Modeling the geometric characteristics of five-dimensionally woven composites

An analytical modeling approach for the prediction of the geometric characteristics of five-dimensional (5D) woven composites has been formulated. The model is driven by readily available data including the weaving parameters and constituent material properties. The new model calculates the individual proportions of fiber in each direction, areal density, overall fiber volume fraction, and laminate thickness. This information is useful for the engineer in the design and manufacture of 5D woven composites. In addition the present model outputs the mathematical definition of the 5D woven composite unit cell, which could be implemented as the geometric input for a downstream analytical model that is capable of predicting the elastic stiffness of 5D woven composites. Input parameters have been sourced from existing published work and the subsequent predictions made by the model are compared with the available experimental data on 5D woven composites.

A metal complex that imitates a micelle

A metal complex with a micelle-like, core-shell structure adopts higher nuclearity in water than in organic solvents, thereby imitating also the growth of a micelle, but through covalent rather than non-covalent aggregation.

A stereocontrolled method for the synthesis of D- and L-2-deoxy-C-nucleosides using an intramolecular Sakurai-type cyclisation reaction

A novel synthetic procedure has been developed that provides access to D/L-2-deoxy-C-nucleosides from 3,4-epoxytetrahydrofuran in seven steps and in moderate to good yields. The key chemical transformation was the Lewis acid catalysed intramolecular cyclisation reaction of an acetal for which the stereochemical outcome was dependent of the reagents' ratio.

The modification of PLA and PLGA using electron-beam radiation

The degradable polymers polylactide (PLA) and polylactide-co-glycolide (PLGA) have found widespread use in modern medical practice. However, their slow degradation rates and tendency to lose strength before mass have caused problems. The aim of this study was to ascertain whether treatment with e-beam radiation could address these problems. Samples of PLA and PLGA were manufactured and placed in layered stacks, 8.1 mm deep, before exposure to 50 kGy of e-beam radiation from a 1.5 MeV accelerator. Gel permeation chromatography testing showed that the molecular weight of both materials was depth-dependent following irradiation, with samples nearest to the treated surface showing a reduced molecular weight. Samples deeper than 5.4 mm were unaffected. Computer modeling of the transmission of a 1.5 MeV e-beam in these materials corresponded well with these findings. An accelerated mass-loss study of the treated materials found that the samples nearest the irradiated surface initiated mass loss earlier, and at later stages showed an increased percentage mass loss. It was concluded that e-beam radiation could modify the degradation of bioabsorbable polymers to potentially improve their performance in medical devices, specifically for improved orthopedic fixation.

Highly selective and efficient hydrogenation of carboxylic acids to alcohols using titania supported Pt catalysts

Selective hydrogenation of carboxylic acids to alcohols and alkanes has been achieved under remarkably mild reaction temperatures and H-2 pressures (333 K, 0.5 MPa) using Pt/TiO2 catalyst.

Gene delivery using dimethyldidodecylammonium bromide-coated PLGA nanoparticles

In this present work we describe a poly(lactic-co-glycolic acid) (PLGA) nanoparticle formulation for intracellular delivery of plasmid DNA. This formulation was developed to encapsulate DNA within PLGA nanoparticles that combined salting out and emulsion evaporation processes. This process reduced the requirement for sonication which can induce degradation of the DNA. A monodispersed nanoparticle population with a mean diameter of approximately 240 nm was produced, entrapping a model plasmid DNA in both supercoiled and open circular structures. To induce endosomal escape of the nanoparticles, a superficial cationic charge was introduced using positively charged surfactants cetyl trimethylammonium bromide (CTAB) and dimethyldidodecylammonium bromide (DMAB), which resulted in elevated zeta potentials. As expected, both cationic coatings reduced cell viability, but at equivalent positive zeta potentials, the DMAB coated nanoparticles induced significantly less cytotoxicity than those coated with CTAB. Fluorescence and transmission electron microscopy demonstrated that the DMAB coated cationic nanoparticles were able to evade the endosomal lumen and localise in the cytosol of treated cells. Consequently, DMAB coated PLGA nanoparticles loaded with a GFP reporter plasmid exhibited significant improvements in transfection efficiencies with comparison to non-modified particles, highlighting their functional usefulness. These nanoparticles may be useful in delivery of gene therapies to targeted cells. (C) 2010 Elsevier Ltd. All rights reserved.

Anionic N,O-ligated Pd(II) complexes: highly active catalysts for alcohol oxidation.

There is a need to develop effective catalytic methods for alcohol oxidation. Pd(II) complexes have shown great promise as catalysts, however a comparatively small number of ligands have been reported so far. Herein we report the use of commercially available anionic N,O-ligands to produce highly active catalysts.

Total synthesis of (+)-A83586C, (+)-kettapeptin and (+)-azinothricin: powerful new inhibitors of beta-catenin/TCF4-and E2F-mediated gene transcription

Herein we describe our asymmetric total syntheses of (+)-A83586C, (+)-kettapeptin and (+)-azinothricin. We also demonstrate that molecules of this class powerfully inhibit beta-catenin/TCF4- and E2F-mediated gene transcription within malignant human colon cancer cells at low drug concentrations.

On the dissolution of non-metallic solid elements (sulfur, selenium, tellurium and phosphorus) in ionic liquids

Ionic liquids are shown to be good solvents for elemental sulfur, selenium, phosphorus and tellurium, and can be designed to maximise the solubility of these elements. The presence of the [S-3](center dot-) radical anion in diluted solutions of sulfur in some ionic liquids has been confirmed, and is the origin of their intense blue colour (cf. lapis lazuli).

Fast, copper-free click chemistry: a convenient solid-phase approach to oligonucleotide conjugation

Solid-phase oligonucleotide conjugation by nitrile oxide-alkyne click cycloaddition chemistry has been successfully demonstrated; the reaction, compatible with all nucleobases, requires no metal catalyst and proceeds under physiological conditions.

Is the pinning of ordinary dislocations in γ-TiAl intrinsic or extrinsic in nature? A combined atomistic and kinetic Monte Carlo approach

We address the question of the observed pinning of 1/2

The effect of temperature and strain rate on the deformation behaviour, structure development and properties of biaxially stretched PET-clay nanocomposites.

The inclusion of a synthetic fluoromica clay in PET affects its processability via biaxial stretching and stretching temperature (95 °C and 102 °C) and strain rate (1 s-1 and 2 s-1) influence the structuring and properties of the stretched material. The inclusion of clay has little effect on the temperature operating window for the PET–clay but it has a major effect on deformation behaviour which will necessitate the use of much higher forming forces during processing. The strain hardening behaviour of both the filled and unfilled materials is well correlated with tensile strength and tensile modulus. Increasing the stretching temperature to reduce stretching forces has a detrimental effect on clay exfoliation, mechanical and O2 barrier properties. Increasing strain rate has a lesser effect on the strain hardening behaviour of the PET–clay compared with the pure PET and this is attributed to possible adiabatic heating in the PET–clay sample at the higher strain rate. The Halpin–Tsai model is shown to accurately predict the modulus enhancement of the PET–clay materials when a modified particle modulus rather than nominal clay modulus is used.

Bis-guanylhydrazone diimidazo[1,2-a:1,2-c]pyrimidine as a novel and specific G-quadruplex binding motif

A bis-guanylhydrazone derivative of diimidazo[1,2-a:1,2-c]pyrimidine has unexpectedly been found to be a potent stabiliser of several quadruplex DNAs, whereas there is no significant interaction with duplex DNA. Molecular modeling suggests that the guanylhydrazone groups play an active role in quadruplex binding.

Selectivity in small molecule binding to human telomeric RNA and DNA quadruplexes

Quadruplex RNAs are less well understood than their DNA counterparts, yet of potentially high biological relevance. The interactions of several quadruplex-binding ligands with telomeric RNA quadruplexes are reported and compared with their binding to the analogous DNA quadruplexes.