Rubber Toughened and Nanoparticle Reinforced Epoxy Composites

Epoxy resins have achieved acceptance as adhesives, coatings, and potting compounds, but their main application is as matrix to produce reinforced composites. However, their usefulness in this field still limited due to their brittle nature. Some studies have been done to increase the toughness of epoxy composites, of which the most successful one is the modification of the polymer matrix with a second toughening phase. Resin Transfer Molding (RTM) is one of the most important technologies to manufacture fiber reinforced composites. In the last decade it has experimented new impulse, due to its favorable application to produce large surface composites with good technical properties and at relative low cost. This research work focuses on the development of novel modified epoxy matrices, with enhanced mechanical and thermal properties, suitable to be processed by resin transfer molding technology, to manufacture Glass Fiber Reinforced Composites (GFRC’s) with improved performance in comparison to the commercially available ones. In the first stage of the project, a neat epoxy resin (EP) was modified using two different nano-sized ceramics: silicium dioxide (SiO2) and zirconium dioxide (ZrO2); and micro-sized particles of silicone rubber (SR) as second filler. Series of nanocomposites and hybrid modified epoxy resins were obtained by systematic variation of filler contents. The rheology and curing process of the modified epoxy resins were determined in order to define their aptness to be processed by RTM. The resulting matrices were extensively characterized qualitatively and quantitatively to precise the effect of each filler on the polymer properties. It was shown that the nanoparticles confer better mechanical properties to the epoxy resin, including modulus and toughness. It was possible to improve simultaneously the tensile modulus and toughness of the epoxy matrix in more than 30 % and 50 % respectively, only by using 8 vol.-% nano-SiO2 as filler. A similar performance was obtained by nanocomposites containing zirconia. The epoxy matrix modified with 8 vol.-% ZrO2 recorded tensile modulus and toughness improved up to 36% and 45% respectively regarding EP. On the other hand, the addition of silicone rubber to EP and nanocomposites results in a superior toughness but has a slightly negative effect on modulus and strength. The addition of 3 vol.-% SR to the neat epoxy and nanocomposites increases their toughness between 1.5 and 2.5 fold; but implies also a reduction in their tensile modulus and strength in range 5-10%. Therefore, when the right proportion of nanoceramic and rubber were added to the epoxy resin, hybrid epoxy matrices with fracture toughness 3 fold higher than EP but also with up to 20% improved modulus were obtained. Widespread investigations were carried out to define the structural mechanisms responsible for these improvements. It was stated, that each type of filler induces specific energy dissipating mechanisms during the mechanical loading and fracture processes, which are closely related to their nature, morphology and of course to their bonding with the epoxy matrix. When both nanoceramic and silicone rubber are involved in the epoxy formulation, a superposition of their corresponding energy release mechanisms is generated, which provides the matrix with an unusual properties balance. From the modified matrices glass fiber reinforced RTM-plates were produced. The structure of the obtained composites was microscopically analyzed to determine their impregnation quality. In all cases composites with no structural defects (i.e. voids, delaminations) and good superficial finish were reached. The composites were also properly characterized. As expected the final performance of the GFRCs is strongly determined by the matrix properties. Thus, the enhancement reached by epoxy matrices is translated into better GFRC´s macroscopical properties. Composites with up to 15% enhanced strength and toughness improved up to 50%, were obtained from the modified epoxy matrices

Optical Properties of Two-Dimensional/Three-Dimensional Composite Perovskite Films

Two-dimensional/three-dimensional (2D/3D) composite perovskites (CPs) are extremely promising for their application in optoelectronics. Although understanding the fundamental optical properties of 2D/3D CPs is of great importance for optimizing the performance of optoelectronic devices, relevant studies still remain far from being sufficient. In this work, by using R-methylbenzylammonium (R-MBA) and R-1-(1-naphthyl)ethylammonium (R-NEA) as the A-site cations, we have synthesized two kinds of 2D/3D CP films, abbreviated as R-MBA- and R-NEA-films, respectively. Impressively, with an increasing temperature from 80 to 300 K, no phase transition or obvious emission shift is observed in both R-MBA- and R-NEA-films, and the latter has stronger electron–phonon coupling strength. Femtosecond transient absorption spectroscopy reveals that the R-NEA-film exhibits faster hot carrier cooling time and shorter biexciton lifetime. This work not only confirms the possibility of regulating the optical properties of 2D/3D CPs by the use of different organic A-site cations but also provides important information for the development of related optoelectronic devices

Direct Intramolecular Conjugate Addition of Simple Alkenes to α,β-Unsaturated Carbonyls Catalyzed by Cu(OTf)₂

An unprecedented intramolecular conjugate addition of simple alkenes to α,β-unsaturated carbonyl compounds has been developed. A simple Lewis acid such as Cu­(OTf)₂ was found to effectively catalyze the reaction, and six- and five-membered cyclic products were obtained in moderate to high yields

Two novel trinuclear cluster-based coordination polymers with 2,6-Di-imidazol-1-yl-pyridine: solvothermal syntheses, crystal structures, properties and Hirshfeld surface analysis

<p>Two novel trinuclear cluster-based coordination polymers {[M₃(dip)(AcO)₆]·(X)}_n (<b>1</b>, M = Cu, X = CH₃OH; <b>2</b>, M = Co, X = 2H₂O) (dip is 2,6-Di-imidazol-1-yl-pyridine), have been synthesised and structurally determined by single crystal X-ray diffraction, element analysis. Crystallographic unit of <b>1</b> consists of three Cu(II), six acetic ions, one dip ligand and one methanol molecule, which formed 1D chain through acetic bridges. The 1D chain further constructed 2-D network through dip ligand bridge which formed 3-D network through π···π interaction. Crystallographic unit of <b>2</b> consists of three Co(II), six acetic ions, one dip ligand and two water molecules. The trinuclear unit further formed a dimmer through dip ligand bridge which constructed 1-D through dip ligand bridge. The 1D chain further constructed 2-D network through π···π interaction. IR and UV–vis spectrum properties of <b>1</b> and <b>2</b> were studied. In addition, Hirshfeld surface analysis was also studied for <b>1</b>.</p

Bioinspired Organocatalytic Aerobic C–H Oxidation of Amines with an <i>ortho</i>-Quinone Catalyst

A simple bioinspired <i>ortho</i>-quinone catalyst for the aerobic oxidative dehydrogenation of amines to imines is reported. Without any metal cocatalysts, the identified optimal <i>ortho</i>-quinone catalyst enables the oxidations of α-branched primary amines and cyclic secondary amines. Mechanistic studies have disclosed the origins of different performances of <i>ortho</i>-quinone vs <i>para</i>-quinone in biomimetic amine oxidations

New Sensors for Quantitative Measurement of Mitochondrial Zn²⁺

Zinc (Zn²⁺) homeostasis plays a vital role in cell function, and the dysregulation of intracellular Zn²⁺ is associated with mitochondrial dysfunction. Few tools exist to quantitatively monitor the buffered, free Zn²⁺ concentration in mitochondria of living cells ([Zn²⁺]_mito). We have validated three high dynamic range, ratiometric, genetically encoded, fluorescent Zn²⁺ sensors that we have successfully used to precisely measure and monitor [Zn²⁺]_mito in several cell types. Using one of these sensors, called mito-ZapCY1, we report observations that free Zn²⁺ is buffered at concentrations about 3 orders of magnitude lower in mitochondria than in the cytosol and that HeLa cells expressing mito-ZapCY1 have an average [Zn²⁺]_mito of 0.14 pM, which differs significantly from other cell types. These optimized mitochondrial Zn²⁺ sensors could improve our understanding of the relationship between Zn²⁺ homeostasis and mitochondrial function

Bioinspired Organocatalytic Aerobic C–H Oxidation of Amines with an <i>ortho</i>-Quinone Catalyst

A simple bioinspired <i>ortho</i>-quinone catalyst for the aerobic oxidative dehydrogenation of amines to imines is reported. Without any metal cocatalysts, the identified optimal <i>ortho</i>-quinone catalyst enables the oxidations of α-branched primary amines and cyclic secondary amines. Mechanistic studies have disclosed the origins of different performances of <i>ortho</i>-quinone vs <i>para</i>-quinone in biomimetic amine oxidations

Image_5_Pan-cancer analysis of AIM2 inflammasomes with potential implications for immunotherapy in human cancer: A bulk omics research and single cell sequencing validation.tif

BackgroundThe absent in melanoma 2 (AIM2) inflammasome is a multi-protein platform that recognizes aberrant cytoplasmic double-stranded DNA(dsDNA) and induces cytokine maturation, release, and pyroptosis. Some studies found that the AIM2 inflammasome was a double-edged sword in many cancers. However, there have been fewer studies on AIM2 inflammasomes in pan-cancer.MethodsGene expression was analyzed using The Cancer Genome Atlas (TCGA) database and The Genotype-Tissue Expression (GTEx) database. Immunohistochemistry (IHC) was used to validate the expression of the AIM2. We used the survival curve to explore the prognostic significance of the AIM2 inflammasomes in pan-cancer. Mutations and methylation of AIM2 inflammasome-related genes (AIM2i-RGs) were also comprehensively analyzed. Single sample gene set enrichment analysis was used to calculate the AIM2 inflammasomes score and explore the correlation of the AIM2 inflammasomes score with immune-related genes and immune infiltrations. The function of AIM2 inflammasomes in pan-cancer was analyzed at the single-cell level. Single-cell transcriptome sequencing (scRNA-seq) data was used to assess the activation state of the AIM2 inflammasomes in the tumor microenvironment.ResultsWe found that AIM2i-RGs were aberrantly expressed in tumors and were strongly associated with prognosis. In pan-cancer, the expression of AIM2i-RGs was positively associated with copy number variation and negatively associated with methylation. In AIM2i-RGs, missense mutations were the predominant type of single nucleotide polymorphism. Moreover, we found that the drugs dimethyloxallyl glycine (DMOG) and Z-LNle-CHO may be sensitive to the AIM2 inflammasomes. The AIM2 inflammasomes score was significantly and positively correlated with the tumor immunity score and the stroma score. In most tumors, the AIM2 inflammasomes score was significantly and positively correlated with CD8+ T cell abundance in the tumor microenvironment. Additionally, the AIM2 inflammasomes score was significantly correlated with immune checkpoint genes in pan-cancer as well as immune checkpoint therapy-related markers including tumor mutational burden (TMB), microsatellite instability(MSI), and tumor immune dysfunction and exclusion(TIDE). scRNA-seq analysis suggested that AIM2 inflammasomes differ significantly among different cells in the tumor microenvironment. IHC confirmed low expression of AIM2 in colorectal cancer.DiscussionAIM2 inflammasomes may be a new target for future tumor therapy It is likely involved in tumor development, and its high expression may serve as a predictor of tumor immunotherapy efficacy.</p

Image_3_Pan-cancer analysis of AIM2 inflammasomes with potential implications for immunotherapy in human cancer: A bulk omics research and single cell sequencing validation.tif

BackgroundThe absent in melanoma 2 (AIM2) inflammasome is a multi-protein platform that recognizes aberrant cytoplasmic double-stranded DNA(dsDNA) and induces cytokine maturation, release, and pyroptosis. Some studies found that the AIM2 inflammasome was a double-edged sword in many cancers. However, there have been fewer studies on AIM2 inflammasomes in pan-cancer.MethodsGene expression was analyzed using The Cancer Genome Atlas (TCGA) database and The Genotype-Tissue Expression (GTEx) database. Immunohistochemistry (IHC) was used to validate the expression of the AIM2. We used the survival curve to explore the prognostic significance of the AIM2 inflammasomes in pan-cancer. Mutations and methylation of AIM2 inflammasome-related genes (AIM2i-RGs) were also comprehensively analyzed. Single sample gene set enrichment analysis was used to calculate the AIM2 inflammasomes score and explore the correlation of the AIM2 inflammasomes score with immune-related genes and immune infiltrations. The function of AIM2 inflammasomes in pan-cancer was analyzed at the single-cell level. Single-cell transcriptome sequencing (scRNA-seq) data was used to assess the activation state of the AIM2 inflammasomes in the tumor microenvironment.ResultsWe found that AIM2i-RGs were aberrantly expressed in tumors and were strongly associated with prognosis. In pan-cancer, the expression of AIM2i-RGs was positively associated with copy number variation and negatively associated with methylation. In AIM2i-RGs, missense mutations were the predominant type of single nucleotide polymorphism. Moreover, we found that the drugs dimethyloxallyl glycine (DMOG) and Z-LNle-CHO may be sensitive to the AIM2 inflammasomes. The AIM2 inflammasomes score was significantly and positively correlated with the tumor immunity score and the stroma score. In most tumors, the AIM2 inflammasomes score was significantly and positively correlated with CD8+ T cell abundance in the tumor microenvironment. Additionally, the AIM2 inflammasomes score was significantly correlated with immune checkpoint genes in pan-cancer as well as immune checkpoint therapy-related markers including tumor mutational burden (TMB), microsatellite instability(MSI), and tumor immune dysfunction and exclusion(TIDE). scRNA-seq analysis suggested that AIM2 inflammasomes differ significantly among different cells in the tumor microenvironment. IHC confirmed low expression of AIM2 in colorectal cancer.DiscussionAIM2 inflammasomes may be a new target for future tumor therapy It is likely involved in tumor development, and its high expression may serve as a predictor of tumor immunotherapy efficacy.</p

Potential Key Bases of Ribosomal RNA to Kingdom-Specific Spectra of Antibiotic Susceptibility and the Possible Archaeal Origin of Eukaryotes

<div><p>In support of the hypothesis of the endosymbiotic origin of eukaryotes, much evidence has been found to support the idea that some organelles of eukaryotic cells originated from bacterial ancestors. Less attention has been paid to the identity of the host cell, although some biochemical and molecular genetic properties shared by archaea and eukaryotes have been documented. Through comparing 507 taxa of 16S–18S rDNA and 347 taxa of 23S–28S rDNA, we found that archaea and eukaryotes share twenty-six nucleotides signatures in ribosomal DNA. These signatures exist in all living eukaryotic organisms, whether protist, green plant, fungus, or animal. This evidence explicitly supports the archaeal origin of eukaryotes. In the ribosomal RNA, besides A2058 in <em>Escherichia coli</em> vs. G2400 in <em>Saccharomyces cerevisiae</em>, there still exist other twenties of sites, in which the bases are kingdom-specific. Some of these sites concentrate in the peptidyl transferase centre (PTC) of the 23S–28S rRNA. The results suggest potential key sites to explain the kingdom-specific spectra of drug resistance of ribosomes.</p> </div