再论能表示为三个真子群的并的群

给出了一个群能表示为三个真子群的并的一个简单证明;证明了一个群只有三个极大子群且能表示为三个真子群的并当且仅当这个群是二元生成2群.

Abstract：

It was discussed many years ago that a group could be the union of three distinct proper subgroups. Recently, the proof has been simplified, but remains complicated. A very simple proof is given for this result in this article, and the finite group that can be written into the union of three distinct proper subgroups and has exactly three maxinmal subgroups is classified.     

CDH1, a Novel Surface Marker of Spermatogonial Stem Cells in Sheep Testis

Spermatogonial stem cells（SSCs） are unique stem cells in adult body that can transmit genetic information to the next generation. They have self-renewal potential and can continuously support spermatogenesis throughout life of a male animal. However, the SSC population is extremely small, isolation and purification of the SSCs is challenging, especially for livestock animals. It has been confirmed that CDH1（cadherin-1, also known as E-cadherin） can be expressed in undifferentiated SSCs of mouse and rats, but it has not been verified in sheep. Here, CDH1 was found as a novel surface marker for sheep SSCs. In this paper, sheep antiCDH1 polyclonal antibodies were prepared and its activity was checked. Using the obtained antibodies and immunohistochemistry analysis, we confirmed that CDH1 can be expressed by SSCs in sheep testis.     

Construction of a New Molecular Barcode for Discriminating Plants and Animals with a Close Genetic Relationship

DNA barcodes have been proposed as a shortcut to provide species identification and as a way to accelerate the discovery of new species. A number of candidate gene regions have been suggested as possible barcodes for animals and plants, but for the identification of recently diverged species and/or varieties with only a few genetic differences it has been reported to be problematic in some cases. This study selected widely cultivated cruciferous vegetables as the primary samples, after failure of discrimination of each species using current DNA barcodes, we performed the fluorescent amplified fragment length polymorphism (F-AFLP) and successfully discriminated each species, subspecies, variety and their cultivar in 74 samples. Then the non-qualitative results obtained from F-AFLP were transformed into two-dimensional barcodes image file of each cultivar via the PDF417 software. This method was also successfully applied to the discrimination of 17 Chinese indigenous pig breeds. The barcode we constructed which greatly reduces the information storage space is genotypes-specific, and can be conveniently decoded into the original data and thereby be conveniently shared and referred to. We believe that it is possible to construct a new data sharing molecular barcode system that could discriminate the subspecies, varieties, cultivars and even individuals with close genetic relationships.     

Studies on Antimicrobial Resistance Transfer In vitro and Existent Selectivity of Avian Antimicrobial-Resistant Enterobacteriaccae In vivo

Increasing antimicrobial resistance （AR） has become a severe problem of public health in the world, whereas control of the AR of bacteria will be based on investigation of the AR mechanism. Furthermore, understanding the existent selectivity of AR organisms from animals can prevent the emergence and diffusion of AR effectively. PCR amplifications of gyrA and parC genes have been performed for detecting fluoroquinolones-resistance （FR） genes. A conjugational transfer test has been carried out using a donor which is resistant to tetracycline （TE）, ampicillin （AMP）, sulfamethoxazole-trimethoprim （SXT）, and a recipient which is sensitive to TE, AMP, and SXT. The AR strains have been passed 20 passages. Two groups of chicken inoculated multi-AR Escherichia coli （E. coli） and multi-AR Salmonella, respectively, are mix-fed. The result shows that amino acid codons of Ser-83 and Asp-87 are mutations from gyrA and there are no mutations from parC genes in all the FR strains. Resistance to TE, AM, and SXT can transfer among E. coli and the conjugal transfer frequency of TE is 3×10^-7. AR can inherit in 20 passages at least. The multi-AR E. coli and Salmonella can be isolated from all chickens three days after inoculation but CIP-resistant strains decrease during the time run out and disappear at 23 days after inoculation. The results indicate that the mutations of gene gyrA are correlative with the FR phenotype. AR genes that are not connected to the chromosome can transfer horizontally and vertically. AR bacteria can diffuse quickly and eliminate naturally from the host if the chicken is not under the pressure of this antibiotic.     

The Discuss of the Formula of Flow Loss and Water Using Coefficient on Seepage Proofed Channel

On the basis of the analysis about present water resource situation in China,the disadvantage of the formula of low loss and water using coefficient on anti-seep channel which have been applying in channel design and water saving irrigation administration will be indicated in the paper.The characteristics of that the loss of conveying water is changeable with the flow changing have been take into account in the new formula.The formula is validated by the example of middle permeable channel(A=1.90,m=0.40).The calculate result is more precision.Also some formula has been given,they can be referred to the worker of the irrigation administration.     

The Estimation Method of Channel Quality

On the basis of the introduction about water saving irrigation that works as a kind of new irrigation pattern,the method of anti-seep quaity estimation of the conveying water and distributing channel which acts as an important engineering measure of water saving irrigation will be introduced in te paper,that is,by means of unit-length of channel‘s water utilization-coefficient(η0)to estimate the quality of channel,and the calculative method has been explained by the example of an actual project.It can be referred to irrigational workers.     

Paths out of poverty: International experience

The global community has committed, as the first priority of the Sustainable Development Goals(SDGs), to end poverty in all its forms everywhere. While the decline of global poverty continues, progress has slowed and remains uneven through different parts of the world. To ensure that no one is left behind in China and beyond, research will be critical to inform paths out of poverty. In this regard, it is valuable to take stock of international experiences and the various pathways out of poverty with a focus on agriculture. Africa's agricultural growth has been largely driven by land expansion and poverty reduction has been the slowest among all regions. South Asia agriculture has been led by diversification of smallholder agriculture and its poverty reduction impact has been large, but its future poverty reduction is limited by rural–urban migration and lack of formal jobs in urban centers. Social protection programs have been used by many Latin American countries as the region is more urbanized than any other developing regions. China's agricultural and economic success was driven by agriculture-led reforms and rural development. These changes brought significantly higher incomes among rural residents, which accounted for highest initial levels of poverty and hunger, and in increased availability of food at affordable prices. Investments in nutrition, health, education, clean water, and good sanitation also complemented progress. The foremost lesson is that smallholder-led agriculture growth in land scarce countries often have the largest impact on poverty reduction. Secondly, nonfarm employment and rural–urban migration must follow once agricultural productivity has reached a certain level. However, premature exiting from agriculture can do more harm. Thirdly, even before large scale poverty reduction through sectoral and regional development is exhausted, social safety nets must be established to cover those who have not benefited from growth and development. Productive social safety nets have proven to be cost-effective in many countries. Urban poverty should also be part of the protection scheme when large proportion of rural population moves to cities.     

Application of Golden Section Method to Channel Transect Design

During the desing of channel transect,the paper brings forward golden section method,which is 0.618 methods.In order to reduce the calculation volume of the natural depth of water h0 and bottom^- width b which apply trial calculation method and graphic method,and improve the calculate precision,the mathematical model has been built up,the writer combines example to explain the train of thought,the result shows that the calculation precision is high,the correctness is tested and verfied by the result which is calculated by hand.It can be referred to the hydroelectric works.     

Automatic image segmentation method for cotton leaves with disease under natural environment

In order to improve the image segmentation performance of cotton leaves in natural environment, an automatic segmentation model of diseased leaf with active gradient and local information is proposed. Firstly, a segmented monotone decreasing edge composite function is proposed to accelerate the evolution of the level set curve in the gradient smooth region. Secondly, canny edge detection operator gradient is introduced into the model as the global information. In the process of the evolution of the level set function, the guidance information of the energy function is used to guide the curve evolution according to the local information of the image, and the smooth contour curve is obtained. And the main direction of the evolution of the level set curve is controlled according to the global gradient information, which effectively overcomes the local minima in the process of the evolution of the level set function. Finally, the Heaviside function is introduced into the energy function to smooth the contours of the motion and to increase the penalty function Φ(x) to calibrate the deviation of the level set function so that the level set is smooth and closed. The results showed that the model of cotton leaf edge profile curve could be obtained in the model of cotton leaf covered by bare soil, straw mulching and plastic film mulching, and the ideal edge of the ROI could be realized when the light was not uniform. In the complex background, the model can segment the leaves of the cotton with uneven illumination, shadow and weed background, and it is better to realize the ideal extraction of the edge of the blade. Compared with the Geodesic Active Contour(GAC) algorithm, Chan-Vese(C-V) algorithm and Local Binary Fitting(LBF) algorithm, it is found that the model has the advantages of segmentation accuracy and running time when processing seven kinds of cotton disease leaves images, including uneven lighting, leaf disease spot blur, adhesive diseased leaf, shadow, complex background, unclear diseased leaf edges, and staggered condition. This model can not only conduct image segmentation of cotton leaves under natural conditions, but also provide technical support for the accurate identification and diagnosis of cotton diseases.     

Mapping of three QTLs for seed setting and analysis on the candidate gene for qSS-1 in rice(Oryza sativa L.)

The lower seed setting is one of the major hindrances which face grain yield in rice.One of the main reasons to cause low spikelet fertility（seed setting）is male sterility or pollen abortion.Notably,pollen abortion has been frequently observed in advanced progenies of rice.In the present study,149 BC₂F₆ individuals with significant segregation in spikelet fertility were generated from the cross between N040212（indica）and Nipponbare（japonica）and used for primary gene mapping.Three QTLs,qSS-1,qSS-7 and qSS-9 at chromosomes 1,7 and 9,respectively,were found to be associated with seed setting.The recombinant analysis and the physical mapping information from publicly available resources exhibited that the qSS-1,qSS-7 and qSS-9 loci were mapped to an interval of 188,701 and 3741 kb,respectively.The seed setting responsible for QTL qSS-1 was further fine mapped to 93.5 kb by using BC₂F₇ population of 1 849 individuals.There are 16possible putative genes in this 93.5 kb region.Pollen vitality tests and artificial pollination indicated that the male gamete has abnormal pollen while the female gamete was normal.These data showed that low seed setting rate relative to qSS-1may be caused by abnormal pollen grains.These results will be useful for cloning,functional analysis of the target gene governing spikelet fertility（seed setting）and understanding the genetic bases of pollen sterility.