Effects of β grain-growth behaviors on lamellar structural evolution and mechanical properties of TC4–DT alloy

Grain-growth behaviors of TC4–DT alloy in a narrow temperature range (990 °C−1050 °C) were systematically investigated, and the effects of which on the lamellar structural evolution and mechanical properties were quantitatively evaluated. Microstructural observations indicated that prior β grain size increased with an increase in heat-treatment temperature and time, which was described by the modified Sellars model. The grain-growth exponent ( n  = 2.741) and activation energy ( Q  = 161.0 kJ mol ^−1 ) during β treatment were confirmed. The α colony size similar to β grain varied significantly with the heat-treatment conditions, while α plate thickness changed slightly. The Hall–Petch equation could qualitatively exhibit the relationships between the lamellar microstructure parameters (prior β grain size, α colony size, and α plate thickness) and mechanical properties (strength, ductility, and impact toughness). The fine prior β grain that contained different orientated α colonies produced more boundaries to hinder dislocation motion and crack propagation, which contributed a more circuitous crack growth path. The results indicated that the control of α colony size was critical to improve the mechanical performance of TC4–DT alloy

The complete mitochondrial genome of Ctenolepisma villosa (Insecta: Zygentoma, Lepismatidae)

In this study, the complete sequence of the mitochondrial DNA (mtDNA) of Ctenolepisma villosa was obtained using next-generation sequencing approaches and de novo assembly. The molecule was found to be 15,488 bp in length. It is the fourth complete mt genome sequence from the Zygentoma. The mt genomes are circular and encode 37 genes and a large non-coding region. The overall structure (gene number, orientation, and order) of the mt genomes is the same as that found in three other sequenced species. All protein-coding sequences except cox1 start with the typical ATN codon. Cox1 begins with TTG, which may be a common codon in Zygentoma insects. Stem-loop structure can be observed in the largest non-coding region thought to be involved in the regulation of replication and transcription of the mitochondrial genome

Bradyrhizobium aeschynomenes sp. nov., a root and stem nodule microsymbiont of Aeschynomene indica

Aeschynomene indica has a distinctive symbiosis with Bradyrhizobium in which nodulation is Nod factorindependent. In this study, we characterised three Gram-negative and rod-shaped strains (83002T, 81013 and 83012) isolated from root nodules of Aeschynomene indica in Shandong Peninsula. The major cellular fatty acids of isolates were C16:0, C18:0, C18:1 x7c 11-methyl, summed feature 3 and summed feature 8. The major polar lipids were phosphatidylethanolamine (PE), aminolipids (AL) and phosphatidylcholine (PC). Phylogenetic analysis based on the 16S rRNA locus showed that they belonged to the Bradyrhizobium genus, and shared the highest similarity to the type strains Bradyrhizobium oligotrophicum S58T and Bradyrhizobium denitrificans LMG 8443T. As expected, analysis of concatenated sequences of six housekeeping genes (atpD, recA, glnII, dnaK, gyrB, and rpoB) and nifH gene proposed that these three strains formed a distinct clade within the genus Bradyrhizobium. The highest average nucleotide identity and DNA-DNA hybridization values of the three strains in comparison to the closest Bradyrhizobium species were 87.5% and 65.3%, respectively, which are far below the threshold of species delineation, and thus confirmed the three strains as a new species. The genome size of strain 83002T is 7.52 Mbp, and the DNA G+C content is 65.42 mol%. Strain 83002T (=KCTC 82266T=MCCC 1K04775T) was chosen as the type strain of the new species, for which the name Bradyrhizobium aeschynomenes sp. nov. was proposed

The Historical Speciation of <i>Mauremys</i> Sensu Lato: Ancestral Area Reconstruction and Interspecific Gene Flow Level Assessment Provide New Insights

<div><p><i>Mauremys</i> sensu lato was divided into <i>Mauremys</i>, <i>Chinemys</i>, <i>Ocadia</i>, and <i>Annamemys</i> based on earlier research on morphology. Phylogenetic research on this group has been controversial because of disagreements regarding taxonomy, and the historical speciation is still poorly understood. In this study, 32 individuals of eight species that are widely distributed in Eurasia were collected. The complete mitochondrial (mt) sequences of 14 individuals of eight species were sequenced. Phylogenetic relationships, interspecific divergence times, and ancestral area reconstructions were explored using mt genome data (10,854 bp). Subsequent interspecific gene flow level assessment was performed using five unlinked polymorphic microsatellite loci. The Bayesian and maximum likelihood analyses revealed a paraphyletic relationship among four old genera (<i>Mauremys</i>, <i>Annamemys</i>, <i>Chinemys</i>, and <i>Ocadia</i>) and suggested the four old genera should be merged into the genus (<i>Mauremys</i>). Ancestral area reconstruction and divergence time estimation suggested Southeast Asia may be the area of origin for the common ancestral species of this genus and genetic drift may have played a decisive role in species divergence due to the isolated event of a glacial age. However, <i>M</i>. <i>japonica</i> may have been speciated due to the creation of the island of Japan. The detection of extensive gene flow suggested no vicariance occurred between Asia and Southeast Asia. Inconsistent results between gene flow assessment and phylogenetic analysis revealed the hybrid origin of <i>M</i>. <i>mutica</i> (Southeast Asian). Here ancestral area reconstruction and interspecific gene flow level assessment were first used to explore species origins and evolution of <i>Mauremys</i> sensu lato, which provided new insights on this genus.</p></div

Chronogram using BEAST 1.8.0 based on mt heavy chain 12 protein-coding genes.

<p>A. Divergence time estimation; B. The trend of temperature change redrawn from Zachos et al.’s results [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0144711#pone.0144711.ref027" target="_blank">27</a>]. The red zone represents the warming period. The blue zone represents the glacial period.</p

Results for ancestral area reconstruction inferred from BBM and S-DIVA based on mt heavy chain 12 protein-coding genes.

<p>The map is from the Central Intelligence Agency (CIA: <a href="https://www.cia.gov/library/publications/the-world-factbook/index.html" target="_blank">https://www.cia.gov/library/publications/the-world-factbook/index.html</a>). Potential original areas are coded as A: East Asia, B: Southeast Asia and Western Palearctic region (C: West Asia + D: West Europe + E: South Europe and North Africa), shown by different colours in the area pie chart.</p

Phylogenetic trees for <i>Mauremys</i> sensu lato reconstructed based on mt heavy chain 12 protein-coding genes.

<p>Numbers of nearby branches are posterior probabilities (PPs, Left) and bootstrap proportions (BPs, Right) recovered from BI and ML analyses, respectively. Four old genera of <i>Mauremys</i> sensu lato are shown using different colours; i.e., red represents <i>Chinemys</i>; green represents <i>Ocadia</i>; purple represents <i>Mauremys</i>; blue represents <i>Annamemys</i>.</p