Optical Profile and Nanostructure Effects in the Charge Carrier Transport and Performance of Photovoltaic Devices

Charge carrier plays a significant role in energy harvesting in photovoltaic devices. Due to recombination, the inadequate charge carrier transport length prevents the devices from achieving efficient absorption by increasing active layer thickness. Fundamental research on the charge transport is important as it is a critical factor to determine the optimal device structures. In this thesis, the charge carrier transport process is studied in photovoltaic devices by linking local characteristic light absorption profiles to photocurrent measurements. Local light absorption profile can be approximated as the free charge generation profile, which determines the average charge transport distance. Together with incident light wavelength, illumination direction effectively controls the generation profile and hence the charge transport distance. And this charge transport distance is demonstrated to relate to recombination that can be measured from photocurrent. Therefore, the charge carrier transport length can be estimated. On the other hand, the potential of the nanostructured solar cells as a key to solve the problem lies between adequate light absorption and efficient charge carrier collection. In this thesis, the discussion focuses on the nanostructured bulk heterojunction (BHJ) organic photovoltaics (OPVs). As photonic crystal nanostructures have been proposed to increase the light trapping effects without increasing the volumes of the active materials, intuitively, it is believed that the nanostructure will affect only the optical absorption. However, in this thesis it is demonstrated that there is a tradeoff between light trapping enhancement and charge carrier collection deterioration due to the nanopatterning effects. Furthermore, the nanopatterning process is shown to affect the material composition in BHJ OPVs as well. Improvement of BHJ OPVs' performance by nanostructures is not a simple task of increasing light absorption. Comprehensive considerations are demonstrated necessary for design of optimal device structures.Doctor of Philosoph

Rumor Detection on Social Media: Datasets, Methods and Opportunities

Social media platforms have been used for information and news gathering, and they are very valuable in many applications. However, they also lead to the spreading of rumors and fake news. Many efforts have been taken to detect and debunk rumors on social media by analyzing their content and social context using machine learning techniques. This paper gives an overview of the recent studies in the rumor detection field. It provides a comprehensive list of datasets used for rumor detection, and reviews the important studies based on what types of information they exploit and the approaches they take. And more importantly, we also present several new directions for future research.Comment: 10 page

Bmi1 Promotes Erythroid Development Through Regulating Ribosome Biogenesis

While Polycomb group protein Bmi1 is important for stem cell maintenance, its role in lineage commitment is largely unknown. We have identified Bmi1 as a novel regulator of erythroid development. Bmi1 is highly expressed in mouse erythroid progenitor cells and its deficiency impairs erythroid differentiation. BMI1 is also important for human erythroid development. Furthermore, we discovered that loss of Bmi1 in erythroid progenitor cells results in decreased transcription of multiple ribosomal protein genes and impaired ribosome biogenesis. Bmi1 deficiency stabilizes p53 protein, leading to upregulation of p21 expression and subsequent G0/G1 cell cycle arrest. Genetic inhibition of p53 activity rescues the erythroid defects seen in the Bmi1 null mice, demonstrating that a p53-dependent mechanism underlies the pathophysiology of the anemia. Mechanistically, Bmi1 is associated with multiple ribosomal protein genes and may positively regulate their expression in erythroid progenitor cells. Thus, Bmi1 promotes erythroid development, at least in part through regulating ribosome biogenesis. Ribosomopathies are human disorders of ribosome dysfunction, including Diamond-Blackfan anemia (DBA) and 5q− syndrome, in which genetic abnormalities cause impaired ribosome biogenesis, resulting in specific clinical phenotypes. We observed that BMI1 expression in human hematopoietic stem and progenitor cells from patients with DBA is correlated with the expression of some ribosomal protein genes, suggesting that BMI1 deficiency may play a pathological role in DBA and other ribosomopathies

Deep Learning-Based Diagnosing Structural Behavior in Dam Safety Monitoring System

Collecting a myriad of prototype data through various types of monitoring sensors plays a virtual important role in many aspects of dam safety such as real-time grasp of safety state, exposure of hidden dangers, and inspection design and construction. However, the current methods of prediction are weak in the long-term sequence of nodes with missing and abnormal error value. Moreover, the limitation caused by the apparatus, environmental factors, and network transmission can lead to the deviation and inconsistency of diagnosis and evaluation of local region. In this paper, we consider the correlation of data on nodes in the entire monitoring network. To avoid the deviation caused by noise and missing value in the single-node data sequence, we calculate the correlation between the multiple sequences. A single-node assessment model based on multiple relevant sequence (SAM) is proposed to improve the accuracy of single node assessment. Given the different nodes of a local region have varying impacts on the evaluation results, a local region evaluation algorithm based on node credibility (LREA) is presented to model the credibility of nodes in order to alleviate inconsistent evaluation results in the local region of dam. LREA can assess the dam’s operation state by considering the variations in credibility and multiple nodes coordination. The experimental results illustrate the LREA can reveal the trends of the monitoring values change in a timely and accurate way, which can elevate the accuracy of evaluation results of dam safety

Circular RNA circZNF652 is overexpressed in osteoarthritis and positively regulates LPS-induced apoptosis of chondrocytes by upregulating PTEN

Circular RNA circZNF652 promotes LPS-induced inflammation, contributing to the development of osteoarthritis (OA), indicating the potential involvement of circZNF652 in OA. This study was carried to explore the involvement of circZNF652 in OA. RT-qPCR was performed to analyse the expression of circZNF652 and PTEN mRNA in synovial fluid samples from 60 OA patients and 60 healthy controls. Correlations between circZNF652 and PTEN mRNA were analysed by Pearson’s correlation coefficient. Overexpression and siRNA silencing of circZNF652 were achieved in chondrocytes, followed by performing RT-qPCR and Western blot to analyse the expression of PTEN. The role of circZNF652 and PTEN in regulating the apoptosis of chondrocytes induced by LPS was analysed by cell apoptosis assay. We found that circZNF652 was overexpressed in OA and positively correlated with PTEN, MMP13, and NF-KB mRNA. In chondrocytes, circZNF652 overexpression increased the expression of PTEN, MMP13, and NF-KB; circZNF652 siRNA silencing decreased the expression of PTEN, MMP13, and NF-KB. Moreover, circZNF652 and PTEN positively regulated the apoptosis of chondrocytes induced by LPS. PTEN overexpression reversed the inhibitory effects of circZNF652 siRNA silencing on cell apoptosis. Therefore, circZNF652 is overexpressed in OA and positively regulates LPS-induced apoptosis of chondrocytes by upregulating PTEN

Extremely low frequency electromagnetic fields promote mesenchymal stem cell migration by increasing intracellular Ca2+ and activating the FAK/Rho GTPases signaling pathways in vitro

Abstract Background The ability of mesenchymal stem cells (MSCs) to migrate to the desired tissues or lesions is crucial for stem cell-based regenerative medicine and tissue engineering. Optimal therapeutics for promoting MSC migration are expected to become an effective means for tissue regeneration. Electromagnetic fields (EMF), as a noninvasive therapy, can cause a lot of biological changes in MSCs. However, whether EMF can promote MSC migration has not yet been reported. Methods We evaluated the effects of EMF on cell migration in human bone marrow-derived MSCs. With the use of Helmholtz coils and an EMF stimulator, 7.5, 15, 30, 50, and 70 Hz/1 mT EMF was generated. Additionally, we employed the l-type calcium channel blocker verapamil and the focal adhesion kinase (FAK) inhibitor PF-573228 to investigate the role of intracellular calcium content, cell adhesion proteins, and the Rho GTPase protein family (RhoA, Rac1, and Cdc42) in EMF-mediated MSC migration. Cell adhesion proteins (FAK, talin, and vinculin) were detected by Western blot analysis. The Rho GTPase protein family activities were assessed by G-LISA, and F-actin levels, which reflect actin cytoskeletal organization, were detected using immunofluorescence. Results All the 7.5, 15, 30, 50, and 70 Hz/1 mT EMF promoted MSC migration. EMF increased MSC migration in an intracellular calcium-dependent manner. Notably, EMF-enhanced migration was mediated by FAK activation, which was critical for the formation of focal contacts, as evidenced by increased talin and vinculin expression. Moreover, RhoA, Rac1, and Cdc42 were activated by FAK to increase cytoskeletal organization, thus promoting cell contraction. Conclusions EMF promoted MSC migration by increasing intracellular calcium and activating the FAK/Rho GTPase signaling pathways. This study provides insights into the mechanisms of MSC migration and will enable the rational design of targeted therapies to improve MSC engraftment

DNA methylation 6 mA and histone methylation involved in multi-/trans-generational reproductive effects in Caenorhabditis elegans induced by Atrazine

Atrazine (ATR), a widely used triazine herbicide, is an environmental endocrine disruptor that can cause health problems. However, whether there are multi/trans-generational reproductive impacts of ATR have not been studied. Therefore, in this study, Caenorhabditis elegans was used as a preferable model organism to identify the multi/trans-generational reproductive toxicity of ATR. Only parental C.elegans (P0) were exposed to different concentrations (0.0004–40 mg/L) for 48 h and the subsequent offspring (F1–F5) were grown under ATR-free conditions and ATR conditions.The results showed that ATR exposure during P0 decreased fecundity, including a reduction in fertilized eggs, oocytes, and ovulation rate, delayed gonadal development, and decreased the relative area of gonad arm and germ cell number. Furthermore, continuous ATR exposure (P0–F5) causes a significant increase in reproductive toxicity in subsequent generations, although no significant toxicity occurred in the P0 generation after exposure to environmental-related concentrations, suggesting that ATR exposure might have cumulative effects. Likewise, parental exposure to ATR caused transgenerational toxicity impairments. Interestingly, only reproductive toxicity, not development toxicity, was transmitted to several generations (F1–F4), and the F2 generation showed the most notable changes. QRT-PCR results showed that genes expression related to DNA methylation 6 mA (damt-1, nmad-1) and histone H3 methylation (mes-4, met-2, set-25, set-2, and utx-1) can also be passed on to offspring. The function of H3K4 and H3K9 methylation were explored by using loss-of-function mutants for set-2, set-25, and met-2. Transmissible reproductive toxicity was absent in met-2(n4256), set-2(ok952), and set-25(n5021) mutants, which suggests that the histone methyltransferases H3K4 and H3K9 activity are indispensable for the transgenerational effect of ATR. Finally, the downstream genes of DNA methylation and histone H3 methylation were determined. ATR upregulated the expression of ZC317.7, hsp-6, and hsp-60. Mitochondrial stress in parental generation dependent transcription 6 mA modifiers may establish these epigenetic marks in progeny

Balance between light trapping and charge carrier collection : electro-photonic optimization of organic photovoltaics with ridge-patterned back electrodes

Light trapping strategies are frequently suggested to improve organic photovoltaic (OPV) cell efficiencies. However, one cannot overlook the side-effects to charge carrier collection which are introduced when seeking optical enhancements. A comprehensive electro-photonic model is utilized to study the optical and electrical effects of patterning poly[[4,8-bis[(2-ethylhexyl)oxy]benzo[1,2-b:4,5-b′]dithiophene-2,6-diyl][3-fluoro-2-[(2-ethylhexyl)carbonyl]thieno[3,4-b]thiophenediyl]] and poly(3-hexylthiophene) based solar cells with simple optical grating structures. It is found that for the most part, optical absorption improvements are attenuated by enhanced electrical losses. Optimized device structures that overcome this tradeoff are proposed and their detailed electro-optical characteristics are discussed. When the hole mobility is smaller than the electron mobility, the results suggest that in general, an inverted structure has a better chance to outperform a flat active layer than a conventional architecture in an OPV cell with the ridge-patterned back electrode