Since 2002 Perimeter Institute has been recording seminars, conference talks, and public outreach events using video cameras installed in our lecture theatres. Perimeter now has 7 formal presentation spaces for its many scientific conferences, seminars, workshops and educational outreach activities, all with advanced audio-visual technical capabilities. Recordings of events in these areas are all available On-Demand from this Video Library and on Perimeter Institute Recorded Seminar Archive (PIRSA).
PIRSA is a permanent, free, searchable, and citable archive of recorded seminars from relevant bodies in physics. This resource has been partially modelled after Cornell University's arXiv.org.
We use coarse-grained molecular-dynamics (MD) simulations to study the fragmentation of sodium dodecyl sulfate micelles under Poiseuille-like flow in a die-extruder geometry. The effect of flow confinement and wetting on spherical micelles is explored. We demonstrate that the interplay between flow and the wettability of the channel determines the size of daughter micelles inside the channel.
Colloidal particles organize spontaneously at fluid interfaces owing to a variety of interactions to form well organized structures that can be exploited to synthesize advanced materials. While the physics of colloidal assembly at isotropic interfaces is well understood the mechanisms that govern interactions between particles at liquid crystal interfaces are not yet clearly established. In particular smectic liquid crystal films offer important degrees of freedom that can be used to direct particles into new structures.
Mineral-associated proteins have been proposed to play a central role not only in assisting the growth of biomineral crystals in hard tissues but also in preventing or limiting mineral formation in soft tissues. The elucidation of protein-biomineral interactions may lead to the design of mineralized tissues with novel properties and most importantly the development of therapies for common diseases such as kidney stones calcification in blood vessels osteoporosis etc. However the mechanism of the interaction at this unique organic-inorganic interface is still poorly understood.
The self-assembled structures formed in binary blends of AB/CD diblock copolymers are studied using self-consistent field theory focusing on cases with attractive A/C and repulsive B/D interactions. The attractive A/C interaction prevents macroscopic phase separation whereas the repulsive B/D interaction promotes B/D separation leading to the formation of complex hierarchical structures. The combination of these features makes the AB/CD blend an ideal model system for the study of hierarchical self-assembly.
Wang et al.
[PNAS 106 (2009) 15160] have found that in several systems, the linear time
dependence of mean-square displacement (MSD) of diffusing colloidal particles,
typical of normal diffusion, is accompanied by a non-Gaussian displacement
distribution (DD), with roughly exponential tails at short times, a situation
termed “anomalous yet Brownian” diffusion. We point out that lack of “direction
memory” in the particle trajectory (a jump in a particular direction does not
Collagen is the main component of connective tissue and the most abundant protein in mammals. The structure of collagen is hierarchical with the triple-helical molecules organizing into fibrils and fibrils contained in higher-order arrangements. A fibril may be considered as a liquid crystal of individual triple helices. Their chiral molecular structure can lead to a macroscopic helical arrangement known as the cholesteric phase which has been observed in fragments of collagen fibrils. The cholesteric orientation can vary with radial distance in the fibril as a double twist.
Lipid bilayers form the basic structure of cellular membranes creating a semi-permeable barrier necessary for separating distinct chemical environments. Hydrophilic pores can form in bilayers that breach the barrier potentially causing cell death or enhance the uptake of hydrophilic molecules. We use molecular dynamics simulations and free energy calculations to investigate pore formation in model bilayers. The free energy barrier for pore formation is much lower in thinner phosphatidylcholine bilayers compared to thicker bilayers.
Recently there has been a large growth of research effort for nanoelectronic devices.Investigations of quantumly coherent nano-meter scale systems whose fabrication has been made possible by recent advances in experimental and sample preparation techniques have revealed that transport properties could be non-Ohmic and G could be quantized. Understanding electron conduction in such devices is an extremely active research topic.
Antimicrobial peptides (AMPs) are known to be active against a wide range of microbes. Cell selectivity is an important quality of AMPs which enables them to preferentially bind to and kill the microbes over host cells. Despite its significance in determining the cell selectivity however the cell-concentration dependence of AMP activity has not been criticality examined. Here we present a coarse-grained model for describing how cell concentrations are implicated in AMP's membrane-perturbing activity and selectivity.