Catalogue Search | MBRL
Are you sure you want to remove the book from the shelf?
{{itemTitle}}
251,970
result(s) for
"cores"
Sort by:
Turbulent convective length scale in planetary cores
Convection is a fundamental physical process in the fluid cores of planets. It is the primary transport mechanism for heat and chemical species and the primary energy source for planetary magnetic fields. Key properties of convection—such as the characteristic flow velocity and length scale—are poorly quantified in planetary cores owing to the strong dependence of these properties on planetary rotation, buoyancy driving and magnetic fields, all of which are difficult to model using realistic conditions. In the absence of strong magnetic fields, the convective flows of the core are expected to be in a regime of rapidly rotating turbulence
1
, which remains largely unexplored. Here we use a combination of non-magnetic numerical models designed to explore this regime to show that the convective length scale becomes independent of the viscosity when realistic parameter values are approached and is entirely determined by the flow velocity and the planetary rotation. The velocity decreases very rapidly at smaller scales, so this turbulent convective length scale is a lower limit for the energy-carrying length scales in the flow. Using this approach, we can model realistically the dynamics of small non-magnetic cores such as the Moon. Although modelling the conditions of larger planetary cores remains out of reach, the fact that the turbulent convective length scale is independent of the viscosity allows a reliable extrapolation to these objects. For the Earth’s core conditions, we find that the turbulent convective length scale in the absence of magnetic fields would be about 30 kilometres, which is orders of magnitude larger than the ten-metre viscous length scale. The need to resolve the numerically inaccessible viscous scale could therefore be relaxed in future more realistic geodynamo simulations, at least in weakly magnetized regions.
Numerical modelling of rotating turbulent convective flows shows that the length scale of convection in planetary cores is set by the flow speed and not by the fluid viscosity.
Journal Article
N6-methyladenosine modification of the 5′ epsilon structure of the HBV pregenome RNA regulates its encapsidation by the viral core protein
Hepatitis B virus (HBV) contains a partially double-stranded DNA genome. During infection, its replication is mediated by reverse transcription (RT) of an RNA intermediate termed pregenomic RNA (pgRNA) within core particles in the cytoplasm. An epsilon structural element located in the 5′ end of the pgRNA primes the RT activity. We have previously identified the N6-methyladenosine (m⁶A)–modified DRACH motif at 1905 to 1909 nucleotides in the epsilon structure that affects myriad functions of the viral life cycle. In this study, we investigated the functional role of m⁶A modification of the 5′ ε (epsilon) structural element of the HBV pgRNA in the nucleocapsid assembly. Using the m⁶A sitemutant in the HBV 5′ epsilon, we present evidence that m⁶A methylation of 5′ epsilon is necessary for its encapsidation. The m⁶A modification of 5′ epsilon increased the efficiency of viral RNA packaging, whereas the m⁶A of 3′ epsilon is dispensable for encapsidation. Similarly, depletion of methyltransferases (METTL3/14) decreased pgRNA and viral DNA levels within the core particles. Furthermore, the m⁶A modification at 5′ epsilon of HBV pgRNA promoted the interaction with core proteins, whereas the 5′ epsilon m⁶A site–mutated pgRNA failed to interact. HBV polymerase interaction with 5′ epsilon was independent of m⁶A modification of 5′ epsilon. This study highlights yet another pivotal role of m⁶A modification in dictating the key events of the HBV life cycle and provides avenues for investigating RNA–protein interactions in various biological processes, including viral RNA genome encapsidation in the context of m⁶A modification.
Journal Article
Effects of cellular membranes and the precore protein on hepatitis B virus core particle assembly and DNA replication
Hepatitis B virus (HBV) is an important human pathogen that chronically infects 254 million people in the world. This virus contains a core particle, which plays an important role in the transport and replication of the viral DNA genome. The major protein constituent of this particle is the viral core protein. In this report, we examined how the subcellular compartments and the related precore protein might affect the core particle structure and viral DNA replication. We found that the subcellular localizations could affect the core particle assembly, and membranes and the precore protein could regulate HBV DNA replication. We also found that the inhibition of autophagic degradation increased the precore protein level, suggesting a role of autophagy in the regulation of precore protein activities. These findings provided important information for further understanding the HBV life cycle, which will aid in the development of novel drugs for the treatment of HBV patients.
Journal Article
Runx3 specifies lineage commitment of innate lymphoid cells
The transcriptional control of lineage commitment to various ILC subsets is incompletely understood. Yokoyama and colleagues show that Runx3 is essential for the normal development of ILC1 and ILC3 cells but not ILC2 cells.
Subsets of innate lymphoid cells (ILCs) reside in the mucosa and regulate immune responses to external pathogens. While ILCs can be phenotypically classified into ILC1, ILC2 and ILC3 subsets, the transcriptional control of commitment to each ILC lineage is incompletely understood. Here we report that the transcription factor Runx3 was essential for the normal development of ILC1 and ILC3 cells but not of ILC2 cells. Runx3 controlled the survival of ILC1 cells but not of ILC3 cells. Runx3 was required for expression of the transcription factor RORγt and its downstream target, the transcription factor AHR, in ILC3 cells. The absence of Runx3 in ILCs exacerbated infection with
Citrobacter rodentium
. Therefore, our data establish Runx3 as a key transcription factor in the lineage-specific differentiation of ILC1 and ILC3 cells.
Journal Article
Novel biomarkers: the RUNX family as prognostic predictors in colorectal cancer
While biomarkers have been shown to enhance the prognosis of patients with colorectal cancer (CRC) compared to conventional treatments, there is a pressing need to discover novel biomarkers that can assist in assessing the prognostic impact of immunotherapy and in formulating individualized treatment plans. The RUNX family, consisting of RUNX1, RUNX2, and RUNX3, has been recognized as crucial regulators in developmental processes, with dysregulation of these genes also being implicated in tumorigenesis and cancer progression. In our present study, we demonstrated a crucial regulatory role of RUNX in CD8 + T and CD103 + CD8 + T cell-mediated anti-tumor response within the tumor microenvironment (TME) of human CRC. Specifically, RUNXs were significantly differentially expressed between tumor and normal tissues in CRC. Patients with a greater proportion of infiltrating CD8 + RUNX1 + , CD103 + CD8 + RUNX1 + , CD8 + RUNX2 + , CD103 + CD8 + RUNX2 + , CD8 + RUNX3 + , or CD103 + CD8 + RUNX3 + T cells demonstrated improved outcomes compared to those with lower proportions. Additionally, the proportions of infiltrating CD8 + RUNX1 + T and CD8 + RUNX3 + T cells may serve as valuable prognostic predictors for CRC patients, independent of other clinicopathological factors. Moreover, further bioinformatic analysis conducted utilizing the TISIDB and TIMER platforms demonstrated significant associations between the members of the RUNX family and immune-infiltrating cells, specifically diverse subpopulations of CD8 + TILs. Our study of human colorectal cancer tissue microarray (TMA) also revealed positive and statistically significant correlations between the expressions of RUNX1, RUNX2, and RUNX3 in both CD8 + T cells and CD103 + CD8 + T cells. Our study comprehensively revealed the varied expressions and prognostic importance of the RUNX family in human colorectal cancer tissues. It underscored their potential as vital biomarkers for prognostic evaluation in colorectal cancer patients and as promising targets for immunotherapy in treating this disease.
Journal Article
Deep ice-core drilling to 800 m at Dome A in East Antarctica
A deep ice core was drilled at Dome A, Antarctic Plateau, East Antarctica, which started with the installation of a casing in January 2012 and reached 800.8 m in January 2017. To date, a total of 337 successful ice-core drilling runs have been conducted, including 118 runs to drill the pilot hole. The total drilling time was 52 days, of which eight days were required for drilling down and reaming the pilot hole, and 44 days for deep ice coring. The average penetration depths of individual runs were 1 and 3.1 m for the pilot hole drilling and deep ice coring, respectively. The quality of the ice cores was imperfect in the brittle zone (650−800 m). Some of the troubles encountered are discussed for reference, such as armoured cable knotting, screws falling into the hole bottom, and damaged parts, among others.
Journal Article
Phase transition boundary between fcc and hcp structures in Fe-Si alloy and its implications for terrestrial planetary cores
The phase transition between a face-centered cubic (fcc) and hexagonal close-packed (hcp) structures in Fe-4wt% Si alloy was examined in an internally resistive heated diamond-anvil cell (DAC) under high-pressure (P) and high-temperature (T) conditions to 71 GPa and 2000 K by in situ synchrotron X-ray diffraction. Complementary laser-heated DAC experiments were performed in Fe-6.5wt% Si. The fcc-hcp phase transition boundaries in the Fe-Si alloys are located at higher temperatures than that in pure Fe, indicating that the addition of Si expands the hcp stability field. The dP/dT slope of the boundary of the entrant fcc phase in Fe-4wt% Si is similar to that of pure Fe, but the two-phases region is observed over a temperature range increasing with pressure, going from 50 K at 15 GPa to 150 K at 40 GPa. The triple point, where the fcc, hcp, and liquid phases coexist in Fe-4wt% Si, is placed at 90-105 GPa and 3300-3600 K with the melting curve same as in Fe is assumed. This supports the idea that the hcp phase is stable at Earth's inner core conditions. The stable structures of the inner cores of the other terrestrial planets are also discussed based on their P-T conditions relative to the triple point. In view of the reduced P-T conditions of the core of Mercury (well below the triple point), an Fe-Si alloy with a Si content up to 6.5 wt% would likely crystallize an inner core with an fcc structure. Both cores from Venus and Mars are currently believed to be totally molten. Upon secular cooling, Venus is expected to crystallize an inner core with an hcp structure, as the pressures are similar to those of the Earth's core (far beyond the triple point). Martian inner core will take an hcp or fcc structure depending on the actual Si content and temperature.
Journal Article
Runx/Cbfβ complexes protect group 2 innate lymphoid cells from exhausted-like hyporesponsiveness during allergic airway inflammation
Group 2 innate lymphoid cells (ILC2s) have tissue-resident competence and contribute to the pathogenesis of allergic diseases. However, the mechanisms regulating prolonged ILC2-mediated T
H
2 cytokine production under chronic inflammatory conditions are unclear. Here we show that, at homeostasis, Runx deficiency induces excessive ILC2 activation due to overly active GATA-3 functions. By contrast, during allergic inflammation, the absence of Runx impairs the ability of ILC2s to proliferate and produce effector T
H
2 cytokines and chemokines. Instead, functional deletion of Runx induces the expression of exhaustion markers, such as IL-10 and TIGIT, on ILC2s. Finally, these ‘exhausted-like’ ILC2s are unable to induce type 2 immune responses to repeated allergen exposures. Thus, Runx confers competence for sustained ILC2 activity at the mucosa, and contributes to allergic pathogenesis.
Group 2 innate lymphoid cells (ILC2) are important mediators for allergy, but how ILC2 are regulated under chronic inflammation is still unclear. Here the authors show that Runx transcription factors, which normally suppresses ILC2 activation at steady state, help promote ILC2 activation and type 2 cytokine production in lung allergy mouse models.
Journal Article
Simulating the vibrational quantum dynamics of molecules using photonics
Advances in control techniques for vibrational quantum states in molecules present new challenges for modelling such systems, which could be amenable to quantum simulation methods. Here, by exploiting a natural mapping between vibrations in molecules and photons in waveguides, we demonstrate a reprogrammable photonic chip as a versatile simulation platform for a range of quantum dynamic behaviour in different molecules. We begin by simulating the time evolution of vibrational excitations in the harmonic approximation for several four-atom molecules, including H
2
CS, SO
3
, HNCO, HFHF, N
4
and P
4
. We then simulate coherent and dephased energy transport in the simplest model of the peptide bond in proteins—
N
-methylacetamide—and simulate thermal relaxation and the effect of anharmonicities in H
2
O. Finally, we use multi-photon statistics with a feedback control algorithm to iteratively identify quantum states that increase a particular dissociation pathway of NH
3
. These methods point to powerful new simulation tools for molecular quantum dynamics and the field of femtochemistry.
By mapping vibrations in molecules to photons in waveguides, the vibrational quantum dynamics of various molecules are simulated using a photonic chip.
Journal Article