לוח שנה משולב

Block copolymer-guided assembly of nanoparticles leads to the formation of nanocomposites with periodic arrangement of nanoparticles, which are important for applications such as photonic devices and sensors. However, linear block copolymers offer limited control over the internal arrangement of nanoparticles inside their hosting domains as well as the long-range ordering of the entire nanocomposite film.
The first part of the talk will focus on the molecular level: how the chemical design of the polymeric system – both compositional and architectural – could be used to tailor chemical interactions and manipulate chain conformation, which, in turn, influence the local nanoparticle distribution inside the domains they segregate in. In the second part I will show how the utilization of topographically patterned substrates could be used not only to align block copolymer domains along a macroscopic coordinate but also to obtain isolated patterns on non-regular features.

One in five people in the US currently experiences a mental illness, and yet, despite significant clinical and pharmacological efforts, little progress has been made against this "silent plague." Recently, however, a number of unconventional psychoactive drugs--notably ketamine, MDMA (ecstasy), psilocybin, and others--have shown dramatic, unprecedented clinical efficacy in treating depression, post-traumatic stress disorder (PTSD), and anxiety disorders, among others. Perhaps because of a history of sociopolitical and legal barriers to the study of these compounds, much still remains to be elucidated about their underlying neural mechanisms. It would appear that the time has come not only to develop a clearer picture of the mechanisms of their psychoactive activity per se, but also to decipher their pharmacological connections to normal and pathological cognitive processes. This can now be done at several scales (from molecular-level to the whole-brain) by using genetically encoded fluorescent biosensors, which non-invasively report drug-induced functional perturbations. In this talk, recent biosensor highlights will be described, promising data on psychoactives presented, and specific future directions sketched. By leveraging biosensors and psychoactive drugs, a mechanistic foundation can built from which real cures to mental illness can be found.

Small molecular weight organic compounds are common across the galaxy and transcend all known biological interactions. Plants, in particular, have evolved a remarkable capacity to produce diverse sets of so-called specialized metabolites from a few simple, inorganic precursors. Already in 1977, Rhoades argued that plant specialized metabolites are likely multifunctional, i.e. that they serve multiple purposes. Multifunctionality may render the production of specialized metabolites more cost effective and may explain their abundance and tight spatiotemporal control in plants. Work over the last decades confirms that specialized metabolites often have a broad range of functions, from growth and development to defense. However, our understanding of how this multifunctionality affects the interactions between plants and higher trophic levels, including herbivores and their natural enemies is limited. In my presentation, I will explore the importance of multifunctional plant metabolites in a multitrophic context by discussing our work on benzoxazinoids, the most abundant specialized metabolites in grasses such as wheat and maize. We find that benzoxazinoids act as direct defenses [1], within-plant defense signaling molecules [2], microbiome modulators [3] and siderophores [4]. At the same time, the western corn rootworm, a specialist maize pest and important agricultural pest, exploits benzoxazinoids as foraging cues [4], protective agents [5] and micronutrient providers [4]. Thus, the multifunctionality of plant specialized metabolites is mirrored in the adaptations of a specialist herbivore, resulting in a tightly interlocked metabolism. We are also starting to unravel how the metabolism of herbivore natural enemies such as entomopathogenic nematodes can be interlocked with the plant and the herbivore to enhance biological control. These findings have implications for our understanding of the ecology and evolution of plant specialized metabolites, and for their use in agricultural pest control.

One of the fundamental functions of the brain is to integrate incoming sensory stimuli, perceive and associate these integrations with internal representations, and make fast and reliable decisions and actions. Although these processes have been extensively studied, we are still missing a comprehensive understanding of the exact spatiotemporal dynamics at a mesoscale level, i.e. at the neuronal population level spanning many cortical and sub-cortical areas. In my opinion, the key to understanding these processes is to measure from large populations of neurons within a single trial as a subject performs a complex behavior. In my talk, I will present a variety of evidence from behaving mice backing up this claim. In one of the projects, we imaged calcium signals from the whole dorsal cortex of mice performing a whisker-based texture discrimination task with a short-term memory component. Mice use different behavioral strategies to solve the task either deploying an active strategy — engaging their body and whiskers towards the approaching texture — or passively awaited the touch. Based on this strategy, short-term memory was located in frontal secondary motor cortex (M2) in active mice whereas in a newly identified posterior area (P) in passive mice. Optogenetic perturbation of these areas impaired performance specifically in the associated strategy. In some cases, mice overcame the perturbation by switching to the alternative strategy. Thus, depending on behavioral strategy within single trials, cortical population activity is routed differentially to hold information either frontally or posteriorly before converging to similar action. Additional projects, using different tasks, neuronal subtypes and during learning highlight the importance of observing and dissecting mesoscale dynamics during complex behaviors.

The talk will describe nonlinear rheology in extreme conditions that change fluid structure and flow mechanisms. Elongational flow of entangled polymers produces near complete molecular alignment but only changes the viscosity by an order of magnitude and does not destroy the confining tube. A transition in the mechanism of shear thinning in lubricants from alignment to thermal activation is shown to be generic and allows simulations to examine whether the viscosity diverges at a finite glass transition temperature.