לוח שנה משולב

The sinking of organic particles in the ocean and their degradation by marine microorganisms drive one of the most conspicuous carbon fluxes on Earth, the biological pump. Yet, the mechanisms determining the magnitude of the pump remain poorly understood, limiting our ability to predict this carbon flux in future ocean scenarios. Current ocean models assume that the biological pump is governed by the competition between sinking speed and degradation rate, with the two processes independent from one another. In this talk, I will demonstrate that contrary to this paradigm, sinking itself is a primary determinant of the rate at which bacteria enzymatically degrade particles in the ocean. By combining video microscopy and microfluidic experiments to directly observe and quantify bacterial degradation of individual organic particles in flow, I will show that even modest sinking speeds of 8 meters per day enhance degradation rates more than 10-fold. I will further discuss the molecular mechanism behind the sinking-enhanced degradation, as well as possible ways by which bacteria can slow the sinking of particles. Finally, using the results obtained from a mathematical model, I will show that the coupling of sinking and degradation may contribute to determining the magnitude of the vertical carbon flux in the ocean, and will outline major open questions in the field.

Nonoscillatory coding and multiscale representation of very large environments in the bat hippocampus

Abstract: The hippocampus plays a key role in memory and navigation, and forms a cognitive map of the world: hippocampal ‘place cells’ encode the animal’s location by activating whenever the animal passes a particular region in the environment (the neuron’s ‘place field’). Over the last 50 years of hippocampal research, almost all studies have focused on rodents as animal models, using small laboratory experimental setups. In my research, I explored hippocampal representations in a naturalistic settings, in a unique animal model – the bat. My talk will outline two main stories: (i) In rodents, hippocampal activity exhibits ‘theta oscillations’. These oscillations were proposed to support multiple functions, including memory and sequence formation. However, absence of clear theta in bats and humans has questioned these proposals. Surprisingly, we found that in bats hippocampal neurons exhibited nonoscillatory phase-coding. This highlights the importance of phase-coding, but not oscillations per se, for hippocampal function across species – including humans. (ii) Real-world navigation requires spatial representation of very large environments. To investigate this, we wirelessly recorded from hippocampal dorsal CA1 neurons of bats flying in a long tunnel (200 meters). Place cells displayed a multifield multiscale code: Individual neurons exhibited multiple place fields of diverse sizes, ranging from 0.6 to 32 meters, and the fields of the same neuron differed up to 20-fold in size. Theoretical analysis showed that the multiscale code allows representing large environments with much better accuracy than other codes. Thus, by increasing the spatial scale, we uncovered a neural code that is radically different from classical spatial codes. Together, these results highlight the power of the comparative approach, and demonstrate that studying the brain under naturalistic settings and behavior enables discovering new unknown aspects of the neural code.

There is Chemistry in Social Chemistry
Abstract: Non-human terrestrial mammals constantly sniff themselves and each-other, and based on this decide who is friend or foe. Humans also constantly sniff themselves and each-other, but the functional significance of this behavior is unknown. Given that humans seek friends who are similar to themselves, we hypothesized that humans may be smelling themselves and others to subconsciously estimate body-odor similarity, and that this may then promote friendship. To test this hypothesis, we recruited non-romantic same-sex friend dyads who had initially bonded instantaneously, or so called click-friends, and harvested their body-odor. In a series of experiments, we then found that objective ratings obtained with an electronic nose, and subjective ratings obtained from independent human smellers, converged to suggest that click-friends smell more similar to each other than random dyads. To then estimate whether this similarity was merely a consequence of friendship, or a driving force of friendship, we recruited complete strangers, smelled them with an electronic nose, and engaged them in non-verbal same-sex dyadic interactions. Remarkably, we observed that dyads who smelled more similar had better dyadic interactions. In other words, we could predict social bonding with an electronic nose. This result implies that body-odor similarity is a causal factor in social interaction, or in other words, there is indeed chemistry in social chemistry.

Given an odd element x in a Lie superalgebra g satisfying [x, x] = 0, we have that x^2 = 0 in the universal enveloping algebra of g, and so for every g-module M, we can define the cohomology DS_x (M) := Ker (x) / Im(x).In fact, DS(M) is a module for the Lie superalgebra g_x := DS_x (g) = Ker ad(x) / Im ad(x), which is a Lie superalgebra of smaller rank than g. For example, if g = gl(m|n) and x is a root vector, then g_x = gl(m − 1|n − 1). Duflo and Serganova defined the functor DS_x from the category of g-modules to the category of g_x-modules which is now called the Duflo–Serganova functor. This minicourse will give an overview of the theory of Duflo–Serganova functors and the recen

The sinking of organic particles in the ocean and their degradation by marine microorganisms drive one of the most conspicuous carbon fluxes on Earth, the biological pump. Yet, the mechanisms determining the magnitude of the pump remain poorly understood, limiting our ability to predict this carbon flux in future ocean scenarios. Current ocean models assume that the biological pump is governed by the competition between sinking speed and degradation rate, with the two processes independent from one another. In this talk, I will demonstrate that contrary to this paradigm, sinking itself is a primary determinant of the rate at which bacteria enzymatically degrade particles in the ocean. By combining video microscopy and microfluidic experiments to directly observe and quantify bacterial degradation of individual organic particles in flow, I will show that even modest sinking speeds of 8 meters per day enhance degradation rates more than 10-fold. I will further discuss the molecular mechanism behind the sinking-enhanced degradation, as well as possible ways by which bacteria can slow the sinking of particles. Finally, using the results obtained from a mathematical model, I will show that the coupling of sinking and degradation may contribute to determining the magnitude of the vertical carbon flux in the ocean, and will outline major open questions in the field.

Functional ultrasound imaging (fUS) is an emerging neuroimaging tool capable of measuring brain-wide vascular signals linked to neuronal activity with a high spatial-temporal resolution (100 µm, 10 Hz) in real-time. This technology is portable, affordable and adaptable to many species, and has already found applications in areas ranging from basic research to the clinic. Focusing on fundamental neuroscience, I will outline some of the recent technical advancements of fUS, such as the capacity to image the entire rodent brain while manipulating specific neuronal circuits with optogenetics. I will exemplify how promising this imaging technique is for shedding new light on the brain-wide circuits underlying behavior, as fUS is one of the few methods that enables imaging of activity deep in the brain of behaving mice.
Zoom link: https://weizmann.zoom.us/j/95406893197?pwd=REt5L1g3SmprMUhrK3dpUDJVeHlrZz09
Meeting ID: 954 0689 3197
Password: 750421

Given an odd element x in a Lie superalgebra g satisfying [x, x] = 0, we have that x^2 = 0 in the universal enveloping algebra of g, and so for every g-module M, we can define the cohomology DS_x (M) := Ker (x) / Im(x).In fact, DS(M) is a module for the Lie superalgebra g_x := DS_x (g) = Ker ad(x) / Im ad(x), which is a Lie superalgebra of smaller rank than g. For example, if g = gl(m|n) and x is a root vector, then g_x = gl(m − 1|n − 1). Duflo and Serganova defined the functor DS_x from the category of g-modules to the category of g_x-modules which is now called the Duflo–Serganova functor. This minicourse will give an overview of the theory of Duflo–Serganova functors and the rece