Structural characterization of radiation‐grafted block copolymer films,using SANS technique

We report small‐angle neutron scattering studies of grafted copolymer films of perfluorinated poly(ethylene propylene), FEP, base polymer and polystyrene, PS, grafted blocks. The films show highly anisotropic scattering patterns, revealing nematic‐like ordering of the crystalline domain structure as a consequence of the processing conditions. Upon grafting, the styrene swells the amorphous domains in the copolymer formation. For styrene content beyond roughly 15%, the amorphous regimes increase on the cost of crystalline domains. To stabilize the rather well‐defined domain structure already given by the original FEP base material, the samples need to be cross‐linked. Without cross‐linking, the nanometer length scale domains vanish, and some large scale structure takes over, likely driven by the immiscibility between FEP and PS. © 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 1660–1668, 2008     

Stereospecific synthesis of an α-mannosidase inhibitor relatedto swainsonine

A stereospecific synthesis of pyrrolidine $\text{2}$, an analog of swainsonine and an inhibitor of lysosomal α-D-mannosidase, is described.     

Monolayer-protected gold nanoparticle coalescence induced by photogenerated radicals

Acyl and alkyl radicals generated photochemically in a solution containing monolayer-protected gold nanoparticles are shown to efficiently liberate the alkylthiolate ligands into the solution as the thioacetyl or alkyl sulfide, respectively. This radical-induced reaction initiates a coalescence of the gold cores to facilitate an increase in core size. The photoinitiated radical reaction also liberates monolayers from two-dimensional gold surfaces.     

Anisotropic thermopower of (TMTSF)2PF6: 1D–2D cross over and SDW ordering

The thermopower of (TMTSF)₂PF₆ has been measured along the a-axis as well as along the b-axis. Marked anisotropy is seen in the whole temperature region studied. Close to 100 K, an anomaly is attributed to cross over from dominating one-dimensionality to dominating two-dimensionality. Precursor effects seen in S_a near T_c are attributed to SDW fluctuations. Well below T_c, both thermopower components exhibit typical semiconducting properties.     

A retro-Diels-Alder reaction to uncover maleimide-modified surfaces on monolayer-protected nanoparticles for reversible covalent assembly

Maleimide-modified monolayer-protected gold nanoparticles (MPGN) are prepared from the protected furan-maleimide via the thermally reversible Diels-Adler reaction when required. These maleimide-MPGNs serve as a general platform allowing for a Diels-Alder reaction with furan-modified MPN to prepare larger 3D networks reversibly. [reaction: see text]     

Structural transitions induced by shear flow and temperature variation in a nonionic surfactant/water system

In this study, we investigate structural transitions of tetraethylene glycol monohexadecyl ether (C(16)E(4)) in D(2)O as a function of shear flow and temperature. Via a combination of rheology, rheo-small-angle neutron scattering and rheo-small-angle light scattering, we probe the structural evolution of the system with respect to shear and temperature. Multi-lamellar vesicles, planar lamellae, and a sponge phase were found to compete as a function of shear rate and temperature, with the sponge phase involving the formation of a new transient lamellar phase with a larger spacing, coexisting with the preceding lamellar phase within a narrow temperature-time range. The shear flow behavior of C(16)E(4) is also found to deviate from other nonionic surfactants with shorter alkyl chains (C(10)E(3) and C(12)E(4)), resembling to the C(16)E(7) case, of longer chain.     

Author index to volume 104

Activation barriers of the title reactions are calculated using a DZ + P basis set with diffuse p functions on negative ions. In the correlation effects, which are large and negative, the importance of single and triple excitations is stressed. The barrier for the reaction of H^? with CH₃F is 12 kJ/mole, in good agreement with experiment, while the barrier for the reaction of F^? with CH₃F is predicted to be 14 kJ/mole.     

Correction of the influence of baseline artefacts and electrode polarisation on dielectric spectra

The deconvolution of biological dielectric spectra can be difficult enough with artefact-free spectra but is more problematic when machine baseline artefacts and electrode polarisation are present as well. In addition, these two sources of anomalies can be responsible for significant interference with dielectric biomass measurements made using one- or two-spot frequencies. The aim of this paper is to develop mathematical models of baseline artefacts and electrode polarisation which can be used to remove these anomalies from dielectric spectra in a way that can be easily implemented on-line and in real-time on the Biomass Monitor (BM). We show that both artefacts can be successfully removed in solutions of organic and inorganic ions; in animal cell and microbial culture media; and in yeast suspensions of varying biomass. The high quality of the compensations achieved were independent of whether gold and platinum electrodes were used; the electrode geometry; electrode fouling; current density; the type of BM; and of whether electrolytic cleaning pulses had been applied. In addition, the calibration experiments required could be done off-line using a simple aqueous KCl dilution series with the calibration constants being automatically calculated by a computer without the need for user intervention. The calibration values remained valid for a minimum of 3 months for the baseline model and indefinitely for the electrode polarisation one. Importantly, application of baseline correction prior to polarisation correction allowed the latter's application to the whole conductance range of the BM. These techniques are therefore exceptionally convenient to use under practical conditions.     

Fast automatic registration of images using the phase of a complex wavelet transform: application to proteome gels

Image registration describes the process of manipulating a distorted version of an image such that its pixels overlay the equivalent pixels in a clean, master or reference image. The need for it has assumed particular prominence in the analysis of images of electrophoretic gels used in the analysis of protein expression levels in living cells, but also has fundamental applications in most other areas of image analysis. Much of the positional information of a data feature is carried in the phase of a complex transform, so a complex transform allows explicit specification of the phase, and hence of the position of features in the image. Registration of a test gel to a reference gel is achieved by using a multiresolution movement map derived from the phase of a complex wavelet transform (the Q-shift wavelet transform) to dictate the warping directly via movement of the nodes of a Delaunay-triangulated mesh of points. This warping map is then applied to the original untransformed image such that the absolute magnitude of the spots remains unchanged. The technique is general to any type of image. Results are presented for a simple computer simulated gel, a simple real gel registration between similar "clean" gels with local warping vectors distributed about one main direction, a hard problem between a reference gel and a "dirty" test gel with multi-directional warping vectors and many artifacts, and some typical gels of present interest in post-genomic biology. The method compares favourably with others, since it is computationally rapid, effective and entirely automatic.