A Hybrid Method for Low Reynolds Number Flow Past an Asymmetric Cylindrical Body

Low Reynolds number fluid flow past a cylindrical body of arbitrary shape in an unbounded, two-dimensional domain is a singular perturbation problem involving an infinite logarithmic expansion in the small parameter ε, representing the Reynolds number. We apply a hybrid asymptotic–numerical method to compute the drag coefficient, C _D and lift coefficient C _L to within all logarithmic terms. The hybrid method solution involves a matrix M , depending only on the shape of the body, which we compute using a boundary integral method. We illustrate the hybrid method results on an elliptic object and on a more complicated profile.     

Microwave enhanced non-alkaline bleaching of mechanical pulps: A new solution to an old problem

Since the granting of our first US patent on microwave induced catalytic decomposition of PCBs some 18 years ago, microwave technology has slowly begun to attract some industrial attention in the last few years. There was no doubt that microwaves had been applied to facilitate the conventional bleaching process of wood pulps in the past but with little or no success. The myth that microwaves can be regarded and manipulated as a rapid heat source probably caused most of the failures of unsuccessful microwave applications. It is therefore necessary to understand the real potential of microwaves as an energy source and to identify the many critical electromagnetic properties of the load (chemical systems), before a final choice of a proper microwave system be designed and installed. In this preliminary report, we demonstrate the real potential of pulsed microwave radiation for non-alkaline bleaching of mechanical pulps. Typically, very high consistency TMP up to 93% can be treated by pulsed microwave in the order of 90 seconds with an average increase of 20 to 25 points in brightness.     

Pentaruthenium-Based Borides Stabilized by Gold(I) Phosphine Units

The pentaruthenium boride cluster [Ru₅(CO)₁₅B]^- has been prepared from [Ru₆(CO)₁₇B]^- but is unstable. The Ru₅(CO)₁₅B-core can be stabilized in the form of [Ru₅(CO)₁₅BAuPR₃] (R=Ph or o-tolyl). Addition of [(Ph₃PAu)₃O][BF₄] to [Ru₅(CO)₁₅B]^- gives the trigold derivative [Ru₅(CO)₁₄B(AuPPh₃)₃] which possesses an novel core structure.     

Adsorptive behavior and electrochemical determination of the anti-fungal agent ketoconazole

The adsorptive properties and electrochemical behavior of ketoconazole, an oral anti-fungal agent, are demonstrated at a glassy carbon electrode. The adsorption of the compound obeys the Frumkin isotherm with an interaction factor (α) of 0.985 and adsorptive coefficient (β) of 1.98 × 10⁶ L mol^–1. The Gibbs energy of adsorption (ΔG) is –3.59 × 10⁴ J mol^–1 at 25?°C. A very sensitive electroanalytical method has been developed for determination of the drug with a detection limit of 4.0 × 10^–11 mol L^–1. Relationships between stripping current and concentration of ketoconazole were linear in the range 10^–6–10^–10 mol L^–1 with different preconcentration periods. The method has been used to measure the ketoconazole content of tablets.     

An algorithm for recognising the exterior square of a matrix

We describe a polynomial-time algorithm for recognising the exterior square of a matrix. The approach involves manipulation of the equations which relate the entries of a matrix and the entries of its exterior square. Conditions are given which are necessary and sufficient for two matrices to have the same exterior square. The definition of the exterior square of a matrix, and the algorithm used to recognise one, are both easily extended to matrix groups.     

Development of Amino Acids Functionalized SBA-15 for the Improvement of Protein Adsorption

Ordered mesoporous materials and their modification with multiple functional groups are of wide scientific interest for many applications involving interaction with biological systems and biomolecules (e.g., catalysis, separation, sensor design, nano-science or drug delivery). In particular, the immobilization of enzymes onto solid supports is highly attractive for industry and synthetic chemistry, as it allows the development of stable and cheap biocatalysts. In this context, we developed novel silylated amino acid derivatives (Si-AA-NH₂) that have been immobilized onto SBA-15 materials in biocompatible conditions avoiding the use of toxic catalyst, solvents or reagents. The resulting amino acid-functionalized materials (SBA-15@AA) were characterized by XRD, TGA, EA, Zeta potential, nitrogen sorption and FT-IR. Differences of the physical properties (e.g., charges) were observed while the structural ones remained unchanged. The adsorption of the enzyme lysozyme (Lyz) onto the resulting functionalized SBA-15@AA materials was evaluated at different pHs. The presence of different functional groups compared with bare SBA-15 showed better adsorption results, for example, 79.6 nmol of Lyz adsorbed per m² of SBA-15@Tyr compared with the 44.9 nmol/m² of the bare SBA-15.     

The Human Melanocyte as a Particular Target for UVA Radiation and an Endpoint for Photoprotection Assessment

The induction of DNA breaks by UVA (320-400 nm) in the nucleus of normal human melanocytes in culture was investigated using single cell gel electrophoresis, also called the comet assay. Endogenous pigment and/or melanin-related molecules were found to enhance DNA breakage: comets were more intense in melanocytes than in fibroblasts, in cells with high melanin content or after stimulation of melanogenesis by supplying tyrosine in the culture medium. After UVA doses where strong comets were observed, neither cytotoxicity nor stimulation of tyrosinase activity were detected. However, the accumulation of p53 protein suggested that cells reacted to genotoxic stress under these experimental conditions. The same approach was used to compare two sunscreens with identical sun protection factors but different UVA protection factors. The results presented in this paper suggest that human melanocytes may be used as a target cell to evidence broadspectrum photoprotection. Moreover, these data appear to be helpful in getting a better understanding of the role of sunlight in the initiating steps of melanocyte transformation.     

Automated Parallel Synthesis of MADIX (Co)Polymers

An automated parallel synthetic approach has been developed for synthesizing polymer libraries by the Macromolecular Design via the Interchange of Xanthates (MADIX) process. The experimental set‐up, parallel polymerizations, characterization, and reproducibility tests are detailed. Examples of acrylic diblock copolymers synthesized in this way are given.

Automated MADIX polymerizations of BA in the presence of a X₁ ‐capped PEA.     

Adapting (4,4) Networks through Substituent Effects and Conformationally Flexible 3,2’:6’,3”-Terpyridines

Coordination networks formed between Co(NCS)₂ and 4’-substituted-[1,1’-biphenyl]-4-yl-3,2’:6’,3”-terpyridines in which the 4’-group is Me (1), H (2), F (3), Cl (4) or Br (5) are reported. [Co(1)₂(NCS)₂]_n·4.5nCHCl₃, [Co(2)₂(NCS)₂]_n·4.3nCHCl₃, [Co(3)₂(NCS)₂]_n·4nCHCl₃, [Co(4)₂(NCS)₂]_n, and [Co(5)₂(NCS)₂]_n·nCHCl₃ are 2D-networks directed by 4-connecting cobalt nodes. Changes in the conformation of the 3,2’:6’,3”-tpy unit coupled with the different peripheral substituents lead to three structure types. In [Co(1)₂(NCS)₂]_n·4.5nCHCl₃, [Co(2)₂(NCS)₂]_n·4.3nCHCl₃, [Co(3)₂(NCS)₂]_n·4nCHCl₃, cone-like arrangements of [1,1’-biphenyl]-4-yl units pack through pyridine…arene π-stacking, whereas Cl…π interactions are dominant in the packing in [Co(4)₂(NCS)₂]_n. The introduction of the Br substituent in ligand 5 switches off both face-to-face π-stacking and halogen…π-interactions, and the packing interactions are more subtly controlled. Assemblies with organic linkers 1–3 are structurally similar and the lattice accommodates CHCl₃ molecules in distinct cavities; thermogravimetric analysis confirmed that half the solvent in [Co(3)₂(NCS)₂]_n·4nCHCl₃ can be reversibly removed.     

Studies of difurylmethane‐maleic anhydride copolymer as an ion‐responsive membrane for the determination of mono‐, di‐ and tri‐valent cations

The synthesis of the difurylmethane‐maleicanhydride(DFM‐MAH) copolymer was done by reacting difurylmethane with maleic acid followed by hydrolysis with sodium hydroxide to produce the anhydride sodium salt. Construction of a sensor with the copolymer as the ion‐exchanger material was done by mixing the copolymer with poly(vinylchloride), PVC, plastic matrix and dibutylphthalate (DBP) plasticizer in tetrahydrofuran (THF) solvent to form a paste. The paste was coated on a piece of silver wire to produce a coated wire electrode (CWE). The response characteristics of the copolymer‐CWE, in potentiometric analysis, were studied for mono‐, di‐ and tri‐valent cations. All the cations studied showed a near‐Nernstian response for concentrations ranging from 5 x 10⁻⁸ M to 1 x 10⁰M in triethanolamine buffer in aqueous media (0.5 M, pH 10.5). The membrane had a composition of 20:20:60 for the copolymer, PVC and DBP.