Investigation of Styrene-Free Unsaturated Polyester Resins for Fiber-Reinforced Composites

Most of existing commercial unsaturated polyester (UPE) resins are typically composed of a UPE and a high amount of highly volatile, flammable, and toxic styrene. The emission of hazardous styrene in the handling of the UPE resins and the preparation and use of fiber-reinforced UPE composites poses severe hazards to people's health and the working environment. In this study, two non-hazardous chemicals have been investigated for the replacement of styrene in the UPE resins. The first chemical is acrylated epoxidized soybean oil (AESO) that is derived from soybean oil and is not toxic and not volatile. The second chemical is methyl cinnamate that is extensively used as a food additive. Styrene-free UPE resins were prepared through combinations of these styrene replacements and three different UPEs. The styrene-free UPE resins were cured without the reinforcement of fibers and then evaluated and characterized for their properties. Kenaf fibers and glass fibers have been investigated as reinforcing fibers for the styrene-free UPE resins. An efficient process of making the fiber-reinforced UPE composites was developed. The viscosity and the pot life of the styrene-free UPE resins under different temperature were studied. The curing behavior of the resins under heat was investigated. The viscoelastic properties of the cured UPE resins and the fiber-reinforced UPE composites were characterized with dynamic mechanical analyses. Mechanical properties such as flexural and tensile properties of the composites were measured. It was found that these styrene replacements were comparable or even superior to styrene in terms of the mechanical properties of the composites. The weight ratio between a styrene replacement and a UPE was studied in detail for maximizing mechanical properties. The curing mechanisms of these styrene-free UPE resins are discussed in detail

Pressure sensitive adhesives based on oleic acid

Existing pressure sensitive adhesives (PSAs) are mostly based on petrochemicals. In this study, a novel PSA based on a renewable material, methyl oleate, was prepared and characterized. Methyl oleate was first epoxidized to form epoxidized methyl oleate that was subsequently hydrolyzed and acidified to form epoxidized oleic acid (EOA) which is an AB-type monomer containing both a carboxylic acid group (A) and an epoxy group (B). Various methods for the preparation of EOA with high purity were extensively studied. EOA was homopolymerized in the presence of a catalyst to generate a polyester that could serve as a PSA. Various catalysts were investigated for their effectiveness on the homopolymerization, and chromium (III) tris(acetylacetonate) was found to be the most effective catalyst. Effects of the EOA purity on the PSA properties of the resulting polyesters were investigated in detail; the EOA purity of at least 97% was found to be required for the preparation of the PSA with superior properties. The crosslinking of the polyesters with very small amount of crosslinking agents was able to further improve the overall properties, especially the aging resistance of the resulting PSAs. Among various crosslinking agents investigated, polymeric methylene diphenyl diisocyanate was the most effective in improvement of the PSA properties. The PSAs were evaluated for their peel strength, tack force, shear resistance, and aging resistance. The PSAs were characterized for their viscoelastic properties, thermal properties, thermal stability, and chemical structures.

Modifications and Trafficking of APP in the Pathogenesis of Alzheimer’s Disease

Alzheimer’s disease (AD), the most common neurodegenerative disorder, is the leading cause of dementia. Neuritic plaque, one of the major characteristics of AD neuropathology, mainly consists of amyloid β (Aβ) protein. Aβ is derived from amyloid precursor protein (APP) by sequential cleavages of β- and γ-secretase. Although APP upregulation can promote AD pathogenesis by facilitating Aβ production, growing evidence indicates that aberrant post-translational modifications and trafficking of APP play a pivotal role in AD pathogenesis by dysregulating APP processing and Aβ generation. In this report, we reviewed the current knowledge of APP modifications and trafficking as well as their role in APP processing. More importantly, we discussed the effect of aberrant APP modifications and trafficking on Aβ generation and the underlying mechanisms, which may provide novel strategies for drug development in AD

Digital Nudging for Online Social Sharing: Evidence from A Randomized Field Experiment

This study investigates the effectiveness of digital nudging for users’ social sharing of online platform content. In collaboration with a leading career and education online platform, we conducted a large-scale randomized experiment of digital nudging using website popups. Grounding on the Social Capital Theory and the individual motivation mechanism, we proposed and tested four kinds of nudging messages: simple request, monetary incentive, relational capital, and cognitive capital. We find that nudging messages with monetary incentive, relational and cognitive capital framings lead to increase in social sharing behavior, while nudging message with simple request decreases social sharing, comparing to the control group without nudging. This study contributes to the prior research on digital nudging by providing causal evidence of effective nudging for online social sharing behavior. The findings of this study also provide valuable guidelines for the optimal design of online platforms to effectively nudge/encourage social sharing in practice

Genome-wide DNA methylation and gene expression analyses in monozygotic twins identify potential biomarkers of depression

Depression is currently the leading cause of disability around the world. We conducted an epigenome-wide association study (EWAS) in a sample of 58 depression score-discordant monozygotic twin pairs, aiming to detect specific epigenetic variants potentially related to depression and further integrate with gene expression profile data. Association between the methylation level of each CpG site and depression score was tested by applying a linear mixed effect model. Weighted gene co-expression network analysis (WGCNA) was performed for gene expression data. The association of DNA methylation levels of 66 CpG sites with depression score reached the level of P < 1 x 10(-4). These top CpG sites were located at 34 genes, especially PTPRN2, HES5, GATA2, PRDM7, and KCNIP1. Many ontology enrichments were highlighted, including Notch signaling pathway, Huntington disease, p53 pathway by glucose deprivation, hedgehog signaling pathway, DNA binding, and nucleic acid metabolic process. We detected 19 differentially methylated regions (DMRs), some of which were located at GRIK2, DGKA, and NIPA2. While integrating with gene expression data, HELZ2, PTPRN2, GATA2, and ZNF624 were differentially expressed. In WGCNA, one specific module was positively correlated with depression score (r = 0.62, P = 0.002). Some common genes (including BMP2, PRDM7, KCNIP1, and GRIK2) and enrichment terms (including complement and coagulation cascades pathway, DNA binding, neuron fate specification, glial cell differentiation, and thyroid gland development) were both identified in methylation analysis and WGCNA. Our study identifies specific epigenetic variations which are significantly involved in regions, functional genes, biological function, and pathways that mediate depression disorder.Peer reviewe