Long-Term Orbit Prediction and Deorbit Disposal Investigation of MEO Navigation Satellites

With the increase in satellites in the medium Earth orbit (MEO) region, there should be a focus on orbit safety in the MEO region. A safe orbit disposal strategy is necessary to maintain the sustainability of the MEO region. This paper focuses on long-term evolution modeling, safety analysis of MEO objects, and different disposal techniques for end-of-life BDS-2 MEO satellites. On the one hand, a long-term numerical evolution model is established, and mean equinoctial elements are adopted to propagate a long-term orbit. Long-term evolution for the MEO region over 100 years is carried out, including the Galileo, BDS, GPS, and GLONASS constellations. The earliest orbit intersection time with other global navigation satellite system (GNSS) constellations is put forward. On the other hand, a dynamic model and an optimization model for disposal orbit are established, which minimize the eccentricity growth within 200 years and the fuel consumption for maneuvering to the disposal orbit. The bounds for the disposal region of BDS MEO satellites are also proposed, which consider the measurement and control error of BDS MEO satellites and the eccentricity bounds for end-of-life BDS MEO satellites. A genetic algorithm is adopted to optimize the orbital elements for end-of-life BDS MEO satellites. In addition, two disposal cases, namely, upraising and reducing the orbit, for end-of-life BDS MEO satellites are simulated. The long-term evolutions for the disposal of orbital elements within 200 years are implemented, and the fuel consumption is calculated. The results show that the current MEO region is relatively safe and that the eccentricity is the most important factor that influences the long-term evolution of safety analysis for BDS MEO disposal orbits. Upraising the orbit is safe for end-of-life BDS MEO satellites. This investigation provides the theoretical foundation for investigating the long-term evolutionary mechanisms of the MEO region and references disposal strategy analysis for decommissioned navigation satellites, and the spent upper stages for other GNSS constellations

Long-Term Orbit Prediction and Deorbit Disposal Investigation of MEO Navigation Satellites

With the increase in satellites in the medium Earth orbit (MEO) region, there should be a focus on orbit safety in the MEO region. A safe orbit disposal strategy is necessary to maintain the sustainability of the MEO region. This paper focuses on long-term evolution modeling, safety analysis of MEO objects, and different disposal techniques for end-of-life BDS-2 MEO satellites. On the one hand, a long-term numerical evolution model is established, and mean equinoctial elements are adopted to propagate a long-term orbit. Long-term evolution for the MEO region over 100 years is carried out, including the Galileo, BDS, GPS, and GLONASS constellations. The earliest orbit intersection time with other global navigation satellite system (GNSS) constellations is put forward. On the other hand, a dynamic model and an optimization model for disposal orbit are established, which minimize the eccentricity growth within 200 years and the fuel consumption for maneuvering to the disposal orbit. The bounds for the disposal region of BDS MEO satellites are also proposed, which consider the measurement and control error of BDS MEO satellites and the eccentricity bounds for end-of-life BDS MEO satellites. A genetic algorithm is adopted to optimize the orbital elements for end-of-life BDS MEO satellites. In addition, two disposal cases, namely, upraising and reducing the orbit, for end-of-life BDS MEO satellites are simulated. The long-term evolutions for the disposal of orbital elements within 200 years are implemented, and the fuel consumption is calculated. The results show that the current MEO region is relatively safe and that the eccentricity is the most important factor that influences the long-term evolution of safety analysis for BDS MEO disposal orbits. Upraising the orbit is safe for end-of-life BDS MEO satellites. This investigation provides the theoretical foundation for investigating the long-term evolutionary mechanisms of the MEO region and references disposal strategy analysis for decommissioned navigation satellites, and the spent upper stages for other GNSS constellations

Mitochondrial genome evolution in the <i>Saccharomyces sensu stricto</i> complex - Fig 4

<p>(A) The nucleotide identities of all mitochondrial genes in the <i>Saccharomyces sensu stricto</i> group. The nucleotide identity was calculated based on the proportion of completely conserved nucleotides in multiple sequence alignments of five <i>SSS</i> yeasts conducted using ClustalOmega. The red bars represent protein-coding genes; the green bar is rRNA; the gray bar is tRNA and the yellow bar is <i>rpm1</i>. (B) Comparison of amino-acid identities among nuclear proteins, nuclear MT proteins and mitochondrial proteins. We identified 3,887 nuclear proteins which are present in all five <i>SSS</i> yeasts. Among them, 618 proteins were located in the mitochondria. The amino-acid identity for each protein was calculated based on the proportion of completely conserved amino-acid residues in the multiple sequences alignment (MSA) results. The dark blue, green and yellow bars represent the distribution of nuclear proteins, nuclear MT proteins and mitochondrial proteins, respectively. The table insert indicates the number of proteins which have identities greater than 90% in three protein sets. The <i>p</i>-values were calculated based on a hypergeometric test whether the number of MT proteins with high identity was significantly greater than those in the other two protein sets. (C) Box-plot comparisons of the dN/dS ratios estimated for the eight MT protein-coding genes between the genus <i>Lachancea</i> and the <i>Saccharomyces sensu stricto</i> linage.</p

The distribution of introns in mtDNAs.

<p><b>(A) <i>cox1</i> gene; (B) <i>cob</i> gene (C) <i>rnl</i> gene.</b> The X axis represents the gene length and the vertical lines indicate the position of introns. The numbers on top represent the relative location of each intron in different yeasts. The rectangular frames indicate Group II introns, which include introns 1, 2 and 10 in <i>cox1</i>, and intron 3 in <i>cob</i>. The triangular frames indicate the Group I introns. The filled frames indicate the introns with embedded ORFs, and the empty frames indicate introns without ORFs.</p

Evolution of gene order within the <i>Saccharomyces sensu stricto</i> group.

<p>Block1 includes <i>rnl</i>, <i>tRNAs</i> (T2,C,H,L,Q,K,R1,G,D,S1,R2,A,I,Y,N,M1) and <i>cox2</i>. Block2 includes <i>tRNAs</i> (F,T1,V), and <i>cox3</i>. Block3 includes <i>tRNA</i> (M2), <i>rpm1</i> and <i>tRNA</i> (P). Block4 includes <i>cox1</i>, <i>atp8</i> and <i>atp6</i>. Block5 includes <i>tRNA</i> (E) and <i>cob</i>. Block6 includes <i>rns</i> and <i>tRNA</i> (W). Block7 includes <i>atp9</i>, <i>tRNA</i> (S2) and <i>var1</i>. The downward and upward black arrows indicate the <i>ori</i> sequences in the positive and negative strands, respectively. The dashed arrows indicate that the <i>ori</i> sequences contain intervening GC clusters.</p

Occurrence and Characterization of <i>Sclerotinia sclerotiorum</i> Causing Fruit Rot on Sweet Cherry in Southern China

Sweet cherry (Prunus avium L.) is widely planted in northern China due to its high economic value, and its cultivation has gradually spread south to warm regions. However, fruit rot, observed on the young fruits, poses a considerable threat to the development of sweet cherry. To determine the causal agent, morphological observation, molecular identification, and pathogenicity tests were performed on isolates obtained from diseased fruits. As a result, Sclerotinia sclerotiorum was identified as the pathogen. Pathogenicity tests on different sweet cherry cultivars indicated that ‘Summit’ was highly sensitive to S. sclerotiorum, whereas ‘Hongmi’ showed significant resistance. Besides sweet cherry, S. sclerotiorum could also infect other vegetable crops we tested, such as cowpea, soybean, tomato, and chili. Fungicide sensitivity and efficacy assays showed that both fludioxonil and pyraclostrobin can effectively inhibit the mycelial growth of S. sclerotiorum and decrease disease incidences on the young fruits of sweet cherry. Furthermore, genome sequencing resulted in a 37.8 Mb assembly of S. sclerotiorum strain ScSs1, showing abundant SNPs, InDels, and SVs with the genome of S. sclerotiorum reference strain 1980 UF-70. The above results provide an important basis for controlling the fruit rot of sweet cherry caused by S. sclerotiorum in China

Design of Seven-core Photonic Crystal Fiber with Flat In-phase Mode for Yb: Fiber Laser Pumping

International audienc

Effect of stock density on the microbial community in biofloc water and Pacific white shrimp (Litopenaeus vannamei) gut microbiota

Biofloc technology is an efficient approach for intensive shrimp culture. However, the extent to which this process can influence the composition of intestinal microbial community is still unknown. Here, we surveyed the shrimp intestinal bacteria as well as the floc water from three biofloc systems with different stock densities. Our study revealed a similar variation trend in phylum taxonomy level between floc bacteria and gut microbiota. Microbial community varied notably in floc water from different stock densities, while a core genus with dominating relative abundance was detected in gut samples. Extensive variation was discovered in gut microbiota, but still clustered into groups according to stock density. Our results indicated that shrimp intestinal microbiota as well as bacteria aggregated in flocs assembled into distinct communities from different stock densities, and the intestinal communities were more similar with the surrounding environment as the increase of stock density and resulting high floc biomass. The high stock density changed the core gut microbiota by reducing the relative abundance of Paracoccus and increasing that of Nocardioides, which may negatively influence shrimp performance. Therefore, this study helps us to understand further bacteria and host interactions in biofloc system.</p

Multi-omics analysis reveals niche and fitness differences in typical denitrification microbial aggregations

Suspended floc and fixed biofilm are two commonly applied strategies for heterotrophic denitrification in wastewater treatment. These two strategies use different carbon sources and reside within different ecological niches for microbial aggregation, which were hypothesized to show distinct microbial structures and metabolic fitness. We surveyed three floc reactors and three biofilm reactors for denitrification and determined if there were distinct microbial aggregations. Multiple molecular omics approaches were used to determine the microbial community composition, co-occurrence network and metabolic pathways. Proteobacteria was the dominating and most active phylum among all samples. Carbon source played an important role in shaping the microbial community composition while the distribution of functional protein was largely influenced by salinity. We found that the topological network features had different ecological patterns and that the microorganisms in the biofilm reactors had more nodes but less interactions than those in floc reactors. The large niche differences in the biofilm reactors explained the observed high microbial diversity, functional redundancy and resulting high system stability. We also observed a lower proportion of denitrifiers and higher resistance to oxygen and salinity perturbation in the biofilm reactors than the floc reactors. Our findings support our hypothesis that niche differences caused a distinct microbial structure and increased microbial ecology distribution, which has the potential to improve system efficiency and stability.</p

Carbon availability shifts the nitrogen removal pathway and microbial community in biofilm airlift reactor

This study investigated the response of nitrogen removal performance and microbial community to different carbon composites in biofilm airlift reactors for wastewater treatment. Three reactors were filled with poly (butylene succinate) and bamboo powder composite at the blending ratio of 9:1, 1:1 and 1:9. Increasing the component of bamboo powder in the carrier reduced the carbon availability and had an adverse effect on nitrate removal efficiency. However, bamboo powder improved the ammonia removal rate which mainly through autotrophic nitrification. Three reactors exhibited distinct microbial compositions in both bacterial and fungal diversity. High inclusion of bamboo power decreased the relative abundance of denitrifiers Denitromonas and increased the relative abundance of nitrifiers, including Nitromonas, Nitrospina and Nitrospira. Moreover, correlation network revealed a competitive interaction between the taxa responsible for ammonia removal and nitrate removal processes. Those results indicated the feasibility of steering nitrogen removal pathway through carrier formulation in wastewater treatment.</p