Professor Shingo Iwami (Graduate School of Science, Nagoya University / Visiting Scientist, iTHEMS), in collaboration with Assistant Professor Keisuke Ejima (Indiana University, USA), has developed a new simulator (computer simulation) to verify when to end isolation of persons infected with a novel coronavirus (COVID-19) through antigen testing.

This will allow us to propose a flexible and safe isolation strategy that can terminate isolation of COVID-19-infected patients as early as possible with negative results of a predetermined number of antigen tests.

Isolation of infected patients is an important means of preventing the spread of infection. While prolonged isolation reduces the risk of secondary infection, it also places various burdens on the person being isolated and the society that supports them.

Using the simulator they have developed, the research group has successfully calculated "the risk of (prematurely) terminating isolation of infectious patients" and "the duration of unnecessary isolation of patients who are no longer infectious (the burden associated with isolation)." As a result, we are now able to propose an appropriate isolation strategy that takes into account individual differences and uses antigen testing to simultaneously reduce risk and burden. As we enter the era of with-colonization, in which social activities are resumed and maintained while infection prevention measures are thoroughly implemented, the successful use of antigen testing will allow for the safe implementation of educational and social activities.

In contrast to the current situation where different isolation standards based on clinical and epidemiological data and empirical rules are adopted in different countries, this study is expected to contribute to the establishment of flexible isolation guidelines based on mathematical models, which are required not only in Japan but also worldwide.

For more details, please visit the Nagoya University research results dissemination site from the related link.

iTHEMS was featured in the August volume of "Sugaku Tsushin" (Japanese magazine published by The Mathematical Society of Japan). Our colleagues, Tetsuo Hatsuda, Ade Irma Suriajaya, Yosuke Kubota, Hiroyasu Miyazaki and Yukimi Goto, have written essays on iTHEMS in the volume. Let's see mathematicians' thoughts on the iTHEMS atmosphere.

In the iTHEMS biology seminar on September 1st, I, Hiroshi Yokota, talked about a theoretical model of chromosome condensation based on Langevin simulation. In this model, the twist and the writhe structures on biopolymer is quantified in a computational manner. In this seminar, I enjoyed the discussion with audiences on the computational method and the definition of the twist and the writhe. Thank you so much!

Reported by Hiroshi Yokota

Dr. Yosuke Mizuno presented the first Event Horizon Telescope (EHT) observations of Sagittarius A* (Sgr A*), the Galactic center source associated with a supermassive black hole. These observations were conducted in 2017 using a global interferometric array of eight telescopes operating at a wavelength 1.3 mm. A variety of imaging and modeling analyses all support an image that is dominated by a bright, thick ring with a diameter of ~50 micro-arcsecond. Using a large suite of numerical simulations, The EHT group demonstrated that the EHT images of Sgr A* are consistent with the expected appearance of a Kerr black hole with mass ∼4 million solar mass, which is inferred to exist at this location based on previous infrared observations of individual stellar orbits, as well as maser proper-motion studies. Their model comparisons disfavor scenarios where the black hole is viewed at high inclination (i > 50 deg), as well as non-spinning black holes and those with retrograde accretion disks. Our results provide direct evidence for the presence of a supermassive black hole at the center of the Milky Way. In the seminar, Dr. Yosuke Mizuno focused on more theoretical interpretation and model comparison to understand the accretion flow properties nearby Sgr A*.

Reported by Shigehiro Nagataki

Title: Impact of Neutrino Cooling on Type-I X-ray Bursts and X-ray Superbursts
Author: Akira Dohi, Nobuya Nishimura, Hajime Sotani, Tsuneo Noda, Helei Liu, Shigehiro Nagataki, Masa-aki Hashimoto
arXiv: http://arxiv.org/abs/2208.14622v1

Title: Functional Renormalization Group Approach to Circuit Quantum Electrodynamics
Author: Takeru Yokota, Kanta Masuki, Yuto Ashida
arXiv: http://arxiv.org/abs/2208.14107v1

Title: Binary-coupling sparse SYK: an improved model of quantum chaos and holography
Author: Masaki Tezuka, Onur Oktay, Enrico Rinaldi, Masanori Hanada, Franco Nori
arXiv: http://arxiv.org/abs/2208.12098v1