Error Analysis of a Fully Discrete Projection Method for Magnetohydrodynamic System

In this paper, we develop and analyze a finite element projection method for magnetohydrodynamics equations in Lipschitz domain. A fully discrete scheme based on Euler semi-implicit method is proposed, in which continuous elements are used to approximate the Navier–Stokes equations and H(curl) conforming Nédélec edge elements are used to approximate the magnetic equation. One key point of the projection method is to be compatible with two different spaces for calculating velocity, which leads one to obtain the pressure by solving a Poisson equation. The results show that the proposed projection scheme meets a discrete energy stability. In addition, with the help of a proper regularity hypothesis for the exact solution, this paper provides a rigorous optimal error analysis of velocity, pressure and magnetic induction. Finally, several numerical examples are performed to demonstrate both accuracy and efficiency of our proposed scheme

PSR J1926-0652: A Pulsar with Interesting Emission Properties Discovered at FAST

We describe PSR J1926-0652, a pulsar recently discovered with the Five-hundred-meter Aperture Spherical radio Telescope (FAST). Using sensitive single-pulse detections from FAST and long-term timing observations from the Parkes 64-m radio telescope, we probed phenomena on both long and short time scales. The FAST observations covered a wide frequency range from 270 to 800 MHz, enabling individual pulses to be studied in detail. The pulsar exhibits at least four profile components, short-term nulling lasting from 4 to 450 pulses, complex subpulse drifting behaviours and intermittency on scales of tens of minutes. While the average band spacing P3 is relatively constant across different bursts and components, significant variations in the separation of adjacent bands are seen, especially near the beginning and end of a burst. Band shapes and slopes are quite variable, especially for the trailing components and for the shorter bursts. We show that for each burst the last detectable pulse prior to emission ceasing has different properties compared to other pulses. These complexities pose challenges for the classic carousel-type models.Comment: 13pages with 12 figure

Convergence analysis of a fully discrete finite element method for thermally coupled incompressible MHD problems with temperature-dependent coefficients

In this paper, we study a fully discrete finite element scheme of thermally coupled incompressible magnetohydrodynamic with temperature-dependent coefficients in Lipschitz domain. The variable coefficients in the MHD system and possible nonconvex domain may cause nonsmooth solutions. We propose a fully discrete Euler semi-implicit scheme with the magnetic equation approximated by Nédélec edge elements to capture the physical solutions. The fully discrete scheme only needs to solve one linear system at each time step and is unconditionally stable. Utilizing the stability of the numerical scheme and the compactness method, the existence of weak solution to the thermally coupled MHD model in three dimensions is established. Furthermore, the uniqueness of weak solution and the convergence of the proposed numerical method are also rigorously derived. Under the hypothesis of a low regularity for the exact solution, we rigorously establish the error estimates for the velocity, temperature and magnetic induction unconditionally in the sense that the time step is independent of the spacial mesh size

A Mixed Finite Element Method for Stationary Magneto-Heat Coupling System with Variable Coefficients

In this article, a mixed finite element method for thermally coupled, stationary incompressible MHD problems with physical parameters dependent on temperature in the Lipschitz domain is considered. Due to the variable coefficients of the MHD model, the nonlinearity of the system is increased. A stationary discrete scheme based on the coefficients dependent temperature is proposed, in which the magnetic equation is approximated by Nédélec edge elements, and the thermal and Navier–Stokes equations are approximated by the mixed finite elements. We rigorously establish the optimal error estimates for velocity, pressure, temperature, magnetic induction and Lagrange multiplier with the hypothesis of a low regularity for the exact solution. Finally, a numerical experiment is provided to illustrate the performance and convergence rates of our numerical scheme

UAVs as remote sensing platforms in plant ecology: Review of applications and challenges

Aims: Unmanned aerial vehicles (UAVs), i.e. drones, have recently emerged as cost-effective and flexible tools for acquiring remote sensing data with fine spatial and temporal resolution. It provides a new method and opportunity for plant ecologists to study issues from individual to regional scales. However, as a new method, UAVs remote sensing applications in plant ecology are still challenged. The needs of plant ecology research and the application development of UAVs remote sensing should be better integrated. Methods: This report provides a comprehensive review of UAV-based remote sensing applications in plant ecology to synthesize prospects of applying drones to advance plant ecology research. Important Findings: Of the 400 references, 59% were published in remote sensing journals rather than in plant ecology journals, reflecting a substantial gap between the interests of remote sensing experts and plant ecologists. Most of the studies focused on UAV remote sensing\u27s technical aspects, such as data processing and remote sensing inversion, with little attention on answering ecological questions. There were 61% of studies involved community-scale research. RGB and multispectral cameras were the most used sensors (75%). More ecologically meaningful parameters can be extracted from UAV data to better understand the canopy surface irregularity and community heterogeneity, identify geometrical characteristics of canopy gaps and construct canopy chemical assemblies from living vegetation volumes. More cooperation between plant ecologists and remote sensing experts is needed to promote UAV remote sensing in advancing plant ecology research

In Vitro and in Vivo Anticancer Activity of Aconitine on Melanoma Cell Line B16

The anti-tumor effect of aconitine in melanoma cell line B16 has been studied in this paper. We found that B16 cells showed significantly reduced growth rates and increased apoptotic effects in the presence of aconitine. Furthermore, aconitine inhibited the PI3K/AKT and MAPK/ERK1/2 signaling pathways, thus regulating the levels of protein and mRNA of PCNA and apoptotic related signaling molecules. Above all, we found that aconitine showed an anti-melanoma effect in suppressing tumor growth in vivo. In conclusion, we show that aconitine may be a useful anticancer drug in the future

Myc-Associated Zinc Finger Protein Promotes Metastasis of Papillary Thyroid Cancer

Background: Myc-associated zinc finger protein (MAZ) plays a role in cancer progression and metastasis. However, the role and underlying molecular mechanism of MAZ in thyroid cancer have not yet been fully elucidated. This study aimed to explore the clinical significance of MAZ in thyroid cancer tissues, and clarify its mechanism in the occurrence and development of thyroid cancer. Methods: The expression level of MAZ protein in thyroid cancer tissues was detected by bioinformatics analysis and immunohistochemistry (IHC). The relationship between the expression level of MAZ and clinicopathological characteristics of thyroid cancer patients was analyzed by multivariate logistic regression analysis. Quantitative reverse-transcription polymerase chain reaction (RT-qPCR) was used to detect the mRNA expression level of MAZ in thyroid cancer cell lines. After MAZ knockdown cell lines were constructed, wound healing and Transwell assays were used to detect the migratory and invasive abilities of cancer cells. Results: The results of IHC showed that the expression level of MAZ protein in thyroid cancer tissues was higher than that in normal adjacent thyroid tissues (p < 0.05), which was consistent with the high expression level of MAZ in thyroid cancer tissues found in The Cancer Genome Atlas (TCGA) database. The results of multivariate logistic regression analysis indicated that the expression level of MAZ was correlated with tumor diameter and tumor capsule of thyroid cancer patients. Moreover, patients with the high MAZ expression level had shorter overall and disease-free survival compared with thyroid cancer patients with the low MAZ expression level (p < 0.05). Further cell function assays indicated that downregulation of MAZ expression level could inhibit the migration and invasion of thyroid cancer cell lines. Moreover, the expression level of epithelial-mesenchymal transition (EMT)-related factor fibronectin 1 (FN1) was obtained from the RNA-seq of MAZ knockdown in thyroid cancer cells. RT-qPCR confirmed that the expression level of FN1 was elevated in MAZ knockdown cell lines (p < 0.05). Bioinformatics analysis indicated that the expression level of FN1 was upregulated in thyroid cancer tissues and had a negative relationship with the expression level of MAZ, as evidenced by correlation analysis. Conclusions: A high expression level of MAZ in thyroid cancer tissues was associated with a poor prognosis of patients. MAZ could affect the progression of thyroid cancer by inducing the EMT process