Fast phase unwrapping algorithm for interferometric applications

A wide range of interferometric techniques recover phase information that is mathematically wrapped on the interval (-pi, pi). Obtaining the true unwrapped phase is a longstanding problem. We present an algorithm that solves the phase unwrapping problem, using a combination of Fourier techniques. The execution time for our algorithm is equivalent to the computation time required for performing eight fast Fourier transforms and is stable against noise and residues present in the wrapped phase. We have extended the algorithm to handle data of arbitrary size. We expect the state of the art of existing interferometric applications, including the possibility for real-time phase recovery, to benefit from our algorithm.     

Micropatterning of Plasma Fluorinated Super-hydrophobic Surfaces

Photolithographic patterning of super-hydrophobic CF₄ plasma fluorinated polybutadiene films is shown to provide sufficient surface energy contrast to facilitate spatially organized deposition of metal salts and polystyrene microspheres from a nebulized mist or solution.     

Phosphine dissociation and diffusion on Si(001) observed at the atomic scale

A detailed atomic-resolution scanning tunneling microscopy (STM) and density functional theory study of the adsorption, dissociation, and surface diffusion of phosphine (PH(3)) on Si(001) is presented. Adsorbate coverages from approximately 0.01 monolayer to saturation are investigated, and adsorption is performed at room temperature and 120 K. It is shown that PH(3) dissociates upon adsorption to Si(001) at room temperature to produce both PH(2) + H and PH + 2H. These appear in atomic-resolution STM images as features asymmetric-about and centered-upon the dimer rows, respectively. The ratio of PH(2) to PH is a function of both dose rate and temperature, and the dissociation of PH(2) to PH occurs on a time scale of minutes at room temperature. Time-resolved in situ STM observations of these adsorbates show the surface diffusion of PH(2) adsorbates (mediated by its lone pair electrons) and the dissociation of PH(2) to PH. The surface diffusion of PH(2) results in the formation of hemihydride dimers on low-dosed Si(001) surfaces and the ordering of PH molecules along dimer rows at saturation coverages. The observations presented here have important implications for the fabrication of atomic-scale P dopant structures in Si, and the methodology is applicable to other emerging areas of nanotechnology, such as molecular electronics, where unambiguous molecular identification using STM is necessary.     

The effect of shell side hydrodynamics on the performance of axial flow hollow fibre modules

Fluid flow and mass transfer experiments have been performed on axial flow hollow fibre modules of varying packing density (32 to 76%). Shell-side pressure drop was found to be proportional to (flowrate)ⁿ, where n varied from about 1.1 at high packing density to 1.5 at low packing density, for shellside Reynolds numbers < 350. Assuming an Ergun-type pressure drop relationship it was found that for packing densities < about 50% the inertial (turbulent) losses exceeded the viscous (laminar) losses. Inspection of cross-sections taken from the middle of modules revealed non-uniform fibre packing with regions of high and low packing density. The cross-sections also change along the length of the module. It is inferred that, in addition to axial flow along fibres, there is also a degree of stream splitting which provides transverse flow across fibres as fluid continuously seeks preferential paths through regions of lower packing density. The presence of transverse flow would explain the higher than expected velocity exponent. Mass transfer experiments involving the removal of oxygen from water flowing through the shell to a sweep gas in the fibre lumens produced higher than expected shell-side mass transfer coefficients. The results are correlated within ± 15% by Sh = (0.53 − 0.58φ)Re^0.53Sc^0.33. The exponent on Re is consistent with entry region conditions, caused by repeated stream splitting and transverse flow. Compared with mass transfer predicted for axial flow through a uniformly packed shell the experimental results are up to 2× higher, with the most significant enhancement at the lower packing densities. The implication of this work is that module design requires a more sophisticated approach than the traditional assumption of laminar flow through parallel axial ducts.     

Inhibition of the histone demethylase JMJD2E by 3-substituted pyridine 2,4-dicarboxylates

Based on structural analysis of the human 2-oxoglutarate (2OG) dependent JMJD2 histone N(ε)-methyl lysyl demethylase family, 3-substituted pyridine 2,4-dicarboxylic acids were identified as potential inhibitors with possible selectivity over other human 2OG oxygenases. Microwave-assisted palladium-catalysed cross coupling methodology was developed to install a diverse set of substituents on the sterically demanding C-3 position of a pyridine 2,4-dicarboxylate scaffold. The subsequently prepared di-acids were tested for in vitro inhibition of the histone demethylase JMJD2E and another human 2OG oxygenase, prolyl-hydroxylase domain isoform 2 (PHD2, EGLN1). A subset of substitution patterns yielded inhibitors with selectivity for JMJD2E over PHD2, demonstrating that structure-based inhibitor design can enable selective inhibition of histone demethylases over related human 2OG oxygenases.     

Iron‐Mediated Cleavage of C?C Bonds in Vicinal Tricarbonyl Compounds in Water

Three of a kind : Vicinal tricarbonyl compounds undergo C? C cleavage mediated by ferric ions (see scheme). The observed cleavage of ninhydrin and dehydroascorbic acid has relevance for amino acid detection and the metabolism of vitamin C.

     

Synthesis of the stabilized active metabolite of clopidogrel

The convergent synthesis of the stabilized active metabolite of clopidogrel was achieved in eleven steps from commercially available 1,2,3,6-tetrahydropyridine and 2-bromo-3′-methoxy acetophenone (MPBr). This synthetic route used a standard Horner–Wadsworth–Emmons reaction allowing the introduction of a Z exocyclic double bond. A selective hydrolysis of an acrylic methyl ester moiety, isolated by an efficient and reliable preparative chiral chromatography at gram scale, released the title compound with a 98% LC purity and d.e. >99%.     

Stable jets of viscoelastic fluids and self-assembled cylindrical capsules by hydrodynamic focusing

We demonstrate formation of long-lived cylindrical jets of a viscoelastic fluid using hydrodynamic focusing. A solution of polyacrylamide in water is driven coaxially with immiscible oil and subjected to strong extensional flow. At high flow rates, the aqueous phase forms jets that are 4-90 microm in diameter and several centimeters long. The liquid surfaces of these jets are then used as templates for assembly of microspheres into novel rigid and hollow cylinders.