[DNA barcoding of 4 species of cheyletid mites based on COI and 18S rRNA gene sequences]

OBJECTIVE

To analyze the sequences of mitochondrial cytochrome C oxidase subunit I gene (COI) and 18S ribosomal RNA gene (18S rRNA), so as to identify the feasible DNA barcodes for 4 species of cheyletid mites and improve the DNA barcoding database for cheyletid mites.

METHODS

Cheyletid mite samples were collected from small-scale flour mills in Fuyang, Wuhu and Tongling cities of Anhui Province from May 2018 to July 2019, extracted and morphologically identified. Then, genomic DNA was extracted from a single cheyletid mite, and the COI and 18S rRNA gene sequences were obtained by PCR amplification, cloning and sequencing. The obtained sequences were aligned using the BLAST software. Multiple sequence alignment was done using the software ClustalX version 1.83 using the known gene sequences from cheyletid mites. The genetic distance was calculated using the software MEGA X, and the phylogenetic tree was created using the maximum likelihood method.

RESULTS

The DNA barcoding results of Cheyletus malaccensis, C. carnifex and Cheletomorpha lepidopterorum were consistent with the morphological identification, while no sequences pertaining to Eucheyletia reticulate were retrieved in the GenBank database. The proportions of A + T were 69.6% and 55.1% in the COI and 18S rRNA sequences of 4 cheyletid mites species, respectively, and the numbers of base substitutions were 137 and 46, respectively. There were 154 to 321 and 58 to 99 inter-species variation loci in the COI and 18S rRNA gene sequences of 4 cheyletid mites species, respectively, and the intra-species genetic distance was all 0.020 or less in the COI and 18S rRNA gene sequences of 4 cheyletid mites species, with inter-species genetic distance of 0.235 to 0.583 and 0.078 to 0.114, respectively. Phylogenetic analysis based on COI and 18S rRNA genes showed that all four species of cheyletid mites were clustered into a branch with a 100% supportive rate, which was consistent with the morphological identification.

CONCLUSIONS

Mitochondrial COI gene is superior to 18S rRNA gene as DNA barcodes for 4 species of cheyletid mites, which is more suitable to be used to investigate the phylogenetic relationship of at genus and species levels.

Accurate ab initio-based adiabatic global potential energy surface for the 2(2)A" state of NH2 by extrapolation to the complete basis set limit

A full three-dimensional global potential energy surface is reported first time for the title system, which is important for the photodissociation processes. It is obtained using double many-body expansion theory and an extensive set of accurate ab initio energies extrapolated to the complete basis set limit. Such a work can be recommended for dynamics studies of the N((2)D) + H2 reaction, a reliable theoretical treatment of the photodissociation dynamics and as building blocks for constructing the double many-body expansion potential energy surface of larger nitrogen/hydrogen containing systems. In turn, a preliminary theoretical study of the reaction N((2)D)+H2(X(1)Σg (+))(ν=0,j=0)→NH(a(1)Δ)+H((2)S) has been carried out with the method of quasi-classical trajectory on the new potential energy surface. Integral cross sections and thermal rate constants have been calculated, providing perhaps the most reliable estimate of the integral cross sections and the rate constants known thus far for such a reaction.

Ab initio-based double many-body expansion potential energy surface for the first excited triplet state of the ammonia molecule

A global single-sheeted double many-body expansion potential energy surface is reported for the first excited triplet state of NH(3). It employs an approximate cluster expansion of the molecular potential that utilizes previously reported functions of the same family for the triatomic fragments. Four-body energy terms have been calibrated from extensive accurate ab initio data so as to reproduce the main features of the title system. A new switching function formalism has been reported to approximate the true multisheeted nature of NH(3)((3)A(2) ('')) potential energy surface, thus allowing the correct behavior at the NH(2)((2)A(")) + H((2)S) and NH(2)((4)A(")) + H((2)S) dissociation limits. The resulting fully six-dimensional potential energy function reproduces the correct symmetry under the permutation of identical atoms, and predicts the correct behavior at all dissociation channels while providing a realistic representation at all interatomic separations. The major attributes of the NH(3) double many-body expansion potential energy surface have also been characterized, and found to be in good agreement, both with the calculated ones from the raw ab initio energies and the theoretical results available in the literature.

Extensive partition operators, gray-level connected operators, and region merging/classification segmentation algorithms: theoretical links

The relation between morphological gray-level connected operators and segmentation algorithms based on region merging/classification strategies has been pointed out several times in the literature. However, to the best of our knowledge, the formal relation between them has not been established. This paper presents the link between the two domains based on the observation that both connected operators and segmentation algorithms share a key mechanism: they simultaneously operate on images and on partitions, and therefore they can be described as operations on a joint image-partition model. As a result, we analyze both segmentation algorithms and connected operators by defining operators on complete product lattices, that explicitly model gray-level and partition attributes. In the first place, starting with a complete lattice of partitions, we initially define the concept of the segmentation model as a mapping in a product lattice, whose elements are three-tuples consisting of a partition, an image that models the partition attributes, and an image that represents the gray-level model associated to the segmentation. Then, assuming a conditional ordering relation, we show that any region merging/classification segmentation algorithm can be defined as an extensive operator in such a complete product lattice, in the second place, we proposed a very similar lattice-based extended representation of gray-level functions in the context of connected operators, that highlights the mathematical analogy with segmentation algorithms, but in which the ordering relation is different. We use this framework to show that every region merging/classification segmentation algorithm indeed corresponds to a connected operator. While this result provides an explanation to previous work in the area, it also opens possibilities for further analysis in the two domains. From this perspective, we additionally study some theoretical properties of a general region merging segmentation algorithm.

In Search of Emerging Magnetic Flux underneath the Solar Surface with Acoustic Imaging

With the method of acoustic imaging in helioseismology, we study an emerging flux region, NOAA 7978, using data taken with instruments of the Taiwan Oscillation Network (TON) and the Michelson Doppler Imager (MDI). Phase-shift maps of NOAA 7978 focusing at different depths are constructed, which show the evolution of emerging magnetic flux. Although the emerging flux below the solar surface is not easy to be directly recognized in the phase-shift maps, average phase shifts over the active region reveal the signature of upward-moving magnetic flux in the solar interior. The average phase shifts in the interior normalized to their surface values are larger at earlier times in both the TON and the MDI data. This suggests that the flux below the surface is moving upward during the development of the active region.