477 research outputs found
Implementation and application of adaptive mesh refinement for thermochemical mantle convection studies
Numerical modeling of mantle convection is challenging. Owing to the multiscale nature of mantle
dynamics, high resolution is often required in localized regions, with coarser resolution being sufficient
elsewhere. When investigating thermochemical mantle convection, high resolution is required to resolve
sharp and often discontinuous boundaries between distinct chemical components. In this paper, we present
a 2-D finite element code with adaptive mesh refinement techniques for simulating compressible thermochemical
mantle convection. By comparing model predictions with a range of analytical and previously
published benchmark solutions, we demonstrate the accuracy of our code. By refining and coarsening
the mesh according to certain criteria and dynamically adjusting the number of particles in each element,
our code can simulate such problems efficiently, dramatically reducing the computational requirements
(in terms of memory and CPU time) when compared to a fixed, uniform mesh simulation. The resolving
capabilities of the technique are further highlighted by examining plume‐induced entrainment in a thermochemical
mantle convection simulation
On the location of plumes and lateral movement of thermochemical structures with high bulk modulus in the 3-D compressible mantle
The two large low shear velocity provinces (LLSVPs) at the base of the lower mantle are prominent features in all shear wave tomography models. Various lines of evidence suggest that the LLSVPs are thermochemical and are stable on the order of hundreds of million years. Hot spots and large igneous province eruption sites tend to cluster around the edges of LLSVPs. With 3-D global spherical dynamic models, we investigate the location of plumes and lateral movement of chemical structures, which are composed of dense, high bulk modulus material. With reasonable values of bulk modulus and density anomalies, we find that the anomalous material forms dome-like structures with steep edges, which can survive for billions of years before being entrained. We find that more plumes occur near the edges, rather than on top, of the chemical domes. Moreover, plumes near the edges of domes have higher temperatures than those atop the domes. We find that the location of the downwelling region (subduction) controls the direction and speed of the lateral movement of domes. Domes tend to move away from subduction zones. The domes could remain relatively stationary when distant from subduction but would migrate rapidly when a new subduction zone initiates above. Generally, we find that a segment of a dome edge can be stationary for 200 million years, while other segments have rapid lateral movement. In the presence of time-dependent subduction, the computations suggest that maintaining the lateral fixity of the LLSVPs at the core-mantle boundary for longer than hundreds of million years is a challenge
The effect of conditional EFNB1 deletion in the T cell compartment on T cell development and function
<p>Abstract</p> <p>Background</p> <p>Eph kinases are the largest family of cell surface receptor tyrosine kinases. The ligands of Ephs, ephrins (EFNs), are also cell surface molecules. Ephs interact with EFNs transmitting signals in both directions, i.e., from Ephs to EFNs and from EFNs to Ephs. EFNB1 is known to be able to co-stimulate T cells <it>in vitro </it>and to modulate thymocyte development in a model of foetal thymus organ culture. To further understand the role of EFNB1 in T cell immunity, we generated T-cell-specific EFNB1 gene knockout mice to assess T cell development and function in these mice.</p> <p>Results</p> <p>The mice were of normal size and cellularity in the thymus and spleen and had normal T cell subpopulations in these organs. The bone marrow progenitors from KO mice and WT control mice repopulated host spleen T cell pool to similar extents. The activation and proliferation of KO T cells was comparable to that of control mice. Naïve KO CD4 cells showed an ability to differentiate into Th1, Th2, Th17 and Treg cells similar to control CD4 cells.</p> <p>Conclusions</p> <p>Our results suggest that the function of EFNB1 in the T cell compartment could be compensated by other members of the EFN family, and that such redundancy safeguards the pivotal roles of EFNB1 in T cell development and function.</p
A Full Quantum Eigensolver for Quantum Chemistry Simulations
Quantum simulation of quantum chemistry is one of the most compelling
applications of quantum computing. It is of particular importance in areas
ranging from materials science, biochemistry and condensed matter physics.
Here, we propose a full quantum eigensolver (FQE) algorithm to calculate the
molecular ground energies and electronic structures using quantum gradient
descent. Compared to existing classical-quantum hybrid methods such as
variational quantum eigensolver (VQE), our method removes the classical
optimizer and performs all the calculations on a quantum computer with faster
convergence. The gradient descent iteration depth has a favorable complexity
that is logarithmically dependent on the system size and inverse of the
precision. Moreover, the FQE can be further simplified by exploiting
perturbation theory for the calculations of intermediate matrix elements, and
obtain results with a precision that satisfies the requirement of chemistry
application. The full quantum eigensolver can be implemented on a near-term
quantum computer. With the rapid development of quantum computing hardware, FQE
provides an efficient and powerful tool to solve quantum chemistry problems
(R)-(−)-N-Isovalerylcamphorsultam
The title compound, C15H25NO3S, was prepared from (R)-(−)camphorsultam and isovaleryl chloride. The asymetric unit contains two independent molecules with slightly different conformations. In the crystal, weak intermolecular C—H⋯O hydrogen bonds link molecules into two independent hydrogen-bonded chains propagating along the a and b axes
Harmony in Confucian thought and building a community of shared future for mankind
A community of shared future for mankind (CSFM) is a new type of international system of win-win cooperation, the essence of which is to advocate for the creation of a harmonious human society. This political concept has many views coming from traditional Confucian thought, especially Confucian ideals of harmony. Interpreting CSFM from the perspective of harmony in Confucian thought can improve understandings of community and accordingly enhance its construction
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