We select the largest sample of Swift gamma-ray bursts (GRBs) so far to reexamine the classification in terms of time duration, hardness ratio, and physical collapse model. To analyze the sample selection effect, we divide the observed Swift GRB sample into four subsamples according to signal-to-noise level, spectral quality, and extended emission. First, we find that only the sample of Swift GRBs with well-measured peak energy can be evidently divided into two types at a boundary of ∼1 s, and other data sets are well described by three Gaussian functions. Using Swift GRBs with known redshift, a Kolmogorov–Smirnov test shows the intrinsic duration distributions of five data sets are equally distributed. Second, we ascertain in the plane of hardness ratio versus duration that the hardness ratio of short GRBs is significantly higher than those of middle classes and long GRBs, while the latter two components are the same in statistics, implying the so-called middle class to be artificial. Third, we apply a collapse model to discriminate the boundaries between collapse and noncollapse Swift bursts. It is interesting to find that a significant fraction, ≥30%, of Swift short GRBs could have originated from the collapsing progenitors, while all long GRBs are produced from the collapsars only. Finally, we point out that short GRBs with extended emission are the main contributors to the noncollapsar population with longer duration.
ABSTRACT. Plant molecular identity (ID) is used to describe molecular characteristics of plants, which should contain all of the necessary information. Using inter-simple sequence repeat (ISSR) primers, molecular ID can be described in a way that reflects the polymerase chain reaction (PCR) conditions, annealing temperature, and the bands obtained in PCR amplification. A new complete molecular ID system is described in this study, which can be easily used and expanded to include more information. Using three cotton cultivars, we analyzed the products of PCR with ISSR primers and discussed the strategy for establishing their molecular ID. Using the segmented naming method, we designate the simple names and the full name systems of these three cultivars.
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