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Cosmic metallicity evolution possibly creates the diversity of star formation modes at different epochs. Gravitational fragmentation of circumstellar discs provides an important formation channel of multiple star systems, including close binaries. We here study the nature of disc fragmentation, systematically performing a suite of two-dimensional radiation-hydrodynamic simulations, in a broad range of metallicities, from the primordial to the solar values. In particular, we follow relatively long-term disc evolution over 15 kyr after the disc formation, incorporating the effect of heating by the protostellar irradiation. Our results show that the disc fragmentation occurs at all metallicities $1$--$0$ $Z_{\odot}$, yielding self-gravitating clumps. Physical properties of the clumps, such as their number and mass distributions, change with the metallicity due to different gas thermal evolution. For instance, the number of clumps is the largest for the intermediate metallicity range of $10^{-2}$--$10^{-5}$ $Z_{\odot}$, where the dust cooling is effective exclusively in a dense part of the disc and causes the fragmentation of spiral arms. The disc fragmentation is more modest for $1$--$0.1$ $Z_{\odot}$ thanks to the disc stabilization by the stellar irradiation. Such metallicity dependence agrees with the observed trend that the close binary fraction increases with decreasing metallicity in the range of $1$--$10^{-3}$ $Z_{\odot}$., Comment: 17 pages, 16 figures, submitted to MNRAS

We investigate the first emergence of the so-called cold accretion, the accretion flows deeply penetrating a halo, in the early universe with cosmological N-body/SPH simulations. We study the structure of the accretion flow and its evolution within small halos with $\lesssim 10^8~{\rm M}_\odot$ with sufficiently high spatial resolutions down to $\sim 1 \ {\rm pc}$ scale. While previous studies only follow the evolution for a short period after the primordial cloud collapse, we follow the long-term evolution until the cold accretion first appears, employing the sink particle method. We show that the cold accretion emerges when the halo mass exceeds $\sim 2.2\times 10^7 \ {\rm M}_\odot\left\{\left(1+z\right)/15 \right\}^{-3/2}$, the ${\it minimum}$ halo masses above which the accretion flow penetrates halos. We further continue simulations to study whether the cold accretion provides the dense shock waves, which have been proposed to give birth to supermassive stars (SMSs). We find that the accretion flow eventually hits a compact disc near the halo centre, creating dense shocks over a wide area of the disc surface. The resulting post-shock gas becomes dense and hot enough with its mass comparable to the Jeans mass $M_{\rm J}\sim 10^{4-5} \ {\rm M}_\odot$, a sufficient amount to induce the gravitational collapse, leading to the SMS formation., 17 pages, 17 figures, accepted for publication in MNRAS

Recent reports demonstrated that mesenchymal stem cells (MSCs) can induce differentiation of neuroblastoma (NB) cells. Dedifferentiated fat cells (DFAT) and MSCs have similar properties. The present study investigated whether DFAT can induce NB cell differentiation and suppress cell proliferation. DFAT was obtained from mature adipocytes isolated from adipose tissue from a ceiling culture. NB cells were cultured in a medium with/without DFAT, and subsequently in a DFAT-conditioned medium (CM) with/without phosphatidylinositol 3 kinase (PI3K) inhibitor. Length of neurites was measured, and the mRNA expression levels of the neurofilament (NF) and tubulin beta III (TUBβ3) were assessed using quantitative real-time reverse transcription polymerase chain reaction. Cell viability was assessed by the water-soluble tetrazolium salt-1 assay. NB cells cultured with DFAT elongated the neurites and upregulated the expression of NF and Tubβ3 compared with the control. However, NB cells cultured in DFAT-CM demonstrated increased cell viability compared with the control. NB cells cultured with DFAT-CM and PI3K inhibitor suppressed cell viability and demonstrated increased neurite length and expression and upregulation of Tubβ3. Therefore, the combined use of DFAT-CM and PI3K inhibitors suppresses the proliferation of NB cells and induces their differentiation. DFAT may offer new insights into therapeutic approaches in NB.

The direct collapse (DC) is a promising mechanism that provides massive seed black holes (BHs) with ∼105 M⊙ in the early universe. To study a long-term accretion growth of a direct-collapse black hole (DCBH), we perform cosmological radiation-hydrodynamics simulations, extending our previous work where we investigated its formation stage. With a high spatial resolution down below the Bondi radius, we show that the accretion rate on to the BH is far below the Eddington value. Such slow mass growth is partly because of the strong radiative feedback from the accreting BH to the surrounding dense gas. Even after it falls into the first galaxy, the accretion rate is substantially suppressed due to the supernova feedback associated with the intense star formation. Moreover, the BH has a large velocity of ∼100 km s−1 relative to the gas, which further reduces the accretion rate. This large relative velocity stems from the fact that the DCBHs form in metal-free environments typically at ∼1 kpc from the galaxy. The BH accelerates as it approaches the galactic centre due to the gravity. The relative velocity never damps and the BH wanders around the outer galactic region. An analytic estimate predicts that the DCBH formation within ∼100 pc around the galactic centre is necessary to decelerate the BH with dynamical friction before z = 7. Since metal enrichment with Z ∼ 10−5−10−3 Z⊙ is expected there, the formation of DCBHs in the metal-enriched environments is preferable for the subsequent rapid growth.

Supermassive stars (SMSs) with $\sim10^{4-5}~\mathrm{M}_{\odot}$ are candidate objects for the origin of supermassive black holes observed at redshift $z$>6. They are supposed to form in primordial-gas clouds that provide the central stars with gas at a high accretion rate, but their growth may be terminated in the middle due to the stellar ionizing radiation if the accretion is intermittent and its quiescent periods are longer than the Kelvin-Helmholtz (KH) timescales at the stellar surfaces. In this paper, we examine the role of the ionizing radiation feedback based on the accretion history in two possible SMS-forming clouds extracted from cosmological simulations, following their evolution with vertically-integrated two-dimensional hydrodynamic simulations with detailed thermal and chemical models. The consistent treatment of the gas thermal evolution is crucial for obtaining the realistic accretion history, as we demonstrate by performing an additional run with a barotropic equation of state, in which the fluctuation of the accretion rate is artificially suppressed. We find that although the accretion becomes intermittent due to the formation of spiral arms and clumps in gravitationally unstable disks, the quiescent periods are always shorter than the KH timescales, implying that SMSs can form without affected by the ionizing radiation., 14 pages, 11 figures, accepted for publication in MNRAS

The evolution of protostellar outflows is investigated under different mass accretion rates in the range $\sim10^{-5}-10^{-2} {\rm M}_\odot$ yr$^{-1}$ with three-dimensional magnetohydrodynamic simulations. A powerful outflow always appears in strongly magnetized clouds with $B_0 \gtrsim B_{\rm 0, cr}$ $=10^{-4} (M_{\rm cl}/100 {\rm M}_\odot){\rm G}$, where $M_{\rm cl}$ is the cloud mass. When a cloud has a weaker magnetic field, the outflow does not evolve promptly with a high mass accretion rate. In some cases with moderate magnetic fields $B_0$ slightly smaller than $B_{\rm 0,cr}$, the outflow growth is suppressed or delayed until the infalling envelope dissipates and the ram pressure around the protostellar system is significantly reduced. In such an environment, the outflow begins to grow and reaches a large distance only during the late accretion phase. On the other hand, the protostellar outflow fails to evolve and is finally collapsed by the strong ram pressure when a massive $(\gtrsim 100 {\rm M}_\odot)$ initial cloud is weakly magnetized with $B_0 \lesssim 100 \mu {\rm G}$. The failed outflow creates a toroidal structure that is supported by magnetic pressure and encloses the protostar and disk system. Our results indicate that high-mass stars form only in strongly magnetized clouds, if all high-mass protostars possess a clear outflow. If we would observe either very weak or no outflow around evolved protostars, it means that strong magnetic fields are not necessarily required for high-mass star formation. In any case, we can constrain the high-mass star formation process from observations of outflows., Comment: Accepted for publication in MNRAS

Purpose Our previous studies demonstrated that mature adipocyte-derived dedifferentiated fat (DFAT) cells possess similar multipotency as mesenchymal stem cells. Here, we examined the immunoregulatory potential of DFAT cells in vitro and the therapeutic effect of DFAT cell transplantation in a mouse inflammatory bowel disease (IBD) model. Methods The effect of DFAT cell co-culture on T cell proliferation and expression of immunosuppression-related genes in DFAT cells were evaluated. To create IBD, CD4+CD45RBhigh T cells were intraperitoneally injected into SCID mice. One week later, DFAT cells (1 × 105, DFAT group) or saline (Control group) were intraperitoneally injected. Subsequently bodyweight was measured every week and IBD clinical and histological scores were evaluated at 5 weeks after T cell administration. Results The T cell proliferation was inhibited by co-cultured DFAT cells in a cell density-dependent manner. Gene expression of TRAIL, IDO1, and NOS2 in DFAT cells was upregulated by TNFα stimulation. DFAT group improved IBD-associated weight loss, IBD clinical and histological scores compared to Control group. Conclusion DFAT cells possess immunoregulatory potential and the cell transplantation promoted recovery from colon damage and improved clinical symptoms in the IBD model. DFAT cells could play an important role in the treatment of IBD.

We study the effects of the magnetic fields on the formation of massive, self-gravitationally bound cores (MBCs) in high-speed cloud-cloud collisions (CCCs). Extending our previous work (Sakre et al. 2021), we perform magnetohydrodynamic simulations following the high-speed (20 - 40 km s$^{-1}$) collisions between two magnetized (4 $\mu$G initially), turbulent clouds of different sizes in the range of 7 - 20 pc. We show that a magnetic field effect hinders the core growth, particularly after a short-duration collision during which cores cannot get highly bound. In such a case, a shocked region created by the collision rapidly expands to the ambient medium owing to the enhanced magnetic pressure, resulting in the destruction of the highly unbound cores and suppression of gas accretion to massive cores. This negative effect on the MBC formation is a phenomenon not seen in the past hydrodynamic simulations of similar CCC models. Together with our previous work, we conclude that the magnetic fields provide the two competing effects on the MBC formation in CCC; while they promote the mass accumulation into cores during a collision, they operate to destroy cores or hinder the core growth after the collision. The duration of collision determines which effect prevails, providing the maximum collision speed for the MBC formation with given colliding clouds. Our results agree with the observed trend among CCC samples in the corresponding column density range; clouds with higher relative velocity require higher column density for the formation of massive stars (Enokiya et al. 2021)., Comment: Submitted to MNRAS journal

The detections of gravitational waves (GW) by the LIGO/Virgo collaborations provide various possibilities for both physics and astronomy. We are quite sure that GW observations will develop a lot, both in precision and in number, thanks to the continuous work on the improvement of detectors, including the expected new detector, KAGRA, and the planned detector, LIGO-India. On this occasion, we review the fundamental outcomes and prospects of gravitational wave physics and astronomy. We survey the development, focusing on representative sources of gravitational waves: binary black holes, binary neutron stars, and supernovae. We also summarize the role of gravitational wave observations as a probe of new physics.

We report a case of neonatal small left colon syndrome (NSLCS) that underwent surgery. A female infant was born at 38 weeks of gestation. The mother had gestational diabetes requiring insulin therapy. The baby was admitted for respiratory distress. Abdominal distension was observed, and the gastric residue increased. Contrast enema revealed a small caliber of the left colon up to the splenic flexure. At 14 days, the full-thickness biopsy of the sigmoid and transverse colons was performed. Pathological diagnosis showed that the sigmoid colon had few ganglion cells, therefore the transverse colostomy was performed. At 6 months of age, a rectal biopsy was performed to confirm the diagnosis of Hirschsprung’s disease; the intestinal plexus and ganglion cells were normal. The surgery was changed from a pull-through to a stoma closure. The postoperative diagnosis was NSLCS, and the course up to 3 years was good without defecation or growth problems.

We investigate the formation of merging binary black holes (BHs) through isolated binary evolution, performing binary population synthesis calculations covering an unprecedentedly wide metallicity range of Population (Pop) I, II, III, and extremely metal-poor (EMP) binary stars. We find that the predicted merger rate density and primary BH mass ($m_1$) distribution are consistent with the gravitational wave (GW) observations. Notably, Pop III and EMP ($< 10^{-2}$ $Z_\odot$) binary stars yield most of the pair instability (PI) mass gap events with $m_1 = 65$--$130$ $M_\odot$. Pop III binary stars contribute more to the PI mass gap events with increasing redshift, and all the PI mass gap events have the Pop III origin at redshifts $\gtrsim 8$. Our result can be assessed by future GW observations in the following two points. First, there are no binary BHs with $m_1=100$--$130$ $M_\odot$ in our result, and thus the $m_1$ distribution should suddenly drop in the range of $m_1=100$--$130$ $M_\odot$. Second, the PI mass gap event rate should increase toward higher redshift up to $\sim 11$, since those events mainly originate from the Pop III binary stars. We find that the following three assumptions are needed to reproduce the current GW observations: a top-heavy stellar initial mass function and the presence of close binary stars for Pop III and EMP binary stars, and inefficient convective overshoot in the main-sequence phase of stellar evolution. Without any of the above, the number of PI mass gap events becomes too low to reproduce current GW observations., 26 pages, 13 figures, 2 tables, ApJ accepted. BSEEMP, a binary population synthesis code used in this paper, is published on github: https://github.com/atrtnkw/bseemp

We study the gravitational fragmentation of circumstellar discs accreting extremely metal-poor ($Z \leq 10^{-3}$ Zsun) gas, performing a suite of three-dimensional hydrodynamic simulations using the adaptive mesh refinement code Enzo. We systematically follow the long-term evolution for 2000 years after the first protostar's birth, for the cases of $Z = 0$, $10^{-5}$, $10^{-4}$, and $10^{-3}$ Zsun. We show that evolution of number of self-gravitating clumps qualitatively changes with $Z$. Vigorous fragmentation induced by dust cooling occurs in the metal-poor cases, temporarily providing about 10 self-gravitating clumps at $Z = 10^{-5}$ and $10^{-4}$ Zsun. However, we also show that the fragmentation is a very sporadic process; after an early episode of the fragmentation, the number of clumps continuously decreases as they merge away in these cases. The vigorous fragmentation tends to occur later with the higher $Z$, reflecting that the dust-induced fragmentation is most efficient at the lower density. At $Z = 10^{-3}$ Zsun, as a result, the clump number stays smallest until the disc fragmentation starts in a late stage. We also show that the clump mass distribution also depends on the metallicity. A single or binary clump substantially more massive than the others appear only at $Z = 10^{-3}$ Zsun, whereas they are more evenly distributed in mass at the lower metallicities. We suggest that the disc fragmentation should provide the stellar multiple systems, but their properties drastically change with a tiny amount of metals., Comment: 20 pages, 14 figures, accepted for publication in MNRAS. Movies of the simulations are available at https://www.youtube.com/playlist?list=PLy0BOLTBcHhaYoWvkp5zZ982amm4QcRaK

We perform the first three-dimensional radiation hydrodynamical simulations that investigate the growth of intermediate-mass BHs (IMBHs) embedded in massive self-gravitating, dusty nuclear accretion disks. We explore the dependence of mass accretion efficiency on the gas metallicity $Z$ and mass injection at super-Eddington accretion rates from the outer galactic disk $\dot{M}_{\rm in}$, and find that the central BH can be fed at rates exceeding the Eddington rate only when the dusty disk becomes sufficiently optically thick to ionizing radiation. In this case, mass outflows from the disk owing to photoevaporation is suppressed and thus a large fraction ($\gtrsim 40\%$) of the mass injection rate can feed the central BH. The conditions are expressed as $\dot{M}_{\rm in} > 2.2\times 10^{-1}~M_\odot ~{\rm yr}^{-1} (1+Z/10^{-2}~Z_\odot)^{-1}(c_{\rm s}/10~{\rm km~s}^{-1})$, where $c_{\rm s}$ is the sound speed in the gaseous disk. With increasing numerical resolution, vigorous disk fragmentation reduces the disk surface density and dynamical heating by formed clumps makes the disk thickness higher. As a result, the photoevaorative mass-loss rate rises and thus the critical injection rate increases for fixed metallicity. This process enables super-Eddington growth of BHs until the BH mass reaches $M_{\rm BH} \sim 10^{7-8}~M_\odot$, depending on the properties of the host dark-matter halo and metal-enrichment history. In the assembly of protogalaxies, seed BHs that form in overdense regions with a mass variance of 3-4$��$ at $z\sim 15-20$ are able to undergo short periods of their rapid growth and transits into the Eddington-limited growth phase afterwards to be supermassive BHs observed at $z>6-7$., 23 pages, 10 figures, submitted to ApJ

We study the early growth of massive seed black holes (BHs) via accretion in protogalactic nuclei where the stellar bulge component is assembled, performing axisymmetric two-dimensional radiation hydrodynamical simulations. We find that when a seed BH with $M_\bullet \sim 10^5~M_\odot$ is embedded in dense metal-poor gas ($Z=0.01~Z_\odot$) with a density of $\gtrsim 100~{\rm cm}^{-3}$ and bulge stars with a total mass of $M_\star \gtrsim 100~M_\bullet$, a massive gaseous disk feeds the BH efficiently at rates of $\gtrsim 0.3-1~M_\odot~{\rm yr}^{-1}$ and the BH mass increases nearly tenfold within $\sim 2$ Myr. This rapid accretion phase lasts until a good fraction of the gas bounded within the bulge accretes onto the BH, although the feeding rate is regulated owing to strong outflows driven by ionizing radiation emitted from the accreting BH. The transient growing mode can be triggered for seed BHs formed in massive dark-matter halos with masses of $\gtrsim 10^9~M_\odot$ at $z\sim 15-20$ (the virial temperature is $T_{\rm vir}\simeq 10^5~{\rm K}$). The host halos are heavier and rarer than those of typical first galaxies, but are more likely to end up in quasar hosts by $z\simeq 6$. This mechanism naturally yields a mass ratio of $M_\bullet/M_\star >0.01$ higher than the value seen in the local universe and the existence of such overmassive BHs provides us a unique opportunity of detecting highly accreting seed BHs at $z\sim 15$ with AB magnitude of $m_{\rm AB} \sim26 - 29$ mag at $2~μ{\rm m}$ (rest-frame 10 eV) by the upcoming observations by the James Webb Space Telescope and Nancy Grace Roman Space Telescope., 28 pages, 11 figures, accepted for publication to ApJ. Movies of the simulation are available at https://www.youtube.com/playlist?list=PLqDrKvxmu0l4fyJ74u5ZYyQ8PmwuNZA32

Background Pediatric patients with genital injuries are often recommended to receive an examination under general anesthesia, however, detailed clinical data of such patients are rarely reported. Methods A single-center retrospective review was conducted in 45 girls less than 16 years of age with genital injuries between January 2005 and December 2018. Results The median patient age was 5.0 years. Forty-two patients were hospitalized, of whom 38 required an examination under general anesthesia and all consequently required surgical repair. The diagnosis obtained after a thorough examination under general anesthesia was inconsistent with the diagnosis obtained at the emergency room in 5 patients. In 20 patients, the source of bleeding was not clarified at the time of initial examination at the emergency room, four of whom later revealed to have vaginal or rectal injuries that had been overlooked during the examination at the emergency room by examinations under general anesthesia. Injuries occurred in the bathroom were the most frequent and tended to be serious. Multiple injuries were found in 10 patients. The exterior of the labia minora was the most commonly injured site, found in 18 patients. Conclusion We analyzed the clinical data of girls with genital injuries in detail, which allowed us to find a detailed classification of injured sites, the characteristics of serious cases and to re-recognize the importance of a thorough examination under general anesthesia.

We review the current status of knowledge concerning the early phases of star formation during cosmic dawn. This includes the first generations of stars forming in the lowest mass dark matter halos in which cooling and condensation of gas with primordial composition is possible at very high redshift ($z > 20$), namely metal-free Population III stars, and the first generation of massive black holes forming at such early epochs, the so-called black hole seeds. The formation of black hole seeds as end states of the collapse of Population III stars, or via direct collapse scenarios, is discussed. In particular, special emphasis is given to the physics of supermassive stars as potential precursors of direct collapse black holes, in light of recent results of stellar evolution models, and of numerical simulations of the early stages of galaxy formation. Furthermore, we discuss the role of the cosmic radiation produced by the early generation of stars and black holes at high redshift in the process of reionization.

We study the formation of very metal-poor stars under protostellar radiative feedback effect. We use cosmological simulations to identify low-mass dark matter halos and star-forming gas clouds within them. We then follow protostar formation and the subsequent long-term mass accretion phase of over one million years using two-dimensional radiation-hydrodynamics simulations. We show that the critical physical process that sets the final mass is formation and expansion of a bipolar HII region. The process is similar to the formation of massive primordial stars, but radiation pressure exerted on dust grains also contributes to halting the accretion flow in the low-metallicity case. We find that the net feedback effect in the case with metallicity $Z = 10^{-2}~Z_{\odot}$ is stronger than in the case with $Z \sim 1~Z_{\odot}$. With decreasing metallicity, the radiation pressure effect becomes weaker, but photoionization heating of the circumstellar gas is more efficient owing to the reduced dust attenuation. In the case with $Z = 10^{-2}~Z_{\odot}$, the central star grows as massive as 200 solar-masses, similarly to the case of primordial star formation. We conclude that metal-poor stars with a few hundred solar masses can be formed by gas accretion despite the strong radiative feedback., 18 pages, 13 figures, accepted for publication in MNRAS

Recent high-resolution simulations demonstrate that disks around primordial protostars easily fragment in the accretion phase before the protostars accrete less than a solar mass. To understand why the gravitational instability generally causes the fragmentation so early, we develop a one-dimensional (1D) non-steady model of the circumstellar disk that takes the mass supply from an accretion envelope into account. We also compare the model results to a three-dimensional (3D) numerical simulation performed with a code employing the adaptive mesh refinement. Our model shows that the self-gravitating disk, through which the Toomre $Q$ parameter is nearly constant at $Q \sim 1$, gradually spreads as the disk is fed by the gas infalling from the envelope. We further find that the accretion rate onto the star is an order of magnitude smaller than the mass supply rate onto the disk. This discrepancy makes the disk more massive than the protostar in an early evolutionary stage. Most of the infalling gas is used to extend the outer part of the self-gravitating disk rather than transferred inward toward the star through the disk. We find that similar evolution also occurs in the 3D simulation, where the disk becomes three times more massive than the star before the first fragmentation occurs. Our 1D disk model well explains the evolution of the disk-to-star mass ratio observed in the simulation. We argue that the formation of such a massive disk leads to the early disk fragmentation., Comment: 22 pages, 14 figures, accepted for publication in ApJ

Amino acid metabolism plays important roles in innate immune cells, including macrophages. Recently, we reported that a lysosomal adaptor protein, Lamtor1, which serves as the scaffold for amino acid–activated mechanistic target of rapamycin complex 1 (mTORC1), is critical for the polarization of M2 macrophages. However, little is known about how Lamtor1 affects the inflammatory responses that are triggered by the stimuli for TLRs. In this article, we show that Lamtor1 controls innate immune responses by regulating the phosphorylation and nuclear translocation of transcription factor EB (TFEB), which has been known as the master regulator for lysosome and autophagosome biogenesis. Furthermore, we show that nuclear translocation of TFEB occurs in alveolar macrophages of myeloid-specific Lamtor1 conditional knockout mice and that these mice are hypersensitive to intratracheal administration of LPS and bleomycin. Our observation clarified that the amino acid–sensing pathway consisting of Lamtor1, mTORC1, and TFEB is involved in the regulation of innate immune responses.

Formation of supermassive stars (SMSs) with mass ~10^4 Msun is a promising pathway to seed the formation of supermassive black holes in the early universe. The so-called direct-collapse (DC) model postulates that such an SMS forms in a hot gas cloud irradiated by a nearby star-forming galaxy. We study the DC SMS formation in a fully cosmological context using three-dimensional radiation hydrodynamics simulations. We initialize our simulations using the outputs of the cosmological simulation of Chon et al. (2016), where two DC gas clouds are identified. The long-term evolution over a hundred thousand years is followed from the formation of embryo protostars through their growth to SMSs. We show that the strength of the tidal force by a nearby galaxy determines the multiplicity of the formed stars and affects the protostellar growth. In one case, where a collapsing cloud is significantly stretched by strong tidal force, multiple star-disk systems are formed via filament fragmentation. Small-scale fragmentation occurs in each circumstellar disk, and more than 10 stars with masses of a few times 10^3 Msun are finally formed. Interestingly, about a half of them are found as massive binary stars. In the other case, the gas cloud collapses nearly spherically under a relatively weak tidal field, and a single star-disk system is formed. Only a few SMSs with masses ~ 10^4 Msun are found already after evolution of a hundred thousand years, and the SMSs are expected to grow further by gas accretion and to leave massive blackholes at the end of their lives., 19 pages, 20 figures, Submitted to MNRAS

In a set-net fishery, a leader net and the related nets guide migratory fish into a box chamber net. Many workers have to visit the set-net and haul the box chamber net for harvesting almost every day, while the net-hauling operation in the early morning is dangerous. An automated net-hauling system using a flexible hose net has been proposed as a manpower-saving measure in such operation. The hose net comprises the brick forms of flexible hoses and is installed on the water bottom below the box chamber net. Compressed air is injected from one edge of the hose net to haul the box chamber net gradually, resulting in cornering fish in the other edge. The purpose of the present study is to observe the motion of the hose net and to analyze its formation in water current. Water tank testing was carried out using a 1/100 scale model of a set-net and a hose net. As a result, the middle part of the hose net was steep enough to corner fish in the end of the box chamber net. The two-dimensional formation of the hose net could be approximated by a catenary curve, while a part of the hose net including air inside was likely to have stiffness. The stiffness of the hose including air inside should be taken into account in the following water tank testing. The experimental results will provide the benchmark for the validation of the numerical model, which will be developed in the future. In addition, numerical analysis as well as water tank testing will reveal the tension on the hose net and mooring ropes for the basic design of the hose net in the future. For realizing the prototype of the hose net, special care should be taken for the explosion of air with decreasing pressure in the floating operation and for the leakage of air through the pinholes, which may be generated by sudden change in water pressure on the flexible hoses and their connectors.

The origin of super-massive black holes in the early universe remains poorly understood. Gravitational collapse of a massive primordial gas cloud is a promising initial process, but theoretical studies have difficulty growing the black hole fast enough. We report numerical simulations of early black hole formation starting from realistic cosmological conditions. Supersonic gas motions left over from the Big Bang prevent early gas cloud formation until rapid gas condensation is triggered in a protogalactic halo. A protostar is formed in the dense, turbulent gas cloud, and it grows by sporadic mass accretion until it acquires 34, 000 solar masses. The massive star ends its life with a catastrophic collapse to leave a black hole—a promising seed for the formation of a monstrous black hole., ビッグバン直後の超音速ガス流が生んだモンスターブラックホールの種. 京都大学プレスリリース. 2017-09-29.

Mechanistic target of rapamycin complex (mTORC)1 integrates intracellular sufficiency of nutrients and regulates various cellular functions. Previous studies using mice with conditional knockout of mTORC1 component proteins (i.e., mTOR, Raptor, and Rheb) gave conflicting results on the roles of mTORC1 in CD4+ T cells. Lamtor1 is the protein that is required for amino acid sensing and activation of mTORC1; however, the roles of Lamtor1 in T cells have not been investigated. In this article, we show that Lamtor1-deficient CD4+ T cells exhibited marked reductions in proliferation, IL-2 production, mTORC1 activity, and expression of purine- and lipid-synthesis genes. Polarization of Th17 cells, but not Th1 and Th2 cells, diminished following the loss of Lamtor1. Accordingly, CD4-Cre–driven Lamtor1-knockout mice exhibited reduced numbers of CD4+ and CD8+ T cells at rest, and they were completely resistant to experimental autoimmune encephalomyelitis. In contrast, genetic ablation of Lamtor1 in Foxp3+ T cells resulted in severe autoimmunity and premature death. Lamtor1-deficient regulatory T cells survived ex vivo as long as wild-type regulatory T cells; however, they exhibited a marked loss of suppressive function and expression of signature molecules, such as CTLA-4. These results indicate that Lamtor1 plays essential roles in CD4+ T cells. Our data suggest that Lamtor1 should be considered a novel therapeutic target in immune systems.

ObjectivesInappropriate activation of neutrophils plays a pathological role in antineutrophil cytoplasmic antibody (ANCA)-associated vasculitis (AAV). The aim of this study was to investigate the functions of semaphorin 4D (SEMA4D) in regulation of neutrophil activation, and its involvement in AAV pathogenesis.MethodsSerum levels of soluble SEMA4D were evaluated by ELISA. Blood cell-surface expression of membrane SEMA4D was evaluated by flow cytometry. To determine the functional interactions between neutrophil membrane SEMA4D and endothelial plexin B2, wild-type and SEMA4D−/− mice neutrophils were cultured with an endothelial cell line (MS1) stained with SYTOX green, and subjected to neutrophil extracellular trap (NET) formation assays. The efficacy of treating human neutrophils with recombinant plexin B2 was assessed by measuring the kinetic oxidative burst and NET formation assays.ResultsSerum levels of soluble SEMA4D were elevated in patients with AAV and correlated with disease activity scores. Cell-surface expression of SEMA4D was downregulated in neutrophils from patients with AAV, a consequence of proteolytic cleavage of membrane SEMA4D. Soluble SEMA4D exerted pro-inflammatory effects on endothelial cells. Membranous SEMA4D on neutrophils bound to plexin B2 on endothelial cells, and this interaction decreased NET formation. Recombinant plexin B2 suppressed neutrophil Rac1 activation through SEMA4D’s intracellular domain, and inhibited pathogen-induced or ANCA-induced oxidative burst and NET formation.ConclusionsNeutrophil surface SEMA4D functions as a negative regulator of neutrophil activation. Proteolytic cleavage of SEMA4D as observed in patients with AAV may amplify neutrophil-mediated inflammatory responses. SEMA4D is a promising biomarker and potential therapeutic target for AAV.

Discovery of high-redshift (z > 6) supermassive black holes (BHs) may indicate that the rapid (or super-Eddington) gas accretion has aided their quick growth. Here, we study such rapid accretion of the primordial gas on to intermediate-mass (10^2 - 10^5 M_sun) BHs under anisotropic radiation feedback. We perform two-dimensional radiation hydrodynamics simulations that solve the flow structure across the Bondi radius, from far outside of the Bondi radius down to a central part which is larger than a circum-BH accretion disc. The radiation from the unresolved circum-BH disc is analytically modeled considering self-shadowing effect. We show that the flow settles into a steady state, where the flow structure consists of two distinct parts: (1) bipolar ionized outflowing regions, where the gas is pushed outward by thermal gas pressure and super-Eddington radiation pressure, and (2) an equatorial neutral inflowing region, where the gas falls toward the central BH without affected by radiation feedback. The resulting accretion rate is much higher than that in the case of isotropic radiation, far exceeding the Eddington-limited rate to reach a value slightly lower than the Bondi one. The opening angle of the equatorial inflowing region is determined by the luminosity and directional dependence of the central radiation. We find that photoevaporation from its surfaces set the critical opening angle of about ten degrees below which the accretion to the BH is quenched. We suggest that the shadowing effect allows even stellar-remnant BHs to grow rapidly enough to become high-redshift supermassive BHs., 19 pages, 12 figures, 8 tables, corrected typos in the appendix

We theoretically investigate the impact of feedback and its metallicity dependence in massive star formation from prestellar cores at all metallicity range. We include the feedback by MHD disk winds, radiation pressure, and photoevaporation solving the evolution of protostars and accretion flows self-consistently. Interestingly, we find that the feedback does not set the upper mass limit of stellar birth mass at any metallicity. At the solar metallicity, the MHD disk wind is the dominant feedback to set the star formation efficiencies (SFEs) from the prestellar cores similar to low-mass star formation. The SFE is found to be lower at lower surface density environment. The photoevaporation becomes significant at the low metallicity of Z < 10−2 Z⊙. Considering this efficient photoevaporation, we conclude that the IMF slope is steeper, i.e., massive stars are rarer at the extremely metal-poor environment of 10−5 − 10−3Z⊙. Our study raises a question on the common assumption of the universal IMF with a truncated at 100M⊙. Since the total feedback strength in the cluster/galaxy scale is sensitive to the number fraction of massive stars, the re-evaluations of IMF at various environments are necessary.

The formation of supermassive stars (SMSs) is a possible pathway to seed supermassive black holes in the early universe. This chapter summarizes recent theoretical efforts to understand their evolution, highlighting effects of very rapid accretion at the rates of $\dot{M}_* \gtrsim 0.1~$M$_\odot$ yr$^{-1}$. Stellar evolution calculations predict that such an accreting SMS has a characteristic feature, i.e., a very large radius that monotonically increases as the stellar mass increases. The radius exceeds $7000$ R$_\odot$ (or $30$ AU) after the star accretes the gas of more than $10^3$ M$_\odot$. We show that the emergence of the "supergiant protostar" stage is a key for the formation of SMSs, because resulting radiative feedback against the accretion flow is substantially weakened during this stage. We also show that these SMSs end their lives while the accretion continues, and that their final fates vary with different accretion rates.

One of the major goals of next-generation space-borne and ground-based telescopes is to detect and characterize the first galaxies that were in place in the first few hundred million years after the big bang. We study the spectral energy distribution (SED) of the first galaxies and discuss the prospects for detection and identification. We consider very young star-forming galaxies at $z=15$ and incorporate the contribution from pre-main-sequence (PMS) stars. Unlike in the present-day galaxies, primordial protostars are not embedded in dusty gas clouds, and hence the light from them can be visible at a wide range of wavelengths. We use MESA code to follow the PMS evolution and use the BT-Settl model to calculate the SED of individual PMS stars. We show that PMS stars contribute to boost the flux in the mid-infrared, and that the galaxy SED at very early evolutionary phases is overall redder than at later phases. The infrared flux contribution is comparable to that caused by emission lines powered by massive stars. We argue that the contribution from PMS stars is important for characterizing young galaxies in the early Universe and also for target selection with future deep galaxy surveys., 5 pages, 4 figures, published online in MNRAS letters

The disk fragmentation is a possible process leading to the formation of Population III stellar binary systems. However, numerical simulations show diverse fates of the fragments; some evolve into stable binaries and others merge away with a central star. To clarify the physics behind such diversity, we perform a series of three dimensional hydrodynamics simulations in a controlled manner. We insert a point particle mimicking a fragment in a self-gravitating disk, where the initial mass and position are free parameters, and follow the orbital evolution for several tens of orbits. The results show great diversity even with such simple experiments. Some particles shortly merge away after migrating inward, but others survive as the migration stalls with the gap-opening in the disk. We find that our results are well interpreted postulating that the orbital angular momentum is extracted by (i) the gravitational torque from the disk spiral structure, and (ii) tidal disruption of a gravitationally-bound envelope around the particle. Our analytic evaluations show the processes (i) and (ii) are effective in an outer and inner part of the disk respectively. There is a window of the gap-opening in the middle, if the envelope mass is sufficiently large. These all agree with our numerical results. We further show that the binaries, which appear for the "survival" cases, gradually expand while accreting the disk gas. Our theoretical framework is freely scalable to be applied for the present-day star and planet formation., 16 pages, 14 figures, published in MNRAS

Following our recent work devoted to the effect of accretion on the pre-main-sequence evolution of low-mass stars, we perform a detailed analysis of episodic excursions of low-mass protostars in the Hertzsprung-Russell (H-R) diagram triggered by strong mass accretion bursts typical of FU Orionis-type objects (FUors). These excursions reveal themselves as sharp increases in the stellar total luminosity and/or effective temperature of the protostar and can last from hundreds to a few thousands of years, depending on the burst strength and characteristics of the protostar. During the excursions, low-mass protostars occupy the same part of the H-R diagram as young intermediate-mass protostars in the quiescent phase of accretion. Moreover, the time spent by low-mass protostars in these regions is on average a factor of several longer than that spent by the intermediate-mass stars in quiescence. During the excursions, low-mass protostars pass close to the position of most known FUors in the H-R diagram, but owing to intrinsic ambiguity the model stellar evolutionary tracks are unreliable in determining the FUor properties. We find that the photospheric luminosity in the outburst state may dominate the accretion luminosity already after a few years after the onset of the outburst, meaning that the mass accretion rates of known FUors inferred from the bolometric luminosity may be systematically overestimated, especially in the fading phase., Comment: 15 pages, 12 figures

In recent years, the discovery of massive quasars at z~7 has provided a striking challenge to our understanding of the origin and growth of supermassive black holes in the early Universe. Mounting observational and theoretical evidence indicates the viability of massive seeds, formed by the collapse of supermassive stars, as a progenitor model for such early, massive accreting black holes. Although considerable progress has been made in our theoretical understanding, many questions remain regarding how (and how often) such objects may form, how they live and die, and how next generation observatories may yield new insight into the origin of these primordial titans. This review focusses on our present understanding of this remarkable formation scenario, based on discussions held at the Monash Prato Centre from November 20--24, 2017, during the workshop "Titans of the Early Universe: The Origin of the First Supermassive Black Holes.", Comment: Solicited review article (accepted) for Publications of the Astronomical Society of Australia. 38 pages, 15 figures, 1 table

Measures to protect vulnerable road users during low-speed maneuvers are required. For example, systems that use cameras to display the vehicle's rearview are popular. However, some vehicles are difficult to equip with a rear view camera system. To avoid a crash when driving in reverse, it is also effective to identify the presence of pedestrians via an audible warning using a device (e.g., clearance sonar). It may be cheaper to install than a rearview camera system. Installation cost is also important for the spread of equipment that reduces a crash. It is necessary to clarify the minimum specifications that balance cost and reduce crashes. Device specifications (e.g., detection distance and response delay) may affect the crash reduction rate. There should be a detection distance required for the sonar to have the same crash reduction effect as the rear view camera system. Thus, in this study, we conducted experiments and obtained data about how a vehicle moves and driver reactions to audible warnings when driving in reverse. Based on the acquired data, a numerical simulation was performed to determine whether a driver could avoid a crash under various circumstances. As a result, it was shown that the clearance sonar must have a detection distance of 0.8 m or more to expect the same effect as a rearview camera system. In other words, to expect sonar to have the same performance as a rearview camera, a detection distance of at least 0.8 m should be set as a specification.

The formation of SMSs is a potential pathway to seed SMBHs in the early universe. A critical issue for forming SMSs is stellar UV feedback, which may limit the stellar mass growth via accretion. In this paper we study the evolution of an accreting SMS and its UV emissivity under conditions of realistic variable accretion from a self-gravitating circumstellar disc. First we conduct a 2D hydrodynamical simulation to follow the long-term protostellar accretion until the stellar mass exceeds $10^4~M_\odot$. The disc fragments due to gravitational instability, creating a number of small clumps that rapidly migrate inward to fall onto the star. The resulting accretion history is thus highly time-dependent: short episodic accretion bursts are followed by longer, relative quiescent phases. We show that the circumstellar disc for the so-called direct collapse model is more unstable and generates greater variability over shorter timescales than normal Pop III cases. We conduct a post-process stellar evolution calculation using the obtained accretion history. Our results show that, regardless of the strong variability of the accretion rates, the stellar radius monotonically increases with almost constant effective temperature at $T_{\rm eff} \simeq 5000$ K as the stellar mass increases. The resulting UV feedback is too weak to hinder mass accretion due to the low flux of stellar UV photons, thus verifying our implicit assumption of no stellar feedback during the hydrodynamic simulations. The insensitivity of stellar evolution to variable accretion is attributed to the fact that typical timescales of variability, $\lesssim 10^3$ years, are too short to affect the stellar structure. We argue that this evolution will continue until the SMS eventually collapses to produce a massive black hole by the general relativistic instability after the stellar mass reaches $\gtrsim 10^5~M_\odot$., Comment: 9 pages, 6 figures, submitted to MNRAS

Aims. The early evolution of protostellar disks with metallicities in the Z = 1.0 − 0.01 Z⊙ range was studied with a particular emphasis on the strength of gravitational instability and the nature of protostellar accretion in low-metallicity systems. Methods. Numerical hydrodynamics simulations in the thin-disk limit were employed that feature separate gas and dust temperatures, and disk mass-loading from the infalling parent cloud cores. Models with cloud cores of similar initial mass and rotation pattern but distinct metallicity were considered to distinguish the effect of metallicity from that of the initial conditions. Results. The early stages of disk evolution in low-metallicity models are characterized by vigorous gravitational instability and fragmentation. Disk instability is sustained by continual mass-loading from the collapsing core. The time period that is covered by this unstable stage is much shorter in the Z = 0.01 Z⊙ models than in their higher metallicity counterparts thanks to the higher rates of mass infall caused by higher gas temperatures (which decouple from lower dust temperatures) in the inner parts of collapsing cores. Protostellar accretion rates are highly variable in the low-metallicity models reflecting the highly dynamic nature of the corresponding protostellar disks. The low-metallicity systems feature short but energetic episodes of mass accretion caused by infall of inward-migrating gaseous clumps that form via gravitational fragmentation of protostellar disks. These bursts seem to be more numerous and last longer in the Z = 0.1 Z⊙ models than in the Z = 0.01 Z⊙ case. Conclusions. Variable protostellar accretion with episodic bursts is not a particular feature of solar metallicity disks. It is also inherent to gravitationally unstable disks with metallicities up to 100 times lower than solar.

We initiated a long-term and highly frequent monitoring project toward 442 methanol masers at 6.7 GHz (Dec >−30 deg) using the Hitachi 32-m radio telescope in December 2012. The observations have been carried out daily, monitoring a spectrum of each source with intervals of 9–10 days. In September 2015, the number of the target sources and intervals were redesigned into 143 and 4–5 days, respectively. This monitoring provides us complete information on how many sources show periodic flux variations in high-mass star-forming regions, which have been detected in 20 sources with periods of 29.5–668 days so far (e.g., Goedhart et al. 2004). We have already obtained new detections of periodic flux variations in 31 methanol sources with periods of 22–409 days. These periodic flux variations must be a unique tool to investigate high-mass protostars themselves and their circumstellar structure on a very tiny spatial scale of 0.1–1 au.