The development of efficient sequencing techniques has resulted in large numbers of genomes being available for evolutionary studies. However, only one genome is available for all amphibians, that of Xenopus tropicalis, which is distantly related from the majority of frogs. More than 96% of frogs belong to the Neobatrachia, and no genome exists for this group. This dearth of amphibian genomes greatly restricts genomic studies of amphibians and, more generally, our understanding of tetrapod genome evolution. To fill this gap, we provide the de novo genome of a Tibetan Plateau frog, Nanorana parkeri, and compare it to that of X. tropicalis and other vertebrates. This genome encodes more than 20,000 protein-coding genes, a number similar to that of Xenopus. Although the genome size of Nanorana is considerably larger than that of Xenopus (2.3 vs. 1.5 Gb), most of the difference is due to the respective number of transposable elements in the two genomes. The two frogs exhibit considerable conserved whole-genome synteny despite having diverged approximately 266 Ma, indicating a slow rate of DNA structural evolution in anurans. Multigenome synteny blocks further show that amphibians have fewer interchromosomal rearrangements than mammals but have a comparable rate of intrachromosomal rearrangements. Our analysis also identifies 11 Mb of anuran-specific highly conserved elements that will be useful for comparative genomic analyses of frogs. The Nanorana genome offers an improved understanding of evolution of tetrapod genomes and also provides a genomic reference for other evolutionary studies.de novo genome | transposable elements | chromosome rearrangement | highly conserved element T he age of genomics has ushered in opportunities to decode the history of evolution in ways unimaginable only a decade ago. More than 100 complete genomes have been sequenced and released for vertebrates. Amphibians, however, are poorly represented among these genomes. Despite the existence of more than 7,000 living species of amphibians, only the genome of Xenopus tropicalis (1) has been published. Xenopus tropicalis, however, falls outside of the Neobatrachia, which contains more than 96% of the known frog species (2). As a result, no neobatrachian genome is available for comparative analyses. Thus, this dearth of amphibian genomes greatly restricts comparative genomic studies of amphibians, and more generally, our understanding of a critical portion of tetrapod genome evolution at the major aquatic to terrestrial transition of vertebrates.Nanorana (Dicroglossidae) includes more than 20 species of frogs native to Asia (research.amnh.org/vz/herpetology/amphibia). In this genus, three species, Nanorana parkeri, Nanorana pleskei, and Nanorana ventripunctata, are endemic to the QinghaiTibetan Plateau (3). In contrast to Xenopus, which is a secondarily derived aquatic obligate, species of Nanorana exhibit the terrestrial adult lifestyle that is typical of most anurans. N. parkeri occurs at elevations ranging from 2,850 to 5,000 m. Because thi...
The presented work aimed at investigating the hydrogasification of low-oxygen semi-coke. For comparison, the hydrogasification of lignite was conducted. Variation of gaseous products concentration and reaction rate of the semi-coke hydrogasification process were investigated. The results shown that the methane yield of low-oxygen semi-coke is 24.8% greater than the lignite, but also the hydrogen consumption reduced greatly; the hydrogasification process can be divided into three stages: hydro-pyrolysis stage, rapid hydrogasification stage and slow speed hydrogasification stage; the difference of the reactive is attributed to different carbon structure forms .
The sound insulation performance of the dash panel has a direct influence on the level of sound absorption of the whole vehicle. Therefore, it is necessary to adopt proper optimization strategies to optimize the dash panel and interior sound pressure response. Firstly, damping loss factor was imported into the dash panel and the coupling model of interior acoustic cavity to compute the sound pressure response of the driver. Sound pressure response had multiple peak noises in the analyzed frequency band. With the increase of the analyzed frequency, Contours for the noise of interior acoustic cavity became increasingly dispersed. Secondly, reverberation chambers on both sides were coupled with the dash panel respectively to establish AML model. In this way, the computational transmission loss would be more consistent with the actual situation. AML method can directly obtain transmission loss without extracting the transmission sound power to compute transmission loss through relevant formulas. In reported papers, there are big differences between simulation and experiment in the low frequency because it is difficult to simulate the real boundary conditions. The computational results of this paper were more consistent with experimental results in the whole frequency band, which indicated that it was more effective to use AML method to compute the transmission loss of the dash panel. Then, a sound package was applied to the dash panel to conduct parametric analysis. Results showed that the thickness of the sound-absorption layer could effectively improve transmission loss over 250 Hz. When the thickness of the sound-absorption layer was 15 mm, transmission loss was relatively optimal. In addition, the thickness of the air layer had little influence on transmission loss. Finally, genetic algorithm was also used to optimize the parameters of sound package of the dash panel. Results showed that the optimized dash panel had a higher average transmission loss and total mass, and the average sound pressure response of the driver also decreased. Additionally, the transmission loss and sound pressure response of the driver optimized by genetic algorithm at each frequency point were improved in the analyzed frequency band to obtain a low-noise and lightweight dash panel.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.