Environmental effects on the strength and impact damage resistance of alumina based oxide/oxide ceramic matrix composites

In this study the effects of high temperature and moisture on the impact damage resistance and mechanical strength of Nextel 610/alumina silicate ceramic matrix composites were experimentally evaluated. Composite laminates were exposed to either a 1050°C isothermal furnace-based environment for 30 consecutive days at 6 h a day, or 95% relative humidity environment for 13 consecutive days at 67°C. Low velocity impact, tensile and short beam strength tests were performed on both ambient and environmentally conditioned laminates and damage was characterized using a combination of non-destructive and destructive techniques. High temperature and humidity environmental exposure adversely affected the impact resistance of the composite laminates. For all the environments, planar internal damage area was greater than the back side dent area, which in turn was greater than the impactor side dent area. Evidence of environmental embrittlement through a stiffer tensile response was noted for the high temperature exposed laminates while the short beam strength tests showed greater propensity for interlaminar shear failure in the moisture exposed laminates. Destructive evaluations exposed larger, more pronounced delaminations in the environmentally conditioned laminates in comparison to the ambient ones. External damage metrics of the impactor side dent depth and area directly influenced the post-impact tensile strength of the laminates while no such trend between internal damage area and residual strength could be ascertained.     

Synthesis of magnetic nanocomposite microparticles for binding of chlorinated organics in contaminated water sources

In this work, the development of novel magnetic nanocomposite microparticles (MNMs) via free radical polymerization for their application in the remediation of contaminated water is presented. Acrylated plant-based polyphenols, curcumin multiacrylate (CMA) and quercetin multiacrylate (QMA), were incorporated as functional monomers to create high affinity binding sites for the capture of polychlorinated biphenyls (PCBs), as a model pollutant. The MNMs were characterized by Fourier transform infrared spectroscopy, thermogravimetric analysis, scanning electron microscopy, dynamic light scattering, and UV–visible spectroscopy. The affinity of these novel materials for PCB 126 was evaluated and fitted to the nonlinear Langmuir model to determine binding affinities (K_D). The results suggest the presence of the polyphenolic moieties enhances the binding affinity for PCB 126, with K_D values comparable to that of antibodies. This demonstrates that these nanocomposite materials have promising potential as environmental remediation adsorbents for harmful contaminants.     

Polyphenol conjugated poly(beta-amino ester) polymers with hydrogen peroxide triggered degradation and active antioxidant release

Oxidative stress has been implicated as a primary or secondary player to numerous diseases. A potential approach to control oxidative stress induced diseases is to deliver small antioxidant compounds to compromised sites at equivalent rates of reactive oxygen species (ROS) generation. This becomes a complicated task as antioxidant molecules typically have poor bioavailability and stability. Antioxidants synthesized into poly(beta-amino ester) (PBAE) crosslinked polymers have shown improved delivery by enhancing stability while allowing controlled release through hydrolysis. The tunable crosslinked networks show significant response to specific oxidizing environments, where free radicals can be present. Curcumin conjugated PBAE bulk films have proportional rates of accelerated degradation, thus faster release of curcumin, in a range of low concentrations of hydrogen peroxide (H₂O₂)_, where 2′2-azobis(2-amidinopropane) dihydrochloride has no substantial impact. This effect suggests the possibility to create a system that releases its therapeutic agent in direct relationship to the need through ROS signaling. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48647.     

Effect of silane structure on the properties of silanized multiwalled carbon nanotube-epoxy nanocomposites

Multiwalled carbon nanotubes (MWCNTs) were functionalized with aminosilanes via an aqueous deposition route. The size and morphology of siloxane oligomers grafted to the MWCNTs was tuned by varying the silane functionality and concentration and their effect on the properties of a filled epoxy system was investigated. The siloxane structure was found to profoundly affect the thermo-mechanical behavior of composites reinforced with the silanized MWCNTs. Well-defined siloxane brushes increased the epoxy T_g by up to 19 °C and significantly altered the network relaxation dynamics, while irregular, siloxane networks grafted to the MWCNTs had little effect. The addition of both types of silanized MWCNTs elicited improvements in the strength of the nanocomposites, but only the well-defined siloxane brushes engendered dramatic improvements in toughness. Because the silanization reaction is simple, rapid, and performed under aqueous conditions, it is also an industrially attractive functionalization route.     

Incorporating in-cylinder pressure data to predict NOx emissions from spark-ignition engines fueled with landfill gas/hydrogen mixtures

A 0.745 L 2-cylinder spark-ignition engine was operated with compressed natural gas and with simulated landfill gas (60% CH₄ and 40% CO₂ by volume) containing hydrogen concentrations of 0, 30%, 40%, and 50% (by volume of the CH₄ in the fuel) at constant rpm. This empirical data was compared with predictions from three existing semi-empirical engine models, using a first-law-based finite heat release model to correlate measured in-cylinder pressure data and burn rate for each fuel mixture. Of the three models only a two zone model incorporating thermal and prompt NO_x came within 25% of predicting the measured NO_x emissions.     

Room-Temperature Solid-Matrix Luminescence Spectroscopy of Pyrene and 1-Hydroxypyrene from Optically Clear Sugar Glasses

Room-temperature solid-matrix luminescence was investigated for two model compounds pyrene and 1-hydroxypyrene from optically clear sugar glasses. Several glasses were investigated. Novel glasses were prepared for the first time from binary mixtures of sugars for spectroscopy. Glasses were prepared from glucose/xylose and glucose/maltose. The glucose/maltose gave a superior glass compared to glucose/xylose. The glucose/maltose glass gave the best room temperature phosphorescence (RTP) for pyrene compared to glasses of glucose and maltose without a heavy atom. The RTP was weak for both pyrene and 1-hydroxypyrene without a heavy atom in the glucose glass. The addition of a heavy atom (12% NaI) gave a 44-fold increase in RTP of pyrene and a 10-fold increase in the RTP of 1-hydroxypyrene. Room temperature fluorescence (RTF) of pyrene and 1-hydroxypyrene were easily observed from all the glass systems studied. However, the pyrene RTF intensity varied with the different sugar glass systems studied. Furthermore, a polymer, polyacrylic acid (PAA), was added to the sugar matrix at the level of 1% and 2% to improve the rigidity of the glass matrix. The observed phosphorescence was weak for pyrene at both the 1% and 2% PAA concentrations. A glass prepared with 2% PAA gave the strongest RTP for pyrene. Addition of 12% NaI with 1% polyacrylic acid did improve the RTP of pyrene but it was less than the RTP of pyrene from a glucose glass with 12% NaI by a factor of 2.7. A glucose glass with 12% NaI was the best system for RTP of pyrene.     

The ORF, regulated synthesis, and persistence-specific variation of influenza C viral NS1 protein

The open reading frame (ORF) and the regulated synthesis of the influenza C viral NS1 protein were analyzed in view of viruses possessing different biological activities. We provide evidence for a 246-amino-acid NS1-ORF, encoded by five viral strains and variants. Prokaryotic expression of the prototype NS1-ORF resulted in a product of 27 kDa, confirming the predicted molecular weight. Using an antiserum raised against recombinant NS1 protein, nonstructural proteins of wild-type virus were detected in infected cells for a limited course of time, whereas a persistent virus variant was characterized by a long-term nonstructural gene expression. As examined by infection experiments, the intracellular distribution of nonstructural protein was nuclear and cytoplasmic, whereas in NS1 gene-transfected cells, the cytoplasmic localization occurred in a fine-grained structure, suggesting an analogy to influenza A viral NS1 protein. Concerning persistent infection, NS1 protein species differing in sizes and posttranslational modifications were observed for a persistent virus variant, as particularly illustrated by a high degree of NS1 phosphorylation. Virus reassortant analyses proved the importance of the NS-coding genomic segment: the minimal viral properties required for the establishment of persistence were transferred with this segment to a monoreassortant virus. Thus the influenza C viral NS1 protein is a 246-amino-acid nuclear-cytoplasmic phosphoprotein that can be subject to specific variations being functionally linked to a persistent virus phenotype.     

Reaction of hypochlorous acid with bovine nasal cartilage comparison to pig articular cartilage

The action of sodium hypochlorite (NaOCl) on bovine nasal cartilage was studied by proton nuclear magnetic resonance (1H-NMR) spectroscopy in order to model degradation processes of cartilage caused by neutrophil-derived hypochlorous acid. Nasal cartilage was chosen as a mean of comparison because it differs from articular cartilage in its composition. It contains some more proteoglycans, i.e. polymeric carbohydrates and less collagen than articular cartilage. This is important for studying the influence of hypochlorous acid on cartilage components (collagen and polysaccharides). Cartilage samples were incubated at 37 degrees C with phosphate buffer in the presence or absence of NaOCl. Supernatants were collected and assayed by NMR-spectroscopy. In the presence of pure phosphate buffer, the supernatants of bovine nasal cartilage were less rich in low molecular mass metabolites (e.g. amino acids, lactate) than articular cartilage. However, intense signals for highly mobile N acetyl groups of cartilage polysaccharides were detectable in nasal cartilage. NaOCl caused an increase in signals for acetate and formiate. Signals for N-acetyl groups rose only during the first 25 minutes of incubation with NaOCl. Then, their concentration decreased markedly. These changes were related to an enhanced release of chondroitinsulfate from nasal cartilage.     

A single course of remission reinduction chemotherapy for acute myelogenous leukemia relapsing after allogeneic bone marrow transplantation is complicated by graft-versus-host disease and followed by sustained complete remission

Graft-versus-host disease (GVHD) remains a major immunological complication after allogeneic bone marrow transplantation (allo-BMT), but also favors development of the beneficial graft-versus-leukemia (GVL) effect. A patient with AML-M4 (inv (16)) is described, who was given non-myeloablative remission reinduction therapy for leukemic relapse (inv (16), trisomy 8) diagnosed on day 184 after HLA-compatible sibling BMT. On day 236, ie about 6 weeks after completion of this course, a clinical syndrome suggestive of acute GVHD grade 3 had developed. Skin biopsy confirmed the clinical diagnosis of GVHD, with a compatible liver biopsy. Transfusion-associated GVHD was ruled out by analysis of short tandem repeat (STR) alleles in the skin biopsy, revealing alleles from donor and recipient but not from third party origin. Cyclosporin A (CsA) therapy, which had been tapered between days 150 and 175, was resumed, resulting in a favorable response and gradual transition to limited chronic GVHD. The patient has since remained in complete remission with an excellent performance status for more than 40 months, without further chemotherapy. Thus this biopsy proven case of GVHD was induced by marrow donor lymphocytes more than 200 days after transplantation and apparently triggered by remission reinduction chemotherapy. The case indicates that intensive non-myeloablative chemotherapy can cure AML relapsing after allo-BMT. The therapeutic effect in this case probably involved a direct pharmacological suppression of the leukemic clone followed by a GVL effect initiated by donor-derived alloreactive T lymphocytes.