Asymptotic analysis of a transport model of organic material through a stratified porous medium: Concentration effect

We consider the transport through capillarity of an organic material inside a porous medium, using Leverett’s model. We first prove an existence result for a weak solution of this nonlinear evolution problem, using a regularization process. We then describe the asymptotic behavior of the solution, when the permeability _kε$k_{\epsilon }$ of the porous medium is associated to a scalar function which only depends on the third variable, assuming that _kε$k_{\epsilon }$ (resp. the inverse of _kε$k_{\epsilon }$) converges to some measure _λ∗${\lambda }_{\ast }$ (resp. λ^∗${\lambda }^{\ast }$). We use Γ-convergence arguments in order to describe this asymptotic behavior. We finally characterize the asymptotic behavior of the problem, considering special choices of the permeability _kε$k_{\epsilon }$, which correspond to stratified porous media, and give a numerical test for a 1D model.     

Multiscale Modeling of Nanocrystalline Materials: A Variational Approach

This paper presents a variational multi-scale constitutive model in the finite deformation regime capable of capturing the mechanical behavior of nanocrystalline (nc) fcc metals. The nc-material is modeled as a two-phase material consisting of a grain interior (GI) phase and a grain boundary (GB) phase. A rate-independent isotropic porous plasticity model is employed to describe the GB phase, whereas a crystal-plasticity model which accounts for the transition from partial dislocation to full dislocation mediated plasticity is employed for the GI phase. Assuming the rule of mixtures, the overall behavior of a given grain is obtained via volume averaging. The scale transition from a single grain to a polycrystal is achieved by Taylor-type homogenization. It is shown that the proposed model is able to capture the inverse Hall-Petch effect. (© 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)     

Anticancer and anti-inflammatory sulfur-containing semisynthetic derivatives of sarcophine

Sarcophine (1), a cembranoid diterpene is known to inhibit the process of tumorigenesis. Sarcophine can be isolated in large amounts from the Red Sea soft coral Sarcophyton glaucum and hence is an ideal target for semisynthetic or biocatalytic modifications. Hydroxylated derivatives of 1 were reported to improve its anticancer activity. Despite the promising results and ready availability, there are limited attempts towards further diversifying the library of sarcophine derivatives. Hence, the current study targets the epoxide ring to generate sulfur-containing derivatives of sarcophine by reacting it with ammonium thiocyanate and Lawesson's reagent. Structure elucidation of the products was based on extensive 1D and 2D NMR and high resolution mass spectrometry, in addition to mechanistic considerations. The effect of these derivatives on highly malignant +SA mammary epithialial cell proliferation is reported. Anti-inflammatory potential of sarcophine and its derivatives is also demonstrated.     

An interlaboratory study to evaluate potential matrix reference materials for herbicides in water

Matrix reference materials (MRM) are essential tools for the validation of analytical protocols. Nowadays, there are no such materials for the determination of herbicides in water. Pesticides stored in acetonitrile and stored on solid phase extraction (SPE) cartridges previously percolated with a water sample spiked with triazines and phenylureas have proven to be good candidates for reference materials because of their satisfactory stability under appropriate temperature conditions. To evaluate the behaviors of these materials containing pesticides and to be analyzed by liquid chromatography, a collaborative study including 15 laboratories has been organized. Observed reproducibility on candidate materials after the removal of extreme results was 16.1% for the vials with pesticides in acetonitrile (at around 0.125 mg/L) directly analyzed, 29.2% for a water sample spiked with the pesticides (at around 0.5 microg/L) analyzed after preconcentration on a cartridge and 26.7% for the cartridges previously percolated with a water containing the pesticides (250 mL at around 0.5 microg/L for each pesticide) analyzed after elution. Such dispersion values are quite compatible with the requirement of a further certification for such materials.     

Thermosolvatochromism of merocyanine polarity indicators in pure and aqueous solvents: relevance of solvent lipophilicity

The following novel solvatochromic probes were synthesized: 2,6-dibromo-4-[(E)-2-(1-alkylpyridinium-4-yl)ethenyl] phenolate, where the alkyl groups are methyl, n-butyl, n-hexyl, and n-octyl, respectively. Solvatochromism of three of these probes (C(1), C(4), and C(8)) was studied in 36 protic and aprotic solvents. A modified linear solvation energy relationship has been applied to the data obtained at 25 degrees C. Correlation of (empirical) polarities with other solvent properties showed more dependence on lipophilicity than on basicity. A similar conclusion has been reached for a series of other solvatochromic indicators. Exceptions are those that carry acidic hydrogens, being biased toward solvent basicity. Thermosolvatochromism has been studied in mixtures of water with methanol, 1-propanol, acetonitrile, and DMSO. Thermosolvatochromic data have been treated according to a model that explicitly considers the presence in bulk solution of three "species": water, organic component, and solvent-water hydrogen-bonded aggregate. Solvation by the latter is favored over solvation by either of the two precursor solvents (aqueous DMSO is an exception). Temperature increase resulted in desolvation of the probes, due to concomitant decrease of the structures of the component solvents. The above-mentioned modified solvation equation has been successfully applied to solvatochromism in aqueous methanol and aqueous 1-propanol.     

Synthesis and chemistry of aryloxygermylene-amine complexes

The synthesis of stable monomeric dimesityloxygermylene-amine (MesO)₂Ge-NR₃ [NR₃ = Et₂NH, (C₆H₁₁)₂NH, Et₃N, dabco, tmeda] and chloromesityloxygermylene-amine MesO(Cl)Ge-tmeda complexes is presented. All compounds have been fully characterized by spectroscopic methods. The insertion reaction of (MesO)₂Ge-tmeda 1a with dimethyl disulfide, bis(trimethylsilyl)peroxide and iodomethane is reported. Cycloaddition reactions with dimethylbutadiene are especially effective without any activation and with dimethyl acetylenedicarboxylate led selectively to compounds 7 and 8. In the latter case, the transient formation of a germirene has been evidenced by a trapping reaction. The structures of 3, 7 and 8 were determined by single-crystal X-ray diffraction.     

Microwaves in organic synthesis: Synthesis of pyridazinones,phthalazinones and pyridopyridazinones from 2‐oxo‐arylhydrazones under microwave irradiation

The phenylhydrazones 1a‐d condensed with ethyl cyanoacetate to yield pyridazinones 2a‐d that reacted with sulphur in presence of piperidine to yield the aminothienopyridazineones 3a,b that reacted with electron poor olefins and acetylenes to yield phthalazines 10‐12. The condensed aminothiophenes 3a,b reacted with dimethylformamide dimethylacetal to yield amidines 13a,b. Compounds 2a,b condensed with dimethylformamide dimethylacetal to yield the trans enamines 16a,b that cyclized readily into the pyridopyridazinones 17a,b on treatment with ammonium acetate in presence of acetic acid. Compounds 2a‐d reacted also with benzylidenemalononitrile to yield the phthalazinones 21a‐d. The reactions were conducted both by microwave heating and conventional heating. Better yields in much shorter reaction times were achieved by microwave heating.     

Optically tunable microcavity in a planar photonic crystal silicon waveguide buried in oxide

We present all-optical tuning and switching of a microcavity inside a two-dimensional photonic crystal waveguide. The photonic crystal structure is fabricated in silicon-on-insulator using complementary metal-oxide semiconductor processing techniques based on deep ultraviolet lithography and is completely buried in a silicon dioxide cladding that provides protection from the environment. By focusing a laser onto the microcavity region, both a thermal and a plasma dispersion effect are generated, allowing tuning and fast modulation of the in-plane transmission. By means of the temporal characteristics of the in-plane transmission, we experimentally identify a slower thermal and a fast plasma dispersion effect with modulation bandwidths of the order of several 100 kHz and up to the gigahertz level, respectively.     

Effect of Bi‐content on hardness and micro‐creep behavior of Sn‐3.5Ag rapidly solidified alloy

In the present paper, the influence of 1, 3, 5 and 10 % Bi (weight %) as ternary additions on structure, melting and mechanical properties of rapidly solidified Sn‐3.5Ag alloy has been investigated. The effect of Bi was discussed based on the experimental results. The experimental results showed that the alloys of Sn‐3.5Ag, Sn‐3.5Ag‐1Bi and Sn‐3.5Ag‐3Bi are composed of two phases; Ag₃Sn IMC embedded in Sn matrix phase, which indicated that the solubility of Bi phase in Sn‐matrix was extended to 3 % as a result of rapid solidification. Bi precipitation in Sn matrix was only observed in Sn‐3.5Ag‐5Bi and Sn‐3.5Ag‐10Bi alloys. Also, addition of Bi decreased continuously the melting point of the eutectic Sn‐3.5Ag alloy to 202.6 °C at 10 % Bi. Vickers hardness of Sn‐3.5Ag rapidly solidified alloy increased with increasing Bi content up to 3 % due to supersaturated solid solution strengthening hardening mechanism of Bi phase in Sn matrix, while the alloys contain 5 and 10 % Bi exhibited lower values of Vickers hardness. The lower values can be attributed to the precipitation of Bi as a secondary phase which may form strained regions due to the embrittlement of Bi atom. In addition, the effect of Bi addition on the micro‐creep behavior of Sn‐3.5Ag alloy as well as the creep rate have been described and has been calculated at room temperature. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Effects of Anisotropy and Drying Air Parameters on Drying of Deformable Porous Media Hydro-Dynamically and Thermally Anisotropic

The purpose of this work was to investigate numerically the drying of saturated deformable porous media. The considered sample is a rectangular porous plate which assumed to be both hydro-dynamically and thermally anisotropic, while the mechanical behavior of the sample is supposed to be isotropic. All walls of the plate are subjected to a convective heat flux. Moreover, the top and bottom walls are allowed the mass transfer. The Darcy–Brinkman extended model was used as the momentum balance equation for the liquid and solid phases. The energy balance equation is based on the local thermodynamic equilibrium assumption between the both phases. The lattice Boltzmann method is used to solve the governing differential equation system. A comprehensive analysis of the effect of anisotropy and the drying air parameters on macroscopic fields is investigated throughout this work.