Electromagnetic emissions from near-horizon region of an extreme Kerr-Taub-Nut black hole

We have studied electromagnetic line emissions from near-horizon region in the extremal Kerr-Taub-NUT black hole spacetime and then probe the effects of NUT charge on the electromagnetic line emissions. Due to the presence of the NUT charge, the equatorial plane is no more a symmetry plane of the KTN spacetime, which leads to that the dependence of electromagnetic line emission on the NUT charge for the observer in the Southern Hemisphere differs from that in the Northern one. Our result indicate that the electromagnetic line emission in the Kerr-Taub-NUT black hole case is brighter than that in the case of Kerr black hole for the observer in the equatorial plane or in the Southern Hemisphere, but it becomes more faint as the observer's position deviates far from the equatorial plane in the Northern one. Moreover, we also probe effects of redshift factor on electromagnetic emission from near-horizon region in the extremal Kerr-Taub-NUT black hole spacetime.Comment: 18 pages, 7 figure

The interactional achievement of familyhood in Vietnamese-Taiwanese international families

Phd ThesisWhile so many studies relating to Vietnamese female spouses in Taiwan have tapped into crucial issues facilitating understanding of this particular social group, none of them deals with face-to-face interaction between Vietnamese female spouses and their Taiwanese family members. This thesis thus tries to bridge the research gap by studying real-life face-to-face interaction in such transnational families with special attention to identifying the interactional relevance and consequentiality of membership categories invoked by the family members and how Taiwanese and Mandarin are used as interactional resources in familial discourse. This study engaged 3 Vietnamese wives in Taiwan along with 14 Taiwanese family members whose mealtime talks were audio-/video‐recorded. Conversation analysis (CA) and membership categorisation analysis (MCA) were adopted to analyse the 7 hours of data collected. It was found (from the corpus of recordings) that a Vietnamese spouse’s deployment of the membership categories ‘Taiwanese’ and ‘Vietnamese’ relates to her use of first-person plural pronouns to form the (literally translated) ‘we + country’ compound. The compound is found to be a distinctive identity-related device used by the Vietnamese participants to engage in self-categorisation. Moreover, it is also an epistemics-related device used by the Vietanamese spouses to ascribe authority or expertise to themselves or their Taiwanese family members in the enactment of 'Vietnamese' or 'Taiwanese'. On the other hand, it was found that the Vietnamese participants orient to Taiwanese and Mandarin as salient resources in admonishment sequences. Specifically, the two languages serve as contextualisation cues and framing devices in 3 different types of admonishment sequences. It is identified that familyhood can be achieved in an admonishment context, in which language varieties are used by adult family members to facilitate their alignment with each other in educating the youngest generation. The research findings suggest that the Vietnamese female spouses can fabricate interactional resources into devices to actively engage in familial communicative events and fulfil their responsibilities as a family member and as a mother. From the discursive construction of national and household identity categories, the Vietnamese spouses have demonstrated how they manage identity work and position themselves in the family; on the other hand, the way that participants negotiate national identities in family discourse have made salient the transnationality pertaining to the families. The study therefore contributes to enriching the understanding of Vietnamese female spouses in Taiwan from a conversation and membership categorisation analytic perspective, and the research findings serve as a reference point for research on cross-border marriage, cross-border couples and interactional patterns in transnational families

Low magnetic field reversal of electric polarization in a Y-type hexaferrite

Magnetoelectric multiferroics in which ferroelectricity and magnetism coexist have attracted extensive attention because they provide great opportunities for the mutual control of electric polarization by magnetic fields and magnetization by electric fields. From a practical point view, the main challenge in this field is to find proper multiferroic materials with a high operating temperature and great magnetoelectric sensitivity. Here we report on the magnetically tunable ferroelectricity and the giant magnetoelectric sensitivity up to 250 K in a Y-type hexaferrite, BaSrCoZnFe11AlO22. Not only the magnitude but also the sign of electric polarization can be effectively controlled by applying low magnetic fields (a few hundreds of Oe) that modifies the spiral magnetic structures. The magnetically induced ferroelectricity is stabilized even in zero magnetic field. Decayless reproducible flipping of electric polarization by oscillating low magnetic fields is shown. The maximum linear magnetoelectric coefficient reaches a high value of ~ 3.0\times10^3 ps/m at 200 K.Comment: 9 pages, 5 figures, a couple of errors are correcte