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.
By including composition fluctuations in our dynamical simulation of the time-dependent Landau-Brazovskii model for a diblock copolymer melt we find that disordered micelles form above the order-disorder transition to a BCC phase. At high-temperatures the micelle number density and volume fraction are effectively zero and the melt is disordered at the molecular level. As we lower the temperature the micelle number density increases gradually and approaches the number density in the BCC phase.
Recent experimental work  suggests that the increased motility of cancer cells observed in a confluent monolayer of normal cells is due to the mechanical mismatch between the two cell types. The soft cancer cell undergoes large deformations and can squeeze between small channels defined by the space between the normal cells. We developed a phase-field model description of cellular monolayers to study such a process. The system is setup as a free-boundary problem where each cell is a highly deformable soft body .
Although a few of very promising methods now exist for extracting free energy profiles of a many-body system from non-equilibrium work performed on it the implementation of these methods have proven to be non-trivial. These methods (most notable of all the Jarzynski equality the FR method and the Brownian dynamic FDT) typically require a proper sampling of the work performed on the system along many trajectories in the available phase space that connect the desired initial and final macrostates.
Tissue topology such as proliferating epithelium topology shows striking similarities for various species. Thissuggests unified mechanism for tissue formation which can be explored with the help of physical or mathematicalmodels. Indeed it has been shown that cell divisions along with local cell rearrangements can reproduce commonlyobserved epithelium topology by using topological models.Tightly packed cells in epithelium resemble polygons. This observation gave rise to models where cells aretreated as polygons in junctional network.
Our research focuses on computer simulations of cationic and Phosphatidylcholine (PC) containing lipid monolayers and their potential applications in drug and gene delivery. The ultimate motivation is to unravel how cationic compounds such as CTAB function for encapsulating novel DNA based drugs and other drugs e.g. protein based drugs into a delivery system. The major advantage of these drugs over traditional chemical agents is their specificity and selectivity.We employed the Berger lipid model to model lipid molecules.
We model the orientational and positional order of tetratically shaped molecules each having four-fold structural symmetryconfined on a spherical surface. Our Monte Carlo simulation shows that at a high molecular density a tetratic orientational orderdevelops in the system accompanied by eight disclinations arranged in an anticube form on the hard spherical surface.
Electrostatic phenomena in soft matter systems are often intriguing or even counterintuitive. DNA condensation by polyvalent counterions is now a classic example by which highly-negatively charged DNA strands attract each other in the presence of poly-cations. Also Mg2+ can stabilize inverted hexagonal phases of lipid aggregates that would otherwise form lamellar phases. Here we discuss another intriguing electrostatic phenomenon: electrostatic modification of lipid membranes by poly-cations.
While successfully reproducing hydrophobic and hydrophilic interactions the Martini model is insufficient to keep a protein folded as it lacks electrostatic interactions. Using split charge equilibration at each time step can yield realistic dynamic bead charges. Combining this with a Drude oscillator based polarization model for all beads will permit modeling of hydrogen bonds to maintain secondary protein structure and will enable more accurate coarse-grained simulations of protein-protein and protein-membrane interactions.
Confinement can influence qualitatively the spatial organization of polymer chains. Cylindrical confinement is of particular interest since it not only stiffens individual chains but also enhances their segregation. Here we discuss a ring copolymer confined in a closed cylindrical space as a model nucleoid (an intracellular space where the bacterial chromosome is confined). When the cylinder and polymer parameters are chosen properly our model explains quantitatively recent experimental results for the spatial organization of the E. coli chromosome.