6 research outputs found
Parallax and Distance Estimates for Twelve Cataclysmic Variable Stars
We report parallax and distance estimates for twelve more cataclysmic
binaries and related objects observed with the 2.4m Hiltner telescope at MDM
Observatory. The final parallax accuracy is typically about 1 mas. For only one
of the twelve objects, IR Gem, do we fail to detect a significant parallax.
Notable results include distances for V396 Hya (CE 315), a helium double
degenerate with a relatively long orbital period, and for MQ Dra
(SDSSJ155331+551615), a magnetic system with a very low accretion rate. We find
that the Z Cam star KT Persei is physically paired with a K main-sequence star
lying 15 arcsec away. Several of the targets have distance estimates in the
literature that are based on the white dwarf's effective temperature and flux;
our measurements broadly corroborate these estimates, but tend to put the stars
a bit closer, indicating that the white dwarfs may have rather larger masses
than assumed. As a side note, we briefly describe radial velocity spectroscopy
that refines the orbital period of V396 Hya to 65.07 +- 0.08 min.Comment: Accepted for Astronomical Journal. 19 pages, no figure
Strategies for the hyperpolarization of acetonitrile and related Ligands by SABRE
(Chemical Equation Presented) We report on a strategy for using SABRE (signal amplification by reversible exchange) for polarizing 1H and 13C nuclei of weakly interacting ligands which possess biologically relevant and nonaromatic motifs. We first demonstrate this via the polarization of acetonitrile, using Ir(IMes)(COD)Cl as the catalyst precursor, and confirm that the route to hyperpolarization transfer is via the J-coupling network. We extend this work to the polarization of propionitrile, benzylnitrile, benzonitrile, and trans-3-hexenedinitrile in order to assess its generality. In the 1H NMR spectrum, the signal for acetonitrile is enhanced 8-fold over its thermal counterpart when [Ir(H)2(IMes)(MeCN)3]+ is the catalyst. Upon addition of pyridine or pyridine-d5, the active catalyst changes to [Ir(H)2(IMes)- (py)2(MeCN)]+ and the resulting acetonitrile 1H signal enhancement increases to 20- and 60-fold, respectively. In 13C NMR studies, polarization transfers optimally to the quaternary 13C nucleus of MeCN while the methyl 13C is hardly polarized. Transfer to 13C is shown to occur first via the 1H - 1H coupling between the hydrides and the methyl protons and then via either the 2J or 1J couplings to the respective 13Cs, of which the 2J route is more efficient. These experimental results are rationalized through a theoretical treatment which shows excellent agreement with experiment. In the case of MeCN, longitudinal two-spin orders between pairs of 1H nuclei in the three-spin methyl group are created. Two-spin order states, between the 1H and 13C nuclei, are also created, and their existence is confirmed for Me13CN in both the 1H and 13C NMR spectra using the Only Parahydrogen Spectroscopy protocol
Remixing Transnational Media: Global Cultural Flows and Their Hermeneutic Navigation in Kenyan DJ Afro Movies
Evaluation of left ventricular strain in patients with arrhythmia based on the 3T MR temporal parallel acquisition technique
Latin American telenovelas and African screen media: from reception to production
Latin American telenovelas began to be widely broadcast on African
screens between the late 1970s and early 1980s, and today are
among the most popular entertainment products on the
continent. The content, aesthetic and narrative format of
telenovelas have become a model for many African video film
producers, who have incorporated some of telenovelas’ defining
elements in their productions in order to attract local audiences.
This special issue analyses the impact of telenovelas’ circulation in
Africa by focusing on the ‘uses’ African audiences and media
producers make of them. Why do telenovelas travel so well
around sub-Saharan Africa? How do African audiences make sense
of them? And what impact do these media products have on local
media entrepreneurs and on the aesthetics and narrative aspects
of the contents they produce? In this introduction we provide
some background and data about the history and the political
economy of telenovelas’ circulation in Africa, and answer the
questions raised above by connecting the finding of the essays
included in the special issue to ongoing debates on the global
circulation of melodrama, on the transformation of African screen
media, and on the performative dimension of African audiences’
engagement with foreign media forms