. In addition to ortholog group identification, MultiMSOAR 2.0 also provides information about gene births, duplications and losses in evolution, which may be of independent biological interest. Our experiments on simulated data demonstrate that MultiMSOAR 2.0 is able to infer these evolutionary events much more accurately than a well-known software tool Notung. The software MultiMSOAR 2.0 is available to the public for free
OrthoDB: the hierarchical catalog of eukaryotic orthologs in 2011
The concept of homology drives speculation on a gene’s function in any given species when its biological roles in other species are characterized. With reference to a specific species radiation homologous relations define orthologs, i.e. descendants from a single gene of the ancestor. The large-scale delineation of gene genealogies is a challenging task, and the numerous approaches to the problem reflect the importance of the concept of orthology as a cornerstone for comparative studies. Here, we present the updated OrthoDB catalog of eukaryotic orthologs delineated at each radiation of the species phylogeny in an explicitly hierarchical manner of over 100 species of vertebrates, arthropods and fungi (including the metazoa level). New database features include functional annotations, and quantification of evolutionary divergence and relations among orthologous groups. The interface features extended phyletic profile querying and enhanced text-based searches. The ever-increasing sampling of sequenced eukaryotic genomes brings a clearer account of the majority of gene genealogies that will facilitate informed hypotheses of gene function in newly sequenced genomes. Furthermore, uniform analysis across lineages as different as vertebrates, arthropods and fungi with divergence levels varying from several to hundreds of millions of years will provide essential data for uncovering and quantifying long-term trends of gene evolution. OrthoDB is freely accessible from http://cegg.unige.ch/orthodb
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