Critical aspects related to processing of carbon nanotube/unsaturated thermoset polyester nanocomposites

Carbon nanotubes (CNTs) have outstanding mechanical, thermal and electrical properties. As a result, particular interest has been recently given in exploiting these properties by incorporating carbon nanotubes into some form of matrix. Although unsaturated polyesters with styrene have widespread use in the industrial applications, surprisingly there is no study in the literature about CNT/thermoset polyester nanocomposite systems. In the present paper, we underline some important issues and limitations during the processing of unsaturated polyester resins with different types of carbon nanotubes. In that manner, 3-roll mill and sonication techniques were comparatively evaluated to process nanocomposites made of CNTs with and without amine (NH₂) functional groups and polyesters. It was found that styrene evaporation from the polyester resin system was a critical issue for nanocomposite processing. Rheological behaviour of the suspensions containing CNTs and tensile strengths of their resulting nanocomposites were characterized. CNT/polyester suspensions exhibited a shear thinning behaviour, while polyester resin blends act as a Newtonian fluid. It was also found that nanotubes with amine functional groups have better tensile strength, as compared to those with untreated CNTs. Transmission electron microscopy (TEM) was also employed to reveal the degree of dispersion of CNTs in the matrix.     

Coupling of pentacarbonyl[(cyclopropyl)methoxymethylene]molybdenum complex with ferrocenyl alkynes: Synthesis of ferrocenyl-substituted cycloheptadienones and cycloheptenediones

Pentacarbonyl[(cyclopropyl)methoxymethylene]molybdenum complex reacts with ferrocenyl alkynes to afford ferrocenyl-substituted 2,4-cycloheptadienones as major products, accompanied by varying amounts of 2-cycloheptene-1,4-diones and/or 2-cyclobutenones. 2-Cycloheptene-1,4-diones are secondary reaction products and result from initially formed 2,4-cycloheptadienones via hydrolysis. In one reaction, a hydroxy-substituted 2,4-cycloheptadienone derivative was isolated, which was not observed previously from similar reactions.     

Iridoid Glucosides from Eremostachys moluccelloides Bunge

From the aerial parts of Eremostachys moluccelloides Bunge , a new iridoid glucoside, lamalbidic acid ( 7 ), was isolated as its choline salt 7a together with six known iridoid glucosides, 5‐deoxysesamoside ( 1 ), 6β‐hydroxy‐7‐epiloganin ( 2 ), lamalbide ( 3 ), shanzhiside methyl ester ( 4 ), sesamoside ( 5 ), and 5‐deoxypulchelloside I ( 6 ). The structures of 7a and 7 (obtained from 7a ) were elucidated by spectroscopic (UV, IR, 1D‐ and 2D‐NMR, and ESI‐MS) methods.     

Rapidly converging threshold value calculations in screened coulomb potential systems: Critical values of the screening parameter for the Yukawa case

In this work, the threshold values of the screening parameter for Yukawa potential systems are obtained by means of a basis set constructed from Laguerre type functions. The Laguerre basis set is modified by an appropriately chosen extra function in order to imitate the true behaviour of the solutions at the boundary points. The method used is a variational scheme and the numerical results are accurate to thirty decimal points. A scaling parameter is also inserted into the structure of the basis functions, the optimized values of which accelerate the convergence. The main goal of this paper is to develop a method which enables us to calculate the threshold values of the screening parameter for low-lying states. The method is quite general and can be extended to all systems whose potentials decay exponentially when the radial variable goes to infinity.     

Factorization of certain evolution operators using lie algebra: Convergence theorems

This work concerns convergence theorems with a sequence of -approximants for exponential evolution operators with Lie operator arguments. A companion paper presents the formulation of the -approximants. The theorems presented in this paper give the conditions which are sufficient for convergence of the sequences. Although the main emphasis will be on convergence properties of the one-dimensional case, the generalization to multidimensional cases is quite straightforward.Supported by the Department of Energy.     

Synthesis, characterization and some properties of novel bis(pentafluorophenyl)methoxyl substituted metal free and metallophthalocyanines

The preparation of some new tetrakis[bis(pentafluorophenyl)methoxyl] substituted metal free and metallophthalocyanine (MPcs) complexes were achieved by the tetramerization of 4-[bis(pentafluorophenyl)methoxy]phthalonitrile with Li metal in pentan-1-ol or metal [Co(II) or Zn(II)] acetates in DMAE, respectively. The structures of the target compounds were confirmed by elemental analysis, IR, UV–vis, ¹H NMR, ¹⁹F NMR and mass spectroscopic methods. MPcs are soluble only in strong and medium polar solvents while the metal free one is soluble in weakly, medium and strong polar solvents. The temperature and frequency dependence of the electrical conductivities were studied on spin coated films of the compounds using dc and impedance spectroscopy techniques in the frequency range from 40 to 10⁵ Hz and within the temperature range from 290 to 440 K. The temperature dependence of the exponent s and conductivity, σ_ac, were completely in agreement with the prediction of the hopping model. The redox properties of the complexes were determined by cyclic voltammetry. The nature of the redox processes was also confirmed using spectroelectrochemical measurements.     

Protein-protein interactions in complex cosolvent solutions.

The effects of various kosmotropic and chaotropic cosolvents and salts on the intermolecular interaction potential of positively charged lysozyme is evaluated at varying protein concentrations by using synchrotron small-angle X-ray scattering in combination with liquid-state theoretical approaches. The experimentally derived static structure factors S(Q) obtained without and with added cosolvents and salts are analysed with a statistical mechanical model based on the Derjaguin-Landau-Verwey-Overbeek (DLVO) potential, which accounts for repulsive and attractive interactions between the protein molecules. Different cosolvents and salts influence the interactions between protein molecules differently as a result of changes in the hydration level or solvation, in charge screening, specific adsorption of the additives at the protein surface, or increased hydrophobic interactions. Intermolecular interaction effects are significant above protein concentrations of 1 wt %, and with increasing protein concentration, the repulsive nature of the intermolecular pair potential V(r) increases markedly. Kosmotropic cosolvents like glycerol and sucrose exhibit strong concentration-dependent effects on the interaction potential, leading to an increase of repulsive forces between the protein molecules at low to medium high osmolyte concentrations. Addition of trifluoroethanol exhibits a multiphasic effect on V(r) when changing its concentration. Salts like sodium chloride and potassium sulfate exhibit strong concentration-dependent changes of the interaction potential due to charge screening of the positively charged protein molecules. Guanidinium chloride (GdmCl) at low concentrations exhibits a similar charge-screening effect, resulting in increased attractive interactions between the protein molecules. At higher GdmCl concentrations, V(r) becomes more repulsive in nature due to the presence of high concentrations of Gdm(+) ions binding to the protein molecules. Our findings also imply that in calculations of thermodynamic properties of proteins in solution and cosolvent mixtures, activity coefficients may not generally be neglected in the concentration range above 1 wt % protein.     

Cytotoxic and apoptotic potential of some coumarin and 2-amino-3-carbonitrile selenophene derivatives in prostate cancer

3-acetyl coumarin derivatives (1a-d) are formed as a result of condensation of salicylaldehyde derivatives and ethyl acetoacetate and were converted into coumarin-selenophene hybrid compounds (2a-d) in the basic medium by modified Gewald reaction in the presence of malononitrile and selenium. Products are characterized by nuclear magnetic resonance (NMR). The prepared compounds are screened for their anticancer activity against DU-145 cell line. In addition, selected target compounds are evaluated for apoptosis and oxidative stress on DU-145 (prostate carcinoma) cell lines.     

Synthesis of ferrocenyl quinolines

A convenient one-pot synthesis of ferrocenyl-substituted quinolines via a molecular iodine-catalyzed reaction of ferrocenylimines with enolizable aldehydes is reported. First, nucleophilic addition of the in situ generated enol to ferrocenylimine produces β-anilinopropionaldehyde, which then undergoes intramolecular Friedel-Crafts reaction to give dihydroquinoline derivative. Finally, subsequent dehydration and aerobic oxidation affords ferrocenyl quinolines.     

Mn(OAc)3-promoted sulfur-directed addition of an active methylene compound to alkenes

Various alkenes substituted at the 1,2-positions by phenyl, thiophene and furan rings were reacted with 3-(4-methoxyphenyl)-3-oxopropanenitrile in the presence of Mn(OAc)₃·2H₂O. The exact structure and configuration of the dihydrofuran derivatives formed were determined. In all cases only one regioisomer was formed. The observed regioselectivity was explained on the basis of the formation of a complex between Mn(OAc)₃, alkene, and 3-(4-methoxyphenyl)-3-oxopropanenitrile, which directs the mode of the addition to the double bond.