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1.
BackgroundZymomonas mobilis is a Gram-negative microaerophilic bacterium with excellent ethanol-producing capabilities. The RecET recombination system provides an efficient tool for direct targeting of genes in the bacterial chromosome by PCR fragments.ResultsThe plasmids pSUZM2a-RecET and pSUZM2a-RecE588T were first developed to co-express RecE or RecE588 and RecT for homologous recombination. Thereafter, the PCR fragments of the tetracycline resistance marker gene flanked by 60 bp of adhA (alcohol dehydrogenase I) or adhB (alcohol dehydrogenase II) homologous sequences were electroporated directly into ZM4 cells harboring pSUZM2a-RecET or pSUZM2a-RecE588T. Both adhA and adhB were replaced by the tetracycline resistance gene in ZM4, yielding two mutant strains, Z. mobilis ZM4 ΔadhA and Z. mobilis ZM4 ΔadhB. These two mutants showed varying extent of reduction in ethanol production, biomass generation, and glucose metabolism. Furthermore, enzyme activity of alcohol dehydrogenase II in Z. mobilis ZM4 ΔadhB exhibited a significant reduction compared to that of wild-type ZM4.ConclusionThis approach provided a simple and useful method for introducing mutations and heterologous genes in the Z. mobilis genome. 相似文献
2.
分析了ilasⅡ系统在应用中需要进行数据库重组和压缩重组的故障,并提出了进行数据库重组和压缩重组的方法及相关问题。 相似文献
3.
This paper studies mathematical properties of h-index sequences as developed by Liang [Liang, L. (2006). h-Index sequence and h-index matrix: Constructions and applications. Scientometrics,69(1), 153–159]. For practical reasons, Liming studies such sequences where the time goes backwards while it is more logical to use the time going forward (real career periods). Both type of h-index sequences are studied here and their interrelations are revealed. We show cases where these sequences are convex, linear and concave. We also show that, when one of the sequences is convex then the other one is concave, showing that the reverse-time sequence, in general, cannot be used to derive similar properties of the (difficult to obtain) forward time sequence. We show that both sequences are the same if and only if the author produces the same number of papers per year. If the author produces an increasing number of papers per year, then Liang’s h-sequences are above the “normal” ones. All these results are also valid for g- and R-sequences. The results are confirmed by the h-, g- and R-sequences (forward and reverse time) of the author. 相似文献
4.
《Electronic Journal of Biotechnology》2014,17(1):46-49
BackgroundThe AdEasy system is a fast-track system for generating recombinant adenoviruses using the efficient homologous recombination machinery between shuttle and adenovirus backbone plasmids in Escherichia coli BJ5183 cells. The key step is homologous recombination in BJ5183 cells, which is driven by RecA activity. However, culture time is stringently limited to reduce the damage to recombinant plasmids by RecA activity. Therefore, rapid identification of recombinant adenoviruses within the limited time-period is critical.ResultsWe developed a simple negative selection method to identify recombinant adenoviruses using colony PCR, which improves the efficiency of adenovirus recombination screening and packaging.ConclusionsThe negative selection method to identify AdEasy adenovirus recombinants by colony PCR can identify the recombined colony within a short time-period, and maximally avoid damage to the recombinant plasmid by limiting recombination time, resulting in improved adenovirus packaging. 相似文献
5.
In this article we introduce the notion of I-acceleration convergence of sequences. We prove the decomposition theorem for I-acceleration convergence of sequences as well as for subsequence transformations. We study different properties of I-acceleration convergence of sequences. 相似文献
6.
信息重组——谈学科信息导航 总被引：5，自引：2，他引：5
信息重组是信息研究的一个新方向，也是知识创新的一个途径。本文阐述了信息重组的重要性，必要性，可能性，以及应用信息重组开展学科信息导航。 相似文献
7.
隐含信息的重组与知识创新 总被引：7，自引：2，他引：5
本文介绍了隐含信息重组与知识知识的内容,认为隐含信息重组是信息研究的方向,知识创新的途径;基于人类认识事物的方法,系统的方法和基于信息库知识变听管理技术,进行隐含信息的重组与知识创新。 相似文献
8.
We present the first experimental demonstration of confined microfluidic droplets acting as discrete negative resistors, wherein the effective hydrodynamic resistance to flow in a microchannel is reduced by the presence of a droplet. The implications of this hitherto unexplored regime in the traffic of droplets in microfluidic networks are highlighted by demonstrating bistable filtering into either arm of symmetric and asymmetric microfluidic loops, and programming oscillatory droplet routing therein. 相似文献
9.
BackgroundMaize is one of the most important crops worldwide and has been a target of nuclear-based transformation biotechnology to improve it and satisfy the food demand of the ever-growing global population. However, the maize plastid transformation has not been accomplished due to the recalcitrant condition of the crop.ResultsIn this study, we constructed two different vectors with homologous recombination sequences from maize (Zea mays var. LPC13) and grass (Bouteloua gracilis var. ex Steud) (pZmcpGFP and pBgcpGFP, respectively). Both vectors were designed to integrate into rrn23S/rrn16S from an inverted repeat region in the chloroplast genome. Moreover, the vector had the mgfp5 gene driven by Prrn, a leader sequence of the atpB gene and a terminator sequence from the rbcL gene. Also, constructs have an hph gene as a selection marker gene driven by Prrn, a leader sequence from rbcL gene and a terminator sequence from the rbcL gene. Explants of maize, tobacco and Escherichia coli cells were transformed with both vectors to evaluate the transitory expression–an exhibition of green and red fluorescent light under epifluorescence microscopy. These results showed that both vectors were expressed; the reporter gene in all three organisms confirmed the capacity of the vectors to express genes in the cell compartments.ConclusionsThis paper is the first report of transient expression of GFP in maize embryos and offers new information for genetically improving recalcitrant crops; it also opens new possibilities for the improvement in maize chloroplast transformation with these vectors.How to cite: Arévalo-Gallegos S, Varela-Rodríguez H, Lugo-Aguilar H, et al. Transient expression of a green fluorescent protein in tobacco and maize chloroplast. Electron J Biotechnol 2020;44. https://doi.org/10.1016/j.ejbt.2020.01.008 相似文献
10.
Previous researchers have attempted to detect significant topics in news stories and blogs through the use of word frequency-based methods applied to RSS feeds. In this paper, the three statistical feature selection methods: χ2, Mutual Information (MI) and Information Gain (I) are proposed as alternative approaches for ranking term significance in an evolving RSS feed corpus. The extent to which the three methods agree with each other on determining the degree of the significance of a term on a certain date is investigated as well as the assumption that larger values tend to indicate more significant terms. An experimental evaluation was carried out with 39 different levels of data reduction to evaluate the three methods for differing degrees of significance. The three methods showed a significant degree of disagreement for a number of terms assigned an extremely large value. Hence, the assumption that the larger a value, the higher the degree of the significance of a term should be treated cautiously. Moreover, MI and I show significant disagreement. This suggests that MI is different in the way it ranks significant terms, as MI does not take the absence of a term into account, although I does. I, however, has a higher degree of term reduction than MI and χ2. This can result in loosing some significant terms. In summary, χ2 seems to be the best method to determine term significance for RSS feeds, as χ2 identifies both types of significant behavior. The χ2 method, however, is far from perfect as an extremely high value can be assigned to relatively insignificant terms. 相似文献
11.
Hemen Dutta 《Journal of The Franklin Institute》2011,348(10):2876-2883
The main aim of this article is to extend the notion of strongly Cesàro summable and strongly lacunary summable real sequences to n-normed linear space valued (n-nls valued) difference sequences. Consequently we introduce the spaces |σ1|(X,?) and Nθ(X,?), respectively, where X is an n-normed space and ? is a difference operator. We investigate these spaces for completeness as well as for the relationship between these spaces. 相似文献
12.
《Journal of The Franklin Institute》2023,360(4):3545-3574
This article considers the problem of prescribed-time stabilization for a class of uncertain high-order nonlinear systems (i.e., systems in the -normal form) with a pre-specified asymmetric output constraint. A core ingredient, tangent-type barrier function, is proposed first by skillfully excavating and assimilating the inherent properties of system nonlinearities. Based on the barrier function, as well as a serial of nested signum functions, the celebrated technique of adding a power integrator is renovated finely to establish a new design approach by which a continuous state feedback prescribed-time stabilizer, along with a tangent-type asymmetric barrier Lyapunov function, can be constructed in a systematic fashion, thereby guaranteeing the performance of prescribed-time state convergence and ensuring the fulfillment of pre-specified output constraints surely. Benefiting from the composite characteristics of the presented tangent-type barrier Lyapunov function and the signum functions, the proposed approach further offers a unified nature in design enabling us to organize a prescribed-time stabilizer that is simultaneously valid and executable for the system undergone or free from output constraints, without the need of changing the controller structure. The effectiveness and superiority of the developed approach are illustrated by a numerical example. 相似文献
13.
Arnold Chen Royal Wang Candace R. S. Bever Siyuan Xing Bruce D. Hammock Tingrui Pan 《Biomicrofluidics》2014,8(6)
The emerging technologies on mobile-based diagnosis and bioanalytical detection have enabled powerful laboratory assays such as enzyme-linked immunosorbent assay (ELISA) to be conducted in field-use lab-on-a-chip devices. In this paper, we present a low-cost universal serial bus (USB)-interfaced mobile platform to perform microfluidic ELISA operations in detecting the presence and concentrations of BDE-47 (2,2′,4,4′-tetrabromodiphenyl ether), an environmental contaminant found in our food supply with adverse health impact. Our point-of-care diagnostic device utilizes flexible interdigitated carbon black electrodes to convert electric current into a microfluidic pump via gas bubble expansion during electrolytic reaction. The micropump receives power from a mobile phone and transports BDE-47 analytes through the microfluidic device conducting competitive ELISA. Using variable domain of heavy chain antibodies (commonly referred to as single domain antibodies or Nanobodies), the proposed device is sensitive for a BDE-47 concentration range of 10−3–104 μg/l, with a comparable performance to that uses a standard competitive ELISA protocol. It is anticipated that the potential impact in mobile detection of health and environmental contaminants will prove beneficial to our community and low-resource environments. 相似文献
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15.
个体由于认知能力的限制,通常集体完成复杂任务,表现出群体智能的现象。而如何提高群体智能一直是重要的研究问题。基于NK模型建立多主体仿真实验,本文探究隔离团队重组对集体问题解决能力的影响。仿真结果表明,团队重组频数与集体表现呈倒U关系,即适当的团队重组可以提高集体问题解决的能力,同时与半隔离团队对比发现,团队重组可以媲美半隔离团队的功能,并且在集体表现上具有更强的稳定性,因此团队重组具有更强的操作性。此外,权变理论分析发现,不存在团队重组时,群体应当保持较大的团队规模,较小的人员流动,较小的个体学习速率;存在团队重组时,群体应该保持较小的团队规模,较小的人员流动率,适当的个体学习速率。此外,在复杂问题面前,团队重组对提高群体解决问题能力的作用更为显著。 相似文献
16.
BackgroundCultivated peanut (Arachis hypogaea. L) represents one of the most important oil crops in the world. Although much effort has been expended to characterize microsatellites or Simple Sequence Repeats (SSRs) in peanut, the quantity and quality of the markers in breeding applications remain limited. Here, genome-wide SSR characterization and marker development were performed using the recently assembled genome of the cultivar Tifrunner.ResultsIn total, 512,900 microsatellites were identified from 2556.9-Mb genomic sequences. Based on the flanking sequences of the identified microsatellites, 7757 primer pairs (markers) were designed, and further evaluated in the assembled genomic sequences of the tetraploid Arachis cultivars, Tifrunner and Shitouqi, and the diploid ancestral species, A. duranensis and A. ipaensis. In silico PCR analysis showed that the SSR markers had high amplification efficiency and polymorphism in four Arachis genotypes. Notably, nearly 60% of these markers were single-locus SSRs in tetraploid Arachis species, indicating they are more specific in distinguishing the alleles of the A and B sub-genomes of peanut. In addition, two markers closely related with purple testa color and 27 markers near to FAD2 genes were identified, which could be used for breeding varieties with purple testa and high-oleic acid content, respectively. Moreover, the potential application of these SSR markers in tracking introgressions from Arachis wild relatives was discussed.ConclusionsThis study reported the development of genomic SSRs from assembled genomic sequences of the tetraploid Arachis Tifrunner, which will be useful for diversity analysis, genetic mapping and functional genomics studies in peanut.How to cite: Ma J, Zhao Y, Chen H, et al. Genome-wide development of polymorphic microsatellite markers and their application in peanut breeding program. Electron J Biotechnol 2020;44. https://doi.org/10.1016/j.ejbt.2020.01.004. 相似文献
17.
We present a new variable-length encoding scheme for sequences of integers, Directly Addressable Codes (DACs), which enables direct access to any element of the encoded sequence without the need of any sampling method. Our proposal is a kind of implicit data structure that introduces synchronism in the encoded sequence without using asymptotically any extra space. We show some experiments demonstrating that the technique is not only simple, but also competitive in time and space with existing solutions in several applications, such as the representation of LCP arrays or high-order entropy-compressed sequences. 相似文献
18.
Bo Han Chen Yang Xiaolong Xu Yuehui Li Ruochen Shi Kaihui Liu Haicheng Wang Yu Ye Jing Lu Dapeng Yu Peng Gao 《国家科学评论(英文版)》2021,8(2)
Contact interface properties are important in determining the performances of devices that are based on atomically thin two-dimensional (2D) materials, especially for those with short channels. Understanding the contact interface is therefore important to design better devices. Herein, we use scanning transmission electron microscopy, electron energy loss spectroscopy, and first-principles calculations to reveal the electronic structures within the metallic (1T′)-semiconducting (2H) MoTe2 coplanar phase boundary across a wide spectral range and correlate its properties to atomic structures. We find that the 2H-MoTe2 excitonic peaks cross the phase boundary into the 1T′ phase within a range of approximately 150 nm. The 1T′-MoTe2 crystal field can penetrate the boundary and extend into the 2H phase by approximately two unit-cells. The plasmonic oscillations exhibit strong angle dependence, that is a red-shift of π+σ (approximately 0.3–1.2 eV) occurs within 4 nm at 1T′/2H-MoTe2 boundaries with large tilt angles, but there is no shift at zero-tilted boundaries. These atomic-scale measurements reveal the structure–property relationships of the 1T′/2H-MoTe2 boundary, providing useful information for phase boundary engineering and device development based on 2D materials. 相似文献
19.
Chun Ruan Xinxing Ouyang Hongzhi Liu Song Li Jingsi Jin Weiyi Tang Yu Xia Bing Su 《国家科学评论(英文版)》2019,6(6):1149
The mammalian target of rapamycin (mTOR) is an evolutionarily conserved Ser/Thr protein kinase with essential cellular function via processing various extracellular and intracellular inputs. Two distinct multi-protein mTOR complexes (mTORC), mTORC1 and mTORC2, have been identified and well characterized in eukaryotic cells from yeast to human. Sin1, which stands for Sty1/Spc1-interacting protein1, also known as mitogen-activated protein kinase (MAPK) associated protein (MAPKAP)1, is an evolutionarily conserved adaptor protein. Mammalian Sin1 interacts with many cellular proteins, but it has been widely studied as an essential component of mTORC2, and it is crucial not only for the assembly of mTORC2 but also for the regulation of its substrate specificity. In this review, we summarize our current knowledge of the structure and functions of Sin1, focusing specifically on its protein interaction network and its roles in the mTOR pathway that could account for various cellular functions of mTOR in growth, metabolism, immunity and cancer. 相似文献
20.
Bio-electrosprays (BESs) provide a means of precisely manipulating cells and thus have the potential for many clinical uses such as the generation of artificial tissues∕organs. Previously we tested the biological safety of this technology with a variety of living cells and also embryos from the vertebrate model organisms Danio rerio (zebrafish) and Xenopus tropicalis (frog). However, the viability and fertility of the treated embryos could not be fully assessed due to animal licensing laws. Here we assay the viability and fertility of Drosophila melanogaster (fruit fly) embryos in conjunction with the bio-electrospray procedure. Bio-electrosprayed Drosophila embryos developed into fully fertile adult flies that were indistinguishable from wild-type. Thus, we demonstrate that the bio-electrospray procedure does not induce genetic or physical damage that significantly affects the development or fertility of a multicellular organism. This study along with our previous investigations demonstrates the potential of this approach to be developed for the precise manipulation of sensitive biological materials. 相似文献