Micellar and surface properties of a poly(methyl methacrylate)-block-poly(N-isopropylacrylamide) copolymer in aqueous solution

Critical micelle concentrations (cmc) of aqueous solutions of poly(methyl methacrylate)-block-poly(N-isopropylacrylamide) were determined at several temperatures by surface tensiometry. Below the lower critical solution temperature (LCST), the low Delta mic H 0 determined can be assigned to the PMMA block being tightly coiled in the dispersed molecular state, so that the unfavorable interactions of hydrophobic entities with water are minimized. Above the LCST the cmc value was found to increase; an anomalous behavior that can be directly related to the micelle-globule transition of the hydrophilic block. Interestingly, above the LCST the surface tension of relatively concentrated solutions was found to depend weakly on temperature not following the usual strong decrease with temperature expected for aqueous solutions.     

Essential oils of Satureja species: insecticidal effect on Culex pipiens larvae (Diptera: Culicidae)

The chemical composition of the essential oils of the wild growing plants of Greek S. spinosa L., S. parnassica subsp. parnassica Heldr.& Sart ex Boiss., S. thymbra and S. montana were determined by GC and GC/MS analysis. The larvicidal activities of the essential oils were assayed against Culex pipiens biotype molestus. The analytical data indicated that various monoterpene hydrocarbons and phenolic monoterpenes constitute the major constituents of the oils, but their concentration varied greatly among the oils examined. The bioassay results indicated that the oils possess significant larvicidal activities and represent an inexpensive source of natural substances mixture that exhibit potentials for use to control the mosquito larvae.     

How wall properties control diffusion in grooved nanochannels: a molecular dynamics study

The effect of a geometrically-rough wall, amplified by its degree of wettability and stiffness on diffusion coefficient in cases of fluid flow in nanochannels is studied by non-equilibrium molecular dynamics. Diffusion coefficient values, either inside the grooves or as average channel values are affected by the rough wall characteristics. A significant anisotropy along the directions parallel and normal to the flow is observed inside the grooves, while a critical value of groove length below which this anisotropy is enhanced exists. Wall wettability is the property that affects diffusion the most and could be a means of controlling its behavior.     

Mushroom Polysaccharides and Lipids Synthesized in Liquid Agitated and Static Cultures. Part I: Screening Various Mushroom Species

The effect of four synthetic media containing glucose (initial concentration 30?g?l^?1) on mycelial growth, exopolysaccharides (EPS) and cellular lipids production was examined in 11 mushroom species after 12 and 16?days of culture in static- and shake-flasks. Fatty acid analysis of cellular lipids produced was also performed. Agitation had a positive effect on biomass production, glucose consumption and lipid biosynthesis. Media that favoured the production of biomass were not suitable for EPS biosynthesis and vice versa. Biomass values varied from ??1.0?g?l^?1 (Lentinula edodes) to ??19?g?l^?1 (Pleurotus ostreatus), while the highest EPS quantity achieved ranged between 1.6 and 1.8?g?l^?1 (for Ganoderma lucidum and L. edodes, respectively). Quantities of total cellular lipids varied between 2.5 and 18.5?% w/w, in dry mycelial mass for the fungi tested. Lipid in dry weight values were influenced by the medium composition. Cellular lipids presented noticeable quantities of poly-unsaturated fatty acids like linoleic acid. Compared to most of the mushrooms tested, lipids of Volvariella volvacea were more saturated. The ability of several mushroom species of our study to produce in notable quantities the above-mentioned added-value compounds renders these fungi worthy for further investigations.     

On the Vekua Pair in Spheroidal Geometry and its Role in Solving Boundary Value Problems

The Vekua pair forms a transformation between the kernel of the Laplace's and the kernel of the Helmholtz's operator. In fact, it provides an interior solution of the Helmholtz's equation once an interior harmonic function is given, and conversely, given an interior solution of the Helmhotz's equation an interior harmonic function is constructed. Consequently, it seems that the Vekua connection offers the perfect ground to obtain solutions of boundary value problems connected with Helmholtz operator. Vekua expressed his transformation in spherical coordinates. Nevertheless, when a change of coordinates is applied, the transformation assumes a much more complicated form, but it still remains a very useful technique for dealing with solutions of the equations of Laplace and Helmholtz. Here we extend the Vekua theory to a new integral transformation pair concerning solutions of the aforementioned operators in exterior domains. In addition, the form of the Vekua transformation is analyzed in spheroidal coordinates and its implication to boundary value problems is investigated.     

Strained graphene as a local probe for plasmon‐enhanced Raman scattering by gold nanostructures

We investigate with Raman spectroscopy how gold nanostructures of different shape, size and geometry locally modify a graphene cover layer through strain. The resulting phonon softening translates into frequency downshifts of up to 85 cm^–1 for the 2D‐mode of graphene. With spatially resolved and excitation dependent Raman measurements we demonstrate that the downshifted Raman peaks exclusively arise from strained graphene subject to plasmonic enhancement by the nanostructures. The signals arise from an area well below the size of the laser spot. They serve as a local probe for the interaction between graphene and intense light fields. (© 2013 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Comparative study of perturbative methods for computing electron transfer tunneling matrix elements with a nonorthogonal basis set

The authors consider the problem of computing tunneling matrix elements for bridge-mediated electron transfer reactions using the Lowdin [J. Math. Phys. 3, 969 (1962); J. Mol. Spectrosc. 13, 326 (1964)] projection-iteration technique with a nonorthogonal basis set. They compare the convergence properties of two different Lowdin projections, one containing the overlap matrix S and the other containing the inverse S-1 in the projected Hamiltonian. It was suggested in the literature that the projected Hamiltonian with S-1 has better convergence properties compared to the projected Hamiltonian with S. The authors test this proposal using a simple analytical model, and ab initio Hartree-Fock calculations on different molecules with several types of basis sets. Their calculations show that, for Gaussian-type basis sets, the projected Hamiltonian containing S has the best convergence properties, especially for diffuse basis sets and in the strong coupling limit. The limit of diffuse basis sets is relevant to tunneling matrix element calculations involving excited states and anionic electron transfer.     

Complex Salts of Lanthanide(III) Nitrates from Di­pyridylamine: Preparation,Structural, and Thermoanalytical ­Investigation

The reaction of a lanthanide(III) nitrate (Ln = Pr, Nd) with the base 2, 2′‐dipyridylamine (dpamH) afforded two very stable microcrystalline compounds. These compounds were characterized as complex salts with the general formula [Ln(NO₃)₆] · 3[dpamH‐H⁺] · H₂O, where the dpamH ligand is not coordinated, but exists in its protonated form serving as counterion (dipyridylammonium cation), as it was revealed by single‐crystal X‐ray diffraction studies. Each one of the nitrate ions is coordinated, however, in a bidentate manner with the lanthanide(III) ion, which obtains coordination number twelve. All organic dpamH‐H⁺ cations are arranged in two columns parallel to the a axis of the cell forming pairs of almost parallel cationic molecules at a distance of about 3.5 Å. Inside each pair the molecules interact by strong π–π interactions. The water molecules, arranged between the inorganic anions [Ln(NO₃)₆]^3–, bridge them by strong hydrogen bonds, involving the water proton and one nitrate oxygen. The lattice can be described as made from successive organic and inorganic alternating parallel columns interacting between them with strong hydrogen bonds. The thermal stability and decomposition mode of the two lanthanide compounds were studied by the simultaneous TG/DTG‐DTA technique and compared with the starting hexahydrate lanthanide(III) salts and the dipyridylamine.     

157-nm Laser ablation of polymeric layers for fabrication of biomolecule microarrays

A new methodology for protein microarray fabrication is proposed based on the ablation of polymer film using laser at 157 nm (F₂). The polymer has been selected among others with the criterion of negligible protein adsorption. Improved results have been obtained by pretreatment of the polymer surface with an inert protein. The use of 157-nm laser radiation allowed very good depth control during the polymeric layer ablation process. In addition the importance of laser ablation at 157 nm is based on the fact that irradiated surfaces indicate limited chemical change due to the fact that laser ablation at 157 nm is only photochemical, thus avoiding excessive surface heating and damage. Results of protein microarray fabrication are presented to illustrate the viability of the proposed method.