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    The Clore Center for Biological Physics

    Date:
    23
    Sunday
    June
    2024
    Lecture / Seminar
    Time: 12:45-14:30
    Title: The role of sign indefinite invariants in shaping turbulent cascades.
    Location: Gerhard M.J. Schmidt Lecture Hall
    Lecturer: Michal Shavit, Postdoctoral fellow
    Organizer: Clore Center for Biological Physics
    Contact: Debbie.hen@weizmann.ac.il
    Details: Lunch will be served at 12:45
    Abstract: Our work answers a nearly 60-year quest to derive the turbulent spectrum of weak ... Read more Our work answers a nearly 60-year quest to derive the turbulent spectrum of weakly interacting internal gravity waves from first principles. The classical wave-turbulence approach didn’t work, as the underlying equation, both in 2D and 3D, is an anisotropic, non-canonical Hamiltonian equation. A key consequence of the non-canonical Hamiltonian is the conservation of a sign-indefinite quadratic invariant alongside the sign-definite quadratic energy. In 2D, this allows us to derive a much simpler kinetic equation. We leverage this simplification into the derivation of solutions of the kinetic equation, one of which is the turbulent spectrum of weakly interacting 2D internal gravity waves. Our spectrum exactly matches the phenomenological oceanic Garrett-Munk spectrum in the limit of large vertical wave numbers and zero rotation. This talk is based on recent joint works with Oliver Bühler and Jalal Shatah arXiv:2311.04183 (to appear soon in PRL). arXiv:2406.06010. FOR THE LATEST UPDATES AND CONTENT ON SOFT MATTER AND BIOLOGICAL PHYSICS AT THE WEIZMANN, VISIT OUR WEBSITE: https://www.biosoftweizmann.com/
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    The Clore Center for Biological Physics- Special seminar

    Date:
    10
    Monday
    June
    2024
    Lecture / Seminar
    Time: 13:00-14:00
    Title: Mixing Artificial and Natural Intelligence: From Statistical Mechanics to AI and Back
    Location: Edna and K.B. Weissman Building of Physical Sciences
    Lecturer: Dr. Michael (Misha) Chertkov
    Organizer: Clore Center for Biological Physics
    Contact: malka.avraham@weizmann.ac.il
    Details: Lunch at 12:30
    Abstract: This presentation will outline recent evolution of AI methodologies, focusing on ... Read more This presentation will outline recent evolution of AI methodologies, focusing on the emergence of Diffusion Models of AI inspired by non-equilibrium statistical mechanics, Transformers, and Reinforcement Learning. These innovations are revolutionizing our approach to reduced, Lagrangian turbulence modeling and are instrumental in formulating and solving new challenges, such as swimming navigation in chaotic environments. More generally, attendees will gain insights into the synergy between AI and natural sciences and understand how this symbiosis is shaping the future of scientific research. This comprehensive vision is relevant to theoretical physicists, applied mathematicians, and computer scientists alike.
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    The Clore Center for Biological Physics

    Date:
    04
    Tuesday
    June
    2024
    Lecture / Seminar
    Time: 13:15-14:30
    Title: Flexoelectricity versus Electrostatics in Polar Nematic Liquid Crystals
    Location: Nella and Leon Benoziyo Physics Library
    Lecturer: Prof. Jonathan Selinger
    Organizer: Clore Center for Biological Physics
    Contact: Debbie.hen@weizmann.ac.il
    Details: lunch will be served at 12:45
    Abstract: In the most common phase of liquid crystals, called the nematic phase, molecul ... Read more In the most common phase of liquid crystals, called the nematic phase, molecules are aligned up or down along some axis, so that the net electrostatic polarization is zero. Recent experiments have found a new class of liquid crystals, called ferroelectric nematic, in which molecules align predominantly in one direction along the axis, leading to a nonzero polarization. From the perspective of statistical mechanics, the ferroelectric nematic phase has two special features. First, it has flexoelectricity, meaning that the polarization induces a splay of the molecular orientation. Second, the energy includes an electrostatic interaction, which favors a domain structure. In this talk, we discuss the competition between those two effects to control the phase behavior. FOR THE LATEST UPDATES AND CONTENT ON SOFT MATTER AND BIOLOGICAL PHYSICS AT THE WEIZMANN, VISIT OUR WEBSITE: https://www.biosoftweizmann.com/
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    The Clore Center for Biological Physics

    Date:
    26
    Sunday
    May
    2024
    Lecture / Seminar
    Time: 13:15-14:30
    Title: Phages vs bacteria warfare: co-evolution and intelligence gathering
    Location: Koffler Accelerator of the Canada Center of Nuclear Physics
    Lecturer: Prof. Yigal Meir
    Organizer: Clore Center for Biological Physics
    Contact: Debbie.hen@weizmann.ac.il
    Details: Lunch will be served at 12:45
    Abstract: The warfare between bacteria and phages - viruses that infect bacteria - has bee ... Read more The warfare between bacteria and phages - viruses that infect bacteria - has been raging for billions of years. During this time both sides have evolved various attack and defense systems. In this talk I will describe 3 related projects: 1. Is there an optimal number of such defense or anti-defense systems? 2. How can different phages which prey on the same bacteria co-exist, in contradiction with the expected competitive exclusion? 3. Some phages have developed the ability to garner environmental information, enabling them to make more "intelligent" decisions. How much is such intelligence worth, in terms of other resources? FOR THE LATEST UPDATES AND CONTENT ON SOFT MATTER AND BIOLOGICAL PHYSICS AT THE WEIZMANN, VISIT OUR WEBSITE: https://www.biosoftweizmann.com/
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    The Clore Center for Biological Physics

    Date:
    07
    Sunday
    April
    2024
    Lecture / Seminar
    Time: 13:15-14:30
    Title: Odd Mechanical Screening: From Metamaterial to Continuum Mechanics of Disordered Solids
    Location: Koffler Accelerator of the Canada Center of Nuclear Physics
    Lecturer: Prof. Michael Moshe
    Organizer: Clore Center for Biological Physics
    Contact: debbie.hen@weizmann.ac.il
    Details: refreshments will be served at 12:45
    Abstract: Holes in elastic metamaterials, defects in 2D curved crystals, localized plastic ... Read more Holes in elastic metamaterials, defects in 2D curved crystals, localized plastic deformations in amorphous solids and T1 transitions in epithelial tissue, are typical realizations of stress-relaxation mechanisms in different solid-like structures, interpreted as mechanical screening. In this talk I will present a mechanical screening theory that generalizes classical theories of solids, and introduces new moduli that are missing from the classical theories. Contrary to its electrostatic analog, the screening theory in solids is richer even in the linear case, with multiple screening regimes, predicting qualitatively new mechanical responses. The theory is tested in different physical systems, including disordered granular solids that do not have a continuous mechanical description. These materials are shown to violate energy conservation and are best described by Odd-Screening: a screening model that does not derive from an energy function. Experiments reveal a mechanical response that is strictly different from classical solid theory and is completely consistent with our mechanical-screening theory. Finally, I will discuss the relevance of this theory to 3D solids and a new Hexatic-like state in 3D matter.
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    The Clore Center for Biological Physics

    Date:
    17
    Sunday
    March
    2024
    Lecture / Seminar
    Time: 13:45-14:30
    Title: On plants and sounds: plants hearing and emitting airborne sounds
    Location: Nella and Leon Benoziyo Physics Library
    Lecturer: Prof. Lilach Hadany
    Organizer: Clore Center for Biological Physics
    Contact: debbie.hen@weizmann.ac.il
    Abstract: The communication of plants with their environment is crucial for their survival ... Read more The communication of plants with their environment is crucial for their survival. Plants are known to use light, odors, and touch to communicate with other organisms, including plants and animals. Yet, acoustic communication is almost unexplored in plants, despite its potential adaptive value. This is the topic of the current talk. We have started exploring plant bioacoustics - what plants hear, and what they “say”. I will describe two major projects: in the first we study plant hearing, testing the responses of flowers to sounds of pollinators; in the second we investigate plant sound emission - we have shown that different species of plants emit brief ultrasonic signals, especially under stress. Using AI we can interpret these sounds and identify plant species and stress condition from the sounds. Potential implications of these projects for plant ecology, evolution and agriculture will be discussed.
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    Chemical and Biological Physics Guest seminar

    Date:
    10
    Sunday
    March
    2024
    Lecture / Seminar
    Time: 16:00-17:00
    Title: Photodynamics of molecular probes in solutions, cells, and organic surfaces
    Location: Perlman Chemical Sciences Building
    Lecturer: Prof. Oleg Vasyutinskii
    Organizer: Department of Chemical and Biological Physics
    Contact: gilad.haran@weizmann.ac.il
    Abstract: The lecture presents recent results obtained in the laboratory of Prof. Oleg Vas ... Read more The lecture presents recent results obtained in the laboratory of Prof. Oleg Vasyutinskii in the Ioffe Institute, St.Petersburg, Russia along several directions of application of modern laser techniques for investigation of the dynamics of molecules relevant for biology and medicine. The particular directions under discussion will be as follows. • Investigation of energy transfer in the excited states of molecular probes in solutions by means of polarized fluorescence spectroscopy. • Pump-and-probe polarization modulation spectroscopy for investigation of sub-picosecond dynamics in excited biomolecules. • Dynamics of singlet oxygen generation and degradation in solutions and on organic surfaces.
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    The Clore Center for Biological Physics

    Date:
    03
    Sunday
    March
    2024
    Lecture / Seminar
    Time: 13:15-14:30
    Title: A Statistical Physics Approach to Bacteria under Strong Perturbations
    Location: Nella and Leon Benoziyo Physics Library
    Lecturer: Prof. Nathalie Q. Balaban
    Organizer: Clore Center for Biological Physics
    Contact: debbie.hen@weizmann.ac.il
    Details: refreshments will be served at 12:45
    Abstract: Statistical physics successfully accounts for phenomena involving a large number ... Read more Statistical physics successfully accounts for phenomena involving a large number of components using a probabilistic approach with predictions for collective properties of the system. While biological cells contain a very large number of interacting components, (proteins, RNA molecules, metabolites, etc.), the cellular network is understood as a particular, highly specific, choice of interactions shaped by evolution, and therefore difficultly amenable to a statistical physics description. Here we show that when a cell encounters an acute but non-lethal stress, its perturbed state can be modelled as random network dynamics. Strong perturbations may therefore reveal the dynamics of the underlying network that are amenable to a statistical physics description. We show that our experimental measurements of the recovery dynamics of bacteria from a strong perturbation can be described in the framework of physical aging in disordered systems (Kaplan Y. et al, Nature 2021). Further experiments on gene expression confirm predictions of the model. The predictive description of cells under and after strong perturbations should lead to new ways to fight bacterial infections, as well as the relapse of cancer after treatment.
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    The Clore Center for Biological Physics

    Date:
    25
    Sunday
    February
    2024
    Lecture / Seminar
    Time: 13:15-14:30
    Title: Tails and (boson) peaks in the glassy vibrational density of states
    Location: Nella and Leon Benoziyo Physics Library
    Lecturer: Avraham Moriel
    Organizer: Clore Center for Biological Physics
    Contact: Debbie.hen@weizmann.ac.il
    Details:
    Abstract: Due to their intrinsic nonequilibrium and disordered nature, glasses feature l ... Read more Due to their intrinsic nonequilibrium and disordered nature, glasses feature low-frequency, nonphononic vibrations, in addition to phonons. These excess modes generate a peak —the boson peak— in the ratio of the vibrational density of state (VDoS) and Debye’s VDoS of phonons. Yet, the excess vibrations and the boson peak are not fully understood. After presenting the experimental evidence of the boson peak, we will discuss additional universal characteristics of glassy low frequency VDoS obtained through numerical simulations. We will then examine a recently analyzed mean-field model capturing the universal low-frequency glassy VDoS characteristics. Combining reanalyzed experimental data and computer simulations, we will observe that the same mean-field model also captures the origin, nature and properties of the boson peak, yielding a unified physical picture of the low-frequency VDoS spectra of glasses. FOR THE LATEST UPDATES AND CONTENT ON SOFT MATTER AND BIOLOGICAL PHYSICS AT THE WEIZMANN, VISIT OUR WEBSITE: https://www.biosoftweizmann.com/
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    The Clore Center for Biological Physics

    Date:
    11
    Sunday
    February
    2024
    Lecture / Seminar
    Time: 13:15-14:30
    Title: Tunable Architecture of Nematic Disclination Lines
    Location: Edna and K.B. Weissman Building of Physical Sciences
    Lecturer: Dr. Hillel Aharoni
    Organizer: Clore Center for Biological Physics
    Contact: Debbie.hen@weizmann.ac.il
    Details: PLEASE NOTE: lunch will be served at 12:45 at the DRORY AUDITORIUM
    Abstract: In this talk, I introduce a theoretical framework to tailor three-dimensional de ... Read more In this talk, I introduce a theoretical framework to tailor three-dimensional defect line architecture in nematic liquid crystals. By drawing an analogy between nematic liquid crystals and magnetostatics, I will show quantitative predictions for the connectivity and shape of defect lines in a nematic confined between two thinly spaced glass substrates. I will demonstrate experimental and numerical verification of these predictions, and identify critical parameters that tune the disclination lines' curvature within an experimental setup, as well as non-dimensional parameters that allow matching experiments and simulations at different length scales. Our system provides both physical insight and powerful tools to induce desired shapes and shape changes of defect lines.
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    Chemical and Biological Physics Guest seminar

    Date:
    07
    Wednesday
    February
    2024
    Lecture / Seminar
    Time: 15:00-16:00
    Title: The Stark effect in quantum dots: from spectral diffusion to coherent control
    Location: Gerhard M.J. Schmidt Lecture Hall
    Lecturer: Dr. Ron Tenne
    Organizer: Department of Chemical and Biological Physics
    Contact: lucio.frydman@weizmann.ac.il
    Abstract: While colloidal quantum dots (CQDs) are already an important building block in e ... Read more While colloidal quantum dots (CQDs) are already an important building block in electro-optical devices, in the realm of quantum science and technology, they are often considered inferior with respect to emitters such as solid-state defects and epitaxial quantum dots. Despite their single-photon emission [1], demonstrations of quantum coherence and control are largely still lacking. The main obstacle towards these is spectral diffusion – stochastic fluctuations in the energy of photons emitted from an individual CQD even at cryogenic temperatures. In this talk, I will present our recent work providing, for the first time, direct and definitive proof that these fluctuations arise from stochastic electric fields in the particle’s nano environment [2]. However, the high sensitivity of CQDs to electric fields, through the quantum-confined Stark effect, can also be perceived as a feature, rather than a bug. I will present future concepts for coherent control of a single photon’s temporal wavefunction through an electric bias. Relying on tools from the terahertz and femtosecond-laser toolboxes [3,4], spectroscopy and control at fast-to-ultrafast (millisecond-to-femtosecond) timescales, will play a detrimental role in fulfilling the unique potential that CQDs hold in the field of quantum optics,. [1] R. Tenne, U. Rossman, B. Rephael, Y. Israel, A. Krupinski-Ptaszek, R. Lapkiewicz, Y. Silberberg, and D. Oron, Super-Resolution Enhancement by Quantum Image Scanning Microscopy, Nature Photonics 13, 116 (2019). [2] F. Conradt, V. Bezold, V. Wiechert, S. Huber, S. Mecking, A. Leitenstorfer, and R. Tenne, Electric-Field Fluctuations as the Cause of Spectral Instabilities in Colloidal Quantum Dots, Nano Lett. 23, 9753 (2023). [3] P. Henzler et al., Femtosecond Transfer and Manipulation of Persistent Hot-Trion Coherence in a Single CdSe/ZnSe Quantum Dot, Physical Review Letters 126, 067402 (2021). [4] P. Fischer, G. Fitzky, D. Bossini, A. Leitenstorfer, and R. Tenne, Quantitative Analysis of Free-Electron Dynamics in InSb by Terahertz Shockwave Spectroscopy, Physical Review B 106, 205201 (2022).
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    The Clore Center for Biological Physics

    Date:
    04
    Sunday
    February
    2024
    Lecture / Seminar
    Time: 13:15-14:30
    Title: Multiscale Lattice Modeling and Simulations of Heterogeneous Membranes
    Location: Nella and Leon Benoziyo Physics Library
    Lecturer: Prof. Oded Farago
    Organizer: Clore Center for Biological Physics
    Contact: malka.avraham@weizmann.ac.il
    Details: Lunch at 12:45
    Abstract: Mixtures of lipids and cholesterol (Chol) have been served as simple model syste ... Read more Mixtures of lipids and cholesterol (Chol) have been served as simple model systems for studying the biophysical principles governing the formation of liquid ordered raft domains in complex biological systems. These mixtures exhibit a rich phase diagram as a function of temperature and composition. Much of the focus in these studies has been given to the coexistence regime between liquid ordered and liquid disordered phases which resembles rafts floating in the sea of disordered lipids. In the talk, I will present a new lattice model of binary [1] and ternary [2, 3] mixtures containing saturated and unsaturated lipids, and Chol. Simulations of mixtures of thousands of lipids and cholesterol molecules on time scales of hundreds of microseconds show a very good agreement with experimental and atomistic simulation observations across multiple scale, ranging from the local distributions of lipids to the macroscopic phase diagram of such mixtures. Importantly, we find that the liquid ordered domains are highly heterogeneous and consist of Chol-poor hexagonally packed gel-like clusters surrounded by Chol-rich regions at the domain boundaries. The presence of such nano-domains within the liquid ordered regions appears as a characteristic feature of the liquid-ordered state, and makes the interpretation of scattering data ambiguous in mixtures not exhibiting macroscopic phase separation.
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    The Clore Center for Biological Physics

    Date:
    28
    Sunday
    January
    2024
    Lecture / Seminar
    Time: 13:15-14:15
    Title: Some organizing principles behind microbial community dynamics
    Location: Nella and Leon Benoziyo Physics Building
    Lecturer: Dr. Amir Erez -Racah
    Organizer: Clore Center for Biological Physics
    Contact: malka.avraham@weizmann.ac.il
    Details: Lunch at 12:45
    Abstract: Microbial ecosystems, pivotal in global ecological stability, display a diverse ... Read more Microbial ecosystems, pivotal in global ecological stability, display a diverse array of species, influenced by complex interactions. When considering environments with changing nutrient levels, we have recently suggested an 'early bird' effect. This phenomenon, which results from changing nutrient levels, initial and fast uptake of resources confers an advantage, significantly altering microbial growth dynamics. In serial dilution cultures with varying nutrient levels, this effect leads to shifts in diversity, demonstrating that microbial communities do not adhere to a universal nutrient-diversity relationship. Using a consumer-resource, serial dilution modeling framework, we simulate scenarios of changing nutrient balance, such as variations in phosphorous availability in rainforest soils, to predict a possible lag in ecosystems response near a loss of diversity transition point. Lastly, we explore the notion of 'microbial debt', a form of the early bird advantage, where microbes initially grow rapidly at the cost of later growth or increased mortality. This dynamic, exemplified in both classical chemostat and serial dilution cultures, reveals that such debt can convey an advantage, with varying outcomes on community structure depending on the nature of the trade-off involved. Together, these studies illuminate some organizing principles behind microbial dynamics, balancing growth and survival in changing environments.
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    The Clore Center for Biological Physics

    Date:
    14
    Sunday
    January
    2024
    Lecture / Seminar
    Time: 13:15-14:15
    Title: Kinetic Choreography: Exploring Protein-DNA Interactions Beyond Affinity & Specificity
    Location: Nella and Leon Benoziyo Physics Building
    Lecturer: Koby Levy
    Organizer: Clore Center for Biological Physics
    Contact: Ariel.amir@weizmann.ac.il
    Abstract: The kinetics of protein–DNA recognition, along with its thermodynamic properti ... Read more The kinetics of protein–DNA recognition, along with its thermodynamic properties, including affinity and specificity, play a central role in shaping biological function. Protein–DNA recognition kinetics are characterized by two key elements: the time taken to locate the target site amid various nonspecific alternatives; and the kinetics involved in the recognition process, which may necessitate overcoming an energetic barrier. In my presentation, I will describe the complexity of protein-DNA kinetics obtained from molecular coarse-grained simulations of various protein systems. The kinetics of protein-DNA recognition are influenced by various molecular characteristics, frequently necessitating a balance between kinetics and stability. Furthermore, protein-DNA recognition may undergo evolutionary optimization to accomplish optimal kinetics for ensuring proper cellular function.
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    Special Clore Seminar - Leenoy Meshulam

    Date:
    09
    Tuesday
    January
    2024
    Lecture / Seminar
    Time: 12:45-13:45
    Title: Bridging scales in biological systems – from octopus skin to mouse brain
    Location: Nella and Leon Benoziyo Physics Building
    Lecturer: Leenoy Meshulam
    Organizer: Clore Center for Biological Physics
    Contact: malka.avraham@weizmann.ac.il
    Details: Lunch will be held at 12:15
    Abstract: For an animal to perform any function, millions of cells in its body furiously i ... Read more For an animal to perform any function, millions of cells in its body furiously interact with each other. Be it a simple computation or a complex behavior, all biological functions involve the concerted activity of many individual units. A theory of function must specify how to bridge different levels of description at different scales. For example, to predict the weather, it is theoretically irrelevant to follow the velocities of every molecule of air. Instead, we use coarser quantities of aggregated motion of many molecules, e.g., pressure fields. Statistical physics provides us with a theoretical framework to specify principled methods to systematically ‘move’ between descriptions of microscale quantities (air molecules) to macroscale ones (pressure fields). Can we hypothesize equivalent frameworks in living systems? How can we use descriptions at the level of cells and their connections to make precise predictions of complex phenomena My research group will develop theory, modeling and analysis for a comparative approach to discover generalizable forms of scale bridging across species and behavioral functions. In this talk, I will present lines of previous, ongoing, and proposed research that highlight the potential of this vision. I shall focus on two seemingly very different systems: mouse brain neural activity patterns, and octopus skin cells activity patterns. In the mouse, we reveal striking scaling behavior and hallmarks of a renormalization group- like fixed point governing the system. In the octopus, camouflage skin pattern activity is reliably confined to a (quasi-) defined dynamical space. Finally, I will touch upon the benefits of comparing across animals to extract principles of multiscale function in biological systems, and propose future directions to investigate how macroscale properties, such as memory or camouflage, emerge from microscale level activity of individual cells.
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    Chemical and Biological Physics Guest seminar

    Date:
    07
    Sunday
    January
    2024
    Lecture / Seminar
    Time: 15:00
    Title: Static and dynamic biophysical properties of tissue microstructure: Insights from advanced in vivo MRI
    Location: Gerhard M.J. Schmidt Lecture Hall
    Lecturer: Dr Noam Shemesh
    Organizer: Department of Chemical and Biological Physics
    Contact: daniella.goldfarb@weizmann.ac.il
    Abstract: In living systems, the tissue micro-architecture consists of myriad cellular and ... Read more In living systems, the tissue micro-architecture consists of myriad cellular and subcellular elements whose density, size/shape distributions, composition, and permeability, endow the tissue with its biological functionality. Dynamic transport mechanisms are further critical for maintaining homeostasis and supporting diverse physiological functions such as action potentials and biochemical signaling. Still, how these biophysical properties change over time and how they couple to activity, remains largely unknown. This is mainly due to the difficulty in mapping these properties in-vivo, longitudinally, and with sufficient specificity. Magnetic Resonance Imaging (MRI), with its capacity for longitudinal studies and wealth of microscopic information leading to multiple contrast mechanisms, provides an outstanding opportunity to decipher these phenomena. In this talk I will discuss our recent advances in diffusion and functional MRI, including novel pulse sequences and biophysical modeling of diffusion processes in the microscopic tissue milieu, which provide, for the first time, the sought-after specificity for density, size, and permeability of particular (sub)cellular elements in tissues. I will show new experiments in rodents proving unique power-laws predicted from biophysical models, revealing axon density and size, as well as cell body density and size, along with validations against ground-truth histology and applications in animal models of disease. Evidence for exchange between the intracellular and extracellular space will also be given, along with a first approach for quantitatively mapping permeability in tissue. I will also introduce correlation tensor MRI (CTI), a new approach for source-separation in diffusional kurtosis, that offers surrogate markers of neurite beading effects, thereby further enhancing specificity, especially in stroke. Finally, I will touch upon dynamic modulations of neural tissue microstructure upon neural activity, and provide evidence for the existence of a neuro-morphological coupling in diffusion-weighted functional MRI signals. Future vistas and potential applications will be discussed.
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    Clore Seminar-Professor Jay Fineberg

    Date:
    07
    Sunday
    January
    2024
    Lecture / Seminar
    Time: 13:15-14:15
    Title: The Fundamental Physics of the Onset of Frictional Motion: How do laboratory earthquakes nucleate?
    Location: Nella and Leon Benoziyo Physics Building
    Lecturer: Prof. Jay Fineberg
    Organizer: Clore Center for Biological Physics
    Contact: malka.avraham@weizmann.ac.il
    Details: Lunch at 12:45
    Abstract: Recent experiments have demonstrated that rapid rupture fronts, akin to earthqua ... Read more Recent experiments have demonstrated that rapid rupture fronts, akin to earthquakes, mediate the transition to frictional motion. Moreover, once these dynamic rupture fronts (“laboratory earthquakes”) are created, their singular form, dynamics and arrest are well-described by fracture mechanics. Ruptures, however, need to be created within initially rough frictional interfaces, before they are able to propagate. This is the reason that “static friction coefficients” are not well-defined; frictional ruptures can nucleate for a wide range of applied forces. A critical open question is, therefore, how the nucleation of rupture fronts actually takes place. We experimentally demonstrate that rupture front nucleation is prefaced by extremely slow, aseismic, nucleation fronts. These nucleation fronts, which are often self-similar, are not described by our current understanding of fracture mechanics. The nucleation fronts emerge from initially rough frictional interfaces at well-defined stress thresholds, evolve at characteristic velocity and time scales governed by stress levels, and propagate within a frictional interface to form the initial rupture from which fracture mechanics take over. These results are of fundamental importance to questions ranging from earthquake nucleation and prediction to processes governing material failure.
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    Chemical and Biological Physics Guest seminar

    Date:
    03
    Wednesday
    January
    2024
    Lecture / Seminar
    Time: 15:00-16:00
    Title: Atomic arrays as programmable quantum processors and sensors
    Location: Gerhard M.J. Schmidt Lecture Hall
    Lecturer: Dr Ran Finkelstein
    Organizer: Department of Chemical and Biological Physics
    Contact: lucio.frydman@weizmann.ac.il
    Abstract: Large arrays of trapped neutral atoms have emerged over the past few years as a ... Read more Large arrays of trapped neutral atoms have emerged over the past few years as a promising platform for quantum information processing, combining inherent scalability with high-fidelity control and site-resolved readout. In this talk, I will discuss ongoing work with arrays of Alkaline-earth atoms. These divalent atoms offer unique properties stemming largely from their long-lived metastable states, which form the basis of the optical atomic clock. I will describe the design of a universal quantum processor based on clock qubits and its application in quantum metrology, and I will address the challenge of generating and benchmarking highly entangled states in an analog quantum simulator. First, we realize scalable local control of individual clock qubits, which we utilize to extend the Ramsey interrogation time beyond the coherence time of a single atom [1]. To realize a universal quantum processor, we demonstrate record high-fidelity two-qubit entangling gates mediated by Rydberg interactions, which we combine with dynamical reconfiguration to entangle clock probes in GHZ states and perform Ancilla-based detection [2]. We then use the narrow clock transition to measure and remove thermal excitations of atoms in tweezers (a technique known as erasure conversion) and generate hyperentangled states of motion and spin [3]. In the second part of the talk, I will describe a different approach for generating large scale entangled states in an analog quantum simulator configuration [4], including error mitigation [5] and benchmarking of a 60-atom simulator [6]. Together, these show the great promise and the large variety of experiments accessed with this emerging platform. [1] A. Shaw*, R. Finkelstein*, R. Tsai, P. Scholl, T. Yoon, J. Choi, M. Endres, Multi-ensemble metrology by programming local rotations with atom movements, arxiv:2303.16885, Nature Physics in press (2023). [2] R. Finkelstein, R. Tsai, A. Shaw, X. Sun, M. Endres, A universal quantum processor for entanglement enhanced optical tweezer clocks, in preparation. [3] P. Scholl*, A. Shaw*, R. Finkelstein*, R. Tsai, J. Choi, M. Endres, Erasure cooling, control, and hyper-entanglement of motion in optical tweezers, arXiv:2311.15580 (2023). [4] J. Choi, A. Shaw, I. Madjarov, X. Xie, R. Finkelstein, J. Covey, J. Cotler, D. Mark, H.Y. Huang, A. Kale, H. Pichler, F. Brandão, S. Choi, and M. Endres, Preparing random states and benchmarking with many-body quantum chaos, Nature 617 (2023) [5] P. Scholl, A. Shaw, R. Tsai, R. Finkelstein, J. Choi, M. Endres, Erasure conversion in a high-fidelity Rydberg quantum simulator, Nature 622 (2023). [6] A. Shaw, Z. Chen, J. Choi, D.K. Mark, P. Scholl, R. Finkelstein, A. Elben, S. Choi, M. Endres, Benchmarking highly entangled states on a 60-atom analog quantum simulator, arXiv:2308.07914 (2023).
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    The Clore Center for Biological Physics

    Date:
    31
    Sunday
    December
    2023
    Lecture / Seminar
    Time: 13:15-14:15
    Title: Erasing information fast and cheap --- How to approach Landauer’s bound?
    Location: Edna and K.B. Weissman Building of Physical Sciences
    Lecturer: Roi Holtzman
    Organizer: Clore Center for Biological Physics
    Contact: malka.avraham@weizmann.ac.il
    Details: Sunday, December 31ST at 13:15 Lunch at 12:45 The seminar will take place in ... Read more Sunday, December 31ST at 13:15 Lunch at 12:45 The seminar will take place in the physics library
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    Abstract: The celebrated Landauer bound is the fundamental universal cost of computation: ... Read more The celebrated Landauer bound is the fundamental universal cost of computation: there must be dissipation of at least kBTlog2 per erasure of one bit. This fundamental bound is reached when the erasure protocol is performed in the slow quasi-static limit. Generally, the faster the erasure protocol, the more dissipation is generated. In this talk, I will present two approaches that challenge this view. First, it will be shown that by the use of a conserved quantity in the system, one can bypass Liouville’s theorem and perform erasure at zero energetic cost. The second approach that will be discussed is considering a system that is weakly coupled to the environment. In that case, one can design an erasure procedure that does not scale with its operation time.
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    Chemical and Biological Physics Guest seminar

    Date:
    17
    Tuesday
    October
    2023
    Lecture / Seminar
    Time: 11:00
    Title: Strong light-matter coupling: from transition metal dichalcogenides to Casimir self-assembly
    Location: Gerhard M.J. Schmidt Lecture Hall
    Lecturer: Prof. Timur O. Shegai
    Organizer: Department of Chemical and Biological Physics
    Contact: Gilad.haran@weizmann.ac.il
    Abstract: Strong light-matter interactions are at the core of many electromagnetic phenome ... Read more Strong light-matter interactions are at the core of many electromagnetic phenomena. In this talk, I will give an overview of several nanophotonic systems which support polaritons – hybrid light-matter states, as well as try to demonstrate their potential usefulness in applications. I will start with transition metal dichalcogenides (TMDs) and specifically discuss one-dimensional edges in these two-dimensional materials (1-2). I will show that TMDs can be etched along certain crystallographic axes, such that the obtained edges are nearly atomically sharp and exclusively zigzag-terminated, while still supporting polaritonic regime. Furthermore, I will show that Fabry-Pérot resonators, one of the most important workhorses of nanophotonics, can spontaneously form in an aqueous solution of gold nanoflakes (3-4). This effect is possible due to the balance between attractive Casimir-Lifshitz forces and repulsive electrostatic forces acting between the flakes. There is a hope that this technology is going to be useful for future developments in self-assembly, nanomachinery, polaritonic devices, and perhaps other disciplines. References: 1) Nat. Commun., 11, 4604, (2020) 2) Laser & Photonics Rev., 17, 2200057, (2023) 3) Nature 597, 214-219, (2021) 4) Nat. Phys. 19, 271-278, (2023)
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    Chemical and Biological Physics Guest Seminar

    Date:
    15
    Thursday
    June
    2023
    Lecture / Seminar
    Time: 11:00
    Title: Ratchet based ion pumps
    Location: Gerhard M.J. Schmidt Lecture Hall
    Lecturer: Dr Gideon Segev
    Organizer: Department of Chemical and Biological Physics
    Contact: omer.yaffe@weizmann.ac.il
    Abstract: Even though highly selective ion pumps can be found in every living cell membran ... Read more Even though highly selective ion pumps can be found in every living cell membrane, artificial, membrane-based ion selective separation is a longstanding unmet challenge in science and engineering. The development of a membrane-based ion separation technology can drive a dramatic progress in a wide range of applications such as: water treatment, bio-medical devices, extraction of precious metals from sea water, chemical sensors, solar fuels and more. In this seminar I will discuss our theoretical and experimental demonstration of ion pumps based on an electronic flashing ratchet mechanism. Electronic flashing ratchets are devices that utilize modulation in a spatially varying electric field to drive steady state current. Like peristaltic pumps, where the pump mechanism is not in direct contact with the pumped fluid, electronic ratchets induce net current with no direct charge transport between the power source and the pumped charge carriers. Thus, electronic ratchets can be used to pump ions in steady state with no electrochemical reactions between the power source and the pumped ions resulting in an “all electric” ion pump. Ratchet-based ion pumps (RBIPs) were fabricated by coating the two surfaces of nano-porous alumina wafers with gold forming nano-porous capacitor-like devices. The electric field within the nano-pores is modulated by oscillating the capacitors voltage. Thus, when immersed in solution, ions within the pores experience a modulating electric field resulting in ratchet-based ion pumping. The RBIPs performance was studied for various input signals, geometries, and solutions. RBIPs were shown to drive ionic current densities of several μA/cm2 even when opposed by an electrostatic force. A significant ratchet action was observed with input signal amplitudes as low as 0.1V thus demonstrating that RBIPs can drive an ionic current with no associated redox reactions. Simulations show that frequency dependent flux inversions in ratchet systems may pave the way towards ion selective RBIPs.
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    Joint Chemical and Biological Physics and Molecular Chemistry and Materials Science Guest Seminar

    Date:
    13
    Tuesday
    June
    2023
    Lecture / Seminar
    Time: 10:00-11:00
    Title: Tunneling and Zero-Point Energy Effects in Multidimensional Hydrogen Transfer Reactions
    Location: Gerhard M.J. Schmidt Lecture Hall
    Lecturer: Dr Yair Litman
    Organizer: Department of Chemical and Biological Physics
    Contact: lucio.frydman@weizmann.ac.il
    Abstract: ydrogen transfer reactions play a prominent role in nature and many technologica ... Read more ydrogen transfer reactions play a prominent role in nature and many technological applications. Despite appearing to be simple reactions, they constitute complex processes where nuclear quantum effects (NQE) such as zero-point energy and nuclear tunneling play a decisive role even at ambient temperature. In this talk, I will show how state-of-the-art methodologies based on the path integral formulation of quantum mechanics in combination with the density functional approximation provide the unique possibility to theoretically address these effects in complex environments. The first part of the talk will focus on the porphycene molecule in the gas phase and adsorbed on metallic surfaces. The porphycene molecule constitutes a paradigmatic example of a molecular switch and has recently received great attention due to its intriguing hydrogen dynamics. I will demonstrate how a correct treatment of NQE, as well as the inclusion of multidimensional anharmonic couplings, are essential to obtain qualitatively correct results regarding the non-trivial temperature dependence of the hydrogen transfer rates and vibrational spectra [1-3]. Finally, I shall also mention some of our recent results for hydrogen diffusion on metals for which non-adiabatic effects, in addition to NQE, play a significant role and can lead to “quantum localization” [4-6]. [1] Y. Litman, J. O. Richardson, T. Kumagai, and M. Rossi, J. Am. Chem. Soc. 141, 2526 (2019) [2] Y. Litman, J. Behler, and M. Rossi, Faraday Discuss. 221, 526 (2020) [3] Y. Litman and M. Rossi, Phys. Rev. Lett. 125, 216001 (2020) [4] Y. Litman, E. S. Pos. C. L. Box, R. Martinazzo, R. J. Maurer, and M. Rossi, J. Chem. Phys. 156, 194106 (2022) [5] Y. Litman, E. S. Pos. C. L. Box, R. Martinazzo, R. J. Maurer, and M. Rossi , J. Chem. Phys. 156, 194107 (2022) [6] O. Bridge, R. Martinazzo, S. C. Althorpe, Y. Litman, in preparation (2023)
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    Soft Matter and Biomaterials: Membrane remodelling in viral infection and migrasome formation

    Date:
    11
    Sunday
    June
    2023
    Lecture / Seminar
    Time: 11:00-12:00
    Location: Perlman Chemical Sciences Building
    Lecturer: Dr. Raya Sorkin
    Organizer: Department of Molecular Chemistry and Materials Science
    Contact: ana.naamat@weizmann.ac.il
    Abstract: Fundamental understanding of physiological processes that occur at biological me ... Read more Fundamental understanding of physiological processes that occur at biological membranes, such as membrane fusion, necessitates addressing not only the biochemical aspects, but also biophysical aspects such as membrane mechanical properties and membrane curvature. In this talk, I will show how we combine membrane model systems, micropipette aspiration, optical tweezers and confocal fluorescence microscopy to study membrane shaping and membrane fusion processes. I will describe a new tool we developed, where we form membrane bilayers supported on polystyrene microspheres which can be trapped and manipulated using optical tweezers. Using this approach, we demonstrate successful measurements of the interaction forces between the Spike protein of SARS CoV-2 and its human receptor, ACE2. We further use bead-supported membranes interacted with aspirated vesicles to reveal the inhibitory effect of membrane tension on hemifusion. I will also describe a particular case of membrane shaping during the formation of the newly discovered organelle termed migrasome. We show that tetraspanin proteins involved in migrasome formation strongly partition into curved membrane tethers, and we reveal a novel, two-step process of migrasome biogenesis.
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    Chemical and Biological Physics Guest Seminar

    Date:
    06
    Tuesday
    June
    2023
    Lecture / Seminar
    Time: 10:00-11:00
    Title: Materials with a twist: atomically controlled interfaces for clean energy
    Location: Perlman Chemical Sciences Building
    Lecturer: Prof Magali Lingenfelder
    Organizer: Department of Chemical and Biological Physics
    Contact: ron.naaman@weizmann.ac.il
    Abstract: Our society faces a critical challenge in shifting from a reliance on carbon-bas ... Read more Our society faces a critical challenge in shifting from a reliance on carbon-based energy to sustainable renewable sources. A key step towards achieving clean energy lies in developing efficient catalysts that can convert chemical energy into electricity or use electrons to generate chemical energy. In our research group, we tackle these challenges by creating customized materials that draw inspiration from nature (biomimicry) and combine principles from interfacial chemistry and surface physics. For this presentation, I focus on the process of photosynthesis as inspiration for the design, characterization, and dynamic nature of functional interfaces that drive energy conversion processes such as CO2 electroreduction and water splitting. I will also discuss the application of cutting-edge scanning probe microscopy, which allows us to visualize dynamic electrochemical processes at the nanoscale (operando imaging). Additionally, I will highlight our use of unconventional strategies that leverage chiral molecules and abundant two-dimensional materials to enhance electrocatalytic conversion processes. (References : Nanoletters, 2021, 21, 2059; Nature Comm., 2022, 13, 3356, IJC 62, 11, 2022).
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    Soft Matter and Biomaterials Seminar: Cytoskeletal dynamics generate active liquid-liquid phase separation.

    Date:
    30
    Sunday
    April
    2023
    Lecture / Seminar
    Time: 11:00-12:00
    Location: Perlman Chemical Sciences Building
    Lecturer: Dr. Alexandra Tayar
    Organizer: Department of Molecular Chemistry and Materials Science
    Contact: ana.naamat@weizmann.ac.il
    Abstract: Liquid-Liquid phase separation (LLPS) has been of fundamental importance in the ... Read more Liquid-Liquid phase separation (LLPS) has been of fundamental importance in the assembly of thermally driven materials and has recently emerged as an organizational principle for living systems. Biological phase separation is driven out of equilibrium through complex enzyme composition, chemical reactions, and mechanical activity, which reveals a gap in our understanding of this fundamental phenomenon. Here we study the impact of mechanical activity on LLPS. We design a DNA-based LLPS system coupled to flows through molecular motors and a cytoskeleton network. Active stress at an interface of a liquid droplet suppressed phase separation and stabilized a single-phase regime well beyond the equilibrium binodal curve. The phase diagram out of equilibrium revealed a 3-dimensional phase space that depends on temperature and local molecular activity. Similar dynamics and structures are observed in simulations, suggesting that suppression of liquid phase separation by active stress is a generic feature of liquid phase separation.
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    Chemical and Biological Physics Guest Seminar

    Date:
    02
    Sunday
    April
    2023
    Lecture / Seminar
    Time: 14:00
    Title: Ab initio approaches to nonequilibrium dynamics and molecular quantum systems
    Location: Gerhard M.J. Schmidt Lecture Hall
    Lecturer: Prof Prineha Narang
    Organizer: Department of Chemical and Biological Physics
    Contact: Gilad.haran@weizmann.ac.il
    Abstract: In this talk, I will present theoretical and computational chemistry approaches ... Read more In this talk, I will present theoretical and computational chemistry approaches to describe excited-states in quantum matter, and predicting emergent states created by external drives. Understanding the role of such light-matter interactions in the regime of correlated electronic systems is of paramount importance to fields of study across chemical and condensed matter physics, and ultrafast dynamics1. The simultaneous contribution of processes that occur on many time and length-scales have remained elusive for state-of-the-art calculations and model Hamiltonian approaches alike, necessitating the development of new methods in computational chemistry. I will discuss our work at the intersection of ab initio cavity quantum-electrodynamics and electronic structure methods to treat electrons, photons and phonons on the same quantized footing, accessing new observables in strong light-matter coupling. Current approximations in the field almost exclusively focus on electronic excitations, neglecting electron-photon effects, for example, thereby limiting the applicability of conventional methods in the study of polaritonic systems, which requires understanding the coupled dynamics of electronic spins, nuclei, phonons and photons. With our approach we can access correlated electron-photon and photon-phonon dynamics2–7, essential to our latest work on driving quantum materials far out-of-equilibrium to control the coupled electronic and vibrational degrees-of-freedom 8–19. In the second part of my talk, I will demonstrate how the same approach can be generalized in the context of control of molecular quantum matter and quantum transduction. As a first example, I will discuss a cavity-mediated approach to break the inversion symmetry allowing for highly tunable even-order harmonic generation (e.g. second- and fourth-harmonic generation) naturally forbidden in such systems. This relies on a quantized treatment of the coupled light-matter system, similar to the driven case, where the molecular matter is confined within an electromagnetic environment and the incident (pump) field is treated as a quantized field in a coherent state. When the light-molecule system is strongly coupled, it leads to two important features: (i) a controllable strong-coupling-induced symmetry breaking, and (ii) a tunable and highly efficient nonlinear conversion efficiency of the harmonic generation processes 20–22. Both of these have implications for molecular quantum architectures. Being able to control molecules at a quantum level gives us access to degrees of freedom such as the vibrational or rotational degrees to the internal state structure. Finally, I will give an outlook on connecting ideas in cavity control of molecules with quantum information science.
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    Chemical and Biological Physics Guest Seminar

    Date:
    23
    Thursday
    March
    2023
    Lecture / Seminar
    Time: 10:00-11:00
    Title: Building and testing semiclassical models for molecular plasmonics
    Location: Perlman Chemical Sciences Building
    Lecturer: Prof Maxim Sukharev
    Organizer: Department of Chemical and Biological Physics
    Contact: Gilad.haran@weizmann.ac.il
    Abstract: Molecular plasmonics has been a hot topic for the past several years. At the hea ... Read more Molecular plasmonics has been a hot topic for the past several years. At the heart of the primary interest in plasmonics is the strong electromagnetic field localization at resonant frequencies corresponding to surface plasmon-polariton modes. Thanks to riveting advancements in nanofabrication technologies, we have achieved nearly 1 nm spatial resolution (and in some cases even below that!) and are able to fabricate a wide variety of nanosystems ranging from nanoparticles of various shapes to metasurfaces comprised of periodic arrays of nanoparticles and/or nanoholes of any imaginable geometry. Such systems have recently emerged as new platforms for strong light-matter interactions. Combined with molecular ensembles, these constructs exhibit a remarkable set of optical phenomena ranging from the exciton-plasmon strong coupling to the second harmonic generation altered by molecular resonances. In this talk I will discuss both linear and nonlinear optical properties of plasmonic materials coupled to quantum emitters of various complexity. I will also introduce a newly developed computational approach that can be used to efficiently simulate a large number of complex molecules driven by electromagnetic radiation crafted at plasmonic interfaces.
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    Joint Chemical and Biological Physics and Molecular Chemistry and Materials Science Guest Seminar

    Date:
    16
    Thursday
    March
    2023
    Lecture / Seminar
    Time: 15:00-16:00
    Title: Synthesis and properties of circulenes and helicenes
    Location: Gerhard M.J. Schmidt Lecture Hall
    Lecturer: Prof Michael Pittelkow
    Organizer: Department of Chemical and Biological Physics
    Contact: oren.tal@weizmann.ac.il
    Abstract: I will discuss the synthesis and properties of a range of aromatic-, anti-aromat ... Read more I will discuss the synthesis and properties of a range of aromatic-, anti-aromatic- and helical aromatic molecules.1 The talk will feature molecules with 'weird' magnetic properties, helical chirality and abnormal reactivity due to close proximity. I will discuss some of the unusual properties (and some of the very trivial and unsurprising properties) of these large well-defined conjugated molecules. I will describe the journey from fundamental studies of the acid-mediated oligomerization of simple 1,4-benzoquinones to the controlled synthesis of heterocyclic [8] circulenes (featuring an antiaromatic planar cyclooctatetraene) and even a larger planar [9] helicene. In the simplest picture two units of benzoquinone gives a dihydroxy-dibenzofuran + water, thus forming a new furan ring. This sets up a 1+1=3 ‘logic’ for elongation of the -system. The synthetic methodology has allowed us to prepare a range of fully conjugated helicenes, including the longest known optically resolved chiral [13] helicenes. The helicenes and circulenes have been explored in a range of properties including as the blue fluorescent component in OLEDs, as G-quadruplex binding ligands and in fundamental studies of antiaromaticity and chirality.
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    Chemical and Biological Physics Guest Seminar

    Date:
    15
    Wednesday
    March
    2023
    Lecture / Seminar
    Time: 15:00-16:00
    Title: Chiral Induced Spin Selectivity, magnetic and the Onsager reciprocity principle
    Location: Gerhard M.J. Schmidt Lecture Hall
    Lecturer: Prof Per Hedegard
    Organizer: Department of Chemical and Biological Physics
    Contact: oren.tal@weizmann.ac.il
    Abstract: The so-called CISS phenomenon refers to the observation, that when electrons are ... Read more The so-called CISS phenomenon refers to the observation, that when electrons are transported through a chiral molecule, as e.g. a helix, then they will emerge spin polarized even though when entering they are not spin polarized. Often this effect is observed using magnetized leads. Remarkably, it seems that many experiments break the Onsager reciprocity principle. Onsager’s principle is very deep and depends on very few assumptions about the system - mainly about behavior under time reversal. I will present a possible solution to this conundrum
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    Soft Matter and Biomaterials: “The Secret Ultrafast Motions of Protein Nanomachines”

    Date:
    12
    Sunday
    March
    2023
    Lecture / Seminar
    Time: 11:00-12:00
    Location: Perlman Chemical Sciences Building
    Lecturer: Prof. Gilad Haran
    Organizer: Department of Molecular Chemistry and Materials Science
    Contact: ana.naamat@weizmann.ac.il
    Abstract: Multiple proteins function as nanomachines, and carry out multiple specific task ... Read more Multiple proteins function as nanomachines, and carry out multiple specific tasks in the cell by alternating chemical steps with conformational transitions. Single-molecule FRET spectroscopy is a powerful tool for studying the internal motions of proteins. In recent years, we have been using this technique to study a range of protein machines, surprisingly finding in each case microsecond-time-scale internal dynamics. What is the role of these fast motions in the much-slower functional cycles of these machines?
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    Soft Matter and Biomaterials Seminar

    Date:
    19
    Sunday
    February
    2023
    Lecture / Seminar
    Time: 11:00-12:00
    Title: Nanotechnology for targeted drug and gene delivery: from basics to clinical applications
    Location: Perlman Chemical Sciences Building
    Lecturer: Prof. Avi Schroeder
    Organizer: Department of Molecular Chemistry and Materials Science
    Contact: ananaamat@gmail.com
    Abstract: Medicine is taking its first steps toward patient-specific cancer care. Nanopart ... Read more Medicine is taking its first steps toward patient-specific cancer care. Nanoparticles have many potential benefits for treating cancer, including the ability to transport complex molecular cargoes, including siRNA and protein, as well as targeting specific cell populations. The talk will explain the fundamentals of nanotechnology, from ‘barcoded nanoparticles’ that target sites of cancer where they perform a programmed therapeutic task. Specifically, liposomes diagnose the tumor and metastasis for their sensitivity to different medications, providing patient-specific drug activity information that can be used to improve the medication choice. The talk will also describe how liposomes can be used for degrading the pancreatic stroma to allow subsequent drug penetration into pancreatic adenocarcinoma and how nanoparticle’ biodistribution and anti-cancer efficacy are impacted by the patient’s sex and, more specifically, the menstrual cycle. The evolution of drug delivery systems into synthetic cells, programmed nanoparticles that have an autonomous capacity to synthesize diagnostic and therapeutic proteins inside the body, and their promise for treating cancer and immunotherapy, will be discussed. References: 1) Theranostic barcoded nanoparticles for personalized cancer medicine, Yaari et al. Nature Communications, 2016, 7, 13325 2) Collagenase nanoparticles enhance the penetration of drugs into pancreatic tumors, Zinger et al., ACS Nano, 13 (10), 11008-11021, 2019 3) Targeting neurons in the tumor microenvironment with bupivacaine nanoparticles reduces breast cancer progression and metastases, Science Advances, Kaduri et al., 7 (41), eabj5435, 2021 4) Nanoparticles accumulate in the female reproductive system during ovulation affecting cancer treatment and fertility, Poley et al., ACS nano, 2022
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    Chemical and Biological Physics Guest Seminar

    Date:
    31
    Tuesday
    January
    2023
    Lecture / Seminar
    Time: 11:00
    Title: Structure and ultrafast dynamics at the water interface revealed by phase-sensitive nonlinear spectroscopy
    Location: Perlman Chemical Sciences Building
    Lecturer: Prof Tahei Tahara
    Organizer: Department of Chemical and Biological Physics
    Contact: Gilad.haran@weizmann.ac.il

    Chemical and Biological Physics Guest Seminar

    Date:
    22
    Sunday
    January
    2023
    Lecture / Seminar
    Time: 12:00
    Title: How crystals flow – plastic deformation of colloidal single crystals
    Location: Gerhard M.J. Schmidt Lecture Hall
    Lecturer: Dr Ilya Svetlizky
    Organizer: Department of Chemical and Biological Physics
    Contact: lucio.frydman@weizmann.ac.il
    Abstract: Plastic (irreversible) deformation of crystals requires disrupting the crystalli ... Read more Plastic (irreversible) deformation of crystals requires disrupting the crystalline order, which happens through nucleation and motion of topological line defects called dislocations. Interactions between dislocations lead to the formation of complex networks that, in turn, dictate the mechanical response of the crystal. The severe difficulty in atomic systems to simultaneously resolve the emerging macroscopic deformation and the evolution of these networks impedes our understanding of crystal plasticity. To circumvent this difficulty, we explore crystal plasticity by using colloidal crystals; the micrometer size of the particles allows us to visualize the deformation process in real-time and on the single particle level. In this talk, I will focus on two classical problems: instability of epitaxial growth and strain hardening of single crystals. In direct analogy to epitaxially grown atomic thin films, we show that colloidal crystals grown on mismatched templates to a critical thickness relax the imposed strain by nucleation of dislocations. Our experiments reveal how interactions between dislocations lead to an unexpectedly sharp relaxation process. I will then show that colloidal crystals can be strain-hardened by plastic shear; the yield strength increases with the dislocation density in excellent accord with the classical Taylor equation, originally developed for atomic crystals. Our experiments reveal the underlying mechanism for Taylor hardening and the conditions under which this mechanism fails.
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    Chemical and Biological Physics Guest Seminar

    Date:
    18
    Wednesday
    January
    2023
    Lecture / Seminar
    Time: 14:00
    Title: Emergent Excitability at Tissue-Tissue Interfaces
    Location: Gerhard M.J. Schmidt Lecture Hall
    Lecturer: Dr Hillel Ori
    Organizer: Department of Chemical and Biological Physics
    Contact: lucio.frydman@weizmann.ac.il
    Abstract: Interfaces between systems with different properties are a common feature of Nat ... Read more Interfaces between systems with different properties are a common feature of Nature. However, the physics of interactions across such interfaces is often neglected. In this talk, I will focus on the case of biological tissue-tissue interfaces and show they can exhibit emergent electrical excitability, a phenomenon that has not been explored before. Using cultured cells and optical tools, I have found that interfaces between tissues with dissimilar electrophysiological properties can behave differently compared to the tissues on either side. In particular, the interface between non-excitable tissues can become excitable. Excitability of cells therefore depends on their position, not just the proteins they express. Moreover, my simulations reveal that interface excitability is extremely robust to parametric variation. I will briefly discuss the roots of this difference in the structures of the underlying dynamical systems, and will show examples of other excitable systems that can exhibit interfacial excitation, such as predator-prey dynamics and oscillating chemical reactions.
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    Chemical and Biological Physics Guest Seminar

    Date:
    16
    Monday
    January
    2023
    Lecture / Seminar
    Time: 14:00
    Title: Less is more: Elucidating cellular transport using simplified cell models
    Location: Gerhard M.J. Schmidt Lecture Hall
    Lecturer: Dr Ran Tivony
    Organizer: Department of Chemical and Biological Physics
    Contact: lucio.frydman@weizmann.ac.il
    Abstract: Cells carefully regulate the movement of solutes across their membrane using an ... Read more Cells carefully regulate the movement of solutes across their membrane using an intricate array of interconnected transport pathways. While beneficial for mediating essential cellular activities, the abundance of complex transport pathways severely limits the elucidation of particular translocation mechanisms in live-cell studies. We alleviate this impediment by taking a reductionist approach to incorporate specific transport pathways (e.g., transport proteins) in simplified artificial cell models, using giant unilamellar vesicles (GUVs) as a biologically-relevant chassis. To gain maximal control over the bioengineering process, we developed an integrated microfluidic platform capable of high-throughput production and purification of monodispersed GUV-based cell models. Using single-vesicle fluorescence analysis, we quantified the passive permeation rate of two biologically important electrolytes, protons (H+) and potassium ions (K+), and correlated their flux with electrochemical gradient buildup across the GUV lipid bilayer. Applying similar analysis principles, we also determined the H+/K+ selectively of two archetypal ion channels, gramicidin A and outer membrane porin F (OmpF). Altogether, our results provide an insight into the transport mechanism of ions across lipid bilayers and set a framework for elucidating protein-based transport in artificial cell models.
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    Chemical and Biological Physics Guest Seminar

    Date:
    21
    Wednesday
    December
    2022
    Lecture / Seminar
    Time: 15:00
    Title: Quantum simulations and interfaces with Rydberg atoms
    Location: Perlman Chemical Sciences Building
    Lecturer: Prof David Petrosyan
    Organizer: Department of Chemical and Biological Physics
    Contact: gershon.kurizki@weizmann.ac.il
    Abstract: Atoms in the highly excited Rydberg states possess unique properties, including ... Read more Atoms in the highly excited Rydberg states possess unique properties, including long lifetimes and huge dipole moments, which facilitate their use in various quantum technology applications. I will discuss recent progress in quantum simulations of many-body physics with strongly-interacting Rydberg atoms and coherent interfaces of Rydberg atoms with superconducting microwave resonators and optical photons, and present some of our results in this research.
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    Chemical and Biological Physics Guest seminar

    Date:
    29
    Tuesday
    November
    2022
    Lecture / Seminar
    Time: 14:00
    Title: Playing the evolution game with DNA oligomers
    Location: Stone Administration Building
    Lecturer: Prof Tommaso Bellini
    Organizer: Department of Chemical and Biological Physics
    Contact: nir.gov@weizmann.ac.il
    Abstract: We introduce a variant of SELEX in-vitro selection to study the evolution of a p ... Read more We introduce a variant of SELEX in-vitro selection to study the evolution of a population of oligonucleotides starting from a seed of random-sequence DNA 50mers (our evolving individuals) and introducing selectivity by an affinity capture gel formed by beads carrying DNA 20mers of fixed sequence that act as targets (our resources). We PCR amplify the captured strands and proceed to the next generation. Because of the simplicity of the process, we could investigate what plays the role of “fitness" in this synthetic evolution process. We find that, across generations, evolution is first driven by the need of binding to the capture gel, while, on a later stages it appear dominated by the emerging of motifs related to inter-individual interactions.
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    Chemical and Biological Physics Guest Seminar

    Date:
    27
    Sunday
    November
    2022
    Lecture / Seminar
    Time: 11:00
    Title: Universal Principles of Tissues in Health and Disease
    Location: Gerhard M.J. Schmidt Lecture Hall
    Lecturer: Dr Miri Adler
    Organizer: Department of Chemical and Biological Physics
    Contact: lucio.frydman@weizmann.ac.il
    Abstract: Our organs and tissues are made of different cell types that communicate with ea ... Read more Our organs and tissues are made of different cell types that communicate with each other in order to achieve joint functions. However, little is known about the universal principles of these interactions. For example, how do cell interactions maintain proper cellular composition, spatial organization and collective division of labor in tissues? And what is the role of these interactions in tissue-level diseases where the healthy balance in the tissue is disrupted such as excess scarring following injury known as fibrosis? In this talk, I will discuss my work in developing theoretical frameworks that explore the collective behavior of cells that emerges from cell-cell communication circuits. I will present work on the cell circuit that controls tissue repair following injury and how it may lead to fibrosis. I will discuss a new approach to explore how cell interactions can be used to provide symmetry breaking and optimal division of labor in tissues, and how this approach can help to interpret complex patterns in real data. I will introduce a new concept in complex networks – network hyper-motifs, where we explore how small recurring patterns (network motifs) are integrated within large networks, and how these larger patterns (hyper-motifs) can give rise to emergent dynamic properties. Finally, I will conclude with future directions that are aimed at revealing principles that unify our understanding of different tissues.
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    Pre-SAAC symposium on soft matter and biophysics

    Date:
    30
    Sunday
    October
    2022
    Conference
    Time: 08:00
    Contact: sam.safran@weizmann.ac.il
    Pre-SAAC symposium on soft matter and biophysics Conference website

    Chemical and Biological Physics Guest Seminar

    Date:
    04
    Thursday
    August
    2022
    Lecture / Seminar
    Time: 11:00
    Title: Exciton-carrier mixtures in monolayer semiconductors
    Location: Gerhard M.J. Schmidt Lecture Hall
    Lecturer: Prof. Alexey Chernikov
    Organizer: Department of Chemical and Biological Physics
    Contact: terry.debesh@weizmann.ac.il
    Abstract: Coexistence of optical and electrical excitations in semiconductors has a long h ... Read more Coexistence of optical and electrical excitations in semiconductors has a long history of research. This scenario typically involves simultaneous presence of Coulomb-bound electron-hole pairs, known as excitons, and free charge carriers. Conceptually similar to related phenomena in the ultra cold atom gases, exciton-carrier mixtures strongly influence the properties of excited semiconductors and their response to external fields. It involves the formation of bound three-particle states known as charged excitons or trions, Fermi polarons, renormalization and screening effects, as well as the Mott-transition in the high-density regime. These phenomena offer fertile ground to merge the realms of optics and transport, motivated by the availability of excitations that are both electrically tunable and couple strongly to light. Van der Waals monolayer semiconductors and layered metal-halide perovskites recently emerged as particularly suitable platforms to study exciton-carrier mixtures due to exceptionally strong Coulomb interactions on the order of many 100’s of meV. In this talk, I will discuss a number of intriguing phenomena associated with coupling of excitons to free charge carriers in these systems. I will present experimental evidence for dressing of excited exciton states by continuously tunable Fermi sea. These quasiparticles are reminiscent of two-electron excitations of the negatively charged hydrogen ion and are subject to autoionization - a unique scattering pathway available for excited states. I will further illustrate the impact of free carriers on the exciton transport revealing non-monotonous density dependence and highly efficient propagation of charged exciton complexes. Finally, I will demonstrate electrically tunable trions in hybrid organic-inorganic semiconductors. These three-particle complexes feature unusually large binding energies combined with substantial mobility at elevated temperatures.
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    A Random Walk in Soft Matter- in honor of Jacob Klein

    Date:
    21
    Tuesday
    June
    2022
    -
    23
    Thursday
    June
    2022
    Conference
    Time: 08:00
    Contact: nir.kampf@weizmann.ac.il
    A Random Walk in Soft Matter- in honor of Jacob Klein Conference website

    Curie-Weizmann meeting on Biological Physics

    Date:
    07
    Tuesday
    June
    2022
    Conference
    Time: 08:00
    Location: David Lopatie Conference Centre
    Organizer: Clore Center for Biological Physics
    Contact: sam.safran@weizmann.ac.il
    Curie-Weizmann meeting on Biological Physics Conference website

    Chemical and Biological Physics Guest Seminar

    Date:
    22
    Sunday
    May
    2022
    Lecture / Seminar
    Time: 11:00-12:00
    Title: Electron Transfer and Spin Selectivity in Biomolecules
    Location: Gerhard M.J. Schmidt Lecture Hall
    Lecturer: Prof Dave Waldeck
    Organizer: Department of Chemical and Biological Physics
    Contact: ron.naaman@weizmann.ac.il

    Chemical and Biological Physics Guest Seminar

    Date:
    22
    Sunday
    May
    2022
    Lecture / Seminar
    Time: 11:00-12:00
    Title: Electron Transfer and Spin Selectivity in Biomolecules
    Location: Gerhard M.J. Schmidt Lecture Hall
    Lecturer: Prof Dave Waldeck
    Organizer: Department of Chemical and Biological Physics
    Contact: ron.naaman@weizmann.ac.il

    Chemical and Biological Physics Guest Seminar

    Date:
    19
    Thursday
    May
    2022
    Lecture / Seminar
    Time: 15:00-16:00
    Title: Single-Molecule Measurements Probe Nanoscale Physics and Chemistry
    Location: Gerhard M.J. Schmidt Lecture Hall
    Lecturer: Prof. Latha Venkataraman
    Organizer: Department of Chemical and Biological Physics
    Contact: oren.tal@weizmann.ac.il
    Abstract: Over the past decade, there has been tremendous progress in the measurement, mod ... Read more Over the past decade, there has been tremendous progress in the measurement, modeling and understanding of structure-function relationships in single molecule circuits. Experimental techniques for reliable and reproducible single molecule junction measurements have led, in part, to this progress. In particular, the scanning tunneling microscope-based break-junction technique has enabled rapid, sequential measurement of large numbers of nanoscale junctions allowing a statistical analysis to readily distinguish reproducible characteristics. Although the break-junction technique is mostly used to measure electronic properties of single-molecule circuits, in this talk, I will demonstrate its versatile uses to understand both physical and chemical phenomena with single-molecule precision. I will discuss some recent experimental and analysis aimed at understanding quantum interference in single-molecule junctions. I will then show an example where molecular structure can be designed to utilize interference effects to create a highly non-linear device. Finally, I will discuss some new areas of research aiming to demonstrate that electric fields can catalyze chemical reactions.
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    Chemical and Biological Physics Special Seminar

    Date:
    18
    Wednesday
    May
    2022
    Lecture / Seminar
    Time: 14:00
    Title: Randomness, Complexity, and Information with Applications to Single-Molecule Science
    Location: Perlman Chemical Sciences Building
    Lecturer: Dmitrii E. Makarov
    Organizer: Department of Chemical and Biological Physics
    Contact: hagen.hofmann@weizmann.ac.il
    Abstract: The mathematical analogy between information and thermodynamical entropy has rec ... Read more The mathematical analogy between information and thermodynamical entropy has recently led to promising developments in chemistry and physics, and information theory tools are increasingly important in chemical and biological data analysis. In this talk I will describe a few of our ideas at the intersection of physical chemistry, information theory, and computer science, with the focus on single-molecule data analysis. Single-molecule experimental studies have opened a new window into the elementary biochemical steps, function of molecular machines, and cellular phenomena. The information contained in single-molecule trajectories is however often underutilized in that oversimplified models such as one-dimensional diffusion or one-dimensional random walk are used to interpret experimental data. I will show that much finer details of single-molecule dynamics, such as conformational memory and static disorder, can be deduced from an analysis that is similar to Shannon’s analysis of printed English; in particular, this method relates conformational memory to the information-theoretical compressibility of single-molecule signals.
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    Physics Hybrid Colloquium

    Date:
    10
    Thursday
    March
    2022
    Colloquium
    Time: 11:15-12:30
    Title: Phase Separation in Biological Cells: lessons from and for physics
    Location: Edna and K.B. Weissman Building of Physical Sciences
    Lecturer: Prof. Samuel Safran
    Organizer: Faculty of Physics
    Contact: tamar.fuchs@weizmann.ac.il
    Abstract: Phase separation is generally a thermodynamic process in which a mixture reaches ... Read more Phase separation is generally a thermodynamic process in which a mixture reaches its lowest free energy state by self-assembling into meso- (or macro-) scale regions that are concentrated or dilute in a given molecular component. Familiar examples include the immiscibility of water and oil, the demixing of metal atoms in alloys, and the mesoscale formation of emulsions such as milk or paint. The fundamental physics behind both the equilibrium and non-equilibrium aspects of phase separation are well understood and this talk will begin with a brief review of those. A rapidly growing body of experiments suggests that phase separation is responsible for the formation of membraneless domains (also known as biomolecular condensates, with length scales on the order of microns) in biological cells. These compartments allow the cell to organize itself in space and can promote or inhibit biochemical reactions, provide regions in which macromolecular assemblies can form, or control the spatial organization of DNA (assembled with proteins as chromatin) in the cell nucleus. I will review some recent examples based on experiments done at the Weizmann Institute on phase separation of proteins and of chromatin in the nucleus and show how physics theory has led to their understanding. In the latter case, a new paradigm is emerging in which the genetic material is not necessarily uniformly distributed within the nucleus but separated into domains which in some cases, have a complex, “marshland”, mesoscale structure. But while many of the equilibrium aspects can be at least semi-quantitatively understood by extensions of statistical physics, biological systems often do not have constant overall compositions as is the case in the examples of oil-water, alloys and emulsions; for example, over time, the cell produces and degrades many proteins. The recent understanding of such strongly non-equilibrium effects has informed the theoretical physics of phase separation and has allowed us to establish a framework in which biological noise can be included. * Collaborations: Omar Arana-Adame, Gaurav Bajpai, Dan Deviri, Amit Kumar (Dept. Chemical and Biological Physics), group of Emmanuel Levy (Dept. Structural Biology) and group of Talila Volk (Dept. Molecular Genetics)
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