• Title/Summary/Keyword: single crossover

Search Result 103, Processing Time 0.031 seconds

Single Crossover-Mediated Markerless Genome Engineering in Clostridium acetobutylicum

  • Lee, Sang-Hyun;Kim, Hyun Ju;Shin, Yong-An;Kim, Kyoung Heon;Lee, Sang Jun
    • Journal of Microbiology and Biotechnology
    • /
    • v.26 no.4
    • /
    • pp.725-729
    • /
    • 2016
  • A novel genome-engineering tool in Clostridium acetobutylicum was developed based on single-crossover homologous recombination. A small-sized non-replicable plasmid, pHKO1, was designed for efficient integration into the C. acetobutylicum genome. The integrated pHKO1 plasmid backbone, which included an antibiotic resistance gene, can be excised in vivo by Flp recombinase, leaving a single flippase recognition target sequence in the middle of the targeted gene. Since the pSHL-FLP plasmid, the carrier of the Flp recombinase gene, employed the segregationally unstable pAMβ1 replicon, the plasmid was rapidly cured from the mutant C. acetobutylicum. Consequently, our method makes it easier to engineer C. acetobutylicum.

Single-Machine Total Completion Time Scheduling with Position-Based Deterioration and Multiple Rate-Modifying Activities

  • Kim, Byung-Soo;Joo, Cheol-Min
    • Industrial Engineering and Management Systems
    • /
    • v.10 no.4
    • /
    • pp.247-254
    • /
    • 2011
  • In this paper, we study a single-machine scheduling problem with deteriorating processing time of jobs and multiple rate-modifying activities which reset deteriorated processing time to the original processing time. In this situation, the objective function is to minimize total completion time. First, we formulate an integer programming model. Since the model is difficult to solve as the size of real problem being very large, we design an improved genetic algorithm called adaptive genetic algorithm (AGA) with spontaneously adjusting crossover and mutation rate depending upon the status of current population. Finally, we conduct some computational experiments to evaluate the performance of AGA with the conventional GAs with various combinations of crossover and mutation rates.

Identification of Meiotic Recombination Intermediates in Saccharomyces cerevisiae (효모 감수분열과정에서의 유전자 재조합 기전 특이적 DNA 중간체의 구조 변화)

  • Sung, Young Jin;Yoon, Sang Wook;Kim, Keun Pil
    • Korean Journal of Microbiology
    • /
    • v.49 no.1
    • /
    • pp.1-7
    • /
    • 2013
  • During meiosis, genetic recombinants are formed by homologous recombination accompanying with the programmed double-strand breaks (DSBs) and strand exchanges between homologous chromosomes. The mechanism is generated by recombination intermediates such as single-end invasions (SEIs) and double-Holliday junctions (dHJs), and followed by crossover (CO) or non-crossover (NCO) products. Our study was focused on the analysis of meiotic recombination intermediates (DSBs, SEIs, and dHJs) and final recombination products (CO and NCO). We identified these meiotic recombination intermediates using DNA physical analysis under HIS4LEU2 "hot spot" system in budding yeast, Saccharomyces cerevisiae. For DNA physical analysis, when the hot spot locus is recognized by restriction enzyme from synchronous meiotic cells, the fragmented DNA that are forming recombination intermediates can be detected and quantified through Southern hybridization analysis. Our study suggests that this system can analyze the structural change of recombination intermediates during DSB-SEI transition, double-Holiday junctions and crossover/non-crossover products in meiosis.

Performance Analysis of Distributed Genetic Algorithms for Traveling Salesman Problem (순회판매원문제를 위한 분산유전알고리즘 성능평가)

  • Kim, Young Nam;Lee, Min Jung;Ha, Chunghun
    • Journal of Korean Society of Industrial and Systems Engineering
    • /
    • v.39 no.4
    • /
    • pp.81-89
    • /
    • 2016
  • Distributed genetic algorithm (DGA), also known as island model or coarse-grained model, is a kind of parallel genetic algorithm, in which a population is partitioned into several sub-populations and each of them evolves with its own genetic operators to maintain diversity of individuals. It is known that DGA is superior to conventional genetic algorithm with a single population in terms of solution quality and computation time. Several researches have been conducted to evaluate effects of parameters on GAs, but there is no research work yet that deals with structure of DGA. In this study, we tried to evaluate performance of various genetic algorithms (GAs) for the famous symmetric traveling salesman problems. The considered GAs include a conventional serial GA (SGA) with IGX (Improved Greedy Crossover) and several DGAs with various combinations of crossover operators such as OX (Order Crossover), DPX (Distance Preserving Crossover), GX (Greedy Crossover), and IGX. Two distinct immigration policies, conventional noncompetitive policy and newly proposed competitive policy are also considered. To compare performance of GAs clearly, a series of analysis of variance (ANOVA) is conducted for several scenarios. The experimental results and ANOVAs show that DGAs outperform SGA in terms of computation time, while the solution quality is statistically the same. The most effective crossover operators are revealed as IGX and DPX, especially IGX is outstanding to improve solution quality regardless of type of GAs. In the perspective of immigration policy, the proposed competitive policy is slightly superior to the conventional policy when the problem size is large.

A Genetic Algorithm for Single Machine Scheduling with Unequal Release Dates and Due Dates (상이한 납기와 도착시간을 갖는 단일기계 일정계획을 위한 유전 알고리즘 설계)

  • 이동현;이경근;김재균;박창권;장길상
    • Journal of the Korean Operations Research and Management Science Society
    • /
    • v.24 no.3
    • /
    • pp.73-82
    • /
    • 1999
  • In this paper, we address a single machine non-preemptive n-job scheduling problem to minimize the sum of earliness and tardiness with different release times and due dates. To solve the problem, we propose a genetic algorithm with new crossover and mutation operators to find the job sequencing. For the proposed genetic algorithm, the optimal pair of crossover and mutation rates is investigated. To illustrate the suitability of genetic algorithm, solutions of genetic algorithm are compared with solutions of exhaustive enumeration method in small size problems and tabu search method in large size problems. Computational results demonstrate that the proposed genetic algorithm provides the near-optimal job sequencing in the real world problem.

  • PDF

A Study on Direct Alcohol Fuel Cells for Portable Powers (휴대전원용 직접 알코올 연료전지의 특성에 관한 연구)

  • Yoon S. R.;Cha S. Y.;Oh I. W.;Hong S. A.;Ha H. Y.
    • Journal of the Korean Electrochemical Society
    • /
    • v.4 no.2
    • /
    • pp.65-69
    • /
    • 2001
  • The potential change, and the crossover of alcohol in a liquid-feed solid polymer electrolyte fuel cell operating at atmosphere and room temperature was investigated. Alcohol crossover was generated from all the alcohol by using the fuel. The single-cell property of direct methanol fuel cell was higher than that of other alcohol species as $31mW/cm^2$ at 0.23 V at 4.5M of methanol.

Reduction of Methanol Crossover in a Direct Methanol Fuel Cell by Using the Pt-Coated Electrolyte Membrane

  • Jung, Eun-Mi;Rhee, Young-Woo;Peck, Dong-Hyun;Lee, Byoung-Rok;Kim, Sang-Kyung;Jung, Doo-Hwan
    • Journal of the Korean Electrochemical Society
    • /
    • v.11 no.1
    • /
    • pp.1-5
    • /
    • 2008
  • A Pt-layer was deposited on the anode side of a Nafion membrane via a sputtering method in order to reduce methanol crossover in a direct methanol fuel cell (DMFC). The methanol permeation and the proton conductivity through the modified membranes were investigated. The performances of the direct methanol fuel cell were also tested using single cells with a Nafion membrane and the modified membranes. The Pt-layers on the membrane blocked both methanol crossover and proton transport through the membranes. Methanol permeability and proton conductivity decreased with an increase of the platinum layer thickness. At methanol concentration of 2 M, the DMFC employing the modified membrane with a platinum layer of 66 nm-thickness showed similar performance to that of a DMFC with a bare Nafion membrane in spite of the lower proton conductivity of the former. The maximum power density of the cell using the modified membrane with a platinum layer of 66 nm-thickness increased slightly while that of the cell with the bare membrane decreased abruptly when a methanol solution of 6M was supplied.

A Study on the Performance Characteristics of Direct Methanol Fuel Cell with Changing of Catalyst Loading (촉매량 변화에 따른 직접 메탄올 연료전지의 성능 특성에 관한 연구)

  • Seo, Sang-Hern;Lee, Chang-Sik
    • Transactions of the Korean hydrogen and new energy society
    • /
    • v.19 no.6
    • /
    • pp.467-473
    • /
    • 2008
  • This study is to investigate the influence of catalyst loading quantity on the direct methanol fuel cell (DMFC) performance. In this paper, Pt-Ru and Pt-black loading as the catalyst were varied from 1 to $4mg/cm^2$ at the anode and cathode, respectively. The experiment was conducted with single fuel cell consisted of $5cm^2$ effective electrode area, serpentine type flow pattern and Nafion 117 membrane. Also, AC impedance and methanol crossover current were measured to investigate the performance loss precisely. As a result, the performance of fuel cell was significantly increased with the increase of cathode catalyst loading. However, the performance did not increase further above a certain Pt-Ru catalyst loading as the increase of anode catalyst loading.

Durability of MEA Using sPEEK Membrane Reinforced with Poly Imide in PEMFC (고분자전해질연료전지에서 폴리이미드 강화 sPEEK막 MEA의 내구성)

  • Lee, Hye-Ri;Na, Il-Chai;Oh, Sung-Jun;Park, Kwon-Pil
    • Korean Chemical Engineering Research
    • /
    • v.55 no.3
    • /
    • pp.296-301
    • /
    • 2017
  • Recently, there are many efforts focused on development of more economical non-fluorinated membranes for PEMFCs (Proton Exchange Membrane Fuel Cells). In this study, sulfonated poly (ether ether ketone) (sPEEK) membrane reinforced with poly imide was made to enhance of membrane durability. In order to test durability of single (un-reinforced) membrane and reinforced membrane MEA (Membrane and Electrode Assembly), degradation accelerated stress test was used. Before and after degradation, I-V polarization curve, hydrogen crossover current, electrochemical surface area, membrane resistance and charge transfer resistance were measured. As a result of experiments, hydrogen crossover current of reinforced MEA was lower than that of single MEA, therefor durability of reinforced MEA was higher than that of single MEA. There was not especially short phenomena in reinforced MEA after degradation accelerated stress test.

High-Frequency Targeted Mutagenesis in Pseudomonas stutzeri Using a Vector-Free Allele-Exchange Protocol

  • Gomaa, Ahmed E.;Deng, Zhiping;Yang, Zhimin;Shang, Liguo;Zhan, Yuhua;Lu, Wei;Lin, Min;Yan, Yongliang
    • Journal of Microbiology and Biotechnology
    • /
    • v.27 no.2
    • /
    • pp.335-341
    • /
    • 2017
  • The complexity of the bacterial recombination system is a barrier for the construction of bacterial mutants for the further functional investigation of specific genes. Several protocols have been developed to inactivate genes from the genus Pseudomonas. Those protocols are complicated and time-consuming and mostly do not enable easy construction of multiple knock-ins/outs. The current study describes a single and double crossover-recombination system using an optimized vector-free allele-exchange protocol for gene disruption and gene replacement in a single species of the family Pseudomonadaceae. The protocol is based on self-ligation (circularization) for the DNA cassette which has been obtained by overlapping polymerase chain reaction (Fusion-PCR), and carries an antibiotic resistance cassette flanked by homologous internal regions of the target locus. To establish the reproducibility of the approach, three different chromosomal genes (ncRNA31, rpoN, rpoS) were knocked-out from the root-associative bacterium Pseudomonas stutzeri A1501. The results showed that the P. stutzeri A1501 mutants, which are free of any plasmid backbone, could be obtained via a single or double crossover recombination. In order to optimize this protocol, three key factors that were found to have great effect on the efficiency of the homologous recombination were further investigated. Moreover, the modified protocol does not require further cloning steps, and it enables the construction of multiple gene knock-in/out mutants sequentially. This work provides a simple and rapid mutagenesis strategy for genome editing in P. stutzeri, which may also be applicable for other gram-negative bacteria.