Gravitational waves from an SMBH binary in M87

In this paper, we study gravitational-wave (GW) emission from a hypothetical supermassive black-hole (SMBH) binary at the center of M87. The existence of a SMBH other than that usually identified with the central AGN is a possible explanation for the observed displacement ($\sim O(1)~{\rm pc}$) between the AGN and the galactic centroid, and it is reasonable to assume consid- ering the evolution of SMBHs through galaxy mergers. Because the period of the binary and the resulting GWs is much longer than the observational time span, we calculate the variation of the GW amplitude, rather than the amplitude itself. We investigate the dependence on the orbital elements and the second BH mass taking the observational constraints into account. The frequency of the GWs is too low to be detected with the conventional pulsar timing array and we propose a new method to detect such low-frequency GWs with the distribution func- tion of pulsar spin-down rates. Although the GWs from a SMBH binary which explains the observed displacement is extremely hard to be detected even with the new method, GWs are still a useful way to probe the M87 center.Comment: 5 pages, 6 figures. Accepted for Publications of the Astronomical Society of Japa

Artificial neural networks for selection of pulsar candidates from the radio continuum surveys

Pulsar search with time-domain observation is very computationally expensive and data volume will be enormous with the next generation telescopes such as the Square Kilometre Array. We apply artificial neural networks (ANNs), a machine learning method, for efficient selection of pulsar candidates from radio continuum surveys, which are much cheaper than time-domain observation. With observed quantities such as radio fluxes, sky position and compactness as inputs, our ANNs output the "score" that indicates the degree of likeliness of an object to be a pulsar. We demonstrate ANNs based on existing survey data by the TIFR GMRT Sky Survey (TGSS) and the NRAO VLA Sky Survey (NVSS) and test their performance. Precision, which is the ratio of the number of pulsars classified correctly as pulsars to that of any objects classified as pulsars, is about 96$\%$. Finally, we apply the trained ANNs to unidentified radio sources and our fiducial ANN with five inputs (the galactic longitude and latitude, the TGSS and NVSS fluxes and compactness) generates 2,436 pulsar candidates from 456,866 unidentified radio sources. These candidates need to be confirmed if they are truly pulsars by time-domain observations. More information such as polarization will narrow the candidates down further.Comment: 11 pages, 13 figures, 3 tables, accepted for publication in MNRA

Something About Marybell

Something About Marybell is a children's book with audio compact disk, in which I combined three art forms: storytelling, illustrating, and music composition. The nature of the story reflects my love of animals, which has been the essence of all my previous works as well. Beyond the technical matters I practiced and obstacles I encountered while working on each of the aforementioned art forms, the most important point I discovered was that all three were consistently interrelated, and I never could develop one medium without considering the others. Working on this project also was a journey to trace my major influences in different subjects. My drawing style is influenced by cartoons and animation films, which are now considered significant artistic styles in Japanese subculture. My music composition reflects a broad influence from many composers' works working in a variety of genres, especially piano works, of all eras. There are two specific works I studied as model works for this project: Poulenc's L'Histoire de Babar le petit éléphant (The Story of Babar the Little Elephant) and Prokofiev's Peter and the Wolf. It was a challenge to blend one stylistic approach into another to accurately realize my musical conception

Protein engineering of conger eel galectins by tracing of molecular evolution using probable ancestral mutants

<p>Abstract</p> <p>Background</p> <p>Conger eel galectins, congerin I (ConI) and congerin II (ConII), show the different molecular characteristics resulting from accelerating evolution. We recently reconstructed a probable ancestral form of congerins, Con-anc. It showed properties similar to those of ConII in terms of thermostability and carbohydrate recognition specificity, although it shares a higher sequence similarity with ConI than ConII.</p> <p>Results</p> <p>In this study, we have focused on the different amino acid residues between Con-anc and ConI, and have performed the protein engineering of Con-anc through site-directed mutagenesis, followed by the molecular evolution analysis of the mutants. This approach revealed the functional importance of loop structures of congerins: (1) N- and C-terminal and loop 5 regions that are involved in conferring a high thermostability to ConI; (2) loops 3, 5, and 6 that are responsible for stronger binding of ConI to most sugars; and (3) loops 5 and 6, and Thr38 residue in loop 3 contribute the specificity of ConI toward lacto-<it>N</it>-fucopentaose-containing sugars.</p> <p>Conclusions</p> <p>Thus, this methodology, with tracing of the molecular evolution using ancestral mutants, is a powerful tool for the analysis of not only the molecular evolutionary process, but also the structural elements of a protein responsible for its various functions.</p