Carbon-branched carbohydrate chirons: synthesis of C-3 and C-4-branched sugar lactones derived from d-erythronolactone

Two carbon chain extensions using a Wittig reaction on both a 1-deoxy ribulose derivative and a C-2-branched erythrose derivative are reported. Subsequent dihydroxylation resulted in the synthesis of C-3 and C-4 methyl-branched sugar lactones, the useful synthetic building blocks. Control of the stereoselectivity of both the Wittig reaction and the dihydroxylation is investigated, and 3-C-methyl and 4-C-methyl d-altrono-1,4-lactones and d-glucono-1,4-lactone and 4-C-hydroxymethyl-d-altrono-1,4-lactone were synthesised.     

Vibrational dynamics of biological molecules: Multi-quantum contributions

High-resolution X-ray measurements near a nuclear resonance reveal the complete vibrational spectrum of the probe nucleus. Because of this, nuclear resonance vibrational spectroscopy (NRVS) is a uniquely quantitative probe of the vibrational dynamics of reactive iron sites in proteins and other complex molecules. Our measurements of vibrational fundamentals have revealed both frequencies and amplitudes of ⁵⁷Fe vibrations in proteins and model compounds. Information on the direction of Fe motion has also been obtained from measurements on oriented single crystals, and provides an essential test of normal mode predictions. Here, we report the observation of weaker two-quantum vibrational excitations (overtones and combinations) for compounds that mimic the active site of heme proteins. The predicted intensities depend strongly on the direction of Fe motion. We compare the observed features with predictions based on the observed fundamentals, using information on the direction of Fe motion obtained either from DFT predictions or from single crystal measurements. Two-quantum excitations may become a useful tool to identify the directions of the Fe oscillations when single crystals are not available.     

Solution-phase synthesis of ICG-001, a β-turn peptidomimetic molecule inhibitor of β-catenin–Tcf-mediated transcription

The solution-phase synthesis of the β-turn peptidomimetic ICG-001, a selective inhibitor of Wnt/β-catenin signalling, which has been found to be important for both initiation and progression of cancers of different tissues and has been exploited as an extremely useful chemogenomic tool, was developed. This route is particularly suitable for the multigram scale preparation of ICG-001.     

(2S,3R,4S,5R)‐Diethyl 2‐(10,10‐dimethyl‐3,3‐dioxo‐3λ6‐thia‐4‐azatricyclo[5.2.1.01,5]decan‐4‐ylcarbonyl)‐5‐phenylpyrrolidine‐3,4‐dicarboxylate: a novel isomorphous‐by‐addition compound

The title compound, C₂₇H₃₆N₂O₇S, (I), is isomorphous by addition with the dimethyl ester analogue [Garner, Dogan, Youngs, Kennedy, Protasiewicz & Zaniewski (2001). Tetrahedron, 57 , 71–85], (II), by replacing two methyl ester H atoms with two methyl groups. With the exception of the conformation of one of the ester groups, the molecules are almost superimposable. Likewise, apart from a slightly larger c axis in (I), few differences in the cell packing of (I) and (II) are found, with both dominated by the same C—H...O hydrogen bonds. Full synthetic and spectroscopic details of (I) are given. The molecular synthesis is important as an example of chiral auxiliary‐assisted 1,3‐dipolar cycloaddition of an azomethine ylid.     

Continuity of Quantum Channel Capacities

We prove that a broad array of capacities of a quantum channel are continuous. That is, two channels that are close with respect to the diamond norm have correspondingly similar communication capabilities. We first show that the classical capacity, quantum capacity, and private classical capacity are continuous, with the variation on arguments e{\varepsilon} apart bounded by a simple function of e{\varepsilon} and the channel’s output dimension. Our main tool is an upper bound of the variation of output entropies of many copies of two nearby channels given the same initial state; the bound is linear in the number of copies. Our second proof is concerned with the quantum capacities in the presence of free backward or two-way public classical communication. These capacities are proved continuous on the interior of the set of non-zero capacity channels by considering mutual simulation between similar channels.     

Supply Chain Optimisation in the Paper Industry

We describe the formulation and development of a supply-chain optimisation model for Fletcher Challenge Paper Australasia (FCPA). This model, known as Paper Industry Value Optimisation Tool (PIVOT), is a large mixed integer program that finds an optimal allocation of supplier to mill, product to paper machine, and paper machine to customer, while at the same time modelling many of the supply chain details and nuances which are peculiar to FCPA. PIVOT has assisted FCPA in solving a number of strategic and tactical decision problems, and provided significant economic benefits for the company.     

Dirac Nodal Arc Semimetal PtSn4: An Ideal Platform for Understanding Surface Properties and Catalysis for Hydrogen Evolution

Conductivity, carrier mobility, and a suitable Gibbs free energy are important criteria that determine the performance of catalysts for a hydrogen evolution reaction (HER). However, it is a challenge to combine these factors into a single compound. Herein, we discover a superior electrocatalyst for a HER in the recently identified Dirac nodal arc semimetal PtSn₄. The determined turnover frequency (TOF) for each active site of PtSn₄ is 1.54 H₂ s^?1 at 100 mV. This sets a benchmark for HER catalysis on Pt‐based noble metals and earth‐abundant metal catalysts. We make use of the robust surface states of PtSn₄ as their electrons can be transferred to the adsorbed hydrogen atoms in the catalytic process more efficiently. In addition, PtSn₄ displays excellent chemical and electrochemical stabilities after long‐term exposure in air and long‐time HER stability tests.     

Vanadium(III) Acetylacetonate as an Efficient Soluble Catalyst for Lithium–Oxygen Batteries

High donor number (DN) solvents in Li—O₂ batteries that dissolve superoxide intermediates in lithium peroxide (Li₂O₂) formation facilitate high capacities at high rates and avoid early cell death. However, their beneficial characteristics also result in an instability towards highly reactive superoxide intermediates. Furthermore, Li—O₂ batteries would deliver a superior energy density, but the multiphase electrochemical reactions are difficult to achieve when operating with only solid catalysts. Herein we demonstrate that vanadium(III) acetylacetonate (V(acac)₃) is an efficient soluble catalyst that can address these problems. During discharge, V(acac)₃ integrates with the superoxide intermediate, accelerating O₂ reduction kinetics and reducing side reactions. During charge, V(acac)₃ acts as a redox mediator that permits efficient oxidation of Li₂O₂. The cells with V(acac)₃ exhibit low overpotential, high rate performance, and considerable cycle stability.     

Reversal of the Hall coefficient sign under homogenization

This work deals with the homogenization of the Hall effect in dimension three. The effective Hall coefficient preserves the bounds of the local Hall coefficient in dimension two. This is not the case in dimension three. We present a three-dimensional composite for which the homogenized Hall coefficient has opposite sign to the local Hall coefficient. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)     

Novel Copolymers as Dispersants/Intercalants/Exfoliants for Polypropylene-Clay Nanocomposites

The use of various copolymers as dispersants/intercalants/exfoliants in polypropylene (PP)-clay nanocomposites based on unmodified montmorillonite clays (NaMMT) has been explored. The primary objective of this research has been to find dispersants that allow PP nanocomposites to be formed by direct melt mixing, that are effective with unmodified clays and that comprise only a minor component of the overall composition both with respect to both clay and PP. Two classes of dispersants were investigated: PEO-based nonionic surfactants and amphiphilic copolymers based on a long chain (meth)acrylate (e.g. octadecyl acrylate) and a more polar comonomer (e.g. maleic anhydride, N-vinylpyrrolidone, methyl methacrylate). The state of dispersion achieved and the properties of the derived nanocomposites were found to depend strongly on both on the level of dispersant and its overall composition but interestingly properties are not particularly dependent on the dispersant architecture (i.e. whether statistical, gradient or block copolymer). The nanocomposites possess a tensile modulus up to 40% greater that the precursor PP while elongation at break and impact strength are significantly improved over “clay alone” composites and reference organoclay-based nanocomposites. Also notable are significantly better thermal and thermo-oxidative stability as compared to both PP and “clay alone” composites. For optimal properties, it is both necessary and desirable that the surfactant should only be a minor constituent (20–50 wt-%) of the composition with respect to clay.