Russian wheat aphids (Diuraphis noxia) in China: Native range expansion or recent introduction?

In this study, we explore the population genetics of the Russian wheat aphid (RWA) (Diuraphis noxia), one of the world’s most invasive agricultural pests, in north-western China. We have analysed the data of 10 microsatellite loci and mitochondrial sequences from 27 populations sampled over 2 years in China. The results confirm that the RWAs are holocyclic in China with high genetic diversity indicating widespread sexual reproduction. Distinct differences in microsatellite genetic diversity and distribution revealed clear geographic isolation between RWA populations in northern and southern Xinjiang, China, with gene flow interrupted across extensive desert regions. Despite frequent grain transportation from north to south in this region, little evidence for RWA translocation as a result of human agricultural activities was found. Consequently, frequent gene flow among northern populations most likely resulted from natural dispersal, potentially facilitated by wind currents. We also found evidence for the longterm existence and expansion of RWAs in China, despite local opinion that it is an exotic species only present in China since 1975. Our estimated date of RWA expansion throughout China coincides with the debut of wheat domestication and cultivation practices in western Asia in the Holocene. We conclude that western China represents the limit of the far eastern native range of this species. This study is the most comprehensive molecular genetic investigation of the RWA in its native range undertaken to date and provides valuable insights into the history of the association of this aphid with domesticated cereals and wild grasses

Discriminating Micropathogen Lineages and Their Reticulate Evolution through Graph Theory-Based Network Analysis: The Case of Trypanosoma cruzi, the Agent of Chagas Disease

Micropathogens (viruses, bacteria, fungi, parasitic protozoa) share a common trait, which is partial clonality, with wide variance in the respective influence of clonality and sexual recombination on the dynamics and evolution of taxa. The discrimination of distinct lineages and the reconstruction of their phylogenetic history are key information to infer their biomedical properties. However, the phylogenetic picture is often clouded by occasional events of recombination across divergent lineages, limiting the relevance of classical phylogenetic analysis and dichotomic trees. We have applied a network analysis based on graph theory to illustrate the relationships among genotypes of Trypanosoma cruzi, the parasitic protozoan responsible for Chagas disease, to identify major lineages and to unravel their past history of divergence and possible recombination events. At the scale of T. cruzi subspecific diversity, graph theory-based networks applied to 22 isoenzyme loci (262 distinct Multi-Locus-Enzyme-Electrophoresis -MLEE) and 19 microsatellite loci (66 Multi-Locus-Genotypes -MLG) fully confirms the high clustering of genotypes into major lineages or "near-clades''. The release of the dichotomic constraint associated with phylogenetic reconstruction usually applied to Multilocus data allows identifying putative hybrids and their parental lineages. Reticulate topology suggests a slightly different history for some of the main "near-clades'', and a possibly more complex origin for the putative hybrids than hitherto proposed. Finally the sub-network of the near-clade T. cruzi I (28 MLG) shows a clustering subdivision into three differentiated lesser near-clades ("Russian doll pattern''), which confirms the hypothesis recently proposed by other investigators. The present study broadens and clarifies the hypotheses previously obtained from classical markers on the same sets of data, which demonstrates the added value of this approach. This underlines the potential of graph theory-based network analysis for describing the nature and relationships of major pathogens, thereby opening stimulating prospects to unravel the organization, dynamics and history of major micropathogen lineages

Self-Heating in FDSOI UTBB MOSFETs at Cryogenic Temperatures and Its Effect on Analog Figures of Merit

This work studies the self-heating (SH) effect in ultra-thin body ultra-thin buried oxide (UTBB) FDSOI MOSFETs at cryogenic temperatures down to 77 K. S-parameter measurements in a wide frequency range, with the so-called RF technique, are employed to assess SH parameters and related variation of analog figures of merit (FoMs) at different temperatures. Contrary to the expectations, the effect of self-heating on analog FoMs is slightly weaker at cryogenic temperatures with respect to room-temperature case. The extracted thermal resistance and channel temperature rise at 300 K and 77 K in short-channel devices are of the same order of magnitude. The observed increase in SH characteristic frequency with temperature reduction emphasizes the advantage of the RF technique for the fair analysis of SH-related features in advanced technologies at cryogenic temperatures

Matrix detailing the thresholds below which no links exist between two near-clades, MLEE below diagonal and microsatellites above.

<p>Matrix detailing the thresholds below which no links exist between two near-clades, MLEE below diagonal and microsatellites above.</p

Networks of <i>Trypanosoma cruzi</i> based on a) MLEE and b) microsatellites.

<p>Networks are represented at the percolation thresholds for each dataset (MLEE: Dp = 0.35; microsatellites: Dp = 0.71). The evolution of the average cluster size (; estimated excluding the largest cluster) is represented on the bottom right of each network. An arrow represents the location on the curve where genetic distance (on the x-axis) corresponds to the percolation threshold (Dp, just before the apparition of the secondary higher cluster, the size of which is projected on the y-axis). Only links with genetic distances (shared allele distance = SAD) smaller than the percolation threshold are represented. A gradient of dark grey to light grey represents decreasing distances among stocks, their relative position have no relationship with their distance but are arranged to minimize the overlap of links and maximize clarity. The threshold at which the six recognized clusters of genotypes (corresponding indeed to the six major near-clades) separate themselves from the most closely related ones are represented by red dashed lines with numbers corresponding to the threshold values. Color code for the near-clades is yellow for TcI, blue for TcII, brown for TcIII, dark blue for TcIV, pink for TcV and green for TcVI.</p

(modified from EDENetwork, [<b>75</b>]): Simplified network of <i>Trypanosoma cruzi</i> including stocks of near-clades I, II and III (respectively yellow, blue and green nodes) and scanned for decreasing thresholds from the (a) fully connected network (all pairwise links included) to the (b) percolation threshold (Dp, all links corresponding to distances superior to Dp excluded) and to (c) a lower threshold chosen to illustrate the sequential split of clusters at decreasing thresholds, and main properties of nodes and networks used herein.

<p>(modified from EDENetwork, <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0103213#pone.0103213-Kivela1" target="_blank">[<b>75</b>]</a>): Simplified network of <i>Trypanosoma cruzi</i> including stocks of near-clades I, II and III (respectively yellow, blue and green nodes) and scanned for decreasing thresholds from the (a) fully connected network (all pairwise links included) to the (b) percolation threshold (Dp, all links corresponding to distances superior to Dp excluded) and to (c) a lower threshold chosen to illustrate the sequential split of clusters at decreasing thresholds, and main properties of nodes and networks used herein.</p

Networks of TcI genotypes characterized with microsatellite data from Lewis et al.

<p>(A) Just above percolation distance (Dp = 0.37), and (B) just below, illustrating the disconnection of the 3 clusters of nodes. According to color code, 3 geographical regions are highlighted: USA (Violet), Brazil (Green) and Andes (Peru and Argentina in Dark Grey, Chile in Light Grey, Bolivia in Black). Colombia in Orange and Venezuela in Yellow green show the intermediate position of stocks isolated in those countries, at the interface of the three clusters.</p

Genetic Distances Spectrum.

<p>The frequency distribution of genetic distances among all stocks (upper line) and among stocks within-near-clade (below) using Shared Alleles Distances with microsatellite (right) and MLEE (left) data.</p

Effective work function engineering by sacrificial lanthanum diffusion on HfON-based 14 nm NFET devices

session C2L-E: Advanced CMOS Device and TechnologyInternational audienceIn this paper, the impact of metallic lanthanum (La) deposited by Radio-Frequency PVD on effective work function (WF eff ) of HfON-based NFET devices in a sacrificial metal gate-first approach is evaluated for the first time. Engineering of WF eff towards N+ without leakage degradation is demonstrated by tuning both the pedestal TiN thickness and the as-deposited metallic La dose. WF eff shift is related to a La-induced interfacial dipole (5), whose value has been correlated to the effective La dose into HfON/SiON stack after diffusion annealing, which has been accurately measured through a spectroscopic method based on La X-Ray Fluorescence (XRF)

Self-Heating in 28 FDSOI UTBB MOSFETs at Cryogenic Temperatures

This work studies, for the first time to the authors’ best knowledge, the self-heating (SH) effect in ultra-thin body ultra-thin BOX (UTBB) FDSOI MOSFETs at cryogenic temperatures down to 77 K. S-parameter measurements in a wide frequency range, with the so-called RF technique, is employed to assess SH parameters and related degradation of analog figures of merit (FoMs) at different temperatures. Contrary to the expectations, the effect of self-heating on analog FoMs is slightly weaker at cryogenic temperatures with respect to room-temperature case. The extracted thermal resistance and channel temperature rise at 300 K and 77 K are of the same order of magnitude. The observed increase in SH characteristic frequency with temperature reduction emphasizes the advantage of the RF technique for the fair analysis of SH-related features in advanced technologies at cryogenic temperatures