Numerical study on permeability characteristics of fractal porous media

The fractal Brownian motion is utilized to describe pore structures in porous media. A numerical model of laminar flow in porous media is developed, and the flow characteristics are comprehensively analyzed and compared with those of homogeneous porous media. Moreover, the roles of the fractal dimension and porosity in permeability are quantitatively described. The results indicate that the pore structures of porous media significantly affect their seepage behaviors. The distributions of pressure and velocity in fractal porous media are both non-uniform;the streamline is no longer straight but tortuous. When Reynolds number Re < 1, the dimensionless permeability is independent of Reynolds number, but its further increase will lead to a smaller permeability. Moreover, due to the higher connectivity and enlarged equivalent aperture of internal channel network, the augment in porosity leads to the permeability enhancement, while it is small and insensitive to porosity variation when ε < 0.6. Fractal dimension also plays a significant role in the permeability of porous media. The increase in fractal dimension leads to the enhancement in pore connectivity and a decrease in channel tortuosity,which reduces the flow resistance and improves the transport capacity of porous media.

水稻组合气象灾害的一个实例研究

气候异常变化对作物生产的影响正日趋增大,但气候异常究竟会以何种方式影响作物生长还鲜见报道。2007 年位于江汉平原(以湖北省荆州市为中心)发生罕见的中稻结实障碍,且田间受害症状表现为典型的高、低温致害症状。通过对田间试验和大范围生产调查,对水稻受害与气候条件之间的关系进行了因果对应分析。结果表明,7 月 20 日~7 月 25 日期间,部分地区有一个罕见的降温过程,日均温低达 20℃,达到籼稻品种孕穗期敏感温度范围;8 月 6 日~8 月 10 日,部分地区出现一个连续高温天气过程,日均温或最高温度达到日均气温 ≥ 30℃或最高气温 ≥ 35℃,将各地受害程度与气象条件进行比对、综合分析,将本年度中稻结实障碍因不同地区分为 3 类,分别为低温主导型、高温主导型和低、高温叠加组合型。其中以低、高温叠加组合型危害程度最重,即它既受到减数分裂期的低温危害也受到了开花期的高温危害。此实例启示,全球气候变暖将会给作物生产造成更为复杂和严重的灾害,相应应对技术的研究显得十分紧迫。

Functional characterization of Bmcap in uric acid metabolism in the silkworm

After a millennium of domestication,numerous silkworm mutants have emerged that exhibit transparent epidermis,which is caused by abnormally low levels of uric acid.We identified the Bombyx mori gene Bmcap(BMSK0003832)as the homolog of cappuccino,a subunit of the biogenesis of lysosome-related organelles complex-1(BLOC-1)that has been extensively characterized in human,mouse,and insect species,by analyzing the amino acid sequences of putative purine metabolism genes.Using the clustered regularly interspaced palindromic repeats(CRISPR)/CRISPR-associated protein 9 system,we disrupted Bmcap,resulting in decreased uric acid levels in the silkworm epidermis and a translucent skin phenotype.In the Bmcap mutant,the purine metabolism,nitrogen metabolism,pyrimidine metabolism,and membrane system were altered compared to the wild type.Biogenesis of lysosome-related organelle complex genes play a role in the pigmentation and biogenesis of lysosome-related organelles(LROs)in platelets,melanocytes,and megakaryocytes.LROs exhibit unique morphologies and functions in various tissues and cells.Investigation of the Bmcap mutant will enhance our understanding of the uric acid metabolic pathway in silkworms,and this mutant offers a valuable silkworm model for LRO studies.

Masculinizer gene controls sexual differentiation in Hyphantria cunea

The Masculinizer gene,Masc,encodes a lepidopteran-specific novel CCCHtype zinc finger protein,which controls sex determination and dosage compensation in Bombyx mori.Considering the potential application of it in pest control,it is necessary to investigate the function of Masc gene in Hyphantria cunea,a globally invasive forest pest.In the present study,we identified and functionally characterized the Masc gene,HcMasc,in H.cunea.Sequence analysis revealed that HcMASC contained the conserved CCCH-type zinc finger domain,nuclear localization signal,and male determining domain,in which the last was confirmed to be required for its masculinization in BmN cell line.However,expression data showed that unlike male-biased expression in B.mori,Hc-Masc gene expresses in main all developmental stages or tissues in both sexes.Clustered regularly interspaced palindromic repeats(CRISPR)/CRISPR-associated protein 9-based disruption of the common exons 1 and 3 of the HcMasc gene resulted in imbalanced sex ratio and abnormal external genitalia of both sexes.Our results suggest that the HcMasc gene is required for both male and female sexual differentiation and dosage compensation in H.cunea and provide a foundation for developing better strategies to control this pest.

Spindle-E is essential for gametogenesis in the silkworm, Bombyx mori

As a defense mechanism against transposable elements,the PIWI-interacting RNA(piRNA)pathway maintains genomic integrity and ensures proper gametogenesis in gonads.Numerous factors are orchestrated to ensure normal operation of the piRNA pathway.Spindle-E(Spn-E)gene was one of the first genes shown to participate in the piRNA pathway.In this study,we performed functional analysis of Spn-E in the model lepidopteran insect,Bombyx mori.Unlike the germline-specific expression pattern observed in Drosophila and mouse,BmSpn-E was ubiquitously expressed in all tissues tested,and it was highly expressed in gonads.Immunofluorescent staining showed that BmSpn-E was localized in both germ cells and somatic cells in ovary and was expressed in spermatocytes in testis.We used a binary transgenic CRISPR/Cas9 system to construct BmSpn-E mutants.Loss of BmSpn-E expression caused derepression of transposons in gonads.We also found that mutant gonads were much smaller than wild-type gonads and that the number of germ cells was considerably lower in mutant gonads.Quantitative real-time PCR analysis and TUNEL staining revealed that apoptosis was greatly enhanced in mutant gonads.Further,we found that the BmSpn-E mutation impacted gonadal development and gametogenesis at the early larval stage.In summary,our data provided the first evidence that BmSpn-E plays vital roles in gonadal development and gametogenesis in B.mori.

Establishment of highly efficient transgenic system for black soldier fly(Hermetia illucens)

The black soldier fly(BSF),Hermetia illucens,is a promising insect for miti-gating solid waste problems as its larvae are able to bioconvert organic waste into valuable biomass.We recently reported a high-quality genome assembly of the BSF;analysis of this genome sequence will further the understanding of insect biology and identify genes that can be manipulated to improve efficiency of bioconversion.To enable genetic manip-ulation of the BSF,we have established the first transgenic methods for this economically important insect.We cloned and identified the ubiquitous actin5C promoter(Hiactin5C-p3k)and 3 endogenous U6 promoters(HiU6:1,HiU6:2,and HiU6:3).The Hiactin5C pro-moter was used to drive expression of a hyperactive variant of the piggyBac transposase,which exhibited up to 6-fold improvement in transformation rate when compared to the wild-type transposase.Furthermore,we evaluated the 3 HiU6 promoters using this trans-genic system.HiU6:1 and HiU6:2 promoters provided the highest knockdown efficiency with RNAi and are thus promising candidates for future Clustered Regularly Interspaced Short Palindromic Repeats(CRISPR)development.Overall,our findings provide valuable genetic engineering toolkits for basic research and genetic manipulation of the BSF.

The RNase III enzyme Dicer1 is essential for larval development in Bombyx mori

MicroRNAs(miRNAs)are important regulators of nearly all aspects of biological processes in eukaryotes.During the biogenesis of miRNAs,the RNase III enzyme Dicer processes double-strand precursor miRNAs into mature miRNAs and promotes the assembly of RNA-induced silencing complexes(RISCs).Dicer has been reported to participate in a wide range of physiological processes,including development and immunity,in some insect species.However,the physiological roles of Dicer in lepidopterans remain poorly understood.In this study,we investigated the function of Bombyx mori Dicer1.We first performed sequence alignment and found that the sequence of functional domains of Dicer1 are varied among Lepidoptera,Diptera,Coleoptera,Blattaria,and Orthoptera.Using a binary clustered regularly interspaced palindromic repeats(CRISPR)/CRISPR-associated protein 9 genome editing approach,we showed that BmDicer1 mutants have arrested development from the 3rd instar into the 4th instar.RNA sequencing analysis indicated that the defects in BmDicer1 mutants are due to dysregulation of genes that encode proteins involved in metabolism,protein degradation,absorption,and renin–angiotensin pathways.Analysis using quantitative real-time polymerase chain reaction showed that mutation of BmDicer1 altered expression of miRNAs and their target genes.Therefore,our study demonstrates the critical roles of BmDicer1 in miRNA biogenesis and larval development in silkworm.

Intersex is required for female sexual development in Hermetia illucens

Sex-determination pathways are extremely diverse.Understanding the mechanism of sex determination in insects is important for genetic manipulation of the pest population and for breeding of economically valuable insects.Although sex determi-nation has been well characterized in the model species Drosophila melanogaster,little is known about this pathway in Stratiomyidae.In the present study,we first identified the Drosophila intersex(ix)homolog in Hermetia illucens,also known as the black soldier fly,which belongs to the Stratiomyidae family and which is an important insect for the con-version of various organic wastes.Phylogenetic analyses and multiple sequence alignment revealed that Hix is conserved compared with Drosophila.We showed that Hix is highly expressed in internal genitalia.Disruption of the Hix gene using CRISPR/Cas9 resulted in female-specific defects in external genitalia and abnormal and undersized ovaries.Taken together,our study furthers our understanding of sex determination in insects and could facilitatebreedingof H.illucens.

BSFbase:The comprehensive genomic resource for a natural recycler,the black soldier fly(Hermetia illucens L.)

Dear Editor,Economic and population growth increasingly consume resources from the environment and present a major challenge regarding the management of waste.The demand for insects as a resource is increasing,as they have the potential to aid in waste recycling and alleviate shortages of natural resources(Ojha et al.,2020).The black soldier fly(BSE,Hermetia illucens L.)is a species native to tropical and subtropical parts of the Americas.

Medical Image Segmentation using PCNN based on Multi-feature Grey Wolf Optimizer Bionic Algorithm

Medical image segmentation is a challenging task especially in multimodality medical image analysis.In this paper,an improved pulse coupled neural network based on multiple hybrid features grey wolf optimizer(MFGWO-PCNN)is proposed for multimodality medical image segmentation.Specifically,a two-stage medical image segmentation method based on bionic algorithm is presented,including image fusion and image segmentation.The image fusion stage fuses rich information from different modalities by utilizing a multimodality medical image fusion model based on maximum energy region.In the stage of image segmentation,an improved PCNN model based on MFGWO is proposed,which can adaptively set the parameters of PCNN according to the features of the image.Two modalities of FLAIR and TIC brain MRIs are applied to verify the effectiveness of the proposed MFGWO-PCNN algorithm.The experimental results demonstrate that the proposed method outperforms the other seven algorithms in subjective vision and objective evaluation indicators.

U1 small nuclear ribonucleoprotein is essential for early larval development in silkworm, Bombyx mori

U1 small nuclear ribonucleoproteins(U1 snRNP)associates with 5ʹsplice sites in the form of ribonucleoprotein particles and is highly conserved among species.The physiological functions of U1 snRNP in a lepidopteran model insect Bombyx mori is mostly unknown.Here,we showed that U1 snRNP plays an important role in the development of silkworm.Knockout of U1 snRNP in silkworm showed either delayed or stationary 1st instar larva development compared with the wild-type group.U1 snRNP deletion mutants exhibited abnormal cellular phenotypes with enlarged cell nucleus,scant cytoplasm and enlarged nuclei.RNA-seq analysis revealed that genes involved in metabolic pathway,biosynthesis of secondary metabolites and steroid hormone biosynthesis were significantly affected by U1 snRNP depletion.Taken together,our study suggests that U1 snRNP homeostasis plays an important role in silkworm development.