Frequency-Dependent Dielectric Permittivity and Water Permeability in Ordered Mesoporous Silica-Grafted Fluorinated Polyimides.

Polymers with a low dielectric constant (Dk) are promising materials for high-speed communication networks, which demand exceptional thermal stability, ultralow Dk and dissipation factor, and minimum moisture absorption. In this paper, we prepared a series of novel low-Dk polyimide films containing an MCM-41-type amino-functionalized mesoporous silica (AMS) via in situ polymerization and subsequent thermal imidization and investigated their morphologies, thermal properties, frequency-dependent dielectric behaviors, and water permeabilities. Incorporating 6 wt.% AMS reduced the Dk at 1 MHz from 2.91 of the pristine fluorinated polyimide (FPI) to 2.67 of the AMS-grafted FPI (FPI-g-AMS), attributed to the free volume and low polarizability of fluorine moieties in the backbone and the incorporation of air voids within the mesoporous AMS particles. The FPI-g-AMS films presented a stable dissipation factor across a wide frequency range. Introducing a silane coupling agent increased the hydrophobicity of AMS surfaces, which inhibited the approaching of the water molecules, avoiding the hydrolysis of Si-O-Si bonds of the AMS pore walls. The increased tortuosity caused by the AMS particles also reduced water permeability. All the FPI-g-AMS films displayed excellent thermooxidative/thermomechanical stability, including a high 5% weight loss temperature (>531 °C), char residue at 800 °C (>51%), and glass transition temperature (>300 °C).

Adsorption Phenomenon of VOCs Released from the Fiber-Reinforced Plastic Production onto Carbonaceous Surface.

The manufacturing of fiber-reinforced plastics has been linked to the discharge of volatile organic compounds (VOCs), particularly toluene and benzene, which have been identified as posing substantial risks to human health and the environment. To counteract this issue, activated carbons have been suggested as a means of reducing VOC emissions through adsorption. The objective of this study was to investigate the adsorption characteristics of toluene and benzene onto activated carbons produced from coal (AC) and coconut shells (CAC). The study was carried out in an aqueous medium. The findings revealed that the AC sample with higher surface characteristics exhibited a higher adsorption capacity (toluene: 196.0784 mg g-1 and benzene: 181.8182 mg g-1) in comparison to the CAC sample (toluene: 135.1351 mg g-1 and benzene: 116.2791 mg g-1). The superior adsorption performance of AC on both VOCs can be attributed to its higher surface characteristics. The Langmuir model was found to be more appropriate than the Freundlich model, as indicated by the higher coefficient of determination (R2) value of the Langmuir isotherm (avg. R2 = 0.9669) compared to that of the Freundlich isotherm (avg. R2 = 0.9654), suggesting the use of a monolayer adsorption mechanism. The adsorption kinetics of the samples were analyzed using the pseudo-first-order and pseudo-second-order models, and the former was found to be more fitting, indicating that the rate of adsorption is directly proportional to the concentration difference between the solution and the sample surface. The adsorption process was found to be spontaneous and favorable based on the positive value of ΔG_ads. Furthermore, the adsorption process was endothermic and disordered, as indicated by the positive values of ΔH_ads and ΔS_ads. The regeneration efficiency of all the samples was secured more than 95% upon the fifth cycle.

Laser direct write of heteroatom-doped graphene on molecularly controlled polyimides for electrochemical biosensors with nanomolar sensitivity.

Fabrication of heteroatom-doped graphene electrodes remains a challenging endeavor, especially on flexible substrates. Precise chemical and morphological control is even more challenging for patterned microelectrodes. We herein demonstrate a scalable process for directly generating micropatterns of heteroatom-doped porous graphene on polyimide with different backbones using a continuous-wave infrared laser. Conventional two-step polycondensation of 4,4'-oxydianiline with three different tetracarboxylic dianhydrides enabled the fabrication of fully aromatic polyimides with various internal linkages such as phenylene, trifluoromethyl or sulfone groups. Accordingly, we leverage this laser-induced polymer-to-doped-graphene conversion for fabricating electrically conductive microelectrodes with efficient utilization of heteroatoms (N-doped, F-doped, and S-doped). Tuning laser fluence enabled achieving electrical resistivity lower than ~13 Ω sq-1 for F-doped and N-doped graphene. Finally, our microelectrodes exhibit superior performance for electrochemical sensing of dopamine, one of the important neurotransmitters in the brain. Compared with carbon fiber microelectrodes, the gold standard in electrochemical dopamine sensing, our F-doped high surface area graphene microelectrodes demonstrated 3 order of magnitude higher sensitivity per unit area, detecting dopamine concentrations as low as 10 nM with excellent reproducibility. Hence, our approach is promising for facile fabrication of microelectrodes with superior capabilities for various electrochemical and sensing applications including early diagnosis of neurological disorders.

Polymer Concentration and Liquid-Liquid Demixing Time Correlation with Porous Structure of Low Dielectric Polyimide in Diffusion-Driven Phase Separation.

Porous polyimide (PI) films are a promising low-k dielectric material for high-frequency data transmission with low signal attenuation. Pores are generated by non-solvent induced phase separation (NIPS) during phase inversion of polymer solution via non-solvent accumulation and solvent diffusion. In this study, aromatic PI was employed as a matrix for NIPS, and the influence of polymer concentration and liquid­liquid demixing time on the morphology of pores in the PI films was investigated. This ensured control over the porous structure of the PI film and provided desirable dielectric properties in a broad frequency range of 100 Hz−30 MHz (1.99 at 30 MHz) and thermal stability (Td5% > 576 °C, Tg > 391 °C). This study addresses the effect of polymer concentration and coagulation time on the morphology and physical properties of PI sponge films and provides guidance on the design and optimization of architectures for polymeric materials requiring pore modification.

Characteristics of Polyphenolic Content in Brown Algae of the Pacific Coast of Russia.

Water and ethanol brown macroalgal extracts of nine species of Laminariales and four species of Fucales of the Pacific coast of Russia were investigated. It has been shown that brown algae species of Agarum, Thalassiophyllum, Fucus and Cystoseira can be a source of the polyphenolic compounds with antioxidant activity. Phenolic content in the ethanol algal extracts (Undaria pinnatifida, Arthrothamnus bifidus, Thalassiophyllum clathrus and Agarum turneri) was 1.1-3.5 times higher than in the water extracts. In Sargassum pallidum and Kjellmaniella crassifolia, the total polyphenolic content was 2.1 and 1.6 times higher, respectively, in water extracts than in ethanol extracts. The maximum radical scavenging activity has been detected in Agarum turneri ethanol extracts (38.8 mg ascorbic acid/g and 2506.8 µmol Trolox equiv/g dry algae). Phlorotannin content varies from 16.8 µg/g dry sample of Costaria costata to 2763.2 µg/g dry sample of Agarum turneri. It is found the content of polyphenolic compounds in brown algae is determined mainly by their species-specificity and by their belonging to the genus. The presence of major phenols in the extract of Thalassiophyllum clathrus, such as phenolic acid (gallic acid), hydroxycinnamic acids (caffeic acid, chlorogenic acid, coumaric acid) and flavonols (kaempferol, quercetin) has been established.

Phase Inversion-Induced Porous Polybenzimidazole Fuel Cell Membranes: An Efficient Architecture for High-Temperature Water-Free Proton Transport.

To cope with the demand for cleaner alternative energy, polymer electrolyte membrane fuel cells (PEMFCs) have received significant research attention owing to their high-power density, high fuel efficiency, and low polluting by-product. However, the water requirement of these cells has necessitated research on systems that do not require water and/or use other mediums with higher boiling points. In this work, a highly porous meta-polybenzimidazole (m-PBI) membrane was fabricated through the non-solvent induced phase inversion technique and thermal cross-linking for high-temperature PEMFC (HT-PEMFC) applications. Standard non-thermally treated porous membranes are susceptible to phosphoric acid (PA) even at low concentrations and are unsuitable as polymer electrolyte membranes (PEMs). With the porous structure of m-PBI membranes, higher PA uptake and minimal swelling, which is controlled via cross-linking, was achieved. In addition, the membranes exhibited partial asymmetrical morphology and are directly applicable to fuel cell systems without any further modifications. Membranes with insufficient cross-linking resulted in an unstable performance in HT-PEMFC environments. By optimizing thermal treatment, a high-performance membrane with limited swelling and improved proton conductivity was achieved. Finally, the m-PBI membrane exhibited enhanced acid retention, proton conductivity, and fuel cell performance.

Proton Transport in Aluminum-Substituted Mesoporous Silica Channel-Embedded High-Temperature Anhydrous Proton-Exchange Membrane Fuel Cells.

Polymer composite membrane technology is promising for enhancing the performance of membrane electrode assemblies for high-temperature fuel cells. In this study, we developed a novel anhydrous proton-exchange polybenzimidazole (m-PBI) composite membrane using Al-substituted mesoporous silica (Al-MCM-41) as a proton-carrier support. The surface-substituted Al-MCM-41 formed effective proton-transport pathways via its periodic hexagonal channel and improved the proton conductivity. The proton conductivity of an m-PBI filled with 9 wt.% filler was 0.356 S cm-1 at 160 °C and 0% humidity, representing an increase of 342% compared to that of a pristine m-PBI. Further, the current density at 0.6 V and maximum power density of m-PBI composite membranes were increased to 0.393 A cm-2 and 0.516 W cm-2, respectively. The enhanced fuel-cell performance was attributed to the proton-transfer channels and H3PO4 reservoirs formed by the mesopores of the Al-MCM-41 shell. The results indicated that Al-MCM-41 is suitable with respect to the hybrid homologues for enhancing the proton transport of the m-PBI membrane.

Amino Acid Composition, Antioxidant, and Cytoprotective Effect of Blue Mussel (Mytilus edulis) Hydrolysate through the Inhibition of Caspase-3 Activation in Oxidative Stress-Mediated Endothelial Cell Injury.

Enhanced oxidative stress plays a central role in promoting endothelial dysfunction, leading to the development of atherosclerosis. In this study, we investigated the protective effects of the hydrolysates derived from blue mussel (Mytilus edulis) against H2O2-mediated oxidative injury in human umbilical vein endothelial cells (HUVECs). The blue mussel hydrolysates were prepared by enzymatic hydrolysis with eight proteases, and blue mussel-α-chymotrypsin hydrolysate (BMCH) showed the highest antioxidant activities in DPPH radical scavenging, ABTS⁺ radical scavenging, and ORAC value compared to those of the other hydrolysates. BMCH also inhibited Cu2+-mediated low density lipoprotein (LDL) oxidation. Treatment of H2O2 resulted in the decreased HUVEC viability whereas pre-treatment with BMCH increased HUVEC viability and reduced reactive oxygen species (ROS) generation. BMCH pre-treatment increased cellular antioxidant capacities, including levels of glutathione (GSH), superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GPx) against H2O2-mediated oxidative stress in HUVECs. Flow cytometry and western blot analysis revealed that BMCH pre-treatment significantly reduced H2O2-mediated HUVEC apoptosis through inhibition of caspase-3 activation. Real-time-qPCR analysis showed that BMCH down-regulated expression of p53 and caspase-3 genes, as well as decreased the bax/bcl-2 ratio. Taken together, these results indicate that BMCH may be useful as functional food ingredients for protecting endothelial dysfunction or related disease.

Protective effect of enzymatic hydrolysates from seahorse (Hippocampus abdominalis) against H2O2-mediated human umbilical vein endothelial cell injury.

Oxidative stress-mediated endothelial dysfunction and LDL oxidation have been implicated in the pathogenesis of atherosclerosis. Thus, the protection of the endothelial cells against oxidative stress-mediated injury and the inhibition of LDL oxidation by the use of antioxidants are a good strategy against atherosclerosis development. Here, we investigated the protective effect and the inhibition of LDL oxidation of seahorse H. abdominalia hydrolysates by Alcalase (SHAH). SHAH showed higher antioxidant activities by measuring DPPH, ABTS+, and ORAC assays than the other hydrolysates. SHAH reduced the formation of thiobarbituric acid reactive substance in Cu2+-induced LDL oxidation. In human umbilical vein endothelial cell (HUVEC), SHAH ameliorated H2O2-mediated HUVEC injury through the restoration of antioxidant enzyme activities and glutathione. In addition, SHAH inhibited HUVEC apoptosis through the down-regulation of caspase-3 and p53 and the increase bcl-2/bax ratio. These results suggested that seahorse H. abdominalia could be developed as potential agents for atherosclerosis.

Molecular Design and Property Prediction of Sterically Confined Polyimides for Thermally Stable and Transparent Materials.

To meet the demand for next-generation flexible optoelectronic devices, it is crucial to accurately establish the chemical structure-property relationships of new optical polymer films from a theoretical point of view, prior to production. In the current study, computer-aided simulations of newly designed poly(ester imide)s (PEsIs) with various side groups (⁻H, ⁻CH3, and ⁻CF3) and substituted positions were employed to study substituent-derived steric effects on their optical and thermal properties. From calculations of the dihedral angle distribution of the model compounds, it was found that the torsion angle of the C⁻N imide bonds was effectively constrained by the judicious introduction of di-, tetra-, and hexa-substituted aromatic diamines with ⁻CF3 groups. A high degree of fluorination of the PEsI repeating units resulted in weaker intra- and intermolecular conjugations. Their behavior was consistent with the molecular orbital energies obtained using density functional theory (DFT). In addition, various potential energy components of the PEsIs were investigated, and their role in glass-transition behavior was studied. The van der Waals energy (EvdW) played a crucial role in the segmental chain motion, which had an abrupt change near glass-transition temperature (Tg). The more effective steric effect caused by ⁻CF3 substituents at the 3-position of the 4-aminophenyl group significantly improved the chain rigidity, and showed high thermal stability (Tg > 731 K) when compared with the ⁻CH3 substituent at the same position, by highly distorting (89.7°) the conformation of the main chain.

MMP-Inhibitory Effects of Flavonoid Glycosides from Edible Medicinal Halophyte Limonium tetragonum.

Limonium tetragonum has been well-known for its antioxidative properties as a halophyte. This study investigated the antimetastasis effect of solvent-partitioned L. tetragonum extracts (LTEs) and isolated compounds on HT1080 mouse melanoma cell model with a focus on matrix metalloproteinase (MMP) activity and TIMP and MAPK pathways. Upregulation and stimulation of MMPs result in elevated degradation of extracellular matrix which is part of several complications such as metastasis, cirrhosis, and arthritis. The anti-MMP capacity of LTEs was confirmed by their MMP-inhibitory effects, regulation of MMP and TIMP expression, and suppression of MAPK pathway. Among all tested LTEs, 85% aq. MeOH and n-BuOH were found to be most active fractions which later yielded two known flavonoid glycosides, myricetin 3-galactoside and quercetin 3-o-beta-galactopyranoside. Anti-MMP potential of the compounds was confirmed by their ability to regulate MMP expression through inhibited MAPK pathway activation. These results suggested that L. tetragonum might serve as a potential source of bioactive substances with effective anti-MMP properties.

Thermomechanical Behavior of Polymer Composites Based on Edge-Selectively Functionalized Graphene Nanosheets.

In this study, we demonstrate an effective approach based on a simple processing method to improve the thermomechanical properties of graphene polymer composites (GPCs). Edge-selectively functionalized graphene (EFG) was successfully obtained through simple ball milling of natural graphite in the presence of dry ice, which acted as the source of carboxyl functional groups that were attached to the peripheral basal plane of graphene. The resultant EFG is highly dispersible in various organic solvents and contributes to improving their physical properties because of its unique characteristics. Pyromellitic dianhydride (PMDA) and 4,4'-oxydianiline (ODA) were used as monomers for constructing the polyimide (PI) backbone, after which PI/EFG composites were prepared by in situ polymerization. A stepwise thermal imidization method was used to prepare the PI films for comparison purposes. The PI/EFG composite films were found to exhibit reinforced thermal and thermo-mechanical properties compared to neat PI owing to the interaction between the EFG and PI matrix.

Dioxinodehydroeckol Enhances the Differentiation of Osteoblasts by Regulating the Expression of Phospho-Smad1/5/8.

Lack of bone formation-related health problems are a major problem for the aging population in the modern world. As a part of the ongoing trend of developing natural substances that attenuate osteoporotic bone loss conditions, dioxinodehydroeckol (DHE) from edible brown alga Ecklonia cava was tested for its effects on osteoblastogenic differentiation in MC3T3-E1 pre-osteoblasts. DHE was observed to successfully enhance osteoblast differentiation, as indicated by elevated cell proliferation, alkaline phosphatase activity, intracellular cell mineralization, along with raised levels of osteoblastogenesis indicators at the concentration of 20 µM. Results suggested a possible intervening of DHE on the bone morphogenetic protein (BMP) signaling pathway, according to elevated protein levels of BMP-2, collagen-I, and Smads. In addition, the presence of DHE was also able to raise the phosphorylated extracellular signal-regulated kinase (ERK) and c-Jun N-terminal kinase (JNK) levels which are also activated by the BMP signaling pathway. In conclusion, DHE is suggested to be a potential bioactive compound against bone loss that could enhance osteoblastogenesis with a suggested BMP pathway interaction.

Fully Solution-Processed and Foldable Metal-Oxide Thin-Film Transistor.

Flexible and foldable thin-film transistors (TFTs) have been widely studied with the objective of achieving high-performance and low-cost flexible TFTs for next-generation displays. In this study, we introduced the fabrication of foldable TFT devices with excellent mechanical stability, high transparency, and high performance by a fully solution process including PI, YOx, In2O3, SWCNTs, IL-PVP, and Ag NWs. The fabricated fully solution-processed TFTs showed a higher transmittance above 86% in the visible range. Additionally, the charge-carrier mobility and Ion/Ioff ratio of them were 7.12 ± 0.43 cm(2)/V·s and 5.53 ± 0.82 × 10(5) at a 3 V low voltage operating, respectively. In particular, the fully solution-processed TFTs showed good electrical characteristics under tensile strain with 1 mm bending and even extreme folding up to a strain of 26.79%. Due to the good compatibility of each component layer, it maintained the charge-carrier mobility over 79% of initial devices after 5,000 cycles of folding test in both the parallel and perpendicular direction with a bending radius of 1 mm. These results show the potential of the fully solution-processed TFTs as flexible TFTs for a next generation devices because of the robust mechanical flexibility, transparency, and high electrical performance of it.

Anti-Inflammatory Activity of Heterocarpin from the Salt Marsh Plant Corydalis heterocarpa in LPS-Induced RAW 264.7 Macrophage Cells.

The inhibitory effect of three chromones 1-3 and two coumarins 4-5 on the production of nitric oxide (NO) was evaluated in LPS-induced RAW 264.7 macrophage cells. Among the compounds tested heterocarpin (1), a furochromone, significantly inhibited its production in a dose-dependent manner. In addition, heterocarpin suppressed prostaglandin E2 (PGE2) production and expression of cytokines such as inducible nitric oxide synthase (iNOS), cyclooxygenase-2 (COX-2), tumor necrosis factor-α (TNF-α), interleukin-1ß (IL-1ß) and interleukin-6 (IL-6).

Phlorotannins suppress adipogenesis in pre-adipocytes while enhancing osteoblastogenesis in pre-osteoblasts.

Osteoporosis, a prevalent bone disease in an aging population, is considered to be closely related to osteoblastogenesis and adipogenesis. As a part of an ongoing trend to develop natural substances that attenuate osteoporotic conditions, edible brown algae E. cava and its bioactive constituents were tested for their effects on adipogenic differentiation in 3T3-L1 fibroblasts and osteoblast differentiation in MC3T3-E1 pre-osteoblasts. Following an activity-based isolation, three phlorotannin derivatives, triphlorethol-A (1), eckol (2) and dieckol (3), were isolated. Anti-adipogenesis effect of phlorotannins at the concentration of 20 µM was observed by reduced lipid accumulation and the suppressed expression of adipogenic differentiation markers. In addition, isolated phlorotannins successfully enhanced the osteoblast differentiation as indicated by increased alkaline phosphatase activity along with raised levels of osteoblastogenesis indicators and intracellular calcification at the concentration of 20 µM. In conclusion, E. cava is suggested as a source for functional food ingredients, especially phlorotannin derivatives that can be utilized for extenuating osteoporosis and obesity.

A case of a mucinous adenocarcinoma arising from a rectal diverticulum.

The occurrence of an adenocarcinoma arising from a rectal diverticulum that causes mechanical ileus is very rare. Recently, we diagnosed a case of a mucinous adenocarcinoma in a rectal diverticulum after an emergent abdominal perineal resection and permanent colostomy by laparotomy. Here, we present a case report and a review of the literature.

Centella asiatica extracts modulate hydrogen peroxide-induced senescence in human dermal fibroblasts.

Centella asiatica (C. asiatica) is a pharmacological plant in South Asia. It has been demonstrated that C. asiatica extracts containing various pentacyclic triterpenes exert healing effects, especially wound healing and collagen synthesis in skin. However, there are few studies on the effect of C. asiatica extracts on stress-induced premature senescence (SIPS). To determine whether H(2) O(2) -induced senescence is affected by C. asiatica extracts, we performed senescence analysis on cultured human dermal fibroblasts (HDFs). We also analysed whole gene expression level using microarrays and showed that 39 mRNAs are differentially expressed in H(2) O(2) -induced HDFs with and without treatment with C. asiatica extracts. These genes regulate apoptosis, gene silencing, cell growth, transcription, senescence, DNA replication and the spindle checkpoint. Differential expression of FOXM1, E2F2, MCM2, GDF15 and BHLHB2 was confirmed using semi-quantitative PCR. In addition, C. asiatica extracts rescued the H(2) O(2) -induced repression of replication in HDFs. Therefore, the findings presented here suggest that C. asiatica extracts might regulate SIPS by preventing repression of DNA replication and mitosis-related gene expression.