Following the first attempt at producing gas from a naturally occurring methane hydrate (MH) deposit in the Daini-Atsumi Knoll in the eastern Nankai Trough area off Honshu Island, Japan in 2013, a ...second attempt was made in April to June of 2017 at a nearby location using two producer wells sequentially and applying the depressurization method. The operation in the first borehole (AT1-P3) continued for 12 days with a stable drawdown of around 7.5 MPa and 41 000 m
3
of methane gas being produced despite intermittent sand-production events. The operation of the other borehole (AT1-P2) followed, with a total of 24 days of flow and 222 500 m
3
of methane gas being produced without sand problems. However, the degree of drawdown was limited to 5 MPa because of a higher water production rate than expected in the second hole. The pressure and temperature sensors deployed in the two producers, along with the two monitoring holes drilled nearby, gathered reservoir response data and information about the long-term MH dissociation processes in the vicinity of the production holes in the temporal and spatial domains. Although the ratio of energy return to the input was considerably larger than that for the depressurization operation, some observations (
e.g.
, the high contrast in the production rates between the two holes and the almost constant or slightly reduced gas production rates) were not predicted by the numerical models. This failure in prediction raises questions about the veracity of the reservoir characteristics modeled in the numerical simulations. This paper presents the operation summaries and data obtained with thought-experiment based-anticipated production behaviors and preliminary analysis of the obtained data as the comparison with expected behaviors. Detailed observations of gas and water production, as well as the pressure and temperature data recorded during the gas flow tests, indicate that the heterogeneous MH distribution within the reservoir was mainly responsible for the discrepancies observed between the anticipated and actual behaviors. Furthermore, the motion of the water that does not originate from MH dissociation introduces complexity, such as the occurrence of concentrated water-producing intervals and unexpected gas production responses to decreases in pressure, into the production behavior. The influence of heterogeneity should be clearly understood for the accurate prediction of gas production behavior based on MH reservoirs.
The second gas production attempt from a methane hydrate (MH) deposit in the eastern Nankai Trough area was made in 2017 with the intensive data acquisition program, and it revealed effects of reservoir characters on the MH dissociation behaviors.
Summary
A platelet activation receptor, C‐type lectin‐like receptor 2 (CLEC‐2), has been identified as a receptor for a platelet‐activating snake venom, rhodocytin. CLEC‐2 protein is highly expressed ...in platelets/megakaryocytes, and at lower levels in liver Kupffer cells. Recently, podoplanin has been revealed as an endogenous ligand for CLEC‐2. Podoplanin is expressed in certain types of tumor cells, fibroblastic reticular cells (FRCs) in lymph nodes, kidney podocytes, and lymphatic endothelial cells, but not in vascular endothelial cells. CLEC‐2 in platelets cannot have access to podoplanin under normal conditions, but they interact with each other under pathologic conditions or during developmental stages, and play various pathophysiologic roles. CLEC‐2 facilitates hematogenous metastasis of podoplanin‐expressing tumors. During development, the interaction between CLEC‐2 and podoplanin in lymphatic endothelial cells or neuroepithelial cells facilitates blood–lymphatic vessel separation and cerebrovascular patterning and integrity, respectively. In adulthood, platelet CLEC‐2 binding to FRCs is crucial for maintenance of the integrity of high endothelial venules in lymph nodes. Podoplanin‐expressing FRC‐like cells have recently been identified in the bone marrow, and facilitate megakaryocyte proliferation and proplatelet formation by binding to megakaryocyte CLEC‐2. Podoplanin is inducibly expressed in liver monocytes and keratinocytes during Salmonella infection and wound healing, and regulates thrombus formation in the liver and controlled wound healing, respectively. By binding to unknown ligands, platelet CLEC‐2 regulates the maintenance of vascular integrity during inflammation, thrombus stability under flow, and maintenance of quiescence of hematopoietic stem cells. Podoplanin is expressed in various cells, and additional roles of the CLEC‐2–podoplanin interaction will be revealed in the future.
Abstract
By performing ideal magnetohydrodynamical (MHD) simulations with weak vertical magnetic fields in unstratified cylindrical shearing boxes with modified boundary treatment, we investigate MHD ...turbulence excited by magnetorotational instability. The cylindrical simulation exhibits extremely large temporal variation in the magnetic activity compared with the simulation in a normal Cartesian shearing box, although the time-averaged field strengths are comparable in the cylindrical and Cartesian setups. Detailed analysis of the terms describing magnetic energy evolution with “triangle diagrams” surprisingly reveals that in the cylindrical simulation the compression of toroidal magnetic field is unexpectedly as important as the winding due to differential rotation in amplifying magnetic fields and triggering intermittent magnetic bursts, which are not seen in the Cartesian simulation. The importance of the compressible amplification is also true for a cylindrical simulation with tiny curvature; the evolution of magnetic fields in the nearly Cartesian shearing box simulation is fundamentally different from that in the exact Cartesian counterpart. The
radial gradient of epicyclic frequency
,
κ
, which cannot be considered in the normal Cartesian shearing box model, is the cause of this fundamental difference. An additional consequence of the spatial variation of
κ
is continuous and ubiquitous formation of narrow high-density (low-density) and weak-field (strong-field) localized structures; seeds of these ring gap structures are created by the compressible effect and subsequently amplified and maintained under the marginally unstable condition regarding “viscous-type” instability.
Abstract
We investigated stellar winds from zero-/low-metallicity low-mass stars by magnetohydrodynamical simulations for stellar winds driven by Alfvén waves from stars with mass M = (0.6–0.8) ...M$\odot$ and metallicity Z = (0–1) Z$\odot$, where M$\odot$ and Z$\odot$ are the solar mass and metallicity, respectively. Alfvénic waves, which are excited by the surface convection, travel upward from the photosphere and heat up the corona by their dissipation. For lower Z, denser gas can be heated up to the coronal temperature because of the inefficient radiation cooling. The coronal density of Population II/III stars with Z ≤ 0.01 Z$\odot$ is one to two orders of magnitude larger than that of a solar-metallicity star with the same mass, and as a result, the mass loss rate, $\dot{M}$, is 4.5–20 times larger. This indicates that metal accretion on low-mass Pop. III stars is negligible. The soft X-ray flux of the Pop. II/III stars is also expected to be ∼1–30 times larger than that of a solar-metallicity counterpart owing to the larger coronal density, even though the radiation cooling efficiency is smaller. A larger fraction of the input Alfvénic wave energy is transmitted to the corona in low-Z stars because they avoid severe reflection owing to the smaller density difference between the photosphere and the corona. Therefore, a larger fraction is converted to the thermal energy of the corona and the kinetic energy of the stellar wind. From this energetics argument, we finally derived a scaling of $\dot{M}$ as $\dot{M}\propto L R_{\star }^{11/9}\,M_{\star }^{-10/9}\,T_{\rm eff}^{11/2}\left\max (Z/Z_{\odot },0.01)\right^{-1/5}$, where L, R⋆, and Teff are the stellar luminosity, radius, and effective temperature, respectively.
We have performed a 2.5-dimensional magnetohydrodynamic simulation that resolves the propagation and dissipation of Alfvén waves in the solar atmosphere. Alfvénic fluctuations are introduced on the ...bottom boundary of the extremely large simulation box that ranges from the photosphere to far above the solar wind acceleration region. Our model is ab initio in the sense that no corona and no wind are assumed initially. The numerical experiment reveals the quasi-steady solution that has the transition from the cool to the hot atmosphere and the emergence of the high speed wind. The global structure of the resulting hot wind solution fairly well agrees with the coronal and the solar wind structure inferred from observations. The purpose of this study is to complement the previous paper by Matsumoto & Suzuki and describe the more detailed results and the analysis method. These results include the dynamics of the transition region and the more precisely measured heating rate in the atmosphere. Particularly, the spatial distribution of the heating rate helps us to interpret the actual heating mechanisms in the numerical simulation. Our estimation method of heating rate turned out to be a good measure for dissipation of Alfvén waves and low beta fast waves.
Context. Planets with masses larger than about 0.1 M⊕ undergo rapid inward migration (type I migration) in a standard protoplanetary disk. Recent magnetohydrodynamical simulations revealed the ...presence of magnetically driven disk winds, which would alter the disk profile and the type I migration in the close-in region. Aims. We investigate orbital evolution of planetary embryos in disks that viscously evolve under the effects of disk winds. The aim is to discuss effects of altered disk profiles on type I migration. In addition, we aim to examine whether observed distributions of close-in super-Earths can be reproduced by simulations that include effects of disk winds. Methods. We perform N-body simulations of super-Earth formation from planetary embryos, in which a recent model for disk evolution is used. We explore a wide range of parameters and draw general trends. We also carry out N-body simulations of close-in super-Earth formation from embryos in such disks under various conditions. Results. We find that the type I migration is significantly suppressed in many cases. Even in cases in which inward migration occurs, the migration timescale is lengthened to 1 Myr, which mitigates the type I migration problem. This is because the gas surface density is decreased and has a flatter profile in the close-in region due to disk winds. We find that when the type I migration is significantly suppressed, planets undergo late orbital instability during the gas depletion, leading to a non-resonant configuration. We also find that observed distributions of close-in super-Earths (e.g., period ratio, mass ratio) can be reproduced. In addition, we show that in some results of simulations, systems with a chain of resonant planets, like the TRAPPIST-1 system, form.
We propose a novel one-dimensional model that includes both shock and turbulence heating and qualify how these processes contribute to heating the corona and driving the solar wind. Compressible MHD ...simulations allow us to automatically consider shock formation and dissipation, while turbulent dissipation is modeled via a one-point closure based on Alfvén wave turbulence. Numerical simulations were conducted with different photospheric perpendicular correlation lengths λ 0 , which is a critical parameter of Alfvén wave turbulence, and different root-mean-square photospheric transverse-wave amplitudes δ v 0 . For the various λ 0 , we obtain a low-temperature chromosphere, high-temperature corona, and supersonic solar wind. Our analysis shows that turbulence heating is always dominant when λ 0 1 Mm . This result does not mean that we can ignore the compressibility because the analysis indicates that the compressible waves and their associated density fluctuations enhance the Alfvén wave reflection and therefore the turbulence heating. The density fluctuation and the cross-helicity are strongly affected by λ 0 , while the coronal temperature and mass-loss rate depend weakly on λ 0 .
Human mitochondrial transcription factor A (TFAM) is a high-mobility group (HMG) protein at the nexus of mitochondrial DNA (mtDNA) replication, transcription, and inheritance. Little is known about ...the mechanisms underlying its posttranslational regulation. Here, we demonstrate that TFAM is phosphorylated within its HMG box 1 (HMG1) by cAMP-dependent protein kinase in mitochondria. HMG1 phosphorylation impairs the ability of TFAM to bind DNA and to activate transcription. We show that only DNA-free TFAM is degraded by the Lon protease, which is inhibited by the anticancer drug bortezomib. In cells with normal mtDNA levels, HMG1-phosphorylated TFAM is degraded by Lon. However, in cells with severe mtDNA deficits, nonphosphorylated TFAM is also degraded, as it is DNA free. Depleting Lon in these cells increases levels of TFAM and upregulates mtDNA content, albeit transiently. Phosphorylation and proteolysis thus provide mechanisms for rapid fine-tuning of TFAM function and abundance in mitochondria, which are crucial for maintaining and expressing mtDNA.
Display omitted
► cAMP-dependent protein kinase (PKA) serine phosphorylates TFAM within HMG1 ► HMG1 phosphorylation of TFAM impairs DNA binding and transcription activation ► Lon protease selectively degrades DNA-free TFAM and is inhibited by bortezomib ► Lon knockdown stabilizes TFAM in mtDNA-deficient cells and upregulates mtDNA
Humans had acquired a tremendously enlarged cerebral cortex containing a huge quantity and variety of cells during evolution. Such evolutionary uniqueness offers a neural basis of our cognitive ...innovation and human‐specific features of neurodevelopmental and psychiatric disorders. Since human brain is hardly examined in vivo with experimental approaches commonly applied on animal models, the recent advancement of sequencing technologies offers an indispensable viewpoint of human brain anatomy and development. This review introduces the recent findings on the unique features in the adult and the characteristic developmental processes of the human cerebral cortex, based on high‐throughput DNA sequencing technologies.
PDF
