Electrical Chain Rearrangement: What Happens When Polymers in Brushes Have a Charge Gradient?

Under the influence of electric fields, the chains in polyelectrolyte brushes can stretch and collapse, which changes the structure of the brush. Copolymer brushes with charged and uncharged monomers display a similar behavior. For pure polyelectrolyte and random copolymer brushes, the field-induced structure changes only the density of the brush and not its local composition, while the latter could be affected if charges are distributed inhomogeneously along the polymer backbone. Therefore, we systematically study the switching behavior of gradient polyelectrolyte brushes in electric fields for different solvent qualities, grafting densities, and charges per chain via coarse-grained molecular dynamics simulations. Similar to random copolymers and pure polyelectrolytes, these brushes show a mixed-phase transition: intermediate states between fully stretched and collapsed are characterized by a bimodal chain-end distribution. Additionally, we find that the total charge of the brush plays a key role in the critical field required for a complete transition. Finally, we find that gradient polyelectrolyte brushes are charge-enriched at the brush–solvent interface under stretched conditions and charge-depleted under collapsed conditions, allowing for control over the local composition and thus the surface charge of the brush due to the inhomogeneous charge along the grafted chains

Electrostatic Fields Stimulate Absorption of Small Neutral Molecules in Gradient Polyelectrolyte Brushes

Molecules can partition from a solution into a polymer coating, leading to a local enrichment. If one can control this enrichment via external stimuli, one can implement such coatings in novel separation technologies. Unfortunately, these coatings are often resource intensive as they require stimuli in the form changes of bulk solvent conditions such as acidity, temperature, or ionic strength. Electrically driven separation technology may provide an appealing alternative, as this will allow local, surface-bound stimuli instead of system-wide bulk stimuli to induce responsiveness. Therefore, we investigate via coarse grained molecular dynamics simulations the possibility of using coatings with charged moieties, specifically gradient polyelectrolyte brushes, to control the enrichment of the neutral target molecules near the surface with applied electric fields. We find that targets which interact more strongly with the brush show both more absorption and a larger modulation by electric fields. For the strongest interactions evaluated in this work, we obtained absorption changes of over 300 % between the collapsed and extended state of the coating.</p

City skin : a cultural hub in Pretoria

Within the contemporary urban renaissance, culture and visual arts act as catalysts for change. Art and culture-led approaches, working across disciplines, provide wide social and economic benefits that affect people, places and communities. The proposed design develops a synthesis between the arts, culture, economy and urban vitality by creating a platform for artists. The goal of the project is to connect Pretoria's multicultural richness and strengthen the network of creativity and cultural regeneration. The project is shaped and informed by the living urban surface in which it is set. It is specific to its site and program, rather than the product of a formal and aesthetically driven vision. The building is allowed to transform into a living connective skin that transforms between the fragments of unforeseen future programs, becoming part of the city skin.Dissertation (MArch(Prof))--University of Pretoria, 2008.Architectureunrestricte

Cardiac myosin binding protein C, adrenergic stimulation and cardiac contractility

Myosin binding protein C remained a perplexing although integral component of the sarcomeric thick filament until the discovery that genetic defects in its corresponding gene is a frequent cause of hypertrophic cardiomyopathy. Basic science investigation subsequently revealed that it is one of the most potent regulators of cardiac contractility. Phosphorylation of its N-terminus upon adrenergic stimulation, causes increased order in myosin heads as well as increased ATPase activity, Fmax and Ca2+-sensitivity of contraction, while its dephosphorylation upon cholinergic stimulation or during low flow ischaemia leads to changes in the sarcomeric thick filament that diminish interaction between myosin heads and actin. This dynamic flux in phosphorylation upon adrenergic stimulation is not only crucial to normal cardiac function and structure, but also vital for protection against ischaemic injury. Genetically-driven deficiency or inadequacy in cMyBPC leads to severe cardiac dysfunction and structural changes, including cardiac hypertrophy and dilation, and particularly attenuates the adaptive increase in left ventricular contractility that follows on β-adrenergic stimulation or pressure overload, resulting in decreased systolic function, and reduced cardiac output

Programmed Articulation Therapy Administered by Supportive Personnel

Using the principles of programmed instruction, a motor skill program was designed to instruct a nonprofessional how to teach a child to make a speech sound, specifically the phoneme /th/ (voiceless) in isolation. A cognitive program describing the speech mechanism and act was also developed to be used in conjunction with the motor skill program. These programs were pretested, then tested using 15 nursing attendants (aides) as subjects. Their presentation was compared to methods used by professionally trained clinicians. Three fully trained and qualified judges rated the performance of both groups. Analysis of the ratings showed that the performance of the aides was comparable to that of the professionally trained clinicians