Oxygen Inhibition Research Articles

Formate-facilitated recovery of wastewater anammox granular sludge from oxygen inhibition: Effects and mechanisms

Oxygen leakage due to poor reactor sealing or accidental aeration can have detrimental impacts on the performance of wastewater anammox processes. Strategies of restoring functionality of anammox consortia are scarce, and providing appropriate chemical reducing reagents may help reduce oxidative damage. This study characterized the responses of anammox granular sludge (AnGS) to oxygen inhibition, and identified formate as an effective promoter capable of facilitating activity recovery, while other organics (acetate, glucose, methanol) were less effective. Upon 12 h of air exposure (DO: 1.2 ± 0.1 mg/L), the total nitrogen removal efficiency of a lab-scale AnGS reactor decreased from 85.15 % to 45.46 %. Compared with natural recovery (without chemical addition), potassium formate at 10 mg COD/L for 3 days significantly increased the total nitrogen removal efficiency, both in the short-term (66.68 % vs 57.09 %, 3 days post inhibition) and long-term (82.34 % vs 72.88 %, 30 days post inhibition). By examining sludge morphology, metagenome and transcriptome, the following potential mechanisms were proposed: 1) rapidly decreasing intracellular ROS; 2) enhancing nitrite turnover; 3) maintaining granular sludge integrity; 4) facilitating interspecies metabolic interactions. The ability of formate to facilitate sludge recovery from oxygen inhibition also implies its potential in mitigating other oxidative stresses in wastewater anammox reactors.

Jing-Si Herbal Tea attenuates oral cancer cell viability, migration, and invasion by regulating epithelial-to-mesenchymal transition and reactive oxygen species accumulation

Background/purposeOral cancer is the sixth most common cancer worldwide and can be life-threatening if not diagnosed and treated in its early stages. Jing-Si Herbal Tea (JSHT), containing eight traditional Chinese medicine-based herbs, is known to suppress the malignancy, growth, and metastasis of several tumor cells, including breast, lung, and colon cancer cells. However, the pharmacological effect of JSHT on oral cancer progression is still unclear. Materials and methodsIn this study, we evaluated the potential of JSHT to arrest the development of oral cancer via induction of cell death by reactive oxygen species (ROS) accumulation and inhibition of migration, invasion, and epithelial-to-mesenchymal transition (EMT). For this purpose, we employed the human tongue squamous cell carcinoma SAS cell line, which we treated with different JSHT concentrations for 24 h, and assessed cell viability, migration, and wound healing capabilities, together with western blotting for measuring expression levels of EMT markers. ResultsSurvival, migration/invasion ability, EMT, and ROS production in the SAS human tongue squamous carcinoma and FaDu human pharynx squamous cell carcinoma cell line were decreased by JSHT treatment via Lon protease-independent mechanisms. ConclusionThis study demonstrates that JSHT could be regarded as a candidate new supplement to existing anticancer therapies and an alternative, orally administered healthcare product for treating oral squamous cell carcinoma.

Gold(I) complexes of the type [AuL{κC-2-C6H4P(S)Ph2}] [L = PTA, PPh3, PPh2(C6H4-3-SO3Na) and PPh2(2-py)]: Synthesis, characterisation, crystal structures, and In Vitro and In Vivo anticancer properties

Four new mononuclear gold (I) compounds of the type [AuL{κC-2-C6H4P(S)Ph2}] {L = PTA (1), PPh3 (2), PPh2(C6H4-3-SO3Na) (3), and PPh2(2-py) (4)} were prepared by scission of the dinuclear compound [Au2{μ-2-C6H4P(S)Ph2}2] by L or via a transmetalation reaction using the organotin reagent 2-Me3SnC6H4P(S)Ph2 and a suitable gold halide precursor. The cytotoxic potential of complexes 1–4 was evaluated against four human cancer cell lines of diverse cellular origin: cervical (HeLa), prostate (PC-3), non-small cell lung adenocarcinoma (A549), and fibrosarcoma (HT-1080). The in vitro cytotoxicity results showed that 1 demonstrated exceptional anticancer activity with IC50 values ranging from 0.08 to 3.5 μM. Complex 3, which contains a sulfonated triphenyl phosphine ligand, displayed the weakest anticancer activity with IC50 values ranging from 3.1 to >50 μM. When compared to the standard chemotherapeutic drug cisplatin, 1 displayed approximately 27-fold greater cytotoxic activity against cervical cancer cells and 3.5- and 7.5-fold greater activities against prostate and fibrosarcoma cancer cells, respectively. Additionally, 1 exhibited 3-fold selectivity for cervical cancer cells compared to non-cancerous HEK-293 cells. Mechanistic investigations revealed that 1 induced apoptosis, which was associated with elevated reactive oxygen species (ROS) and inhibition of the intracellular enzyme thioredoxin reductase. Furthermore, 1 exhibited notable antiangiogenic characteristics in an in vivo model using transgenic zebrafish Tg(fli1a:EGFP). In vivo studies using mouse xenograft models showed that complex 1 displayed superior inhibition of tumour growth (82 %) compared to the clinical drug cisplatin (29 %). Overall, these results highlight the potential of gold (I) compounds as novel antitumour agents.

A review on layerless 3D printing: challenges and applications

Purpose This paper aims to provide a full introduction, new classification, comparison and investigation of the challenges as well as applications of layerless 3D printing, which is one of the industry 4.0 pioneers. Design/methodology/approach Given the significance and novelty of uniform 3D printing, more than 250 publications were collected and reviewed in an unbiased and clear manner. Findings As a result, the majority of uniform parts printed in polymer form are known up to this point. In a novel division for better researchers’ comprehension, uniform printing systems were classified into three categories: oxygen inhibition (OI), liquid lubrication (LL) and photon penetration (PP), and each was thoroughly investigated. Furthermore, these three approaches were evaluated in terms of printing speed, precision and accuracy, manufacturing scale and cost. Originality/value The parameters of each approach were compared independently, and then a practical comparison was conducted among these three approaches. Finally, a variety of technologies, opportunities, challenges and advantages of each significant method, as well as a future outlook for layerless rapid prototyping, are presented.

Ablation resistance and high-temperature insulation capacity of TiB2-B4C modified Al-coated carbon fibre/boron phenolic resin ceramizable composites

The inherent susceptibility to oxidation limits the application of carbon fibre/phenolic resin composites (CF/Ph) in the thermal protection of hypersonic vehicle engines. Herein, TiB2-B4C modified Al-coated carbon fibre/boron phenolic resin ceramizable composites were fabricated. The optimal ceramizable composite (T30C10) exhibited excellent ablation resistance and high-temperature insulation capacity at a linear ablation rate and bottom-surface temperature of -0.00768 mm/s and 129.8 °C, respectively. Oxygen consumption and inhibition, carbon fixation, and self-healing effects contributed to the excellent ablation resistance, and the effects of the Al coatings and carbothermal reduction reactions led to excellent high-temperature insulation capacities.

Oxime esters: Potential alternatives to phosphine oxides, for overcoming oxygen inhibition in material jetting applications

Material jetting technology is emerging as a prominent technique within the additive manufacturing domain for printing multi-material objects. Despite its various advantages, including high printing resolution, oxygen inhibition remains the main issue for UV-curable materials. Oxime esters are interesting photoinitiators for this application due to their ability to undergo a photocleavage reaction followed by decarboxylation, limiting the diffusion of oxygen. A series of four commercially available oxime esters were studied as Type I photoinitiators, with the photoinitiating ability and photochemical properties of two of them never having been investigated before. Initially, their UV–visible absorption properties were studied, revealing significant absorption up to 420nm. Photopolymerization kinetic studies indicate that the oxime esters can outperformed benchmark photoinitiators such as phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide (BAPO) by reaching around 80% of double bond conversion in 12µm layer under air (for O-16) against 60% for BAPO under the same conditions. Finally, the oxime esters were tested in 3D-inkjet printing applications, displaying highly promising results with tack-free surfaces.

Melastoma dodecandrum lour. Protects against cerebral ischemia–reperfusion injury by ameliorating oxidative stress and endoplasmic reticulum stress

Ethnopharmacological relevanceMelastoma dodecandrum Lour. (MD), a traditional Chinese medicine used by the She ethnic group, has been used to treat cerebral ischemia-reperfusion (CIR) injury due to its efficacy in promoting blood circulation and removing blood stasiss; however, the therapeutic effects and mechanisms of MD in treating CIR injury remain unclear. AimTo investigate the protective effects of MD on CIR injury, in addition to its impact on oxidative stress, endoplasmic reticulum (ER) stress, and cell apoptosis. Materials and methodsThe research was conducted using both cell experiments and animal experiments. The CCK-8 method, immunofluorescence staining, and flow cytometry were used to analyze the effects of MD-containing serum on oxygen-glucose deprivation/reperfusion (OGD/R)-induced PC12 cell viability, reactive oxygen species (ROS) clearance, anti-inflammatory, neuroprotection and inhibition of apoptosis. Furthermore, 2,3,5-Triphenyl tetrazolium chloride staining, hematoxylin and eosin staining, Nissl staining, and immunohistochemistry were used to detect infarct size, pathological changes, Nissl corpuscula and neuronal protein expression in middle cerebral artery occlusion (MCAO) rats. Polymerase chain reaction and Western Blotting were conducted in cell and animal experiments to detect the expression levels of ER stress-related genes and proteins. ResultsThe MD extract enhanced the viability of PC12 cells under OGD/R modeling, reduced ROS and IL-6 levels, increased MBP levels, and inhibited cell apoptosis. Furthermore, MD improved the infarct area in MCAO rats, increased the number of Nissl bodies, and regulated neuronal protein levels including Microtubule-Associated Protein 2 (MAP-2), Myelin Basic Protein (MBP), Glial Fibrillary Acidic Protein (GFAP), and Neurofilament 200 (NF200). Additionally, MD could regulate the expression levels of oxidative stress proteins malondialdehyde (MDA), nitric oxide (NO), superoxide dismutase (SOD), and catalase (CAT). Both cell and animal experiments demonstrated that MD could inhibit ER stress-related proteins (GRP78, ATF4, ATF6, CHOP) and reduce cell apoptosis. ConclusionThis study confirmed that the therapeutic mechanism of the MD extract on CIR injury was via the inhibition of oxidative stress and the ER stress pathway, in addition to the inhibition of apoptosis.

Involvement of BcNAC083 in 1-MCP-induced delayed yellowing of pak choi (Brassica rapa subsp. Chinensis) through the regulation of reactive oxygen species metabolism and inhibition of major chlorophyll catabolic genes

Leaf yellowing is a typical senescence feature in postharvest pak choi. Plant-specific NAC transcription factors (TFs) are crucial regulators of plant senescence. In this study, a senescence-related NAC TF, BcNAC083, was investigated to identify its transcriptional regulation effects on the yellowing of pak choi by treatment with 1-methylcyclopropene (1-MCP). Applying 5.0 µL L–1 1-MCP alleviated yellowing and maintained a low respiration rate, high chlorophyll content, and relatively complete chloroplast structure in pak choi during storage. However, 10 μL L–1 ethylene accelerated yellowing, as demonstrated by the higher respiration rate, lower chloroplast structural integrity and chlorophyll content. In contrast to ethylene treatment, 1-MCP suppressed the activity of the reactive oxygen species (ROS) metabolism-related enzymes superoxide dismutase (SOD), catalase (CAT), ascorbic peroxidase (APX), and lipoxygenase (LOX), and correspondingly reduced superoxide anion (O2·–), hydrogen peroxide (H2O2), and malondialdehyde (MDA) accumulation. 1-MCP treatment also suppressed the transcript levels of ROS metabolic genes, including BcRBOHC, BcRBOHD, BcSOD, BcCAT, BcAPX, and BcLOX, and inhibited the activity of the chlorophyll catabolic enzymes chlorophyllase (CLH), Mg-de-chelatase, and pheophytin pheophorbide hydrolase (PPH) and transcript levels of associated genes, including BcCLH1/2, BcPPH1/2, BcPAO, BcNYC1, BcSGR1/2, BcHCAR, BcRCCR, and BcCAO. The expression of BcNAC083 was probably induced by ROS and was downregulated by 1-MCP and upregulated by ethylene. Molecular biology experiments determined that BcNAC083 bound directly to and activated the promoters of the chlorophyll metabolism-related genes BcCLH1, BcPPH1, BcNYC1, and BcHCAR. Importantly, transient overexpression of BcNAC083 stimulated the endogenous genes (NbCLH1, NbPPH1, NbNYC1, and NbHCAR) expression in tobacco leaves, resulting in rapid chlorophyll breakdown and leaf degreening. Treatment with 1-MCP may alleviated the yellowing of pak choi by inhibiting ROS accumulation and the transcriptional regulation of BcNAC083, which had positive regulatory effects on major chlorophyll metabolic genes.

Electrochemical and mechanical characterization of thermosets as fluorine‐free cathode binders for Li‐ion batteries

AbstractThis study demonstrates fluorine‐free cross‐linked (meth)acrylate polymers as alternatives to polyvinylidene fluoride (PVDF) in LiNi0.33Mn0.33Co0.33O2 (NMC111) cathodes. We determine the effects of thermal initiator content, polymer content, and curing environment for two polymer chemistries: a flexible acrylate polymer, and a stiff methacrylate polymer. Electrodes are manufactured and tested for final electrochemical performance and mechanical properties. The results show that the flexible acrylate polymer exhibits higher rate capability compared to the stiff methacrylate polymer because calendering fractures the brittle network of stiff polymer. Electrode adhesion to the current collector and cohesion between particles are found to be a strong function of thermal initiator ratio and oxygen inhibition. Furthermore, there exists an optimal binder concentration that maximizes rate capability performance. Under the right conditions, the two polymers exhibit comparable performance to PVDF electrodes. These results provide important implications for designing cross‐linked polymers as cathode binder alternatives to PVDF.

A UV-curable silicone acrylate anti-smudge coating containing tertiary amines and Ti with the ability to prevent oxygen inhibition

UV curing technology has numerous advantages such as a fast curing speed, environmental friendliness, energy conservation, and thus it is widely used in industrial production and out daily life. Free-radical polymerization is the primary mechanism for UV curing technology. However, free-radical polymerization is susceptible to oxygen inhibition, which leads to incomplete curing when this approach is employed in the air. This paper describes a new silicone acrylate prepolymer, four double bonds and a tertiary amine group at each end of the prepolymers can effectively solve the oxygen inhibition. We synthesized an alkoxymethacryloxy titanium monomer (Ti-MA). This monomer was mixed with the prepolymer and UV cured, which resulted in improved coating properties. The results showed that the double bond conversion of the prepolymer reached 90.66 ± 0.5 % at 20 s, and the residual adhesion rate also exceeded 90 %. The hardness of the coating could reach pencil hardness level 4H with the addition of Ti-MA, and the water contact angle reached 104.5 ± 0.2°, as well as excellent anti-smudge and anti-fingerprint properties. This study provides a new method to solve the oxygen inhibition problem, which has a broad application prospect in the field of coatings.

Waterborne bio-based UV-thermal dual-curable coatings with excellent mechanical properties and thermal resistance based on citric acid modified epoxidised soybean oil

Waterborne bio-based UV-curable coatings have attracted enormous attentions due to their environment friendliness and safety. However, residual neutralizing agents, long-chain aliphatic hydrocarbons derived from epoxidised soybean oil, and the oxygen inhibition inherent in the UV curing process often cause poor thermal resistance and mechanical properties of the epoxidised soybean oil-based waterborne bio-based UV-curable coatings. Herein, the epoxidised soybean oil was hydrophilized by citric acid and poly (ethylene glycol) diglycidyl ether without the use of neutralizing agents. The hydrophilized epoxidised soybean oil was subsequently compounded with bisphenol A epoxy resin to prepare high-performance waterborne bio-based epoxy methacrylates. Finally, a high-performance waterborne bio-based UV-thermal dual-curable coating was obtained by blending waterborne bio-based epoxy methacrylates with waterborne isocyanate curing agent. The results demonstrated that waterborne bio-based epoxy methacrylates possess high bio-based content, low viscosity, and remarkable storage stability. Furthermore, waterborne bio-based UV-thermal dual-curable coatings with high cross-linking density exhibited outstanding mechanical properties and thermal resistance. For example, the waterborne bio-based UV-thermal dual-curable coatings P0805I4 exhibits a breaking elongation of 30.75%, maximum tensile strength of 16.68 MPa, T10% at 285.33 °C, and adhesion class level of 0. Our research not only introduces high-performance waterborne bio-based UV-thermal dual-curable coatings, thereby extending the application domains of soybean oil-derived waterborne bio-based coatings, but also presents a valuable strategy for advancing high-performance, sustainable, waterborne, and environmentally friendly materials.

Unraveling the Electron Transfer in Cupriavidus necator – Insights Into Mediator Reduction Mechanics

AbstractCupriavidus necator, despite lacking direct electron transfer capabilities, demonstrates efficient reduction of various redox mediators in oxygen‐free cultivation within bioelectrochemical systems. This study investigates the reduction site of ferricyanide through inhibition and expression rate analysis of oxygen and nitrate respiration chain complexes, comparing aerobic cultivation conditions with fructose as carbon and electron donor to autotrophic (CO2/H2/O2) and anodic cultivation conditions (fructose/anode). Azide inhibition identified cytochrome c oxidase as the primary complex facilitating electron transfer to ferricyanide, with a secondary role proposed for nitrite reductase NirS, demonstrating a 3.9±1.1‐fold higher expression when exposed to anodic conditions. The 2.9±0.6‐fold increase in the expression of the natural porin OmpA under anodic conditions implies its potential involvement in ferricyanide uptake. Additionally, chemically permeabilizing cell membranes with cetyltrimethylammonium bromide doubles ferricyanide reduction rates without an anode present, offering insights for optimizing redox mediation in C. necator based bioelectrochemical systems. This study opens up new possibilities for the targeted optimization of mediated electron transfer in C. necator and other organisms.

Insights into Photopolymerization at the Nanoscale Using Surface Plasmon Resonance Imaging.

Near-field photopolymerization (NFPP) driven by surface plasmon resonance has attracted increasing attention in nanofabrication. This interest comes from the nanometer-scale control of polymer thickness, due to the confinement of the evanescent wave within a highly restricted volume at the surface. In this study, a novel approach using a multi-spectral surface plasmon resonance instrument is presented that gives access to real-time images of polymer growth during NFPP with nanometer sensitivity. Using the plasmonic evanescent wave for both polymerization and real-time sensing, the influence of irradiance, concentration of dye, and initiator are investigated on the threshold energy and kinetics of NFPP. How oxygen inhibition in the near field strongly affects photopolymerization is highlighted, more than in the far field.

Inhibition, Recovery and Stabilization of MBR-Anammox Process: Enhancing Nitrogen Removal by Biochar-supported Nano Zero-valent Iron Adoption

Anaerobic ammonium oxidation (Anammox) is recognized as a promising option to energy-neutral wastewater treatment, yet difficulties encountered in practice due to its poor stability. This work investigated the effects of biochar-supported nano zero-valent iron (nZVI-BC) on nitrogen removal performance of anammox process. Three membrane bioreactors (MBRs) suitable for slowly growing anammox bacteria was operated for 100 days, undergoing startup, dissolved oxygen (DO) inhibition, performance recovery and stabilization periods. The results showed that nZVI-BC adoption could improve the nitrogen removal efficiency (NRE) by 5.5–27.3 % and 3.1–20.7 % and nitrogen removal rate (NRR) by 5.4–28.6 % and 3.2–22.9 %, compared with control group and biochar adoption, respectively. Throughout the experimental periods, nZVI-BC was conducive to enrich anammox bacteria and increased the functional gene copies associated with anammox metabolism. Meanwhile, co-occurrence network analysis promulgated that nZVI-BC boosted the robustness and interaction of microbial community. Furthermore, the electrochemical analysis of the extracellular polymeric substance (EPS) revealed that nZVI-BC adoption augmented the extracellular electron transport (EET) process of anammox biomass. Metagenomic sequencing revealed that nZVI-BC reinforced the complete dissimilatory nitrate reduction to ammonium (DNRA) pathway in Candidatus Brocadia, the dominant anammox bacteria, potentially reducing nitrate production and enhancing nitrogen removal. The study manifested the possibility of nZVI-BC to improve the anammox robustness and nitrogen removal performance, and provided operational guidance for its engineering application.

Exploring the Therapeutic Potential of Triptonide in Salivary Adenoid Cystic Carcinoma: A Comprehensive Approach Involving Network Pharmacology and Experimental Validation.

Salivary Adenoid Cystic Carcinoma (ACC) is characterized by a highly invasive and slow-growing pattern, and its etiology remains unidentified. Triptonide (TN) has demonstrated efficacy as a pharmacotherapeutic agent against ACC. Nonetheless, the specific targets and mechanism of molecular action underlying the effectiveness of TN in treating ACC have not been elucidated. By integrating network pharmacology within laboratory experiments, this research delves into the prospective targets and molecular mechanisms associated with the application of TN in treating ACC. Initially, pertinent targets associated with TN against ACC were acquired from public databases. Subsequently, a combination of network pharmacology and bioinformatics analysis was utilized to screen the top 10 hub targets and key signal pathways of TN-treating ACC. Finally, in vitro experiments involving various molecular assays were conducted to evaluate the biological phenotypes of cells following TN treatment, encompassing assessments of apoptosis levels, plate migration, and other parameters, thereby validating pivotal genes and pathways. A total of 23 pertinent targets for TN in relation to ACC were identified, with the top 10 hub genes being MAPK8, PTGS2, RELA, MAPK14, NR3C1, HDAC1, PPARG, NFKBIA, AR, and PGR. There was a significant correlation between the TNF signaling pathway and the treatment of ACC with TN. In vitro experiments demonstrated that TN treatment elevated RELA phosphorylation while concurrently reducing MAPK14 phosphorylation and inducing G2/M arrest. TN exhibited the ability to enhance the apoptosis rate through increased caspase-3 activity, elevated levels of Reactive Oxygen Species (ROS), mitochondrial dysfunction, and inhibition of cell migration. There is a potential therapeutic role for TN in the treatment of ACC through the activation of the TNF signaling pathway. Among the identified candidates, MAPK8, HDAC1, PTGS2, RELA, NR3C1, PPARG, NFKBIA, AR, and PGR emerge as the most pertinent therapeutic targets for TN in the context of ACC treatment.

The reusage of different wastes by using the multiple's effect technique for sustainable gasoline production.

The unused garbage which is accumulating the landfills, such as raw materials, could be reused for synthetic gasoline production. This study presents the multiple's effect technique, which is based on the reusage of different non, party and sorted municipal solid wastes (MSW), or biogas for syngas, converted into synthetic gasoline. The novelties of this technique include a basic multiple's effect parameter (MUW), which present a level of waste sorting, an effect of oxygen inhibition into different wastes, a simplified mathematical model and simulation with an Aspen Plus® simulator using the retrofitted methanol plan converted into the synthetic gasoline production. This technique includes a circular economy by using a circulated purified flue gas as raw material, co-products of hydrogen and water. This technique was tested on an existing methanol process, replacing natural gas with different alternatives of wastes or biogas for the synthetic gasoline production. The best alternative was the sorted MSW, which could generate an additional profit of 4.8 MEUR/a, including the garbage and CO2 emission reductions of 0.106·106 t/a and of 0.084 ·106 t/a.

Niobium carbide MXenzyme-Driven comprehensive cholesterol regulation for photoacoustic image-guided and anti-inflammatory photothermal ablation in atherosclerosis

Foam cells play a pivotal role in the progression of atherosclerosis progression by triggering inflammation within arterial walls. They release inflammatory molecules that attract additional immune cells, leading to further macrophage recruitment and plaque development. In this study, we develop an osteopontin (OPN) antibody-conjugated niobium carbide (Nb2C-aOPN) MXenzyme designed to selectively target and mildly ablate foam cells while reducing inflammation in the plaque microenvironment. This approach utilizes photonic hyperthermia to decrease plaque size by enhancing cholesterol regulation through both passive cholesterol outflow and positive cholesterol efflux. Nb2C-aOPN MXenzyme exhibits multiple enzyme-mimicking properties, including catalase, superoxide dismutase, peroxidase and glutathione peroxidase, and acts as a scavenger for reactive oxygen and nitrogen species. The inhibition of reactive oxygen and nitrogen species synergizes with photothermal ablation to promote positive cholesterol efflux, leading to reduced macrophage recruitment and a shift in macrophage phenotype from M1 to M2. This integrative strategy on cholesterol regulation and anti-inflammation highlights the potential of multifunctional 2D MXenzyme-based nanomedicine in advancing atherosclerotic regression.

Influence of surface finishing on the outcome of a 3-point bending test in polymer-based dental composits assessed by qualitative and quantitative fractography

ObjectivesThe aim of the study was to evaluate the influence of surface finishing in three polymer-based composits (composits) on the result of a 3-point bending test using quantitative and qualitative fractography as well as microstructural characteristics. Materials and methods270 rectangular specimens (n = 30) of three composits were prepared, stored and tested according to NIST No. 4877. Prior testing, the samples were subjected to three surface treatments: 1) no treatment, to preserve the oxygen inhibition layer, 2) with FEPA P1200 (ANSI equivalent grit 600) SiC paper abraded surface, and 3) polished surface. A three-point bending testing was employed, followed by quantitative (assessment of reason for failure and fracture pattern) and qualitative (fracture mirror measurements) fractography, 3D and 2D surface imaging, surface roughness, reliability and Fe-SEM analysis. The mirror radius that runs in the direction of constant stress was used to calculate the mirror constant (A) using Orr's equation. Uni- and multifactorial ANOVA, Tukey's post hoc test, and Weibull analysis was performed for statistical analysis. ResultsSurface finishing has less influence on the fracture pattern, reliability and mechanical parameters and has no influence on the mirror constant. The amount of inorganic filler has a direct impact on flexural strength and modulus, while the ranking of materials was independent of surface treatment. Failures initiated by volume defects were the most common failure mode (77.0%) with surface defects accounting for 14.9% (edge) and 7.7% (corner). Polishing resulted in lower peak-to valley height compared to no treatment, both 3–4 times lower compared to the 600 grit treatment. The increase in roughness within the analyzed range did not lead to an increase in surface-related failures. ConclusionsThe clear dominance of volume defects in all examined materials as a cause of material fracture reduces the impact of roughness on the measured properties. This insight was only possible using qualitative and quantitative research fractography.

Overcoming oxygen inhibition in UV photolithography for the fabrication of low-loss polymer waveguides.

Perfluorinated acrylate polymer materials exhibit low absorption loss at 1310 and 1550 nm, but molecular oxygen inhibits their photocuring. We propose a novel, to our knowledge, UV photolithography method incorporating a pre-exposure process for fabricating low-loss perfluorinated acrylate polymer waveguides. During the pre-exposure process, a partially cured thin layer forms on the core layer, effectively overcoming oxygen inhibition in subsequent lithography. Furthermore, the functional group contents of the polymerized materials were characterized by a Raman spectrometer to analyze the development reaction under the pre-exposure layer. Utilizing this improved method, we fabricated a straight waveguide with a length of 21 cm. The experiments showed that the propagation losses are 0.14 dB/cm at 1310 nm and 0.51 dB/cm at 1550 nm. The inter-channel cross talk for a core pitch of 250 µm was measured as low as -49 dB at 1310 nm. Error-free NRZ data transmission over this waveguide at 25 Gb/s was achieved, showcasing the potential in optical interconnect and communication applications.

Effects of various beverages on characteristics of provisional restoration materials.

To investigate the effect of common beverages on four currently used provisional restoration materials: Protemp®4, Integrity®, polymethyl methacrylate(PMMA) block, and acrylic resin. Flowable resin composite is included as a control group. Each material was formed into disks of 10-mm diameter and 4-mm thickness (N = 40) by loading the material into acrylic molds. The exposed surface in the mold was covered using a glass slide to prevent an oxygen inhibition layer, and polymerization then proceeded. The solidified disks were placed in distilled water for 24 h. These samples (n = 8) were then immersed for 14 days in one of four different beverages: water, orange juice, cola, and coffee. Changes in color dimension, hardness, and roughness were observed and then analyzed using two-way repeated analysis of variance. The provisional materials had more obvious changes in all three color dimensions than the flowable resin composite. Integrity showed the biggest changes, followed by acrylic resin and PMMA block, whereas Protemp had the smallest changes. The hardness of all the materials significantly decreased after immersion in any of the beverages for 14 days. There were no changes in surface roughness when the materials were immersed in distilled water. The surface roughness of the PMMA block significantly decreased in orange juice whereas that of Integrity and acrylic resin significantly increased in cola. Different kinds of provisional materials had different degrees of staining due to their composition. Moisture had a significant influence on the hardness of materials, and the acidity of cola significantly roughened the surface of the provisional materials.