Group theory is a powerful tool to explore fundamental symmetry constraints for the physical properties of crystal structures,
e.g.
it is well-known that only a few components of the elastic ...constants are independent due to the symmetry constraint. This work further applies group theory to derive constraint relationships for high-order elastic constants with respect to the orientation angle, where the constraint relationships are more explicit than the traditional tensor transformation law. These analytic symmetry constraints are adopted to explain the molecular dynamics simulation results, which disclose that the high-order elastic constants are highly anisotropic with an anisotropy percentage of up to 25% for the hexagonal boron nitride monolayer. The elastic constant is a basic quantity in the mechanics field, so its high anisotropy shall cause strong anisotropy for other mechanical properties. Based on the anisotropic high-order elastic constants, we demonstrate that Poisson's ratio is highly anisotropic for the hexagonal boron nitride at large strains. These findings provide fundamental insights into the symmetry dependence of high-order elastic constants and other mechanical properties.
Group theory was utilized to study the orientation dependence of high-order elastic constants of h-BN, and the anisotropic effects induced by nonlinear Poisson phenomena using anisotropic elastic constants were investigated.
The MYC oncogene is overexpressed in hepatocellular carcinoma (HCC) and has been associated with widespread microRNA (miRNA) repression; however, the underlying mechanisms are largely unknown. Here, ...we report that the c‐Myc oncogenic transcription factor physically interacts with enhancer of zeste homolog 2 (EZH2), a core enzymatic unit of polycomb repressive complex 2 (PRC2). Furthermore, miR‐101, an important tumor‐suppressive miRNA in human hepatocarcinomas, is epigenetically repressed by PRC2 complex in a c‐Myc‐mediated manner. miR‐101, in turn, inhibits the expression of two subunits of PRC2 (EZH2 and EED), thus creating a double‐negative feedback loop that regulates the process of hepatocarcinogenesis. Restoration of miR‐101 expression suppresses multiple malignant phenotypes of HCC cells by coordinate repression of a cohort of oncogenes, including STMN1, JUNB, and CXCR7, and further increases expression of endogenous miR‐101 by inhibition of PRC2 activation. In addition, co‐overexpression of c‐Myc and EZH2 in HCC samples was closely associated with lower expression of miR‐101 (P < 0.0001) and poorer prognosis of HCC patients (P < 0.01). Conclusions: c‐Myc collaborates with EZH2‐containing PRC2 complex in silencing tumor‐suppressive miRNAs during hepatocarcinogenesis and provides promising therapeutic candidates for human HCC. (Hepatology 2014;59:1850–1863)
Cryopreservation induces transcriptomic and epigenetic modifications that strongly impairs sperm quality and function, and thus decrease reproductive performance. N.sup.6-methyladenosine (m.sup.6A) ...RNA methylation varies in response to stress and has been implicated in multiple important biological processes, including post-transcriptional fate of mRNA, metabolism, and apoptosis. This study aimed to explore whether cryopreservation induces m.sup.6A modification of mRNAs associated with sperm energy metabolism, cryoinjuries, and freezability. The mRNA and protein expression of m.sup.6A modification enzymes were significantly dysregulated in sperm after cryopreservation. Furthermore, m.sup.6A peaks were mainly enriched in coding regions and near stop codons with classical RRACH motifs. The mRNAs containing highly methylated m.sup.6A peaks (fts vs. fs) were significantly associated with metabolism and gene expression, while the genes with less methylated m.sup.6A peaks were primarily involved in processes regulating RNA metabolism and transcription. Furthermore, the joint analysis of DMMGs and differentially expressed genes indicated that both of these play a vital role in sperm energy metabolism and apoptosis. Our study is the first to reveal the dynamic m.sup.6A modification of mRNAs in boar sperm during cryopreservation. These epigenetic modifications may affect mRNA expression and are closely related to sperm motility, apoptosis, and metabolism, which will provide novel insights into understanding of the cryoinjuries or freezability of boar sperm during cryopreservation.
AbstractThe method of characteristics (MOC) with the limitation of Courant’s stability condition is widely used in simulation of unsteady flow in a pipeline. However, the relatively complex method of ...implicit (MOI) provides the advantages of unconditional convergence and mutual independence between time and space mesh parameters. This study combines the MOC and MOI to simulate pipeline unsteady flow and hydropower transient processes. The boundary conditions for the coupled method are introduced and validated by simulating the water hammer in uniform and variable area duct, and the water-level fluctuation in a surge tank. Subsequently, the coupled methods are applied to study the transient processes in two hydropower stations: one is to determine the water-level fluctuation in the surge tank and investigate the effect of water inertia in the connecting pipe on the water hammer pressure, and the other is to determine the solution for the water hammer in a variable-area draft in a pump turbine system by comparing the results with actual measurements. The results show that the coupled method is effective in simulating water hammer in pipelines and transient processes of hydropower system.
This paper presents the simulation and the analysis of the transient process of a Francis turbine during the load rejection by employing a one-dimensional and three-dimensional (1-D-3-D) coupling ...approach. The coupling is realized by partly overlapping the 1-D and 3-D parts, the water hammer wave is modeled by defining the pressure dependent density, and the guide vane closure is treated by a dynamic mesh method. To verify the results of the coupling approach, the transient parameters for both typical models and a real power station are compared with the data obtained by the 1-D approach, and good agreements are found. To investigate the differences between the transient and steady states at the corresponding operating parameters, the flow characteristics inside a turbine of the real power station are simulated by both transient and steady methods, and the results are analyzed in details. Our analysis suggests that there are just a little differences in the turbine outer characteristics, thus the traditional 1-D method is in general acceptable. However, the flow patterns in the spiral casing, the draft tube, and the runner passages are quite different: the transient situation has obvious water hammer waves, the water inertia, and some other effects. These may be crucial for the draft tube pulsation and need further studies.
Post-thawed sperm quality parameters vary across different species after cryopreservation. To date, the molecular mechanism of sperm cryoinjury, freeze-tolerance and other influential factors are ...largely unknown. In this study, significantly dysregulated microRNAs (miRNAs) and mRNAs in boar and giant panda sperm with different cryo-resistance capacity were evaluated. From the result of miRNA profile of fresh and frozen-thawed giant panda sperm, a total of 899 mature, novel miRNAs were identified, and 284 miRNAs were found to be significantly dysregulated (195 up-regulated and 89 down-regulated). Combined analysis of miRNA profiling of giant panda sperm and our previously published data on boar sperm, 46, 21 and 4 differentially expressed (DE) mRNAs in boar sperm were believed to be related to apoptosis, glycolysis and oxidative phosphorylation, respectively. Meanwhile, 87, 17 and 7 DE mRNAs in giant panda were associated with apoptosis, glycolysis and oxidative phosphorylation, respectively. Gene ontology (GO) analysis of the targets of DE miRNAs showed that they were mainly distributed on membrane related pathway in giant panda sperm, while cell components and cell processes were tied to the targets of DE miRNAs in boar sperm. Finally, Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis of DE mRNAs indicated that most of these DE mRNAs were distributed in membrane signal transduction-related pathways in giant panda sperm, while those in boar sperm were mainly distributed in the cytokine-cytokine receptor interaction pathway and inflammatory related pathways. In conclusion, although the different freezing extenders and programs were used, the DE miRNAs and mRNAs involved in apoptosis, energy metabolism, olfactory transduction pathway, inflammatory response and cytokine-cytokine interactions, could be the possible molecular mechanism of sperm cryoinjury and freeze tolerance.
Background
Currently, amrubicin is used as first‐line in the treatment of patients with small‐cell lung cancer (SCLC). However, the effect of amrubicin‐based treatment in extensive‐disease (ED) SCLC ...remains controversial. Thus, we conducted a meta‐analysis of randomized controlled trials (RCTs) to assess the efficacy and safety of amrubicin‐based regimen in the treatment of patients with ED‐SCLC.
Methods
RCTs published in PubMed, Web of Science, Embase, and ClinicalTrials.gov were systematically reviewed. Eligible studies were these that evaluated the efficacy and safety profiles of amrubicin‐based regimen in ED‐SCLC. Outcomes included progression‐free survival (PFS), overall survival (OS), overall response rate (ORR), and adverse events. Results were expressed with hazard ratio (HR) with 95% confidence intervals (CIs), and risk ratio (RR) with 95% CIs.
Results
Four RCTs involving a total of 740 patients met the inclusion criteria and were included in this meta‐analysis. Amrubicin‐based regimen was not associated with significantly prolonged PFS (HR = 1.07, 95% CI: 0.90–1.30; P = 0.463) and OS (HR = 1.07, 95% CI: 0.89–1.29; P = 0.443) in patients with ED‐SCLC. However, it significantly improved ORR (RR = 1.14, 95% CI: 1.04–1.25; P = 0.008). Subgroup analysis demonstrated that neither amrubicin alone nor in combination with cisplatin prolonged the PFS and OS, and only the combination therapy significantly increased ORR. The incidence of grade ≥3 adverse events was comparable between amrubicin‐containing and other treatment groups (RR = 1.42, 95% CI: 0.78–2.58; P = 0.248). However, amrubicin‐based treatment induced a significantly higher incidence of febrile neutropenia (RR = 3.32, 95% CI: 2.04–5.41; P < 0.001), anemia (RR = 1.44, 95% CI: 1.06–1.97; P = 0.022), leukopenia (RR = 2.17, 95% CI: 1.41–3.33; P < 0.001), neutropenia (RR = 1.33, 95% CI: 1.04–1.70; P = 0.021), and interstitial lung disease (RR = 1.58, 95% CI: 1.21–1.98; P < 0.001).
Conclusion
Amrubicin‐based regimen used as first‐line had no survival benefits in patients with ED‐SCLC. But it significantly improved ORR. Further well‐conducted, large‐scale trials are needed to validate these findings.
To fully understand the evolution of flow structures and pressure fluctuations in the S-shaped region of pump-turbines, three dimensional (3D) numerical simulations were carried out for a model ...pump-turbine at four different guide-vane openings (GVOs). We found that special backflow vortex structures (BFVSs) form around the runner inlet. The backflow location shifts from the hub side to the shroud side and then to the midspan, as the operating point moves from the best efficiency point to the zero discharge point along the S-shaped characteristic curve. At large GVO, if the discharge is relatively large, the flow separations at the runner inlet are primarily driven by the local adverse pressure gradient, resulting in hub and shroud side backflows. At small GVO or small discharge, the separations are mainly dominated by the centrifugal force, resulting in backflow at the guide-vane midspan section. The locally distributed BFVSs enhance the local rotor-stator interaction (RSI) in the vaneless space, leading to different pressure fluctuating intensities along the spanwise direction for high frequency components. On the other hand, the rotating stall is the main cause of the uneven distributions of low frequency pressure fluctuations along the vaneless space between runner and guide-vanes.
In this article, the three-dimensional unsteady multiphase flow is simulated in the whole passage of Francis hydraulic turbine. The pressure pulsation is predicted and compared with experimental data ...at positions in the draft tube, in front of runner, guide vanes and at the inlet of the spiral case. The relationship between pressure pulsation in the whole passage and air admission is analyzed. The computational results show: air admission from spindle hole decreases the pressure difference in the horizontal section of draft tube, which in turn decreases the amplitude of low-frequency pressure pulsation in the draft tube; the rotor-stator interaction between the air inlet and the runner increases the blade-frequency pressure pulsation in front of the runner.
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