How much graphene in space?

The possible presence of graphene in the interstellar medium (ISM) is examined by comparing the interstellar extinction curve with the ultraviolet absorption of graphene calculated from its dielectric functions experimentally obtained with the electron energy loss spectroscopy (EELS) method. Based on the absence in the interstellar extinction curve of the [Formula: see text] π-π* electronic interband transition of graphene, we place an upper limit of [Formula: see text] of C/H on the interstellar graphene abundance, exceeding the previous estimate by a factor of [Formula: see text]3 which made use of the dielectric functions measured with the spectroscopic ellipsometry (SE) method. Compared with the SE method which measures graphene in air (and hence its surface is contaminated) in a limited energy range of [Formula: see text]0.7-5 [Formula: see text], the EELS probes a much wider energy range of [Formula: see text]0-50 [Formula: see text] and is free of contamination. The fact that the EELS dielectric functions are substantially smaller than that of SE naturally explains why a higher upper limit on the graphene abundance is derived with EELS. Inspired by the possible detection of C24, a planar graphene sheet, in several Galactic and extragalactic planetary nebulae, we also examine the possible presence of C24 in the diffuse ISM by comparing the model IR emission of C24 with the observed IR emission of the Galactic cirrus and the diffuse ISM towards l = 44°20' and b = -0°20'. An upper limit of [Formula: see text] on C24 is also derived from the absence of the characteristic vibrational bands of C24 at [Formula: see text]6.6, 9.8, and 20 [Formula: see text] in the observed IR emission.

[Research Progress on the Detection Method of DNA Methylation and Its Application in Forensic Science].

As an important part of epigenetic marker, DNA methylation involves in the gene regulation and attracts a wide spread attention in biological auxology, geratology and oncology fields. In forensic science, because of the relative stable, heritable, abundant, and age-related characteristics, DNA methylation is considered to be a useful complement to the classic genetic markers for age-prediction, tissue-identification, and monozygotic twins' discrimination. Various methods for DNA methylation detection have been validated based on methylation sensitive restriction endonuclease, bisulfite modification and methylation-CpG binding protein. In recent years, it is reported that the third generation sequencing method can be used to detect DNA methylation. This paper aims to make a review on the detection method of DNA methylation and its applications in forensic science.