News
161 news in 2023
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2023-01-20
Seminar Report
ABBL-iTHEMS Joint Astro Seminar by Dr. Nanae Domoto on January 20, 2023
Binary neutron star (NS) merger is a promising site for the rapid neutron capture nucleosynthesis (r-process). The radioactive decay of newly synthesized elements powers electromagnetic radiation, as called kilonova. The detection of gravitational wave from a NS merger GW170817 and the observation of the associated kilonova AT2017gfo have provided with us the evidence that r-process happens in the NS merger. However, the abundance pattern synthesized in this event, which is important to understand the origin of the r-process elements, is not yet clear. In this talk, Ms. Domoto first introduced an overview and current understanding of kilonova. Then, she discussed her recent findings of elemental features in photospheric spectra of kilonova toward identification of elements. Reported by Shigehiro Nagataki
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2023-01-17
Seminar Report
ABBL-iTHEMS Joint Astro Seminar by Dr. Arno Vanthieghem on November 24, 2022
On November 24th, Dr. Arno Vanthieghem (Princeton University) gave a talk about the energy equipartition in Weibel-mediated shock waves. Shock waves relevant to astrophysical phenomena, such as supernovae and gamma-ray bursts, form via collective plasma processes. In the so-called collision-less shock waves, how exactly the different plasma species (thermal and suprathermal ions and electrons) share energy through dissipation is an open question. In the talk, he gave a broad overview and described the current understanding of this issue based on his recent studies. He carried out analytical kinetic estimates, semi-analytical Monte Carlo calculations, and ab-initio Particle-In-Cell simulations to tackle this issue in a wide range of shock velocities ranging from relativistic to non-relativistic regimes. In particular, he has introduced a theoretical model that can describe electron heating through the interplay between pitch-angle scattering in the microturbulence and the coherent electrostatic field induced by the difference in inertia between species. He has shown how successfully the model can be applied to unmagnetized shocks (shocks formed in a plasma without a background magnetic field). During and after the seminar, we had very fruitful discussions. We are grateful for the excellent talk and the great opportunity to have a face-to-face conversation with him. Reported by Hirotaka Ito
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2023-01-16
Seminar ReportiTHEMS Biology Seminar by Dr. Tetsuya Kobayashi on September 8, 2022
On September 8th, I invited Dr. Testuya Kobayashi, and he talked about hessian geometric structure of equilibrium and nonequilibrium chemical reaction newtworks. He offered a topic on chemical reaction networks. He discussed central issues in biophysics and quantitative biology with recent work from their laboratory. This seminar had a special focus on researchers in the physical and mathematical sciences. However, it was also accessible to biological researchers. In particular, the discussion on the landscape was in line with each biological field. Reported by Daiki Kumakura
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2023-01-16
Seminar ReportiTHEMS Biology Seminar by Mr. Daiki Kumakura on January 12, 2023
On January 12, I spoke about the basics of microbial ecology and the application of our field of research and life. First, I gave an introduction of where microbes can live. Then I talked about the application of enzymes of different microbes. And then, I talked about how to study microbiomes, especially metagenomic analysis. Finally, I talked about our project, the hot springs microbiome project. Our project is proceeding in several steps, so I talked about the perspective of our analysis. In this seminar, I focused on the researchers who are not familiar with microbial ecology. This allowed me to share my interest in microbial ecology. Reported by Daiki Kumakura
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2023-01-16
Seminar ReportABBL-iTHEMS Joint Astro Seminar by Dr. Conor Omand on December 20, 2022
Many energetic supernovae are thought to be powered by the rotational energy of a highly-magnetized, rapidly-rotating neutron star. The emission from the associated luminous pulsar wind nebula (PWN) can affect the system in different ways, including accelerating the ejecta, ionizing the ejecta, and breaking the spherical symmetry through hydrodynamic instabilities or large scale asymmetries. Modeling the observables from these processes; the light curves, spectrum, and polarization; is essential from understanding the nature of the central engine. Dr. Ommand presented the results of a radiative transfer study looking at the effects of a PWN on the supernova nebular spectrum, and the preliminary results from a more physically motivated light curve model for parameter inference, and a study examining the polarization that arises due to hydrodynamic instabilities in the ejecta of engine-driven supernovae. Reported by Shigehiro Nagataki
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2023-01-16
Seminar Report
ABBL-iTHEMS Joint Astro Seminar by Dr. Shinya Wanajo on January 13, 2023
The discovery of an electromagnetic counterpart (kilonova) associated with GW170817 confirms that binary neutron star (NS) mergers are at least one of sites of r-process nucleosynthesis. However, there is no observational evidence that black hole (BH)-NS mergers are r-process sites. In this talk, Dr Wanajo overviewed the latest work of nucleosynthesis based on long-term hydrodynamics simulations of NS-NS and BH-NS mergers covering early dynamical and late post-merger mass ejections. Dr. Wanajo also briefly discussed a possible constraint on nuclear equations of state. Reported by Shigehiro Nagataki
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2023-01-12
Paper of the WeekWeek 3, January 2023
Title: Numerical studies on the finite-temperature CP restoration in 4D SU(N) gauge theory at $θ=π$ Author: Akira Matsumoto, Kohta Hatakeyama, Mitsuaki Hirasawa, Masazumi Honda, Jun Nishimura, Atis Yosprakob arXiv: http://arxiv.org/abs/2301.03879v1 Title: Spin conductivity spectrum and spin superfluidity in a binary Bose mixture Author: Yuta Sekino, Hiroyuki Tajima, Shun Uchino arXiv: http://arxiv.org/abs/2301.03031v1 Title: Apolipoprotein A1 and high-density lipoprotein limit low-density lipoprotein transcytosis by binding scavenger receptor B1 Author: Karen Fung, Tse Wing Winnie Ho, Zizhen Xu, Dante Neculai, Catherine A. A. Beauchemin, Warren L. Lee, Gregory D. Fairn doi: https://doi.org/10.1101/2022.08.08.503162 Title: Utility of Human In Vitro Data in Risk Assessments of Influenza A Virus Using the Ferret Model Author: Hannah M. Creager, Troy J. Kieran, Hui Zeng, Xiangjie Sun, Joanna A. Pulit-Penaloza, Katie E. Holmes, Anders F. Johnson, Terrence M. Tumpey, Taronna R. Maines, Catherine A. A. Beauchemin Journal Reference: Journal of Virology doi: https://doi.org/10.1128/jvi.01536-22
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2023-01-07
Seminar ReportiTHEMS Biology Seminar by Dr. Yusuke Himeoka on November 17, 2022
On last November, Dr. Yusuke Himeoka at the University of Tokyo told us about a mysterious phenomena of bacterial cells, called "dormancy". The title of his talk was "Emergence of growth and dormancy from a kinetic model of the Escherichia coli central carbon metabolism". Starting from a network model of metabolism, he theoretically discussed how dormancy emerges at bacterial cells. During and after the talk, there were lively discussions. Thank you so much, Himeoka-san! Reported by Gen Kurosawa
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2023-01-06
Seminar Report
iTHEMS Biology Seminar by Dr. Katsuhiko Sato on January 5, 2023
In iTHEMS biology seminar on January 5, Katsuhiko Sato (Hokkaido University) talked about a theoretical model of cell migration. First, he gave us the overview about cell migration. The dominant forces for the cell migrations are believed to the hydrostatic pressure in the cell, the contraction force by actomyosins and the frictions. Next, he constructed a mechanical model of the cell migration in an elegant manner. In this mechanical model, the cell migration dynamics is described by the balance between the energy and the dissipation. The dissipation describes the frictions. The energy includes the hydrostatic pressure, the contraction force, bending energy and the surface tension. Then, he introduced the cell polarization into the surface tension. By using this mechanical model, he demonstrated the unidirectional movement and the rotation of the cell cluster. We enjoyed the discussion with Sato-san on the detail of the modeling and its result. Thank you very much for a great talk, Sato-san! Reported by Hiroshi Yokota
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2023-01-05
Paper of the WeekWeek 2, January 2023
Title: Site-suitability difference and the expectation of species richness difference in stochastic two-subcommunity models Author: Ryosuke Iritani doi: https://doi.org/10.1101/2023.01.01.522407 Title: Clasper presentations of Habegger-Lin's action on string links Author: Yuka Kotorii, Atsuhiko Mizusawa arXiv: http://arxiv.org/abs/2212.14502v1
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2023-01-04
Research News
RIKEN NEWS: The Power of Open Science to Defeat Pandemics
Catherine Beauchemin (Deputy Program Director, iTHEMS) is interviewed in the Winter issue of RIKEN NEWS 2023. COVID-19 can only transmit if an infected person infects an uninfected person. So if 100% of sick people stayed home, there would be zero new cases, and COVID-19 would be over. Since transmission relies on the behaviour of each individual, to manage or even end COVID-19 requires the cooperation of every person in society. This is the big challenge we continue to face even now. Misinformation has become a big problem in society. People trust their own opinion and that of their friends and family more than facts. There is also a tendency to distrust government officials, pharmaceutical companies, news media and scientists. Sometimes it is true that such people or organizations will lie or exaggerate, so it is reasonable and important for a person to be skeptical. In fact, skeptical thinking is essential in science: we need to open our mind to new results, especially those that contradict our assumptions and hypotheses. So what can be done? I think the best way to combat misinformation and build a lasting trust with the public is complete transparency, by openly (free/re-usable) sharing data and scientific analyses with the general public, so people around the world can independently verify the facts. To read more, please see the related link.
161 news in 2023