The Martian satellite Phobos is criss-crossed by linear grooves and crater chains whose origin is unexplained. Anomalous grooves are relatively young, and crosscut tidally predicted stress fields as ...Phobos spirals towards Mars. Here we report strong correspondence between these anomalous features and reaccretion patterns of sesquinary ejecta from impacts on Phobos. Escaping ejecta persistently imprint Phobos with linear, low-velocity crater chains (catenae) that match the geometry and morphology of prominent features that do not fit the tidal model. We prove that these cannot be older than Phobos' current orbit inside Mars' Roche limit. Distinctive reimpact patterns allow sesquinary craters to be traced back to their source, for the first time across any planetary body, creating a novel way to probe planetary surface characteristics. For example, we show that catena-producing craters likely formed in the gravity regime, providing constraints on the ejecta velocity field and knowledge of source crater material properties.
The flow of ferronanofluid due to a rotating disk finds its significant place in biomedical sciences, pharmaceuticals, electronics, aerodynamics etc. Entropy generation appears in the ...systems/processes where its minimization is needed because it prohibits the decay of available energy which in turn boosts the efficiency of the associated thermal systems where it matters the most. In view of these added advantages, the flow and heat transfer behavior of ferronanofluid subject to slip, suction, electromagnetic field, Darcy-Forchheimer effect, and viscous dissipation, Ohmic heating and thermal radiation has been explored within this research. In addition, the role of entropy minimization associated with the flow concern has been analyzed. The apposite governing equations are numerically treated via shooting method. The important outcome of the study include infusion of more porous matrix develops controlled rotating flow due to both deformed disks. Rise in slip parameter augments flow velocity for stretched RD while that shows the adverse effect for shrunk RD. Controlled rate of heat transportation due to enhanced convective heating is significant for shrunk RD than that of stretched RD. Further, low Prandtl fluids, low molecular heat conduction and liquid friction yield entropy minimization thereby leading to uplift efficiency of thermal systems.
Human intestinal epithelial organoids (IEOs) are increasingly being recognised as a highly promising translational research tool. However, our understanding of their epigenetic molecular ...characteristics and behaviour in culture remains limited.
We performed genome-wide DNA methylation and transcriptomic profiling of human IEOs derived from paediatric/adult and fetal small and large bowel as well as matching purified human gut epithelium. Furthermore, organoids were subjected to in vitro differentiation and genome editing using CRISPR/Cas9 technology.
We discovered stable epigenetic signatures which define regional differences in gut epithelial function, including induction of segment-specific genes during cellular differentiation. Established DNA methylation profiles were independent of cellular environment since organoids retained their regional DNA methylation over prolonged culture periods. In contrast to paediatric and adult organoids, fetal gut-derived organoids showed distinct dynamic changes of DNA methylation and gene expression in culture, indicative of an in vitro maturation. By applying CRISPR/Cas9 genome editing to fetal organoids, we demonstrate that this process is partly regulated by TET1, an enzyme involved in the DNA demethylation process. Lastly, generating IEOs from a child diagnosed with gastric heterotopia revealed persistent and distinct disease-associated DNA methylation differences, highlighting the use of organoids as disease-specific research models.
Our study demonstrates striking similarities of epigenetic signatures in mucosa-derived IEOs with matching primary epithelium. Moreover, these results suggest that intestinal stem cell-intrinsic DNA methylation patterns establish and maintain regional gut specification and are involved in early epithelial development and disease.
ABSTRACT
We derive a general dispersion relation for linearly polarized transverse magnetohydrodynamic (MHD) waves in an inhomogeneous, viscous, and resistive coronal plasma. We assume density ...structuring along the direction of polarization of the wave. In the linear regime and for an incompressible and homogeneous plasma, where the criterion of ignorable coordinates is satisfied, our solution corresponds to the customary Alfvén wave, which is basically dissipated by shear viscosity or resistivity. However, the assumption of density stratification along the direction of polarization of waves breaks down the criterion of ignorable coordinates, due to which transversal wave perturbations become compressible and, consequently, compressive viscosity turns out to be an important process. We find that for a typical coronal plasma with a magnetic field of 5 to 22 G, transverse body waves with a period of less than 10 s can dissipate energy on a time scale comparable to the coronal radiative time in their antisymmetric mode. Thus, it is possible that linearly polarized transverse wave perturbations dissipated by ion compressive viscosity maintain a hot coronal temperature.
The significance of the local skin friction as well as the heat transfer rate on the motion of water
H
2
O
and ethylene glycol
C
2
H
6
O
2
conveying metallic and metallic oxide nanoparticles (e.g., ...Al, Cu, Zn, Al
2
0
3
, CuO and ZnO) along a vertical thin needle is needed to improve the performance of chemical reactors, heat exchangers, pharmaceutical equipment and hybrid-powered engines. This led to the investigation of mixed convection flow and heat transfer of some nanofluids, in which the thermal conductivity and viscosity vary nonlinearly with the volume fraction. For simplifying the present investigation, appropriate variables were introduced successfully in the mathematical formulation to convert the governing nonlinear partial differential equations to coupled ordinary differential equations (ODEs). Moreover, the resulting ODEs were solved numerically via a robust differential quadrature algorithm. Furthermore, a comparative study with the existing literature is found to be in an excellent agreement. The enhancement of heat transfer in nanofluids is ascertained by increasing the convection ratio. Generally, the maximum improvement in the local skin friction was perceived for the flows of zinc–water-based nanofluids (
Zn
–
H
2
O
) with the upsurge in the volume fraction of the nanoparticles
Zn
. On the contrary, the highest enhancement in the heat transfer rate was revealed for the flows of copper–ethylene glycol-based nanofluids (
Cu
–
C
2
H
6
O
2
) with the increase in the weight percent of the
Cu
nanomaterial loading.
MXenes are a new family of two-dimensional (2D) nanomaterials. They are inorganic compounds of metal carbides/nitrides/carbonitrides. Titanium carbide MXene (Ti3C2-MXene) was the first 2D ...nanomaterial reported in the MXene family in 2011. Owing to the good physical properties of Ti3C2-MXenes (e.g., conductivity, hydrophilicity, film-forming ability, elasticity) various applications in wearable sensors, energy harvesters, supercapacitors, electronic devices, etc., have been demonstrated. This paper presents the development of a piezoresistive Ti3C2-MXene sensor followed by experimental investigations of its dynamic response behavior when subjected to structural impacts. For the experimental investigations, an inclined ball impact test setup is constructed. Stainless steel balls of different masses and radii are used to apply repeatable impacts on a vertical cantilever plate. The Ti3C2-MXene sensor is attached to this cantilever plate along with a commercial piezoceramic sensor, and their responses for the structural impacts are compared. It is observed from the experiments that the average response times of the Ti3C2-MXene sensor and piezoceramic sensor are 1.28±0.24μs and 31.19±24.61μs, respectively. The fast response time of the Ti3C2-MXene sensor makes it a promising candidate for monitoring structural impacts.
ABSTRACT
In this paper, we characterize transverse oscillations as either Alfvénic or Landau-type in an incompressible non-ideal magnetohydrodynamic (MHD) fluid. We consider shear viscosity and ...magnetic diffusivity as dissipation mechanisms to derive a general dispersion relation for the incompressible MHD waves. The solutions of this dispersion relation for k as a function of ω – denoting by the source for any value of θ up to which magnetic tension acts as restoring force and dominates over internal friction forces – result in four roots, as follows. Two roots, which have a high phase velocity $c_{\rm A}\cos\theta $ are identified as almost undamped propagating Alfvén waves. The other two roots, which have a phase velocity $(2c_{\rm A}\cos\theta)/(\sqrt{\eta/\nu} + \sqrt{\nu/\eta})$, result in Alfvénic-type disturbances of a much shorter decay length than the wavelength. In contrast, when internal frictional forces start dominating over magnetic tension (i.e. for the propagation perpendicular to the background magnetic field, where the tension in the magnetic field becomes zero), the solutions of the dispersion are akin to Landau-type transverse oscillations. Transverse waves of this type were initially reported by Landau in an ordinary viscous fluid. However, our study corresponds to MHD visco-resistive fluid. The prediction for these lateral propagating transverse waves to be of Landau type may be very useful to explain the heating of observed filamentary structures across the magnetic field on a very small spatial scale in the solar coronal plasma, wherein the heating rate is directly proportional to the operating frequency of the driver, while its damping length is inversely proportional to the square root of the frequency.
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