Conquer the fine structure splitting of excitons in self-assembled InAs/GaAs quantum dots via combined stresses

Eliminating the fine structure splitting (FSS) of excitons in self-assembled quantum dots (QDs) is essential to the generation of high quality entangled photon pairs. It has been shown that the FSS has a lower bound under uniaxial stress. In this letter, we show that the FSS of excitons in a general self-assembled InGaAs/GaAs QD can be fully suppressed via combined stresses along the [110] and [010] directions. The result is confirmed by atomic empirical pseudopotential calculations. For all the QDs we studied, the FSS can be tuned to be vanishingly small ($<$ 0.1 $\mu$eV), which is sufficient small for high quality entangled photon emission.Comment: 4 pages, 3 figure, 1 tabl

Dynamic analysis of offshore wind turbine blades under the action of wind shear and fluctuating wind

Aiming at large-scale offshore wind turbine blades, governing equations in fluid domain and motion equations in structural domain with geometric nonlinearity were built by the aid of ALE method. A three dimensional model under fluid-structure interaction (FSI) was established by using UG software and Geometry module, and numerical calculation for FSI vibration characteristics of wind turbine blades under the effects of wind shear and fluctuating wind was carried out based on ANSYS Workbench. The results indicate that the contribution of the combined action to displacement and Mises stress chiefly derives from the wind shear effect, which not only causes a comparatively larger increase for the maximum displacement and Mises stress, but also becomes bigger and bigger with the increase of average wind speed, and the fluctuating wind effect is insignificant. The maximum value of Mises stress in the blade section appears at the relative wingspan of 0.55, the maximum Mises stress varying with relative span length decreases progressively from the middle to both sides of the blade, and the contribution of wind shear effect alone, the combined action or wind speed increment to stress also shows the same change rule. Furthermore, in the maximum stress section along wingspan, Mises stress along the direction of blade thickness or chord length respectively presents two distribution laws, and reaches the maximum on the blade surface

Influences of wind and rotating speed on the fluid-structure interaction vibration for the offshore wind turbine blade

For the 5MW offshore wind turbine blade, the control and discrete equations of the fluid domain and structural domain were established respectively, and the calculation formulas of blade loads and damping coefficient were given. Furthermore, the blade entity modeling was completed by using UG and ANSYS Workbench. Based on it, the numerical calculation of blade vibration characteristics under different wind and rotating speeds was carried out, and the reliability verification was conducted by the wind tunnel test. The results of calculation indicate that the numerical results of the first principal stresses at the blade surface along the span-wise direction are consistent with the results of wind tunnel test, which verifies the reliability of the theory and numerical models. Both the influences of the bidirectional fluid-structure interaction (BFSI) and the rotation effect on the characteristics of blade vibration should be underlined. The increase of wind or rotating speed results in the nonlinear increase of the maximum span-wise displacement of the blade and of the Mises-stresses. Under different wind or rotating speed, the blade’s maximum displacement occurs at its tip, its maximum Mises-stresses appear at the relative wingspan of 0.55, and the contribution of rotating speed and average wind speed to the displacement or Mises-stress along the span-wise direction is similar

Temperature Dependent Empirical Pseudopotential Theory For Self-Assembled Quantum Dots

We develop a temperature dependent empirical pseudopotential theory to study the electronic and optical properties of self-assembled quantum dots (QDs) at finite temperature. The theory takes the effects of both lattice expansion and lattice vibration into account. We apply the theory to the InAs/GaAs QDs. For the unstrained InAs/GaAs heterostructure, the conduction band offset increases whereas the valence band offset decreases with increasing of the temperature, and there is a type-I to type-II transition at approximately 135 K. Yet, for InAs/GaAs QDs, the holes are still localized in the QDs even at room temperature, because the large lattice mismatch between InAs and GaAs greatly enhances the valence band offset. The single particle energy levels in the QDs show strong temperature dependence due to the change of confinement potentials. Because of the changes of the band offsets, the electron wave functions confined in QDs increase by about 1 - 5%, whereas the hole wave functions decrease by about 30 - 40% when the temperature increases from 0 to 300 K. The calculated recombination energies of exciton, biexciton and charged excitons show red shifts with increasing of the temperature, which are in excellent agreement with available experimental data

Identification of potential key genes associated with termination phase of rat liver regeneration through microarray analysis

Background and objective: Liver regeneration (LR) is a complex process influenced by various genes and pathways, the majority of the of research on LR focus on the initiation and proliferation phase while studies on termination phase is lacking. We aimed to identify potential genes and reveal the underlying the molecular mechanisms involved in the precise regulation of liver size during the termination phase of LR. Materials and methods: We obtained the rat liver tissue gene datasets (GSE63742) collected following partial hepatectomy (PH) from the Gene Expression Omnibus (GEO) of the National Center for Biotechnology Information (NCBI), from which, this study screened the late stage LR samples (7 days post-PH) using the R/Bioconductor packages for the identification of differentially expressed genes (DEGs). Afterwards, we performed enrichment analysis using the database for annotation visualization and integrated discovery (DAVID) online tool. Moreover, the Search Tool for the Retrieval of Interacting proteins (STRING) database was employed to construct protein-protein interaction (PPI) networks based on those identified DEGs; the PPI network was then used by Cytoscape software to predict hub genes and nodes. Animal experimentation (Rat PH model) was performed to acquire liver tissues which were then used for western blot analysis to verify our results. Results: The present study identified together 74 significant DEGs, among which, 51 showed up-regulation while 23 presented as down-regulated. As revealed by KEGG pathway enrichment analysis, DEGs were mostly related to pathways such as retinol metabolism, steroid hormone synthesis, transforming growth factor-β (TGF-β) and mitogen-activated protein kinase (MAPK) signaling. In addition, as suggested by GO enrichment analysis, DEGs were mostly related to the cyclooxygenase P450 pathway, negative regulation of Notch signaling pathway, aromatase activity, steroid hydroxylase activity, exosomes, and extracellular domain. Analyses based on STRING database and Cytoscape software identified genes like Ste2 and Btg2 as the hub genes in the termination stage LR. The obtained results were confirmed by Western blot analysis. Conclusions: Taken together, the microarray analysis in this study suggests that DEGs such as Ste2 and Btg2 are the hub genes, which are associated with the regulation of termination stage LR, while the molecular mechanisms are possibly related to the MAPK and TGF-β signal transduction pathways

Evaluation of high mobility group box 1 protein as a presurgical diagnostic marker reflecting the severity of acute appendicitis.

RIGHTS : This article is licensed under the BioMed Central licence at http://www.biomedcentral.com/about/license which is similar to the 'Creative Commons Attribution Licence'. In brief you may : copy, distribute, and display the work; make derivative works; or make commercial use of the work - under the following conditions: the original author must be given credit; for any reuse or distribution, it must be made clear to others what the license terms of this work are.OBJECTIVES: To validate the role of high mobility group box-1(HMGB1) in diagnosis of acute appendicitis (AA) with different pathological severity. METHODS: According to the pathologically diagnosis, 150 patients underwent appendectomies between Jan. 2007 and Dec, 2010 were divided into acute simple, acute suppurative and acute gangrenous appendicitis as group 1, 2 and 3, respectively. Each patient group contains 50 sex and age matched cases to make comparison with 50 healthy volunteers. The mRNA and protein expression levels of serum HMGB1 were determined by real-time quantitative PCR and enzyme linked immunosorbent assay (ELISA). Serum High-sensitivity C-reactive protein (hs-CRP) levels were determined by rate nephelometric immunoassay. RESULTS: In comparison with health volunteers, relative HMGB1 mRNA levels in group 1, 2 and 3 were significantly increased 3.05 ± 0.51,8.33 ± 0.75 and 13.74 ± 1.09 folds, reflecting a tendency of augmented severity. In accordance, serum protein levels of HMGB1 were 10.97 ± 1.64, 14.42 ± 1.56 and 18.08 ± 2.41 ng/ml in 3 patient groups, which are significantly higher than that of healthy volunteers' 5.47 ± 0.73 ng/ml. hs-CRP levels were 12.85 ± 3.41, 21.04 ± 1.98 and 31.07 ± 5.46 ng/ml in 3 patients groups compared with 2.06 ± 0.77 ng/ml in controls. The concentrations of HMGB1 and hs-CRP were both positively correlated with disease severity. CONCLUSION: Serum HMGB1 constitutes as a valuable marker in diagnosis of AA. Positively correlated with hs-CRP level, mRNA and protein expression of HMGB1 to a certain extent reflected the severity of AA

Ultrasound-targeted microbubble destruction mediated herpes simplex virus-thymidine kinase gene treats hepatoma in mice

<p>Abstract</p> <p>Objective</p> <p>The purpose of the study was to explore the anti-tumor effect of ultrasound -targeted microbubble destruction mediated herpes simplex virus thymidine kinase (HSV-TK) suicide gene system on mice hepatoma.</p> <p>Methods</p> <p>Forty mice were randomly divided into four groups after the models of subcutaneous transplantation tumors were estabilished: (1) PBS; (2) HSV-TK (3) HSV-TK+ ultrasound (HSV-TK+US); (4) HSV-TK+ultrasound+microbubbles (HSV-TK+US+MB). The TK protein expression in liver cancer was detected by western-blot. Applying TUNEL staining detected tumor cell apoptosis. At last, the inhibition rates and survival time of the animals were compared among all groups.</p> <p>Results</p> <p>The TK protein expression of HSV-TK+MB+US group in tumor-bearing mice tissues were significantly higher than those in other groups. The tumor inhibitory effect of ultrasound-targeted microbubble destruction mediated HSV-TK on mice transplantable tumor was significantly higher than those in other groups (p < 0.05), and can significantly improve the survival time of tumor-bearing mice.</p> <p>Conclusion</p> <p>Ultrasound-targeted microbubble destruction can effectively transfect HSV-TK gene into target tissues and play a significant inhibition effect on tumors, which provides a new strategy for gene therapy in liver cancer.</p

Competition between DNA Methylation, Nucleotide Synthesis, and Antioxidation in Cancer versus Normal Tissues

Global DNA hypomethylation occurs in many cancer types, but there is no explanation for its differential occurrence or possible impact on cancer cell physiology. Here we address these issues with a computational study of genome-scale DNA methylation in 16 cancer types. Specifically, we identified (i) a possible determinant for global DNA methylation in cancer cells and (ii) a relationship between levels of DNA methylation, nucleotide synthesis, and intracellular oxidative stress in cells. We developed a system of kinetic equations to capture the metabolic relations among DNA methylation, nucleotide synthesis, and antioxidative stress response, including their competitions for methyl and sulfur groups, based on known information about one-carbon metabolism and trans-sulfuration pathways. We observed a kinetic-based regulatory mechanism that controls reaction rates of the three competing processes when their shared resources are limited, particularly when the nucleotide synthesis rates or oxidative states are high. The combination of this regulatory mechanism and the need for rapid nucleotide synthesis, as well as high production of glutathione dictated by cancer-driving forces, led to the nearly universal observations of reduced global DNA methylation in cancer. Our model provides a natural explanation for differential global DNA methylation levels across cancer types and supports the observation that more malignant cancers tend to exhibit reduced DNA methylation levels. Insights obtained from this work provide useful information about the complexities of cancer due to interplays among competing, dynamic biological processes