Structural Diversity and Defensive Properties of Norditerpenoid Alkaloids

We have tested the insect antifeedant and toxic activity of 43 norditerpenoid alkaloids on Spodoptera littoralis and Leptinotarsa decemlineata including eserine (physostigmine), anabasine, and atropine. Antifeedant effects of the test compounds were structure- and species-dependent. The most active antifeedants to L. decemlineata were 1,14-diacetylcardiopetaline (9) and 18-hydroxy- 14-O-methylgadesine (33), followed by 8-O-methylconsolarine (12), 14-O-acetyldelectinine (27), karakoline (7), cardiopetaline (8), 18-O-demethylpubescenine (13), 14-O-acetyldeltatsine (18), takaosamine (21), ajadine (24), and 8-O-methylcolumbianine (6) (EC50 < 1 microg/cm2). This insect showed a moderate response to atropine. S. littoralis had the strongest antifeedant response to 24, 18, 14-O-acetyldelcosine (19), and delphatine (29) (EC50 < 3 microg/cm2). None of the model substances affected the feeding behavior of this insect. The most toxic compound to L. decemlineata was aconitine (1), followed by cardiopetalidine (10) (% mortality > 60), 14-deacetylpubescenine (14), 18-O-benzoyl-18-O-demethyl-14-O-deacetylpubescenine (17), 14-O-acetyldelcosine (19), 14-deacetylajadine (25) and methyllycaconitine (30) (% mortality > 45). Orally injected S. littoralis larvae were negatively affected by 1, cardiopetaline (8), 10, 1,14-O-acetylcardiopetalidina (11), 12, 14, 1,18-O-diacetyl-19-oxo-gigactonine (41), olivimine (43), and eserine in varying degrees. Their antifeedant or insecticidal potencies did not parallel their reported nAChR binding activity, but did correlate with the agonist/antagonist insecticidal/antifeedant model proposed for nicotininc insecticides. A few compounds [14, tuguaconitine (38), 14-demethyldelboxine (40), 19, dehydrodelsoline (36), 18-O-demethylpubescenine (13), 41, 9, and delcosine (23)] had selective cytotoxic effects to ward insect-derived Sf9 cells. None were cytotoxic to mammalian CHO cells and none increased Trypanosoma cruzi mortality. The selective cytotoxic effects of some structures indicate that they can act on biological targets other than neuroreceptors.     

Fast detection of exact clones in business process model repositories

As organizations reach higher levels of business process management maturity, they often find themselves maintaining very large process model repositories, representing valuable knowledge about their operations. A common practice within these repositories is to create new process models, or extend existing ones, by copying and merging fragments from other models. We contend that if these duplicate fragments, a.k.a. exact clones, can be identified and factored out as shared subprocesses, the repository's maintainability can be greatly improved. With this purpose in mind, we propose an indexing structure to support fast detection of clones in process model repositories. Moreover, we show how this index can be used to efficiently query a process model repository for fragments. This index, called RPSDAG, is based on a novel combination of a method for process model decomposition (namely the Refined Process Structure Tree), with established graph canonization and string matching techniques. We evaluated the RPSDAG with large process model repositories from industrial practice. The experiments show that a significant number of non-trivial clones can be efficiently found in such repositories, and that fragment queries can be handled efficiently.     

Polymeric thin films of controlled complex refractive index formedby the electrostatic self-assembled monolayer process

This letter reports a method, the electrostatic self-assembled monolayer process, for the synthesis of multilayer thin-film materials with controlled complex refractive index. By incorporating appropriate precursor molecules in each monolayer and organizing the physical order of the multiple monolayers through the material, it is possible to achieve designed complex refractive index properties. In this work, the real part of the refractive index of materials formed by this process was controlled from 1.424 to 1.615, and the imaginary part was controlled from 0.00001 to 0.035, both at a wavelength of 550 nm. To our knowledge, this is the first time that experimental measurements of self-assembled thin films are presented to demonstrate that this method is useful for the design and synthesis of thin films of controllable refractive index     

Synthesis and properties of new derivatives of poly[9‐(2,3‐epoxypropyl)carbazole]

BACKGROUND: Carbazole derivatives are well known to exhibit interesting electro‐ and photo‐active properties due to their hole‐transporting ability, strong absorption in the ultraviolet spectral region and blue‐light emission. One of the most widely studied materials among carbazole‐containing oligomers is poly[9‐(2,3‐epoxypropyl)carbazole] (PEPK). The main field of application of this oligomer is electrophotographic microfilming. It is also used for the manufacture of multicolour slides and in the photothermoplastic recording of information. Unfortunately, due to its high ionization potential, which reaches 5.86 eV, the possibilities of application of this compound in optoelectronic devices are rather limited. RESULTS: PEPK‐based charge transporting oligomers, incorporating hydrazone moieties, are reported. The oligomers were prepared by chemical modification of PEPK. The materials obtained were examined using various techniques including differential scanning calorimetry and ultraviolet, infrared and NMR spectroscopy. Electron photoemission spectra of layers of the synthesized oligomers showed ionization potentials (I_p) in the range 5.4–5.5 eV. CONCLUSION: The synthesized oligomers possess a larger π‐conjugated system and show ionization potentials of ca 5.4 eV. Therefore, they are more suitable for use in optoelectronic devices with quicker photoresponse than unmodified PEPK. Copyright © 2008 Society of Chemical Industry     

Characterization and thermal degradation kinetics of poly(l‐lactide) nanocomposites with carbon nanotubes

The purpose of this research was to study the thermal degradation kinetics of nanocomposites of poly(l ‐lactide) (PLLA) with carbon nanotubes (CNT) in order to provide further insight into their thermal stability. Nanocomposites were prepared by solvent casting with 1, 3, and 5% by weight of pristine CNT (P‐CNT) or functionalized CNT (F‐CNT), and were characterized using infrared spectroscopy, transmission electron microscopy, differential scanning calorimetry, thermogravimetric analysis, and dynamic‐mechanical‐thermal analysis. The kinetic parameters of thermal decomposition were determined employing Coats‐Redfern method to calculate the reaction order and E₂ function model to calculate the activation energy (Ea). We found no major changes in PLLA glass transition temperatures due to CNT presence, but melt‐crystallization temperature increased slightly in some composites. In general, composites consisting of 3% or 5% of F‐CNT had superior thermal stability than did pure polymer or P‐CNT composites. This improved thermal stability was revealed by slightly higher degradation and onset temperatures, and Ea obtained from kinetic analysis. In addition, 3% or 5% of F‐CNT in PLLA composites slightly enhanced the storage modulus above the glass transition. Therefore, functionalization promoted, in some extent, better morphology and dispersion of CNT into the matrix, which was responsible for improved thermal stability and thermomechanical performance of composites at higher temperatures relative to pure polymer. POLYM. ENG. SCI., 55:710–718, 2015. © 2014 Society of Plastics Engineers     

In vitro and in vivo inhibition of Hass avocado polyphenol oxidase enzymatic browning by paeonol, β-cyclodextrin,and paeonol:β-cyclodextrin inclusion complex

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Assessment of production efficiency,physicochemical properties and storage stability of spray-dried propolis,a natural food additive,using gum Arabic and OSA starch-based carrier systems

The aim of this work was to obtain propolis in a powder, alcohol-free, water-dispersed and shelf-stable form. Propolis extract was spray-dried using gum Arabic and octenyl succinic anhydride (OSA) starch as carriers in two different weight ratios (1:4 and 1:6). Spray-dried propolis samples were evaluated for morphology, moisture, water activity, water dispersibility, hygroscopicity, particle size, particle distribution, entrapping efficiency, stability, isotherms and antioxidant properties. The spray-drying process produced round particles with sizes ranging from 15 to 24 μm. This process preserved the antioxidant activity of propolis and also allowed propolis to be obtained in a powder form, which was stable during storage at room temperature, had low hygroscopicity and was highly dispersible in cold water. The application of this technology could increase the use of propolis in various industrial applications, such as an antimicrobial and as an antioxidant in food.     

Structural chirality of cholesteric liquid crystal produces atropisomerism: Chiroptical polyisocyanides from achiral monomer in cholesteric liquid crystal matrix

1-Naphthyl isocyanide was polymerized with Ni(II) catalyst in a cholesteric matrix at the liquid crystal (LC) temperature range. The resultant polymers showed optical activity. In this reaction, the structural chirality of cholesteric LC effectively functions to impart one-handed helicity on the corresponding polymers as an optically active atropisomer.     

Liquid crystalline polyamines containing side dendrons: Toward the building of ion channels based on polyamines

In this article, we modified poly[2-(aziridin-1-yl)ethanol] (PAZE) with the dendron 3,4,5-tris[4-(n-dodecan-1-yloxy)benzyloxy]benzoic acid, to obtain liquid crystalline columnar polyamines. The chemical modification reaction was first tuned on a model compound, N,N-dimethyl-2-hydroxyethylamine. The best results were obtained by the esterification method with N,N'-dicyclohexylcarbodiimide at room temperature, in the presence of 4-dimethylaminopyridine. The obtained copolymers showed higher char yield than starting PAZE. In all cases they exhibited small crystalline portions after annealing and columnar mesophases, as inferred by DSC, XRD and POM. The dimension of the unit cell resulted slightly narrower than in the case of the copolyethers bearing the same dendron. This is probably due to the presence of a longer spacer in PAZE, which allows better accommodating of the side tapered group.     

Impact of Condensates Containing Chloride and Sulphate on the Corrosion in Automotive Exhaust Systems

The chemical composition of condensates recovered from a test car was systematically analysed in this study. It was found that most condensates contain a higher concentration of chloride than that of sulphate. In order to understand the effect of sulphate on the pitting behaviour of 436SS and to predict whether pitting will occur in these condensates, pitting potentials were determined in a 0.2M sulphate solution with varying chloride concentration by using the potentiodynamic cyclic polarization curve method. The results demonstrate that sulphate prevents pitting initiation of 436SS when the concentration of sulphate is higher than that of chloride. However, no inhibitory effect of sulphate was observed when the sulphate concentration is lower than the chloride concentration. As the condensate recovered from the muffler contains more chloride than sulphate, the muffler is most likely suffering from pitting. This was confirmed by the microscopic observation of the corroded muffler from the test car.