Design and Analysis of an Active Helical Drive Downhole Tractor

During oil-gas well drilling and completion, downhole tools and apparatus should be conveyed to the destination to complete a series of downhole works. Downhole tractors have been used to convey tools in complex wellbores, however a very large tractive force is needed to carry more downhole tools to accomplish works with high efficiency. A novel serial active helical drive downhole tractor which has significantly improved performance compared with previous work is proposed. All previously reported helical drive downhole tractors need stators to balance the torque generated by the rotator. By contrast, the proposed serial downhole tractor does not need a stator; several rotator-driven units should only be connected to one another to achieve a tractive force multifold higher than that was previously reported. As a result, the length of a single unit is shortened, and the motion flexibility of the downhole tractor is increased. The major performance indicators, namely, gear ratio, velocity, and tractive force, are analyzed. Experimental results show that the maximum tractive force of a single-unit prototype with a length of 900 mm is 165.3 kg or 1620 N. The analysis and experimental results show that the proposed design has considerable potential for downhole works.

Whole‑genome transcriptome and DNA methylation dynamics of pre‑implantation embryos reveal progression of embryonic genome activation in buffaloes

Background During mammalian pre-implantation embryonic development(PED),the process of maternal-to-zygote transition(MZT)is well orchestrated by epigenetic modification and gene sequential expression,and it is related to the embryonic genome activation(EGA).During MZT,the embryos are sensitive to the environment and easy to arrest at this stage in vitro.However,the timing and regulation mechanism of EGA in buffaloes remain obscure.Results Buffalo pre-implantation embryos were subjected to trace cell based RNA-seq and whole-genome bisulfite sequencing(WGBS)to draw landscapes of transcription and DNA-methylation.Four typical developmental steps were classified during buffalo PED.Buffalo major EGA was identified at the 16-cell stage by the comprehensive analy-sis of gene expression and DNA methylation dynamics.By weighted gene co-expression network analysis,stage-spe-cific modules were identified during buffalo maternal-to-zygotic transition,and key signaling pathways and biological process events were further revealed.Programmed and continuous activation of these pathways was necessary for success of buffalo EGA.In addition,the hub gene,CDK1,was identified to play a critical role in buffalo EGA.Conclusions Our study provides a landscape of transcription and DNA methylation in buffalo PED and reveals deeply the molecular mechanism of the buffalo EGA and genetic programming during buffalo MZT.It will lay a foundation for improving the in vitro development of buffalo embryos.

An Insight on Small Molecule Induced Foot-Print Free Naive Pluripotent Stem Cells in Livestock

Bona fide embryonic stem cell (ESC) lines from livestock species have been challenging to derive and maintain, contrasting mouse and human ESCs. However, induced pluripotent stem cells (iPSC) generated by reprogramming somatic cells tender an option, as they display characteristic features of ESC. The comprehension that induced pluripotent stem cells (iPSC) could be created with in no time also holds the potential of allowing pluripotent cells to be derived from animal models vital in biomedical research. Endeavors to produce bona fide pluripotent stem cells (PSC) from livestock have been going on for more than two decades. But, attempts to derive bona fide livestock iPS cells have met with limited success. Recently it’s been reported that small molecules can augment reprogramming efficiency and may be used to substitute few or all transcription factors used for reprogramming. It is assumed that the reprogramming factors are conserved among species, and this small molecule reprogramming approach will probably apply to livestock species as well. So this review will focus mainly on the accomplishments of small molecules on accelerating cell reprogramming and obtaining naive pluripotency, and raise a new insight on, exogenous genes free, livestock naive iPSC generation with a new bullet, small molecule.

旋流分离对天然气水合物除砂提纯的影响

针对固态流化开采方法开采海底天然气水合物含砂量大导致开采效率低的问题,提出原位分离工艺,设计了旋流分离装置,基于该装置利用CFD数值模拟方法研究了固相(砂和水合物颗粒)直径、入口浆体流量及浆体中砂浓度对装置分离性能的影响。结果表明,在研究范围内,砂和水合物分离效率大部分高于60%,最高达98.72%,压降大部分低于0.5 MPa,最低至0.03MPa。砂粒分离效率随固相粒径增大先增大后趋于平稳,随浆体入口流量增大先增大后减小,随砂浓度增大而降低;水合物分离效率随固相粒径增大先增大后趋于平稳,随浆体入口流量增大先增大后减小,随砂浓度增大而降低。溢流口和底流口压降几乎不随固相粒径变化,随砂浓度和浆体入口流量增大而增大。固相粒径、入口流量、砂浓度对分离性能有较大影响,在砂粒径大于20?m、水合物粒径大于40?m、浆体入口流量约5 m3/h、入口砂浓度不超过25vol%的条件下分离性能良好。

Individual variation in buffalo somatic cell cloning efficiency is related to glycolytic metabolism

Mammalian individuals differ in their somatic cell cloning efficiency,but the mechanisms leading to this variation is poorly understood.Here we found that high cloning efficiency buffalo fetal fibroblasts(BFFs)displayed robust energy metabolism,looser chromatin structure,high H3 K9 acetylation and low heterochromatin protein 1α(HP1α)expression.High cloning efficiency BFFs had more H3 K9 ac regions near to the upstream of glycolysis genes by Ch IP-seq,and involved more openness loci related to glycolysis genes through ATAC-seq.The expression of these glycolysis genes was also found to be higher in high cloning efficiency BFFs by q RT-PCR.Two key enzymes of glycolysis,PDKs and LDH,were confirmed to be associated with histone acetylation and chromatin openness of BFFs.Treatment of low cloning efficiency BFFs with PS48(activator of PDK1)resulted in an increase in the intracellular lactate production and H3 K9 acetylation,decrease in histone deacetylase activity and HP1αexpression,less condensed chromatin structure and more cloning embryos developing to blastocysts.These results indicate that the cloning efficiency of buffalo somatic cells is associated with their glycolytic metabolism and chromatin structure,and can be improved by increasing glycolytic metabolism.