Events
Condensed Matter Seminar
NMR-STM of metals at an atomic scale
Mr. Vladi Pankrushin
Physics department, BGU
Mon, 19 Jan 2026, 11:10
Sacta-Rashi Building for Physics (54), room 207
Abstract: STM-NMR and STM-ESR are two methods to receive spectroscopic information on an atomic scale, while the common methods could achieve that on macroscopic samples. The research focuses on studying the abilities and limitations of the method, especially in scanning heavy metals. Heavy metals have unique challenges compared to other samples, such as - low resonance frequencies, high density of state and strong quadrupole interactions. Studying the ability of measuring metals at an atomic scale may be extremely helpful in the semiconductor industry and in medicine.
Condensed Matter Seminar
Hidden magnetic phases and field-induced spin dynamics in the i-MAX compounds
Mr. Dror Yahav
Physics department, BGU
Mon, 19 Jan 2026, 11:35
Sacta-Rashi Building for Physics (54), room 207
Abstract: New NMR and AC susceptibility measurements of various i-MAX samples, (Mo2/3RE1/3)2AlC, where RE stands for Rare Earth (including RE=Gd, Tb, Dy, Ho, and Er), show several surprising findings, including the emergence of a high field ordered canted antiferromagnetic (AFM) phase, with intriguing magnetic properties not measured before and possible re-entrance of magnetic phases for the Dy, Ho, Er compounds with the Tb compound acting as a turning point in RE compounds. In addition, the canted AFM phase transition field curiously decreases while increasing the atomic number of the RE at the expense of the lower AFM phase. In the
Tb compound spin dynamics in the kHz range appear at B~0.2T up to B~6T, not displayed in other RE i-MAX samples, implementing a non-trivial superparamagnetic structure with Mydosh parameter Φ~0.168(5). The measurements point towards complex magnetic structure in the i-MAX compounds, demonstrating a non-trivial evolution of their phase diagram while increasing both the atomic number of the RE element and the external field.
Physics Colloquium
Critical transitions and self-organization in sleep dynamics
Prof. Ronny Bartsch
BIU
Tue, 20 Jan 2026, 16:00
Ilse Katz Institute for Nanoscale Science & Technology (51), room 015
Abstract: Traditionally, sleep is considered to operate according to the
classical principle of homeostasis, where physiological variables
relax back to equilibrium after perturbation. However, the complex
dynamics of sleep-stage transitions and brief arousals, which
constitute the sleep micro-architecture at time scales of seconds to
minutes, cannot be understood within this framework.
We show that arousals are intrinsic components of healthy sleep and
exhibit scale-invariant temporal organization characterized by
power-law statistics, while sleep-stage durations display exponential
behavior with characteristic time scales. The coexistence of these two
fundamentally different processes within a single regulatory mechanism
is a hallmark of non-equilibrium systems exhibiting self-organized
criticality.
We further demonstrate that this critical behavior is sustained by
structured coupling between active and quiet states, leading to
long-range temporal correlations across the sleep period. Disruptions
of this organization are associated with alterations in sleep
micro-architecture observed in sleep disorders. Together, these
findings suggest that sleep operates in a non-equilibrium critical
regime at short time scales, providing a unifying physical framework
for understanding arousals, sleep-stage transitions, and sleep
stability.
Biological and soft-matter physics
Self-organized shape changes in elastic active gels
Prof. Kinjal Dasbiswas
Dept. of Physics & Center for Cellular and Biomolecular Machines, UC Merced
Thu, 22 Jan 2026, 12:10
Sacta-Rashi Building for Physics (54), room 207
Abstract: Living systems utilize fundamental physics in the form of mechanical forces and geometric cues to move and change shape. A central question motivating our research is: how does biological matter utilize mechanical forces to form ordered structures and change shape? As a prototype of active biological materials capable of self-organized shape change, we explain experimental findings on cytoskeletal gel extracts by our collaborators at the Bernheim laboratory. Despite having identical composition of the biopolymer actin, molecular motor myosin and the crosslinker fascin, these gels contract and buckle into different shapes depending on the initial gel aspect ratio: thinner gels tend to wrinkle, while thicker gels tend to form domes. By incorporating motor-generated active stresses, alignment of active fibers, and stress-dependent myosin binding kinetics into a network-fluid (poroelastic) model, we qualitatively capture the observed trends in gel contraction dynamics measured using particle image velocimetry (PIV). We then show how a geometric elastic model for thin sheets can relate the 3D buckled shapes to strain rates predicted by the poroelastic model. Our findings have implications for shape changes during tissue morphogenesis and bio-inspired soft materials design.
Biological and soft-matter physics
New Computational Approaches to Understanding the Z Ring in Live Bacteria
Mr. Guy Alis
Dept of Physics, BGU
Thu, 29 Jan 2026, 12:10
Sacta-Rashi Building for Physics (54), room 207
Abstract: One of the fundamental characteristics of living organisms is their ability to reproduce. Owing to their relative simplicity, bacterial cell division has been extensively studied over the past sixty years. Yet, because of their small size, the internal structures of living bacteria remain challenging to resolve. This highlights the need for non-invasive methods that can overcome current resolution limits and uncover the inner mechanisms that enable bacteria to develop and proliferate.
In order for a bacterium to split into two, it first builds an internal ‘belt’ at its middle. This structure, called the Z ring, is made of a protein that assembles into a circular band just under the cell membrane. The Z ring acts like a flexible scaffold: it marks where the cell will divide and helps coordinate processes that lead to cell division. Even though it plays a central role, the small size and constantly changing shape make the Z ring difficult to observe directly in living cells.
In this talk, I will present a Monte-Carlo-based fitting strategy for identifying protein clusters within the Z ring. By using stochastic sampling to navigate a high dimensional parameter space, this approach overcomes the limitations of traditional deterministic fitting methods and yields high confidence cluster estimates. I will then introduce a robust method for tracking and characterizing protein dynamics, and briefly examine a complementary center of mass approach. Finally, I will present several simulation models at different levels of coarse graining that help interpret the physical principles driving Z ring organization.
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