24 results on '"KO NAKAMURA"'
Search Results
2. SNEWPY: A Data Pipeline from Supernova Simulations to Neutrino Signals
- Author
-
Amanda L. Baxter, Segev BenZvi, Joahan Castaneda Jaimes, Alexis Coleiro, Marta Colomer Molla, Damien Dornic, Tomer Goldhagen, Anne Graf, Spencer Griswold, Alec Habig, Remington Hill, Shunsaku Horiuchi, James P. Kneller, Rafael F. Lang, Massimiliano Lincetto, Jost Migenda, Ko Nakamura, Evan O’Connor, Andrew Renshaw, Kate Scholberg, Christopher Tunnell, Navya Uberoi, Arkin Worlikar, and The SNEWS Collaboration
- Subjects
Supernova neutrinos ,Particle astrophysics ,Supernovae ,Astrophysics ,QB460-466 - Abstract
Current neutrino detectors will observe hundreds to thousands of neutrinos from Galactic supernovae, and future detectors will increase this yield by an order of magnitude or more. With such a data set comes the potential for a huge increase in our understanding of the explosions of massive stars, nuclear physics under extreme conditions, and the properties of the neutrino. However, there is currently a large gap between supernova simulations and the corresponding signals in neutrino detectors, which will make any comparison between theory and observation very difficult. SNEWPY is an open-source software package that bridges this gap. The SNEWPY code can interface with supernova simulation data to generate from the model either a time series of neutrino spectral fluences at Earth, or the total time-integrated spectral fluence. Data from several hundred simulations of core-collapse, thermonuclear, and pair-instability supernovae is included in the package. This output may then be used by an event generator such as sntools or an event rate calculator such as the SuperNova Observatories with General Long Baseline Experiment Simulator (SNOwGLoBES). Additional routines in the SNEWPY package automate the processing of the generated data through the SNOwGLoBES software and collate its output into the observable channels of each detector. In this paper we describe the contents of the package, the physics behind SNEWPY, the organization of the code, and provide examples of how to make use of its capabilities.
- Published
- 2022
- Full Text
- View/download PDF
3. A configuration of model predictive PID control
- Author
-
Ko NAKAMURA and Tohru KAWABE
- Subjects
mpc (model predictive control) ,pid control ,heat conduction system ,mobile robot ,Mechanical engineering and machinery ,TJ1-1570 ,Engineering machinery, tools, and implements ,TA213-215 - Abstract
Although PID control is still widely used in the industry, it isn't answered a high performance demand. On the other hand, the model predictive control (MPC) is paid attention as effective control but it takes much cost to introduce MPC instead of the PID control since the MPC structure quite different from the PID control. To defeat such situation, this paper proposes a model predictive PID Control method. In this method, the PID control gains are derived by solving the constrained optimization problem based on MPC algorithm without using inverse matrixes. The numerical simulations show that the proposed method is effective for various control systems.
- Published
- 2016
- Full Text
- View/download PDF
4. A new electrode structure of IrOx/Bi-doped SrRuO3 for highly reliable La-doped Pb (Zr, Ti)O3-based ferroelectric memories.
- Author
-
Wensheng Wang, Takashi Eshita, Kazuaki Takai, Ko Nakamura, Mitsuaki Oikawa, Nozomi Sato, Soichiro Ozawa, Kouichi Nagai, Satoru Mihara, Yukinobu Hikosaka, Hitoshi Saito, Manabu Kojima, Kenji Nomura, and Hideshi Yamaguchi
- Subjects
ELECTRODES ,FERROELECTRICITY ,LANTHANUM ,ENERGY consumption ,IRIDIUM - Abstract
We successfully developed a lanthanum (La)-doped Pb (Zr,Ti)O
3 (PLZT) based ferroelectric capacitor (FC) using a new electrode material of bismuth (Bi) doped SrRuO3 (B-SRO) aiming at reduction of energy consumption of ferroelectric random access memory (FeRAM) by suppressing the leakage current of its FC. Our employed B-SRO layer is effective for suppressing the leakage current due to reducing atomic interdiffusions of Iridium and lead between IrOx top electrode (TE) and PLZT. Space charge limited conduction (SCLC) is dominant in the leakage current of the FC with B-SRO, while defect assisted conduction possibly includes in the leakage current of FC without B-SRO in addition with the SCLC. Switchable polarization, depending on the B-SRO thickness, has largest value for 1.0-1.5 nm thick B-SRO. Excellent imprint and switching (fatigue) endurances is proven on the FC with 1 nm thick BSRO. [ABSTRACT FROM AUTHOR]- Published
- 2024
- Full Text
- View/download PDF
5. Optimal Time Point for Evaluation of Response to Pembrolizumab Treatment in Japanese Patients With Metastatic Urothelial Carcinoma.
- Author
-
TERUO INAMOTO, RYO SATO, YUTO MATSUSHITA, TAIZO UCHIMOTO, KO NAKAMURA, KAZUMASA KOMURA, KAZUKI NISHIMURA, YUSUKE YANO, KYOSUKE NISHIO, SHOKO KINOSHITA, TATSUO FUKUSHIMA, TOMOHISA MATSUNAGA, KEITA NAKAMORI, TAKESHI TSUTSUMI, TAKUYA TSUJINO, HIROFUMI UEHARA, KIYOSHI TAKAHARA, HIDEAKI MIYAKE, and HARUHITO AZUMA
- Subjects
JAPANESE people ,TRANSITIONAL cell carcinoma ,TERMINATION of treatment ,PEMBROLIZUMAB ,MULTIVARIATE analysis - Abstract
Background/Aim: The duration of pembrolizumab use in actual daily practice might be shorter than that in clinical trials because termination of pembrolizumab therapy is at the discretion of the physician. We retrospectively reviewed the response to pembrolizumab in Japanese patients with metastatic urothelial carcinoma (mUC) in relation to the time to response (TTR). Patients and Methods: The records of 165 patients treated with pembrolizumab for mUC were retrospectively analyzed. Response was evaluated at 2, 4, 6 and 8 months. TTR along with time to best response were analyzed. Phase II-III clinical trials were also reviewed to compare the TTR and time to best overall response. Results: The median patient age was 70 years. The objective response rate in the total cohort was 27.1% (42 out of 155 patients). Median TTR was 2.4 months and the time to best response was 3.1 months. Radiological evaluation at each time point significantly predicted overall survival (OS). Considering the evaluation of response at 2, 4, 6 and 8 months, the response at later time points tended to predict OS better. Multivariate analysis showed that the evaluation of response at 8 months (hazard ratio=1.91, 95% confidence interval=1.16-3.16 months; p<0.01) and best response during the treatment (hazard ratio=1.69, 95% confidence interval=1.17-2.44; p<0.01) independently predicted improved OS. Conclusion: Given that response when evaluated at a later point during pembrolizumab treatment more favorably reflected improved survival than when assessed earlier, physicians may be encouraged to wait until at least the termination of pembrolizumab treatment to determine the best response. [ABSTRACT FROM AUTHOR]
- Published
- 2023
- Full Text
- View/download PDF
6. Tissue Distribution of Cisplatin by Intra-arterial Infusion Route in Comparison to Systemic Route: Implication to Therapy for Node-positive Bladder Cancer.
- Author
-
ATSUSHI ICHIHASI, TERUO INAMOTO, TAIZO UCHIMOTO, KO NAKAMURA, KAZUMASA KOMURA, YUSUKE YANO, KAZUKI NISHIMURA, SHOKO KINOSHITA, KYOSUKE NISHIO, TATSUO FUKUSHIMA, KEITA NAKAMORI, TOMOHISA MATSUNAGA, TAKESHI TSUTSUMI, TAKUYA TSUJINO, HIROFUMI UEHARA, KIYOSHI TAKAHARA, KAZUHIRO YAMAMOTO, RYUJI KATO, YOSHIO IJIRI, and TETSUYA HAYASHI
- Subjects
CISPLATIN ,BLADDER cancer ,LYMPH nodes ,CANCER chemotherapy ,MEDICAL care ,MEDICAL personnel - Abstract
Background/Aim: In clinical practice, platinumbased systemic chemotherapy works to shrink pelvic lymph nodes. Intra-arterial (IA) bolus infusion may result in more favorable results than systemic chemotherapy. In the present study, we investigated the distribution of cisplatin administrated by IA infusion in varying organs, specifically focusing on the node tissue, in comparison with the intravenous (IV) route. Materials and Methods: Under anesthesia, cisplatin 0.42 mg/body was administrated by IA or IV infusion in rats to mimic a balloon-occluded arterial infusion model used in clinical practice. The kidney, bladder, lymphatic tissue, and peripheral blood were extracted to analyze the amount of cisplatin by inductively coupled plasma-mass spectrometry. Results: Concertation of cisplatin by IA infusion was higher than that by the IV route in the peripheral blood and kidney. IA infusion led to a significantly high concentration of cisplatin in the bladder compared to IV infusion (1.3±0.452 vs. 0.2 ppb/mg ± 0.055, p=0.050). Furthermore, the IA method led to an extremely high concentration of cisplatin in the lymphatic tissue compared to the IV method (0.1±0.036 vs. 13.3±5.36, p=0.048). Conclusion: High cisplatin accumulation in the lymphatic tissue and bladder by IA administration may have a potential role for treating patients with node-positive bladder cancer. [ABSTRACT FROM AUTHOR]
- Published
- 2023
- Full Text
- View/download PDF
7. Diffuse supernova neutrino background from extensive core-collapse simulations of 8-100 M☉ progenitors.
- Author
-
Shunsaku Horiuchi, Kohsuke Sumiyoshi, Ko Nakamura, Fischer, Tobias, Summa, Alexander, Tomoya Takiwaki, Hans-Thomas Janka, and Kei Kotake
- Subjects
SUPERGIANT stars ,BLACK holes ,NEUTRINOS ,SUPERNOVAE ,COMPUTER simulation - Abstract
We revisit the diffuse supernova neutrino background in light of recent systematic studies of stellar core collapse that reveal the quantitative impacts of the progenitor conditions on the collapse process. In general, the dependence of the core-collapse neutrino emission on the progenitor is not monotonic in progenitor initial mass, but we show that it can, at first order, be characterized by the core compactness. For the first time, we incorporate the detailed variations in the neutrino emission over the entire mass range 8-100M☉, based on (i) a long-term simulation of the core collapse of an 8.8M☉ ONeMg core progenitor, (ii) over 100 simulations of iron core collapse to neutron stars, and (iii) half a dozen simulations of core collapse to black holes (the 'failed channel'). The fraction of massive stars that undergo the failed channel remains uncertain, but in view of recent simulations which reveal high compactness to be conducive to collapse to black holes, we characterize the failed fraction by considering a threshold compactness above which massive stars collapse to black holes and below which the final remnant is a neutron star.We predict that future detections of the diffuse supernova neutrino background may have the power to reveal this threshold compactness, if its value is relatively small as suggested by interpretations of several recent astronomical observations [ABSTRACT FROM AUTHOR]
- Published
- 2018
- Full Text
- View/download PDF
8. Multimessenger signals of long-term core-collapse supernova simulations: synergetic observation strategies.
- Author
-
Ko Nakamura, Shunsaku Horiuchi, Masaomi Tanaka, Kazuhiro Hayama, Tomoya Takiwaki, and Kei Kotake
- Subjects
- *
SUPERNOVAE , *CATACLYSMIC variable stars , *GALACTIC center , *GALACTIC nuclei , *ELECTROMAGNETIC fields - Abstract
The next Galactic supernova is expected to bring great opportunities for the direct detection of gravitational waves (GW), full flavour neutrinos, and multiwavelength photons. To maximize the science return from such a rare event, it is essential to have established classes of possible situations and preparations for appropriate observations. To this end, we use a long-term numerical simulation of the core-collapse supernova (CCSN) of a 17 M☉ red supergiant progenitor to self-consistently model the multimessenger signals expected in GW, neutrino, and electromagnetic messengers. This supernova model takes into account the formation and evolution of a protoneutron star, neutrino-matter interaction, and neutrino transport, all within a two-dimensional shock hydrodynamics simulation. With this, we separately discuss three situations: (i) a CCSN at the Galactic Center, (ii) an extremely nearby CCSN within hundreds of parsecs, and (iii) a CCSN in nearby galaxies within several Mpc. These distance regimes necessitate different strategies for synergistic observations. In a Galactic CCSN, neutrinos provide strategic timing and pointing information. We explore how these in turn deliver an improvement in the sensitivity of GW analyses and help to guarantee observations of early electromagnetic signals. To facilitate the detection of multimessenger signals of CCSNe in extremely nearby and extragalactic distances, we compile a list of nearby red supergiant candidates and a list of nearby galaxies with their expected CCSN rates. By exploring the sequential multimessenger signals of a nearby CCSN, we discuss preparations for maximizing successful studies of such an unprecedented stirring event. [ABSTRACT FROM AUTHOR]
- Published
- 2016
- Full Text
- View/download PDF
9. Systematic features of axisymmetric neutrino-driven core-collapse supernova models in multiple progenitors.
- Author
-
Ko NAKAMURA, Tomoya TAKIWAKI, Takami KURODA, and Kei KOTAKE
- Subjects
- *
NEUTRINO astrophysics , *SUPERNOVAE , *NICKEL , *NEUTRON stars , *NEUTRINOS - Abstract
We present an overview of two-dimensional (2D) core-collapse supernova simulations employing a neutrino transport scheme by the isotropic diffusion source approximation. We study 101 solar-metallicity, 247 ultra metal-poor, and 30 zero-metal progenitors covering zero-age main sequence mass from 10.8M⊙ to 75.0M⊙. Using the 378 progenitors in total, we systematically investigate how the differences in the structures of these multiple progenitors impact the hydrodynamics evolution. By following a long-term evolution over 1.0 s after bounce, most of the computed models exhibit neutrino-driven revival of the stalled bounce shock at ~200-800 ms postbounce, leading to the possibility of explosion. Pushing the boundaries of expectations in previous one-dimensional studies, our results confirm that the compactness parameter ξ that characterizes the structure of the progenitors is also a key in 2D to diagnosing the properties of neutrino-driven explosions. Models with high ξ undergo high ram pressure from the accreting matter onto the stalled shock, which affects the subsequent evolution of the shock expansion and the mass of the protoneutron star under the influence of neutrino-driven convection and the standing accretion-shock instability. We show that the accretion luminosity becomes higher for models with high ξ, which makes the growth rate of the diagnostic explosion energy higher and the synthesized nickel mass bigger. We find that these explosion characteristics tend to show a monotonic increase as a function of the compactness parameter ξ. [ABSTRACT FROM AUTHOR]
- Published
- 2015
- Full Text
- View/download PDF
10. Neutrino Process in Core-collapse Supernovae with Neutrino Self-interaction and MSW Effects.
- Author
-
Heamin Ko, Myung-Ki Cheoun, Eunja Ha, Motohiko Kusakabe, Takehito Hayakawa, Hirokazu Sasaki, Toshitaka Kajino, Masa-aki Hashimoto, Masaomi Ono, Mark D. Usang, Satoshi Chiba, Ko Nakamura, Alexey Tolstov, Ken’ichi Nomoto, Toshihiko Kawano, and Grant J. Mathews
- Published
- 2020
- Full Text
- View/download PDF
11. One-, Two-, and Three-dimensional Simulations of Oxygen-shell Burning Just before the Core Collapse of Massive Stars.
- Author
-
Takashi Yoshida, Tomoya Takiwaki, Kei Kotake, Koh Takahashi, Ko Nakamura, and Hideyuki Umeda
- Subjects
SUPERGIANT stars ,GRAVITATIONAL collapse ,MACH number ,STELLAR evolution ,STELLAR mass ,SUPERNOVA remnants ,SUPERNOVAE - Abstract
We perform two- (2D) and three-dimensional (3D) hydrodynamics simulations of convective oxygen-shell burning that takes place deep inside a massive progenitor star of a core-collapse supernova. Using a one-dimensional (1D) stellar evolution code, we first calculate the evolution of massive stars with an initial mass of 9–40 M
⊙ . Four different overshoot parameters are applied, and a CO-core mass trend similar to previous works is obtained in the 1D models. Selecting eleven 1D models that have a coexisting silicon and oxygen layer, we perform 2D hydrodynamics simulations of the evolution for ∼100 s until the onset of core collapse. We find that convection with large-scale eddies and the turbulent Mach number of ∼0.1 is obtained in the models having a Si/O layer with a scale of 108 cm, whereas most models that have an extended O/Si layer up to a few ×109 cm exhibit lower turbulent velocity. Our results indicate that the supernova progenitors that possess a thick Si/O layer could provide the preferred condition for perturbation-aided explosions. We perform the 3D simulation of a 25 M⊙ model, which exhibits large-scale convection in the 2D models. The 3D model develops large-scale (ℓ = 2) convection similar to the 2D model; however, the turbulent velocity is lower. By estimating the neutrino emission properties of the 3D model, we point out that a time modulation of the event rates, if observed in KamLAND and Hyper-Kamiokande, could provide important information about structural changes in the presupernova convective layer. [ABSTRACT FROM AUTHOR]- Published
- 2019
- Full Text
- View/download PDF
12. Ferroelectric random access memory with high electric properties and high production yield realized by employing an AlOx underlying layer of Pt bottom electrode for a La-doped lead zirconate titanate capacitor.
- Author
-
Wensheng Wang, Kenji Nomura, Ko Nakamura, Takashi Eshita, Soichiro Ozawa, Hideshi Yamaguchi, Kazuaki Takai, Junichi Watanabe, Satoru Mihara, Yukinobu Hikosaka, Hitoshi Saito, Yuji Kataoka, and Manabu Kojima
- Abstract
Although ferroelectric random access memory (FRAM) has superior electric properties, its downside is that it has a relatively larger cell area in comparison other non-volatile memories. We tried to apply TiO
x , and AlOx to an underlying layer (TiOx -UL, AlOx -UL) instead of our previously used Ti underlying layer (Ti-UL) for the La-doped lead zirconate titanate (PLZT) capacitor to obtain a high polarization value aiming to a lowering cell area. The failed bit ratio of the FRAM with TiOx -UL was found to be higher than that with AlOx -UL even though polarization values of the PLZT capacitor with both underlying layers are almost the same and much higher than that with Ti-UL. It is strongly suggested that the imprint induced in PLZT by charged defect is a main cause of bit failure by fail-bit analysis. X-ray diffraction and atomic force microscopy observations shows that charged defect density in PLZT over TiOx -UL is possibly higher than that in PLZT over AlOx -UL due to surface roughness of underlying layers. [ABSTRACT FROM AUTHOR]- Published
- 2019
- Full Text
- View/download PDF
13. Improvement of ferroelectric random access memory manufacturing margin by employing Pt/AlO x bottom electrode for the La-doped Pb(Zr,Ti)O3 ferroelectric capacitor.
- Author
-
Kenji Nomura, Wensheng Wang, Hideshi Yamaguchi, Ko Nakamura, Takashi Eshita, Soichiro Ozawa, Kazuaki Takai, Satoru Mihara, Yukinobu Hikosaka, Makoto Hamada, Manabu Kojima, and Yuji Kataoka
- Abstract
In our previous works on La-doped Pb(Zr,Ti)O
3 (PLZT) growth on a Pt/Ti bottom electrode, the O2 content in postdeposition annealing (PDA) was found to play an important role in obtaining good electrical characteristics and high manufacturing yield of ferroelectric random access memory (FeRAM). The optimal O2 content of around 2% inhibits the growth of randomly oriented La-doped Pb(Zr,Ti)O3 (PLZT) grains near the PLZT surface, resulting in the growth of highly {111}-oriented PLZT. We found that the Pt bottom electrode grown on an AlOx layer can further suppress the formation of randomly oriented PLZT grains near the PLZT surface and increases the optimal O2 content range from 2 to 50%, which can enlarge the manufacturing process margin of PDA. It is proven that the AlOx layer blocks the diffusion of lead oxides (PbOx ) from PLZT to SiO2 interlayers through Pt and promotes pyrochlore-perovskite transformation near the bottom electrode during PDA. [ABSTRACT FROM AUTHOR]- Published
- 2018
- Full Text
- View/download PDF
14. Development of highly reliable ferroelectric random access memory and its Internet of Things applications.
- Author
-
Takashi Eshita, Wensheng Wang, Kenji Nomura, Ko Nakamura, Hitoshi Saito, Hideshi Yamaguchi, Satoru Mihara, Yukinobu Hikosaka, Yuji Kataoka, and Manabu Kojima
- Abstract
Ferroelectric random access memory (FRAM) has been commercialized for about 20 years and its reliability has been well proven all over the world. In the recent Internet of Things (IoT) era, it also plays important roles to particularly in edge computing because of its high writing speed, high rewriting endurance, and low writing energy consumption. We review the history of semiconductor memories using ferroelectrics and overview the progresses of the new ferroelectrics and promising ferroelectric applications in the future. [ABSTRACT FROM AUTHOR]
- Published
- 2018
- Full Text
- View/download PDF
15. Progenitor Mass Distribution of Core-collapse Supernova Remnants in Our Galaxy and Magellanic Clouds Based on Elemental Abundances.
- Author
-
Satoru Katsuda, Tomoya Takiwaki, Nozomu Tominaga, Takashi J. Moriya, and Ko Nakamura
- Subjects
SUPERNOVA remnants ,GALAXIES ,COSMIC abundances ,STELLAR initial mass function ,MAGELLANIC clouds - Abstract
We investigate a progenitor mass distribution of core-collapse supernova remnants (CCSNRs) in our Galaxy and Large and Small Magellanic Clouds for the first time. We count the number of CCSNRs in three mass ranges divided by the zero-age main-sequence (ZAMS) mass, M
ZAMS ; A: MZAMS < 15 M⊙ , B: 15 M⊙ < MZAMS < 22.5 M⊙ , C: MZAMS > 22.5 M⊙ . A simple compilation of progenitor masses in the literature yields a progenitor mass distribution of fA : fB : fC = 0.27:0.27:0.46, where f is the number fraction of the progenitors. The distribution is inconsistent with any standard initial mass functions (IMFs). We notice, however, that previous mass estimates are subject to large systematic uncertainties because most of the relative abundances (X/Si) are not good probes for the progenitor masses. Instead, we rely only on the Fe/Si ratio, which is sensitive to the CO core mass (MCOcore ) and MZAMS . Comparing Fe/Si ratios in SN remnants in the literature with the newest theoretical model, we estimate 33 MCOcore and MZAMS , leading to a revised progenitor mass distribution of fA : fB : fC = 0.47:0.32:0.21. This is consistent with the standard Salpeter IMF. However, the relation between MCOcore and MZAMS could be affected by binary evolution, which is not taken into account in this study and should be considered in future work to derive a better progenitor mass distribution estimate. [ABSTRACT FROM AUTHOR]- Published
- 2018
- Full Text
- View/download PDF
16. Intermediate-mass Elements in Young Supernova Remnants Reveal Neutron Star Kicks by Asymmetric Explosions.
- Author
-
Satoru Katsuda, Mikio Morii, Hans-Thomas Janka, Annop Wongwathanarat, Ko Nakamura, Kei Kotake, Koji Mori, Ewald Müller, Tomoya Takiwaki, Masaomi Tanaka, Nozomu Tominaga, and Hiroshi Tsunemi
- Subjects
NEUTRON stars ,ASTROPHYSICAL magnetic fields ,ANISOTROPY ,EXPLOSIONS ,SUPERNOVA remnants - Abstract
The birth properties of neutron stars (NSs) yield important information about the still-debated physical processes that trigger the explosion as well as on intrinsic neutron-star physics. These properties include the high space velocities of young neutron stars with average values of several 100 km s
−1 , with an underlying “kick” mechanism that is not fully clarified. There are two competing possibilities that could accelerate NSs during their birth: anisotropic ejection of either stellar debris or neutrinos. Here we present new evidence from X-ray measurements that chemical elements between silicon and calcium in six young gaseous supernova remnants are preferentially expelled opposite to the direction of neutron star motion. There is no correlation between the kick velocities and magnetic field strengths of these neutron stars. Our results support a hydrodynamic origin of neutron-star kicks connected to asymmetric explosive mass ejection, and they conflict with neutron-star acceleration scenarios that invoke anisotropic neutrino emission caused by particle and nuclear physics in combination with very strong neutron-star magnetic fields. [ABSTRACT FROM AUTHOR]- Published
- 2018
- Full Text
- View/download PDF
17. Impact of Neutrino Opacities on Core-collapse Supernova Simulations.
- Author
-
Kei Kotake, Tomoya Takiwaki, Tobias Fischer, Ko Nakamura, and Gabriel Martínez-Pinedo
- Subjects
NEUTRINO astrophysics ,SUPERNOVAE ,SIMULATION methods & models ,STAR formation ,ASTRONOMICAL observations - Abstract
The accurate description of neutrino opacities is central to both the core-collapse supernova (CCSN) phenomenon and the validity of the explosion mechanism itself. In this work, we study in a systematic fashion the role of a variety of well-selected neutrino opacities in CCSN simulations where the multi-energy, three-flavor neutrino transport is solved using the isotropic diffusion source approximation (IDSA) scheme. To verify our code, we first present results from one-dimensional (1D) simulations following the core collapse, bounce, and ∼250 ms postbounce of a star using a standard set of neutrino opacities by Bruenn. A detailed comparison with published results supports the reliability of our three-flavor IDSA scheme using the standard opacity set. We then investigate in 1D simulations how individual opacity updates lead to differences with the baseline run with the standard opacity set. Through detailed comparisons with previous work, we check the validity of our implementation of each update in a step-by-step manner. Individual neutrino opacities with the largest impact on the overall evolution in 1D simulations are selected for systematic comparisons in our two-dimensional (2D) simulations. Special attention is given to the criterion of explodability in the 2D models. We discuss the implications of these results as well as its limitations and the requirements for future, more elaborate CCSN modeling. [ABSTRACT FROM AUTHOR]
- Published
- 2018
- Full Text
- View/download PDF
18. Estimating the core compactness of massive stars with Galactic supernova neutrinos.
- Author
-
Shunsaku Horiuchi, Ko Nakamura, Tomoya Takiwaki, and Kei Kotake
- Subjects
- *
NEUTRINOS , *SUPERNOVAE , *LEPTONS (Nuclear physics) , *ACCRETION (Astrophysics) , *ASTROPHYSICAL fluid dynamics , *STATISTICAL correlation , *SIMULATION methods & models - Abstract
We suggest the future detection of neutrinos from a Galactic core-collapse supernova can be used to infer the progenitor’s inner mass density structure. We present the results from 20 axisymmetric core-collapse supernova simulations performed with progenitors spanning initial masses in the range 11–, and focus on their connections to the progenitor compactness. The compactness is a measure of the mass density profile of the progenitor core and recent investigations have suggested its salient connections to the outcomes of core collapse. Our simulations confirm a correlation between the neutrinos emitted during the accretion phase and the progenitor’s compactness, and that the ratio of observed neutrino events during the first hundreds of milliseconds provides a promising handle on the progenitor’s inner structure. Neutrino flavor mixing during the accretion phase remains a large source of uncertainty. [ABSTRACT FROM AUTHOR]
- Published
- 2017
- Full Text
- View/download PDF
19. Control of La-doped Pb(Zr,Ti)O3 crystalline orientation and its influence on the properties of ferroelectric random access memory.
- Author
-
Wensheng Wang, Kenji Nomura, Hideshi Yamaguchi, Ko Nakamura, Takashi Eshita, Soichiro Ozawa, Kazuaki Takai, Satoru Mihara, Yukinobu Hikosaka, Makoto Hamada, and Yuji Kataoka
- Abstract
We investigated the crystallization mechanisms of sputter-deposited La-doped Pb(Zr,Ti)O
3 (PLZT) on a Pt/Ti metal stack in the postdeposition annealing (PDA) at 600 °C in O2 -mixed Ar ambient. As-deposited amorphous PLZT generally transforms to a perovskite phase over 550 °C through a metastable pyrochlore phase during the PDA. We found that the O2 content of the PDA ambient crucially affects the pyrochlore-perovskite transformation (PPT) speed. While an O2 content much higher than 2% of the PDA ambient suppresses PPT, an O2 content much lower than 2% enhances PPT. An O2 content around of 2% of the PDA suppresses PPT near the surface of PLZT and simultaneously keeps PPT fast in the inner regions of PLZT in the pyrochlore phase because of the O2 diffusion limit from the PLZT surface, eventually resulting in almost only the growth of highly {111} oriented columnar PLZT on Pt, which reveals better electric properties than those obtained by the PDA with the ambient of O2 contents much higher or lower than 2%. [ABSTRACT FROM AUTHOR]- Published
- 2017
- Full Text
- View/download PDF
20. Multi-messenger signals from core-collapse supernovae.
- Author
-
Ko Nakamura, Shunsaku Horiuchi, Masaomi Tanaka, Kazuhiro Hayama, Tomoya Takiwaki, and Kei Kotake
- Abstract
The next Galactic supernova is expected to bring great opportunities for the direct detection of gravitational waves, full flavor neutrinos, and multi-wavelength photons. To prepare for appropriate observations of these multi-messenger signals, we use a long-term numerical simulation of the core-collapse supernova and discuss detectability of the signals in different situations. By exploring the sequential multi-messenger signals of a nearby CCSN, we discuss preparations for maximizing successful studies of such an unprecedented stirring event. [ABSTRACT FROM AUTHOR]
- Published
- 2016
- Full Text
- View/download PDF
21. Circular Polarizations of Gravitational Waves from Core-Collapse Supernovae: A Clear Indication of Rapid Rotation.
- Author
-
Kazuhiro Hayama, Takami Kuroda, Ko Nakamura, and Shoichi Yamada
- Subjects
- *
SUPERNOVAE , *GRAVITATIONAL waves , *CIRCULAR polarization - Abstract
We propose to employ the circular polarization of gravitational waves emitted by core-collapse supernovae as an unequivocal indication of rapid rotation deep in their cores just prior to collapse. It has been demonstrated by three dimensional simulations that nonaxisymmetric accretion flows may develop spontaneously via hydrodynamical instabilities in the postbounce cores. It is not surprising, then, that the gravitational waves emitted by such fluid motions are circularly polarized. We show, in this Letter, that a network of the second generation detectors of gravitational waves worldwide may be able to detect such polarizations up to the opposite side of the Galaxy as long as the rotation period of the core is shorter than a few seconds prior to collapse. [ABSTRACT FROM AUTHOR]
- Published
- 2016
- Full Text
- View/download PDF
22. Short-Lived Radioisotope 98Tc Synthesized by the Supernova Neutrino Process.
- Author
-
Takehito Hayakawa, Heamin Ko, Myung-Ki Cheoun, Motohiko Kusakabe, Toshitaka Kajino, Usang, Mark D., Satoshi Chiba, Ko Nakamura, Alexey Tolstov, Ken'ichi Nomoto, Masa-aki Hashimoto, Masaomi Ono, Toshihiko Kawano, and Mathews, Grant J.
- Subjects
- *
RADIOISOTOPE decay , *NEUTRINOS , *SOLAR system - Abstract
The isotope 98Tc decays to 98Ru with a half-life of 4.2×106 yr and could have been present in the early Solar System. In this Letter, we report on the first calculations of the production of 98Tc by neutrino-induced reactions in core-collapse supernovae (the ν process). Our predicted 98Tc abundance at the time of solar system formation is not much lower than the current measured upper limit raising the possibility for its detection in the not too distant future. We show that, if the initial abundance were to be precisely measured, the 98Tc nuclear cosmochronometer could be used to evaluate a much more precise value of the duration time from the last core-collapse supernova to the formation of the solar system. Moreover, a unique and novel feature of the 98Tc ν-process nucleosynthesis is the large contribution (~20%) from charged current reactions with electron antineutrinos. This means that 98Tc becomes a unique new ν-process probe of the temperature of the electron antineutrinos. [ABSTRACT FROM AUTHOR]
- Published
- 2018
- Full Text
- View/download PDF
23. Optimal Time Point for Evaluation of Response to Pembrolizumab Treatment in Japanese Patients With Metastatic Urothelial Carcinoma.
- Author
-
Inamoto T, Sato R, Matsushita Y, Uchimoto T, Nakamura KO, Komura K, Nishimura K, Yano Y, Nishio K, Kinoshita S, Fukushima T, Matsunaga T, Nakamori K, Tsutsumi T, Tsujino T, Uehara H, Takahara K, Miyake H, and Azuma H
- Abstract
Background/aim: The duration of pembrolizumab use in actual daily practice might be shorter than that in clinical trials because termination of pembrolizumab therapy is at the discretion of the physician. We retrospectively reviewed the response to pembrolizumab in Japanese patients with metastatic urothelial carcinoma (mUC) in relation to the time to response (TTR)., Patients and Methods: The records of 165 patients treated with pembrolizumab for mUC were retrospectively analyzed. Response was evaluated at 2, 4, 6 and 8 months. TTR along with time to best response were analyzed. Phase II-III clinical trials were also reviewed to compare the TTR and time to best overall response., Results: The median patient age was 70 years. The objective response rate in the total cohort was 27.1% (42 out of 155 patients). Median TTR was 2.4 months and the time to best response was 3.1 months. Radiological evaluation at each time point significantly predicted overall survival (OS). Considering the evaluation of response at 2, 4, 6 and 8 months, the response at later time points tended to predict OS better. Multivariate analysis showed that the evaluation of response at 8 months (hazard ratio=1.91, 95% confidence interval=1.16-3.16 months; p<0.01) and best response during the treatment (hazard ratio=1.69, 95% confidence interval=1.17-2.44; p<0.01) independently predicted improved OS., Conclusion: Given that response when evaluated at a later point during pembrolizumab treatment more favorably reflected improved survival than when assessed earlier, physicians may be encouraged to wait until at least the termination of pembrolizumab treatment to determine the best response., Competing Interests: The Authors declare that they have no conflicts of interest in connection with this article., (Copyright 2023, International Institute of Anticancer Research.)
- Published
- 2023
- Full Text
- View/download PDF
24. Tissue Distribution of Cisplatin by Intra-arterial Infusion Route in Comparison to Systemic Route: Implication to Therapy for Node-positive Bladder Cancer.
- Author
-
Ichihashi A, Inamoto T, Uchimoto T, Nakamura KO, Komura K, Yano Y, Nishimura K, Kinoshita S, Nishio K, Fukushima T, Nakamori K, Matsunaga T, Tsutsumi T, Tsujino T, Uehara H, Takahara K, Yamamoto K, Kato R, Ijiri Y, Hayashi T, and Azuma H
- Subjects
- Rats, Animals, Infusions, Intra-Arterial, Tissue Distribution, Platinum, Cisplatin therapeutic use, Urinary Bladder Neoplasms drug therapy, Urinary Bladder Neoplasms pathology
- Abstract
Background/aim: In clinical practice, platinum-based systemic chemotherapy works to shrink pelvic lymph nodes. Intra-arterial (IA) bolus infusion may result in more favorable results than systemic chemotherapy. In the present study, we investigated the distribution of cisplatin administrated by IA infusion in varying organs, specifically focusing on the node tissue, in comparison with the intravenous (IV) route., Materials and Methods: Under anesthesia, cisplatin 0.42 mg/body was administrated by IA or IV infusion in rats to mimic a balloon-occluded arterial infusion model used in clinical practice. The kidney, bladder, lymphatic tissue, and peripheral blood were extracted to analyze the amount of cisplatin by inductively coupled plasma-mass spectrometry., Results: Concertation of cisplatin by IA infusion was higher than that by the IV route in the peripheral blood and kidney. IA infusion led to a significantly high concentration of cisplatin in the bladder compared to IV infusion (1.3±0.452 vs. 0.2 ppb/mg ± 0.055, p=0.050). Furthermore, the IA method led to an extremely high concentration of cisplatin in the lymphatic tissue compared to the IV method (0.1±0.036 vs. 13.3±5.36, p=0.048)., Conclusion: High cisplatin accumulation in the lymphatic tissue and bladder by IA administration may have a potential role for treating patients with node-positive bladder cancer., (Copyright © 2023, International Institute of Anticancer Research (Dr. George J. Delinasios), All rights reserved.)
- Published
- 2023
- Full Text
- View/download PDF
Catalog
Discovery Service for Jio Institute Digital Library
For full access to our library's resources, please sign in.