Chemical patterning of ultrathin polymer films by direct-write multiphoton lithography

We applied 2-photon laser ablation to write subdiffraction nanoscale chemical patterns into ultrathin polymer films under ambient conditions. Poly(ethylene glycol) methacrylate brush layers were prepared on quartz substrates via surface-initiated atom-transfer radical polymerization and ablated to expose the underlying substrate using the nonlinear 2-photon absorbance of a frequency-doubled Ti:sapphire femtosecond laser. Single-shot ablation thresholds of polymer films were ~1.5 times smaller than that of a quartz substrate, which allowed patterning of nanoscale features without damage to the underlying substrate. At a 1/e(2) laser spot diameter of 0.86 μm, the features of exposed substrate approached ~80 nm, well below the diffraction limit for 400 nm light. Ablated features were chemically distinct and amenable to chemical modification.     

Hydro­gen bonding in proton‐transfer compounds of 8‐quinolinol (oxine) with aromatic sulfonic acids

The crystal structures of the proton‐transfer compounds of 8‐quinolinol (oxine) with the aromatic sulfonic acids 2‐amino­benzene­sulfonic acid (orthanilic acid) and 8‐hydroxy‐7‐iodo­quinoline‐5‐sulfonic acid (ferron) have been determined. In both 8‐hydroxy­quinolinium 2‐amino­benzene­sulfonate, C₉H₈NO⁺·C₆H₆NO₃S⁻, (I), and 8‐hydroxyquino­linium 8‐hydroxy‐7‐iodo­quinoline‐5‐sulfonate ses­qui­hydrate, C₉H₈NO⁺·C₉H₆INO₄S⁻·1.5H₂O, (II), extensive hydrogen‐bonding interactions, together with significant cation–cation [in (I)] and cation–anion [in (II)] π–π stacking associations, give rise to layered polymer structures.     

Optimisation of the self-assembly process: production of stable,alginate-based polyelectrolyte nanocomplexes with protamine

The aim of this work was to investigate the possibility of covalent cross-linker-free, polyelectrolyte complex formation at the nanoscale between alginic acid (as sodium alginate, ALG) and protamine (PROT). Optimisation of the self-assembly conditions was performed by varying the type of polymer used, pH of component solutions, mass mixing ratio of the components and the speed and order of component addition on the properties of complexes. Homogenous particles with nanometric sizes resulted when an aqueous dispersion of ALG was rapidly mixed with a solution of PROT. The polyelectrolyte complex between ALG and PROT was confirmed by infrared spectroscopy. To facilitate incorporation of drugs soluble at low pH, pH of ALG dispersion was decreased to 2; however, no nanoparticles (NPs) were formed upon complexation with PROT. Adjusting pH of PROT solution to 3 resulted in the formation of cationic or anionic NPs with a size range 70–300 nm. Colloidal stability of selected alginic acid low/PROT formulations was determined upon storage at room temperature and in liquid media at various pH. Physical stability of NPs correlated with the initial surface charge of particles and was time- and pH-dependent. Generally, better stability was observed for anionic NPs stored as native dispersions and in liquids covering a range of pH.

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Schematic presenting the formation and size of alginate/protamine nanoparticles

     

Sensitivity to isolated and concurrent intensity and fundamental frequency increments by cochlear implant users under natural listening conditions

Sensitivity to acoustic cues in cochlear implant (CI) listening under natural conditions is a potentially complex interaction between a number of simultaneous factors, and may be difficult to predict. In the present study, sensitivity was measured under conditions that approximate those of natural listening. Synthesized words having increases in intensity or fundamental frequency (F0) in a middle stressed syllable were presented in soundfield to normal-hearing listeners and to CI listeners using their everyday speech processors and programming. In contrast to the extremely fine sensitivity to electrical current observed when direct stimulation of single electrodes is employed, difference limens (DLs) for intensity were larger for the CI listeners by a factor of 2.4. In accord with previous work, F0 DLs were larger by almost one order of magnitude. In a second experiment, it was found that the presence of concurrent intensity and F0 increments reduced the mean DL to half that of either cue alone for both groups of subjects, indicating that both groups combine concurrent cues with equal success. Although sensitivity to either cue in isolation was not related to word recognition in CI users, the listeners having lower combined-cue thresholds produced better word recognition scores.     

Cases where the linear canonical transform of a signal has compact support or is band-limited

A signal may have compact support, be band-limited (i.e., its Fourier transform has compact support), or neither ("unbounded"). We determine conditions for the linear canonical transform of a signal having these properties. We examine the significance of these conditions for special cases of the linear canonical transform and consider the physical significance of our results.     

A note on the role of the branching ratio in the transfer of resonance radiation

The significance of the branching ratio in problems involving the transfer of resonance radiation in a gas is discussed. The apparent disagreement between the results of two recent calculations on the optically pumped slab is shown to reside in the different values for the branching ratio assumed by the authors. It is shown that the results of Van Trigt for the asymptotic eigenvalues and eigenfunctions of the Biberman-Holstein equation, for a branching ratio of unity, can readily be extended to the case of arbitrary branching ratio, thus considerably enlarging the domain of applicability of these results.     

Ground states of molecules. 67.MNDO Calculations for compounds containing iodine

MNDO has been parametrized for iodine. Since d atomic orbitals (AOS ) are not included, the calculations are restricted to I^I. Heats of formation, molecular geometries, ionization energies, and dipole moments are reproduced with useful accuracy.     

Mechanismus der Anionenadsorption an den Eisenoxid-und Chromoxid-Wasser-Grenzfl?chen

Ohne Zusammenfassung     

The role of contrasting temporal amplitude patterns in the perception of speech

Despite a lack of traditional speech features, novel sentences restricted to a narrow spectral slit can retain nearly perfect intelligibility [R. M. Warren et al., Percept. Psychophys. 57, 175-182 (1995)]. The current study employed 514 listeners to elucidate the cues allowing this high intelligibility, and to examine generally the use of narrow-band temporal speech patterns. When 1/3-octave sentences were processed to preserve the overall temporal pattern of amplitude fluctuation, but eliminate contrasting amplitude patterns within the band, sentence intelligibility dropped from values near 100% to values near zero (experiment 1). However, when a 1/3-octave speech band was partitioned to create a contrasting pair of independently amplitude-modulated 1/6-octave patterns, some intelligibility was restored (experiment 2). An additional experiment (3) showed that temporal patterns can also be integrated across wide frequency separations, or across the two ears. Despite the linguistic content of single temporal patterns, open-set intelligibility does not occur. Instead, a contrast between at least two temporal patterns is required for the comprehension of novel sentences and their component words. These contrasting patterns can reside together within a narrow range of frequencies, or they can be integrated across frequencies or ears. This view of speech perception, in which across-frequency changes in energy are seen as systematic changes in the temporal fluctuation patterns at two or more fixed loci, is more in line with the physiological encoding of complex signals.