Multisensory processes in birds: From single neurons to the influence of social interactions and sensory loss.

World experiences involve multisensory stimulation that arises simultaneously from multiple sources. Yet, we experience a coherent and unified world. Many studies have focused on how sensory information from distinct modalities are integrated and showed that numerous behavioural and cognitive benefits are provided by multisensory processes. Much work has been done with mammalian models but research on avian species also expands our knowledge on multisensory processes. Avian species exhibit a great diversity of behaviours and these species have provided evidence that multisensory processes benefit by the learning that occurs in natural situations. Cross-modal influences on the control of sensorimotor processes occur in circumstances of sensory loss. Also, studies suggest pervasive multisensory influences throughout the avian brain. This review summarizes research done on the imprinting behaviour of precocial bird species, on the ability of barn owls to detect prey and on the vocal communication of songbirds.

Transformer-Induced Metamorphosis of Polymeric Nanoparticle Shape at Room Temperature.

Controlled polymerizations have enabled the production of nanostructured materials with different shapes, each exhibiting distinct properties. Despite the importance of shape, current morphological transformation strategies are limited in polymer scope, alter the chemical structure, require high temperatures, and are fairly tedious. Herein we present a rapid and versatile morphological transformation strategy that operates at room temperature and does not impair the chemical structure of the constituent polymers. By simply adding a molecular transformer to an aqueous dispersion of polymeric nanoparticles, a rapid evolution to the next higher-order morphology was observed, yielding a range of morphologies from a single starting material. Significantly, this approach can be applied to nanoparticles produced by disparate block copolymers obtained by various synthetic techniques including emulsion polymerization, polymerization-induced self-assembly and traditional solution self-assembly.

Shape-Controlled Nanoparticles from a Low-Energy Nanoemulsion.

Nanoemulsion technology enables the production of uniform nanoparticles for a wide range of applications. However, existing nanoemulsion strategies are limited to the production of spherical nanoparticles. Here, we describe a low-energy nanoemulsion method to produce nanoparticles with various morphologies. By selecting a macro-RAFT agent (poly(di(ethylene glycol) ethyl ether methacrylate-co-N-(2-hydroxypropyl) methacrylamide) (P(DEGMA-co-HPMA))) that dramatically lowers the interfacial tension between monomer droplets and water, we can easily produce nanoemulsions at room temperature by manual shaking for a few seconds. With the addition of a common ionic surfactant (SDS), these nanoscale droplets are robustly stabilized at both the formation and elevated temperatures. Upon polymerization, we produce well-defined block copolymers forming nanoparticles with a wide range of controlled morphologies, including spheres, worm balls, worms, and vesicles. Our nanoemulsion polymerization is robust and well-controlled even without stirring or external deoxygenation. This method significantly expands the toolbox and availability of nanoemulsions and their tailor-made polymeric nanomaterials.

Sensory substitution reveals a manipulation bias.

Sensory substitution is a promising therapeutic approach for replacing a missing or diseased sensory organ by translating inaccessible information into another sensory modality. However, many substitution systems are not well accepted by subjects. To explore the effect of sensory substitution on voluntary action repertoires and their associated affective valence, we study deaf songbirds to which we provide visual feedback as a substitute of auditory feedback. Surprisingly, deaf birds respond appetitively to song-contingent binary visual stimuli. They skillfully adapt their songs to increase the rate of visual stimuli, showing that auditory feedback is not required for making targeted changes to vocal repertoires. We find that visually instructed song learning is basal-ganglia dependent. Because hearing birds respond aversively to the same visual stimuli, sensory substitution reveals a preference for actions that elicit sensory feedback over actions that do not, suggesting that substitution systems should be designed to exploit the drive to manipulate.

Conformationally tuned antibacterial oligomers target the peptidoglycan of Gram-positive bacteria.

The recent rise of antibiotic resistance amongst Staphylococcus aureus (S. aureus) populations has made treating Staph-based infections a global medical challenge. Therapies that specifically target the peptidoglycan layer of S. aureus have emerged as new treatment avenues, towards which bacteria are less likely to develop resistance. While the majority of antibacterial polymers/oligomers have the ability to disrupt bacterial membranes, the design parameters for the enhanced disruption of peptidoglycan outer layer of Gram-positive bacteria remain unclear. Here, the design of oligomeric structures with favorable conformational characteristics for improved disruption of the peptidoglycan outer layer of Gram-positive bacteria is reported. Molecular dynamics simulations were employed to inform the structure design and composition of cationic oligomers displaying collapsed and expanded conformations. The most promising diblock and triblock cationic oligomers were synthesized by photo-induced atom transfer radical polymerization (photo ATRP). Following synthesis, the diblock and triblock oligomers displayed average antibacterial activity of ~99% and ~98% for S. aureus and methicillin-resistant S. aureus (MRSA), respectively, at the highest concentrations tested. Importantly, triblock oligomers with extended conformations showed significantly higher disruption of the peptidoglycan outer layer of S. aureus compared to diblock oligomers with more collapsed conformation, as evidenced by a number of characterization techniques including scanning electron, confocal and atomic force microscopy. This work provides new insight into the structure/property relationship of antibacterial materials and advances the design of functional materials for combating the rise of drug-resistant bacteria.

Tailoring Polymer Dispersity in Photoinduced Iron-Catalyzed ATRP.

Although dispersity (D) plays an important role in controlling polymer properties, there are very few chemical methods that can sufficiently tune it. Here we report a simple, batch, and environmentally benign photoinduced iron-catalyzed ATRP methodology that enables the efficient control of D for both homopolymers and block copolymers. We show that by judiciously varying the concentration of the FeBr3/TBABr catalyst, a range of dispersities can be obtained (1.18 < D < 1.80) while maintaining monomodal molecular weight distributions. High end-group fidelity was confirmed by MALDI-ToF-MS and was further supported by the efficient synthesis of in situ block copolymers where the dispersity of the second block could be controlled upon demand. Importantly, through the use of low ppm amounts of the catalyst, perfect temporal control could be attained during intermittent "on/off" cycles. This work considerably expands the chemical toolbox for tuning D of homo- and block copolymers.

Architecture Effects in Complex Spherical Assemblies of (AB)n-Type Block Copolymers.

Molecular architecture plays a key role in the self-assembly of block copolymers, but few studies have systematically examined the influence of chain connectivity on tetrahedrally close-packed (TCP) sphere phases. Here, we report a versatile material platform comprising two blocks with substantial conformational asymmetry, A = poly(trifluoroethyl acrylate) and B = poly(dodecyl acrylate), and use it to compare the phase behavior of AB diblocks, ABA triblocks, and (AB)n radial star copolymers with n = 3 or 4. Each architecture forms TCP sphere phases at minority A block compositions (fA < 0.5), namely, σ and A15, but with differences in the location of order-order phase boundaries that are not anticipated by mean-field self-consistent field theory simulations. These results expand the palette of polymer architectures that readily self-assemble into complex TCP structures and suggest important design considerations when targeting specific phases of interest.

Tuning Dispersity by Photoinduced Atom Transfer Radical Polymerisation: Monomodal Distributions with ppm Copper Concentration.

Dispersity significantly affects the properties of polymers. However, current methods for controlling the polymer dispersity are limited to bimodal molecular weight distributions, adulterated polymer chains, or low end-group fidelity and rely on feeding reagents, flow-based, or multicomponent systems. To overcome these limitations, we report a simple batch system whereby photoinduced atom transfer radical polymerisation is exploited as a convenient and versatile technique to control dispersity of both homopolymers and block copolymers. By varying the concentration of the copper complex, a wide range of monomodal molecular weight distributions can be obtained (D=1.05-1.75). In all cases, high end-group fidelity was confirmed by MALDI-ToF-MS and exemplified by efficient block copolymer formation (monomodal, D=1.1-1.5). Importantly, our approach utilises ppm levels of copper (as low as 4 ppm), can be tolerant to oxygen and exhibits perfect temporal control, representing a major step forward in tuning polymer dispersity for various applications.

Effect of Polymerization Components on Oxygen-Tolerant Photo-ATRP.

Photo-ATRP has recently emerged as a powerful technique that allows for oxygen-tolerant polymerizations and the preparation of polymers with low dispersity and high end-group fidelity. However, the effect of various photo-ATRP components on oxygen consumption and polymerization remains elusive. Herein, we employ an in situ oxygen probe and UV-vis spectroscopy to elucidate the effects of ligand, initiator, monomer, and solvent on oxygen consumption. We found that the choice of photo-ATRP components significantly impacts the rate at which the oxygen is consumed and can subsequently affect both the polymerization time and the dispersity of the resulting polymer. Importantly, we discovered that using the inexpensive ligand TREN results in the fastest oxygen consumption and shortest polymerization time, even though no appreciable reduction of CuBr2 is observed. This work provides insight into oxygen consumption in photo-ATRP and serves as a guideline to the judicious selection of photo-ATRP components for the preparation of well-defined polymers.

Tailoring polymer dispersity and shape of molecular weight distributions: methods and applications.

The width and shape of molecular weight distributions can significantly affect the properties of polymeric materials and thus are key parameters to control. This mini-review aims to critically summarise recent approaches developed to tailor molecular weight distributions and highlights the strengths and limitations of each technique. Special emphasis will also be given to applications where tuning the molecular weight distribution has been used as a strategy to not only enhance polymer properties but also to increase the fundamental understanding behind complex mechanisms and phenomena.