Experimental Characterization and Biological Assessments of Polymeric Mesh Implants

In use since the 1960s, polypropylene (PP) biomaterials are common in commercially available hernia meshes due to their high tensile strength, good flexibility, and chemical resistance. The in vivo environment is highly variable, exposing mesh implants to oxidizing species and mechanical strains caused by normal healing, tissue integration, and the immediate and chronic inflammatory responses. As a result, changes in mesh implant materials can occur in vivo, including morphological changes, chemical changes and mechanical changes. The broad objective of this dissertation was to explore mechanisms of material changes in polymeric mesh implants after in vivo exposure using experimental characterization and biological assessments. Biological assessments included mesh implants retrieved from patients after hernia repair surgery (mesh explants) to explore potential degradation mechanisms, specifically the impact of clinical characteristics for triggering material changes in pore size, surface chemistry, crystallinity and stiffness consistent with PP degradation. Development of an automated photogrammetric pore size and pore pattern recognition technique provided quantitative measurements of mesh pore size reduction and mesh contraction in mesh explants. Mesh class (pore size) was a factor affecting material changes in normalized crystallinity and reduced stiffness was observed in mesh explants from patients with infection. Experimental characterization included two studies. In vitro simulated PP mesh degradation explored specific mechanisms that potentially contributed to PP material changes. The synergistic effect of reactive oxygen species (ROS) associated with chronic inflammation/infection and mechanical strains on PP mesh degradation was experimentally simulated. PP mesh degradation was observed in simulated ROS solutions made of 1.63M hydrogen peroxide (H2O2)/ 0.05M cobalt chloride (CoCl2), but the synergistic effect was not observed in the same simulated ROS solutions with applied low mechanical strains. A second experimental characterization involved surface modification of polymeric mesh implants for improved hernia mesh fixation with a hydrogel adhesive, called a “bio-adhesive mesh fixation system”. The “bio-adhesive mesh fixation system” combined two patented technologies of poly-glycidyl methacrylate/human serum albumin (PGMA/HSA) grafting and a poloxamine hydrogel adhesive. Its experimental maximum adhesive strength was approximately 2 times higher than that of unmodified mesh, which was achieved by mechanical interlock of the hydrogel tissue adhesive into the PP mesh pores and chemical bonding of the grafted albumin. Mesh explants retrieved from patients were valuable resources to explore material changes and the degradation mechanisms in highly variable in vivo conditions. Assessments of mesh explants were challenging due to the unknown mesh material properties before implantation and the uncontrolled nature of patient variables inherent in retrieval analysis. Compared to biological assessments, experimental characterization for in vitro simulation and mesh fixation system contributed to understanding mesh behavior in a controlled condition and building the foundation for predicting mesh behavior in physiological conditions

A SYSTEMATIC REVIEW OF COLLABORATIVE WRITING IMPLEMENTATION IN K-12 SECOND LANGUAGE CLASSROOMS

In recognizing that writing is a social act, collaborative writing has received increased attention in second language (L2) classrooms. A large body of research literature explores the varied ways of L2 collaborative writing development in tertiary education settings, but relatively little is known about the implementation of collaborative writing in K-12 classrooms. In this study, the authors systematically reviewed a total of 12 peer-reviewed empirical studies on the use of collaborative writing in K-12 L2 classrooms to provide new insights into this particular context. Comprehensive analysis has been conducted, including the research context, writing task, mode of interaction, research focus, and assessment. The findings reveal that the majority of the selected studies have involved K-12 students learning English as a target language with diverse writing tasks. Three different collaborative writing approaches have been implemented in K-12 classrooms of L2, including face-to-face, online, and a blend of both styles. The main research foci of the reviewed literature are writing processes, writing outcomes, and collaborative writing affordances. Diverse assessment methods are utilized to measure L2 writers’ writing process and product. Drawing on the analyses, the researchers discuss the pedagogical implications and research strands that deserve further examination

Subgraph Frequency Distribution Estimation using Graph Neural Networks

Small subgraphs (graphlets) are important features to describe fundamental units of a large network. The calculation of the subgraph frequency distributions has a wide application in multiple domains including biology and engineering. Unfortunately due to the inherent complexity of this task, most of the existing methods are computationally intensive and inefficient. In this work, we propose GNNS, a novel representational learning framework that utilizes graph neural networks to sample subgraphs efficiently for estimating their frequency distribution. Our framework includes an inference model and a generative model that learns hierarchical embeddings of nodes, subgraphs, and graph types. With the learned model and embeddings, subgraphs are sampled in a highly scalable and parallel way and the frequency distribution estimation is then performed based on these sampled subgraphs. Eventually, our methods achieve comparable accuracy and a significant speedup by three orders of magnitude compared to existing methods.Comment: accepted by KDD 2022 Workshop on Deep Learning on Graph

An Explorative Study on Document Type Assignment of Review Articles in Web of Science, Scopus and Journals' Website

Accurately assigning the document type of review articles in citation index databases like Web of Science(WoS) and Scopus is important. This study aims to investigate the document type assignation of review articles in web of Science, Scopus and Journals' website in a large scale. 27,616 papers from 160 journals from 10 review journal series indexed in SCI are analyzed. The document types of these papers labeled on journals' website, and assigned by WoS and Scopus are retrieved and compared to determine the assigning accuracy and identify the possible reasons of wrongly assigning. For the document type labeled on the website, we further differentiate them into explicit review and implicit review based on whether the website directly indicating it is review or not. We find that WoS and Scopus performed similarly, with an average precision of about 99% and recall of about 80%. However, there were some differences between WoS and Scopus across different journal series and within the same journal series. The assigning accuracy of WoS and Scopus for implicit reviews dropped significantly. This study provides a reference for the accuracy of document type assigning of review articles in WoS and Scopus, and the identified pattern for assigning implicit reviews may be helpful to better labeling on website, WoS and Scopus

Chromosomal DNA deletion confers phage resistance to Pseudomonas aeruginosa.

Bacteria develop a broad range of phage resistance mechanisms, such as prevention of phage adsorption and CRISPR/Cas system, to survive phage predation. In this study, Pseudomonas aeruginosa PA1 strain was infected with lytic phage PaP1, and phage-resistant mutants were selected. A high percentage (~30%) of these mutants displayed red pigmentation phenotype (Red mutant). Through comparative genomic analysis, one Red mutant PA1r was found to have a 219.6 kb genomic fragment deletion, which contains two key genes hmgA and galU related to the observed phenotypes. Deletion of hmgA resulted in the accumulation of a red compound homogentisic acid; while A galU mutant is devoid of O-antigen, which is required for phage adsorption. Intriguingly, while the loss of galU conferred phage resistance, it significantly attenuated PA1r in a mouse infection experiment. Our study revealed a novel phage resistance mechanism via chromosomal DNA deletion in P. aeruginosa

Control-enhanced quantum metrology under Markovian noise

Quantum metrology is supposed to significantly improve the precision of parameter estimation by utilizing suitable quantum resources. However, the predicted precision can be severely distorted by realistic noises. Here, we propose a control-enhanced quantum metrology scheme to defend against these noises for improving the metrology performance. Our scheme can automatically alter the parameter encoding dynamics with adjustable controls, thus leading to optimal resultant states that are less sensitive to the noises under consideration. As a demonstration, we numerically apply it to the problem of frequency estimation under several typical Markovian noise channels. Through comparing our control-enhanced scheme with the standard scheme and the ancilla-assisted scheme, we show that our scheme performs better and can improve the estimation precision up to around one order of magnitude. Furthermore, we conduct a proof-of-principle experiment in nuclear magnetic resonance system to verify the effectiveness of the proposed scheme. The research here is helpful for current quantum platforms to harness the power of quantum metrology in realistic noise environments.Comment: 9 pages, 5 figure

DDT-RELATED PROTEIN4-IMITATION SWITCH alters nucleosome distribution to relieve transcriptional silencing in Arabidopsis

DNA methylation is a conserved epigenetic modification that is typically associated with silencing of transposable elements and promoter methylated genes. However, some DNA-methylated loci are protected from silencing, allowing transcriptional flexibility in response to environmental and developmental cues. Through a genetic screen in Arabidopsis (Arabidopsis thaliana), we uncovered an antagonistic relationship between the MICRORCHIDIA (MORC) protein and the IMITATION SWITCH (ISWI) complex in regulating the DNA-methylated SUPPRESSOR OF DRM1 DRM2 CMT3 (SDC) reporter. We demonstrate that components of the plant-specific ISWI complex, including CHROMATIN REMODELING PROTEIN11 (CHR11), CHR17, DDT-RELATED PROTEIN4 (DDR4), and DDR5, function to partially de-repress silenced genes and transposable elements (TEs), through their function in regulating nucleosome distribution. This action also requires the known transcriptional activator DNAJ proteins, providing a mechanistic link between nucleosome remodeling and transcriptional activation. Genome-wide studies revealed that DDR4 causes changes in nucleosome distribution at numerous loci, a subset of which is associated with changes in DNA methylation and/or transcription. Our work reveals a mechanism for balancing transcriptional flexibility and faithful silencing of DNA-methylated loci. As both ISWI and MORC family genes are widely distributed across plant and animal species, our findings may represent a conserved eukaryotic mechanism for fine-tuning gene expression under epigenetic regulation

Immune mechanism of gut microbiota and its metabolites in the occurrence and development of cardiovascular diseases

The risk of cardiovascular disease (CVD) is associated with unusual changes in the human gut microbiota, most commonly coronary atherosclerotic heart disease, hypertension, and heart failure. Immune mechanisms maintain a dynamic balance between the gut microbiota and the host immune system. When one side changes and the balance is disrupted, different degrees of damage are inflicted on the host and a diseased state gradually develops over time. This review summarizes the immune mechanism of the gut microbiota and its metabolites in the occurrence of common CVDs, discusses the relationship between gut-heart axis dysfunction and the progression of CVD, and lists the currently effective methods of regulating the gut microbiota for the treatment of CVDs

Identification of key genes and pathways in human clear cell renal cell carcinoma (ccRCC) by co-expression analysis

Human clear cell renal cell carcinoma (ccRCC) is the most common solid lesion within kidney, and its prognostic is influenced by the progression covering a complex network of gene interactions. In our study, we screened differential expressed genes, and constructed protein-protein interaction (PPI) network and a weighted gene co-expression network to identify key genes and pathways associated with the progression of ccRCC (n = 56). Functional and pathway enrichment analysis demonstrated that upregulated differentially expressed genes (DEGs) were significantly enriched in response to wounding, positive regulation of immune system process, leukocyte activation, immune response and cell activation. Downregulated DEGs were significantly enriched in oxidation reduction, monovalent inorganic cation transport, ion transport, excretion and anion transport. In the PPI network, top 10 hub genes were identified (TOP2A, MYC, ALB, CDK1, VEGFA, MMP9, PTPRC, CASR, EGFR and PTGS2). In co-expression network, 6 ccRCC-related modules were identified. They were associated with immune response, metabolic process, cell cycle regulation, angiogenesis and ion transport. In conclusion, our study illustrated the hub genes and pathways involved in the progress of ccRCC, and further molecular biological experiments are needed to confirm the function of the candidate biomarkers in human ccRCC