Synthesis of Poly(silyne-co-hydridocarbyne) for Silicon Carbide Production

Pre-ceramic polymers have previously been shown to be polymeric precursors to silicon carbide, diamond and diamond-like carbon. Here, we report the synthesis of a pre-ceramic polymer, poly(silyne-co-hydridocarbyne), which was electrochemically synthesized from one monomer containing both silicon and carbon in its structure. The polymer is soluble in common solvents such as CHCl₃, CH₂Cl₂ and THF. Since the polymer contains both silyne and carbyne on its backbone, it can be easily converted to silicon carbide upon heating under an ambient inert atmosphere, or to SiO₂ under ambient air atmosphere. Poly(silyne-co-hydridocarbyne) was characterized with UV/Vis spectroscopy, FTIR, ¹H-NMR, GPC and Raman spectroscopy. Conversion of the polymer to SiC ceramic was accomplished by heating at 1000 and 750°C under an argon atmosphere and characterized with optical microscopy, SEM, X-Ray and Raman spectroscopies.     

Design,Synthesis, and Evaluation of Novel 2H-Benzo[b][1,4]thiazin-3(4H)-one Derivatives as New Acetylcholinesterase Inhibitors

Alzheimer’s disease (AD) is a slowly progressive neurodegenerative disease that causes dementia in people aged 65 and over. In the present study, a series of thiadiazole hybrid compounds with benzothiazine derivatives as acetylcholinesterase inhibitors were developed and evaluated for their biological activity. The AChE and BChE inhibition potentials of all compounds were evaluated by using the in vitro Ellman method. The biological evaluation showed that compounds 3i and 3j displayed significant inhibitory activity against AChE. Compounds 3i and 3j showed IC₅₀ values of 0.027 µM and 0.025 µM against AChE, respectively. The reference drug donepezil (IC₅₀ = 0.021 µM) also showed significant inhibition against AChE. Further docking simulation also revealed that these compounds (3i and 3j) interacted with the active site of the enzyme similarly to donepezil. The antioxidant study revealed that compounds 3i and 3j exhibited greater antioxidant effects. An in vitro blood–brain barrier permeability study showed that compounds 3i and 3j are promising compounds against AD. The cytotoxicity study of compounds 3i and 3j showed non-cytotoxic with an IC₅₀ value of 98.29 ± 3.98 µM and 159.68 ± 5.53 µM against NIH/3T3 cells, respectively.     

Preparation of fluorinated methacrylate/clay nanocomposite via in‐situ polymerization: Characterization,structure, and properties

Novel fluorinated coating containing well‐dispersed silicate nanolayers is successfully produced via in‐situ free radical polymerization of 2,2,2‐trifluoroethyl methacrylate in the presence of vinylbenzyl‐functionalized montmorillonite with different loading. The organic modification of sodium montmorillonite is achieved through an ion exchange reaction with triphenylvinylbenzylphosphonium chloride as surfactant prepared before use by reaction with vinylbenyl chloride and phosphine. The following in‐situ polymerization in the presence of organomodified clay leads to fluorinated nanocomposites with of partially exfoliated and intercalated morphologies, as determined via XRD and TEM analysis. The nanoscale dispersion of clay layers is also evidenced by thermal analysis; a moderate decrease of the glass transition temperature about 2–8 °C compared to their virgin PMATRIF and an improvement of their thermal stability as evidenced by TGA. The wettability of the nanocomposite films is also studied by contact angle measurements with water. The incorporation of organomodified clays not only increases the hydrophobicity of the fluorinated polymers but also improves the surface properties of obtained nanocomposites. Compared the virgin homopolymer, the mechanical properties of the nanocomposites are reduced by addition of organomodifed clay at temperature from 30 to 60 °C, whereas this trend is gradually decreased at higher temperature. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55, 411–418     

Hydrophobic coatings from photochemically prepared hydrophilic polymethacrylates via electrospraying

Linear poly(hydroxyethyl methacrylate‐co‐methyl methacrylate) P(HEMA‐co‐MMA) and poly(dimehylaminoethyl methacrylate‐co‐methyl methacrylate) P(DMAEMA‐co‐MMA) and their corresponding hyperbranched copolymers were synthesized by conventional photoinitiated free radical polymerization and self‐condensing vinyl polymerization (SCVP) using Type I and Type II photoinitiators, respectively. Then, the polymers were processed by electrospraying in N, N‐dimethylformamide. The surface of the resulting electrospray coatings was examined by SEM, XPS, and WCA then compared with those prepared by drop casting. Regardless of the structural nature of the polymers, electrospraying allows the preparation of rough surface that shows more hydrophobic behavior. Electrospray coatings with linear and hyperbranched copolymers exhibited WCA as ～150° and ～130°, respectively, indicating that branching reduces the WCA. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55, 1338–1344     

Ultraviolet Radiation‐Induced Downregulation of SERCA2 Mediates Activation of NLRP3 Inflammasome in Basal Cell Carcinoma

Basal cell carcinomas (BCCs) account for majority of skin malignancies in the United States. The incidence of BCCs is strongly associated with exposure of ultraviolet (UV) radiation. Nucleotide‐binding domain, leucine‐rich‐repeat‐containing family, pyrin domain‐containing 3 (NLRP3) inflammasome plays an important role in innate immune responses. Different stimuli such as toxins, microorganisms and particles released from injured cells activate the NLRP3 inflammasome. Activated NLRP3 results in activation of caspase‐1, which cleaves pro‐IL‐1β to active IL‐1β. In this study, we have shown that NLRP3 is expressed in human basal cell carcinomas. The proximal steps in activation of NLRP3 inflammasome are not well understood. Here, we have attempted to elucidate a critical role for Ca²⁺ mobilization in activation of the NLRP3 inflammasome by UVB exposure using HaCaT keratinocytes. We have demonstrated that UVB exposure blocks Ca²⁺ mobilization by downregulating the expression of sarco/endoplasmic reticulum Ca²⁺‐ATPase (SERCA2), a component of store‐operated Ca²⁺ entry that leads to activation of the NLRP3 inflammasome.     

Enhanced Production of Poly-γ-glutamic Acid by <Emphasis Type="Italic">Bacillus licheniformis</Emphasis> TISTR 1010 with Environmental Controls

Bacillus licheniformis TISTR 1010 was used for glutamic acid-independent production of poly-γ-glutamic acid (γ-PGA). A fed-batch production strategy was developed involving feedings of glucose, citric acid, and ammonium chloride at specified stages of the fermentation. With the dissolved oxygen concentration controlled at ≥50% of air saturation and the pH controlled at ~7.4, the fed-batch operation at 37 °C afforded a peak γ-PGA concentration of 39.9 ± 0.3 g L^?1 with a productivity of 0.926 ± 0.006 g L^?1 h^?1. The observed productivity was nearly threefold greater than previously reported for glutamic acid-independent production using the strain TISTR 1010. The molecular weight of γ-PGA was in the approximate range of 60 to 135 kDa.     

Solanum anguivi Lam. Fruits: Their Potential Effects on Type 2 Diabetes Mellitus

Type 2 diabetes mellitus (T2DM) is a complex metabolic disorder of glucose homeostasis associated with a status of insulin resistance, impaired insulin signaling, β-cell dysfunction, impaired glucose and lipid metabolism, sub-clinical inflammation, and increased oxidative stress. Consuming fruits and vegetables rich in phytochemicals with potential antidiabetic effects may prevent T2DM and/or support a conservative T2DM treatment while being safer and more affordable for people from low-income countries. Solanum anguivi Lam. fruits (SALF) have been suggested to exhibit antidiabetic properties, potentially due to the presence of various phytochemicals, including saponins, phenolics, alkaloids, ascorbic acid, and flavonoids. For the saponin fraction, antidiabetic effects have already been reported. However, it remains unclear whether this is also true for the other phytochemicals present in SALF. This review article covers information on glucose homeostasis, T2DM pathogenesis, and also the potential antidiabetic effects of phytochemicals present in SALF, including their potential mechanisms of action.     

Synthesis,characterization, and thermally activated curing of oligosiloxanes containing benzoxazine moieties in the main chain

Oligosiloxanes containing thermally curable benzoxazine units in the main chain have been synthesized. For this purpose, first the diallyl functional monomer is synthesized through the Mannich and ring closing reaction of 4,4′‐isopropylidenediphenol (bisphenol A), formaldehyde and allylamine. Hydrosilylation reaction of the resulting diallylic monomer (B‐ala) with 1,1,3,3‐tetramethyldisiloxane (TMDS) in the presence of Pt catalyst yields the corresponding poly(B‐ala‐tetramethyl disiloxane)s (PBTMDS) with the molecular weights in the range of 1800–4100 Da. The structures of the precursor diallyl monomer and the resulting polymers are confirmed by FT‐IR and ¹H NMR analysis. Curing behavior of both the monomer and polymers has also been studied by Differential Scanning Calorimetry (DSC). Flexible free standing transparent films of the oligosiloxanes are obtained by solvent casting from dichloromethane solution on Teflon plates. The films preserve shape and, to some extent, toughness after thermal curing between 100 and 180 °C. Thermal properties of the cured polymers are also investigated by thermogravimetric analysis (TGA). © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 804–811, 2009     

Poly(styrene‐b‐tetrahydrofuran)/clay nanocomposites by mechanistic transformation

Synthesis of poly(styrene‐block‐tetrahydrofuran) (PSt‐b‐PTHF) block copolymer on the surfaces of intercalated and exfoliated silicate (clay) layers by mechanistic transformation was described. First, the polystyrene/montmorillonite (PSt/MMT) nanocomposite was synthesized by in situ atom transfer radical polymerization (ATRP) from initiator moieties immobilized within the silicate galleries of the clay particles. Transmission electron microscopy (TEM) analysis showed the existence of both intercalated and exfoliated structures in the nanocomposite. Then, the PSt‐b‐PTHF/MMT nanocomposite was prepared by mechanistic transformation from ATRP to cationic ring opening polymerization (CROP). The TGA thermogram of the PSt‐b‐PTHF/MMT nanocomposite has two decomposition stages corresponding to PTHF and PSt segments. All nanocomposites exhibit enhanced thermal stabilities compared with the virgin polymer segments. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 2190–2197, 2009     

Dependence on dilution of critical and compensation temperatures of a two-dimensional mixed spin-1/2 and spin-1 system

In this study, dependence on site dilution of critical and compensation temperatures of a two-dimensional mixed spin-1/2 and spin-1 system has been investigated with Monte Carlo simulation. The dependence of the thermal and magnetic behaviors on dilution of mixed spin system has been discussed. We have shown that the critical and compensation temperatures of diluted mixed spin system linearly decrease with increasing number of diluted sites.