Deflagration characteristics of freely propagating flames in magnesium hydride dust clouds

The flame propagation processes of MgH_(2)dust clouds with four different particle sizes were recorded by a high-speed camera.The dynamic flame temperature distributions of MgH_(2)dust clouds were reconstructed by the two-color pyrometer technique,and the chemical composition of solid combustion residues were analyzed.The experimental results showed that the average flame propagation velocities of 23μm,40μm,60μm and 103μm MgH_(2)dust clouds in the stable propagation stage were 3.7 m/s,2.8 m/s,2.1 m/s and 0.9 m/s,respectively.The dust clouds with smaller particle sizes had faster flame propagation velocity and stronger oscillation intensity,and their flame temperature distributions were more even and the temperature gradients were smaller.The flame structures of MgH_(2)dust clouds were significantly affected by the particle sinking velocity,and the combustion processes were accompanied by micro-explosion of particles.The falling velocities of 23μm and 40μm MgH_(2)particles were 2.24 cm/s and 6.71 cm/s,respectively.While the falling velocities of 60μm and 103μm MgH_(2)particles were as high as 15.07 cm/s and 44.42 cm/s,respectively,leading to a more rapid downward development and irregular shape of the flame.Furthermore,the dehydrogenation reaction had a significant effect on the combustion performance of MgH_(2)dust.The combustion of H_(2)enhanced the ignition and combustion characteristics of MgH_(2)dust,resulting in a much higher explosion power than the pure Mg dust.The micro-structure characteristics and combustion residues composition analysis of MgH_(2)dust indicated that the combustion control mechanism of MgH_(2)dust flame was mainly the heterogeneous reaction,which was affected by the dehydrogenation reaction.

Microbiome research outlook:past,present,and future

With its critical role in human health and disease,the microbiome has transformed modern biology.Over the past few years,microbiome research has evolved rapidly,with microbiologists gradually shifting their focus from cataloging microorganisms in the human microbiome to understanding their functional roles and how they interact with the host.Here,we present the global trends in microbiome research and summarize the past and current work on microbiome published in Protein&Cell.

Seven facts and five initiatives for gut microbiome research

The gut microbiome has attracted increasing attention over the past 15 years.Along with the fast-growing body of research literature and media reports,the public's opinions on the gut microbiome have begun to appear polarized.Some believe that the gut microbiome is at the core of human health and is related to every single disease.To the opposite,some people question the scientific basis of gut microbiome studies and criticize that many of them are farfetched;there is even a joke spreading in the biomedical research field—"keeping gut microbiome in mind,no mechanism is hard to find".

Genomic evolution during locoregional recurrence in colorectal cancer determined by whole-exome sequencing: a retrospective observational study

Objective:The genomic landscapes of metastatic colorectal cancer(mCRC)have been extensively studied;however,the genetic mechanisms underlying the locoregional recurrence(LR)of CRC remain unclear.The objective of our study was to investigate genomic evolution during LR in CRC using high-throughput sequencing.Methods:Twenty-three CRC patients with matched primary and LR tissues were recruited from Nanfang Hospital and Zhejiang Cancer Hospital between January 2011 and December 2018.The last date of follow-up was March 2020.Tissue samples were analyzed by whole-exome sequencing and the genomic profiles were depicted by single nucleotide variation,mutational signature,copy number variation,clonal architecture,and other features.The evolutionary process was speculated with comparison of the genetic variations between primary and LR lesions.The disseminating clusters from primary to LR lesions were identified by variant allele frequency dynamics.Furthermore,the early-recurrent biomarker was explored by comparing the indel signature between early-and late-recurrent patients.The study was approved by the Institutional Review Board of Nanfang Hospital of Southern Medical University(approval No.2020010)on September 11,2020.Results:The results highlighted distinct origins of LR between patients with high microsatellite instability and microsatellite stability.LR lesions evolved independently in patients with high microsatellite instability,while LR lesions were highly clonally related to the primary lesions in patients with microsatellite stability.Late-acquired variations in LR lesions encompassed a wide range of driver genes involved in histone methylation,DNA replication,T cell activation,PDCD1 gain,and LMNA loss.Furthermore,clonal analysis of the disseminating cells identified a dominant polyclonal seeding pattern during LR.The indel signature ID4 was associated with significantly shorter disease-free survival in patients with relapsed CRC according to a public dataset.Conclusion:These findings pose a challenge for the development of new approaches targeting the interactions of multiple clones in the establishment of LR and in terms of optimizing the clinical management of susceptible patients.