Direct Integration of the Collisionless Boltzmann Equation in Six-dimensional Phase Space: Self-gravitating Systems

We present a scheme for numerical simulations of collisionless self-gravitating systems which directly integrates the Vlasov--Poisson equations in six-dimensional phase space. By the results from a suite of large-scale numerical simulations, we demonstrate that the present scheme can simulate collisionless self-gravitating systems properly. The integration scheme is based on the positive flux conservation method recently developed in plasma physics. We test the accuracy of our code by performing several test calculations including the stability of King spheres, the gravitational instability and the Landau damping. We show that the mass and the energy are accurately conserved for all the test cases we study. The results are in good agreement with linear theory predictions and/or analytic solutions. The distribution function keeps the property of positivity and remains non-oscillatory. The largest simulations are run on 64^6 grids. The computation speed scales well with the number of processors, and thus our code performs efficiently on massively parallel supercomputers.Comment: 35 pages, 19 figures. Submitted to the Astrophysical Journa

Cosmological Vlasov-Poisson Simulations of Structure Formation with Relic Neutrinos: Nonlinear Clustering and the Neutrino Mass

We present the results of cosmological simulations of large-scale structure formation with massive neutrinos. The phase-space distribution of the cosmic relic neutrinos is followed, for the first time, by directly integrating the six-dimensional Vlasov-Poisson equations. Our novel approach allows us to represent free streaming and clustering of neutrinos, and their gravitational interaction with cold dark matter accurately. We thus obtain solutions for the collisionless dynamics independent of conventional N-body methods. We perform a suite of hybrid N-body/Vlasov simulations with varying the neutrino mass, and systematically examine the dynamical effects of massive neutrinos on large-scale structure formation. Our simulations show characteristic large-scale clustering of the neutrinos and their coherent streaming motions relative to dark matter. The effective local neutrino "temperature" around massive galaxy clusters varies by several percent with respect to the cosmic mean; the neutrinos in clusters can be hotter or colder depending on the neutrino mass. We study a number of statistics of the large-scale structure and of dark matter halos in comparison with those obtained by N-body simulations and/or by perturbation theory. Our simulations mark an important milestone in numerical cosmology, and pave a new way to study cosmic structure formation with massive neutrinos.Comment: 21 pages, accepted for publication in Ap

The Temperature Structure of the Warm-Hot Intergalactic Medium

We study the temperature structure of the intergalactic medium (IGM) using a large cosmological N-body/SPH simulation. We employ a two-temperature model for the thermal evolution of the ionized gas, in which the relaxation process between electrons and ions is explicitly included. In the diffuse, hot IGM, the relaxation time is comparable to the age of the Universe and hence the electron temperature in post-shock regions remains significantly smaller than the ion temperature. We show that, at the present epoch, a large fraction of the warm/hot intergalactic medium (WHIM) has a well-developed two temperature structure, with typical temperature differences of order a factor of a few. Consequently, the fraction of metals in various ionization states such as OVI, OVII, and OVIII, as well as their line emissivities, can differ locally by more than an order of magnitude from those computed with a single temperature model. It is thus necessary to follow the evolution of the electron temperature explicitly to determine absorption and emission by the WHIM. Although equipartition is nearly achieved in the denser intracluster medium (ICM), we find an appreciable systematic deviation between the gas-mass weighted electron temperature and the mean temperature even at half the virial radii of clusters. There is thus a reservoir of warm (Te < 1keV) gas in and around massive clusters. Our results imply that relaxation processes need to be considered in describing and interpreting observational data from existing X-ray telescopes as well as from future missions designed to detect the WHIM, such as the Diffuse Intergalactic Oxygen Surveyor and the Missing Baryon Explorer.Comment: Revised. A typo in equation (2) correcte

Low-latency adiabatic quantum-flux-parametron circuit integrated with a hybrid serializer/deserializer

Adiabatic quantum-flux-parametron (AQFP) logic is an ultra-low-power superconductor logic family. AQFP logic gates are powered and clocked by dedicated clocking schemes using ac excitation currents to implement an energy-efficient switching process, adiabatic switching. We have proposed a low-latency clocking scheme, delay-line clocking, and demonstrated basic AQFP logic gates. In order to test more complex circuits, a serializer/deserializer (SerDes) should be incorporated into the AQFP circuit under test, since the number of input/output (I/O) cables is limited by equipment. Therefore, in the present study we propose and develop a novel SerDes for testing delay-line-clocked AQFP circuits by combining AQFP and rapid single-flux-quantum (RSFQ) logic families, which we refer to as the AQFP/RSFQ hybrid SerDes. The hybrid SerDes comprises RSFQ shift registers to facilitate the data storage during serial-to-parallel and parallel-to-serial conversion. Furthermore, all the component circuits in the hybrid SerDes are clocked by the identical excitation current to synchronize the AQFP and RSFQ parts. We fabricate and demonstrate a delay-line-clocked AQFP circuit (8-to-3 encoder, which is the largest delay-line-clocked circuit ever designed) integrated with the hybrid SerDes at 4.2 K up to 4.5 GHz. Our measurement results indicate that the hybrid SerDes enables the testing of delay-line-clocked AQFP circuits with only a few I/O cables and is thus a powerful tool for the development of very large-scale integration AQFP circuits.Comment: 7 pages, 6 figure

Thorough elucidation of synthesis and structure of poly(glycerol) functionalized nanodiamonds

Poly(glycerol) (PG) is one of the most promising platforms for the surface modification of nanomaterials especially for in vivo applications. Since the “grafting-from” process is facile to functionalize the nanomaterial surface covalently through the ring-opening polymerization of glycidol (GD), it has been applied to a variety of nanomaterials. The resulting numerous hydroxy groups in the hyperbranched structure serve as scaffolds for further functionalization and provide good dispersibility under physiological conditions. On the other hand, nanodiamond (ND) is a nanomaterial most intensely worked with PG because of its prominent properties including fluorescence from color centers. Despite the wide-spread use, the process has not been extended to be scalable and controllable. In addition, the structural details of PG chain on ND surface are yet elusive. In this work, we develop more scalable and safer PG functionalization of NDs by dropwise-addition of GD to ethylene glycol (EG) suspension of ND. The resulting PG amount can be controlled or even estimated by the reaction conditions (weights of GD, ND and EG) and the ND properties (diameter and oxygen content). The structure of PG chain was qualitatively and quantitatively analyzed by ¹³C nuclear magnetic resonance (NMR) and dynamic light scattering (DLS) measurements. Based on these results, the structure of PG is elucidated

Three-dimensional visualization of thoracodorsal artery perforators using photoacoustic imaging

Introduction: Diagnostic imaging modalities to evaluate the three-dimensional distribution of thoracodorsal artery perforators (TDAPs) are lacking. In this study, TDAPs were visualized and characterized using photoacoustic imaging. Material and methods: In this study, 34 sites in the lateral chest wall of 18 individuals were analyzed. The region extending 5 cm ventral and 5 cm dorsal to the lateral edge of the latissimus dorsi (LD) and 5–15 cm from the posterior axillary fold was scanned using photoacoustic imaging. The largest perforator closest to the edge of the LD was characterized. The location of the stem portion and the orientation of the longest cutaneous branch of the perforator were described. The relationship between the maximal depth of delineation on photoacoustic images and the depth of the deep fascia was assessed. Results: On average, 2.6 perforators (range, 1–5 perforators) were visualized in the region of interest. The distribution of the TDAP stem portion was similar to that in previous studies. Cutaneous branches were preferentially oriented in a medial-caudal direction. The length of delineated cutaneous branches varied (range, 7–78 mm) depending on the thickness of the subcutaneous layer. Vessels under the LD were observed when the subcutaneous layer was thin. Conclusion: Photoacoustic imaging can successfully visualize TDAPs in three dimensions. Visualization of TDAPs varied by the thickness of the subcutaneous layer. A thin deep fascia of the LD might be a cause of deep laser penetration

大腸癌肝転移におけるCD200発現の臨床的意義

Background: Approximately 30% of patients diagnosed with colorectal cancer (CRC) develop liver metastases. We evaluated the role of CD200, a potent immunosuppressive molecule, in colorectal liver metastases (CRLM). Methods: We examined 110 patients who underwent curative liver resection for CRLM at our institution between 2000 and 2016. Based on the results of immunohistochemical analysis, the patients were divided into high-CD200 (n = 47) and low-CD200 (n = 63) expression groups. The relationships between CD200 expression and various clinicopathological outcomes were investigated. Results: The overall survival (OS) of patients in the high-CD200 group was significantly worse than that in the low-CD200 group (p = 0.009). Multivariate analysis showed that the independent prognostic factors in CRLM were maximum tumor size > 30 mm (p = 0.002), preoperative carcinoembryonic antigen level > 20 ng/mL (p < 0.001), primary CRC N2-3 (p = 0.049), and high-CD200 expression (p = 0.004). Furthermore, CD4+, CD8+, and CD45RO+ tumor-infiltrating lymphocytes in CRLM were significantly higher in the low-CD200 group than in the high-CD200 group (p = 0.005, p = 0.001, and p < 0.001, respectively). In addition, patients who had received preoperative chemotherapy had higher CD200 expression than those who had not received preoperative chemotherapy, and OS was significantly worse in patients in the high-CD200 group who had received preoperative chemotherapy. Conclusions: CD200 expression was an independent prognostic factor in CRLM. CD200 may play a critical role in tumor immunity in CRLM, and can therefore be used as a potential therapeutic target in CRLM.博士（医学）・乙第1497号・令和3年3月15日© 2021. Society of Surgical Oncology.© Springer Nature Singapore Pte Ltd. 2020This is a post-peer-review, pre-copyedit version of an article published in Annals of Surgical Oncology. The final authenticated version is available online at: https://doi.org/10.1245/s10434-020-09471-w