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Facilitated by recent establishment of terrestrial networks and satellite constellations of Automatic Identification System (AIS) receivers, ship trajectories are becoming increasingly available and the size of recorded trajectories is getting larger. Large sets of trajectories create problems of storing, transmitting and processing data. Using appropriate methods, an accurate representation of the original trajectories can be obtained by compressing redundant information, while maintaining the main characteristic elements. In this paper, a new scheme and the implementation of the Douglas-Peucker (DP) algorithm are presented, which can simplify AIS trajectories by extracting characteristic points. As for the simplification threshold, the solo parameter of the DP algorithm, a new AIS-based minimum ship domain evaluation method is proposed and acts as criteria for simplification threshold determination. Finally, a validation is made to examine the effectiveness of the DP simplification algorithm and the rationality of the simplification threshold. The result indicates that the DP algorithm can simplify AIS trajectories effectively; the simplification threshold is scientific and reasonable.
Combining the long serial analysis of gene expression (LongSAGE) and the generation of longer cDNA fragments from serial analysis of gene expression tags for gene identification (GLGI) technique, a new strategy called modified GLGI (M-GLGI) was developed to isolate unknown 3′ expressed sequence tags (ESTs) and discover novel genes. A 17 bp LongSAGE tag was used as sense primer instead of a 10-base SAGE tag; PCR reaction was performed under an appropriate annealing temperature for each tag; universal DNA polymerase was used in PCR amplification instead of Pfu enzyme; a common cloning strategy using pMD-18T vector and Escherichia coli DH5α cells were used instead of a special vector and competent cells. Moreover, ESTs isolated by M-GLGI had 3′ ends with the polyadenylation signals and poly(dA) tails. This method is more sensitive for identifying genes expressed in low abundance than conventional EST sequencing.
This study used three winter wheat (Triticum aestivum L.) genotypes (H6756, H311 and SP8581) to compare the effects of sampling time, callus induction media, differentiation media and rooting media on in vitro culture of young spikes in wheat. In all these three genotypes, the frequencies of green plantlet differentiation were high when their young spikes were cultured between the stages of protective glume primordium formation and pistil and stamen primordium formation, but low at other stages. The optimum medium for callus induction was Murashige and Skoog (MS) medium+2 mg/l 2,4-dichlorophenoxyacetic acid (2,4-D). The optimum green plantlet differentiation medium was MS medium. Some abnormal plantlets regenerated from calli. When these plantlets were transferred to another differentiation medium [MS+1.0 mg/l 1-naphthaleneacetic acid (NAA)+0.2 mg/l 6-benzylaminopurine (6-BA)], shoot formation and elongation were induced. This allowed 90.91% of them to develop into normal green plantlets. The optimum rooting medium was 1/2MS+0.2 mg/l 3-Indolylacetonitrile (IAA)+80 g/l sucrose. An efficient regeneration system for young spike culture of wheat was set up based on such methods. Using this wheat-regeneration system, young spikes and immature embryos of 17 genotypes of wheat were in vitro cultured to study and compare the callus induction frequencies and green plantlet differentiation frequencies. The results of two successive years showed that in 15 out of the 17 genotypes (88.24%) the green plantlet differentiation frequencies were higher than those of immature embryos by 6.2–65.1%. These results showed that the regeneration system established in this trial for young spike culture of wheat was effective.
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