Spatial-Modulated Physical-Layer Network Coding Based on Block Markov Superposition Transmission for Maritime Relay Communications

As an alternative to satellite communications,multi-hop relay networks can be deployed for maritime long-distance communications.Distinct from terrestrial environment,marine radio signals are affected by many factors,e.g.,weather conditions,evaporation ducting,and ship rocking caused by waves.To ensure the data transmission reliability,the block Markov superposition transmission(BMST)codes,which are easily configurable and have predictable performance,are applied in this study.Meanwhile,the physical-layer network coding(PNC)scheme with spatial modulation(SM)is adopted to improve the spectrum utilization.For the BMST-SMPNC system,we propose an iterative algorithm,which utilizes the channel observations and the a priori information from BMST decoder,to compute the soft information corresponding to the XORed bits constructed by the relay node.The results indicate that the proposed scheme outperforms the convolutional coded SM-PNC over fast-fading Rician channels.Especially,the performance can be easily improved in high spatial correlation maritime channel by increasing the memory m.

Evolutionary analysis of Omicron variant BF.7 and BA.5.2 pandemic in China

On December 7,2022,China adjusted public health control measures,there have been widespread of SARS-CoV-2 infections in Chinese mainland.As the number of infected people increased,the mutation probability of SARS-CoV-2 is also raised.Therefore,it is of great importance to monitor SARS-CoV-2 variants and its mutations in China.In this current study,665 SARS-CoV-2 genomes from China deposited in the public database were used to analyze the proportion of different variants;to determine the composition of variants in China across different provinces;and analyze specific mutation frequency,focusing on 12 immune escape residues.The results showed that no new mutations were generated on the 12 immune escape residues.The evolutionary analysis of the BF.7 variant circulating in China showed that there is an independent evolutionary branch with unique mutation sites,officially named BF.7.14 by PANGO.This variant may have been imported from Russia to Inner Mongolia at the end of September 2022 and continued its spread in China.The evolutionary analysis of BA.5.2 variant shows that the variant is composed of two sub-variants,named BA.5.2.48 and BA.5.2.49 by PANGO,respectively.This variant may have been imported from abroad to Beijing at the beginning of September 2022 and formed two sub-variants after domestic transmission.Finally,this study showed that current epidemic variants in China were already circulating in other countries,and there were no additional mutations on immune escape residues that could pose a threat to other countries.

Origin and evolutionary analysis of the SARS-CoV-2 Omicron variant

The severe acute respiratory syndrome coronavirus 2(SARS-CoV-2)has evolved rapidly into new variants throughout the pandemic.The Omicron variant has more than 50 mutations when compared with the original wild-type strain and has been identified globally in numerous countries.In this report,we analyzed the mutational profiles of several variants,including the per-site mutation rate,to determine evolutionary relationships.The Omicron variant was found to have a unique mutation profile when compared with that of other SARS-CoV-2 variants,containing mutations that are rare in clinical samples.Moreover,the presence of five mouse-adapted mutation sites suggests that Omicron may have evolved in a mouse host.Mutations in the Omicron receptor-binding domain(RBD)region,in particular,have potential implications for the ongoing pandemic.

“Mutation blacklist”and “mutation whitelist”of SARS-CoV-2

Over the past two years,scientists throughout the world have completed more than 6 million SARS-CoV-2 genome sequences.Today,the number of SARS-CoV-2 genomes exceeds the total number of all other viral genomes.These genomes are a record of the evolution of SARS-CoV-2 in the human host,and provide information on the emergence of mutations.In this study,analysis of these sequenced genomes identified 296,728 de novo mutations(DNMs),and found that six types of base substitutions reached saturation in the sequenced genome population.Based on this analysis,a“mutation blacklist”of SARS-CoV-2 was compiled.The loci on the“mutation blacklist”are highly conserved,and these mutations likely have detrimental effects on virus survival,replication,and transmission.This information is valuable for SARS-CoV-2 research on gene function,vaccine design,and drug development.Through association analysis of DNMs and viral transmission rates,we identified 185 DNMs that positively correlated with the SARS-CoV-2 transmission rate,and these DNMs where classified as the“mutation whitelist”of SARS-CoV-2.The mutations on the“mutation whitelist”are beneficial for SARS-CoV-2 transmission and could therefore be used to evaluate the transmissibility of new variants.The occurrence of mutations and the evolution of viruses are dynamic processes.To more effectively monitor the mutations and variants of SARS-CoV-2,we built a SARS-CoV-2 mutation and variant monitoring and pre-warning system(MVMPS),which can monitor the occurrence and development of mutations and variants of SARSCoV-2,as well as provide pre-warning for the prevention and control of SARS-CoV-2(https://www.omicx.cn/).Additionally,this system could be used in real-time to update the“mutation whitelist”and“mutation blacklist”of SARS-CoV-2.

Massive‐scale genomic analysis reveals SARS‐CoV‐2 mutation characteristics and evolutionary trends

The severe acute respiratory syndrome coronavirus 2(SARS‐CoV‐2)pandemic resulted in significant societal costs.Hence,an in‐depth understanding of SARS‐CoV‐2 virus mutation and its evolution will help determine the direction of the COVID‐19 pandemic.In this study,we identified 296,728 de novo mutations in more than 2,800,000 high‐quality SARS‐CoV‐2 genomes.All possible factors affecting the mutation frequency of SARS‐CoV‐2 in human hosts were analyzed,including zinc finger antiviral proteins,sequence context,amino acid change,and translation efficiency.As a result,we proposed that when adenine(A)and tyrosine(T)bases are in the context of AM(M stands for adenine or cytosine)or TA motif,A or T base has lower mutation frequency.Furthermore,we hypothesized that translation efficiency can affect the mutation frequency of the third position of the codon by the selection,which explains why SARS‐CoV‐2 prefers AT3 codons usage.In addition,we found a host‐specific asymmetric dinucleotide mutation frequency in the SARS‐CoV‐2 genome,which provides a new basis for determining the origin of the SARS‐CoV‐2.Finally,we summarize all possible factors affecting mutation frequency and provide insights into the mutation characteristics and evolutionary trends of SARS‐CoV‐2.