Syntheses and biological activities of polymers containing methacryloyl‐2‐oxy‐1,2,3‐propanetricarboxylic acid or 5‐fluorouracil

A series of novel copolymers, poly(methacryloyl‐2‐oxy‐1,2,3‐propanetricarboxylic acid‐co‐exo‐3,6‐epoxy‐1,2,3,6‐tetrahydrophthalic acid) [poly(MTCA‐co‐ETAc)], poly(methacryloyl‐2‐oxy‐1,2,3‐propanetricarboxylic acid‐co‐hydrogenethyl‐exo‐3,6‐epoxy‐1,2,3,6‐tetrahydrophthalate) [poly(MTCA‐co‐HEET)], and poly(methacryloyl‐2‐oxy‐1,2,3‐propanetricarboxylic acid‐co‐α‐ethoxy‐exo‐3,6‐epoxy‐1,2,3,6‐tetrahydrophthaloyl‐5‐fluorouracil) [poly(MTCA‐co‐EETFU)], were prepared from corresponding monomers by photopolymerizations at 25°C for 48 h. The polymers were identified by FTIR, ¹H‐NMR, and ¹³C‐NMR spectroscopies. The number‐average molecular weights of the fractionated polymers determined by GPC were in the range from 9400 to 14,900 and polydispersity indices were 1.2–1.4. The in vitro IC₅₀ values of polymers against mouse mammary carcinoma (FM3A), mouse leukemia (P388), and human histiocytic lymphoma (U937) as cancer cell lines and mouse liver cells (AC2F) as a normal cell line were much higher compared to that of 5‐fluorouracil (5‐FU). The in vivo antitumor activities of monomers and polymers against mice bearing sarcoma 180 tumor cell line were better than those of 5‐FU. The inhibition of DNA replication and antiangiogenesis activities of MTCA and copolymers were better compared to those of 5‐FU. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 94: 57–64, 2004     

Isolation of the polysaccharidase-producing bacteria from the gut of sea snail, <Emphasis Type="Italic">Batillus cornutus</Emphasis>

This study was conducted to isolate microorganisms from the gut of the marine turban shell, Batillus cornutus, which inhabits the mainland of South Korea and primarily feeds on brown algae. We were interested in isolating such gut bacteria by considering their potential to produce the polysaccharidases required for digestion of brown seaweeds and isolated three different bacteria from the gut of Batillus cornutus. The isolated bacteria were identified as Bacillus sp. JMP-A, Bacillus sp. JMP-B and Staphylococcus sp. JMP-C. The organisms were evaluated for their ability to produce polysaccharidases such as cellulase, alginate lyase, laminarinase and kelp-lyase. Bacillus sp. JMP-A and Bacillus sp. JMP-B showed a clear zone of CMC hydrolysis with a radius 1.10 (±0.057) and 3.88 cm (±0.088), respectively, whereas Staphylococcus sp. JMP-C showed no zone of CMC hydrolysis. SEM analysis confirmed that the ability of the bacterial isolates to degrade kelp differs and is correlated with kelp-lyase production. The cell free extract of the Bacillus sp. JMP-A isolate showed the highest activities of CM-cellulase, α-cellulase, laminarinase and kelp-lyase, which were 22.76, 27.10, 66.59 and 64.36 U/mg, respectively. Meanwhile, the amount of sugars released was higher during the saccharification of kelp by dialyzed intracellular enzymes of the bacterial isolates than when dialyzed extracellular enzyme was used. Experimental results of dialyzed enzymatic saccharification of the kelp demonstrated that use of partially purified enzymes was effective for glucose production.     

Effects of selected water chemistry variables on copper pitting propagation in potable water

The pit propagation behavior of copper (UNS C11000) was investigated from an electrochemical perspective using the artificial pit method. Pit growth was studied systematically in a range of HCO₃⁻, SO₄²⁻ and Cl⁻ containing-waters at various concentrations. Pit propagation was mediated by the nature of the corrosion products formed both inside and over the pit mouth (i.e., cap). Certain water chemistry concentrations such as those high in sulfate were found to promote fast pitting that could be sustained over long times at a fixed applied potential but gradually stifled in all but the lowest concentration solutions. In contrast, Cl⁻ containing waters without sulfate ions resulted in slower pit growth and eventual repassivation. These observations were interpreted through understanding of the identity, amount and porosity of corrosion products formed inside and over pits. These factors controlled their resistive nature as characterized using electrochemical impedance spectroscopy. A finite element model (FEM) was developed which included copper oxidation kinetics, transport by migration and diffusion, Cu(I) and Cu(II) solid corrosion product formation and porosity governed by equilibrium thermodynamics and a saturation index, as well as pit current and depth of penetration. The findings of the modeling were in good agreement with artificial pit experiments. Malachite, bronchantite, cuprite, nantokite and atacamite corrosion products were both observed in experiment and predicted by the model. Stifling and/or repassivation occurred when the resistance of the corrosion product layer became high enough to lower the pit bottom potential and pit current density such as 10^-5 A/cm² could be attained with thick and dense layer. The ramifications of these findings towards pit propagation characteristics in potable waters will be discussed with improved insight into the roles of Cl⁻ and SO₄²⁻ ions.     

The Effect of Silver Chloride Formation on the Kinetics of Silver Dissolution in Chloride Solution

The precipitation and growth of AgCl on silver in physiological NaCl solution were investigated. AgCl was found to form at bottom of scratches on the surface which may be the less effective sites for diffusion or the favorable sites for heterogeneous nucleation. Patches of silver chloride expanded laterally on the substrate until a continuous film formed. The ionic transport path through this newly formed continuous film was via spaces between AgCl patches. As the film grew, the spaces between AgCl patches closed and ion transport was primarily via micro-channels running through AgCl patches. The decrease of AgCl layer conductivity during film growth were attributed to the clogging of micro-channels or decrease in charge carrier concentration inside the micro-channels. Under thin AgCl layer, i.e. on the order of a micrometer, the dissolution of silver substrate was under mixed activation-Ohmic control. Under thick AgCl layer, i.e. on the order of tens of micrometers, the dissolution of silver substrate was mediated by the Ohmic resistance of AgCl layer.     

The fabrication of graphitic thin films with highly dispersed noble metal nanoparticles by direct carbonization of block copolymer inverse micelle templates

Ordered arrays of Au or Ag nanoparticles supported on two-dimensional graphitic carbon films were prepared by direct carbonization of stabilized asymmetric polystyrene-block-poly(4-vinyl pyridine) (PS-b-P4VP) inverse micellar films loaded with metal precursors. Crosslinked PS-b-P4VP thin film templates with metal precursors selectively distributed in P4VP domains were converted to carbonaceous thin films having well-defined, highly dispersed metal nanoparticle (NP) arrays by ultraviolet (UV) irradiation under vacuum and subsequent carbonization. Mesoporous carbon films were also obtained after extracting the metal NPs by sonication in selected solvents. PS-b-P4VP was employed not only as carbon source, but also as template for introducing metal NPs in a nanopatterned configuration. The characteristic features and properties of thus generated hybrid carbon nanostructures were investigated by microscopy, UV–visible spectroscopy, X-ray photoelectron spectroscopy, X-ray diffraction measurement, and Raman spectroscopy.     

Improved performance of simulated moving bed process using column‐modified feed

A “FeedCol” strategy was developed to improve separation performance in simulated moving bed (SMB) processes. In the FeedCol operation, a short chromatographic column was simply added to the SMB unit and feed was supplied by a pulse input through the column to the SMB process. Because the feed was made in the shape of partially separated chromatographic peaks through the column, the purities in the raffinate and extract products were improved efficiently in the SMB process. All the performance parameters for a binary mixture with low selectivity (α = 1.1) were better for the FeedCol operation than for the conventional SMB operation (2‐2‐2‐2). Because the feed injection through the feed column was synchronized with the SMB process during the switching period, two new operating variables were introduced: injection length and injection time. Their effects on the suggested strategy were evaluated in terms of performance parameters through a detailed simulation study. © 2010 American Institute of Chemical Engineers AIChE J, 2011     

Preparation and characterization of polyimide/modified layered double hydroxide nanocomposites

Polyimide (PI)/modified layered double hydroxide (m‐LDH) nanocomposites were prepared in this study. For this work, m‐LDHs were prepared from layered double hydroxides (LDHs) through an anionic exchange reaction with pyromellitic dianhydride (PMDA), succinic acid or terephthalic acid. PMDA and 4,4′‐oxydianiline were used to make the poly(amic acid) precursor for PI. X‐ray diffraction and transmission electron microscopy measurements confirmed that the PMDA‐modified LDH (PMH) and terephthalic acid‐modified LDH (TMH) were well dispersed in the PI matrix. For the succinic acid‐modified LDH, some of the LDH was intercalated with the succinic acid molecules but most maintained its original structure. Thus, the PI/PMH and PI/TMH nanocomposites exhibited improved mechanical, thermal and electrical properties compared to pure PI. The PMH has aromatic groups and is expected to have better π–π interactions with the PI chains than the other m‐LDHs. Thus, the PI/PMH nanocomposites exhibited the best properties among the nanocomposites investigated. Copyright © 2010 Society of Chemical Industry     

连续时间模糊随机系统分析：状态空间模型分析

研究了连续时间模糊随机系统理论，给出了连续时间模糊随机系统的态变模糊订值映射的定义，讨论并解决了连续时间模糊随机系统的状态空间模型分析。     

Discomfort luminance level of head-mounted displays depending on the adapting luminance

The Images in an immersive head-mounted display (HMD) for virtual reality provide the sole source for visual adaptation. Thus, significant, near-instantaneous increases in luminance while viewing an HMD can result in visual discomfort. Therefore, the current study investigated the luminance change necessary to induce this discomfort. Based on the psychophysical experiment data collected from 10 subjects, a prediction model was derived using four complex images and one neutral image, with four to six levels of average scene luminance. Result showed that maximum area luminance has a significant correlation with the discomfort luminance level than average, median, or maximum pixel luminance. According to the prediction model, the discomfort luminance level of a head-mounted display was represented as a positive linear function in log₁₀ units using the previous adaptation luminance when luminance is calculated as maximum area luminance.     

Sodium azide and metal chelator effects on 2,2‐diphenyl‐1‐picrylhydrazyl (DPPH) radical scavenging compounds from methylene blue photosensitized lard

Thermal oxidation of edible oils can generate 2,2‐diphenyl‐1‐picrylhydrazyl (DPPH) radical scavenging compounds from oxidized lipids (RSOLs). However, effects of photosensitization on the formation of RSOLs have not been reported yet. Methylene blue (MB) photosensitization and involvement of singlet oxygen and transition metals on the RSOL formations were determined in stripped lard oils. RSOLs were formed in lard containing MB and visible light irradiation only. Addition of sodium azide decreased RSOLs with concentration dependent manner, which implies singlet oxygen was involved on the RSOL formation. Ethylenediammetetraacetic acid (EDTA), a well known metal chelator, accelerated the formation of RSOLs through protecting the decomposition of MB photosensitizer. Results from p‐anisidine values showed that RSOLs from photosensitization may not be formed from the same pathways compared to thermal oxidation. Practical application: Understanding mechanisms of lipid oxidation can help extend the shelf‐life of foods. Photosensitization plays important roles in accelerating the rates of lipid oxidation. The results of this study showed that foods containing photosensitizers can generate radical scavenging compounds from oxidized lipids (RSOLs) under visible light irradiation and singlet oxygen is involved in the formations of these compounds. However, these compounds may not share the same pathways with thermally oxidized lipids. Metal chelating agents accelerated the rates of lipid oxidation and formation of RSOLs which implies that metal chelators can act as prooxidant. Careful considerations are necessary on the addition of metal chelators because non‐polar photosensitizers can act a prooxidant.