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Shell cross-linked nanoparticles (SCKs) presenting surface- and bioavailable biotin functional groups were synthesized via a mixed micelle methodology, whereby co-micellization of chain terminal biotinylated poly(acrylic acid)-b-poly(methyl acrylate) (PAA-b-PMA) and nonbiotinylated PAA-b-PMA were cross-linked in an intramicellar fashion within the shell layer of the mixed micelles, between the carboxylic acid groups of PAA and the amine functionalities of 2,2'-(ethylenedioxy)diethylamine. The hydrodynamic diameters (D(h)) of the micelles and the SCKs with different biotinylated block copolymer contents were determined by dynamic light scattering (DLS), and the dimensions of the SCKs were characterized with tapping-mode atomic force microscopy (AFM) and transmission electron microscopy (TEM). The amount of surface-available biotin was tuned by varying the stoichiometric ratio of the biotinylated PAA-b-PMA versus the nonbiotinylated PAA-b-PMA, as demonstrated with solution-state, binding interaction analyses, an avidin/HABA (avidin/4'-hydroxyazobenzene-2-carboxylic acid) competitive binding assay, and fluorescence correlation spectroscopy (FCS). The avidin/HABA assay found the amount of available biotin at the surface of the biotinylated SCK nanoparticles to increase with increasing biotin-terminated block copolymer incorporation, but to be less than 25% of the theoretical value. FCS measurements showed the same trend.

Acoustic and visual methods were used to track and observe humpback whales off the island of Hawai'i. Sixty-two singing whales were located acoustically in water depths from 10 to 305 fathoms (mean 126 fathoms; 1 fathom = 1.828 m). This indicates that singers are not confined within the 100-fathom contour, although nearshore waters had a higher density of singers. The separation distance between singers (mean 5.1 km) was found to be significantly greater than that between nonsinging singletons (mean 2.1 km), supporting the hypothesis that song functions to maintain spacing between singers. The mean speed of singers determined from visual data was 1.79 km/h and from acoustic data 1.6 km/h. Some singers actively swam while singing. Other singers continued singing while affiliating with or being joined by other whales. The correlation between breaching and the cessation of singing suggests that the sounds of aerial behavior can convey information to other whales. These observations suggest the need to expand the traditional interpretations of the behavior of singing humpback whales obtained from visual observations alone.RCsumC : Des mCthodes acoustiques et visuelles ont semi a repdrer et a observer des Rorquals a bosse au large de l'ile d'Hawai'i. Soixante-deux rorquals chanteurs ont Ct C repCrCs par leurs cris a des profondeurs de 10 a 305 brasses (moyenne 126 brasses; 1 brasse = 1.828 m), ce qui indique que les chanteurs ne sont pas restreints aux 100 premikres brasses, mCme si les chanteurs sont gCnCralement prCsents en plus grand nombre dans les eaux cdtikres. La distance entre deux chanteurs (moyenne 5,l km) s'est avCrCe significativement plus ClevCe que la distance entre deux individus non chanteurs (moyenne 2,l km), ce qui appuie l'hypothkse selon laquelle les cris servent a assurer l'espacement entre les chanteurs. La vitesse moyenne des chanteurs a Ct C estimCe a 1,79 km/h d'aprks les donnCes visuelles et a 1,6 km/h d'aprks les donnCes acoustiques. Certains rorquals chanteurs nageaient mCme en Cmettant leurs cris. D'autres ont continud d'dmettre leurs cris tout en s'associant a d'autres rorquals ou a l'approche d'autres rorquals. La corrClation entre les sauts hors de l'eau et 1'arrCt des chants semble indiquer que les bruits reliCs aux comportements aCriens peuvent fournir de l'information aux autres rorquals. Ces observations nous enjoignent de remettre en question les interprktations traditionnelles du comportement des rorquals chanteurs ClaborCes seulement a partir d'observations visuelles. [Traduit par la RCdaction]

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The mechanism of morphological phase transitions was studied for rod-shaped supramolecular assemblies comprised of a poly(acrylic acid)-block-poly(methyl acrylate)-block-polystyrene (PAA 90-b-PMA80-b-PS100) triblock copolymer in 33% tetrahydrofuran͞water after perturbation by reaction with a positively charged water-soluble carbodiimide. Tetrahydrofuran solvation of the hydrophobic core domain provided the dynamic nature required for the rod-to-sphere phase transition to be complete within 30 min. The intermediate morphologies such as fragmenting rods and pearl-necklace structures were trapped kinetically by the subsequent addition of a diamino crosslinking agent, which underwent covalent crosslinking of the shell layer. Alternatively, shellcrosslinked rod-shaped nanostructures with preserved morphology were obtained by the addition of the crosslinking agent before the addition of the carbodiimide, which allowed for the shell crosslinking to be performed at a faster rate than the morphological reorganization. The formation of robust shell-crosslinked nanostructures provides a methodology by which the morphological evolution processes can be observed, and it allows access to otherwise thermodynamically unstable nanostructures. The versatility of the solution-state assembly of block copolymers (1, 2) has attracted much interest toward the preparation of unique nanostructured materials possessing different compositions, shapes, and structures (3-12). Controlled assembly of block copolymers depends on a number of factors. The equilibrium between micellar assemblies and individual polymer chains involves a delicate balance of supramolecular polymerpolymer and polymer-solvent interactions, which provides a lever of enthalpic and entropic control (13) for the directed evolution of micellar morphologies with changes in the solution conditions. Studies to determine the kinetics of block copolymer micellization (14-16) and the kinetics and mechanisms for transformation of assembly morphologies (17-19) have become active areas of research. For a given block copolymer composition, the introduction of ions and alteration of the solution pH (20-22), modification of the solvent composition (23-25), and changes in the polymer concentration (26, 27) have been found to effect reorganization of block copolymer supramolecular assemblies. The identification of methodologies that allow for observation (28) and accurate manipulation (19) of the supramolecular assembly processes is critical for the preparation and development of advanced nanostructured materials.Spherical, rod-like, and vesicular assemblies are observed commonly for the supramolecular assembly of amphiphilic block copolymers. The covalent stabilization of such assemblies is facilitated by regioselective crosslinking chemistry (29, 30), performed within the core domain, throughout the shell layer, or at an intermediate radial layer. It is interesting to note that as focus has shifted from fullerenes to carbon nanotubes for carbon-based nanostructures, interest also has ...